For automotive designers and manufacturers, finding ways to increase fuel economy has become a primary—and increasingly complicated—goal. In the U.S., regulations now focus on a requirement that every automaker achieve a corporate average fuel economy (CAFE) of 54.5 mpg by 2025. Such dramatic improvements once seemed impractical or impossible, but today they are the new reality for automakers.
In response to these emissions regulations and to the evolving preferences of consumers, automakers have generated a “Technical Tsunami”—the waves of change resulting in new technologies and new materials like aluminum, magnesium, carbon fiber, advanced high-strength steels, and vehicle-wide proliferation of advanced electronics. Many of these require specialized training to repair. In 2015 alone, automakers introduced 142 new or redesigned vehicle models.
The aluminum-intensive 2015 Ford F-150 shed 700 lb (318 kg) compared with previous models. The drastic material change to the F-150, with its longstanding reputation as one of America’s best-selling vehicles, caused the industry to stand up and take notice.
Maintaining a standard of vehicle repair safety with aluminum
As progress has been made toward adopting aluminum for automotive structures, industry leaders have realized that, to keep aluminum vehicles safe, they must consider not just their manufacturing process but also their repair. Collision repair facilities needed to be confident that their technicians knew how to properly achieve complete, safe, and quality repairs on aluminum structures.
Technicians across the industry are learning the necessary new methods for working with aluminum as part of the I-CAR Welding Training & Certification program.
Prior to the launch of the F-150, I-CAR and Ford Motor Co. worked together to create and make an I-CAR training curriculum for collision repair technicians. Historically, vehicles debut before the training begins. The F-150 structural repair training course FOR06 has become one of the most popular courses in I-CAR’s history. In particular, the program emphasizes processes for welding, riveting, and rivet bonding aluminum vehicles.
Welding aluminum—not difficult, just different
Welding aluminum is not more difficult than welding steel, but it requires a different mindset in a number of areas.
Setup space—One best practice that is often recommended by vehicle makers when repairing aluminum vehicles is to set up an environment separate from the steel welding area. The concern is that steel particles in the air could contaminate aluminum and possibly cause corrosion if exposed to water over time.
Equipment—When repairing steel bodies, technicians commonly employ MAG (metal active gas) welding, using a shielding gas that is 75% argon and 25% carbon dioxide—a mixture known as C-25. Aluminum, however, requires the use of MIG (metal inert gas) welding with a shielding gas composed of 100% argon.
Argon is specified because it offers good cleaning action on the metal being welded. Aluminum materials immediately form a thin coat of aluminum oxide on their surfaces when exposed to air. Moreover, aluminum oxide melts at 3725°F (2050°C), while aluminum itself melts at 1200°F (650°C), so the aluminum would melt before its oxide covering does. The aluminum oxide must be removed, or the technician will be trying to weld through it, which is certain to produce a less-than-desirable weld.
Technicians should use contact tips specifically designed for aluminum, with an oversized hole for the electrode wire. These tips are stamped with an “A” or “AL.” Similarly, shielding gas nozzles must be larger than those used with steel to accommodate the increased gas flow.
Further, to avoid contaminating aluminum surfaces with steel particles, separate hand tools are often used. Cutting tools and abrasives should be dedicated specifically to aluminum as well to avoid cross-contamination.
Preparation—Before starting to weld aluminum, technicians need to remove any coatings from the surface and then wipe it clean with a solvent to eliminate any surface contamination. They should use sandpaper or a stainless steel brush to remove the aluminum oxide from the weld zone and clean the area again immediately before the welding operation begins.
Technique—Creating welds with aluminum differs from working with steel. Technicians should use the push technique, rather than the pull technique. This method enhances the ability of the shielding gas to clear aluminum oxide from the aluminum.
Also, the electrode wire should stick out farther from the welding torch, and the torch should be held farther back from the welding surface. Note that the technician should always use the electrode wire recommended by the vehicle maker.
Typically, more amperage is required for welding aluminum than for steel, and the welding transfer method is different. When working with steel, generally the short-circuit method is employed so that, when the electrode hits the steel, it short circuits and breaks off. For aluminum, however, the preferred transfer technique is a pulsed spray in which the weld bead breaks off before it is sprayed into the molten puddle.
Whereas steel holds heat from the welding torch in one area, aluminum transfers the heat throughout the part. Because of this greater heat transfer efficiency and aluminum’s low melting point, the welding speed should start slowly but then increase as the welding torch moves across the panel.
To avoid cold starts with aluminum, the technician should create a run-on tab or use a machine with a pre-heating feature. At the end of the weld, craters tend to form in aluminum, so the tech should activate an extra trigger pull when completing the weld, or make a run-off tab.
The new frontier: What’s next?
To master the curves in the road ahead, we need the right equipment, training, and qualified technicians—along with an appetite for learning. Given the dramatic changes in vehicles, it is imperative that the collision repair industry support a robust and earnest “Learning Culture,” building businesses that treat learning and knowledge as strategic assets that need to be managed, developed, and maintained.
Once we understand the nature of this new road, we’ll be prepared to enter the new frontier of aluminum welding, building an even better framework for approaching whatever game-changing material or innovation is sure to be down the road.
Jason Bartanen, Director of Industry Technical Relations for I-CAR, wrote this article for Automotive Engineering. I-CAR is a not-for-profit education, knowledge, and solutions organization designed to support the evolving needs of the Collision Repair Inter-Industry.