Progress in Low Transformation Temperature (LTT) Filler Wires: Review

Excessive tensile residual stresses and distortion may develop in welding of steels depending on the phase transformation temperature as it plays an important role on their formation during welding. The development of distortion in the welded steel structures lead to timeenergy consuming and environmentally detrimental correction operations whereas the presence of tensile residual stresses may intolerably dagrade the fatigue properties of the welded components. The amount of distortion developed in steel welds may be reduced and compressive residual stresses can be induced without any preheating or postweld treatment by lowering the transformation temperature with the use of proper filler wire, i.e. so-called low-transformation-temperature (LTT) welding wire. Thus, the welded structures with compressive residual stresses display better properties such as fatigue life, stress corrosion cracking (SCC), resistance to cold-cracking, and service life properties. However, the fracture toughness may be reduced slightly. The residual stresses and distortion developed in high stregth steel welded structures play an important role on the reliability and cost efficiency of these joints. In this study, the state-of-art of the low transformation temperature filler wires, which is recently developed by tailoring its chemical composition to lower the MS temperature, and their effects on the residual stress formation, fatigue life, and cold-cracking are discussed in detail.

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