Method for making high-strength high-toughness martensitic stainless steel seamless pipe

摘要

A method of producing a high-strength high-toughness martensitic stainless steel seamless pipe which includes heating a martensitic stainless steel raw material to an austenitic range and subjecting the raw material to piercing and elongating to form an original pipe. The original pipe is cooled to form a structure substantially composed of martensite in the original pipe. The original pipe is reheated to a temperature in the dual-phase range between the Ac1 transformation point and the Ac3 transformation point, and is subjected to finishing rolling at an initial rolling temperature T ( DEG C) between the Ac1 transformation point and the Ac3 transformation point. The original pipe is then cooled to form a processed pipe. The processed pipe is tempered at a temperature below the Ac1 transformation point. The reduction in area R in the finishing rolling step may be in the range of 10% to 90%, and the initial rolling temperature T and the reduction in area R may satisfy the relationship: 800 ≤ T - 0.625R ≤ 850.