As the market for Electric Vehicles (EVs) continues to grow, new vehicle designs are driving demand for lighter and more robust parts and systems that can be economically produced at scale. Increased aluminum content in vehicles, as well as the need for maintenance-free and reliable liquid cooling of batteries and electronics, have led to a dramatic increase in the use of friction stir welding (FSW). Because of its unique processing characteristics and post-weld properties, friction stir welding on a vehicle has proven to be the best option for a number of reasons. Below we’ll take a closer look at the most common applications where FSW has been adopted and why.
Increased range and efficiency requirements for vehicles have driven the need for lighter components while the availability of new high-strength aluminum alloys has allowed the use of aluminum in locations on car bodies previously not possible.
Both of these factors have fostered the adoption of aluminum tailor-welded blanks. Tailor-welded blanks are individual sheets of aluminum of varying thicknesses and/or alloys that are welded together to form a panel with weight and strength properties that cannot be produced by other means. A tailor-welded blank has strength where needed and is light where it can be while reducing overall cost.
Because of its highly repeatable nature, desirable post-weld joint properties of low distortion and fine-grained microstructure, and ability to weld dissimilar alloys, FSW has become the joining method of choice for producing aluminum tailor-welded banks.
Friction Stir Welding: Automotive Power Electronics Enclosures
EVs feature unique electrical components that deal with high voltages and currents, known as powertrain controllers. The FSW process can generate cost and performance benefits over standard methods of securing lids on finished electronics boxes while providing a hermetically robust seal. The main alternatives here for this type of welding for electric cars are a cover that is screwed on and sealed with either a dispensed adhesive, a form-in-place gasket, or an inserted rubber seal.
The cost savings that can be achieved by using FSW comes from reduced BOM cost (screws, clips, adhesive, gaskets, etc.), reduced adhesive curing time, simplified component design, and reduced upstream processing of parent parts. Bond’s customers have reported cost savings in the $1-2 range per enclosure when these assemblies are produced with FSW over other methods. From this perspective, it is easy to see how friction stir welding for electric cars becomes quite attractive.
FSW for Power Electronics and Battery Tray Liquid Cooling Circuits
Another application for FSW is liquid-cooled electronics, whether it be power electronics or chilled battery trays. In either case, a robust seal is needed to contain the pressurized coolant and to promote heat transfer.
The competing technologies are much the same as previously described, but because the pressures to be sealed are much higher, the number of screws is much higher, and the stiffness requirements are greater. In addition to the material savings, FSW allows a much lower profile for this assembly, saving probably around 10mm or so of thickness in an average application. Given the large area of garden variety controllers and chill plates, this is quite a bit of volume saved.
FSW chill plates can also be welded across the middle, which is a problem for screwed covers, as this creates leak points. This is also a significant part of the height benefit, as the covers are thinner in the middle than cast covers, which adds to the cost savings.
FSW continues to gain traction as a preferred method both for joining lightweight aluminum body panels and sealing critical electronics and liquid coolant circuits. Bond Technologies is a proven leader in both the design and construction of FSW machines, and tooling for high-volume production applications. We offer a full line of friction welding technologies, from compact machines up to large-scale multi-axis, multi-spindle systems. Let Bond Technologies help you find the best FSW solution for your application. For more information regarding our products or services, or to discuss options for welding on a vehicle, contact us today.