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Technical terms-2
Bake
Heat in an oven to a low controlled temperature to remove gases or to harden a binder.
Batch
Amount or quantity of core or mold sand or other material prepared at one time.
Bimetal
Casting, usually centrifugal, made of two different metals, fused together.
Blasting (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 surface of the work pieces. Small, irregular particles of steel
or iron are used as the abrasive in grit blasting, and steel or iron balls in shot blasting.
Blister
A shallow blow with a thin film of the metal over it appearing on the surface of a casting.
Blow Holes
Irregular shaped cavities with smooth walls produced in a casting when gas is entrapped during
mold filling. The gas sources may be air, binder decomposition products or gases dissolved in the
molten steel.
Boil
Agitation of a bath of metal caused by the liberation of a gas beneath its surface.
Bond
Bonding substance or bonding agents - any material other than water, which, when added to
foundry sands, imparts bond strength.
Bond Strength
Property of a foundry sand to offer resistance to deformation.
Bright Annealing
A process carried out usually in a controlled furnace atmosphere, so surface does not oxidize,
remaining bright.
Brinell Hardness
The value of hardness of a metal on an arbitrary scale representing kg/mm², determined by
measuring the diameter of the impression made by a ball of given diameter applied under a
known load. Values are expressed in Brinell Hardness Numbers, BHN.
Brittle Fracture
Fracture with little or no plastic deformation. Smoothing machined holes or outside surfaces of
castings by drawing, pushing on, or more broaches (special cutting tools) through the roughed out
hole.
Bulk Density
The ratio of the weight of a material to its over-all volume (including any inherent porosity).
Calcination
A high-temperature reaction whereby one solid material dissociates to form a gas and another
solid. It is one step in the production of cement.
Calorimetry
Technique for studying phase transitions by measuring thermal effects, i.e., taking off or releasing
the heat in the course of the transitions.
Carbide
A compound of carbon with one or more metallic elements.
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Carbonitriding
A process in which a ferrous alloy is case hardened by first being heated in a gaseous atmosphere
of such composition that the alloy absorbs carbon and nitrogen simultaneously, and then being
cooled at a rate that will produce desired properties.
Carburizing
A form of case hardening that produces a carbon gradient inward from the surface, enabling the
surface layer to be hardened by either quenching directly from the carbonizing temperature or by
cooling to room temperature, then reaustenitizing and quenching.
Case Hardening
A process of hardening a ferrous alloy so that the surface layer or case is made substantially
harder than the interior or core. Typically case hardening process are carburizing, carbonitriding,
and nitriding.
Cast iron
Generically, a ferrous alloy, the carbon content of which is greater than the maximum solubility in
austenite at the eutectic temperature. Most commercial cast irons contain between 3.0 and 4.5
wt% C, and between 1 and 3 wt% Si.
Casting
Article obtained by pouring liquid metal into a hollow form, where it solidifies. Its macrostructure
is similar to that of an ingot, however, usually without a columnar zone.
Cathodic protection
A means of corrosion prevention whereby electrons are supplied to the structure to be protected
from an external source such as another more reactive metal or a dc power supply.
Cation
A positively charged metallic ion
Cavitation
The formation and collapse of cavities or bubbles within a liquid.
Cement
A substance (often a ceramic) that by chemical reaction binds particulate aggregates into a
cohesive structure. With hydraulic cements the chemical reaction is one of hydration, involving
water.
Cementite
A compound of iron and carbon commonly known as iron carbide and having the approximate
chemical structure, Fe3C. Cementite is characterized by an orthorhombic crystal structure.
Centrifugal Casting
Casting made in molds which are rotating so as to produce a centrifugal force in the molten metal.
Cermet
A composite material consisting of a combination of ceramic and metallic materials. The most
common cermets are the cemented carbides, composed of an extremely hard ceramic (e.g., WC,
TiC), bonded together by a ductile metal such as cobalt or nickel.
Charpy Impact Test
A pendulum-type single-blow impact test in which the specimen, usually notched, is supported at
both ends as a simple beam and broken by a falling pendulum. The energy absorbed in fracture, as
impact strength or notch toughness.
Chill (External)
Metal, graphite or carbon blocks that are incorporated into the mold or core to locally increase the
rate of heat removal during solidification and reduce shrinkage defects.
