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What is Stainless Steel

What is Stainless Steel?

Table of Contents

Stainless steel is stainless, corrosion resistance as the main characteristic, and chromium content of at least 10.5%, the maximum carbon content of not more than 1.2% of the steel.
Stainless steel is short for stainless acid-resistant steel, resistant to weak corrosive media such as air, steam, water is called stainless steel; and will be resistant to chemically corrosive media (acid, alkali, salt and other chemical leaching) corrosion of steel is called acid-resistant steel.
Due to the differences in the chemical composition of the two and their corrosion resistance is different, ordinary stainless steel is generally not resistant to chemical media corrosion, while acid-resistant steel is generally stainless. The term “stainless steel” does not simply refer to a stainless steel, but indicates that more than one hundred industrial stainless steel, each stainless steel developed in its specific application has good performance. The key to success is first to identify the application and then to determine the correct steel grade. There are usually only six steel grades related to the application area of building construction. They all contain 17 to 22 percent chromium, and the better grades also contain nickel. The addition of molybdenum can further improve atmospheric corrosion, especially the resistance to corrosion of atmospheres containing chlorides.
In general, the hardness of stainless steel is higher than that of aluminum alloys, and the cost of stainless steel is higher than that of aluminum alloys.

The historical origin of stainless steel

The invention and use of stainless steel goes back to the First World War period. At that time, the British guns in the battlefield, always due to the chamber wear can not be used and shipped back to the rear. Military production department ordered Brearley to develop high-strength wear-resistant alloy steel, specifically to study the solution to the problem of wear of the chamber. Brearley and his assistant collected various types of steel produced at home and abroad, a variety of different properties of alloy steel, performance experiments on a variety of different properties of machinery, and then select the more applicable steel made of guns. One day, they experimented with an alloy steel containing a large amount of chromium, and after the wear-resisting experiment, it was found that this alloy was not wear-resistant, indicating that this could not be made into a gun, so they recorded the experiment results and threw it to the corner. One day, a few months later, an assistant came rushing in with a shiny piece of steel and said to Brearley, “Sir, this is the alloy steel I found when cleaning the warehouse from Mr. Maura, do you experiment to see what special effect it actually has!” “Good!” Brierly looked at the shiny and dazzling steel and said happily.
Experimental results proved: it is a piece of stainless steel that is not afraid of acids, alkalis and salts. This stainless steel was invented by the German Maura in 1912, however, Maura does not know what use this stainless steel.
Brearley heart calculations: “This is not wear-resistant but corrosion-resistant steel, can not make guns, whether it can do tableware?” He said dry, hands-on production of stainless steel fruit knives, forks, spoons, fruit plates and folding knives and so on.

Brearley invented stainless steel in 1916 to obtain the British patent and began mass production, so far, from the trash heap of stainless steel found by chance will become popular around the world, Henry Brearley is also known as the “father of stainless steel.

Elements in Stainless Steel

Chemical elements are known to have more than 100 kinds of industrial materials used in steel can be encountered in about more than 20 kinds of chemical elements. For people in the fight against corrosion for long term practice of this particular form of stainless steel series, the most commonly used in a dozen elements, in addition to the basic elements of the composition of steel other than iron, the performance of stainless steel and organizations most affected.
The elements are: Carbon, Chromium, Nickel, Manganese, Silicon, Molybdenum, Niobium, Titanium and Miobium, Nitrogen, Copper, Cobalt, Aluminum, Sulfur and Selenium.
These elements, in addition to carbon, silicon, other than nitrogen, are located in the periodic table of chemical elements of transition. In fact the application of the stainless steel tube industry at the same time there are several elements as well as a dozen, when the number of elements co-exist in a continuum of stainless steel tubing, they separate the impact of the presence of more much more complex, because in this cases not only have to consider the role of the various elements of their own, and they should pay attention to the impact of each other, so the organization decided to stainless steel pipe of various elements in the sum of the impact.

1. Various elements on the performance of stainless steel and the impact and role of organizations

1-1. Chromium in the stainless steel a decisive role in stainless steel is a decision of only one element, that is, chromium, stainless steel each contain a certain amount of chromium. To date, no non-chromium stainless steel. Chromium stainless steel performance decision has become the main element, the fundamental reason is to add chromium as an alloying element, the internal contradiction of campaign in favor of resistance to the development of corrosion damage.
Such a change can be obtained from the following description:

  • 1. Chromium Fe-based solid solution so that the electrode potential to improve;
  • 2. Chromium electronic absorption of iron so that iron-passivated.

Anodic passivation is due to be prevented from arising from reaction of metal and alloy corrosion resistance phenomenon can be improved. Passivation of metals and alloys constitute the theory of many major film theory, deals with the electronic order of adsorption.

The influence of chromium on the properties of stainless steel
Chromium plays a decisive role in the corrosion resistance of stainless steel, in the definition of stainless steel, ω (Cr) ≥ 10.5%, which is the main element of stainless steel, the higher the corrosion resistance, the higher the chromium content, the higher the corrosion resistance. This is because the steel can form Cr2O3 in oxidizing media as a stable surface protection film of the matrix (about 10 μm), resulting in passivation, in which the chromium layer is enriched into a film.
At the same time, chromium effectively increases the electrode potential of the solid solution (ferrite, martensite or austenite), so that the electrode potential of the original iron (mild steel) from negative to positive, so that the steel from corrosion. With the addition of chromium stainless steel, the electrode potential changes by volume with n/8. When the chromium content per atom is 1/8, 2/8, 3/8.. . 8, or 12.5%, 25%, 37.5%…. The larger the molar fraction, the higher the electrode potential and the weaker the corrosion. The atomic concentration of chromium compared to 1/8 (or 12.5%, molar fraction), if 11.7% by mass, the chromium content of chromium stainless steel is generally above 12% (by mass). When the chromium atomic content reaches 25%, a secondary mutation occurs, when the corrosion resistance of chromium steel is further improved.
In addition, chromium has a good effect on the mechanical properties and process properties of stainless steel. Chromium can improve the hardenability of stainless steel, in the low-alloy organization has been widely used. Such as reducing the rate of transformation of chromium austenite to ferrite and carbide, so that the isothermal transformation diagram of austenite is shifted to the right, thus reducing the critical cooling rate of stainless steel quenching, thus improving the hardenability of steel some martensitic stainless steel air quenched martensite available.
Chromium can improve the oxidation resistance of stainless steel, with the increase of chromium content in steel, oxidation resistance significantly increased. In martensitic chromium stainless steel, oxidation resistance is 4 to 9 times higher than ordinary stainless steel, martensitic chromium stainless steel can not withstand the surface temperature of about 700 to 850 ℃.
Chromium is the only valuable element in passivated steel and stainless steel that gives good corrosion resistance for industrial use. As the chromium content increases, it can improve the resistance to atmospheric corrosion. In oxidizing media (such as dilute nitric acid), with the increase in chromium content, the corrosion resistance of stainless steel increases; but in reducing media, with the increase in chromium content, the corrosion resistance of stainless steel decreases.
Chromium can affect the physical properties of steel as follows: chromium can increase the lattice constant of steel, than the chromium content increases linearly with volume, and significantly reduces the thermal conductivity of iron-chromium alloy, but also increases the resistance of steel. The resistance of martensitic chromium stainless steel is 4 to 6 times that of ordinary stainless steel. Under quenched conditions, the hardness and tensile strength of the steel are reduced due to the increased stability of chromium ferrite. Under annealed conditions, the chromium content of low-carbon iron-chromium alloys increases, increasing strength and hardness and slightly decreasing elongation.
The maximum solubility of chromium in pure γ-iron is about 12.0%; at ω(C) ≈ 0.5%, the maximum solubility in austenite is about 20%. The solubility in pure α-iron is infinity. In Cr-Mn-N steels the solubility of N can be increased. The chromium carbides formed in the steel tend to be less than manganese and less than tungsten. In Cr steels, this temperature increases the strength and wear resistance of high-carbon steels.

1-2. Carbon in the stainless steel tubing in the dual nature of carbon steel is the industry one of the key elements, steel and organizational performance to a large extent determined by the carbon content in steel and its distribution in the form of the impact of carbon stainless steel is particularly significant. Carbon in the stainless steel on the impact of organizations mainly in two ways, on the one hand is stable austenite carbon element, and the extent of the role of a large (approximately 30 times for nickel), on the other hand, as a result of the affinity of carbon and chromium is large, with the formation of chromium – series of complex carbides. Therefore, the candle from the intensity and decay properties, both in terms of carbon in the role of stainless steel are mutually contradictory.

Recognizing the impact of the law, we can use from different requirements of different carbon content stainless steel. For example, most widely used in industry, but also the stainless steel at least – 0Crl3 – 4Cr13 five standard steel grades chromium amount is 12 – 14%, that is, the carbon to form chromium carbide and chromium factors taken into account after determined that the purpose is to make the combination of carbon and chromium as chromium carbide, the solid solution of chromium in the amount of not less than 11.7% of the minimum amount of chromium.

No.5 on the steel is due to the different carbon content, strength and corrosion resistance is also differentiated, 0Cr13 – 2Crl3 better corrosion resistance of steel but lower than the 3Crl3 and 4Cr13 strength steel, used in the manufacture of the structure of many parts, after As the No. 2 steel with higher carbon intensity will be high and more used in the manufacture of springs, cutting tools, such as high strength and wear-resistant parts. Another example is in order to overcome the 18-8 Cr-Ni stainless steel intergranular corrosion, can be carbon steel to 0.03% below, or by adding chromium and carbon affinity than the larger elements (titanium or niobium), so that does not form a carbide chromium, Another example is when the high hardness and wear resistance as a major requirement, we can increase the carbon content of steel at the same time to suitably increase the amount of chromium so that not only satisfy the requirements of the hardness and wear resistance, but also take into account – will be corrosion-resistant function, used for industrial bearings, has a stainless steel blade measuring and 9Cr18 and 9Cr17MoVCo steel, although the carbon content as high as 0.85 – 0.95%, due to their chromium also increased accordingly, it is still guaranteed the corrosion resistance of requirements.

Generally speaking, the current industry access to the application of the carbon content of stainless steel pipe are relatively low, most of the carbon content of stainless steel in the 0.1 – 0.4%, and acid-resistant carbon steel with 0.1 to 0.2% of the majority. Greater than 0.4% carbon content of stainless steel grade is only a small fraction of the total, which is used because in most conditions, to corrosion-resistant stainless steel is always the primary purpose. In addition, the lower carbon content is also a process for some requirements, such as the ease of welding and cold deformation.

1-3. Nickel in the role of stainless steel and chromium in the play after the Nickel is an excellent corrosion-resistant materials, is also an important steel alloying elements. Nickel in the austenitic stanless steel pipe is the formation of the elements,such as 304,316,321.but the low-carbon steel to obtain pure nickel austenite, the volume of nickel to achieve 24%; and only when 27 percent nickel steel, in some medium resistance significant changes in corrosion. Thus alone can not constitute a nickel stainless steel. But at the same time the existence of nickel and chromium in the stainless steel, the nickel-containing stainless steel but has many valuable properties. Based on the above circumstances, we can see that nickel as alloying elements in the role of stainless steel is that it allows high-chromium steel changes, so that corrosion resistance of stainless steel and certain to improve process performance.

The role of nickel in stainless steel
Nickel is an alloying element that forms austenite, but the role of nickel and chromium has only been fully proved. If only nickel is used, the pure nickel structure in the low-carbon austenite phase needs to have a nickel content of more than 24% (mass fraction). In fact, it needs to have a nickel content of 27% (mass fraction) in order to significantly improve the corrosion resistance of stainless steel. Therefore, nickel is not used alone as an alloy element in stainless steel.
When nickel and chromium are combined, the role of nickel in improving the corrosion resistance of steel can be clearly shown. For example, adding a small amount of nickel to ferritic stainless steel can change the single-phase microstructure of ferrite into austenite ferrite phase, so that its strength can be improved through heat treatment. If the content of nickel is further increased, it can become single-phase austenite, such as ω (CR) =18% steel containing 8% nickel by mass can obtain complete austenite. This is the widely used chromium nickel austenitic 18-8 stainless steel, which has high corrosion resistance, good deformation and weldability, and is not magnetic.
The role of nickel in stainless steel and the role of chromium in stainless steel nickel is an excellent corrosion-resistant material and an important alloy element in steel. Nickel is a forming element in austenitic stainless steel, such as 304, 316 and 321. However, in order to obtain pure nickel austenite in low carbon steel, the nickel content should reach 24%; Only when the nickel content reaches 27%, the corrosion resistance of steel in some media will change significantly. Therefore, nickel stainless steel cannot be formed by this alone. However, due to the existence of nickel and chromium in stainless steel, stainless steel containing nickel has many valuable properties. Based on the above situation, we can see that the role of nickel as an alloy element in stainless steel is that it can change the high chromium steel, so as to improve the corrosion resistance and process performance of stainless steel.
Nickel in pure α- The maximum solubility of Fe is 25% – 30%. At this time, it stays in ferrite which still contains carbon. Its function is to make the solid solubility of steel not harden. The passivation of nickel expands the range of improving corrosion resistance, especially in non oxidizing media (such as sulfuric acid).
The formation tendency of Ni Fe carbides is weaker than that which can promote graphitization, and weakens the hardenability of the steel, which is insensitive to the cold impact of the steel. In carbon steel and high carbon steel with effective concentration, austenite is preferentially retained during quenching.

1-4. Manganese and Nitrogen can substitute for Ni-Cr-Ni stainless steel, Cr-Ni austenitic steels. Although many of the advantages, but in recent decades as a result of nickel-based heat-resistant nickel alloy and the heat below 20% of the large number of strong steel development and applications, as well as the growing chemical industry of the increasing demand of stainless steel The greater the amount of the nickel deposits less concentrated in a few areas, it appeared in the world and the need for nickel in the conflict area. Therefore, in stainless steel alloys and many other fields (such as a large forging steel, tool steel, heat strong steel, etc.), especially the lack of nickel resources of the country, carried out extensive section of nickel and nickel on behalf of other elements in the scientific research and production practice, in this regard the research and application is based on a relatively large number of manganese and nitrogen to replace the stainless steel and heat-resistant nickel steel.

For the role of manganese and nickel austenitic similar. But to be more exact, the role of manganese does not lie in the formation of austenite, but it reduced the critical quenching rate of steel in cooling to increase the stability of austenite and suppress the decomposition of austenite, so that the formation of high temperature austenite to room temperature is maintained. In improving the corrosion resistance of steel, the manganese plays a minor role, such as manganese steel increased from 0 to 10.4% change, do not make steel in the air with the acid corrosion resistance of significant change. This is because the manganese to iron-based solid solution to increase the electrode potential does not help the formation of the protective role of the oxide film is very low, so the industry although some of the austenitic manganese steel alloys (such as 40Mn18Cr4, 50Mn18Cr4WN, ZGMn13 steel, etc.), but they can not be used as the use of stainless steel. Manganese in steel is about the role of a stable austenitic nickel half, that is 2% of nitrogen in steel is the role of austenite

stability and the role of larger than nickel. For example, to save with 18% chromium steel austenitic at room temperature under the body to manganese and nitrogen on behalf of low-nickel stainless steel and nickel chromium nickel element nitrogen does not induce manganese steel has been applied in industry, and some has successfully replaced the classic chrome-nickel stainless steel 18-8.

1-5. Titanium or Niobium is to prevent intergranular corrosion.

1-6. Molybdenum and Copper can increase some of the corrosion resistance of stainless steel.

1-7. Other elements on the performance of stainless steel and organizational impact

More than nine major elements of stainless steel performance and the impact of organizations, in addition to these elements and organizational performance of stainless steel elements of a greater impact, the stainless steel contains a number of other elements. Some, like steel and general for the regular deposit of impurity elements, such as silicon, sulfur and phosphorus. Also some specific purpose in order to join, such as cobalt, boron, selenium, and other rare earth elements. From the stainless steel corrosion resistance of the nature of the main, these elements have been discussed in relation to the nine elements are non-key aspects, although the case, but can not be completely ignored because their performance of stainless steel and organizations have also taken place in the same impact.

Silicon is a ferrite forming element, in general, always keep the stainless steel for the impurity elements. Cobalt as alloying elements in steel by the application of small, this is because the high price of cobalt and in other ways (such as high-speed steel, carbide, cobalt-based heat-resistant alloys, magnetic or hard magnetic alloy, etc.) has a more important purposes. Stainless steel in the general increase in the cobalt alloy elements for not more commonly used stainless steel, such as 9Crl7MoVCo (including 1.2-1.8% cobalt) plus cobalt, the purpose is not to improve corrosion resistance and to improve hardness, which are mainly used for stainless steel slicing machinery manufacturing cutting tools, such as scissors and blades.

Boron high-chromium ferritic stainless steel Crl7Mo2Ti plus 0.005% of boron, can in boiling 65% acetic acid can enhance the corrosion resistance. Add small amount of boron (0.0006 – 0.0007%) austenitic stainless steel will enable the plastic to improve the thermal state. A small amount of boron due to the formation of low melting point eutectic, so that when austenitic steel welding hot cracking tendency to increase, but contains more boron (0.5 – 0.6%) when it prevents the emergence of hot cracking . When containing 0.5 – 0.6% of boron, the formation of austenite – two-phase boride organizations to lower the melting point of weld. Coagulation bath temperature is below half the melting zone, the base metal in the cooling of the tensile stress generated by the liquid is. Solid- state under the weld metal, is at this time without causing cracks even in the near seam zone formed a crack, it can be in liquid – solid metal by filling the pool. B-containing austenitic stainless steel of the Cr-Ni in the atomic energy industry has a special purpose.

Phosphorus in the general impurity elements are stainless steel, but its in danger of austenitic stainless steel in general is not as significant in steel, it allows a higher concentration, if the information up to 0.06%, to control in favor of smelting. Individual austenite manganese steel output of about 0.06% phosphorus (such as 201 stainless steel). The use of phosphorus on the strengthening of the role of steel as well as age-hardening increases phosphorus alloying elements of stainless steel, PH17-10P steel (containing 0.25% phosphorus) is a PH-HNM steel (containing 0.30 P) and so on.

Sulfur and selenium in the general stainless steel is also often of impurity elements. However, China and Canada to the stainless steel 0.2 – 0.4% of sulfur, can improve the cutting performance of stainless steel, selenium also has the same effect. Sulfur and selenium to improve the cutting performance of stainless steel because they reduce the toughness of stainless steel, such as the 18-8 Cr-Ni stainless steel in general the impact of the value of up to 30 kg / cm 2. Containing 0.31% sulfur 18-8 steel (0.084% C, 18.15% Cr, 9.25% Ni) the impact of the value of 1.8 kg / cm2; containing 0.22% selenium 18 -8 steel (0.094% C, 18.4% Cr, 9% Ni) the impact of a value of 3.24 kilograms / square centimeters. Both sulfur and selenium to reduce the corrosion resistance of stainless steel, so the practical application of them as a stainless steel alloy of the rare element.

Rare-earth element rare-earth element used in stainless steel pipe, the key is to improve the process performance. Crl7Ti such as the steel and steel plus Cr17Mo2Ti a small number of rare earth elements, can be eliminated in ingot caused by hydrogen bubbles and the reduction of cracks in the slab. Austenitic and austenitic – ferritic stainless steel in 0.02 – 0.5% increase in the rare earth elements (Ce-La alloy), can significantly improve the performance of forging. Had a 19.5 percent containing chromium, nickel 23% copper and molybdenum austenitic manganese steel, due to thermal processing performance in the past only the production of castings, after the increase of rare earth elements can be rolled into various sections.

Main characteristics of stainless steel

Weldability

The requirements of welding performance vary depending on the use of the product. A class of tableware on the welding performance is generally not required, even including some of the pot enterprises. But the vast majority of products need raw materials welding performance is good, like the second class tableware, insulation cups, steel pipes, water heaters, water dispensers, etc.

