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DECARBURIZATION. Loss of carbon from the surface of a ferrous alloy as a result of heating in a medium, usually including oxygen, which reacts with carbon.
DEFORMATION TEST. An AFS sand property test which is determined on an instrument such as the Dietest Universal Sand Strength Testing Machine. The test determines the amount of deformation in thousandths of an inch that occurs before a sand specimen ruptures.
DEGASSER. A material for removing gases from molten metals and alloys (usually nonferrous metals).
DEGREE OF RAMMING. A measure of the amount of compaction which has occurred in a molding operation. (See RAMMING.)
DELAVAUD PROCESS. A centrifugal process employed chiefly for making cast iron pipe.
DEOXIDATION. Removal of dissolved oxygen from molten ferrous alloys, usually accomplished by adding materials with a high affinity for oxygen, the oxides of which are either gaseous or which readily form slags.
DEWAXING. The process of melting out the expendable wax pattern from an investment mold by heating, usually at temperatures less than 121°C (250°F).
DIATOMACEOUS EARTH. A hydrous form of silica which is soft, light in weight and consists mainly of microscopic shells of diatoms or other marine organisms. Widely used for furnace insulation.
DIE CASTING. A high production casting process in which the molten metal (usually a nonferrous alloy) is forced under greater than atmospheric pressure into a water cooled metal mold cavity.
DIELECTRIC OVEN. A rapid curing high frequency electric oven used to cure cores which are bonded with non-conducting materials.
DIP COAT. In solid and shell mold investment casting, a fine ceramic coating applied as a slurry to the pattern to produce maximum surface smoothness, followed by a cheaper investment material.
DIRECT-ARC FURNACE. An electric arc furnace in which the metal being melted is one of the poles.
DIRECTIONAL SOLIDIFICATION. The solidification of molten metal in a casting in such a manner that feed metal is always available for that portion that is just solidifying.
DISPERSED SHRINKAGE. Small shrinkage cavities dispersed through a casting, which are not necessarily a cause for rejection.
DISTRIBUTION, SAND GRAIN. Variation or uniformity in the particle size which comprise sand aggregate when properly screened by U.S. Standard Sieves.
DOWNCOMER. In air pollution control, a pipe for conducting gases down into a conditioner for subsequent cleaning.
DRAG. Lower or bottom section of a mold or pattern. Originally called a nowel.
DRAW. (noun) A term sometimes used to denote a shrink appearing on the surface of a casting or a riser.
DRAW. (verb) To remove the cope or drag from a pattern plate or in the pattern from the cope or drag.
DRAW BAR. A bar used for lifting the pattern from the sand mold.
DRAW PLATE. A plate attached to a pattern to facilitate drawing of the pattern from the mold.
DRIED SAND. Sand which has been dried by a mechanical drier prior to its use in core making.
DROP. A casting defect caused by dropping of sand from the cope or other overhanging section, which results in a casting defect known as a drop after the mold has been poured.
DROSS. Metal oxides in or on the surface of molten metal.
DRY PERMEABILITY. The property of a molded mass of bonded or unbonded sand, dried at (104° to 110°C) (220° to 230°F) and cooled to room temperature, that allows passage of gases resulting during pouring of molten metal into a mold.
DRY SAND MOLD. A mold from which the moisture content has been removed by suitably heating the mold prior to pouring molten metal therein.
DRY STRENGTH. The maximum strength of a molded sand specimen that has been thoroughly dried at 220°-230°F (104°-110°C) and cooled to room temperature. Also known as dry bond strength.
DUCTILITY. The property permitting permanent deformation without rupture in a material by stress in tension.
DUPLEXING. A method of producing molten metal of desired analysis, the metal being melted in one furnace and refined in a second.
DURVILL PROCESS. A casting process that involves a rigid attachment of the mold in an inverted position above the crucible. The metal is poured by tilting the entire assembly, causing the metal to flow along a connecting laader and down the side of the mold.
DUST. Small solid particles created by breaking up larger particles by any process.
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