Welding Terminology: The Complete Glossary Every Welder Needs

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding terminology can seem like a foreign language to beginners. After teaching welding for 15 years, I have seen countless students get overwhelmed by acronyms like GMAW, GTAW, and SMAW.

Welding terminology is the specialized vocabulary used in the welding industry to describe processes, equipment, materials, positions, and quality standards. Mastering this language is essential for clear communication on job sites, in fabrication shops, and during certification exams. This guide covers every major welding term you will encounter, with simple explanations and pronunciation guides for all those confusing acronyms.

I have organized this guide to start with the most commonly used terms and build toward more technical concepts. Each section includes practical examples from real welding situations. Whether you are just starting your welding career or preparing for certification, understanding these terms will help you communicate like a professional welder.

Quick Reference: Essential Welding Acronyms

Before diving into detailed definitions, here is a quick reference table for the most common welding acronyms you will hear in the shop. I have included pronunciations because seeing these written and hearing them spoken can be completely different.

Acronym	Pronunciation	Full Name	Common Name
MIG	mig	Metal Inert Gas	Wire welding
TIG	tig	Tungsten Inert Gas	Heliarc
SMAW	ess-maw	Shielded Metal Arc Welding	Stick welding
GMAW	gee-maw	Gas Metal Arc Welding	MIG welding
GTAW	gee-taw	Gas Tungsten Arc Welding	TIG welding
FCAW	eff-caw	Flux-Cored Arc Welding	Flux core
SAW	saw	Submerged Arc Welding	Sub arc
CWI	see-double-you-eye	Certified Welding Inspector	Inspector
WPS	double-you-pee-ess	Welding Procedure Specification	Procedure
PPE	pee-pee-ee	Personal Protective Equipment	Safety gear

Welding Process Terminology

Arc Welding Processes

Arc welding is a group of welding processes that use an electric arc to melt and join metals. The arc creates intense heat, up to 20,000 degrees Fahrenheit in some processes. Understanding the different arc welding processes is fundamental because each has specific applications where it excels.

Shielded Metal Arc Welding (SMAW)

SMAW is a manual arc welding process that uses a consumable electrode coated in flux. As the welder strikes an arc, the flux coating melts and creates a shielding gas cloud that protects the weld puddle from atmospheric contamination. The flux also forms a layer of slag over the cooling weld, which protects it further.

I have taught SMAW to hundreds of students. It is forgiving of surface contamination and works outdoors in wind because the flux provides its own shielding. Common applications include construction, pipeline welding, shipbuilding, and repair work. The main disadvantages are slow travel speeds, frequent electrode changes, and slag removal between passes.

Key SMAW Terms:

• Stick electrode: The consumable rod used in SMAW, typically 14 inches long
• Flux coating: Material covering the electrode that creates shielding gas and slag
• Slag: Byproduct of flux combustion that covers and protects the cooling weld
• Electrode holder: The device that grips the electrode, commonly called a “stinger”

Gas Metal Arc Welding (GMAW / MIG)

GMAW (pronounced “gee-maw”) is an arc welding process that uses a continuously fed consumable wire electrode and an external shielding gas. The wire is fed through a welding gun, which also delivers the shielding gas around the arc. Because the wire feeds continuously, the welder does not need to stop to change electrodes.

Known commonly as MIG welding (Metal Inert Gas), GMAW is the easiest process to learn. I have seen complete beginners produce acceptable welds within an hour of picking up a MIG gun. The continuous wire feed allows for long welds without stopping. The process is clean, with minimal slag to remove.

GMAW uses different shielding gases depending on the application. Pure carbon dioxide (CO2) provides deep penetration at lower cost. Argon and CO2 mixtures (commonly 75% argon, 25% CO2 called C25) produce a smoother arc with less spatter. Pure argon or helium mixtures are used for aluminum welding.

Key GMAW Terms:

• Wire feeder: Motorized device that pushes welding wire from the spool to the gun
• Contact tip: Copper nozzle tip that transfers current to the wire
• MIG gun: Handheld torch that directs wire and gas to the weld joint
• Stick-out: Distance from contact tip to arc, typically 3/8 to 1/2 inch
• Spatter: Metal droplets that spray around the weld, more common with CO2 gas

Gas Tungsten Arc Welding (GTAW / TIG)

GTAW (pronounced “gee-taw”) uses a non-consumable tungsten electrode to create the arc. Filler metal is added manually by the welder dipping a rod into the weld puddle. The process uses inert shielding gas, typically pure argon or argon-helium mixtures, to protect the weld area.

Commonly called TIG welding (Tungsten Inert Gas), this process produces the highest quality welds of any arc welding method. I use TIG when appearance matters or when welding thin materials and exotic metals like titanium and magnesium. The welder has precise control over heat input and filler metal addition.

TIG requires the most skill. The welder must simultaneously manipulate the torch with one hand, feed filler rod with the other, and control the foot pedal that adjusts amperage. This coordination takes months to master. The trade-off is beautiful, clean welds with no spatter and minimal cleanup.

Key GTAW Terms:

• Tungsten: Non-consumable electrode made from tungsten or tungsten alloy
• Filler rod: Metal rod manually added to the weld puddle
• Torch: GTAW handpiece that holds the tungsten and directs gas flow
• Gas lens: Optional accessory that creates laminar gas flow for better coverage
• Foot pedal: Foot-controlled amperage adjustment for precise heat control

Flux-Cored Arc Welding (FCAW)

FCAW (pronounced “eff-caw”) is similar to GMAW but uses a tubular wire filled with flux rather than solid wire. The flux inside the wire provides shielding, allowing welding without external gas in some applications. There are two types: self-shielded (FCAW-S) which needs no gas, and gas-shielded (FCAW-G) which uses both flux and external gas.

Self-shielded flux core is excellent for outdoor work because wind does not blow away the shielding. I have used FCAW-S on bridge projects where wind would make GMAW impossible. Gas-shielded flux core offers higher deposition rates than solid wire, making it productive for heavy fabrication.

The downsides include more smoke and fumes than solid wire, slag that requires removal, and a more aggressive arc that can be harder to control for beginners. Flux-cored wire is also more expensive than solid MIG wire.

Key FCAW Terms:

• Tubular wire: Hollow wire filled with flux materials
• Self-shielded: FCAW-S process that relies only on internal flux for shielding
• Gas-shielded: FCAW-G process using both flux and external shielding gas
• Deposition rate: Amount of weld metal deposited per hour, FCAW excels here

Submerged Arc Welding (SAW)

SAW (pronounced “saw”) is a high-productivity arc welding process where the arc is concealed beneath a blanket of granular flux. A continuously fed consumable electrode provides the filler metal. The flux melts to form a protective slag and can also add alloying elements to the weld.

This process is used in heavy fabrication where long, continuous welds are needed. I have seen SAW used in shipyards, pressure vessel manufacturing, and structural steel fabrication. The submerged arc produces deep penetration and can weld thick materials in a single pass.

