1. Combination weld joints may include plug welds and continuous welds in locations such as the lower rocker panel. This joint was made with a 1 mm skin welded to 2.5 mm structure.
2. This two pass butt joint with backing weld shows good penetration, proper fill and no spatter. Destructive testing indicated a passing weld.
3. Open butt welds on thin metal (1 mm) can be accomplished with ample fusion, minimal distortion and no spatter. This will be a common weld for cosmetic panel repairs.
4. Oscillating the torch during the welding process can produce weld beads similar to TIG. This style was done to increase penetration in the T-type joint shown.
5. No oscillation was done for this 1 mm to 2.5 mm T-joint weld. Directing more heat to the base plate still allowed plenty of fusion to the top.Throughout the past five or six years, representatives of vehicle manufacturers, welding equipment manufacturers, training providers and I-CAR have concluded that there is a shortfall of knowledge for most collision technicians when it comes to metals technology, and in particular, the process of fusion welding and aluminum welding.Currently, the MIG welders being used in collision repair facilities are marginal for welding structural aluminum (2.5 mm or thicker), and none is capable of welding thin aluminum outer panels. The feeling was that technicians would weld these thin panels with TIG welding machines. Unfortunately, as said before, this process requires a higher skill of eye/hand coordination than MIG or Oxy-gas welding. Technicians would be required to seek formal training to master this skill, plus buy another welding machine.Explaining this dilemma to the welding machine manufacturers—extensively done during I-CAR program development throughout the past several years—has helped produce positive changes. New welding machines are being designed to provide a wider variety of welding capabilities specific to the collision repair industry, with the goal being to make it possible for one welder to perform weld joints on both thick and thin steel and aluminum. There are some technologies now available for use in collision repair. The pulsed-arc metal transfer method of MIG welding, for example, is now available. Also known as pulsed-spray, or the pulser method, there are some benefits of using it instead of the standard short-circuit MIG welding process.Beginning with Training
As with any new tool, equipment, product or procedure, additional training will be required to make the process successful. Participants of the I-CAR aluminum repair programs and welding test admit they know little about the process of welding aluminum and further admit their shortcomings in the technical information of the science of fusion welding. So in the graduation to advanced welding of aluminum on vehicles, some major schooling will be required. Operation of these welding units will require more than a short visit and basic introduction of the machine by the salesperson. Listening and talking to other technicians about what works best for them won’t replace the training requirements associated with aluminum welding, which includes pulse welding.Technicians are going to need to know more technical information and grasp a thorough understanding of electricity, welder terminology, heat transfer and fusion, identification of weld quality, and fine tuning of the welding machine. This requirement goes far beyond the material furnished with the owner’s manual.Technicians will also be required to master the techniques of welding aluminum. It is not difficult--just different. Techniques for controlling just the “Cold Start” and “Hot Stop” will require hours of practice to become proficient. Technicians will not learn aluminum welding just by conducting welds on customer’s cars.To get this training, contact your local vocational school or community college’s welding department about welding itself, and how to weld with the new “synergic” technology—welders with microchip, internal computers. Make sure to explain that you will be working with thin materials, so you don’t need to learn about shipbuilding or heavy industrial processes. Visit the facility and examine the equipment it provides for training and be sure to look for lighter capacity welders. Also ask the following questions: Are they an “I-CAR Welding Qualification Test (WQT)” center? Do they offer evening classes? Will you be provided specific training to your needs? And, when can you begin?Participating in the I-CAR “Aluminum Weld Qualification Test (AWQT)” may also be helpful. The program differs from the steel test in that technicians receive four hours of technical information followed with four hours of supervised weld training prior to the test. Contact I-CAR or check its Web site at www.i-car.com for locations and times in your area.Future Trends
Tremendous strides in solid state electronics and “chip” technology have given manufacturers the ability to provide one welding machine with the capability to allow many welding processes. These new welders can provide options of TIG, Stick, Flux-core, MIG of both steel and aluminum, plus welding in the combined ranges of your present 110V and 230V wire feed machines.Pre-programmed microcomputer units can measure, adjust and maintain the interrelationships among variables such as the wire feeder (amperage) and the power (voltage). Operators can still make ultra fine-tuned adjustments as needed with the new synergic technology.Pulse welding (gmaw-p)
