GLUING METAL TOGETHER

Welding Basics and Tips

TIG, MIG, stick, plasma arc, submerged arc, laser, gas… Some of these terms may be foreign to a small group, but racers know they are meant to fuse two pieces of metal together in a method known as welding. It’s actually a highly technical operation but one which has become pretty straight forward in both welding machines and human experiences.

While there are those several different processes of welding, there are really only two which are popularly used in the race car industry; that being TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas).

Very simply, MIG is a process whereby wire is stored on a roll inside the welding machine and fed through the cabling into the molten weld puddle that the wire initiates. A mix of argon and CO2 is also fed through the cabling to surround the molten puddle and keep it free from contamination.

TIG welding is very similar to gas welding where the combination of the two gases (acetylene and oxygen) provides a flame which produces a puddle of molten metal. A separate filler rod is then fed into the puddle by the operator to assist in joining two separate pieces of metal together. In TIG welding, an electrical charge through a piece of tungsten metal produces the aforementioned “puddle,” after which a filler material is fed into the puddle in the same manner as gas welding. The shielding gas is most commonly used is a straight argon although in some cases a mix of argon and helium can be substituted.

Prior to the days when TIG (Tungsten Inert Gas) welding machines became popular, racers would typically use an oxygen-acetylene torch to weld their cars and other things together.

Anytime you heat a piece of metal, it changes its characteristics. Keeping those characteristic changes to a min¬imum is the objective. TIG welding ac¬complishes that. This is not meant that it should be the only process used as MIG welding has its benefits, one of which is speed. MIG welding is a very simple and fast process that in reality can almost be perfected by anyone in about a half-hour’s time. TIG welding on the other hand, can take a lot longer to perfect, especially when it comes to aluminum welding, even though alumi¬num can be MIG welded also.

Speaking of MIG welding aluminum, a typical MIG welding machine utilizes a spool of filler material inside the machine. That filler wire is “pushed” through the machine’s hosing out to the torch and work piece. As far as MIG welding aluminum is concerned, because the aluminum filler wire is soft, it cannot be “pushed” through the machine’s hosing. This requires a separate spool gun/torch where the wire is stored directly at the torch and fed into the molten puddle from there.

There really has not been a lot of technological breakthroughs in welding technology over the years with one exception: welding machines themselves. In most welding ma-chines used in shops, there resides an internal transformer and rectifier which is used to provide the required amper¬age with which to weld by switching AC (alternating current) shop electric to DC (direct current) amperage for welding. Inverter welding machines have now changed that landscape. An inverter machine does away with the transformer and rectifier, using so¬phisticated microprocessors to provide the current change. This enables the machines to be extremely light, and in some cases, portable. It also allows the machines to be extremely programma¬ble for a number of instances. That is the future of welding machines.

Our race trailer used to house a big TIG welding machine driven by a generator-style engine. When it became time to upgrade, we asked the local welding supply company for a reference as to the type machine they suggested, them knowing full-well the type welding we did at the race track. In walked the salesman with a Lincoln welding machine not much bigger that a small suitcase.

“No, get that thing out of here. There is no way that machine can weld as good as our large welder.”

“Try it for a while,” was his comment.

That “little” machine will just about out-weld anything including the larger shop units we have, along with the addition of being able to weld aluminum which requires a different setting.

As we mentioned earlier, a welding machines converts AC shop electric into DC for welding. It’s here where the constant polarity flows in one direction only and is used in the welding of steel.

As for aluminum, a machine needs to be switched to AC where the electric current reverses it’s direction many times a second. Because aluminum has an oxide layer on the material, that layer must be removed in order to get a clean weld, accomplished by the polarity change allowing for effective aluminum welding.

In MIG welding, the amperage and feed rate of the wire is preset on the machine by the operator. It’s this process which is used in a number of production facilities that makes the MIG welding process relatively easy to develop the skill required.

TIG welding on the other hand, requires a combination of hand dexterity because you’re using one hand to control the torch while feeding the filler wire in with your other hand. The amount of amperage of the torch can also be controlled with the use of a foot pedal rheostat which allows the amperage to be controlled but takes into account a third body part, your foot. There are torches available where the rheostat is located on the torch itself, but most welders in race shops will utilize a foot pedal. The use of a foot pedal is extremely handy especially when welding alumi¬num where the weld amper¬age can be increased to get the pud¬dle started followed by reducing the amperage slightly to continue the weld. When welding various thicknesses of metal, the same amperage setting can be maintained on the machine, while the actual amperage is controlled by the foot pedal.

There are two key “tips” when it comes to welding. The first is a steady hand. This doesn’t mean that if you have a bad case of the “shakes,” you won’t be able to weld, instead regardless of MIG or TIG; and even stick welding; bracing your torch hand against some sort of object will enable you to keep a steady hand on the torch. MIG welding is a little more forgiving in that aspect but still an important facet.

Next involves the term “cleanliness is next to Godliness,” also relevant in welding. The cleaner the material, the better the weld. Most hot rolled steel will have a greyish outer scaling on it. That scaling can contaminate the weld and should be sanded off prior to welding. Aluminum is extremely finicky to cleanliness. While in some cases, steel can be welded that is dirty or contam¬inated with oil, not so with aluminum. This makes the repair of aluminum products such as cracked oil pans ex¬tremely hard unless they are cleaned thoroughly.

While this might just be the basics, welding still requires a skill, one which takes experience, experience that can only be accomplished by doing.

SOURCE

Lincoln Electric
www.lincolnelectric.com