Effect of initial jaw distance and preheating pulses in eliminating oxide entrapment and weld failures in flash butt welds

Flash butt weld failure due to oxide entrapment is one of the primary causes of wheel rim failures. The welding process parameter plays a critical role in eliminating the oxides from the bond line. Experimental investigations to understand the effect of initial jaw distance (IJD) and the number of preheating pulses (NP) on the upsetting length (UL) were studied. It was observed that IJD and NP played a critical role in altering the peak temperature achieved at the interface. Higher peak temperature at the interface helped achieve a larger upset length, forming a defect-free weld. Failure analysis of the flash butt welded fractured surface revealed the presence of penetrators/cold spots and oxide inclusion. The study suggested that a sufficient upset length was necessary to expel oxides/cold spots formed during welding for obtaining defect-free joints. Furthermore, increasing the preheating pulses smoothened the abutting edges and significantly reduced the defects. The presence of Goss, Rotated Goss, and Cube textures at the fusion zone of flash butt weld were found to be the enabler for crack propagation during post-weld forming operations once the crack has been initiated.