Tokyo, Japan - Mazda, which developed what it claimed was the world's first direct spot-joining technology to join steel and aluminium in 2004, has evolved the system further.
It was first used on the Mazda RX-8 sports car, using friction heat to join aluminium sheets. Now it will fuse the boot lid to its hinges on the latest Mazda MX-5 sports car due to go on sale towards the end of this year.
Until now, welding different metals such as steel and aluminium was difficult. However, by optimising the rotating tool shape and joining characteristics, and by using galvanised steel on one side, joining steel and aluminium has been made possible.
The process is similar to that of joining two pieces of aluminium, when a joining gun holds the parts from both sides with a welding tool. The joining tool is then made to spin while force is applied, which in turn generates frictional heat that subsequently joins the aluminium materials to the steel sheet.
Galvanised steel helps to prevent galvanic corrosion that results from the contact of two metals.
Compared with riveting or clinching, steel and aluminium spot friction-welding makes it easier to join materials that are difficult to deform, such as aluminium castings and high-tensile steel. Costs can be reduced because riveting becomes unnecessary.
This innovative technology makes it simple to join steel and aluminium and improves the potential for coupling aluminium parts to steel vehicle bodies.
The process contributed significantly to Mazda's vehicle weight reduction efforts during the development of the Mazda MX-5 as well as to reducing costs.
Mazda has applied for more than 20 patents related to this technology.