I-CAR AWQT key terms

The distance from the end of the GMAW gun's contact tip to the surface of the workpiece. Too long reduces current density and shielding coverage; too short can cause tip burn-back and spatter buildup.

The rate at which filler wire is pushed through the gun, usually expressed in inches or meters per minute. Along with voltage it sets the welding current and therefore penetration and bead profile.

A power-source mode in which the machine automatically adjusts voltage and arc characteristics to match the selected wire feed speed and material. Reduces operator setup error on thin automotive steels.

The volume of shielding gas delivered per unit time, typically set in liters per minute or cubic feet per hour. Too little allows porosity; too much creates turbulence that draws in air.

The percentage of a ten-minute period a welding machine can operate at a given output without overheating. Exceeding it causes thermal shutdown or reduced output during production repairs.

The machine that converts input power into the controlled current and voltage needed for arc welding. Its characteristic curve, constant voltage for GMAW, determines how the arc self-regulates.

A documented set of parameters, including process, filler, gas, current, and travel speed, approved for a specific joint. Technicians must follow the applicable WPS rather than improvising settings.

The documented test results proving that a welding procedure produces sound joints when made and destructively tested to a recognized standard. It supports the WPS but does not replace OEM repair instructions.

A process in which electrodes clamp the panels and pass current to form a molten nugget at the faying interface. Squeeze force, current, and time must match the steel grade and stack-up.

The mating interface between two overlapping panels where the resistance spot weld nugget forms. Cleanliness and contact at this interface control whether a sound nugget develops.

The clamping pressure applied by the spot welding gun during squeeze, weld, and hold time. Insufficient force causes expulsion and surface marking; excessive force can collapse thin or high-strength panels.

The measured width of the fused zone in a resistance spot weld, checked by peel or plug test. It must meet the minimum size specified for the panel thickness and steel type.

A destructive check in which a chisel or special tool separates a spot weld, leaving a plug of one panel pulled from the other. Plug size and shape indicate nugget quality.

Molten metal ejected from the weld zone during resistance or arc welding, often as sparks or surface blow-through. It signals excessive current, poor fit-up, contamination, or insufficient electrode force.

A joining process using a GMAW-type arc to melt a low-melting filler such as silicon bronze while the base steel stays solid. Common on galvanized and high-strength panels where fusion welding is restricted.

A copper-based filler wire, typically containing silicon and sometimes tin, used for MIG brazing of steel. It melts well below steel and wets the surface to form a joint without fusing the base metal.

The ability of molten filler to spread and bond smoothly over the base metal surface. Good wetting depends on cleanliness, correct heat input, and suitable shielding gas.

A corrosion-protective layer on galvanized or zinc-coated steel. It must be considered during welding because vaporized zinc can cause porosity and fume exposure, and removal or restoration may be required.

A formable steel that gains strength during paint-bake thermal cycles. Repairs must respect heat limits because excessive welding heat can alter its final properties.

A family of steels with complex microstructures giving high strength at reduced thickness. They often require specific welding processes, heat limits, and OEM-approved joining methods during collision repair.

The region of base metal whose microstructure changes from welding heat without melting. In high-strength steels it can soften or harden, affecting the strength of the repaired joint.

Corrosion driven by contact between dissimilar metals in the presence of an electrolyte. Joining aluminum to steel creates a risk that requires isolation and OEM-specified fastening or adhesive methods.

Connecting two different metals, such as aluminum and steel, where direct fusion is generally unsuitable. Approved methods include rivets, adhesives, and specialized fasteners per OEM instructions.

A fastener driven through the top panel and flared into the lower panel without a pre-drilled hole. It is a common OEM-approved method for aluminum and dissimilar-metal body joints.

A hard, electrically insulating film that forms rapidly on aluminum surfaces. It must be removed immediately before welding to prevent incomplete fusion and porosity.

A GTAW mode in which current reverses direction periodically. The reverse half-cycle cleans the aluminum oxide layer while the forward half-cycle provides penetration, making AC common for aluminum.

Gas pockets trapped in solidified weld metal, appearing as internal or surface voids. Causes include contamination, moisture, poor gas coverage, and vaporized coatings.

A discontinuity where weld metal fails to bond to the base metal or to a previous pass. It often results from insufficient heat, poor cleaning, or wrong travel angle.

A hole melted completely through a panel because heat input exceeded what the thickness could absorb. It is common on thin-gauge sheet and is corrected by reducing current or increasing travel speed.

The amount of thermal energy delivered per unit length of weld, influenced by current, voltage, and travel speed. It controls penetration, distortion, and the extent of the heat-affected zone.

A sample joint made with production settings and then cut, bent, or pulled to reveal internal quality. It verifies that equipment and technique produce acceptable welds before work on the vehicle.

Visual and mechanical examination of a completed weld for size, profile, fusion, and defects. It confirms the repair meets the OEM and industry acceptance criteria before refinishing.

The gear worn to reduce welding hazards, including helmet with proper shade, gloves, flame-resistant clothing, and eye protection. Selection must match the process and task.

The darkness rating of the auto-darkening or passive filter lens. It must suit the process and current so the arc is visible without exposing the eyes to harmful radiation.

Local exhaust or ventilation that removes metal oxide and gas byproducts from the breathing zone. It is essential when welding coated or galvanized steel and in confined shop areas.

The vehicle manufacturer's published instructions for sectioning, joining, and corrosion protection. These instructions take precedence over general shop practice and must be followed for a compliant repair.

Cutting a replacement panel or structural part at a manufacturer-approved location and joining it to the remaining original metal. Cut points, backing, and weld types are specified by the OEM.

A conductive coating applied to mating surfaces before welding to limit corrosion at the joint. It must be OEM-approved and compatible with the joining process used.