Introduction to Welding Processes 151

“Introduction to Welding Processes” provides a comprehensive overview of the most commonly used welding processes, including oxyfuel welding, gas metal arc welding, gas tungsten arc welding, flux-cored arc welding, and shielded metal arc welding. In addition, it continues to develop students’ understanding of measurements in welding and covers the Welding Procedure Specification from writing through testing and finally use.

This class continues to develop the general understanding of welding begun in “Introduction to Welding” with a more comprehensive overview of each of the most common welding processes. It covers welding variables and presents an in-depth discussion of welding discontinuities that is continued in “Overview of Weld Defects.”

Class Details

Class Name:
Introduction to Welding Processes 151
Description:
“Introduction to Welding Processes” provides a comprehensive overview of the most commonly used welding processes, including oxyfuel welding, gas metal arc welding, gas tungsten arc welding, flux-cored arc welding, and shielded metal arc welding. In addition, it continues to develop students’ understanding of measurements in welding and covers the Welding Procedure Specification from writing through testing and finally use.

This class continues to develop the general understanding of welding begun in “Introduction to Welding” with a more comprehensive overview of each of the most common welding processes. It covers welding variables and presents an in-depth discussion of welding discontinuities that is continued in “Overview of Weld Defects.”
Version:
2.0
Difficulty:
Beginner
Number of Lessons:
19
Related 1.0 Classes:
Arc Welding Processes 120, Overview of Weld Types 130

Class Outline

  • Welding as a Process
  • Oxyfuel Cutting and Welding
  • SMAW
  • GMAW
  • GTAW
  • FCAW
  • Welding Theory Review
  • Electrode Types
  • Essential Welding Variables
  • SCLAMPS
  • Fit-Up and Joint Preparation
  • Measuring Joints and Weld Size
  • Discontinuities, Testing, and Visual Inspection
  • Welding Variables Review
  • Welding Procedure Specifications
  • Welding According to a Welding Procedure Specification
  • Interactive: Welding According to a Welding Procedure Specification
  • Writing a Welding Procedure Specification
  • Final Review

