What is the difference between Q420B and Q345 plate

What is the difference between Q420B and Q345 plate

What is the difference between Q420B and Q345 plate?

First of all, both Q420B plate and Q345 plate belong to low-alloy high-strength steel plate, and are used for building and engineering structures.

1. The chemical compositions of Q420B and Q345 plate are different:
Chemical composition of Q420B plate: C ≤ 0.20, Si ≤ 0.50, Mn ≤ 1.70, P ≤ 0.035, S ≤ 0.035, Nb ≤ 0.07, V ≤ 0.20, Ti ≤ 0.20, Cr ≤ 0.30, Ni ≤ 0.80, Cu ≤ 0.30, N ≤ 0.015, Mo ≤ 0.20.
Chemical composition of Q345 plate: C ≤ 0.18-0.20, Si ≤ 0.50, Mn ≤ 1.70, P ≤ 0.035, s ≤ 0.035, Nb ≤ 0.07, V ≤ 0.15, Ti ≤ 0.20, Cr ≤ 0.30, Ni ≤ 0.50, Cu ≤ 0.30, N ≤ 0.012, Mo ≤ 0.10.

2. The mechanical properties of Q420B and Q345 plate are different:
The mechanical properties of Q345 plate are: yield strength ≥ 265 MPa, tensile strength 450-600 MPa, elongation after fracture ≥ 17%, impact energy 27J.
The mechanical properties of Q420B plate are: yield strength ≥ 340 MPa, tensile strength 500-680 MPa, elongation after fracture ≥ 18%, impact energy 34J.

Q420B plate is the steel plate with yield strength of 420 MPa, the latter B means low temperature impact at 20℃, and Q345 plate is steel plate with yield strength of 345 MPa.