Introduction to Welding 141

“Introduction to Welding” provides the foundational understanding of welding and welding processes on top of which process-specific knowledge and a more comprehensive understanding of welding in general is built. The class introduces the different welding processes as well as their general attributes and applications. In addition, it reviews joint and weld types, covers measurements which pertain to welding, discusses welding procedure specifications, and, finally, gives the user information on emerging welding practices and their effect on the practice of welding and the economy.

“Introduction to Welding” builds foundational knowledge necessary for the educational development of any welder. Moreover, it exposes the user to conceptual ideas of welding theory and less-common welding practices such as laser welding.

Class Details

Class Name:
Introduction to Welding 141
Number of Lessons:
Related 1.0 Class:
Overview of Weld Types 130

Class Outline

  • Basics of Welding
  • Common Welding Processes
  • Welding with Lasers
  • Other Emerging Welding Practices
  • The Impact of Emerging Welding Practices
  • Welding Processes
  • Workpiece Materials
  • Structural Shapes and Workpieces
  • Joint Types
  • Weld Types
  • Weld Types, Joint Types, and Structural Shapes
  • The Welding Procedure Specification
  • Understanding the Welding Procedure Specification
  • WPS review
  • Weld Gages
  • Steel Rules, Gage Blocks, and Go/No-Go Gages
  • Combination Squares and Protractors
  • Calipers and Micrometers
  • Using a Caliper and Micrometer to Measure a Part
  • Measurements in Welding


  • Define welding.
  • Describe common welding processes.
  • Describe laser beam welding processes.
  • Describe emerging welding practices.
  • Describe the impact of emerging welding practices.
  • Describe weldable materials.
  • Describe structural shapes that are commonly joined using welding processes.
  • Identify common joint types.
  • Identify common weld types.
  • Describe welding procedure specifications.
  • Describe the welding procedure specification.
  • Describe weld gages.
  • Describe gage blocks, go/no-go gages, and steel rules.
  • Describe combination squares and protractors.
  • Describe calipers and micrometers.

