| 摘要 |
Disclosed is a method for producing a seamless steel pipe, comprising subjecting a billet having a component composition of, in terms of mass%, C (0.15 to 0.35%), Si (0.05 to 0.5%), Mn (0.1 to 1.5%), Cr (0.2 to 1.5%), Mo (0.1 to 1.5%), Ti (0.005 to 0.50%), Al (0.001 to 0.50%), and as the remainder, Fe and impurities in which the content of Ni is 0.1% or less, the content of P is 0.04% or less, the content of S is 0.01% or less, the content of N is 0.01% or less, and the content of O is 0.01% or less to hot-piercing and hot-rolling, and further performing a heating treatment, wherein direct quenching is performed from when the temperature of a steel pipe after hot-rolling is not lower than an Artransformation point and thereafter the heating treatment is performed at a temperature of 450°C or higher but not higher than an Actransformation point in heating treatment equipment provided in connection with a quenching device which performs the direct quenching, further the steel pipe having been subjected to the heating treatment is heated again, and quenching is performed from a temperature not lower than an Actransformation point, and then tempering is performed at a temperature not higher than the Actransformation point. The method does not have a bad effect on the performance of the product and can prevent the occurrence of delayed fracture such as shock cracking or season cracking. |
