The protective gas dew point is too high or the hydrogen content is too low. The pre-washing time is insufficient before heating, residual oxygen exists in the furnace, and the steel coil is annealed in an oxidizing atmosphere.

The band is not bright. The surface of the protective gas cold rolled coil is caused by the oil film rupturing and the steel strip is in direct contact with the work roll.

The protective gas cold rolled coil surface exhibits an irregular or island-like black, brown pattern.

The emulsion is not exhausted at the exit of the rolling mill, and carbonized upon heating to form spots;

Cold rolled crosscut	Plate thickness	Plate width	Processing length	Diagonal tolerance	Dimension precision
0.2-0.6	90-1800	200-6000	±0.5/2000	±0.3/2000	20
0.6-1.0	90-1800	200-6000	±0.5/2000	±0.5/2000	25
1.0-2.0	90-1800	200-6000	±1/2000	±0.8/2000	35
2.0-4.0	150-1800	200-12000	±1/2000	±0.8/2000	35
4.0-6.0	200-2000	400-12000	±1.5/2000	±1.0/2000	35