GTAW Applications 331
This class provides a comprehensive overview of gas tungsten arc welding (GTAW) parameters and techniques. To successfully perform GTAW, an appropriate polarity, power source, electrode type, shielding gas, and filler metal must be used. Welders must also use the right starting method for the application and choose specific welding techniques to meet the requirements of the application. Common GTAW welding techniques include walking the cup, dipping, and lay-wire.
GTAW is used for many welding applications because it can create strong, visually appealing welds on a variety of materials. After taking this class, users will be familiar with the various factors to consider when performing GTAW. This knowledge will prepare them to successfully create quality GTAW welds.
Number of Lessons 23
- GTAW Overview
- GTAW Applications
- Base Metal Preparation
- Electrical Parameters
- AC Cleaning and Penetration
- GTAW Power Sources
- GTAW Processes and Electrical Parameters Review
- Electrode Selection
- Electrode Classification
- Electrode Preparation
- Electrode Extension and Arc Length
- Shielding Gas
- Gas Flow Rate
- Filler Metal Selection
- Cup Selection
- GTAW Equipment and Consumables Review
- Scratch and Touch Starting
- High-Frequency Starting
- Walking the Cup
- Adding Filler Metal
- Common Mistakes in GTAW
- PPE for GTAW
- Final Review
- Describe GTAW.
- Describe common uses for GTAW.
- Describe how to prepare metals for GTAW.
- Explain how electrical parameters affect GTAW.
- Describe the effects of AC half cycles on GTAW.
- Distinguish between transformer and inverter GTAW power sources.
- Distinguish between different GTAW electrodes.
- Describe AWS classification for tungsten electrodes.
- Distinguish between different GTAW electrode preparation techniques and their applications.
- Describe electrode extension. Describe arc length.
- Describe shielding gases used for GTAW.
- Explain how gas flow affects GTAW.
- Describe filler metal for GTAW.
- Distinguish between different GTAW cups and their applications.
- Describe scratch starting for GTAW. Describe touch starting for GTAW.
- Describe high-frequency starting for GTAW.
- Describe the walking-the-cup technique.
- Distinguish between the dipping and lay-wire techniques.
- Describe common mistakes in GTAW.
- Describe personal protective equipment for GTAW.
The standard three-pronged residential electrical outlet. 115-volt outlets can support inverter power sources for GTAW processes using up to 100 amps.
A residential electrical outlet used to power large appliances and machines. Transformer power sources for GTAW processes require 220-volt outlets.
Alternating current. Electricity that reverses direction at regularly recurring intervals of time. In the United States, AC reverses 60 times per second, or 60 hertz (Hz).
A setting that allows a welder to adjust how long the two half cycles of an alternating current waveform last. AC balance enables welders to increase the electrode positive (EP) half cycle to provide cleaning or to increase the electrode negative (EN) half cycle to improve penetration.
A solvent that can be used to clean certain types of contaminants from a surface. Acetone is extremely effective but also highly flammable.
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.
AC. Electricity that reverses direction at regularly recurring intervals of time. In the United States, alternating current reverses 60 times per second, or 60 hertz (Hz).
A ceramic compound made of aluminum and oxygen. Alumina, also known as aluminum oxide, is the most common material used to make GTAW cups.
A nonferrous, silvery-white metal that is soft and light and has a high strength-to-weight ratio. Aluminum is one of the most difficult metals to weld.
A ceramic compound made of aluminum and oxygen. Aluminum oxide, also known as alumina, is the most common material used to make GTAW cups.
American Welding Society
AWS. The non-profit organization that regulates industrial standards for welding. The American Welding Society also promotes the welding industry in the United States.
The amount of current flowing in a circuit. Amperage is measured in amperes (A), or amps.
A. A unit of measurement that indicates the amount of current flowing in a circuit. Amperes are also called amps.
A. A unit of measurement that indicates the amount of current flowing in a circuit. Amps is another name for amperes.
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.
The distance that electricity travels from the tip of the electrode to the weld puddle. Arc length is generally kept as short as possible in GTAW.
A heavy inert gas commonly used as a shielding gas for arc welding processes. Argon is much heavier than air, so it effectively shields the weld area.
Welding that does not use filler metal and simply melts the base metals at the joint. Autogenous welding, also known as fusion welding, often creates weld joints that are stronger than the base metals.
