Introduction to GTAW 262

"Introduction to GTAW” defines gas tungsten arc welding (GTAW), describes the tools used in GTAW, and discusses the various factors that should be considered when using GTAW. GTAW, or TIG welding, is a precise welding process that uses a nonconsumable tungsten electrode and inert shielding gas. GTAW can be used on a wide variety of metals, and can be performed manually or with the use of semi-automated or totally automated systems.

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 and requires practice to master, but the improved weld quality is vital to certain applications. By the end of this class, users will be able to define GTAW, identify the tools used in GTAW, and describe the various GTAW processes and applications.

Class Details

Class Name:
Introduction to GTAW 262
Version:
2.0
Difficulty:
Intermediate
Number of Lessons:
26
Related 1.0 Classes:
What Is Arc Welding? 110, Arc Welding Processes 120, Electrical Power for Arc Welding 140, GTAW Applications 240, Arc Welding Power Sources 260

Class Outline

  • Gas Tungsten Arc Welding
  • Advantages and Disadvantages of GTAW
  • GTAW Equipment
  • Torch Operation
  • Types of Torches
  • Torch Components
  • Torch Components
  • GTAW Basics Review
  • Types of Electrodes
  • Electrode Characteristics
  • GTAW Safety
  • Electrode and Safety Review
  • Shielding Gases
  • Current
  • Amperage
  • Voltage
  • Shielding Gases and Power Review
  • Electrode Preparation: Balling
  • Electrode Preparation: Grinding
  • Balling and Grinding Tungsten Electrodes
  • Joint Preparation
  • GTAW Preparation
  • GTAW Operation
  • GTAW in Process
  • Pulsed Gas Tungsten Arc Welding
  • GTAW Preparation and Operation Review

Objectives

  • Define GTAW.
  • Contrast the advantages and disadvantages of GTAW.
  • Describe GTAW equipment.
  • Describe the proper operation of GTAW torches.
  • Describe the types of GTAW torches.
  • Identify GTAW torch components.
  • Describe the types of electrodes used in GTAW processes.
  • Describe the characteristics of GTAW electrodes.
  • Describe GTAW safety procedures.
  • Describe the different types of shielding gases used for GTAW applications.
  • Describe the types of current required for GTAW processes.
  • Describe amperage as it relates to GTAW processes.
  • Describe voltage as it relates to GTAW processes.
  • Describe how to prepare electrodes for GTAW operations using balling.
  • Describe how to prepare electrodes for GTAW operations using grinding.
  • Describe how to prepare joints for GTAW processes.
  • Describe considerations welders should make prior to welding.
  • List the steps of GTAW operation.
  • Define GTAW-P.

