WELDING APPARATUS FOR STUDS OF ANNULAR CROSS-SECTION

摘要

For arc-welding studs of substantially annular crosssection, a stud holder 1 is surrounded by an electromagnet coil 5, the magnetic field of which is applied to the welding gap through a magnetic flux guiding portion 6, 7 so as to generate a magnetic field component extending radially of the stud 4 within the gap. This radial field component exerts a circumferential force on the arc to move it along the annular face of the hollow stud 4 thereby securely welding the stud 4 to the workpiece 2 along its entire annular cross-section. In order to minimise coupling of the magnetic field into the conductive workpiece 2, the flux guiding portion has a frusto-conical magnetic field former 7, the generatrix of which points to the welding zone 8, with the pole surface 9 formed at the tip of the field former 7 closely surrounding the welding gap.