The selection and quality of raw materials for construction of steel structure engineering is very important, which directly affects the quality of steel structure engineering. But for raw materials, users generally do not understand, today, we distinguish steel structure materials and structural steel types and specifications.

If you want to make a distinction between the types of steel, there can be several kinds of distinction, according to the use can be divided into: structural steel, tool steel and special steel; According to smelting methods, it can be divided into: Bessemer steel and open hearth steel; According to the deoxidation method can be divided into: boiling steel (F), semi-killed steel (B), killed steel (Z) and special killed steel (TZ); According to the forming method, it can be divided into: rolled steel (hot rolled, cold rolled), forged steel and cast steel; According to the chemical composition can be divided into: carbon steel and alloy steel. Carbon steel and alloy steel are generally used in steel structure construction.

Carbon structural steels are divided into five types: Q195, Q215, Q235, Q355 and Q275. The higher the yield strength, the higher the carbon content, strength and hardness, and the lower the plasticity. Among them, Q235 has good performance in use, processing and welding. It is a commonly used steel in steel structure engineering construction, and carbon structural steel is often used in steel structure engineering. Q235 and Q355 are commonly used in China.

Low alloy steels are those in which one or more small amounts of alloying elements are added during steelmaking and the total amount is less than 5%. Low alloy steels have higher strength because they contain alloying elements. Its grade is expressed in the same way as carbon structural steel grade. The commonly used low alloy steel is Q345, Q235, Q420 and so on, which is also one of the steels commonly used in steel structure engineering construction.

The above two kinds of steel are classified into grade A, B, C and D, with A to D indicating the quality from low to high. However, the quality grade of low-alloy steel is E more than that of carbon steel, with five grades. In the engineering drawings of steel structures, we will see the steel type, such as Q235B, which represents the distinction between carbon structural steels with strength, such as Q235, which represents the yield point (σ S) of 235 MPa. The steel number can be marked after it to indicate the quality grade.