What Is Welding?- Definition | Types of Welding

What is Welding?

Welding is a manufacturing process that uses heat, pressure, or both to fuse two or more parts together to form a joint as the parts cool. Welding is commonly used with metals and thermoplastics, but can also be used with wood. The completed welded joint can be called weldment.

Some materials require the use of special processes and techniques. Some are considered “non-weldable”. This term is not usually found in dictionaries, but is useful and descriptive in engineering.

The part to be joined is called the base material. Materials that are added to form a joint are called fillers or consumables. Based on the shape of these materials, they can be called substrates or tubes, flux-cored wires, consumable electrodes (for arc welding), etc.

Consumables are usually chosen to be similar in composition to the base metal, so they form a homogeneous weld, but there are cases, such as welding of brittle cast iron, where fillers of very different compositions are used and so the properties are very different. These welds are called dissimilar welds.

A completed welded joint is sometimes called a weldment.

Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure, or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.

Definition of welding

Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure, or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.

How Does Welding Work?

Welding is done by joining two materials together without any adhesive. Unlike soldering and brazing, which use low melting point adhesives, welding joins two workpieces directly.

Most of the welding that is done today is divided into one of two categories: arc welding and torch welding.

Arc welding uses an electric arc to melt the work material and filler metal (sometimes called a welding rod) to welding joints. Arc welding involves connecting a ground wire to the welding material or other metal surfaces.

Another wire called electrode lead is placed in the material to be welded. An electric arc occurs when that lead moves away from the material. It’s a bit like the spark you get when you remove the jumper cable from a car battery. The arc melts the workpiece along with the filler material that helps to bond the parts together.

Filling filler in a weld joint requires a steady hand and an eye for detail. As the rod melts, the welder must continuously feed the filler into the joint using small, steady back-and-forth motions. These movements are what give weld its unique look. Moving the arc too fast or too slow, too close or too far from the material can result in a poor weld.

Shielded metal arc welding (SMAW or stick welding), gas metal arc welding (more commonly known as metal inert gas welding or MIG) and gas tungsten arc welding (often referred to as TIG or tungsten inert gas welding) are examples of arc welding.

Each of these three common methods has its own strengths and weaknesses. For example, stick welding is cheap and easy to learn. It is also slower and less flexible than other methods. Conversely, TIG welding is difficult to master and requires complex welding rigs. However, TIG welding produces high quality welds and can weld materials that otherwise cannot.

Torch welding represents another common welding method. This process typically uses an oxyacetylene torch to melt the workpiece and welding rod. The welder controls the torch and the rod simultaneously, giving you more precise control over the weld. Torch welding has become less common in industry, but is still often used for maintenance work as well as in sculptures.

Types of Welding

There are four main types of welding. MIG – Gas Metal Arc Welding (GMAW), TIG – Gas Tungsten Arc Welding (GTAW), Stick – Shielded Metal Arc Welding (SMAW), and Flux-cored – Flux-cored Arc Welding (FCAW). We dive deeper into each type of welding here.


MIG welding is one of the most common types of welding that beginners should learn. MIG welding is used in the automotive industry to repair vehicle exhausts and to construct homes and buildings. Arc welding that uses a continuous wire called an electrode. It also uses a shielding gas that passes through the welding gun and protects it from contamination.

MIG welding is actually two different types of welding. The former uses bare wire and the latter uses flux cores. MIG bare wire can be used to join thin metal strips. Flux core MIG welding can be used outdoors as no flow meter or gas source is required. MIG welding is usually the welding of choice for DIY and amateur welders who don’t have the money to spend on expensive equipment.


Like MIG, TIG welding uses an arc, but is also one of the most difficult welding techniques to master. Tungsten electrodes are used in TIG welding. Tungsten is one of the hardest metal materials. It does not melt and does not burn.

TIG welding can be done by a process called fusion, with or without filler metal. TIG also uses an external gas source such as argon or helium.

TIG welding requires both hands. Hold the TIG torch with one hand and guide the rod with the other. This torch produces heat and an arc that is used to weld the most common metals including aluminum, steel, nickel alloys, copper alloys, cobalt and titanium.

The TIG welder can be used to weld steel, stainless steel, chromoly, aluminum, nickel alloys, magnesium, copper, brass, bronze and even gold. TIG is a useful welding process for bike frames, lawn mowers, door handles, fenders, etc.

