Steel Material for Machine Structural Use Having Excellent Contact Pressure Fatigue Strength

Abstract

There is provided a steel material with superior surface pressure fatigue strength, comprising a machine structural steel used for power transmission components such as gears and shafts used in automobiles, industrial machines, and the like. The steel material comprises in mass %: C: 0.15 to 0.35%; Si: 0.30 to 0.95%; Mn: 0.10 to 1.00%; P: 0 to 0.030%; S: 0 to 0.030%; Cr: 0.80 to 2.30%; Cu: 0 to 0.30%; Al: 0.008 to 0.500%; O: 0 to 0.0030%; N: 0.0020 to 0.0300%; Ni: 0 to 3.00%; Mo: 0 to 0.29%; Ti: 0 to 0.200%; Nb: 0 to 0.20%; and B: 0 to 0.0050%; and the balance Fe and unavoidable impurities. The steel material has, in mass %, a parameter represented by Si+Cr-2Mn of 1.05 or more and a parameter represented by 0.7Si+2.5Mn+2.0Cr+2.5Ni+4.0Mo of 6.30 or less.

1 . A machine structural steel material with superior surface pressure fatigue strength, the steel material comprising in mass %:
 C: 0.15 to 0.35%;   Si: 0.30 to 0.95%;   Mn: 0.10 to 1.00%;   P: 0 to 0.030%;   S: 0 to 0.030%;   Cr: 0.80 to 2.30%;   Cu: 0 to 0.30%;   Al: 0.008 to 0.500%;   O: 0 to 0.0030%;   N: 0.0020 to 0.0300%;   Ni: 0 to 3.00%;   Mo: 0 to 0.29%;   Ti: 0 to 0.200%;   Nb: 0 to 0.20%;   B: 0 to 0.0050%; and   the balance Fe and unavoidable impurities,   wherein the steel material has, in mass%, a parameter represented by Si+Cr-2Mn of 1.05 or more and a parameter represented by 0.7Si+2.5Mn+2.0Cr+2.5Ni+4.0Mo of 6.30 or less.   
     
     
         2 . The machine structural steel material according to  claim 1 , wherein the steel material consists of in mass %: C: 0.15 to 0.35%; Si: 0.30 to 0.95%; Mn: 0.10 to 1.00%; P: 0 to 0.030%; S: 0 to 0.030%; Cr: 0.80 to 2.30%; Cu: 0 to 0.30%; Al: 0.008 to 0.500%; O: 0 to 0.0030%; N: 0.0020 to 0.0300%; Ni: 0 to 3.00%; Mo: 0 to 0.29%; Ti: 0 to 0.200%; Nb: 0 to 0.20%; and B: 0 to 0.0050%; 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, Nb, and B. 
     
     
         4 . The machine structural steel material according to  claim 2 , wherein the steel material is substantially free of Ni, Mo, Ti, Nb, and B. 
     
     
         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 0.29%. 
     
     
         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 0.29%. 
     
     
         7 . The machine structural steel according to  claim 1 , wherein the steel material comprises, in mass %, at least one or more of Ti: 0.020 to 0.200%, Nb: 0.02 to 0.20%, and B: 0.0003 to 0.0050%. 
     
     
         8 . The machine structural steel according to  claim 2 , wherein the steel material comprises, in mass %, at least one or more of Ti: 0.020 to 0.200%, Nb: 0.02 to 0.20%, and B: 0.0003 to 0.0050%. 
     
     
         9 . The machine structural steel material according to  claim 1 , comprising, in mass %, at least one or more of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.29% and at least one or more of Ti: 0.020 to 0.200%, Nb: 0.02 to 0.20%, and B: 0.0003 to 0.0050%. 
     
     
         10 . The machine structural steel material according to  claim 2 , comprising, in mass %, at least one or more of Ni: 0.20 to 3.00% and Mo: 0.05 to 0.29% and at least one or more of Ti: 0.020 to 0.200%, Nb: 0.02 to 0.20%, and B: 0.0003 to 0.0050%.