Jfe Steel Corporation

Yasue Koyama

Yoshikazu Kawabata

Motoaki Itadani

Takaaki Toyooka

Kei Sakata

Yasuhide Ishiguro

Takatoshi Okabe

Akira Yorifuji

Masatoshi Aratani

Masanori Nishimori

Masayuki Sakaguchi

Masayoshi Ishida

A steel pipe blank having a composition containing 0.5% or less C and 85% or more Fe in terms of mass percent is heated, and stretch-reducing is then performed so that the diameter decrease ratio is 15% or more and the rolling finishing temperature is (the Artransformation point&#x2212;10)&#xb0; C. or lower. Consequently, a structure in which the ratio of X-ray diffraction intensity obtained from the plane in which the &#x3c;100&#x3e; direction of crystal grains is preferentially oriented parallel to the circumference direction and the &#x3c;011&#x3e; direction of crystal grains is preferentially oriented parallel to the rolling direction of the steel pipe to that obtained for a three-dimensionally randomly oriented sample is 3.0 or more is formed, and the r-value is increased, thereby improving the magnetic properties of the steel pipe.

Steel pipe with good magnetic properties and method of producing the same

The invention provides a high-carbon steel pipe having superior cold workability and induction hardenability, and a method of producing the steel pipe. The method comprises the steps of heating or soaking a base steel pipe having a composition containing C: 0.3 to 0.8%, Si: not more than 2%, and Mn: not more than 3%, and then carrying out reducing rolling on the base steel pipe at least in the temperature range of (Ac , transformation point &minus;50&deg; C.) to Ac , transformation point with an accumulated reduction in diameter of not less than 30%. A structure in which the grain size of cementite is not greater than 1.0 &mgr;m is obtained, thus resulting in improved cold workability and induction hardenability.

High carbon steel pipe excellent in cold formability and high frequency hardenability and method for producing the same

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Chiyoda-ku, Japan

Yasue Koyama