What is the difference between Q245R and Q345R?

Q245R and Q345R are both low alloy steel grades used for pressure vessel applications in China. While they have some similarities, there are differences in terms of composition, mechanical properties, and application. Here's a comparison between Q245R and Q345R:

Chemical Composition:

Q245R: The chemical composition of Q245R typically includes carbon (C) content up to 0.20%, manganese (Mn) content ranging from 0.40-0.60%, silicon (Si) content up to 0.35%, phosphorus (P) content ≤0.025%, sulfur (S) content ≤0.015%, and trace amounts of other elements.

Q345R: The chemical composition of Q345R typically includes carbon (C) content up to 0.20%, manganese (Mn) content ranging from 0.50-1.60%, silicon (Si) content up to 0.55%, phosphorus (P) content ≤0.025%, sulfur (S) content ≤0.015%, and trace amounts of other elements.

Mechanical Properties:

Q245R: The minimum yield strength of Q245R is 245 MPa (35,500 psi), and the minimum tensile strength is 400-520 MPa (58,000-75,400 psi). The elongation at break is typically around 22%.

Q345R: The minimum yield strength of Q345R is 345 MPa (50,000 psi), and the minimum tensile strength is 510-640 MPa (74,100-92,800 psi). The elongation at break is typically around 21%.

Application:

Q245R: Q245R is primarily used for the fabrication of pressure vessels and boilers that operate at moderate temperatures. It is suitable for applications involving mediums such as liquefied petroleum gas (LPG), natural gas, and crude oil.

Q345R: Q345R is used for the production of pressure vessels and boilers that operate at high temperatures. It is suitable for applications involving mediums with higher operating temperatures, such as hydrogen, ammonia, and methanol.

It's important to consider these differences in composition, mechanical properties, and application when choosing between Q245R and Q345R for a specific pressure vessel or boiler application. It is advisable to consult the relevant standards and specifications, such as GB 713 and GB/T 713, for detailed information and requirements related to these steel grades.