① For Class A and D ship plates, cleanliness requirements are ≤0.008s, ≤0.015P, Class E requirements are ≤0.005%S, ≤0.010%P, Class F requirements are ≤0.002%S, and ≤0.005%P. For steel plates for naval vessels, to ensure NDT≤-550C, it is required to be ≤0.002%S, ≤0.005%P, ≤40ppmN, ≤10ppmO and ≤1.0ppmH. The refining process is essential.
② Grades A and D can be delivered by hot rolling and controlled rolling. Grades E and F allow normalizing or thermomechanical rolling. It is necessary to distinguish the gap between controlled rolling and thermomechanical rolling. The current standard stipulates that no E-class and F-class ship plates can be produced without heat treatment conditions.
③ The quality requirements of steel also include requirements for shape and dimensional accuracy, requirements for ultrasonic flaw detection and requirements for performance stability.