| Summary: | In order to change the cooling rate of weld pool, in-situ laser post-heating was irradiated behind the weld pool during gas tungsten arc welding in a U-type hot cracking test. The solidification cracking occurrence based on the cooling rate change was observed. The high temperature ductility curve and thermal strain curve were calculated to investigate the relationship between solidification cracking behaviour and cooling rate. The high temperature ductility curve was obtained based on the combination of the critical strain and solidification brittleness temperature range. An in-situ observation technique was used to measure the critical strain. The solidification initiation and completion temperatures were estimated by the metallurgical analysis model. The thermal strain curve was calculated using a finite element simulation method. The high temperature ductility curve did not significantly changed according to the welding conditions. However, the decrease of cooling rate deteriorated yield strength distribution and increased both the stress applied to the weld bead and the slope of thermal strain curve, increasing vulnerability to solidification cracking.
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