Introduction to GTAW 262

"Introduction to GTAW” describes gas tungsten arc welding (GTAW), the tools and equipment it uses, and various factors that should be considered when using it. GTAW is a precise welding process that uses a non-consumable tungsten electrode and inert shielding gas. GTAW can be used on a wide variety of metals and can be performed manually, semi-automatically, or automatically.

GTAW gives the welder increased control over the weld, which allows for the fabrication of stronger and higher quality welds. The process can be complex, but the improved weld quality is vital for certain applications. After taking this class, users will be familiar with GTAW and be prepared to learn the more detailed, technical aspects of this process.

Class Details

Class Name:
Introduction to GTAW 262
Difficulty:
Intermediate
Number of Lessons:
23

Class Outline

  • Gas Tungsten Arc Welding
  • Advantages and Disadvantages of GTAW
  • GTAW Equipment
  • Shielding Gases
  • Current and Polarity
  • Amperage
  • Voltage
  • GTAW Gases and Electricity Review
  • GTAW Torches
  • Torch Components
  • Types of Torches
  • GTAW Electrodes
  • Types of Electrodes
  • GTAW Torch and Electrode Review
  • Electrode Preparation: Grinding
  • Electrode Preparation: Balling
  • Grinding and Balling Electrodes
  • Joint Considerations
  • Joint Preparation
  • GTAW Operation
  • Pulsed Gas Tungsten Arc Welding
  • GTAW Safety
  • GTAW Preparation and Operation Review

Objectives

  • Describe GTAW.
  • Contrast the advantages and disadvantages of GTAW.
  • Describe GTAW equipment.
  • Describe the different types of shielding gases used for GTAW.
  • Describe the different types of current used for GTAW.
  • Describe amperage as it relates to GTAW.
  • Describe voltage as it relates to GTAW.
  • Describe GTAW torch operation.
  • Identify GTAW torch components.
  • Distinguish between the different types of GTAW torches.
  • Describe the characteristics of GTAW electrodes.
  • Identify different types of GTAW electrodes.
  • Describe the grinding method of preparation for GTAW electrodes.
  • Describe the balling method of preparation for GTAW electrodes.
  • Describe the grinding method of preparation for GTAW electrodes. Describe the balling method of preparation for GTAW electrodes.
  • Describe important considerations for designing GTAW joints.
  • Describe how to prepare joints for GTAW.
  • Describe GTAW operation.
  • Describe GTAW-P.
  • Describe GTAW safety precautions.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
abrasive A material or tool consisting of hard particles used to wear down, rub away, or machine material. Abrasive materials are often used to grind GTAW electrodes.
AC Alternating current. Current that reverses direction at regularly recurring intervals of time. In the United States, AC reverses 60 times per second, or 60 hertz.
air-cooled torch A type of welding torch that uses gas to cool the torch. Air-cooled torches, also known as gas-cooled torches, are often used for low-current applications.
alloying elements A material deliberately added to a metal in order to enhance or change its properties. Alloying elements can improve the strength, ductility, hardness, and toughness of a finished weld.
alloys A metal consisting of a mixture of two or more elements, one of which must be a metal. Alloys combine the beneficial properties of the mixed elements.
alternating current AC. Current that reverses direction at regularly recurring intervals of time. In the United States, alternating current reverses 60 times per second, or 60 hertz.
alumina A chemical compound made of aluminum and oxygen. Alumina, also known as aluminum oxide, is used to make GTAW torch cups.
aluminum A lightweight, highly conductive, silvery metal. Aluminum is one of the most difficult metals to weld.
aluminum oxide A chemical compound made of aluminum and oxygen. Aluminum oxide, also known as alumina, is used to make GTAW torch cups.
amperage The amount of current flowing in a circuit. Amperage is measured in amperes (A), or amps.
amps A. 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 arc generates heat that melts the base metals and filler metal during welding.
arc stability A measure of a welding arc's consistency and predictability. Arc stability is essential during the welding process.
argon A heavy inert gas commonly used as a shielding gas for arc welding. Argon is much heavier than air, so it effectively shields the weld area.
