Effect of a longitudinal magnetic field on arc motion and joint structure of a hollow stud

Given the non-uniform melting of the end face of a joint and the local non-fusion of the joint in large-diameter hollow stud welding, to research the law of arc motion, the joint-forming quality, weld microstructure and mechanical properties in the process of hollow stud welding propelled by a longitudinal magnetic field were investigated in this study. The results reveal that under the influence of a longitudinal magnetic field, the arc on the end of a stud is affected by the Lorentz force and spirals downward. In the welding process, with an increase in magnetic field intensity, the arc uniformly burns the stud end face, preventing local non-fusion and resulting in a well-shaped joint. Under the action of magnetic field stirring, eutectoid ferrite is broken, the content of eutectoid ferrite and bainite is diminished, the nucleation barrier is reduced and the grain is refined. Under the action of a longitudinal magnetic field, the shear strength of the hollow stud welded joint rises to 312 MPa, surpassing the strength of a joint welded without a magnetic field.