Glossary of Steel Terms

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Idiomorph
A particle of a phase the has a regular external shape.

Immersed Scanning
In ultrasonics, a planned, systematic movement of the beam relative to the object being inspected, the search unit being coupled to this object through a column of liquid. In most cases the object and the search unit are submerged in water.

Impact Energy (Impact Value)
The amount of energy required to ffracture a material, usually measured by means of an Izod or Charpy test. The type of speciment and testing conditions affect the values and therfore should be specified.

Impact Test
Test designed to determine the resistance of metal to breakage by impact, usually by concentrating the applied stress to a notched specimen.

Impact Test
A test to determine the behavior of materials when subjected to high rates of loading,usually in bending, tension, or torsion. The quantity measured is the energy absorbed in breaking the specimen by a single blow, as in the Charpy or Izod.

Impact Test
A test for determining the behaviour of materials when subjected to high rates of loading under conditions designed to promote fracture, usually in bending, tension or torsion. The quantity measured is the energy absorbed when the specimen is broken by a single blow.

Impurities
Elements or compounds whose presence in a material is undesired.

Inclusion
A nonmetallic material in a solid metallic matrix.

Inclusions
Particles of impurities (usually oxides, sulfides, silicates, etc.) that are held mechanically or are formed during the solidification or by subsequent reaction within the solid metal.

Inclusions
Non,etallic materials in a solid metallic matrix.

Indentation Hardness
The resistance of a meterial to indentation. This is the usual type osf hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load.

Induction Hardening
Quench hardening in which the heat is generated by electrical induction.

Induction Hardening
A process of hardening a ferrous alloy by heating it above the transformation range by means of electrical induction, and then cooling as required.

Induction Heating
A process of heating by electrical induction.

Inert-Gas Shielded-Arc Welding
Arc welding in an inert gas such as argon or helium.

Ingot
A casting suitable for hot working or remelting.

Ingot
A casting for subsequent rolling or forging.

Ingot Iron
Commercially pure iron.

Ingot Iron
Commercially pure open-hearth iron.

Inhibitor
A substance which retards some specific chemical reaction. Pickling inhibitors retard the sissolution of metal without hindering the removal of scale from steel.

Intercrystalline
Between crystals, or between grains. Same as intergranular.

Interleaving
The placing of a sheet of paper between two adjacent layers of metal to facilitate handling and shearing of rectangular sheets, or to prevent sticking or scratching.

Intermediate Annealing
An annealing treatment given to wrought metals following cold work hardening for the purpose of softening prior to further cold working.

Internal Oxidation
Formation of oxides beneath the surface of a metal.

Interrupted Aging
The aging of an alloy at two or more temperatures by steps, and cooling to room termperature after each step. Compare with progressuve aging.

Interrupted Quenching
Quenching in which the metal object being quenched is removed from the quenching medium while the object is at a temperature substantially higher than that of the quenching medium.

Interstitial Solid Solution
A solid solution in which the solute atoms occupy (interstitial) positions between the atoms in the structure of the solvent.

Intracrystalline
Within or across crystals or grains. Same as transcrystalline and transgranular.

Investment Casting
(1) Casting metal into a mold produced by surrounding (investing) an expendable pattern with a refractory slurry that sets at room temperature after which the wax, plastic, or frozed mercury pattern is removed through the use of heat. Also called precision casting, or lost-wax process. (2) A casting made by the process.

Irom
(Chemical symbol Fe.) Element No. 26 of the periodic system; Atomic weight 55.85. A magnetic silver white metal of high tensile strength, ductile and malleable. Melting point of pure iron about 2795 (degrees) F. Chemically iron is chiefly base forming. The principal forms of commercial iron are steel, cast iron and wrought iron.

Iron
An element that has an average atomic number of 55.85 and that always, in engineering practice, contains small but significant amounts of carbon. Thus iron-carbon alloys containing less than about 0.1% C may be referred to as irons. Alloys with higher carbon contents are always termed steels.

Ironing
Thinning the walls of deep drawn articles by reducing the clearance between punch and die.

Isothermal Annealing
A process in which a ferrous alloy is heated to produce a structure partly or wholly austenitic, and is then cooled to and held at a temperaure that causes transformation of the austenite to a relatively soft ferrite-carbide aggregate.

Isothermal Transformation
A change in phase at any constant temperature.

Isothermal Transformation (IT) Diagram
A diagram that shows the isothermal time required for transformation of austenite to commence and to finish as a function of temperature. Same as time-temperature-transformation (TTT) diagram or S-curve.

Izod Test
A pendulum type of single-blow impact test in which the specimen, usually notched, is fixed at one end and broken by a falling pendulum. The energy absorbed, as measured by the subsequent rise of the pendulum, is a measure of impact strength or notch toughness.

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