Classes of steel:

•    Crucible steel: Describes a number of different techniques for making steel in a crucible. Its manufacture is essentially a refining process which is dependent on preexisting furnace products

•    Carbon steel: Composed of iron and ≤2.1% carbon, accounts for 90% of steel production. High strength low alloy steel has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase.

•    Spring steel: A low or no alloy, medium carbon steel or high carbon steel with very high strength. Objects made of spring steel return to their original shape despite significant bending or twisting. Used a lot in cars with their key component being silicon.

•    Alloy steel: Contains non-carbon elements and alloyed with a variety of elements in total amounts of between 1.0% and 50% by weight to improve its mechanical properties.

•    Maraging steel: Alloyed with nickel and other elements, but unlike most steel contains almost no carbon at all. This creates a very strong but still malleable metal.

•    Stainless steel: Contains minimum of 11% chromium often combined with nickel, to resist corrosion.
•    Weathering steel: Such as cor-ten which is weathered by acquiring a stable, rusted surface and so can be used un-painted.

•    Tool steel: Alloyed with large amounts of tungsten and cobalt or other elements to maximize  hardening, improved temperature resistance.

•    An alloy; consists mostly of iron and has carbon content of between 0.2% and 2.1%

•    Carbon is the most common alloying material and hardens the iron in the steel. Manganese, chromium, vanadium and tungsten can be used also

•    Varying the amount of alloying elements and the form of their presence in the steel controls qualities such as the hardness, ductility, and tensile strength of the resulting steel.

•    Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

•    Two distinguishing factors from wrought and cast iron are steel's increased rust resistance and better weldability.

•    Three most common types of heat treatment: annealing, quenching and tempering. Quenching and tempering results in a more ductile and fracture-resistant metal.