Objectives

  • Describe the welding process.
  • Define oxyfuel processes.
  • Define SMAW.
  • Define GMAW.
  • Define GTAW.
  • Define FCAW.
  • Explain the different types of electrodes.
  • Explain essential welding variables.
  • Describe SCLAMPS.
  • Explain fit-up and joint preparation.
  • Describe tools for measuring joints and weld size.
  • Explain discontinuities and how they can be detected.
  • Describe a welding procedure specification.
  • Explain how to weld according to a welding procedure specification.
  • Explain how to write a welding procedure specification.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
AC Alternating current. A current which reverses direction at regularly recurring intervals of time. Alternating current is often used with welding processes which require external shielding gas.
acetylene A colorless, flammable gas. Acetylene is the most commonly used gas for mixing with oxygen to fuel oxyfuel torches.
acid etch testing A test used to isolate small defects or areas of soft metal in a complete weld. Typically, a weld is cut into a cross-section and an acidic material is rubbed onto the exposed interior of the weld, causing small defects to become visible.
adhesive fastening A process that binds materials together using a non-metallic material. Paste, glue, and tape are examples of common adhesives.
alternating current AC. A current which reverses direction at regularly recurring intervals of time. AC is often used with welding processes which require external shielding gas.
alternating current AC. A current which reverses direction at regularly recurring intervals of time. Alternating current is often used with welding processes which require external shielding gas.
American Welding Society AWS. A professional organization that supports the welding industry and promotes welding and related processes. The AWS provides industry-standard code and certification procedures.
amperage A measurement that indicates the amount of current flowing in a circuit, which is measured in amperes. More amperage usually creates a deeper weld pool.
amperes 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 heat generated by the arc melts the base metals and filler metal during welding.
AWS American Welding Society. A professional organization that supports the welding industry and promotes welding and related processes. The AWS provides industry-standard code and certification procedures.
base metals The pieces of metal being welded together. Base metal influences weld type and welding process.
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.
butane A type of liquid fuel used in gas-powered soldering torches. Butane is sometimes blended with gasoline or used as lighter fluid.
calipers A handheld measuring instrument with at least one set of jaws. Calipers include indicators on the top of the instrument that expand to measure internal diameters.
carbon A common, nonmetallic element found in all types of steel. SMAW electrodes always contain at least a small amount of carbon.
certified welding engineer CWE. An engineer who is certified by the American Welding Society to inspect finished welds and to direct welding operations. Certified welding engineers must have a thorough knowledge of welding codes and processes.
Charpy v-notch testing A test in which a small slot is cut into the surface of the material and the material is then broken across that slot using a weighted pendulum. Charpy testing allows inspectors to not only measure the strength of a weld but also to examine it for internal defects.
consumable electrode An electrode that becomes filler metal during the process of welding. Consumable electrodes are used in many welding processes.
consumable electrode An electrode that conducts electricity to the arc but also melts into the weld as a filler metal. Many consumable electrodes also provide shielding that protects the arc and weld puddle.
contact tip The device located inside the welding gun that conducts electricity to the electrode and directs the wire electrode into the weld joint. Contact tips are usually made of copper.
copper A ductile, thermally and electrically conductive metal. GMAW electrodes have a copper coating.
current The flow of electricity through a circuit. Current is measured in amperes.
cutting The act of separating a workpiece into two or more pieces. Methods of cutting include sawing, oxyfuel cutting, and plasma cutting.
cutting The act of separating a workpiece into two or more pieces. Oxyfuel cutting uses an additional high-pressure stream of oxygen to cut metal.
DC Direct current. A current formed when electrons flow in one continuous direction. DC current can be used in most welding processes.
deoxidizers A material that removes oxygen from the molten weld puddle and arc. Deoxidizers prevent oxygen from ruining a weld bead.
destructive testing Forms of testing that damage or destroy the workpiece being tested. Destructive testing is ideal for determining the strength of a weld.
direct current DC. A current formed when electrons flow in one continuous direction. Direct current can be used in most welding methods.
direct current DC. A current formed when electrons flow in one continuous direction. Direct current can be used in most welding processes.
electromagnetic testing The practice of using an electric current or magnetic field to determine if a weld is defective. Internal defects in a weld will return an electromagnetic response.
essential variables A welding variable which is necessary for the successful completion of the finished weld. Examples of essential variables are joint type and weld type.
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 which solidifies quickly. Fast-freeze electrodes are useful for vertical or overhead welding positions.
FCAW Flux-cored arc welding. An arc welding process that uses a continuously fed consumable electrode with a flux core wrapped within an outer metal sheath. FCAW can be a semi-automatic or automatic process.
ferrous metals Metals that contain iron. Ferrous metals are usually slightly easier to weld than nonferrous metals.
filler metal A type of metal sometimes added to the joint in welding. Filler metal adds to the strength and mass of the welded joint.
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.
fillet weld gages A gage used to measure fillet welds. Fillet weld gages are designed only to determine whether or not a fillet weld is within a certain specification and cannot make precise measurements.
fillet welds A type of weld that is triangular in shape and joins two surfaces at right angles to one another. Fillet welds are the most common types of welds.
