Introduction to Common Welding Processes

Published by Trails Less Traveled on February 6th, 2006

Introduction

Let’s be honest, these days you can’t even install most bolt-on components without a welder. A good welder is an essential part of a growing collection of tools that it seems like we need to acquire in order to work on our vehicles. Behind basic hand tools and maybe an angle grinder, I’d say that it’s one of the most essential tools to have in your garage if you plan on building almost anything for your off-road vehicle. There are many different types of welding processes, but let’s begin by describing the three most common in VERY basic terms. I’m planning to spend a lot of time writing about welding processes, techniques and equipment in future articles, so I thought we should start at the beginning.

ARC-Welding

Shielded metal arc welding just called arc welding or stick welding) is extremely popular used all over the world because the equipment is uncomplicated and there are very few moving parts, which makes it inexpensive, durable and relatively easy to operate. An electric current is passed between a flux-coated consumable electrode and the material being welded. The flux-coating on the electrode creates a shielding gas as the filler material is distributed, so no additional shielding gas is required. Slag forms over the weld to further protect the weld from contamination (the brittle slag is easily chipped away after the weld has cooled).

ARC welding is especially well suited to the industrial and agricultural industries, but it wouldn’t be my first choice for more than a few, specific jobs related to automotive fabrication. It’s difficult to manipulate a stick welder in tight spaces and we don’t generally work on thick enough material to need an ARC welder. An example of one exception might be welding the inner steering knuckles onto a heavy-duty 1-ton front axle housing, where an ARC welder could provide excellent penetration on some of the thickest materials we are likely to encounter. I haven’t had too many occasions to use an arc welder outside of high-school shop class, but here are a few examples for reference.

These engine-mounts were ARC welded to the framerails in my CJ7 only because I didn’t have access to any other type of welder at the time. The welds are definitely strong and look decent, but I would have preferred to use a MIG welder if I had the choice.

We had to make a quick field-repair to one of our 4Runners using an ancient arc welder after we broke rear shock mounts while prerunning part of the San Felipe 250 race during a week-long trip into Mexico. We found a local mechanic that allowed us to use his shop and equipment, but this is a picture illustrating exactly what NOT to do while welding. What else can I say? We were working with limited resources.

TIG-WELDING

A skillfully applied TIG weld is hard to mistake for any other welding process. It’s absolutely beautiful to anyone that can appreciate the craftsmanship that goes into every step in the process. The operator holds a tungsten-tipped electrode in one hand and a filler rod in the other, operating a foot pedal that controls the electrical current. It is a time consuming and involved process, very well suited to projects that require a great deal of precision and uniformity. Concentrated and controlled application of heat results in less distortion, which can be important when working with thin material or on projects where close dimensions/tolerances need to be maintained.

TIG welding is the most common welding process used in the aerospace industry. It’s also the favored welding process among high-end automotive fabricators. There are many valid reasons for that popularity and countless applications where no other welding process is an acceptable substitute. Painstaking care is taken to ensure that those small, uniform beads are applied with the ideal amount of filler material and penetration. I’ve heard people say that TIG welding can save 20-40lbs over a similar tubular chassis that was MIG welded, without compromising any strength. That’s a pretty significant weight savings. TIG welding is also excellent for welding non-ferrous materials like aluminum and exotic alloys like titanium.

This picture shows one of the welders at OMF Performance TIG welding an inner beadlock ring onto an Alcoa wheel for one of our project vehicles. TIG welding bead-locks onto aluminum wheels is essential to ensure that the wheels are strong, airtight and balanced.

Our friends at Cortina Cycles TIG-welded this AN fitting from Earls onto a cast aluminum water pump housing for our Dodge 360-powered CJ7.

MIG-Welding

After making all those points about the benefits of TIG welding, I’ve got to say that I think it’s also widely over-used and often employed for aesthetic benefits more than anything else. The average fabricator shouldn’t feel any need to spend the time TIG welding something if MIG welding will get the job done. Take the example of a Chrom-Moly rollcage: TIG welded Chrom-Moly parts must be properly heat-treated in order to realize the maximum the potential of the material and welding process. How many fabricators are really sending all their TIG welded chassis and parts out to be stress-relieved and heat-treated? Taking that idea a step further, I’ve even heard it argued by material experts that MIG welding Chrom-Moly can actually produce stronger parts (compared to similar TIG welded parts that haven’t been heat-treated) because the additional heat from the MIG welding process effectively anneals the welded joints.

MIG welding is much faster and more user-friendly than TIG welding. An electrode (filler rod) is fed from a spool within the welder through the welding gun. When the trigger is depressed, it also releases shielding gas that protects the weld area from oxygen. That’s really all there is to it. Just squeeze the trigger and go. At least that will get you started. It can take years to figure out all the subtleties and techniques that will produce the best quality welds.

Using our Millermatic 251 MIG welder, we spend a lot more time bending and fitting tubes than actually welding them into place. We tack-welded all of these rollcage tubes into place and then finish-welded everything at the same time. Working in stages allows us to verify our final measurements and tube placement before it’s too late. Breaking a tack-weld to make any changes only requires a light touch with an angle grinder fitted with a cut-off wheel.

This is a detail-shot at the driver’s-side dash junction of the rollcage in the previous picture. This is not an example of an ideal MIG-weld, but it has good penetration and will hold together well in a crash.

110V vs. 220V MIG Welders

When shopping for a MIG welder, one of the first decisions that you will need to make is whether to purchase a 110 or 220-volt machine. The major considerations really come down to intended use and budget. Give some thought to what type of material you will be working with most often. I’m typically working with 1/8” and thinner material fabricating rollcages or working on chassis or suspension components, but it was important to me to have the ability to turn up the heat and sink a weld into thicker material when I need to.

I’ve used many 110-volt welders and some of the better machines are adequate for the home fabricator. With that said, it can be frustrating to hit the wall when using a 110-volt welder. Fabricating things like receiver hitches from 1/4” material can be done using a 110-volt MIG welder, but prepping your material will be essential and you might need to use flux-core wire to get maximum penetration. Employing any of the tricks that it takes to weld thicker materials with a 110-volt welder is time-consuming and you can only push the limits so far.

This is a decent weld was made using a Lincoln SP-175 with .035” flux-cored wire and joined a 1.5x.120-wall tubing to the framerails on a Toyota 4Runner nicely (this is how we fixed the field repairs we had to make in Mexico).

When using 110-volt MIG welders, I actually prefer to use flux-cored wire most of the time because it offers better penetration on thicker material and it’s easier to use outside because it does not require any shielding gas. Flux-cored wire does produce a significant amount of welding splatter, as seen in the picture above. There are a few commercially available products that reduce the amount of splatter that will stick to the material being welded, but Pam (the cooking spray) is an inexpensive and common substitute.

MillerMatic 251 Product Review

Next month we’ll review the Millermatice 251 MIG welder and all of the accessories required to get up and running. Here are some links to places with more information to read in the meantime.