PROCESS FOR MANUFACTURING MARTENSITE STAINLESS STEEL PIPE

摘要

A process for efficiently manufacturing a martensite stainless steel pipe through shortening of the time required for cooling for quenching in the heat treatment operation. The process for manufacturing a martensite stainless steel pipe involves a heat treatment operation including the heating step of heating a steel pipe until its external surface temperature reaches a given temperature from (transformation point A3 + 20°C) to 980°C; the first cooling step of cooling the heated steel pipe with water until its external surface temperature reaches a given temperature of 350°C or higher; the second cooling step of cooling the water-cooled steel pipe with air until its external surface temperature reaches a given temperature of 250°C or below; and the third cooling step of cooling the air-cooled steel pipe with water or air until its external surface temperature reaches an ordinary temperature. The process is characterized in that the rate of cooling of steel pipe in the first cooling step is determined in accordance with the wall thickness of the steel pipe so that the external surface temperature recuperative heat quantity of the steel pipe in the second cooling step is 50°C or below.