Metal Casting Glossary

A B C D E F G H I J K L M N O P Q R S T U V W XYZ

(A)

Addition Agent

Material mixed to a charge of molten metal which is in bath or ladle. This is done to bring alloy to the required specifications. It can also be a reagent which is added to the plating bath..

ADI

Austempered Ductile Iron: Iiron grade that has high ductility, high strength created through heat treating.

Allowance (Tolerance)

The specified clearance - the minimum clearance or maximum interference permissible between mating parts.

Alloy

A material exhibiting metallic properties and composed of two or more chemical elements. Out of these at least one should be metal. Generally it possesses properties unique from those of the components. For examples, Brass is an alloy of copper and zinc.

Annealing

It comprises of heating the metal first and then slowly cooling it. This is done to reduce the brittleness and increasing the strength.

Antioch Process

A plaster molding process comprising 50% sand, 40% gypsum, and 8% fibrous talc mixed with water in the ratio of 100 parts material to 50 parts water.

Anodizing

A process tat coats aluminum by anodic treatment. This results in the formation of a thin film of aluminum oxide of extreme hardness.

(B)

Bake

The Heat generated in an oven to produce a low controlled temperature that removes gases or hardens a binder.

Binder

It's the bonding agent or a material used commonly as an additive to mold or core sand. This adds strength or plasticity in a "green" or dry state. Oil, clay, resin, pitch, etc. are typically used as binders. Billet These are semi finished products that are hot rolled from ingots. They are further processed into rods, bars , tubes etc

Bushing

A sleeve that can be metallic or nonmetallic. It is usually removable. When placed in a body it resists wear, erosion, etc.

Blasting (Blast Cleaning)

A mechanism for cleaning and finishing metal objects by using an air blast or centrifugal wheel. This throws abrasive particles against the surface of the work pieces. Small and irregular shaped particles of steel or iron are used as abrasive in grit blasting, whereas steel or iron balls are applied in shot blasting.

Brazing

This process is used for joining metals and alloys by fusion of nonferrous alloys that have melting points above 800 degree F, but lower than those of the metals being joined.

(C)

Carbon Steel

A kind of Steel that owes its properties mainly to various percentages of carbon but without substantial quantities of other alloying elements. Carbon steel is also known as ordinary steel or straight carbon.

Case Hardening

A method of hardening a ferrous alloy . The surface layer or case is made significantly harder than the interior or core. Carburizing , carbonitriding, and nitriding are typical case hardening processes.

Cavitation

The formation and subsequent collapse of cavities or bubbles within a liquid.

Chill (External)

Graphite, metal or carbon blocks that are added to the mold or core . This helps to locally increase the rate of heat removal during solidification as well as reduce shrinkage defects.

Chill (Internal)

A metallic device or insert placed in molds or cores at the surface of a casting to increase the rate of heat removal. It also helps in directional solidification and reducing shrinkage defects. The internal chill later becomes part of the casting itself.

Clay, Refractory

A clay with qualities like resisting high temperatures, and possessing strong bonding powers.

Corrosion

A continual chemical or electrochemical attack on a metal surface, triggered by atmosphere, moisture or other agents.

(D)

Damping Capacity

It refers to the ability of absorbing vibration. More precisely, as the quantity of work dissipated into heat by a unit volume of material in course of a completely reverse cycle of unit stress.

Degassing

A chemical reaction taking place because of a compound added to molten metal for removing gases from the metal. Inert gases are preferred in this operation.

Draft

Draft refers to the taper on vertical surfaces of a pattern. It allows easy withdrawal of the pattern from a compacted sand mixture. It facilitates the process without the usual problems of distortion, tearing of the sand , excessive rapping and tearing of the mold walls affecting.

Drier (Dryer)

Material like sodium perborate and manganese oleate, mixed to a core or mold mixture. This helps to remove water content.

Differential Heat Treatment

A type of heating process in which the temperature is varied within the object . This helps in giving different properties to different parts after the cooling process.

(E)

Elongation

It measures a material's ductility. It indicates the percentage by which a material will deform before permanent deformation . The higher the percent, the more ductile the material..

