Hot-rolled coil is made of slab as raw material, and after heating, it is made into strip steel by rough rolling mill and finishing mill. The hot steel strip from the last rolling mill of finishing rolling is cooled to the set temperature by laminar flow, and then coiled into steel coil by the coiler. The cooled steel coil will undergo different finishing operations according to the different needs of users. Line processing becomes steel plate, flat coil and slit steel strip products.