Carbon structural steel:
Carbon steel for special purposes, such as bridge steel, marine steel, etc., basically adopts the expression of carbon structural steel, but the letter indicating the purpose is added at the end of steel grade.
2. High quality carbon structural steel:
The two digits at the beginning of the steel grade indicate the carbon content of the steel, expressed in tens of thousands of the average carbon content. For example, for steel with an average carbon content of 0.45%, the steel number is "45", which is not a sequence number, so it can not be read as 45 steel. High quality carbon structural steel with high manganese content should be marked with manganese element, such as 50Mn.
Rimming steel, semi killed steel and high quality carbon structural steel for special purpose shall be specially marked at the end of steel grade, for example, the steel grade of semi killed steel with average carbon content of 0.1% is 10B.
High quality carbon structural steel is supplied according to chemical composition and mechanical properties. The content of sulfur, phosphorus and non-metallic inclusions in the steel is less, which indicates that the quality and the uniformity of structure are good. It is often used in various important mechanical structure parts which need heat treatment.