Low Transformation Temperature Welding Consumables For Residual Stress Management: Consumables Development And Testing Qualification

Residual stresses induced during joining are major contributors to the overall stresses in the vicinity of structural weld joints. Undesirable tensile residual stress is observed in low-carbon structural steel weld joints upon completion of solidification and after the weld is cooled to room temperature. This harmful stress makes the welded joints more prone to fatigue failure. The use of low-transformation-temperature welding (LTTW) wires, producing martensitic transformation close to room temperature, was validated as a technique to manage the residual stresses and improve the fatigue strength of the welded joints. Compressive residual stresses are produced around the weld metal formed by LTTW consumables by taking advantage of the expansion associated with martensitic transformation at low temperature. When the phase-induced  volumetric expansion counteracts and negates the thermal contraction, a compressive residual stress in the fusion zone is developed. This work introduces the guidelines for identifying and qualifying newly developed LTTW filler metals. Microstructures, microhardness, and distortion behavior were analyzed for welds made with experimental welding wires and compared with that in a weld produced using a commercial welding wire.