SAW requires minimal operator skill because it is often automated. The main limitation is that it must be performed in flat or horizontal positions. The flux blanket prevents the arc from being visible, making monitoring difficult without specialized equipment.

Oxy-Fuel Welding (OAW)

Oxy-fuel welding (pronounced “ox-ee-fuel”) uses a combination of oxygen and a fuel gas to create a flame that melts the base metal and filler rod. The most common fuel gas is acetylene, though propane, natural gas, and propylene are also used. Oxy-acetylene welding was the primary welding method before arc welding became widespread.

Today, oxy-fuel welding is primarily used for maintenance and repair, brazing, and cutting. The equipment is relatively inexpensive and portable. I keep an oxy-acetylene setup in my shop for heating bent metal, brazing thin sheet metal, and cutting thick steel where a plasma cutter is not available.

The flame temperature reaches approximately 6,000 degrees Fahrenheit with oxy-acetylene, hot enough to melt most metals. The welder controls the flame characteristics by adjusting the oxygen-to-fuel ratio: a neutral flame has equal amounts, a carburizing flame has excess fuel, and an oxidizing flame has excess oxygen.

Key OAW Terms:

• Torch: Handpiece that mixes and directs oxygen and fuel gas
• Tip: Removable nozzle that determines flame size and characteristics
• Neutral flame: Balanced oxygen-to-fuel ratio, most common for welding
• Carburizing flame: Excess fuel, used for certain hard-facing applications
• Oxidizing flame: Excess oxygen, used for cutting rather than welding

Resistance Welding

Resistance welding uses heat generated by electrical resistance to the current flow. Workpieces are clamped between copper electrodes, and pressure is applied as current flows. The resistance at the contact point creates heat that melts and joins the metal. No filler metal is used in resistance welding.

Resistance Spot Welding (RSW)

Spot welding joins overlapping metal sheets at discrete points. Copper electrodes clamp the sheets together on both sides, and current flows through the workpieces. The resistance generates heat that melts a small spot, fusing the sheets. This is the primary method used in automotive assembly to join car body panels.

Resistance Seam Welding (RSEW)

Seam welding creates a continuous weld by replacing spot welding electrodes with wheel-shaped electrodes that rotate as the workpieces pass between them. The result is a series of overlapping spot welds that form a gas-tight seam. Common applications include fuel tanks, radiators, and other container fabrication.

Projection Welding

Projection welding uses embossments or projections on one workpiece to concentrate current flow at specific points. When the projections are forced against the flat surface, they melt and create welds at those locations. This allows multiple welds to be made simultaneously in a single cycle.

Energy Beam Welding

Energy beam welding processes use a focused beam of high-energy particles to melt and join metals. These processes offer extremely precise, high-quality welds with minimal heat input to the surrounding material.

Electron Beam Welding (EBW)

EBW uses a focused beam of high-velocity electrons to join materials. The process must occur in a vacuum chamber because electrons would be scattered by air molecules. EBW produces deep, narrow welds with minimal distortion. It is used in aerospace, automotive, and nuclear industries for precision applications.

Laser Beam Welding (LBW)

Laser welding uses a focused laser beam to melt and join materials. Unlike electron beam welding, LBW can be performed in air. The high energy density allows for narrow heat-affected zones and fast welding speeds. Applications range from medical devices to automotive body panels to electronics manufacturing.

Solid-State Welding

Solid-state welding processes join metals without melting the base material. Instead, they use pressure, heat, or both to create a metallurgical bond through diffusion or plastic deformation.

Friction Stir Welding (FSW)

FSW uses a rotating tool with a pin that plunges into the joint between two workpieces. The friction generates heat that softens the metal without melting it. As the tool travels along the joint, it mechanically stirs the material together, creating a solid-state bond. Originally developed for aluminum, FSW is now used for copper, magnesium, and even steel.

Friction Welding

Friction welding rotates one workpiece against another under pressure. The friction generates heat that softens the material at the interface. Once sufficient heat is generated, rotation stops and pressure increases to forge the parts together. This process is commonly used to join shafts, tubes, and other cylindrical components.

Cold Welding

Cold welding joins clean, oxide-free metal surfaces through pressure alone without heat. The atoms at the interface bond when brought into close contact. This works best with soft, ductile metals like aluminum and copper. Applications include wire splicing and electrical connections.

Diffusion Bonding

Diffusion bonding holds workpieces together under high pressure at elevated temperatures for an extended period. Atoms diffuse across the interface, creating a solid-state bond. This process is used for dissimilar metal joints and applications where minimal distortion is critical.

Specialized Welding Processes

Plasma Arc Welding (PAW)

PAW is similar to GTAW but uses a constricted arc that passes through a copper orifice. The constriction creates a plasma column with higher energy density and better directional control than a standard TIG arc. The keyhole mode of PAW can penetrate thick materials in a single pass. Aerospace and precision industries use PAW for critical applications.

Electroslag Welding (ESW)

ESW is a highly productive process for welding thick materials in a single vertical pass. An electric arc is initially struck to melt a flux layer, creating a conductive slag pool. Once the slag pool is established, the arc extinguishes and current flows through the conductive slag, which melts the filler wire and base metal. ESW is used for heavy fabrication like ship hulls and pressure vessels.

Stud Welding

Stud welding joins a metal stud or fastener to a workpiece by welding one end of the stud to the surface. In drawn arc stud welding, an arc melts the stud tip and base metal, then the stud is plunged into the molten pool. This process is widely used in construction to attach shear connectors to steel beams and in automotive assembly for numerous threaded fasteners.

Equipment and Component Terminology

Power Sources

The welding power source provides the electrical current needed to create the welding arc. Understanding the different types and their characteristics is essential for selecting the right equipment for each application.

Constant Current (CC)

Constant current power sources maintain a relatively stable amperage regardless of arc length changes. When the welder changes the distance between the electrode and workpiece, the voltage changes to maintain the set amperage. This characteristic makes CC power sources ideal for SMAW and GTAW, where the welder manually controls the arc length.

I use CC machines for stick and TIG welding because they provide consistent weld penetration even when my hand movements cause slight arc length variations. The output characteristic curve shows a steep slope, meaning small voltage changes accompany large amperage changes.

Constant Voltage (CV)

Constant voltage power sources maintain a relatively stable voltage output. The amperage varies with changes in arc length. When the arc length decreases, amperage increases, which melts more wire and automatically restores the arc length. This self-regulating characteristic makes CV power sources ideal for GMAW and FCAW, where continuous wire feeding would otherwise cause arc length variations.

Transformer

Transformer welders use a large copper-wound transformer to convert incoming power to welding current. They are simple, reliable, and can handle harsh environments. I have seen transformer welders still running after 30 years of daily use. The main disadvantage is weight: transformer machines are heavy and less portable than modern alternatives.