Ethyl Silicate

Consisting predominantly of tetra ethyl silicate with some polysilicates when hydrolyzed with water forms alcohol and silicic acid. Colour of the liquid is light brown. Uses: bonding agent in investment molding.

Electrode

Electrodes are basically compressed graphite or carbon cylinder or rod . It is used to conduct electric current in carbon arc welding,electric arc furnaces, arc lamps, etc.

Erosion

Abrasion of metal or other material by liquid or gas. It gets accelerated by pressure of solid matter particles in suspension.

Expanded Metal

A rigid, metal sheet or plate made of carbon or stainless steel, aluminum, and a variety of alloys. It is slit and expanded (drawn) into an open mesh pattern . That makes it stronger, lighter and more rigid than the original material.

(F)

Fabrication

Two or more parts that are joined usually by welding to produce a finished assembly. The components can be a combination of cast and wrought materials.

Finish Allowance

The quantity of stock usually left on the surface of a casting for the machining process.

Fusion

Transformation from a solid to a fluid state caused by heat.

Finishes

The appearance on the surface of various metals after final treatment like rolling, etc has been done. For example The following finish can be taken as a standard in its particular field.

Aluminum Sheet

(1) Bright one side. (2) Commercially Bright. (3) Bright both sides (4) Embossed Sheets (Produced by using embossed rolls.)

(G)

Gate

Gate is the point where molten metal enters the casting cavity. In general Gate is referred to as a term to indicate the entire assembly of connected columns and channels carrying the metal from the top of the mold to the part forming the casting cavity. Also applied to indicate the pattern parts that form the passages, or to the metal that fills them.

Grain Refiner

Refers to material added to a liquid metal or alloy that produces a fine grain size after solidification..

Graphite

Carbon crystal in hexagonal shape. Generally foliated or granular massive. Shows black color ,gives metallic luster, and is soft. Used as lubricants ,crucibles, foundry facings etc. Can be produced artificially by passing alternating current through a mix of petroleum coke and coal tar pitch.

Grade

Indicates the grade of an iron, usually denoted by three successive numbers, the first is tensile strength (KSI), the second yield strength (KSI), and the third the elongation Percent.

(H)

Homogenizing

A heating process at high temperature that is intended to eliminate or lessen chemical segregation by diffusion.

HSLA

Stands for High Strength Low Alloy Steel. Shows relatively high strength and impact properties. The carbon level is also low and the alloying additions are considerably less than 5 weight percent.

Hardenability

The property that determines the depth and distribution of hardness induced by quenching in a ferrous alloy.

Hot Tear

Hot tear is referred to the irregularly shaped fracture in a casting. This is formed before completion of metal solidification , because of stresses set up due to steep thermal gradients within the casting and rigidity of the core or mold material

Holding Furnace

A small furnace for maintaining molten metal at the proper pouring temperature and which is usually supplied from a large melting unit.

(I)

Inclusion(s)

Particles of refractory materials , slag , sand or deoxidation products that gets trapped in the casting during solidification process.

Ingot

Casting that is forged or hot worked later. Also refers to the form used for convenient handling of aluminum,cast iron and other metals.

Iron, Malleable

A mixture that is formed of iron and carbon, includes also smaller amounts of silicon, manganese, phosphorus, and sulphur. After it is cast ( as carbides) gets converted structurally by heat treatment into a matrix of ferrite that contains nodules of temper carbon (graphite).

Isotope

Elements having the having the same atomic number, but differing in the number of neutrons and hence resulting in the mass number. Example is Carbon.

Induction Heating

The process in which of heating by electrical resistance and hysteresis losses induced by subjecting a metal to the varying magnetic field surrounding a coil carrying an alternating current.

(J)

Jolt Machine

It is referred to the Molding machine that packs or rams the sand particles around the pattern . It raises the table on which the flask, sand and pattern are mounted by a few inches thus allowing the whole to drop suddenly. Generally the table is raised pneumatically, and the process is repeated till the desired sand density is reached.

Jet Tapping

A process that is used to tap a melting furnace by firing a small explosive charge rather than using oxygen lance. It consists of an explosive charge that is confined in a plastic case surrounded by a body-shaped like hollow bullet.

