Effect of External Constant Magnetic Field on Weld Nugget of Resistance Spot Welded Dual-Phase Steel DP590

The applications of magnetic field in metal casting and welding processes have drawn much attention of researchers. However, the effect of external magnetic field on nugget formation of resistance spot welding (RSW) is still lack of understanding. In this paper, the effect of a radially oriented constant magnetic field generated by a pair of ring-shaped permanent magnets on the weld nugget of RSW was experimentally investigated. The nugget diameter, microhardness, and mechanical performance were compared between welds with and without the external magnetic field. Results showed that, under the action of the external magnetic field, the weld nugget got wider with an increase in diameter by nearly 10%. Besides, the Vickers hardness in fusion zone (FZ) of the welding joint was more uniform. As a result, the RSW joints welded under the constant magnetic field exhibited better mechanical performance in tensile-shear tests. Therefore, the application of the external constant magnetic field could be an effective way to control the weld quality of RSW by affecting its melting and crystallization process.