ASTM A302/A302M specification covers manganese-molybdenum and manganese-molybdenum-nickel alloy steel plates intended particularly for welded boilers and other pressure vessels. According to their strength levels, the plates are available in four grades: Grades A, B, C, and D. The maximum thickness of plates is limited only by the capacity of the chemical composition to meet the specified mechanical property requirements. The steel shall be killed and shall conform to fine grain size requirements. The plates shall be subjected to tension test to determine the tensile strength, yield strength, and elongation.ASTM A302/A302M standard main steel grade:ASTM A302/A302M ASTM A302 Grade A,B,C,D(A302GRA,B,C,D).