Introduction to Welding 141
Introduction to Welding introduces common welding processes and workpiece materials as well as joint and weld types. It also discusses joint preparation, discontinuities, welding procedure specifications, and testing and inspection methods for welding.
This class provides the foundational knowledge necessary for the educational development of any welder. This knowledge is the basis on top of which more comprehensive and process-specific knowledge is built.
Number of Lessons 18
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- Basics of Welding
- Common Welding Processes
- Weldable Materials
- Welding Basics Review
- Structural Material Shapes
- Joint Types
- Weld Types
- Shapes, Joints, and Welds Review
- Joint Preparation
- Discontinuities and Defects
- Welding Procedure Specifications
- Testing and Inspection
- Welding Considerations Review
- Weld Gages
- Calipers and Micrometers
- Steel Rules and Go/No-Go Gages
- Protractors and Combination Squares
- Measuring Device Review
- Describe welding.
- Describe common welding processes.
- Describe weldable materials.
- Describe structural shapes that are commonly joined using welding processes.
- Identify common joint types.
- Identify common weld types.
- Describe joint preparation.
- Describe common weld discontinuities and defects.
- Describe welding procedure specifications.
- Describe testing and inspection methods for welds.
- Describe weld gages.
- Describe calipers and micrometers.
- Describe steel rules and go/no-go gages.
- Describe combination squares and protractors.
A tool designed to allow a welder to establish a 45-degree angle. A 45-degree holder is a typical feature of a combination square.
A tool designed to allow a welder to establish a 90-degree angle. A 90-degree holder is a typical feature of a combination square.
A colorless, flammable gas often mixed with oxygen to fuel oxyfuel torches. Acetylene is required for oxyfuel welding.
acid etch testing
A destructive testing method used to isolate small defects or areas of soft metal in a completed weld. Acid etch testing typically involves cutting a weld into a cross-section and rubbing an acidic material onto the exposed interior of the weld, causing small defects to become visible.
AM. The process of joining or solidifying materials to make an object based on a three-dimensional computer model. Additive manufacturing methods typically build up layers of material to create an object.
The joining of two or more materials using adhesive substances such as pastes, gels, glues, and tape. Adhesive bonding can be used to join similar and dissimilar materials.
A nonferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.
American Petroleum Institute
API. A non-profit organization that regulates industrial standards for the oil and natural gas industry. The American Petroleum Institute publishes codes that are used for welding operations on oil pipelines or related materials.
American Society of Mechanical Engineers
ASME. An organization that publishes technical materials and sets industrial and manufacturing standards. The American Society of Mechanical Engineers publishes welding codes.
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.
A tool designed specifically for measuring and setting weld angles. An angle gage, or welding protractor, typically consists of a rectangular head with an adjustable arm that can be locked in position at specific angles.
angle of preparation
The angle between the fusion faces of base materials. The angle of preparation often dictates the ideal weld type.
The fixed block on a micrometer that is located opposite the spindle. The anvil provides a backstop for the part during measurement.
The area in which electricity moves between the electrode and the workpiece. The heat generated by the arc melts the base metals and filler metal during welding.
A group of welding processes that use electricity to generate the heat needed to melt the base metals. Arc welding is portable and economical, making it the most common form of welding.
automatic weld size gage
AWS gage. A weld gage designed to inspect reinforcement on groove welds and leg length, throat size, concavity, and convexity on fillet welds. An automatic weld size gage is a versatile tool for inspecting finished welds.
Metals that are welded together to form a joint. The base metal and its properties influence the weld type, welding process, and electrode.
A long, thin part along which another part is designed to slide. A beam is an integral part of many measuring instruments.
A destructive testing method in which a small sample of a weld is bent into a U-shape. Bend testing allows inspectors to observe strength, flexibility, and some discontinuities.
bridge cam gage
A weld gage designed to inspect the leg length and throat size of fillet welds, the reinforcement of groove welds, and other features. A bridge cam gage can also inspect undercut, porosity, misalignment, and angle of preparation.
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.
A joint created between two parts that lie in the same plane. Butt joints are simple, common joints.
A measuring instrument that includes one or more sets of jaws and a scale marked with unit divisions. Calipers often include one set of jaws to measure outer diameters and another set of jaws to measure internal diameters.
A common metal that is an alloy of iron and carbon. Carbon steel is one of the most commonly welded metals.
An alloy of iron, carbon, and silicon that contains at least 2.0% carbon. Cast irons generally need some form of heat treatment to be welded with satisfactory results.
A simple tool used to find the center of a cylinder. Center squares can also be used to find the diameter of a circle.
An imaginary line that runs through the center of an object or divides it into two equal halves. The centerline of a cylindrical part can be found using a combination square.
