MTTC Welding Trade Test key terms

The maximum airborne concentration of a hazardous substance, such as welding fume or manganese, that a worker may be exposed to over a set time period under workplace safety regulations.

A capture system placed close to the arc or flame that pulls fume and gases away before they reach the welder's breathing zone, typically through a hood, arm, or table slot.

A semi-automatic welding gun with built-in vacuum ports near the nozzle that captures smoke at the source and carries it through a hose to a filter unit.

A written authorization issued before welding, cutting, or grinding begins in a designated area, confirming fire watches, combustibles removal, and precautions are in place.

A trained person assigned to monitor sparks and slag during and after hot work, with authority to stop the job and extinguish fires, remaining on station for a required period.

A sudden release of intense radiant energy and molten metal caused by an arc fault or short circuit, capable of burning skin and eyes and igniting clothing.

Ultraviolet radiation injury to the cornea and conjunctiva from viewing an arc without proper filter protection, causing pain, tearing, and sensitivity to light hours later.

A scale rating the darkness of a welding filter lens; higher numbers block more visible and ultraviolet light and are chosen based on process and amperage.

A welding machine that holds amperage nearly steady as arc length changes, giving the welder direct control of current and making it suited to shielded metal arc and gas tungsten arc welding.

A machine whose output voltage stays nearly fixed while current varies widely with wire feed speed and arc length, the standard characteristic for gas metal arc and flux cored welding.

The percentage of a ten-minute period a power source can operate at a rated output without overheating, such as sixty percent at 200 amps.

A gas or gas mixture supplied around the arc to exclude atmospheric oxygen and nitrogen, protecting the molten weld pool from contamination and oxidation.

A process using a continuously fed consumable wire electrode and an externally supplied shielding gas, often called MIG welding, suited to high-deposition semi-automatic work.

A GMAW mode in which the wire touches the pool, extinguishes the arc, and transfers metal as a droplet before the arc reignites, producing low heat input for thin material.

A high-current GMAW mode where fine molten droplets stream axially across the arc without shorting, giving deep penetration and smooth beads on thicker plate.

Deflection of the arc from its intended path by magnetic forces, often near ground connections or at the ends of joints, causing inconsistent penetration and spatter.

The device connecting the work lead to the workpiece to complete the welding circuit; its placement affects arc stability and magnetic deflection.

A drawing method showing a three-dimensional object as aligned two-dimensional views, typically a front view plus top and side views arranged by first- or third-angle convention.

A dashed line on a drawing indicating an edge or feature not visible in the current view, used to locate internal holes, slots, or passages.

A line of alternating long and short dashes marking an axis of symmetry or the center of a hole pattern, used to lay out locations and check symmetry.

A drawing notation with a reference line, arrow, and supplementary elements that specifies weld type, size, length, location, and process for a joint.

The total included angle between the prepared faces of a groove weld joint, controlling access for the electrode and fusion into the sidewalls.

The angle formed between one prepared joint face and a line perpendicular to the plate surface, usually half of the total groove angle on a symmetrical V joint.

The separation left between the two members at the joint root before welding, which allows penetration through the thickness and influences root bead shape.

The first weld bead deposited at the bottom of a joint, which must fuse both root faces completely and forms the foundation for subsequent passes.

Material such as a metal strip, ceramic tile, or flux layer placed behind the joint root to support the molten pool and help control penetration.

The base metal region adjacent to the weld that is altered by heat without melting, where hardness, toughness, and microstructure can change significantly.

Heating base metal before welding to slow cooling, reduce thermal gradients, and lower the risk of cracking in thick sections or hardenable steels.

A calculated value combining carbon and other alloying elements to estimate a steel's hardenability and its susceptibility to cold cracking during welding.

A chromium-nickel steel with a face-centered cubic structure that is nonmagnetic in the annealed condition and prone to sensitization and hot cracking if not controlled.

The precipitation of chromium carbides at grain boundaries in austenitic stainless steel during certain heating, leaving chromium-depleted zones that are vulnerable to corrosion.

The documented test record showing that a welded test coupon made under a specific procedure met required mechanical and visual tests.

A written document listing the variables, ranges, and techniques a welder must follow to produce a weld that complies with a qualified procedure.

A welding parameter, such as process, filler classification, or preheat, that must be changed only within stated limits because it affects weld mechanical properties.

Examination of welds and joints by eye, aided by lighting, magnification, and gauges, to detect surface discontinuities, undercut, and dimensional nonconformance.

A set of formed metal tools used to measure fillet weld leg and throat size, reinforcement height, undercut depth, and fit-up gaps on completed joints.

A groove melted into the base metal along the weld toe or root that is left unfilled by filler metal, reducing cross-sectional thickness and acting as a stress riser.

The width of material removed by a cutting torch or arc, which must be accounted for in layout and which affects cut quality and part dimensions.

The nearly vertical marks left on a flame-cut edge when the cutting oxygen stream lags behind the torch travel, indicating excessive speed or improper tip selection.

The ability of a liquid filler to flow into a narrow joint gap by surface tension and wetting, the mechanism that draws brazing and soldering filler into a lap joint.

A chemical compound applied during brazing, soldering, or welding that dissolves oxides and shields the joint from air so filler metal can wet and flow.