Electric arc welding: Processes and innovations

Introduction

Electric arc welding has been of paramount importance in the metallurgical industry since its inception in the late 19th century. Over time, it has evolved from a rudimentary process to an advanced technique that allows metals to be joined efficiently, using an electric arc as a heat source. Initially, it was based on a carbon electrode, but with the development of consumable metal electrodes, the process became more consistent and adaptable to various applications.

Nowadays, it is essential for several industrial sectors, standing out for its precision, speed and capacity to adapt to different materials and thicknesses. This article presents the main arc welding processes, their applications and recent innovations that have improved their efficiency and quality.

What is electric arc welding and how does it work?

It is a process that joins metals by means of localized fusion produced by the intense heat of an electric arc, which is formed between an electrode (consumable or not) and the base material; as the electrode melts, it creates a filler material that forms the weld. The arc produced can reach temperatures of up to 6,000 °C, sufficient to melt both the electrode and the edge of the base metal.

The use of a power source, which can be either alternating current (AC) or direct current (DC), provides the necessary energy for the process. DC is preferred for thinner materials due to its greater stability, while AC is used for thicker elements.

During the process, a protective gas or flux coating is used to prevent atmospheric contamination, ensuring the quality of the joint. After melting, the metals solidify, creating a strong and durable joint, relevant characteristics of a welding process that can be applied to a wide variety of metals and thicknesses.

Elements that make up this type of welding

• Electric arc: It is what is generated between the electrode and the work piece, providing the necessary heat to melt the metals and perform the welding.
• Consumable electrode: In many arc welding processes, a metal electrode is used which is consumed during the process and transfers the current to the base material.
• Shielding gas: A gas, such as argon or carbon dioxide, is used to protect the weld pool from air and prevent oxidation.
• Power source: An electrical source, such as a transformer or inverter, is required to generate the current to maintain the arc.
• Weld pool: The metal melted by the heat of the arc forms what is called the weld pool. This metal then cools and solidifies, forming the welded joint.

Why is electric arc welding so popular?

Since its origin in the late 19th century, electric arc welding has been central to the metalworking industry. Introduced by Nikolay Benardos in 1881 with a carbon electrode, and perfected by C.L. Coffin in 1890 with consumable metal electrodes, this process has continually evolved. Its popularity lies in its versatility, allowing a variety of metals and thicknesses to be joined in virtually any position.

In addition, it stands out for its high deposition speed and cost-effectiveness, adaptable to both manual and automated processes, making it a precise tool for mass production. Its precision and efficiency have constantly improved thanks to technological innovations, making it the most widely used welding technique in the world.

Main types of electric arc welding

This type of welding encompasses a variety of processes, each with specific characteristics and adapted to different industrial applications and types of materials. The main ones are listed below:

Stick welding (SMAW)

Also known as shielded metal arc or stick welding, it is one of the most conventional methods, using a consumable coated electrode that acts as a heat source and filler material. The electric arc is established between the electrode and the work piece, melting both to form the weld bead. The electrode coating creates a protective atmosphere that prevents oxidation during the process.

It is widely used in construction and repair, its portability and simplicity make it ideal for applications in outdoor environments, in metals with impurities; being special for structural and pipe welding, where working conditions can be complicated.

Gas-shielded metal arc welding (GMAW)

This GMAW welding process uses a continuous wire as electrode and a shielding gas (inert or active) that surrounds the arc, avoiding oxidation and contamination. This type of welding is made up of two types: MIG (Metal Inert Gas) which uses an inert gas such as argon, ideal for welding aluminum and other non-ferrous metals; and MAG (Metal Active Gas) where an active gas such as carbon dioxide or gas mixtures are used, suitable for welding steel.

These methods are valued for their high speed and efficiency, being preferred in industries with mass production such as automotive and the manufacture of metal structures, pipes, and equipment.

Gas tungsten arc welding (GTAW)

Also known as TIG (Tungsten Inert Gas) welding, this process uses an electric arc between a non-consumable tungsten electrode and the base material, while an inert gas, typically argon, protects the weld area from atmospheric contamination. The filler material is introduced externally, allowing greater control over the process and the amount of material deposited.

It is a slow welding method, but its high precision and quality of finish make it ideal for applications requiring corrosion resistance and high quality aesthetic finishes, such as aerospace and critical pipeline fabrication. Precise control of variables, such as heat and speed, minimizes deformation in thin materials.

Submerged arc welding (SAW)

This method is characterized by using a granular flux that completely covers the arc, allowing the weld to be made without exposure to air, which reduces spatter and increases efficiency. It is a highly efficient and automated process, ideal for heavy industrial applications where long, high-strength welds are required, such as in the fabrication of piping and metal structures. In addition, this process allows for greater weld penetration and consistent quality.

