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What is Super Duplex Stainless Steel

What is Super Duplex Stainless Steel?

Super duplex stainless steel is a category of stainless steels that are specially formulated for very high corrosion resistance. While similar to other duplex stainless steels, super duplex has an increased amount of chromium, molybdenum and nickel. With this higher alloy content, super duplex stainless steel is extremely resistant to pitting and corrosion in a wide range of environments. As such, it’s often used in the chemical processing industry, oil and gas industry and desalination plants in seawater applications.
Super Duplex Stainless Steel is an iron base precipitation-hardened alloy with good strength and corrosion resistance that can be used in many environments. It is highly resistant to chloride stress corrosion cracking (SCC), pitting, crevice corrosion and general corrosive attack in both fresh water and salt water environments.
Super duplex stainless steels are alloyed high performance duplex steels with pitting resistance greater than 40 (based on Cr% + 3.3Mo% + 16N%).
Super duplex steels with high chromium content provide excellent resistance to acids, acid chlorides, corrosive solutions and other environments in the chemical/petrochemical, pulp and paper industries and are often used as a replacement for 300 series stainless steels, high nickel super austenitic steels and nickel based alloys.
The chemical composition based on high levels of chromium, nickel and molybdenum improves intergranular corrosion and pitting resistance. The addition of nitrogen promotes structural hardening through an interstitial solid solution mechanism, thereby increasing yield strength and ultimate strength values without compromising toughness.
In addition, the two-phase organization ensures higher resistance to pitting and stress corrosion cracking compared to conventional stainless steels.

20220608042412 11115 - What is Super Duplex Stainless Steel

Chemical Composition of Super Duplex Stainless Steel

UNS Designation C Mn P S Si Ni Cr Mo N Cu Others
UNS S31200 0.030 2.00 0.045 0.030 1.00 5.5–6.5 24.0–26.0 1.20–2.00 0.14–0.20 . . . . . .
UNS S31260 0.030 1.00 0.030 0.030 0.75 5.5–7.5 24.0–26.0 2.5–3.5 0.10–0.30
0.20
–0.80
W 0.10
–0.50
UNS S31500 0.030
1.20
–2.00
0.030 0.030
1.40
–2.00
4.3–5.2 18.0–19.0 2.50–3.00 0.05–0.1 . . . . . .
UNS S31803 0.030 2.00 0.030 0.020 1.00 4.5–6.5 21.0–23.0 2.5–3.5 0.08–0.20 . . . . . .
UNS S32001 0.030
4.00
–6.00
0.040 0.030 1.00 1.0–3.0 19.5–21.5 0.60 0.05–0.17 1.00 . . .
UNS S32003 0.030 2.00 0.030 0.020 1.00 3.0-4.0 19.5-22.5 1.50-2.00 0.14-0.20 . . . . . .
UNS S32101 0.040 4.0-6.0 0.040 0.030 1.00 1.35-1.70 21.0-22.0 0.10-0.80 0.20-0.25
0.10
-0.80
. . .
UNS S32202 0.030 2.00 0.040 0.010 1.00 1.00–2.80 21.5–24.0 0.45 0.18–0.26 . . . . . .
UNS S32205 0.030 2.00 0.030 0.020 1.00 4.5–6.5 22.0–23.0 3.0–3.5 0.14–0.20 . . . . . .
UNS S32304 0.030 2.50 0.040 0.040 1.00 3.0–5.5 21.5–24.5 0.05–0.60 0.05–0.20
0.05
–0.60
. . .
UNS S32506 0.030 1.00 0.040 0.015 0.90 5.5–7.2 24.0–26.0 3.0–3.5 0.08–0.20 . . .
W 0.05
–0.30
UNS S32520 0.030 1.50 0.035 0.020 0.80 5.5–8.0 23.0–25.0 3.–5. 0.20–0.35
0.50
–3.00
. . .
UNS S32550 0.04 1.50 0.040 0.030 1.00 4.5–6.5 24.0–27.0 2.9–3.9 0.10–0.25
1.50
–2.50
. . .
UNS S32707 0.030 1.50 0.035 0.010 0.50 5.5–9.5 26.0–29.0 4.0–5.0 0.30–0.50 1.0 max
Co 0.5
–2.0
S32750 0.030 1.20 0.035 0.020 0.80 6.0–8.0 24.0–26.0 3.0–5.0 0.24–0.32 0.50 . . .
UNS S32760 0.030 1.00 0.030 0.010 1.00 6.0–8.0 24.0–26.0 3.0–4.0 0.20–0.30
0.50
–1.00
W 0.50
–1.00
UNS S32808 0.030 1.10 0.030 0.010 0.50 7.0–8.2 27.0–27.9 0.80–1.20 0.30–0.40 . . .
W 2.10
–2.50
UNS S32900 0.08 1.00 0.040 0.030 0.75 2.5–5.0 23.0–28.0 1.00–2.00 . . . . . . . . .
UNS S32906 0.030
0.80
–1.50
0.030 0.030 0.80 5.8–7.5 28.0 –30.0 1.50–2.60 0.30–0.40 0.80 . . .
UNS S32950 0.030 2.00 0.035 0.010 0.60 3.5–5.2 26.0–29.0 1.00–2.50 0.15–0.35 . . . . . .
UNS S33207 0.030 1.50 0.035 0.010 0.80 6.0–9.0 29.0–33.0 3.0–5.0 0.40–0.60 1.0 . . .
UNS S39274 0.030 1.00 0.030 0.020 0.80 6.0–8.0 24.0–26.0 2.5–3.5 0.24–0.32
0.20
–0.80
W 1.50
–2.50
UNS S39277 0.025 0.80 0.025 0.002 0.80 6.5–8.0 24.0–26.0 3.00–4.00 0.23–0.33
1.20
–2.00
W 0.80
–1.21
UNS S82011 0.030
2.0
–3.0
0.040 0.020 1.00 1.00–2.00 20.5–23.5 0.10–1.00 0.15–0.27 0.50 . . .
UNS S82441 0.030
2.50
–4.00
0.035 0.005 0.70 3.0–4.5 23.0–25.0 1.00–2.00 0.20–0.30
0.10
–0.80

