The Official Guide to Different Welding Processes
Since the discovery of metal ores in ancient times, mankind has continuously tried to expand the productivity and quality of the welding and casting processes. As a result, welding can be performed using countless methods: some versatile, some specialized, some common today, and others obsolete.
In this guide, we will be discussing some of the commonly used welding processes and some of the more obscure ones. Knowing the different types of welding processes and how to weld with different types of materials is essential to getting any job done– no matter what the circumstances and tools are available. For this guide, we have arranged all terms alphabetically so you can easily find the welding process you are looking for.
Boiler and pressure vessel welding
Boilers and pressure vessels often require a significant degree of circumferential welding. Because of this, many portions of these components are welded using positioners that rotate the vessel during welding. Since some vessels can be quite thick, many fabricators try to implement high-productivity parameters and processes when possible, such as submerged arc welding. Of course, complex vessels may require the use of handheld processes such as GMAW/MIG when parts can be welded in position or gas-shielding flux-cored welding for out-of-position weld joints. Again, when mechanization can be used, it often is; special equipment exists for welding fittings, boiler tube walls, and large longitudinal seams.
Carbon arc welding
Carbon arc welding is a type of welding that uses an electric arc to create heat. The carbon arc welding process uses an electrode made of carbon, which is attached to a power source. The carbon electrode is then placed next to the metal that needs to be welded. When the carbon electrode is turned on, it creates an electric arc that produces heat. This heat is then used to weld the two pieces of metal together. The carbon arc welding process is often used for welding metals that are difficult to weld, such as aluminum and stainless steel.
Ceramic welding is a method of joining two pieces of ceramic material together by melting and fusing them. This process can be done using a variety of methods, including arc welding, resistance welding, and laser welding. Ceramic welding is often used in applications where traditional methods of joining, such as bolting or soldering, are not possible or not effective. For example, ceramic welding can be used to create hermetic seals that prevent leaks in electronic devices. Ceramic welding can also be used to create strong joints between dissimilar materials, such as metals and ceramics. When done correctly, ceramic welding can create a joint that is just as strong, if not stronger, than the base materials.
Electron beam welding
The application of electron beam welding is very similar to laser welding, although the principle of operation is quite different. The fundamentals are similar to those powering tube technology: in a vacuum environment, electricity is applied to a “grid,” which heats and emits electrons which can then be focused to create sufficient energy density for welding. Electron beam welding is most commonly used for high-precision welding of small components made of exotic alloys.
Explosive welding literally uses explosives to join similar—and even dissimilar—metal alloys together without melting either of the two. The process is expensive, so it is most often used to produce clad steel plates.
After preparing the blast zone, explosive powder and the two plates to be welded are stacked and separated by a calculated amount using spacers. When ignition begins at an edge or corner, the rapid deflection of the top plate as the explosion spreads creates a high-temperature air jet between the plates that removes all surface contaminants and forces the two plates together. Cold welding then occurs at the microstructural level.
Flux core welding
Flux core welding is abbreviated as FCAW. The term refers to two distinct processes: gas-shielded and self-shielded flux-cored arc welding (FCAW-G and FCAW-S, respectively).
The process is functionally similar to MIG, but instead, the wire electrode produces a slag during welding. This slag must be removed after welding but helps improve resistance to surface contaminants, facilitates high-amperage welding, and can also allow out-of-position welding at more productive parameters than MIG.
Self-shielded flux cored welding does not require an external shielding gas like FCAW-G, so it is a popular choice for construction. Gas-shielded flux-cored welding is popular in heavy equipment, shipbuilding, and railcar fabrication.
Friction generates heat; generating enough friction using large machinery generates enough heat to facilitate friction welding. Friction Welding is a solid-state welding process; the base metals are not melted but heated to within the plastic range and then intermixed.
One application of friction welding is the joining of round sections. Here, one or both workpieces are rotated and introduced to each other at a very high velocity. Once the parts reach the plastic range, an offset is applied. Doing this pushes contaminants out of the weld zone, producing a very high-quality weld.
Friction stir welding
Friction Stir Welding (FSW) is a subset of friction welding. What makes the process unique is that instead of rotating or linearly oscillating the base metal, a specialized vertical mill and machine tool are used to generate sufficient friction.
Friction stir welding was supposedly discovered accidentally during an out-of-control machining process. It requires a significant amount of downward force to plunge a specialized machine tool into the workpiece and maintain rotation of the tool as it progresses along the weld joint.
FSW is typically used on relatively-thin panels for aerospace and similar applications having difficult-to-weld low-weight alloys.
