GTAW Applications 331

“GTAW Applications” provides an overview of the practical applications of the gas tungsten arc welding process. It covers all parts of the process, including personal protective equipment, power supplies, polarity, amperage, electrodes, shielding gas, cups, starting the arc, filler metal, welding techniques, possible defects, and professional and industrial applications.

“GTAW Applications” is essential for any welder who requires an in-depth understanding of GTAW. Its focus on application extends "Intro to GTAW" to the practical sphere, paving the way for hands-on learning of GTAW welding.

Class Details

Class Name:
GTAW Applications 331
Number of Lessons:
Additional Language:
Related 1.0 Class:
GTAW Applications 240

Class Outline

  • Overview of GTAW
  • GTAW Personal Protective Equipment
  • Preparing Metals for GTAW
  • Polarity and Amperage
  • AC Cleaning and Penetration
  • GTAW Power Sources
  • Preparation, Power Sources, Polarity, and Amperage
  • Electrode Composition
  • Electrode Classification
  • Electrode Sizes and Preparation
  • Electrode Selection
  • Shielding Gas
  • Gas Flow
  • Extension and Arc Length
  • Selecting a GTAW Cup
  • Scratch and Lift Starting
  • High-Frequency Starting
  • GTAW Variables
  • Filler Metal Selection
  • The Dipping and Lay-Wire Techniques
  • Walking the Cup
  • Common Mistakes in GTAW
  • GTAW Applications
  • GTAW: Final Review


  • Describe GTAW.
  • Describe personal protective equipment for GTAW.
  • Describe how to prepare metals for GTAW.
  • Explain how polarity and amperage affect GTAW.
  • Describe how to balance cleaning and penetration for welding aluminum.
  • Distinguish between transformer and inverter GTAW power sources.
  • Distinguish between different GTAW electrodes.
  • Describe classifications for tungsten electrodes.
  • Describe different ways to prepare GTAW electrodes.
  • Explain how shielding gas choices affect GTAW.
  • Explain how gas flow affects GTAW.
  • Define extension. Define arc length.
  • Distinguish between different GTAW cups and their applications.
  • Describe GTAW scratch starting. Describe GTAW lift starting.
  • Describe GTAW high-frequency starting.
  • Explain how to select filler metal for GTAW.
  • Contrast the dipping and lay-wire techniques.
  • Describe how to use the walk-the-cup technique to weld.
  • Describe common mistakes in GTAW.
  • Describe common uses for GTAW.