  • A. Maximum, unless a range or minimum is indicated. Where ellipses (…) appear in this table, there is no minimum and analysis for the element need not be determined or reported.
  • B. Designation established in accordance with Practice E527 and SAE J1086 PREN.
  • C. % Cr + 3.3 × % Mo + 16 × % N $ 41.
  • D. % Cr + 3.3 × % Mo + 16 × % N $ 40.

Mechanical Properties of 2507 Super Duplex Stainless Steel

Tensile Strength, Mpa Yield Strength, MPa Elongation, % Hardness, HB
800 min 550 min 15 min 310 max

Tensile Strength and Hardness of Super Duplex Stainless Steel

Grade Tensile strength, min., ksi [MPa] Yield strength, min., ksi [MPa] Elongation in 2 in., or 50mm, min, % Hardness, Max Brinell
S31803 90 [620] 65 [450] 25 290
S32205 95 [655] 70 [485] 25 290
S31500 92 [630] 64 [440] 30 290
S32550 110 [760] 80 [550] 15 297
S31200 100 [690] 65 [450] 25 280
S31260 100 [690] 65 [450] 25 290
S32001 90 [620] 65 [450] 25 290
S32304 100 [690] 65 [450] 25 290
S32750 116 [800] 80 [550] 15 310
S32760 109 [750] 80 [550] 25 300
S32950 100 [690] 70 [480] 20 290
S32520 112 [770] 80 [550] 25 310

Heat Treatment of super duplex stainless steel

2507 duplex steel shall be solution annealed and quenched after hot forming or cold forming. Solution annealing shall be performed at a minimum of 1925 ° F. Rapid air or water quenching shall be carried out immediately after annealing. For maximum corrosion resistance, heat treated products shall be pickled and rinsed.

UNS Designation Temperature Quenching
S31803 1870-2010 °F [1020-1100°C] Rapid cooling in air or water
S32205 1870-2010 °F [1020-1100°C] Rapid cooling in air or water
S31500 1800-1900 °F [980-1040°C] Rapid cooling in air or water
S32550 1900 °F [1040°C] min. Rapid cooling in air or water
S31200 1920-2010 °F [1050-1100°C] Rapid cooling in water
S31260 1870-2010 °F [1020-1100°C] Rapid cooling in water
S32001 1800-1950 °F [982-1066°C] Rapid cooling in air or water
S32003 1850-2050 °F [1010-1120°C] Rapid cooling in air or water
S32101 1870 °F min Quenched in water or Rapidly cooling in other means
S32202 1870-1975 °F [1020-1080°C] Rapid cooling in air or water
S32506 1870-2050 °F [1020-1120°C] Rapid cooling in air or water
S32304 1700-1920 °F [925-1050°C] Rapid cooling in air or water
S32750 1880-2060 °F [1025-1125°C] Rapid cooling in air or water
S32760 2010-2085 °F [1100-1140°C] Rapid cooling in air or water
S32950 1820-1880 °F [990-1025°C] Rapid cooling in water
S32520 1975-2050 °F [1080-1120°C] Rapid cooling in air or water

