864 Modern Welding Carbon monoxide: A colorless, odorless, toxic gas that unites readily with oxygen to form carbon dioxide (CO2). Carbon steel: An alloy of iron and controlled amounts of carbon. Carburizing fl ame: A reducing oxyfuel gas fl ame in which there is an excess of fuel gas, resulting in a carbon-rich fl ame zone beyond the inner cone. Casehardening: Adding carbon to the surface of a mild steel object and heat treating it to produce a hard surface. Cast aluminum: Aluminum that is shaped by pouring it into a mold and then solidifying it by cooling. Castings: Metallic forms that are produced by pouring molten metal into a shaped container or cavity called a mold. Cast iron: A hard, brittle, nonmalleable commercial alloy of iron, 1.7%–4.5% carbon, and silicon that is cast in a mold. Cast-weld assembly: An assembly in which cast parts are fi xed in place by welding. Cathode: Electrical term for a negative terminal. Caustic solution: A solution that is capable of eating away a material by chemical action. Celsius: Temperature scale in SI Metric. Cementite: The compound also known as iron carbide (Fe3C). It contains 6.67% carbon. Center line: A line, composed of long and short dashes, that is drawn through the exact center of a circular part or hole in a drawing. Centrifugal: Relating to a force directed outward from the center of rotation. Chain intermittent weld: Type of intermittent weld in which the welds on either side of the joint begin and end at the same spot. Chamfer: See Bevel. Charge: Used to describe a batch of metal that is being processed in a furnace. Charpy: A type of impact testing machine which strikes the specimen with a swinging hammer. The specimen is placed against an anvil with supports 40mm apart. Check valve: A valve that allows a liquid or gas to fl ow in only one direction. It closes when fl ow in the opposite direction is attempted. Chemical analysis: A test to determine the chemical makeup of a metal. Chemical cleaning: Using a solvent to remove oil and grease from parts. Chemical corrosion: Deterioration of metal due to expo- sure to corrosive chemicals. Chemical fl ux cutting (OC-F): Oxyfuel gas cutting process that uses a chemical fl ux to help in cutting some materials. Chill: To cool rapidly. Chipping hammer: A pointed hammer used to remove slag from weld beads. Chip test: The removal of a small sample of metal with a chisel so that the metal’s structure can be analyzed. Chlorination: A process in which dry chlorine gas is passed through a molten aluminum alloy to remove trapped oxides and dissolved gases. Chrome-molybdenum steels: Relatively corrosion-resistant steels that contain from 0.5% to 9.0% chromium and from 0.5% to 1.0% molybdenum. They are used when strength at high temperatures is required. Circuit: The path of electron fl ow from a source through components and connections back to the source. Cladding: A somewhat thick layer of material applied to a surface to improve resistance to corrosion or other agents that tend to wear away the metal. Clearance: The gap or space between adjoining or mating surfaces. Coalescence: The intermixing or growing together of mate- rials into one body while being welded. Coated electrode: A nonstandard term. See Covered electrode. Code: Written requirements for developing and testing work procedures. Cofferdam: A structure built around the structure being welded in order to keep water out of the working area of a project. Also called a coffer or caisson. Coherent: Term used to describe waves of light that are in-phase and move together. Cohesion: Sticking together through the attraction of molecules. Coke: Fuel used in a blast furnace to reduce iron ore. It is produced by heating soft (bituminous) coal that is in a closed container until the gases and impurities are driven off. Coking: Driving out combustible gases from coal. Cold welding (CW): A process that makes use of high pres- sure and no outside heat to force metal parts to fuse. Cold work: A metal part on which a permanent strain has been placed by an outside force while the metal is below its recrystallization temperature. Cold working: Bending (deforming) metal at a temperature lower than its recrystallization temperature. Collet body: GTAW torch component that contacts and centers the collet and transfers the electrical current to the collet. Color test: A visual test that identifi es categories of metals based on their color. Combination ac and dc arc welding power sources: Power sources that include transformers with a dc rectifi er, motor- or engine-driven generators with a dc rectifi er, and inverters. Combined stresses: A stress type that is more complex than simple tension, compression, or shear. Combustible: Flammable, easily ignited. Commutator: The collection of copper bars or segments that are connected to the armature coil windings in a generator. Complete fusion: Fusion that has occurred over the entire fusion surface of a base metal being welded. Complete joint penetration: A situation in which weld metal completely fi lls the groove and fuses with the base metal through its entire thickness. Compression fi ttings: Type of fi tting commonly used on small copper or steel tubing. A threaded nut is tightened over the tube and onto the threaded fi tting to form a tight seal. Compressive strength: The greatest stress developed in a material under compression.