Effect of travel speed on solidification cracking in autogenous tungsten inert gas arc welding of low-alloy steel sheet

Abstract

A study has been made of the combined effects of composition and travel speed on solidification cracking in the autogenous tungsten inert gas arc welding of low-alloy steel sheet. Data were obtained using the Huxley cracking test for steels to specifications En 24, SAE 4130, and ASTM A 387 B with a range of carbon, sulphur, phosphorus, and oxygen contents. A strong and complex effect of travel speed on cracking susceptibility was revealed, the form of the relationship being determined by the composition of the steel. At high carbon, high sulphur, high phosphorus, and/or low oxygen contents cracking was severe at low speeds but fell progressively to low values at high speeds. At low carbon, low sulphur, low phosphorus, and/or high oxygen contents cracking was low at both low and high speeds with a maximum at an intermediate speed. It is demonstrated that increased travel speed decreases the transverse crack-promoting forces at the rear of the pool but increases the length of the crack-susceptible zone. These effects are used to account for the reported interaction of composition and speed on cracking behaviour. Consideration is given to the significance of the results for welding production and welding test procedure with these steels.