1. Raw materials commonly used in cold-formed steel production
Because cold-formed steel is widely used in all walks of life, the raw materials used include many kinds, such as ordinary carbon steel, high-quality carbon structural steel, low-alloy steel, atmospheric corrosion resistant steel, stainless steel, coating materials (galvanized plate, aluminium plate, etc.), color coated plate, copper, aluminium alloy, titanium alloy and so on.
The specific varieties, brands and relevant standards of various raw materials are as follows:
Carbon structural steel
Commonly used grades of carbon structural steel are Q195, Q215, Q235, etc.
High Quality Carbon Structural Steel
Commonly used high quality carbon structural steels are: 08, 10, 08F, 08Al, etc.
low alloy steel
Commonly used low alloy steels are: 16Mn,
Atmospheric corrosion resistant steel
Common grades of atmospheric corrosion resistant steels are as follows: (GB4172 weather resistant steels for welded structures) 16CuCr, 12MnCuCr, 15MnCuCr, 15MnCuCr-QT; (GB4171 high weather resistant structural steels) 09CuPCrNi-A, 09CuPCrNi-B, 09CuP; (WISCO Enterprise Standard: Atmospheric corrosion resistant steels for vehicles: 09CuPCrNi, 09CuPTiRE)
Container steel grades are: NSF345 (instead of Japan SPAH), NSF390 (instead of Japan NAW50), J335 (instead of Japan SS34), J490 (instead of Japan SM50A);
Commonly used stainless steel grades are: 1Cr18Ni9 (AISI-302, JIS-SU302), 0Cr18Ni9 (AISI-304, JIS-SU304), 1Cr18Ni12 (AISI-305, JIS-SU305), 0Cr17Ni12Mo2 (AISI-316, JIS-SU316), etc.
In roll forming, materials with common use and machinability are usually used. Hot-dip galvanized steel sheets with 100-350g/m2 zinc layer weight are usually used.
Colour coated sheet
The types of surface coatings for color coated panels are acrylic acid, polyester, silicon modified polyester, polyvinylidene fluoride, polyvinyl chloride-plastic sol, organic sol and PVC film.
Copper is a kind of material which is easy to roll forming. Commonly used include copper, brass and so on.
Aluminum has the characteristics of corrosion resistance, excellent processability and beautiful appearance. The common roll forming methods are pure aluminium, aluminium-manganese series and aluminium-magnesium series.
2. Problems needing attention in using different raw materials in roll forming
The material selection of cold-formed steel products is based on the needs of users. In order to produce qualified products, the roll shape design should correctly formulate the cold bending forming process according to the characteristics of materials. In the process of making roll forming process, the following problems need to be carefully studied.
A. Chemical constituents of raw materials:
Different materials have different chemical compositions, which have different effects on the properties of steel. Special attention should be paid to the chemical composition of the selected materials in the roll profile design of unconventional new products. According to their characteristics, the influence of different elements on the forming process should be fully considered. For example:
The strength and other properties of carbon steel mainly depend on the form of carbon and the shape, size and distribution of carbides, that is, the metallographic structure of steel. Due to the influence of raw materials, smelting methods and process operation, a small amount of other elements, such as silicon, manganese, sulfur, phosphorus, copper, chromium and nickel, often exist in carbon steel. These elements are generally treated as impurities or residual elements in carbon steel, rather than as alloying elements. Some of these elements play a beneficial role in steel, while others have adverse effects, such as copper, chromium, nickel and so on, on the cold bending processing and welding properties of carbon steel.
Alloy elements dissolved in solid solution will generally increase the hardening rate of cold bending process of steel and make the steel strip hard and brittle, which is disadvantageous to cold bending process.