Job Roles



Vocabulary Term Definition
115-volt outlet The standard three-prong household electrical outlet. 115-volt outlets can support inverter power sources for GTAW processes up to 100 amps.
220-volt outlet A household outlet commonly used to power large appliances. Transformer welding power sources for GTAW require 220-volt outlets.
AC Alternating current. An electrical current which reverses direction at regularly recurring intervals of time. AC current is used to weld aluminum in GTAW.
AC balance The amount of electrode negative or electrode positive in an AC current. Electrode positive provides superior cleaning action while electrode negative increases penetration.
acetone A solvent that can be used to clean certain types of contaminants from a surface. Acetone is extremely effective but also highly flammable.
alternating current AC. An electrical current which reverses direction at regularly occurring intervals of time. AC current is used to weld aluminum in GTAW.
alumina A chemical compound of aluminum and oxygen also called aluminum oxide. Alumina is used to make GTAW cups.
aluminum A nonferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.
aluminum oxide A chemical compound of aluminum and oxygen also called alumina. Aluminum oxide is used to make GTAW cups.
American Welding Society AWS. A professional organization that supports the welding industry and promotes welding and related processes. The American Welding Society provides industry-standard code and certification procedures.
amperage A measurement that indicates the amount of current flowing in a circuit. Amperage is measured in amperes.
amps A unit of measurement that indicates the amount of current flowing in a circuit. Amps are properly referred to as amperes.
arc The area in which electricity jumps from the electrode to the workpiece. The heat generated by the arc melts the base metals and filler metal during welding.
arc length The distance from the electrode to the workpiece in an arc welding application. Arc length is generally kept as short as possible in GTAW.
argon A colorless, odorless inert gas. Argon is commonly used as shielding gas.
balling Shaping the tip of a GTAW electrode into a small sphere. Balling is typically done by setting the welding power source to DC electrode positive and using it to melt the tip of the electrode.
brake cleaner An aerosol chemical containing tetrachloroethylene that is typically used to clean automotive brakes. Brake cleaner must never be used to clean workpieces for welding.
brass brush A brush with brass bristles. Brass brushes are used to break up aluminum or magnesium oxide for welding.
brittle A hard material that breaks instead of bends when subjected to force or pressure. Glass is an example of a brittle substance.
cerium Ce. A soft, ductile metal which oxidizes easily. Cerium is often combined with tungsten to make ceriated GTAW electrodes.
chlorinated solvent A solvent containing chlorine. Chlorinated solvents cannot be used to clean workpieces for welding because they can create deadly fumes, including phosgene.
conductor A chemically inactive substance that does not react with other materials. Inert gases can protect molten metal from atmospheric contamination.
contamination The presence of foreign matter in a completed weld. Contamination nearly always results in a weld defect.
copper A reddish metal that is very ductile, thermally and electrically conductive, and corrosion-resistant. Copper is often welded using GTAW.
cowhide A thick, durable leather made from cow hide. Cowhide is often used to make gloves for welding.
cubic feet per hour CFH. A measure of a total volume of gas flow per hour. Cubic feet per hour is used to calculate ideal shielding gas flow for GTAW.
cubic meters per hour CMH. A measure of a total volume of gas flow per hour. Cubic meters per hour is used to calculate ideal shielding gas flow for GTAW.
cup A device attached to the front of the torch body on a GTAW torch that directs inert shielding gas over the weld area. The size of the cup influences shielding gas flow.
current The flow of electricity through a circuit. Current is measured in amperes, or amps.
DC electrode negative DCEN. A DC current which flows from the workpiece into the electrode. DCEN is used for GTAW welding on steel and copper.
DC electrode positive DCEP. A DC current which flows from the electrode into the workpiece. DCEP is not commonly used in GTAW.
DCEN Direct current electrode negative. DC which flows from the workpiece into the electrode. DCEN is used for GTAW welding on steel and copper.
DCEP Direct current electrode positive. DC which flows from the electrode into the workpiece. DCEP is not commonly used in GTAW.
deerskin A soft, pliable leather made from deer hide. Deerskin is often used to make GTAW-specific welding gloves.
defects A discontinuity which renders a weld unusable. Workpieces with defects must be either ground down and re-welded or discarded.
defects Any one of the various discontinuities that can cause a weld to fail. Weld defects include porosity, incomplete fusion, weld cracking, and undercut.
diamond wheel A grinding or cutting wheel covered with tiny particles of diamond abrasive. Diamond cutting wheels are ideal for cutting tungsten electrodes.
diffuse To evenly spread a gas or liquid over an area. A gas lens is often used to diffuse shielding gas during GTAW.
dipping technique A GTAW filler metal technique in which the welder repeatedly dips the rod into the weld puddle during welding. The dipping technique can be used to manipulate the size of a weld with exceptional precision.
direct current DC. An electrical current that flows in one continuous direction. DC can be used for most welding methods.
