Many consider welding to simply be an activity that requires multiple pieces of metal to be joined together by some form of heat. This is typically true. The application of heat to metal allows them to have enhanced malleability which also allows them to be joined together in a single joint – don’t forget that when the heat is applied, one must also apply pressure to the pieces of metal to make sure that they are joined. Welding has been around for quite some time. Before it was known as the “welding” that we know it as it was called “forge welding” which basically meant that 2 pieces of metal were being joined together.
In short, forge welding required the welder to use an open flame to develop enough heat to make the metals that were meant to be welded malleable. Eventually, this method of welding began to die out. As energy sources were harnesses gas and electric welding methods were harnessed to keep the welders safer in the workplace. More tools than we care to think about have been created by welders. This is because of the wide applications that welding has in construction as well as in everyday life.
Welding is a process that has a wide variety of application to everyday life. It’s important to keep in mind that these applications also require that each of the welding processes be diversified.
The most widely known welding types are Electroslag, Arc, Gas Metal-Arc, Plasma Arc, Metal Inert Gas, Gas Tungsten Arc, Shielded-Metal Arc, Tungsten Inert Gas, and Submerged Arc. However, these are all Arc welding processes – there are a variety of processes including,
- Oxyfuel Gas Welding
- Resistance Welding
- Solid-State Welding
As well as a few others. Below, we’ll go over each type of welding (the broad type) as well as a few subcategories.
What is Arc Welding?
Arc welding is a fusion process that uses an electric arc from power supply (either AC or DC) that creates a heat around 6500 degrees Fahrenheit which melts the metal at the joint. One can guide an arc mechanically or manually along the joint.
Metals used in arc welding react to the nitrogen and oxygen in the air when they’re heated to the degrees possible by the arc. To help prevent the negative effects of the reaction to the metal, a slag (protective shielding gas) is used to reduce the weld’s contact with the air. The weld is finished to once it cools and solidifies.
Video credits to Weld.com. It’s a very thorough introduction to arc welding.
Arc Welding sub-types
| Type | N | AWS | Characteristics | Applications |
|---|---|---|---|---|
| Carbon Arc Welding | (181) | CAW | Inexpensive Low operator skill Easily automated Low distortion (historical) | (historical) |
| Bare Metal Arc Welding | (113) | BMAW | Consumable electrode, no flux or shielding gas | historical |
| Flux Cored Arc Welding | 136 137 | FCAW FCAW-S | Continuous Consumable electrode-filled with flux | industry construction |
| Gas Metal Arc Welding | 131 135 | GMAW | Continuous consumable electrode and shielding gas | Industry |
| Gas Tungsten Arc Welding | 141 | GTAW | Non consumable electrode, slow, high quality welds | Aerospace, Construction, Tool and Die |
| Plasma Arc Welding | 15 | PAW | Non-consumable electrode, constricted arc | Tubing, instrumentation |
| Shielding Metal Arc Welding | 111 | SMAW | Consumable electrode covered in flux, can weld any metal as long as they have the right electrode | Construction, outdoors, maintenance |
| Magnetically Impelled Arc Butt | 185 | MIAB | both tube ends are electrodes; no protection gas; arc rotates fast along edge by applied magnetic field | pipelines and tubes |
| Atomic Hydrogen Welding | (149) | AHW | Two metal electrodes in hydrogen atmosphere | Historical |
What is Oxy-fuel Gas Welding?
Oxy-fuel welding is a blanket term uses to describe welding processes that use the combustion of both Oxygen and fuel to produce enough heat for fusion welding. Oxy-fuel processes entail the use of a flame (that’s produced near the end of the welding torch) to melt the parent metal with / without filler metal. The actual fuel and gas are placed inside of a chamber where they’re mixed (this chamber is a part of the welding torch.
With oxy-fuel welding you may relinquish a few of the benefits that you get with arc welding but, you receive some of the following benefits:
- Welders get decent control over the heat input, filler metal addition, and temperature (all independently)
- The flame chemistry can be altered from carburizing through neutral to oxidizing.
