Welding

Introduction to Welding Processes 151

Introduction to Welding Processes provides a comprehensive overview of the most commonly used welding processes, including shielded metal arc welding, gas metal arc welding, flux-cored arc welding, gas tungsten arc welding, and oxyfuel welding. It also covers laser welding and other emerging welding practices. In addition, it discusses the many variables necessary to perform any welding process, as well as how to read a welding procedure specification (WPS).

After taking this class, users will have a foundational understanding of several common welding processes and the variables they rely on. This information prepares users to select appropriate weld processes and variables for different applications.

  • Difficulty Beginner

  • Format Online

  • Number of Lessons 18

  • Language English

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Course Outline
  • Welding Processes
  • Shielded Metal Arc Welding
  • Gas Metal Arc Welding
  • Flux-Cored Arc Welding
  • Gas Tungsten Arc Welding
  • Arc Welding Review
  • Oxyfuel Welding
  • Other Welding Processes
  • Laser Welding
  • Other Emerging Welding Processes
  • The Impact of Emerging Welding Processes
  • Welding Processes Review
  • Essential Welding Variables
  • Workpiece Materials
  • Nonessential Welding Variables
  • Welding Procedure Specifications
  • Reading a Welding Procedure Specification
  • Final Review
Objectives
  • Describe welding processes.
  • Describe shielded metal arc welding.
  • Describe gas metal arc welding.
  • Describe flux-cored arc welding.
  • Describe gas tungsten arc welding.
  • Describe oxyfuel processes.
  • Describe other common welding processes.
  • Describe laser beam welding.
  • Describe other emerging welding processes.
  • Describe the impact of emerging welding processes.
  • Identify essential welding variables.
  • Identify workpiece materials suitable for different welding processes.
  • Identify nonessential welding variables.
  • Describe welding procedure specifications.
  • Identify sections of a welding procedure specification.
Glossary
vocabulary term
Definition

acetylene

A colorless, flammable gas often mixed with oxygen to fuel oxyfuel torches. Acetylene is required for oxyfuel welding.

active

A substance that reacts with other elements. GMAW uses both active and inert gas as shielding.

additive manufacturing

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.

alternating current

AC. Current that reverses direction at regularly recurring intervals of time. In the United States, alternating current reverses 60 times per second, or 60 hertz.

aluminum

A nonferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.

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.

amperage

The amount of current flowing in a circuit. Amperage is measured in amperes (A), or amps.

amperes

A. A unit of measurement that indicates the amount of current flowing in a circuit. Amperes are usually referred to as amps.

arc

The area in which electricity jumps from the electrode to the workpiece. The arc generates heat that melts the base metals and filler metal during welding.

arc length

The distance that electricity must travel from the tip of the electrode to the workpiece. Maintaining proper arc length is important for preventing weld defects.

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 welders

A machine or system that performs welding processes without human intervention. Automated welders may use robotics or computer numerical control (CNC).

automation

The use of self-regulated equipment, processes, or systems that meet manufacturing requirements with limited human intervention. Automation can be achieved with robots or computer numerical control (CNC) machines.

axial spray transfer

A type of GMAW metal transfer in which the metal at the end of the electrode melts into small, fine droplets that transfer to the weld puddle. Axial spray transfer creates a stable arc and little spatter.

base metals

Metals that are welded together to form a joint. The base metal and its properties influence the weld type, welding process, and electrode.

brazing

A joining process in which a filler metal is melted at a temperature above 840°F (450°C) but below the melting point of the base metals to form a joint. Brazing differs from welding because only the filler metal is melted.

carbon

A common nonmetallic element found in all types of steel. Carbon is added to the filler metal in an SMAW electrode to help strengthen the joint.

carbon steel

A common metal that is an alloy of iron and carbon. Carbon steel is one of the most commonly welded metals.

cast iron

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.

ceramics

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.

Certified Welding Inspector

CWI. A person certified by the American Welding Society (AWS) to inspect welds and interpret AWS and other codes. Certified Welding Inspectors must be able to identify possible welding discontinuities and defects, use measuring instruments, and monitor any repairs.

coils

A bundle of conducting wire that is wrapped continuously around a magnetic core. Coils create a magnetic field when current passes through them.

consumable electrodes

An electrode that conducts electricity to the arc but also melts into the weld as filler metal. Some consumable electrodes also provide shielding that protects the arc and weld puddle.

copper

A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. GMAW electrodes have a copper coating.

current

The flow of electricity through a circuit. Current is measured in amperes (A), or amps, and controls the heat of the arc.

cutting

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.

deoxidizers

A material that removes oxygen from the molten weld puddle. Deoxidizers prevent oxygen from ruining a weld bead.

direct current

DC. Current that flows in one continuous direction. Direct current is required for several common welding processes.

double-groove welds

A weld that consists of two groove welds on either side of a joint. Double-groove welds are strong and often require less filler metal than single-groove welds.

dual-beam laser welding

A type of laser beam welding (LBW) that uses two lasers instead of one to melt materials together. Dual-beam laser welding is cleaner and produces fewer weld defects than conventional LBW.

electrical resistance

The force that opposes the flow of 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. The flow of electrons causes the flow of electricity.

electron beam welding

EBW. A welding 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.

electron gun

An electrical device that emits a narrow stream of electrons. Electron guns are used to provide the electron beam in electron beam welding (EBW).