Corrosion resistance

The vast majority of stainless steel products require good corrosion resistance, like one or two types of tableware, kitchenware, water heaters, drinking fountains, etc. Some foreign businessmen on the product also do corrosion resistance test: NACL aqueous solution heated to boiling, pour off the solution after a period of time, wash and dry, weigh the loss, to determine the degree of corrosion (Note: product polishing, because of the composition of the sand cloth or sandpaper containing Fe, will lead to test (when the surface rust spots)

Polishing performance

Today’s society, stainless steel products in the production of general polishing process, only a few products such as water heaters, drinking fountains, etc. do not need polishing. Therefore, this requires the polishing performance of raw materials is very good. The main factors affecting the polishing performance are the following.

  • ① Raw material surface defects. Such as scratches, pockmarks, over acid washing, etc..
  • ② Raw material material problems. Hardness is too low, polishing is not easy to polish bright (BQ sex is not good), and hardness is too low, in deep drawing surface prone to orange peel phenomenon, thus affecting the BQ sex. High hardness of BQ sex is relatively good.
  • ③ After deep drawing of the product, the surface of the area with great deformation will also be small black spots and RIDGING, which affects the BQ property.

Heat resistance performance

Heat resistance performance refers to the high temperature stainless steel can still maintain its excellent physical and mechanical properties.
The effect of carbon: carbon in austenitic stainless steel is a strong formation and stabilization of austenite and expand the austenite zone of the element. The ability of carbon to form austenite is about 30 times that of nickel, and carbon is an interstitial element that can significantly improve the strength of austenitic stainless steel by solid solution strengthening. Carbon can also improve the stress and corrosion resistance of austenitic stainless steel in highly concentrated chlorides (such as 42% MgCl2 boiling solution).
However, in austenitic stainless steel, carbon is often regarded as a harmful element, mainly due to the corrosion resistance of stainless steel in some conditions (such as welding or heating by 450 – 850 ℃), carbon can be formed with the chromium in the steel of high chromium Cr23C6 type carbon compounds thus leading to local chromium depletion, so that the corrosion resistance of steel, especially intergranular corrosion resistance decreased. Therefore. 60s since the new development of chromium-nickel austenitic stainless steel is mostly less than 0.03% carbon content or 0.02% ultra-low carbon type, you can know that with the carbon content is reduced, the steel intergranular corrosion susceptibility is reduced, when the carbon content is less than 0.02% to have the most obvious effect, some experiments also pointed out that carbon will also increase the chromium austenitic stainless steel pitting corrosion points tendency. Due to the harmful effects of carbon, not only in the austenitic stainless steel smelting process should be required to control the carbon content as low as possible, but also in the subsequent process of hot and cold processing and heat treatment to prevent the stainless steel surface carbonization, to avoid chromium carbide precipitation.

Corrosion resistance

When the amount of chromium in steel atomic number of not less than 12.5%, can make a sudden change in the electrode potential of steel, from negative to positive electrode potential. Stop electrochemical corrosion.

Types of stainless steel

Stainless steel is often divided into: martensitic steel, ferritic steel, austenitic steel, austenitic-ferritic (duplex) stainless steel and precipitation-hardening stainless steel, etc. according to the tissue state. In addition, it can be divided into: chromium stainless steel, chromium-nickel stainless steel and chromium-manganese-nitrogen stainless steel, etc. according to the composition. There are also special stainless steels used for pressure vessels “GB24511_2009_stainless steel plates and strips for pressure-bearing equipment”.

What is ferritic stainless steel

Ferritic steel is a low-carbon chromium stainless steel containing more than 14% chromium, and chromium stainless steel containing more than 27% chromium of any carbon content. Those belonging to this category are Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28, etc.
Conventional ferritic/martensitic steels can only reach a maximum working temperature of 550 to 600 °C. OxideDispersion St rengthened (ODS) ferritic steels can increase the working temperature to 700 °C. ODS ferritic steels have a BCC crystal structure and have very low irradiation swelling at 200 dpa neutron irradiation. In addition, ODS ferritic steels have excellent oxidation and corrosion resistance. The development of ODS ferritic steels is of great significance to improve the thermal efficiency of reactors, reduce environmental pollution, and ensure the safety and long-life operation of reactors.
The alloying elements (Fe, Cr, Ti, W, Ta, C) are required to meet the requirements of low activation, and the determination of Cr content should take into account ductility, fracture toughness and corrosion resistance. The most commonly used process for the preparation of ODS ferritic steels is hot extrusion: first, Y2O3 particles are uniformly dispersed in the matrix using mechanical alloying (MA) in a high-purity Ar atmosphere, and then the alloy powder is confined in a mild steel tube and hot extruded at 1150°C. The hot extruded master tube is cold rolled in multiple passes, and intermediate heat treatment is carried out between each pass, resulting in a thin-walled clad tube after the final heat treatment.
There are two keys to the preparation of ODS ferritic steel: first, to obtain uniformly distributed nano-oxide particles and appropriate amount of residual α2Fe, thus improving creep properties; second, to prepare thin-walled clad tubes by hot extrusion process and to change the elongated grain morphology to eliminate material anisotropy. Focus on the analysis of Y2O3 particle dissolution / analysis, the formation of residual α2Fe, thin-walled cladding tube preparation process of intermediate heat treatment and change the elongated grain shape.

What is austenitic stainless steel

Austenitic stainless steel is a stainless steel with austenitic organization at room temperature. When the steel contains about 18% Cr, 8%-25% Ni and about 0.1% C, it has a stable austenitic organization. Austenitic chromium-nickel stainless steel including the famous 18Cr-8Ni steel and on the basis of this increase in Cr, Ni content and the addition of Mo, Cu, Si, Nb, Ti and other elements developed by the high Cr-Ni series of steel. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but the strength is low, it is not possible to strengthen it through phase transformation, and can only be strengthened through cold working, such as the addition of S, Ca, Se, Te and other elements, it has good machinability.
Austenitic stainless steel production process performance is good, especially chromium-nickel austenitic stainless steel, the use of conventional means of producing special steel can be smoothly produced a variety of commonly used specifications of the plate, pipe, strip, wire, bar and forgings and castings. Due to the high content of alloying elements (especially chromium) and low carbon content, the use of electric arc furnace plus argon oxygen decarburization (AOD) or vacuum deoxidation decarburization (VOD) method of mass production of such stainless steel, for advanced grades of small batch products can be used in vacuum or non-vacuum non-induction furnace smelting, if necessary, plus electroslag remelting.
Chromium-nickel austenitic stainless steel excellent thermoplastic makes it easy to apply forging, rolling, hot perforation and extrusion and other thermal processing, ingot heating temperature of 1150 – 1260 ℃, deformation temperature range is generally 900 – 1150 ℃, containing copper, nitrogen and titanium, niobium stabilization of steel grades rely on low temperature, while high chromium, molybdenum steel grades rely on high temperature. Due to poor thermal conductivity, holding time should be longer. The workpiece can be air-cooled after thermal processing. Chromium manganese austenitic stainless steel thermal cracking sensitivity is strong, ingot open billet to small deformation, multiple passes, forgings should be stacked cold. Can be cold-rolled, cold-drawn and spinning and other cold processing processes and stamping, bending, rolled edges and folding and other forming operations. Chromium-nickel austenitic stainless steel processing hardening tendency is weaker than chromium-manganese steel, a cold deformation after annealing can reach 70% to 90%, but chromium-manganese austenitic stainless steel due to deformation resistance, processing hardening tendency is strong, should increase the number of intermediate softening annealing. General intermediate softening annealing treatment for 1050 – 1100 ℃ water cooling.
Austenitic stainless steel can also be produced castings. In order to improve the fluidity of the steel, improve casting performance, casting steel alloy composition should be adjusted: improve the silicon content, relax the chromium, nickel content of the interval, and improve the impurity element sulfur content limit.
Austenitic stainless steel should be solid solution treatment before use, in order to maximize the steel carbide and other precipitation phase solid solution to the austenite matrix, but also to homogenize the organization and stress relief, so as to ensure excellent corrosion resistance and mechanical properties. The correct solid solution treatment system for 1050 – 1150 ℃ after heating water cooling (thin parts can also be air-cooled). Solution treatment temperature depends on the degree of steel alloying: no molybdenum or low molybdenum steel grades should be lower (≤ 1100 ℃), and more highly alloyed grades such as 00Cr20Ni18Mo-6CuN, 00Cr25Ni22Mo2N, etc. should be higher (1080 – 1150 ℃).
Production widely used in advanced technology, such as furnace refining rate of 95% or more, continuous casting ratio of more than 80%, high-speed rolling mill and fine, fast forging machine and other commonly promoted. Especially in the smelting and processing process to achieve electronic computer control, to ensure the reliability and stability of product quality and performance.

What is duplex stainless steel

Duplex Stainless Steel (DSS), refers to the ferrite and austenite each about 50%, generally less phase content needs to reach a minimum of 30% of the stainless steel. In the case of lower C content, Cr content in 18% to 28%, Ni content in 3% to 10%. Some steels also contain Mo, Cu, Nb, Ti, N and other alloying elements.
This type of steel has both austenitic and ferritic stainless steel characteristics, compared with ferritic, plasticity, higher toughness, no room temperature embrittlement, intergranular corrosion resistance and welding performance are significantly improved, while also maintaining a ferritic stainless steel 475 ℃ brittleness and high thermal conductivity, with super plasticity and other characteristics. Compared with austenitic stainless steel, high strength and resistance to intergranular corrosion and chloride stress corrosion has been significantly improved. Duplex stainless steel has excellent resistance to pore corrosion and is also a nickel saving stainless steel.
Since its birth in the United States in the 1940s, duplex stainless steel has been developed into the third generation. Its main feature is that the yield strength can reach 400-550MPa, which is two times that of ordinary stainless steel, so it can save material and reduce the cost of equipment manufacturing. In terms of corrosion resistance, especially the media environment is relatively harsh (such as seawater, high chloride ion content) conditions, duplex stainless steel resistance to pitting, crevice corrosion, stress corrosion and corrosion fatigue performance is significantly better than ordinary austenitic stainless steel, can be comparable to high-alloy austenitic stainless steel.

Performance characteristics of duplex stainless steel

Due to the characteristics of two-phase organization, through the correct control of chemical composition and heat treatment process, duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel, it will have the excellent toughness and weldability of austenitic stainless steel and ferritic stainless steel has a higher strength and resistance
Chloride stress corrosion resistance combined together, it is these superior properties make duplex stainless steel as a weldable structural materials developed rapidly, since the 80s has become and martensitic, austenitic and ferritic stainless steel alongside a steel class. Duplex stainless steel has the following performance characteristics.

  • (1) Molybdenum-containing duplex stainless steel has good resistance to chloride stress corrosion under low stress. General 18-8 austenitic stainless steel in more than 60 ° C neutral chloride solution is prone to stress corrosion fracture, in trace amounts of chloride and hydrogen sulfide industrial media with this type of stainless steel manufactured heat exchangers, evaporators and other equipment have a tendency to produce stress corrosion fracture, while duplex stainless steel has good resistance.
  • (2) Molybdenum-containing duplex stainless steel has good resistance to pore corrosion. In the same pore corrosion resistance equivalent value (PRE = Cr% + 3.3Mo% + 16N%), duplex stainless steel and austenitic stainless steel critical pore corrosion potential is similar. Duplex stainless steel and austenitic stainless steel pore corrosion resistance is comparable to AISI 316L. Containing 25% Cr, especially the high chromium duplex stainless steel containing nitrogen resistance to pore corrosion and crevice corrosion performance exceeds that of AISI 316L.
  • (3) Has good resistance to corrosion fatigue and wear corrosion performance. In some corrosive media conditions, suitable for making pumps, valves and other power equipment.
  • (4) Good overall mechanical properties. Have high strength and fatigue strength, yield strength is 18-8 austenitic stainless steel 2 times. The elongation of the solid solution state reaches 25%, and the toughness value AK (V-notch) is above 100J.
  • (5) Good weldability, low thermal cracking tendency, generally no preheating before welding, no heat treatment after welding, can be welded with 18-8 austenitic stainless steel or carbon steel and other dissimilar species.
  • (6) Containing low chromium (18% Cr) duplex stainless steel heat processing temperature range than 18-8 type austenitic stainless steel, resistance is small, without forging, direct rolling open billet production steel plate. Containing high chromium (25% Cr) duplex stainless steel hot processing than austenitic stainless steel is slightly more difficult, can produce plates, tubes and wires and other products.
  • (7) Cold processing than 18-8 austenitic stainless steel process hardening effect is large, in the tube, plate bear deformation at the beginning, need to apply greater stress to deformation.
  • (8) Compared with austenitic stainless steel, the thermal conductivity is large, the coefficient of linear expansion is small, suitable for use as the lining of equipment and the production of composite plates. Also suitable for making the core of the heat exchanger, heat transfer efficiency is higher than austenitic stainless steel.
  • (9) There are still various brittle tendencies of high chromium ferritic stainless steel, should not be used in working conditions higher than 300°C. The lower the chromium content in duplex stainless steel, the less hazardous the brittle phase such as σ.

The use of duplex stainless steel

Used for refining, fertilizer, paper, petroleum, chemical and other seawater resistant high temperature resistant concentrated nitric acid and other heat exchangers and cold showers and devices.

The structure and type of duplex stainless steel

Duplex stainless steel has the characteristics of both austenitic stainless steel and ferritic stainless steel because of the austenitic + ferrite duplex organization, and the content of the two phase organizations are basically equivalent. Yield strength up to 400Mpa – 550MPa, is two times the ordinary austenitic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has high toughness, low brittle transition temperature, intergranular corrosion resistance and welding performance are significantly improved; while retaining some characteristics of ferritic stainless steel, such as 475 ℃ brittleness, high thermal conductivity, small coefficient of linear expansion, superplasticity and magnetic properties. Compared with austenitic stainless steel, duplex stainless steel has high strength, especially the yield strength is significantly improved, and pore corrosion resistance, stress corrosion resistance, corrosion fatigue resistance and other properties have also been significantly improved.
Duplex stainless steel according to its chemical composition classification, can be divided into Cr18 type, Cr23 (without Mo) type, Cr22 type and Cr25 type four categories. For the Cr25 type duplex stainless steel can be divided into ordinary and super duplex stainless steel, which is used more Cr22 type and Cr25 type. Duplex stainless steel used in China is mainly produced in Sweden, the specific grades are: 3RE60 (Cr18), SAF2304 (Cr23), SAF2205 (Cr22), SAF2507 (Cr25).

Classification of duplex stainless steel

The first category is a low-alloy type, the representative grade UNS S32304 (23Cr-4Ni-0.1N), the steel does not contain molybdenum, PREN value of 24-25, in the stress corrosion resistance can be used instead of AISI304 or 316.
The second category is a medium-alloy type, the representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N), PREN value of 32-33, its corrosion resistance between AISI 316L and 6% Mo + N austenitic stainless steel.
The third category is a high-alloy type, generally containing 25% Cr, also contains molybdenum and nitrogen, some also contain copper and tungsten, the standard grade UNSS32550 (25Cr-6Ni-3Mo-2Cu-0.2N), PREN value of 38-39, the corrosion resistance of this type of steel is higher than 22% Cr duplex stainless steel.
The fourth category is a super duplex stainless steel type, containing high molybdenum and nitrogen, the standard grade UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), some also contain tungsten and copper, PREN value greater than 40, can be applied to harsh media conditions, with good corrosion resistance and mechanical properties, comparable with super austenitic stainless steel.

What is precipitation hardening stainless steel

Precipitation-hardening stainless steel is a type of high-strength stainless steel, referred to as PH steel, in which different types and quantities of strengthening elements are added to the chemical composition of stainless steel, and different types and quantities of carbides, nitrides, carbon-nitrides and intermetallic compounds are precipitated through the precipitation-hardening process to both improve the strength of the steel and maintain sufficient toughness.
Classification of precipitation hardening stainless steel
According to the content of the main alloying elements in the steel and the hardening elements added and divided into four categories, namely.

  • (1) Martensitic precipitation-hardening stainless steel, containing generally low 0.1% carbon. Strengthened by the addition of hardening elements (copper, aluminum, titanium and aluminum, etc.) to compensate for the lack of strength. Chromium content is generally higher than 17%, and the addition of a moderate amount of nickel to improve corrosion resistance.
  • (2) Martensitic aging stainless steel, containing no more than 0.03% carbon to ensure the toughness, corrosion resistance, weldability and workability of the martensitic matrix, containing not less than 12% chromium to ensure corrosion resistance. In addition to the addition of the alloying element cobalt to further improve the heat treatment of steel.
  • (3) Semi-austenitic, i.e., transition precipitation hardening stainless steel, containing not less than 12% chromium. Low carbon content, and aluminum as its main precipitation hardening element this type of steel than martensitic precipitation hardening stainless steel has a better overall performance.
  • (4) Austenitic precipitation hardening stainless steel, is in the quenched state and aging state are stable austenitic organization of stainless steel, containing nickel (higher than 25%) and manganese are high, containing chromium higher than 13% to ensure good corrosion resistance and oxidation resistance usually add titanium, aluminum, vanadium or phosphorus as precipitation hardening elements, while adding trace amounts of boron, vanadium, nitrogen and other elements, in order to obtain excellent overall performance.

What is martensitic stainless steel

Martensitic steel (MS-MartensiticSteel) microstructure is almost entirely martensitic. Mainly through high temperature austenitic tissue rapid quenching transformation into slatted martensitic tissue, can be achieved by hot rolling, cold rolling, martensitic steel has a high tensile strength, its maximum strength of up to 1600MPa, the need for tempering treatment to improve its plasticity, so that it still has sufficient forming properties at such a high strength, is the highest strength level of commercial high-strength steel plate steel. Usually can only be produced by roll forming or stamping simple-shaped parts, mainly used for forming parts such as door bumpers with low requirements to replace tubular parts and reduce manufacturing costs. Martensitic steel is mainly 600MPa or more some high strength steel, such as 800MPa or more levels of construction machinery steel, 600MPa or more levels of pressure vessels and storage tanks steel. Generally, there are two production processes: online quenching and tempering and post-rolling quenching and tempering (tempering treatment). The high strength of martensite is due to the high density of dislocations, fine twins, carbon bias, and the martensite squareness of the interstitial solid solution. The morphology of low-carbon martensite is basically lath-like, lath-like between the small angle grain boundaries, lath within a high density of dislocations, and sometimes can be seen between the distribution of twin crystal martensite lath. However, the quenched martensite plastic toughness is poor, generally martensitic steel after quenching are to be tempered through the tempering process to adjust the steel strength and toughness match.
Martensitic stainless steel chromium content is generally in the range of 12%-18%, when the chromium exceeds 15%, it is often necessary to add a certain amount of nickel or appropriate to increase the carbon content to balance the organization.
This type of steel is heated to high temperatures when the organization for austenite, cooled to room temperature, transformed into martensite, so you can heat treatment to strengthen. Generally used in the quenched-tempered (tempered) state.
Martensitic stainless steel has the following types.