Inverter

Inverter welders convert incoming AC power to DC, then use high-speed switching to create high-frequency AC, which is then transformed and rectified to welding output. This technology allows for smaller, lighter machines with advanced features. Inverters offer better arc characteristics, improved energy efficiency, and often include AC output for TIG welding aluminum.

Modern inverter welders weigh less than 50 pounds compared to 200+ pounds for transformer equivalents. I switched to inverters for mobile welding because I can easily carry one to job sites. The trade-off is that inverters have more complex electronics that can be sensitive to moisture and rough handling.

Engine-Driven Welder

Engine-driven welders combine an internal combustion engine with a welding generator. These machines provide welding power in locations without electrical service. They are essential for construction sites, pipeline welding, farm repair, and emergency power applications. Most engine drives can also generate AC power for tools and lights while welding.

Electrodes and Consumables

Electrode

In welding, an electrode is a conductor through which current flows. Electrodes can be consumable (melting to become part of the weld) or non-consumable (not melting). In SMAW, the electrode is the coated rod that melts. In GTAW, the tungsten electrode does not melt. The term can be confusing because it refers to different components in different processes.

Filler Metal

Filler metal is material added to a weld joint to fill the gap or increase the weld metal volume. Filler metal comes as rods for SMAW and GTAW, wire for GMAW and FCAW, and strips for SAW. The filler metal composition must be compatible with the base metal to produce a sound weld.

Stick Electrode (SMAW)

Stick electrodes consist of a metal core wire surrounded by flux coating. The American Welding Society (AWS) classification system specifies the electrode type, strength, and characteristics. For example, E7018 indicates an electrode with 70 ksi tensile strength, all-position capability, and low-hydrogen coating with iron powder.

Common SMAW Electrodes:

AWS Classification	Coating Type	Key Characteristics	Common Applications
E6010	Cellulose sodium	Deep penetration, dig-in arc	Root passes on pipe, rusty steel
E6011	Cellulose potassium	AC compatible, fast-freeze slag	All-position maintenance, AC welders
E6013	Rutile	Smooth arc, easy restrike	Light fabrication, sheet metal
E7018	Low hydrogen	High strength, crack resistant	Structural steel, high-strength applications
E7024	Rutile iron powder	High deposition, flat/horizontal only	Heavy fabrication, fillet welds

Flux

Flux is a material used to prevent, dissolve, or facilitate removal of oxides and other undesirable substances. In SMAW, the coating on the electrode is flux. In SAW, flux is granular material poured over the arc. Flux performs several functions: it shields the arc from atmospheric contamination, stabilizes the arc, adds alloying elements, and forms slag that protects the cooling weld.

Slag

Slag is the non-metallic byproduct of flux melting during welding. It covers the cooling weld metal, protecting it from oxidation and allowing slower cooling. After welding, slag must be removed through chipping or wire brushing. Slag removal between weld passes is critical to prevent slag inclusions in multi-pass welds.

Torches, Guns, and Accessories

Electrode Holder

The electrode holder (also called a stinger) grips the SMAW electrode and connects the welding cable to the electrode. It must provide secure electrical contact and insulate the welder from the current. Quality holders have insulated jaws, replaceable parts, and comfortable grips for extended use.

Ground Clamp

The ground clamp (also called work clamp) connects the work cable to the workpiece, completing the electrical circuit. A good ground connection is essential for consistent welding performance. I have spent hours troubleshooting welding problems only to find a loose or dirty ground connection was the cause.

MIG Gun

The MIG gun is the handheld torch used in GMAW. It houses the contact tip, nozzle, and gas diffuser. The gun directs the wire electrode and shielding gas to the weld joint. Guns are rated by amperage capacity: 200 amp guns for light work, 400-600 amp guns for heavy industrial applications.

Contact Tip

The contact tip is a replaceable copper component inside the MIG gun that transfers electrical current to the wire electrode. It must be sized correctly for the wire diameter. Worn contact tips cause poor arc starting, erratic arc behavior, and excessive spatter.

Nozzle

The nozzle (or shroud) directs shielding gas around the arc in MIG and flux-cored welding. It attaches to the gun and surrounds the contact tip. Nozzles come in various shapes and sizes. Larger nozzles provide better gas coverage but may restrict visibility in tight spaces.

TIG Torch

The TIG torch holds the tungsten electrode, directs shielding gas, and may include a water-cooling passage for high-amperage applications. The torch includes a collet that grips the tungsten, a collet body that holds the collet, and a back cap that provides tension. Gas lenses are optional accessories that improve gas flow consistency.

Tungsten Electrode

Tungsten electrodes for GTAW come in different types based on alloying additions:

• Pure tungsten (green): Used for AC TIG welding aluminum
• Ceriated (orange): Good for AC welding, easier starting than pure
• Lanthanated (gold): All-position performance, good for AC and DC
• Thoriated (red): DC welding, excellent arc stability, contains thorium (radioactive)
• Zirconiated (brown): AC welding, high current capacity

Wire Feeders and Auxiliary Equipment

Wire Feeder

A wire feeder is a motorized device that pulls welding wire from a spool and pushes it through the welding cable to the gun. Wire feeders can be separate units or built into the power source. They have adjustable speed controls that regulate wire feed rate, which directly affects amperage and weld bead size.

Drive Rolls

Drive rolls pull the wire from the spool and push it toward the gun. They come in different configurations: V-knurled for solid wire, U-groove for flux-cored wire, and smooth V-knurled for aluminum. Using the wrong drive rolls can deform the wire, causing feeding problems and poor weld quality.

Regulator

A regulator attaches to a shielding gas cylinder and reduces the high cylinder pressure to a usable working pressure. It also includes a flowmeter to measure gas flow rate. Proper gas flow is critical: too little causes porosity, too much wastes gas and can create turbulence that pulls air into the arc.

Flowmeter

The flowmeter measures and displays the shielding gas flow rate, typically in cubic feet per hour (CFH) or liters per minute (LPM). Standard GMAW flow is 25-40 CFH. TIG welding typically uses 15-25 CFH. I check my flowmeter before every welding session to ensure proper gas coverage.

Joint Types and Weld Geometry

A welding joint is the configuration where two or more workpieces are joined together. Understanding joint terminology is essential for reading welding symbols, preparing weld joints properly, and selecting the appropriate welding process.

Basic Joint Types

Joint Type	Configuration	Common Applications
Butt Joint	Two parts in same plane, edge to edge	Pipe seams, structural connections
T-Joint	One part perpendicular to surface of another	Structural attachments, stiffeners
Corner Joint	Two parts at right angles forming an L	Box fabrication, frames
Lap Joint	Two overlapping parts in parallel planes	Sheet metal, spot welds
Edge Joint	Two parallel parts, edges aligned	Sheet metal seams, low stress applications

Butt Joint

A butt joint joins two members that are in approximately the same plane. A square butt joint has no edge preparation. For thicker materials, the edges are prepared (beveled) to allow penetration to the root. Butt joints are used when the joint must be as strong as the base material and are common in pressure vessels, piping, and structural applications.