atmospheric contaminants Any element of the surrounding environment that can impact the quality and strength of a finished weld. Atmospheric contaminants are usually ambient gases such as oxygen and nitrogen.
automatic A type of welding process in which a computer or a robot controls both the welding equipment and the weld variables. In automatic welding, the welder is responsible for setting and controlling the specialized settings for the computer or robot.
back cap A component on the back of the torch body that tightens to allow the collet to grip the electrode. Back caps, also known as torch caps, are designed to match standard tungsten electrode lengths.
background current The lower amperage setting used as the baseline current level for pulsed welding processes. Background current provides intervals of lower heat input during GTAW-P.
balling An electrode preparation process in which the tip of the tungsten electrode is formed into a sphere. Balling is required for AC welding with transformer power sources.
base metals Metals that are welded together to form a joint. The base metal and its properties influence the type of welding and the type of electrode that should be used.
brittle A material's unwillingness to be drawn, stretched, or formed. Brittle metals tend to break if subjected to these forces.
burnthrough A discontinuity in which weld metal from one side of a joint melts through to the other. Burnthrough can leave an open hole in the joint, which must then be ground down and re-welded.
CC Constant current. A power supply that maintains a flow of current that varies only slightly with changes in voltage. CC power sources are used in gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW).
cerium A soft, ductile metal that oxidizes easily. Cerium is often combined with tungsten to make ceriated GTAW electrodes.
circuit A controlled path for electricity. All arc welding processes require a closed electrical circuit that includes a source, path, load, and control.
collet The component of the torch that holds the electrode. The collet and the collet body make up the two-piece collet set.
collet body The component of the torch that holds the collet in place. The collet body and the collet make up the two-piece collet set.
collet set A set of two components used to secure the electrode in the torch. The collet set consists of the collet and the collet body, which are usually made of copper.
constant current CC. A power supply that maintains a flow of current that varies only slightly with changes in voltage. Constant current power sources are used in gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW).
coolant A substance, usually liquid, used to reduce or maintain the temperature of a component during a manufacturing process. Coolants are used to keep some GTAW torches from overheating.
copper A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper is often used in electrical components.
cup A device attached to the front of the torch body that directs shielding gas over the weld area. GTAW cups are also known as nozzles.
current The flow of electricity through a circuit. Current is measured in amperes (A), or amps, and controls the heat of the arc.
current-carrying capacity The maximum current an electrode can carry without deteriorating. Electrodes with good current-carrying capacity can have long service lives when used properly.
cut lengths A unit of filler metal that is manually added to the weld puddle by the welder. Cut lengths, also known as filler rods, usually match the composition of the base metal and can add beneficial mechanical properties to the finished joint.
DC Direct current. Current that flows in one continuous direction. DC is required for several common welding processes.
defects An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A defect is an unacceptable discontinuity.
deposition rate The rate at which an electrode melts into the molten weld puddle to form a weld. Deposition rate is measured in pounds per hour (lb/hr) or grams per minute (g/m).
direct current DC. Current that flows in one continuous direction. Direct current is required for several common welding processes.
direct current electrode negative DCEN. Current that always flows in one continuous direction from the negative electrode to the positive workpiece. Direct current electrode negative polarity is also known as straight polarity, but this is a nonstandard term.
direct current electrode positive DCEP. Current that always flows in one continuous direction from the negative workpiece to the positive electrode. Direct current electrode positive polarity is also known as reverse polarity, but this is a nonstandard term.
discontinuities An irregularity in the specified and expected composition of a weld. A discontinuity is not always a defect.
drooping The slight variation of welding voltage that occurs when using a constant current power source. In GTAW, drooping may occur when the welder raises or lowers the welding torch.
duty cycle The amount of time in a ten-minute period that an electrical device can perform at the rated output before it must rest to prevent overheating. Duty cycle ratings are given as a percentage of the ten-minute period.
electric shock The flow of electricity through the body. Electric shock can be fatal.
electrical conductivity A material's ability to conduct an electrical current. Electrical conductivity allows welding electrodes to create an arc, and electrodes with higher conductivity tend to have very stable arcs.
electrode cable The path used in arc welding to conduct electricity from the power source to the electrode. The electrode cable connects the power source to the welding torch.
