Carburized steel part having excellent low cycle bending fatigue strength

Abstract

A carburized steel part having excellent low cycle bending fatigue strength which is comprised of a steel material which contains, by mass %, C: 0.1 to 0.6%, Si: 0.01 to 1.5%, Mn: 0.3 to 2.0, P: 0.02% or less, S: 0.001 to 0.15%, N: 0.001 to 0.03%, Al: 0.001 to 0.06%, and O: 0.005% or less and has a balance of substantially iron and unavoidable impurities and which is carburized and quenched, and then tempered, which steel part has a surface hardness of HV550 to HV800 and a core hardness of HV400 to HV500.

1 . A carburized steel part having excellent low cycle bending fatigue strength which is comprised of a steel material which contains, by mass %, 
       C: 0.1 to 0.6%, 
       Si: 0.01 to 1.5%, 
       Mn: 0.3 to 2.0%, 
       P: 0.02% or less, 
       S: 0.001 to 0.15%, 
       N: 0.001 to 0.03%, 
       Al: 0.001 to 0.06%, and 
       O: 0.005% or less and has 
       a balance of substantially iron and unavoidable impurities and 
       which is carburized and quenched, and then tempered,
 said steel part characterized in that 
 it has a surface hardness of HV550 to HV800 and a core hardness of HV400 to HV500. 
 
     
     
         2 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said low cycle bending fatigue strength is 20 kN or more. 
     
     
         3 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, B: 0.0002 to 0.005%. 
     
     
         4 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel further contains, by mass %, Cr: 1.20 to 3.0%. 
     
     
         5 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, Ti: 0.01 to 0.2%. 
     
     
         6 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, one or more of Mo: less than 0.1%, Cu: less than 0.1%, and Ni: less than 0.1% as unavoidable ingredients. 
     
     
         7 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, one or more of Mo: 0.1 to 1.5%, Cu: 0.1 to 2.0%, and Ni: 0.1 to 5.0%. 
     
     
         8 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, one or both of Nb: 0.01 to 0.2% and V: 0.03 to 0.2%. 
     
     
         9 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said steel material further contains, by mass %, one or more of Ca: 0.0002 to 0.005%, Zr: 0.0003 to 0.005%, and Mg: 0.0003 to 0.005%. 
     
     
         10 . A carburized steel part having excellent low cycle bending fatigue strength as set forth in  claim 1 , characterized in that said carburized steel part is a differential gear or transmission gear.