Engineer of Record

EOR. An engineer who is responsible for verifying that a WPS complies with the applicable codes and qualifying the WPS. The Engineer of Record must have a thorough knowledge of welding codes and processes.

fast-fill electrodes

An SMAW electrode designed to lay down a large amount of weld metal in a small amount of time. Fast-fill electrodes are useful for creating wide, strong welds.

fast-freeze electrodes

An SMAW electrode designed to lay down a weld bead that solidifies quickly. Fast-freeze electrodes are useful for vertical or overhead welding positions.

FCAW

Flux-cored arc welding. A semi-automatic or automatic arc welding process that uses a continuously fed consumable electrode with an inner core of flux. FCAW includes self-shielded flux-cored arc welding (FCAW-S) and gas-shielded flux-cored arc welding (FCAW-G).

ferrous metals

A metal that contains iron. Ferrous metals are the most common type of welded materials.

filler metal

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.

fill-freeze electrodes

An SMAW electrode that has both fast-fill and fast-freeze characteristics. Fill-freeze electrodes fill a joint quickly and solidify quickly.

flux

A nonmetallic material used to protect the weld puddle and arc from atmospheric contamination. Flux can be used to coat an electrode, as in shielded metal arc welding (SMAW), or contained within the core of an electrode, as in flux-cored arc welding (FCAW).

flux-cored arc welding

FCAW. A semi-automatic or automatic arc welding process that uses a continuously fed consumable electrode with an inner core of flux. Flux-cored arc welding includes self-shielded flux-cored arc welding (FCAW-S) and gas-shielded flux-cored arc welding (FCAW-G).

friction

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.

friction stir spot welding

FSSW. A type of friction stir welding (FSW) that is used to make spot welds. Friction stir spot welding inserts a rotating tool into two metals to blend the workpieces together.

friction stir welding

FSW. A welding process that 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 that creates strong welds without the use of filler metal.

FSW

Friction stir welding. A welding process that uses a rotating tool to soften and blend the edges of two pieces of metal to create a weld. FSW is a versatile process that creates strong welds without the use of filler metal.

fuel gases

A gas that can store potential energy and release it as thermal energy or that can be used to perform work. Fuel gases are mixed with oxygen to perform oxyfuel processes such as welding and cutting.

fumes

Potentially hazardous gases and particulate matter generated at the electric arc during welding processes. Fumes include particulates from the electrode, shielding gas, base metal, and any coatings included in a process.

gas cylinder

A metal container that stores gases. Gas cylinders are built specifically for each gas and have different properties depending on the gas.

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).

gas-shielded FCAW

FCAW-G. A flux-cored arc welding process that uses a flux-filled tubular wire electrode and an external shielding gas. Gas-shielded FCAW provides double shielding.

globular transfer

A type of GMAW metal transfer in which the metal at the end of the electrode melts into a large ball and drops to the workpiece. Globular transfer deposits large amounts of metal into the weld puddle.

GMAW

Gas metal arc welding. An arc welding process in which a bare wire electrode and shielding gas are fed to the weld through a welding gun. GMAW 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.

GTAW

Gas tungsten arc welding. A precise arc welding process that uses a nonconsumable tungsten electrode and inert shielding gas. GTAW is also known as tungsten inert gas welding (TIG welding).

hybrid laser arc welding

HLAW. A welding process that 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 processes

A welding process that uses a combination of two different welding processes at the same time. Hybrid welding processes usually offer improvements over their component processes.

hybridization

The combination of two concepts or practices to form a new one. Hybrid laser arc welding is an example of hybridization.

hydrogen

A colorless, odorless gas that is the most abundant element on the planet. Hydrogen is sometimes mixed with oxygen to make oxyfuel.

inert

A substance that is not chemically reactive. Many shielding gases are inert.

iron

A common silver-white metal found in nature as ore. Iron is alloyed with carbon to make steel.

joint

The meeting point of two materials that are fused together. Welding creates a permanent joint.

joint type

The configuration in which two or more workpieces are joined. There are five basic welding joint types: butt, corner, edge, lap, and T-joints.

keyhole

A cavity formed in the surface of a workpiece during welding. The keyhole fills with molten metal from the workpiece or electrode to create a weld.

laser beam welding

LBW. A welding process that uses a laser to create a weld. Laser beam welding makes deep, strong, clean welds, but it is expensive and requires either automation or highly trained welders.

laser beams

An intense beam of coherent, collimated, monochromatic light that can be precisely aimed and controlled. Laser beams can be used to weld or cut weld materials.

lasers

A device that generates an intense beam of light that can be precisely aimed and controlled. Lasers produce heat that can be used to create precise, strong welds.

