The Influence of Flash Welding Parameters on the Microstructure and Mechanical Performance of Dissimilar Steel Welded Joints

In the present paper, duplex stainless steel was utilized as an insert for welding high manganese steel frog to high-carbon steel rail under three flash welding processes. The effect of the number of flashes and upsetting force on mechanical performance and microstructure of the welded joints was studied. The results showed that the impact energy of the inserts after welding experienced a significant reduction in the 524-6 (with the number of flashes reduced to 6) and 772-8 (with the upsetting force increased to 772 kN) welded joints compared to the 524-8 welded joint (with an upsetting force of 524 kN and 8 flashes). The other mechanical performances of the welded joints under the three states did not differ significantly. No cracks were observed in the transition regions between the high manganese steel and the insert in any of the three welded joints. Nevertheless, notable micro-voids were present in the 524-6 welded joint. The ferrite in the insert of the 524-6 joint was distributed in a horizontal streamline and continuous strip shape. Conversely, in the 524-8 and 772-8 welded joints, the ferrite was distributed in an arch bridge shape. However, the arch amplitude of the ferrite bridge in the insert of the 772-8 welded joint was larger, and the center of the insert was contained a greater number of ferrites. Furthermore, the severe stress concentration in the middle of the insert of the 524-6 and 772-8 welded joints, coupled with the large amount of ferrite in the middle of the insert of the 772-8 welded joint, were the primary reasons for the diminished impact energy of the insert for these two joints.