High-quality carbon structural steel: In addition to carbon (C) element and a certain amount of silicon (Si) (generally not exceeding 0.40%) and manganese (Mn) (generally not exceeding 0.80%) for deoxidation, the steel can be as high as 1.20% Alloying elements, free of other alloying elements (except residual elements). This steel must guarantee chemical composition and mechanical properties. The content of sulfur (S) and phosphorus (P) impurity elements is generally controlled below 0.035%. If it is controlled below 0.030%, it is called high-grade high-quality steel, and "A" should be added after the grade, such as 20A; if P is controlled below 0.025%, and S is controlled below 0.020%, it is called super high-quality steel. "E" should be added after the grade to show the distinction. For other residual alloying elements brought into steel from raw materials, such as chromium (Cr), nickel (Ni), copper (Cu), etc., the content is generally controlled at Cr≤0.25%, Ni≤0.30%, Cu≤0.25%. Some grades have manganese (Mn) content up to 1.40%, known as manganese steel.

High-quality carbon structural steel relies on adjusting the carbon (C) content to improve the mechanical properties of the steel. Therefore, according to the level of carbon content, this steel can be divided into:

Low carbon steel - the carbon content is generally less than 0.25%, such as 10, 20 steel, etc.;

Medium carbon steel - the carbon content is generally between 0.25-0.60%, such as 35, 45 steel, etc.;

High carbon steel - the carbon content is generally greater than 0.60%. This type of steel is generally not used in the manufacture of steel pipes.

In fact, there is no clear boundary between their carbon content.

This type of steel is produced in large quantities and has a wide range of uses. Generally rolled (forged) into round, square, flat and other profiles, plates and seamless steel pipes. It is mainly used in the manufacture of general structural and mechanical structural parts, as well as arc