Welding: What is it, Definitions, Types, Processes

One of the most essential construction-related activities is welding. While there are other processes that can bind materials together, welding is the only one that can do so with metals. But most people are unaware that welding now goes beyond that definition, even already capable of binding wood and plastic. Also, not a lot of people know that it comes in different types.

The good news if you’re looking at becoming a welder – there’s currently a shortage in the industry for those possessing the skills we’re going to describe below.

Definition of Welding

For many, welding is defined as the process where two metals are joined together using extreme heat. Most people are aware of this definition, but they cannot distinguish it from other similar processes, namely soldering or brazing, and that pressure alone or combined with heat can also weld materials.

Not a lot of people are aware that welding is limited to bonding the same kind of material only. This means welding metal to metal is doable, but not metal to steel or any other combination of varying base materials. The same material should be used to ensure a strong weld; not doing so will prevent the two materials from being joined together permanently, which is the goal of welding.

And among welding, soldering, and brazing, welding produces the strongest joints when the welder does it correctly.

What is Welding?

In a nutshell, welding involves bonding two parent or base materials together that are of the same type using either heat or pressure, or even both. As a result, the two separate parent materials end up becoming one.

While welding usually involves only the base materials, filler materials can also be added when welding. Metal is added to the weld to strengthen the joint formed, while certain gases are used for shielding the weld to prevent oxidation or contamination that can weaken the joint formed.

High heat from a welding tool or machine, such as a blowtorch, is used to melt a part or section of the base material where the other one will be attached to. This softens that area or creates a molten pool of material where the material to be joined is attached to. This pool or soften material is set to cool down and once it resolidifies, the two materials are now joined to form one single material.

Pressure can also be used to weld materials together. This pressure alone may be enough to successfully weld the materials involved, or this pressure is used together with the heat generated by the pressure exerted over the base materials that need to be joined together.

Types of Welding

Contrary to what most people think, welding is not just about using a welding machine to join two metals together. In fact, there are different types of welding present, which are listed below:

  • Stick Welding – also known as the Shielded Metal Arc Welding or SMAW, it is named as such because the use of welding rods or sticks is essential for welding. These rods consist of the filler material that binds the metals and flux that aids in the binding process of the molten metals and at the same time protects them. Stick welding considered the most popular in developing countries due to its low cost, despite the weaker weld produced.

Stick welding is used in a variety of applications and industries, such as construction, aerospace, shipbuilding, marine, petroleum, nuclear, field repair, mining, structural welding, steel fabrication, and manufacturing.

  • Metal Inert Gas or MIG Welding – the second most popular type, the Gas Metal Arc Welding or GMAW technique involves the use of a welding stick or gun where an electrode current-connected consumable wire passes through. It forms an electric arc that produces enough heat to weld, while at the same time releasing a shielding gas. Wire welding has gained popularity due to its ease of use.

MIG welding is typically used in manufacturing, construction, automotive, and other industrial processes.

  • Tungsten Inert Gas or TIG Welding – this type follows the same process as that of wire or MIG welding, but it specifically involves the use of a non-consumable electrode containing Tungsten to create the required arc. TIG welding is now the most popular due to its ability to create a clean weld and high-purity, which results in a superior weld.

TIG welding is commonly used in doing repairs and creating art, as well as in the automotive and aerospace industries.

FCAW is best for doing general repairs, as well as in manufacturing, shipbuilding, underwater welding, and pipeline welding.

  • Submerged Arc Welding or SAW – while it also uses flux, this type differs from the flux-cored arc welding because welding occurs under a blanket of loose or granular flux. This results in fewer fumes and ultraviolet light, making it the safest type.

SAW is commonly used in industrial projects, especially in vessel and structural construction.

  • Electroslag Welding – typically used on thick metals that are non-ferrous, it involves melting flux to form a molten slag or pool where an electric arc will pass through. The pool will eventually reach the electrode to extinguish the arc.

Electroslag welding is also typically used for industrial purposes, such as castings, vessels, structures, ships, machinery, and pressure vessels.

  • Electrogas Welding – shares the same process as electroslag welding, but the electric arc present is deliberately left alone. Also, the arc is known to be positioned vertically and allows welding to occur in a single pass.

Electrogas welding is best for the construction of storage tanks, blast and chemical furnaces, vertical vessels, bridges, and ships.

  • Atomic Hydrogen Welding or AHW – slowly becoming obsolete, this type involves using two metal tungsten electrodes in an atmosphere containing hydrogen. This will cause the hydrogen to break apart and recombine, generating heat needed for welding.

AHW is suitable for any application where rapid welding is a must.

