NOCTI Study Guide

Welding
Uses extreme heat to join or fuse pieces of metal together.
Pressure Welding
The metal is heated to a softened state by electrodes. Pressure is applied and the metal is joined.
Fusion Welding
Pieces of metal are heated to the melting point, joined together, and allowed to cool.
Weld Root
The part of the joint where the wire electrode is directed.
Weld Face
The exposed surface of the weld on the side that has been welded.
Weld Penetration
Indicated by the height of the exposed surface of the weld on the back side. Full weld penetration is needed to assure maximum weld strength.
Burn Mark
An indication of good weld penetration.
Burn-Through
Results from penetrating too much into the lower base metal, which burns a hole through the back side of the metal.
Weld Legs
The width and height of the weld bead.
Weld Throat
Refers to the depth of the triangular cross section of the weld.
Joint Fit-Up
Refers to holding work pieces tightly together, in alignment to prepare for welding.
Metal Inert Gas Welding (MIG)
Offers more advantages than other methods for welding high-strength steels and high-strength, low alloy steel component parts used in modern cars.
Tungsten Inert Gas (TIG)
Uses a handheld rod and gas-shielded arc, is often recommended when welding aluminum alloy body panels
Heat Effect Zone
The area around the weld that becomes adversely hot.
Welding Blankets
Thick covers made of fire-resistant cloth for protecting vehicle surfaces from heat, sparks, and weld splatter.
Electronic Shielding
Needed when welding near on-board computers and sensor wiring.
DC Reverse Polarity
Means the wire (electrode) is positive and the workpiece is negative.
Welding Filter Lens
Sometimes called a filter plate, a shaded glass welding helmet insert for protecting your eyes from ultraviolet burns.
Welding Current
Affects the base metal penetration depth, the speed at which the wire is melted, arc stability, and the amount of weld splatter.
Undercutting
Producing a weld surface level lower than base metal.
Heat Sink Compound
A paste that can be applied to parts to absorb heat and prevent warpage.
Flat Welding
Means the pieces are parallel with the bench or shop floor.
Horizontal Welding
Has the pieces turned sideways.
Vertical Welding
Has the pieces turned upright.
Overhead Welding
Has the workpieces turned upside down.
Tack Weld
A tack, relatively small, temporary MIG spot weld that is used instead of a clamp or sheet metal screw to tack and hold the fit in place while proceeding to make a permanent weld.
Continous Weld
An uninterrupted seam or bead is laid down in a slow, steady, ongoing movement.
Plug Weld
Made in a drilled or punched hole through the outside piece (or pieces).
Spot Weld
In an MIG spot weld, the arc is directed to penetrate both pieces of metal, while triggering a timed impulse of wire feed.
Lap Weld
In the MIG lap spot technique, the arc is directed to penetrate the bottom piece and the puddle is allowed to flow into the edge of the top piece.
Stitch Weld
A series of connecting or overlapping MIG spot welds, creating a continuous seam.
Insert
Backing strip, made of the same metal as the base metal can be placed behind the weld.
Aluminum Electrode Wire
Classified by series, according to the metal or metals the alluminum is alloyed with and whether the alluminum is heat treated.
Destructive Test
A test piece of the same metal as the welded piece and with the same panel thickness.
Nondestructive Test
To confirm a spot weld after it has been made, use a chisel and hammer and proceed.
Neutral Flame
The standard flame is said to be a neutral flame.
Carburizing Flame
Also called a surplus or reduction flame, is obtained by mixing slightly more acetylene than oxygen.
Oxidizing Flame
Obtained by mixing slightly more oxygen than acetylene.
Heat Crayons
Also called thermal paint, can be used to determine the temperature of the alluminum or other metal being heated.
Brazing
Applied only to places for sealing.
Plasma Arc Cutting
Creates an intensely hot air stream, which melts and removes metal over a very small area.