セミオーステナイト系析出硬化形ステンレス鋼SUS631の冷間圧延鋼はくの強度および破壊機構に関する研究 : 疲労挙動とそのフラクトグラフィー

抄録

In order to clarify the fatigue behavior and fracture micromechanism for cold rolled steel foil of semi-austenitic precipitation hardening stainless steel SUS631 so as to evaluate its fatigue characteristics, fatigue tests and hardness measurements before and after the fatigue tests were carried out on the stainless steel foil of 0.05mm in thickness for as-received material and two kinds of ageing treated materials. The fracture surface of these foil specimens was observed by Scanning Electron Microscopy (SEM). The main results obtained are summarized as follows. (1) The fatigue strength of as-received material was improved by ageing hardening treatment, the fatigue limit of the material ageing treated at 753 K for 1 hour was larger than that at 703 K for 1 hour. (2) After fatigue testing, the hardness of as-received material was increased, but the hardness of ageing hardening treated materials was decreased. The variations in the hardness before and after fatigue tests for these materials indicated that as-received material showed cyclic hardening behavior, and ageing hardening treated materials showed cyclic softening behavior. (3) From these observed results of the fracture surface and the cross section of fatigue cracks, there were distinctions in the crack growth path, failure pattern and fracture micromechanism on these materials, furthermore, the fatigue behavior of the foil material was very different from that of a bulk material.