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


NISA
National Industrial Sand Association

Nital
A solution of nitric acid in alcohol use as an etching agent in ferrous metallography.

Nitriding
A surface hardening process involving heating in a atmosphere of ammonia, or in contact with a nitrogen-bearing material, so as to promote the absorption of nitrogen.

Nitrogen Flush
Bubbling nitrogen gas through a metal melt under vacuum (as with valve bronze), to improve tensile properties and pressure tightness.

Nobake Binder
A synthetic liquid resin sand binder that hardens completely at room temperature, generally not requiring baking, used in Cold-Setting process.

Nodular Iron
Iron of a normally gray cast iron type that has been suitably treated with a nodularizing agent so that all, or the major portion of its graphitic carbon, has a nodular or spherulitic form as cast. Often referred to as Ductile Iron.

Nondestructive Testing
(Inspection) Testing or inspection that does not destroy the object being tested or inspected.

Nonferrous
A negative term; refers to alloy in which the predominate metal or solvent is not iron.

Normal Segregation
Concentration of alloying constituents that have low melting points in those portions of a casting that solidify last.

Normalizing
Heating a ferrous alloy to a suitable temperature above the transformation temperature Ac3, followed by cooling at a suitable rate, usually in still air to a temperature substantially below the transformation range.

Nucleation
1) (homogeneous) the initiation of solid crystals from the liquid stage, or initiation of solid crystals from the liquid stage, or a new phase within a solid, without outside interference - rarely occurs, 2) (heterogeneous) foreign particles altering the liquid-solid interface energy during phase changes.

Oil Quenching
Quenching in oil. See Quenching

Open Grain Structure
A defect wherein a casting, when machined or fractured, appears to be coarse grained and porous; usually due to a shrink area.

Optimum Moisture
That moisture content which results in developing the maximum of any property of a sand mixture.

Orange Peel
A pebble-grained surface that develops in the mechanical forming of sheet metals with coarse grains.

Oven, Drying
A furnace or oven for drying molds or cores.

Overaging
Aging a precipitation-hardening alloy under conditions of time and temperature greater than those required to obtain maximum strength or hardness.

Overheated
A term applied when, after exposure to an excessively high temperature, a metal develops an undesirable coarse grain structure, but is not necessarily damaged permanently. Unlike burned structure, the structure produced by overheating can be corrected by suitable heat treatment, by mechanical work, or by a combination of the two.

Overstressing
Permanently deforming a metal by subjecting it to stresses that exceed the elastic limit.

Oxidation
Any reaction of an element with oxygen. In a narrow sense, oxidation means the taking on of oxygen by an element or compound, and on the basis of the electron theory, it is a process in which an element loses electrons.

Oxide
A compound of oxygen with another element.

Oxidizing Atmosphere
An atmosphere resulting from the combustion of fuels in an atmosphere where excess oxygen is present, and with no unburned fuel lost in the products of combustion.

Packing or Packing Material
Sand, gravel, mill scale or similar materials used to support castings packed in annealing pots to prevent possible warpage under high temperatures.

Padding
The process of adding metal to a cross section of a casting wall, usually extending from a riser, to ensure adequate feed to a localized area where a shrink would occur if the added metal were not present.

Parted Pattern
A pattern made in two or more parts.

Parting Line
A line on a pattern or casting corresponding to the separation between the cope and drag portions of a sand mold.

Passivity
The property of some metals to become abnormally inactive towards certain reagents.

Pattern
A form of wood, plastic, metal, or other material around which molding material is placed to make a mold.

Pattern Draft
The taper on vertical elements in a pattern which allows easy separation of pattern from compacted sand mixture.

Pattern Layout
Full-sized drawing of a pattern showing its arrangement and structure features.

Patternmaker
A craftsman engaged in production of foundry patterns from wood, plastic, or metals, such as aluminum, brass, etc.

Pearlite
A lamella aggregate of ferrite and carbide; the structure of pearlite can appear fine or coarse depending on processing.

Penetration, Metal
Condition where molten metal has penetrated into the sand, resulting in a mixture of metal and sand adhering to the casting.

Perlite
A highly siliceous volcanic rock which can be expended by heating into a porous mass of particles. Perlite can be used as an insulation in foundry sand mixtures. Not to be confused with Pearlite.

