Characteristics of EN 10025-3 S420N Steel
High Strength and High Toughness
Yield Strength: ≥420 MPa (for thickness ≤16 mm), with a gradient decrease as thickness increases (e.g., dropping to 380 MPa for thickness >16 mm), meeting heavy-duty structural load-bearing requirements.
Tensile Strength: 450–630 MPa (some data indicate 510–680 MPa), balancing strength and plastic deformation capacity.
Low-Temperature Toughness: Charpy V-notch impact energy ≥34 J at -20°C (some data indicate ≥40 J), suitable for structural components in cold regions, such as Nordic bridge projects.
Excellent Weldability
Carbon Equivalent Control: ≤0.47% (calculated per EN 10025 formula), with a crack sensitivity coefficient (Pcm) ≤0.25%, enabling preheat-free welding for plates ≤150 mm thick and reducing construction costs.
Welding Process Compatibility: Applicable to various methods, including arc welding and gas welding, with minimal welding joint deformation and crack susceptibility, ensuring stable quality.
Good Fatigue and Corrosion Resistance
Fatigue Resistance: Grain refinement through normalizing improves fatigue life under dynamic loads (e.g., a 40% extension in fatigue life for Liebherr crane booms using S420N).
Corrosion Resistance: Contains chromium (Cr ≤0.30%) and copper (Cu ≤0.30%), with significantly enhanced atmospheric and seawater corrosion resistance after galvanizing or coating, extending service life.
Strict Chemical Composition and Process Control
Low-Carbon Design: Carbon content ≤0.20% (some data indicate ≤0.09%), balancing strength and cold crack susceptibility in welding.
Alloy Element Synergy: Manganese (Mn 1.00%–1.60%) improves hardenability, while niobium (Nb ≤0.05%) and vanadium (V ≤0.20%) refine grains, and aluminum (Alt ≥0.02%) fixes nitrogen, optimizing overall performance.
Clean Steel Refining: Techniques such as KR desulfurization (≤0.002%) and RH vacuum degassing (hydrogen ≤1.5 ppm) reduce inclusions and enhance material uniformity.