discontinuities An irregularity in the specified and expected composition of a weld. A discontinuity is not always a defect.
electrode extension A measurement of the length from the tip of the GTAW electrode to the cup. Electrode extension should generally be about 1 to 1.5 times the diameter of the electrode.
electrode negative A current which flows through the workpiece into the electrode. Electrode negative is typically used for GTAW.
electrode positive A current which flows through the electrode into the workpiece. Electrode positive GTAW can cause damage to the tungsten.
electromagnetic radiation Radiant energy which can be released by many different electrical processes. Electromagnetic radiation is a particular concern in high-frequency GTAW start systems, as it can interfere with nearby electronics.
filler metal Metal deposited into the weld to add strength and mass to the welded joint. In some arc welding processes, the electrode acts as the filler metal.
flame-retardant A piece of clothing or other personal protective equipment that is designed to protect the wearer from flames or sparks. Flame-retardant PPE is used for welding.
flat position A welding position in which the face of the weld is horizontal. In GTAW, argon is typically used as a shielding gas during flat-position welding.
foot pedal A small pedal used to control amperage and to initiate the arc in GTAW. Foot pedals can be either wireless or wired.
freehand welding Welding without walking the cup or using another method to brace the welding torch. Since the torch is not steadied by anything other than the welder’s hand, the quality and appearance of the finished weld are directly dependent on the skill of the welder.
fume extractor Any device that uses suction to remove the smoke and gases generated by welding from the welding area. A fume extractor should always be used during welding.
gas lens A specially designed screen assembly that attaches to the welding torch and gas nozzle to maintain a smooth, even flow of shielding gas. A gas lens increases shielding gas coverage.
gas tungsten arc welding GTAW. A very precise arc welding process that uses a nonconsumable tungsten electrode. Gas tungsten arc welding is also referred to as TIG welding.
grinding Shaping or otherwise wearing away material using an abrasive. Grinding GTAW electrodes to a sharp point facilitates arc shape and control.
heat resistance Designed to withstand high temperatures. Heat-resistant tools can be used in high-heat applications without fear of deformation or damage.
helium A light, colorless, nonflammable inert gas. Helium is commonly used as shielding gas.
high-frequency start HF start. A method of arc starting which involves holding the electrode close to the workpiece and depressing a button or foot pedal to start a current. The high-frequency current leaps from the electrode to the workpiece and an arc is established.
horizontal position A common welding position in which the workpiece is horizontal. In GTAW, argon is typically used as a shielding gas during horizontal-position welding.
hot rolled A process that passes heated metal between two rolls in order to flatten and lengthen the metal. Hot rolling leaves a tough scale on the metal.
impact resistant Designed to resist impact. Impact-resistant tools generally do not break under normal use.
incomplete fusion A weld discontinuity in which the weld metal and base metal or adjoining weld beads are not fully fused. Incomplete fusion significantly weakens the integrity of a weld.
inert A type of gas that is inactive and is not chemically reactive. Many shielding gases are inert.
International Organization for Standardization ISO. An organization based in Switzerland that develops and publishes standards for its international membership base. The International Organization for Standardization provides classifications for tungsten electrodes.
inverter A device which is designed to convert AC outlet power to DC power. Inverters can quickly and easily switch between AC current and DC current.
inverter power sources A welding power source which uses an inverter to supply power. Inverter power sources are small, easily portable, and versatile, but expensive.
ions An electrically charged atom or molecule. Positively charged ions are used to remove oxides from aluminum or magnesium in AC GTAW.
kidskin A soft, pliable leather made from goat hide. Kidskin is often used to make GTAW-specific welding gloves.
lanthanum La. A rare-earth metal with many industrial and medical applications. Lanthanum is used to make lanthanated GTAW electrodes.
lava A naturally occurring, heat- and crack-resistant stone used to make GTAW cups. Lava is also called hydrous aluminum silicate.
lay-wire technique A GTAW filler metal addition technique in which the welder repeatedly dips the rod into the weld puddle during welding. The dipping technique can be used to manipulate the size of a weld with exceptional precision.
lift start A method of arc starting in GTAW. To lift start the arc, the tip of the electrode is touched to the workpiece to initiate a current and then lifted slightly to form the arc.
magnesium A grayish white, extremely light metal that is brittle and has poor wear resistance. Aluminum-magnesium alloys have excellent weldability.
mill scale A tough surface contaminant composed mainly of iron oxides. Mill scale must be removed before welding steel.
nonconsumable tungsten electrode An electrode made of tungsten which does not melt during welding. Nonconsumable tungsten electrodes are used in GTAW.
