Automotive Design and Production

FEB 2014

Automotive Design & Production is the one media brand invested in delivering your message in print, online, via email, and in-person to the right automotive industry professionals at the right time.

Issue link: https://adp.epubxp.com/i/248071

Contents of this Issue

Navigation

Page 33 of 51

AD&P; > February 2014 > FEATURE > Welding Mixed Materials, Multiple Ways > Zachary Peterson > zpeterson@autofieldguide.com pressure, it melts and forms a metallurgical bond, essentially a friction weld. Miles says FBJ could be used to weld a high-strength steel A- or B-pillar and aluminum roof, or to join lighter-weight materials into parts of the car door. "Our process is a technical success, now we need to go forward to make it commercially viable," he adds. Miles and his team continue to research FBJ with assistance from stir welding machinemaker MegaStir (megastir.com) and Oak Ridge National Laboratory (ornl.gov). Magnetic pulse welding: What happens when you drive one metal workpiece (e.g., a 4-in. diameter aluminum tube) into another (e.g., a steel shaft) with a massive magnetic pulse (>1-million amps through the coil in 100 msec) at 900 mph? If the setup is right, then the coalesce of the two materials, a metal to metal bond. That's essentially magnetic pulse welding (MPW), which is a "cold" process. p Cold metal transfer welding uses very little current by retracting the wire to create a "hot-cold, hot-cold" pattern up to 90 times per second. Cold Metal Transfer Another viable method for welding dissimilar materials, especially ultra-thin (0.3 to 0.8 mm) sheets, is an arc welding process known as "cold metal transfer" (CMT). What happens is that there is a digitally controlled wire feeder. As soon as an arc is detected as the wire reaches the weld pool, the weld wire is retracted and the weld current is lower, so that there is a droplet deposited. This has been described as a "hot-cold, hot-cold" process because the wire retracts—applies heat and then removes it—up to 90 times per second. Compared to conventional welding, CMT requires less current for the same amount of material deposition, which means there is comparatively low heat input. Fronius (fronius.com), which makes CMT welding systems, describes this process as the "most stable weld process in the world." Advantages include a low thermal input and a stable arc, which doesn't produce spatter because the short circuit is controlled and the current is kept low. Dana (dana.com) has used MPW for more than 10 years to weld aluminum and steel driveshaft components. Although it might seem like a lot of energy is used, according to Dana, it uses 100 times less energy than the equivalent metal inert gas (MIG) weld. Before Dana adopted the MPW process, conventional driveshafts required bolting a CV joint to a companion fange from the axle or transmission because it was impossible to weld a heat-treated bearing element. A thermal welding process would distort the joint. By adopting the "cold," magnetic approach, driveshafts design options increased. "Our MPW process allows us to join steel and aluminum components to create a wide variety of innovative driveshaft designs," says Jim Duggan, a chief engineer at Dana. "The result is a bond that outperforms conventional MIG welding and other metallurgical processes." The process also works for joining nonmetallic materials such as composites, polymers, and rubbers. 32

Articles in this issue

Links on this page

Archives of this issue

view archives of Automotive Design and Production - FEB 2014