GTAW Applications 240

This class describes the GTAW process and the variables that affect welding current, electrode selection, electrode preparation, and arc-starting methods. Includes an Interactive Lab.


Class Name:
GTAW Applications 240
This class describes the GTAW process and the variables that affect welding current, electrode selection, electrode preparation, and arc-starting methods. Includes an Interactive Lab.
Number of Lessons:
Additional Language:

Class Outline

  • Objectives
  • What Is GTAW?
  • Pros and Cons of GTAW
  • Metals Welded with GTAW
  • GTAW Equipment
  • GTAW Torches
  • Parts of the GTAW Torch
  • Tungsten Electrodes
  • Electrode Characteristics
  • Shielding Gases
  • DC or AC Selection
  • Amperage
  • Voltage
  • GTAW Electrode Preparation
  • GTAW Joint Preparation
  • The Touch Start Method
  • The High-Frequency Start Method
  • GTAW Torch Manipulation
  • Running a GTAW Bead
  • Summary


  • Define GTAW.
  • Distinguish GTAW from other arc welding processes.
  • Identify common metals welded with GTAW.
  • Describe characteristics of common GTAW equipment.
  • Distinguish between gas-cooled and water-cooled torches.
  • Identify parts of the GTAW torch.
  • Describe common types of tungsten electrodes.
  • Describe characteristics of typical tungsten electrodes.
  • Describe the characteristics of shielding gases used for GTAW.
  • Distinguish between using DC or AC for GTAW.
  • Describe GTAW amperage characteristics.
  • Describe the factors that affect voltage for GTAW.
  • Describe common methods for tungsten electrode preparation.
  • Describe common methods for preparing a joint for GTAW.
  • Describe the touch start method.
  • Describe the high-frequency start method.
  • Explain how to manipulate a GTAW torch.
  • Explain how to run a weld bead using GTAW.


