Resistance Spot Joining with Load Staging for Solid-Phase Bonds
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Solution Overview
Problem
The existing resistance spot joining methods and apparatuses face challenges in achieving improved joining quality, particularly in solid-phase point joining processes where the quality of the joint between metal workpieces is not consistently high.
Innovation Solution
A resistance spot joining method and apparatus that involves forming protrusions on workpieces using pressing shafts and electrodes, reducing the contact area by adjusting the pressing force, applying a current to soften the protrusions, and then joining them under a higher load to achieve a solid-phase bond without melting, thereby enhancing the joining quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional resistance spot joining method is used, then the joining process is simple, but the joining quality is not consistently high
Solution Approach 1:
The joining process is divided into multiple distinct stages: protrusion formation with first load, load reduction to second load, current application, and final joining with third load. Each stage serves a specific function in achieving high-quality joints, transforming a single-step process into a multi-phase controlled sequence that improves manufacturing precision
Solution Approach 2:
Protrusions are formed on the workpieces before the actual joining occurs. This preliminary action creates localized contact points that concentrate heat during the current application phase, ensuring consistent and high-quality joining while managing the complexity through structured process design
2Temperature
If the pressing force is reduced to reduce contact area, then heat concentration improves, but the joining strength may be insufficient
Solution Approach 1:
The pressing force is applied periodically in three distinct phases: initially high to form protrusions, then reduced to allow heat concentration during current application, and finally increased again to achieve strong joining. This periodic variation in load ensures both heat concentration and joining strength are achieved at appropriate moments in the process
Solution Approach 2:
The process utilizes phase transitions in the material state, creating protrusions that concentrate heat during a reduced-load phase, then transitioning to a high-load phase for final joining. The controlled reduction and increase of pressing force manages the thermal and mechanical phases to achieve both heat concentration and strength
3Quantity of substance
If a first load is applied to form protrusions, then the contact area is sufficient for current flow, but the heat concentration is dispersed
Solution Approach 1:
The contact area is segmented into protrusion contact points rather than a continuous surface. This segmentation is achieved by first forming protrusions with adequate contact area, then reducing the load to concentrate heat at these discrete points during current application, effectively managing both contact area and heat concentration
Solution Approach 2:
The process creates local quality differences by forming protrusions that concentrate material at specific points. When load is reduced, heat concentrates at these localized protrusion contact points rather than being dispersed across the entire contact area, achieving high temperature at critical locations while maintaining sufficient overall contact area
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
The method effectively increases the joining quality by concentrating heat at the central contact area, removing plating layers, and ensuring a strong, solid-phase bond between the workpieces, improving the overall joining process.
Implementation Method 1
forming a protrusion on each of the first workpiece and the second workpiece by pressing the first workpiece and the second workpiece with a first load
Implementation Method 2
applying a current to the first workpiece and the second workpiece in a state in which the second load is applied from the pressing shaft and the pressing member
Implementation Method 3
joining a contact interface of the first workpiece and a contact interface of the second workpiece to each other by pressing the first workpiece and the second workpiece with a third load larger than the second load
Data Source
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AI summary
A resistance spot joining method includes: a protrusion forming step of forming a protrusion (W11) on at least one of a first workpiece (W10) and a second workpiece (W20) by pressing the first and second workpieces with a first load by a pressing shaft (11) and a pressing member (12); a load reducing step of reducing an area of contact between the first and second workpieces by reducing a pressing force from the pressing shaft and the pressing member such that a second load (F2) is applied to the first and second workpieces; a current applying step of applying a current to the first and second workpieces; and a joining step of joining contact interfaces of the first and second workpiece (W10, W20) to each other by pressing the first and second workpieces with a third load.