Common steel grades of color steel coil
In China, for the selection of color-coated steel coils, users are relatively less concerned about steel grades. Because most domestic color-coated steel plate production plants have fewer types of steel, most of which are DC51 (because the hot-rolled plate or hard-rolled coil they purchase is basically the same type of steel), and some color-coated steel plate plants with hot-dip galvanizing production lines It is very difficult to produce full-hard steel (S550) or high-strength steel (S350, etc.) by hot-dip galvanizing annealing, because they cannot control the quality and chemical composition of the substrate. As a result, quality stability is poor, resulting in large fluctuations in performance, resulting in deterioration of the profiled sheet.
For buildings, the bearing weight (wind load, snow load, construction personnel and machinery), the span of the building, and the design of purlins all depend on the strength of the steel plate. In other words, foreign countries have corresponding standards. Such as ASTM653 and ASTM792 in the United States, JISG3302 and JISG3321 in Japan, and EN10215 and EN10147 in Europe. According to the steel types, it is divided into CQ (commercial grade), DQ (general stamping), HSS (high-strength structural steel), FH (full-hard steel).
DQ for general stamping
Because the general construction color plates are roll forming or composite sandwich, the stamping performance of the material is not high, so it is rarely used in the construction field (except for some door and window color plates).
HSS high strength structural steel
According to the European standard HSS can be divided into 4-5 steel grades with different strengths, but since ordinary CQ grade materials can already replace low-strength HSS steels, steel grades with yield strengths of 280Mpa and 345Mpa are more commonly used in the market. TSTE28 and TS350GD produced by Baosteel are these two steel grades.
Compared with ordinary CQ, HSS steel has several advantages: (1) Due to the low yield strength, the steel has good fire resistance and shock resistance. (2) For thicker steel plates, it can manufacture large-span arched plates. (3) For general exterior wall and roof panels, it can be appropriately thinner than CQ material, thereby saving material consumption.
FH full hard steel
It is a kind of steel that improves the yield strength of steel plates by controlling the annealing temperature. According to the international standard, the yield strength is ≥550Mpa and the tensile strength is ≥570Mpa. This type of material has high strength and low elongation, and is suitable for forming steel plates with shallow shape, which can greatly save materials when used. Therefore, countries scramble to research and develop this kind of steel. In foreign standards, materials with high strength and good elongation are also described. For example, HSLA (low alloy high strength) is used to add strengthening alloying elements during steelmaking, but due to high strength, there is a limit to increasing the reduction rate during rolling in steel mills, so the thinner color-coated sheet as a maintenance structure is used. HSLA grades are rarely used (another disadvantage is their high cost).
According to Baosteel's years of experience in using steel grades, the guarantee of the final product shape of color-coated steel plates is closely related to the strength grade of the steel plate, the shape of the profiled steel plate and the processing machine.
In general, the more processing passes, the better the shape of the board, and the slower the processing speed, the better the shape of the board. For the profiled steel plate, the shape of the shallow wave plate is better than that of the high wave plate. For the strength of the steel sheet, the tendency of the shape to be deteriorated after the strength processing is more obvious. Another reason for the relatively poor shape of high-strength steel is that many color coating manufacturers only rely on reducing the annealing temperature of hot-dip galvanizing to increase the yield strength of the material, which will lead to unbalanced mechanical properties in the width direction of the steel plate. This imbalance is caused by the uneven temperature of the strip across the width, and the temperature drop may cause the temperature in some parts to be lower than the annealing temperature for recrystallization of the steel sheet.
Post time: Jun-28-2022