A quantitative study of the effect of composition on vveld solidification cracking in lovv-alloy steels

Abstract

A study has been made of the effects of material composition on weld metal soldification cracking in the autogenous tungsten-inert gas arc welding of thin low-alloy steel sheet. Published data obtained for about eighty steels have been examined by regression analysis to produce a linear relationship between cracking susceptibility and composition which is both simpler and superior to earlier complex expressions. Using the Huxley cracking test new data were obtained for a range of steels to specifications En 24, SAE 4130 and ASTM A387B as well as several aircraft compositions. The results confirmed the crack-promoting influences of sulphur, phosphorus, and carbon already identified in the cracking relationship, and also revealed a major crack-inhibiting effect of oxygen. These findings were used to produce the following expression linking cracking and composition for these steels under the standardized conditions of the Huxley weld cracking test, i.e. the crack susceptibility factor (CSF) =42 (wt-%C)+847 (wt-%S)+265 (wt-%P)–10 (wt-%Mo)–3042 (wt-%O)+19. The scope and limitations of this type of formula are discussed in terms of its value in demonstrating and predicting the effects of composition on crack susceptibility.