非金属介在物のデータベース作成と高強度鋼の疲労強度推定法の標準化

抄録

Nonmetallic inclusions cause relatively low fatigue strength for high strength steels and also cause a large scatter of fatigue strength. A method of inclusion count on the basis of statistics of extreme is proposed to evaluate material quality. By combining the new inclusion counting method and fatigue strength prediction equation proposed by Murakami et al., the lower bound of scatter band of fatigue strength can be predicted. The square root of the projection area of inclusion √area is the crucial parameter both in inclusion counting and fatigue strength prediction.
The detabase of cumulative frequency of the maximum inclusion size √area_max of various commercial steels is presented. The scatter bands in rotating-bending fatigue strength of back up roll steel are estimated by the proposed method and are comfirmed to be in good agreement with the experimental results.