American Welding Society. The non-profit organization that regulates industrial standards for welding. The AWS also promotes the welding industry in the United States.
A component on the back of the torch body that tightens to allow the collet to grip the electrode. The length of the back cap and the capacity of the torch determine the length of the tungsten electrode.
Having a round, spherical or hemispherical shape. Balled GTAW electrode tips are used for AC welding with transformer power sources.
An electrode preparation process in which the tip of a tungsten electrode is formed into a small sphere. Balling is typically done by setting the welding power source to DCEP and using the current to melt the tip of the electrode.
An aerosol chemical containing tetrachloroethylene that is typically used to clean automotive brakes. Brake cleaner must never be used to clean welding workpieces because it can create deadly gases such as phosgene.
Unwilling to be drawn, stretched, or formed. Brittle metals tend to break if subjected to these forces.
The final pass of a multi-pass weld. The cap pass covers the entire joint with a layer of weld metal and determines the appearance of the finished weld.
A common metal that is an alloy of iron and carbon. The amount of carbon in a carbon steel affects its strength, ductility, and malleability.
Capable of destroying organic or inorganic materials by chemical action. Caustic solutions made of soda or nitric acid may be used to remove surface oxide layers.
A tungsten electrode that contains a small percentage of cerium. Ceriated electrodes are usually 2% cerium and 98% tungsten.
A soft, ductile metal that oxidizes easily. Cerium is often combined with tungsten to make ceriated GTAW electrodes.
A solvent that contains chlorine. Chlorinated solvents cannot be used to clean welding workpieces because they can create deadly gases such as phosgene.
A material that allows electricity to flow. Conductors are typically metals.
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).
Any element or substance not original to a weld that may impact the quality and strength of a finished weld. Contaminants in welds include oxygen and nitrogen.
A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper is often welded using GTAW.
The ability of a material to resist deterioration and chemical breakdown due to surface exposure in a particular environment. Corrosion resistance is an important physical property of finished welds.
A thick, durable leather made from the skin of a cow. Cowhide is often used to make gloves for welding.
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.
The flow of electricity through a circuit. The amount of current in a circuit is known as amperage and is measured in amperes (A), or amps.
The maximum amperage an electrode can carry without deteriorating. Electrodes with good current-carrying capacity can have long service lives when used properly.
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.
Direct current. Current that flows in one continuous direction. DC can be used for most welding methods.
Direct current electrode negative. Current that always flows in one continuous direction from the negative electrode to the positive workpiece. DCEN polarity is used for GTAW on steel and copper.
Direct current electrode positive. Current that always flows in one continuous direction from the negative workpiece to the positive electrode. DCEP polarity is not commonly used in GTAW.
A soft, pliable leather made from the hide of a deer. Deerskin is often used to make GTAW-specific welding gloves.
An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A defect is an unacceptable discontinuity.
A material that removes oxygen from the molten weld puddle and arc. Deoxidizers prevent oxygen from ruining a weld bead.
An abrasive wheel covered with tiny particles of diamond. Diamond wheels are ideal for cutting tungsten electrodes.
Spreads evenly spread from an area of high concentration to an area of low concentration. A gas lens is often used to diffuse shielding gas during GTAW.
A GTAW filler metal addition technique in which the welder repeatedly dips the end of the filler rod into the weld puddle. The dipping technique is typically used when running stringer beads to better control heat input.
DC. Current that flows in one continuous direction. Direct current can be used for most welding methods.
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 used for GTAW on steel and copper.
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 not commonly used in GTAW.
An irregularity in the specified and expected composition of a weld. A discontinuity that exceeds the part design's tolerance is a defect.
The distance from the tip of the electrode to the end of the torch cup. Electrode extension should generally be less than or equal to three times the electrode diameter.
EN. The portion of the alternating current cycle during which electricity flows from the negative electrode to the positive workpiece. The electrode negative half cycle concentrates heat in the workpiece and improves penetration.
EP. The portion of the alternating current cycle during which electricity flows from the negative workpiece to the positive electrode. The electrode positive half cycle improves fusion and provides a cleaning effect.
EMF. The area in and around an energized conductor that exhibits electric and magnetic properties. Electromagnetic fields produce forces that can interfere with electronic devices, including pacemakers.