Jacket, Mold

A wood or metal form that is slipped over a mold made up in a snap or slip flask. It supports the four sides of the mold during pouring. During the pouring period Jackets and mold weights gets shifted from one row of molds to another.

(K)

Kelvin Temperature Scale

The unit of measurement here equals that of the centigrade degree and according to which absolute zero is 0 degrees, equivalent to -273.16°Centigrade.

Knock Out

Removing casting and sand from a flask

Killed Steel

Molten steel placed in a ladle, furnace, or crucible (Generally treated with aluminum, silicon, or manganese) until more gas gets evolved and the metal perfectly quiet.

Kiln

Refers to an oven or furnace that is used for burning, calcimining or drying purposes.

KC (Plane-stress fracture toughness)

The value of the stress intensity at which crack propagation becomes quicker in sections that are thinner than those in which plane-strain conditions prevail. Units of measurement are MPa/m or ksi/in.

(L)

Ladle

Metal receptacles lined with refractories. Used for transporting and pouring molten metal. Various types of ladles include bottom-pour, hand bull, crane,etc

Lining

This gets placed inside refractory layer of firebrick, clay, sand, or other material in a furnace.

Lost Foam Process

A type of casting process in which the foam pattern gets removed from the cavity as the molten metal gets poured.

Liquid Contraction

Shrinkage or contraction of the molten metal as it cools from higher temperature to lower in the liquid state.

(M)

Machinability

The process in which the part is cut, turned, broached, etc., by machine tools.

Machine Allowance

Stock that is added to the part to permit machining to make it reach the final dimensions.

Malleability

The capability to be permanently deformed without getting ruptured in the process.

Martensite

A constituent found in hardened steel, has a needle like microstructure.

Mechanical Properties

The properties that reveals elastic and inelastic reaction when force is applied , or the relationship between stress and strain. Examples are the modulus of elasticity, tensile strength, and fatigue limit. However, a word of caution , the term should not be used interchangeably with 'physical properties.'

(N)

Nobake Binder

Refers to synthetic liquid resin sand binder which hardens completely at normal room temperature. Primarily used in the Cold Setting process.

No-Bake Process

Molds/cores that gets produced with a resin bonded air setting sand. This process is also known as the air set process because molds gets hardened under normal atmospheric conditions.

Negative Quenching (Negative Hardening)

Accelerated cooling taking place in water or oil, at a temperature below the critical range

Normalizing

The process of heating a ferrous alloy to a desired temperature above the transformation temperature Ac3. Followed by cooling usually in still air to a temperature substantially below the transformation range.

Negative Thermoie Heat Exchange

Typically used in In shell molding to improve the mass-surface ratio by simulating profile geometry of pattern or core cavity on the underside. This boosts running temperature of high projections by at least 25%

(O)

Open Flame Furnace

Contrary to the crucible furnace, in the open-flame furnace the metal charge is confined to the refractory lining. Here the flame and products of combustion comes in direct proximity with the metal.

Open Grain Structure

Generally a defect , where a casting, when machined or fractured , appears to be coarse grained and porous. This is because of shrink area.

Overaging

The process of aging a precipitation-hardening alloy under time and temperature conditions , greater than those required to obtain maximum strength or hardness.

Oxidation

Reaction of any element with oxygen gas.

Open-Hearth Furnace

Refers to a furnace for melting metal. The bath is heated by the combustion of hot gases over the surface of the metal and the radiation from the roof. Furnace fuel may be powdered coal , producer gas, coke-oven gas or oil.

(P)

Padding

The method of adding some extra material to a cross-section of a casting wall, that extends from a riser to ensure adequate feed to a localized area . This prevents sharing. Finally it must be machined off casting.

Permeability

The property that allows mold material passage of gases.

Pins

Locating pins made of hardened steel that are used on flasks to ensure proper registering of cope and drag molds

Porosity

Holes produced in the castings due to gases trapped in the mold, appearing as shrinkage cavities.

Purging

The process of eliminating air and other undesirable gases from furnaces or heating boxes.

