Glossary 865 Concave weld face: A weld with the center of its face below the weld edges. Conductivity: A measure of how well electrical current passes through a material. Conductor: A substance capable of readily transmitting electricity or heat. Cone: The inner visible fl ame shape of a neutral or nearly neutral fl ame. Connectors: Insulated terminals on welding leads that allow the leads to be quickly connected to or discon- nected from the welding supply. Constant current: Amperage that changes very little in relation to changes in voltage. Constant current power sources: An arc welding machine that produces constant current. Constant current transformer-rectifi er: A transformer- rectifi er–type welding machine that produces constant current. Constant voltage: Voltage that changes very little in rela- tion to changes in amperage. Constricting: Reducing in size or diameter, as in a constricted arc, constricting orifi ce, or constricting nozzle. Constricting nozzle: The part of the PAC torch that acceler- ates and concentrates the arc and plasma fl ow to create a cutting jet. Consumable electrodes: Electrodes that melt and become part of the weld. Contact tip: See Contact tube. Contact tube: The part of a welding gun that transfers the electrical current from the welding gun to the electrode wire. Continuous casting: Metal that is cast in a continuous form. Continuous casting process: A method of casting metal in an open-ended mold so that metal is fed into and cools in the mold in a continuous form. Continuous current: Uninterrupted current used to create a continuous seam weld. Continuous weld: Making the complete weld in one nonstop operation. Continuous weld pool: A molten pool of metal that is carried along the seam of the parts to be welded together. Contoured: Shaped. Contract: An agreement between the manufacturer or builder of a product and the buyer regarding the way the product will be built. Controller: The heart of a machining or robotic system. It contains the program that controls the welding or machining variables. Convex: Curved outward. Convex weld: A weld with the face above the weld edges. Cooling stresses: Stresses resulting from uneven distribu- tion of heat during cooling. Copper-based electrodes: A class of SMAW electrodes composed mainly of copper. Corner joint: The junction formed by edges of two pieces of metal touching each other at an angle of about 90° (a right angle). Corrosion: The chemical and electrochemical interaction of a metal with its surroundings that causes it to deteriorate. Corrosion embrittlement: The loss of ductility or work- ability of a metal due to corrosion. Corrosion fatigue: The effect of repeated stress in a corro- sive atmosphere, characterized by shortened life of the part. Couplant: A material placed between the transducer and the metal test surface during ultrasonic testing. Coupon: A piece of metal used as a test specimen. Covered electrode: A metal rod used in arc welding. It has a covering of materials to aid in the arc welding process. Cover lens or plate: A removable pane of clear glass or plastic used to protect the expensive welding fi lter lens. Cover pass: The fi nal weld pass in a multipass weld. Crack: A break or separation in rigid material running more or less in one direction. Cracking: The action of opening a valve slightly, then closing it immediately. Cracking is used to blow out any dust in the valve orifi ce. Crater: A depression in the face of a weld, usually at the termination of a weld. The crater is visible after a weld has cooled. Creep: Permanent deformation caused by stress or heat or both. Crescent motion: Movement of a torch or electrode in a crescent pattern to create a weave bead. Crevice corrosion: Deterioration of a metal caused by a concentration of dissolved salts, metal ions, oxygen, or other gases in pockets that are not disturbed by the fl uid stream. This buildup eventually causes deep pitting. Critical defect size: The size a discontinuity must be to become a defect. Critical temperatures: The temperatures at which phase changes or structural changes occur in a metal. Cross-wire resistance welding: Welding using machines in which wires are crossed and held beneath a single electrode or multiple electrodes. Current passes between wires where they cross and creates a resistance spot weld at that point. Crown: The curved or convex surface of fi nished weld. Crowned: Built up above the surface of the parent metal. Crucible: The vessel in an induction furnace in which the metal is heated. Cryogenics: Term for the study of physical phenomena at temperatures below –50°F (–46°C). Cryogenic steels: Steel alloys that maintain their strength at very low temperatures. Cup: A nonstandard term. See Nozzle. Cupola furnace: A type of furnace used to produce cast iron. Current analyzer: A handheld meter that can use a coil probe to measure current through resistance welded equipment and weldment. Cutting head: The part of a cutting machine or cutting equipment to which a cutting torch or tip is attached. Cutting outfi t: A term used in oxyfuel gas cutting to refer to all equipment required to perform a cut.