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Title:
HIGH STRENGTH FORGED STEEL AND LARGE FORGED COMPONENT
Document Type and Number:
WIPO Patent Application WO/2017/126239
Kind Code:
A1
Abstract:
The present invention relates to high strength forged steel used in manufacturing large forged products. Said high strength forged steel is characterized in: having a composition with prescribed chemical elements in prescribed contents, the balance being Fe and unavoidable impurities; the metal structure mainly comprising bainite, martensite or a combined structure thereof; the average crystal grain diameter of the steel structure from a superficial position of 5 mm depth from the surface to an intermediate position at ¼ thickness being 50 µm or less; and in the crystal grain diameter distribution, the difference between the peak value for crystal grain diameter at the superficial position and the peak value for the crystal grain diameter at the intermediate position being 10 µm to 30 µm. Moreover, it is preferable that for the high strength forged steel, the total index when measured using the K0 method of DIN 50602-1985, which is a non-metallic inclusion assessment method, is not more than 10.

Inventors:
TAKAOKA, Hiroyuki
Application Number:
JP2016/085923
Publication Date:
July 27, 2017
Filing Date:
December 02, 2016
Export Citation:
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Assignee:
KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) (2-4 Wakinohama-Kaigandori 2-chome, Chuo-ku Kobe-sh, Hyogo 85, 〒6518585, JP)
International Classes:
C22C38/00; B21J5/00; C22C38/46; C21D8/06; C21D9/28; C21D9/30; F16C3/06
Foreign References:
JP2010082662A2010-04-15
JP2005344149A2005-12-15
JP2010242119A2010-10-28
Other References:
TOMOYA SHINOZAKI ET AL.: "New approach for higher output of 4-cycle diesel engines: improving fatigue strength of solid-type crankshafts", KOBE STEEL ENGINEERING REPORTS, vol. 59, no. 1, 2009, pages 94 - 97
Attorney, Agent or Firm:
KOTANI, Etsuji et al. (Osaka Nakanoshima Building 2nd Floor, 2-2 Nakanoshima 2-chome, Kita-ku, Osaka-sh, Osaka 05, 〒5300005, JP)
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