Mechanical Engineering Dictionary-Casting Process - ObjectiveBooks

Mechanical Engineering Dictionary-Casting Process

Important Terms and their Meaning of Mechanical Engineering- Casting Processes:

AERATOR – A device for fluffing (or decreasing the density of) and cooling the sand by the admixture of air.

AIR GATE – A vertical channel for the removal of gases from the mould; checking of the filling of the mould cavity with metal and feeding up the casting with metal during solidification.

AIR HOLE – Hole in a casting caused by air or gas trapped in the metal during solidification.

AIRLESS BLAST CLEANING – A process whereby the abrasive material is applied to the object being cleaned by centrifugal force generated by a rotating vane type wheel.

ANTIPIPING (material) – Usually refers to an insulating material placed on the top of a sprue or riser that keeps the metal in liquid or semi liquid form for a long period of time and minimizes the formation of the usual conical pipe or shrink in the top of a sprue or riser.

ARBOR – A metal barrel, frame, or plate to support or carry part of a mould or core.

ATMOSPHERIC RISER – Blind riser which employs atmospheric pressure to aid feeding.

BACK DRAFT – Taper or draft which prevents removal of pattern from the mould.

BACKING SAND – Sand between the facing sand and the flask.

BAKED CORE – The core which has been subjected to heating or baking until it is thoroughly dry, as opposed to green sand core which is used in the moist state.

BASIN – A cavity on top of the cope into which molten metal is poured before it enters the sprue.

BEDDED IN MOULD – is the mould, the bottom half of which is made in the sand in the floor of the foundry. It may be covered with a cope, or cast open, according to the type of work.

BINDER – Material used to hold the grains of sand together in moulds or cores. May be cereal, oil, clay, resin, pitch etc.

BINDER, PLASTIC (resin) – Synthetic resin material used to hold grains of sand together in moulds or cores, may be phenol formaldehyde or urea formaldehyde thermosetting types.

BLACKING – Carbonaceous material for coating mould or core surfaces.

BLACK LEAD – Graphite for facing moulds and cores.

BLAST CLEANING – Removal of sand or oxide scale from castings by the impinging action of sand, metal shot or grit projected under air, water or centrifugal pressure.

BLEED – Molten metal oozing out of a casting stripped or removed from the mould before solidification.

BLENDED SAND – Mixture of sands of different grain sizes, clay content etc. to produce one, possessing characteristics more suitable for foundry use.

BLIND RISER – An internal riser which does not reach to the exterior of the mould.

BLISTER – Defect on the surface of a casting appearing as a shallow blow with a thin film of metal over it.

BLOWN CASTINGS – Castings in which bubbles, or blowholes, have been caused through gases, steam etc., generated when the mould is cast, finding their way into the metal.

BOND CLAY – Any clay suitable for use as a bonding material in the moulding sand.

BORIC ACID – Inhibitor used in facing sand for magnesium base and aluminium base alloys high in magnesium to prevent reaction with moisture in the sand.

BORON TRICHLORIDE – A product used for degasification of aluminium alloys.

BOSSES – Bosses are often located on a wall of a casting and should be so designed that a heavy section of metal leads to the riser.

BOT – Clay wedge used in a cupola to stop the hole through which the metal is run.

BUCKLE – Defect in a casting surface appearing as an indentation resulting from an expansion scab.

BURN ON – Adhesion of sand to the casting, usually due to the metal penetrating into the sand.

BURN OUT – Usually refers to the removal of the disposable wax or plastic pattern in the investment moulding process by heating the mould gradually to a sufficiently high temperature to consume any carbonaceous residues.

BUTT RAMMAR – The flat end of the moulders rammer.

CALCIUM BORIDE – An alloy of calcium and boron corresponding (when pure) to the formula CaB6 containing about 61% boron and 39% calcium, and used in deoxidation and degasification of nonferrous metals and alloys.

CALCIUM MANGANESE SILICON – An alloy containing 17 to 19% calcium, 8 to 10% manganese, 55 to 60% silicon and 10 to 14% iron used as a scavenger for oxides, gases and non-metallic impurities in steel.

