Gas Tungsten Arc Welding (GTAW), also known as Tungsten Inert Gas (TIG) welding, is the metal joining process that uses a non-consumable tungsten electrode to produce the weld. The process involves a controlled arc that melts the base material and filler metal, all under a protective atmosphere of inert gas, typically argon or helium, which shields the weld from contaminants.
The welding process is known for its precision and versatility. Whether it’s the aerospace sector, the construction of high-performance race cars, or the delicate work of crafting fine jewelry, GTAW is the go-to process for achieving the highest quality welds in the industry.
From its origins in the 1930s to its modern-day applications, the process has continually evolved, incorporating advanced technology to enhance precision and control. Let’s dive into the fascinating world of Gas tungsten arc welding, exploring its history, machine setup, and applications.
History
In the early 1940s, Tom Piper and Russell Meredith developed a welding process named Heliarc for Northrop Aircraft, an experimental aircraft made from magnesium designated XP-56.
The welding process used a tungsten electrode arc and helium as a shielding gas. It is now referred to as gas tungsten arc welding in America and tungsten inert gas welding in Europe. Further developments were made to the process, and air-cooled and water-cooled torches were introduced to improve shielding.
Initially, the electrode overheated quickly, and despite tungsten’s high melting point temperature, particles of tungsten were spread on the weld. To fix the issue, the polarity of the electrode was changed from positive to negative.
But it is also not the complete solution. Finally, alternating current units were developed to stabilize the arc and produce high-quality welds. During the 1950s, various advancements were made to the process, including using carbon dioxide as an alternative to more expensive argon and helium.
But it was unacceptable as weld quality was reduced. Advancements continued during the following decades, and today, a number of variations of GTAW exist.
Gas Tungsten Arc Welding Machine Setup
Below, we have discussed the complete machine setup of this welding technique.
1. Welding Torch
GTAW welding torches are equipped with cooling systems using air or water. A water cooling system is required for high-current welding, while an air cooling system is required for low-current welding.
The internal part of the torch is made of hard alloys of copper or brass, which allows it to transmit current and heat effectively. The tungsten electrode is held firmly in the center of the torch to provide a constant flow of shielding gas.
The torch’s body is made of insulating plastic, which makes it heat-resistant and electric-resistant. The size of the nozzle depends on the amount of shielded area.
2. Power Supply
This welding technique uses a constant current power source. The only reason behind this is that GTAW applications are manual or semi-automatic. If a constant voltage power source is used, maintaining a suitably steady arc distance is difficult.
It can also cause dramatic heat variations and make welding more difficult.
3. Polarity
The preferred polarity required for the GTAW depends on the type of metal being welded. When welding steels, titanium, nickel, and other metals, direct current with a negatively charged electrode is employed.
It generates heat by emitting electrons, which travel across the arc, increasing the temperature of the base material. Direct current with a positively charged electrode is used for shallow welds as less heat is generated.
4. Electrode
Tungsten or tungsten alloy electrodes are used in gas tungsten arc welding. Tungsten has the highest melting temperature, 3,422 degrees Celsius, which prevents the electrode from being consumed during welding.
The length of the electrode can range from 75 to 610 millimeters, and its diameter can be between 0.5 and 6.4 millimeters.
5. Shielding Gas
Shielding gas protects the welding area from atmospheric gases such as nitrogen and oxygen. The selection of shielding gas depends on the type of material being welded, joint design, and desired final weld appearance.
Argon is the commonly used shielding gas for the GTAW, as it prevents defects due to a varying arc length. When combined with alternating current, it produces a high-quality weld and a good final weld appearance.
Another commonly used shielding gas is helium. It is used to increase the weld penetration in a joint, increase the welding speed, and weld metals with high conductivity, such as aluminum and copper.
The only drawback of using helium is that it decreases the weld quality associated with a varying arc length. A mixture of Argon and helium is also used in GTAW. They can increase the control of the heat input and increase the welding speed and quality.
How Does Gas Tungsten Arc Welding Work?
During the GTAW process, an electric arc is struck between the tungsten electrode and the workpiece. The heat generated by the arc melts the base metal, and if necessary, a filler metal is added to the molten pool to create the weld.
The welder controls the arc length, which is the distance between the electrode and the workpiece, to maintain a stable arc and ensure a consistent weld bead. The welder may also manipulate the torch and filler rod to achieve the desired weld profile.
However, it requires a high level of skill and coordination, as the welder must manually control the welding variables while maintaining the correct torch angle and speed.
Pros and Cons of Gas Tungsten Arc Welding
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What is Gas Tungsten Arc Welding Used For?
The welding process is primarily used in the aerospace industry. GTAW is also used to weld workpieces in many other industries, including manufacturing space vehicles.
GTAW is also used in maintenance and repair work, especially repairing components made of magnesium and aluminum. As the weld produced from GTAW has the same chemical integrity as the original base material, its welds are highly resistant to corrosion over a long period, making it ideal for sealing spent nuclear fuel canisters before burial.
Frequently Asked Questions
1. What are the common challenges associated with GTAW?
Common challenges in GTAW include maintaining a stable arc, controlling the heat input to avoid warping or burning through thin materials, and ensuring proper shielding gas coverage to prevent oxidation and contamination of the weld. Proper technique and practice are essential to overcome these challenges.
2. What materials can be welded using GTAW?
GTAW is versatile and can be used to weld various materials, including stainless steel, aluminum, magnesium, copper, and titanium.
3. What are the advantages of GTAW?
GTAW provides high-quality, precise welds with excellent control over the weld bead. It produces clean welds with minimal spatter and can be used on thin and thick materials.
4. What type of shielding gas is used in GTAW?
Argon is the most commonly used shielding gas in GTAW. Sometimes, a mixture of argon and helium is used to improve heat transfer and welding speed.
5. What are the common applications of GTAW?
GTAW is commonly used in industries requiring high-quality welds, such as aerospace, automotive, and piping systems. It is ideal for welding thin sections of stainless steel and non-ferrous metals.
Wrapping Up
Gas tungsten arc welding, or Tungsten inert gas welding, is a precise welding process that produces high-quality, clean welds in a wide range of industries, from aerospace to medical devices.
While it requires a high level of skill and can be slower than other methods, GTAW’s benefits make it an indispensable tool.
