Electrode Force The electrode force used for projection welding depends on the metal being welded, the projection design, and the number of projections in the joint. The force should be adequate to flatten the projections completely when they reach the welding temperature, bringing the workpieces in contact. Excessive force will prematurely collapse the projections and the weld nuggets will be ring-shaped, with incomplete fusion in the center. The welding machine must be capable of mechanically following the workpiece with the electrodes as the projections collapse. Slow follow-up will cause metal expulsion before the workpieces are together. The sequence of events during the formation of a projection weld is shown schematically in Figure 2.10. In Figure 2.10(A), the projection is shown in contact with the mating sheet. In (B), the current has started to heat the projection to welding temperature. In (C), the electrode force causes the heated projection to collapse rapidly and then fusion takes place. The completed weld is shown in (D).
Electrode Force The electrode force used for projection welding depends on the metal being welded, the projection design, and the number of projections in the joint. The force should be adequate to flatten the projections completely when they reach the welding temperature, bringing the workpieces in contact. Excessive force will prematurely collapse the projections and the weld nuggets will be ring-shaped, with incomplete fusion in the center. The welding machine must be capable of mechanically following the workpiece with the electrodes as the projections collapse. Slow follow-up will cause metal expulsion before the workpieces are together. The sequence of events during the formation of a projection weld is shown schematically in Figure 2.10. In Figure 2.10(A), the projection is shown in contact with the mating sheet. In (B), the current has started to heat the projection to welding temperature. In (C), the electrode force causes the heated projection to collapse rapidly and then fusion takes place. The completed weld is shown in (D).
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