  • AWS SENSE Level 1


Vocabulary Term Definition
abrasive A material consisting of hard particles used to wear down, rub away, or machine material.
AC Current that regularly reverses the direction of its flow. AC is often used in GTAW to weld aluminum and magnesium alloys.
aluminum A silvery white metal that is soft, light, and an effective conductor. GTAW is sometimes the first choice for welding aluminum.
amperage A measurement that indicates the amount of current flowing in a circuit, which is measured in amperes. FCAW amperage is determined by wire speed.
argon An inactive gas commonly used as shielding. Argon is much heavier than air, so it effectively shields the weld area.
balling An electrode preparation process in which the tip of the tungsten electrode is formed into a hemispherical ball. This shape is required for AC and DCEP welding.
burnthrough Excessive melt through or a hole in the base metal. Extremely high welding temperatures can cause burnthrough.
butt joint A type of joint between two metal parts that lie in the same plane. A butt joint is the most common joint type.
carbon steel A steel that is made up of iron and carbon, without any additional materials.
ceramic A nonmetallic material made from clay and hardened by firing at a high temperature. GTAW nozzles are often made of ceramic because of its resistance to high temperatures.
collet set A two-piece set, usually made of copper, which secures the electrode in the torch. Standard collet sizes are made to fit each standard size tungsten electrode.
conductor A material that allows for the flow of electricity. For a successful arc weld, electrodes and base metals must be good conductors.
constant current welder A welder that uses current that varies slightly with changes in voltage. Constant current, or CC, is often used in gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW).
constant voltage welder A welder that uses voltage that varies slightly with changes in current. Constant voltage, or CV, is often used for gas metal arc welding (GMAW) and flux-cored arc welding (FCAW).
copper A reddish metal that is very ductile, thermally and electrically conductive, and corrosive resistant. Copper is often used to make electrical wire.
corrosion resistance A metal's ability to resist attack by other elements and chemicals.
cup Another name for the nozzle in GTAW.
cylinder pressure gauge The device that indicates the amount of shielding gas present in the gas cylinder.
DCEN An abbreviation for direct current electrode negative. DCEN is another way of expressing direct current with straight polarity.
DCEP An abbreviation for direct current electrode positive. DCEP is another way of expressing direct current with reverse polarity.
deposition rate The rate at which an electrode melts into the molten weld puddle to form a weld.
drooping A characteristic of welding current that occurs when using a constant current welder. Even though current is constant in GTAW, when the welder raises or lowers the welding torch, current varies slightly.
ductility A metal's ability to be drawn, stretched, or formed without breaking.
duty cycle The amount of time in a ten-minute period that an electrical device can perform work without overheating. If a welding gun has a 30% duty cycle, it can operate for three consecutive minutes and must rest for seven.
electrode extension The distance from the end of the contact tip to the end of the electrode.
electrode preparation The use of processes that prepare the tungsten electrode before welding. Grinding and balling are common electrode preparation processes.
filler metal Metal deposited into the weld that often adds strength and mass to the welded joint. GTAW sometimes uses filler metal that is added independently of the tungsten electrode.
filler passes A single progression of welding with the purpose of filling the joint with metal. GTAW is generally not used for filler passes due to its slow deposition rate.
flux-cored arc welding An arc welding process that uses a continuously fed consumable electrode that contains flux in a hollowed-out center. It is also referred to as FCAW.
foot pedal A type of control that, when pressed by the welder, initiates frequency. Pushing the pedal all the way down increases amperage.
frequency The rate at which an electrical current alternates, expressed as the number of cycles per unit of time. Frequency is typically measured in Hertz (Hz) or cycles per second.
gas cylinder An external device used to house shielding gas. Shielding gas flows from the gas cylinder, to the gas hose, to the welding gun.
gas lens A specially designed screen assembly that attaches to the welding torch and gas nozzle to maintain a longer shielding gas flow.
gas metal arc welding An arc welding process in which a bare wire electrode and inert or active shielding gas is fed to the weld through a welding gun. It is also referred to as GMAW or MIG welding.
gas tungsten arc welding A very precise arc welding process that uses a nonconsumable tungsten electrode. It is also referred to as GTAW or TIG welding.
gas-cooled torch A type of welding torch that uses shielding gas to cool the torch. Gas-cooled torches are often used for low-current applications.
grinding The use of an abrasive to wear away at the surface of metal and change its shape. Grinding is often used for tungsten electrodes to maintain the required shape.
grinding wheel A wheel coated with an abrasive that is used to grind a workpiece.
groove angle The total angle of the groove in between workpieces. GTAW joints must have wide groove angles to accommodate for torch manipulation.
groove face The exposed surface of the groove weld in between workpieces.
GTAW The American Welding Society abbreviation for gas tungsten arc welding.
hand control A type of control mounted on the welding torch, which initiates frequency. Hand controls allow the welder more freedom to move.
heat-affected zone The portion of the base metal that has not been melted, but its mechanical properties have been altered by the heat of welding.
helium An inactive gas commonly used as shielding. Helium is much lighter than air and can escape the weld area quickly.
hemispherical ball A half circle of molten metal formed on the tip of the tungsten electrode. The hemispherical ball is formed during the balling process.
high-frequency start method An arc starting method in which high voltage is used to generate a spark between the electrode and the workpiece to establish an arc. With this method, the electrode does not touch the workpiece.
inert gas A type of gas that does not react with other elements. Argon and helium are inert gases.
ionize To convert something into ions, which are atoms that carry positive and negative electrical charges. With high-frequency start, high voltage ionizes the gas, which conducts the current.
joint preparation A variety of processes that prepare base metals before welding. This can involve preheating, cutting, or other preparations.
machining The process of removing metal by producing chips through the use of cutting tools.
magnesium A grayish white, extremely light metal that is also brittle and has poor wear resistance.
nickel alloy A metal that contains nickel, which is a hard, malleable, silvery white metal used in various alloys to add strength, toughness, and impact resistance to metals.
nonconsumable tungsten electrode An electrode made of tungsten that is not melted by welding heat and does not become part of the molten weld metal.
nonferrous alloy A metal that does not contain iron. Aluminum and copper are common nonferrous metals.
nozzle A device attached to the front of the torch body that directs inert shielding gas over the weld area. GTAW nozzles are typically made of ceramic.
oxide film A chemical compound that contains oxygen, which forms a thin layer on the surface of metals when exposed to air. Oxide film should be removed before welding.
pure tungsten electrode A type of tungsten electrode made with at least 99.5 percent tungsten. Pure tungsten electrodes are primarily used with AC for welding aluminum and magnesium.
reactive metal A type of metal that undergoes a chemical reaction when combined with elements such as oxygen, hydrogen, or nitrogen. Reactive metals include titanium, nickel, and magnesium.
remote control A device used to control a welding sequence or welding current. GTAW uses hand controls and foot controls to control current.
root passes A single progression of welding in the root of a joint.
shielding gas A gas that protects the weld puddle and arc from reacting negatively with the atmosphere. GTAW shielding gas is supplied by a cylinder and flows through the welding torch.
shielding gas flowmeter The device that controls the amount of shielding gas that flows to the weld area.
taper A gradual decrease in the width of an object. Tungsten electrodes are tapered to a point.
thermal conductivity The rate at which heat flows through metal.
thoriated tungsten electrode A type of tungsten electrode that contains approximately 2 percent thorium. Thoriated tungsten electrodes have higher conductivity and generally last longer.
thorium A heavy, radioactive element used in tungsten electrodes.
TIG welding Another name for gas tungsten arc welding or GTAW.
titanium A silver-gray, strong, but lightweight metal known for its corrosion resistance. Titanium is often used in the aerospace industry.
torch body The metallic part of the welding torch that holds the electrode and collet set.
torch cap A cap on the back of the torch body that allows the collet to grip the electrode when tightened. Torch caps are designed to match standard tungsten electrode lengths.
touch start method An arc starting method in which the tungsten electrode contacts the workpiece to create a short circuit and an arc. This method is not used for critical work because it may cause electrode contamination.
tungsten A gray metal that is very strong at elevated temperatures. Tungsten is used to make nonconsumable electrodes.
tungsten inclusion A piece of tungsten entrapped in the weld metal. Tungsten inclusions contaminate the weld.
turbulence An upset in the even flow of shielding gas to the welding area. Turbulence causes gas to swirl, and as a result, mix with outside air. Turbulence is often the result of excessive shielding gas.
undercut A groove melted into the base material, usually along the toes of the weld, that produces a weak spot in the weld.
voltage The electrical force or pressure that causes current to flow in a circuit.
water-cooled torch A type of welding torch that uses water to cool the torch and power cable. Water-cooled torches are often used for high-current applications.
welding machine Equipment used to perform the welding operation. A welding machine is used in an automatic welding process.
welding torch The device that holds the tungsten electrode, delivers shielding gas to the weld area, and insulates the welder from the welding current.
zinc-based alloy An alloy that contains zinc, a bluish-white metal most often used in brass and bronze.
zirconiated tungsten electrode A type of tungsten electrode, which contains small amounts of zirconium oxide. Zirconiated tungsten electrodes combine the characteristics of pure tungsten and thoriated tungsten electrodes.
zirconium oxide A white, crystalline powder used in zirconiated tungsten electrodes.