What is the production process of SPCC cold-rolled coil?
A: The typical process is: hot-rolled raw material coil → pickling (removing oxide scale) → cold rolling (multi-pass rolling) → annealing (eliminating work hardening) → leveling (adjusting sheet shape and surface finish) → finishing (slitting and packaging) → finished product.
What impact does the annealing process have on the performance of SPCC cold-rolled coil?
A: Annealing is a key process in SPCC production, its purpose being to eliminate work hardening caused by cold rolling and restore plasticity. Insufficient annealing temperature will lead to excessively high steel hardness and stamping cracks; excessively high annealing temperature will result in coarse grains, reducing strength and surface finish.
What are the surface defects of SPCC cold-rolled coil? What are the common causes?
A: Common defects and their causes:
Scratches: Impurities or burrs on the surface of the rolling rolls and guide rolls, or caused by friction during winding;
Pockmarks: Oxide scale on the surface of the hot-rolled raw material was not properly pickled, or the surface of the cold-rolling rolls is rough;
Waviness: Uneven distribution of rolling force, or uneven temperature during annealing leading to poor sheet shape;
Rust spots: Humid storage environment for finished products, or uneven application of rust-preventive oil.
What is the thickness tolerance standard for SPCC cold-rolled coils?
A: According to JIS G 3141 standard, the thickness tolerance varies depending on the thickness range. For example:
Thickness ≤ 1.0mm, tolerance is ±0.05mm;
Thickness 1.0~2.0mm, tolerance is ±0.07mm;
Specific tolerance grades (e.g., ordinary grade, precision grade) should be referred to the order agreement.
How to determine if the surface quality of SPCC cold-rolled coils is acceptable? A: The following requirements must be met: the surface must be free of obvious scratches, pits, rust spots, peeling, and other defects; the surface finish must meet the agreed standard (e.g., Ra≤1.6μm); and visual inspection or surface roughness tester testing must be performed according to the standard.