T-Joint

A T-joint occurs when the surface of one member is approximately 90 degrees to the axis of the other member. Most T-joints use fillet welds on both sides for maximum strength. Applications include attaching stiffeners to plate, welding braces to structural members, and joining components at right angles.

Corner Joint

A corner joint forms an L-shape between two parts whose edges meet at approximately 90 degrees. These joints can be either closed corner (edges butting together) or open corner (edges spaced apart). Corner joints are used for box fabrication, tanks, and frames.

Lap Joint

A lap joint joins two overlapping members in parallel planes. The overlap distance is typically 3-5 times the material thickness. Lap joints are easier to fit up than butt joints because they require less precise edge preparation. They are common in sheet metal work and for joining dissimilar thicknesses.

Edge Joint

An edge joint joins the edges of two parallel members. Edge joints are not recommended for high-load applications because they have minimal surface area for fusion. They are typically used for sheet metal seams where loads are light, or for cosmetic welds.

Weld Types

Groove Weld

A groove weld is made in a groove between workpieces or between the edges of workpieces. Groove welds can penetrate completely through the joint (complete joint penetration) or only partway (partial joint penetration). Groove welds are used when maximum joint strength is required, typically in butt joints.

Fillet Weld

A fillet weld has a triangular cross-section and joins two surfaces at approximately right angles. The size of a fillet weld is measured by the leg length. Fillet welds are the most common weld type in structural fabrication because they require minimal joint preparation and are easy to produce.

Plug and Slot Welds

Plug welds are made through holes in one overlapping member into another member. Slot welds are similar but use elongated holes rather than round holes. These welds are alternatives to spot welds or rivets in certain applications and are used to join overlapping members where access is limited.

Spot Weld

A spot weld is a resistance weld made between or upon overlapping members where the weld area is approximately circular. Spot welding does not require filler metal and joins metals at discrete points. It is the primary joining method in automotive body assembly.

Seam Weld

A seam weld is a continuous resistance weld made between or upon overlapping members. The weld may be made in overlapping circular spots (resistance seam welding) or as a continuous seam. Seam welds produce gas-tight and liquid-tight joints.

Groove Designs

For thicker materials, groove preparation is necessary to ensure proper penetration. The groove type designation comes from the shape of the cross-section.

Groove Type	Description	Typical Thickness Range
Square Groove	No bevel, square edges	Up to 1/4 inch (thin materials)
V-Groove	Single bevel on each piece forming V	1/4 to 3/4 inch
Bevel Groove	One piece beveled, other square	When access from one side only
U-Groove	Curved bottom in groove	Thick materials, reduced weld metal
J-Groove	One piece with U-shaped bevel	Thick materials, one-sided access
Double V, U, J	Groove prepared on both sides	Very thick materials, symmetry

Weld Zone Terminology

Root

The root is the point in a weld joint farthest from the welder. In a groove weld, the root is at the bottom of the groove. Achieving proper root penetration is critical for joint strength. Incomplete root penetration is a common defect that can lead to joint failure.

Face

The face is the exposed surface of a weld on the side from which the welding was done. The face should be relatively smooth with consistent reinforcement. Face reinforcement is the weld metal extending beyond the surface of the base material.

Toe

The toe is the junction between the weld face and the base metal. In a fillet weld, there are two toes. Undercut at the toe is a common defect where a groove has melted into the base metal adjacent to the weld toe, creating a stress concentration point.

Throat

Throat measurements are used to size fillet welds. The theoretical throat is the distance from the joint root to the theoretical hypotenuse of the largest right triangle that can fit in the cross-section. The actual throat is the shortest distance from the root to the face of a fillet weld. The effective throat accounts for any joint penetration beyond the root.

Reinforcement

Weld reinforcement is weld metal that extends beyond the surface of the base material. Some reinforcement is beneficial, as it ensures the weld throat is not smaller than the base material. However, excessive reinforcement can create stress concentrations and is considered a defect.

Leg Size

Leg size is the distance from the joint root to the toe of a fillet weld. Leg size is used to specify fillet weld dimensions on drawings. For a given leg size, the throat (the effective load-carrying dimension) is approximately 0.707 times the leg size for equal-leg fillet welds.

Joint Preparation Terms

Bevel Angle

The bevel angle is the angle between the prepared edge of a member and a plane perpendicular to the surface of the member. Bevel angles typically range from 30 to 60 degrees depending on the welding process, joint design, and material thickness.

Groove Angle

The groove angle is the total included angle of the groove between workpieces. In a single-V groove, this is twice the bevel angle. Larger groove angles allow better electrode access but require more weld metal.

Root Opening

Root opening (also called root gap) is the separation at the joint root between the workpieces. Proper root opening allows the welder to achieve penetration to the root. Too little opening prevents proper penetration. Too much requires excessive weld metal and can cause burn-through.

Root Face

The root face (also called land) is the portion of the joint root that is not beveled or chamfered. A root face provides a surface for the initial weld pass to bridge across. Root faces are typically 1/16 to 1/8 inch thick.

Backing

Backing is material placed at the root of a weld joint to support molten weld metal. Backing can be metal (backing bar or strip), ceramic (backing tape), or the weld metal itself (backing weld). Backing allows full penetration on joints where access is limited to one side.

Welding Position Terminology

Welding positions describe the orientation of the weld joint relative to gravity. Different positions require different techniques and are designated by number/letter codes in welding specifications.

Plate Welding Positions

Position Code	Weld Type	Position Name	Description
1G	Groove	Flat	Weld face horizontal, joint on top surface
2G	Groove	Horizontal	Weld axis horizontal, joint vertical
3G	Groove	Vertical	Weld axis vertical, welded upward (3G up) or downward
4G	Groove	Overhead	Weld overhead, welder below the joint
1F	Fillet	Flat	Weld made on top surface, approximately horizontal
2F	Fillet	Horizontal	Weld axis horizontal, one surface vertical
3F	Fillet	Vertical	Weld axis vertical, similar to 3G
4F	Fillet	Overhead	Weld overhead, similar to 4G

Pipe Welding Positions

1G Pipe (Rolled)

Pipe is rotated during welding so the welder maintains the flat position. This is the easiest pipe welding position because the welder can stay in an optimal body position while the pipe rotates beneath them.

2G Pipe

The pipe axis is vertical and the pipe is not rotated. Welding is done in the horizontal position around the pipe circumference. This position is more challenging than 1G but easier than fixed position welding.

5G Pipe (Fixed)

The pipe axis is horizontal and the pipe is not rotated. The welder must weld around the entire pipe circumference, progressing through flat, horizontal, vertical, and overhead positions. This is a common certification test position.

