1.What is the core logic behind classifying the hardness grades of cold-rolled coils?
The more thorough the annealing, the softer the material (suitable for deep drawing); the greater the cold rolling deformation or the absence of annealing, the higher the hardness (suitable for simple bending or structural parts).
2.How are standards categorized in China's metallurgical industry?
Extra soft: Used for particularly complex deep drawing processes.
Soft: Used for deep stamping
Semi-soft: Used for general stamping
Low hardness: Used for general machining
Cold-hardened: without annealing, extremely hard, only suitable for simple bending.
3.How were stamping performance classified according to the old Chinese national standard?
Z-grade (Deepest Drawing): Softest, highest elongation.
S-grade (Deep Drawing): Medium.
P-grade (General Drawing): Relatively hard.
4.How to confirm the standard?
Check the quality certificate or grade suffix of the cold-rolled coil you have. If it is SPCC-1, it means fully hard; SPCC-8 means 1/8 hard; SPCC-A means annealed soft material.
5.How to test thin plates?
If the sheet thickness is less than 1.5mm, it is not recommended to directly measure HRB (as the anvil effect can easily lead to inflated values). Instead, surface Rockwell hardness (HR15T/HR30T) or Vickers hardness (HV) should be used for acceptance testing.