TWI Industrial Member Report Summary 968/2010
By V Kumar and C Lee
Weld metal is often deposited on the surface of components using arc welding processes to obtain the desired surface properties. One of the major concerns in arc welding based overlay is dilution or the change in chemistry of weld metal through mixing of base metal. Standards such as ASME Section IX for qualification of welding procedures state that heat input for the first weld layer is an essential variable, ie a change in heat input over 110% of that qualified requires requalification. The same heat input can be achieved by proportionally varying the welding current and speed. For many processes this can have a different effect on the penetration depth and hence on dilution. The extent of overlap between adjacent weld beads is also a key variable influencing dilution.
This investigation tried to understand the effect of welding parameters on dilution and corrosion resistance and evaluated the performance/benefits of some of the advanced welding techniques for surfacing application. Comments have been made on the appropriateness in using only the heat input as an essential variable in weld overlaying.
Effect of process variables on dilution in weld overlay produced using tungsten inert gas (TIG) and metal inert gas (MIG) welding processes.
Performance of selected advanced welding techniques in weld overlaying.
Effect of dilution on corrosion resistance using droplet cell corrosion testing technique.