A negatively charged particle that orbits the nucleus of an atom. The flow of electrons causes the flow of electricity.
The diameter of the opening of a GTAW cup through which shielding gas flows. Cups are available in a range of exit diameters for different application requirements.
Welding that occurs on a jobsite and not in a welding facility. Field welding typically occurs outdoors.
Any pass of a multi-pass weld that occurs after the root pass and before the cap pass. Fill passes build up the amount of filler metal in the joint and increase penetration.
Metal deposited into the weld to add strength and mass to the welded joint. Filler metal for GTAW comes from filler rods, not the electrode.
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.
Made of materials that are designed to resist burning and withstand heat. Flame-resistant materials are essential to welding safety.
The amount of shielding gas that is delivered in a specific amount of time. Flow rate is usually measured in standard cubic feet per hour (SCFH) or liters per minute (l/min).
A type of remote control that a welder raises or lowers to initiate or adjust electrical current during welding. Foot pedals are often used with the touch and high-frequency start methods but not with scratch starting.
Welding without walking the cup or using another method to brace the welding torch. In freehand welding, the quality and appearance of the finished weld are directly determined by the skill of the welder since the welder's hand is the only thing holding the torch steady.
The number of complete AC cycles that occur in one second. Frequency is measured in hertz (Hz).
Any device that uses suction to remove gases and particulate matter from the environment. A fume extractor should always be used during welding.
A cloud-like area above the arc containing welding gases, metallic fumes, and particulates. The fume plume can present an inhalation risk if safety precautions are not followed.
Welding that does not use filler metal and simply melts the base metals at the joint. Fusion welding, also known as autogenous welding, often creates weld joints that are stronger than the base metals.
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.
A specially designed screen assembly that fits inside the cup of a GTAW torch. The gas lens creates a longer, smoother shielding gas flow.
gas metal arc welding
GMAW. An arc welding process in which a bare wire electrode and shielding gas are fed to the weld through a welding gun. Gas metal arc welding electrodes can be cut into filler rods for use in GTAW.
The device used to control the amount of gas flowing from a gas cylinder during welding. Gas regulators consist of a control valve and a flow meter or gauge that indicates the volume of gas.
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).
Shaping or otherwise wearing away material using an abrasive. Grinding is used to prepare pointed and truncated GTAW electrodes.
A type of weld designed to join two workpiece edges, two workpiece surfaces, or one surface and one edge. Groove welds often have an opening between the workpieces that provides space to contain weld metal.
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).
The portion of an AC cycle during which current flows in one specific direction. In GTAW, the electrode negative half cycle transfers heat to the base metals and the electrode positive half cycle provides a cleaning action.
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).
A lightweight inert gas sometimes used as a shielding gas for arc welding. Helium is much lighter than air.
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.
hot rolled steel
Steel that is heated and passed between two rollers in order to flatten and lengthen it. Hot rolled steel is covered in tough mill scale.
The process of flattening and lengthening metal by heating it and passing it between two rollers. Hot rolling leaves a tough mill scale on the metal.
hydrous aluminum silicate
A naturally occurring, heat- and crack-resistant stone. Hydrous aluminum silicate, also known as lava, is used to make GTAW cups.
A discontinuity that occurs when the weld metal and base metal or adjoining weld beads are not fully fused. Incomplete fusion significantly weakens the integrity of a weld.
incomplete joint penetration
IJP. A discontinuity characterized by an unpenetrated and unmelted area in a joint that occurs when weld metal does not extend through the full thickness of the joint. Incomplete joint penetration can significantly weaken the integrity of a weld.
A substance that is not chemically reactive. GTAW requires inert shielding gases.
inverter power sources
A welding machine that uses a series of components including inverters and transistors to convert input electricity to usable power. Inverter power sources are small, portable, and energy-efficient, but expensive.
An electrical device that uses transistors to increase the frequency of supplied electricity and convert DC to AC. Inverters allow welding power sources to be smaller and more efficient.
An electrically charged atom or molecule. When using AC for GTAW, positively charged ions can help remove surface oxides from aluminum and magnesium.
A metallic compound containing iron and oxygen. Iron oxides, such as rust and mill scale, are formed by a chemical reaction between iron and oxygen.
