Pulsed Spot Welding for Multilayer Joints With Less Spatter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In spot welding, achieving reliable joining of metal plates with different thicknesses while minimizing spatter is challenging, as the contact resistance and nugget growth rates vary significantly between thick and thin plates.
Innovation Solution
A spot welding method using a pulse-shaped welding current waveform with peak and non-peak states, where the current control is initiated only when the effective value of the welding current reaches a predetermined target range, ensuring proper timing for nugget growth and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power distribution time between electrode chips is extended to ensure sufficient nugget growth, then welding reliability is improved, but nugget grows too much and protrudes from corona bond causing spatter
Solution Approach 1:
The patent applies periodic pulsed current instead of continuous current. The current is supplied in multiple cycles with each cycle containing a peak current period for nugget growth and a non-peak current period for heat dissipation. This periodic action allows the nugget to grow to appropriate size while preventing excessive growth and spatter.
Solution Approach 2:
The patent dynamically adjusts the current amplitude between peak and non-peak states during the welding process. The control unit varies the current characteristics in real-time based on the welding stage, transitioning from high current for nugget formation to reduced current for heat dissipation, thereby controlling nugget growth rate and preventing spatter.
2Ease of manufacture
If continuous power distribution is used to weld multiple metal plates with different thicknesses, then welding process is simplified, but nugget growth rate varies between thick and thin plates causing spatter
Solution Approach 1:
The patent uses periodic pulsed current with alternating peak and non-peak periods to address different nugget growth rates. During peak current periods, nuggets between thick plates grow adequately; during non-peak periods, heat dissipates to prevent excessive growth. This resolves the spatter issue caused by uniform continuous current while maintaining a relatively simple welding process.
Solution Approach 2:
The patent changes the current parameter dynamically by switching between peak and non-peak current states. The control unit adjusts current amplitude and timing to compensate for differences in nugget growth rates between thick and thin plates, preventing spatter while keeping the welding process straightforward.
3Object-generated harmful factors
If short power distribution time is used to prevent nugget protrusion and spatter, then spatter is reduced, but nugget cannot grow to necessary size for reliable welding
Solution Approach 1:
The patent employs periodic pulsed current where peak current periods provide sufficient energy for nugget growth to necessary size, and non-peak current periods allow heat dissipation to prevent nugget protrusion and spatter. This multi-cycle approach achieves both adequate nugget size and spatter reduction for reliable welding.
Solution Approach 2:
The patent performs preliminary nugget growth during peak current periods before the non-peak cooling periods begin. This ensures the nugget reaches necessary size early in the welding process, and subsequent non-peak periods merely prevent excessive growth and spatter without compromising welding reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for reliable joining of multilayer metal plates by controlling the nugget growth and reducing spatter occurrence, while ensuring efficient energy use for forming proper-sized nuggets.
Implementation Method 1
power is distributed between a pair of electrode chips in a state in which the plurality of metal plates is sandwiched between the pair of electrode chips, and in this manner, a nugget is generated between the plurality of metal plates
Implementation Method 2
a contact resistance between thick plates is greater than a contact resistance between a thin plate and a thick plate
Data Source
AI summary
This spot welding method is a method for joining workpieces being a layered body of three or more metal sheets by supplying welding current. The welding current has a pulse-like waveform wherein a peak state in which the current reaches or is maintained to be within a set peak current range and a non-peak state in which the current is lowered from the peak current range to a set bottom current, and is then increased toward the peak current range again are alternately achieved. In the non-peak state, in the case where an effective value Irms of the welding current is lowered, and reaches a predetermined effective value target range, a current control process for increasing the welding current toward the peak current range is started.