The aerospace and automotive industries, like other industrial markets, use TIG welding. It is also a great welding type for Iowa, as it is very useful for farmers to weld wagon frames, fenders and other vital equipment.


Want to bring welding home? The main advantage of stick welding is its portability. Stick welding is used in construction, maintenance and repair, underwater pipelines and industrial production. In this type of welding, shielded metal arc welding is used, which is better known as stick welding.

Stick welding, which is also called arc welding, is done in the old way. Stick welding is a bit more difficult to learn than MIG welding, but if you want to try it at home, stick welding equipment can be purchased for a fraction of the cost. Stick electrode welding rods are used in stick welding.  

Use consumables protected electrodes or sticks. Stick softens and joins the metal by heating it with an electric arc between a coated metal electrode and a base metal workpiece. When the stick melts, the protective coating also melts, shielding the welding area from oxygen and other gases in the air.


This type of welding is similar to MIG welding. In fact, MIG welders are often twice as expensive as FCAW welders. As with MIG welding, the wire that acts as the electrode and filler metal is threaded through the rod. This is where things start to change. In FCAW, the wire has a flux core that forms a gas shield around the weld. This eliminates the need for an external gas source.

FCAW is a type of high temperature welding, so it is suitable for thicker and heavier metals. For this reason, it is often used to repair heavy equipment. It is an efficient process with little waste. It is economical because no external gas is needed. However, some slag remains which needs to be cleaned up a bit to get a good weld.


Plasma arc welding is a precision technique commonly used in aerospace applications with metals as thick as 0.015 inches. Examples of these applications are engine blades and air seals. Plasma arc welding is technically very similar to TIG welding, but it has an embedded electrode and uses ionized gas within the arc to generate heat.

A typical gas combination is argon as the plasma gas and argon and 2-5% hydrogen as the shielding gas. Helium can be used as a plasma gas, but the high temperature of helium reduces the amperage of the nozzle.

Want to know more about Plasma Welding? Check out this article.


This type of welding can be used on metals or thermoplastics. As the name suggests, a laser is used as a heat source to create the weld. Works on carbon steel, stainless steel, HSLA steel, titanium and aluminum. It is widely used in manufacturing industries such as the automotive industry because it can be easily automated with robotics.


A type of welding in which a high-speed electron beam uses kinetic energy to generate heat to join two materials. This is a very hard welding method that is done mechanically and mainly in a vacuum.


Gas welding is rarely used and has mostly been replaced by TIG welding. Gas welders require oxygen and acetylene and are very portable. Sometimes they are used to weld car exhaust parts together.


Atomic hydrogen welding is a type of ultra-high temperature welding, formerly known as atomic arc welding. In this type of welding, two tungsten electrodes are protected with hydrogen gas. It can reach temperatures higher than an acetylene torch and can be done with or without filler metal. This is an old form of welding that has been replaced in recent years by MIG welding.


It is an advanced welding process used to vertically join the thin edges of two metal sheets. The weld is made between the edges of the two panels, not outside the joint.

A copper electrode wire passes through a consumable metal guide tube that acts as a filler material. When an electric current is applied, an arc is created that begins welding at the bottom of the seam and slowly moves upward, creating a weld instead of the seam as it progresses. It is an automated process and is done by machines.

Types Of Welds

1. Fillet Welds

Fillet welding refers to the process of joining two pieces of metal vertically or at an angle. These welds are commonly called tee joints, two pieces of metal perpendicular to each other, or lap joints, two pieces of metal that are overlap and welded on their edges.

The weld is triangular in shape and depending on the skill of the welder, it can be concave, flat or convex. Welders use fillet welds when connecting flanges to pipes and substructure welding sections and when bolts are not strong enough and wear easily.

A fillet weld joins two surfaces perpendicularly and creates a nearly right angle between them. This style of welding can be classified into the following subgroups:

  • Full Fillet filling. For full fillet welds, the weld size is equal to the thickness of the thin wall parts being joined.
  • Staggered intermittent fillet weld. An obscure alternating fin weld is characterized by the formation of two offset alternating weld lines on either side of the joint.
  • Chain alternating fillet welding. Interrupted fillet welds form a chain of two interrupted fillet weld lines approximately opposite each other on either side of the T joint.

The versatility and low cost of fillet welds make them one of the most widely used joints in the welding industry. Typical applications include:

  • Connecting flanges to pipes
  • Bracing connections
  • Shear tabs
  • Cover plates
  • Column bases
  • Seam and stitch welds

2. Groove Welds

A groove weld is defined as an opening between two joint members that provides space for the insertion of metal. After fillet welds, groove welds are the most widely used welds. The second most common method of welding is groove welding.