Gas welding uses the heat generated by the combustion of flammable gas to melt the base metals. The process is adjacent to oxy-fuel (or oxy-acetylene) welding, although gas welding does not take advantage of oxygen to increase the combustion temperature. For this reason, gas welding is mostly used for joining thin base metals having relatively low melting points: lead, tin, pewter, brass, etc. It is also possible to use the equipment for brazing or soldering. Common fuel gasses include acetylene, propane, and polypropylene.
Hardfacing is a specialized application of welding that uses high-alloy filler metals to deposit weld beads onto wear points of equipment as a means of extending the lifespan of those components.
The alloys typically deposit a chromium-carbide deposit for severe abrasion resistance, a martensitic steel deposit for metal-to-metal abrasion and generally balanced performance, or austenitic manganese steel for severe impact resistance.
Hardfacing alloys are most often available as stick electrodes and self-shielded flux-cored wires to facilitate field repair of earthmoving and agricultural equipment, although solutions for manufacturing also exist.
Like chemical and nuclear energy, light is a type of energy that can be transformed into heat. Laser welding does this by focusing a high-powered coherent laser beam into a very small area using advanced optics.
Laser welding has found great success when coupled with automation since the process can provide very high travel speeds. The automotive industry was an early adopter of laser welding technology, and its use continues to grow every day in similar commercial applications. In addition to welding, the use of lasers is popular as a cutting process. The process can be used on a wide range of materials such as steel, stainless steel, aluminum, and even exotic alloys.
MIG is an acronym for Metal Inert Gas. The process is more formally known as Gas Metal Arc Welding (GMAW).
MIG welders use a continuously fed wire electrode to conduct a welding arc and provide filler metal into the weld pool. Argon/carbon-dioxide shielding gas mixtures protect the weld from atmospheric contamination when welding carbon, low-alloy, and stainless steels. The process is especially popular for manufacturing as the process can produce high-quality welds with great productivity. The process can be used to weld out-of-position at the expense of productivity and depth of fusion when short-circuit transfer is used.
MIG welding aluminum
MIG/GMAW is a popular choice for higher-productivity welding of aluminum compared to TIG/GTAW. MIG is especially popular for welding thick aluminum, although it can be used to weld thinner materials by implementing short-circuit transfer and/or pulsed waveforms.
Here, the process typically utilizes pure argon or argon/helium blends to protect the weld pool. Filler metals are available in a range of alloys, although 4043, 4943, and 5356 are the most common for many structural aluminum base metals. Since aluminum wire is so delicate, specialized welding torches are often used. The two primary types are “spool guns” and “push-pull guns.”
Orbital welding is a subset of the GTAW/TIG welding process that is most often used for automatically welding small-diameter tubing with very high weld quality. For example, orbital welding is a popular choice in sanitary applications and in the aerospace industry.
One type of orbital welding system consists of an unconventional welding torch that clamps around the weld joint so that the welding electrode performs a full revolution around the weld joint. The result is an autogenous weld (a weld without filler addition) in an inert atmosphere (although an internal shielding gas purge may still be required in some applications).
Oxy acetylene welding (brazing)
Oxy-acetylene welding is a subset of oxy-fuel welding that utilizes the combustion of a mixture of acetylene and oxygen gasses to melt the base metal. The combustion temperature of this gas mixture is higher than fuel gas alone and helps create a flame cone that is more neutral and less carburizing. Oxy-acetylene is less popular than in the past but still maintains a good degree of versatility.
Pipe welding is a very diverse field that includes larger-diameter pipelines as well as the smaller-diameter piping systems found in power generation and refining facilities. Some of these systems implement higher alloy base metals such as chrome-moly steels, high-temperature grades of stainless steel, and even nickel alloys. When root pass integrity is a must, many applications lend well to GTAW/TIG. After depositing the root and hot pass, it is often possible to switch processes. Since many fitted systems require in-position welding, stick/SMAW remains a popular choice, although gas-shielded flux-cored electrodes for many of these alloys exist as a higher-productivity option.
Pipeline welding often refers to onshore transmission and distribution pipe welding. The difference between transmission and distribution pipe is often a matter of pipe diameter—transmission being the larger of the two—but the welding techniques for each are often similar.
Double joining (or jointing) is typically performed in a shop environment and serves to help reduce the amount of field welding required by joining 2 ~20 ft. pipe sections using SAW or GMAW.
Field welding typically employs stick welding (SMAW). Most often, a 6010 cellulosic-type electrode is used to deposit an “open root” weld, and the remaining passes of the weld joint are performed using low-hydrogen electrodes of a strength that more closely matches the base metal strength and toughness.
Plasma arc welding
In plasma arc welding (PAW), a non-consumable electrode is first used to generate a welding arc which in turn ionizes a gas to generate plasma, a very high-temperature state of matter.
