Friday, 31 March 2006 17:00

Are we ready for aluminum vehicles?

Written by Timothy W. Morgan

Since before the 1970s aluminum has been present in automobile manufacturing processes. Normally found in hoods, deck lids, bumper reinforcements, seat tracks and engine cradles, more manufacturers are coming to market with aluminum structures. While an aluminum structure used to be considered as exotic, more aluminum is arriving in vehicles at a quick pace. 

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Jaguar XJ front frame rail fixtured to spec with Car-O-Liner's Universal Fixture Kit. 
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Jaguar XJ rear frame rail fixtured with Car-O-Liner Universal Fixture Kit and Car-O-Tronic Measuring to verify results. 

While using aluminum parts to replace steel can give a weight savings of 40-50%, if the structure is designed with aluminum characteristics from the beginning, a weight savings of up to 65% is possible.

Aluminum was originally discovered in 1808 in Britain, it quickly has been noted to be the largest chemical elements on earth. The element must be extracted from bauxite ore, which is a complicated process. While aluminum has many alloy designs, it is generally identified internationally with series classifications of 1000 to 8000. The difference in alloys is determined by the amount of magnesium, silicon, and copper.

The added elements classifications are: 1000-aluminum (99% Pure), 2000-copper added, 3000-manganese content, 4000-silicon is included, 5000-contains magnesium, 6000-silicon and magnesium added. 7000 series contains zinc, while the 8000 series has lithium and other chemicals. The most common classifications used in vehicle manufacturing is 5000 and 6000 series. Some aluminum's are heat treatable which will strengthen the material through the heat, quenching and aging process.

Processes used to manufacture aluminum into automobiles include extrusions, stamped parts, hydraforming, and cast.

Current vehicles utilizing complete aluminum structures include Audi A8, Jaguar XJ series, BMW Z8, Aston Martin Vanquish, Ford GT, and soon the Chevrolet Corvette model Z O6. The BMW 5 and 6 series has a combination of steel body and an aluminum front section.

Aluminum also includes good corrosion characteristics when properly maintained and designed. Aluminum has a natural corrosion effect which protects itself with an oxidation film when it is exposed to the elements. This oxidation occurs naturally immediately after the material is cleaned.

This corrosive affect can be accelerated when aluminum and steel contact each other. This process is known as galvanic corrosion. Repairs to aluminum can be affected if steel and aluminum contact. This contact can be from tools, or environmental issues that must be maintained in order to prevent this type of contamination.

Facility requirements

Because of atmospheric affects of aluminum compared to steel the vehicle needs to be

protected from contaminants in the air. These contaminants, mainly airborne metal grindings, can find their way into pinch welds, panel seams, and joints. For this reason, aluminum repairs should be performed in a separate area of the shop. Some manufacturers require a clean room similar to a spray booth, while some manufacturers require curtaining to contain the area during the repair.

All manufacturers do agree that the tools used on aluminum must be separated from those used on steel. The tools should be contained in a separate area and stored away from tools contacting steel. Even basic hand tools, sockets, and body hammers that contact aluminum should not be mixed with tools used on steel. This 'clean room' also needs plenty of ventilation to maintain air mass, and high intensity lighting as you would have in a spray area.

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What can be repaired

Car-O-Liner Academy

Car-O-Liner Academy offered training to the company's sales, technical and training staff in aluminum welding and panel repairs. With instructors from both Sweden and the United States, the participants received hands-on training of aluminum MIG/MAG welding as well as MIG brazing for steel. Both of these welding methods are becoming more popular and Car-O-Liner wants to continue its efforts as the global leader in collision repairs and welding. 

Furthermore, the attendees received training on panel repair techniques using both an Induction Heater and Aluminum stud welder for removing dents.

Robert Hornedo, Pacific Collision Equipment Company, stated that "the training received will expand Pacific Collision Equipment's offering of tools and training for his customer base in which high-end vehicles are becoming more aluminum intensive and small repairs can be a better economical solution than panel replacement."

Repair processes depend on individual manufacturers. While BMW relies on replacement of affected areas with procedures using adhesive and rivets, Jaguar utilizes GMAW (MIG) welding and rivets depending on repair area. Audi again relies on welding in most locations. All vehicles have crush zones designed in the rail ends which typically require replacement.

BMW, for instance, has four procedures for replacement on the aluminum front section of the 5 and 6 series vehicles. A lower rail tip, upper radiator support section, complete lower rail, and complete upper apron and strut tower. Each procedure requires vehicle specific training to insure the repair is performed to correct standards. BMW offers model-specific training to all BMW dealer collision facilities, and/or independents sponsored by the dealer. This training utilizes the tools, parts and processes to complete all four repairs. BMW also states no pulling on the aluminum portion of the vehicle, but from the cowl forward the vehicle is steel.

Audi, which has been repairing aluminum on the A8 for the longest period of time, has elected to set up certified facilities across the nation to which damaged vehicles are transported. by the manufacturer to one of the certified facilities. Audi has joined in a training partnership with I-CAR to help provide the necessary technician model-specific training.

Jaguar also has chosen to set up certified facilities for repair in two classifications: non-structural and structural. The non-structural facility can perform repairs that do not require structural panel adjustment or replacement. The structural shops are outfitted with special structural holding equipment to fixture the new parts in place and a welder that has specific parameters to weld each repair technique. The training which is specific to the Jaguar model is also performed by I-CAR at their training center in Appleton, Wisconsin. Both the structural and non-structural facility must meet special requirements and have equipment that is approved by Jaguar for the repair.

Not the perfect metal yet

One of the problem characteristics of aluminum is the cracking of material. Depending on its composition, material can be porous and crack as pulling is performed. Aluminum does not have the same elasticity of steel. Sometimes low heat can be used from an induction heater to warm the area prior to moving the material a minimal amount. The adjoining areas connected can be affected by the movement. Adhesives and rivet strength can be affected by the movement. Individual vehicle manufacturers dictate how much if any pulling can be performed.

Where will aluminum go in the future? Manufacturers are weighing out the possibilities. But don't expect it to go away anytime soon. Although steel manufacturers are not going to walk away without a fight, even more materials that are lighter and stronger are on the horizon. Technicians need to be prepared.

Timothy W. Morgan is the Global Director of Technical Training for Car-O-Liner. Morgan's vast experience in the collision industry includes former technician, shop manager, business owner, and director/educator of a collision repair-training program for a technical college. He has spoken at NACE, AASP/Northeast, Collision Concepts, Beijing China International Collision Repair Tech Exchange Seminar and I-CAR International Conventions on structural repairs and productivity issues. Morgan is an ASE Certified 'Master' technician for collision repair and completed I-CAR training. Additionally he is a past I-CAR Welding Test Administrator, and has received the 'Blue Seal of Excellence' from ASE and recognition from I-CAR for his assistance and on going support to their operations, and a member of the Society of Automotive Engineers (SAE).

 

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