(Q)

Quenching

Fast cooling of the hardening material. This is done by immersion of the object to be hardened in water, oil. additionally solutions of salt or organic compounds in water can also be used.

Quench Severity

Characterized by the H value , relates to the rate of temperature change during quenching.

(R)

Refractory

Usually a heat-resistant , non-metallic material used for furnace linings etc. Ceramics, which is resistant to high temperatures, molten metal, and slag is the preferred material.

Refractory Clay

A clay that fuses at pce 25 (1590°C, 2894°F) or higher.

Rebonding

Adding new bonding material to already used molding sand so that it can be be re-used to produce molds.

Recrystallization

A process whereby a new, strain-free grain structure replaces the distorted grain structure of cold-worked metals during annealing above a specific minimum temperature.

Recrystallization Temperature

The lowest temperature at which the new, strain-free grain structure replaces the distorted grain structure of cold-worked metals during continuous annealing. Important factors to be considered are time, purity of the metal, and extent of prior deformation.

(S)

Shrinkage

It is the difference in volume between liquid metal and solid metal. It can also be used to describe the casting defects i.e. shrinkage cavity.

Sieve

It is a device with meshes of wire or other material for separating fine material from coarse material.

Sintering Point

The temperature at which the molding material begins to adhere to the casting, or in a test when the sand coheres to a platinum ribbon under controlled conditions.

Slag

A fused nonmetallic material used to protect molten metal from the air and to extract certain impurities.

Slurry

A flowable mixture of refractory particles suspended in a liquid.

Sprue

A vertical passageway that takes the molten metal from the pouring basin to the runner.

Stereolithography Apparatus (SLA)

Equipment used for computerized building of three-dimensional models and patterns.

Stripping

Removing the pattern from the mold or core from core box

(T)

Temper

Reheating hardened, normalized or mechanically worked steel to a temperature below the critical range to soften it and improve impact strength. The moisture content of a sand at which any certain physical test value is obtained, i.e., temper with respect to green compressive strength, permeability, retained compressive strength, etc. To mix material with enough liquid to develop desired molding properties

Tensile Strength (Ultimate Tensile Strength, UTS)

A measure of the amount of mechanical stress a material can withstand before it fractures. Measured in pounds per square inch (PSI), or thousands of pounds per square inch (KSI)

Thermal Conductivity

The property of matter by which heat energy is transmitted through particles in contact.

Thermocouple

A device for measuring temperatures by the use of two dissimilar metals in contact; the junction of these metals gives rise to a measurable electrical potential, which varies with the temperature of the junction.

Trimming

Removing fins, gates, etc. from castings.

(U)

Upset

Additions done to any flask part for increasing height or depth.

Upgrading

The removal and repair of discontinuities for raising the quality level of the casting.

(V)

Vacuum Casting

A casting in which metal is melted and poured under very low atmospheric pressure.

Vertical Axis Casting Machine

A centrifugal casting machine in which the axis of rotation of the mold is vertical.

Vibrator

A mechanical device, operated by compressed air or electricity, used to loosen a pattern from a mold by jarring or vibration as it is withdrawn from the sand.

Void

A shrinkage cavity produced in casting during solidification

(W)

Wax

Class of substances of plant, animal, or mineral origin, insoluble in water, partly soluble in alcohol, either, etc.

Wax Pattern

A precise duplicate, allowing for shrinkage, of the casting and required gates, usually formed by pouring or injecting molten wax into a die or mold.

Wear

The undesired deterioration of a component by the removal of material from its surface.

White Cast Iron

Cast iron in which substantially all the carbon is present in the form of iron carbide, and which has a white fracture.

(XYZ)

Yield

Comparison of the finished casting weight visa -vis the total weight of metal poured in a mold. Denoted as a percentage , indicating the relationship of the weight of casting to the total composite weight of the casting and its gating system.

Yield Ratio

Denoting, ratio of yield strength to ultimate tensile strength

Zircon

Naturally occurring zirconium silicate, chemically called ZrSiO4 containing 67.23% zirconium oxide, ZrO4, and 32.77% silica, SiO2, It is used as a molding medium in steel foundries.