公开(公告)号：EP3611286A1

公开(公告)日：2020-02-19

申请号：EP18784444.4

申请日：2018-04-10

Applicant: NHK Spring Co., Ltd.

Inventor： AKANUMA, Toshiyuki ,  SHIRAISHI, Tohru ,  IWAGAKI, Yohei ,  TAKAHASHI, Keita ,  HIRAI, Shun

IPC: C22C38/00 ,  C21D1/06 ,  C21D7/06 ,  C21D9/02 ,  C22C38/46 ,  F16F1/06 ,  C22C38/54

Abstract: A C-condensed layer is formed on the surface of a wire material at a uniform thickness and in a narrow range, and appropriate compression residual stress distribution is imparted to the wire material after it is formed, so that a compression coil spring of high durability and with sag resistance can be provided. The compression coil spring includes a steel wire material containing, hereinafter in weight%, 0.5 to 0.7 % of C, 1.2 to 3.0 % of Si, 0.3 to 1.2 % of Mn, 0.5 to 1.9 % of Cr and 0.05 to 0.5 % of V as necessary components, one or more kinds selected from not more than 1.5 % of Ni, not more than 1.5 % of Mo and not more than 0.5 % of W as freely selected components, and iron and inevitable impurities as the remainder; the C-condensed layer which exceeds the average concentration of C contained in the steel wire material exists at a surface layer part, and the thickness of the C-condensed layer is within 0.01 to 0.05 mm along the entire circumference of the steel wire material.