A soft, pliable leather made from the hide of a goat. Kidskin is often used to make GTAW-specific welding gloves.
A tungsten electrode that contains a small percentage of lanthanum. Lanthanated electrodes are typically 1-2% lanthanum.
A rare-earth metal with many industrial and medical applications. Lanthanum is combined with tungsten to make lanthanated GTAW electrodes.
A naturally occurring, heat- and crack-resistant stone. Lava, also known as hydrous aluminum silicate, is used to make GTAW cups.
A GTAW filler metal addition technique in which the welder holds the filler rod in the joint and moves the electrode and arc over it. Using the lay-wire technique while walking the cup can create wider, more fluid weld puddles.
liters per minute
l/min. A unit of measurement for fluid flow that indicates the number of liters flowing past a certain point in one minute. Liters per minute is used to measure shielding gas flow rate for welding processes.
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.
A characteristic that describes how a material reacts when subjected to a force that attempts to stretch, compress, bend, dent, scratch, or break it. Mechanical properties include tensile strength, toughness, ductility, and hardness.
A carbon steel that contains less than 0.30% carbon. Mild steels, also known as low-carbon steels, are generally tough, ductile, and easily welded.
A tough surface contaminant composed mainly of iron oxides. Mill scale must be removed before welding steel.
A tungsten electrode that contains small percentages of multiple different oxide additives, such as 1.5% lanthanum, 0.8% yttrium, and 0.8% zirconium. Multi-oxide electrodes have long life spans and are resistant to contamination.
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.
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.
A chemical compound containing oxygen and one other element. Oxides can cause weld defects if they are not removed from the surface of a workpiece, but certain oxides are used to provide beneficial properties to tungsten electrodes.
A chemical compound of oxygen and one other element that is intentionally added to tungsten to improve the performance of GTAW electrodes. Oxide additives enhance the electrode's emissions to improve arc starting and stability.
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.
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 GTAW usually includes a welding helmet, jacket, safety glasses, and gloves.
A colorless toxic gas released when chlorinated cleaning solvents react with arc radiation during welding. Phosgene exposure can cause difficulty breathing, eye irritation, heart failure, seizures, permanent brain damage, or death.
A characteristic that describes how a material responds to environmental, electrical, magnetic, and thermal forces. Physical properties include corrosion resistance, thermal conductivity, and electrical conductivity.
Having a conical shape that comes to a sharp end. Pointed GTAW electrode tips are used for DC welding at low amperages.
Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current flows.
A discontinuity characterized by the appearance of tiny voids or cavities in a weld bead, resulting from trapped gas. Excessive porosity can weaken a weld.
An end option that delivers shielding gas to the weld area after the arc is terminated for 10-30 seconds. Post-flow protects the solidifying weld puddle and the electrode from atmospheric contamination.
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.
A start option that delivers shielding gas to the weld area before the arc is initiated. Pre-flow ensures that the arc will be properly shielded once it is initiated.
A container designed to hold liquids or gases at high pressures. Pressure vessels include gas cylinders and tanks.
A borosilicate glass manufactured under license from Corning Incorporated. Pyrex is used to make transparent GTAW cups.
Emitting radiation. The thoriated electrodes often used in GTAW are mildly radioactive.
An electrical device that converts AC power to DC power. Rectifiers allow current to flow in one direction only.
A breathing device worn to prevent inhalation of hazardous substances. Respirators may purify air from the environment or supply air to the wearer.
The first pass of a multi-pass weld. The root pass joins two separate base metals together and provides the foundation for subsequent passes.
Protective eyeglasses with metal or plastic frames and impact-resistant lenses that may or may not offer vision correction. Safety glasses for welding applications must also have protective side shields.
An arc starting method that involves dragging the tip of the electrode against the workpiece. The scratch start method is a high-voltage starting method that does not require a control device.
A gas that protects the weld puddle and arc from atmospheric contamination. Shielding gas is supplied by a cylinder and flows through the welding torch.
A ceramic compound made from silicon and nitrogen. Silicon nitride has an extremely high melting point, which makes it an ideal material for GTAW cups.
A chemical substance used to dissolve another material. Solvents are often used to remove surface contaminants such as grease or oil before welding.
