The forging stage of a medium frequency spot welding machine refers to the process where the electrode continues to exert pressure on the weld point after the welding current is cut off. During this stage, the weld point is compacted to ensure its solidity. When the power is cut off, the molten core begins to cool and crystallize within the enclosed metal shell, but it may not shrink freely.
Without pressure, the weld point is prone to shrinkage holes and cracks, which can affect its strength. Electrode pressure must be maintained after power-off until the molten core metal completely solidifies, and the duration of forging depends on the thickness of the workpiece.
For thicker workpieces with thicker metal shells around the molten core, increased forging pressure may be necessary, but the timing and duration of increased pressure must be controlled carefully. Too early application of pressure may cause molten metal to squeeze out, while too late application may result in the metal solidifying without effective forging. Typically, increased forging pressure is applied within 0-0.2 seconds after power-off.
The above describes the general process of weld point formation. In actual production, special process measures are often adopted based on different materials, structures, and welding quality requirements.
For materials prone to hot cracking, additional slow cooling pulse welding techniques may be used to reduce the solidification rate of the molten core. For quenched and tempered materials, post-weld heat treatment between the two electrodes may be performed to improve the brittle quenching structure caused by rapid heating and cooling.
In terms of pressure application, saddle-shaped, stepped, or multi-step electrode pressure cycles may be used to meet the welding requirements of parts with different quality standards.
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Post time: Mar-07-2024