Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Toshiharu Abe

Yuji Arai

Shigeru Nakamura

Kunio Kondo

Tomohiko Omura

Keiichi Nakamura

Keiichi Kondo

Kaori Kawano

Hideki Takabe

Masakatsu Ueda

Taro Ohe

Tomoki Mori

Shigeru Kidani

Yuichi Yano

Koichi Ikeda

Kuniaki Tomomatsu

A method for suppressing shock and storage cracking when manufacturing seamless steel pipes comprises hot piercing and hot rolling a billet consisting of, by mass percent controlled amounts of C, Si, Mn, Cr, Mo, Ti, and Al, with the balance being Fe and impurities of Ni, P, S, N, and O also in controlled amounts. Further heat treatment is performed, wherein a hot rolled steel pipe is direct quenched from a temperature of not lower than the Artransformation point and the pipe is then subjected to heat treatment at a temperature of not lower than 450&#xb0; C. and not higher than the Actransformation point in heat treatment equipment for performing direct quenching. The steel pipe subjected to the heat treatment is reheated, quenched from a temperature of not lower than the Actransformation point, and tempered at a temperature of not higher than the Actransformation point.

Method for manufacturing seamless pipes

An oil country tubular good for expansion according to the invention is expanded in a well. The oil country tubular good for expansion has a composition containing, in percentage by mass, 0.05% to 0.08% C, at most 0.50% Si, 0.80% to 1.30% Mn, at most 0.030% P, at most 0.020% S, 0.08% to 0.50% Cr, at most 0.01% N, 0.005% to 0.06% Al, at most 0.05% Ti, at most 0.50% Cu, and at most 0.50% Ni, and the balance consisting of Fe and impurities, and a structure having a ferrite ratio of at least 80%. The oil country tubular good for expansion has a yield strength in the range from 276 MPa to 379 MPa and a uniform elongation of at least 16%. Therefore, the oil country tubular good according to the invention has a high pipe expansion characteristic.

Oil country tubular good for expansion in well and manufacturing method thereof

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.[Mo]&#x2266;exp(5)+5&#x2003;&#x2003;(a)

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

Method for manufacturing high chromium system seamless steel pipe

Growing community of inventors

Osaka, Japan

Toshiharu Abe