The difference between Q345D steel and Q355D steel

Q345 steel is a Chinese standard low alloy high strength structural steel, with the designation of "Q" representing the yield strength and the number indicating the minimum yield strength. Q345 steel has good mechanical properties, low temperature performance, plasticity, and weldability. It is widely used in bridges, vehicles, ships, buildings, pressure vessels, etc.

The chemical composition of Q345 steel typically includes elements like carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, and other trace elements. Its yield strength is generally between 345 MPa and 500 MPa, depending on the thickness and heat treatment conditions. The tensile strength of Q345 steel can range from 470 MPa to 630 MPa.

Q345D steel and Q355D steel are both grades of Chinese low alloy high strength structural steel, with the main difference being their yield strength.

Q345D steel has a yield strength of 345 MPa, while Q355D steel has a yield strength of 355 MPa. This means that Q355D steel has a slightly higher yield strength and is generally considered to be a stronger material than Q345D.

In terms of chemical composition, both grades of steel are similar and include elements like carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, and other trace elements. They also have good mechanical properties, low-temperature performance, plasticity, and weldability.

Both Q345D and Q355D steel are commonly used in a variety of applications such as bridges, buildings, vehicles, and machinery, among others. The choice between the two will depend on the specific requirements of the application and the level of strength needed.

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