scope:

The rapid growth of the use of aluminum in automobiles in recent years brings with it the inevitable need to repair damage that occurs in service. This manual addresses welding and its role in repair activity. The principal focus is on sheet products but the techniques and processes described are applicable to other wrought aluminum product forms. There are two principal welding processes in use today: gas metal-arc (GMA) welding and gas tungsten-arc (GTA) welding. These processes are popularly known as MIG and TIG, respectively. These two processes, coupled with a variety of joint configurations, provide the capability to complete essentially all anticipated repair requirements.

GTA (TIG) welding is widely used for welding relatively thin aluminum sections ranging from 0.015 to 3/16 in. In this process, an arc is established between a nonconsumable tungsten electrode and the aluminum parts to be welded, with a shield of inert gas enveloping the arc and weld pool.

The types of equipment and operating parameters used in GTA welding are noted, as are the functioning of the equipment and precautions that must be observed to ensure proper usage and safety. This publication also covers arc shielding gases and filler metal used with various parent metal alloys.

The choice of filler alloy in the welding of aluminum is an important factor in eliminating weld cracking, and the nominal compositions of some filler alloys are listed and analyzed for appropriate applications. Proper GTA welding techniques are examined, accompanied by a table of typical practices. It is noted that some training is needed to weld aluminum body sheet but this can usually be accomplished in a few days.

GMA (MIG) welding is more suitable for heavier gauges but can be used on metal as thin as 0.030 in., especially when welding to a heavier sheet, a heavier extrusion or with backing. The GMA process is generally a higher speed welding method than GTA and can be more difficult to control on light sheet.

Power sources and the equipment to be used for GMA welding are discussed, as are types of wire feeders and a table listing typical practices for the process. Proper GMA welding techniques are explained and a table on typical practices is included.

Resistance spot welding, commonly used in automobile construction, is not practical for repair activity because equipment is costly relative to the limited amount it can be used.

Also examined are machine welding, weld finishing and performance; and safe welding practices are cited. The overall topic of welding aluminum is covered in greater detail in The Aluminum Association Publication 23, entitled "Welding Aluminum: Theory and Practice," from which much of the material in this publication has been drawn. This publication also deals with issues of preparation for welding and for postweld finishing.

Finally, it should be noted that oftentimes the welding of light gauge sheet as used in automobiles is considered to be "difficult." This is a normal reaction to undertaking new procedures, especially when they bear a similarity to the procedures for welding of steel. We suggest that the repairer simply think of welding aluminum sheet as "different." With this approach and by following the recommendations in this publication, the welding of aluminum will quickly become a regular part of the repairer's wide range of skills.