TOKYO -- Mazda Motor Corp. will use an innovative method to join steel and aluminum on the re-engineered MX-5 Miata sports car.
The underlying technology was used to join aluminum parts on the RX-8 sports car.
But this is the first time it has been used to join steel to aluminum, Mazda says.
Until now, welding two different metals such as steel and aluminum has been difficult. That has limited the ability of carmakers to combine the two materials in a single part.
To join aluminum to aluminum, Mazda uses a so-called joining gun to hold the two parts together. The joining tool then spins while force is applied. That creates frictional heat which, like the heat from a traditional weld, joins the two pieces.
To join steel to aluminum, Mazda uses steel that has been galvanized on one side.
Galvanized steel, which is steel coated with zinc, helps prevent corrosion that results from the contact of two types of metal.
By spinning and creating heat, the joining tool pushes aside the zinc coating. Then the heat bonds the two metals together.
A residual layer of zinc remains on the metal surrounding the precise point where the two metals are joined, preventing the metals from oxidizing.
The technology is superior to riveting because it can be used to join materials that are difficult to deform, such as aluminum castings and high-tensile steel.
Welding would reduce the rigidity of the joined metals.
Mazda is using the technology to join the trunk lid and bolt retainer for the MX-5. Use of the technology cuts weight and reduces cost, the company says.
The redesigned car goes on sale this summer in the United States.
Mazda has applied for more than 20 patents related to the technology. The automaker sees the technology as having applications in a wide range of industrial uses beyond the auto industry.
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