The following video shows the long stick-out (LSO) process is a submerged arc welding method designed to maximize productivity. Its principle is based on the natural resistivity of the welding wire. By increasing the length of the electrical stick-out (the distance between the contact nozzle and the arc point), the wire is preheated before entering the arc, which facilitates its fusion. This preheating allows, at the same amperage, the deposition rate to increase, even doubling compared to a conventional stick-out. Courtesy of: Lincoln Electric Asia Pacific.

Flux cored arc welding (FCAW)

It is a variation of traditional electric arc welding, in which a tubular electrode with a flux core inside is used. The electric current generates an arc between the electrode and the base material, generating the heat necessary to melt the metal and form the joint. The electrode’s flux core provides protection against oxidation by generating a protective atmosphere, similar to stick welding (SMAW), but with greater speed, efficiency and applicability.

Advantages and disadvantages of these types of welding

This is a widely used welding process in industry, but like any technique, it has both advantages and limitations that must be considered when choosing the right method for each application.

Advantages

• Process versatility: It can weld different types of metals (steel, aluminum, alloys) and adapt to multiple processes (SMAW, GMAW, GTAW, SAW, FCAW).
• High-strength welds: High arc penetration and the use of gas or flux protect joints from contamination, providing strong welds resistant to mechanical stress.
• Efficient automation: Easily adapts to automated systems, which improves weld accuracy and repeatability, reducing manual intervention and human error.
• Portability: The welding equipment is lightweight and easy to transport, ideal for repairs and work in outdoor or remote locations.
• High productivity: Enables fast metal deposition, increasing efficiency in mass production and reducing run times.
• Thick metal welding: Has the ability to weld materials of different thicknesses, from thin sheets to large sections, making it a useful option for different manufacturing needs.
• Ability to work in adverse conditions: It can operate in difficult weather conditions, such as wind or rain, without compromising weld quality, making it suitable for outdoor work.

Disadvantages

• Requires high technical skill: Electric arc welding requires highly skilled operators to ensure the quality of the joints, avoiding defects such as porosity and cracks.
• Emission of fumes and toxic gases: Fumes and noxious gases are generated during the process and are dangerous without adequate ventilation.
• Limitations in thin materials: It is not ideal for welding thin metals, since the intense heat can cause distortions or deformations in the parts.
• Waste generation: Produces more waste and slag compared to other methods, which can increase operating costs and require additional cleanup.
• Safety risks: There is a risk of electric current burns and eye damage due to sparks and ultraviolet radiation, so specialized personal protective equipment is required.
• Environmental impact: It emits polluting gases such as nitrogen oxides and carbon dioxide, contributing to air pollution, and consumes a large amount of electrical energy.
• Metal embrittlement: The process can cause hardened and brittle zones in the weld, increasing susceptibility to cracks and structural failures in the material.

Recent innovations in electric arc welding

Continuous innovations in electric arc welding are focused on improving the efficiency, quality and sustainability of the process. Recent advances include automation with cobots, along with artificial intelligence (AI) and machine vision, which enable greater precision and adaptation to complex geometries. Simulation and offline programming reduce downtime, while high-frequency inverters optimize welding parameters, minimizing thermal distortion.

Multifunctional equipment and synergistic systems automatically adjust process variables, reducing errors. In addition, more compact equipment with intuitive interfaces and improved filler materials, such as filler wires with advanced alloys that increase mechanical strength and corrosion resistance, have been developed. High-purity shielding gases improve the final quality of welds.

In terms of energy efficiency, new power supplies decrease consumption and emissions, while processes are becoming cleaner and more sustainable. One innovative field is the integration of arc welding with additive manufacturing, which, together with technologies such as lasers, allows the creation of parts with customized geometries.

In addition, numerical control systems have been improved, enabling greater precision and repeatability, especially in large-scale production. Real-time monitoring has advanced, allowing operators to detect defects or misalignments during the process, improving quality and reducing rework.

The use of new welding materials, such as wires with advanced coatings and optimized shielding gases, improves joint quality, reduces production times and operating costs in the industry.

Conclusions

Electric arc welding is one of the most advanced and versatile techniques in metal joining. In addition to generating high strength welds, its adaptability to a wide range of materials and thicknesses makes it fundamental in the welding industry. Over the years, technological innovations have optimized its efficiency through the development of automated equipment, more precise power sources and advanced filler materials.

Processes such as GMAW, SMAW and TIG welding continue to expand the range of industrial applications, while the incorporation of numerical control systems and robotic automation ensure greater precision and repeatability. These improvements, together with greater sustainability and reduced emissions, ensure that these processes maintain their position as a necessary technique in the development of modern infrastructure and advanced manufacturing.

References

1. https://www.taylor-studwelding.com/blog/types-of-arc-welding
2. https://testbook.com/electrical-engineering/electric-arc-welding-diagram-principle-and-advantages
3. https://ukmetalsexpo.com/5-exciting-innovations-in-welding/