Low-Resistance Electrodes for Dissimilar Metal Rivet Joining
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Solution Overview
Problem
The existing resistance welding method for joining different metal materials requires high current to melt aluminum and penetrate the rivet, but high electrode resistance exceeds the transformer's rating, preventing sufficient current flow.
Innovation Solution
Using electrodes with electrical resistance values lower than or equal to the sum of the metal members' and rivet's resistance, made of a copper alloy containing chromium, to reduce the overall electrical resistance and allow high current flow during pressurization and energization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high current is used to melt aluminum and enable rivet penetration, then the joining effectiveness is improved, but the transformer rating is exceeded when electrode resistance is high
Solution Approach 1:
The patent changes the material parameter of the electrodes from conventional materials to copper alloy containing chromium, which has lower electrical resistance. This parameter change allows high current to flow through the welding circuit without exceeding the transformer's rating, thereby enabling effective aluminum melting and rivet penetration while maintaining reliable operation within equipment specifications.
Solution Approach 2:
The patent applies local quality by using copper alloy electrodes with specific chromium content at the critical location where current enters the workpiece. This localized material optimization reduces resistance at the electrode-workpiece interface, enabling high current density at the welding zone without overloading the entire power supply system.
2Reliability
If conventional electrodes are used, then the transformer rating is maintained, but high current cannot flow to achieve effective aluminum melting and rivet penetration
Solution Approach 1:
The patent changes the material parameter of the electrodes from conventional materials to copper alloy containing chromium, which has lower electrical resistance. This parameter change allows high current to flow through the welding circuit without exceeding the transformer's rating, thereby enabling effective aluminum melting and rivet penetration while maintaining reliable operation within equipment specifications.
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
Enables high current flow without upgrading the transformer, ensuring effective penetration and strong joint formation between metal members, as demonstrated by achieving current values up to 15 kA during the embedding step.
Implementation Method 1
embedding the rivet into the metal member by pressurization and energization using the first electrode and the second electrode
Implementation Method 2
preparing, as the first electrode and the second electrode, two electrodes that satisfy a condition in which each of electrical resistance values of the first and second electrodes is lower than or equal to a sum of an electrical resistance value of the plurality of metal members to be joined and an electrical resistance value of the rivet
Data Source
AI summary
A method for joining different kinds of metal materials includes: preparing a rivet, a plurality of metal members, and a first electrode and a second electrode, each having shanks and electrode portions provided at the tips of the shanks; sandwiching the rivet and the plurality of metal members between a first electrode and a second electrode; and embedding the rivet into the metal member by pressurization and energization using the first electrode and the second electrode. The preparation step includes preparing, as the first electrode and the second electrode, two electrodes that satisfy a condition in which each of electrical resistance values of the first and second electrodes is lower than or equal to a sum of an electrical resistance value of the plurality of metal members to be joined and an electrical resistance value of the rivet.