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Abstract

There is provided a steel material with small heat treatment deformation, comprising a machine structural steel used for components for power transmission, such as gears and shafts used in automobiles, industrial machines, and the like. In the steel material, the Ms point of the steel material comprising a machine structural steel, comprising in mass %: C: 0.20 to 0.30%; Si: 0.10 to 1.50%; Mn: 0.10 to 1.20%; P: 0.030% or less; S: 0.030% or less; Cr: 1.30 to 2.50%; Cu: 0.30% or less; Al: 0.008 to 0.300%; O: 0.0030% or less; and N: 0.0020 to 0.0300%; and the balance Fe and unavoidable impurities, is 460° C. or less; a ratio (J9/J1.5) of hardness J9 at a distance of 9 mm from the quenched end of the steel material to hardness J1.5 at a distance of 1.5 mm from the quenched end of the steel material, as measured by Jominy end quenching method, is in a range of from 0.70 to 0.85; and a ratio (J11/J1.5) of hardness J11 at a distance of 11 mm from the quenched end of the steel material to hardness J1.5 is in a range of from 0.67 to 0.78.

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