Resistance Spot Joining with Protrusion Heating for Solid-Phase Bonds
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Solution Overview
Problem
The existing resistance spot joining methods and apparatuses face challenges in improving joining quality, particularly in achieving solid-phase joining without melting the workpieces, which affects the strength and reliability of the bonded interfaces.
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 heat the protrusions, and then joining them under controlled loads to achieve solid-phase welding, thereby enhancing the joining quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pressing force is applied to form protrusions on workpieces, then the protrusions are formed for joining, but the contact area between workpieces becomes too large which reduces heating efficiency
Solution Approach 1:
The pressing shafts are used to preliminarily form protrusions on the workpieces before the actual joining process. This preliminary action creates the necessary geometric features that will concentrate heat during the subsequent resistance welding, solving the contradiction by preparing the workpiece geometry in advance to enable better heating concentration without requiring excessive pressing force during heating.
Solution Approach 2:
The pressing force is localized to specific areas where protrusions are formed, rather than being uniformly distributed. This creates local variations in the workpiece geometry that concentrate the heating effect at specific contact points between protrusions, thereby improving heating efficiency while maintaining overall joining quality.
2Temperature
If electrodes are used to apply current for heating, then the workpieces are heated for joining, but the heat distribution becomes uneven affecting joining quality
Solution Approach 1:
The electrode design creates localized heating zones at the contact points between protrusions. By shaping the electrodes to match the protrusion geometry, the current density is concentrated at specific locations, creating uniform heat distribution across all contact points while maintaining the ability to join workpieces effectively.
3Temperature
If pressing force is reduced to decrease contact area, then heating efficiency improves, but the workpieces cannot be properly held together during joining
Solution Approach 1:
The pressing shafts perform the function of holding workpieces together during the heating phase by maintaining contact between the formed protrusions. This preliminary holding action is sufficient to keep workpieces aligned without requiring excessive pressing force, thereby allowing efficient heating while maintaining proper positioning throughout the joining process.
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 ensuring that only the central portions of the protrusions generate heat, allowing for precise plastic deformation and solid-phase joining without melting, resulting in improved bond strength and reliability.
Implementation Method 1
forming a protrusion on at least one 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
AI summary
A resistance spot joining method includes: a protrusion forming step of forming a protrusion on at least one of a first workpiece and a second workpiece by pressing the first and second workpieces with a first load by a pressing shaft and a pressing member; 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 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 to each other by pressing the first and second workpieces with a third load.