Permanent Mold
A metal mold of two or more parts; not an ingot mold. It is used repeatedly for the production of many castings of the same form.

Phase Diagram
A graphic representation of the equilibrium temperature and composition limits of phase fields reactions in an alloy system. In a binary system, temperature is usually the ordinate and composition the abscissa. Ternary and more complex systems require several two-dimensional diagrams to show the temperature - composition variables completely. In al...

Photomicrograph
A photograph of the grain structure of a metal as observed when optically magnified more than 10 diameters. The term micrograph may be used.

Physical Metallurgy
The science concerned with the physical and mechanical characteristics of metals and alloys.

Pitting
A form of wear characterized by the presence of surface cavities, the formation of which is attributed to processes such as fatigue, local adhesion, cavitation or corrosion.

Plane Strain
A stress condition in linear elastic fracture mechanics in which there is zero strain in a direction normal to both the axis of applied tensile stress, and the direction of crack growth. Under plane strain conditions, the plane of fracture instability is normal to the axis of the principal tensile stress.

Plastic Deformation
Permanent distortion of a material under the action of applied pressure.

Postheating
A process used immediately after welding whereby heat is applied to the weld zone, either for tempering, or for providing a controlled rate of cooling, in order to avoid a hard or brittle structure.

Pouring
Transfer of molten metal from furnace to ladle, ladle to ladle, or ladle into molds.

Pouring Cup
The flared section of the top of the downsprue. It can be shaped by hand in the cope, or be a shaped part of the pattern used to form the downsprue; also may be baked core cup placed on the top of the cope, over the downsprue.

Precipitation Hardening
A process of hardening an alloy in which a constituent precipitates from a supersaturated solid solution.

Precipition Heat Treatment
Any of the various aging treatments conducted at elevated temperatures to improve certain mechanical properties through precipitation from solid solution.

Preheating
A general term for heating material, as a die in die casting, as a preliminary to operation, to reduce thermal shock and prevent adherence of molten metal.

Primary Choke
(Choke) That part of the gating system which most restricts or regulates the flow of metal into the mold cavity.

Process Capability
The amount of variation in the output of a controlled manufacturing process, the range defined by plus or minus three standard deviations.

Proeutectoid
The constituent that separates out of a solid solution before the formation of eutectoid.

psi
Pounds per square inch.

Quenching
Rapid cooling or hardening; normally achieved by immersion of the object to be hardened in water, oil, or solutions of salt or organic compounds in water.

Radiant Heat
Heat communicated by radiation and transmitted by electromagnetic waves.

Radioactive Isotopes
Varieties of an element possessing the same chemical characteristics, but emitting detectable radiations, by means of which they can be identified and traced.

Radioactive Material
Any compound or element which may emit any or all of the following; alpha and beta particles, electrons, photons neutrons and gamma, and all other emissions which produce ionization directly or indirectly.

Ramming
Packing sand in a mold by raising and dropping the sand pattern flask on a table. Jolt squeezers, jarring machines, and jolt rammers are machines using this principle.

Range
The difference between the highest and lowest values of a measurable attribute of the output of a process.

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

Recrystallization Temperature
The lowest temperature at which the distorted grain structure of a cold-worked metal is replaced by a new, strain-free grain structure, during prolonged annealing. Time, purity of the metal, and prior deformation are important factors.

Reduction
The removal of oxygen or addition of hydrogen.

Refractory
1) Heat-resistant material, usually non-metallic, used for furnace linings etc., 2) the quality of resisting heat.

Repair Welding
Any welding carried out after delivery to the end user, e.g., after the casting has been in service.

Revert
Recycled sprues, gates, risers, defective castings and machine chips.

Rigging
Gates, risers, loose pieces, etc., needed on the pattern to produce a sound casting.

Riser
Reservoir of molten metal from which casting feeds as it shrinks during solidification.

Riser Height
The distance from the top of the riser when liquid rises to the top of the riser neck. Riser height when solid is usually several inches less than when liquid because of contraction and loss of feed metal to the casting.

Riser-Gating
Practice of running metal for the casting through the riser to help directional solidification.

Riser, Blind
A riser that does not break through the top of the cope, and is entirely surrounded by sand; opened to the atmosphere by means of a firecracker core.

Riser, Open
Conventional form of riser usually located at the heaviest section of the casting, and extending through the entire height of the cope.

