Microstructure and properties evaluations of spot-welded ferritic steel sheets via static magnetic field

Ferritic steel spot nuggets were produced with or without a static magnetic field. The microstructures and properties evaluations of the nuggets with or without a static magnetic field were investigated. Disordered columnar grains and some equiaxed grains among the columnar grains with a static magnetic field were discovered in this study. Based on the evaluations of the microstructure and properties, the nugget mechanisms, strengthening mechanisms, and infrared behavior of the joint were discovered. The diameter and strength of each nugget were improved with the application of a static magnetic field. The welding time and the welding force can both influence the nugget characteristics via a static magnetic field. The tensile strength of the spot joint regularly varied with magnetic field; the maximum value was 245 MPa, 11%, which was approximately 30% higher than that of the nugget without magnetic field (187 MPa, 3.8%). The magnetization force applied on the dendrite at the same time can cause the columnar dendrite to deform, break and deflect from the direction of solidification.