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. In GTAW, abrasive materials are often used to grind electrodes.
AC Alternating current. A flow of electricity that reverses direction at regularly recurring intervals of time. In the United States, AC alternates 60 times per second, or 60 hertz.
air-cooled torches A type of welding torch that uses shielding gas to cool the torch. Air-cooled torches, also known as gas-cooled torches, are often used for low-current applications.
alloying element A material deliberately added to a metal in order to enhance or change its properties. Alloying elements are different from inclusions, which are present in a metal naturally or by accident.
alternating current AC. A flow of electricity that reverses direction at regularly recurring intervals of time. In the United States, AC alternates 60 times per second, or 60 hertz.
alumina A chemical compound of aluminum and oxygen. Alumina, also known as aluminum oxide, is used to make GTAW nozzles or cups.
aluminium oxide A chemical compound of aluminum and oxygen. Aluminum oxide, also known as aluminum, is used to make GTAW nozzles or cups.
aluminum A lightweight, highly conductive, silvery metal. Aluminum is one of the most difficult metals to weld.
amperage A measurement that indicates the amount of current flowing in a circuit. Amperage is measured in 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 stability The measure of how consistent a welding arc is during the welding process. A stable arc remains focused and does not flutter or wander from the weld area.
argon A colorless, odorless, inert gas. Argon is much heavier than air.
atmospheric contamination Any element of the surrounding environment that can impact the quality and strength of a finished weld. Atmospheric contamination is usually the result of ambient gases such as oxygen or nitrogen.
automatic Welding equipment that is controlled by settings on a computer or a robot. Welders play a minimal role in automatic welding processes.
axis The imaginary line a tool revolves around. Axes are useful in determining the position of a tool and how other objects relate to that tool in space.
back cap A cap 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 level of current in a pulsed welding process. Background current provides intervals of lower heat input during GTAW-P welding.
balling An electrode preparation process in which the tip of the tungsten electrode is formed into a sphere. The balled shape is required for AC and DCEP welding.
base metals One of the two or more metals to be welded together to form a joint. The type of base metal is one factor in determining the need for filler metal during GTAW.
brittle A material's unwillingness to be drawn, stretched, or formed. Brittle metals tend to break if subjected to these forces.
burnthrough Excessive melt through or a hole in the base metal. Burnthrough can be caused by extremely high welding temperatures.
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. Arc welding requires a closed electrical circuit.
collet The torch component that holds the tungsten firmly in the torch. Collets, along with collet bodies, are part of the two-piece collet set.
collet body The component of the torch that holds the collet in place. Collet bodies, along with collets, make up the two-piece collet set.
collet set A two-piece set, usually made of copper, that secures the electrode in the torch. Standard collet sizes are made to fit each standard size tungsten electrode.
compressed gas cylinder An external device used to house shielding gas. Shielding gas flows from the gas cylinder, through the gas hose, to the welding torch.
conductivity The measure of a material’s ability to conduct heat or electric current. Conductivity allows welding electrodes to create an arc.
constant current power source A welding power source that maintains a steady current even when voltage changes. GTAW requires a constant current power source.
constant voltage power sources A power source that maintains a steady voltage while amperage changes. Some arc welding processes use a constant voltage power source.
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-carrying capacity The maximum current an electrode can carry without deteriorating. Electrodes with good current carrying capacity can have long work-lives when used properly.
cut lengths A unit of filler metal that is manually added to the weld pool by the welder. Composition of the cut lengths, also known as filler rods, will usually match that of the base metal and can add beneficial mechanical properties to the finished joint.
defects A failing, deficiency, or imperfection on a workpiece or part, or in a weld. Defects can lead to catastrophic failure of a workpiece, weld, or part.
dependent variable An aspect of a process that is affected by other changeable facets of that process. In GTAW, voltage is a dependent variable because it changes in relation to current, tip shape, arc length, as well as other aspects.
deposition rate An estimate of the melt-off rate, or the amount of filler metal deposited into a weld joint. The deposition rate is measured in pounds per hour (lb/hr) or grams per minute (g/m).
direct current DC. A current formed when electricity flows in one continuous direction. Many welding methods can use a DC current.
direct current electrode negative DCEN. Current that travels in only one direction, with straight polarity. In DCEN, or straight polarity, the electrode is the negative pole of the welding arc and the workpiece is the positive pole.
direct current electrode positive DCEP. Current that travels in only one direction, with reverse polarity. In DCEP, or reverse polarity, the electrode is the positive pole of the welding arc and the workpiece is the negative pole.
discontinuities An irregularity in a welded part that is not necessarily a defect. Discontinuities can be discovered during visual inspection.
drooping A characteristic of welding voltage where voltage varies slightly when using a constant current power source. In GTAW, drooping may occur when the welder raises or lowers the welding torch.
ductility A metal's ability to be drawn, stretched, or formed without breaking or cracking. Metals with good ductility include copper, gold, and others.
duty cycle The percentage of time that a welding torch can operate in a ten minute period at its rated output without overheating. Duty cycles are designed to maximize torch life and optimize performance.
electrical conductivity A material's ability to conduct an electrical current. Electrodes with good electrical conductivity tend to have very stable arcs.
electrode extension A measurement of the length from the tip of the GTAW electrode to the nozzle or cup. Electrode extension, also known as electrode stickout, should generally be about two to three times the diameter of the electrode.
