"Welding"

By Hugh Holloway

At the May Membership meeting, samples of TIG welding were displayed. A couple of people asked, "What can be welded on an automobile, and how is it done?" The following is a brief outline of the welding process.

Welding is a fusion of metal by a heat process that brings the edges of the metals to be joined to the temperature of the melting point. With a proper weld, the strength of the joint is as good as, or often better than the original metal. There are basically four types of welding processes. Oxygen/Acetylene gas welding uses a mixture of those two gases using a hand held torch. Usually, a filler material in the shape of a long narrow rod is hand applied to the melting puddle as torch heat is applied to the metal to be joined. Oxygen/Acetylene welding generates a lot of heat, which is difficult to control. It is more suitable for welding heavier metal of ¼ inch thick or greater. In this process, the metals to be joined must be free of contamination, rust, or paint. Oxygen/Acetylene welding equipment can be purchased for a moderate amount of money. Oxygen/Acetylene welding has a moderate to difficult learning curve.

The next welding process, Arc welding is a process in which the heat being used to fuse the metal is generated by two heavy metal electrodes connected to a special transformer to create a high energy electric arc to melt the metal. This is the simplest type of welding, and takes little skill to use. However, it produces the crudest welds, with much splatter and slag. The depth of penetration and quality of an Arc weld is often questionable. It is also the cheapest equipment to purchase, around 150 to 500 dollars for the entry level. The advantage of Arc welding is that you can weld rusted and moderately contaminated or painted surfaces with little preparation of the joints. Arc welding is sometimes referred to as "Stick Welding" due to the shape of the hand held electrodes.

A third type of welding, known as Metal Inert Gas (MIG) welding, is very popular. The equipment can be purchased for a moderate sum of money (500 to 1000 dollars and even less), has a moderate learning curve, and produces fast, decent welds with little spatter and oxidation. The wire electrode, which is consumed in the process, is fed continuously through a hand held device, which also is connected to a bottle of inert gas such as argon, carbon dioxide, are a combination of the two. The gas shields the melted weld puddle from atmospheric contamination (Oxygen and Nitrogen, which are the principal components of air). And it produces a weld with no oxidation contamination. This process produces a superior weld and is often seen in body shops and the home shop/garage. One disadvantage of the MIG process is that it is difficult to control a steady arc at the electrode.

The fourth type of welding is called Tungsten Inert Gas welding (TIG). TIG welding is the king of the welding process, producing the highest quality of welds. The process involves a hand held device that holds a tungsten electrode connected to a transformer to produce an exceptionally stable arc to generate heat. The hand device also is connected to a bottle of pure Argon gas, to shield the weld from atmospheric contamination. (Oxidation, which will cause brittle of cracked welds) Unlike the MIG process, the TIG electrode is not wire fed, and is not consumed in the weld process. For TIG you also use a filler rod to fill the joint, similar to the Oxygen/Acetylene Process. What makes the TIG process so superior is the fact that the current supplied to the arc is controlled by setting the maximum desired with a control on the transformer, and then being able to vary the current from zero to maximum with a foot pedal similar to the accelerator pedal on an automobile. This gives absolute control of the amount of heat being applied to the weld joint. There is a narrow heat band, with deep penetration, and the surrounding metal is not heat soaked. With this process you can produce quality welds on very thin steel with no distortion of the metals being joined (which will happen in all of the other weld processes due to heat soaking of the surrounding metal). TIG is also the only proper way to weld aluminum and stainless and exotic metals. Some of the disadvantages of TIG are that the equipment is expensive, it requires the highest learning curve, it is the slowest of the weld processes, and is not used in thicker metals (generally over ¼ inch thick. With the introduction of modern state of the art inverter systems to replace transformers, TIG equipment is becoming more affordable to the home hobbyist, with entry levels around the three thousand dollar price range. Now, to the question "Where would you use welding on your automobile?" All automobiles contain metal somewhere within their structures. The older cars, generally prior to the 1980 era, usually have heavy steel frames that the body is mounted on. Newer cars have Uni-body construction, which eliminates the frame, but the body still has metal reinforcements. Often, frames and uni-bodys have to be repaired by welding due to crash damage, or corrosion due to age. Most car bodes are constructed of thin sheet metal, which is spot welded at the factory from many sub-assemblies to create the whole body. When the body of a car is damaged, there is almost always welding involved in repairing the body panels. Our antique and vintage cars are almost always the victims of rust and corrosion in such areas as floor pans, trunk pans, lower door areas, and body rocker panels, and fender quarter panels. While many repairs can be seen with bondo and other temporary repair techniques, this method will not halt corrosion or contribute to structural integrity. The only proper way is to cut out the damaged metal and weld in new repair panels. There are many vendors that sell replacement body panels for new and old cars. However, there are some repairs in which the replacement parts musts be fabricated by the person doing the repair. Take a visit to some of your welding buddies, and see how some cars in pretty sorry looking condition can be made to look young and new again. You just may want to invest in some welding equipment. The information presented here is just a snapshot of the welding process. There are many books and manuals available that can give you a comprehensive understanding of each of the welding processes, and the considerations of the type of metals to be welded.