An investigation of the mechanism of splitting which occurs in tensile specimens of high strength low alloy steels

Abstract

A study has been conducted to investigate the metallurgical cause of splitting that is sometimes observed to accompany regular fracture in tensile and Charpy impact specimens. The susceptibility of a steel to tensile specimen splitting (TSS) has been shown to depend on both the composition as well as the processing of Cb (Nb) and V bearing high-strength, low-alloy steels. This study has revealed that Fe3C, either as grain boundary precipitate or in pearlite of a particular distribution, was the microstructural feature which seemed to be responsible for the TSS in the steels investigated. The compositional and processing factors influenced the susceptibility of specimens to TSS by controlling the Fe3C precipitation. There was no correlation between the susceptibility of a microstructure to TSS and its short transverse ductility. This result indicates that the occurrence of splitting in broken tensile or impact specimens is neither related to nor a good predictor of the probability of occurrence of the lamellar tearing that may occur during welding. A mechanism is presented which establishes the link between composition, processing, microstructure, splitting susceptibility and short transverse ductility.