1. The effect of welding current
As can be seen from the equation, current has a greater effect on heat production than resistance and time. Therefore, it is a strictly controlled parameter in the spot welding process. The key causes of current variation are grid voltage vibrations and impedance changes in the secondary circuit of the AC welder. Impedance variations are due to geometric changes in the circuit or the introduction of different amounts of magnetic metal in the secondary circuit. As for the DC welder, the secondary circuit impedance variation has no significant effect on the current.
In addition to the total welding current, the current density also has a significant effect on the heating. After shunting the weld joint, increasing the electrode contact area or bump size reduces the current density and welding heat, resulting in a significant decrease in joint strength.
2. The effect of welding time
In order to ensure the size of the core and the strength of the welded joint, welding time and welding current can complement each other. In order to obtain a certain strength of the welded joint, it is advisable to choose a high current and a short time (strong conditions, also known as strong specifications), or a low current and a long time (weak conditions, also known as weak specifications). The choice of strong conditions depends on the function of the metal. The thickness and power of the welding machine used. However, there is still an upper current and time limit regarding the current and time required for different functions and thicknesses of the metal. The lower limit, beyond which a qualified fusion core will not be caused.
3. The effect of electrode pressure
As the electrode pressure increases, the electrode pressure has a significant effect on the total resistance R between the two electrodes and R decreases significantly. At this time, although the welding current increases slightly, but can not affect the reduction in heat production caused by the reduction in R. Therefore, the solder joint strength always decreases with increasing electrode pressure. While increasing the electrode pressure, the welding current is increased or the welding time is extended to fill the effect of reduced resistance and to keep the joint strength fixed. Choosing this welding condition is beneficial to improve the stability of the welded joint strength. Too little electrode pressure can lead to spattering, which also reduces the weld joint strength.
4. The effect of electrode raw material function
Since the contact area of the electrode determines the current density, . The resistivity and thermal conductivity of the raw material of the electrode are related to the occurrence and loss of heat, so the form and raw material of the electrode have a significant effect on the melting nucleus. With the deformation and wear of the electrode extremities, the contact area increases and the strength of the welded joint decreases.
