Passing the Torch
As aluminum gains on steel in auto-body structure, these 10 tips will transform you into a shop superhero for the brave new world of welding.
No spoiler alert here: Aluminum is the auto industry’s new super metal. Its strength is exceptional for a lightweight metal, and its flexibility in usage for vehicle bodies, structural components, decoration and styling mean that it will work with just about any application in which designers are seeking ways to lighten vehicle systems to improve fuel economy.
Aluminum is helping manufacturers respond to government regulations requiring corporate average fuel economy of 54.5 miles per gallon by 2025. Ford Motor Co. proved that aluminum can stand up to the American way of driving when it introduced the aluminum-intensive 2015 F-150, with its all-aluminum body that weighs 700 pounds less than previous models.
Ford and other automakers earlier had developed concept cars or production vehicles built mostly, or entirely, of aluminum – the Audi A8, the Jaguar XJ, the Corvette Stingray, the Ford P2000 – but these primarily were vehicles for lower volume production. The F-150 traditionally has been one of the best-selling vehicles in America, a huge market-pleaser, and the switch from steel to aluminum in the vehicle has shifted aluminum into a new gear.
At the same time that vehicle makers have been ramping up their capabilities for producing lighter-weight cars and trucks with aluminum alloys, the collision repair industry has realized that repair technicians need to learn new skills and techniques for complete, safe and quality repairs. Working with aluminum in collision repair facilities is different from working with steel. In the hands of an untrained technician, aluminum repairs can weaken a vehicle’s structure and potentially pose mortal danger to drivers and passengers in a subsequent accident.
As insurance companies increasingly have encouraged collision repair facilities to add training in aluminum to their certifications, dealers and independent professional repair facilities have turned to I-CAR, a not-for-profit organization that provides education, knowledge and solutions to the collision repair industry. I-CAR develops training courses for technicians. It has become renowned for its training and certification in vehicle welding and began training professionals in dealing with aluminum repairs two decades ago.
Now I-CAR annually trains thousands of technicians, and last year about 3,150 technicians completed a specially designed welding and training program to learn how to repair the F-150 and other vehicles that use aluminum extensively.
Working with welding equipment and material manufacturers, I-CAR experts have produced training programs describing specific welding techniques for aluminum. From those publications, I-CAR has developed “10 Tips for Safe, Complete and Quality Aluminum Welding Repairs.” These recommendations cover the technician’s tools, processes and environment when welding the new generation of aluminum-based vehicles and are highlighted here to provide an overview of what makes aluminum welding different from conventional steel welding.
The 10 Tips
Separate your setup area. Aluminum is vulnerable to galvanic corrosion over time when it comes in contact with other metals, such as steel, in the presence of water. It’s important, therefore, to avoid contaminating aluminum surfaces with steel dust particles that may be present in the facility. The best way to achieve this is to set up a different area within the facility that is dedicated solely to aluminum repairs. At the minimum, the aluminum welding area should be curtained off.
Clean the aluminum before welding. Aluminum invariably combines with air to create a thin aluminum oxide coating on the metal’s surface. This coating will melt at 3,725°F, but the aluminum metal melts at 1,200° F. This means that, if the oxide were allowed to remain on the metal, the aluminum would melt before its coating does, and the repair technician would be trying to weld through the coating. The result would likely be a hit-and-miss weld. It’s essential, then, to remove oxide coatings from the area being welded by using a stainless steel brush or sandpaper and then to wipe the metal clean with a solvent before welding. Follow the initial cleaning with another cleaning right before you begin welding.
Put away your steel hand tools. You should work with an entirely separate set of hand tools when welding aluminum. All abrasives and cutting tools used in the aluminum repair process should be reserved just for aluminum work, so that they don’t contaminate the aluminum with steel particles. Some cutting and grinding discs are designated for aluminum only. They don’t clog in the way that discs designed for steel do.
Use a different type of shielding gas. When they repair steel, technicians take for granted that they will be using C-25 shielding gas, composed of 75 percent argon and 25 percent CO2. With aluminum, however, they need to use100 percent argon. The argon serves a special purpose in this instance: It does a great job of cleaning the oxide from the metal right before the weld is made.
Remember “A Tip.” When making repairs with a welding torch, you must use a special tip designed for use with aluminum. These tips are often marked with an “A” or “AL” and are fabricated with an oversize hole, recognizing that the electrode wire will expand from the heat. In the same way, the nozzles for shielding gas need to be bigger than those used with steel, because they must allow for a higher gas-flow rate.
Push, don’t pull. Steel welding can be carried out in either of two ways: pulling or pushing the weld bead. In aluminum welding, you want to use the push technique to preheat the area being welded and to improve the cleaning action from the argon shielding gas.
A difference that sticks out. Be sure to use the electrode wire that is designated by the vehicle maker for the particular aluminum alloy you are welding. The wire should stick out farther from the welding torch than it normally would in steel welding, and therefore you will hold the torch farther away from the surface when welding.
Pulse is a plus. In another variation from steel welding, the conventional short-circuit method should be avoided. Rather than relying on the electrode to hit the metal, short circuit and break off, welders working with aluminum should use a pulsed spray. In this transfer method, the weld bead breaks off prior to being sprayed into the molten metal.
Walk before you run. Aluminum spreads heat from the welding torch throughout the material being welded, while steel holds the heat in just the area where it is being applied. Because of its ability to transfer heat with high efficiency and its low melting point, aluminum requires a specific welding technique. You should begin moving the torch slowly and then increase the speed as the torch runs across the surface.
Run a tab. It’s important to avoid cold starts when welding aluminum. You should either produce a run-on tab or use a welding machine that has a pre-heat setting. To prevent craters from forming in aluminum at the end of the weld, give the trigger an extra pull to create a run-off tab.
I-CAR is training technicians across the United States to use these aluminum-specific welding methods and has developed complete aluminum repair programs jointly with automakers. (For more information on I-CAR courses, visit www.i-car.org.) With programs like these, professionals will do a much better and safer job when repairing aluminum.