Nitrocarburized microalloyed steel member

Abstract

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; Si; Mn; S; Cu; Ni; and Cr having fitting content ranges. 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.

Description

technical field [0001] The present invention relates to a non-quenched and tempered steel part having a nitrocarburized layer formed on the surface. Background technique [0002] [Patent Document 1] Japanese Unexamined Patent Publication No. 09-030632 [0003] [Patent Document 2] Japanese Unexamined Patent Publication No. 06-128690 [0004] [Patent Document 3] Japanese Unexamined Patent Publication No. 05-279795 [0005] [Patent Document 4] Japanese Unexamined Patent Publication No. 05-279794 [0006] [Patent Document 5] Japanese Unexamined Patent Publication No. 09-324258 [0007] [Patent Document 6] JP-A-2002-226939 [0008] [Patent Document 7] JP-A-2005-264270 [0009] Since crankshafts for vehicles are used in an environment where large torsional loads and bending loads are repeatedly applied, excellent static strength and fatigue strength are required. On the other hand, since it is a large and complex-shaped component, it is generally manufactured from non-quench...

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