Significant system parameters influencing HAZ properties in 9% Ni steel

The relative influence of welding system parameters oil the properties of the heat affected zone (HAZ) in 9%Ni steel has been investigated via a fractional factorial experiment. The HAZ properties evaluated were the dimensions in two locations, the hardness, and the impact strength. The independent variables were bevel preparation method, welding process, heat input, plate thickness, joint design, and position of the weldment. The study indicated that heat input, bevel preparation method, and an aliased interaction between the bevel preparation method and the joint design must he controlled to minimise the extent of the HAZ at the plate surface. The width of the HAZ measured at plate mid-thickness is a function of plate thickness, heat input, and two aliased interactions: between welding process and joint design; and that determined for the surface HAZ (interaction between joint design and bevel preparation method). Hardness was significantly affected by thickness, welding process, position, and heat input as well as by an aliased interaction between thickness and joint design. Impact strength was most influenced by two aliased interactions, both including the bevel preparation method. Weld position was found to affect HAZ impact values significantly.