The process appears similar to TIG/GTAW and may be handheld or automated. However, in plasma arc welding, the plasma column—as opposed to the arc itself—is used for joining the base metals. Using the right combinations of parameters allows for “keyhole” welding of relatively thick base metals, which reduces material preparation requirements.
The process is typically used in high-purity applications, although the overall number of equipment and consumable vendors is somewhat low compared to other processes.
Plastic welding is a process of joining plastic materials together using high heat. The plastic materials are melted and then allowed to cool, forming a strong bond. Plastic welding is used in many industries, including the automotive, aerospace, and electronics industries. Plastic welding can be used to join plastic parts together or to repair plastic components. Plastic welding is a reliable and cost-effective way to join plastic materials, and it can be used on a variety of different plastic types.
Polymer & composite welding
Polymer & composite welding is a type of welding that is used to join two pieces of material together by using heat and pressure. It is commonly used in the manufacturing and construction industries as it is a strong and durable way to join two pieces of material together. This type of welding can be used on a variety of materials, including metals, plastics, and composites making it a versatile and reliable way to join two pieces of material together.
Pulsed MIG is more formally known using the acronym GMAW-P. It is similar to MIG welding except that advanced equipment is used to “pulse” welding amperage between a higher “peak” and a lower “background.” Pulsed MIG typically reduces welding heat input for a given wire feed speed which can be beneficial for reducing distortion or welding thin materials. For a given amperage, pulsed MIG can be used to help improve deposition rates and productivity.
Many pulse-capable welding power sources offer synergic control, meaning that the pulse waveform is automatically adjusted to provide optimal performance as the welder adjusts wire feed speed.
Resistance welding leverages the electrical resistance of the base metal to generate heat as a large amount of current is passed through the base metals. Pressure is also applied to the workpieces to ensure metal-to-metal contact during heating, fusion, and cooling.
Resistance welding is an umbrella term covering a range of related processes, of which the most common are resistance spot welding and resistance seam welding. Projection and cross-wire welding are further subdivisions that utilize the fundamentals of resistance welding for specialized applications.
The process is commonly employed on steel, aluminum, and stainless steel sheet metal components.
Robotic welding has conventionally employed large industrial-scale 5-6 axis robot arms. While these arms are capable of large work envelopes and excellent productivity, they are not always the most user-friendly: programming know-how and robotic safety often require a significant amount of training.
However, the world of automated welding has not remained stagnant. New technologies continue to be developed, which makes interacting with robots safer and easier when smaller tasks are at hand. An example of this is the BotX robotic welder. This system is a cobot—a more collaborative robot— design to help ease the transition into the world of welding automation.
Solid state welding
Solid state welding is an umbrella term covering a range of welding processes that do not actually melt the base metal during welding.
The solid-state processes are useful for exotic alloys that are difficult to weld by conventional arc welding processes that cause the base metal to reach temperatures that introduce significant microstructural changes.
Friction (and friction stir) welding are some of the most commercially-viable applications of solid state welding, although processes such as ultrasonic and explosion welding have some specialized uses.
Spot welding (abbreviated RSW) is a type of resistance welding. What makes the process unique is that the energy is focused in a small area, producing a small, generally circular-shaped weld nugget in a very short amount of time.
What the weld nugget lacks in size, it often makes up for in quantity: a large component, such as an automobile body, may have thousands of spot welds.
An industrial spot welding gun typically features a welding transformer integrated into a pneumatic or hydraulic clamping system. These guns may be placed on welding robots, incorporated into complex fixturing, or be pedestal mounted.
Stone soldering is a process in which two pieces of stone are joined together using a conductive material. The most common conductive material used in stone soldering is copper. Stone soldering is typically used for repairing cracks or breaks in stone, as well as for joining two pieces of stone together. Stone soldering can be done by hand or with the use of a machine. When done by hand, the process is very similar to welding. First, the conductive material is placed between the two pieces of stone. Next, heat is applied to the conductive material, which melts it and joins the two pieces of stone together. Stone soldering is a very strong method of joining two pieces of stone together and can be used on both natural and man-made stones.
Stick welding, also known as shielded metal arc welding (SMAW) is a versatile process that uses a consumable electrode (a “rod”) to transmit the welding arc and deposit filler metal into the weld pool. Equipment requirements for stick welding are minimal: a welder only needs a power source, an electrode holder and leads, and stick rods which are available in a wide range of alloy compositions.
SMAW is typically a slower process than MIG, but it is useful when welding outdoors, out-of-position, or over less-than-ideal base metal conditions. For these reasons, it remains a popular choice in the construction industry and for oil/gas/refinery transmission and process piping.
Stud welding uses either capacitive discharge or a conventional welding arc to attach a specially-designed stud—often threaded and available in a wide range of sizes—to the base material.