overhead position The welding position in which welding is performed from the underside of the joint. In GTAW, helium is often used as a shielding gas for overhead-position welding.
oxide A chemical compound containing oxygen and another element. Oxide composition determines how the metal must be prepared for welding.
oxides 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.
pacemakers Small medical devices which are implanted in the chest to control an abnormal or inconsistent heartbeat. Pacemakers can malfunction around high-frequency GTAW start systems.
personal protective equipment PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment for GTAW includes a welding helmet, gloves, safety glasses, long pants, and a long-sleeved shirt.
phosgene A deadly gas released when welding a workpiece that has been cleaned with a chlorinated solvent such as brake cleaner. Phosgene exposure can cause suffocation, heart failure, seizures, permanent brain damage, or death.
plate A flat piece of raw material from which parts are made. Thick plate often requires the addition of helium as a shielding gas in order to ensure sufficient penetration when welding with GTAW.
polarity The direction of electrical current flow. Polarity can indicate direct or alternating current flow.
porosity A discontinuity characterized by the appearance of tiny voids or bubbles on a weld bead, resulting from trapped gases in a material. Excessive porosity can weaken a weld.
post-flow Shielding gas flow which protects the hardening weld after the arc has been extinguished. Around five seconds of post-flow is considered ideal for most welds.
power sources A machine which is the source for the electrical current used for welding. GTAW power sources include transformers and inverters.
pre-flow Shielding gas flow which begins before the arc is initiated. Pre-flow is intended to shield the weld before welding actually begins.
Pyrex A borosilicate glass manufactured under license from Corning Incorporated. Pyrex is used to make translucent GTAW cups.
radioactive Any object which emits radiation. The thoriated electrodes often used in GTAW are mildly radioactive.
rectifier An electrical device that converts AC power to DC power. Rectifiers allow current to flow in one direction only.
respirator A breathing device worn to prevent inhalation of hazardous substances. Respirators may purify air from the environment or supply air to the wearer.
scratch start A method of arc starting. To scratch start the arc, the tip of the electrode is “scratched” against the workpiece like a match.
shielding gas A gas that surrounds and protects molten metal from contamination during welding. Shielding gas is used in GMAW, GTAW, and gas-shielded FCAW.
silicon nitride A form of ceramic made from silicon and nitrogen. Silicon nitride has an extremely high melting point, which makes it an ideal material for GTAW cups.
solvent A chemical used to dissolve another material. Solvents are often used to dissolve surface contaminants such as grease or oil.
spatter Liquid metal droplets expelled from the welding process. The amount of spatter that a welding process yields usually depends on the electrode and the welder's skill.
steel A metal consisting of iron and carbon, usually with small amounts of other elements. Steel is the most common metal used in manufacturing.
steel brush A brush with steel bristles. Steel brushes are used to remove mill scale from steel.
sticking When an electrode touches the workpiece during welding and becomes stuck. Sticking can contaminate both the electrode and the workpiece.
tensile strength A material's ability to resist forces that attempt to pull it apart or stretch it. Materials with high tensile strength tend to deform, bend, or stretch before breaking.
thoriated electrodes GTAW electrodes which are composed of thorium and tungsten, usually at a ration of 2% to 98%. Thoriated electrodes are slightly radioactive, and certain precautions must be taken during their use.
thorium Th. A radioactive metal sometimes used as nuclear fuel. Thorium can also be combined with tungsten to make thoriated GTAW electrodes.
transformer A device used in an electrical circuit that reduces the voltage of incoming electrical power. Transformers are often used in GTAW power supplies.
transformer power sources A welding power source which uses a transformer to supply power. Transformer power sources are comparatively inexpensive, but large and inefficient.
tungsten A hard, gray metal with a very high melting point. Tungsten is used to make nonconsumable electrodes for GTAW.
tungsten inclusion A discontinuity in which small particles of tungsten become lodged in the weld metal. Tungsten inclusion can significantly decrease the strength of a finished weld.
tungsten inert gas welding TIG welding. A very precise arc welding process that uses a nonconsumable tungsten electrode. Tungsten inert gas welding is also referred to as GTAW.
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.
ultraviolet UV. Harmful invisible light rays that can burn the eyes and skin. Ultraviolet light is produced by most arc welding processes.
voltage A measure of electrical pressure or potential known as electromotive force. Voltage is measured in volts.
walking the cup A GTAW technique in which the cup rests on the workpiece and the welder rotates the cup back and forth over the weld puddle. Walking the cup can be used to create even, visually pleasing welds.
weld puddle The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.
workpiece The part that is being welded. In GTAW, the current which creates the arc flows through the workpiece.
zirconium Zr. A gray-white metal with a strong resistance to corrosion. Zirconium is used to make zirconiated GTAW electrodes.