The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 18, 2001
Filed:
Feb. 26, 1999
Takaaki Toyooka, Aichi, JP;
Akira Yorifuji, Aichi, JP;
Masanori Nishimori, Aichi, JP;
Motoaki Itadani, Aichi, JP;
Yuji Hashimoto, Aichi, JP;
Takatoshi Okabe, Aichi, JP;
Taro Kanayama, Aichi, JP;
Masahiko Morita, Okayama, JP;
Saiji Matsuoka, Okayama, JP;
Nobuki Tanaka, Aichi, JP;
Osamu Furukimi, Chiba, JP;
Takaaki Hira, Chiba, JP;
Kawasaki Steel Corporation, Hyogo, JP;
Abstract
A steel pipe containing fine ferrite crystal grains, which has excellent toughness and ductility and good ductility-strength balance as well as superior collision impact resistance, and a method for producing the same are provided. A steel pipe containing super-fine crystal grains can be produced by heating a base steel pipe having ferrite grains with an average crystal diameter of di (&mgr;m), in which C, Si, Mn and Al are limited within proper ranges, and if necessary, Cu, Ni, Cr and Mo, or Nb, Ti, V, B, etc. are further added, at not higher than the Ac,transformation point, and applying reducing at an average rolling temperature of &thgr;m (°C.) and a total reduction ration Tred (%) within s temperature range of from 400 to Ac,transformation point, with di, &thgr;m and Tred being in a relation satisfying a prescribed equation.