Machine Structural Steel Material Having Low Heat-Treatment Deformation

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.

1 . A machine structural steel material with small heat treatment deformation, the steel material being 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: more than 0% and 0.30% or less;   Al: 0.008 to 0.300%;   O: 0.0030% or less;   N: 0.0020 to 0.0300%; and   the balance Fe and unavoidable impurities,   wherein the steel material comprising the steel has a martensitic transformation start temperature (Ms point) of 460° C. or less;   a value of (J9/J1.5) calculated by following equation (1) using hardness J1.5 at a distance of 1.5 mm and hardness J9 at a distance of 9 mm from a quenched end of the steel material, as measured by Jominy end quenching method for the steel material, is in a range of from 0.70 to 0.85; and   a value of (J11/J1.5) calculated by following equation (2) using hardness J1.5 at a distance of 1.5 mm and hardness J11 at a distance of 11 mm is in a range of from 0.67 to 0.78:
   ( J 9 /J 1.5)=(hardness at distance of 9 mm from a quenched end, as measured by Jominy end quenching method)/(hardness at distance of 1.5 mm from a quenched end, as measured by Jominy end quenching method)  Equation (1); and
 
   ( J 11 /J 1.5)=(hardness at distance of 11 mm from a quenched end, as measured by Jominy end quenching method)/(hardness at distance of 1.5 mm from a quenched end, as measured by Jominy end quenching method)  Equation (2).
 
   
     
     
         2 . The machine structural steel material according to  claim 1 , wherein the steel material further comprises, in mass %,
 one or two of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.50%.   
     
     
         3 . The machine structural steel material according to  claim 1 , wherein the steel material further comprises, in mass %,
 one or two of Ti: 0.020 to 0.200% and Nb: 0.02 to 0.20%.   
     
     
         4 . The machine structural steel material according to  claim 1 , wherein the steel material further comprises, in mass %,
 one or two of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.50%, and   one or two of Ti: 0.020 to 0.200% and Nb: 0.02 to 0.20%.