CALCIUM SILICON – An alloy of calcium, silicon and iron containing 28 to 30% calcium, 60-65% silicon and 6% max iron, used as a deoxidizer and degasifier for steel and cast iron.

CASTING – Metal poured into a mould to form an object. Act of pouring molten metal into a mould.

CASTING STRAINS – Strains resulting from internal stresses created during cooling of a casting.

CAVITY, MOULD or DIE – Impression or impressions in a mould or die that give the casting its shape.

CENTRIFUGAL CASTING – Process of filling moulds by pouring the metal into sand or metal mould revolving about either it’s horizontal or vertical axis and continues pouring the metal into the mould that is being revolved before solidification of metal is complete. Molten metal is moved from the center to the periphery by centrifugal action.

CERAMIC MOULD – Mould in which the refractory and binder are such that when fired at high temperature, a rigid structure is formed. The mould can be made in a flask or in the form of a shell.

CEREAL – Substance derived from corn flour, which is added to core and moulding sands to improve their properties for casting production.

CHALK TEST – Method of crack detection which consists of applying a penetrating liquid to the excess from the surface which is then coated with whiting or chalk. After a short time, the penetrant seeps out of the cracks into the whiting, causing an appreciable difference in whiteness.

CHAMOTTE – Coarsely graded refractory material prepared from calcined clay and ground firebrick mulled with raw clay, used in steel foundries.

CHAPLET – A metallic insert or support to hold the core in position in the mould.

CHEEK – Intermediate sections of a flask inserted between cope and drag.

CHILL – A metal object placed on the outside or inside a mould cavity to induce more rapid cooling at that point and thereby produce hard zone i.e., hard, unmachinable surface.

CHILL TEST – Method of determining the suitability of a gray iron for specific castings through its chilling tendency, as measured from the tip of a wedge shaped test bar.

CHILLED IRON – Cast iron poured against a chill to produce a hard unmachinable surface.

CHOKE – Restriction in a gating system to control the flow of metal beyond that point.

CHVORINOV’S RULE – Solidification time is proportional to the square of the volume of the metal and inversely proportional to the square of the surface area.

CLEANING – Process of removing sand, surface blemishes etc. from the exterior and interior surfaces of a casting. Includes degating, tumbling, or abrasive blasting, grinding off gate stubs.

COD – A sand projection left behind in the mould by some patterns. Strictly speaking it is a core.

COLD SHUT – Where two streams of metal do not unite thoroughly in a casting.

COMBINATION DIE – A die casting die having two or more cavities of dissimilar parts.

CONTRACTION – Act or process of a casting becoming smaller in volume and/or dimensions during the solidification of the metal or alloy which composes the casting.

COPE – The upper or top most section of a flask, mould or pattern.

COPE (false) – A temporary cope which is used only to establish the parting line.

CORE – Separable part of the mould, usually made of sand and generally baked, to create openings and various shaped cavities in the castings. Also used to designate the interior portion of an iron base alloy which after case hardening is substantially softer than the surface layer or case.

CORE BINDER – Any material used to hold the grains of core sand together.

CORE BOX – Box with an opening in which the core is formed.

CORE PRINT – An extension of the pattern for locating the core or an extension of the mould cavity for locating the core.

CORE (ram up) – Core attached to the pattern and rammed up in the mould, where it remains when the pattern is withdrawn.

CORE SHIFT – Defect resulting from movement of the core from its proper position in the mould cavity.

CORE VENTS – A wax product, round or oval in form, used to form the vent passage in the core.

CRUSH – Casting defect appearing as an indentation in the surface due to displacement of sand in the mould, usually at the joint surfaces.

CUTS – Defects in castings resulting from erosion of the sand by the molten metal pouring over the mould or core surface.

DEGASSIFIER – A material employed for removing gases from metals and alloys.

DEOXIDIZER – A material used to remove oxygen or oxides from metals and alloys.

DESULPHURIZER – A material used to remove sulphur from molten metals and alloys.

DIE CASTING – Pouring molten metal under pressure into metal moulds.

DIRECTIONAL SOLIDIFICATION – It refers to the solidification which proceeds along a cast member in the direction of the hotter metal.

DIRT – Any extraneous material entering a mould cavity and usually forming a blemish on the casting surface.

