A Guide to Choosing the Right Channel Steel

What is a channel steel?

Channel steel is a long steel bar with a grooved cross-section, and is a section steel with a complex cross-section.

Classification of channel steel

Channel bars are divided into ordinary channels and light channels. The specifications of hot-rolled common channel are 5-40#. The specifications of hot-rolled variant channel steel supplied by agreement between supply and demand are 6.5-30#. Channels are mainly used in building structures, vehicle manufacturing, other industrial structures and fixed cabinets, etc. Channels are also often used in conjunction with I-beams.
Channels can be divided into 4 types according to shape: cold-formed equal-sided channels, cold-formed unequal-sided channels, cold-formed inward-rolled channels, cold-formed outward-rolled channels.
According to the theory of steel structure, it should be the flange of the channel to be stressed, that is to say, the channel should be standing, not lying down.

Numbering of channel steel

• ① International chemical element symbols and national symbols are used to indicate the chemical composition, and Arabic letters are used to indicate the composition content. Such as: China, Russia 12CrNi3A.
• ② With a fixed number of digits to indicate the steel series or numbers; such as: the United States, Japan, 300 series, 400 series, 200 series.
• ③ With Latin letters and order to form the serial number, only to indicate the use.

Specification of channel steel

The specification of channel steel is mainly expressed by the height (h), leg width (b), waist thickness (d) and other dimensions, domestic channel steel specifications from 5-40, that is, the corresponding height of 5-40cm.
At the same height, light channel steel has narrower legs, thinner waist and lighter weight than ordinary channel steel. 18-40 gauge is large channel steel, 5-16 gauge is medium channel steel. Imported channel steel is marked with the actual specification size and related standards. Import and export orders of channel steel are generally made after determining the corresponding carbon knotted (or low alloy) steel number to the specifications required in use. Except for the specification number, there is no specific composition or performance series for channel bar.
The delivery length of channel bar is divided into two types of fixed length and double length, and the tolerance value is specified in the corresponding standard. The length selection range of domestic channel steel is divided into 5-12m, 5-19m and 6-19m depending on the specification number. The length selection range of imported channel steel is generally 6-15m.

The appearance requirements of channel steel

The allowable deviation of the surface quality and geometry of the channel steel is specified in the standard. The general requirement is that the surface should not have harmful defects, no significant twist, the allowable value of the channel steel wave bend (sickle bend) and the value of the relevant parameters of each specification channel shape (h, b, d, t, etc.), tolerance values. The main manifestations of incorrect channel geometry are: angle, leg expansion and leg and so on.

Theoretical weight calculation formula of channel steel

W = 0.00785 × waist thickness [height + e (leg width-waist thickness)]

For example: 80mm×43mm×5mm weight per m of channel steel. It is found from the metallurgical product catalog that the channel steel t is 8, R is 8, r is 4, then the weight per m = 0.00785 × [80 × 5 + 2 × 8 × (43 – 5) + 0.349 × (82 – 42)] = 8.04kg.

Channel steel specification table

Specifications	Height	Leg width	Lumbar thickness	Cross-sectional area (cm²)	Theoretical weight
5#	50	37	4.5	6.928	5.438
6.3#	63	40	4.8	8.451	6.634
6.5#	65	40	4.3		6.709
8#	80	43	5	10.248	8.045
10#	100	48	5.3	12.748	10.007
12#	120	53	5.5		12.059
12.6#	126	53	5.5	15.692	12.319
14#a	140	58	6	18.516	14.535
14#b	140	60	8	21.316	16.733
16#a	160	63	6.5	21.962	17.24
16#b	160	65	8.5	25.162	19.752
18#a	180	68	7	25.699	20.174
18#b	180	70	9	29.299	23
20#a	200	73	7	28.837	22.637
20#b	200	75	9	32.837	25.777
22#a	220	77	7	31.846	24.999
22#b	220	79	9	36.246	28.453
25#a	250	78	7	34.917	27.41
25#b	250	80	9	39.917	31.335
25#c	250	82	11	44.917	35.26
28#a	280	82	7.5	40.034	31.427
28#b	280	84	9.5	45.634	35.832
28#c	280	86	11.5	51.234	40.219
30#a	300	85	7.5		34.463
30#b	300	87	9.5		39.173
30#c	300	89	11.5		43.883
32#a	320	88	8	48.513	38.083
32#b	320	90	10	54.913	43.107
32#c	320	92	12	61.313	48.131
36#a	360	96	9	60.91	47.814
36#b	360	98	11	68.11	53.466
36#c	360	100	13	75.31	59.118
40#a	400	100	10.5	75.068	58.928
40#b	400	102	12.5	83.068	65.208
40#c	400	104	14.5	91.068	71.488

