The process of producing hot rolled strip with thickness of 1.2 ~ 8mm in hot strip mill. Strip steel width under 600mm is called strip steel; Over 600mm is called wide strip steel. The first strip hot rolling mill was put into operation in the United States in 1905, producing strip with width of 200mm. The technical and economic indexes of hot strip mill are superior and develop rapidly. In the industrial developed countries, the output of hot rolled wide strip steel before 1950 accounted for about 25 percent of the total steel production, which reached about 50 percent in the 1970s. The raw material of hot rolled strip is continuous casting slab or initial rolling slab with a thickness of 130 ~ 300mm. After the slab is heated in the heating furnace, it is sent to the rolling mill to form strips of 1.00 ~ 25.4mm thick and rolled into steel coils. Rolled steel is ordinary carbon steel, low alloy steel, stainless steel and silicon steel. It is mainly used as raw material for cold-rolled strip steel, welded pipe, cold bend and welded section steel. Or used for making various structural parts, containers, etc.