Foundry 101
Glossary of Terms
Common casting, foundry, and quality terms, explained in plain language.
A
- Aging
- A change in the metallurgical structure of an alloy occurring over a period of time following casting, which affects the properties and dimensions.
- AQL (Acceptable Quality Level)
- A quality level established on a prearranged system of inspection using samples selected at random.
- As-cast condition
- Casting without subsequent heat treatment.
B
- Binder
- The bonding agent used as an additive to mold or core sand to impart strength or plasticity in a “green” or dry state.
- Brinell hardness
- A hardness test that measures the size of an indentation left by a large hardened steel or carbide ball.
- Burn-on sand
- Sand adhering to the surface of the casting that is extremely difficult to remove.
C
- Casting yield
- The weight of the casting divided by the total weight of metal injected into the die, expressed as a percentage.
- Cavity
- The recess in the die in which the casting is formed.
- Chaplet
- A small metal insert or spacer used in molds to provide core support during the casting process.
- Charge
- A given weight of metal introduced into the furnace.
- Chill
- A metal insert in the sand mold 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.
- Cold shut
- A defect where metal flowing from different directions in the mold fails to fuse, leaving a line that looks like a crack. Usually caused by metal that is too cold.Learn more →
- Cope
- The top half of a horizontally parted mold.
- Core
- A sand or metal insert in a mold to shape the interior of the casting or that part of the casting that cannot be shaped by the pattern.
- Core assembly
- An assembly made from a number of cores.
- Core wash
- A liquid suspension of a refractory material applied to cores and dried (intended to improve surface of casting).
- Corebox
- The wooden, metal or plastic tool used to produce cores.
- Coreless induction furnace
- An electric induction furnace in which water-cooled coils that carry electrical current surround the charge material. Magnetic fields are established, and voltage is induced by a flow of electric current. The resistance of the charge metal to the current flow produces sufficient heat to melt the metal.
- Coreprint
- A projection on a pattern that leaves an impression in the mold for supporting the core.
- Crush
- The displacement of sand at mold joints.
- Cupola
- A cylindrical, straight shaft furnace (usually lined with refractories) for melting metal in direct contact with coke by forcing air under pressure through openings near its base.
- Cure
- To harden.
D
- Defect
- Imperfections in a cast part – such as porosity, inclusions, cracks, cold shuts and others.
- DFMEA (Design Failure Mode and Effects Analysis)
- A structured engineering analysis used to identify and reduce risks in a product's design before it goes to manufacturing.
- Die
- A metal form used as a permanent mold for die casting or for a wax pattern in investment casting.
- Die casting
- Molten metal is injected under pressure into steel dies, then the die opens and the part is ejected. Suited to high volumes, near net shapes, and fine detail.Learn more →
- Dowel
- A pin of various types used in the parting surface of parted patterns or dies to assure correct registry.
- Draft
- Taper on the vertical sides of a pattern or corebox that permits the core or sand mold to be removed without distorting or tearing of the sand.
- Drag
- The bottom half of a horizontally parted mold.
E
- Ejector pins
- Movable pins in pattern dies that help remove patterns from the die.
- Elongation
- Amount of permanent extension in the vicinity of the fracture in a tensile test, expressed as a percentage.
F
- Facing sand
- The sand used to surround the pattern that produces the surface in contact with the molten metal.
- Feeder
- Sometimes referred to as a “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.
- Fillet
- Curved juncture of two surfaces.
- Finish allowance
- The amount of stock left on the surface of a casting for machining.
- Finish mark
- A symbol (f, fl, f2, etc.) appearing on the line of a drawing that represents the edge of the surface of the casting to be machined or otherwise finished.
- Flash
- Excess metal that escapes where the two halves of a mold meet. It can be trimmed off and the casting salvaged.Learn more →
- Flask
- A rigid metal or wood frame used to hold the sand of which a mold is formed and usually consisting of two parts, cope and drag.
G
- Gas porosity
- A condition existing in a casting caused by the trapping of gas in the molten metal or by mold gases evolved during the pouring of the casting.