A hard, brittle material that can withstand high temperatures and resist corrosion. Ceramics include traditional materials such as brick, clay, and glass, as well as more advanced materials.
Charpy V-notch testing
A destructive testing method that involves cutting a small slot in the surface of a material and breaking the material across the slot using a weighted pendulum. Charpy V-notch testing allows inspectors to not only measure the strength of a weld but also examine it for internal defects.
A measuring instrument that consists of a steel rule with multiple attachments that allow it to measure many different dimensions. Combination squares typically include a protractor, a 45-degree holder, a 90-degree holder, and a center square.
The degree to which a surface curves inward. Weld concavity can be measured by an automatic weld size gage.
The degree to which a surface curves outward. Weld convexity can be measured by an automatic weld size gage.
A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper can be welded by only a limited number of welding processes.
A joint created between two parts located at angles to one another. Corner joints require large amounts of filler metal.
The flow of electricity through a circuit. Current is measured in amperes (A), or amps, and controls the heat of the arc.
The act of separating a workpiece into two or more pieces. Cutting can be done with traditional methods, such as milling or sawing, or more advanced methods, such as oxyfuel and plasma cutting.
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 testing method that damages or destroys the workpiece being tested. Destructive testing is ideal for determining the strength of a weld.
A type of display that uses a special encoder attached to a machine to convert information into a numerical measurement. Digital readouts can display very precise measurements.
An irregularity in the specified and expected composition of a weld. Discontinuities are not always defects.
A material's ability to be drawn, stretched, or formed without breaking. Ductility is more common in softer metals.
A joint created between the aligned edges of two parallel parts. Edge joints, or parallel joints, are useful for joining plate metal workpieces.
The force that opposes the flow of electrical current. Electrical resistance creates heat, which can be used for welding.
A device in an electrical circuit that conducts electricity. A welding electrode can also act as filler metal.
A nondestructive testing method that uses an electric current or magnetic field to determine if a weld is defective. Electromagnetic testing can reveal internal defects in a weld.
A standard system of measurements based on the inch, pound, and degree Fahrenheit. The English system of measurement is primarily used in the United States.
The exposed surface of a weld. The face of a weld may be convex, concave, or flush with the workpiece.
A metal that contains iron. Ferrous metals are the most common type of welded materials.
Metal deposited into the weld that often adds strength and mass to the welded joint. In some welding processes, the electrode acts as the filler metal.
A triangular weld made to join two surfaces at right angles to each other. Fillet welds are the most common type of welds.
fillet weld gage
A weld gage designed to determine whether or not a fillet weld is within specified tolerances. Fillet weld gages are used to check a weld's leg length and throat size.
A measure of the closeness between two parts that are to be welded. Proper fit-up occurs when parts fit together without extra spaces or gaps.
flux-cored arc welding
FCAW. An arc welding process that uses a continuously fed consumable electrode with an inner core of flux. Flux-cored arc welding is quick, precise, and portable, and it can be used outdoors.
A force that resists motion between the contact surfaces of two objects. Friction generates heat that can be used to weld pieces of metal together.
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 is also sometimes referred to as metal inert gas welding (MIG welding) or metal active gas welding (MAG welding), but these terms are nonstandard in the United States.
gas tungsten arc welding
GTAW. A precise arc welding process that uses a nonconsumable tungsten electrode and inert shielding gas. Gas tungsten arc welding is also known as tungsten inert gas welding (TIG welding).
An inspection instrument with two ends that are inserted into or placed around a part feature to determine whether it is within tolerance or not. Go/no-go gages simply indicate whether a part passes or fails inspection and do not provide measurements.
The use of an abrasive to cut the surface of a workpiece and change its shape. Grinding can be used to shape workpieces before welding.
A weld made in the opening between two parts that provides space to contain weld metal. Groove welds are used on all joints except lap joints.
A destructive testing method that determines how a material responds to external forces that attempt to scratch, penetrate, or indent it. Hardness testing is widely used both in welding and in general machining.
hollow structural sections
HSS. A structural support with a hollow interior that may be left empty to reduce weight or filled with a substance such as concrete. Hollow structural sections are often square-shaped or round and may also be called structural tubing.
A structural support beam with a cross-section that resembles the letter "I." I-beams are useful in a wide variety of industrial applications.
A discontinuity in which the weld metal and base metal or adjoining weld beads are not fully fused. Incomplete fusion significantly weakens the integrity of the weld.
A discontinuity characterized by an unpenetrated and unfused area in a joint. Incomplete penetration occurs when weld metal does not extend through the thickness of the joint.
ID. The interior surface of an object. Inside diameter can be measured by calipers.
