The high quality PPGI corrugated roofing sheet is mainly used in construction, home appliances, automobiles, machinery, electronics, manufacturing, and light industry. Common steel grades for galvanized sheets are: general commodity coil (CQ), structural galvanized sheet (HSLA), stamped galvanized sheet (DQ) deep-drawn hot-dip galvanized sheet (DDQ), bake-hardened hot-dip galvanized sheet ( BH), duplex steel (DP), TRIP steel (phase change induced plastic steel). There are usually two ways to cool galvanized sheets: air-cooled and water-cooled. 1. The galvanized sheet is immersed in a molten zinc bath to adhere a thin layer of zinc to the surface. It is mainly produced by the continuous galvanizing process, that is, the coiled steel plate is continuously immersed in a zinc-plated plating tank to form a galvanized steel sheet; the alloyed galvanized sheet. This steel sheet is also produced by hot dip, but immediately after it is discharged, it is heated to about 500 ° C to form an alloy coating of zinc and iron. This galvanized sheet has good adhesion and weldability of the coating. 2. Galvanized sheets can be divided into two types: in-line annealing and off-line annealing according to different annealing methods, and they are called the protective gas method and flux method.