electrode extension The distance from the tip of the GTAW electrode to the torch cup. Electrode extension should generally be about two to three times the diameter of the electrode.
electrode negative EN. The stage of the alternating current cycle during which electricity flows from the negative electrode to the positive workpiece. The electrode negative stage concentrates heat in the workpiece and improves penetration.
electrode positive EP. The stage of the alternating current cycle during which electricity flows from the negative workpiece to the positive electrode. The electrode positive stage improves fusion and provides a cleaning effect.
electrons A negatively charged particle that orbits the nucleus of an atom. The flow of electrons causes the flow of electricity.
filler metal Metal deposited into the weld that often adds strength and mass to the welded joint. Filler metal for GTAW comes from filler rods, not the electrode.
filler rods A unit of filler metal that is manually added to the weld puddle by the welder. Filler rods, also known as cut lengths, usually match the composition of the base metal and can add beneficial mechanical properties to the finished joint.
flowmeter The device that indicates and controls the volume of shielding gas that flows to the welding torch. The flowmeter consists of a flow gauge that measures the volume and an adjustment valve that controls the volume.
foot pedal A type of remote control that a welder raises or lowers to change electrical current during welding. Pushing the foot pedal all the way down increases amperage.
fume extractor Any device that uses suction to remove gases from the environment. Fume extractors are also called hoods.
gas cylinder An external device used to house shielding gas. Shielding gas flows from the gas cylinder through the gas hose and then to the welding torch.
gas lens collet body A specially designed screen assembly that fits inside the cup of a GTAW torch. The gas lens collet body creates a longer, smoother shielding gas flow.
gas tungsten arc welding GTAW. A precise arc welding process that uses a non-consumable tungsten electrode and inert shielding gas. Gas tungsten arc welding is also known as tungsten inert gas welding (TIG welding).
gas-cooled torch A type of welding torch that uses gas to cool the torch. Gas-cooled torches, also known as air-cooled torches, are often used for low-current applications.
grinding Shaping or otherwise wearing away material using an abrasive. Grinding is used to prepare GTAW electrodes.
grinding wheel A rotating wheel coated with an abrasive material that is used to grind objects. Grinding wheels can be used to shape and grind tungsten electrodes for GTAW.
groove angle The angle of the groove between two workpieces being welded together. Groove angles for GTAW joints must be wide enough to accommodate torch manipulation.
groove face The exposed surface of the groove between two workpieces. The groove face must experience complete fusion to create a quality GTAW weld.
GTAW Gas tungsten arc welding. A precise arc welding process that uses a non-consumable tungsten electrode and inert shielding gas. GTAW is also known as tungsten inert gas welding (TIG welding).
hand controls A type of remote control mounted on the welding torch that a welder uses to change electrical current during welding. Hand controls allow the welder freedom to move, unlike foot pedals.
heat input The amount of thermal energy transferred to the workpiece during welding. Heat input is measured in kilojoules per inch (kJ/in.) or kilojoules per millimeter (kJ/mm).
helium A lightweight inert gas sometimes used as a shielding gas for arc welding. Helium is much lighter than air.
hemispherical Having a three-dimensional half-circular shape. Hemispherical or spherical balls of molten metal form on the tip of tungsten electrodes during balling electrode preparation processes.
HF start High-frequency start. An arc starting method that uses a high voltage to generate a spark between the electrode and the workpiece to establish an arc. For the HF start method, the welder holds the electrode near the workpiece and uses a control device to start a high-frequency current that provides the spark.
high-frequency start HF start. An arc starting method that uses a high voltage to generate a spark between the electrode and the workpiece to establish an arc. For the high-frequency start method, the welder holds the electrode near the workpiece and uses a control device to start a high-frequency current that provides the spark.
high-nickel alloys A metal that contains a high percentage of nickel. High-nickel alloys are often used for their strength at high temperatures.
hot cracking The formation of fractures in a weld due to stress placed on thin materials or materials with low tensile strength during solidification. Aluminum and aluminum alloys often experience hot cracking.
hydrogen A colorless, odorless gas that is the most abundant element on the planet. Hydrogen exposure can cause weld metal to crack.
inert A substance that is not chemically reactive. GTAW requires inert shielding gases.
