| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material for high temperature carburizing in which the generation in the coarsening of grains can be suppressed even in the case of being carburized at a high temperature exceeding 1,000°C, and which has excellent machinability as well. SOLUTION: The steel material for high temperature carburizing has a composition comprising, by mass, 0.10 to 0.30% C, 0.030 to 0.060% Nb, 0.0010 to 0.0030% Ti, 0.005 to 0.015% V,≤0.060% Al and 0.0185 to 0.0300% N, and, regarding carbonitride and nitride in the steel material before carburizing treatment, the total of the precipitation amounts of compound carbonitrides [NbTi(CN)], [NbV(CN)] and [NbTiV(CN)] is 0.010 to 0.040% by mass%, also, the precipitation amount of AlN satisfies≤0.015% by mass%, further, the number of the compound carbonitrides with the diameter of >20 to 80 nm is≥500 pieces/1000μm<SP>2</SP>in total, and the structure of the matrix is composed of a ferrite-pearlite structure or a ferrite-pearlite-bainite structure in which the ratio of bainite is≤15%. COPYRIGHT: (C)2008,JPO&INPIT
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