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Title:
WORKPIECE MADE OF HIGH STRENGTH STEEL HAVING EXCELLENT NOTCH FATIGUE STRENGTH, AND METHOD FOR PRODUCING THE SAME
Document Type and Number:
Japanese Patent JP2011084813
Kind Code:
A
Abstract:

To provide a workpiece made of a high strength steel which is composed of a low alloy TRIP type annealed martensitic steel (TAM steel) having high hardenability and high notch fatigue strength by controlling the componential addition of the chemical composition and heat treatment conditions without depending on forging temperature, forging ratio or the like.

The workpiece has a composition comprising 0.1 to 0.7% C, ≤2.5% Si, 0.5 to 2% Mn, ≤1.5% Al, one or more kinds selected from Nb, Ti and V by 0.01 to 0.3% in total, ≤2.0% Cr, ≤0.5% Mo, ≤1.0% Ni, Cr, and Mo and Ni by ≤2.0% in total and ≤0.005% B, and in which the concentration of carbon in retained austenite is 0.7 to 1.5 mass%, and a value(Ceq*) obtained by removing the C content from carbon equivalent (Ceq) is 0.3 to <0.6%, and the balance Fe with inevitable impurities: the value(Ceq*) is Ceq*=Ceq-C=Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14.


Inventors:
SUGIMOTO KOICHI
FUJI DAIKI
YOSHIKAWA NOBUO
TAKAHASHI TERUHISA
ARAI GORO
Application Number:
JP2010206956A
Publication Date:
April 28, 2011
Filing Date:
September 15, 2010
Export Citation:
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Assignee:
USUI KOKUSAI SANGYO KK
UNIV SHINSHU
NOMURA UNISON CO LTD
International Classes:
C22C38/00; B21J5/00; B23P13/00; C21D8/00; C21D9/08; C22C38/58; F02M55/02
Domestic Patent References:
JP2005336526A2005-12-08
JP2007070660A2007-03-22
JP2002129285A2002-05-09
JP2007231353A2007-09-13
Attorney, Agent or Firm:
Yoshitaka Oshida