Aluminium killed steel & deoxidation of steel.

Definition: Steel deoxidized with aluminum in order to reduce the oxygen content to a minimum so that no reaction occurs between carbon and oxygen during solidification.

Deoxidized steel is steel that has some or all of the oxygen removed from the melt during the steelmaking process. Liquid steels contain dissolved oxygen after their conversion from molten iron, but the solubility of oxygen in steel decreases with temperature. As steel cools, excess oxygen can cause blowholes or precipitate FeO. Therefore, several strategies have been developed for deoxidation. This may be accomplished by adding metallic deoxidizing agents to the melt either before or after it is tapped, or by vacuum treatment, in which carbon dissolved in the steel is the deoxidizer.

Alloy Steel.

Steel is considered to be an alloy steel when either (1) the maximum of the range given for the content of alloying elements exceeds one or more of the following percentages: manganese 1.65, silicon 0.60, copper 0.60; or (2) a definite range or definite minimum quantity of those elements considered alloys is specified. For example, chromium, molybdenum and nickel.
Annealing: Heating to holding at a suitable temperature, followed by cooling at a suitable rate, for such purposes as:
inducing softness
improving machinability
improving cold working properties
obtaining a desired structure
removing stresses
When applicable, the more specific terms, full annealing, isothermal annealing or sub-critical annealing could be used:-
Full annealing. Heating to and holding at some temperature above the transformation range, followed by cooling slowly by the transformation range.
Isothermal Annealing. Heating to and holding at some temperature above the transformation range, then cooling to and holding at a suitable temperature until the austenite to pearlite transformation is complete, and finally cooling freely.
Sub-Critical Annealing. Heating to and holding at some temperature below the transformation range, followed by cooling at a suitable rate.