Applicability of low transformation temperature welding consumables to increase fatigue strength of welded high strength steels

•LTT consumables were used to increase the fatigue strength of welded high strength steels.•Welds with transformation temperatures close to 200°C resulted in the highest fatigue strength.•The LTT effect depends on the weld metal transformation temperatures.•High fatigue strengths were achieved for welded high strength steels with varying strength levels. Application of Low Transformation Temperature (LTT) consumables in welding is a recent approach to increase the fatigue strength of welds. In this paper high strength steels with yield strengths ranging from 650 to 1021MPa were fillet and butt welded using different LTT and conventional consumables. The effects of weld metal chemical composition on phase transformation temperatures, residual stresses and fatigue strength were investigated. Lower transformation start temperatures and hence lower tensile or even compressive residual stresses were obtained close to the weld toe for LTT welds. Fatigue testing showed very good results for all combinations of LTT consumables and high strength steels with varying strength levels. For butt welds, the characteristic fatigue strength (FAT) of LTT welds at 2million cycles was up to 46% higher when compared to corresponding welds made with conventional filler materials. In fillet welds, a minimum FAT improvement of 34% and a maximum improvement of 132% was achieved when using LTT wires. It is concluded that different LTT consumables can successfully be employed to increase fatigue strength of welds in high strength steels with yield strength up to 1021MPa. Weld metals with martensite transformation start temperatures close to 200°C result in the highest fatigue strengths.