In addition to carbon, carbon steel generally contains bai small amount of silicon, manganese, sulfur, phosphorus, but not iron. Du carbon steel is just iron. "Iron" is the term used to distinguish copper, aluminium and lead from the rest of the zhi species. In fact, iron is steel, and in the past it was conventionally divided into "cast iron" and "wrought iron"; "cast iron" is called iron, and "wrought iron" is called steel. "Carbon steel" is a kind of classification of steel, which can be divided into "carbon steel" and "alloy steel".

For example, all kinds of steel plates, rebar, profiles, common, are "carbon steel". For example, various grades of saw blades, drills, cutting tools, stainless steel, black steel is a "alloy steel".