- Gate (ingate)
- The portion of the runner where the molten metal enters the mold cavity.
- Green sand
- Moist clay-bonded molding sand.
H
- Heat
- A single furnace charge of metal.
- Heat treatment
- A combination of heating and cooling operations timed and applied to a metal or alloy in the solid state in a manner that will produce desired mechanical properties.
- Hot tear / heat check
- Raised lines of metal on a casting's surface caused by cracks in the mold or, for die casting, in the steel die from thermal cycling. Usually cosmetic.Learn more →
- Hotbox process
- A resin-based process that uses heated metal coreboxes to produce cores.
I
- IATF 16949
- The automotive industry's quality management system standard, published in 2016 to replace ISO/TS 16949. It builds on ISO 9001 with automotive-specific requirements.
- Inclusions
- Particles of slag, refractory materials, sand or deoxidation products trapped in the casting during pouring solidification.
- Investment casting
- A pattern casting process in which a wax or thermoplastic pattern is used. The pattern is invested (surrounded) by a refractory slurry. After the mold is dry, the pattern is melted or burned out of the mold cavity, and molten metal is poured into the resulting cavity.Learn more →
- ISO 14000
- A family of international environmental management standards, with ISO 14001 as its core standard defining the requirements for an Environmental Management System (EMS).
- ISO 9001
- Globally recognized standard for quality management. Its requirements define how to establish, implement, maintain, and continually improve a quality management system (QMS), helping organizations meet customer expectations and demonstrate their commitment to quality.
L
- Ladle
- A container used to transfer molten metal from the furnace to the mold.
- Lead time
- The total time from placing a purchase order to receiving the goods, or delivering them to the customer.
- Locating pad
- A projection on a casting that helps maintain alignment for machining operations.
- Locating surface
- A casting surface to be used as a basis for measurement in making secondary machining operations.
- Lost foam casting
- A foam pattern coated in ceramic is packed in loose sand; molten metal vaporizes the foam and takes its place. Allows complex shapes with no draft.Learn more →
- Low pressure casting
- The furnace is pressurized to push molten aluminum up a riser tube into the die, filling it slowly and steadily for a dense, low-porosity casting.Learn more →
M
- Mechanical properties
- Those properties of a material that reveal the elastic and inelastic properties when force is applied. This term should not be used interchangeably with “physical properties.”
- Metal injection molding (MIM)
- Fine metal powder mixed with a binder is injection molded, then the binder is removed and the part is sintered. Suited to small, complex steel parts with tight tolerances.Learn more →
- Misrun
- A defect where molten metal does not completely fill the mold, also called a short pour. Causes include a broken mold, too little metal, or poor fluidity.Learn more →
- Mold
- Normally consists of a top and bottom form, made of sand, metal or any other investment material. It contains the cavity into which molten metal is poured to produce a casting of definite shape.
- Mold cavity
- The impression in a mold produced by removal of the pattern. It is filled with molten metal to form the casting.
- Mold coating
- (See core wash.)
- Mold shift
- A defect where the two halves of a mold, or a core, are misaligned, offsetting part of the casting. Common in sand casting and prevented with alignment pins.Learn more →
N
- Nobake process
- Molds/cores produced with a resin-bonded air-setting sand. Also known as the airset process because molds are left to harden under normal atmospheric conditions.
P
- Part number
- A unique alphanumeric code used to identify a part. The format varies from customer to customer.
- Parting line
- The line showing the separation of the two halves of the mold.
- Pattern
- The wood, metal, foam or plastic shape used to form the cavity in the sand. A pattern may consist of one or many impressions and would normally be mounted on a board or plate complete with a runner system.
- Pattern draft
- The taper allowed on the vertical faces of a pattern to permit easy withdrawal of the pattern from the mold or die. (See draft.)
- Patternmaker’s shrinkage
- The shrinkage allowance made on all patterns to compensate for the change in dimensions as the solidified casting cools in the mold from freezing temperature of the metal to room temperature. The pattern is made larger by the amount of shrinkage characteristic of the particular metal in the casting and the amount of resulting contraction to be encountered.
