Red Seal Welder key terms

The clothing and gear a welder wears to prevent injury, such as a welding helmet with proper filter shade, flame-resistant jacket, leather gloves, safety boots, and respiratory protection where fume exposure requires it.

The intense visible and ultraviolet light given off by an electric arc, which can burn exposed skin and eyes. Filter lenses and surrounding screens protect the welder and nearby workers from exposure.

The numbered lens darkness selected for a welding process and current level. Higher amperage or more intense processes need a higher shade number to keep arc radiation at a safe level for the eyes.

The controlled procedure for entering a tank, vessel, or pit with limited access and poor natural ventilation, requiring atmospheric testing, an attendant, a rescue plan, and often a hot work permit before welding begins.

A written authorization confirming that fire hazards have been controlled before welding, cutting, or gouging starts, including removal of combustibles, fire watch assignment, and checks of surrounding areas and openings.

A person assigned to watch for and extinguish fires during and after hot work, staying in the area for a required period after the work stops to catch smoldering material that may ignite later.

The procedure for isolating and de-energizing equipment so it cannot start or release stored energy while a welder services or works on it. Each worker applies a personal lock and tag.

Local exhaust ventilation that captures smoke and metal fume at the arc before it reaches the welder's breathing zone, reducing exposure to manganese, chromium, and other harmful particulate.

A welding supply that holds current nearly steady as arc voltage changes, which is the characteristic needed for shielded metal arc and gas tungsten arc welding so arc length variation does not swing amperage wildly.

A welding supply that holds voltage nearly steady while current changes with wire feed and arc length, which suits gas metal arc and flux cored arc welding because the self-regulating arc controls deposition.

The percentage of a ten-minute period a power source can operate at a stated output without overheating. A 60 percent duty cycle at 200 amps allows six minutes of welding at that current.

The rate at which filler wire is pushed into the arc, usually set in inches or metres per minute. On a constant voltage system it is the main control of welding current and deposition rate.

The volume of protective gas delivered per unit time, set with a regulator and flowmeter. Too little allows porosity from air; too much causes turbulence that also draws in air and wastes gas.

A gas or gas mixture supplied around the arc to exclude air and stabilize the arc. Argon, helium, carbon dioxide, and oxygen blends are chosen to suit the process, metal, and transfer mode.

The welding current carried per unit area of electrode cross section. Increasing it raises melt-off rate and penetration, which is why small-diameter electrodes at high amperage deposit faster but risk overheating.

The insulated clamp that grips a covered electrode and carries welding current to it. It must be sized for the amperage used and kept with insulation intact to prevent shock and arc strikes.

The device that connects the work lead to the workpiece and completes the welding circuit. A poor connection causes erratic arcs, resistance heating, and possible arcing at unintended points.

The shorthand marking on a drawing that shows weld type, size, length, spacing, and location relative to the joint, read together with the reference line, arrow, and tail.

The horizontal line in a welding symbol to which the arrow, weld symbols, dimensions, and tail attach. Symbols above the line mean the weld is on the arrow side; below means the other side.

The side of a joint indicated by the arrow of a welding symbol. A weld symbol placed above the reference line applies to the arrow side, while one below applies to the other side.

The shaping of edges before welding, such as bevel angle, root gap, and root face, which allows full penetration and sound fusion in thicker material. It is usually specified on the drawing.

A list on or with the drawing that gives the parts, sizes, material specifications, and quantities needed to build the assembly, used for cutting lists and material takeoff.

The body-centered cubic form of iron that exists at room temperature in plain carbon steel. Its amount and distribution strongly affect strength, ductility, and toughness of the weld and heat-affected zone.

The face-centered cubic form of iron stable at high temperature, able to dissolve much more carbon than ferrite. Its transformation on cooling determines the microstructure and hardness of the weld.

A hard, brittle structure formed when steel cools fast enough that carbon cannot diffuse out of solution. It raises hardness and cracking risk, so preheat and controlled cooling are used to limit it.

The base metal next to the weld that has been heated but not melted. Its properties change with the thermal cycle and it is often where hardness, toughness loss, or cracking occurs.

A calculated number combining carbon with other alloying elements to estimate how readily a steel hardens and cracks during welding. Higher values generally call for more preheat and controlled heat input.

Heating the base metal before welding to a specified temperature to slow cooling, reduce hardness, and help hydrogen escape. It is commonly required for thick sections and higher-carbon or alloy steels.

The temperature of the workpiece measured between passes, which must stay within a specified range. Too high can reduce toughness; too low can promote hard, crack-prone structures.

Delayed cracking caused by hydrogen trapped in the weld, often appearing hours after cooling in hard microstructures under restraint. Low-hydrogen electrodes, clean surfaces, and preheat reduce the risk.

