Strength is an important aspect of steel and a number of alloys provide it, including copper and manganese. A copper alloy is beneficial to structurally used steels, while both manganese and copper work as agents for hardening the metal. Manganese is good for keeping the steel from wearing out easily. Nickel and chromium are still other alloying agents used as strengtheners.
A number of alloying agents make steel heavily resistant to corrosion. Chromium fights against such corrosion and also enables the metal to resist the effects of heat or abrasion. Copper also improves resistance to any corrosion, and nickel works well to fight against destructive materials, such as hydrochloric acid. Chromium is also a guard against threats such as nitric acid.
The machinability of steel is accomplished by using manganese and sulfur. A bonding between sulfur and manganese creates the manganese sulfide element that enables the pliability of the steel. The metal can then be more freely cut, used and adapted because of the sulfur addition.
Sulfur and manganese have further uses as well. During the refining process they both work as deoxidizers to ensure that any unwanted gas escapes containment in the steel. Aluminum is another alloying agent that accommodates this deoxidation and also refines the grain.