electrode stickout A measurement of the length from the tip of the GTAW electrode to the nozzle or cup. Electrode stickout, also known as electrode extension, should generally be about two or three times the diameter of the electrode.
filler metal A type of metal that is sometimes added to a joint in welding processes. Filler metal adds to the strength and mass of the welded joint.
filler rod A unit of filler metal that is manually added to the weld pool by the welder. Composition of the filler rods, also known as cut lengths, will usually match that of the base metal and can add beneficial mechanical properties to the finished joint.
flux cored arc welding FCAW. An arc welding process that uses a continuously fed consumable electrode that contains flux at its core. FCAW systems usually require constant voltage power sources.
foot pedal A type of remote control that, when pressed by the welder, changes electrical frequency. Pushing the pedal all the way down increases amperage.
fume extraction Any system that uses suction to remove the smoke and gases generated by welding or welding equipment. Various types of fume extraction systems are used in a wide range of welding applications.
fusion The joining together of two different surfaces or materials by way of molten metal and welding. In GTAW, fusion can only be attained when the torch can be comfortably manipulated.
gas lens collet body A specially designed screen assembly that fits inside the nozzle of a GTAW torch. The gas lens collet body creates longer, smoother shielding gas flow.
gas metal arc welding GMAW. An arc welding process in which a bare wire electrode and inert or active shielding gas are fed to the weld through a welding gun. GMAW is also referred to as MIG welding.
gas regulator The device that indicates the amount of shielding gas present in the gas cylinder. Gas regulators commonly express the measurement of the amount of gas in the cylinder through pounds per square inch (psi).
gas tungsten arc welding GTAW. A precise arc welding process that uses a nonconsumable tungsten electrode. GTAW is also known as TIG welding.
gas-cooled torches A type of welding torch that uses shielding gas to cool the torch. Gas-cooled torches, also known as air-cooled torches, are often used for low-current applications.
grinding The use of an abrasive to remove minor imperfections on a material. In GTAW, grinding is used to prepare tungsten tips of an electrode for welding.
grinding wheel A rotating wheel coated with an abrasive that is used to grind objects. Grinding wheels can be used to shape and grind tungsten electrodes for GTAW.
groove angle The total angle of the groove in between the two workpieces being welded together. GTAW joints must have wide groove angles to accommodate torch manipulation.
groove face The exposed surface of the groove weld in between workpieces. In GTAW, a quality weld is made when the groove face experiences complete fusion.
GTAW Gas tungsten arc welding. A precise arc welding process that uses a nonconsumable tungsten electrode. GTAW is also known as TIG welding.
hand controls A type of remote control mounted on the welding torch that initiates or changes electrical frequency. Hand controls allow the welder freedom to move.
heat input The amount of energy transferred to the workpiece. Lower heat inputs can limit the formation of the heat-affected zone.
helium A light, colorless, inert gas. Helium is much lighter than air.
high-frequency start HF start. A method of arc starting that involves holding the electrode close to the workpiece and depressing a button or foot pedal to start a high-frequency current. In HF starts, the current leaps from the electrode to the workpiece and an arc is established.
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 high-frequency start methods, the electrode does not touch the workpiece.
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 defects in the weld which results from stress in thin materials or materials with low tensile strength during solidification. Aluminum and aluminum alloys often experience hot cracking.
hydrogen A gas that is the lightest and most abundant element in the universe. Too much hydrogen near the weld metal can cause cracking.
inert A type of gas that is not chemically reactive. GTAW requires inert shielding gases.
inverter power sources A welding power source that uses an inverter to supply power. Inverter power sources are small, easily portable, and versatile but expensive.
ionization The process of a substance becoming positively or negatively charged. Ionization occurs when the substance either gains or loses electrons.
ions An atom with an extra or missing electron or electrons. Ions can be either positively or negatively charged.
joint preparation A variety of processes that prepare base metals before welding. This often includes preheating, cutting, or other preparations.
joint type The specification of how two base metals should be connected. 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 used to make lanthanted GTAW electrodes.
lift start method An arc starting method in which the tungsten electrode contacts the workpiece to create a short circuit and an arc. The touch start method is not used for some applications because it may cause electrode contamination.
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 alloy. Magnesium combines 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.
nitrogen A colorless, odorless, tasteless gas that naturally exists in the atmosphere. Nitrogen can ruin a weld bead.
nonconsumable tungsten electrode An electrode made of tungsten that is not melted by the heat generated by welding. The nonconsumable tungsten electrode does not become part of the weld puddle.
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 classified or categorized position by a welder. 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 aren’t 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 the metals.
pacemakers Small medical devices that are implanted in the chest to control an abnormal or inconsistent heartbeat. GTAW high-frequency start systems can interfere with pacemakers.
peak current A surge of current that lasts for a brief time. Peak current is used in GTAW-P.
perpendicular Two lines or axes that meet at right angles. When grinding GTAW electrodes, the electrode should be in a perpendicular position to the axis of the grinding wheel.
personal protective equipment PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment for GTAW processes may include respirators, welding masks, gloves, and leather clothing.
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.
porous An object that has many openings or voids. Porous welds have reduced strength and reliability.
power cable A cord that acts as the conduit for electrical power from the power source to the torch. Power cables are separate from the lines that feed gas and water to the torch, though the water in water-cooled torches drains through a line in the power cable.
