The Effect of Forging Ratio on the Fatigue Strength of Hot Work Tool Steel with Reduced Inclusions

Abstract

In this study, the effect of forging ratio on the fatigue strength of improved hot work tool steels was investigated. A lot of unclear points on this topic still need to be clarified. This study investigates the characteristics of the improved hot work tool steels through static bending test and fatigue test, followed by SEM and EBSD analyses. Bending test showed positive and negative effects induced by higher forging ratio, whereas fatigue test underlines a decrease of the fatigue strength and limit at same condition. SEM observation revealed that fatigue crack initiation occurs at inclusion near the specimen surface. A higher forging ratio induces a needle-shaped microstructure, certainly favoring earlier initiation of the fatigue crack.