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MetalTek International - Metallurgy glossary
Category: Agriculture and Industry > Glossary of Metallurgical Terms
Date & country: 22/08/2013, US
Words: 477


Skin
A thin surface layer different chemically or structurally from the main mass of a metal object.

SLA
Stereolithography Apparatus

Slag Trap
An enlargement, dam, or extrusion in the gating or runners system in a mold for the purpose of preventing molten slag particles from entering the mold cavity.

Slurry
A term loosely applied to any clay-like dispersion. It may be used to wash ladles or other refractory linings to impart a smooth surface; as a bonding addition to molding sand, as a thin loam over specially made molds, or as a mixture to fine joints or cracks of a core, etc.

Smelting
A metallurgical thermal process in which a metal is separated in fused form from nonmetallic materials, or other undesired metals with which it is associated.

Softening
A process used to soften metals through annealing or tempering.

Solidification
The physical process of change from a liquid to a solid state. See Casting Analysis of Solidification (13kB)

Solidification, Shrinkage
The decrease in size accompanying the freezing of a molten metal.

Spalling
Buckling or flaking off of the surface material.

Specific Gravity
A numerical value representing the weight of a given substance, as compared with the weight of an equal volume of water at 39

Specific Heat
Equivalent to thermal capacity, or the quantity of heat required to produce a unit change in the temperature of a unit mass.

Specific Volume
Volume of one gram of a substance at a specific temperature, usually 68

Spout
A trough through which the metal flows from the furnace to the ladle.

Sprue Hole
The opening through which the metal is poured into the cope to run into the casting cavity.

Stainless Steel
A wide range of steels containing chromium, or chromium and nickel, exhibiting high resistance to corrosion.

Steel
An alloy of iron and carbon that may contain other elements, and in which the carbon content does not exceed about 1.7%; it must be malleable at some temperature while in the as-cast state.

Stereolithography Apparatus
(SLA) Equipment used for computerized building of three-dimensional models and patterns. Enables the data representation of a CAD solid model to be directly converted into a plastic model of a casting.

Stock Allowance
Material added to a part to allow for surface preparation or precise dimensioning by machining.

Stopper Rod
A device in a bottom-pour ladle for controlling the flow of metal through the nozzle into the casting. The stopper rod consists of a steel rod, protecting sleeves, and a graphite stopper head. It may also be a single piece manufactured from graphite.

Streamline Flow
Steady flow of liquid without turbulence. Generally, not experienced in metalcasting.

Stress-Corrosion Cracking
Spontaneous failure of metals by cracking under combined conditions of corrosion and stress, either residual or applied.

Stress, Relieving
A heat treatment to reduce residual stresses, followed by sufficiently slow cooling to minimize development of new residual stresses.

Stress, Residual
Those stresses set up in a metal as a result of nonuniform plastic deformation, or the unequal cooling of a casting.

Structure
(Cast Structure) The size and disposition of the constituents of a metal as cast.

Superalloy
An alloy developed for very high temperature use, where relatively high stresses are encountered, and where oxidation resistance is needed.

Supercooling
Lowering the temperature of a molten metal below its liquidus during cooling.

Superheat
Any increment of temperature above the melting point of a metal; sometimes construed to be any increment of temperature above normal casting temperatures introduced for the purpose of refining, alloying, or improving fluidity.

Supersaturated
Metastable solution in which the dissolved material exceeds the amount the solvent can hold in normal equilibrium at the temperature and under the other conditions that prevail.

Surfacing
Depositing a filer metal on a metal surface by any method to obtain certain desired properties or dimensions.

Swell
A casting defect consisting of an increase in metal section due to the displacement of sand by metal pressure.

Temper
1) Reheating hardened, normalized, or mechanically worked steel to a temperature below the critical range to soften it and improve impact strength. 2) The moisture content of a sand at which any certain physical test value is obtained, e.g., temper with respect to green compressive strength, permeability, retained compressive strength, etc. 3) To m...

Temper Brittleness
Brittleness that results when certain steels are held within or cooled slowly through a certain range of temperature below the transformation range. The brittleness is revealed by notched-bar impact tests at room temperature or lower temperatures.

Temper Stressing
Quenching in water from the tempering temperature to improve fatigue strength.

Temperature
Degree of warmth or coldness in relation to an arbitrary zero measured on one or more of accepted scales, as Centigrade, Fahrenheit, etc.

Temperature, Holding
1) Temperature above the critical phase transformation range at which castings are held as a part of the heat treatment cycle, 2) The temperature maintained when metal is held in a furnace, usually prior to pouring.

Temperature, Pouring
The temperature of the metal as it is poured into the mold.

Tempered Martensite
Martensite that has been heated to produce to BCC iron and a fine dispersion of iron carbide.

Tensile Strength
The maximum stress in uniaxial tension testing, which a material will withstand prior to fracture. The ultimate tensile strength is calculated from the maximum load applied during the test, divided by the original cross-sectional area.

