TWI Industrial Member Report Summary 291/1985
By N Bailey
An examination has been made of the application of metal powder additions to triple arc welds used for single pass welding of 30mm microalloyed plate. An agglomerated Fe-Mn-Mo-Ti-B powder was employed to provide alloying as well as to increase the deposition efficiency. In addition to increasing the deposition rate bv up to ~35% and reducing the arc energy from 20 to 14kJ/mm for a single pass weld, the use of metal powder required thinner backing bars. For one weld, a ceramic backing was used at a current well above that recommended by the manufacturer for welding without metal powder. Without metal powder additions, toughness of both weld metal and HAZ were poor. Although the reduction in heat input did not give improved HAZ toughness, a significant improvement was found in the weld metal, where toughness of the weld without metal powder bad been impaired by aluminium transferred from the parent plate into the weld. Alloying from the powder and reduced dilution led to a reduction in the 27J transition temperature by 120°C when conventional triple arc welding was modified by the addition of metal powder and the use of a ceramic backing.