Abstract: Cracking morphology in the fusion zone of HQ130 high strength steel was researched by "the y-silt test" and "three point bend test", ultrasonic test and microscope. HQ130+QJ63 high strength steel was welded by Ar+CO2 gas shielded arc welding under the condition of no-preheat. Experimental results indicated that welding crack produced in the partially melted zone of the weld root of HQ130 steel side and propagated parallel to the fusion zone. The cracking developed alternatively between the weld and the partially melted zone, and is not strictly to rupture at W/F boundary surface. Controlling weld heat input (E) about 16 kJ/cm could make the cracking rate to be lowest and satisfy the performance requirement of welded joint zone.

Key words: High strength steel, Fusion zone, Cold cracking