ベイナイト型非調質鋼の組織と機械的性質に及ぼす合金元素の影響と切欠き材の疲労強度

概要

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Influence of carbon, manganese, chromium, and vanadium contents on mechanical properties and microstructures of bainitic microalloyed steels are investigated. The fatigue limit of the bainitic steels were compared with the ferritic-pearlitic steels with smooth and notched specimens. The hardness are increased by increase in content of each alloying element. The carbon equivalent for hardness (Ceq) can be described by the following equation Ceq=C(mass%)+0.23 ×Mn(mass%)+0.26 ×Cr(mass%)+0.31 × V(mass%). Carbon, manganese, and chromium decrease toughness but vanadium improves both toughness and hardness. Additionally, vanadium is effective in improvement of 0.2% proof. This reason is estimated that microstructures of bainitic steel i.e. martensite-austenite constituent (M-A constituent) are refined by vanadium addition. The fatigue strength of bainitic steels with smooth specimen is lower than ferritic-pearlitic steels for the same hardness. However, it is higher in the case of notched specimen. This is because bainitic steels have better notch sensitivity.
電気製鋼研究会の論文