● Adding pressure

The pressure applied during the welding process of a spot welding machine is an important factor in generating heat. Pressure application is the mechanical force applied to the welding area. By applying pressure, the contact resistance is reduced, resulting in uniform resistance values and preventing local heating during welding, resulting in uniform welding effect.

● Power on time

The electrification time is also an important factor in generating heat. The heat generated by electrification is released through conduction. Even if the total heat is constant, the highest temperature at the welding site varies due to different electrification times, and the welding results are also different.

● Current waveform

The best combination of heating and pressurization in time is very important for the spot welder, so the temperature distribution at each instant in the welding process must be appropriate. According to the material and size of the welded object, a certain amount of current flows through the contact area for a certain period of time. If the pressure is applied slowly, it will cause local heating and worsen the welding effect of the spot welding machine. In addition, if the current suddenly stops, sudden cooling of the welding part will cause cracks and material embrittlement. Therefore, a small current should be applied before or after the main current passes, or pulses should be added to the rising and falling currents.

[Example] Thick plates and stamped products have deformation and strain. In order to ensure a tight bonding between the plates after welding, a small current is used for preheating before the main current.

For materials that may undergo thermal hardening or cracking, after the main current flows, a small current is applied for post heating to achieve annealing treatment.

● Surface states of materials

The contact resistance is a factor directly related to the heating of the contact part. When the applied pressure is constant, the contact resistance is determined by the Surface states of the weldment, that is, after the material is determined, the contact resistance is determined by the fine concave convex and oxide film on the metal surface. Small bumps and bumps are beneficial for obtaining the expected heating range of the contact resistance, but due to the presence of oxide film, the resistance increases, leading to local heating, so it should still be removed