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Chill (Internal)
A metallic device / insert in molds or cores at the surface of a casting or within the mold to
increase the rate of heat removal, include directional solidification and reduce shrinkage defects.
The internal chill may then become a part of the casting.
Cleavage plane
Lattice plane on which cleavage occurs as, e.g., {100} in BCC, {0001} in HCP, and 111 in diamond
structures. The facets of cleavage surface are commonly parallel to the cleavage plane.
Climb
Displacement of a portion of an edge dislocation onto a parallel slip plane caused by the
contraction (or extension) of its extra-plane, owing to vacancy (or self-interstitial) transport to the
dislocation line.
Close-packed direction/row
Straight line in a crystal lattice, along which rigid spheres of equal radii representing the atoms are
in contact. These directions are: ⟨ 110⟩ in FCC structure, ⟨ 111⟩ in BCC, and⟨ ⟩ in HCP.
Close-packed plane
Lattice plane with the maximum lattice point density: {111} in FCC lattice, {110} in BCC, and {0001}
in HCP. They are characterized by the maximum interplanar spacing.
Coalescence
Merging of adjacent particles of the same phase, i.e., subgrains, grains, precipitates, pores, etc. In
the case of crystalline particles, coalescence must be accompanied by the disappearance of their
interface and the simultaneous rotation of at least one of the particles. With regard to precipitates
and pores coalescence is sometimes used erroneously instead of coarsening.
Coarse-grained [Material]
characterized by a mean grain size greater than ..
Coarsening
Thermally activated process resulting in an increase of the mean size of matrix grains (grain
coarsening or grain growth) or precipitates and pores (see Ostwald ripening). The driving force for
coarsening is a decrease of the total interfacial energy per unit volume.
Cold deformation
Procedure of plastic deformation well below the recrystallization temperature.
Coefficient of Expansion
Unit increase in size resulting from a unit increase in temperature; measured in inches per inch per
degree Fahrenheit (in/in/1/2°F) or in millimeter per millimeter per degree Celsius
(mm/mm/1/2°C).
Coercivity (or coercive field, Hc)
The applied magnetic field necessary to reduce to zero the magnetic flux density of a magnetized
ferromagnetic or ferrimagnetic material.
Cohesion
The force by which like particles are held together. It varies with different metals and depends
upon molecular arrangement due to heat treatment.
Coining
A process of straightening and sizing casting by die pressing, a process for shaping metal.
Cold-Box Process
Any core binder process that uses a gas or vaporized catalyst to cure a coated sand while it is in
contact with the core box at room temperature.
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Cold Cracking
Cracks in cold or nearly cold metal due to excessive internal stress caused by contraction. Often
brought about when the mold is too hard or casting is of unsuitable design.
Cold Lap
Wrinkled markings on the surface of an ingot or casting from incipient freezing of the surface.
Cold Shot
Small globule of metal embedded in but not entirely fused with the casting.
Cold Shut
Casting defect caused by imperfect fusing or discontinuity of molten metal coming together from
opposite directions in a mold, or due to folding of the surface. It may have the appearance of a
crack or seam with smooth, rounded edges.
Cold Work
Plastic deformation of a metal at room temperature. Substantial increases in strength and
hardness may occur.
Collapsibity
The requirement that a sand mixture break down under the pressure and temperatures developed
during casting, in order to avoid hot tears or facilitate the separation of the sand and the casting.
Color Etching
A micro-etch resulting from the formation of a thin film of a definite compound of the metal
Columnar Structure
A coarse structure of parallel columns of grains, which is caused by highly directional solidification.
Columnar zone
Typical feature of ingot macrostructure; it is formed by dendrites growing in nearly the same
direction, tightly to each other.
Component
A chemical constituent (element or compound) of an alloy that may be used to specify its
composition.
Composite
Material designed of chemically different and insoluble constituents.
Compression Test
Imposing a dead load on a small cylindrical test piece to determine compressive strength,
expressed in pounds per sq. in.
Compressive Strength (Yield)
The maximum stress in compression that can be withstood without plastic deformation or failure.
Conduction
The transmission of heat, sound, etc. by the transferring of energy from one particle to another.
