ACID BRITTLENESS. Brittleness of steel resulting from use of acid solutions to remove scale, clean and electroplate.
Brittleness is caused by the absorption of hydrogen into the metal from the acid solutions (also called hydrogen
AGING. (a) Generally any change in properties with time which occurs at relatively low temperature (room or elevated)
after a final heat treatment of a cold marking operation. Aging is a process in which the trend is toward restoration of real
equilibrium and away from an unstable condition induced by a prior operation.
(b) Specifically the formation of a new phase by cooling a solid solution to super saturated state and allowing the super
saturated solution to partially return to equilibrium by the formation of a less concentrated solid solution and a new phase.
AIR HARDENING. An alloy which does not require quenching from a high temperature to harden. Hardening of the
material occurs simply by cooling in air from above critical temperature. The term refers only to the ability of the material
to harden in air and does not imply any definite analysis or composition.
AIR COOLING/QUENCHING. Cooling from an elevated temperature in air, still or forced.
ALLOY. A mixture with metallic properties composed of two or more elements of which at least one is a metal.
However, a metal is not designated an "alloy" based on elements incidental to its manufacture. For example; iron,
carbon, manganese, silicon, phosphorus, sulphur, oxygen, nitrogen and hydrogen are incidental to the manufacture of
plain carbon steel. It does not become an "alloy steel" until the elements are increased beyond regular composition or
until other elements (metal) are added in significant amounts for a specific purpose.
ALLOY ELEMENTS. Chemical elements comprising an alloy, usually limited to the metallic elements added to modify
the basic metal properties.
ANNEALING. Generally it is a controlled heating procedure which leads to maximum softness, ductility and formability.
The annealing procedure is utilized for the following:
After ductility, toughness, electrical, magnetic, or physical properties.
Refine crystalline structure.
Produce a definite micro-structure.
ANNEALING FULL. A controlled heating procedure which leads to maximum softness, ductility and formability.
ANNEALING, ISOTHERMAL. Heating of a ferritic steel to a austenite structure (fully or partial) followed by cooling to
and holding at a temperature that causes transformation of the austenite to a relatively soft ferrite and carbide structure.
ANODIC OXIDE COATING. A thin film of aluminum oxide formed on the surface of aluminum and aluminum alloy parts
by electro-chemical means.
AS CAST. Condition of a casting as it leaves the mold with no heat treatment.
AUSTENITE. A solid solution of iron carbide in gamma iron. It forms when the metal solidifies and remains a solution
until it cools to about 7320C (1350°F).
Theoretically the solution would remain if the iron or steel were cooled instantaneously from a bright red heat to
atmospheric temperature, but in practice, this degree of rapidity is impracticable, and only a portion of the austenite is
preserved by rapid cooling. Addition of certain alloying elements such as nickel and manganese preserves austenite
below 1C (0F).
BARK. The decarburized skin or layer just beneath the scale found after heating steel in an oxidizing atmosphere.
BASE METAL. The metal to which other elements are added to form an alloy possessing specific properties.
BESSEMER PROCESS. A process for making steel by blowing air through molten pig iron contained in a suitable
vessel. The process is one of rapid oxidation primarily of silicon and carbon.