Electric Welding - A Comprehensive Treatise on the Practice of the Various Resistance and Arc Welding Processes, Covering Descriptions of the Machines and Apparatus Used and the Applications Both in Manufacturing and Repair Work #261928

Resistance Welding. In the resistance, incandescent or Thomson electric welding process, the metals to be welded are brought into intimate contact by being held closely together by metal clamps actuated by springs or levers, so as to permit a constant pressure on the parts to be welded, even after the metal at the welding surfaces becomes plastic. The parts to be welded form an electric circuit, and the resistance at the point of contact between the two surfaces to be welded pro duces a welding temperature in a very short time; the metal parts are then forced together and thus welded. A distinct feature of the resistance welding process is that the interior of the metal is raised to a welding temperature before the surface reaches that heat, so that, if the exterior surface is welded, it is certain that the interior is also properly welded, since it is at a somewhat higher heat. When work is heated for welding in a forge, the opposite conditions take place. A perfect weld may be indicated on the surface, but this weld may cover an imperfect joint inside.