Conductivity (Thermal)
The quantity of heat that flows through a material measured in heat units per unit time per unit of
cross-sectioned area per unit of length, (electrical) the quantity of electricity that is transferred
through a material of know cross-section and length.
Constituent
A micrographically distinguishable part of an alloy or mixture.
Contamination
presence of small percentages of deleterious elements in an alloy adversely affecting the alloy's
mechanical properties and/or casting soundness.
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Contraction
The volume change occurring in metals (except antimony and bismuth) and alloys on solidification
and cooling to room temperature.
Contraction Cracks
Cracks formed by restriction of the metal while contracting in the mold; may occur just after
solidification (called a hot tear) or a short time after the casting has been removed from the mold.
Controlled Atmosphere
Any gas or mixture of gases that prevents or retards oxidation and decarburization.
Convection
The motion resulting in a fluid from the differences in density. In heat transmission, this meaning
has been extended to include both forced and natural motion or circulation.
Converter
A furnace in which a gas, usually air, is blown through the molten bath or crude metal for the
purpose of oxidizing impurities.
Conveyor, Vibratory
A materials-handling device used usually with shakeout operations, to help clean sand from the
castings as they are moved from one place to another in the foundry and as a feeding device to
regulate materials flow. Operations with vibrational energy.
Cooling, Controlled
A process of cooling from an elevated temperature in a predetermined manner used to produce a
desired microstructure to avoid hardening, cracking or internal damage.
Cooling Curve
A curve showing the relationship between time and temperature during the solidification and
cooling of a metal sample. Since most phase changes involve evolution or absorption of heat,
there may be abrupt changes in the slope of the curve.
Core
A performed sand aggregate inserted in a mold to shape the interior or that part of a casting
which cannot be shaped by the pattern.
Core Binder
Any material used to hold the grains of core sand together.
Core Blow
A gas pocket in a casting adjacent to a core cavity caused by entrapping gases from the core.
Core Box, Combination
Core box and core dryers from the same pattern. One half is used as a half core box and a core
drier.
Coring (Metallurgical)
Variable composition due to the solidification characteristics of an alloy. Typically these
compositional differences occur on a micro scale, the distances between compositional extremes
being controlled by the solidification structure of the alloy.
Corrosion
Gradual chemical or electrochemical attack on a metal by atmosphere, moisture or other agents,
Cover
A protective blanket laid on a melt to exclude oxidizing atmosphere and in the case of magnesium
to prevent its igniting. Neutral covers simply protect metal from atmosphere; reacting covers
contain an agent such as a deoxidizer.
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Crack, Hot Tear
A rupture occurring in a casting at or just below the solidifying temperature by a pulling apart of
the soft metal, caused by thermal contraction stresses.
Creep
The flow or plastic deformation of metals held for long periods of time at stresses lower than the
normal yield strength. The effect is particularly important if the temperature of stressing is in the
vicinity of the recrystallization temperature of the metal.
Creep Limit
The maximum stress that will result in creep at a rate lower than an assigned rate.
Critical Cooling Rate
The minimum rate of continuous cooling just enough to prevent undesired transformations.
Cross Section
A view of the interior of an object that is represented as being cut in two, the cut surface
presenting the cross section of the object.
Crucible
A ceramic pot or receptacle made of materials such as graphite or silicon carbide, with relatively
high thermal conductivity, bonded with clay or carbon, and used in melting metals; sometimes
applied to pots made of cast iron, steel, or wrought steel.
Crucible Furnace
A furnace fired with coke, oil, gas, or electricity in which metals are melted in a refractory crucible.
Crystal
A physically homogeneous solid in which the atoms, ions, or molecules are arranged in a threedimensional repetitive pattern.
Crystalline
The state of a solid material characterized by a periodic and repeating three-dimensional array of
atoms, ions, or molecules.
Crystallinity
For polymers, the state wherein a periodic and repeating atomic arrangement is achieved by
molecular chain alignment.
Crystallization (glass-ceramics)
The process in which a glass (noncrystalline or vitreous solid) transforms to a crystalline solid.
Crystal Lattice
The way atoms are arranged in a crystal. Spacewise, there are only 14 different lattices.
Crystalline Fracture
Fracture of a brittle metal, showing definite crystal faces in the fractured surface.
Curing Time (No Bake)
That period of time needed before a sand mass reaches maximum hardness.