The examination of a part during or after its creation to confirm that it adheres to specifications. During inspection, welders can identify and correct defects.
A common silvery-white metal found in nature as ore. Iron is alloyed with carbon to make steel.
A stationary or movable feature that allows a device to open and close around an object. A caliper usually has two sets of jaws to measure both outer and inner diameters.
The meeting point of two materials that are fused together. Welding creates a permanent joint.
A variety of processes that prepare base metals before welding. Joint preparation can involve cleaning, machining, preheating, or other operations.
The configuration in which two or more workpieces are joined. There are five basic joint types: butt, corner, edge, lap, and T-joints.
A joint created between the edge of one part and the surface of an overlapping parallel part. Lap joints provide more stress resistance than butt joints.
The side of a fillet weld that connects the toe to the root. Leg length determines the size of a fillet weld.
To ensure that an object is perfectly horizontal. A combination square can be used to level workpieces.
liquid penetrant testing
A nondestructive testing method that uses a fluorescent liquid or dye to detect surface flaws. Liquid penetrant testing requires an inspector to apply a penetrant and then a developer to reveal weld discontinuities.
The process of removing material to form an object. Traditional machining methods, such as milling, turning, and drilling, remove metal using cutting tools.
A simple measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Machinist's rules are also called steel rules.
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.
magnetic particle testing
A nondestructive testing method that involves magnetizing the part to be inspected and then covering it with tiny iron oxide particles that accumulate in any cracks or seams. Magnetic particle testing uses magnetic fields and electric currents to reveal discontinuities.
The joining of two or more materials with devices called fasteners. Mechanical fastening is often used for parts that require disassembly and reassembly.
A naturally occurring material with high strength, hardness, and electrical and thermal conductivity. Metals are categorized as either ferrous or nonferrous.
A standard system of measurements based on the meter, kilogram, and degree Celsius. The metric system of measurement is internationally recognized.
A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil to close around a part. Micrometers provide more precise measurements than calipers.
A hard, silver-white metal that is easily manipulated. Nickel is often used in alloys.
A testing method that does not destroy the workpiece or weld being tested. Nondestructive testing is ideal for large or expensive workpieces.
A metal that does not contain a significant amount of iron. Common nonferrous metals include aluminum, titanium, copper, and nickel.
OD. The exterior surface of an object. Outside diameter can be measured by calipers or micrometers.
OFW. A fusion welding process that uses a flame produced by a mixture of oxygen and acetylene gas. Oxyfuel welding is also known as oxyacetylene welding.
A colorless, odorless, tasteless gas that naturally exists in the atmosphere. Oxygen is the primary gas used in oxyfuel welding.
Extending in the same direction and equally distant from one another at all points. Parallel lines or objects never intersect.
A joint created between the aligned edges of two parallel parts. Parallel joints, or edge joints, are useful for joining plate metal workpieces.
An intersection of two lines or objects that meet at right angles to one another. Perpendicular lines create angles measuring exactly 90 degrees.
A flat surface that extends infinitely in any direction in two dimensions. Components lying in the same plane are joined by butt joints.
A synthetic polymer characterized by light weight, good formability, and high corrosion resistance. Plastic is typically joined using specialized processes, but it can also be welded by laser beam welding (LBW) or ultrasonic welding.
A weld made in a circular hole in one part to join it to another part positioned directly beneath it. Multiple plug welds are usually required to form a strong joint.
A discontinuity characterized by the appearance of tiny voids on a weld bead, resulting from trapped gases in a material. Excessive porosity can weaken a weld.
The degree to which an instrument can repeatedly indicate the same measurement over time. Precision is also called repeatability because it will provide the same results under unchanged conditions.
A mechanical force exerted on an object. Pressure can be used to join materials during welding.
A tool used to measure angles. A basic protractor is a semi-circular device with angle measurement markings.
A nondestructive testing method that uses an X-ray machine to examine the interior of a completed weld. Radiographic testing is expensive and time-consuming and therefore is typically only used in situations where the weld must be perfect.
A welding process that joins parts using heat obtained from the resistance to the flow of electric current. Resistance welding also applies pressure to weld the parts together.
An angle that measures exactly 90 degrees. A right angle is formed by two perpendicular lines or objects.
A triangle containing exactly one 90-degree angle. A fillet weld roughly resembles a right triangle.
The point at which the back of a weld intersects the surfaces of the base metals. Some welds have openings located at the root.
A hollow structural support with a circular cross-section. Round tubing is often used in plumbing and automotive exhausts.
A standard of measurement that is often displayed as a series of lines. The lines on a scale indicate measurement unit divisions.
A continuous weld made on or between the surfaces of overlapping parts. Seam welds are often used for tanks or pipes.