inverter power sources A welding machine that contains an inverter and operates with variable frequencies and amplitudes. Inverter power sources are energy efficient.
ionization The process of a substance becoming positively or negatively charged. Ionization occurs when the substance either gains or loses electrons.
ions A charged atom or molecule. An ion can be either positive or negative depending on whether it has a shortage or surplus of electrons.
joint preparation A variety of processes that prepare base metals before welding. Joint preparation often includes preheating, cleaning, machining, or other operations.
joint type The configuration in which two or more workpieces are joined. There are five basic joint types: butt, corner, edge, lap, and T-joint.
lanthanum A rare-earth metal with many industrial and medical applications. Lanthanum is combined with tungsten to make lanthanated GTAW electrodes.
liquid-cooled torch A type of welding torch that uses coolant to cool the torch and power cable. Liquid-cooled torches, also known as water-cooled torches, are often used for high-current applications.
machining The process of removing material to form an object. Machining is used in GTAW to remove any possible surface defects from the base metals prior to welding.
magnesium A grayish-white, extremely light metal that is brittle and has poor wear resistance. Magnesium can be combined with aluminum to create an alloy with excellent weldability.
mill scale A tough surface contaminant composed mainly of iron oxides. Mill scale must be removed from a metal before it can be welded.
multi-oxide electrodes Tungsten electrodes that contain small percentages of multiple different alloying elements. Multi-oxide electrodes perform similarly to thoriated electrodes but have the advantage of being non-radioactive.
nitrogen A colorless, odorless, tasteless gas that naturally makes up 78% of breathable air. Nitrogen can ruin a weld bead.
non-consumable electrode An electrode that only conducts electricity to the arc and does not melt from the heat of the arc generated during welding. GTAW uses a non-consumable tungsten electrode.
nozzle A device attached to the front of the torch body that directs shielding gas over the weld area. GTAW nozzles are also known as cups.
out-of-position welds Welds that are not made in a flat position. Out-of-position welds are often done with electrodes that have smaller diameters to prevent spillage.
oxide A chemical compound containing oxygen and one other element. Oxides can cause weld defects if they are not removed from a workpiece.
oxygen A colorless, odorless, tasteless gas that naturally exists in the atmosphere. In welding, too much oxygen causes cracking and rusting in metals.
pacemakers A small medical device that is implanted in the chest to control an abnormal or inconsistent heartbeat. High-frequency start systems can interfere with pacemakers.
parallel Extending in the same direction and equally distant from one another at all points. Parallel lines or objects never intersect.
peak current The higher amperage setting used in short intervals for pulsed welding processes. Peak current increases heat input to facilitate fusion in GTAW-P.
penetration The depth to which the arc heat melts the joint below the surface of the base metals. Penetration is directly affected by the amount of amperage.
personal protective equipment PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment for welding usually includes a welding helmet, jacket, safety glasses, and gloves.
porosity A weld 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.
porous Having many openings or voids. Porous welds have reduced strength and reliability.
power cable A conductor that acts as the path for electrical power to travel from the power source to the torch. Power cables are separate from the lines that feed gas and coolant to the torch, though the coolant in liquid-cooled torches drains through a line in the power cable.
power source The device that provides the electricity needed to perform arc welding. Power sources can be plugged into wall outlets or use mechanical devices such as motors or generators to produce electricity.
pressure gauge The device that indicates the amount of shielding gas present in the gas cylinder. The pressure gauge detects the level of gas pressure and displays it on a dial.
pulsed gas tungsten arc welding GTAW-P. A variation of gas tungsten arc welding (GTAW) that alternates rapidly between two different current levels. Pulsed gas tungsten arc welding uses a higher peak current and a lower background current.
radioactive Emitting radiation. The thoriated electrodes often used in GTAW are mildly radioactive.
recirculating pump A device that moves fluids through a closed system using mechanical action. Recirculating pumps can be used to help cool liquid-cooled GTAW torches.
remote control A device used to control welding current during a welding process. Remote controls used during GTAW include hand controls and foot pedals.
respiratory Relating to the organs involved in the breathing of air. Respiratory organs include the nose, esophagus, and lungs.