Controlled heating of a completed weldment to a set temperature and holding period, then slow cooling, to relieve residual stress, soften hard zones, or restore specified properties.

Internal stress locked into a weldment by uneven heating, cooling, and shrinkage. It can cause distortion or cracking and is managed by sequencing, restraint control, peening, or heat treatment.

Unwanted change in shape or dimensions caused by weld shrinkage. It is controlled by balanced sequences, backstep welding, proper fit-up, presetting, and limiting heat input.

A technique in which short weld segments are deposited opposite to the general direction of progress, so each pass starts on already cooled metal, which spreads heat and reduces distortion and cracking.

The space left between the prepared edges at the root of a joint before welding. It allows penetration to the root and must match the procedure for the process and thickness used.

The first weld pass made at the bottom of a joint, which establishes penetration and forms the foundation for later passes. Defects here are hard to remove, so it is closely controlled.

Material placed behind the root to support the molten pool and help control penetration. It may be permanent, such as a steel strip, or removable, such as ceramic or copper.

A short weld used to hold parts in alignment until the main welds are made. Tacks must be sized and cleaned so they fuse fully into the finished joint rather than leaving a defect.

The alignment and spacing of parts before welding, including gap, mismatch, and squareness. Poor fit-up causes distortion, incomplete fusion, and rework that no welding technique can fully correct.

Cavities in a weld caused by gas trapped as the metal solidifies. It commonly results from moisture, oil, paint, drafts, or inadequate shielding gas coverage.

Nonmetallic slag trapped in the weld, usually from poor cleaning between passes or incorrect travel angle in flux-based processes. It reduces section thickness and acts as a stress raiser.

Removal of slag, spatter, and oxide between weld passes so each new pass fuses to clean metal. Skipping it is a common cause of slag inclusions and incomplete fusion.

A lack of bonding between the weld metal and base metal or between passes, caused by low heat input, wrong angle, fast travel, or contamination. It is a serious defect in loaded joints.

A groove melted into the base metal along the weld toe that is left unfilled. It thins the section and concentrates stress, and is corrected by travel angle, arc length, and current control.

Examination of the completed weld and surrounding area by eye, often with a magnifier and light, to find surface defects such as undercut, porosity, cracks, and poor profile before other testing is chosen.

A surface method in which a penetrant is applied, excess removed, and a developer draws trapped penetrant out to reveal cracks and pores. It works on nonporous materials and detects surface-breaking flaws only.

A surface and near-surface method that magnetizes ferromagnetic material and applies iron particles, which gather at discontinuities. It reveals cracks and laps but cannot be used on austenitic stainless steel.

A volumetric inspection method using X-rays or gamma rays to produce an image of internal weld condition, revealing porosity, slag, and lack of penetration. It requires radiation safety controls.

A volumetric method that sends high-frequency sound into the weld and reads reflections from internal flaws such as cracks and lack of fusion. It needs a trained operator and a smooth surface.

The width of material removed by a cutting process. It must be allowed for in layout so the finished part keeps the required dimensions, and it widens with higher amperage or faster travel.

The angled marks left on a cut edge when the cutting jet lags behind its travel. Excessive drag indicates travel speed, pressure, or tip condition that needs correction.

A process that heats steel to its ignition temperature with a fuel gas flame and then cuts it with a stream of pure oxygen. It suits carbon steel and is unsuitable for aluminium and stainless steel.

A process using a carbon electrode and compressed air to melt and blow away metal for removing welds or preparing a groove. It must be followed by grinding to remove carbon contamination.

A process that constricts an arc through a small orifice to produce a very hot jet that cuts metals including stainless steel and aluminium. It gives narrow kerfs and fast travel on thin material.

A written document giving the variables a welder must follow for a particular joint, such as process, filler, current range, preheat, and pass sequence. It is supported by a qualified procedure test record.

The record of the test weld made to prove a welding procedure produces sound results under the specified variables. It documents actual conditions and test outcomes and supports the written procedure.

Testing of an individual welder's ability to produce acceptable welds to a given standard, recorded with the process, position, thickness, and joint type covered so the welder knows the limits of the certification.

The orientation of the joint during welding, such as flat, horizontal, vertical, or overhead. Position changes how gravity affects the pool and which techniques and current settings are suitable.

The energy delivered per unit length of weld, calculated from voltage, current, and travel speed. It controls cooling rate and therefore hardness, toughness, and distortion in the finished joint.

The rate at which the arc moves along the joint. It affects bead size, penetration, heat input, and the risk of undercut or incomplete fusion, so it is a controlled variable in most procedures.