Honda engineers can weld steel to aluminum, showcased in the new Accord

December 2012 - Until now, a line weld, or continuous weld, has not been applicable to welding steel with aluminum. Honda Motor Co. Ltd., Tokyo, has developed the technology and applied it to the world’s first subframe of a mass-production vehicle. Engineers believe this patent-protected technology will change the industry.

From a manufacturing standpoint, engineers needed a way to reduce the weight of vehicles substantially while keeping costs low. “We were researching the technology to overlap aluminum on aluminum and used  friction stir welding (FSW) to weld from the beginning,” says Tetsuya Miyahara, chief engineer, Honda R & D Co. Ltd. Automobile R & D Center. “From there we extended the research to develop FSW to overlap aluminum on steel. This was planned as an extension of the technology.”

The new North American 2013 Accord subframe is made from aluminum and steel and was made available to customers in September. Honda plans to expand the application to future models. “We spent approximately five years developing technology to weld different materials and approximately 10 years for manufacturing technology research,” he says.

“Our engineers are researching different metal combinations to reduce weight, using aluminum for hood panels in some products, but this is the actual joining of two different metals,” says Ron Lietzke, media relations at Honda of America Mfg. Inc. in Marysville, Ohio.

The subframe is assembled with the engine and then installed in the vehicle during manufacturing. “You can see the difference between the aluminum and steel in the subframe because the aluminum is not painted and the steel is,” he adds. “You can distinctly see the two pieces that are welded together.”

Adapting infrastructure

In order to expand its FSW line, Honda is installing industrial robots that are configured to join metals by using the FSW continuous process. “Similar to other industrial robotic processes, robotic equipment needs to be installed to implement the FSW technology,” Miyahara adds. Adding the robots isn’t a huge overhaul to the production process, Miyahara says robotic systems are installed routinely so for integration with other manufacturing operations. 

FSW works by generating a new and stable metallic bonding between steel and aluminum by moving a rotating tool on the top of the aluminum, which is lapped over the steel with high pressure, according to a press release from Honda. This high pressure allows the welding strength to become equal to or above conventional metal inert gas welding.

The process allows for weight reduction and improved rigidity of the suspension mounting point by 20 percent when comparing the 2013 Accord to older models, such as the 2008 Accord. There is also a significant reduction in manufacturing energy, saving more than 50 percent in electric power. Applying sealing material to the hybrid structure inhibits rust. The process also uses the world’s first nondestructive inspection using an infrared camera/laser. Compared to commercial devices, the robots need only about one-tenth the floor space.

Honda says the system can also be used for aluminum-to-aluminum welding, allowing for mass production of a full-aluminum subframe. “I believe this technology helped us to further evolve in weight reduction and expanded the possibility to contribute to the environment and fuel efficiency,” Miyahara says. MM