Formation Process Of Welding Spot Of Energy Storage Spot Welder

The spot welding process of the energy storage spot welding machine can be divided into three stages that are connected with each other: pre-pressurization, electric heating and forging. The electrode pressure is pre-applied to make the weldment in close contact at the weld. Electrical heating is for the formation of the required molten core between the weldments. Forging is a process in which the electrodes continue to squeeze the solder joints after cutting off the welding current, which has a compacting effect on the solder joints.

The electrode pressure is pre-applied to make the weldment in close contact at the weld. If the pressure is insufficient, the contact resistance will be too large, causing the weldment to burn through or the electrode working surface to be burned. Therefore, the electrode force should reach a predetermined value before electrification to ensure that the contact resistance between the electrode and the weldment and between the weldment and the weldment remains stable.

Electrical heating is for the formation of the required molten core between the weldments. When energized under pre-applied electrode pressure, the maximum current density exists in the metal cylinder between the contact surfaces of the two electrodes. The contact resistance between the weldments and the resistance of the weldments themselves generate considerable heat, and the temperature is also very high. high. Especially at the contact surface between the weldments, it melts first, forming a molten core. The contact resistance between the electrode and the weldment also generates heat, but most of it is carried away by the water-cooled copper alloy electrode, so the temperature at the contact between the electrode and the weldment is much lower than that at the contact between the weldments. Under normal circumstances, the melting temperature cannot be reached. The metal around the cylinder has low current density and low temperature. The metal near the molten core has a high temperature and reaches a plastic state. Under the action of pressure, welding occurs to form a plastic metal ring, which tightly surrounds the molten core. Make molten metal spill out.

Forging is a process in which the electrodes continue to squeeze the solder joints after cutting off the welding current, which has a compacting effect on the solder joints. After the power is turned off, the molten core begins to cool and crystallize in the closed metal "shell", and the shrinkage is not free. If there is no pressure at this time, the solder joints are prone to shrinkage and cracks, which will affect the strength of the solder joints. If there is electrode extrusion, the resulting extrusion deformation allows the nugget to shrink freely and become dense. Therefore, the electrode pressure must continue to be maintained after the power outage until the nugget metal is completely solidified before it can be released. The duration of forging depends on the thickness of the weldment. For steel plates with a thickness of 1-8mm, it is generally 0.1-2.5 seconds.

The above is the general process of solder joint formation. In actual production, some special process measures are often adopted according to different materials, structures and requirements for welding quality. For example, for materials with a large tendency to thermal cracks, a spot welding process with additional slow cooling pulses can be used to reduce the solidification speed of the nugget; for the welding of quenched and tempered materials, post-weld heat treatment can be performed between the two electrodes to improve the rapid Brittle quenched structure produced by heating and cooling; in terms of pressure, electrode pressure cycles such as saddle shape, stepped shape or multiple stepped shapes can be used. Welding parts to meet different quality requirements.