Addressing the Challenges of Welding Aluminum in Auto Body Repair | MillerWelds

Addressing the Challenges of Welding Aluminum in Auto Body Repair

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To increase vehicle fuel efficiency and better meet industry regulations, aluminum is gaining popularity in the automotive industry. This can pose unique challenges in auto body welding.
A person MIG welding aluminum in an auto body shop

The rise of aluminum

Corporate Average Fuel Economy (CAFE) regulations are partially driving the the industry’s move toward lighter-weight vehicles. These regulations are intended to improve the average fuel economy of cars and lightweight trucks sold in the U.S. Increasingly stringent standards recently issued by the U.S. Department of Transportation and the U.S. Environmental Protection Agency added to those regulations, requiring the average fuel economy to be the equivalent of 54.5 mpg for cars and light-duty trucks by model year 2025.

Because aluminum can be used at thinner gauges while still providing high strength, it can be used to reduce total vehicle weight and meet these requirements. The strength of aluminum, despite its thinner dimensions, helps reduce vehicle weight without sacrificing integrity or performance.

Aluminum is often used for frames and body panels, especially in larger vehicles. Today, some auto manufacturers are fabricating entire bodies from aluminum (e.g. the 2015 Ford F-150 all-aluminum-body truck). This transition makes aluminum welding a growing market in auto body repair, since these vehicles will inevitably need repairs.

Welding thin gauge aluminum like that used in many of the automotive applications poses several challenges. These issues are difficult for experienced aluminum welding operators to address and even more so for auto body technicians with no prior experience welding aluminum.

To undertake these challenges, it’s important to use equipment and consumables designed specifically for aluminum. Keep in mind some best practices that can help drive success when welding aluminum for auto repairs.

Challenges of aluminum

The main challenges posed by welding thin gauge aluminum are warping, distortion and burn-through.

Because aluminum quickly transfers heat away from the weld area, establishing the weld pool takes more energy than when welding steel. However, because aluminum has a relatively low melting point, thin sections are also especially prone to burn-through and warping. Therefore, controlling heat input during the welding process is key to addressing these issues.

Another common issue is the feedability of aluminum wire, which is softer and can be harder to feed through a gun than other filler metals. Depending on the application and the specific aluminum wire, it may be necessary to use a spool gun, push-pull gun or standard MIG gun when welding this material. Using larger diameter wires can provide more consistent wire feeding and reduce wire “birdnesting” at the drive rolls. Birdnesting is the tangling of the wire between the drive roll and the liner. Clearing it requires the welding operator to stop welding, cut the wire, discard the wire in the gun and refeed new wire through the line, which makes it a time-consuming and costly problem to address.

Auto body welding

As more auto manufacturers use aluminum in vehicles and aluminum welding in auto body repair becomes more common, shops will need to train technicians and/or welding operators who typically haven’t welded the material as to the proper techniques, power source settings and welding parameters. Those making the repairs will also need to become certified to weld on aluminum vehicles or those with aluminum components.

Auto body repair shops should also invest in new equipment specifically designed for welding aluminum.

Choosing a machine with the capability for pulsed MIG welding is critical, as this process is among the best options to control the heat input. Auto repair shops should have an aluminum-dedicated machine that is at least 230 volts and has pulsed MIG capabilities for welding 18 gauge to 1/8-inch thick aluminum. It is important to use the machine only for aluminum, as sharing it for steel welding projects, for example, can pull dust, dirt or other contaminants into the wire feeder, resulting in quality issues.

Learning proper aluminum cleaning techniques is another way auto body shops can prepare for the transition to aluminum welding. Getting the material as clean as possible and removing the layer of aluminum oxide on the surface of the material is key. This may pose a challenge in repairing vehicles that have been on the road, where dirt and gravel can become imbedded into the base material. Greater care and attention to details during the cleaning process will be absolutely essential.

When cleaning, technicians or welding operators must first use a solvent such as acetone to remove grease or other impurities. Then use a stainless steel brush to remove the aluminum oxide prior to welding.

A system designed for aluminum

When choosing welding equipment and consumables for aluminum welding, many manufacturers offer systems or welding packages designed to work together. These packages include the power source, wire, gun and other consumables, such as the nozzle, contact tip and liner.

These packages are designed as a turnkey welding solution, particularly helpful for those with limited experience welding aluminum. These systems feature simplified setup, intuitive interfaces and consistent arc performance, making it easier to execute quality repairs.

For these systems, there are some considerations when it comes to the gun. Some dedicated aluminum systems use a push-pull or a spool gun, while others, including newer ones designed for aluminum body repairs, require a standard MIG gun since auto manufacturers have specified a thicker, stronger aluminum wire for these auto repair jobs (.047 inch diameter, 5554 or 5356 alloy). Auto body shops should always consult the manufacturer for proper wire specifications and gun requirements.

For those using a standard MIG gun, it is important to use a nylon or plastic liner to help the aluminum wire slide through easier. It also prevents shaving of the soft aluminum wire, which can lead to clogs that cause poor wire feeding. A standard gun with a head tube that has a 30-degree angle instead of a 45-degree angle is a good option, as it creates less drag for more consistent wire feeding.

Choosing the most appropriate power source, wire, gun and other consumables are all important factors for success in welding aluminum. Choosing the right welding process is another key step.

Pulsed MIG in auto body welding

Because aluminum is such a good conductor of heat, conventional short circuit transfer isn’t a good method for welding this material. Pulsed MIG is a modified spray transfer process that is preferred and more consistent for welding aluminum.

Depending on the wire feed speed, during the pulsing process, the power source switches between a high peak current and a low background current 30 to 400 times per second. The peak current pinches off a spray transfer droplet and propels it toward the weldment. The background current maintains the arc, but because the heat input is too low, metal transfer will not occur. The peak current pulse ensures good fusion, overcoming concerns related to cold lap, a common weld defect. The background current lowers heat input, addressing the burn-through and warping issues commonly associated with spray transfer MIG welding.

Because the surrounding structure must be protected from the heat of the arc during welding, pulsing technology offers a distinct advantage in these applications. Namely, it controls heat input. As a result, a technician can make required repairs without damaging surrounding parts on a vehicle going back into service.

Tips to help ensure success

Even for experienced welding operators, welding new aluminum can pose challenges. Repair welding on aluminum on a vehicle exposed to dirt, mud, gravel and other impurities can be even more challenging.

To achieve success in aluminum auto repair applications, proper cleaning, training, and choosing aluminum-specific welding equipment and consumables are critical.