Metal-Cored Welding GMAW Consumables Development for Girth Welding of X-100 Pipe

Metal-cored wire electrodes with different compositions were used to make girth weld joints at a heat input of 0.7–0.8 kJ/mm. Design of experiments methodology was used to create a response surface primarily in carbon (C), manganese (Mn) and nickel (Ni) space in steel containing molybdenum (Mo), titanium (Ti), and boron (B) additions. This allowed the modeling of all-weld-metal yield strength, tensile strength and Charpy impact toughness as a function of weld metal composition. Results indicated that weld metal yield and tensile strengths have a linear dependence on the %C, %Mn and %Ni content of the weld. The Charpy impact toughness behavior at −20° C was more complex, initially showing a dependence on %C and %Ni in small scale trials, and subsequently showing a dependence on the %oxygen (O) and %Mn content in full scale production trials. These results can be combined for graphical optimization of the response surface to identify regions in weld metal composition that contain the desired weld metal yield, tensile and Charpy impact toughness for design of metal-cored wire electrodes for the welding of X-100 pipe. These results and their implications for design of girth welds in X-100 pipe are presented in this study.