  • (1) Ordinary Cr13 steel such as 1Cr13, 2Cr13, 3Cr13 and 4Cr13 and so on for the most commonly used steel. These steels can be hardened by high-temperature heating after air-cooling, quenching the strength, hardness with the increase in carbon content, but corrosion resistance and plasticity, toughness is subsequently reduced. The first two types of steel are mainly used in the medium temperature corrosive medium and require medium strength structural parts, the latter two types of steel are mainly used for high strength, high wear resistance and corrosion resistance requirements of certain parts.
  • (2) Hot martensitic steel is based on Cr12 after complex alloying of martensitic steel, such as 2Cr12WMoV, 2Cr12MoV, 2Cr12Ni3MoV, etc.. Likewise, they can be hardened by air cooling after high temperature heating. These steels not only have high instantaneous strength at medium temperature, but also have excellent medium-temperature durability and creep properties, good stress corrosion resistance and hot and cold fatigue properties. Very suitable for the production of 500-600 ℃ and below the wet and hot conditions of the work of the load-bearing parts, complex forgings and welded parts. This type of steel in the addition of Mo, W, V at the same time, often then raise the carbon some, so its hardening tendency is greater, generally by the tempering treatment. This is a new type of martensitic high-strength steel. Its characteristics
  • (3) Ultra-low carbon complex martensitic steel. This is the carbon content down to 0.05% or less, and add nickel (w (Ni) = 4%-7%), in addition to a small amount of Mo, Ti or Si, etc.. High strength and high toughness can be obtained by quenching and tempering treatment with ultra-fine complex phase organization. Can also be used in the quenched state, because the low-carbon martensite organization and no hard brittleness. This type of steel is suitable for barrels, pressure vessels and low-temperature parts.
  • (4) Martensitic heat-resistant steel can be broadly divided into two categories of a simple Cr13 type of horse 2Cr13, etc.; the other is based on Cr12 type of multiples, such as 1Cr13, gold-reinforced martensitic steel, such as Cr12Ni2W2MoV, Cr12WMoNiB, etc.. The former is generally used for corrosion resistance and require a certain strength of the parts, such as turbine blades; the latter is mainly used as a hot steel, such as the main steam pipe of thermal power plants. The common feature of both is the high-temperature heating after air-cooling has a great tendency to harden, generally after tempering treatment to give full play to the performance characteristics of such steel. Although martensitic heat-resistant steel alone for a class, but can be found ordinary Cr13 martensitic stainless steel and hot strong martensitic stainless steel is also heat-resistant steel.

Martensitic stainless steel containing 13%-18% chromium, quenched and tempered state, used for turbine blades (lower carbon content), medical surgical tools, measuring tools, springs, etc. (higher carbon content); martensitic precipitation hardening stainless steel, chromium-nickel content than the former is high, by high temperature solution, quenching, and then in 400-500 ℃ aging treatment, in the martensitic matrix precipitation of a large number of matrix manipulation with the co-grid The second phase of the relationship, used in chemical pressure vessels, aircraft structures, etc. Martensitic heat-resistant steel containing chromium 7.5%-20.5%, containing 0.15%-0.85% carbon and a variety of alloying elements, tempered at 650-700 ℃, the formation of fine carbide dispersion in the matrix, mainly used for automotive and other engine valves, turbine blades, nozzles, bolts, etc. Maraging steel, containing higher nickel 18%-25%, molybdenum 5%, cobalt 8% and a small amount of titanium and aluminum, after solid solution air cooling and then aging treatment at 480 ℃.

Strengthened by the precipitation of intermetallic compounds in martensite, it is generally used for important structural parts in aviation, aerospace and marine technology, such as rocket engine cases, aircraft landing gear, important molds, etc. due to its high cost.

What are the pros and cons of stainless steel?

Stainless steel is a very strong and durable material that can be used for a wide variety of projects. It is easy to clean and maintain, which means your finished product will look great for years to come. Here are some of the pros and cons of stainless steel:
Stainless steel is rust free, stain free, and corrosion free, so it should last forever!
Stainless Steel is very easy to clean and maintain. You can just wipe it down with soap water then rinse it off. This makes Stainless Steel a good choice if you have pets or young children who might dirty other materials like wood or plastic. Stainless Steel can also be painted in any color you choose which makes it perfect for matching any decor style from modern sleek designs all the way back through history’s most popular styles like Victorian or contemporary design styles as well!
Stainless Steel has been around since 1820 when Sir Henry Bessemer invented this new form of metal; today there are over 1 million tons produced annually worldwide making up 75% all manufactured metals globally!  However because this material can still scratch easily in certain situations (e.g., touching another metal), you’ll probably want something else if that’s an issue: colored aluminum might work better depending on what type of project you’re doing (and whether or not they’ll be touching each other).  Also note that while there are many different grades available based on their composition – stainless steels are not all created equal either so remember to ask about these differences first before buying one made out specifically for what purpose!”)    }
stainless steel is rust free, stain free, and corrosion free.
Stainless steel is a metal alloy that’s resistant to rust and corrosion. It’s extremely strong, making it a suitable choice for outdoor projects like railings, gates, and fences. Stainless steel is also a good option if your project will get wet frequently (such as your deck railing).
Stainless steel comes in two basic types: austenitic and ferritic. Austenitic stainless steels are magnetic and have lower nickel content than ferritic varieties; they don’t corrode as easily as ferritic alloys do—but they’re much more expensive than their counterparts. Ferritic alloys are less expensive but can still be used effectively for many applications; however, these types of stainless steels tend to be more susceptible to corrosion from chloride exposure than other kinds of alloys.
stainless steel is very easy to clean and maintain.
Stainless steel is a very durable material that can be used for many household items. The material is easy to clean and maintain, making it extremely practical for use in kitchens, bathrooms, and other common areas of the house.
Stainless steel is also resistant to rust and corrosion. It can be cleaned with soap and water or disinfectant wipes or sprays without having to worry about it becoming damaged through overuse of harsh chemicals or improper cleaning techniques!
This means you don’t have to worry about maintaining your stainless steel products; they will last longer because they aren’t as susceptible as other materials would be under similar circumstances (especially when exposed regularly).
Stainless steel is affordable in most cases.
Stainless steel is an affordable option in most cases. The price of stainless steel varies depending on the type and grade of the steel, but it typically falls between $0.50 and $1 per pound. This is lower than the cost of copper (which can be as high as $2 per pound), but higher than aluminum ($0.10-$0.30 per pound). In general, however, stainless steel tends to be more expensive than other materials—such as aluminum or copper—when considering both initial costs and long-term maintenance costs over time.
In many cases you’re looking at a material that’s just under half the price of copper or aluminum, but with better corrosion resistance thanks to those chromium or nickel components we mentioned earlier!
You can buy stainless steel in a variety of colors and finishes and it can be custom made.
Stainless steel is a beautiful color and it can be made in almost any shape, which makes it the perfect option for custom designs.
Stainless steel is also available in many different finishes including brushed, polished, satin and hammered as well as other options. This means you can choose the look that will best suit your needs.
Stainless steel is highly durable, however it can still scratch.
Stainless steel is a durable material, but it can still be scratched. The best way to avoid this is to buy stainless steel with a protective coating or finish. If you’re not sure what type of protective coating you want, ask your local commercial kitchen equipment dealer for their recommendations.
You can also use stainless steel for many projects in your home and office, such as building shelves or tables and making chairs out of pipe fittings!
Stainless steel might be your best choice for a material in your next project
Stainless steel is durable, affordable and easy to clean. Many people choose stainless steel for their kitchen appliances because of its long-lasting quality. Stainless steel can also be found in bathroom fixtures, such as showerheads and faucets.
Stainless steel is easy to maintain because it requires minimal care: You just need to wipe the surface clean with soap and water or a special cleaning solution once in a while. You can also use conical brushes made specifically for cleaning sinks that have hard-to-reach spots (like behind the spout).
It’s also possible to customize your stainless steel product by picking out exactly which color finish you want—from bright silver alloys with mirror reflectivity all the way down through matte black finishes—or what kind of pattern you want on top (think brushed aluminum). This versatility makes it an attractive choice for many DIYers looking for something sleekly modern yet affordable enough not break their budget completely!
Stainless steel is one of the best materials for any project. It is durable, low maintenance and easy to clean. If you are looking for a material that will not rust, stain or corrode then stainless steel might be the answer for you!

What is the disadvantage of stainless steel?

Stainless steel contains nickel.

Nickel is a known carcinogen, and its inclusion in stainless steel cookware can cause skin irritation and respiratory problems. A study in 2008 revealed that nickel sulfate is released when cooking acidic foods with stainless steel pots and pans, which can lead to neurological problems. The U.S. Food and Drug Administration (FDA) notes that long-term exposure to nickel may cause cardiovascular problems as well.
Stainless steel is not as thermo-conductive as carbon steel.
This means that it’s slower at transferring heat from the pan to your food, which can make a difference in how quickly you’re able to bring something to a boil or even just browning meat. The same principle applies when using it for cooking: if you want your pan handle to be cool enough for safe handling after cooking with high heat, you may not want stainless steel because of its poorer conductivity.
Stainless steel is expensive.
Stainless steel is more expensive than carbon steel. The cost of stainless steel varies depending on the grade of stainless steel and the size of your order. In general, however, you should expect that it will be more expensive than carbon steel.
In addition to being higher in price, there are other disadvantages as well:
The disadvantages of stainless steel is that it contains Nickel and isn’t as thermo-conductive as carbon steel.
Stainless steel is not as thermally conductive as carbon steel. Stainless steel contains nickel, which is a heavy metal that can cause cancer, skin rashes, and allergic reactions in some people.

What is the advantage of stainless steel?

Stainless steel is a product of advanced metallurgy that is often used within the manufacturing industry. It is a versatile material and has many advantages over other metals. Let’s explore some of the benefits and uses of stainless steel!
Strength
Stainless steel is often used in a variety of applications, such as building and construction, medical equipment, aerospace, food processing and many other fields. It’s also a popular choice for cookware because it resists rusting and corrosion.
While stainless steel can be used as a structural material in building construction, it’s usually only used for small parts such as handrails or door frames. This is because stainless steel is much more expensive than other metals like aluminum or copper. In addition to being strong enough to be used in a variety of applications (see below), stainless steel resists corrosion from moisture better than most other alloys used by humans today
Oxidation and oxidation resistance
What is oxidation?
Oxidation is the process by which a substance loses electrons. Metals are naturally prone to oxidation, but stainless steel has a higher resistance than other metals and can be used in many environments where other metals would rust or corrode.
Cost
Stainless steel is more expensive than other metals. A stainless steel carafe can cost $30 while a copper version will cost $15. However, this doesn’t mean that all stainless steel objects are more expensive than other materials. For example, a quality chef’s knife made of high carbon steel will be more expensive than one made of stainless steel but not as good in quality or performance; it won’t hold an edge as well and will require frequent sharpening.
Conductivity
Stainless steel is a great conductor of both heat and electricity. That’s because stainless steel is a good conductor, which means it can easily pass on electrical charges. If you’re looking for something that conducts these two elements well, look no further than stainless steel!
Stainless steel is a durable, sturdy material that resists corrosion and rust.
Stainless steel is a strong, durable material that resists corrosion and rust. It can be used for many applications because it is resistant to wear and tear, heat and cold. For example, if you have a stainless steel sink in your kitchen then you won’t have to worry about using chemicals like bleach or ammonia on it because these chemicals will not damage the sink.
Stainless steel can also be used as a heat exchanger or as the outer layer of a refrigerator or freezer unit because they are resistant to extreme temperatures. This means that they will not rust when exposed to moisture at high temperatures.
The next time you need a strong, resilient material, consider stainless steel. It is affordable and versatile, making it useful for a wide variety of applications. We hope this guide has given you the information to determine if stainless steel is right for your needs!

Chemical Composition of Stainless Steel

Stainless steel is composed of various elements to enhance the corrosion resistance of the steel. The main alloying component in all stainless steel metals is chromium (minimum 10.5%).

The elemental chemical composition of stainless steel is mainly composed of iron (Fe) and chromium (Cr), and other alloying elements in the chemical composition include carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), nickel (Ni), molybdenum (Mo), titanium (Ti), nitrogen (N) and copper (Cu). Only when the Cr percentage composition reaches a certain value, this steel has corrosion resistance. Therefore, the chromium content of stainless steel metal is usually at least 10.5%.
The following table lists the chemical composition of stainless steel alloys, including austenitic SS 304, 304L 316, 316L, 321, 303, 302, 301, 904L, 201, etc., martensitic SS 440A, 440B, 440C, 420, etc., ferritic SS 430, duplex stainless steels 2205, 2507, 329, etc.
Note: UOS (unless otherwise specified)

Stainless Steel Chemical Composition Chart, Percentage (%)
Stainless Steel C, ≤ Mn, ≤ P, ≤ S, ≤ Si, ≤ Cr Ni Mo N, ≤ Other Elements, ≤, UOS
304 0.08 2.00 0.045 0.03 1.00 18.0-20.0 8.0-11.0
304L 0.03 2.00 0.045 0.03 1.00 18.0-20.0 8.0-12.0
316 0.08 2.00 0.045 0.030 1.00 16.0-18.0 10.0-14.0 2.00-3.00
316L 0.03 2.00 0.045 0.030 1.00 16.0-18.0 10.0-14.0 2.00-3.00
321 0.08 2.00 0.045 0.03 1.00 17.0-19.0 9.0-12.0 0.10 ≥ Ti 5×(C+N), ≤ 0.70
201 0.15 5.50-7.50 0.06 0.03 1.00 16.0-18.0 3.5-5.5 0.25
202 0.15 7.50-10.00 0.06 0.03 1.00 17.0-19.0 4.0-6.0 0.25
205 0.12-0.25 14.0-15.5 0.06 0.03 1.00 16.5-18.0 1.0-1.7 0.32-0.40
301 0.15 2.00 0.045 0.03 1.00 16.0-18.0 6.0-8.0 0.10
301L 0.03 2.00 0.045 0.03 1.00 16.0-18.0 6.0-8.0 0.20
301LN 0.03 2.00 0.045 0.03 1.00 16.0-18.0 6.0-8.0 0.07-0.20
302 0.15 2.00 0.045 0.03 0.75 17.0-19.0 8.0-10.0 0.10
302B 0.15 2.00 0.045 0.03 2.00-3.00 17.0-19.0 8.0-10.0 0.10
303 0.15 2.00 0.2 ≥0.15 1.00 17.0-19.0 8.0-10.0
303Se 0.15 2.00 0.2 0.06 1.00 17.0-19.0 8.0-10.0 Se 0.15
304H 0.04-0.10 2.00 0.045 0.03 0.75 18.0-20.0 8.0-10.5
304N 0.08 2.00 0.045 0.03 1.00 18.0-20.0 8.0-11.0 0.10-0.16
304LN 0.03 2.00 0.045 0.03 1.00 18.0-20.0 8.0-11.0 0.10-0.16
305 0.12 2.00 0.045 0.03 1.00 17.0-19.0 11.0-13.0
308 0.08 2.00 0.045 0.03 1.00 19.0-21.0 10.0-12.0
309 0.2 2.00 0.045 0.03 1.00 22.0-24.0 12.0-15.0
309S 0.08 2.00 0.045 0.03 1.00 22.0-24.0 12.0-15.0
309H 0.04-0.10 2.00 0.045 0.03 0.75 22.0-24.0 12.0-15.0
309Cb 0.08 2.00 0.045 0.03 1.00 22.0-24.0 12.0-16.0 ≥ Cb 10 x C, ≤1.10
309HCb 0.04-0.10 2.00 0.045 0.03 0.75 22.0-24.0 12.0-16.0 ≥ Cb 10 x C, ≤1.10
310 0.25 2.00 0.045 0.03 1.5 24.0-26.0 19.0-22.0
310S 0.08 2.00 0.045 0.03 1.5 24.0-26.0 19.0-22.0
310H 0.04-0.10 2.00 0.045 0.03 0.75 24.0-26.0 19.0-22.0
310Cb 0.08 2.00 0.045 0.03 1.5 24.0-26.0 19.0-22.0 ≥ Cb 10 x C, ≤ 1.10
310 MoLN 0.02 2.00 0.03 0.01 0.5 24.0-26.0 20.5-23.5 1.60-2.60 0.09-0.15
314 0.25 2.00 0.045 0.03 1.50-3.00 23.0-26.0 19.0-22.0
316H 0.04-0.10 2.00 0.045 0.03 0.75 16.0-18.0 10.0-14.0 2.00-3.00
316Ti 0.08 2.00 0.045 0.03 1.00 16.0-18.0 10.0-14.0 2.00-3.00 0.1 ≥ Ti 5 × (C + N), ≤0.70
316Cb 0.08 2.00 0.045 0.03 1.00 16.0-18.0 10.0-14.0 2.00-3.00 0.1 ≥ Cb 10 × C, ≤ 1.10
316N 0.08 2.00 0.045 0.03 1.00 16.0-18.0 10.0-14.0 2.00-3.00 0.10-0.16
316LN 0.03 2.00 0.045 0.03 1.00 16.0-18.0 10.0-13.0 2.00-3.00 0.10-0.16
317 0.08 2.00 0.045 0.03 1.00 18.0-20.0 11.0-15.0 3.0-4.0 0.1
317L 0.03 2.00 0.045 0.03 0.75 18.0-20.0 11.0-15.0 3.0-4.0 0.1
317LM 0.03 2.00 0.045 0.03 0.75 18.0-20.0 13.5-17.5 4.0-5.0 0.2
317LMN 0.03 2.00 0.045 0.03 0.75 17.0-20.0 13.5-17.5 4.0-5.0 0.10-0.20
317LN 0.03 2.00 0.045 0.03 0.75 18.0-20.0 11.0-15.0 3.0-4.0 0.10-0.22
321 0.08 2.00 0.045 0.03 1.00 17.0-19.0 9.0-12.0 0.1 ≥ Ti 5 × (C + N), ≤ 0.70
321H 0.04-0.10 2.00 0.045 0.03 0.75 17.0-19.0 9.0-12.0 ≥ Ti 4 × (C + N), ≤ 0.70
334 0.08 1.00 0.03 0.015 1.00 18.0-20.0 19.0-21.0 Al 0.15-0.60, Ti 0.15-0.60
347 0.08 2.00 0.045 0.03 1.00 17.0-19.0 9.0-12.0 ≥ Cb 10 × C, ≤ 1.00
347H 0.04-0.10 2.00 0.045 0.03 0.75 17.0-19.0 9.0-13.0 ≥ Cb 8 × C, ≤ 1.00
347LN 0.005-0.020 2.00 0.045 0.03 1.00 17.0-19.0 9.0-13.0 0.06-0.10 Cb 0.20-0.50, 15 × C ≥
348 0.08 2.00 0.045 0.03 1.00 17.0-19.0 9.0-12.0 Cb 10×C-1.10, Ta 0.10, Co 0.20
348H 0.04-0.10 2.00 0.045 0.03 0.75 17.0-19.0 9.0-13.0 (Cb + Ta) 8×C ≥ , 1.00 ≤, Ta 0.10, Co 0.20
2205 0.03 2.00 0.03 0.02 1.00 22.0-23.0 4.5-6.5 3.0-3.5 0.14-0.20
2304 0.03 2.5 0.04 0.03 1.00 21.5-24.5 3.0-5.5 0.05-0.60 0.05-0.60
255 0.04 1.5 0.04 0.03 1.00 24.0-27.0 4.5-6.5 2.9-3.9 0.10-0.25 Cu 1.50-2.50
2507 0.03 1.2 0.035 0.02 0.8 24.0-26.0 6.0-8.0 3.0-5.0 0.24-0.32 Cu ≤0.50
329 0.08 1.00 0.04 0.03 0.75 23.0-28.0 2.0-5.00 1.00-2.00
403 0.15 1.00 0.04 0.03 0.5 11.5-13.0
405 0.08 1.00 0.04 0.03 1.00 11.5-14.5 0.5 Al 0.10-0.30
410 0.08-0.15 1.00 0.04 0.03 1.00 11.5-13.5
410S 0.08 1.00 0.04 0.03 1.00 11.5-13.5 0.6
414 0.15 1.00 0.04 0.03 1.00 11.5-13.5 1.25-2.50
416 0.15 1.25 0.06 ≥0.15 1.00 12.0-14.0
416Se 0.15 1.25 0.06 ≥0.06 1.00 12.0-14.0 Se 0.15
420 0.15, ≥ 1.00 0.04 0.03 1.00 12.0-14.0
420F 0.30-0.40 1.25 0.06 ≥0.15 1.00 12.0-14.0 0.5 Cu 0.60
420FSe 0.20-0.40 1.25 0.06 0.15 1.00 12.0-14.0 0.5 Se 0.15; Cu 0.60
422 0.20-0.25 0.50-1.00 0.025 0.025 0.5 11.0-12.5 0.50-1.00 0.90-1.25 V (0.20-0.30), W (0.90-1.25)
429 0.12 1.00 0.04 0.03 1.00 14.0-16.0
430 0.12 1.00 0.04 0.03 1.00 16.0-18.0
430F 0.12 1.25 0.06 ≥0.15 1.00 16.0-18.0
430FSe 0.12 1.25 0.06 0.06 1.00 16.0-18.0 Se 0.15
439 0.03 1.00 0.04 0.03 1.00 17.0-19.0 0.5 0.03 ≥ Ti [0.20+4(C+N)], ≤ 1.10; Al 0.15
431 0.2 1.00 0.04 0.03 1.00 15.0-17.0 1.25-2.50
434 0.12 1.00 0.04 0.03 1.00 16.0-18.0 0.75-1.25
436 0.12 1.00 0.04 0.03 1.00 16.0-18.0 0.75-1.25 ≥ Cb 5×C, ≤ 0.80
440A 0.60-0.75 1.00 0.04 0.03 1.00 16.0-18.0 ≤0.75
440B 0.75-0.95 1.00 0.04 0.03 1.00 16.0-18.0 ≤0.75
440C 0.95-1.20 1.00 0.04 0.03 1.00 16.0-18.0 ≤0.75
440F 0.95-1.20 1.25 0.06 0.15 1.00 16.0-18.0 0.5 Cu ≤0.60
440FSe 0.95-1.20 1.25 0.06 0.06 1.00 16.0-18.0 0.5 Se ≤0.15; Cu ≤0.60
442 0.2 1.00 0.04 0.04 1.00 18.0-23.0 0.6
444 0.025 1.00 0.04 0.03 1.00 17.5-19.5 1.00 1.75-2.50 0.035 Ti+Cb 0.20+4 × (C+N)-0.80
446 0.2 1.5 0.04 0.03 1.00 23.0-27.0 0.75 0.25
800 0.1 1.5 0.045 0.015 1.00 19.0-23.0 30.0-35.0 Cu 0.75; ≥ FeH 39.5; Al 0.15-0.60
800H 0.05-0.10 1.5 0.045 0.015 1.00 19.0-23.0 30.0-35.0 Cu 0.75; ≥ FeH 39.5; Al 0.15-0.60
904L 0.02 2.00 0.045 0.035 1.00 19.0-23.0 23.0-28.0 4.00-5.00 0.1 Cu 1.00-2.00
Alloy 20 0.07 2.00 0.045 0.035 1.00 19.0-21.0 32.0-38.0 2.00-3.00 Cu 3.0-4.0; ≥ Nb 8 × C; ≤1.00
XM-1 0.08 5.0-6.5 0.04 0.18-0.35 1.00 16.00-18.0 5.0-6.5 Cu 1.75-2.25
XM-2 0.15 2.00 0.05 0.11-0.16 1.00 17.0-19.0 8.0-10.0 0.40-0.60 Al 0.60-1.00
XM-5 0.15 2.5-4.5 0.2 ≥0.25 1.00 17.0-19.0 7.0-10.0
XM-6 0.15 1.50-2.50 0.06 ≥0.15 1.00 12.0-14.0
XM-10 0.08 8.0-10.0 0.045 0.03 1.00 19.0-21.5 5.5-7.5 0.15-0.40
XM-11 0.04 8.0-10.0 0.045 0.03 1.00 19.0-21.5 5.5-7.5 0.15-0.40
XM-15 0.08 2.00 0.03 0.03 1.50-2.50 17.0-19.0 17.5-18.5
XM-17 0.08 7.50-9.00 0.045 0.03 0.75 17.5-22.0 5.0-7.0 2.00-3.00 0.25-0.50
XM-18 0.03 7.50-9.00 0.045 0.03 0.75 17.5-22.0 5.0-7.0 2.00-3.00 0.25-0.50
XM-19 0.06 4.0-6.0 0.045 0.03 1.00 20.5-23.5 11.5-13.5 1.50-3.00 0.20-0.40 Cb 0.10-0.30, V 0.10-0.30
XM-21 0.08 2.00 0.045 0.03 0.75 18.0-20.0 8.0-10.5 0.16-0.30
XM-27 0.01 0.4 0.02 0.02 0.4 25.0-27.5 0.5 0.75-1.50 0.015 Cu 0.20; Cb 0.05-0.20; (Ni + Cu) 0.50
XM-33 0.06 0.75 0.04 0.02 0.75 25.0-27.0 0.5 0.75-1.50 0.04 Cu 0.20; Ti 0.20-1.00; ≥ Ti 7(C+N)
XM-34 0.08 2.5 0.04 ≥0.15 1.00 17.5-19.5 1.50-2.50
PH 13-8Mo 0.05 0.2 0.01 0.008 0.1 12.25-13.25 7.5-8.5
15-5 PH 0.07 1 0.04 0.03 1 14.0-15.5 3.5-5.5 2.5-4.5 Cu; 0.15-0.45 Nb
17-4 PH 0.07 1 0.04 0.03 1 15.5-17.5 3.0-5.0 3.0-5.0 Cu; 0.15-0.45 Nb
17-7 PH 0.09 1 0.04 0.04 1 16.0-18.0 6.5-7.75 0.75-1.5 Al
Stainless Steel C, ≤ Mn, ≤ P, ≤ S, ≤ Si, ≤ Cr Ni Mo N, ≤ Other Elements, ≤, UOS

