WORKPIECE MADE OF HIGH STRENGTH STEEL HAVING EXCELLENT NOTCH FATIGUE STRENGTH, AND METHOD FOR PRODUCING THE SAME

• Main Authors: FUJI DAIKI, YOSHIKAWA NOBUO, TAKAHASHI TERUHISA, ARAI GORO, SUGIMOTO KOICHI
• Format: Patent
• Language: English
• Published: 28.04.2011
• Subjects: ALLOYS; BLASTING; CHEMISTRY; COMBINED OPERATIONS; COMBUSTION ENGINES; FERROUS OR NON-FERROUS ALLOYS; FORGE FURNACES; FORGING; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; HAMMERING; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MACHINE TOOLS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; MECHANICAL ENGINEERING; MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVINGMATERIAL; METAL-WORKING NOT OTHERWISE PROVIDED FOR; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; OTHER WORKING OF METAL; PERFORMING OPERATIONS; PRESSING METAL; PUNCHING METAL; RIVETING; SUPPLYING COMBUSTION ENGINES IN GENERAL, WITH COMBUSTIBLEMIXTURES OR CONSTITUENTS THEREOF; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS; UNIVERSAL MACHINE TOOLS; WEAPONS

PROBLEM TO BE SOLVED: 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. SOLUTION: 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. COPYRIGHT: (C)2011,JPO&INPIT