6G Pipe (Fixed Inclined)

The pipe axis is approximately 45 degrees from horizontal and the pipe is not rotated. The 6G position is considered the most difficult because the welder must work in all positions with restricted access and body positioning. This position is typically required for pipe welding certification in the construction and pipeline industries.

Directional Welding Terms

Forehand Welding (Push)

Forehand welding is when the torch or electrode is angled in the direction of travel. In MIG welding, this is called pushing. Forehand welding produces a wider, flatter bead with less penetration. I use forehand technique on thin materials to reduce burn-through risk and for cosmetic welds where appearance matters.

Backhand Welding (Drag)

Backhand welding is when the torch or electrode is angled opposite the direction of travel. In MIG welding, this is called dragging. Backhand welding produces a narrower, more convex bead with deeper penetration. I use backhand technique on thicker materials where maximum penetration is needed.

Vertical Up

Welding upward on a vertical joint requires using techniques to prevent molten metal from falling. Weave patterns are used to allow each section to cool slightly before moving on. Vertical up produces better penetration than vertical down but is slower and more difficult.

Vertical Down

Welding downward on a vertical joint relies on gravity to help move the weld metal. Vertical down is faster and easier but produces shallower penetration. It is typically used on thinner materials where burn-through is a concern.

Travel Angle

Travel angle is the angle between the electrode and a line perpendicular to the weld axis in the plane of welding. For drag techniques, this angle is typically 5-15 degrees. For push techniques, it is typically 15-30 degrees. Incorrect travel angle can cause spatter, poor penetration, and excessive undercut.

Work Angle

Work angle is the angle between the electrode and a line perpendicular to the weld axis, measured in a plane perpendicular to the weld axis. Work angle determines how heat is distributed between the two members being joined. For a T-joint, a 45-degree work angle distributes heat equally. Adjusting the work angle can compensate for members of different thicknesses.

Materials and Shielding Terminology

Base Materials

The base metal (or parent metal) is the material being welded. Understanding base material properties is critical because different materials require different welding procedures, filler metals, and techniques.

Mild Steel (Carbon Steel)

Mild steel contains approximately 0.05-0.25% carbon and is the most common welding material. It is relatively easy to weld using any common process. Mild steel is used in structural applications, automotive fabrication, and general manufacturing. Preheat is generally not required unless the material is very thick or the ambient temperature is very low.

Stainless Steel

Stainless steel contains chromium (at least 10.5%) which provides corrosion resistance. The most common type for welding is 304 austenitic stainless steel. Stainless steel has lower thermal conductivity than carbon steel, which causes heat to concentrate in the weld zone. It also has higher thermal expansion, which can cause distortion. I use lower heat input and faster travel speeds when welding stainless to prevent carbide precipitation and maintain corrosion resistance.

Aluminum

Aluminum presents unique welding challenges. It has an oxide layer that melts at a much higher temperature than the base metal and must be removed during welding. Aluminum conducts heat away from the weld zone rapidly, requiring higher amperage. It is also prone to porosity from trapped hydrogen. AC TIG welding is the preferred method for aluminum because the alternating current helps break up the oxide layer.

Cast Iron

Cast iron contains high carbon content (2-4%) which makes it brittle and difficult to weld. Welding cast iron requires special procedures including preheat, low heat input, and slow cooling. I have welded cast iron engine blocks and pump housings using nickel-based filler rods and peening the weld to relieve stress. Even with proper technique, cast iron repairs can be challenging and are not guaranteed to last.

Exotic Alloys

Materials like titanium, magnesium, Inconel, Monel, and Hastelloy require specialized welding procedures. Titanium is extremely reactive and must be welded under inert gas coverage on both the front and back sides of the joint. Magnesium is highly flammable and presents fire hazards. Nickel alloys like Inconel are used in high-temperature applications but require careful control of heat input and filler metal selection.

Filler Metal Terminology

AWS Classification

The American Welding Society classifies filler metals using alphanumeric codes that specify tensile strength, composition, and characteristics. For example, ER70S-6 indicates a solid steel electrode (ER), 70 ksi minimum tensile strength, solid wire (S), with specific chemical composition (6).

Solid Wire

Solid wire is a continuous solid metal electrode used in GMAW. It requires external shielding gas. Solid wire produces clean welds with minimal spatter when used with appropriate gas shielding. ER70S-6 is the most common solid wire for carbon steel welding.

Metal Cored Wire

Metal cored wire is tubular like flux-cored wire but contains metal powder rather than flux. It provides higher deposition rates than solid wire while requiring less amperage. Metal cored wire produces less slag than flux-cored but still requires gas shielding.

Low Hydrogen Electrodes

Low hydrogen electrodes (such as E7018) have coating formulations that minimize hydrogen introduction into the weld. Hydrogen can cause cracking in high-strength steels, making low hydrogen electrodes essential for structural and pressure vessel welding. These electrodes must be kept dry, typically in an oven at 250-300 degrees Fahrenheit, to maintain their low hydrogen properties.

Shielding Gas Terminology

Shielding gas protects the weld area from atmospheric contamination. The choice of gas affects arc characteristics, penetration profile, spatter levels, and weld appearance.

Gas/Mixture	Common Name	Applications
100% CO2	Carbon dioxide	Short circuit MIG, deep penetration, low cost
75% Ar / 25% CO2	C25	Most common GMAW mix, general purpose
90% Ar / 10% CO2	C10	Short circuit, pulsed spray, less spatter
98% Ar / 2% O2	98/2	Stainless steel spray transfer
100% Argon	Pure argon	Aluminum, TIG welding, root passes
Ar/He Mixtures	Tri-mix, Quad-mix	Aluminum, stainless, specialized applications

Argon

Argon is an inert gas heavier than air. It is the primary shielding gas for TIG welding and is commonly mixed with CO2 for MIG welding. Argon produces a stable arc with minimal spatter. Pure argon is required for welding aluminum because it helps clean the oxide layer.

Carbon Dioxide (CO2)

CO2 is an active gas that chemically reacts with the weld pool. It produces deep penetration at low cost but generates more spatter than argon mixtures. Pure CO2 is commonly used for short circuit MIG welding in fabrication shops.

Helium

Helium is an inert gas lighter than air. It produces a hotter arc than argon, which is beneficial for welding thick materials and highly conductive metals like aluminum and copper. Helium is expensive and is typically mixed with argon to balance cost and performance.

Tri-Mix

Tri-mix gases typically combine argon, helium, and CO2. They are used for specialized applications like spray transfer welding of stainless steel or welding aluminum in MIG processes. The exact composition varies based on the application.

Weld Defects and Discontinuities

Discontinuity vs Defect

A discontinuity is any interruption in the typical structure of a material. Not all discontinuities are defects. A discontinuity becomes a defect when it exceeds the acceptance criteria of the applicable code or specification. Understanding this distinction is important for weld inspection and quality control.

I have seen many welds rejected because inspectors and welders did not understand that some discontinuities are acceptable within code limits. The acceptance criteria vary depending on the application: pressure vessels have different requirements than structural steel, which differs from automotive welds.

