Dissimilar Metal Plate Joining via Selective Resistance Heating
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Solution Overview
Problem
Conventional methods for joining dissimilar metal plates, such as aluminum and steel, face challenges in achieving sufficient joint strength due to differences in volume resistivity, leading to excessive heating and potential voids in the higher resistivity metal plate.
Innovation Solution
A method involving overlaying dissimilar metal plates with a pair of electrodes contacting the surface of the higher resistivity metal plate, supplying current to resistance-heat it below its melting point, and using the heat to partially melt the lower resistivity metal plate, forming an intermetallic compound for joining, while avoiding excessive heating of the higher resistivity metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a larger amount of current is supplied to the lower resistivity metal plate to melt it, then the melting of the lower resistivity metal plate is achieved, but excessive current is supplied to the higher resistivity metal plate causing voids and insufficient joint strength
Solution Approach 1:
The patent applies local quality by making the heating process asymmetric: the higher resistivity metal plate is heated to a specific temperature range (below its melting point but above the lower resistivity metal's melting point), while the lower resistivity metal plate is allowed to melt. This localized temperature control ensures that each metal plate receives appropriate heat treatment based on its specific properties, preventing void formation in the higher resistivity plate while achieving melting in the lower resistivity plate for proper joining.
Solution Approach 2:
The patent changes the temperature parameter control by specifying that the higher resistivity metal plate be heated to a temperature lower than its melting point but higher than the melting point of the lower resistivity metal plate. This parameter differentiation allows selective melting of the lower resistivity metal while keeping the higher resistivity metal in a solid state, thereby preventing void formation and ensuring strong joint formation through intermetallic compound generation.
2Ease of manufacture
If conventional resistance spot welding is used to join dissimilar metal plates, then the joining process is simple, but voids are generated in the higher resistivity metal plate leading to insufficient joint strength
Solution Approach 1:
The patent modifies the conventional resistance spot welding parameters by controlling the heating temperature of the higher resistivity metal plate to be below its melting point but above the melting point of the lower resistivity metal plate. This parameter adjustment maintains the simplicity of the resistance welding process while preventing void formation and ensuring adequate joint strength through proper intermetallic compound formation.
3Temperature
If the higher resistivity metal plate is heated to its melting point, then sufficient heat is generated for joining, but voids are created and joint strength is compromised
Solution Approach 1:
The patent applies local quality by implementing differential temperature control: the higher resistivity metal plate is heated to a specific temperature range that is below its melting point but above the melting point of the lower resistivity metal plate. This localized temperature differentiation ensures that the higher resistivity metal plate does not form voids while still generating sufficient heat to melt the lower resistivity metal plate and form strong intermetallic compounds for joining.
Solution Approach 2:
The patent changes the temperature parameter by specifying that the higher resistivity metal plate be heated to a temperature lower than its melting point but higher than the melting point of the lower resistivity metal plate. This parameter optimization prevents void formation in the higher resistivity metal while ensuring adequate heating for proper joining through intermetallic compound generation.
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 enhances joint strength by preventing voids and excessive heating, ensuring a strong and coherent joint without melting the higher resistivity metal, and allows for secure joining without pressurizing the plates against each other.
Implementation Method 1
supplying current between the pair of electrodes so as to resistance-heat the second metal present in a current-flowing region through which the current flows
Implementation Method 2
partially melting the first metal plate with heat from the resistance-heated second metal
Data Source
AI summary
A method for joining two dissimilar metal plates having different volume resistivity with enhanced joint strength. The method includes overlaying a first metal plate made of first metal and a second metal plate made of second metal with higher volume resistivity and higher melting point in comparison with the first metal, bringing a pair of electrodes into contact with the surface of a portion of the second metal plate overlapping the first metal plate, supplying current between the electrodes so as to resistance-heat the second metal present in a current-flowing region to a temperature lower than the melting point of the second metal and higher than the melting point of the first metal, thereby partially melting the first metal plate with the heat so that an intermetallic compound is generated between the first and second metal plates, and thus joining the first and second metal plates via the intermetallic compound.