HOT-WORKED STEEL PRODUCT FOR SURFACE HARDENING

• Main Authors: USUI YUSUKE, OFUJI YOSHIHIRO
• Format: Patent
• Language: English
• Published: 23.08.2012
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

PROBLEM TO BE SOLVED: To provide hot-worked steel products for surface hardening, capable of suppressing coarsening of austenitic grains generated in carburizing or carbo-nitriding and having an excellent cold forgeability, thereby capable of eliminating softening/annealing.SOLUTION: The hot-worked steel products for surface hardening has a chemical composition including 0.10-0.30% of C, 0.50% or less of Si, 0.15-1.5% of Mn, 0.04% or less of P, 0.005-0.07% of S, 0.7-3.0% of Cr, 0.01-0.05% of Al, 0.007-0.030% of N, 0.02-0.07% of Nb, and 0.00004% or less of H, with the remainder being Fe and unavoidable impurities. The proportion of Nb deposited as Nb(C, N) of Nb in steel is 85% or more, a number density of Nb(C, N) having a diameter of 100 nm or more is 5 pieces/100 μmor less, and a standard deviation of ferrite grain sizes is 0.15 or less. The hot-worked steel products for surface hardening may include one or more of 0.50% or less of Mo, 0.20% or less of V and 0.50% or less of Ti, in place of a part of Fe.