- Equipment is relatively inexpensive and portable
Oxy-fuel Welding sub-types
| Name | N | AWS | Characteristics | Applications |
|---|---|---|---|---|
| Air acetylene Welding | (321) | AAW | Chemical welding process, not popular | Limited |
| Oxyacetylene welding | 311 | OAW | Combustion of acetylene with oxygen produces high-temperature flame, inexpensive equipment | Maintenance, repair |
| Oxygen/Propane welding | 312 | Combustion of acetylene with oxygen produces high-temperature flame, inexpensive equipment | ||
| Oxyhydrogen welding | 313 | OHW | Combustion of hydrogen with oxygen produces flame | Limited |
| Pressure gas welding | PGW | Gas flames heat surfaces and pressure produces the weld | Pipe, railroad rails (limited) |
What is Resistance Welding?
Resistance welding is the process of joining metals through the application of pressure and a current for a period. The advantage of resistance welding is that one doesn’t need anything other than the materials used to create the weld (it’s an economical choice).
Resistance Welding sub-types
Name | N | Characteristics | Applications | |
|---|---|---|---|---|
| Resistance spot welding | 21 | Two pointed electrodes apply pressure and current to two or more thin workpieces | Automobile industry, Aerospace industry | |
| Resistance seam welding | 22 | Two wheel-shaped electrodes roll along workpieces, applying pressure and current | Aerospace industry, steel drums, tubing | |
| Projection welding | 23 | Semi-Automatic, Automatic, Welds are localized at predetermined points. | ||
| Flash welding | 24 | |||
| Upset welding | 25 | Butt joint surfaces heated and brought together by force |
What is Solid-State Welding?
Solid State Welding is a joining process that doesn’t have either a vapor or liquid phase. Not only that but it uses pressure and doesn’t have to use temperature. For solid state welding to take place the cohesive forces between atoms and metal are used.
Solid-State Welding sub-types
| Name | N | AWS | Characteristics | Applications |
|---|---|---|---|---|
| Coextrusion Welding | CEW | Dissimilar metals are extruded through the same die | Joining of corrosion resistant alloys to cheaper alloys or alloys with more favorable mechanical properties |
|
| Cold pressure welding | 48 | CW | Joining of soft alloys such as copper and aluminium below their melting point | Electrical contacts |
| Diffusion welding | 45 | DFW | No weld line visible | Titanium pump impellor wheels |
| Explosion welding | 441 | EXW | Joining of dissimilar materials, e.g. corrosion resistant alloys to structural steels | Transition joints for chemical industry and shipbuilding. Bimetal pipelines |
| Electromagnetic pulse welding | Tubes or sheets are accelerated by electromagnetic forces. Oxides are expelled during impact | Automotive industry, pressure vessels, dissimilar material joints |
||
| Forge welding | (43) | FOW | The oldest welding process in the world. Oxides must be removed by flux or flames. | Damascus steel |
| Friction welding | 42 | FRW | Thin heat affected zone, oxides disrupted by friction, needs sufficient pressure | Aerospace industry, railway, land transport |
| Friction stir welding | FSW | A rotating non-consumable tool is traversed along the joint line | Shipbuilding, aerospace, railway rolling stock, automotive industry |
|
| Hot pressure welding | HPW | Metals are pressed together at elevated temperatures below the melting point in vacuum or an inert gas atmosphere | Aerospace components |
|
| Hot isostatic pressure welding | 47 | HPW | A hot inert gas applies the pressure inside a pressure vessel, i.e. an autoclave | Aerospace components |
| Roll welding | ROW | Bimetallic materials are joined by forcing them between two rotating wheels | Dissimilar materials |
|
| Ultrasonic welding | 41 | USW | High-frequency vibratory energy is applied to foils, thin metal sheets or plastics. | Solar industries-. Electronics. Rear lights of cars. Diapers. |