Thermal Conductivity
The property of matter by which heat energy is transmitted through particles in contact. For engineering purposes, the amount of heat conducted through refractories is usually given in Btu per hour for one square foot of area, for a temperature difference of one degree Fahrenheit, and for a thickness of one inch, Btu/hr

Thermal Contraction
The decrease in a linear dimension and volume of a material accompanying a change of temperature.

Thermal Expansion
The increase in a linear dimension and volume of a material accompanying a change of temperature.

Thermal Fatigue
Failure resulting from rapid cycles of alternate heating and cooling.

Thermal Shock
Stress developed by rapid and uneven heating of a material.

Thermography
1) The technique of obtaining a photographic record of heat distribution in a solid or fluid.

Tolerance
The permissible deviation of a dimension from the nominal or desired value. Minimum clearance between mating parts.

Tool Steel
Any high-carbon or alloy steel used to make a cutting tool for machining metals and for metal-casting dies.

Toughness
The ability of the metal to absorb energy and to deform plastically during fracture. Toughness values obtained in testing depend upon the test temperature, the rate of loading, the size of the test specimen, as well as the presence of a notch and its acuity.

Transfer Ladle
A ladle that may be supported on a monorail or carried in a shank and used to transfer metal from the melting furnace to the holding furnace, or from furnace to pouring ladles.

Transformation
(Temperature) The critical temperature at which a change in phase occurs. To distinguish between the critical points in heating and cooling those in heating are referred to as the Ac points (c for Chauffage or heating) and those in cooling, Ar. (r for Refroidissement)

Turntable
The base on which a centrifugal casting mold rests.

Ultrasonic Testing
A nondestructive method of testing metal for flaws based on the fact that ultrasonic waves are reflected and refracted at the boundaries of a solid medium.

Upgrading
In castings, the removal and repair of discontinuities to raise the quality level of the casting beyond that which can be economically achieved by good foundry practice.

Upper Yield Point
(also Yield Point) Denoted in yield point phenomenon as a distinct break from the elastic region accompanied by a drop in load, yet prior to plastic deformation in the stress-strain curve in a low-carbon steel.

Vacuum Casting
A casting in which metal is melted and poured under very low atmospheric pressure; a form of permanent mold casting where the mold is inserted into liquid metal, vacuum is applied, and metal drawn up into the cavity.

Vacuum Degassing
The use of a vacuum technique to remove dissolved gases from molten alloys.

Vacuum Refining
Melting in a vacuum, usually by electrical induction, to remove gaseous contaminants from the metal.

Venting
Perforation with a vent wire of the sand over and around a mold cavity to assist in the escape of the gases.

Vertical Axis Casting Machine
A centrifugal casting machine in which the axis of rotation of the mold is vertical.

Virgin Metal
(Primary Metal) Metal extracted directly from the ore; not previously used.

Viscosity
The resistance of fluid substance to flowing, quantitatively characteristic for an individual substance at a given temperature and under other definite external conditions.

Void
A shrinkage cavity produced in casting during solidification.

Warpage
Deformation other than contraction that develops in a casting between solidification and room temperature; also, distortion occurring during annealing, stress relieving, and high-temperature service.

Water Test
To subject a casting to water pressure in such a manner that any porous areas will show leakage.

Wax Pattern
1) 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, 2) wax molded around the parts to be welded by a termite welding process.

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

Weld Bead
The built-up portion of a fusion weld, formed either from the filler metal or the melting of the parent metal.

Welding
A process used to join metals by the application of heat. Fusion welding, which includes gas, arc, and resistance welding, requires that the parent metals be melted.

Welding Electrode
A metal or alloy in rod or wire forms used in electric arc welding to maintain the arc, and at the same time supply molten metal or alloy at the point where the weld is to be accomplished.

Welding Shielded-Arc
Electric-arc welding in which the molten weld metal is protected from the atmosphere. An inert gaseous atmosphere or fluxcoated electrode may be employed.

Welding Stress
That stress resulting from localized heating and cooling of metal during welding.

Welding, Arc
Welding accomplished by using an electric arc that can be formed between a metal or carbon electrode and the metal being welded; between two separate electrodes, as in atomic hydrogen welding or between the two separate pieces being welded, as in flash welding.

Welding, Autogenous
Method of uniting two pieces of metal by melting their edges together without solder or any added welding metal, as by the thermite process that employs a medium of finely divided aluminum powder and oxide, or iron by which a temperature of some 2982.2

X-Ray
Form of radiant energy with wavelength shorter than that of visible light, and with the ability to penetrate materials that absorb or reflect ordinary light. X-rays are usually produced by bombarding a metallic target with electrons in a high vacuum. In nuclear reactions it is customary to refer to photons originating in the nucleus as gamma rays a...

Yield
Comparison of casting weight to total weight of metal poured into mold.

Yield Ratio
The ratio of yield strength to ultimate tensile strength.

Yield Strength
The stress at which a material exhibits a specified limiting permanent strain.

Young's Modulus
(E) See Modulus of Elasticity