High toughness steel material and method of producing steel pipes using same

摘要

A steel material and a steel pipe made by using the same are provided which are to be used in severe oil well environments. Such a highly tough oil well steel pipe can be produced by rolling the base material, quenching the rolling product from the austenite region and tempering the same so that the relationship between the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries and the austenite grain size (according to ASTM E 112) can be defined by the formula (a) given below. In this manner, steel pipes suited for use even under oil well environments becoming more and more severe can be produced while satisfying the requirements that the cost should be rationalized, the productivity improved and energy saved. <?in-line-formulae description="In-line Formulae" end="lead"?>[Mo]<=EXP(G-5)+5 (a)<?in-line-formulae description="In-line Formulae" end="tail"?>