LBW

Laser beam welding. A welding process that 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 has a very low melting point.

low-alloy steel

A steel that contains small amounts of intentionally added materials that change the properties of the metal. Low-alloy steels commonly include manganese, molybdenum, and nickel.

low-hydrogen electrodes

An SMAW electrode used to weld metals that are susceptible to cracking. Low-hydrogen electrodes are ideal for awkward welding positions.

magnesium

A grayish white, extremely light metal that is brittle and has poor wear resistance. Magnesium can be combined with aluminum to create an alloy with excellent weldability.

manganese

A hard, brittle, gray-white metal often added to electrodes. Manganese acts as a deoxidizer and increases strength and hardness in the weld.

metal transfer

The deposition of filler metal into a weld. Metal transfer methods differ depending on the welding process.

metallurgical properties

The measurable characteristics that describe a completed weld's qualities and capabilities. Metallurgical properties include a variety of physical and mechanical properties, such as strength.

mobile robot

A robot that is able to move through space and perform various industrial tasks. Mobile robots include wheeled robots, legged robots, and flying robots.

natural gas

A naturally occurring, flammable fossil fuel composed mainly of methane. Natural gas is sometimes used in oxyfuel cutting.

neutral flame

A flame with a balanced proportion of oxygen and acetylene. A neutral flame is preferable for oxyfuel welding.

nickel

A hard silver-white metal that is easily manipulated. Nickel is often used in alloys.

nonconsumable electrode

An electrode that only conducts electricity to the arc and does not melt from the heat of the arc generated during welding. GTAW uses a nonconsumable tungsten electrode.

nonferrous metals

A metal that does not contain a significant amount of iron. Common nonferrous metals include aluminum, titanium, copper, and nickel.

oxidize

To chemically combine and react with oxygen. Oxyfuel cutting uses oxygen to oxidize and corrode metal.

oxyacetylene welding

A fusion welding process that uses a flame produced by a mixture of oxygen and acetylene gas. Oxyacetylene welding is also known as oxyfuel welding (OFW).

oxyfuel welding

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.

oxygen

A colorless, odorless, tasteless gas that naturally exists in the atmosphere. Oxygen is the primary gas used in oxyfuel welding.

plastics

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.

polarity

Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current flows.

prequalified WPS

pWPS. A welding procedure specification that is known to create successful welds because it adheres to specific standards published by the American Welding Society (AWS). Prequalified WPSs do not have to be tested.

pressure

A mechanical force exerted on an object. Pressure can be used to join materials during welding.

procedure qualification record

PQR. A record of the testing done on a weld. A procedure qualification record is filed with its companion welding procedure specification (WPS).

propane

A colorless, flammable gas created during petroleum refinement processes that can be used in oxyfuel cutting. Propane is similar to propylene but outputs lower heat as it burns.

propylene

A colorless, flammable gas created during petroleum refinement processes that can be used in oxyfuel cutting. Propylene is similar to propane but outputs higher heat as it burns.

pulling

Moving an electrode that is angled ahead of the weld puddle along the workpiece in the backhand direction to deposit weld metal into a joint. Pulling can be performed at different pull angles for joints with different requirements.

pulse spray transfer

GMAW-P. A type of GMAW metal transfer that alternates rapidly between two different current levels. During pulse spray transfer, one droplet of metal forms on the end of the electrode at a time.

pulsed gas tungsten arc welding

GTAW-P. A variation of gas tungsten arc welding (GTAW) that alternates rapidly between two different current levels. Pulsed gas tungsten arc welding uses a higher peak current and a lower background current.

pushing

Moving an electrode that is angled behind the weld puddle along the workpiece in the forehand direction to deposit weld metal into a joint. Pushing can be performed at different push angles for joints with different requirements.

resistance welding

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.

robot

A mechanized device that can be programmed to automatically manipulate materials, parts, tools, and other devices to perform a variety of tasks. Robots often perform complicated and repetitive tasks.

robotic welding

A type of automated welding that uses robots to move the welding gun or torch. Robotic welding is a specialized form of soft automation often used in automobile production.

seam welds

A continuous weld made on or between overlapping metal parts. Seam welds are often used for tanks or pipes.

self-shielded FCAW

FCAW-S. A flux-cored arc welding process that relies on the flux within a tubular wire electrode to provide shielding for the weld area. Self-shielded FCAW does not require an external shielding gas.

