How to balance high strength and weldability in common carbon steel plates for building steel structures to ensure the reliability of large component connections?
Publish Time: 2026-02-03
In modern large-scale building steel structure projects, common carbon steel plates, as core load-bearing materials, must withstand enormous static and dynamic loads while requiring extensive on-site welding for component connections. However, high strength and good weldability are often contradictory: increasing strength usually means increasing carbon equivalent, and an increase in carbon equivalent significantly reduces the material's weldability, easily leading to problems such as cold cracking and heat-affected zone embrittlement. Achieving a scientific balance between the two, ensuring the structural safety and connection reliability of high-rise buildings, large-span stadiums, or bridge nodes throughout their entire life cycle, has become a key issue jointly addressed by materials engineers and structural designers.1. Carbon Equivalent Control: The "Golden Ruler" of WeldabilityThe weldability of common carbon steel plates is mainly determined by their chemical composition, but it increases the tendency to harden. Taking Q355 steel, widely used in construction, as an example, its yield strength reaches 355 MPa. However, by strictly controlling the carbon content and optimizing the alloy ratio, the carbon equivalent is kept below 0.40%, thus maintaining good weldability while ensuring strength.2. Microalloying and Controlled Rolling and Cooling: A Metallurgical Path Combining Strength and ToughnessModern high-performance construction common carbon steel plates generally employ microalloying combined with controlled rolling and cooling processes. During rolling, microalloying elements precipitate fine carbonitrides, inhibiting austenite grain growth; subsequent accelerated cooling promotes the formation of fine ferrite-pearlite or bainite structures. This fine-grain strengthening mechanism can significantly improve strength and toughness without relying on high carbon content. More importantly, the fine and uniform microstructure reduces the grain coarsening tendency in the weld heat-affected zone, slowing down softening and embrittlement, ensuring that the area near the weld still possesses sufficient ductility and crack resistance.3. Welding Process Matching: A Systematic Guarantee from Materials to ConstructionEven if the material itself has good weldability, improper processes can still lead to failure. Therefore, strict measures are required in the construction of steel structures, including preheating, interpass temperature control, low-hydrogen welding materials, and post-weld hydrogen removal treatment. For thick plates or high-restraint joints, preheating slows down the cooling rate and prevents martensitic transformation; using low-hydrogen welding rods or gas-shielded welding reduces the risk of hydrogen-induced cracking from the source. Furthermore, modern BIM technology can accurately simulate the welding sequence and residual stress distribution, optimizing construction plans and minimizing deformation and cracking risks. This synergistic approach of "materials-design-process" is the core of ensuring the long-term reliability of large welded joints.4. Standards and Certifications: Institutional Guarantees for ReliabilityThe chemical composition, mechanical properties, and welding qualification of common carbon steel plates for structural use are subject to mandatory requirements. Steel mills must provide complete material certificates and pass third-party welding process qualification. In super high-rise buildings or important public buildings, HAZ simulation tests are even required for each batch of steel plates to verify their actual weldability.In conclusion, the balance between high strength and weldability achieved by common carbon steel plates in building steel structures is not a single technological breakthrough, but rather the result of a deep integration of materials metallurgy, process control, and engineering practice. It allows skyscrapers to rise from the ground without fear of wind and earthquakes, and allows cross-river bridges to stand firm for centuries—forming the backbone of modern cities by combining the rigidity of steel with the flexibility of welds.
