Q345B steel VS Q345R steel

Difference in the mechanical properties
1. Q345B material: It is a low carbon alloy steel (c <0.2%), with good comprehensive performance, good low temperature performance, cold stamping performance, welding performance and machinability.
2. Q345R material: It is a special plate for pressure vessels with a yield strength of 345MPa. It has good comprehensive mechanical properties and process performance. In addition to the requirements for tensile strength and elongation to be improved compared to Q345 (16Mn) steel, impact toughness is also required.

The difference in production process
1. Q345B steel: The external execution standard is: gb709, and the internal execution standard is: gb / t1591-94. Due to the implementation of the standard, this steel plate allows for negative tolerance delivery. The latest implementation standard is GB / T1591-2018.
2. Q345R steel: 16Mng, 16MnR, and 19Mng are combined into Q345R. It is ordinary low alloy steel, and it is commonly used in boilers and pressure vessels. The delivery status is: hot rolled or normalized, which is a 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.

The difference in application
1. Q345B steel plates are used in bridges, vehicles, ships, buildings, pressure vessels, etc.
2. Q345R steel: At present, it is the most widely used and most used steel plate for pressure vessels in China.