Porosity

Porosity is cavity-type discontinuities formed by gas entrapment during solidification. Porosity appears as small round voids in the weld metal. It can be scattered throughout the weld, clustered in specific areas, or aligned in a linear pattern. Porosity is caused by moisture, contamination, inadequate shielding gas, or incorrect welding parameters.

Gas Porosity

Gas porosity results from gases released during welding becoming trapped in the solidifying weld metal. Common gas sources include moisture in electrode coatings, oil or grease on the base metal, and atmospheric contamination from inadequate shielding. Keeping materials clean and dry is the best prevention.

Cluster Porosity

Cluster porosity appears as groups of pores concentrated in a localized area. This type often indicates a specific problem like hitting a rusty area, oil spot, or arc starting/stopping issues. I most often see cluster porosity when welding through primer or paint that was not properly cleaned from the joint area.

Cracking

Cracks are linear discontinuities that can be catastrophic in welded structures. Cracks are generally unacceptable regardless of size because they can propagate under load and cause failure. Different types of cracks occur at different times and from different causes.

Longitudinal Cracks

Longitudinal cracks run parallel to the weld axis. They can occur in the weld metal or the heat-affected zone. Causes include high restraint, high sulfur content in the base metal, excessive travel speed, or concave weld beads. Proper joint design, reduced restraint, and correct procedures help prevent longitudinal cracking.

Transverse Cracks

Transverse cracks run perpendicular to the weld axis. These often occur in the heat-affected zone rather than the weld metal itself. Contributing factors include high hardness, high hydrogen content, and excessive restraint. Preheat and post-weld heat treatment can help prevent transverse cracking.

Crater Cracks

Crater cracks occur at the end of a weld where the arc was broken. When the arc stops, the center of the crater cools and shrinks rapidly, creating stress that can crack. Proper crater filling techniques, including backing up slightly before breaking the arc, prevent these cracks.

Toe Cracks

Toe cracks occur at the weld toe where the weld meets the base metal. They are often caused by excessive hydrogen, high hardness in the heat-affected zone, or high restraint. Low hydrogen electrodes, preheat, and proper joint design help prevent toe cracks.

Root Cracks

Root cracks occur at the root of the weld, often on the first pass. Causes include inadequate root opening, poor fit-up, high restraint, and hydrogen contamination. Proper root opening, clean base metal, and appropriate preheat reduce root crack risk.

Heat-Affected Zone (HAZ) Cracks

The heat-affected zone is the base metal adjacent to the weld that was not melted but was affected by the welding heat. HAZ cracks occur in this area, often hours or days after welding (delayed cracking). They are caused by hydrogen diffusion into a susceptible microstructure. Preheat, post-heating, and low hydrogen practices are the primary prevention methods.

Hydrogen Cracking

Also called cold cracking or delayed cracking, hydrogen cracking occurs when hydrogen atoms diffuse into the weld metal and heat-affected zone. The hydrogen collects at stress points and causes cracking hours or even days after welding is complete. Prevention includes using low hydrogen electrodes, keeping electrodes dry, preheating the base metal, and applying post-weld heat treatment.

Solidification Cracks

Solidification cracks occur during weld metal solidification as the grain structure forms. They are caused by impurities segregating at grain boundaries as the metal freezes. High sulfur, phosphorus, or carbon content increases susceptibility. Proper filler metal selection, adequate root opening, and appropriate travel speed help prevent solidification cracking.

Lamellar Tearing

Lamellar tearing occurs beneath the weld in rolled steel products that have poor through-thickness ductility. It happens when high shrinkage stresses act on the rolled material. Lamellar tearing is particularly problematic in T-joints and corner joints on thick plate. Using steel with controlled through-thickness properties and joint designs that reduce through-thickness stress can prevent lamellar tearing.

Fusion and Penetration Issues

Lack of Fusion (LOF)

Lack of fusion occurs when the weld metal does not fuse completely with the base metal or previous weld pass. The unfused area creates a crack-like discontinuity that can cause failure. Causes include incorrect travel angle, too high travel speed, insufficient amperage, or improper joint preparation. I often see lack of fusion when beginners try to weld too fast or use the wrong work angle.

Incomplete Fusion

Incomplete fusion is similar to lack of fusion but specifically refers to fusion failure at the weld root or between weld passes. It can occur between weld passes in multi-pass welds or between the weld and groove face. Proper cleaning between passes, correct welding parameters, and appropriate joint design prevent incomplete fusion.

Lack of Penetration (LOP)

Lack of penetration occurs when the weld metal does not reach the root of the joint. The joint appears filled from the outside but has a void at the root. Causes include insufficient amperage, too small electrode, improper joint preparation, or incorrect welding technique. Proper root opening, correct amperage, and suitable technique ensure complete penetration.

Incomplete Penetration

Incomplete penetration is the condition where the weld metal does not extend completely through the joint thickness. It differs from lack of penetration in that it may be an intentional design (partial penetration weld) or an unintentional condition. Complete joint penetration is required for many structural and pressure applications.

Surface Discontinuities

Undercut

Undercut is a groove melted into the base metal adjacent to the weld toe or root. Undercut reduces the cross-sectional area of the base metal and creates stress concentration points. Causes include excessive amperage, too fast travel speed, incorrect angle, or improper weaving technique. Slight undercut is often acceptable within code limits, but excessive undercut requires repair.

Overlap

Overlap occurs when weld metal extends beyond the weld toe or root but does not fuse to the base metal. It creates a notch that can become a stress concentration point. Overlap is typically caused by insufficient amperage, slow travel speed, or incorrect electrode manipulation. The overlapped portion must be removed and the area rewelded when it exceeds acceptance criteria.

Excessive Reinforcement

Excessive reinforcement is weld metal that extends beyond the surface of the base metal more than allowed by the applicable code. While some reinforcement is beneficial, excessive reinforcement creates stress concentrations and adds unnecessary weight. It is caused by slow travel speed or excessive amperage. Grinding down to acceptable limits is the typical remedy.

Insufficient Reinforcement

Insufficient reinforcement occurs when the weld face is below the surface of the base material. This condition reduces the effective throat of the weld, potentially weakening the joint. Causes include fast travel speed, insufficient amperage, or improper technique. The weld must be built up with additional weld metal to correct the condition.

Convexity and Concavity

Convexity refers to weld metal that protrudes above the base material surface. Concavity refers to weld metal that is below the surface. Both conditions can be acceptable within limits depending on the code. Excessive convexity creates stress concentrations. Excessive concavity reduces weld throat and strength.

Spatter

Spatter consists of metal droplets expelled during welding that land on the base metal surface. While spatter is generally considered a cosmetic issue, excessive spatter can indicate underlying problems with parameters or gas coverage. Spatter must be removed before painting or coating. Proper gas flow, correct polarity, and appropriate parameters reduce spatter.