Allowable deviation of channel steel (mm)

Model		Allowable deviation, mm
		Height (h)	Leg width (b)	Waist thickness (d)
5-8		±1.5	±1.5	±0.4
>8-14		±2.0	±2.0	±0.5
>14-18			±2.5	±0.6
>18-30		±3.0	±3.0	±0.7
>30-40			±3.5	±0.8

The allowable deviation of the average leg thickness of the channel steel is ± 0.06t, the bending deflection shall not exceed 0.15d, the outer edge inclination of the channel steel leg shall not be greater than 1.5% b for one leg and 2.5% b for both legs, and the passivation of the leg end and shoulder shall not allow the round bar with a diameter equal to 0.18t to pass through; The bending of channel steel per meter shall not be greater than 3mm, and the total bending shall not be greater than 0.3% of the total length, and there shall be no obvious torsion.

The main uses of channel steel

Channel steel is mainly used in building structure, curtain wall engineering, mechanical equipment and vehicle manufacturing. In use, it is required to have good welding and riveting properties and comprehensive mechanical properties. The raw material billet for the production of channel steel is carbon steel with a carbon content of not more than 0.25%.

The raw material billet for producing channel steel is carbon steel or low alloy steel billet with carbon content not more than 0.25%.

The production process of channel steel

The production of channel steel is divided into five steps, and each step is introduced one by one as follows.
The first step: raw material inspection: check whether the profile size of the prepared buttress channel is qualified, if it is not qualified, it needs to be corrected or replaced by the metal material.
Step 2: Scribing.
a) According to the length of the size of the butt after the scribing on the angle ready to butt, scribe before the line should meet two requirements.

• (1) To ensure that the minimum length of the butt channel steel to be greater than 200mm.
• (2) The length direction should be left with a margin of 2 – 3mm.

b) The principle of scribing is that the cutting line on the two wing plates of the channel should be perpendicular to the web, and the cutting line on the web should be at an angle of 45°.
Step 3: Cutting: Use semi-automatic flame cutting machine to cut metal material along the scribing line. After cutting material, use semi-automatic flame cutting machine or grinding wheel machine to open 45° single V-shaped bevel on the inner side of the channel steel. The cutting surface should be smooth and flat with no gap.
Step 4: Assembling: Before assembling, put the two prepared channels upside down on the platform, then adjust the straightness and gap of the two channels and spot weld to fix them.
Step 5: Welding: Gas shielded welding (GMAW) is used to weld, and to reduce welding deformation, the channels should be spot welded together in pairs back-to-back before welding, first welding the bevel side on the wing plate, then welding the bevel of the web plate, after the bevel side welding is completed. Open into pairs Step 6: Points to note: The main concern in the case of welding is that the weld is not firm and the welding stress is too large. The wall thickness of the section steel is thin, butt welding itself is the most unreliable. So, you can add a liner at the butt joint and weld with fillet welds. Control the amount of deformation after welding, you can use rigid fixing for welding, which can avoid deformation. Process attention to reduce the stress. Connecting with bolts also needs liner plate, pay attention to the size, number and spacing of bolts. You also have to calculate whether the thin wall of the section itself will be crushed, and the solution is to weld a patch plate and then drill bolt holes. The principle is that the strength of the butt joint is not weaker than the other parts, and there is no greater stress.