Comparison Conversion of Stainless Steel

U.S.A. Germany German France Japan Italy U.E. Spain Russia
AISI DIN17006 W.N. 17007 AFNOR JIS UNI EURONORM UNE GOST
201 SUS 201
301 X 12 CrNi 17 7 1.431 Z 12 CN 17-07 SUS 301 X 12 CrNi 1707 X 12 CrNi 17 7 X 12 CrNi 17-07
302 X 5 CrNi 18 7 1.4319 Z 10 CN 18-09 SUS 302 X 10 CrNi 1809 X 10 CrNi 18 9 X 10 CrNi 18-09 12KH18N9
303 X 10 CrNiS 18 9 1.4305 Z 10 CNF 18-09 SUS 303 X 10 CrNiS 1809 X 10 CrNiS 18 9 X 10 CrNiS 18-09
303 Z 10 CNF 18-09 SUS 303 Se X 10 CrNiS 1809 X 10 CrNiS 18-09 12KH18N10E
Se
304 X 5 CrNi 18 10 X 5 CrNi 18 12 1.4301 1.4303 Z 6 CN 18-09 SUS 304 X 5 CrNi 1810 X 6 CrNi 18 10 X 6 CrNi 19-10 08KH18N10 06KH18N11
304 N SUS 304N1 X 5 CrNiN 1810
304H SUS F 304H X 8 CrNi 1910 X 6 CrNi 19-10
304L X 2 CrNi 18 11 1.4306 Z 2 CN 18-10 SUS 304L X 2 CrNi 1911 X 3 CrNi 18 10 X 2 CrNi 19-10 03KH18N11
X 2 CrNiN 18 10 1.4311 Z 2 CN 18-10-Az SUS 304LN X 2 CrNiN 1811
305 Z 8 CN 18-12 SUS 305 X 8 CrNi 1812 X 8 CrNi 18 12 X 8 CrNi 18-12
Z 6 CNU 18-10 SUS XM7 X 6 CrNiCu 18 10 4 Kd
309 X 15 CrNiSi 20 12 1.4828 Z 15 CN 24-13 SUH 309 X 16 CrNi 2314 X 15 CrNi 23 13
309S SUS 309S X 6 CrNi 2314 X 6 CrNi 22 13
310 X 12 CrNi 25 21 1.4845 SUH 310 X 22 CrNi 2520 20KH23N18
310S X 12 CrNi 25 20 1.4842 Z 12 CN 25-20 SUS 310S X 5 CrNi 2520 X 6 CrNi 25 20 10KH23N18
314 X 15 CrNiSi 25 20 1.4841 Z 12 CNS 25-20 X 16 CrNiSi 2520 X 15 CrNiSi 25 20 20KH25N20S2
316 X 5 CrNiMo 17 12 2 1.4401 Z 6 CND 17-11 SUS 316 X 5 CrNiMo 1712 X 6 CrNiMo 17 12 2 X 6 CrNiMo 17-12-03
316 X 5 CrNiMo 17 13 3 1.4436 Z 6 CND 17-12 SUS 316 X 5 CrNiMo 1713 X 6 CrNiMo 17 13 3 X 6 CrNiMo 17-12-03
316 F X 12 CrNiMoS 18 11 1.4427
316 N SUS 316N
316 H SUS F 316H X 8 CrNiMo 1712 X 5 CrNiMo 17-12
316 H X 8 CrNiMo 1713 X 6 CrNiMo 17-12-03
316 L X 2 CrNiMo 17 13 2 1.4404 Z 2 CND 17-12 SUS 316L X 2 CrNiMo 1712 X 3 CrNiMo 17 12 2 X 2 CrNiMo 17-12-03 03KH17N14M2
X 2 CrNiMoN 17 12 2 1.4406 Z 2 CND 17-12-Az SUS 316LN X 2 CrNiMoN 1712
316 L X 2 CrNiMo 18 14 3 1.4435 Z 2 CND 17-13 X 2 CrNiMo 1713 X 3 CrNiMo 17 13 3 X 2 CrNiMo 17-12-03 03KH16N15M3
X 2 CrNiMoN 17 13 3 1.4429 Z 2 CND 17-13-Az X 2 CrNiMoN 1713
X 6 CrNiMoTi 17 12 2 1.4571 Z6 CNDT 17-12 X 6 CrNiMoTi 1712 X 6 CrNiMoTi 17 12 2 X 6 CrNiMoTi 17-12-03 08KH17N13M2T 10KH17N13M2T
X 10 CrNiMoTi 18 12 1.4573 X 6 CrNiMoTi 1713 X 6 CrNiMoTI 17 13 3 X 6 CrNiMoTi 17-12-03 08KH17N13M2T 10KH17N13M2T
X 6 CrNiMoNb 17 12 2 1.458 Z 6 CNDNb 17-12 X 6 CrNiMoNb 1712 X 6 CrNiMoNb 17 12 2 08KH16N13M2B
X 10 CrNiMoNb 18 12 1.4583 X 6 CrNiMoNb 1713 X 6 CrNiMoNb 17 13 3 09KH16N15M3B
317 SUS 317 X 5 CrNiMo 1815
317L X 2 CrNiMo 18 16 4 1.4438 Z 2 CND 19-15 SUS 317L X 2 CrNiMo 1815 X 3 CrNiMo 18 16 4
317 L X 2 CrNiMo 18 16 4 1.4438 Z 2 CND 19-15 SUS 317L X 2 CrNiMo 1816 X 3 CrNiMo 18 16 4
330 X 12 NiCrSi 36 16 1.4864 Z 12NCS 35-16 SUH 330
321 X 6 CrNiTi 18 10 X 12 CrNiTi 18 9 1.4541 1.4878 Z 6 CNT 18-10 SUS 321 X 6 CrNiTi 1811 X 6 CrNiTi 18 10 X 6 CrNiTi 18-11 08KH18N10T
321H SUS 321H X 8 CrNiTi 1811 X 7 CrNiTi 18-11 12KH18N10T
329 X 8 CrNiMo 27 5 1.446 SUS 329J1
347 X 6 CrNiNb 18 10 1.455 Z 6 CNNb 18-10 SUS 347 X 6 CrNiNb 1811 X 6 CrNiNb 18 10 X 6 CrNiNb 18-11 08KH18N12B
347H SUS F 347H X 8 CrNiNb 1811 X 7 CrNiNb 18-11
904L 1.4539 Z 12 CNDV 12-02
X 20 CrNiSi 25 4 1.4821
S31803 X 2 CrNiMoN 22 5 1.4462
S32760 X 3 CrNiMoN 25 7 1.4501 Z 3 CND 25-06Az
403 X 6 Cr 13 X 10 Cr 13 X 15 Cr 13 1.4000 1.4006 1.4024 Z 12 C 13 SUS 403 X 12 Cr 13 X 10 Cr 13 X 12 Cr 13 X 6 Cr 13 12Kh13
405 X 6 CrAl 13 1.4002 Z 6 CA 13 SUS 405 X 6 CrAl 13 X 6 CrAl 13 X 6 CrAl 13
X 10 CrAl 7 1.4713 Z 8 CA 7 X 10 CrAl 7
X 10 CrAl 13 1.4724 X 10 CrAl 12 10Kh13SYu
X 10 CrAl 18 1.4742 X 10 CrSiAl 18 15Kh18SYu
409 X 6 CrTi 12 1.4512 Z 6 CT 12 SUH 409 X 6 CrTi 12 X 5 CrTi 12
X 2 CrTi 12
410 X 6 Cr 13 X 10 Cr 13 X 15 Cr 13 1.4000 1.4006 1.4024 Z 10 C 13 Z 12 C 13 SUS 410 X 12 Cr 13 X 12 Cr 13 X 12 Cr 13 12Kh13
410S X 6 Cr 13 1.4 Z 6 C 13 SUS 410S X 6 Cr 13 X 6 Cr 13 08Kh13

Density of Stainless Steel

The following table lists the density of stainless steel 304, 316, 303, 304L, 316L and other AISI type stainless.

Note:

  • 1 g/cm3 = 1 kg/dm3
  • The specific weight value in the following table is equal to the density value (g/cm3, metric).
Density of Stainless Steel
Stainless Steel Density (g/cm3), or specific weight Density (kg/m3) Density (lb/in3) Density (lb/ft3)
304304L, 304N 7.93 7930 0.286 495
316316L, 316N 8.0 8000 0.29 499
201 7.8 7800 0.28 487
202 7.8 7800 0.28 487
205 7.8 7800 0.28 487
301 7.93 7930 0.286 495
302, 302B, 302Cu 7.93 7930 0.286 495
303 7.93 7930 0.286 495
305 8.0 8000 0.29 499
308 8.0 8000 0.29 499
309 7.93 7930 0.286 495
310 7.93 7930 0.286 495
314 7.72 7720 0.279 482
317, 317L 8.0 8000 0.29 499
321 7.93 7930 0.286 495
329 7.8 7800 0.28 487
330 8.0 8000 0.29 499
347 8.0 8000 0.29 499
384 8.0 8000 0.29 499
403 7.7 7700 0.28 481
405 7.7 7700 0.28 481
409 7.8 7800 0.28 487
410 7.7 7700 0.28 481
414 7.8 7800 0.28 487
416 7.7 7700 0.28 481
420 7.7 7700 0.28 481
422 7.8 7800 0.28 487
429 7.8 7800 0.28 487
430, 430F 7.7 7700 0.28 481
431 7.7 7700 0.28 481
434 7.8 7800 0.28 487
436 7.8 7800 0.28 487
439 7.7 7700 0.28 481
440 (440A, 440B, 440C) 7.7 7700 0.28 481
444 7.8 7800 0.28 487
446 7.6 7600 0.27 474
501 7.7 7700 0.28 481
502 7.8 7800 0.28 487
904L 7.9 7900 0.285 493
2205 7.83 7830 0.283 489

Mechanical Properties of Stainless Steel

Required mechanical properties are normally given in purchase specifications for stainless steel. Minimum mechanical properties are also given by the various standards relevant to the material and product form. Meeting these standard mechanical properties indicates that the material has been properly manufactured to an appropriate quality system. Engineers can then confidently utilise the material in structures that meet safe working loads and pressures.

Mechanical properties specified for flat rolled products are normally tensile strength, yield stress (or proof stress), elongation and Brinell or Rockwell hardness. Property requirements for bar, tube, pipe and fittings typically state tensile strength and yield stress.

Yield Strength of Stainless Steel

Unlike mild steels, the yield strength of annealed austenitic stainless steel is a very low proportion of the tensile strength. Mild steel yield strength is typically 65-70% of the tensile strength. This figure tends to only be 40-45% in the austenitic stainless family.

Cold working rapidly and greatly increases the yield strength. Some forms of stainless steel, like spring tempered wire, can be cold worked to lift the yield strength to 80-95% of the tensile strength.

Hardness of Stainless Steel

Hardness is the resistance to penetration of the material surface. Hardness testers measure the depth that a very hard indenter can be pushed into the surface of a material. Brinell, Rockwell and Vickers machines are used. Each of these has a different shaped indenter and method of applying the known force. Conversions between the different scales are therefore only approximate.

Martensitic and precipitation hardening grades can be hardened by heat treatment. Other grades can be hardened through cold working.

Tensile Strength of Stainless Steel

Tensile strength is generally the only mechanical property required to define bar and wire products. Identical material grades may be used at various tensile strengths for completely different applications. The supplied tensile strength of bar and wire products directly relates to the final use after fabrication.

Spring wire tends to have the highest tensile strength after fabrication. The high strength is imparted by cold working into coiled springs. Without this high strength the wire would not function properly as a spring.

Such high tensile strengths are not required for wire to be used in forming or weaving processes. Wire or bar used as raw material for fasteners, like bolts and screws, needs to be soft enough for a head and thread to be formed but still strong enough to perform adequately in service.

Grade
Tensile Strength
min.
ksi [MPa]
Yield Strength
min.
ksi [MPa]
Elongation
in 2in or 50mm length %
(min)
Hardness (Max) ASTM E18
Brinell
Hardness (Max) ASTM E18
Rockwell
201 95 [655] 38 [260] 35 219 HBW 95 HRB
304 75 [515] 30 [205] 35 192 HBW 90 HRB
304L 70 [485] 25 [170] 35 192 HBW 90 HRB
304H 75 [515] 30 [205] 35 192 HBW 90 HRB
304N 80 [550] 35 [240] 35 192 HBW 90 HRB
309S 75 [515] 30 [205] 35 192 HBW 90 HRB
309H 75 [515] 30 [205] 35 192 HBW 90 HRB
310S 75 [515] 30 [205] 35 192 HBW 90 HRB
310H 75 [515] 30 [205] 35 192 HBW 90 HRB
316 75 [515] 30 [205] 35 192 HBW 90 HRB
316L 70 [485] 25 [170] 35 192 HBW 90 HRB
316H 75 [515] 30 [205] 35 192 HBW 90 HRB
316Ti 75 [515] 30 [205] 35 192 HBW 90 HRB
317 75 [515] 30 [205] 34 192 HBW 90 HRB
317L 75 [515] 30 [205] 35 192 HBW 90 HRB
321 75 [515] 30 [205] 35 192 HBW 90 HRB
321H 75 [515] 30 [205] 35 192 HBW 90 HRB
347 75 [515] 30 [205] 35 192 HBW 90 HRB
TP347H 75 [515] 30 [205] 35 192 HBW 90 HRB
N08904 71 [490] 31 [215] 35 192 HBW 90 HRB
N08020 80 [550] 35 [240] 30 217 HBW 95 HRB
800
N08800
Cold Work
75 [515] 30 [205] 30 192 HBW 90 HRB
800H
N08810
65 [450] 25 [170] 30 192 HBW 90 HRB
800HT
N08811
65 [450] 25 [170] 30 192 HBW 90 HRB
N10276 100 [690] 41 [283] 40    
N06022 100 [690] 45 [310] 45    
S31803 90 [620] 65 [450] 25 290 HBW 30 HRC
S31803 90 [620] 65 [450] 25 290 HBW 30 HRC
S32101
101 [700]
Wall≤0.187 in. [5.00 mm]
77 [530]
Wall≤0.187 in. [5.00 mm]
30 290 HBW 30 HRC
S32205 95 [655] 70 [485] 25 290 HBW 30 HRC
S32550 110 [760] 80 [550] 15 297 HBW 31 HRC
S32304
100 [690]
OD 1 in. [25 mm] and Under
87 [600]
OD over 1 in. [25 mm]
65 [450]
OD 1 in. [25 mm] and Under
58 [400]
OD over 1 in. [25 mm]
25
25
290 HBW
30 HRC
S32750 116 [800] 80 [550] 15 300 HBW 32 HRC
S32760 109 [750] 80 [550] 25 300 HBW

Physical Properties of Stainless Steel

The reason for choosing stainless steel is normally due to advantages given by physical properties such as corrosion resistance.

