D

D (Fordath) Process: Shell molding in which the shell is made by blowing sand into a box like heated structure so that a shell of controlled thickness is created.

Datum Points (Pop marks, Gage Marks): Punch marks on a tensile test piece indicating gage length for elongation.

Daubing: Filling of cracks in molds or cores by specially prepared pastes or coatings to prevent a mechanical penetration of metal into these cracks during pouring. Also, the final plastering or coating of the cupola or ladle after shrinkage has taken place during the drying period. Clay slurry or clay wash with various coating compounds are applied.

dB: See Decibel.

DC (Direct Chill) Casting: A continuous method of making ingots or billets or extrusion by pouring the metal into a short mold. Sometimes called semi-continuous casting.

Dead Annealing: See Annealing.

Deadburned: A term applied to refractory materials obtained by calcining at a temperature high enough to form a product inert to atmospheric moisture
and carbon dioxide, and less apt to contract.

Deadburned Dolomite: Dolomite burned at high temperature with additions of an agent, such as oxide of iron.

Deadhead: The useless metal projecting on a casting which corresponds to the position of a riser in the mold.

Dead Steel: Fully killed steel, also applied to steel which fails to respond to heat treatment.

Decalescence: See Iron-Iron Carbide Diagram.

Decant: 1. Pour from one vessel to another, 2. pour off molten metal without disturbing the sludge.

Decarburization: Loss of carbon from the surface of a ferrous alloy as a result of heating in a medium, usually oxygen, that reacts with the carbon.

Decibel (dB): Unit for measuring the ratio amounts of acoustical power; one-tenth of a bel.

Deepbed Filter: A gas filter in air pollution control, consisting of a loosely packed mat of fibrous materials; not practical where high grain loadings
are encountered.

Deep Etching: Macroetching; etching, for examination at a low (less than 1OX) magnification, in a reagent that attacks the metal to a much greater extent than normal for microscopic examination. Gross features may be developed; i.e., abnormal grain size, segregation, cracks or grain flow.

Deformation Test: An AFS test using an instrument such as the Dietert Universal Sand-Strength Testing machine (with deformation accessory) to
determine the amount in inches that the sand specimen is compressed before it ruptures.

Degasser: A material employed for removing gases from molten metals and alloys.

Degassing: Usually a chemical reaction resulting from a compound added to molten metal to remove gases from the metal. Often inert gases are
used in this operation.

Degassing Flux: A flux for removing gas from a melt.

Degree of Ramming: The extent of hardness to,which a sand mold is rammed.

Delay Screen (Skim Gate (Erroneously), Skim Strainer):  A small piece of perforated light gage tinned sheet steel or of copper, aluminum and/or magnesium alloys, frequently placed in the pouring basin at the top of the downsprue. It delays the flow of metal long enough to allow the basin to fill before it melts to permit only clean metal from the bottom of the basin to enter the downsprue. Delay screens are also used elsewhere in the gating system.

Dendrite: Solidified metal characterized by a treelike pattern composed of many branches formed during cooling; also termed pine tree and fir tree crystal.
See Coring.

Densitometer: Instrument utilizing the photoelectric principle to determine the degree of darkening of developed photographic film.

Density: The mass per unit volume of a substance, usually expressed in grams per cubic centimeter or in pounds per cubic foot.

Density (Photographic): Logarithm of opacity of exposed and processed film. Opacity is the reciprocal of transmission; transmission is the ratio of transmitted to incident intensity. Density is used to denote the degree of darkening of photographic film.

Deoxidation: Removal of excess oxygen from molten metal, usually accomplished by adding materials with a high affinity for oxygen, the oxides of which
are either gaseous or readily form slags.

Dephosphorization: Elimination of phosphorus from molten steel.

Dermatitis: An inflammation of the skin, may be caused by allergy to certain casting adjuncts, as resins; particularly in the shell process.

Descale: Remove the fire scale from the surface of casting.

Design Base Line: The noise spectrum which is the goal of any particular noise reduction program.

Designations: Type of metal named, as steel, malleable, nonferrous, etc.

Delsulfurization: Removal of sulfur from the molten metal by addition of suitable compounds.

Desulfurizer: A material used to remove sulfur from molten metals and alloys. Also, a form of holding ladle or basin in which the molten metal and
desulfurizing material are brought into contact.

Detroit Cup Test:  A cupping test for sand, using a steel ball as plunger, the depth of cup being shown on a dial.

DeVries Test: A test to give the relative hardness of deep hardening steels.

Dew Point: The temperature at which moist air will become saturated and condensation of water vapor will take place.

