What is the difference of chemical composition between Q345D seamless pipe and Q690D steel?
The chemical composition of Q345D seamless pipe is as follows: C ≤ 0.18, Si ≤ 0.50, Mn ≤ 1.70, P ≤ 0.030, S ≤ 0.025, Nb ≤ 0.07, V ≤ 0.15, Ti ≤ 0.20, Cr ≤ 0.30, Ni ≤ 0.50, Cu ≤ 0.30, N ≤ 0.012, Mo ≤ 0.10, Al ≥ 0.015.

Q345D seamless pipe has good comprehensive mechanical properties, low-temperature impact toughness, cold stamping, machinability and weldability.

Chemical composition of Q690D steel:
C≤0.18, Si≤0.60, Mn≤2.0, P≤0.030, S≤0.025, Nb≤0.11, V≤0.12, Ti≤0.20, Cr≤1.00, Ni≤0.80, Cu≤0.80, N≤0.015, Mo≤0.30, B≤0.004, Al≤0.015.

Q690D steel has high strength, good plasticity and toughness, good weldability, and good cold and hot properties. Q690D steel is mainly used to manufacture various large engineering structural components and construction machinery. Because of its high strength and good toughness, it can reduce the self weight of components and meet the requirements of large-scale and lightweight engineering components and equipment under the condition of ensuring strength, stiffness and reliability.