How Does Welding Work?

Welding is a fusion process where two or more different metals and thermoplastic components are joined together with the help of high-temperature heat or pressure or both. It helps combine smaller, simpler objects to produce more complex structures.

During the welding process, parts are combined by melting a filler material (such as steel) at the joining point. The combination is achieved with three main techniques: gas welding, arc welding, or laser welding.

In this post, we’ll take a detailed look at how welding works, the process of combining different parts, and the main types of welding that are used by professionals.

The fundamentals of welding

You first need to understand that welding is different from soldering or brazing. With soldering, a filler material is burned between two components that are held closely together. Only the filler material burns and connects to both parts, forming a bond.

With welding, the base metals, or plastics are burned as well, causing them to melt and combine with the filler to form a more secure and sturdier bond.

Different types of welding

More than a dozen types of different welding processes are used to weld metals, plastics, or wood together. They can be divided into two broad categories; pressure-based welding and heating-based processes.

Within the heating category, you can find different welding techniques such as the simpler oxy-fuel technique to the high-tech process involving laser beam welding.

However, when it comes down to practical and commercial applications, only four types of welding are commonly used by most welders. These include MIG, TIG, Stick, and flux-cored arc welding. Each welding type comes with certain advantages and disadvantages, and a welder needs to have the proper training to use them effectively.

How welding works

In this guide, we will focus on the arc welding fusion process. It involves a variety of arc application approaches and joint types for getting the required joint. The most common types of welding joints are;

  • Butt joint: This forms 135-180° angle connections between two metal ends
  • Lap joint: This weld is used for 0-5° angle connection between two overlapping pieces
  • T joint: It can be used to connect one part’s edge to another part’s face in an angle of 5-90°
  • Corner joint: This joint forms a 30-135° connection between two metal edges or ends
  • Edge joint: A common weld joint between the edges of two parts that could be anywhere between 0-30° degree

During the welding process, welders mostly work with two types of materials that they need to look out for.

  • Parent Material: This includes the multiple metal parts that are joined together during the welding process.
  • Fillers or Consumables Material: These are the additional materials that are heated up in the arc and deposited over or under the surface of joints to help create a stronger bond.

Parent materials used in welding

Welding can be carried out for a variety of materials, including metals, plastics, and even wood. Each of them requires different temperatures and welding methods.

Metal welding involves heating metal parent material, which then melts and combines with other materials to create a strong weld joint. A high temperature is delivered to the work area, which creates a pool of molten material that cools down to form a joint. Usually, this joint is just as strong, if not stronger, than the parent material itself.

A shielding gas can be used to protect the molten weld puddle and filler metals from becoming contaminate or oxidized by the environment.

Apart from metals, you can also join plastics together through the welding process. Heat is applied to the plastic parent material in three stages. First, the surface area is prepared and brought together through pressure. Heat is applied in short, controlled bursts. The materials are allowed to cool, while pressure continues to be applied to the materials for creating the weld.

Heating methods can be categorized as either internal or external, depending on the exact process used for welding.

Wooden parent material can also be joined together through welding. The materials are subjected to a great deal of pressure and then heated through linear friction movement that creates heat on the surface to bond the workpieces together. The wood welding process is quite fast and creates a sturdy end result without the use of adhesives or nails.

Different types of welding processes

Stick, MIG, and TIG welding is the most common types of arc-based techniques used in metal welding. Let’s look at each of these methods briefly here.

How does stick welding work?

The shielded metal arc welding, aka stick welding, is a welding method that involves delivering an electrode to the welding point where the arc melts and joins metals together.

The welding gun consists of a core wire that is designed to create a high-temperature arc at the tip of the electrode. The arc is brought close to the workpiece and quickly withdrawn while still remaining quite close to the joint area to create temperatures that can go up to 6500°F to melt the parent metal.

To get the best results, the surface area of the molten metal is kept protected from oxides and nitrates that may be present in the environment. This makes stick welding ideal for use in pipeline welding, construction, steel metal casting, and heavy equipment repair.

Stick welding technique is one of the cheapest and least costly methods of combining metal parts. It is also one of the most portable methods as stick welding guns can be used in confined spaces with ease. Shielding gas is not used in stick welding, unlike TIG or MIG welding techniques, and you can use stick welding even when you are outside or working in strong wind or rain.

Another benefit is that stick welding can be used on dirty or slightly rusted metals. It is a suitable method for welding projects where you can simply not use the TIG or MIG techniques.

However, there are some disadvantages of stick welding as well. For a start, it has lower consumable efficiency, as there is quite a lot of waste of filler material when welding in this way. The operator must also be highly skilled and efficient in working with outdoor conditions or confined spaces. Stick welding also takes more time to complete weld projects, and it is going to take you a bit longer than other methods to master the required skills. It is also more difficult to use stick welding for complex or delicate projects that require extreme precision or efficiency.

The stick welding method has been around for a longer time and usually considered obsolete when compared to the MIG or TIG anti-aging methods. The process requires a lot of manual handling, which makes it more difficult for newer techniques. However, the process is necessary for some situations where it is difficult to use TIG or MIG welding due to the position or angle of materials or type of materials used.

Stick welding is a very low-cost solution that does not require a lot of investment into expensive equipment. The quality of the final weld may not be the best, mostly because this technique only allows shallow penetration, cracking, and porosity. Stick welding joints are also more vulnerable to severe weather conditions.

How does MIG welding work?