In addition to corrosion resistance, the advantageous physical properties of stainless steel include:

  • High and low temperature resistance
  • Ease of fabrication
  • High Strength
  • Aesthetic appeal
  • Hygiene and ease of cleaning
  • Long life cycle
  • Recyclable
  • Low magnetic permeability

Corrosion Resistance of Stainless Steel

Corrosion is the gradual degradation of a metal through a chemical reaction (usually electrochemical) with its surroundings. It affects material properties such as mechanical strength, appearance, and resistance to liquids and gases.
Although stainless steels are often chosen for their corrosion resistance, they are not immune to corrosion. The resistance of stainless steel to corrosion in a given environment depends on the combination of its chemical composition and environmental aggressiveness.

How Corrosion Occurs

If the minimum chromium content of stainless steel is approximately 10.5%, the corrosion resistance of stainless steel is attributed to the thin passivation film that forms spontaneously on its surface in an oxidizing environment.
The electrochemical reaction leading to corrosion is effectively stopped as the film adheres firmly to the metal substrate and protects it from contact with the surrounding environment. If localized damage, such as a scratch, the film can be “healed” by spontaneous repassivation in an oxidizing environment.
All types of corrosion affecting stainless steel are associated with permanent damage to the passivation film, through complete or partial breakdown. Factors such as chemical environment, pH, temperature, surface finish, product design, manufacturing methods, contamination and maintenance procedures all affect the corrosion behavior of steel and the type of corrosion that can occur.
Corrosion can be divided into two categories: wet corrosion and high temperature corrosion.

The assessment of corrosion resistance in any particular environment, therefore, usually involves a consideration of specific corrosion mechanisms.

These mechanisms are principally:

  • Crevice corrosion
  • Pitting corrosion
  • Intergranular corrosion (or intercrystalline)(IC)
  • Stress corrosion cracking (SCC)
  • Bimetallic (galvanic) corrosion

Stainless steel tube are generally very corrosion resistant and will perform satisfactorily in most environments. The limit of corrosion resistance of a given stainless steel depends on its constituent elements which means that each grade has a slightly different response when exposed to a corrosive environment. Care is therefore needed to select the most appropriate grade of stainless steel for a given application. As well as careful material grade selection, good detailing and workmanship can significantly reduce the likelihood of staining and corrosion.

Pitting corrosion: Pitting is a localised form of corrosion which can occur as a result of exposure to specific environments, most notably those containing chlorides. In most structural applications, the extent of pitting is likely to be superficial and the reduction in section of a component is negligible. However, corrosion products can stain architectural features. A less tolerant view of pitting should be adopted for services such as ducts, Stainless Steel and containment structures. If there is a known pitting hazard, then a molybdenum bearing stainless steel will be required.

Crevice corrosion: Crevice corrosion is a localised form of attack which is initiated by the extremely low availability of oxygen in a crevice. It is only likely to be a problem in stagnant solutions where a build-up of chlorides can occur. The severity of crevice corrosion is very dependent on the geometry of the crevice; the narrower (around 25 micro-metres) and deeper the crevice, the more severe the corrosion. Crevices typically occur between nuts and washers or around the thread of a screw or the shank of a bolt. Crevices can also occur in welds which fail to penetrate and under deposits on the steel surface.

Bimetallic galvanic corrosion: Bimetallic (galvanic) corrosion may occur when dissimilar metals are in contact in a common electrolyte (e.g. rain, condensation etc.). If current flows between the two, the less noble metal (the anode) corrodes at a faster rate than would have occurred if the metals were not in contact.

The rate of corrosion also depends on the relative areas of the metals in contact, the temperature and the composition of the electrolyte. In particular, the larger the area of the cathode in relation to that of the anode, the greater the rate of attack. Adverse area ratios are likely to occur with fasteners and at joints. Carbon steel bolts in stainless steel members should be avoided because the ratio of the area of the stainless steel to the carbon steel is large and the bolts will be subject to aggressive attack. Conversely, the rate of attack of a carbon steel member by a stainless steel bolt is much slower. It is usually helpful to draw on previous experience in similar sites because dissimilar metals can often be safely coupled under conditions of occasional condensation or dampness with no adverse effects, especially when the conductivity of the electrolyte is low.

The prediction of these effects is difficult because the corrosion rate is determined by a number of complex issues. The use of potential tables ignores the presence of surface oxide films and the effects of area ratios and different solution (electrolyte) chemistry. Therefore, uninformed use of these tables may produce erroneous results. They should be used with care and only for initial assessment.

Austenitic stainless steels usually form the cathode in a bimetallic couple and therefore do not suffer corrosion.  Contact between austenitic stainless steels and zinc or aluminium may result in some additional corrosion of the latter two metals. This is unlikely to be significant structurally, but the resulting white/grey powder may be deemed unsightly. Bimetallic corrosion may be prevented by excluding water from the detail (e.g. by painting or taping over the assembled joint) or isolating the metals from each other (e.g. by painting the contact surfaces of the dissimilar metals). Isolation around bolted connections can be achieved by non-conductive plastic or rubber gaskets and nylon or teflon washers and bushes. This system is a time consuming detail to make on site and it is not possible to provide the necessary level of site inspection to check that all the washers and sleeves have been installed properly.

The general behaviour of metals in bimetallic contact in rural, urban, industrial and coastal environments is fully documented in PD 6484 ‘Commentary on corrosion at bimetallic contacts and its alleviation’.

Stress corrosion cracking (SCC)

The development of stress corrosion cracking (SCC) requires the simultaneous presence of tensile stresses and specific environmental factors. It is uncommon in normal building atmospheres. The stresses do not need to be very high in relation to the proof stress of the material and may be due to loading and/or residual effects from manufacturing processes such as welding or bending. Caution should be exercised when stainless steel members containing high residual stresses (e.g. due to cold working) are used in chloride rich environments (e.sg. swimming pools enclosures, marine, offshore).

General (uniform) corrosion

General corrosion is much less severe in stainless steel than in other steels. It only occurs when the stainless steel tubing is at a pH value < 1.0. Reference should be made to tables in manufacturers’ literature, or the advice of a corrosion engineer should be sought, if the stainless steel is to come into contact with chemicals.

Intergranular attack and weld decay

When austenitic stainless steel are subject to prolonged heating between 450-8500 C, the carbon in the steel diffuses to the grain boundaries and precipitates chromium carbide. This removes chromium from the solid solution and leaves a lower chromium content adjacent to the grain boundaries. Steels in this condition are termed ‘sensitised’. The grain boundaries become prone to preferential attack on subsequent exposure to a corrosive environment. This phenomenon is known as weld decay when it occurs in the heat affected zone of a weldment.

Grades of stainless steel which have a low carbon content (-0.03%) will not become sensitised, even for plate thicknesses up to 20 mm when welded by arc processes (giving rapid heating and cooling). Furthermore, modern steelmaking processes mean that a carbon content of 0.05% or less is generally achieved in the standard carbon grades 304 and 316, so these grades will not be prone to weld decay when welded by arc processes.

Other related mechanism can also occur, which include:

  • Erosion – corrosion
  • Corrosion fatigue

Localised corrosion is often associated with chloride ions in aqueous environments. Acidic conditions (low PH) and increases in temperature all contribute to localised mechanisms of crevice corrosion and pitting corrosion. The addition of tensile strength, whether applied by loading or from residual stress, provides the conditions for stress corrosion cracking (SCC). These mechanisms are all associated with a localised breakdown of the passive layer. A good supply of oxygen to all surface of the steel is essential to maintaining the passive layer but higher levels of chromium, nickel, molybdenum & nitrogen all help in their individual ways to prevent these forms of attack.Resistance to localised forms of corrosion

As a general rule increased corrosion resistance can be expected by moving through the grades:

1.4512 to 1.4016 409 to 430 increasing chromium from 11 to 17%
1.4301 304 adding nickel which aids the reformation of the passive layer if it is disturbed
1.4401 316 adding molybdenum reduces the effectiveness of chloride ions in locally breaking down the passive layer
1.4539 and 1.4547 904L and 6% molybdenum grades further increases in chromium, nickel and molybdenum result in overall improved localised corrosion resistance

Duplex grades such as S32205 (1.4462/S31803) are specifically designed to combat SCC by ‘balancing’ the structure to increase its strength, but additionally molybdenum and nitrogen enhance the pitting resistance, which in turn has the additional benefit in improving their SCC resistance.

Stainless steels are generally considered to be resistant to uniform corrosion in a given environment if the corrosion rate does not exceed 0.1 mm/year. Resistance to uniform corrosion usually increases with increasing chromium, nickel and molybdenum content.
All stainless steels have good corrosion resistance. Low alloy grades resist corrosion under normal conditions. Higher alloys resist corrosion in most acidic and alkaline solutions and chloride environments.

The corrosion resistance of stainless steel depends on its chromium content. Typically, the chromium content of stainless steel is at least about 10.5%. The chromium in the alloy forms a self-healing protective transparent oxide layer that forms spontaneously in air. The self-healing nature of the oxide layer means that its corrosion resistance remains unchanged, regardless of the manufacturing method used. Even if the material surface is cut or damaged, it will heal itself and remain corrosion resistant.

Heat Treating of Stainless Steel

Forged stainless steels are solution annealed after machining and hot working to dissolve carbides and sigma. carbides may form during heating in the 425 to 900°C (800 to 1650°F) range or during slow cooling in this range. Sigma tends to form at temperatures below 925°C (1700°F). Specifications typically call for solution annealing at 1035C (1900°F) with rapid quenching. Grades containing molybdenum are typically solution annealed at higher temperatures of 1095 to 1120°C (2000 to 2050°F) to better homogenize the molybdenum.
Stainless steel can be stress relieved. Several stress relieving treatments are available. Follow the guidelines.
Stress redistribution at 290 to 425°C (550 to 800°F), below the sensitization range.
When stainless steel sheet and bar are cold deformed greater than 30% and subsequently heated to 290-425°C (550-800°F), peak stresses are significantly redistributed and both tensile and yield strengths increase. stress redistribution heat treatment at 290-425°C (550-800°F) will reduce movement in later machining operations and is occasionally used to increase strength. Since stress redistribution treatments are performed at temperatures below 425°C (800°F), carbide precipitation and intergranular corrosion sensitization (IGA) are not a problem for higher carbon grades.
Stress relief at 425 to 595°C (800 to 1100°F) is usually sufficient to minimize distortion that would otherwise exceed dimensional tolerances after machining. Only low carbon “L” grades or stable 321 and 347 grades should be used in weldments stress relieved above 425°C (800°F) because the higher carbon grades are sensitive to IGA when heated above 425°C (800°F).
Stress relief at 815 to 870°C (1500 to 1600°F) is occasionally required when fully stress relieved components are required. Only low carbon “L” grades 321 and 347 should be used in assemblies that are heat treated in this range. Even when using low carbon and stable grades, it is best to test for IGA sensitivity according to ASTM A262 to ensure that there is no sensitization during the stress relief treatment in this temperature range.
For assemblies that will be used in the temperature range of 400 to 900°C (750 to 1650°F), heat stabilization is occasionally performed at 900°C (1650°F) for a minimum of 1 to 10 hours. Heat stabilization is designed to agglomerate carbides, thereby preventing further precipitation and intergranular corrosion (IGA). For stress relief at 815 to 870°C (1500 to 1600°F), it is best to test for IGA sensitivity in accordance with ASTM A262.

Electrolytic polishing of stainless steel

Most stainless steels can be successfully electropolished. However, electrolytic polishing of sulfide free processing grades does not provide a high standard of surface finish. The anodic dissolution of thin surface layers is in principle similar to electrolytic polishing that can be performed on other metals. The removal of approximately 20 to 40 microns leaves a smooth surface that optimizes the corrosion resistance of the steel in any given environment.
Stainless steel electrolytic polishing process
This process uses a relatively low voltage between 12 and 18 volts, but a high current between 750 and 3000 amps. This results in an anode current density of approximately 20 to 40 amps/m2. The stainless steel part being electrolytically polished is the anode in this DC electrolyzer. The electrolyte used is usually a mixture of phosphoric acid and sulfuric acid.
The process takes about 10-20 minutes.
The process results in a “peak” or high point of preferential dissolution on the surface of the part. This results in a net smoothing of the surface, which also facilitates the removal of surface stresses left by the mechanical polishing pretreatment. Contaminants and debris left behind by mechanical surface preparation can also be removed by electrolytic polishing. However, scratches and visible surface irregularities are less likely to be removed by electrolytic polishing. Non-metallic inclusions on the steel surface may be more visible after electropolishing than after mechanical polishing methods. Electrolytic polishing can be used to check the integrity of the casting surface.
The design of the clamping fixture is critical, especially on complex shapes, as it affects the consistency of the polished surface and reduces the risk of gas streaking. Both hydrogen and oxygen are dual products of the process, with the oxygen coming from the stainless steel “anode”. This means that there is no risk of hydrogen embrittlement in stainless steel during the electrolytic polishing process.
Advantages of electropolishing stainless steel surfaces
Optimizes the corrosion resistance of finished stainless steel parts. Eliminates micro cracks on the surface. The electropolished surface should be completely passivated, eliminating the need for further passivation treatments.
Can be used for complex shapes such as wire radiator grilles where mechanical polishing is difficult or impossible.
Improve surface reflectivity.
Removes machined burrs from small parts, thereby reducing the risk of surface contamination from previous mechanical polishing. This provides the added benefit of easier and more efficient cleaning in the use of electropolished items.
In paper and textile processing applications, there is less tendency for contact material to adhere (filter cake) to the component surface and for fibers to “snag”.
Improved surface cleanliness compared to machined surfaces.
Lower bacterial growth rates in food industry applications.
Reduced surface stress on machined components. Improved fatigue life of electropolished stainless steel springs, especially when compared to normal shot peening.
Elimination of clogging surface gases in items operating under high vacuum conditions.

Surface Roughness of Stainless Steel

The roughness average for different manufacturing processes in micrometers and microinches. The values are shown with a typical range and a less frequent range for each manufacturing process.

  Average Range
  Less Frequent Range

Manufacturing
Process
Roughness Average
Top Number – Micrometers
Bottom Number – (Microinches)
  50 (2000) 25 (1000) 12.5 (500) 6.3 (250) 3.2 (125) 1.6 (63) 0.80 (32) 0.40 (16) 0.20 (8) 0.10 (4) 0.05 (2) 0.025 (1) 0.012 (.5)
Flame Cutting                                                    
Snagging                                                    
Sawing                                                    
Planing, Shaping                                                    
Drilling                                                    
Chemical Milling                                                    
EDM Elect Discharge Machining                                                    
Milling                                                    
Broaching                                                    
Reaming                                                    
Electron Beam                                                    
Laser                                                    
Electro-Chemical                                                    
Boring, Turning                                                    
Barrel Finishing                                                    
50 (2000) 25 (1000) 12.5 (500) 6.3 (250) 3.2 (125) 1.6 (63) 0.80 (32) 0.40 (16) 0.20 (8) 0.10 (4) 0.05 (2) 0.025 (1) 0.012 (.5)
Electrolytic Grinding                                                    
Roller Burnishing                                                    
Grinding                                                    
Honing                                                    
Electro-Polish                                                    
Polishing                                                    
Lapping                                                    
Super Finishing                                                    
Sand Casting                                                    
Hot Rolling                                                    
Forging                                                    
Permanent Mold Casting                                                    
Investment Casting                                                    
Extruding                                                    
Cold Rolling, Drawing                                                    
Die Casting                                                    
50 (2000) 25 (1000) 12.5 (500) 6.3 (250) 3.2 (125) 1.6 (63) 0.80 (32) 0.40 (16) 0.20 (8) 0.10 (4) 0.05 (2) 0.025 (1) 0.012 (.5)

Ra = Roughness, average in micro-meters & micro-inches

China’s old standard (finish) China New standard (roughness) Ra American Standard(microns), Ra American Standard (Micro-inch), Ra
▽ 4 6.3 8.00 320
6.30 250
▽ 5 3.2 5.00 200
4.00 160
3.20 125
▽ 6 1.6 2.50 100
2.00 80
1.60 63
▽ 7 0.8 1.25 50
1.00 40
0.80 32
▽ 8 0.4 0.63 25
0.50 20
0.40 16
China Old Grade China New
Ra
China New
Rz
USA micron
Ra
USA microinch
Ra
▽ 1 50 200    
▽ 2 25 100    
▽ 3 12.5 50    
▽ 4 6.3 25 8.00 320
6.30 250
▽ 5 3.2 12.5 5.00 200
4.00 160
3.20 125
▽ 6 1.6 6.3 2.50 100
2.00 80
1.60 63
▽ 7 0.8 6.3 1.25 50
1.00 40
0.80 32
▽ 8 0.4 3.2 0.63 25
0.50 20
0.40 16
▽ 9 0.2 1.6 0.20 12.5
10
8
▽ 10 0.1 0.8 0.10  
RMS (microinch) RMS
(µm)
Ra (microinch) Ra
(µm)
Grit Size
80 58
47
34
17
14
2.03 1.47
1.2
0.6
0.43
0.36
71 52
42
30
15
12
1.32-1.90
0.46-0.64
0.3-0.4
0.18-0.38
≤0.15
≤0.08
80 120
150
180
240
320
400

Machining surface finish chart: Ra vs RMS

USA Ra(µm) USA Ra (Micro inch) USA RMS (Micro inch) Machining Finish Method
50.0 2000 2200 The most coarse machining or good rough casting surfaces
25.0 1000 1100 Machining marks very obvious. Rough turning, boring, planning, drilling
12.5 500 550 Machining marks obvious. Normal turning, boring, planning, drilling, grinding
8.00 320 352 Machining marks visible. Normal turning, boring, planning, drilling , grinding
6.30 250 275 Machining marks visible. Normal turning, boring, planning, drilling , grinding
5.00 200 220 Machining marks not obvious. But still visible. Normal turning, boring, planning, drilling, grinding.
4.00 160 176 Machining marks not obvious. But still visible. Normal turning, boring, planning, drilling, grinding.
3.20 125 137.5 Machining marks not obvious. But still visible. Normal turning, boring, planning, drilling, grinding.
2.50 100 110 Machining marks blur, but direction obvious. Number controlled turning, boring, planning, drilling, grinding.
2.00 80 88 Machining marks blur, but direction obvious. Number controlled turning, boring, planning, drilling, grinding.
1.60 63 69.3 Machining marks blur, but direction obvious. Number controlled turning, boring, planning, drilling, grinding.
1.25 50 55 Machining marks direction blur, but still visible. Number controlled turning, boring, planing, drilling, grinding.
1.00 40 44 Machining marks direction blur, but still visible. Number controlled turning, boring, planing, drilling, grinding.
0.80 32 35.2 Machining marks direction blur, but still visible. Number controlled turning, boring, planing, drilling, grinding.
0.63 25 27.5 Machining marks direction blur. Reaming, grinding, boring, rolling.
0.50 20 22 Machining marks direction blur. Reaming, grinding, boring, rolling.
0.40 16 17.6 Machining marks direction blur. Reaming, grinding, boring, rolling.
0.20 12.5 13.75 Machining marks direction invisible. Grinding, super machining
0.20 10 11 Machining marks direction invisible. Grinding, super machining
0.20 8 8.8 Machining marks direction invisible. Grinding, super machining
0.10 4 4.4 Surface dark gloss. Surper machining

Ra is the arithmetic average of surface heights measured across a surface. Simply average the height across the microscopic peaks and valleys.

Ra and RMS are both representations of surface roughness, but each is calculated differently.

Ra is calculated as the Roughness Average of a surfaces measured microscopic peaks and valleys.

RMS is calculated as the Root Mean Square of a surfaces measured microscopic peaks and valleys. Each value uses the same individual height measurements of the surfaces peaks and valleys, but uses the measurements in a different formula.