Job Roles



Vocabulary Term Definition
45-degree holder A tool designed to allow a welder to establish a 45° angle. A 45° holder is a typical feature on a combination square.
90-degree holder A tool designed to allow a welder to establish a 90° angle. A 90° holder is a typical feature on a combination square.
adjustable weld size gage AWS gage. A weld gage designed to check the tolerances of fillet and groove welds. An adjustable weld size gage can measure concavity and convexity, along with other features.
alloy steel A steel containing intentionally added materials that change the property of the metal. Alloy steels commonly include elements such as manganese, molybdenum, and nickel.
aluminum A nonferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.
angle beams A light beam appearing in profile like the shape of the letter L. Angle beams are used in light-duty structural applications.
angle of preparation The angle between the fusion faces of base materials. The angle of preparation often dictates the ideal weld type.
anvil The fixed jaw on a micrometer or a set of calipers. An anvil provides the backstop for the part during measurement.
arc 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.
arc 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.
automated Any equipment, process, or system that is controlled robotically. Automated machines are sometimes informally referred to as robots.
automation The automatic control of equipment, a process, or a system. Automated machines are sometimes informally referred to as robots.
base metal The pieces of metal being welded together. Base metals influence weld type and welding process.
beam A long, thin part upon which another part is designed to slide. A beam is an integral part of many measuring instruments.
bridge cam gage A gage designed to measure weld features or weld joints. A bridge cam gage can measure undercut, pitting, misalignment, angle of preparation, and fillet weld throat size and leg length.
butt joint A type of joint created between two metal parts that lie in the same plane. Butt joints are the most common joint type.
caliper A handheld instrument that includes one or more set of jaws to measure various part dimensions. A caliper includes indicators on the top of the instrument that expand to measure internal diameters.
carbon steel A common metal that is an alloy of iron and carbon. Carbon steel is one of the most commonly welded metals.
center square A simple tool used to find the center of a cylinder. Center squares can also be used to find the diameter of a circle.
centerline An imaginary line that divides a shape into two equal halves. A centerline can be found using a combination square.
channel beams A beam appearing in profile as the shape of the letter C. Channel beams are weak and typically used to reinforce larger pieces.
clamps Devices used to hold a tool or workpiece in place. Clamps are usually composed of two parallel arms which can be moved towards each other to fasten the clamp to a solid surface.
combination square A steel rule with attachments to allow it to make many different measurements. Combination squares can measure a number of different features, including angles.
concavity Curving inward like the inside of a bowl. Many fillet welds have concave faces.
convexity Curving outward like the exterior part of a circle. Many fillet welds have convex faces.
copper A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper can be welded with a limited number of welding processes.
corner joint A type of joint created between two metal parts located at right angles to one another. Corner joints require large amounts of weld metal.
crown The highest part of the weld face, extending beyond the weld throat. The depth of the weld crown is measured as the distance between its highest point and the weld throat.
digital readout A type of readout that uses a special encoder attached to a machine that transfers information to a numerical display. Digital readouts can display very precise measurements.
discontinuities An irregularity in the specified and expected composition of a weld. Discontinuities are not always defects.
double-groove welds A weld that has groove welds on both sides of the joint. Double-groove welds are strong and often require less filler metal than single-groove welds.
dual-beam laser welding A variant of laser beam welding that uses two lasers instead of one. Dual-beam laser welding is cleaner and produces fewer weld defects than conventional LBW.
edge joint A type of joint in which the surface of the two metal parts to be joined are parallel to one another and the weld is made at their common edges. Edge joints are useful for joining plate metal workpieces.
electrical resistance A measure of a part's resistance to the flow of an electrical current. Electrical resistance creates heat, which can be used for welding.
electrode A device in an electrical circuit that conducts electricity. A welding electrode can also act as filler metal.
electron A negatively charged particle that orbits the nucleus of an atom. Electrons are involved in electrical conductivity.
electron beam welding EBW. A metal joining process that uses a narrow stream of electrons to produce a highly concentrated heat source. Electron beam welding is usually performed in a vacuum to keep the beam from dissipating.
English measurements A standard system of measurements based on the inch, pound, and degrees Fahrenheit. English measurements are primarily used in the United States.
filler metal A type of metal sometimes added to the joint in fusion welding. Filler metal adds to the strength and mass of the welded joint.
fillet gages A device that determines whether or not a fillet weld is within specified tolerances. Fillet gages are a specific kind of weld gage.
fillet weld A type of weld that is triangular in shape and joins two surfaces at right angles to each other. Fillet welds are the most common types of welds.
flux A non-metallic material, usually either coating or inside a welding electrode. Flux protects the weld puddle and cooling metal from atmospheric contamination.
flux-cored arc welding FCAW. An arc welding process that uses a continuously fed consumable electrode that contains flux in a hollowed-out center. Flux-cored arc welding is quick and precise, can be used outdoors, and is easily portable.
