Welding Terms

AC or Alternating Current - electric current that reverses direction periodically. Sixty cycle current travels in both directions sixty times per second.

Arc Length - the distance from the end of the electrode to the point where the arc makes contact with the work surface.

Base Metal - the material to be welded. Butt Joint - a joint between two members aligned approximately in the same plane.

Crater - a pool, or pocket, that is formed as the arc comes in contact with the base metal.

DC or Direct Current - electric current which flows only in one direction. The polarity (+ or -) determines which direction the current is flowing.

DC Reverse Polarity - occurs when the electrode holder is connected to the positive pole of the welding machine. Reverse Polarity directs more heat into melting the electrode rather then the work piece. It is used on thinner material.

DC Straight Polarity - occurs when the electrode holder is connected to the negative pole of the welding machine. With straight polarity more heat is directed to the work piece for better penetration on thicker material.

Electrode - a coated metal wire having approximately the same composition as the material being welded.

Fillet Weld - approximately a triangle in cross-section, joining two surfaces at right angles to each other in a lap, T or corner joint.

Flux - a coating, when heated, that produces a shielding gas around the welding area. This gas protects the parent and filler metals from impurities in the air. Flux Cored Arc Welding (FCAW) - also called Gasless, is a welding process

used with a wire-feed welding machine. The weld wire is tubular with flux material contained inside for shielding.

Gas Metal Arc Welding (GMAW) - also called MIG, is a welding process used with a wire feed welding machine. The wire is solid and an inert gas is used for shielding.

Gas Tungsten Arc Welding (GTAW)

-also called TIG, is a welding process used with welding equipment with a high frequency generator. The arc is created between a non-consumable tungsten electrode and the work piece. Filler metal may or may not be used.

Inverter - Technology that converts high voltage AC input power into high amperage DC welding output power through the use of transistor-bridge and constant current rectifier instead of a heavy traditional transformer.

Lap Joint - a joint between two overlapping members in parallel planes. MIG - See “Gas Metal Arc Welding.” Open Circuit Voltage (OCV) - the voltage between the electrode and the ground clamp of the welding machine when no current is flowing (not welding). The OCV determines how quickly the arc is struck.

Overlap - occurs when the amperage is set too low. In this instance, the molten metal falls from the electrode without actually fusing into the base metal. Porosity - gas pockets, or cavities, formed during weld solidification. They weaken the weld.

Penetration - the depth into the work piece that has been heat effected by the arc during the welding process. A good weld achieves 100% penetration meaning that the entire thickness of the work piece has been heated and resolidified. The heat

effected area should be easily seen on the opposite side of the weld.

Shielded Metal Arc Welding (SMAW) - also called Stick, is a welding process with uses a consumable electrode to support the arc. Shielding is achieved by the melting of the flux coating on the electrode.

Slag - a layer of flux soot that protects the weld from oxides and other contaminants while the weld is solidifying (cooling). Slag should be removed after weld has cooled.

Spatter - metal particles thrown from the weld which cool and harden on the work surface. Spatter can be minimized by using a spatter resistant spray on the work piece before welding.

Stick - See “Shielded Metal Arc Welding.”

Tack Weld - weld made to hold parts in proper alignment until final welds are made.

TIG - See “Gas Tungsten Arc Welding.” Travel Angle - the angle of the electrode in the line of welding. It varies from 5º to 45º depending on welding conditions.

T Joint - made by placing the edge of one piece of metal on the surface of the other piece at approximately a 90º angle. Undercut - a condition that results when welding amperage is too high. The excessive amperage leaves a groove in the base metal along both sides of the bead which reduces the strength of the weld. Weld Pool or Puddle - a volume of molten metal in a weld prior to its solidification as weld metal.

Weld Bead - a narrow layer or layers of metal deposited on the base metal as the electrode melts. Weld bead width is typically twice the diameter of the