Steel Material for Machine Structural Use Reduced in Thermal Deformation

Abstract

Disclosed is 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. The steel material comprises in mass %: C: 0.16 to 0.35%; Si: 0.10 to 1.50%; Mn: 0.10 to 1.20%; P: 0 to 0.030%; S: 0 to 0.030%; Cr: 1.3 to 2.5%; Cu: 0 to 0.30%; Al: 0.008 to 0.800%; O: 0 to 0.0030%; N: 0.0020 to 0.0300%; Ni: 0 to 3.00%; Mo: 0 to 0.50%; Ti: 0 to 0.200%; Nb: 0 to 0.20%; and the balance Fe and unavoidable impurities.

1 . A machine structural steel material with small heat treatment deformation, the steel material comprising in mass %:
 C: 0.16 to 0.35%;   Si: 0.10 to 1.50%;   Mn: 0.10 to 1.20%;   P: 0 to 0.030%;   S: 0 to 0.030%;   Cr: 1.30 to 2.50%;   Cu: 0 to 0.30%;   Al: 0.008 to 0.800%;   O: 0 to 0.0030%;   N: 0.0020 to 0.0300%;   Ni: 0 to 3.00%;   Mo: 0 to 0.50%;   Ti: 0 to 0.200%;   Nb: 0 to 0.20%; and   the balance Fe and unavoidable impurities,   wherein the steel material has a martensitic transformation start temperature (Ms point) of 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 is in a range of from 0.68 to 0.97, as measured by a Jominy end quenching method; 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 at a distance of 1.5 mm from the quenched end of the steel material is in a range of from 0.63 to 0.94.   
     
     
         2 . The machine structural steel material according to  claim 1 , wherein the steel material consists of in mass %: C: 0.16 to 0.35%; Si: 0.10 to 1.50%; Mn: 0.10 to 1.20%; P: 0 to 0.030%; S: 0 to 0.030%; Cr: 1.30 to 2.50%; Cu: 0 to 0.30%; Al: 0.008 to 0.800%; O: 0 to 0.0030%; N: 0.0020 to 0.0300%; Ni: 0 to 3.00%; Mo: 0 to 0.50%; Ti: 0 to 0.200%; Nb: 0 to 0.20%; and the balance Fe and unavoidable impurities. 
     
     
         3 . The machine structural steel material according to  claim 1 , wherein the steel material is substantially free of Ni, Mo, Ti, and Nb. 
     
     
         4 . The machine structural steel material according to  claim 2 , wherein the steel material is substantially free of Ni, Mo, Ti, and Nb. 
     
     
         5 . The machine structural steel material according to  claim 1 , wherein the steel material comprises, in mass %, one or two of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.50%. 
     
     
         6 . The machine structural steel material according to  claim 2 , wherein the steel material comprises, in mass %, one or two of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.50%. 
     
     
         7 . The machine structural steel material according to  claim 1 , wherein the steel material comprises, in mass %, one or two of Ti: 0.020 to 0.200% and Nb: 0.02 to 0.20%. 
     
     
         8 . The machine structural steel material according to  claim 2 , wherein the steel material comprises, in mass %, one or two of Ti: 0.020 to 0.200% and Nb: 0.02 to 0.20%. 
     
     
         9 . The machine structural steel material according to  claim 1 , wherein the steel material 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%. 
     
     
         10 . The machine structural steel material according to  claim 2 , wherein the steel material 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%.