Arc Strike

An arc strike is a discontinuity resulting from accidentally striking an arc outside the weld joint. Arc strikes create localized hard spots and can initiate cracks. They are particularly problematic in high-strength steels and pressure-containing applications. Arc strikes must be avoided through careful welding practices and must be repaired by grinding and potentially post-weld heat treatment when they occur.

Distortion

Distortion is the dimensional change that results from welding due to thermal expansion and contraction. It is not a defect per se but must be controlled to meet dimensional requirements. Several types of distortion occur:

Angular Distortion

Angular distortion occurs when the joint angle changes from its intended value. This commonly happens in V-groove welds where more weld metal is placed on one side of the neutral axis than the other, causing the parts to rotate.

Longitudinal Distortion

Longitudinal distortion is lengthwise shrinkage caused by weld metal contraction as it cools. It can cause a welded assembly to be shorter than intended.

Transverse Shrinkage

Transverse shrinkage occurs perpendicular to the weld axis. In butt welds, this brings the parts closer together. In fillet welds, it can cause the parts to rotate toward each other.

Bowing and Bending

Bowing occurs when welds on one side of an asymmetrical section cause the part to bend. Bending also results from unbalanced weld placement. Proper sequencing and balanced weld placement help prevent bowing.

Testing and Inspection Terminology

Nondestructive Testing (NDT)

Nondestructive testing (also called nondestructive examination, NDE) evaluates weld quality without damaging the material. NDT methods allow inspection of completed welds to ensure they meet quality requirements without cutting or otherwise compromising the welded assembly.

Visual Testing (VT)

Visual testing is the most common and least expensive inspection method. A qualified inspector examines the weld surface with the naked eye or with magnification and aids such as borescopes. Visual inspection can detect surface discontinuities such as undercut, porosity, cracks, incomplete fusion, and incorrect weld size. Proper lighting and surface preparation are essential for effective visual testing.

Radiographic Testing (RT)

Radiographic testing uses X-rays or gamma rays to create an image of the internal weld structure. Radiation passes through the weld, and variations in material density create variations in the exposed image. Radiography can detect internal porosity, slag inclusions, lack of fusion, cracks, and incomplete penetration. It is particularly useful for inspection of piping and pressure vessel welds.

Ultrasonic Testing (UT)

Ultrasonic testing uses high-frequency sound waves to inspect welds. A transducer sends sound waves into the material, and reflections from discontinuities are displayed on a screen. Ultrasonic testing can detect cracks, lack of fusion, inclusions, and measure material thickness. It requires skilled operators but provides immediate results and does not present radiation hazards like radiography.

Magnetic Particle Testing (MT/MPI)

Magnetic particle testing detects surface and slightly subsurface discontinuities in ferromagnetic materials. The weld is magnetized, and iron particles are applied. Discontinuities disrupt the magnetic field, attracting particles and creating visible indications. MT is excellent for detecting cracks that are not visible to the naked eye but is limited to magnetic materials.

Dye Penetrant Testing (PT/LPI)

Dye penetrant testing (also called liquid penetrant inspection) detects surface-breaking discontinuities in any material. A colored penetrant is applied to the clean surface and allowed to enter any discontinuities. Excess penetrant is removed, and a developer is applied that draws penetrant out of discontinuities, creating visible indications. PT can detect cracks, porosity, and laps that are open to the surface.

Eddy Current Testing (ET)

Eddy current testing uses electromagnetic induction to detect surface and near-surface discontinuities. A coil carrying alternating current creates changing magnetic fields that induce eddy currents in the test material. Discontinuities change the eddy current flow, which is detected by the coil. ET is commonly used for tube and pipe inspection and for measuring coating thickness.

Destructive Testing

Tensile Test

A tensile test pulls a welded specimen apart in tension to measure strength and ductility. The test determines ultimate tensile strength, yield strength, and elongation. Tensile testing is commonly required for procedure qualification and material certification.

Bend Test

Bend tests evaluate ductility and soundness by bending a welded specimen. Types include guided bend, free bend, root bend, face bend, and side bend tests. The bent surface is examined for cracks and other discontinuities. Bend tests are standard for welder and procedure qualification.

Charpy Impact Test

The Charpy test measures toughness by striking a notched specimen with a pendulum. The energy absorbed in breaking the specimen indicates the material’s toughness, particularly at low temperatures. Impact testing is critical for structures subject to dynamic loading or low-temperature service.

Hardness Test

Hardness testing measures a material’s resistance to indentation. Common methods include Brinell, Rockwell, and Vickers tests. Hardness testing evaluates the heat-affected zone for excessive hardness that could indicate reduced ductility or increased susceptibility to cracking.

Macro Etch

A macro etch test involves polishing and etching a cross-section of a weld to reveal its internal structure. The etched specimen shows weld passes, penetration, fusion, and discontinuities. Macro etching is commonly used for procedure qualification and failure analysis.

Fillet Break Test

A fillet break test fractures a fillet weld specimen to examine the fractured surface for discontinuities. The test evaluates the internal soundness of fillet welds and is commonly used for welder qualification tests.

Inspection Personnel

Certified Welding Inspector (CWI)

A CWI is an individual certified by the American Welding Society to inspect welds and verify compliance with applicable codes and specifications. CWI certification requires passing a comprehensive examination covering welding processes, inspection methods, and code requirements. Most structural welding contracts require CWI inspection.

NDT Technician

NDT technicians are qualified to perform specific nondestructive testing methods. The American Society for Nondestructive Testing (ASNT) establishes qualification levels: Level I (can perform tests), Level II (can perform and interpret tests), and Level III (can establish procedures and train technicians).

Safety and PPE Terminology

Personal Protective Equipment (PPE)

Welding Helmet

A welding helmet protects the face and eyes from arc flash, sparks, and spatter. Helmets come with passive (fixed shade) or auto-darkening lenses. Auto-darkening helmets have become popular because they allow clear vision when not welding and instant darkening when the arc strikes.

Lens Shade

The lens shade number indicates the darkness of the welding filter. Higher shade numbers provide more protection. Shade requirements depend on the welding process and amperage: SMAW typically requires shade 10-14, MIG welding shade 10-13, and TIG welding shade 8-12. Using too light a shade can cause eye damage. Too dark a lens reduces visibility.

Safety Glasses

Safety glasses should be worn under the welding helmet at all times to protect the eyes from slag and spatter when the helmet is raised. Impact-resistant glasses with side shields meet OSHA requirements for most welding applications.

Welding Gloves

Welding gloves protect hands from heat, sparks, and ultraviolet burns. Different glove types suit different processes: MIG gloves are lighter for dexterity, TIG gloves are thinner for finger sensitivity, and stick gloves are heavy-duty for maximum protection. I keep different gloves for each process I use regularly.

Welding Jacket

A welding jacket or sleeves protect the arms and torso from arc flash, sparks, and heat. Jackets are made from leather, flame-resistant cotton, or synthetic materials. Leather provides the best protection but is heavy and hot. Flame-resistant cotton offers lighter protection for general fabrication.

