In-depth Explanation of Welding Current Curve in Medium Frequency Inverter Spot Welding Machines

The welding current curve plays a crucial role in the welding process of medium frequency inverter spot welding machines. It represents the variation of welding current over time and has a significant impact on the quality and characteristics of the resulting weld. This article provides a detailed explanation of the welding current curve in medium frequency inverter spot welding machines.

1. Current Ramp-Up: The welding current curve begins with a ramp-up phase, where the welding current gradually increases from zero to a predetermined value. This phase allows for the establishment of a stable electrical contact between the electrodes and the workpieces. The ramp-up duration and rate can be adjusted based on the material, thickness, and desired welding parameters. A controlled and smooth current ramp-up helps in minimizing spattering and achieving a consistent weld nugget formation.
2. Welding Current Pulse: Following the current ramp-up, the welding current enters the pulse phase. During this phase, a constant current is applied for a specific duration, known as the welding time. The welding current pulse generates heat at the contact points, causing localized melting and subsequent solidification to form a weld nugget. The duration of the welding current pulse is determined by factors such as material type, thickness, and desired weld quality. Proper control of the pulse duration ensures adequate heat input and avoids overheating or underheating of the workpieces.
3. Current Decay: After the welding current pulse, the current gradually decays or decreases back to zero. This phase is important for controlled solidification and cooling of the weld nugget. The rate of current decay can be adjusted to optimize the cooling rate and prevent excessive heat input to the surrounding areas, minimizing distortion and preserving the material’s properties.
4. Post-Pulse Current: In some welding applications, a post-pulse current is applied after the welding current pulse and before the complete decay of the current. The post-pulse current helps in refining the weld nugget and improving its mechanical properties by promoting solid-state diffusion and grain refinement. The duration and magnitude of the post-pulse current can be adjusted based on the specific welding requirements.

Understanding the welding current curve in medium frequency inverter spot welding machines is essential for achieving high-quality and reliable welds. The controlled ramp-up, welding current pulse, current decay, and potential use of post-pulse current contribute to the overall welding process, ensuring proper heat input, solidification, and cooling. By optimizing the welding current curve based on the material, thickness, and desired weld characteristics, manufacturers can achieve consistent and satisfactory results in their spot welding applications.