| 摘要 |
PROBLEM TO BE SOLVED: To provide NiCrMoV steel (for refining) exhibiting high strength and high toughness even without using carbide forming elements such as Nb and ta, and to provide a cast forged steel member using the NiCrMoV steel. SOLUTION: In NiCrMoV steel for refining, it is mainly formed of a bainitic structure in which the number of acicular cementite of >=1μm length is controlled to <=0.15 pieces/μm2 on the average in the observed field. This NiCrMoV steel for refining is subjected to quenching in which heating is executed at 800 to 1000 deg.C for at least one time or quenching and normalizing for at least one time, respectively, and tempering in which holding is executed at 500 to 700 deg.C for 3 to 60 hr for at least one time, by which NiCrMoV steel exhibiting high strength and high toughness can be obtd. The NiCrMoV steel obtd. in this way is suitable as the material for a large cast forged steel member.
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