Process for producing carbonitrided part

Abstract

A process for producing a carbonitrided part comprising the steps of preparing a base steel part, having a composition comprising, in mass percent, C: 0.10 to 0.24%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less, with the balance being Fe and impurities and performing the following steps 1-4 in sequence. Step 1 is carburizing the base steel part under a carburizing atmosphere at a temperature of 900 to 950° C. Step 2 is carbonitriding the base steel part carburized according to step 1 under a carbonitriding atmosphere at a temperature of 800 to 900° C. with a nitrogen potential of 0.2 to 0.6%. Step 3 is quenching the base steel part carbonitrided according to step 2. Step 4 is tempering the base steel part quenched according to step 3 at a temperature of more than 250° C. to not more than 350° C.

1 - 2 . (canceled) 
     
     
         3 . A process for producing a carbonitrided part, comprising the steps of:
 preparing a base steel part, having a composition comprising, in mass percent, C: 0.10 to 0.24%, Si: 0.15 to 1.0%, Mn: 0.30 to 1.0%, Cr: 0.40 to 2.0%, S: 0.05% or less, with the balance being Fe and impurities;   performing treatments including the following steps 1 to 4 in sequence:   Step 1: Carburizing the base steel part under a carburizing atmosphere at a temperature of 900 to 950° C.;   Step 2: Carbonitriding the base steel part carburized according to step 1 under a carbonitriding atmosphere at a temperature of 800 to 900° C. with a nitrogen potential of 0.2 to 0.6%;   Step 3: Quenching the base steel part carbonitrided according to step 2;   Step 4: Tempering the base steel part quenched according to step 3 at a temperature of more than 250° C. to not more than 350° C.   
     
     
         4 . The process for producing a carbonitrided part according to  claim 3 , characterized in that the base steel further contains, in mass percent, Mo: 0.50% or less in lieu of a part of Fe.