This standard specifies the ordering content, size, shape, weight and allowable deviations, technical requirements, test methods, inspection rules, packaging, marking and quality certificates for hot-rolled and forged seamless steel round tube blanks for high pressure. This standard is applicable to hot-rolled round tube blanks with a nominal diameter of 50mm to 400mm and forged round tube blanks with a nominal diameter of 60mm to 1000mm for the manufacture of high-pressure seamless steel pipes. Steel ingots for direct pipe making can also refer to this standard.