DEVICE ARRAY FOR MANUFACTURING SEAMLESS STEEL PIPE OR TUBE AND MANUFACTURING METHOD FOR DUPLEX STAINLESS STEEL SEAMLESS PIPE OR TUBE USING SAME

摘要

Provided are a device array for manufacturing a seamless steel pipe or tube and a method for manufacturing a high-strength duplex stainless steel seamless pipe or tube for oil wells with superior low-temperature toughness. The device array for manufacturing a seamless steel pipe or tube, which has provided therein a heating device for heating steel material, a piercing and rolling device for forming hollow material by performing piercing and rolling of the steel material that has been heated, and a rolling device for forming a seamless steel pipe or tube of a prescribed shape by performing processing on the hollow material, has a cooling device provided on the output side of the rolling device. This device array is used to perform piercing and rolling on heated steel material having a stainless steel composition and then perform processing on the same with the rolling device, after which, when the surface temperature of the hollow piece before cooling with the cooling device is treated as a cooling initiation temperature, cooling is carried out to a cooling stop temperature of 600°C or greater with a temperature difference of at least 50°C from the cooling initiation temperature at an average cooling rate of 1.0°C/s or greater by outside surface temperature.