Respirator

Welding produces fumes that can be hazardous if inhaled. Respirators filter harmful particles and gases from the air. For most general welding, a N95 or P100 filter respirator provides adequate protection. For stainless steel or galvanized steel welding, specific filters for metal fumes may be required. Air-supplied respirators provide the highest protection in confined spaces or high-exposure applications.

Hazards and Health Effects

Arc Flash

Arc flash is the intense light and ultraviolet radiation produced by the welding arc. Even brief exposure can cause a painful condition called flash burn or arc eye. The condition feels like sand in the eyes and typically develops hours after exposure. Prevent arc flash by always wearing appropriate eye protection.

Arc Eye (Photokeratitis)

Arc eye is a painful eye condition caused by UV exposure, essentially a sunburn on the cornea. Symptoms include pain, light sensitivity, tearing, and a feeling of grit in the eyes. The condition typically heals in 1-2 days with supportive care, but prevention through proper eye protection is essential.

Metal Fume Fever

Metal fume fever is a flu-like condition caused by inhaling metal fumes, particularly from welding galvanized steel or zinc. Symptoms include fever, chills, nausea, headache, and muscle aches that appear 4-12 hours after exposure. The condition typically resolves within 24-48 hours once exposure stops.

Manganism

Manganism is a neurological condition caused by chronic manganese exposure from welding fumes. Symptoms resemble Parkinson’s disease and include tremors, slowed movement, and psychological changes. Proper ventilation and respiratory protection prevent manganese overexposure.

Protective Environments

Welding Curtain

A welding curtain is a translucent screen that blocks UV radiation while allowing some visibility. Curtains protect nearby workers from arc flash without completely isolating the welding area. They should be placed around any welding operation where others may be exposed to UV radiation.

Fume Extractor

A fume extractor removes welding fumes from the breathing zone. Units range from small portable extractors to large fixed systems. Local exhaust ventilation at the source of fume generation is most effective. Fume extractors are essential when welding materials that produce hazardous fumes or in confined spaces.

Confined Space

A confined space has limited access and is not designed for continuous occupancy. Tanks, vessels, and large pipes are examples. Welding in confined spaces requires special precautions including ventilation, air monitoring, and sometimes a designated attendant outside the space. Hot work permits are typically required.

Hot Work Permits

A hot work permit is a document that authorizes welding or other hot work in areas where fire hazards exist. The permit typically requires fire watch personnel, fire extinguisher availability, combustible material removal or protection, and verification that the work area is safe for hot work. I have seen hot work permits prevent multiple potential fires by ensuring fire safety measures are in place.

Fire Watch

Fire watch is a person assigned to monitor for fires during and after hot work operations. The fire watch maintains visual contact with the work area and has fire extinguishing equipment available. Fire watch typically continues for at least 30 minutes after welding stops to catch any smoldering fires that may develop.

Certifications and Standards Terminology

American Welding Society (AWS)

The American Welding Society is the primary organization for welding standards and certification in the United States. AWS develops welding codes, specifications, and certification programs that are widely adopted in industry.

CWI – Certified Welding Inspector

The CWI certification is the most recognized welding inspection credential. CWIs are qualified to inspect welds, develop welding inspection procedures, and verify compliance with codes. Certification requires passing a comprehensive exam and has renewal requirements every three years.

CW – Certified Welder

The Certified Welder program tests welder skill without requiring theory knowledge. welders deposit test coupons according to provided procedures, and the welds are evaluated by an AWS Certified Welding Inspector. Certification is process and position specific.

CWE – Certified Welding Educator

CWE certification is for welding instructors and teachers. It demonstrates knowledge of welding processes, teaching methods, and safety practices. CWE is valuable for vocational teachers and corporate trainers.

Welding Codes and Standards

AWS D1.1

AWS D1.1 is the Structural Welding Code – Steel. It is the most commonly used welding code in the United States for building and bridge construction. D1.1 covers welder qualification, welding procedure requirements, inspection criteria, and fabrication standards for structural steel.

AWS D1.2

AWS D1.2 is the Structural Welding Code – Aluminum. It provides requirements for welding aluminum structures similar to how D1.1 covers steel. Aluminum welding requires different procedures and criteria due to the material’s unique properties.

ASME Section IX

ASME Section IX is the Welding, Brazing, and Fusing Qualification section of the ASME Boiler and Pressure Vessel Code. It is used for qualifying welding procedures, welders, and welding operators for pressure-containing applications. Most power plant, refinery, and pressure vessel fabrication requires ASME Section IX qualification.

API 1104

API 1104 is the Standard for Welding of Pipelines and Related Facilities. It covers welding procedures, welder qualification, inspection, and repair requirements for pipelines. API 1104 is the primary code used in oil and gas transmission pipeline construction.

Qualification Documents

WPS – Welding Procedure Specification

A WPS is a written document that provides direction to the welder for making production welds. It specifies required and nonessential variables including process, base metal, filler metal, shielding gas, amperage range, voltage range, travel speed, and other parameters. Welders must follow the WPS to make code-compliant welds.

PQR – Procedure Qualification Record

A PQR documents the test results from welding a procedure qualification test coupon. It contains the actual parameters used, test results from destructive and nondestructive examination, and acceptance determination. The PQR supports the WPS and demonstrates that the procedure produces welds meeting code requirements.

WPQ – Welder Performance Qualification

A WPQ (also called welder qualification test) documents a welder’s ability to make sound welds according to a specific procedure. The welder deposits test coupons that are examined visually and often through destructive testing. A qualified welder may weld within the essential variable limits of their qualification.

Industry Slang and Colloquialisms

Every industry develops its own shorthand and slang, and welding is no exception. Understanding these informal terms helps you communicate naturally with experienced welders and understand shop talk.

Slang Term	Formal Term	Usage Context
Rod	SMAW electrode	“Grab me a 7018 rod”
Stinger	Electrode holder	“Pass me the stinger”
Birdhouse	Poor weld joint preparation	“Who built this birdhouse?” (criticizing bad fit-up)
Mud-rolling	Poor welding technique, excessive filler	“Stop mud-rolling and actually weld”
Sugar	Granular weld metal surface (poor technique)	“That weld looks like sugar”
Popping	Arc instability, spatter	“The machine is popping”
Stacking dimes	Desirable rippled weld appearance	“He’s stacking dimes on that TIG weld”
Buggered up	Damaged or ruined	“That thread is buggered up”
Heliarc	GTAW/TIG welding (brand name reference)	“Run a Heliarc bead on that”
Burn rod	Welding at excessive amperage	“You’re burning that rod up too hot”
Cold rod	Welding at insufficient amperage	“That’s a cold rod, turn up the heat”
Puddle pusher	Inexperienced welder (derogatory)	Shop banter

Frequently Asked Questions