Cold-Cracking Control in Low-Alloy Steel Welds

Abstract

<p>BAZ microstructure stress and hydrogen level are the fundamental factors influencing the cold cracking susceptibility of the HAZ. Implant testing at various hydrogen levels over a range of steel compositions and heat inputs shows how the microstructure and hydrogen level influence the critical stress necessary for cold-cracking.</p> <p>Based on implant test data, a correlation formula predicting the critical stress necessary for cold cracking for given HAZ hardness martensite in the HAZ and hydrogen level, is proposed. Employing this correlation, together with prediction of martensite in the HAZ and HAZ hardness, based on heat transfer caculations, martensite-composition-cooling rate relations and hardness-composition-cooling rate relations, an algorithms which can predict the critical stress necessary for cracking for given implant composition, cooling rate and hydrogen level, is constructed.</p> <p>This method of predicting the critical stress necessary for cold cracking is an improvement over the existing regression formulas for estimating cold-cracking susceptibility.</p> <p>This formula has been successfully adapted to predict cold-cracking susceptibility data as obtained through other tests such as rigid restraint, and to recommend prehear levels necessary to avoid cold-cracking. Development and use of implant testing machine with an automatic welding and loading facility is also reported.</p>