868 Modern Welding Electrode diameter: The width of a cylindrical or tubular electrode. Electrode extension: The length of unmelted electrode extending beyond the end of the collet. Electrode face: The part of the electrode that contacts the work. Electrode lead: Electrical conductor between the welding machine and the electrode holder. Electrode skid: Sliding of an electrode along the work surface during spot, seam, or projection welding. Electrolysis: A chemical change or decomposition created by passing electricity through a solution of the material or through the substance while it is in a molten state. Electrolyte: The fl uid in an electrolytic cell. Electromagnet: A device in which a magnetic fi eld is produced by a coil carrying an electric current. The coil surrounds a mass of ferrous material which also becomes magnetized. Electromotive force: Energy that causes the fl ow of electric current. Measured in volts. Electron: One of the fundamental parts of an atom. It has a small negative electrical charge. Electron beam welding (EBW): Focused stream of elec- trons that heats and fuses metals. Electronic controller: A device which controls the vari- ables in a welding process, such as in automatic welding or when using robotics. Electroslag welding (ESW): A process using molten slag to melt the base metal. As the weld progresses verti- cally, the molten metal, slag, and fl ux are held in place by water-cooled moving shoes. Element: A substance that cannot be divided into simpler substances. Elongation: The percentage increase in the length of a specimen when it is stressed to its yield strength. Embrittlement: Reducing the normal ductility of a metal by a physical or chemical change. Emits: Gives off. Employers: Individuals or institution that hire employees and offer a salary or wages to the worker in exchange for work performed. Encoder: A device used to translate mechanical motion and position into an electrical output. An encoder has very fi ne lines that can identify and communicate the posi- tion of a servo or stepper motor. Erosion: A gradual reduction in the size of an object as a result of a liquid or gas impacting on it. Essential variables: Variables that, when changed, have a signifi cant effect on the mechanical properties of the weldment. Etch: Treat with acids to bring out features, such as the grain boundaries and microstructures in the metal. Eutectic alloy: A mixture of metals that has a melting point lower than that of any of the metals in the mixture, or of any other mixture of these metals. Eutectic point: The point on a graph of solidus and liquidus temperatures where the alloy begins to melt and completely melts at one temperature. Exciter: A small generator electrically connected to the fi eld windings of a large generator in order to keep a constant voltage on the main fi elds and to prevent them from reversing their polarity. Exit diameter: Diameter of the nozzle opening closest to the arc. Exothermic: The ability to release heat. The exothermic cutting process uses rods that release a great deal of heat as they burn. Exothermic process: A self-consuming process in which fuel wires, once ignited, continue to burn as long as oxygen is available to support the burning. Explosion welding (EXW): A process that joins metal as powerful shock waves create pressure to cause metal fl ow and resultant fusion. Expulsion weld: Resistance spot weld that squirts (expels) molten metal. Extrusion: A process in which a metal, normally in its plastic state, is pushed with great force through dies that are cut in the shape of the desired cross section. Eye of the weld pool: A bright fl ake of oxide on the surface of the weld pool. F Face-centered cubic structure: The structure of austenite, in which there is one atom at each corner of the cube and also one in the center of each face. Face of a weld: The exposed surface of the weld. Face reinforcement: The distance from the top of the weld face to the surface of the base metal. Fahrenheit: The temperature scale used in the United States. Its symbol is °F. Fatigue: A condition of metal leading to cracks under repeated stresses below the tensile strength of the material. Fatigue limit: Stress limit below which a material can be expected to withstand any number of stress cycles. Fatigue strength: The greatest amount of stress that a metal will withstand for a certain number of stress cycles without cracking. Feathering: The grinding of a tack weld. Feedback: Information about welding variables that is fed back to the welding controller during welding. Feedback control: Adjustments made to welding variables or mechanical devices (such as robots or positioners) as a result of feedback received by the controller. Feed rate: Speed at which a material passes through the welding gun in a unit of time. Ferrite: Iron that contains very small amounts of carbon. It has a body-centered cubic structure. Ferrite banding: Bands of free ferrite that line up in the direc- tion the metal was worked. Bands are parallel. Ferritic stainless steels: Stainless steels that contain from 10.5% to 30% chromium. Ferrous metals: Iron and its alloys. Field weld symbol: A symbol used when welds are to be made away from the shop. It is a small fl ag located at the arrow end of the reference line.