Cold rolling: with hot rolled steel coil as raw material, after pickling to remove the oxide skin for cold continuous rolling, the finished product is rolled hard roll, because of the cold hardening caused by continuous cold deformation of the rolled hard roll strength, hardness, toughness and plastic index decline, so the stamping performance will deteriorate, can only be used for simple deformation parts. Hard roll can be used as raw material in hot dip galvanizing plant because hot dip galvanizing units are equipped with annealing line. Rolled hard coil weight is generally 6~13.5 tons, steel coil at room temperature, hot rolled pickling coil continuous rolling. The inner diameter is 610mm.