| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength steel for a machine structure, which is used as a base material for a bar-type machine component that is required to have a deeply carbonized surface and excellent workability, such as a pulley for CVT, shows excellent hardenability while minimizing an amount of an expensive element to be added for improving the hardenability, such as Cr, Mo and Ni, and has the excellent workability before being heat-treated. SOLUTION: The high-strength steel for the machine structure superior in hardenability includes specified contents of C, Si and Mn; and further at least one element selected from the group consisting of Nb, Ti, Zr, Ta and Hf in such an amount as to satisfy the following expression (1): SC≥1.0×10<SP>-4</SP>, wherein SC=SA+SB in case of SB>0.0 and SC=SA in case of SB≤0.0, wherein SA represents "[Nb ]/92.9", namely, a value obtained by dividing the content (mass%) of Nb in the steel by its atomic weight; and SB represents "[Ti]/47.9+[Zr]/91.2+[Ta]/181+[Hf]/178-[N]/14", namely, a value obtained by subtracting a value obtained by dividing a nitrogen content (mass%) by the atomic weight of N from the total sum of values obtained by dividing respective contents (mass%) of Ti, Zr, Ta and Hf in the steel by the respective atomic weights. COPYRIGHT: (C)2007,JPO&INPIT
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