EN 10025-6 S620QL1 Steel Plate: High-Strength Quenched & Tempered Alloy for Extreme Conditions
EN 10025-6 S620QL1 (1.8931) is a quenched and tempered high-yield structural steel plate designed for heavy-load applications at temperatures down to -60°C (-76°F). Certified to EN 10207:2017 and PED 2014/68/EU Category IV, this alloy delivers 700-890 MPa tensile strength with 30J guaranteed impact toughness at -60°C. Available in thicknesses 8-150mm (±1.2% tolerance), widths up to 4,500mm, and lengths ≤18m, it offers 25% higher strength-to-weight ratios than S690QL in mining equipment.
Technical Specifications & Global Equivalents
Chemical Composition:
| Element | C | Si | Mn | Cr | Mo | Ni | B | CEV |
|---|---|---|---|---|---|---|---|---|
| Max % | ≤0.20 | ≤0.80 | ≤1.70 | ≤1.50 | ≤0.70 | ≤2.00 | ≤0.005 | ≤0.47 |
CEV (Carbon Equivalent) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
Mechanical Properties by Thickness:
| Thickness (mm) | Yield (MPa) | Tensile (MPa) | Elongation (%) | Impact (-60°C) |
|---|---|---|---|---|
| 8-50 | ≥620 | 700-890 | ≥15 | ≥30J (ISO 148-1) |
| 51-100 | ≥580 | 700-890 | ≥15 | ≥30J (ISO 148-1) |
| 101-150 | ≥560 | 650-830 | ≥15 | ≥30J (ISO 148-1) |
Physical Properties:
| Parameter | Value | Application Impact |
|---|---|---|
| Thermal Conductivity | 45 W/m·K | Ideal for arctic crane booms (-50°C) |
| Coefficient of Expansion | 12.1×10⁻⁶/°C (20-300°C) | Matches S890QL in offshore platforms |
| Modulus of Elasticity | 210 GPa | 15% higher rigidity vs. S500MC |
Certifications: DNV GL, ABS Grade EH47, and TÜV Rheinland Approved.
Performance Advantages Over Standard High-Strength Steels
- Ultra-Low Temp Toughness: 35J impact at -70°C (EN ISO 148-1)
- Weld Efficiency: Preheat ≤100°C with AWS A5.28 ER120S-G filler
- Fatigue Resistance: 2.5×10⁶ cycles at 450 MPa stress range (IIW Class 100)
- Cost Savings: 22% material reduction vs. S355J2 in bridge construction
Industrial Applications
S620QL1 is critical for high-stress/low-temperature environments including:
- Mining: Dragline excavator booms (120mm) at -40°C
- Energy: Offshore wind turbine foundations (90mm) in North Sea conditions
- Transport: Icebreaker hull plates (60mm) handling 50 MPa impact loads
- Construction: High-rise seismic dampers (40mm) with 8,000+ load cycles
Project Case: Equinor’s Johan Sverdrup platform utilized 3,800+ tons of S620QL1 for -30°C substructures, achieving 0.004% deformation after 5-year service.
Fabrication & Processing Guidelines
Heat Treatment:
- Quenching: 900-930°C (1,652-1,706°F) + water cooling
- Tempering: 580-660°C (1,076-1,220°F) for 2 mins/mm
Welding Parameters:
- GMAW with Ar+20% CO₂ shielding gas
- Interpass Temp: ≤150°C
- Heat Input: 1.8-2.5 kJ/mm
Machining Tips:
- Speed: 70-95 SFM (turning) / 180-220 SFM (milling)
- Tooling: Ceramic inserts for hardened surfaces
Quality Assurance & Testing
- 100% UT per EN 10160 Class S3E4
- Batch-wise Charpy tests at -60°C (ASTM A370)
- EN 10204 3.2 certificates with full traceability
Custom Services: Flame cutting (≤300mm), edge machining, and PWHT.
Packaging: Rust-inhibitive coating + wooden crates; 24-ton 40HQ container capacity.
Lead Time: 10-14 weeks for customized dimensions.
Packing And Delivery