Benefits of super duplex stainless steel

  • High strength;
  • High resistance to pitting, crevice corrosion resistance;
  • High resistance to stress corrosion cracking, corrosion fatigue and erosion;
  • Excellent resistance to chloride stress-corrosion cracking;
  • High thermal conductivity;
  • Low coefficient of thermal expansion;
  • Good sulfide stress corrosion resistance;
  • Low thermal expansion and higher heat conductivity than austenitic steels;
  • Good workability and weldability;
  • High energy absorption.

Why use super duplex stainless steel?

You can use super duplex stainless steel for a wide range of applications. Here are some common uses:

  • Industrial equipment, such as valves and pumps

  • Transportation items, like cars and planes

  • Food processing and beverage manufacturing equipment, including pipes and vessels

  • Medical devices that come into contact with human blood or body fluids, such as surgical instruments (This consideration is especially important for hospitals that need to minimize the risk of contamination.)

Strength in the Duplex Family

Super duplex is the strongest of all duplex steels, with a yield strength of 200 ksi (1380 MPa). Super duplex stainless steel is used in extremely harsh environments and is resistant to corrosion by seawater, fresh water and many acids. It has a low coefficient of thermal expansion and can be used for cryogenic applications.

The Super Duplex Difference

Super Duplex is a nickel-chromium-molybdenum alloy that has higher strength than austenitic stainless steel. This means you can use less material to manufacture a part, which saves money and weight.

Super Duplex also has higher corrosion resistance than other non-ferrous alloys, making it an ideal choice for harsh environments or corrosive media. It offers excellent oxidation resistance in the temperature range of 1200°C to 1400°C (2200°F -2500°F).

Application of super duplex stainless steel

Super duplex stainless steel is a type of stainless steel that combines strength and superior corrosion resistance. In fact, it can withstand cathodic protection (a technique used to prevent corrosion in some materials), making it an extremely useful material for marine environments.

Duplex stainless steels are a family of high-performance alloys that combine the advantages of austenitic and ferritic characteristics, making them ideal for a wide range of applications.

With its broad range of uses and applications, super duplex stainless steel is an ideal material for many industries. Some examples include:

  • Heat exchangers, tubes and pipes for production and handling of gas and oil;
  • Heat exchangers and pipes in desalination plants;
  • Mechanical and structural components;
  • Power industry FGD systems;
  • Piping systems;
  • Pipes in process industries handling solutions containing chlorides;
  • Utility and industrial systems, rotors, fans, shafts and press rolls where the high corrosion fatigue strength can be utilized;
  • Cargo tanks, vessels, piping and welding consumables for chemical tankers;
  • High-strength, highly resistant wiring.
  • Electronics manufacturing — In addition to its superior anti-corrosion properties, super duplex also offers excellent resistance to heat and oxidation while being lighter than other alloys. This makes it well suited for use in consumer electronics where weight may be an issue or when high temperatures are expected.
  • Surgical instruments — The strength of super duplex helps protect surgeons from cross-contamination as they work with surgical instruments during operations on patients who have open wounds or incisions (such as those who have undergone surgery).
  • Oil & gas production — Superduplex’s superior strength makes it perfect for use in oil & gas production where its ability to withstand chemicals allows workers more freedom during their jobs without worrying about damaging their tools or equipment due to corrosion issues caused by exposure.

How to weld super duplex stainless steel

Welding super duplex stainless steel requires advanced equipment and skill compared to other types of stainless steel but following the right steps will ensure you have success when welding it.

Don’t use a filler metal with more than 25% nickel content.

If you plan to use a filler metal with more than 25% nickel content, make sure that the discoloration is expected and acceptable in your application. If not, consider using a filler metal with less than 25% nickel content.

Discoloration can be an indication of a poor weld or other issues, such as contamination or improper workmanship.

Match the filler metal strength to the base material.

When you’re welding super duplex stainless steel, it’s important to match the filler metal strength to the base material. Super duplex is more brittle than other stainless steel grades and is more resistant to corrosion. This makes it difficult for welders who are used to working with other types of stainless steel because they may not know how much force they need to apply when welding super duplex.

The nickel content in super dupex is higher than other types of grade 304 or 316L stainless steels, but this doesn’t mean that you need a stronger filler metal. As long as you use the right equipment and follow all safety precautions, your welds will be just fine!

Use low heat input when TIG welding.

