Whether you are a professional or amateur gearhead, the automotive shop you work in requires a lot of tools, technology, and know-how to bring a project from start to finish. In that process, welding is one of many critical skills in the world of automotive fabrication and repair. Like all skills, staying sharp on the tools and techniques used in automotive welding can certainly pay dividends by making your work higher quality, faster, and easier.
Welding Processes for Intake and Exhaust Fabrication & Repair
Intake and exhaust components often utilize either Gas Metal Arc Welding (aka MIG) or Gas Tungsten Arc Welding (aka TIG). When comparing the two processes, TIG offers a much greater degree of control at the expense of speed and ease of use while MIG offers improved speed and ease of use at the expense of precision. It is possible to fabricate complete systems using either process, but muffler repair shops working on consumer-grade and OEM components typically employ MIG, while custom fabrication typically employs TIG.
Many of these custom fabrications (an example being intake manifolds) utilize exotic materials such as titanium to help reduce weight. The difficulty in forming these materials to the desired radii often require “pie cuts” to be pieced together, which requires a lot of precise welding and fabrication know-how. Here, TIG has a distinct advantage, since the ability to feed filler wire independently of the heat source allows for sufficient penetration while producing aesthetically pleasing welds requiring minimal—if any–post-weld finishing.
A power source such as the Miller Dynasty 200 AC/DC TIG Welder allows for direct-current (DC) operation on carbon, stainless, low-alloy steels such as “chrome-moly” (often AISI 4130 and similar steels), and titanium. With a button press and a change of filler wire, it is possible to weld aluminum and magnesium using the power source’s alternating current (AC) output.
A Tip for Welding Intake and Exhaust Components:
Keep Gaps to a Minimum. Spending time learning layout theory can greatly reduce the time spent achieving perfect fit-up. Like painting, spending time with preparation is key to reducing headache later.
Welding Processes for Body Panel Fabrication & Repair
Sheet metal body panel work almost exclusively uses MIG. Even compared to intake and exhaust components, autobody panels are quite thin. This challenge may be amplified by corrosion that may be present when repairs must be performed.
Fortunately, the thinness that makes autobody work challenging often means that less expensive, lower-output welding power sources can be used with good end results. Likewise, welds are typically finished—sanded smooth—after welding, meaning that the precise control of TIG is often unnecessary.
”Even compared to intake and exhaust components, autobody panels are quite thin. This challenge may be amplified by corrosion that may be present when repairs must be performed.”
Keep in mind that automotive manufacturers are designing vehicles to utilize more aluminum. GMAW can still be used successfully, but it helps to have a power source that can accommodate either “push-pull” or “spool gun” style welding torches. An example of such a power source is the Millermatic 251 MIG Wire Feed Welder, although this power source has a greater output capability than is needed for most autobody work.
The majority of autobody work utilizes 0.023-0.035” diameter solid wires used in a short-circuit transfer mode requiring less than 200 amps of output power. For this reason, even some of the smallest commercially available units can be used successfully with great results.
As an aside, plasma cutting is an excellent way to cut problem areas out of body panels, whether they are steel or aluminum. As with welding the thinnest of these components means that a smaller unit can be used.
A Tip for Body Panel Fabrication & Repair
When a groove weld on a butt joint is unavoidable, consider using a copper backing bar (held behind the area to be welded) to act as a heat-sink and help minimize “blow through.”
Welding Processes for Frame Fabrication & Repair
Automotive frame components tend to utilize thicker base metals than autobody and intake/exhaust components. For this reason, it helps to have a little greater output.
The decision to use MIG or TIG depends on the preference of the fabricator and the nature of the component. Some fabricators prefer the control of TIG when constructing custom roll cages requiring many small-diameter tubular connections, but MIG can be used just as successfully with the right selection of wire diameter, welding parameters, and technique.
If you’re unsure if MIG or TIG would be best for your application, multi-process welders are available that allow both processes to be used with a single power source. In addition to process capability, most equipment specification sheets provide suggestions regarding the maximum thickness that the equipment can be used to weld. Trying to use insufficient amperage for the material thickness and joint preparation may lead to issues such as lack of fusion.
As with body panels, plasma is a very fast way to make cuts on components that are tricky to bring to tools such as shears and bandsaws. The torch can be angled slightly to help prepare parts for welding by placing a bevel on the cut edge.
A Tip for Frame Fabrication and Repair
When welding critical components such as automotive frames, a little practice can go a long way. Consider developing a “welding procedure” that outlines the parameters that you will use to produce a high-quality weld. Taking cross-sections of practice pieces can show if the parameters you intend to use are offering sufficient base metal fusion and bead size/shape.
Getting the Equipment You Need
Because welding is just one of many skills required during automotive repair and custom fabrication, the welding power source may not get daily use in your garage. Welder rentals or financing the equipment can be an excellent way to become familiar with a new process, test drive some new equipment, or gain some additional capability for a single job. In addition to providing equipment, the expertise of welding rental professionals can be leveraged to determine which process may be best for application, budget, and skill set.
