ばねの遅れ破壊に関する研究委員会報告（Ⅱ期）その2 ─ ばねの遅れ破壊形態の把握およびそれを再現する試験片方法の確立 ─

ばねの高硬度化が進むにつれて、遅れ破壊の危険性は高まりつつあり，適正かつ安全な評価方法を確立しなければならない。またその評価方法が統一されれば同じ指標で公平な判断ができて，評価する側にとっても工数削減につながることが予想される．前報では遅れ破壊評価で重要な拡散性水素を正確に測るための除錆方法や市場から入る水素量の見積もりおよび水素が侵入しやすいばねの摩耗も含めた影響因子について報告した．本報では，ばねの遅れ破壊形態を把握し，ばねの破壊形態を再現した試験片方法の提案を目的とした実験を行い，いくつかの試験法を提案する．

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.

Delayed fracture, Diffusible hydrogen, Torsion test, Cyclic corrosion test, Spring steel SAE9254