Mazda Motor Corporation has developed what it says is the world’s first direct spot-joining technology to join steel and aluminum.
Mazda used an earlier variant of this technology in 2003 in the development of the Mazda RX-8 sports car, applying friction heat to join separate aluminum sheets.
The technology has evolved, and will be used to join the trunk lid and bolt retainer (picture at right) for the updated Mazda MX-5 due to go on sale around the world in the latter half of 2005.
Up to now, welding two different metals such as steel and aluminum has been a difficult task. Mazda tackles it by optimizing the rotating tool shape and joining characteristics, and by using galvanized steel on one side.
A joining gun holds the parts from both sides, and then spins while force is applied. This generates frictional heat that subsequently joins the aluminum materials to the steel sheet metal. Galvanized steel helps prevent the galvanic corrosion that results from the contact of two different types of metal.
Compared with conventional joining techniques such as riveting or clinching, steel and aluminum spot friction welding makes it easier to join materials that are difficult to deform, such as aluminum casting and high tensile steel. Additionally, manufacturing costs can be reduced because riveting becomes unnecessary.
One of the other potential payoffs for making it simpler to join aluminum to steel: weight reduction. And weight reduction leads to reduced fuel use.
Mazda has applied for over twenty patents related to this technology.