MIG welding, aka gas metal arc welding (GMAW), involves a continuous electrode to pass through a welding gun that heats up and joins metals together. The MIG operator needs to pull a trigger on the gun to feed the consumable electrode to the workpieces.

This technique of welding creates an arc between the base material and the gun that heats the material until it reaches the melting point. The puddle of molten pieces is what makes it possible to get different metals to join with one another.

MIG welding can be used for a wide variety of metals, including stainless steel, carbon steel, copper, magnesium, nickel, aluminum, and silicon bronze.

The main advantage of using MIG style welding is that it reduces wastage thanks to the better electrode delivery efficiency to the workpiece. It lowers the need for weld clean up, lowers heat input to work area, and reduces fumes during welding. More importantly, MIG welding is the easiest welding technique to learn, making it quite suitable for beginners or DIY enthusiasts.

If you look at the disadvantages, MIG welding does have some issues. First, you need an external shielding gas for the electrode. MIG welding machines also have a rather high cost and require additional equipment to work. The positions and work angles for welding are limited. For example, you cannot use this technique for overhead or vertical welding. You also cannot make tack welds with thicker materials efficiently. Lastly, to use this welding technique successfully, all the workpiece surfaces must be free from dirt and rust.

For effective MIG welding, you must adjust the power settings correctly to match the thickness of the material. The welding speed is also a major factor that affects the penetration and strength of the weld. If you decrease the speed of electrode delivery, you will be able to increase penetration to the metal. You can use a variety of calculators to compare the different settings that you need for the welding power on a specific project.

Shielding gas is an essential factor to consider for MIG welding. MIG welding requires an externally supplied shielding gas that covers the electrode and protects it from external environments. The most commonly used gases in MIG welding are Argon, Helium, Oxygen, and Carbon Dioxide. Each of them provides its unique advantages.

Carbon Dioxide (CO2) is the most common of the reactive gases that are used in MIG welding. It is generally the least expensive of the common shielding gases that are used. It is also the only shielding gas that can be used in its pure form without the addition of another inert gas. This is what makes CO2 the most popular shielding gas.

Many professional welders also use a mixture of between 75 – 95 percent Argon and 5 – 25 percent CO2. This combination provides more desirable arc stability and puddle control that causes lower spatter than pure CO2.

MIG welding is most commonly used in the automotive industry. MIG welding creates a firm weld that can withstand tremendous forces effectively. Automotive repairs and construction usually require strength and versatility, and MIG welding is quite suitable for this purpose. Other common areas where MIG welding is used include robotics, branding, construction, and maritime industry.

How does TIG welding work?

Tungsten Inert Gas (TIG) welding, aka Heliarc welding, is another well-known welding process in which a non-consumable tungsten electrode is used to heat and melt the base parent metal. Since Tungsten has a very high melting point, the electrode does not dissolve under intense heat that is required to create metal joints.

This removes the need for filler materials that you need with MIG welding. The metal combination is achieved simply through the electrode arc. However, you can add an external filler rod into the molten puddle to create a weld bead that enhances the mechanical properties of the metal. Whether to use a filler or not really depends on the type of project that you are working on.

The main benefit of using the TIG welding method is that it allows you to work with very thin or delicate materials. It does not create a lot of spatter or metal deposits on the welding joint. TIG produces high-quality, clean welds, and weld beads offer a highly aesthetic-looking finish. The metal joints are strong and effective, offering the same level of sturdiness as the parent material.

There some downsides of TIG welding as well. First, there is a high cost. TIG equipment is quite expensive and may not suit part-time welders. It requires external shielding gas to protect the electrode, which is both expensive and difficult to manage. The method has a higher learning curve than MIG welding. TIG welders must be skilled operators. If you are not using extra deposit material, a TIG weld may not be as strong as MIG welds that are reinforced by additional metal deposits.

Similar to MIG welding, you will need an external gas supply, usually argon, helium, and carbon dioxide mixtures. TIG welding is most commonly used in piping systems, aerospace, and motorcycle or bike welding.

The TIG welding technique has become quite popular among welders these days. This is because TIG welding offers a clean and smooth finish. It provides a higher degree of purity for the final output than you can get with any other welding method. TIG is most commonly used for welding stainless steel metal pieces. However, it is also a suitable choice for other metals, including aluminum, copper, magnesium, and nickel, etc.

TIG welding is generally used in industries where nonferrous metals are prevalent in products. This includes industries like tubing, vehicle, and bicycle manufacturing, as well as the repair and maintenance of various types of tools made from aluminum, copper, magnesium, and stainless steel.

The role of flux and shielding gas in welding

Flux is generally used in MIG welding to generate the shielding gas that protects the arc. It is a chemical coating that covers the filler rod that burns off while the electrode is running. As the flux burns, it produces a shielding gas that prevents oxidation of the weld base and filler material.

Flux can be made from a wide variety of compounds depending on the application and filler material that is used in welding. It offers many benefits to the welding process.

The primary use of flux is to help protect the base of the metal weld and filler material from oxygen and other ambient gases present in the environment. It creates a barrier called the shielding gas, protecting the arc and weld puddle from environmental forces. Flux creates a more purified environment for the arc to exist and operate inside.

In TIG welding, the shielding gas is directly fed to the weld surface to keep the new metal joint clean from impurities. These impurities, also known as inclusions, can otherwise contaminate the metal and create porosity that weakens the joint.

Last but not least, the shielding gas controls the arc, helping the arc come up to a higher temperature to create the puddle of liquid metal.