公开(公告)号：US11378147B2

公开(公告)日：2022-07-05

申请号：US16559137

申请日：2019-09-03

Applicant: NHK SPRING CO., LTD.

Inventor： Takeshi Suzuki ,  Yoshiki Ono ,  Shimpei Kurokawa ,  Kosuke Shibairi

IPC: F16F1/02 ,  C21D9/02 ,  C22C38/04 ,  C22C38/02 ,  C21D7/06 ,  C21D1/18 ,  C22C38/18 ,  C21D8/06 ,  B24C1/10

Abstract: A spring consists of, by mass %, 0.5 to 0.7% of C, 1.0 to 2.0% of Si, 0.1 to 1.0% of Mn, 0.1 to 1.0% of Cr, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities. The spring has a structure including not less than 65% of bainite and 4 to 13% of residual austenite by area ratio in a cross section. The spring has a compressive residual stress layer in a cross section from a surface to a depth of 0.35 mm to D/4, in which D (mm) is a circle-equivalent diameter of the cross section. The spring has a high hardness layer with greater hardness than a center portion by 50 to 500 HV from a surface to a depth of 0.05 to 0.3 mm.