Investigation of High Frequency Resistance Welding (HFRW) Variables on microstructure and mechanical properties of dissimilar joints between chromium-molybdenum low alloy steel tubes to chromium high alloy steels

In this research, the effect of high-frequency resistance welding (HFRW) parameters on microstructure and mechanical properties of seamless 2.25Cr-1Mo ferritic steel as spiral (helical) finned tube used in industrial boilers was investigated. So HFRW was implemented on actual (Industrial) samples by changing multiple parameters including Current, Electric Potential, Welding Speed (Rotation Speed) and Pitch, then metallography, fusion weld, tensile strength and hardness tests were performed on various sections of the samples according to ASTM and international standard. The results of metallographic and mechanical properties tests indicated that in order to obtain a minimum of 90 percent welding diffusion, depends on optimum welding parameters, fin tip and tube tip position of resistance welding, hydraulic pressure jack setting on squeeze roller and pitch FPI (fin per inch) to dissimilar joints between chromium-molybdenum low alloy steels tube to chromium high alloy steels of coil strips. Furthermore as the lower pitch and fin thickness are selected, the higher quality of fin tube welding diffusion is achieved.