Microstructure and properties of as welded duplex stainless steel

Abstract

Butt welds of duplex stainless steel plate (grade 2205) have been produced using grade 2209 consumables for a variety of welding processes employed in the shipbuilding industry. The welding processes were used initially with interpass temperatures in the range 250–350°C. When the interpass temperature was controlled to below 150°C, the average ferrite content increased in the weld metal and in the heat affected zone (HAZ). Controlling the interpass temperature did not dramatically affect the properties in the mechanical tests performed. Heat inputs were in some instances higher than those used previously, but this did not adversely affect weld metal and HAZ properties. No evidence of intermetallic phase precipitation was found, by TEM of thin foils, in any of the weld metal in the processes used. There was evidence of fine particle precipitation of M₂₃C₆ in the HAZ regions. The level of precipitation observed is acceptable for the final application as all the mechanical test and corrosion test requirements were comfortably met. There was evidence that the HAZ was an area of higher strain: dislocation density was high and deformation bands, twinning, and stacking faults were present.