Casting

A generic term referring to a process where a fluid material (usually a molten alloy) is made to flow into a shaped mold cavity where it solidifies; this method is used to produce complex component shapes and properties difficult to achieve otherwise.

A guide as to the surface finish that is achievable using different casting techniques is shown below:

the solid area shows the normal limits achievable using these techniques

As-Cast Condition

Casting without subsequent heat treatment.

Back Draft

Reverse taper which would prevent removal of a pattern from a mould or a core from a corebox.

Bar, Flask

A rib in the cope of a tight flask to help support the sand.

Backing Sand

The bulk of the sand in the flask

The sand compacted on top of the facing sand that covers the pattern.

Binder

The bonding agent used as an additive to mould or core sand to impart strength of plasticity in a dry state.

Blasting or Blast Cleaning

A process for cleaning or finishing metal objects by use of an air blast or centrifugal wheel that throws abrasive particles against the surfaces of the work pieces. Small irregular particles of metal are used as the abrasive in grit blasting; sand in sand blasting; and steel balls in shot blasting.

Bleeder

A defect wherein a casting lacks completeness due to molten metal draining or leaking out of some part of the mould cavity after pouring has stopped.

Blow Holes

Voids or holes in a casting that may occur due to entrapped air or shrinkage during solidification of heavy sections.

Burn-On Sand

Sand adhering to the surface of the casting that is extremely difficult to remove.

Burn-Out

Firing a mould at a high temperature to remove pattern material residue.

Casting Yield

The weight of casting or castings divided by the total weight of metal poured into the mould, expressed as a percent.

Centrifugal Casting

A process of filling moulds by: 1) pouring metal into a sand or permanent mould that is revolving about either its horizontal or its vertical axis.

2) pouring metal into a mould that is subsequently revolved before solidification of the metal is complete.

Centrifuge Casting

A casting technique in which the mould is spun and the molten metal is poured in the centre.

Cavity

The portion of a cast which forms the external shape.

Chaplet

A small metal insert or spacer used in moulds to provide core support during the casting process.

Charge

A given weight of metal introduced into the casting furnace.

Chill

A metal insert in the sand mould used to produce local chilling and equalize rate of solidification throughout the casting.

Cleaning

Removal of runners, risers, flash, surplus metal and sand from a casting.

CO2 Process

Moulds and cores made with sand containing sodium silicate are instantly hardened by permeating the sand with carbon dioxide gas.

Coining

A press metal-working operation which establishes accurate dimensions of flat surfaces or depressions under predominantly compressive loading.

Cold Shot

Small globule of metal embedded in, but not entirely fused with the casting.

Cold Shut

A casting defect caused by imperfect fusing of molten metal coming together from opposite directions in a mould or due to folding of the surface.

Collapsible Core

A metal insert made in two or more pieces to permit withdrawal from an undercut mould surface.

Cope

The top half of a horizontally parted mould.

Core

A sand or metal insert in a mould to shape the interior of the casting or that part of the casting that cannot be shaped by the mould pattern. The portion of the cast which forms the internal shape.

Core Assembly

An assembly made from a number of cores.

Corebox

The wooden, metal or plastic tool used to produce cores.

Coreprint

A projection on a pattern that leaves an impression in the mould for supporting the core.

Core Wash

A liquid suspension of a refractory material applied to cores and dried (intended to improve surface of casting).

Crush

The displacement of sand at mould joints.

Cuploa

A cylindrical, straight shaft furnace (usually lined with refractories) fro melting metal in direct contact with coke by forcing air under pressure through openings near its base.

Cure

To harden.

Die

A metal form used as a permanent mould for die casting or for wax pattern in investment casting.

Die Casting

A casting process in which the molten metal is forced under pressure into a metal mould cavity.

Die Cavity

The impression in a die into which pattern material is forced.

Directional Solidification

The solidification of molten metal in a casting in such a manner that liquid feed metal is always available for that portion that is just solidifying.

Draft

Taper on the vertical sides of a pattern or corebox that permits the core or sand mould to be removed without distortion or tearing of the sand. Angle of draft varies and is dependant on surface length as well as process employed during cast. For sand casting a draft of about 2° to 3° is required.

Draft (Pattern)

The taper on the sides of pattern which are perpendicular to the parting plane that allows the pattern to be withdrawn from the mould without breaking the edges of the mould.

Ejector Pins

Movable pins in the pattern die that "push" to remove cast pattern from the dies.

External Undercut

Any recess or projection on the outside of the die block which prevents its removal from the cavity.

Facing Sand

The sand used to surround the pattern that produces the surface in contact with the molten metal.