Several welding methods of channel steel

The construction industry continues to grow, so that more building materials are introduced into the market, and the national standard channel steel is one of them, and widely used, so we have to learn to familiarize ourselves with all aspects of the advantages of the national standard channel steel and the production process, then the national standard channel steel welding method and welding form is how, what are the methods? Let’s learn together!
Next we will introduce three welding methods, the first is the electrode arc welding; the second is carbon dioxide (COz) gas shielded welding; the third is submerged arc welding.
a. Welding rod arc welding
Stick arc welding, also known as manual arc welding, hand arc welding or flux-coated electrode arc welding, is a method of welding using hand-operated welding rods for welding electric flesh welding. The principle of electrode arc welding is to melt the metal by using the heat of the arc generated by the welding rod and the work piece. During the welding process, the electrode flux melts and decomposes, generating gas and slag. Under the joint protection of gas and slag, the harmful effects of the surrounding air are effectively excluded, and the desired weld is obtained through metallurgical reactions between the molten metal and slag at high temperature, reduction and purification of the metal.
b. Carbon dioxide (COz) gas shielded welding
Carbon dioxide (Cq) gas shielded welding is a welding technology developed in the 1950s, according to the degree of automation is divided into fully automatic co, Eagle shielded welding and semi-automatic co, gas shielded welding two, in the construction of national standard channel steel is mainly used in the semi-automatic co.

• (1) CO: gas shielded welding characteristics and welding requirements.
• (2) The composition of the semi-automatic gas shielded welding machine. Semi-automatic C0,gas shielded welding machine is generally composed of arc welding power source, wire feeding mechanism, wire, gas and other parts.

c. Submerged arc welding
The submerged arc tick is electric i in the granular ch flux layer, well in the cavity burning automatic d connection method, the radiation heat of the arc makes the weld, off the wire and flux melting, evaporating to form a gas, row away from the arc around the melt puddle to form a closed cavity, the arc is in this cavity stable combustion. The upper part of the cavity is a layer of melted flux, that is, slag film am, this layer of slag film can not only effectively protect the molten pool metal, guard the operation of the arc radiation no longer shoot out, at the same time, the melting of a large number of flux on the molten pool metal has the role of reduction, purification and alloying.
The main difference between submerged arc welding and manual welding is that it is mainly used to start the arc, maintain a stable burning arc, transport the wire, the movement of the arc, as well as the end of welding to fill the arc pit and other actions, all of which are achieved by using the submerged arc since the work.

How to inspect the channel steel?

How to choosing the right channel steel? We need to check the quality of channel steel. There are three elements in the inspection of channel steel:

• Finished product inspection;
• Sign inspection;
• Mechanical property inspection.

Finished product inspection
All the channel steel must be inspected by the appearance, appearance inspection by visual inspection method.
Inspection items:

• a) The surface of the channel steel parent material shall not have cracks, surface porosity, surface slag, scars, folding and other defects with depths exceeding the standard deviation. Defects for which the depth cannot be judged should be measured after complete removal by the repair and grinding method.
• b) The amount of wrong edge in the width direction of the channel should meet the requirements of the corresponding specifications and product standards.
• c) The depth and length of surface depression should meet the requirements of the corresponding specifications and product standards. Several points of the channel steel size inspection method are as follows: Check the height of the waist shall prevail, check the leg width shall be exempted from the influence of waist unevenness, check the bending deflection measured with straightedge and stopper, check the leg end of channel steel, shoulder obturation measured with sample plate and round bar, measurement shall not make the diameter equal to 0.18t round bar through the obturation part.

Sign inspection
The standard of channel steel is ASTM A36.
The information on the label must be clear and complete.
The date of shipment is based on the testing time of the day.
All checking personnel should be systematically trained and have the corresponding qualification certificate.
Mechanical properties test of channel steel
Each work shift should be tensile test of channel steel, the specimen is intercepted on one of the channel steel.

On behalf of a batch of channel steel tensile test results failed, you can take two other channel steel from the same batch of channel steel, each taking a sample retest, if the retest results are qualified, then in addition to the initial inspection sampling failed channel steel, the batch of channel steel can be judged qualified and should be accepted, if the retest sample has a sample or two sample test results failed, then the batch of untested channel steel should be sampled one by one test.