When TIG welding, use a low heat input. This is because the metal has a high nickel content, which means it’s more difficult to melt than other types of stainless steel. To reduce temperature and prevent excessive oxidation, use low amperage (5-10 amps), voltage (18-25 volts), frequency (50 kHz), duty cycle (10%), current (2-3 amps) and power supply settings that are appropriate for your material thicknesses.

Do not overweld.

Overwelding can cause porosity, which is a condition where gas escapes from the weld and forms bubbles in the metal. It is one of the most common problems in welding stainless steel. Overwelding can also cause discoloration, distortion and cracking. In addition, it will reduce strength because of the reduced intergranular material present after welding.

Welding direction is important.

Welding direction is important. It’s all about the grain.

  • Welding direction should be with the grain, not against it (perpendicular to it).

  • Welding direction should be at a 90 degree angle to the grain, as seen from above.

  • We’ll also talk about welding in parallel to the grain, which results in less distortion than perpendicular welds and has other advantages as well; this will come up later on when we talk about filler metal selection.

Minimize your weld size.

You can minimize your weld size by using as small a weld as possible. The smaller your weld, the less heat you need to apply and dissipate, resulting in lower heat affected zones (HAZ).

Keep heat-affected zones to a minimum.

  • Keep the heat input to a minimum.

  • Use a small weld.

  • Use a filler metal with low nickel content (less than 1%).

Be aware of heat tinting in low-temperature applications.

  • Be aware of heat tinting in low-temperature applications.

  • Heat tinting can occur when welding at lower temperatures, and it can affect the surface appearance of your welds. This can be avoided by using a higher heat input or by preheating to 350°F/177°C before welding.

  • For welds that have heat tinting, you can use a cleaner like Cleaner No. 957 to remove the discoloration from the stainless steel.

Super duplex stainless steel can be tricky to work with but following the right steps will ensure you have success when welding it.

Super duplex stainless steel is a nickel-based superalloy that can be hard to work with. The material itself is strong, but it’s difficult to weld because of its hardness and high melting point. However, following the right techniques will ensure you have success when welding this type of stainless steel.

One way to avoid problems when welding super duplex stainless steel is by using a preheater or induction heater on the parts before you start welding. These methods help reduce cooling time and prevent cracking in your welds. This reduces any risk of damage during the process, which can cause further issues later on down the road if not attended to immediately after completing production runs involving this particular material type.

In conclusion, it is important to remember that super duplex stainless steel can be an extremely valuable metal when working in the welding industry. It is a great option for projects where strength and corrosion resistance are required. However, it can be difficult to work with at times due to its complex microstructure and high level of ferrite. By following these tips, you will make sure that your next project involving this metal goes smoothly.

Super duplex stainless steel VS duplex stainless steel

Super duplex steel is a stainless steel with a dual microstructure, consisting of austenite and ferrite phases. This high strength stainless steel has increased resistance to chloride corrosion and stress corrosion cracking. With its higher strength than the ordinary duplex grades, super duplex stainless steels offer some advantages, such as:
• High-strength construction
• Longer life cycles
• Lower cost of ownership through extended service life and less maintenance
Introduction to super duplex stainless steel
Super duplex stainless steel is a precipitation-hardened stainless steel. The key difference between super duplex and other types of stainless steels is that it contains a high amount of chromium (over 20%). This makes the material more resistant to corrosion and oxidation.
A superalloy is an alloy with a very high melting temperature, usually above 1873°F (1000°C). Superalloys are typically used in applications where extreme temperatures are present or needed, such as jet engines or rocket engines.
Introduction to duplex stainless steel
Duplex stainless steels are low carbon and low alloy steels containing a maximum of 10.5% chromium, 2.5% nickel and 0.5% molybdenum (the term duplex is used because doping with copper gives the alloy corrosion resistance similar to that of austenitic grades). The addition of small amounts of molybdenum makes the material more resistant to pitting from chloride ion attack than 304 or 316 stainless steels, at least in the temperature range where pitting occurs.
There are two types of duplexes: 004-type with 4% nickel and 18/8-type with 8% nickel which have different compositions but both contain at least 70% ferrite iron. The 004-type has an ultimate tensile strength between 382 MPa (55 ksi) and 480 MPa (70 ksi), while the 18/8-type has a minimum yield strength between 723 MPa (110 ksi) and 890 MPa (140 ksi). Ferritic martensitic steel can be divided into three groups:

  • 1st group – ductile type alloys
  • 2nd group – semi-ductile type alloys
  • 3rd group – brittle type alloys

