METHOD FOR PRODUCING SEAMLESS TUBE

WIPO Patent Application WO/2006/106802

A1

A method for producing a seamless tube while reducing the inner surface scratches comprising a piercing step, in which the relations shown by expressions (1)-(3) are simultaneously satisfied if the diameter of a billet is R(m), the crack length in the axially central portion of the billet is r(m), and two times of the amount of rotation of the billet during the time from when the billet touches a rolling roll until the billet reaches a boring plug is N. 0≤r/R≤0.13...(1), r/R≥-0.13N+0.13...(2), r/R≤-0.065N+0.39...(3). Even if a cast piece of wide ferrite temperature range is used, poor piercing and inner surface scratches of the tube are prevented from occurring and a high-quality seamless tube can be produced inexpensively.

Sasaki, Kenichi c/o Sumitomo Metal Industries Ltd. (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 54100, JP)
Murao, Nobutoshi c/o Sumitomo Metal Industries Ltd. (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 54100, JP)

PCT/JP2006/306619

October 12, 2006

March 30, 2006

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SUMITOMO METAL INDUSTRIES, LTD. (5-33, Kitahama 4-chome Chuo-ku, Osaka-sh, Osaka 41, 54100, JP)
Sasaki, Kenichi c/o Sumitomo Metal Industries Ltd. (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 54100, JP)
Murao, Nobutoshi c/o Sumitomo Metal Industries Ltd. (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 54100, JP)

B21B19/04; C22C38/00; C22C38/58; B21B19/00; C22C38/00; C22C38/58

Mori, Michio (M. MORI PATENT OFFICE, Amagasaki Building 17-23,Higashinaniwa-cho 5-chome, Amagasaki-sh, Hyogo 92, 66008, JP)

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