What causes warping and distortion in cold-rolled steel?
This is often caused by uneven coil tension distribution or uneven cooling during the rolling process. The material edges experience significant differences in force, leading to internal stress accumulation and deformation.
What causes uneven thickness in cold-rolled steel?
This is primarily caused by uneven pressure distribution or roll wear during cold rolling.
What are the causes and solutions for uneven hardness in cold-rolled steel?
Uneven hardness is often caused by inaccurate rolling temperature control, especially during multiple cold rolling and annealing steps, where large temperature gradients lead to variations in grain morphology. This can be addressed by introducing an online temperature monitoring system combined with an automated annealing process.
What is under-pickling?
After pickling, steel strip is left with unwashed scale on the surface. This is called under-pickling. This results in a dark or splotchy surface. In severe cases, the scale is pushed in, forming black spots.
What is over-pickling?
Over-pickling occurs when metal remains in the acid solution for an extended period of time, gradually developing a rough, pitted surface. What causes rust to reappear on the surface of cold-rolled steel after pickling?
A small amount of acid solution remaining on the surface of the strip after pickling, or if it is not completely dried after cleaning, can cause rust on the strip surface.
What is overspeed strip breakage?
During the fourth rolling pass, the coil diameter is small at the start, and the speed increases too quickly, exceeding the coiler's maximum speed, causing strip breakage.