How Does Tungsten Inert Gas (TIG) Welding Works?

Tungsten inert gas welding (TIG), also known as gas tungsten arc welding, uses an electric arc struck between a non-consumable tungsten alloy electrode and the metal workpiece to be welded. The non-consumable tungsten electrode delivers the current to the welding arc.

An inert gas such as argon protects and cools the tungsten and weld puddle. This welding process is precise and versatile and is used to produce high-quality welds and protect the welding area from atmospheric contamination with an inert gas such as argon. Well, in this reading, we’ll explore what TIG welding is, its applications, parts, equipment, diagram, and how it works. We’ll also explore the advantages and disadvantages of TIG welding.

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What is TIG Welding?

GTAW, also known as tungsten inert gas (TIG) welding, is a welding process that uses a non-consumable tungsten electrode to produce welds. It is protected from oxidation or atmospheric contamination by an inert shielding gas (argon or helium). TIG welding is commonly used for welding thin sections of stainless steel and non-ferrous metals like aluminum, magnesium, and copper alloys.

GTAW allows greater control over the weld than competing processes, but is more complex and slower than other welding techniques. Plasma arc welding, a related process, uses a different torch for a more focused welding arc.

TIG welding is a precision process used for creating high-quality welds on thin materials. It uses a non-consumable tungsten electrode for arc stability and allows for the addition of filler material. TIG welding is versatile and requires skill in controlling heat and filler material, resulting in clean, aesthetically pleasing welds.

Applications of TIG Welding

TIG welding is a widely used process in various industries, particularly in aerospace, automotive, repair, and art fields. It is particularly effective in welding thin workpieces, particularly nonferrous metals, and is suitable for small diameter, thin wall tubing.

TIG welding is particularly useful in repairing tools and dies made of aluminum and magnesium. The process is particularly useful in welding refractory, sheet, and reactive materials.

TIG welding is particularly useful in aerospace, where aircraft and spacecraft are constructed, and in the automotive industry, where safe and secure construction is crucial. TIG welding is also used in various repair applications, such as fixing child’s toys and repairing aluminum tools.

Diagram of TIG welding

Diagram of TIG Welding GTAW

Related: How Does Metal Inert Gas (MIG) Welding Works?

TIG Welding Parts and Equipment

The major components in GTAW or TIG welding include power source, non-consumable tungsten electrode, inert gas supply, and welding Torch.

Power Source

TIG welding requires a constant, drooping power source for stable heat input. Alternating current (AC) and direct current (DC) power sources are available for different material types and weld outputs. AC welding maintains heat without overheating base materials like aluminium and magnesium.

DC power electrode negative pinpoints energy flow to targeted areas, appealing to all metals except aluminium and magnesium. DC power electrode positive is rarely used in TIG welding due to rapid heat input.  Cleaning Action can be obtain by revealing shiny oxides on the weld pool’s surface.

Non-Consumable Tungsten Electrode

Tungsten electrodes are a crucial component in welding due to their high melting temperature, offering excellent electrical conductivity without being consumed. These electrodes can be alloyed to improve their properties, depending on the weld type.

Pure tungsten electrodes (green) offer good arc stability when using AC current, while thoriated electrodes (1% thorium yellow; 2% red; 3% purple) have a high current carrying capacity and maintain the tip shape longer. Lanthaned electrodes (1% lanthanium black, 1.5% gold, 2% blue) are non-radioactive alloyed with lanthanum oxide, characterized by excellent arc stability and low erosion rate.

Cerium lanthanium electrodes (2% cerium grey) have great arc starting but less current capacity. Zirconiated electrodes (0.7-0.9% zirconium white, 0.15-0.5% brown) combine tungsten with zirconium oxide, offering high resistance to contamination and longer electrode life.

Cerium lanthanium electrodes (pink) combine ceriated and lanthaned electrodes, offering simplified arc ignition and a long life span.

Inert Gas Supply

The welding process involves the use of a TIG torch and an inert gas, such as argon, to protect the weld pool from contamination and impurities.

This gas flow is crucial in preventing oxidation and impurities from the atmosphere while the metals are melted and fused. Other combinations of hydrogen and argon, or helium and argon, are also used depending on factors like metals to be welded and welding speed.

Welding Torch

A welding torch is a mechanical tool used for melting and fusing metals. There are two types: air-cooled TIG torches, which have only one gas input and are prone to overheating, and water-cooled TIG torches, which have a gas input and output for water lines, ideal for larger projects requiring rapid cooling. However, these torches require a water cooler system to be installed.

