Product introduction 

Bridge steel plates are high-strength, high-toughness, weather-resistant special steel plates specially used to build the main structures of various bridges (main beams, bridge decks, piers, connecting plates, etc.), including highway, railway, cross-sea/cross-river bridges, etc. They belong to the core category of engineering structural steel and must meet the strict requirements of bridges in their long-term service life, such as bearing dynamic loads (vehicle and train collisions), complex environments (wind and rain, corrosion, temperature changes), and structural safety redundancy.

Core features

1. High Strength and High Load-Bearing Capacity

It must withstand the bridge's deadweight (dead load), traffic loads (live load), wind loads, and seismic loads.

2. Excellent Low-Temperature Toughness

Bridges must operate in temperatures between -40°C and 60°C. Steel can become brittle and fracture easily at low temperatures. Therefore, the steel plate must have an impact energy (Akv) of 34J or higher at low temperatures (e.g., -40°C or -60°C).

3. Weathering and Corrosion Resistance

Bridges are exposed to the outdoors for long periods of time and are susceptible to corrosion from rain, moisture, industrial waste gases (such as sulfur dioxide), and marine salt spray (for sea-crossing bridges). Therefore, most bridge steel plates are weathering steel (which forms a dense oxide film on the surface to resist corrosion by adding alloying elements such as Cu, Cr, and Ni). Alternatively, they must possess good Weldable to withstand subsequent anti-corrosion coatings (such as zinc-rich paint or other anti-corrosion coatings).

4.Excellent Weldable

Bridge structures must be joined using welding. After welding, the steel plates must be free of defects such as cracks and pores. Therefore, the carbon equivalent (Ceq) of the steel plates must be strictly controlled (typically ≤ 0.45%) to ensure that the toughness of the heat-affected zone (HAZ) is not significantly reduced during welding and that the steel meets the requirements of on-site welding processes (such as manual welding, submerged arc welding, and gas shielded welding).

5.Excellent fatigue resistance.

 Repeated traffic from vehicles and trains creates fatigue loads on bridges. Long-term fatigue loads can easily lead to fatigue cracks in steel plate welds or areas of stress concentration. Therefore, bridge steel plates must undergo fatigue testing to ensure they can withstand millions of load cycles without fatigue failure.

Grade

Production and inspection standards for steel plates for bridges

1.Core production process

The steel plates used in bridges are mostly medium-thick plates (generally 6 to 100 mm thick, and up to 150 mm or more in special parts)：

Blast furnace ironmaking → Converter Steelmaking →Refining →Rolling →Heat Treatment

2.Strict inspection requirements

-Mechanical property testing: Tensile testing (measuring yield strength, tensile strength, and elongation), impact testing (low-temperature impact energy), and bend testing (testing plasticity to prevent weld cracking).

-Chemical composition testing: Spectroscopic or chemical analysis verifies that the carbon, manganese, silicon, copper, and chromium content meet standards.

-Nondestructive testing: Ultrasonic testing (UT) is used to detect internal defects such as layered and inclusions in the steel plate (national standards require a flaw detection level of ≥ II).

-Surface quality testing: Surface defects such as cracks, pitting, and scratches are inspected. The depth of defects must not exceed 5% of the plate thickness.

Application areas

Bridge steel plates are the "skeleton" of bridge structures and are used for the following purposes:

Main beams: The primary load-bearing structure of a bridge (such as box girders and T-beams), typically constructed from Q355q-Q460q steel plates.

Deck system: The load-bearing plates beneath the deck pavement require wear and corrosion resistance and are typically constructed from Q355qNH weathering steel.

Piers and supports: These support vertical loads and require high strength and stability, and are typically constructed from thick Q355q-Q420q steel plates.

Connecting plates and stiffeners: The critical connection between the main beam and supports requires excellent Weldable and is typically constructed from thin Q355q steel plates.