Ultrasonic analysis of cracking propagation morphology in the fusion zone of high strength steel

Cracking morphology in the fusion zone of HQ130 high strength steel was researched by the y-slit test, three-point bend test, ultrasonic test and microscope. HQ130 and QJ63 high strength steels were welded by Ar+CO sub 2 gas shielded arc welding under the condition without preheating. Experimental results indicated that welding cracks were produced in the partially melted zone of the weld root of HQ130 steel side and propagated parallelly to the fusion zone. The cracks were developed alternatively between the weld and the partially melted zone, and were not strictly ruptured at the W/F (weld metal/fusion zone) boundary surface. Controlling weld heat input (E) about 16 kJ/cm could make the cracking rate lowest and satisfy the performance requirement of welded joint zone.