| 摘要 |
<p>A steel for heat treatment, which exhibits high strength and high toughness even when the heat treatment (such as quenching and tempering) of the steel is conducted under conventional conditions in an after stage. The steel for heat treatment contains C: 0.10 to 0.70mass%, Mn: 0.1 to 3.0mass%, Al: 0.005 to 2.0mass%, P: 0.050mass% or less, S: 0.50mass% or less, O: 0.0030mass% or less, N: 0.0200mass% or less, and one or more selected from the group consisting of Ti: 0.30mass% or less and Nb: 0.30mass% or less with the balance being Fe and unavoidable impurities, and has a TH value of 1.0 or above as calculated according to the formula: ({Ti}/48 + {Nb}/93) × 104 and grain diameters of 10µm or below. {Ti} and {Nb} refer respectively to the contents of Ti and Nb in precipitates of 5 to 100nm in size as determined about their respective extraction residues.</p> |