DRAFT – Taper allowed on the vertical faces of a pattern to permit removal of it from the sand mould without excessive rapping or tearing of the mould walls.

DRAG – The lower or bottom section of a mould or pattern.

DRY SAND MOULD – A mould made of prepared moulding sand dried thoroughly before being filled with metal.

EROSION SCAB – Casting defect occurring where the metal has been agitated, boiled, or has partially eroded away the sand, leaving a solid mass of sand and metal at that particular spot.

EXPENDABLE PATTERN – In investment moulding, the wax or plastic pattern that is left in the mould and later melted and burned out.

EXPANSION SCABS – Rough thin layers of metal partially separated from the body of the casting by a thin layer of sand and held in place by a thin vein of metal.

EXTERNAL CHILLS – Various materials of high heat capacity such as
metals, graphite etc. forming parts of walls of the mould cavity to
promote rapid heat extraction from molten metal.

EXTERNAL PRESSURE CASTINGS – In this process, highly fluid metal is forced under considerable external pressure into metal moulds, the pressure being maintained until solidification is complete.

FACING SAND – Specially prepared sand in the mould adjacent to the pattern to produce a smooth casting surface.

FALSE CHEEK – A cheek used in making a three part mould in a two part mould.

FALSE ODDSIDE – Permanent odd side made of plaster or other material.

FEED HEAD – A reservoir of molten metal provided to compensate for contraction of metal as it solidifies, by the feeding down of liquid metal to prevent voids. Also called a RISER.

FILLETS – Properly positioned fillets materially increase the strength and soundness of the castings. They reduce shrinkage cracks and erosion of sand at sharp intersections.

FIN – A thin piece of metal projecting from a casting at the parting line or at the junction of the cores or of cores and mould etc.

FLASH – Thin fin or web of metal extending from the casting along the joint line as a result of poor contact between cope and drag moulds.

FLASK – Container in which a mould is made.

FLOW OFF GATE – Channel cut from the mould to the riser.

FLUORESCENT CRACK DETECTION – Application of fluorescent liquid to a part, then removing the excess from the surface, which is then exposed to ultraviolet light. Cracks show up as fluorescent lines.

GAS HOLES – Rounded cavities caused by generation or accumulation of gas or entrapped air in a casting, holes may be spherical, flattened or elongated.

GATE – The location where the molten metal enters the casting cavity.

GATED PATTERN – One or more patterns with gating systems attached.

GATING SYSTEM – Combination of channels, cavities and other elements of a casting mould which are intended ·to feed molten metal into a mould, fill in the latter, and feed up the casting with metal during solidification.

GRAVITY DIE CASTING – is one in which the fluid metal is poured by hand into the metal moulds and around metal cores. The only pressure applied is that exerted by the head of metal in the pouring gate.

GREEN SAND – Prepared moulding sand in the moist or as mixed condition.

GREEN SAND MOULD – Mould made and cast in damp sand.

GUIDE PIN – The pin used to locate the cope in the proper place on the drag.

HORN GATE – A curved gate in the shape of a horn arranged to permit entry of molten metal at the bottom of the casting cavity.

HOT TEARS – Cracks in castings formed at elevated temperatures, usually by contraction stresses.

IMPRESSION – Cavity in a die casting die or in a mould.

INCLUSIONS – Particles of slag, sand or other impurities such as oxides, sulphides, silicates etc., trapped mechanically during solidification or formed by subsequent reaction of the solid metal.

IN GATE – Channel out from the bottom of the runner into the mould. It is used in cases where the runner does not enter the mould direct.

INJECTION – Forcing molten metal into a die casting die.

INOCULATION – Process of adding some material to molten metal in the ladle for the purpose of controlling the structure to an extent not possible by control of chemical analysis and other normal variables.

INSULATING SLEEVE – Hollow cylinders or sleeves formed of gypsum, diatomaceous earth, pearlite, vermiculite etc., placed in the mould at sprue and riser locations to decrease heat loss and rate of solidification of the metal contained in them.

INTERNAL CHILLS – Solid pieces of metal or alloy, similar in composition to the casting, placed in the mould prior to filling it with molten metal.