Dewaxing: The process of melting out the expendable wax pattern from an investment mold by the application of heat, usually at temperatures less
than 250 F (121 C).

Dextrin: Soluble gummy carbohydrate formed by the decomposition of starch by heat, acids or enzymes; it is used in core compounds, mold compounds, mold washes, core pastes and other compounds requiring high dry compressive strengths.

Diameters: In microscopy, an indication of the amount of magnification. 1000 diameters=1000 times original size.

Diammonium Phosphate: Used to fireproof clothing of foundry workers.

Diaphragm Shell Molding Machine: An arrangement for applying a squeeze pressure with a high-temperature silicone rubber diaphragm.

Diaspore Clay: A rocklike mineral consisting chiefly of diaspore (HAIO.,) bonded by fire clay substance with an alumina content higher than 63%.

Dia-Tester  (Wolpert Hardness Tester): A hardness testing machine using the Vickers or Brinell ball indenter,

Diathermometer: An instrument for examining the thermal resistance or the heat conducting power of objects.

Diatomaceous Earth (infusorial Earth): A hydrous form of silica which is soft, light in weight and consists mainly of microscopic shells of diatoms or other marine organisms. It is widely used for furnace insulation.

Die:  A metal block used in forming materials by casting , molding, stamping, threading or extruding.

Die Assembly: The parts of a die stamp or press that hold the die and locate it for the punches.

Die Casting (Brit. Pressure Die Casting): A rapid, watercooled permanent mold casting process, an out growth of casting printer’s lead, still quite limited t nonferrous metals. There are three types: the plunge type operated hydraulically, mechanically or by corn pressed air with or without a gooseneck; the direct-air injection which forces metal from a gooseneck into the die, and the Cold-Chamber 1,Machine. All force the metal into the die with a pressure greater than that of gravity flow.

Die Coating: See Release Agent.

Die Insert: A removable liner or part of a die body or punch.

Die Sinking: Forming or machining a depressed pattern in a die.

Dielectric Oven (Dryer): A rapid drying high frequency electric oven used to bake cores.

Die Set: In stamping, the parts of the press that hold the die and locate it in proper relation to the punches.

Dietert Process: A patented process for the production of P,,precision molds involving blowing a contoured core around a pattern to form half a mold.

Dirt Trap: A well employed in a gating system to en trap the first metal poured, which may contain dirt o unwanted particles. See Slag Trap.

Dirty Casting: A casting containing an excessive amount of nonmetallic inclusions in the body of ‘he metal.

DIS: Ductile Iron Society.

Disappearing Filament Pyrometer (Optical Pyrometer):  A telescope in which a hot body is viewed through: an eyepiece; temperature is measured by the matching color of a calibrated lamp filament with color, of hot metal.

Dispersed Shrinkage: Small shrinkage Cavities dispersed through, the casting, which — not necessarily cause for rejection.

Disruptive Strength: Maximum strength of a metal when subjected to three principal tensile stresses at right angles to one another and of equal magnitude.

Dissolved Carbon: Carbon in solution in steel in either the liquid or solid state.

Distorted Pattern: A pattern untrue to the specified dimensions.

Distortion: See Warpage.

Distribond: A siliceous clay containing Bentonite used as a bond in molding sands.

Distribution, Sand Grain: Variation or uniformity in particle s’@ize of a sand aggregate when properly screened by U.S. Standards screens.

Disturbed Metal: The cold worked metal formed on a polished surface during the processes of grinding and polishing.

Divorced Pearlite (Granular Pearlite, Spheroidite, Spheroidized Cementite): Pearlite in which the cementite has been spheroidized by prolonged annealing just below the Ac, point, or by annealing at the same temperature after cold working.

Dolomite: A mineral calcium-magnesium carbonate (Ca, Mg (CO:,).,) used as a flux in iron melting and smelting; also as a base in refractories.

Dose: A quantity of radiation measured at a certain point expressed in roentgens, rems or rads.

Dose, Absorbed: The amount of energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest (expressed in rads).

Dose, Exposure: Quantity of radiation measured in air in roentgens without backscatter at a given point.

Dose Meter, Integrating: Ionization chamber and measuring system designed for determining total radiation administered during an exposure. In medical radiology the chamber is usually designed to be placed on the patient’s skin. A device may be included to terminate the exposure when it
has reached a desired value.

Dose Rate: Dose per unit time.

Dosimeter: Instrument used to detect and measure an accumulated dosage of radiation; in common usage it is a pencil size ionization chamber with a built-in self-reading electrometer; used for personal monitoring. See Dosimeter, Pocket.