The smallest change in a measurement that an instrument is capable of detecting. Instruments with greater sensitivity provide more accurate readings.
shielded metal arc welding
SMAW. An arc welding process that uses a flux-coated rod as a consumable electrode. Shielded metal arc welding is also called stick welding or manual welding.
A weld made in an elongated hole in one part to joint it to another part positioned directly beneath it. Slot welds are stronger than plug welds but require more filler metal.
The component of a micrometer that advances toward the anvil to make contact with and measure a part. The spindle advances when the thimble is rotated.
A small weld made on or between the surfaces of overlapping parts. Multiple spot welds are generally required to join parts.
A hollow structural support with a square-shaped cross-section. Square tubing is often used in welded steel frames.
A type of steel that contains at least 10.5% chromium and exhibits excellent hardness and corrosion resistance. Stainless steel can be welded with many different welding processes.
A simple measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Steel rules are also called machinist's rules.
An alloy of iron and carbon containing less than 2.0% carbon. Steels often contain other elements to enhance various aspects of the metal.
A force that attempts to deform an object. Excess stress may cause a part to break.
A structural support with a cross-section that resembles the letter "L." Structural angles are used in light-duty structural applications.
A structural support with a cross-section that resembles the letter "C." Structural channels are relatively weak and typically used to reinforce larger pieces.
A structural support with a hollow interior that may be left empty to reduce weight or filled with a substance such as concrete. Structural tubing is often square-shaped or round and may also be called hollow structural sections (HSS).
submerged arc welding
SAW. An arc welding process that uses a consumable wire electrode and a layer of flux over the weld to shield the arc. Submerged arc welding has no visible arc and produces a clean, spatter-free weld.
The examination of a part to ensure that it performs its intended function. Different methods of testing are used to ensure that finished welds meet their requirements.
A material's ability to conduct heat. Thermal conductivity depends on the material's structure and temperature.
A ring or cylinder that fits around the spindle of a micrometer. The thimble is turned by hand to advance the spindle.
The distance between a weld's root and a line drawn between the weld toes. The throat helps determine a weld's size and strength.
A joint created between the edge of one part and the surface of a second, perpendicular part that resembles the letter "T." T-joints are very common joints that are simple to create.
The point at which a weld's face meets the base metal. A line drawn between the toes marks the top of the weld's effective throat.
An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.
A force that twists a part. Torsion can weaken or break a workpiece.
transverse tensile testing
A destructive testing method that uses a machine to attempt to pull a welded joint apart. Welds pass transverse tensile testing if the base metal breaks before the weld does.
A nondestructive testing method that uses high-frequency sound waves to discover surface and interior defects. In ultrasonic testing, changes in the signal indicate flaws.
A welding process that uses high-frequency acoustic vibrations to permanently bond two separate components together. Ultrasonic welding is used by some sheet lamination machines in additive manufacturing (AM).
An undesired gap left along the edge of a finished weld. Undercut is unsightly but does not necessarily indicate a bad weld.
A type of scale consisting of two sets of opposing line markings with different divisions. A vernier scale is generally included on both manual calipers and micrometers.
A visual assessment of surface defects. Visual inspection is one of the most commonly used nondestructive testing methods for finished welds.
visual weld acceptance criteria gage
V-WAC gage. A weld gage designed to inspect undercut, porosity, and groove weld root and face reinforcement. Visual weld acceptance criteria gages can be used to determine whether a weld meets specifications.
A device used to determine whether or not a weld is within specified tolerances. Weld gages are designed to determine whether or not a weld is within a certain specification and cannot make precise measurements.
The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.
The shape of the weld used to join workpieces. There are six main weld types: fillet, groove, plug, slot, spot, and seam welds.
A person who performs welding. Some resource materials may also refer to the welding power source as a welder.
A joining process that permanently bonds two separate components together. Welding uses heat, with or without pressure and friction, or a combination of methods to make a new part.
A collection of laws or standards that outline practices for a particular welding application. Welding codes ensure safe welding practices and high-quality welded products.
The position in which a joint is to be welded. Welding position can influence electrode or filler metal choice.
welding procedure specification
WPS. A written document that contains all the necessary and specific information for creating a qualified weld. Welding procedure specifications must be approved and tested before welding can begin.
A tool designed specifically for measuring and setting weld angles. A welding protractor, or angle gage, typically consists of a rectangular head with an adjustable arm that can be locked in position at specific angles.
A part undergoing some type of manufacturing process. The workpiece may be subject to cutting, welding, forming, or other operations.
A bluish-white metal that is corrosion resistant and has a relatively low melting point. Zinc may be combined with aluminum to create alloys, but these generally have poor weldability.