Weld optimization with new Low Temperature Transformation fillermaterials

Abstract: In this study, evaluation of typical weld geometry, residual stresses and fatigue properties of two new LTT consumables have been performed. The literature survey discusses the topics of LTT consumables regarding fatigue life, chemical composition, dilution, crack phenomena and fatigue crack repair, impact toughness, weld residuals stress and weldgeometry. The experimental part of the project included LTTMAG welding trials, fatigue specimen development and production, fatigue testing and weld residual stress measurements. All welding were performed using mechanised MAG spray arc welding, performed on 8mm and 10mm thick DOMEX 650MC as rolled steel plates. The initial trials focused on finding good weld parameter to be used for the fatigue specimen production. For the specimen production, optimisation of the robot weld path, weld geometry and weld parameters were performed. Evaluations of the weld results were done in a standard metallurgical manner, and assessed according to current standard documentation. After the specimen production, fatigue testing were performed and evaluated. Residual stress levels were measured through Xray diffraction in as welded state. Observations and results have been presented and discussed. The most interesting results are: - The two LTT filler reduced the tensile weld residual stressby 45% respectively 30% compared to the conventional MCW weld filler. -The fatigue testing of the two LTT fillers resulted in a characteristic Natural Mean FAT of 127 MPa respectively 115MPa. -In weld position PB, the LTT weld consumable gave betterweld toe radius against the flange plate compared to the conventional MCW filler.