Feeder

Also called "riser", it is part of the gating system that forms the reservoir of molten metal necessary to compensate for losses due to shrinkage as the metal solidifies.

Flask

A rigid metal or wood frame used to hold the sand of which a mould is formed and usually consisting of two parts, cope and drag.

Foundry Returns

Metal (of unknown composition) in the form of gates, sprues, runners, risers and scraped castings returned to the furnace for re-melting.

Gas Porosity

A condition existing in a casting caused by the trapping of gas in the molten metal or by mould gases evolved during the pouring of the casting.

Green Sand

A moulding sand that has been tempered with water and is employed for casting when still in the damp condition.

Green Sand Mould

A mould composed of moist moulding sand and not dried before being filled with molten metal.

Hotbox Process

A resin-based process that uses heated metal coreboxes to produce cores.

Hot tear

Irregularly shaped fracture in a casting resulting from stresses set up by steep thermal gradients within the casting during solidification.

Inclusions

Particles of slag, refractory materials, sand or deoxidation products trapped in the casting during pouring solidifications.

Internal Shrinkage

A void or network of voids within a casting caused by inadequate feeding of that section during solidification.

Inverse Chill

The condition in a casting section where the interior is mottled or white, while the other sections are gray iron

Also known as Reverse Chill, Internal Chill and Inverted Chill.

Investment Casting Process

A pattern casting process in which a wax or thermoplastic pattern is used

The pattern is invested (surrounded) by a refractory slurry. After the mould is dry, the pattern is melted or burned out of the mould cavity, and molted metal poured into the resulting cavity.

Loose Piece

1) Core box; part of a core box which remains embedded in the core, and is removed after lifting off the core box. 2) Pattern; laterally-projecting part of a pattern so attached that it remains in the mould until the body of the pattern is drawn. Back-draft is avoided by this means. 3) Part of a permanent mould which remains on the casting, and is removed after casting is ejected from the mould.

Lost Wax Process

A casting process in which an expendable pattern made of wax or similar material is melted or burned out of the mould rather than being drawn out.

Lost Foam

A casting process in which a foam pattern is replaced by molten in a flask filled with loose sand to form a casting.

Master Pattern

The object from which a die can be made; generally a metal model of the part to be cast with process shrinkage.

Mould

The form, made of sand, metal or refractory material, which contains the cavity into which molten metal is poured to produce a casting of desire shape.

Mould Cavity

The impression in a mould produced by removal of the pattern. It is filled with molten metal to form the casting

Gates and risers are not considered part of the mould cavity.

Mould Shift

A casting defect which results when the parts of the mould do not match at the parting line.

Mould Wash

A slurry of refractory material, such as graphite and silica flour, used in coating the surface of the mould cavity to provide an improved casting surface.

Mould Weight

A weight that is applied to the top of a mould to keep the mould from separating.

Moulding Machine

A machine for making moulds.

Nitriding

A process of shallow case hardening in which a ferrous alloy, usually of a special composition, is heated in an atmosphere of ammonia, or in contact with nitrogenous material, to produce surface hardening by formation of nitrites, without quenching.

Nobake Process

Moulds/cores produced with a resin bonded air-setting sand.

also known a the airset process because moulds are left to harden under ambient conditions.

Parting Line

A mark or line produced on the cast, formed at the junction of the parting dies.

Patternmaker’s Shrinkage

Contraction allowance made on patterns to compensate for the decrease in dimensions as the solidified casting cools in the mould from freezing temperature of the metal to room temperature. Pattern is made larger by the amount of contraction that is characteristic of the particular metal to be used.

Porosity

Holes in the produced casting due to gasses trapped in the mould, the reaction of molten metal with moisture in the molten sand, or the imperfect fusion of chaplets with molten metal.

Rod

A heavy wire or bar in a sand core used for reinforcing.

Runner

The portion of the gate assembly that connects the down gate (sprue) with the casting ingate or riser

The term also applies to that part of the pattern which forms the runner.

Runout Casting

Unintentional escape of molten metal from a mould.

Shrink Hole

A hole or cavity in a casting resulting from shrinkage and insufficient feed metal, and formed during solidification.

Shrinkage

Decrease in volume of the metal as it solidifies.

Shrinkage Cavity

Void left in cast metals as a result of solidification shrinkage.

Shrinkage Defect

Jagged hole or spongy area of a casting lined with dendrites: generally due to insufficient feeding of molten metal during solidification. Not to be confused with Patternmaker’s shrinkage.

See also: Aluminium, Blowhole, Bronze, Centrifuge Casting, Continuous Casting, Cope, Die Casting, Direct Chill Casting, Draft Angle, Flashing, Investment Casting, Iron, Sand Casting.

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Subjects: Mechanical Engineering