What are the differences between Q345B and Q345R steel?

Q345B: It is a low-carbon alloy steel (c <0.2%), with good overall performance, low temperature performance, cold stamping performance, welding performance and machinability.
Q345R: It is a special plate for pressure vessels with a yield strength of 345MPa. Q345R pressure vessel steel has good comprehensive mechanical properties and technological performance. In addition to the tensile strength and elongation requirements higher than Q345 (16Mn) steel, it is also required to ensure impact toughness.
 

Difference in producing standard

Q345B: The external execution standard is: gb709, and the internal execution standard is: gb / t1591-94. Due to the implementation of the standard, such steel plates are allowed to be delivered with negative tolerances. The latest implementation standard is GB / T1591-2018.
Q345R: 16Mng and 16MnR, 19Mng merged into Q345R. It is ordinary low alloy steel, and is commonly used in boiler and pressure vessels. The delivery status is divided into hot rolled or normalized, which belongs to low alloy steel. The performance is similar to that of Q345 (16Mn), the tensile strength is between 510-640, the elongation is greater than 21%, and the zero-degree V-shaped impact energy is greater than 34J. Q345R process reference standard GB713-2014.
 

Difference in application

Q345B low alloy steel is used in bridges, vehicles, ships, buildings, pressure vessels, etc.
Q345R steel is currently the most widely used and most used steel plate for pressure vessels in China.
 

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