Effect of different welding positions on microstructure and low temperature impact toughness of 9Ni steel weld

The microstructure and low temperature impact toughness of 9Ni steel welds with different welding positions were studied. The impact fracture morphology and the microstructure of the weld were analyzed. The results show that there was a big difference in low temperature impact toughness between horizontal welding and vertical welding joints. The low temperature impact absorption energy of horizontal welding was 110 J, and the low temperature impact absorption energy of vertical welding was 74 J. The growth direction of the columnar crystal in the transverse weld and the interlaminar reheat equiaxed crystal zone were beneficial to hinder the crack propagation. The growth direction of columnar crystals in the weld metal of vertical welding was parallel to the direction of crack propagation, which was not conducive to hindering the propagation of cracks. There was almost no reheat equiaxed crystal zone in the weld metal of vertical welding.