Domestic color coated steel plate selection users are relatively least concerned about the steel grades. Because most color-coated steel sheet factories in China have only one kind of steel, that is DC51 (because the hot-rolled sheet or rolled coil they
purchased is basically a kind of steel), some color-coated steel sheet factories with hot-dip galvanizing production line try to produce all-hard steel (S550) or high strength steel (S350) by hot-dip galvanizing annealing, but it is very difficult.
Because they can not control the quality and chemical composition of the substrate, poor quality stability and poor stability lead to large fluctuations in performance, which will lead to the deterioration of profiled sheet metal.
For buildings, bearing weight (wind load, snow load, construction personnel and machinery), span of buildings, purlin distance design and so on all depend on the strength of steel plate. For building maintenance structure with color coated and aluminized galvanized sheet, there are corresponding standards abroad. Such as ASTM 653 and ASTM 792 in the United States, JISG3302 and JISG3321 in Japan, EN10215 and EN10147 in Europe, etc.
The steel can be classified into CQ (general commercial grade), DQ (general stamping), HSS (high strength structural steel) and FH (all hard steel).
CQ (Common Commercial Grade): It is most commonly used, such as TST01Z, TDC51 or TSGCC produced by Baosteel. Its yield strength before painting is between 260 and 320 MPa. After color coating, if the substrate is aluminium killed steel, the ultimate strength will be improved, accompanied by the deterioration of elongation. The tensile strength of the steel ranges from 350 MPa to 400 MPa, and its yield strength ratio is slightly higher than that of the structural steel.
DQ (general stamping): Because the general building color panels are roll-formed or composite sandwich, the stamping performance of materials is not required, so they are rarely used in the construction field (except for some door and window color panels).
HSS (High Strength Structural Steel): According to the European Standard HSS, it can be divided into 4-5 kinds of steel with different strength. But because the ordinary CQ grade material can replace the low strength HSS steel, the steel grades with yield strength 280 MPa and 345 MPa are widely used in the market. The TS280GD and TS350GD produced by Baosteel are the two kinds of steel. Compared with ordinary CQ, HSS steel has several advantages: 1. Because of its low yield strength, it has good fire resistance and seismic resistance; 2. For thicker steel plate, it can produce large-span arch plate; 3. For general external wall and roof panel, it can be thinner than CQ material, thus saving material consumption.
FH (All Hard Steel): A kind of steel which improves the yield strength of steel plate by controlling annealing temperature. According to the international general standard, the yield strength is more than 550 MPa and the tensile strength is more than 570 MPa. This kind of material has high strength and low elongation. It is suitable for the use of shallow shaped steel plate, which greatly saves the use of materials. It is also a kind of steel developed by various countries. Materials with high strength and good elongation are also described in foreign standards. HSLA (Low Alloy High Strength) is used in steelmaking to add strengthening alloy elements, but because of its high strength, it is carried out in iron and steel works. Increasing the reduction rate during rolling is limited, so HSLA steel is seldom used in thin color coated sheets as enclosure structure (another disadvantage is high cost).
In order to ensure the shape of the final product of color coated steel plate, the strength grade of steel plate, the shape of profiled steel plate and the processing machine are closely related.