The roll gap value at both ends of the sickle-shaped hot rolling mill roll is different; the guide ruler feeds the strip plate incorrectly, and the two sides of the strip plate extend differently; the hot rolling mill roll is not preheated well, and the roll shape is incorrect; the emulsion spray is uneven or the nozzle is blocked; The sheet was misaligned during calender rolling.

Usually the thickness of the hot-rolled sheet is 6-8 mm. The minimum thickness is 2.5mm-3.0mm. Due to the large temperature drop during the hot rolling process, it is difficult to continue the hot rolling to a thinner thickness, while the cold rolling easily causes the rolled piece to continue to become thinner.