SURFACE TREATMENT FOR STEEL MEMBER

PURPOSE:To regulate the whole surface of a nitride surface layer which is formed in the subsequent stage to a practically uniform height reduced in ruggedness by setting the surface roughness of an alloy steel member before the formation of a nitride surface layer at a value lower than the surface roughness at the time of working treatment by a mechanical means after the formation of the nitride surface layer. CONSTITUTION:Since the surface roughness at the time of first mechanical surface working is set at a value lower than that after the formation of a nitride surface layer, the height of the whole surface of the nitrogen compound layer can be practically uniformized. Accordingly, the polishing allowance of the nitride surface layer can be reduced at the time of subsequent polishing surface working and the occurrence of the small thickness part and the lost part at the surface layer can be prevented, and, as a result, the thickness as a whole can be uniformized and also increased.