1. Q345 steel is general and does not specify the quality grade; q345b steel is clear and the quality grade is B.
2. Q345 steel does not require inspection of impact performance; Q345B steel requires qualified impact performance at room temperature (20 degrees room temperature impact).
3. Q345 steel does not specify the carbon content of the steel; the carbon content of Q345B steel is 0.20%.
4. Q345 steel is a grade of carbon structural steel. Q means the yield strength; 345 means the value of the yield point, and the unit is MPa.
5. Q345 steel means carbon structural steel with a yield point (σs) of 345MPa. The following letters indicate the quality grade, and there are five grades of A, B, C, D, and E.
