Galvalume plate/coil is widely used in building materials, home appliances, automobiles, environment, machinery, ships and many other fields of an alloy coated steel plate/coil. Galvalume plate/coil is a kind of alloy coated steel plate/coil which is covered with aluminium-zinc alloy on the surface of the steel plate, and is composed of 55% aluminum, 43.4% zinc and 1.6% silicon solidified at 600℃. The whole structure is composed of aluminium-iron-Silica-zinc, forming a dense four-element junction crystal.