Liquid metal droplets expelled from the welding process. Spatter can leave undesirable particles of metal on a workpiece surface.
A type of steel that contains at least 10.5% chromium and exhibits excellent hardness and corrosion resistance. Stainless steels have good weldability if the right welding procedures are followed.
standard cubic feet per hour
SCFH. A unit of measurement for fluid flow that indicates the number of cubic feet flowing past a certain point in one hour. Standard cubic feet per hour is used to measure shielding gas flow rate for welding processes.
An alloy of iron and carbon containing less than 2.0% carbon. Steels often contain other elements to enhance various aspects of the metal.
Adherence of the electrode tip to the workpiece. Sticking may occur when the electrode touches the workpiece and can lead to contamination of both the electrode and the workpiece.
A weld bead formed by moving the electrode in a straight line along the joint. Stringer beads are often created using the dipping technique in GTAW.
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.
The ability of a material to transmit heat. Helium's high thermal conductivity allows it to transfer more heat to the weld.
A tungsten electrode that contains a small percentage of thorium, which is slightly radioactive. Thoriated electrodes are usually 1% or 2% thorium.
A mildly radioactive metal sometimes used as nuclear fuel. Thorium can also be combined with tungsten to make thoriated GTAW electrodes.
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 that requires the welder to initiate current using a control device.
An electrical device that uses magnetic induction to reduce the voltage of incoming electricity and output a lower voltage. Transformers are used in welding power sources to provide a usable low-voltage, high-amperage current.
transformer power sources
A welding machine that uses a large transformer to convert input electricity to usable power. Transformer power sources are relatively inexpensive but large and inefficient.
An electrical device used to rapidly switch power on and off. Transistors are used in inverter power sources to increase frequency and convert DC to AC.
The rate at which the electrode moves along the joint to make a weld. Travel speed determines the size of the weld bead and is measured in inches per minute (ipm) or millimeters per minute (mm/min).
Having a blunt shape that ends with a flat surface. Truncated GTAW electrode tips are used for both AC and DC welding with inverter power sources and high amperages.
A dense, brittle, gray metal that has excellent conductivity and the highest melting point of all pure metals. Tungsten, also known as wolfram, is used to make non-consumable electrodes for GTAW.
A discontinuity that occurs when small particles of the tungsten electrode break off and combine with the weld metal. Tungsten inclusion can significantly decrease the strength of a finished weld.
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).
A disturbance in the even flow of shielding gas to the welding area that causes the gas to swirl and mix with atmospheric gases. Turbulence is often the result of using an excessively fast flow rate.
UV. Harmful invisible light rays that can burn the eyes and skin. Ultraviolet light is produced by most arc welding processes.
To change from a solid or a liquid to a gas. Positive ions can vaporize surface oxide particles during the electrode positive half cycle of an AC waveform.
A means of providing fresh air. Welding requires proper ventilation for the safety of the welder.
The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).
V. A unit of measurement that indicates the amount of electrical force or pressure in a circuit. Volts indicate voltage.
walking the cup
A GTAW technique in which the welder rests the torch cup on the workpiece and rotates the torch handle to move the cup back and forth while progressing along the joint. Walking the cup helps maintain consistent arc length and creates strong, even welds.
A visual representation of how current behaves over time. An AC waveform represents one cycle, or the time it takes for current to flow, pause, reverse direction, and then pause again.
A weld bead formed by moving the electrode side to side along the joint in an oscillating motion. Weave beads are wider than stringer beads.
The exposed surface of a weld. The weld face may be convex, concave, or flush with the workpiece.
The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.
A heat-resistant head covering that consists of a hard face-guard and a dark-tinted filter plate. Welding helmets protect welders from flying debris and the intense ultraviolet light produced by the arc.
A tool with wire filaments used to clean the surface of a workpiece. Wire brushes can be used to prepare base metals before welding or to clean finished welds.
A dense, brittle, gray metal that has excellent conductivity and the highest melting point of all pure metals. Wolfram, also known as tungsten, is used to make non-consumable electrodes for GTAW.
A tungsten electrode that contains a small percentage of zirconium. Zirconiated electrodes are typically 0.3% or 0.8% zirconium.
A gray-white metal with a strong resistance to corrosion. Zirconium is combined with tungsten to make zirconiated GTAW electrodes.