scratch start An arc starting method that involves scratching the tip of the electrode against the workpiece. The scratch start method is a high-voltage starting method.
semi-automatic A type of welding process that is partially controlled by computerized or robotic systems. In semi-automatic GTAW, settings can be automated while a welder operates the welding torch.
shielding gas A gas that protects the weld puddle and arc from reacting with the atmosphere. GTAW shielding gas is supplied by a cylinder and flows through the welding torch.
slag Cooled flux that forms on top of the weld bead. Slag protects the cooling metal and is then chipped off.
solvents A chemical substance used to dissolve another material. Solvents can be used to clean base metals and joints prior to welding.
spatter Liquid metal droplets expelled from the welding process. Spatter can leave undesirable particles of metal on a workpiece surface.
stainless steels A type of steel that contains more than 15% chromium and exhibits excellent corrosion resistance. Stainless steel can be welded using many methods.
steel A metal consisting of iron and carbon, usually with small amounts of purposefully added alloys such as manganese, phosphorous, sulfur, or silicon. Steel is often used as a test metal on which to start the arc when balling an electrode tip.
taper A gradual decrease in the width of an object. In GTAW, tungsten electrodes must be sharpened into a long taper with a point.
thermal conductivity A material's ability to conduct heat. Thermal conductivity depends on the material's structure and temperature.
thorium A mildly radioactive metal sometimes used as nuclear fuel. Thorium can also be combined with tungsten to make thoriated GTAW electrodes.
torch body The main part of a welding torch that is held by the welder. The torch body is a plastic component to which the other parts of the torch attach.
torch cap A component on the back of the torch body that tightens to allow the collet to grip the electrode. Torch caps, also known as back caps, are designed to match standard tungsten electrode lengths.
touch start An arc starting method that involves touching the tip of the electrode to the workpiece to create a short circuit and then lifting the electrode slightly to form the arc. The touch start method is a low-voltage starting method and is not recommended for some applications because it may cause contamination.
transformer power sources A welding machine that uses a transformer to supply electricity. Transformer power sources are relatively inexpensive, but large and inefficient.
transformers A device used in an electrical circuit that reduces the voltage of incoming electrical power. Transformers are often used in welding power sources.
travel speed The speed at which the welder moves the electrode along the seam to make a weld. Travel speed is one of the factors that determines the heat of the arc.
tungsten A dense, brittle, gray metal that has excellent conductivity and the highest melting point of all pure metals. Tungsten is used to make non-consumable electrodes for GTAW.
tungsten inert gas welding TIG welding. A precise arc welding process that uses a non-consumable tungsten electrode and inert shielding gas. Tungsten inert gas welding is properly known as gas tungsten arc welding (GTAW).
ultraviolet UV. Harmful invisible light rays that can burn the eyes and skin. Ultraviolet light is produced by the electric arc used for welding.
ventilation A means of providing fresh air. Welding requires proper ventilation for the safety of the welder.
voltage The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).
water-cooled torch A type of welding torch that uses coolant to cool the torch and power cable. Water-cooled torches, also known as liquid-cooled torches, are often used for high-current applications.
weld bead The end product of a joint that has been welded. Weld beads are formed using a variety of different techniques.
weld puddle The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.
welding procedure specifications WPS. A written document that contains all the necessary and specific information for a welding project. Welding procedure specifications must be approved and tested before welding can begin.
welding torch The instrument used to hold an electrode and conduct electricity to the arc during welding. The welding torch may also deliver shielding gas to the weld area.
wet The process of a liquid filler metal spreading over a solid surface. Molten metals that wet easily create smooth welds.
wire brushes A hand tool with an abrasive wire filament. Wire brushes can be used to clean the surfaces of base metals prior to welding.
work cable The path used in arc welding to conduct electricity from the power source to the workpiece. The work cable attaches to the workpiece via the work clamp.
work clamp A component that connects the work cable to the workpiece. The work clamp provides ground for the welding circuit.
workpiece A part undergoing some type of manufacturing process. The workpiece may be subject to cutting, welding, forming, or other operations.
zirconium A gray-white metal with a strong resistance to corrosion. Zirconium is combined with tungsten to make zirconiated GTAW electrodes.