Runner
A channel through which molten metal or slag is passed from one receptacle to another; in a mold, the portion of the gate assembly that connects the downgate, or sprue, with the casting ingate or riser. The term also applies to similar portions of master patterns, pattern dies, patterns, investment molds, and finished castings.

Runner Extension
In a mold, that part of a runner which extends beyond the farthest ingate as a blind end. It acts as a dirt trap since the first rush of metal along the runner will pick up any loose particles of sand or dirt, and carry them into the extension (not into the mold cavity).

Runner Riser
A conventional runner, usually in the horizontal plane, which permits flow of molten metal to the ingate, and is large enough to act as a reservoir to feed the casting.

Runout
A casting defect caused by incomplete filling of the mold due to molten metal draining or leaking out of some part of the mold cavity during pouring; escape of molten metal from a furnace, mold, or melting crucible.

Sag
A decrease in metal section in casting due to sagging of the cope or core.

Sand
In metalcasting, a loose, granular material high in SiO2, resulting from the disintegration of rock. The name sand refers to the size of grain, and not to mineral composition. Diameter of the individual grains can vary from approximately 6, to 270 mesh. Most foundry sands are made up principally of the mineral quartz (silica). Reason for this is th...

Sand Casting
Metal castings produced in sand molds.

Sand Control
Procedure whereby various properties of foundry sand, such as fineness, permeability, green strength, moisture content, etc., are adjusted to obtain castings free from blows, scabs, veins, and similar defects.

Sand Porosity
Volume of the pore spaces or folds in a sand. (Not synonymous with permeability).

Sand Reclamation
Processing of used foundry sand grains by thermal, attraction or hydraulic methods, so that it may be used in place of new sand without substantially changing current foundry sand practice.

Scaling
(Scale) Surface oxidation, partially adherent layers of corrosion products, left on metals by heating or casting in air or in other oxidizing atmospheres.

Scanning Electron Microscope
(SEM) An instrument used for obtaining microstructure images, using an electron beam. The micrographs obtained give depth perception of the metal being observed.

Scrap
(Metal) Metal to be remelted; includes scrapped machinery fabricated items such as rail or structural steel and rejected castings.

Seam
A surface defect on a casting related to but of lesser degree than a Cold Shut; a ridge on the surface of a casting caused by a crack in the mold face.

Segregation
A concentration of alloying elements at specific regions, usually as a result of the primary crystallization of one phase with the subsequent concentration of other elements in the remaining liquid.

SFSA
Steel Founders' Society

Shakeout
1) The operation of removing castings from the mold 2) a mechanical unit for separating the molding materials from the solidified metal casting.

Shear
A type of deformation in which parallel planes in the metal crystals slide so as to retain their parallel relation.

Shear Modulus
(G) In a torsion test, the ratio of the unit shear stress to the displacement caused by its per unit length in the elastic range. Units are Pa or psi.

Shear Strain
Elastic displacement produced by pure shear loading.

Shear Strength
Maximum shear stress a material is capable of withstanding without failure.

Shear Stress
Load per unit area parallel to the plane of contact.

Shell Molding
A process for forming a mold from resin-bonded sand mixtures brought in contact with pre-heated (300-500

Shift
A casting defect caused by mismatch of cope and drag, or of cores and mold.

Shot blasting
(Shot Peening) Casting cleaning process employing a metal abrasive (grit or shot) propelled by centrifugal or air force.

Shrink
The difference in volume between liquid metal and solid metal, or the void (shrink hole) left in a casting because of it.

Shrinkage
1) Liquid, contraction in volume as metal cools to solidification, 2) solidification, contraction in volume when the metal passes from the liquid to the sold at the freezing point (may expend over a range), 3) solid, the contraction on cooling from freezing point to normal temperature, 4) the decrease in dimension in clays occurring when drying at ...

Shrinkage Cracks
Cracks that form in metal as result of the pulling apart of grains by contraction before complete solidification.

Silica Sand
Sand with a minimum silica content of 95% used for forming casting molds.

Simultaneous Engineering
Refers to the process where user/designer and producer interact to reduce lead time and improve the efficiency of a part. This process is faster and more efficient than the traditional sequential process of design and manufacture.

Skimming
Removing or hold back dirt or slag from the surface of the molten metal before or during pouring.