Glossary 873 Interview: A meeting between prospective employer and prospective employee. Inverter: A special transformer-type welding power source that changes incoming ac current to dc, then back to very-high-frequency ac current. Inverter switcher: A series of silicon-controlled rectifi ers (SCRs) or transistors that are turned on and off very rapidly and invert dc into very high-frequency, square wave ac. Ion: An atom or a group of atoms that becomes positively or negatively charged as a result of having gained or lost one or more electrons. Also, a free electron. Ionization: Adding or removing electrons from atoms or molecules to create ions. Ionized: A term that means that some of the electrons in a gas have broken away from their atoms. Iron carbide: The compound also known as cementite (Fe3C). It contains 6.67% carbon. Iron-carbon diagram: A diagram that shows the critical temperatures for the varying amounts of carbon in iron that form steels or cast irons. Iron ore: An ore from which iron can be extracted. Izod test: Type of test for impact strength that is made by striking the test piece with a measured downstroke of a pendulum. The specimen, usually notched, is held by one end in a vise. Energy absorbed, which is measured by the upward swing of the pendulum, indicates the impact strength of the specimen. J Jig: A device that holds the work and guides a drill or tool during a cutting operation. Job application: A form on which a prospective employee lists relevant skills and experience. Jog switch: A switch used to feed wire to the gun at a rela- tively slow speed to prevent kinking the wire. Joint: Line or area where two pieces are joined in an assembly. Joint effi ciency: Strength of a welded joint, given as a percentage of the strength of the base metal. Joint geometry: The shape and dimensions of a (weld) joint, in cross section, prior to welding. Joint penetration: The depth of weld metal and base metal fusion in a welded joint. K Kerf: Width of material removed by a cutting operation. Keyhole: A hole at the leading edge of the weld pool. The keyhole, if visible, ensures that the joint has proper penetration. Keyhole method: Welding method used to ensure complete penetration in a groove weld. K illed steel: Steel that has been deoxidized (treated with a strong agent to reduce the oxygen content). Deoxidizing is carried to the point where no reaction takes place between carbon and oxygen as the metal solidifi es. Kilopascal (kPa): The unit of pressure in SI Metric (one thousand pascals). See Pascal. Kilovolt amperes: Thousands of watts. Knife switch: A device used to complete the welding circuit during underwater welding. The knife switch is above water and is used to electrically connect the welding leads to the welding power supply. KVA (kilovolt-ampere) rating: The input or primary circuit rating for a resistance welding transformer. L Lack of fusion: A type of weld defect caused by lack of union between the weld metal and the base metal. Ladle: Large vessel into which steel is poured prior to casting. Ladle degassing: Process that removes gases from steel produced by basic oxygen furnaces. Laminate: Sheets or bars made up of two or more metal layers built up to form a structural member. Also, the process of forming a metallic product with two or more bonded layers. Lap joint: A joint in which the edges of the two metals to be joined overlap. Laser: Light amplifi cation by stimulated emission of radiation. Laser beam cutting: Laser cutting method that uses a constant beam. Laser beam drilling (LBD): The use of lasers to drill extremely small diameter holes to exact depths. Laser beam welding (LBW): Process in which a single- frequency light beam concentrates a small spot of heat to fuse small, light metal materials. Latent heat: The heat added or removed from a substance as it undergoes phase change. Layer: A certain weld metal thickness made of one or more passes. Lead: A wire carrying electricity from the power source to the electrode holder or to the ground clamps. LED: Light-emitting diode. This is a small, bright light, often powered by as little as 5 volts dc. Left side view: The view on a working drawing that shows the shape and size of an object’s left side. Leg of fi llet weld: Distance from the point where the base metals touch at the root of the joint to the toe of the fi llet. Length dimension: Used to indicate the length of each weld on intermittent welds. Lens: Specially treated glass or plastic through which a welder may look at an intense fl ame without being injured by the harmful rays or glare. Letter drill sets: Drill sets that come in sizes “A” (0.234″) to “Z” (0.413″). Light-emitting diode (LED): A small, bright light, often powered by as little as 5 volts dc. Light metal: A low-density metal such as aluminum, magnesium, titanium, beryllium, or their alloys. Liner: The electrode wire carrier in a GMAW welding gun. Liquefi ed petroleum (LP): A compressed hydrocarbon gas used mostly for cutting, soldering, and brazing.