Groove welding is the placement of a nut in the groove between two parts to be joined. The type of weld used determines how the seams, joints or surfaces are prepared.

Groove welding allows parts to be joined on the same plate by placing a weld bead in a groove between the parts. The main types of groove welds are:

  • Flare-bevel weld
  • Flare-V weld
  • Single-bevel groove weld
  • Single-J groove weld
  • Single-U groove weld
  • Single-V groove weld
  • Square groove weld

The groove welding process is generally slow and difficult compared to other forms of welding and usually requires special chamfers on one or both sides to join.

However, it produces a strong weld that is easily inspected and provides excellent strain control. Common applications for groove welding include:

  • Moment connections
  • Column splices
  • Hollow structural steel (HSS) connections

3. Surfacing Weld

These are welds consisting of one or more strings or weave beads deposited that are joined to an unbroken surface to obtain desired properties or dimensions.

Surfacing is a welding process used to apply a hard, wear-resistant metal layer to the surface or edge of worn parts. One of the most economical ways to increase and maintain the life of construction machinery, tools and equipment.

A surfacing weld is composed of one or more stringer or weave beads. Surface treatments, also called hardfacing or wear, are often used to repair worn shafts, gears, or cutting edges.

The most common types of surfacing welds include:

Surface welding is commonly used to add a wear-resistant metal layer to an object to strengthen its surface or restore worn areas. In this case, welding is done using a metal with higher wear resistance than the base material.

This technology is one of the most cost-effective ways to protect and extend the life of equipment and tools used in aggressive and high-wear applications. Surface welding can also be used in combination with butt joints to improve the quality of the final weld.

4. Plug Welding

Plug welding, also called rosette welding, is when two metals are joined together by a weld that is placed in a small circular hole. This process usually involves overlapping two metals, with the upper metal having a hole for the weld deposit.

Plug welding is an alternative to spot welding used by car manufacturers with poor access to a spot welder. Commonly used in DIY auto restoration to replace spot welds on panel flanges that were originally spot welded.

Plug welds, when done correctly, are stronger than original spot welds. Rally car manufacturers often use this technique and it is acceptable in UK MOT tests as an alternative to spot welding used to repair older cars.

Other applications include:

  • Welding rods inside a pipe
  • Joining metals that differ in thickness
  • Auto body manufacturing and repair

5. Slot Weld

A slot weld joins the surface of one material to another through an elongated hole. The hole can be open at one end and partially or completely filled with welding material.

It is a weld that joins a slotted hole in one member of a lap or tee joint to the surface of another member exposed through the hole. This hole may be open on one side and may be partially or completely filled with weld metal.

A slot weld joins one surface to another through a slotted hole. The difference between plug and slot welds is that the shape of plug welds is determined by diameter while the shape of slot welds is determined by diameter and length.

Depending on the part specification, the hole may be open at one end or the hole may be partially or completely filled with weld material.

Slot welds are useful when the part design requires overlap between two surfaces. The special applications of slot welding are:

  • Transmitting shear force in lap joints
  • Preventing buckling in overlapped parts

6. Flash Weld

Flash welding is a resistance welding method that does not require filler metal. During the flash welding process, an electric current is applied to create resistance between the two surfaces to be joined. When two surfaces come into contact with a small contact, an electric current flow and the material melts.

The molten material is ejected from the joint as a spray of molten particles, creating a unique flushing action. Oxides and other contaminants are removed from the interface and form a thermally softened region at the edge of the two surfaces.

Once the material has melted enough, a force is applied to bond the surfaces together. This facilitates the creation of butt welds without molten material at the joint.

The flash welding process is fast, cost-effective and can fuse dissimilar metals with different melting points. Flash welding is often used:

  • Joining sections of mainline rail in railway construction
  • Connecting thick workpieces such as chains or pipes
  • Merging metal sheets, rods, and bars

7. Seam Weld

Seam welding is the process of joining two similar or dissimilar materials in a joint using electric current and pressure. Seam welding is possible due to the contact resistance created between the two metals. When current passes between metals, heat is generated in small gaps.

This process is mainly used for metals because they easily conduct electricity and can withstand relatively high pressures. When current passes between metals, heat is generated in small gaps. Electrodes maintain and control the flow of electricity.

