Notch toughness of boron-treated high-strength structural steels

AbstractA study of high-strength Cr-B structural steels as alternatives to Cr-Mo steels was conducted to clarify the effects of chemical composition and cooling rate from the tempering temperature on the notch toughness. As compared with standard Cr-Mo steels, boron grades were found to be more sensitive to reversible temper embrittlement because of the absence of Mo. Alloy additions such as Si and V are not appropriate measures to improve toughness. Phosphorus content and cooling rate from the tempering temperature are the critical factors affecting the impact toughness. Low-phosphorus steels with less than 0·005% P show equivalent toughness to that of standard Cr-Mo grades.