High Temperature Properties Stainless Steel

Stainless steel have good strength and good resistance to corrosion and oxidation at elevated temperatures. Stainless steel are used at temperatures up to 1700° F for 304 and 316 and up to 2000 F for the high temperature stainless grade 309(S) and up to 2100° F for 310(S). Stainless steel is used extensively in heat exchanger, super-heaters, boiler, feed water heaters, valves and main steam lines as well as aircraft and aerospace applications.

Figure.1 gives a broad concept of the hot strength advantages of stainless steel in comparison to low carbon unalloyed steel. Table 1 shows the short term tensile strength and yield strength vs temperature. Table 2 shows the generally accepted temperatures for both intermittent and continuous service.

With time and temperature, changes in metallurgical structure can be expected with any metal. In stainless steel, the changes can be softening, carbide precipitation, or embrittlement. Softening or loss of strength occurs in the 300 series (304, 316, etc.) stainless steel at about 1000° F and at about 900° F for the hardenable 400 (410<, 420, 440) series and 800° F for the non-hardenable 400 (409, 430) series (refer to Table 1).

Carbide precipitation can occur in the 300 series in the temperature range 800 – 1600° F. It can be deterred by choosing a grade designed to prevent carbide precipitation i.e., 347 (Cb added) or 321 (Titanium added). If carbide precipitation does occur, it can be removed by heating above 1900° and cooling quickly.

Hardenable 400 series with greater than 12% chromium as well as the non-hardenable 400 series and the duplex stainless steel are subject to embrittlement when exposed to temperature of 700 – 950° F over an extended period of time. This is sometimes call 885F embrittlement because this is the temperature at which the embrittlement is the most rapid. 885F embrittlement results in low ductility and increased hardness and tensile strength at room temperature, but retains its desirable mechanical properties at operating temperatures.

High Temperature Property Stainless Steel - What is Stainless Steel

Table 1 Short Term Tensile Strength vs Temperature (in the annealed condition except for 410)

Temperature
304

& TS

ksi
316

YS

ksi
309

& TS

ksi
309S

YS

ksi
310

& TS

ksi

310S
YS
ksi

410*

TS

ksi

YS

ksi
430

TS

ksi

YS

ksi
Room Temp. 84 42 90 45 90 45 110 85 75 50
400°F 82 36 80 38 84 34 108 85 65 38
600°F 77 32 75 36 82 31 102 82 62 36
800°F 74 28 71 34 78 28 92 80 55 35
1000°F 70 26 64 30 70 26 74 70 38 28
1200°F 58 23 53 27 59 25 44 40 22 16
1400°F 34 20 35 20 41 24 10 8
1600°F 24 18 25 20 26 22 5 4

heat treated by oil quenching from 1800° F and tempering at 1200° F

Table 2 Generally Accepted Service Temperatures

Material
Intermittent

Service Temperature

Continuous

Service Temperature

Austenitic    
304 1600°F (870°C) 1700°F (925°C)
316 1600°F (870°C) 1700°F (925°C)
309 1800°F (980°C) 2000°F (1095°C)
310 1900°F (1035°C) 2100°F (1150°C)
Martensitic    
410 1500°F (815°C) 1300°F (705°C)
420 1350°F (735°C) 1150°F (620°C)
Ferritic    
430 1600°F (870°C) 1500°F (815°C)

It may seem to be illogical that the “continuous” service temperature would be higher than the “intermittent” service temperature for the 300 series grades. The answer is that intermittent service involves “thermal cycling”, which can cause the high temperature scale formed to crack and spall. This occurs because of the difference in the coefficient of expansion between the stainless steel and the scale. As a result of this scaling and cracking, there is a greater deterioration of the surface than will occur if the temperature is continuous. Therefore the suggested intermittent service temperatures are lower. This is not the case for the 400 series (both ferritic and martensitic grades). The reason for this is not known.

Drawn and spun stainless steels

Austenitic stainless steels have strong work-hardening properties, which affect many forming techniques. Higher levels of mechanical power or lower levels of available capacity are required compared to carbon steel. Machining stainless steel requires higher hardness tools and machinery.

Drawing stainless steel

This is a forming operation in which a flat plate is pressed into cylindrical and rectangular shapes by means of a punch and die set. The work is preferably performed in a double-action press, using a pad or platen to block the material during the forming process, thus avoiding wrinkling of the part flange.

In the austenitic system, the drawing characteristics of similar materials can vary significantly depending on their precise chemical composition.

Generally used mechanical and hydraulic can be used for stainless steel drawing operations, but again their capacity is significantly reduced. For deep-drawing work, hydraulic presses are preferred because speed and pressure can be precisely controlled.

A punch and die radius nominally 5 to 10 times the thickness of the material will allow for smooth drawing of flat sheets. Too large a radius will cause wrinkling and too small a radius will limit the amount of reduction achieved.

For deep drawing work, several interstage annealing operations are required to achieve a high depth to diameter ratio. If lubricants are used to assist in drawing, these should be removed prior to annealing. Descaling after annealing and before further processing is critical.

Certain plastic protective coatings applied to sheet products can remain in place during the drawing process and will act as an aid to stamping.

For information only, annealing of austenitic stainless steels is performed at 1050/1120ºC followed by rapid cooling.

Spinning stainless steel

Spinning can be done to form cylindrical and bowl shaped parts. This is usually a one-step operation using a round-headed tool on a spinning mandrel. Hand and power tools are used.

Bending stainless steel

Stainless steel can be formed in the same manner and using the same types of equipment as other alloy steels. There are some differences in technical applications, which are explained below. The information in this article is dedicated to austenitic stainless steels, which are the most commonly used family of stainless steels.

Austenitic stainless steels have strong work-hardening properties, which affect many forming techniques. Higher levels of mechanical power or lower levels of available capacity are required compared to carbon steels. Machining stainless steel requires higher hardness tools and machinery.

All fabrication processes should be performed in a clean environment and, if possible, in a dedicated environment.

Bending flat steel materials and bars

Stainless steel flat/plate and bar products can be bent using a pressure brake or bending machine. Due to the work-hardening properties of stainless steel, work should be performed as quickly as possible and a degree of over-bending is required to counteract bending springback. No attempt should be made to use a sharper bending inside radius than the material thickness under consideration.

Tube bending

Tubular pipes and bends exist for a large number of construction and process applications. Guidelines can be developed for the pipe bending process, but first-hand experience must be gained to obtain regular and reliable results.

Tubes can be satisfactorily bent using a rotary bender where one end of a straight stainless steel tube is clamped and the machine former rotates to pull the tube to the design radius. Alternatively, bending in hydraulics will push a radius head onto the tube, forcing the tube into a roller die.

When considering internal or subcontract pipe bending, the quantity involved will have a significant impact, as will the complexity of the final shape.

The centerline bend radius for stainless steel material is generally considered to be a minimum of 2 x pipe diameter.

Welding stainless steel

Austenitic stainless steels are easy to weld, with or without filler wire. By far, they are the most common family of stainless steels used in manufacturing.

Super austenitic (i.e., pitting resistance greater than 40), ferritic, superferritic, martensitic and austenitic-ferritic (duplex/super duplex) stainless steels require more control when welding and may involve post-weld heat treatment or special welding consumables.

The main objectives when producing welded joints are to

Ensure that a good weld meets the corrosion and mechanical properties of the base material.

Select a welding process that meets productivity requirements, but has the least possible distortion and requires minimal post-weld trimming.

The following factors should be considered when selecting a welding process.

Joint type and material thickness.

Welding location and work environment, such as a fabrication shop or field.

Manual or mechanized methods that increase productivity and repeatable quality.

Availability of appropriate filler materials, which are often over-alloyed to enhance the corrosion resistance of the weld deposit and may be critical to prevent weld cracking.

General Guidelines

Avoid excessive heat input and high weld interlayer temperatures. Austenitic stainless steels have a high coefficient of thermal expansion and a low electrical conductivity, so higher heat input will result in excessive distortion and residual stresses.

Design criteria and/or metallurgical transformation due to welding may require the selection of mismatched welding consumables to achieve toughness levels at low temperatures or to improve the corrosion resistance of the weld metal.

It is important to retain fabrication facilities dedicated to stainless steel where possible. In addition, use protective handling equipment and tools dedicated to stainless steel fabrication to avoid contamination from contact with carbon steel.

If in doubt about welding and fabrication techniques, it is recommended that the supplier/manufacturer of the base material or welding consumables be consulted.

When shielding gas is required, consult your supplier for the latest information on recommended gas composition.

When new grades of materials need to be welded, especially ferritic, martensitic and duplex alloys, contact your consumable manufacturer for welding process information and filler material recommendations.

Post-weld touch-ups may require the use of pickling paste or other corrosive substances. Consult your material supplier before use.

Welding Health and Safety

Welding Manufacturers Association Publication No. 236, 1994, “Hazards of Welding Fume,” states that it is particularly important to provide adequate fume emissions when welding stainless steel in buildings or confined spaces, as recommended. Consult your welding consumables supplier for information and advice.

Brazing stainless steel

Most stainless steel types can be brazed, with the exception of titanium or niobium stable grades. The three main methods commonly used for brazing stainless steel are:
  • Brazing in air using flux
  • Brazing under reducing atmosphere
  • Vacuum brazing
  • Brazing in air with flux

For brazing stainless steel in air with flux, low-temperature silver brazing alloys are usually used. Details of such filler materials are given in Table AG in EN 1044:1999, which includes 56% Ag:Cu:In:Ni with a melting range of 600-710 C and 60% Ag:Cu:Sn with a melting range of 602-718 C.

It is recommended for use in cases where corrosion failure of the brazed joint seam is expected. Filler containing cadmium and zinc can cause corrosion of stainless steel as the phases formed can cause some preferential corrosion.

The flux used is usually a mixture of alkali metal salts and is solid at room temperature. It needs to be melted before starting to dissolve the oxide film on the surface of the stainless steel to be joined. The flux must remain sufficiently fluid, even in the presence of large amounts of dissolved oxide, to “flush” it out of the capillary gap through the advancing front of the molten brazing alloy.

To do this, the flux must become active and start dissolving the oxide at a temperature at least 50C below the solid phase line temperature of the brazing alloy used, and remain active and continue to dissolve the oxide at a temperature at least 50C above the liquid phase line of the brazing material used.

The flux must also be able to wet and remain on the vertical surface, and the residue should be easily removed from the workpiece at the end of the brazing cycle. No single flux can meet all of these requirements, so a whole range of proprietary fluxes can be used. the various flux families are described in detail in EN1045:1999.

In general, solder flux is best applied as a paste to the joint. The solder paste should be applied uniformly to the mating surfaces of the joint and to the area immediately adjacent to the joint, with particular attention to applying an amount of solder to any sharp edges on the component near the joint.

It is better to pre-apply flux to the component than to the joint during the heating cycle.

The key points to consider when using flux for air brazing are summarized below:
  • The amount of solder applied to the joint needs to be sufficient
  • Brazing time should be as short as possible
  • Brazing temperature should be as low as possible

The heat input to the workpiece should be balanced so that no part of the joint experiences too high a temperature.

Brazing under reductive atmosphere

Since the mid-1990s, stainless steel reducing atmosphere furnace brazing technology has developed rapidly and is expanding. This is in response to the automotive industry’s demand for stainless steel fuel rails and systems.

In this type of application, chemical reduction of the surface oxide is relied upon to provide an oxide free surface to allow wetting and flow of the molten filler material. It is for this reason that brazing is typically performed in a continuous conveyor furnace that is lined with a heat resistant alloy to contain the atmosphere.

In furnaces used for reducing atmosphere brazing, careful control of hydrogen, oxygen and water vapor levels is important.

Typically, copper or copper-based alloys are used as filler materials for reducing atmosphere furnace brazing, which means that brazing temperatures typically exceed 1085C

Vacuum brazing

In most applications of vacuum brazing stainless steel, high temperature brazing filler metals are used. A wide range of materials is available as listed in Table NI of EN 1044:1999.

The vacuum brazing temperature is usually “high”, i.e. over 1000 C. This provides the opportunity for some heat treatment during the brazing operation cycle.

As part of the process, the furnace can be “backfilled” with inert gas to help “flush” any residual air from the capillary path of the part to be brazed. This gas is removed prior to the start of the brazing operation. After the filler has solidified, inert gas can be used to accelerate cooling.

General Principles of Machining Stainless Steel

The most common and most frequently machined stainless steel are the austenitic stainless steel types, such as grades 304/304L/304H and 316/316L. These are characterised by their high work hardening rates and poor chip breaking properties during machining. This article covers the important issues that influence the successful machining of these steel.

Machine and tooling rigidity

When machining stainless steel it important to ensure that there is no dwell or rubbing caused by machine vibration or tool chatter. Machines must ‘substantial’ and capable of making the deep cuts needed in machining austenitic stainless steel without slowing down the set feed or surface speeds. Small training or ‘hobbies’ lathes and milling machines intended for machining mild steel, brass etc. are unlikely to be substantial enough for the successful machining of stainless steel.

Machines should not be prone to excessive vibration in the machine bed, drives and gear boxes or at the cutting tool or its mountings. Large overhangs of tool shank out of the tool box should be avoided. The distance between the cutting tip and toolbox support should be as short as practicable and the shank cross section as substantial as possible. This can also help in dissipating heat away from the cutting faces. Arbours for supporting barrel milling cutters should be stout as short as possible. The arbour supports should be as close as possible to the ends of the cutter to provide maximum support.

Some ‘squealing’ as the metal is being cut is not unusual, but can indicate that the tool may be wearing and need replacing.

Tool materials

Either high speed steel (HSS) (wrought or sintered) or cemented carbide tools can be used for machining stainless steel.

High speed steel

Either tungsten or molybdenum high speed steel HSS can be used. These are particularly useful in machining operations involving high feed and low speed machining operations where there are variable cutting edge stresses induced from complex tool shapes. 

The tungsten types (eg T15) can be useful for their good abrasion resistance and red hardness. The molybdenum high speed steel HSS are more widely used, AISI M42 being useful for applications such as milling cutters where a good combination of hardness, s and strength are required at lower cutting speeds. M42 has better hardness than grades like the more common AISI M2, but may not be as tough however. 

If the tools are prone to edge chipping, use a tougher grade, eg M2, M10 If tools are burning, use a higher red hardness grade, eg M42, T15 If the tools are wearing, use a more abrasion resistant grade, eg T15

Cemented carbides

Cemented carbides are normally used for machining stainless steel where higher speeds or higher feeds than those that can be produced using high speed steel HSS are required. Either disposable insert or brazed-on tips (where lower cutting speeds can be tolerated) can be used and are composed of either tungsten carbides or a blend of tungsten and other metal carbides, including titanium, niobium, and chromium. The carbides are bonded with cobalt. The ‘straight’ tungsten carbides grades are used for machining austenitic and duplex stainless steel and the ‘complex’ carbides are used for machining martensitic and ferritic family grades.

Coated carbides have the additional benefit of improved wear resistance and resistance to breakage. Consequently they are capable of higher cutting speeds compared to un-coated carbide tools.

The wide range of carbide tools available usually means that machining trials are needed to get the optimum machining characteristics for specific situations.

Tool geometry and sharpness

It is essential to keep the cutting tools sharp when machining stainless steel. Careful grinding and honing of the tool faces to give accurate and sharp face angles is important. This helps optimise: tool life finish, accuracy and tolerances productivity between regrinds and reduce:
  • tool breakages
  • power requirements

Re-sharpening should be done as soon as the quality of the cut has deteriorated.

Machine grinding using properly dressed wheels, free from glazing, is preferable to hand grinding to get the necessary accuracy of tool geometry.

Correct tool geometry is important for minimising swarf build up on the tool faces. Swarf build up can also result in increased machine power requirements and poor surface finish on the machined surfaces. Tool relief angles must be flat. Concave relief faces can result in tool chipping or breakage due to the reduced support of the cutting edge.

Where possible the tool faces should incorporate chip curlers or breakers as austenitic stainless steel are prone to forming long spiralling turnings that can easily wrap around the tool and tool post. These can easily become entangled around the tooling and are difficult and time consuming to remove. In extreme cases the tool can become jammed by entangled turnings.

Lubrication and cooling

It is essential that cutting fluids are used when stainless steel are machined. This is due to the combination effects of the deep cuts and high feed rates needed to overcome the effects of work hardening, and the low thermal conductivity of the austenitic stainless steel, restricting the flow of heat away from the machined faces. Overheating stainless steel surfaces, characterised by the formation of heat tint colours, during machining can impair corrosion resistance and so must be avoided. If formed pickling the surface can be used to restore corrosion resistance on the finished part. Overheating can also result in distortion that can be difficult to compensate for or correct.

The lubrication provided by cutting fluids also helps reduce tool wear and wash away the machining swarf. Generally cooling is more important than lubrication with faster the cutting speeds and so high cutting fluid flow rates are normally used when machining stainless steels.

Either mineral oils or water soluble emulsifiable oils can be used. Minerial oils are more suited to severe machining operations with heavy loads at low speeds or where HSS tools are being used. Emulsifiable oils are used for machining at higher speeds with carbide tooling.

Mineral oils

Sulphurized, chlorinated or sulpho-chlorinated mineral oils can be used with additions of up to 10% fatty oils for machining non-free machining grades. Paraffin is used to dilute these oils, in oil/paraffin ratios between 1/5 for high speeds and light feed work to 1/1 for slower speed and heavier feed machining.

If excessive wear is being experienced, consider using greater dilutions. If the cutting edge is tending to burn, consider reducing the dilution.

Emulsifiable oils

These oils are diluted with water and provide better cooling than the paraffin diluted mineral oils. If extreme pressure (EP) emulsifiable oils are used, more sever machining operations can be supported. It is important that dilution is done by adding oil to water, not water to oil so that the correct form of emulsion, with the right lubrication and cooling properties, is formed.

After machining all traces of the cutting fluid should be removed from the surface so that the stainless steel surface can self-passivate. Under certain circumstances acid passivation should be considered.

Cutting tools for stainless steel

Because of its strength and versatility, stainless steel is widely used in various fields. The halls, doors and windows of the building are made of stainless steel. The owner uses stainless steel in the kitchen and buys electrical appliances made of stainless steel. However, in order to use this material, various tools must be used to cut the steel into various sizes.

Laser cutting 

Stainless steel is processed by laser melting cutting. Both CO2 lasers and solid-state lasers are suitable for this application. CO2 lasers are the first choice for cutting thick materials. The CO2 laser cuts stainless steel and construction steel at a cutting speed of 18 m / min with a material strength of 1 mm. In micro material processing, solid-state lasers (fiber lasers, pulsed nd:yag) are usually used for laser cutting stainless steel. According to the thickness of steel, the cutting width can reach 20 microns. These laser cuts usually have slag free mass and minimal heat affected zone.

Plasma cutter 

Plasma cutter, sometimes called plasma torch, uses inert gas. The gas, or sometimes compressed air, is extruded at a high speed through a nozzle. Then the gas is divided into two parts by an electric current, and a plasma flow is generated from the gas. The plasma basically melts the metal, thus cutting.

Water jet cutter

Water jet cutting machine is used to cut stainless steel in a very simple way. As its name implies, it uses a small stream of water that advances at a very high speed. Water shoots out with great pressure and “erodes” the metal. This method is usually used when cutting at high temperature is not an option.

Reciprocating saw

By far, the cheapest and roughest way to cut stainless steel is to use a reciprocating saw. Reciprocating saws are sometimes referred to as “sawteeth”. Reciprocating saws for cutting stainless steel will have a long metal cutting blade that can be used at various speeds. These saws are not used for fine detail work, but for basic, rough cutting procedures.

Theoretical weight calculation of stainless steel products

Stainless steel plate/steel strip reference formula: Stainless steel plate weight (kg) = length (m) * width (m) * thickness (mm) * density ρ (g/cm³).