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.

shielding

A gas that protects the weld puddle and arc from reacting negatively with the atmosphere. Shielding can be provided by an external supply of gas or by a type of flux materials.

shielding gas

A gas that protects the weld puddle and arc from reacting with the atmosphere. Shielding gas is used in GMAW, GTAW, and gas-shielded FCAW.

short circuit transfer

GMAW-S. A type of GMAW metal transfer in which the electrode touches the workpiece to produce a short circuit and high current that causes a violent transfer of metal. Short circuit transfer uses low amperages and small electrodes.

slag

Cooled flux that forms on top of the weld bead. Slag protects the cooling metal and is chipped off after the weld puddle cools.

SMAW

Shielded metal arc welding. An arc welding process that uses a flux-coated rod as a consumable electrode. SMAW is also called stick welding or manual welding.

soldering

A joining process in which a filler metal is melted at temperatures below 840°F (450°C) to form a joint between two base metals. Soldering is often used for delicate projects, such as jewelry and electronics.

sonotrode

A device that directly applies ultrasonic vibrations to the surface of a material. A sonotrode makes up part of the ultrasonic stack used for ultrasonic welding.

spatter

Liquid metal droplets expelled from the welding process. Spatter can leave undesirable dots of metal on a workpiece surface.

spot welds

A small welded area on or between overlapping metal parts. Multiple spot welds are generally required to join parts.

stainless steel

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.

standard WPS

SWPS. A welding procedure specification that is written by the organization that will complete the weld. Standard WPSs must be written and qualified if no applicable prequalified WPSs can be found.

steel

An alloy of iron and carbon containing less than 2.0% carbon. Steels often contain other elements to enhance various aspects of the metal.

stick welding

An arc welding process that uses a flux-coated rod as a consumable electrode. Stick welding is also known as shielded metal arc welding (SMAW) or manual welding.

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.

testing

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.

titanium

A silver-white metal that has high strength-to-weight ratio and corrosion resistance. Titanium is more difficult to weld than iron or steel.

travel speed

The rate at which the welder moves the electrode along the seam to make a weld. Travel speed determines the size of the weld bead.

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 for GTAW.

ultrasonic stack

A device used for ultrasonic welding that consists of a transducer, a booster, and a sonotrode. Ultrasonic stacks convert electrical signals into mechanical vibrations.

ultrasonic welding

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.

undercut

An undesired gap left along the edge of a finished weld. Undercut is unsightly but does not necessarily indicate a bad weld.

vacuum chamber

A sealed enclosure from which all air and gas is removed. Vacuum chambers are used in electron beam welding (EBW) to prevent the electron beam from dissipating.

voltage

The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).

weaving

Moving the electrode in a back-and-forth motion to deposit weld metal into a joint. Weaving creates an even layer of weld metal and produces wide, strong welds.

weld bead

The end product of a welded joint. Weld beads are formed using a variety of techniques.

weld defects

An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A weld defect is an unacceptable discontinuity.

weld metal

The portion of a weld that has been melted during welding. Weld metal may be composed either of base metal or a combination of base metal and filler metal.

weld passes

One progression of welding along a joint. Each weld pass creates a weld bead.

weld puddle

The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.

weld type

The shape of the weld used to join workpieces. There are six main weld types: fillet, groove, plug, slot, spot, and seam welds.

welding

A joining process that permanently bonds two separate components together. Welding uses heat, with or without pressure or friction, or a combination of methods to make a new part.

welding code

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.

welding gun

A welding instrument that conducts electricity, guides the electrode, and, in some cases, releases shielding gas. Welding guns are used in some automatic and semi-automatic welding processes.

welding position

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 a welding project. A welding procedure specification cannot be written or approved until the procedures it describes are tested.

welding torch

The instrument used to generate the arc or flame for welding. The welding torch may hold an electrode or release gases that produce a flame.

whipping

Moving the electrode around in a circle and withdrawing it slightly to deposit weld metal into a joint. Whipping is typically used to form stringer beads.

wind-blocking equipment

A tent, shroud, or other structure intended to prevent shielding gas from being dispersed by wind during the welding process. Wind-blocking equipment is necessary in order for some welding processes to be used outdoors.

wire feeder

A small device that feeds a supply of consumable electrode wire to a welding gun. Wire feeders are either built inside or set beside the power source.

workpieces

A part undergoing some type of manufacturing process. The workpiece may be subject to cutting, welding, forming, or other operations.

WPS

Welding procedure specification. A written document that contains all the necessary and specific information for a welding project. A WPS cannot be written or approved until the procedures it describes are tested.

zinc

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.