fill-freeze electrodes A SMAW electrode that has both fast-fill and fast-freeze characteristics. Fill-freeze electrodes fill a joint quickly and solidify quickly.
fit-up A measure of the closeness between two parts that are to be welded. Good fit-up will help to ensure a quality weld.
flux A nonmetallic material used to protect the weld puddle and solid metal from atmospheric contamination. Almost all welding processes use either flux or shielding gas to shield the weld.
flux-cored arc welding FCAW. An arc welding process that uses a continuously fed consumable electrode with a flux core wrapped within an outer metal sheath. Flux-cored arc welding can be a semi-automatic or automatic process.
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 bare wire electrode and shielding gas are fed to the weld through a welding gun. GMAW is also referred to as MIG welding.
gas tungsten arc welding GTAW. A very precise arc welding process that uses a nonconsumable tungsten electrode. GTAW is also referred to as TIG welding.
gas-shielded FCAW FCAW-G. A flux-cored arc welding process that uses a tubular wire electrode filled with flux and an external shielding gas. Gas-shielded FCAW provides double shielding protection.
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 referred to as MIG welding.
grinding 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.
groove welds A type of weld that consists of weld metal contained within an opening between two part surfaces. Groove welds are used on all joints except lap joints.
GTAW Gas tungsten arc welding. A very precise arc welding process that uses a nonconsumable tungsten electrode. GTAW is also referred to as TIG welding.
hardness testing Standardized experiments designed to determine how a material responds to external forces that attempt to scratch, penetrate, or indent the material. Hardness testing is widely used both in welding and in general machining.
hydrogen A colorless, odorless gas, and the most abundant element on the planet. Hydrogen is sometimes mixed with oxygen to make oxyfuel.
inert A type of gas that is inactive and is not chemically reactive. Many shielding gases are inert.
joint The meeting point of two materials that are fused together. Welding creates a permanent joint.
joint The meeting point of two materials that are joined together. Welding creates a permanent joint.
joint design The design of a given joint. Different joint designs can require different weld types or welding processes.
joint position The position in which a joint is to be welded. Joint position can influence electrode or filler metal choice.
joint preparation A variety of processes that prepare base metals before welding. Joint preparation can involve preheating, cutting, or other preparations.
length The distance from the electrode to the workpiece in an arc welding application. Not maintaining proper arc length can cause several different weld defects.
low-hydrogen electrodes A SMAW, GMAW, GTAW, or FCAW electrode used to weld metals that are susceptible to cracking. Low-hydrogen electrodes are useful in a variety of different welding situations.
machining The process of removing material to form an object. Traditional machining methods, such as milling, turning, and drilling, remove metal using cutting tools.
magnetic particle inspection A method of inspection in which the part to be inspected is magnetized and then covered with tiny iron oxide particles. The particles accumulate in any cracks or seams, which can then be seen.
manganese A hard, brittle, gray-white metal. Manganese is often added to SMAW electrodes to act as a deoxidizer and increase strength and hardness in the weld.
mechanical fastening A process that joins two materials using a clamping force. Examples of mechanical fasteners include screws, bolts, and nails.
metal transfer methods The way in which filler metal is deposited into a weld. Different welding processes use different metal transfer methods.
metallurgical properties The measurable properties of a completed weld. Metallurgical properties are affected by a weld's essential variables.
micrometers A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.
motion The action by which a weld bead is created. Motion can describe pushing, pulling, weaving, or whipping.
natural gas A naturally occurring fossil fuel composed mainly of methane. Natural gas is sometimes used in oxyfuel cutting and welding.
neutral flame A flame with a balanced proportion of oxygen and acetylene. A neutral flame is preferable for oxyfuel welding.
nonconsumable electrode An electrode which is not used up during the process of welding. GTAW uses a nonconsumable electrode made from tungsten.
nondestructive testing Forms of testing that do not destroy the workpiece or weld being tested. Nondestructive testing is ideal for large or expensive workpieces.
nonessential variables Welding variables which do not affect the metallurgical properties of a weld but still influence weld quality. The acronym SCLAMPS describes several important nonessential variables.
nonferrous metals A metal that does not contain a significant amount of iron. The most commonly used nonferrous metals are aluminum and copper.
oxyacetylene welding Oxyfuel welding which uses a mixture of oxygen and acetylene to weld. Oxyacetylene welding is the most common type of oxyfuel welding.
oxyfuel welding A fusion welding process that uses a flame produced by gas containing oxygen and a gas fuel. Oxyfuel can also be used for cutting.
oxygen A colorless, odorless, tasteless gas that naturally exists in the atmosphere. Oxygen is the primary gas used in oxyfuel welding.
passes A single layer of weld metal deposited into or onto the joint. Multiple passes are sometimes required to create a sufficiently strong weld.
polarity Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current tends to flow.
powder coating A coating technology in which the coating is manufactured by blending the binder, additives, and other materials through a heated extrusion process. SMAW electrodes are powder coated with flux materials.
prequalified WPS A welding procedure specification that is known to create successful welds because it adheres to specific standards published by the American Welding Society. Prequalified WPSs do not have to be tested.
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.
propane A flammable gas that can be used in oxyfuel cutting. Propane is also known as propylene.
propylene A flammable gas that can be used in oxyfuel cutting. Propylene is also known as propane.
pulled Moving the electrode along the workpiece away from the direction of welding. Different joint requirements will often require different pull angles.
pulsed gas tungsten arc welding GTAW-P. Pulsed Gas Tungsten Arc Welding is similar to conventional GTAW except that the current is delivered in pulses. GTAW-P allows the weld to cool between pulses.