Pulse welding is an advanced form of spray transfer that occurs in pulses at regular intervals. At the peak of current level, a droplet is formed and transferred to the base. During the low-current side, or “background,” the arc is maintained. However, no metal transfer occurs. This advanced form of welding provides advantages over many other types of welding and has eliminated most of the disadvantages.The most noticeable advantages include the following: elimination of spatter, all position welding, minimum cold lapping, increased control of heat for thin metals, lower wire feed speeds, higher control of the weld process and less distortion. These advantages give the technician an improved weld in quality and appearance.Arc control, something new for the technician, adjusts the frequency and background current. As arc control is raised, the frequency increases, and thus the droplet transfer rate increases as well.Pulse-on-pulse (gmaw-pp)
The newest design from the equipment manufacturers is this additional function of pulsing within the pulse cycle. Two distinct pulses are used rather than one, and the peak current, background current and frequency are the same for both the high and low energy pulses. Metal transfer occurs during the high-energy pulse, and cooling occurs during the low energy pulse. This action at a regular time interval provides an ultra uniform ripple pattern with adequate cooling between transfers, which allows for welding of very thin material. Welding Trials
Having used basic, industrial types of welders and on the other end of the spectrum, welders with more advanced technology, it’s quite interesting to compare and contrast their capabilities and drawbacks. To help compare these differing types of welders, weld positions and materials I used were the same as the I-CAR AWQT. Weld joints used were butt weld (with backing), 2.5 mm to 2.5 mm; fillet weld (lap joint), 1 mm on 2.5 mm; and plug weld, 1 mm on 1 mm. Weld positions for all welds were vertical and overhead. Material alloy was 5000 series for the 2.5-mm plates and 6000 series for the 1-mm plates.
In addition, supplementary joints were done, including the following: Butt joint without backing, both 2.5 mm and 1 mm; fillet joint of 2.5 mm to 2.5 mm; and plug joint of 1 mm to 2.5 mm. These weld joints were done to see the range of each machine’s capability.The industrial welder used was capable of MIG (GMAW), Pulsed MIG (GMAW-P), and Flux Core (FCAW), with a 230V single-phase power supply using 100 percent Argon gas and .035 filler wire of 5356 alloy, where welding was done with a spool-gun. My first experience of pulse welding using an industrial style unit introduced me to the setting requirements and machines choices. Learning the settings and functions of the welder came easy. Welding was conducted with the alloy and thickness indicated above on 3-in. by 5-in. coupons. Welds were first performed in the flat position. Welding in vertical and overhead positions only required minor adjustments. However, vertical welds could be done in either vertical-up or vertical-down positions, although it was far less challenging to do vertical up.Welds of 1 mm to 1 mm plug welds, and the lap weld of 1 mm to 2.5 mm was satisfactory and could pass the visual and destructive testing of the I-CAR AWQT standards.Welds of the 2.5 mm to 2.5 mm butt joint with backing welds, however, could not meet AWQT standards of I-CAR. This weld is made with a gap of two to three times the thickness of the base material, in two passes. Visual inspection appeared O.K., however, during the destructive phase, welds failed. Lack of full penetration to the backing resulted from the machine being under size in maximum amperage.Although this machine would provide ample capacity for cosmetic panel repair, questions exist about technicians being able to perform quality and safe structural welds. This manufacturer is working on providing a newer machine specific to the needs of the collision repair industry.The more technologically advanced welder was capable of MIG, MIG Pulse, Flux Core as above plus MIG Pulse on Pulse (GMAW-PP), DC TIG and Stick. It had a 230-volt single-phase power supply using 100 percent argon gas and .045 filler wire of 5356 alloy welding the 2.5-mm and 1-mm plates. All welding was conducted using a push-pull lead, although a spool-gun is available. This welding required a higher learning curve since there were so many various capabilities available. It would be comparable to stepping out of an old car with an AM radio and manual everything into a new, high-end vehicle with all the bells and whistles. You need some kind of introduction to the new functions. The same goes with welding. Again, introduction to the settings and functions was done welding with the flat position. Welds all appeared to be good. Vertical position was then done, and I was impressed in the ability and ease to make welds in both directions. Overhead welds were not a problem and also appeared to be good.All weld positions and joints were destructively tested and passed I-CAR standards.Additional weld joints were also conducted. A lap joint of 1 mm with 5