Stainless steel round bar/wire reference formula: Stainless steel round bar weight(kg)=(diameter(mm)/2)*(diameter(mm)/2)*π*length(m)*densityρ(g/cm³)/1000.

Stainless steel round pipe reference formula: stainless steel round pipe weight (kg)=((OD(mm)/2)*(OD(mm)/2)-(ID(mm)/2)*(ID(mm)/2))*π*length(m)*densityρ(g/cm³)/1000; **wall thickness(mm)=(OD(mm)-ID(mm))/2.

Stainless steel square tube reference formula: stainless steel square tube weight (kg) = (section length (mm)*2 – section width (mm)*2 – wall thickness (mm)*4) * wall thickness (mm) * length (m) * density ρ(g/cm³)/1000.

Stainless steel equilateral angle reference formula: stainless steel equilateral angle weight (kg) = (section side length (mm)*2 – side thickness (mm) * length (m) * density ρ (g/cm³) / 1000; ** [1] according to the national standard GB/T706-2008 equilateral angle, the actual weight of the angle calculation formula is more complex. Because GB/T706-2008 states that the radius of the inner arc of the edge end (r1) and the radius of the inner arc (r) in the cross-section of the angle is not used as a delivery condition, combined with the actual delivery state of the angle in production circulation, this reference formula is given; [2] according to the equilateral angle section area formula given in GB/T706-2008: S = d * (2 * b – d) + 0.215 * (r² -2r1²), the exact stainless steel equilateral angle theoretical weight (kg) = cross-sectional area S (mm²) * length (m) * density ρ (g/cm³) / 1000.

Stainless steel unequal angle reference formula: stainless steel equal angle weight (kg) = (cross-sectional edge length 1 (mm) + cross-sectional edge length 2 (mm) – side thickness (mm)) * length (m) * density ρ (g/cm³) / 1000; ** [1] based on unequal angle national standard GB/T706-2008, the actual weight of the angle calculation formula is more complex. Because GB/T706-2008 states that the radius of the inner arc of the edge end (r1) and the radius of the inner arc (r) in the cross-section of the angle is not used as a delivery condition, combined with the actual delivery state of the angle in production circulation, this reference formula is given; [2] according to the unequal angle cross-sectional area formula given in GB/T706-2008: S = d * (B + b – d) + 0.215 * (r ²-2r1²), the exact stainless steel unequal angle steel theoretical weight (kg) = cross-sectional area S (mm²) * length (m) * density ρ (g/cm³) / 1000.

Stainless steel channel reference formula: stainless steel channel weight (kg) = (section height (mm) * section waist thickness (mm) + (section leg width (mm) – section waist thickness (mm)) * section average leg thickness (mm) * 2) * length (m) * density ρ (g/cm³) / 1000; [1] according to the national standard GB/T706-2008, channel steel actual weight The calculation formula is more complicated. Because GB/T706-2008 states that the inner radius of the arc (r1) and the inner radius of the arc (r) of the side end in the cross-section of the channel are not used as delivery conditions, this reference formula is given in conjunction with the actual delivery state of the channel in production circulation; [2] according to the formula for calculating the cross-sectional area of the channel given in GB/T706-2008: S=h*d+2*t*(b-d)+0.349(r ²-r1²), the exact theoretical weight of stainless steel channel (kg) = cross-sectional area S (mm²) * length (m) * density ρ (g/cm³) / 1000.

Stainless steel I-beam reference formula: stainless steel I-beam weight (kg) = (section height (mm) * section waist thickness (mm) + (section leg width (mm) – section waist thickness (mm)) * section average leg thickness (mm) * 2) * length (m) * density ρ (g/cm³) / 1000; [1] according to the I-beam national standard GB/T706-2008, I-beam The actual weight calculation formula is more complicated. Because GB/T706-2008 states that the radius of the inner arc (r1) and the radius of the inner arc (r) of the side end in the I-beam cross-section are not used as delivery conditions, this reference formula is given in combination with the actual delivery state of I-beam in production circulation; [2] according to the formula for calculating the cross-sectional area of I-beam given in GB/T706-2008: S=h*d+2*t*(b-d)+ 0.615(r²-r1²), the exact theoretical weight of stainless steel I-beam (kg) = cross-sectional area S(mm²) * length (m) * density ρ(g/cm³)/1000.

Stainless steel L-beam reference formula: stainless steel L-beam weight (kg) = (long side width (mm) * long side thickness (mm) + (short side width (mm) – long side thickness (mm)) * short side thickness (mm)) * length (m) * density ρ(g/cm³) / 1000; [1] according to the L-beam national standard GB/T706-2008, L-beam actual weight calculation formula is more complicated. Although GB/T706-2008 does not state that the inner radius of arc (r1) and inner radius of arc (r) at the side end in the cross-section of L-shaped steel are not used as delivery conditions, this reference formula is given in conjunction with the actual delivery state of L-shaped steel in production circulation; [2] according to the formula for calculating the cross-sectional area of L-shaped steel given in GB/T706-2008: S=B*D+d*(b-D)+ 0.215*(r²-r1²), the exact theoretical weight of stainless steel L-beam (kg) = cross-sectional area S(mm²)*length (m)*density ρ(g/cm³)/1000.

Stainless steel square steel reference formula: stainless steel square steel weight (kg) = cross-sectional length (mm) * cross-sectional width (mm) * length (m) * density ρ(g/cm³)/1000.

Stainless steel wire rope reference formula: stainless steel wire rope weight(kg)=diameter(mm)*diameter(mm)*hundred meters coefficient*length(m)/100.

Stainless Steel “L” and “H” Grades

Austenitic grades are alloys typically used in stainless steel applications. Austenitic grades are not magnetic. The most common austenitic alloy is iron-chromium-nickel steel, widely known as the 300 series. Austenitic stainless steel tubes are the most corrosion resistant of the stainless steel group due to their high chromium and nickel content, and have exceptionally good mechanical properties. They cannot be hardened by heat treatment, but can be significantly hardened by cold working. Straight Slope

Austenitic stainless steel straight grades have a maximum carbon content of 0.08%. There is a misconception that straight grades contain at least 0.035% carbon, but this is not required in the specification. There is no minimum carbon requirement as long as the material meets the physical requirements of the straight grade.

“L” Grade

The “L” grade is used to provide additional corrosion resistance after welding. The letter “L” after the stainless steel tube type indicates low carbon (e.g. 304L). The carbon content is kept at or below 0.035% to avoid carbide precipitation. Carbon in steel precipitates when heated in the critical temperature range of 800°F to 1600°F, combining with chromium and collecting at grain boundaries. This causes the steel to lose chromium in solution and promotes corrosion near the grain boundaries. This is minimized by controlling the amount of carbon. For weldability, use the “L” grade. You may ask why all stainless steels are not produced in “L” grade.

There are several reasons.
  • “L” grade is more expensive.
  • Carbon has high physical strength at high temperatures.
  • The higher the carbon content, the greater the yield strength.

Frequently the mills are buying their raw material in “L” grades, but specifying the physical properties of the straight grade to retain straight grade strength. A case of having your cake and heating it too. This results in the material being dual certified 304/304L; 316/316L, etc.

“H” grade

The “H” grade has a minimum carbon content of 0.04% and a maximum of 0.10% and is indicated by the letter “H” after the alloy. The “H” grade is primarily required when the material will be used at extreme temperatures, as the higher carbon helps the material maintain strength at extreme temperatures.

You may hear the phrase “solution annealed”. This simply means that carbides that may have precipitated (or moved) to grain boundaries are re-dissolved (dispersed) into the metal matrix by the annealing process. The “L” grade is used where annealing after welding is not possible, such as in the field of welded pipes and fittings.
Type 304 The most common of austenitic grades, containing approximately 18% chromium and 8% nickel. It is used for chemical processing equipment, for food, dairy, and beverage industries, for heat exchangers, and for the milder chemicals. 
Type 316 Contains 16% to 18% chromium and 11% to 14% nickel. It also has molybdenum added to the nickel and chrome of the 304. The molybdenum is used to control pit type attack. Type 316 is used in chemical processing, the pulp and paper industry, for food and beverage processing and dispensing and in the more corrosive environments. The molybdenum must be a minimum of 2%. 
Type 317 Contains a higher percentage of molybdenum than 316 for highly corrosive environments. It must have a minimum of 3% “moly”. It is often used in stacks which contain scrubbers. 
Type 317L Restricts maximum carbon content to 0.030% max. and silicon to 0.75% max. for extra corrosion resistance. 
Type 317LM Requires molybdenum content of 4.00% min. 
Type 317LMN Requires molybdenum content of 4.00% min. and nitrogen of .15% min. 
Type 321
Type 347 
These types have been developed for corrosive resistance for repeated intermittent exposure to temperature above 800 degrees F. Type 321 is made by the addition of titanium and Type 347 is made by the addition of tantalum/columbium. These grades are primarily used in the aircraft industry. 

Difference between 304 304L and 321

304 stainless steel is a low carbon chromium-nickel stainless steel and heat resistant steel, slightly better than type 302 in terms of corrosion resistance.

321 stainless steel is known as a stable grade of stainless steel and is a chromium-nickel steel containing titanium. It is recommended for parts manufactured by welding, which cannot be subsequently annealed. It is also recommended for parts with good resistance to intergranular corrosion for use at temperatures from 800°F to 1850°F (427 to 816°C). The titanium element in 321 stainless steel makes it more resistant to the formation of chromium carbide.

321 stainless steels are essentially made from 304 stainless steel. They differ in the very small amount of titanium added. The real difference is their carbon content. The higher the carbon content, the greater the yield strength. 321 stainless steel has advantages in high temperature environments due to its excellent mechanical properties. Compared to alloy 304, 321 stainless steel has better ductility and resistance to stress fracture. In addition, 304L can be used to resist sensitization and intergranular corrosion.

The real problem with most collectors/UPPIPE is the difference in the coefficient of thermal expansion (CTE), which expands as the blockage gets hot and contracts as it cools. You want a material that expands and contracts at the same rate as a cast iron block. This puts less stress on the seal (gasket/flange). Most leaks (other than improper installation) are caused by this mismatched CTE. This is why the stock exhaust manifold is cast iron, meaning it has a carbon content of 2% or more.
  • 321 = (17-19Cr, 9-12Ni + titanium)

As for the dual designation theory, this is incorrect. l stands for low carbon.

  • 304 L grade low carbon, usually 0.035% max
  • 304 grade medium carbon, usually 0.08% max

Grade 316 vs. Grade 316L vs. 316Ti Stainless Steel

Grade 316Ti stainless steel tubing is traditionally specified by German engineers and users, Werkstoff No. 1.4571. Type 316Ti is an improved corrosion-resistant chromium-nickel steel alloy with high levels of molybdenum and some titanium. It is not a typical free-machining grade and therefore is not recommended for difficult high-speed machining processes.

Grade 316Ti is essentially a standard carbon 316 type with titanium stabilization similar in principle to that of 304 (1.4301) type to produce 321 (1.4541). Titanium is added to reduce the risk of intergranular corrosion (IC) after heating in the temperature range of 425-815°C.

Intergranular corrosion when austenitic stainless steels are heated for long periods of time in the temperature range of 425-815°C, carbon in the steel diffuses to the grain boundaries and precipitates chromium carbide. This removes the chromium from the solid solution and leaves a low chromium content near the grain boundaries. Steels in this condition are called “sensitive steels”. When subsequently exposed to corrosive environments, the grain boundaries are susceptible to preferential corrosion. This type of corrosion is called intergranular corrosion (IC) and used to be called “weld corrosion”.

The addition of titanium reduces the risk of intergranular corrosion because the formation of titanium carbide takes precedence over chromium carbide, which serves to maintain the correct distribution of chromium throughout the stainless steel tube structure.

The result is that the chromium in the region where the carbon nitride forms near the grain boundary is not depleted to the extent that localized corrosion may occur in the grain boundary region.

An alternative method of reducing the risk of intergranular corrosion is to reduce the carbon content to less than 0.03%. In this way, the resistance to intergranular corrosion of 316 grade is practically the same as 316Ti 320S31/1.4571. This is the basis for the 316L types (1.4404 and 316S13/1.4432).

Are 316Ti and 316L interchangeable?

In most cases, the two grades can be considered interchangeable, with 316L (1.4404) being suitable for applications where 316Ti (1.4571) is specified. There is no practical advantage to specifying 316Ti type in preference to 316L in aqueous corrosive media or ambient temperatures. In some cases, 316L (1.4404/1.4432) grade may be a better choice.

Mechanical Properties

However, the presence of titanium in 316Ti (1.4571) does increase the mechanical strength, especially at higher temperatures than 600°C. Therefore, care must be taken when choosing 1.4404 as a substitute under these conditions. However, the impact properties of 316Ti (1.4571) may be poorer at ambient temperatures compared to 1.4404/1.4432.

Machinability

Machinability of 316Ti (1.4571) may also be an issue, as titanium carbide particles may cause higher tool wear and may not be as easily cold formed or cold headed as 1.4404/1.4432 types.

Polishing

Titanium carbide in 316Ti (1.4571) can also cause problems that require a high standard of polished surface finish. Titanium carbide particles are dragged out during the polishing process, creating a “comet tail” streak on the polished surface. This is similar to grade 1.4541 (321) and is not recommended for use in the now obsolete BS1449 Pt2 (now replaced by BSEN 10088:2-1995 Top Coat 1P/2P), a “No8” bright mechanical polish.

Corrosion resistance

There is also some evidence that Type 316Ti (1.4571) may have poorer resistance to pitting and stress corrosion cracking than Type 1.4404/1.4432, although it can be assumed that the general corrosion resistance is broadly similar. Titanium stabilized 316Ti (1.4571) grade may also be susceptible to “knife line erosion” in the heat affected zone of the weld, very close to the fusion zone where the carbon nitride redissolves in the solid steel matrix.

Weldability

It can be assumed that 316Ti (1.4571) and 1.4404/1.4432 have similar weldability. Neither grade can be “easier” or “better” to weld than the other. Niobium stabilized fillers (welding consumables) should be used to weld 316Ti (1.4571), especially where high temperature weld strength may be important. In other cases, the “316L” filler should have a weld metal water corrosion resistance that matches the “parent” 316Ti (1.4571) “316Ti” material.

347 stainless Steel VS 321 stainless Steel

Alloy 321 (UNS S32100) is a very stable stainless steel. When the temperature reaches 800-1500 ° F (427-816 ° C) and chromium carbide precipitates, it still has good intergranular corrosion resistance. Because of the addition of titanium in the composition, 321 stainless steel can still maintain stability in the case of chromium carbide formation. However, the addition of coltan and tantalum to maintain the stability of alloy 347.

Because of its excellent mechanical properties, 347 stainless steel has advantages in high temperature environment. Compared with 304 alloy, 347 alloy stainless steel has better ductility and stress fracture resistance. In addition, 304L can also be used to resist sensitization and intergranular corrosion.

321 and 347 alloys are commonly used for long-term operation at 800-1500 ° F (427-816 ° C) at high temperature. If the application only involves welding or short-time heating, use 304L instead.  

The advantages of 321 and 347 alloys in high temperature operation also depend on their good mechanical properties. Compared with 304 and 304L, 321 and 347 have better creep stress resistance and stress rupture resistance. This allows these stable alloys to withstand pressures that still comply with the ASME Boiler code and pressure vessel code at higher temperatures. Therefore, the maximum service temperature of 321 and 347 alloys can reach 1500 ° F (816 ° C), while 304 and 304L is limited to 800 ° F (426 ° C). 321 and 347 also have high carbon content varieties, and their UNS numbers are S32109, the same as S34709, 304 and 430.

Chemical composition

ASTM A240 and ASME SA-240:

Component Unless otherwise specified, the weight percentage is the maximum value listed in the table
321 347
Carbon* 0.08 0.08
Manganese 2 2
Phosphorus 0.045 0.045
Sulfur 0.03 0.03
Silicon 0.75 0.75
Chromium 17.00-19.00 17.00-19.00
Nickel 9.00-12.00 9.00-13.00
Coltan + Tantalum** 10xc min 1.00 Max
Tantalum
Titanium** 5x (c + n) min 0.70 Max
Cobalt
Nitrogen zero point one zero
Iron rest rest

* The carbon content of grade H is 0.04/0.10%.

** Grade H minimum stabilizers are different formulations.

Uniform corrosion

Alloys 321 and 347 have similar resistance to general corrosion as unstable NiCr 304. The corrosion resistance of alloys 321 and 347 may be affected by prolonged heating in the temperature range of chromium carbide.In most environments, the corrosion resistance of the two alloys is similar; However, the corrosion resistance of alloy 321 in strong oxidizing environment is slightly lower than that of alloy 347 after annealing. Therefore, alloy 347 is superior in water environment and other low temperature environment. When exposed to the temperature range of 800 ° F-1500 ° F (427 ° c-816 ° C), the overall corrosion resistance of alloy 321 is much worse than that of alloy 347. Alloy 347 is mainly used in high temperature applications, which require strong sensitization resistance to prevent intergranular corrosion at lower temperatures.

20220402034659 38418 - What is Stainless Steel

Intergranular corrosion

Unstable nickel steels such as alloy 304 are sensitive to intergranular corrosion, and alloy 321 and alloy 347 are developed and applied in this field.Chromium carbide precipitates at grain boundaries when unstable chromium nickel steels are exposed to temperatures ranging from 800 ° F to 1500 ° F (427 ° C to 816 ° C) or slowly cooled in this temperature range. When placed in some corrosive medium, these grain boundaries are eroded first, which may weaken the efficiency of the metal and may disintegrate completely.In organic media or corrosive water, milk or other dairy products or atmospheric conditions, even if there is a large amount of carbide precipitation, it will rarely produce intergranular corrosion. When welding thin plates, because the time staying in the temperature range of 800 ° F – 1500 ° F (427 ° c-816 ° C) is very short, it is not easy to produce intergranular corrosion, so unstable grades can be competent. The extent to which carbides precipitate is harmful depends on the length of time the alloy is exposed to the temperature range of 800 ° F to 1500 ° F (427 ° C to 816 ° C) and the corrosive medium. Welding thicker plate is that although the heating time is longer, due to the unstable l grade, the carbon content is 0.03% or less, and the precipitation of carbide is not enough to harm this grade.The strong sensitization resistance and intergranular corrosion resistance of the stable 321 and alloy 347 stainless steels are shown in the table below. (copper copper sulfate-16% sulfuric acid test (ASTM a262, practice E)). Before the test, the annealed steel samples were treated by soaking and photosensitizing at 1050 ° F (566 ° C) for 48 hours.There is no intergranular corrosion in alloy 347, which indicates that they are not sensitized when exposed to this thermal environment. The low corrosion rate of alloy 321 shows that although it has suffered some intergranular corrosion, its corrosion resistance is better than that of alloy 304L in these environments. In this test environment, all of these alloys are much better than the ordinary alloy 304 stainless steel.In general, alloys 321 and 347 are used for making heavy welding equipment that cannot be annealed and for equipment operating in or slowly cooling from 800 ° F to 1500 ° F (427 ° C to 816 ° C).

Stress corrosion cracking

Alloy 321 and 347 austenitic stainless steels are sensitive to stress corrosion cracking in halides, similar to that of alloy 304 stainless steel. This result is due to their similar nickel content. The conditions leading to stress corrosion cracking are: (1) exposure to halide ions (generally chlorides), (2) residual tensile stress, (3) ambient temperatures above 120 ° F (49 ° C). Cold deformation in forming operations or thermal cycles encountered in welding operations can produce stresses. Stress relief heat treatment after annealing or cold deformation may reduce the stress level. Stable alloys 321 and 347 are suitable for stress-free and intergranular corrosion of unstable alloys.321 and 347 are particularly useful in environments where the stress corrosion of unstable austenitic stainless steels (e.g., alloy 304) occurs in the presence of polysulfate. If the unstable austenitic stainless steel is exposed to the temperature where sensitization will occur, chromium carbide precipitation will be produced at the grain boundary. When cooled to room temperature in a sulfur-containing environment, sulfide (usually hydrogen sulfide) reacts with water vapor and oxygen to form polysulphuric acid, which erodes and sensitizes grain boundaries. Under the condition of stress and intergranular corrosion, the stress corrosion cracking of polysulfate occurs in the refinery environment where sulfides are common. The stable alloys 321 and 347 have the anti sensitization ability in the temperature rising operation environment, which solves the stress corrosion cracking problem of polysulfoxylic acid. If the operating conditions can cause sensitization, these alloys should be used under thermal stability conditions in order to achieve the best sensitization resistance.

