Classification of round steel

　　Round steel refers to solid strip steel with circular section. Its specification is expressed in diameter, in millimetres (mm). For example, "50mm" means round steel with a diameter of 50mm.

　　Round steel is divided into hot rolled, forged and cold drawn. The specification of hot rolled round steel is 5.5-250mm. Among them, 5.5-25mm small round steel is mostly supplied in bundles of straight bars, often used as reinforcement, bolts and various mechanical parts; Round steel larger than 25 mm is mainly used for manufacturing mechanical parts, seamless steel pipe blank, etc.

　　Classification by chemical composition

　　Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to its chemical composition (i.e. carbon content).

　　According to the quality of steel, it can be divided into ordinary carbon steel and high-quality carbon steel.

　　According to the different manganese content, it can be divided into two steel groups: ordinary manganese content (0.25~0.8%) and high manganese content (0.7~1.0% and 0.9~1.2%). Manganese can improve the hardenability of steel, strengthen ferrite, and improve the yield strength, tensile strength and wear resistance of steel. Generally, "Mn" is added after the grade of steel with high manganese content, such as 15Mn and 20Mn, to distinguish it from carbon steel with normal manganese content.

　　According to the purpose, it can be divided into carbon structural steel and carbon tool steel.

　　Carbon structural steel is divided into five grades according to the yield strength of steel:

　　Q195、Q215、Q235、Q255、Q275

　　Materials of round steel: Q195, Q235, 10 #, 20 #, 35 #, 45 #, Q215, Q345, 12Cr1Mov, 15CrMo, 304, 316, 20Cr, 40Cr, 20CrMo, 35CrMo, 42CrMo, 40CrNiMo, GCr15, 65Mn, 50Mn, 50Cr, 3Cr2W8V, 20CrMnTi, 5CrMnMo, etc.