How Does Welding Work? An Overview of Welding Processes

How Does Welding Work? An Overview of Welding Processes

How Does Welding Work? An Overview

Welding is more than just a spark and a flash of light; it is a complex process that requires skill, precision, and knowledge. While most people are aware of what welding is, few actually understand how it works. We’re here to shed some light on the welding process and explain how it works. Below, you’ll find an overview of the steps involved in welding and the science behind it.

How Welding Works

At its heart, welding is a process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together. But beyond the basic mechanics, understanding why welding works requires seeing the underlying principles and forces at play.

Welding relies on the principle of atomic bonding. When two metal surfaces are heated to their melting points, their atomic structures become more mobile and can intermingle. As the materials cool, the atoms from each piece bond to form a solid, continuous structure. This atomic bonding is what gives welded joints their strength.

The Principles of Welding

Heat and Melting:

  • Thermal Energy: Welding involves the application of intense heat generated by various methods such as electric arcs, lasers, or gas flames. This heat is essential to raise the temperature of the metals to their melting points, creating a molten pool. The source of this thermal energy can vary significantly:
  • Electric Arcs: Commonly used in arc welding techniques like MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding, electric arcs generate heat by creating an electrical discharge between an electrode and the workpiece.
  • Lasers: Laser welding uses focused beams of light to produce extremely high temperatures with precision, ideal for applications requiring minimal heat-affected zones.
  • Gas Flames: Oxy-fuel welding employs a flame produced by the combustion of oxygen and a fuel gas, such as acetylene, to generate heat.
  • Phase Transition: As the metals in the welding area are heated, they transition from a solid to a liquid state, forming a molten pool. This phase transition is key because it allows the materials to mix on an atomic level. Once the heat source is removed, the molten metal cools and solidifies, creating a solid weld.


  • Coalescence: When the molten pool solidifies, the atoms from the different materials mix, forming a strong bond. This bond is typically stronger than the original metals because the fusion zone often has a refined microstructure. This refined microstructure results from the rapid heating and cooling cycles during welding, leading to improved properties such as tensile strength and hardness.


  • Solid-State Welding: Unlike fusion welding, solid-state welding processes do not rely on melting the materials. Instead, they use pressure and mechanical force to achieve bonding. Key methods include:
  • Friction Welding: This process generates heat through mechanical friction between the workpieces, followed by applying pressure to form a solid-state bond. The frictional heat softens the materials without melting them, allowing for the formation of a strong weld upon cooling.
  • Ultrasonic Welding: Ultrasonic vibrations are applied to the workpieces under pressure, creating localized frictional heat that facilitates bonding at the interface. This technique is commonly used for joining thin or delicate materials, such as electronics or medical devices.

In both fusion and solid-state welding, the precise control of heat and pressure is vital to achieving a high-quality weld.

Types of Welding Techniques

There are various types of welding, and each has unique characteristics and applications. The type of welding best for you will depend on the type of material you’re working with, your experience level, and the project at hand. Here are some of the most common welding techniques used in various industries:

  • Gas Metal Arc Welding (MIG): This method uses a consumable electrode wire and shielding gas to join two metal pieces together. It is commonly used in the automotive, construction, and manufacturing industries.
  • Tungsten Inert Gas Welding (TIG): Gas tungsten arc welding (GTAW) uses a non-consumable tungsten electrode and shielding gas to melt the base materials. TIG welding produces precise, high-quality welds and is often used for thin or delicate materials.
  • Shielded Metal Arc Welding (SMAW): Commonly known as stick welding, this method uses a flux-coated electrode and an electric current to create the weld. It is a versatile process that can be used on various types of metals in different positions.
  • Flux-Cored Arc Welding (FCAW): Similar to MIG welding, FCAW also uses a continuously fed consumable electrode wire. However, it has a flux-cored wire that creates its own shielding gas, making it suitable for outdoor welding.
  • Laser Beam Welding (LBW): A focused laser beam is used to melt and join metal pieces together in this method. It produces precise and high-quality welds, making it popular in the aerospace industry.

Each welding type will require different tools and equipment, as well as different techniques. However, all welding processes involve the same basic principles of melting and fusing metal.

Welding Tools and How They Work

To successfully weld, you will need a variety of tools and equipment. Here are some of the most important tools and how they work:

Welding Machine: These machines provide the necessary energy source to heat the workpieces to their melting points. In electric arc welders, an electrical current flows through an electrode to the metal surface, creating an arc that generates intense heat.

Electrodes: Electrodes conduct electrical currents in the welding arc. Consumable electrodes also provide filler material for the weld, while non-consumable electrodes require a separate filler material.

Welding Torch: Welding torches control the flow of gas and electricity to the weld area. In MIG and TIG torches, a trigger or foot pedal controls the current, while in oxy-acetylene torches, valves control the gas flow.

Shielding Gas Supply: Provides a protective atmosphere around the weld pool to prevent contamination from atmospheric gases like oxygen and nitrogen. Common gases include argon, helium, and carbon dioxide, used alone or in mixtures.

These are just a few of the tools and their functions, but each welding process will require additional equipment, such as specific electrodes or gas mixtures. It is important to understand the purpose and proper use of each tool to ensure a successful weld.

Get High-Quality Pipe Welding Tools with H&K Fabrication

Whether you are a beginner or an experienced welder, we hope this post has helped you get a better understanding of how welding works. If you are planning to take on a pipe welding project, having the right tools is essential for achieving high-quality results. H&K Fabrication offers a wide range of pipe welding tools that are designed to make your job easier and more efficient. From pipe-fitting squares to roll-out wheels, we have everything you need to ensure precision and accuracy in your welding projects. Browse our catalog today!