- Permanent mold casting
- Molten metal is gravity poured into reusable steel molds; sand cores can form internal features. Lower tooling cost than die casting.Learn more →
- Permeability
- The property of a mold material to allow passage of mold/core gases during the pouring of molten metal.
- PFMEA (Process Failure Mode and Effects Analysis)
- A structured analysis used to identify and reduce risks in the manufacturing process that produces a part.
- Physical properties
- Properties of matter such as density, electrical and thermal conductivity, expansion and specific heat. This term should not be used interchangeably with “mechanical properties.”
- Pig iron
- Blocks of iron to a known metal chemical analysis that are used for melting (with suitable additions of scrap, etc.) for the production of ferrous castings.
- Pilot or sample casting
- A casting made from a pattern produced in a production die to check the accuracy of dimensions and quality of castings that will be made.
- PPAP (Production Part Approval Process)
- Formal documentation proving that a supplier can consistently make a part that meets all engineering requirements before full production begins.
- PPM (Parts per million)
- Measures the number of defective parts found per one million parts received or shipped.
R
- Refractory
- Heat-resistant ceramic material.
- Reject rate
- Ratio of the number of parts scrapped to the total number of parts manufactured, expressed as a percentage.
- Revision level
- A letter or number identifying the version of a drawing or part.
- Riser
- (See feeder).
- Rockwell hardness
- A hardness test that measures how deep an indenter penetrates into a material under a major load.
- Runner system (gating system)
- The set of channels in a mold through which molten metal is poured to fill the mold cavity. The system normally consists of a vertical section (downgate or sprue) to the point where it joins the mold cavity (gate) and leads from the mold cavity through vertical channels (risers or feeders) (Fig. 3).
S
- Sand casting
- Molten metal is poured into a mold made by packing treated sand around a pattern; the mold is broken to remove the casting. Works for all metals and complex internal passages, with low tooling cost.Learn more →
- Sand inclusions
- Cavities or surface imperfections on a casting caused by sand washing into mold cavity.
- Scrap
- (a) Any scrap metal melted (usually with suitable additions of pig iron or ingots) to produce castings; (b) reject castings.
- Shakeout
- The process of separating the solidified casting from the mold material.
- Shell molding
- A heated pattern forms a thin shell of resin-bonded sand that becomes the mold. Gives smoother surfaces and closer tolerances than sand casting, often used for gray and ductile iron.Learn more →
- Shrinkage porosity
- Voids formed when metal freezes and blocks the flow of feed metal to the last sections to solidify. Usually caused by insufficient risering.Learn more →
- Slag
- A fused nonmetallic material that protects molten metal from the air and extracts certain impurities from the melt.
- Slag inclusions
- Casting surface imperfections similar to sand inclusions but containing impurities from the charge materials, silica and clay eroded from the refractory lining, and ash from the fuel during the melting process. May also originate from metal-refractory reactions occurring in the ladle during pouring of the casting.
- Slurry
- A flowable mixture of refractory particles suspended in a liquid.
- Sodium silicate/CO2 process
- Molding sand is mixed with sodium silicate and the mold is gassed with CO2 gas to produce a hard mold or core.
- Sprue (downsprue, downgate)
- The channel, usually vertical, that the molten metal enters.
- Squeeze casting
- Also called liquid forging: molten metal is poured into a die and pressure is applied until it solidifies, combining casting and forging for low porosity.Learn more →
T
- Tensile strength
- The maximum load in tension which a material will withstand prior to fracture.
- Test bar
- Standard specimen bar designed to permit determination of mechanical properties of the metal from which it was poured.
- Test lug
- A lug cast as a part of the casting and later removed for testing purposes.
- TS 16949
- The former automotive quality management standard (ISO/TS 16949), covering design, development, production, and service of automotive-related products. Replaced by IATF 16949 in 2016.
V
- Vacuum assist
- The action of voiding the die casting die of gasses during and prior to the flow of molten metal to form the casting.
- Vent
- An opening or passage in a mold or core to facilitate escape of gases when the mold is poured.
Foundry 101
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