Classification Method of Q345B Seamless Steel Pipe

Q345B is used for steel pipe. Q represents the yield of the material, and the latter 345 refers to the yield value of the material.
Q345B steel pipe is 16Mn steel pipe, which is one of seamless steel pipe products.  16Mn is the material in steel. The name of steel in the past. Now called the law: Q345B. 16Mn is a series of low alloy steel. In this series, it is the most common material or steel plate grade. The carbon content of Q345B steel pipe is about 0.16%. It is proposed to use Mn alone because five elements (carbon C, silicon Si, manganese Mn, phosphorus P, sulfur s) have high manganese content, so it is recommended to use Mn alone. About 1.20-1.60%. Special treatment heat treatment: control rolling, normalizing and other Z-direction properties: z15, z25, Z35. Main features: good comprehensive performance, good low temperature performance, cold stamping performance, good welding performance and machinability.


Weight formula of Q345B steel pipe [(outer diameter wall thickness * wall thickness] * 0.02466 = kg / M (weight per meter)


Q345B steel pipe process:
Hot rolling (seamless steel tube extrusion): round tube blank → heating → piercing → three roller cross rolling, continuous rolling or extrusion → pipe transfer → sizing (or reducing diameter) → cooling → empty tube → straightening → hydraulic test (or defect detection) → marking → storage.
Cold drawing (rolling) seamless steel pipe: round tube blank → heating → piercing → head → annealing → pickling → oiling (copper plating) → multi pass cold drawing (cold rolling) → hollow tube → heat treatment → straightening → hydraulic test and inspection) → marking → storage.


Difference between Q235 and Q345:
Difference: the lower limit of yield strength of Q235 is 235mpa, while that of Q345 is 345mpa.
The alloy content of the two is different: Q235 is ordinary carbon steel, Q345 is low alloy steel.