Glossary

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.

Inclusions

Particles of impurities (usually oxides, sulfides, silicates, aluminates) that are formed during solidification. Inclusions are generally described as nonmetallic. The test procedure for measuring the micro cleanliness or severity of inclusion content is ASTME-45.

Induction Hardening

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

Ingot/ingot cast

Historically, after steel had been melted and refined, it was cast into ingot molds. These are vertical, very thick walled boxes of gray iron with a cavity in the middle the size of the desired ingot. Steel is poured into this cavity and allowed to solidify. The steel contracts in volume as it solidifies and pulls away from the mold to form the ingot. Once the ingot is removed from the mold, it is to be hot-rolled into a slab for further processing.

Inhibitor

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

Inter-granular corrosion

Localized attack at grain boundaries, with relatively little corrosion of the grains. As corrosion proceeds, the grains fall out and the metal or alloy disintegrates. Austenitic stainless steels are susceptible to inter-granular corrosion if heated in the 800°F to 1500°F range which causes “sensitization” or Chromium depletion adjacent to the grain boundaries.

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 progressive 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.

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.

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.