friction The resistance between the contact surfaces of two objects. Friction generates heat, which means that it can be used to weld pieces of metal together.
friction stir spot welding FSSW. A variant of friction stir welding. In friction stir spot welding, a rotating tool blends the workpieces together at the spot where it has been inserted, creating a weld.
friction stir welding FSW. A welding process which uses a rotating tool to soften and blend the edges of two pieces of metal to create a weld. Friction stir welding is a versatile process which creates strong welds without the use of filler metal.
FSW Friction stir welding. A welding process which uses a rotating tool to soften and blend the edges of two pieces of metal to create a weld. FSW is a versatile process which creates strong welds without the use of filler metal.
gage blocks A hardened steel block that is manufactured with highly accurate dimensions. Gage blocks are available in a set of standardized lengths.
gas metal arc welding GMAW. An arc welding process in which a wire electrode and inert or active shielding gas are fed to the weld through a welding gun. Gas metal arc welding is also referred to as MIG welding.
gas tungsten arc welding GTAW. A very precise arc welding process that uses a nonconsumable tungsten electrode. Gas tungsten arc welding is also referred to as TIG welding.
go/no-go gages A gage with two ends that are made to go around or inside a part. Go/no-go gages are designed to accurately gage part fit.
groove weld A type of weld made in the opening between the surface of two parts that provides space to contain weld metal. Groove welds are used on all joints except lap joints.
hollow structural section HSS. A steel structural beam with a hollow interior to reduce weight or to allow filling with a substance such as concrete. HSSs are also known as square beams.
hybrid laser arc welding HLAW. A welding process which uses both laser welding and arc welding at the same time. Hybrid laser arc welding offers the ability to rapidly create a deep, strong weld.
hybrid welding process A term used to refer to a welding process which consists of two different welding processes used at the same time. Hybrid welding processes usually offer improvements over their component processes.
hybridization The combining of two concepts or practices to form a third. Hybridization is commonly used to create hybrid welding processes for automated welding.
I-beams A beam consisting of one vertical structure connecting two shorter horizontal structures. I-beams are useful in a wide variety of industrial applications.
inside diameter ID. The interior diameter of a hole in a workpiece. Inside diameter is an important measurement not only in welding but in general machining.
inspector A person who examines or compares a part with various tools and techniques to determine its conformance to specifications. An inspector fulfills an important role in manufacturing and fabrication.
iron A common, easily-obtained metal found in nature as ore. Iron is alloyed with carbon to make steel.
jaws A holding or measuring device designed to close around a part. A caliper usually has two sets of jaws to measure both outer and inner diameters.
joint The meeting point of two materials that are fused together. Welding creates a permanent joint.
joint preparation A variety of processes that prepare base metals before welding. Joint preparation can involve preheating, cutting, or other preparations.
joint types The configuration in which two or more workpieces are joined. Common joint types for welding include butt, corner, edge, and lap joints.
keyhole The opening in a workpiece created by the action of welding. The keyhole fills with molten metal from the workpiece or electrode to create a weld.
lap joint A joint formed where two surfaces overlap one another. Lap joints provide more stress resistance than butt joints.
lapped Machined with fine abrasives to create an ultra-smooth surface. Lapped surfaces are often referred to as mirror finish.
laser beam welding LBW. A welding process which uses a laser to create a weld. Laser beam welding makes deep, strong, clean welds, but it is expensive and requires either automation or a highly trained welder.
lasers A device that generates an intense beam of light that can be precisely aimed and controlled. Lasers can be used to create precise, strong welds.
LBW Laser beam welding. A welding process which uses a laser to create a weld. LBW makes deep, strong, clean welds, but it is expensive and requires either automation or highly trained welders.
lead A bluish-white metal that is very soft and ductile. Lead is used as a soldering alloy and as a sound dampener.
leg The portions of the weld from the toe to the root. Leg length is one determinant of the strength of the weld.
level To ensure that an object is perfectly horizontal. A level is also a tool used to level objects.
low-alloy steel A steel that contains small amounts of intentionally added materials that change the properties of the metal. Low-alloy steel commonly contains the elements manganese, molybdenum, and nickel.
machinist’s rule A simple, relatively imprecise measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Machinist's rules are also called steel rules.
magnesium A grayish white, extremely light metal that is brittle and has poor wear resistance. Aluminum-magnesium alloys have excellent weldability.
metric measurements A standard system of measurements based on the meter, kilogram, and degrees Celsius. The metric system is internationally recognized.
micrometer A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are either digital or use a vernier scale.
nickel A silver-white metal that is easily manipulated. Nickel is often used in alloys.
Nuclear Regulatory Commission NRC. A U.S. government agency that exists in order to ensure that nuclear technology is handled safely. The Nuclear Regulatory Commission dictates standards for welds used in facilities that handle nuclear material.
outside diameter OD. The exterior diameter of a spherical or cylindrical object. Outside diameter is an important measurement not only in welding but in general machining.
