Cold crack sensitivity of welded joints in 1 000 MPa grade copper-rich nanoprecipitate-strengthened steel

To evaluate the cold crack sensitivity of welded joints in ultra-low carbon 1 000 MPa grade copper-rich nanoprecipitate-strengthened steel, a systematic study was conducted by theoretical calculation and inclined Y-shaped groove welding crack tests. The compositional applicability of existing cold crack sensitivity formulas were analyzed. According to the characteristics, composition range of the nanoprecipitate-strengthened steel and the results of inclined Y tests, a new applicable cold crack sensitivity formula was proposed to evaluate the cold crack tendency of the ultra-low carbon nanoprecipitate-strengthened steel. The influence of preheating temperatures on the cold cracking of welded joints was investigated, and an appropriate preheating temperature for welding was determined. The results showed that the cold crack sensitivity index of the steel was 0.252. There were no cracks in the base metal and heat affected zone under the condition of no preheating welding, indicating that the steel plate has excellent welding performance. The susceptibility to cold cracking in welded joints was significantly reduced with the elevation of pre-weld preheating temperature. When the preheating temperature was 105 ℃, the crack rate of test weld and heat affected zone was 0.