INVESTMENT MOULDING – Moulding using a pattern of wax, plastic or other material which is invested or surrounded by a moulding medium in slurry or liquid form. After the moulding medium has solidified, the pattern is removed by heating the mould, leaving a cavity for reception of molten metal. Also called LOST WAX PROCESS or PRECISSION MOULDING.

LADLE – Metal receptacle lined with refractory for transportation of molten metal.

LOAM – A course, strongly bonded moulding sand used for loam and dry sand moulding.

LOAM MOULDING – A system of moulding especially for large castings, wherein the supporting structure is constructed of brick. Coatings of loam are applied to form the mould face.

MAGNETIC CRACK DETECTION – Method of locating cracks in materials which can be magnetized, done by applying magnetizing force and applying finely divided iron powder which then collects in the region of the crack.

MASTER PATTERN – The pattern from which the working pattern is cast.

MATCH – A form of wood, plaster of Paris, sand, or other material on which an irregular pattern is laid or supported while the drag is being rammed.

MATCH PLATE – A metal or other plate on which patterns, split along the parting line, are mounted back to back with the gating system to form an integral piece.

METAL PENETRATION – Defect in the casting surface which appears as if the metal has filled the voids between the sand grains without displacing them.

MOULD CAVITY – Impression left in the sand mould by the pattern. Also called MOULD.

MOULD CLAMPS – Devices used to lock or hold cope and drag together.

MOULD HARDENER – In sand moulds in which sodium silicate is the binder, injection of CO2 causes a chemical reaction which results in a rigid structure.

MOULD WASH – Usually an aqueous emulsion containing various organic or inorganic compounds or both, which is used to coat the face of a mould cavity. Materials include graphite, silica flour etc.

MOULDING SAND – Mixture of sand and clay suitable for mould making.

MOULD WEIGHTS – Weights placed on top of moulds to offset internal and ferrostatic pressure.

MOULDABILITY – The ability of the sand mixture to fill in perfectly the cavity of a flask with a pattern or a corebox.

MULTIPLE MOULD – Composite mould made up of stacked sections. Each section incorporates a complete gate for casting. All castings are poured from a central downgate.

ODDSIDE – Support used for supporting a pattern whilst the drag is being rammed up.

OPEN SAND CASTING – A casting poured in a mould which has no cope or other covering.

PARTING COMPOUND – Material dusted or sprayed on a pattern or mould to prevent adherence of sand.

PATTERN – Model of wood, metal, plaster or other material used in making a mould.

PATTERN ALLOWANCES – The dimensions on the pattern differ from those on the drawing to allow for metal shrinkage, distortion, core shift, draft and machine finish. Such allowances are made by the pattern-maker.

PEEN – Small end of a moulders rammer.

PERMANENT MOULD – A long life mould into which metal is poured by gravity.

PILOT CASTING – Usually the first casting made from a production pattern and examined for dimensional accuracy, quality and other features before the pattern is placed on the line.

PIT MOULD – Mould in which the lower portions are made in a suitable pit or excavation in a foundry floor.

PLASTER MOULDING – Gypsum or plaster of Paris is mixed with fibrous talc, with or without sand, and with water to form a slurry, that is poured around a pattern. In a short period of time, the mass sets or hardens sufficiently to permit removal of the pattern. The mould so formed is baked at elevated temperature to remove, all moisture prior to use.

PLASTICITY – The ability of the sand mixture to acquire the outlines of a pattern or corebox under the action of external forces and retain the shape acquired without destruction.

PLASTIC PATTERN – Pattern made from any of the several thermosetting type synthetic resins such as phenol formaldehyde, epoxy etc. Small patterns may be cast solid, but large ones are usually produced by laminating with glass cloth.

POURED SHORT – Casting which lacks completeness due to the cavity not being filled with molten metal.

POURING CUP – Part of the mould that receives the molten metal from the pouring ladle and transfers it further into the cavity of the mould.

PRINT – Wooden projection put on to a pattern to provide supports for the cores in a mould.

PROGRESSIVE SOLIDIFICATION – is the freezing of the metal from the mould metal interface toward the center of the cavity.

PUSHUP – An indentation in the casting surface due to displacement (expansion) of the sand in the mould.