Difference between Duplex and Super Duplex Steel

The main difference between duplex and superduplex is that superduplex has a higher yield strength and corrosion resistance than duplex. Superduplex is more expensive than duplex, but it’s still less than nickel-based alloys. In addition to being more resistant to corrosion and high temperatures, superduplex also has a lower coefficient of thermal expansion (CTE), making it easier to work with in many ways.
Superduplex steels are harder to machine than their duplex counterparts because they have a higher hardness level (HRC 58–60). In addition, they’re more difficult to weld as well because of the high melting point of the steel—around 1,250°C (2,280°F).
Grade
Grade is a term used to describe the quality of a material. It is assigned to both metals and alloys, and it can be used to determine if the metal has been produced using the highest quality manufacturing processes.
Super duplex steel is an alloy that consists of nickel and chromium. Duplex stainless steel also contains nickel, but instead of chromium, it includes molybdenum as well.
Characteristics of Duplex Stainless Steel
Duplex stainless steel is a super-alloy that is highly resistant to corrosion.
Duplex stainless steel is a heat-treated, precipitation-hardened, high-strength alloy.
Duplex stainless steel is a precipitation-hardened, high-strength alloy
Yield Strength and Elongation
Super duplex stainless steel has a higher yield strength than duplex stainless steel. This means that super duplex steel is able to withstand more stress before it breaks or deforms. Although the difference may be slight, this makes super duplex stainless steel ideal for applications that demand high strength and durability such as ball bearings, gears and fasteners.
Duplex stainless steels are more malleable than austenitic steels which means they are able to withstand more force before breaking or deforming. In other words, if two pieces of material were subjected to the same amount of force by an external load (for example: pulling them apart), then the material with lower yield point will deform first (i.e., stretch). This characteristic is known as elongation effectiveness factor which measures how much a metal stretches when subjected to an applied load; high elongation means less stress on your part!
Corrosion Resistance of Super Duplex Stainless Steel
Corrosion Resistance
Super duplex stainless steel is resistant to pitting and crevice corrosion. It does not suffer from stresses that can lead to stress corrosion cracking. Super Duplex is also resistant to chloride pitting corrosion and does not form hydrogen embrittlement under normal conditions.
Crystallographic structure of Super Duplex Stainless Steel
Super duplex stainless steel has a face-centered cubic crystal structure, with a very high hardness and strength. It has a high thermal conductivity and low coefficient of thermal expansion, which makes it suitable for applications in high temperature environments. Super duplex steel also has a very good electrical resistivity and weldability, making it an ideal material for oilfield equipment.
Manufacturing Process of Super Duplex Stainless Steel
Super duplex stainless steel is made by powder metallurgy.
The product is then cold rolled to the desired shape and size.
Super Duplex Stainless Steel is hot rolled to the desired shape and size.
It can also be extruded into a tube, which makes it useful for high resistance welds or brazing applications such as piping or heating coils that require high strength materials in order to handle pressure changes at higher temperatures on an industrial scale without breaking apart due to any stress applied against them during operation (this property makes them ideal candidates for use in these kinds of conditions). In addition, they are often forged into blocks so they can be used more easily without needing machinery like lathes or mills which would make working with these types difficult otherwise.
Super duplex steel has superior strength and corrosion resistance than ordinary stainless steel.
Super duplex steel is a nickel-copper-iron alloy. It has superior strength and corrosion resistance than ordinary stainless steel. It can be used in high temperature applications such as nuclear reactors, chemical processing equipment (CPE), petrochemical plants and other environments that are corrosive to ordinary stainless steels.
Super duplex alloys are much better than conventional duplex grades in terms of corrosion resistance at high temperatures due to the copper addition which makes them more resistant to stress corrosion cracking (SCC). SCC is one of the most common forms of surface damage in hot circulating water systems and superduplex grades have been specifically designed with this problem in mind.
It’s not easy to make sense of all the different grades and types of stainless steel. But by understanding the differences, you can make better decisions when it comes time to purchase. As always, we’re happy to help!

Conclusion

This is a high-level introduction to super duplex stainless steel. It is one of the strongest and most durable types of steel you can buy, with an effective combination of ferritic and austenitic microstructure. The higher chromium content, for example, enables improved resistance to corrosion, which makes it useful for its durability in applications like oil rigs. Its strength also allows for thinner materials to be used in construction projects; this is especially useful for weight-saving measures in aerospace applications. The alloy itself has also been patented as S32750 or 2507 by Sandvik AB under their trade name SUPERDUPLEX 2520

Source: China 2507 Pipe Fittings 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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