Effect of Alloying Elements on the Toughness of Bainite in Medium Carbon Low Alloy Steels

Abstract

The effect of C (0.25-0.45%), Ni (0-2.6%), Mo (0-0.5%) and Cr (0-2.2%) contents on the toughness of the as formed and tempered bainite was investigated in 0.4%C-0.8%Mn-1.1%Cr-0.25% Mo steels, and factors which affect the toughness of bainite were discussed. Bainite was formed in the isothermal transformation. Increase of C, Ni and Cr contents and rise of transformation temperature raised the transition temperature of bainite. The results were attributed to the increase of both fracture facet size and carbide length and the latter was more deteriorate. In the increase of Cr content, another factor might be also necessary to be taken into account for the full interpretation of the results. Addition of molybdenum lowered the transition temperature of tempered bainite mainly by the relief of the temper embrittlement.