Acid Lining - The inner bottom and lining of a melting furnace composed of materials having an acid reaction if in contact with a molten slag (sand, siliceous rock, or silica bricks).

Acid Steel - Steel melted in a furnace having an acid bottom and lining and under a slag with acid reaction. The term has no reference to the acidity of the steel.

Aging - The spontaneous change in the properties of a metal usually associated with the recovery of metal from an unstable condition produced by quenching (quench aging) or by cold working (strain aging). Age hardening and aging are terms commonly used synonymously. See also "Precipitation Hardening".

Aircraft Quality Steel - Steel which has been tested during manufacture and as approved suitable for production of aircraft parts. Special precautions are taken to assure the best possible quality in making steel to pass aircraft quality inspection. The severity of steel inspection varies with the type of application and the amount of stress to be imposed upon the part. Final interpretations are dependent upon the application for which the steel is specified.

Alloy – A material with metallic properties composed of two or more elements of which at least one is a metal.

Annealing - Annealing generally refers to the heating and controlled cooling of solid material for the purpose of removing stresses, making it softer, refining its structure or changing its ductility, toughness or other properties. Specific heat treatments covered by the term annealing include black annealing, blue annealing, box annealing, bright annealing, full annealing, graphitizing, malleabilizing and process annealing.

As Rolled - When bars are hot rolled and allowed to cool in the air, they are said to be in the "as rolled" or natural condition.

Austenite - A phase in steels which consists of the gamma form of iron with carbon in solid solution. Austenite is tough, non-magnetic and tends to work-harden rapidly when cold is worked in those steels which are austenitic at ordinary temperatures.

Austenitic Steel -Steel which has a stable austenitic structure at normal (room) temperatures.