power sources A device that generates electricity. Arc welding power sources can be plugged into a wall outlet, or they can generate electricity through the use of a mechanical device like a motor or generator.
pulsed gas tungsten arc welding GTAW-P. A very precise arc welding process that uses a nonconsumable tungsten electrode and alternates rapidly between using pulse current and background current. GTAW-P is also known as TIG pulse welding.
recirculating pump A device that moves fluids through a closed circuit using mechanical action. Recirculating pumps can be used to help cool gas-cooled GTAW torches.
remote control A device used to control welding current during a welding process. GTAW uses hand controls and foot controls as remote controls for current.
respiratory Any object or processes relating to the organs involved in the breathing of air. Respiratory organs include the nose, esophagus, and lungs.
reverse polarity Current that travels in only one direction, with reverse polarity. In reverse polarity, or DCEP, the electrode is the positive pole of the welding arc and the workpiece is the negative pole.
scratch start method A method of arc starting. For the scratch start method, welders 'scratch' the tip of the electrode against the workpiece as though lighting a match.
semi-automatic Manufacturing processes that are partially controlled by computerized or robotic systems. In GTAW, processes like wire speed feed can be automated while a welder operates the welding torch.
sheet metal A metal under 1/4 in. (6.35 mm) thick. In GTAW processes, welding sheet metal generally requires one amp of welding power for every 0.001 in. (0.025 mm).
shielded metal arc welding SMAW. An arc welding process that uses a flux-coated consumable rod electrode. SMAW is also referred to as stick welding
shielding gas Gas that protects the weld pool and arc from reacting with the atmosphere. GTAW shielding gas is supplied by a cylinder and flows through the welding torch.
shielding gas flow meter The device that controls the amount of shielding gas that flows to the weld area. Proper use of the shielding gas flow meter can help improve weld quality by preventing atmospheric contamination in the weld pool.
slag Cooled flux that forms on top of the weld bead. Slag protects 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 is a safety risk that can cause burns or fire.
spatter Liquid metal droplets expelled from the welding process. Spatter is a safety risk that can cause burns or fires.
standard cubic feet per hour SCFH. A measurement of gas flow that indicates how many cubic feet of gas pass by a stationary point in one hour under standard conditions of temperature, pressure, and humidity. Standard cubic feet per hour is the measurement used to set flow rate for GTAW processes.
standard cubic meters per hour SCMH. A measurement of gas flow that indicates how many cubic meters of gas pass by a stationary point in one hour under standard conditions of temperature, pressure, and humidity. Standard cubic meters per hour are used to measure the gas flow rate in GTAW processes.
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.
straight polarity Current that travels in only one direction, with straight polarity. In straight polarity, or DCEN, the electrode is the negative pole of the welding arc and the workpiece is the positive pole.
taper A gradual decrease in the width of an object. In GTAW, tungsten electrodes must be sharpened into a long taper with a point.
thoriated tungsten electrodes A type of tungsten electrode that contains thorium. Thoriated tungsten electrodes have high conductivity.
thorium A radioactive metal sometimes used as nuclear fuel. Thorium can also be combined with tungsten to make thoriated GTAW electrodes.
TIG welding Tungsten inert gas welding. A precise arc welding process that uses a nonconsumable tungsten electrode. TIG welding is also known as GTAW.
tip shape The shape of the tip of the electrode. For GTAW, the tip shape must be either balled or ground to work properly.
torch body The part of the torch held by the welder. Torch bodies are also called handles.
torch cap A cap 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.
transformers A device used in an electrical circuit that reduces the voltage of incoming electrical power. Transformers are often used in GTAW power supplies.
travel speed The speed at which the welder moves the electrode along the joint to make a weld. Travel speed is one of the factors that determines the heat in 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 nonconsumable electrodes.
tungsten inert gas welding TIG welding. A precise arc welding process that uses a nonconsumable tungsten electrode. TIG welding is also known as GTAW.
ultraviolet UV. Harmful invisible light rays that can burn the eyes and skin. The electric arc in welding procedures produces ultraviolet light.
ventilation A means of providing fresh air. For the safety of the welder, welding requires proper ventilation.
voltage A measure of electrical pressure or potential. In GTAW, voltage is a dependent variable and is affected by other variables such as current, tip shape, arc length, and the type of shielding gas.
voltage A measure of electrical pressure or potential. Voltage is measured in volts.
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.
weld bead The end product of a joint that has been welded. Beads are formed using a variety of different techniques.
weld pool The pool of molten metal that is created by the heat of a welding torch. Weld pools may contain base and filler metals.
welders A person who operates welding equipment. Welders using GTAW processes must be especially skilled.
welding procedure specifications WPS. A written document that contains all the necessary and specific information regarding the applications of a welding project. Welding procedure specifications must be approved and tested before welding can begin.
welding torch The device that holds the electrode. The welding torch delivers shielding gas to the weld area and insulates the welder from the welding current.
wet The measure of how well a liquid spreads over a surface. Molten metals that wet joints easily create smooth welds.
wire brushes A hand tool with an abrasive wire filament. Wire brushes can be used to clean a workpiece prior to welding or as a finishing tool to clean a machined part.
work lead A cable that is connected to the workpiece by a clamp and provides a return path for the electricity that flows from a welding torch. Work leads are essential for closing the circuit of an arc welding system.
workpiece A part undergoing some type of manufacturing process. Workpiece can refer to material that is being welded, cut, or machined, among other processes.
zirconium A gray-white metal with a strong resistance to corrosion. Zirconium is used to make zirconiated GTAW electrodes.