Steel is an alloy consisting of iron and carbon. The chemical and physics properties of steel are dependent on the chemical composition of the steel itself.
Standard steels can be classified into three major groups: carbon, alloy and stainless steels. Each of these groups has similar chemical and physical properties with variations based on the elements contained within the steel. Tool steels have additional carbon that makes them hard and wear resistant.
The alloy elements involved do not exceed these limits: 1 percent carbon; 0.6 percent copper; 1.65 percent manganese; 0.4 percent phosphorus; 0.6 percent silicon; and 0.05 percent sulfur. (See Reference 1) These steels have similar properties to iron. The more carbon included, the harder and stronger the metal but the more difficult to weld and less ability to deform without cracking.
These steels contain alloy elements of amounts higher than the carbon steels including steels containing elements not found in carbon steels: nickel, chromium, cobalt and more. Compared to carbon steels, these steels have greater toughness, strength, wear resistance and hardness but they typically require some sort of heat treatment to achieve them.
Stainless steels contain at least 10 percent chromium regardless of other elements involved. There are three grades of stainless steels: austenitic (18 percent chromium and 8 percent nickel); ferritic (very little nickel and either 17 percent chromium or 12 percent chromium with aluminum or titanium); and martensitic (12 percent chromium and no nickel). (See Reference 1) Stainless steel is typically corrosion-resistant and does not rust as easily as ordinary steel.
Naturally, tool steel is a variety of steels that are made into tools. It is generally heat-treated and has a particular hardness, ability to hold a sharp edge, resistance to deformation and a resistance to abrasion.