What are the differences between Q345B and Q345R steel plate

What are the differences between Q345B and Q345R steel plate?
First of all, in terms of material type, Q345B is a low-carbon alloy steel (C<0.2%) with good comprehensive performance, low temperature performance, cold stamping performance, welding performance and machinability. Q345R steel plate is a special plate for pressure vessels with yield strength of 345MPa. It has good comprehensive mechanical and technological properties. In addition to the requirements for tensile strength and elongation higher than Q345 (16Mn) steel, it is also required to ensure the impact toughness.

The executive standards of Q345B and Q345R steel plates are different:
The executive standard of Q345B is GB/T1591. Q345R is a commonly used steel for boiler and pressure vessel. The delivery status includes hot rolling or normalizing, which belongs to low alloy steel. The properties are similar to those of Q345 (16Mn). The tensile strength is 510-640, the elongation is greater than 21%, and the zero degree V-shaped impact energy is greater than 34J. The technical standard of Q345R steel plate is GB/T713.

The specific uses of Q345B and Q345R steel plates are different:
Q345B: It is applied to bridges, vehicles, ships, buildings, pressure vessels, etc.
Q345R: It is one of the most widely used steel plates for pressure vessels.