15.6 Other Weld Types
Cameron Kjeldgaard
The AWS publishes a master chart of welding and joining processes. Each of these processes has specific considerations and exploring all each in detail is beyond the scope of this chapter. However, the categories are worth a brief discussion here.
This book has dedicated chapters for four arc welding processes. There are many more than four processes, but they all operate on the same principle. Arc welding uses the heat generated by the electrical resistance of a high current jumping an air gap to weld.
Oxy-fuel welding bears much similarity to manual arc welding processes, except a chemical heat source—the combustion of a gas blend—is used to melt base and filler metals. This type of heat source is much colder than the ones used in arc welding, and thus oxy-fuel welding processes are much slower.
Resistance welding, discussed in the previous section, passes a high current through a tightly fit weld joint. The electrical resistance of the material itself creates the heat for welding. These processes are best suited to assembly line-style manufacturing environments, with the welding carried out in an automated process.
Brazing and soldering are not technically welding processes, with the distinction that the base metal is never melted and fused into the joint. Instead, only the filler metal becomes molten and is drawn into the joint by a heat source. The strength of braze joints and solder joints are directly proportional to the surface area of the joint. Therefore they work best in joints that have a large area, such as a lap joint with a large amount of overlap. The primary difference between brazing and soldering is the temperature at which they are carried out and the type of filler metal used.
An interesting category of welding processes is solid-state welding. The mechanics and principles of these processes are highly varied. Friction and friction stir welding use the heat of friction and high pressure to join parts. Explosion welding uses the force generated by the detonation of plastic explosives to join materials, some combinations of which cannot be joined reliably by any other process. Ultrasonic welding uses high-frequency sound waves to vibrate materials together. These are just a few examples of solid-state welding.
There are a host of other joining processes without dedicated categories. Some, like electroslag welding and thermite welding, use the heat of chemical reactions to join pieces. Other processes, like laser beam welding and electron beam welding, fire streams of highly charged particles at a weld joint to achieve fusion.
Recall that the goal of this chapter is to help you build a vocabulary for a competent career in welding. You do not need to know how to perform each of these welding processes, but familiarity with them will help you understand what is being said around you.
