What are the quality requirements for the surface of No. 20 steel

The surface quality requirements of No. 20 steel:
1. The No. 20 steel plate shall not have visually visible delamination, and the surface of the steel plate shall not have defects such as cracks, bubbles, folds, inclusions, scars, and pressed oxide scales that are harmful to use.

2. The No. 20 steel plate is not allowed to have thin iron oxide scale or rust that hinders the inspection of surface defects, and pitting, concave surface, scratches and other local defects whose unevenness is not more than half of the thickness tolerance of the steel plate, and the minimum thickness of the steel plate should be guaranteed.

3. Local defects on the surface of the No. 20 steel plate are allowed to be cleaned up, and the cleaned area should be smooth and without edges and corners, and the minimum thickness of the steel plate should be guaranteed.

4. Flame cutting is allowed for No. 20 steel plates with a thickness greater than 30mm, but steel plates that require heat treatment should be carried out flame cutting before heat treatment.