  • Carbon Arc Welding or CAW – known as the first type of arc welding, the CAW technique uses a carbon electrode that is non-consumable to heat the metals together, eventually welding them. This type is also becoming obsolete.

CAW is known for being suitable for use with copper, repairing cast iron parts with bronze, galvanized steel, and for thinner materials.

  • Energy Beam Welding or EBW – involves placing the parent materials in a total vacuum and shooting a beam of electrons to those materials at high velocity. The electrons fired are converted to heat that is needed to melt the materials and weld them. It has two specific types available: electron beam welding and laser beam welding

EBW is used for a wide variety of industries, namely aerospace, research, defense, medical, power generation, electronics, oil and gas, and automotive.

  • Gas Welding – best known as oxyacetylene welding or oxyfuel welding, fuel gases are mixed with pure oxygen to adjust the temperature of the flame of a welding torch used for welding. Gas welding is considered as one of the oldest types of welding.

Gas welding is normally used in manufacturing, as well as in the aircraft and automotive industries.

  • Resistance Welding – force is applied to both ends of the metal to be joined and an electric current is applied nearby to create the extreme heat required for welding. Various techniques of resistance welding include seam welding, spot welding, flash welding, upset welding, butt welding, and projection welding.

Resistance welding is best for industrial, aerospace, and automotive applications.

Among the different types of welding used, arc welding is the most widely used in various industries. Arc welding is a broad category that covers stick welding, MIG welding, TIG welding, flux-cored arc welding, submerged arc welding, electroslag welding, electrogas welding, atomic hydrogen welding, and carbon arc welding and is used in a wide variety of industries. All these require electricity to generate the arc required for welding.

Not a lot of people know that welding can also be done underwater, but only for specific types. Hyperbaric welding is a specialized type that can be done via either wet welding or dry welding. Wet welding often uses the stick welding type, with the bubbles produced by the flux acting as a shield to prevent electrocution of the welder. On the other hand, dry welding involves creating a hyperbaric chamber surrounding the area before welding following the chosen type.

Welding Processes

Aside from choosing what type to use, welders also concern themselves with choosing among the welding processes available to determine which one is most suitable for their project. Which process to choose mainly depends on the type of joint, whether edge, T, butt, corner, or lap, and the material to be joined together.

The welding processes available are broadly categorized into two: fusion welding and pressure welding.

Fusion welding is the process many are most familiar with since it involves heat to weld materials together. The edges of the parent material are heated so that when they cool down and harden, they are already joined together. Using filler material and inert gases are optional, and no pressure is needed to weld these materials together. The different types mentioned above fall under fusion welding.

It should be noted that fusion welding requires at least one of the parent materials to have a solid-state solubility, as this determines their weldability. If the parent material is non-soluble in the solid state, it will require a soluble material for welding to be possible.

On the other hand, pressure welding involves the use of external pressure to the joints to be welded. Producing these joints are done through either solid state welding, which involves adding pressure at temperatures below the materials’ melting points, or fusion state welding that requires doing so at above melting point temperatures.

Unlike fusion welding, pressure welding requires that the joints or ends of the material are free of contaminants, particularly oxides and films that are non-metallic in nature. These joints should be completely clean to ensure that the joint made between the materials is the strongest possible.

Pressure welding is normally used when the materials involved are known for being ductile or whose ductility increases as the temperature also increases. Some examples are:

  • Cold pressure welding – welds materials, specifically for electric components, wires, and sheets, without requiring heat to do so.
  • Explosive welding – necessary if the parent materials are dissimilar metals whose joints require welding, such as for cladding. This solid-state process involves using explosives to weld materials together. These explosives cause one of the materials to accelerate toward the other and weld them together.
  • Friction welding – two metals are rubbed together and the friction between them generates the heat needed to weld them. This is also suitable for dissimilar metals, but it can also be used for similar ones
  • Inertial welding – similar to friction welding, but it involves rotating one of the materials to the other, with the latter remaining stationary. This is ideal for alloys with high strength
  • Induction welding – mostly used for pipes and tubes, it involves using an induction coil that electromagnetically produces the heat required for welding. The tube or pipes involved pass through the coil at high speeds, which causes heating on its edges and are squeezed together to form a seam that joins them together.
  • Percussion welding – involves using quick electrical discharges to form an arc that has a high temperature. This discharge causes pressure to be applied to the materials involved, welding them together. This is also suitable for joining dissimilar metals
  • Ultrasonic welding – vibrations are produced through sound waves at high frequency, and these cause the materials to bond together. This is normally used for welding thin sheets and plastics.

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