Resistance spot welding is widely used in industries such as automotive and sheet metal due to its high efficiency, quality, and ease of automation. However, the welding parameters can be technically challenging for beginners. This article will introduce you to spot welding parameters and provide examples of how to set them.
The three core parameters of spot welding are:
Welding Pressure
Welding Current
Welding Time
Different combinations of these parameters can lead to significant differences in welding efficiency.
Joule’s Law in Welding
The basis for adjusting resistance spot welding parameters is Joule’s Law:
Q=I2RT
Our goal is to generate enough heat through a certain current under pressure to produce a qualified weld nugget. Based on Joule’s Law, to increase heat, we can use:
Higher welding current
Longer welding time
Lower welding pressure
However, in practice, there may be cases of insufficient weld nuggets or excessive heat, leading to issues like spatter, sparks, or internal defects. In such cases, we need to reduce the welding current, shorten the welding time, or increase the welding pressure. Different situations require different parameter adjustments.
Parameter Combinations for Different Materials
When using a spot welder on different materials, the parameter combinations will vary.
For low carbon steel welding, which has a higher resistance and lower strength, the parameter adjustments are relatively straightforward. For thin sheet welding, a welding time of 100-200 ms, a current of 6-8 kA, and a pressure of 2-7 kN can achieve good nugget formation. For thicker low carbon steel, you may need to extend the welding time or use a multi-pulse welding method to facilitate nugget formation and growth. Too short a time may result in incomplete nugget growth, leading to non-circular welds and insufficient penetration.
When welding aluminum sheets, especially rust-resistant or hard aluminum, the parameters differ due to the material’s good conductivity, thick oxide layer, and relatively high tensile strength. Aluminum spot welding typically requires high current and short time. For military-grade aluminum, an acid pickling process is often used to remove the oxide layer, while civilian products usually do not undergo surface treatment. Therefore, breaking through the surface Al₂O₃ to achieve effective nugget formation can be challenging. Moreover, the electrode lifespan can degrade rapidly after multiple welds.
For thin aluminum sheets, a welding time of 100-160 ms, a current of 15-25 kA, and a pressure of 2-6 kN, combined with highly conductive electrodes and strong water cooling, can achieve good nugget formation.
Importance of Sample Testing
Different materials and thicknesses will affect the parameter settings. Therefore, it is crucial to conduct sample testing before welding a metal product. If you are looking to order a DC spot welder for welding M10 automotive carbon steel nuts, it is advisable to consult the spot welder manufacturer for preliminary testing. This will help determine the best parameters and the most suitable model before purchasing the machine.
About Agera
Agera is a Chinese manufacturer of resistance welding machines, producing spot welders, projection welders, butt welders, and seam welders. If you have welding needs and require assistance, please contact us. Our engineers are ready to help you solve your welding challenges.
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