pushed Moving the electrode along the workpiece in the direction of welding. Different joint requirements will often require different push angles.
pushed Moving the electrode along the workpiece in the direction of welding. Pushing may occur at different angles depending on the joint requirements.
rules A simple measuring instrument consisting of a long, thin metal strip with a marked scale of unit divisions. Rules are often called steel or machinist's rules.
SCLAMPS An acronym which stands for shielding, current, length, amperage, motion, polarity, and speed. Each of the SCLAMPS factors is crucial in determining the quality of the final weld.
SCLAMPS An acronym which stands for shielding, current, length, amperage, motion, polarity, and speed. Each of these factors is crucial in determining the quality of the final weld.
self-shielded FCAW FCAW-S. A flux-cored arc welding process that uses a tubular wire electrode filled with flux. Self-shielded FCAW is a portable and efficient process.
shielded metal arc welding SMAW. An arc welding process that uses a flux-coated consumable rod electrode. SMAW is also referred to as stick welding.
shielding A layer of inert or slightly reactive gas that protects the weld puddle and arc from atmospheric contamination. Shielding gas is either used externally or generated from flux contained in the electrode.
shielding gas A gas that surrounds and protects melted metal from oxidation during welding. Shielding gas is used in GMAW, GTAW, and gas-shielded FCAW.
slag Cooled flux that forms on top of the weld bead. Slag protects the cooling metal and, after the weld puddle cools, is chipped off.
SMAW Shielded metal arc welding. An arc welding process that uses a flux-coated consumable rod electrode. SMAW is also referred to as stick 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.
spatter Liquid metal droplets expelled from the weld puddle during the welding process. Spatter can leave undesirable dots of metal on a workpiece surface.
speed The rate at which the welder moves the electrode along the joint to make a weld. Travel speed determines the size of the weld bead.
spot welds A small welded area between or upon overlapping metal parts. Multiple spot welds are generally required to join parts.
stick welding An arc welding process that uses a flux-coated consumable rod electrode. Stick welding is more commonly known as shielded metal arc welding.
tensile strength A material's ability to resist forces that attempt to pull it apart or stretch it. The tensile strength of most metal allows it to deform, bend, or stretch before it breaks, while materials with less tensile strength will break sharply and suddenly.
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.
transverse tensile testing A test wherein a machine is used to attempt to pull a welded joint apart. If the base metal breaks before the weld does, the weld is considered good.
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.
tungsten A gray metal that is very strong at elevated temperatures. Tungsten is used to make the nonconsumable electrodes used for GTAW welding.
undercut A gap left in a finished weld that should have been filled with weld metal. Undercut is unsightly but does not necessarily indicate a bad weld.
visual inspection A visual assessment of surface defects. Visual inspection is one of the most commonly used nondestructive inspection methods for composites.
voltage A measure of electrical pressure or potential known as electromotive force. Voltage is measured in volts.
weaved Movement of the electrode in a back and forth motion to deposit weld metal into a joint. Weaving is used to make a wide, strong weld.
weld bead The line of filler metal created by welding. An even weld bead with good penetration will create a strong weld.
weld defect A discontinuity that causes a weld to fail. Weld defects include porosity, incomplete fusion, weld cracking, and undercut.
weld discontinuities An irregularity in the specified and expected composition of a weld. A discontinuity is not always a defect.
weld puddle The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint.
welding A joining process that uses heat, pressure, 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 gun An instrument used in some automatic and semi-automatic welding processes. The welding gun conducts electricity, guides the electrode, and in some cases releases shielding gas.
welding procedure specification WPS. A written document that contains all necessary and specific information regarding the application of a welding project. A welding procedure specification cannot be written or approved until the procedures it describes are tested.
welding process The procedure by which a weld is completed. Welding processes include SMAW, FCAW, GMAW, and GTAW.
welding process The process by which a weld is completed. Welding processes include SMAW, FCAW, GMAW, and GTAW.
welding torch A tool used to generate the flame or arc for welding. In oxyfuel welding, air is pumped into the torch and converted to plasma at the tip of the torch.
welding variables Components of the welding process. Welding variables can be either essential or nonessential.
whipped A technique typically used for forming a stringer bead that involves moving the electrode around in a circle and withdrawing it slightly. The technique is repeated to form a bead.
whipped A technique typically used for forming a stringer bead that involves moving the electrode around in a circle and withdrawing it slightly. Whipping is repeated to form a bead.
wind-blocking equipment A tent, shroud, or other structure intended to prevent shielding gas from being dispersed by wind during the process of welding. Some welding processes require wind-blocking equipment if they are to be used outdoors.
wire feed The rate at which consumable electrode wire is fed to a GMAW welding gun. Wire feed rate helps to determine the GMAW metal transfer process.
wire feeder A small device used to feed consumable electrode wire through a GMAW welding gun. Wire feeders are built into some GMAW power sources.
workpiece The part or parts that are being welded. In arc welding, the current which creates the arc runs through the workpieces.
WPS Welding procedure specification. A written document that contains all necessary and specific information regarding the application of a welding project. A WPS cannot be written or approved until the procedures it describes are tested.
x-ray testing The use of an x-ray machine to examine the interior of a completed weld. X-ray testing is expensive and time-consuming and therefore is typically only used in situations where the weld must be perfect.