What are common surface defects in cold-rolled steel?

What is cold-rolled steel?
Cold-rolled steel is produced by rolling hot-rolled steel at room temperature. It features excellent surface quality, high dimensional accuracy, and superior mechanical properties. It is widely used in the automotive, home appliance, and machinery manufacturing industries.
Why does work hardening occur in cold-rolled steel?
After cold rolling, the grains of steel strip are flattened, elongated, the crystal lattice is distorted, and the grains are broken, resulting in a decrease in the metal's plasticity and an increase in its strength and hardness. This phenomenon is called work hardening.
How can work hardening in cold-rolled steel be eliminated?
Most steel strips must undergo recrystallization annealing during processing to eliminate work hardening and restore the metal's plasticity and toughness.
What are common surface defects in cold-rolled steel?
Common surface defects include scratches, indentations, wrinkles, black spots, rust, and pits.
What causes scratches on the surface of cold-rolled steel?
They are usually caused by improper contact between mechanical components during material preparation or rolling, such as tiny particles or impurities on the roller surface or jamming of conveyor equipment. What causes and solutions for wrinkles in cold-rolled steel?
Wrinkles are caused by uneven stress distribution during the cold rolling process. The main causes are uneven material thickness, improper tension control, or excessive rolling reduction. These can be addressed by optimizing rolling process parameters, properly selecting rolling speed, tension, and thickness reduction, and using high-precision thickness measurement equipment.
What are the shape defects of cold-rolled steel?
Common shape defects include warping, distortion, wavy edges, and uneven edges.