Overview of Q345B Steel and Its Core Properties

Q345B steel is one of the most widely used low-alloy high-strength structural steels in China, standardized under GB/T 1591. It is known for its excellent combination of strength, weldability, and toughness, making it ideal for both structural and engineering applications. The designation "Q345" represents a minimum yield strength of 345 MPa, while "B" indicates its impact testing at 20°C.

Chemically, Q345B steel typically contains carbon (≤0.20%), manganese (1.0–1.6%), silicon (≤0.55%), and trace amounts of sulfur and phosphorus. This balanced composition ensures high mechanical strength without compromising formability. It also provides consistent performance under low temperatures and dynamic stress.

Mechanically, the steel delivers a yield strength of ≥345 MPa and tensile strength between 470–630 MPa, with an elongation of ≥21%. Its toughness and low carbon equivalent value make it easy to weld using all conventional techniques without preheating for thin sections.

Common product forms include plates, H-beams, angles, and seamless pipes, which are widely used in construction, bridges, machinery, and transportation industries. Q345B's cost-efficiency and high strength-to-weight ratio enable engineers to design lighter and stronger structures with reduced material usage.

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