This type of weld can be created in two ways:

  • Resistance seam welding. Resistance seam welding is an adaptation of spot welding that uses a motor wheel instead of a fixed rod on the welding electrode. Common applications include sheet metal processing and the manufacture of automotive parts such as fuel tanks, radiators and steel drums.
  • Friction seam welding. Friction seam welding uses friction instead of an electrode to generate heat. This allows the surfaces to merge into the solid phase, thus eliminating the occurrence of interdiffusion. Friction seam welding is often preferred for materials that are inherently difficult to weld using conventional arc welding methods.

Benefits of seam welding include:

  • Provides sturdy, durable welds
  • Relatively easy to perform
  • Ideal for manufacturing liquid- and gas-tight vessels

8. Spot Weld

Spot welding (also called resistance spot welding) is a resistance welding process. This welding process is primarily used to weld two or more metal sheets by applying pressure and heat from an electric current to the weld area.

This is done by placing a copper alloy electrode with the surface of the sheet, where pressure and current are applied, and heat is generated as the current flows through a resistant material such as low carbon steel.

Spot welding is relatively easy and inexpensive, making it a popular welding choice in several major industries, including:

  • Automotive
  • Aerospace
  • Construction
  • Electronics
  • Metal furniture building
  • Railway

9. Upset Weld

Upset welding (UW)/resistance butt welding is a welding technique that produces coalescence simultaneously over the entire area of abutting surfaces or progressively along a joint, by the heat obtained from resistance to electric current through the area where those surfaces are in contact.

Apply pressure before starting heating and maintain pressure during heating. The equipment used for flux welding is very similar to flash welding equipment. Available only if the parts to be welded have equal cross-sections.

Adjacent surfaces must be carefully prepared to provide adequate heating. The difference in flash welding is that the parts are clamped with a welding machine and force is applied to them for a tight connection.

A high amperage current then passes through the junction and heats the junction surface. When they are heated to the proper forging temperature, a disturbing force is applied and the current is interrupted. Fusion occurs due to the high temperature and pressure of work on joint surfaces. After cooling, the power is released and welding is completed.

The intrusion welding process has several distinct advantages, including:

  • High-quality welds with fewer fusion defects
  • Compatibility with a wide variety of standard and difficult-to-weld materials
  • Welding equipment that is easy to control, operate, and maintain

Advantages Of Welding

  • Welded joints are strong and may be stronger than the base metal.
  • Can weld different materials.
  • Welding can be done anywhere and does not require a long distance.
  • Offers a sleek look and simplicity of design.
  • They can be done in any shape, any direction.
  • Can be automatic.
  • Provides a perfectly rigid joint.
  • Easy addition and modification of existing structures.

Disadvantages of welding

  • Members may be distorted during welding due to uneven heating and cooling.
  • They are permanent joints, so welds must be cut to separate them.
  • High initial investment.

Application Of Welding

Welding is commonly used in pressure vessels, bridges, buildings, aircraft and spacecraft, rail vehicle and shipbuilding, automotive, electrical, electronics and defense industries, pipelines and railways, and nuclear power plants. Installation.

  • Fabrication of sheet metal.
  • Automotive and aerospace industries.
  • Connecting ferrous and non-ferrous metals.
  • Joining of thin metals.


What is Welding?

Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.

How Does Welding Work?

Welding works by joining two materials together without a separate binder material. Unlike brazing and soldering, which use a binder that has a lower melting point, welding joins the two workpieces directly together.

What are the 4 Types of Welding?

There are four main types of welding. MIG – Gas Metal Arc Welding (GMAW), TIG – Gas Tungsten Arc Welding (GTAW), Stick – Shielded Metal Arc Welding (SMAW) and Flux-cored – Flux-cored Arc Welding (FCAW).

How much do welders make a year?

How much does a welder make? Well, in welding, you can make anywhere from $29,000 to $117,000 per year, with the median annual salary being $58,000. Experience and education level factor into how much a welder earns. Excellent skill and experience can lead to higher pay.

What are the 7 basic types of welding?

Basic types of welding:
1. MIG Welding – Gas Metal Arc Welding (GMAW)
2. TIG Welding – Gas Tungsten Arc Welding (GTAW)
3. Stick Welding – Shielded Metal Arc Welding (SMAW)
4. Flux Welding – Cored Arc Welding (FCAW)
5. Energy Beam Welding (EBW)
6. Atomic Hydrogen Welding (AHW)
7. Gas Tungsten-Arc Welding.
8. Plasma Arc Welding.