The Research Committee Report on Evaluation of Delayed Fracture Properties for Spring Steels Second Activity Part 2 —Grasping Delayed Fracture Pattern of Coil Spring and Establishing Test Method Used Test Piece Reproduced it—

Abstract

The risk of delayed fracture tends to increase by increasing hardness of coil spring, and to establishing suitable and safe evaluation method test method is essential. Once the evaluation method is standardized, automotive maker and spring maker can make fair judgement based on common criteria. It is expected that spring maker can reduce evaluation cost. Previous report was to establish hydrogen analysis method to separate hydrogen occurred in the rust remained on material surface. And was to estimate maximum hydrogen content entered from automotive environment. What are the dominant factor of spring to promote hydrogen penetration caused by grinding was also discussed. This study reports experiment results to confirm an evaluation method of test piece to monitor delayed fracture by holding coil spring simulating fracture pattern in the market. This paper proposes an evaluation method using test piece to reproduce fracture pattern in the market.