Difference between Q345A, Q345B and Q345C welded steel pipe

In GB/T13793-2008 standard, Q345A, Q345B, Q345C welded steel pipe there are obvious differences.

First, the difference in chemical composition
These three types of welded steel pipe are low-alloy high-strength structural steel. Among them, Q345A on sulfur, phosphorus and other impurity elements of relatively loose control. Q345B on impurity elements of more stringent control. Q345C in the most stringent control of impurity elements, and may contain some micro-alloying elements to further optimize its performance.

Second, different performance characteristics
Strength: the yield strength of the three are not less than 345MPa, but in practical applications will be slightly different. Q345B and Q345C strength stability is relatively better, to maintain more stable mechanical properties in long-term use.
Toughness: Q345C has the best toughness and is less likely to fracture when subjected to impact loads, Q345B has the second best toughness and Q345A is relatively weak. Especially in the low temperature environment, Q345C welded steel pipe is more reliable.
Welding performance: Although all three have good welding performance, but because of the different chemical composition, the choice of welding process parameters will make a difference. The appropriate welding process can ensure the quality and strength of welded joints.

Third, the applicable scene is different
Q345A welded steel pipe is suitable for general engineering structures, relatively low performance requirements of the occasion, such as some common building support structures, etc. Q345B welded steel pipe can be used for more important engineering structures, in construction, machinery manufacturing and other fields play an important role. Q345C welded steel pipe is suitable for the environment is more harsh, the performance requirements of higher occasions, such as cold areas of large-scale engineering structures and bear dynamic loads of large equipment to ensure the safety and reliability of the project.