Electric arc shape and weld bead geometry analysis under the electromagnetic constriction and expansion effect

Arc-based welding processes are susceptible to the magnetic field effects. The electric arc shape, the current density, and the welding energy can influence the weld pool and weld properties, providing an additional degree of freedom for process control. This study analyzed the electromagnetic effect in constriction and expansion on arc shape changing and also the consequence on the weld bead geometry. The results demonstrated that with the electromagnetic field action, the electric arc cross-section was changed from cylindrical to elliptical, and that the greater the coils' excitation, the greater the effect. It was also observed that with the coil excitation current inversion, the ellipse orientation rotates 90 degrees and that the greater the arc constriction (transversally to weld), the greater the penetration and the shorter the bead width. Furthermore, the greater the electric arc expansion (transversally to weld), the lower the penetration and the greater the bead width. The ellipse is rotated electrically without the need for mechanical movement or reassembly, which makes it easy and agile to rotate the ellipse. The coils are electrically powered which allows a continuous range of excitation current (0 to 10 A) and consequently of forces acting on the change in the electric arc shape. With the coil excitation current increase, there is an electric arc area reduction and, therefore, a current density and heat intensity increase. The use of this device allows an additional independent parameter in arc welding processes and allows different weld bead geometries for the same welding current.

Automated summary

Arc-based welding processes are affected by magnetic field effects, changing the shape of the electric arc to elliptical. By controlling the excitation current of the coils, the width and penetration of the weld bead can be altered.