oxyfuel welding OFW. A fusion welding process that uses a flame produced by a mixture of oxygen and another fuel gas, usually acetylene. Oxyfuel welding is sometimes called oxyacetylene welding or gas welding.
pipes A long, hollow cylinder. Pipes can be composed of plastic, metal, fiberglass, or other materials and are useful in a wide variety of industrial applications.
plastic A synthetic polymer characterized by light weight, good formability, and high corrosion resistance. Plastic is typically joined using specialized processes, though it can also be welded by laser beam welding.
plug weld A type of weld made by joining one metal part with a circular hole to another metal part positioned directly beneath it. Multiple plug welds are usually required to form a strong joint.
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.
precision The dispersion of measurements or fineness of readings. Precise readings show very little variation.
preheating The application of heat to a base metal immediately before welding. Preheating helps reduce hardness in the metal.
protractor A tool that can be used to measure or create an angle. Welding protractors generally consist of two movable arms and are fastened to the workpiece with clamps or magnets.
resistance welding A group of welding processes 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.
right angle An angle which is exactly 90 degrees. The two sides of every right angle are always perpendicular.
right triangle A triangle containing exactly one 90° angle. A fillet weld roughly resembles a right triangle from the side.
robot welders Robots used to perform a welding process. Robot welders are common in automobile manufacturing.
seam welds A type of continuous weld made between or upon overlapping metal parts. Seam welds are often used for tanks or pipes.
sensitivity The minimum input required to produce a noticeable output on a measuring device. Instruments with greater sensitivity provide more accurate readings.
shielded metal arc welding SMAW. An arc welding process that uses a flux-coated consumable electrode. Shielded metal arc welding is also referred to as stick welding.
shielding gas A gas that surrounds and protects melted metal from oxidation. Shielding gas is used to protect the weld puddle from atmospheric contamination in some welding processes.
slot weld A type of weld made by joining one metal part with an elongated hole to another metal part positioned directly beneath it. Slot welds are stronger than plug welds but require more filler metal.
spindle A rotating component on a micrometer that advances toward the anvil to make contact with and measure the part. A spindle is a common component of all micrometers.
spot welds A type of small weld made between or upon overlapping metal parts. Multiple spot welds are generally required to join parts.
square beams A square support beam that is usually hollow. Square beams are also called hollow structural section beams.
stainless steel A type of steel that contains more than 11% chromium and exhibits excellent hardness and corrosion resistance. Stainless steel can be welded with many different welding processes.
steel rule A simple, relatively imprecise measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Steel rules are also called machinist's rules.
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.
thimble A ring or cylinder that fits around the spindle of a micrometer. The thimble is turned by hand to advance the spindle.
throat The shortest distance between the weld root and a line drawn between the weld toes. The throat helps determine a weld's size and strength.
titanium A silvery-white metal that has high strength-to-weight ratio and corrosion resistance. Titanium is more difficult to weld than iron or steel.
T-joint A joint formed when the edge of one part is welded to the surface of another part in the shape of a T. T-joints are a very common joint type.
tolerances An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.
torsion A force that twists a part. Torsion can weaken or break a workpiece.
travel speed The speed at which the welder moves the electrode along the joint to make a weld. Travel speed determines the size of the weld bead.
ultrasonic welding An industrial technique that uses acoustic, high-frequency vibrations to permanently bond together two separate components. Ultrasonic welding is used by some sheet lamination machines.
undercut An undesired gap along the edge of a finished weld. Undercut is unsightly but does not necessarily indicate a bad weld.
vernier scale A type of scale consisting of two opposing line markings with different divisions. A vernier scale is generally included on both manual calipers and micrometers.
visual weld acceptance criteria gage V-WAC gage. A weld gage designed to measure fillet welds. The visual weld acceptance criteria gage ensures that welds meet standards established by the United States Nuclear Regulatory Commission.
weld defects A weld discontinuity that can cause a weld to fail. Weld defects include porosity, incomplete fusion, weld cracking, and undercut.
weld gage A device designed to measure different parts of a weld. Weld gages are available in many different varieties.
weld types Different kinds of welds used for different welding applications. Weld types generally determine the joint type to be used.
welder The person who performs a weld. Some resource materials may also refer to the welding power source as a welder.
welding A joining process that uses heat, friction, or a combination of methods to fuse two materials together permanently. Welding is used in a variety of industries from auto manufacturing to aerospace engineering.
welding procedure specification WPS. A written document that contains all necessary and specific information regarding a welding project. Welding procedure specifications must be approved and tested before welding can begin.
workpieces The parts that are being welded. In arc welding, the current which creates the arc runs through the workpieces.
wring To bring two flat surfaces together so that they adhere. Wringing gage blocks together in various combinations forms a variety of lengths.
zinc A bluish-white metal that is corrosion resistant and has a relatively low melting point. Aluminum-zinc alloys generally have poor weldability.