What is the difference between Q245R steel and Q345R steel

Q245R steel and Q345R steel are two commonly used materials for pressure vessel steel plates.

Comparison of chemical composition between Q245R steel and Q345R steel

Q245R steel Q345R steel

C≤0.20 C:≤0.20

Si ≤0.35 Si:≤0.55

Mn 0.50-1.10 Mn:1.20--1.70

Cu ≤0.30 Cu:≤0.30

Ni ≤0.30 Ni:≤0.30

Cr ≤0.30 Cr:≤0.30

Mo ≤0.08 Mo:≤0.08

Nb ≤0.050 Nb:≤0.050

V ≤0.050 V:≤0.050

Ti ≤0.030 Ti:≤0.030

Alt ≥0.020 Alt:≥0.020

P≤0.025 P:≤0.025

S ≤0.0.010 S:≤0.010

Q245R steel and Q345R steel have the same restriction indexes of other elements except for the content of silicon and manganese. From the analysis of the weldability of steel, the weldability of steel has a great relationship with its chemical composition, and the carbon content has the greatest influence. Because the carbon content in the steel increases, the plasticity decreases, the hardening tendency increases, and cracks are prone to occur. Generally, steel contains a variety of alloying elements, and their effects are comprehensive. Therefore, carbon content is often used to estimate the weldability of steel. It is generally believed that the weldability of steel with Ceq < 0.45% is better.

Due to the increase in manganese content of Q345R steel, its carbon content is higher than that of Q245R steel. The notch sensitivity of Q345R steel is larger than that of Q245R, the fatigue strength is lower, and cracks are more likely to occur during welding. Therefore, in some cases, attention should be paid to the influence of medium factors on these two materials.

To sum up, when choosing Q245R steel and Q345R steel as pressure vessel materials, the influence of factors such as chemical composition, medium, mechanical properties, and price of steel should be fully considered, in order to reasonably select these two materials.

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