How should we judge the superiority and inferiority condition of channel steel?

With the increasing demand for channel steel in the market, there are more and more channel steel manufacturers on the market, and more and more channel steel products, and the technology of producing channel steel is also uneven, so inferior channel steel is very common in the channel steel industry, and customers are defensive when buying. Here, the channel steel manufacturer Huyuan building materials to teach you how to reasonably determine the merits of the channel steel condition, to avoid being deceived!

• 1. Inferior channel steel manufacturers products containing impurities, steel density is small, and usually the size of the super poor serious, in the absence of vernier calipers, it can be weighed to check.
• 2. Poor quality channel surface scratch easily, this is due to the production equipment is rudimentary, easy to produce burrs and other scratch the surface of the steel, deep scratches will also reduce the strength of the channel.
• 3. Inferior channel steel without metallic luster, shoddy material rolling temperature is not standard, can not be rolled according to the specified austenite area, the channel steel performance naturally can not meet the standard.
• 4. High quality channel steel manufacturers produce channel steel with uniform composition, high tonnage of cold shear, smooth and neat cutting head end, while the shoddy channel steel material is poor, the cutting head end often appears uneven and lusterless.
• 5. Inferior channel steel cross-section is oval, some manufacturers in order to save materials, finished rollers before the second press down amount is large, not only will make the strength of steel greatly reduced, but also does not meet the standards of the shape size.
• 6. Due to the rudimentary production equipment, the material of inferior channel steel is uneven, with many impurities and easy to produce scars on the surface.

How to choose channel steel manufacturers reasonably?

In the construction industry, channel steel manufacturers are considered to be one of the most important factors. In fact, many people choose to use channels because they have been in use for a long time. However, choosing a channel steel manufacturer is not an easy task, as there are so many products on the market and pricing is inconsistent. How do we choose in a logical way? There are four main ways: reputation, after-sales service, production facilities and product quality.
The first one is to see the reputation.
The first thing to see is the reputation of the channel steel manufacturer, which, as I mentioned earlier, is to check the reputation of the channel steel manufacturer. If a company has been in business for more than 10 years, this means it has a good reputation and is trustworthy. If many customers have done business with them in the past, this shows that they are also reliable and trustworthy. Also, if over time you can see more and more products on the website as they produce high quality products and use advanced technology to improve efficiency, then this shows that they are also committed to providing high quality service!
The second thing to look for is after-sales service.
After a product is sold, the manufacturer should provide a reasonable warranty and technical support. If you use a channel steel manufacturer in China, they will provide both services. Because they have years of experience in manufacturing channel products, they know how to make channel products better than other manufacturers. Therefore, if you want to choose a channel steel manufacturer wisely, it is necessary for you to see if the channel steel manufacturer you choose can satisfy these two factors
Third, look at the production equipment.
The production of channel steel is an important factor in manufacturer selection. High quality production equipment can ensure efficient production process and good product quality. The production equipment should be able to meet various process requirements at different times, so before choosing a manufacturer, we must first double-check whether it meets your requirements.
Fourth, look at the quality of the product.
Quality is the most important factor in choosing a channel steel manufacturer, and it can be determined by the equipment and staff. In addition to product quality, you should also pay attention to the production process, materials and packaging.
By choosing a channel steel manufacturer reasonably, you can choose a more favorable channel product, reduce costs and improve economic efficiency.
In addition to price, there are other factors that influence the choice of channel steel products.

• Strength.
• Welding performance and weld quality.
• Heat treatment temperature, color, processing method, etc.

Conclusion

In conclusion, the most important thing to look for in selecting a channel steel manufacturer is its reputation, after-sales service and production facilities. Attention should also be paid to the quality of the product. Before buying a channel steel product, it is necessary for you to know its cost.

Source: China Channel Steel Manufacturer – Yaang Pipe Industry Co., Limited (www.epowermetals.com)