Copper Spot Welding Projections for Localized Heat Generation
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Solution Overview
Problem
Resistance spot welding is ineffective for joining highly electrically conductive copper workpieces due to the high conductivity of copper, which makes it difficult to generate sufficient resistive heat, and traditional electrodes can be thermally damaged by the high current required.
Innovation Solution
The method involves providing copper workpieces with a plurality of projections on their faying surfaces, allowing an electric current to concentrate heat within these projections, collapsing them to form a metallurgical joint, and using spot welding electrodes with a sufficient surface area to apply compression and direct the current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional resistance spot welding is used on copper workpieces, then the high electrical conductivity of copper prevents sufficient heat generation, but increasing the current to generate heat causes thermal damage to traditional electrodes
Solution Approach 1:
The faying surface is segmented into multiple discrete projections instead of a continuous surface. This segmentation concentrates the electrical current through the small contact areas of the projections, generating sufficient heat locally without requiring excessive overall current that would damage the electrodes.
Solution Approach 2:
The projections create localized regions of high current density at their contact points with the opposing workpiece surface. This local quality change enables heat generation precisely where needed for welding, while the rest of the electrode surface remains cooler and undamaged.
2Temperature
If projections are added to the faying surface to concentrate heat, then heat concentration improves, but the device complexity increases
Solution Approach 1:
The projections are formed on the faying surfaces in advance of the welding operation through stamping or other forming processes. This preliminary action prepares the surfaces to concentrate heat effectively during welding, eliminating the need for complex real-time control systems or specialized electrode designs.
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 enables a robust and efficient joining of copper workpieces by concentrating heat within the projections, forming a strong metallurgical joint while minimizing damage to the electrodes, thus overcoming the challenges of high conductivity and thermal issues.
Implementation Method 1
The electrical current is sufficient to generate and concentrate heat within the plurality of projections to collapse the plurality of projections to establish a metallurgical joint
Implementation Method 2
applying a compression force against the first metal workpiece and the second metal workpiece to urge the first faying surface toward the second faying surface
Data Source
AI summary
A method of joining overlapping copper workpieces. The method includes overlapping a first copper workpiece with a second copper workpiece such that a plurality of projections on a second faying surface of the second copper workpiece are in contact with the first faying surface of the first copper work piece at a joining location where a metallurgical joint is ultimately established. The method further includes applying a compression force against a first exterior surface of the first copper workpiece and a second exterior surface of the second copper workpiece to urge the faying surfaces together, and passing an electric current at the joining location through the first and the second copper workpieces. The electric current flows through the plurality of projections to generate sufficient heat to effectuate the collapsing of the plurality of projections to bring the first second faying surfaces into contact to establish the metallurgical joint.