RAMMER – Tool used in a foundry for ramming the sand.

RAPPING – Tapping of the pattern with a mallet in order to loosen it as it is drawn from the mould.

RAPPING BAR – A pointed bar (or rod) made of steel or other metal, which is inserted vertically into a hole in a pattern or driven into it, then struck with a hammer on alternate sides to cause vibration and loosening of the pattern from the sand.

RELIEF SPRUE – The second sprue at opposite end of the runner to relieve pressure created during pouring operation.

RIBS – are used primarily as stiffeners and reinforcing members. If properly designed and located in difficult castings, serve to check the possibility of hot tears or cracks during solidification.

RISER – Reservoir of molten metal attached to the casting to compensate for the internal contraction of the casting during solidification.

RUNNER – The portion of the gate assembly which connects the downgate or sprue with the casting.

SAG – Defect which appears as an increase or decrease in metal section due to sinking of sand in the cope (decreased section) or sagging in the core (increased section).

SAND BLAST – Sand driven by a blast of compressed air (or steam). Used to clean castings, to cut, polish or decorate glass and other hard substances.

SCAB – A blemish on the casting caused by eruption of gas from the mould face.

SEAM – Surface defect on a casting similar to a cold shut, but not as severe.

SEMICENTRIFUGAL CASTING – is one in which the mould, usually a stacking of several flat sand or die moulds, is rotated about a vertical axis.

SHOT – Abrasive blast cleaning material.

SHRINKAGE ALLOWANCES – are provided to take care of the contraction in dimensions of the solidified casting as it cools from its freezing temperature to room temperature.

SHRINK HOLE – A hole or cavity in a casting resulting from contraction and insufficient feed metal, and formed during the period the metal changed from the liquid to the solid state.

SHELL MOULDING – Process in which clay free silica sand coated with a thermosetting resin or mixed with the resin is placed on a heated metal pattern for a short period of time to form a partially hardened shell. The unaffected sand mixture is removed for further use. The pattern and the shell are then heated further to harden or polymerize the resin sand mix, and the shell is removed from the pattern.

SKIMMING GATE – Part of the mould that retains non-metallic inclusions or impurities and delivers sound metal further into the runners.

SLEEK – Term meaning to make smooth. It is applied to the trowelling of a sand surface.

SLUSH CASTING – Casting made by pouring an alloy into a metal mould, allowing it to remain sufficiently long to form a thin solid shell, and then pouring out the remaining metal.

SNAG – Removal of fins and rough places on a casting by means of grinding.

SNAP FLASK – Moulding box, hinged on one side so that it may be opened to allow the finished mould to be removed.

SPRIGS – Small pegs of wood or metal used to strengthen weak portions of a mould or to assist in the mending up of a damaged mould.

SPRUE – The vertical portion of the gating system where the molten metal first enters the mould.

STACK MOULDING – Moulding method in which the half mould forms the cope and drag. They are placed on top of the other and moulds stacked one over the other are poured through a common sprue.

STRICKLE – Piece of wood by means of which surplus sand is removed from a moulding box or other surface. They may also be used to shape sand surfaces into any required shape.

SURVIVABILITY – The ability of a moulding mixture to retain its initial properties for a specified length of time.

TRUE CENTRIFUGAL CASTING – is used for producing thin or thick walled hollow cylinders with a bore concentric with the outside.

VENT – Channel made in the sand in the vicinity of a mould to allow steam, gases etc., generated when sand and molten metal come into contact with one another, to escape.

VENT ROD – A piece of wire or rod to form the vents i.e., holes in the sand, for the escape of gases.

VENT WAX – Wax in rod shape placed in the core during manufacture. In the oven the wax is melted out leaving a vent or passage.

WASH – Casting defect resulting from erosion of sand. Also refers coating materials applied to moulds, cores etc.

WASTER – Faulty casing.

WHIRL GATE – Gating system in which the metal enters a circular reservoir at a tangent and so whirls around, leaving dirt and slag behind before passing into the mould cavity.

WHISTLERS – Small openings from isolated mould cavities to allow gases to escape easily.

YIELDABILITY – The ability of the sand mixture to decrease in volume so as not to limit the contraction of a solidifying casting.

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