Analysis of Precision Spot Welding Process of Precision Spot Welding Machine
The precision spot welding of precision spot welding machines is divided into two types: continuous precision spot welding and preheating precision spot welding, with the latter having an additional preheating stage compared to the former.
Process analysis of precision spot welding
The basic procedure of precision spot welding includes three stages: preheating, precision welding, and forging. There is no preheating stage during continuous precision spot welding.
1. Preheating only has a preheating stage for precision spot welding
1) Raise the end face temperature of the welded component to facilitate smooth welding at higher starting speeds or lower equipment power, while reducing welding allowance and saving materials.
2) Slow down the temperature distribution in depth, widen the heating zone, and slow down the cooling rate of the welded part, in order to facilitate the plastic deformation generated during top forging and the easy removal of liquid metal and its surface oxides, while also reducing the quenching tendency of the welded part.
Substantive preheating precision spot welding is the process of heating the workpiece with intermittent current pulses before the precision welding stage, using rapid heating during short circuiting and uniform heating during gaps to evenly heat the end face of the workpiece to a predetermined temperature, and then entering the precision welding and forging stage. Generally, during preheating, the approach speed of the welded component is greater than the initial speed of continuous precision welding. After short circuiting, the welded component quickly separates into an open circuit after a slight delay, entering the uniform heating period. After a uniform heating delay, it approaches the original speed again, and this process is repeated until it is heated to the predetermined temperature.
Preheating can be controlled by counting (number of short circuits), timing, or stroke (preheating allowance), each with its own advantages and disadvantages. After preheating, the approach speed of the welded part is reduced to the point where it can be forcibly transferred to the precision welding stage, so that the heat input method and energy of preheating can be adjusted arbitrarily, and the process transition point is stable. Sometimes a natural conversion method is also used. At this time, the approach speed of the welded part during preheating must be selected from the initial approach speed of precision welding. When the end face of the welded part heats up to a certain value, it can naturally switch to precision welding. However, the conversion point fluctuates more due to factors such as grid voltage fluctuations. Sometimes, it returns to the preheating state shortly after switching to precision welding. Although it can still switch to precision welding again, the actual precision welding allowance will have significant changes. After the precision welding is normal, the function of returning to the preheating state must be cut off. To compensate for the uneven preheating caused by the unevenness of the welded end face, a precision leveling stage can be added before preheating.
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