Mazda Motor Corp. (Hiroshima, Japan) claims it has developed the world’s first process for joining aluminum body parts using friction heat. The friction stir welding technology was first used to assemble the hood and rear doors of the new Mazda RX-8, a four-door, four-seat sports car.

Traditionally, resistance welding has been the most feasible technology for joining aluminum body parts. However, it requires that a large current be instantaneously passed through the aluminum. This approach uses a large amount of electricity and requires large, specialized equipment.

Mazda engineers have developed a welding gun that holds the parts from both sides with a welding tool. While force is applied, the tool spins which, in turn, generates frictional heat. This heat is utilized to soften the aluminum and form a joint.

According to Hisakazu Imaki, Maxda executive vice president, there are three advantages to using friction stir welding to join aluminum parts:

• Reduced energy consumption. The only energy consumed is the electricity needed to rotate and apply force to the welding tool in order to create frictional heat. Energy consumption needed to weld aluminum parts has been reduced by 99 percent.
• Reduced equipment investment. Imaki claims Mazda “has achieved a 40 percent reduction in equipment investment compared to that of resistance welding for aluminum.”
• Improved work environment. Unlike resistance welding, no weld spatter occurs during the joining process.