Glossary 867 Direct current electrode positive (DCEP): Direct current fl ow from the work (cathode) to the electrode (anode). Direct current reverse polarity (DCRP): A nonstandard term. See Direct current electrode positive. Direct current straight polarity (DCSP): A nonstandard term. See Direct current electrode negative. Discontinuity: Any abrupt change or break (cracks, seams, laps, bumps, or changes in density) in the shape or struc- ture of a part. Distilling process: Process of producing zinc in which the zinc is refi ned by vaporizing the zinc out of the ore and then condensing the zinc vapors. Distortion: Warping of a part of a structure. Dive table: A table used to determine how long a diver can remain at a given depth. Table also specifi es pause depths and times to make a safe assent to the surface. Downhill: Welding with a downward progression. Downhill welding: The weld is started at the 12 o’clock posi- tion and is welded downward to the 6 o’clock position. Downslope: A decreasing current. Downslope current: Gradual decrease in current at the end of a weld. Drag: The offset distance between the actual and theoret- ical exit points of the cutting oxygen stream, measured on the exit side of the material. Drag angle: The top of the electrode leads the welding end of the electrode, and the welding arc is pointing back toward the weld bead. Also called drag travel angle. Drag electrodes: SMAW electrodes that can only be used in the fl at and horizontal positions. Drag travel angle: The top of the electrode leads the welding end of the electrode, and the welding arc is pointing back toward the weld bead. Also called drag angle. Drawing: A shop term sometimes used mistakenly for the term tempering in the heat treatment of metal. Dressing: Reshaping of the electrode. Droop curve machines: Welding machines that have a steep volt-ampere curve. Also called droopers. Droopers: Welding machines that have a steep volt-ampere curve. Also called droop curve machines. Dross: Oxidized metal or impurities that may form on molten metals. It often forms on the other side of metal that is fl ame or arc cut. Dry spot welding: An underwater welding method in which the welding takes place in a small chamber built from Lexan, while the welder remains outside the chamber. Dry welding: Underwater welding where the water is removed from the welding area. Also called hyperbaric welding. Dual fl ow plasma arc cutting: Plasma arc cutting in which a shielding gas is used. Dual source with inverter switching: Two power supplies in one unit. An inverter creates ac current. A second power supply provides only dc current, and is used to produce additional current when the electrode is positive. Ductile: Able to be worked without cracking. Ductile cast iron: A type of cast iron that is created by adding magnesium or cerium as an alloying element. Also called nodular cast iron. Ductile crack propagation: Slow development of cracks and noticeable warping or deformation caused by an outside pressure. Ductility: The ability of a material to be changed in shape without cracking or breaking. Duty cycle: The percentage of time in a 10-minute period that an arc welding machine can be used at its rated output without overloading. A resistance welding machine duty cycle is usually calculated over a 1-minute period. Dynamic pressure: The pressure measured when the gas is fl owing. E Economizer: A device that shuts off gas fl ow and holds an oxyfuel torch when it is not in use. Gas fl ow is immedi- ately restored when the torch is lifted from the cradle. Eddy current inspection (ET): An inspection method that uses an ac coil to induce eddy currents into a part. A discontinuity in the part interrupts the fl ow of the eddy currents. Edge joint: A joint between the edges of two or more parallel parts. Edge preparation: The shaping of the edges of the joint prior to welding. Edge weld: Weld produced on an edge joint. Effective penetration: The greatest depth at which ultra- sonic transmissions can effectively detect discontinuities. Effective throat: On a fi llet weld, the least distance from the root of a weld to the weld face, not counting any rein- forcements. See also Joint penetration. Elastic deformation: A temporary change of dimensions caused by stress. The part returns to its original dimen- sions when the stress is removed. Elasticity: Ability of a material to regain its original size and shape after deformation. Elastic limit: The greatest stress to which a structure may be subjected without causing permanent deformation. Electrical power input requirements: The type of power required to operate a particular model or class of welding machine. Electrical resistance heating: Heating that occurs due to resistance to electrical current. Electric arc spraying: A nonstandard term. See Arc spraying. Electric arc spray method: Metal surfacing method in which wire material melted by an arc between two current-carrying wires is sprayed onto the part to be surfaced. Electric motor-driven carriage: Torch guide device that has a variable-speed motor that allows the carriage to move along its track at any desired speed. Electrochemical corrosion: Corrosion caused by current fl ow between the contact areas of two dissimilar metals. Electrode: Terminal point to which electricity is brought in the welding operation and from which the arc is produced to do the welding. In most electric arc welding, the elec- trode is usually melted and becomes a part of the weld. Electrode angle: The position of the electrode in relation to the material being welded.