高濃度浸炭鋼のショットピーニング処理後の残留応力分布に及ぼす浸炭層硬さおよび炭化物の影響

概要

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The super carburizing is a promising heat treatment to strengthen case hardened parts such as gears and other automotive parts. The bending fatigue strength is improved with the increase of sufrace hardness and residual stress produced by shot peening. However, it will be a probability that the residual stress changes with material hardness and carbide in carburized case.The present work investigated about the effect of hardness, retained austenite and carbide in carburized case on residual stress. As a result, it was clearfied that the increase of residual stress by shot peening on super carburizing steel can be evaluated by the average hardness of carburized case and was hardly influenced by the retained austenite. In addition, the carbide in carburized case was effective to dispersion hardening of martensite, therefore, the average hardness of carburized case on super carburizing steel was higher than that of eutectoid carburizing steel and the plastic flow area of super carburizing steel became smaller than that of eutectoid carburizing steel. For this reason, the increase of the residual stress on super carburizing steel was smaller than that of eutectoid carburizing steel.Furthermore, the bending fatigue test was also refered.