Nitrocarburized microalloyed steel member

摘要

A nitrocarburized microalloyed steel member consists of a microalloyed steel that includes a nitrocarburized layer on a surface, a cross-sectional structure of which steel except for the nitrocarburized layer includes a ferrite and pearlite structure. The microalloyed steel mainly consists of Fe and has a composition: C having a content of 0.30 mass % or more and 0.50 mass % or less; Si having a content of 0.05 mass % or more and 0.30 mass % or less; Mn having a content of 0.50 mass % or more and 1.00 mass % or less; S having a content of 0.03 mass % or more and 0.20 mass % or less; Cu having a content of 0.05 mass % or more and 0.60 mass % or less; Ni having a content of 0.02 mass % or more and 1.00 mass % or less; and Cr having a content of 0.05 mass % or more and 0.30 mass % or less. If the contents of the Cu, the Ni, and the Cr are represented by WCu, WNi, and WCr mass %, respectively, and composition parameters F1 and F2 are 185WCr+50WCu and 8+4WNi+1.5WCu-44WCr, respectively, then the composition parameters F1 and F2 satisfy F1>20 and F2>0.