How Does TIG Welding Works?

The working of tungsten inert gas welding is less complex and can be easily understood. It operates under a similar principle to MIG welding; the base metal and bonding materials are melted by the heat generated by an electrical current. it then cools and forms a solid joint. Although there is still a huge difference between the welding despite the similarities.

The TIG welding process involves adjusting the machine to the right settings, such as current and voltage, and setting the correct pressure for inert gas in the supply tank. The TIG torch should be modified according to the project requirements, choosing an electrode with the correct diameter and TIG collet. Clean protective gear is crucial for clear vision during welds.

After preparing, welding the metals together is essential, considering factors like arc length, travel speed, and torch angle. TIG welds can run without filler material, melting the base metals, but can be used with filler rods or metal coils if needed. TIG cold welding, despite its popularity, lacks fusion due to reduced heat input and is ineffective in creating strong, permanent joints.

Differences between MIG and TIG welding

TIG welding is a unique welding process that uses a non-consumable electrode and separate filler material, unlike MIG welding which uses a continuous, consumable wire electrode. TIG welding is commonly used for joining pipes and thin materials due to its low heat input, preserving the microstructure of metals.

It is preferred for thicker materials, as it is lower cost and has high weld speeds. TIG welding rarely creates spatter and requires light polishing to remove discoloration. It is preferred when the workpiece is not coated or painted, such as in welding stainless steel and aluminium.

The use of filler metal is optional for TIG welding, but it requires both hands and control the heat input with the pedal simultaneously. Most welders start out as MIG operators and transition later into TIG welding. TIG welding is not a plug-and-play process, but it is highly versatile due to its adjustable features, such as amperage flow, pulse amount, AC/DC output, and inert gas flow.

The table below shows the difference between TIG and MIG welding:

MIG Welding TIG Welding
Metal inert gas (MIG) welding utilizes a consumable electrode that is continuously fed into the welding zone from a wire pool. Tungsten inert gas (TIG) welding utilizes a non-consumable electrode (so it remains static and intact during welding).
The electrode itself melts down to supply the necessary filler metal required to fill the root gap between base metals. So electrode acts as filler metal (no additional filler is required). If required, the filler metal is supplied additionally by feeding a small diameter filler rod into the arc. So filler metal is supplied separately.
The composition of electrode metal is selected based on the parent metal. Usually, the metallurgical composition of electrode metal is similar to that of base metal. An electrode is always made of tungsten with a small proportion of other alloying elements (like thorium).
It is suitable for homogeneous welding. It cannot be carried out in autogenous mode welding as filler is applied inherently. It is particularly suitable for autogenous mode welding. However, it can also be employed for homogeneous or heterogeneous modes by supplying additional filler.
The electrode-cum-filler for MIG welding comes in the form of a small diameter (0.5 – 2 mm) and very long (several hundred meters) wire that is wound in a wire pool. TIG welding filler typically comes in the form of a small diameter (1 – 3 mm) and short length (60 – 180 mm) rod.
Due to its very large length, the filler electrode can be fed for a longer duration without replacement. Due to the short length, frequent replacement of filler is required. This interrupts the welding process unintentionally.
MIG welding is commonly carried out either in AC or in DCEP polarity so that electrodes can be melted and deposited at a faster rate. TIG welding is commonly carried out either in AC or DCEN polarity to increase electrode life.
The filler deposition rate is very high, so the process is highly productive. The filler deposition rate is low. In this sense, it is not very productive.
MIG welding usually produces a spatter. This causes the loss of costly filler metal. TIG welding is mostly free from spatter.
The quality and appearance of weld beads are not very good. It can easily produce defect-free reliable joints with a good appearance.
It does not lead to a tungsten inclusion defect. TIG welding sometimes leads to a tungsten inclusion defect (occurred when a melted/broken part of the tungsten electrode gets embedded into the weld bead).

Related: How Does Shielded Metal Arc Welding (SMAW) Works?

Advantages and Disadvantages of TIG Welding

Tungsten inert gas TIG Welding is a highly efficient method for joining metals, offering advantages such as the ability to work with a wide variety of metals, producing high-quality, and precise welds, and being done automatically or manually.

However, TIG welding has some disadvantages, such as its inability to work with thicker sheets of metal, the need for skilled workers, potential eye damage from high-intensity lights, high costs, and a slow process.

Despite these drawbacks, TIG welding remains a crucial method for welding critical joints and producing high-quality, high-purity welds. Its advantages also make it suitable for various applications, making it a versatile and cost-effective option for welding various metals.

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