Mazda Motor Corporation claims to have developed the world's first aluminium joining technology using friction heat to be applied in the aluminium body assembly process for cars, saying that energy consumption is reduced by approximately 99% compared to resistance welding.

The new technology drastically reduces energy consumption and requires little equipment investment. The technology has been introduced for the rear doors and bonnet of the RX-8 sports car launched to the press in Japan this week.

Up until now 'resistance welding' has been the most feasible joining technology available for assembling aluminium body parts of commercially produced vehicles. However, resistance welding requires that a large current be instantaneously passed through the aluminium. This approach not only uses a large amount of electricity, but also requires large, specialised equipment.

Through the new spot joining method developed by Mazda, a welding gun holds the parts from both sides with a welding tool. The welding tool is then made to spin while force is applied, which in turn generates frictional heat. This heat is utilised to soften the aluminium and generate plastic flow to join the parts.

The only energy consumed in this latest joining technology is the electricity needed to rotate and apply force to the welding tool in order to create frictional heat. As the process eliminates the need for the large current and coolant/compressed air required for conventional resistance welding, energy consumption has successfully been reduced by about 99% in the case of aluminium, and 80% for steel. This significantly reduces impact on the environment while having the same or greater level of joint strength.

The new technology has simplified the overall joining system, as unlike 'resistance welding,' a large current is unnecessary, which in turn eliminates the need for large-scale electricity supply facilities and specialised joining equipment. This has achieved a 40% reduction in equipment investment compared to that of 'resistance welding' for aluminium, and around the same level for standard steel.

Unlike traditional 'resistance welding,' no weld spatter occurs during the process, resulting in a significantly improved work environment.

Use of aluminium for cars is one important approach to make vehicles lighter, which leads to enhanced fuel efficiency and improvements in safety and dynamic performance. In the future, it is expected that aluminium will be widely introduced in many areas. Previously, it was difficult to join parts with welding methods such as 'resistance,' 'arc' and 'laser,' due to the fact that aluminium is a much better conductor of electricity and heat than steel. In addition, other methods presented cost issues. For example, 'riveted joints' use expensive rivets, resulting in higher joining costs, while 'mechanical clinching' requires large equipment.

This energy- and cost-saving aluminium welding technology through the utilisation of friction heat, developed ahead of other global makers, has widened the future possibilities for the application of aluminium in cars. At the same time, it is also beneficial for all manufacturers that use aluminium in their work, and is expected to significantly contribute to environmental conservation in a wide range of fields.