Carbon steel is a metal alloy that is formed by combining iron and carbon. Steel usually is considered to be carbon steel when the proportions of other trace elements in it do not exceed constant percentages. The maximum percentages typically are 1.65 percent for manganese and 0.6 percent for copper and silicon. The copper percentage must be at least 0.4 percent. Steel that also contains higher or specified quantities of other elements, such as nickel, chromium or vanadium, is called alloy steel.
Manufacturers add carbon to iron to solidify the structures in it and strengthen the resulting metal. It's one of the most cost-effective alloying materials, and altering the amount of carbon changes the properties of the steel. Carbon steels can be classified as low-carbon steels, medium-carbon steels, high-carbon steels and ultrahigh-carbon steels.
Steels with very low amounts of carbon, about 0.05 percent to 0.3 percent, are called low-carbon steels and are similar to iron. They are very ductile, which makes them hard to machine. They are used to make flat-rolled sheets or steel strips that are utilized to create ships, wire products, car bodies, domestic appliances, tin plates and more. Low-carbon steels are cheaper, but they cannot be altered by heat treatment, which is why they generally are used for fabrication and paneling purposes.