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Q345D Steel: Exceptional Performance for Harsh Environments
Q345D is a high - quality low - alloy high - strength structural steel in China, specified according to the national standard GB/T 1591. The "Q" represents "yield strength" in Chinese pinyin, "345" indicates that the minimum yield strength of this steel is 345 MPa, and "D" means it must pass an impact test at - 20℃, highlighting its outstanding low - temperature toughness.
The most prominent feature of Q345D is its excellent low - temperature performance. Unlike other steel grades, it can maintain good toughness and prevent brittle fracture even in extremely cold conditions, ensuring the safety and stability of structures. Additionally, it combines high strength with good plasticity and weldability, allowing for easy processing and fabrication. Its corrosion resistance is also relatively good, which extends the service life of components.
In terms of chemical composition, Q345D is mainly composed of iron with carefully added alloying elements. The carbon content is generally controlled below 0.20% to balance strength and toughness. Manganese, with a content of about 1.0 - 1.6%, improves strength and hardenability. Silicon (≤ 0.55%) plays a role in deoxidation and enhancing strength. Trace amounts of vanadium, niobium, or titanium are added to refine the grain structure, optimizing mechanical properties. Strict limits are set for harmful impurities: phosphorus ≤ 0.035% and sulfur ≤ 0.035% to guarantee reliable performance.
Q345D is widely used in environments with high requirements for low - temperature performance. In the construction of bridges in cold regions, it is used for main load - bearing structures to resist the impact of cold climates. It is also applied in the manufacturing of large - scale mechanical equipment used in frigid areas, such as mining machinery in high - latitude regions. In the petrochemical industry, especially for equipment operating in cold - temperature environments, Q345D is the material of choice due to its reliable performance under harsh conditions.