Stud welding is especially popular in the structural/construction industry to assist in making bolted connections. In these applications, a special welding gun/torch is used to hold the stud, transmit current during welding, and to plunge the stud into the workpiece during welding. This plunge helps to achieve a high-quality weld without shielding gas, although large studs may require the use of a ceramic ferrule that surrounds the stud and is removed after welding.
Submerged arc welding
It is possible to perform submerged arc welding (SAW) without a welding helmet or jacket because the arc is covered by a granular flux during welding. The process allows welding at very high amperages for welding a wide range of thicknesses at very high travel speeds with excellent quality.
However, the process is limited to the flat and horizontal welding positions and is typically mechanized to provide weld consistency. Flux handling and slag removal are inconveniences of the process, although SAW remains very popular for circumferential and longitudinal seam welds on beams, tanks, and vessels found in the structural and oil/gas industries.
Thermite welding uses a compound known as thermite—a blend of iron oxide and aluminum oxide—as the filler metal and heat source. This compound is ignited using the combustion of a magnesium wire. Once ignited, the thermite undergoes a rapid exothermic chemical reaction that melts the pieces to be joined. The space between the base metals is filled with the by-product of the reaction: molten iron. The process is common for fast and easy railway repair. Here, a special ceramic mold is used to contain the thermite, the chemical reaction, and then shape the molten metal that is produced. After welding, the mold and excess iron is removed.
TIG is an acronym for Tungsten Inert Gas. The process is more formally known as Gas Tungsten Arc Welding (GTAW).
TIG uses a non-consumable tungsten electrode to conduct a welding arc that melts the base metal. During welding, the welder may manually add filler metals into the weld pool. To prevent atmospheric contamination of the weld, the process typically uses argon—which is inert—as a shielding gas.
TIG is a popular choice for thin materials, small weldments, and “exotic” base metals ranging from aluminum and titanium to nickel and other non-ferrous alloys. The process is, however, typically slower than MIG/GMAW and FCAW.
Welding automation involves distancing the welder from the tasks typically performed within the welding process: controlling arc length, feeding filler wire, progressing along the joint, etc. A standout example of a complete welding automation solution includes mounting a MIG/GMAW welding torch or spot welding gun to a 6-axis robot arm common in industrial applications.
It is possible, however, to implement partial automation of the process using mechanization. An example of this “lower tech” implementation of automation principles is a welding carriage or positioner. Here, the operator must make minor adjustments to maintain proper torch positioning, but the process of moving along the joint is controlled by machinery.
While the term “underwater welding” conjures an image of a scuba-clad diver with a welding stinger in hand, this image portals only “wet” welding. “Wet” underwater welding is accomplished using specially coated stick welding (SMAW) electrodes. Because the shielding environment generated by the stick electrodes can displace the water, welds can be of generally good quality.
Another distinction of underwater welding is “dry” in the sense that a specially designed enclosure encases the area to be welded. The water in this enclosure is removed. Some enclosures are large enough to encase the welder, while others allow manipulation of equipment using gloves in a manner like a sandblasting cabinet.
Types of metals that can be welded
If there is a metal that needs to be welded, there is often a process that can be used to join it. However, not all processes are practical outside of theoretical or research environments. Some processes are more economically feasible, while others may allow the improvement of metallurgical properties or weld quality. Below are examples of metals, how they can be melded and why.
Exotic metal welding
Low-alloy steel, carbon steel, stainless steel, and aluminum have the greatest tonnage of welded assemblies produced. For this reason, the term “exotic metals” could be technically applied to any metal that is not one of the above but titanium, magnesium, and nickel alloys are examples having a relatively common application. Nickel alloys are a popular choice in high-temperature and corrosive environments found in the oil/gas and chemical processing industries.
Precious metal welding
Various precious metals such as silver, gold, platinum, etc., are actually not too difficult to weld using popular and conventional welding methods. The key difficulty is the need for high-precision processes to make small autogenous welds.
Gas and oxy-fuel welding setups are the norms for many smiths and jewelers since torch tips having very small orifices can focus the heat of the flame quite finely.
However, “higher-tech” solutions such as laser and electron beam welding can be used for even higher precision. GTAW can be used in theory, but one has to be mindful of the tungsten size and the minimum amperage capabilities of the power source used.
Count on Red-D-Arc for welder rentals and welding automation equipment
With so many resources and terms to know within the welding process and the industry, it’s hard to keep everything straight. To get the most up-to-date welding rentals, education, and equipment, reach out to the team at Red-D-Arc today. Our years of experience and knowledge will guide you in the right direction for your next welding project, rental or in-depth understanding of the welding industry and applications.
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