Factors which must be taken into account when choosing a suitable welding or joining process are:
- material type
- product form: plate or tubular
- quality and strength requirements
- degree of mechanization
- capital cost
Although consideration of these factors will identify the most suitable welding process, the choice within a company may be restricted by the cost of implementing a new process, availability of plant or current workforce skill. Welding and joining processes available to the welding engineer can be separated into the following generic types:
- power beam
- Solid state
The suitability of the processes for welding and joining materials, joint types and components are shown in below Table.
Suitability of the processes for welding and joining materials, joint types and components
In selecting a suitable process, consideration must also be given to the type of application, for example, the portability of equipment, whether it can be used on site, whether it is manual or mechanised, and the overall cost of the welding plant.
Stick/Arc welding (SMAW)
This common method of welding was invented in the year 1802 and involves the use of a consumable electrode that has a flux-coated core wire that gives electric current. When in contact with the metal being welded an electric arc is created at the gap generating high temperatures of up to 6500o F. This heat melts the electrode and the metal thus creating a weld. This welding method is beneficial in that it does not require shielding gas and is effective on rusty metals. However, thin metals can complicate the process, necessitating the presence of a skilled and experienced operator.
Arc welding is best used on heavy metals of size 4mm and above and is used in repairing heavy equipment, steel erection, and pipeline welding as well as in the manufacturing and construction industry.
Metal Inert Gas (MIG) welding or GMAW
This common type of welding was perfected in the 1960s. MIG welding uses a gun that is continuously fed with a consumable electrode. The process uses an external gas to shield the welded metal from environmental factors like oxygen making it continuous and quick. This method is easy to learn, produces less welding fumes, has high electrode efficiency and requires less heat input. However, the equipment is costly, the process does not work effectively on thick materials and it requires an external shielding gas.
MIG welding works well with a variety of alloys like stainless steel, aluminum, silicon bronze, magnesium, copper and nickel. It is used in automotive repairs, construction, plumbing, robotics, fabrication and maritime repairs.
Tungsten Inert Gas (TIG) welding or GTAW
This welding method, released in the year 1941, is a difficult and time-consuming welding process that requires a high level of skill and focus. An autogenous weld can be created by melting two pieces of metal together without filler metal. TIG produces high quality and spatter free welds of various alloys that can be very thin. However, it requires a highly skilled operator and external shielding gas and does not work on rusty or dirty materials.
TIG welding is best used in aerospace welding, vehicle, motorcycle and bike manufacturing, tubing and in high precision welds.
Flux-Cored Arc Welding
This method of welding is similar to SMAW except that it uses tubular wire-filled flux in place of a solid wire. It can be self-shielded or dual shielded with an additional external gas. It is used in welding thick materials, heavy equipment repair, and construction as well as in steel erection.
Welding processes have highly evolved in recent years giving rise to a variety of new and innovative methods. As such, it is necessary that you understand these techniques so that you know which one is right for your job. This will largely dictate who you will want to hire to complete it. Every method of welding has distinct advantages and disadvantages, and you will want to take the time to consider which process will be optimal for your application.