| 摘要 |
PURPOSE:To prevent the expulsion and surface flash in the intermediate layer of laminated metallic plates by providing a cooling period when current conduction is stopped upon ending of preheating time and executing the main current conduction in succession thereto. CONSTITUTION:Laminated metallic plates having an electrical insulating layer are preheated by current conduction and after the cooling time by >=0.02sec non- current conduction upon ending of the preheating time, the laminated metallic plates are subjected to main current conduction and are joined by welding. A relay R1 stops the welding current upon ending of the preheating time and a relay R2 resumes the conduction of the welding current upon ending of the cooling time. A relay R3 stops the welding current upon ending of the main weld time. The respective time are determined by a voltage comparator circuit 11, a timer T2 and a timer T3. |
