Carbon steel is an iron-carbon alloy with a carbon content of 0.0218%-2.11%. It generally contains small amounts of silicon, manganese, sulfur, and phosphorus. The higher the carbon content in carbon steel, the greater the hardness and strength, but the lower the plasticity. There are different ways to classify carbon steel. According to the amount of carbon content of carbon steel, it an be divided into three categories: low carbon steel, medium carbon steel and high carbon steel.