Pressure in the spot welding process is an important factor in generating heat. Pressure is the mechanical force applied to the weld. By reducing the contact resistance through pressure, the resistance value is uniform, which can prevent local heating during welding and make the welding effect uniform.
2. Energizing time
The time of energization is also an important factor in generating heat. The heat generated by energizing is transferred by conduction. Even if the total heat is determined, the maximum temperature at the weld differs due to different energizing times, and the welding results are different.
3. Current waveform
The optimal combination of heating and pressurization is very important for the spot welder, so the temperature distribution at each moment of the welding process must be appropriate. Depending on the material and size of the welded material, a certain amount of current flows for a certain period of time. For heating of the contact area, a slow pressurization can cause local heating and deteriorate the welding effect of the spot welder. In addition, if the current is stopped sharply, the sudden cooling of the welded part can produce cracks and material embrittlement. Therefore, small currents should be passed before and after the main current passes, or pulses should be added to the upper and lower currents.
4. Surface condition of the material
Contact resistance is a factor directly related to the heating of the contact area. When a certain pressure is applied, the contact resistance determines the surface state of the weld, i.e., after the material is determined, the contact resistance depends on the small dimples and oxide film on the metal surface. The small bump facilitates the heating range desired by the contact resistance, but the increased resistance leads to local heating due to the presence of the oxide film and should therefore be removed.