Dosimeter, Pocket: A pocket ionization chamber containing its own electrometer. An auxiliary charging device is usually necessary.

Double Annealing: As applied to hypoeutectoid steel, a process of heating to above the upper critical point (AC,) and holding at that temperature until complete solution of the carbide has been achieved then cooling rapidly and reheating immediately to above A:, and slowly cooling.

Double Impression Method: A way of determining approximate Brinell hardness by placing a hardened steel ball between a specimen of known hardness
and the metal to be tested and pressurizing in an arbor press.

Doubleburned: Deadburn; not to be mistaken for two firings.

Double Skin (Bottom Splash, Ingot Shell, Plaster): A defect consisting of a secondary layer of metal sometimes found on top-poured ingots.

Double Tempering: A retempering operation sometimes necessary for steel containing retained austenite which breaks down during cooling from the first tempering to form a new and hence untempered martensite.

Dowel: 1.  A wooden or metal pin of various types used in the parting surface of parted patterns and core boxes, 2. in diecasting dies, metal pins to ensure correct registry of cover and ejector halves.

Downcomer:In air pollution control, a pipe for conducting gases down into a conditioner and subsequent cleaning.

Downgate: See Downsprue.

Downhand Welding: Welding deposited along a horizontal line and surface.

Downsprue (Sprue, Downgate): The first channel, usually vertical, which the molten metal enters; so-called because it conducts metal down into the mold.

Downtime: Time lost from normal casting activity, due to unscheduled interruption.

Dozzle: A refractory feeder head raised to white heat and inserted in the top of a crucible steel ingot mold.

Draft, Pattern:See Pattern Draft.

Drag: Lower or bottom section of a mold or pattern.

Draw A: Term used for 1.  to temper, 2.  to remove pattern from mold, 3.  an external contraction defect on surface of mold, 4) a form of porosity defect
due to insufficient venting at the corners of castings.

Drawback: Part of a mold of green sand that may be drawn back to clear overhanging portions of the patterns.

Drawing: Removing pattern from the mold or mold from pattern in production work. See also Tempering.

Draw Peg: A wooden peg used for drawing patterns.

Draw Plate:  A plate attached to a pattern to facilitate drawing of a pattern from the mold.

Draw Screw: A threaded rod with an eye screwed into a pattern to enable it to be drawn from the mold.

Draw Spike: A steel spike used to rap and draw a pattern from the sand; it is driven into the wood of the pattern, as opposed to a Draw Screw, which is threaded.

Dried Sand: Sand which has been dried by mechanical dryer prior to use in core making.

Drier (Dryer): A material, as alcohol ammonium nitrate, sodium perborate and manganese oleate, added to a core or mold mixture to remove or
reduce the water content,

Drillings, Test: Chips, or small particles of metal removed from a test specimen for chemical analysis.

Drop (Dropout):  A casting defect caused by sand dropping from the cope or other overhanging section.

Drop Ball:  A heavy weight, usually ball or pear shaped, dropped from a height to break large pieces of metal scrap. Also used to strengthen warp castings.

Drop Gate: A term for a pouring gate or runner leading directly into the top of the mold.

Drop Off or Drop Out: Sand falling from the Cope of a mold. See Drop.

Drum Ladle: A cylindrical refractory-lined ladle that is completely enclosed. A removable cover at the pouring spout permits addition of molten metal.

Drum, Magnetic: An electrically energized pulley or drum used for removing magnetic materials from sand, nonferrous borings and turnings, etc.

Dry Analysis: A term applied to spectrographic analysis.

Dry and Baked Compression Test:  An AFS test to determine the maximum compressive stress that a baked sand mixture is capable of developing.

Dryer, Core: See Core Driers.

Dryer, Dielectric: See Dielectric Oven.

Drying Plate: See Core Plate.

Dry Pan: A grinding machine of heavy rollers or millers resting on a bed. Screens or slits allow fine material to pass through.

Dry Permeability: The property of a molded mass of sand bonded or unbonded, dried at 220-230 F (105-110 C) and cooled to room temperature,that allows passage of gases resulting during pouring of molten metal into a mold.

Dry Sand Casting: The process in which the sand molds are dried at above 212 F (100 C) before using.

Dry Sand Core: See Core.

Dry Sand Mold: A mold from which the moisture has been removed by heating.

Dry Strength, or Dry Bond Strength: The maximum compressive, shear, tensile or transverse strength of a sand mixture which has been dried at 220 to 230 F (105 to 110 C) and cooled to room temperature.

Dust: Small solid particles created by the breaking up of larger particles by any process.