Pitting corrosion / crevice corrosion

The pitting and pitting resistance of stable alloys 321 and 347 in chloride containing environments is similar to that of alloy 304 or 304L stainless steel because of their similar chromium content. Generally speaking, for unstable and stable alloys, the upper limit of chloride content in the water environment is 100 parts per million, especially in the presence of interstitial corrosion. The higher content of chloride ion will lead to crevice corrosion and pitting corrosion. In severe conditions with higher chloride content, lower pH and / or higher temperature, molybdenum containing alloys such as alloy 316 should be considered. The stable alloys 321 and 347 passed the 5% salt spray test (ASTM B117) for 100 hours, and the tested samples did not produce rust and discoloration. However, if these alloys are exposed to salt spray from the sea, pitting corrosion, crevice corrosion and severe discoloration may occur. Exposure of alloys 321 and 347 to the marine environment is not recommended.

High temperature oxidation resistance

The oxidation resistance of 321 and 347 is comparable to other 18-8 austenitic stainless steels. Expose the sample to high temperature laboratory atmosphere. If the samples are taken out from the high temperature environment and weighed regularly, the degree of rust formation can be calculated. The test results are expressed by weight change (mg / cm2), taking the average of the minimum values of two different samples tested. The main difference between 321 and 347 is the fine alloy additive, but does not affect the oxidation resistance. Therefore, these test results are representative for both levels. However, the oxidation rate is affected by inherent factors such as the exposure environment and the form of the product, so these results should only be considered as the normal values for these grades of oxidation resistance.

Physical properties

The physical properties of alloys 321 and 347 are quite similar, but in fact, they can be regarded as the same. The values listed in the table are applicable to both alloys.If properly annealed, alloy 321 and 347 stainless steels mainly contain austenite and titanium carbide or niobium carbide. A small amount of ferrite may or may not appear in the microstructure. A small amount of sigma phase may be formed if exposed to temperatures between 1000 ° F and 1500 ° F (593 ° c-816 ° C) for a long time.Heat treatment does not harden the stable alloy 321 and 347 stainless steels.The total heat transfer coefficient of metal depends not only on the thermal conductivity of metal, but also on other factors. In most cases, the heat dissipation coefficient of the film, rust scale and surface condition of the metal. Stainless steel keeps the surface clean, so it has better heat transfer than other metals with higher thermal conductivity.

Magnetic conductivity

Stable alloys 321 and 347 are generally not magnetic. In the annealed state, its magnetic conductivity is less than 1.02. The permeability changes with composition and increases with cold working. The permeability of weld with ferrite will be higher.

Mechanical properties

Ductility at high temperature

Typical mechanical properties of alloys 321 and 347 at high temperatures are shown in the table below. At 1000 ° F (538 ° C) and above, the strength of these stabilized alloys is significantly higher than that of the unstable 304 alloy.

Alloys 321h and 347h (uns32109 and s34700) with high carbon content have higher strength at temperatures above 1000 ° F (537 ° C). The ASME maximum allowable design stress data of alloy 347h show that the strength of this grade is higher than that of alloy 347 with low carbon content. Alloy 321h is not permitted for Section VIII applications and is limited to temperatures of 800 ° F (427 ° C) or less for section III applications.

Creep and stress rupture properties

Typical creep and stress rupture data for alloy 321 and 347 stainless steels are shown in the table below. The creep and stress rupture strength of the stabilized alloy is higher than that of the unstable alloy 304 and 304L at high temperature. These superior properties of alloy 321 and 347 make it suitable for high temperature service pressure parts, such as our common boilers and pressure vessels.

Impact strength

The impact toughness of 321 and 347 is very good both indoors and in the environment below zero.

Fatigue strength

In fact, the fatigue strength of each metal is affected by corrosion environment, surface finish, product morphology and average stress. For this reason, it is not possible to use an exact number to represent the fatigue strength values under all operating conditions. The fatigue limit of alloy 321 and 347 is about 35% of its tensile strength.

Welding

Austenitic stainless steel is considered to be the most easily welded alloy steel and can be welded with all fusion materials, as well as resistance welding.

Two factors should be considered in the production of austenitic stainless steel welding joints: 1) to maintain its corrosion resistance, 2) to avoid cracking.

Attention must be paid to maintaining the stabilizing elements in alloys 321 and 347 during welding. Alloy 321 is more likely to lose titanium, while alloy 347 is more likely to lose coltan. Carbon in oil and other sources of pollution and nitrogen in the air need to be avoided. Therefore, it is necessary to keep clean and protect inert gas when welding stable alloy or unstable alloy.

When welding the metal with austenite structure, it is easy to split during operation. Due to this reason, a small amount of ferrite is needed to reduce the crack sensitivity of alloy 321 and 347 to the minimum. The stainless steel containing coltan is more prone to hot cracking than the stainless steel containing titanium.

The matching filler metal can be used for welding of alloy 321 and 347. The matching filler metal of alloy 347 can also be used for welding of alloy 321.

These stable alloys can be added to other stainless steels or carbon steels. Alloy 309 (23% cr-13.5% Ni) or nickel based filler metals can be used for this purpose.

How to choose stainless steel

To choose the right stainless steel, you must first select the correct grade of stainless steel and nickel alloy. Stainless steels contain many standard grades, with significant differences in chemical composition, corrosion resistance, physical properties, and mechanical properties between grades. Selecting the most appropriate grade for a particular application will give you satisfactory results at the lowest cost. When selecting a grade, material properties should be considered.

Slope properties to consider for selection include

Corrosion resistance; sulfur resistance; strength, ductility and ambient temperature use; processing technology adaptability study; cleaning procedure adaptability; stability of use properties; strength wear and erosion resistance; anti-adhesive corrosion; reflective action magnetic thermal conductivity; thermal expansion; resistivity; sharpness; hardness; dimensional stability.

Corrosion resistance is usually the most important characteristic of stainless or heat resistant steels, but in applications, corrosion resistance is the most difficult to assess. Under natural conditions, corrosion resistance is relatively easy to determine in pure chemical solutions. However, localized corrosion, such as stress corrosion cracking, crevice corrosion, pitting corrosion, and intergranular corrosion (present in HAZ) is much more complex than general corrosion. Although this localized corrosion does not cause extensive damage to the structure, it may not lead to the expected or even fatal failure.

Therefore, the construction and selection of stainless steel must carefully consider these factors during design. Corrosion may increase through the medium, trace impurities alarmingly, the impurities in the medium is difficult to predict, but even a concentration of a few parts per million can have serious consequences. In the case of warming, the corrosion rate, curing and carburization may be affected, although small changes in the atmosphere can greatly accelerate the corrosion of metals.

Despite these complexities, we can combine the recommendations of steel manufacturers to select the appropriate rule of thumb for most steel applications. However, it is important to understand one thing: the data obtained by corrosion testing of materials is used to predict a specific bias in performance. Even the data from this work is limited by the fact that corrosion resembles some of these media and may be substantially different due to slight variations in corrosion coefficients. For demanding applications, both studies require a large amount of data, comparative analysis, and sometimes bootstrapping or operational testing.

The mechanical performance of the operating temperature is the primary consideration, but sometimes other temperature requirements are ignored to achieve satisfactory performance. Therefore, products intended for use at subzero temperatures must have operating performance, and while a constant operating temperature may be much higher, operating performance at room temperature is also important.

Product selection needs to take into account not only the need for performance, but also the need for handling and cleaning. Materials that can be processed with specific characteristics (easy to form or weld) are usually used over others, but rather materials with relatively good properties and higher processing costs. Even the cleaning process can influence the choice of steel. Sometimes, even though the degree of sensitization in the working conditions is not important, the carbon stabilized material in the welding process to be used may be ignored.

The welding process of the material needs to be placed in a cleaning medium, such as nitric acid-hydrofluoric acid, which when sensitized will corrode stainless steel. For some specialized applications, the other properties listed in the list are critical. However, they are rarely considered in many other applications. Surface finish is important for many applications, and sometimes stainless steel is used because it has a beautiful surface that is available in a variety of options. Depending on the appearance, smoothness, and other characteristics, or the choice of cleaning surface. Surface cleaning is not as easy as it sometimes is and may require an existing test surface. The choice of surface layer may affect the type of choice, and the choice of surface layer may in turn affect the choice of material grade, as the durability of the surface layer varies with the grade of the surface layer. The strong corrosion resistance of the surface layer in a corrosive solution (lower alloy content will corrode the steel) maintains the brightness.

Life Cycle Costing of Stainless Steel

Sometimes stainless steel is considered to be an expensive material. However, experience has shown that using a corrosion resistant material in order to avoid future maintenance, downtime and replacement costs can produce economic benefits which far outweigh higher initial material costs.

Life cycle costing (LCC) quantifies all the costs – initial and ongoing – associated with a project or installation. It uses the standard accountancy principle of discounted cash flow to reduce all those costs to present day values. This allows a realistic comparison to be made of the options available and the potential long term benefits of using stainless steel to be assessed against other material selection.

The present day value represent the amount of money which would have to be invested today in order to meet all the future operating costs – including running costs, maintenance, replacement and production lost through downtime. These are added to the initial costs to give the total LCC:

Life Cycle Costing LCC - What is Stainless Steel

In the formula:

    AC = initial materials acquisition costs

    IC = initial fabrication and installation costs

    N = desired service life of project in years

    i = discount rate (calculated from interest and inflation rates)

    OC = operating and maintenance costs in year n

    LP = lost production and downtime costs in year n

    RC = replacement costs in year n

Once the cost data have been gathered, the calculation of the life cycle cost is straightforward. Software packages are available which prompt the user to collect the relevant data, carry out the calculation and allow different options to be compared easily.

Example (Refer to “Applications for stainless steel in the water industry”)

Galvanised carbon steel and Type 316 stainless steel were both candidate materials for ductwork to remove odorous fumes in a sewage inlet works. The galvanised steel required a multi-stage site-applied painted coating whereas the stainless steel could be installed in a single operation. The galvanised steel was expected to need maintenance every 5 years, and replacement after 15 years. The stainless steel equipment was designed for a 30 year service life, with maintenance every 10 years. A 10% interest rate and 5% inflation rate were assumed, giving a discount rate of 4.76%.

Stainless Steel Present Value - What is Stainless Steel

Not only was the stainless steel option only slightly more expensive initially (because of the lower installation cost) but it showed a distinct life cycle cost advantage following the anticipated replacement of the galvanised steel plant after 15 years (refer to graph). The stainless steel option was chosen.

Stainless steel in energy saving and emission reduction

In the past, stainless steel in many applications for high-grade, aesthetic considerations to improve the standard of living needs.

Stainless steel is not an indispensable necessity for people’s lives. From the perspective of “energy saving and emission reduction”, in order to avoid the “greenhouse effect”, stainless steel should be regarded as a sustainable development of the necessities of life.

In the production process, stainless steel compared with ordinary carbon steel, has obvious energy saving and emission reduction benefits. Generally speaking, in steel production. The use of electric furnace steelmaking from the beginning to hot rolled stainless steel coil, stainless steel products far short process production technology, the integrated energy consumption of 280 kg per ton of steel; including the use of ironmaking system began, to the ordinary carbon steel hot rolled steel coil so far, the long process of the integrated energy consumption of 625 kg per ton of steel and ordinary carbon steel.

Production of stainless steel than carbon steel energy saving of more than 55%. From the use of electric furnace steel, stainless steel hot rolled coil products. So far, the steel CO2 emissions of stainless steel short process production technology reached 507 kg; including the start of the use of ironmaking system; ordinary carbon steel hot rolled steel coil end of ordinary carbon steel long process CO2 emissions reached 1860 kg of steel per ton. The production of stainless steel is a long process of carbon steel production, which can reduce CO2 emissions by more than 72%.

Considering the short process of stainless steel production accounts for about 70% of the total production of stainless steel, the long process of carbon steel production accounts for about 90% of the total production of carbon steel. The overall average social composite energy consumption of tons of steel and stainless steel is 383.5 kg, and the average social composite energy consumption of carbon steel is 590.5 kg. Social average stainless steel carbon dioxide emissions of 912.9 kg, the social average carbon steel carbon dioxide emissions of 1724.7 kg. This shows that the production of 1 ton of stainless steel hot rolled coil, than the production of 1 ton of ordinary carbon steel hot rolled coil, can save more than 35% of energy consumption, can reduce more than 47% of carbon dioxide emissions.

Second, in the field of application, the advantages of stainless steel are more obvious. As stainless steel is a fine product, with no rust, corrosion resistance, appearance and high strength, 100 percent recyclable and other characteristics, in practical applications, can further show the social benefits of energy saving and emission reduction. For example, the use of

Stainless steel hot-rolled steel coil is the production of new stainless steel and ordinary carbon steel manufacturing trucks, the use of national material general open wagon compared with stainless steel trucks, can reduce the initial steel consumption by 15%, the whole life cycle can reduce steel consumption of about 55%. Based on the full life of steel tons of coal consumption, can save more than 75%. Therefore, each additional production of 1 ton of stainless steel, can replace more than 4 tons of carbon steel. Only stainless steel manufacturing process and applications

Process considerations than ordinary carbon steel, stainless steel energy saving 84.25%, reducing carbon dioxide emissions by 87.16%.

In addition, according to the International Stainless Steel Forum (ISSF) survey, the carbon dioxide emissions of 1 ton of cold-rolled stainless steel sheet produced by TISCO are 13% lower than the carbon dioxide emissions of 1 ton of cold-rolled stainless steel sheet produced in any other country or region. Discussed here are the only stainless steel manufacturing process and application process steel energy-saving these two factors, taking into account the ordinary carbon steel than stainless steel energy-saving, reducing carbon dioxide emissions. In fact, since the use of stainless steel production wagon weight than the use of carbon steel production wagon weight is lighter, but also can save a lot of energy consumption of traction power during transportation, further reducing C02 emissions.

Further consider the use of stainless steel in nuclear applications, so that the promotion of nuclear energy is possible, compared with thermoelectric power to further reduce CO emissions. In water supply and drainage systems, by reducing water pollution and waste, thus further reducing CO2 emissions. The application in water treatment, desalination applications, in clean food applications, in order to improve energy efficiency applications, in 100 percent recyclable applications, etc.

The stainless steel “energy saving” and avoiding the “greenhouse effect” has a greater impact.

Applications of stainless steel

Stainless steel’s corrosion and stain resistance, low maintenance, relatively low cost and familiar luster make it an ideal base material for many commercial applications. Stainless steel is available in more than 150 grades, 15 of which are the most common. The alloy is milled into coils, sheets, plates, bars, forgingsflangeswire and tubing for cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment, and as an automotive and aerospace structural alloy and construction material for large buildings. Storage tanks and tankers used to transport orange juice and other food products are often made of stainless steel because of its corrosion resistance and antibacterial properties. This also affects its use in commercial kitchens and food processing plants because it can be steam cleaned, sterilized, and does not require painting or other surface treatments.

Stainless steel is also used in jewelry and watches. The most commonly used stainless steel alloy is 316L. It can be reworked by any jeweler and will not oxidize or blacken.

Some firearms use stainless steel parts as an alternative to blued or phosphated steel. Some pistols, such as the Smith & Wesson Model 60 and the Colt M1911, can be made entirely of stainless steel. This provides a high-gloss finish similar to the appearance of nickel plating; however, unlike plating, the finish will not flake, peel, or wear from friction (such as repeatedly removing it from the holster over a period of time), nor will it rust from scratching.

Some aftermarket automotive parts manufacturers use stainless steel only for short shift levers and weighted gear knobs.

Can stainless steel rust?

Rust is a reddish-brown coating that forms on the surface of iron or steel when the metal oxidizes and dissolves in water. Stainless steel is an alloy that contains at least 10.5 percent chromium, which makes it resistant to rust. Stainless steel can still rust in certain conditions. If your stainless steel item is damaged in a way that exposes the metal underneath, you can use an abrasive to remove the rust. You can also buff out surface scratches with water and baking soda. If your stainless steel item has been soaked in saltwater, you should clean off the salt with dish soap, rinse it with water and use a soft cloth to buff away any remaining rust spots. To keep stainless steel from rusting, always dry your stainless steel items after washing them and keep them away from saltwater.”

Rust is a reddish-brown coating that forms on the surface of iron or steel when the metal oxidizes and dissolves in water. Rusting occurs when iron combines with oxygen in the presence of water, forming iron oxide (Fe2O3). The rate at which rust forms depends on several factors, including moisture content, temperature and humidity. In other words:

Rust is a reaction between iron and oxygen (or water) that causes oxidation of your metal piece.

While rust technically refers to any type of corrosion on metal surfaces, we’re most familiar with its reddish hue. Rust may appear as small spots or large swaths across a surface depending on how much contact there was with water or air during exposure to it—and what kind of alloy was used for your stainless steel product!

Stainless steel is an alloy that contains at least 10.5 percent chromium, which makes it resistant to rust.

Chromium is a metal that contains many different compounds and is resistant to rust. When exposed to oxygen, iron can corrode and form rust if there are other elements present in the air or water surrounding it. This process can be slowed by adding chromium to your stainless steel kitchenware, but it will never be completely immune from oxidation because even stainless steel has trace amounts of copper in its composition (which means you’ll always want to avoid using copper pots on your stove top).

Stainless steel can still rust in certain conditions.

While stainless steel is not susceptible to rusting, it can still corrode and degrade over time if the surface is scratched or exposed to harsh conditions. This includes exposure to saltwater, acidic substances, high temperatures and moisture.

If your stainless steel item is damaged in a way that exposes the metal underneath, you can use an abrasive to remove the rust. You can also buff out surface scratches with water and baking soda.

  • Use a fine grit sandpaper to remove any rust from the metal.

  • Use a toothbrush to scrub off any remaining rust particles or residue left by the sandpaper (this will prevent further buildup of rust).

  • Use a soft cloth to buff out any scratches or corrosion caused by removing corrosion with an abrasive like sandpaper (buffing will make your item shine).

  • Apply stainless steel cleaner as directed on its packaging (use cleaning products specifically for stainless steel) and then wipe clean with a soft cloth or paper towel.

  • For added shine, apply polish as directed on its packaging then wipe clean immediately after applying.

If your stainless steel item has been soaked in saltwater, you should clean off the salt with dish soap, rinse it with water and use a soft cloth to buff away any remaining rust spots. Dry your stainless steel item after washing it. Keep your stainless steel item away from saltwater as much as possible to prevent future corrosion.

To keep stainless steel from rusting, always dry your stainless steel items after washing them and keep them away from saltwater.

The best way to prevent rust from forming on your stainless steel is by not leaving it in water. If you have a sink full of dishes, take them out immediately and hand-dry them. If you are washing something in the dishwasher, remove it as soon as possible and place it somewhere dry.

If you have a shower with lots of steam, try using a squeegee to wipe away any excess moisture before drying off your items with a towel or cloth. This will help prevent condensation from forming on your item and causing rusting later on down the road when temperatures drop again.

When doing yard work such as gardening or working on vehicles outside during cold weather months, make sure that all tools used outdoors are dried thoroughly before storing so they don’t rust over time!

However, if you are not careful and let your stainless steel item get damaged, it may rust. The best way to avoid this problem is by drying off your items and storing them somewhere where they won’t get wet.

Source: China Stainless Steel Pipes Manufacturer – Yaang Pipe Industry (www.epowermetals.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at [email protected]

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