EN 10025-6 S550Q Steel Plate | S550Q QT High Structural Steel
What is EN 10025-6 S550Q Steel Plate?
SHH STEEL is a professional China Mill-Direct Exporter of high-strength structural steel plates. We are pleased to offer EN 10025-6 S550Q Steel Plate (Material Number 1.8904), a quenched and tempered grade engineered for structural applications that demand higher strength than the S460 series.
S550Q belongs to the family of EN 10025-6 steel plate products covering high-yield-strength steels in the quenched and tempered condition. After quenching and tempering, this grade achieves a minimum yield strength of 550 MPa (up to 50 mm thickness) while maintaining adequate impact toughness at –20°C. The refined tempered microstructure provides an excellent balance of strength, ductility and weldability for heavily loaded welded structures.
SHH STEEL supplies S550Q plates in thicknesses ranging from 6 mm to 150 mm, widths up to 3000–4000 mm and lengths up to 12000–18000 mm. Custom cutting, ultrasonic testing, surface treatment and third-party inspection services are available. Every plate is delivered with a full EN 10204 3.1 Mill Test Certificate, ensuring complete traceability from the producing mill.
Material Specification
| Parameter | Requirement / Availability |
|---|---|
| Governing Standard | EN 10025-6 |
| Steel Designation | S550Q (1.8904) |
| Delivery Condition | Quenched and Tempered (Q) |
| Product Form | Flat steel plate |
| Thickness Range | 6 mm – 150 mm (thicker plates on request) |
| Width / Length | Up to 3000–4000 mm / 12000–18000 mm |
| Certification | EN 10204 3.1 / 3.2 |
| Additional Testing | UT, Z-test, third-party inspection available |
Chemical Composition
Chemical composition is controlled in accordance with EN 10025-6 for both ladle (heat) analysis and product analysis.
Ladle Analysis (Cast Analysis)
| Element | Maximum (%) |
|---|---|
| Carbon (C) | 0.20 |
| Silicon (Si) | 0.80 |
| Manganese (Mn) | 1.70 |
| Phosphorus (P) | 0.025 |
| Sulfur (S) | 0.015 |
| Chromium (Cr) | 1.50 |
| Nickel (Ni) | 2.00 |
| Molybdenum (Mo) | 0.70 |
| Copper (Cu) | 0.50 |
| Niobium (Nb) | 0.06 |
| Vanadium (V) | 0.12 |
| Titanium (Ti) | 0.05 |
| Boron (B) | 0.005 |
| Nitrogen (N) | 0.015 |
Product Analysis
| Element | Maximum (%) |
|---|---|
| Carbon (C) | 0.22 |
| Silicon (Si) | 0.86 |
| Manganese (Mn) | 1.80 |
| Phosphorus (P) | 0.030 |
| Sulfur (S) | 0.017 |
| Chromium (Cr) | 1.60 |
| Nickel (Ni) | 2.10 |
| Molybdenum (Mo) | 0.74 |
| Copper (Cu) | 0.55 |
| Niobium (Nb) | 0.07 |
| Vanadium (V) | 0.14 |
| Titanium (Ti) | 0.06 |
| Boron (B) | 0.006 |
| Nitrogen (N) | 0.016 |
The alloying system is designed to provide sufficient hardenability for quenching while keeping the carbon equivalent within a range that still allows satisfactory welding after tempering.
Mechanical Properties
| Nominal Thickness (mm) | Min. Yield Strength ReH | Tensile Strength Rm | Min. Elongation A | Impact Energy (longitudinal) |
|---|---|---|---|---|
| ≤ 50 | 550 MPa | 640 – 820 MPa | 16 % | 30 J at –20 °C |
| 50 < t ≤ 100 | 530 MPa | 640 – 820 MPa | 16 % | 30 J at –20 °C |
| 100 < t ≤ 150 | 490 MPa | 590 – 770 MPa | 16 % | 30 J at –20 °C |
Density is approximately 7.85 g/cm³.
Delivery Conditions
All S550Q plates are supplied in the quenched and tempered condition as required by EN 10025-6. The quenching and tempering heat treatment produces the required high strength and toughness combination.
Additional processing options available from SHH STEEL:
- Shot blasting and shop primer application
- Ultrasonic testing in accordance with EN 10160
- Through-thickness (Z-direction) testing to Z15, Z25 or Z35
- Independent third-party inspection (SGS, BV, TUV, Lloyd’s Register, etc.)
- Precision cutting (flame, plasma or water-jet)
Tolerances
Dimensional tolerances are in accordance with EN 10029. Customers may select the required class for thickness, width, length and flatness. Both mill edges and cut edges (flame or plasma) can be supplied according to project requirements. Tighter tolerances are available by special agreement.
Weldability
S550Q is a high-strength quenched and tempered steel. Successful welding requires careful attention to preheating, heat input and the use of low-hydrogen consumables to maintain toughness in the heat-affected zone.
Recommended welding consumables:
| Welding Process | Suggested Consumables |
|---|---|
| SMAW (Stick) | E8018-G, E9018-G |
| GMAW / MAG | ER80S-G, ER90S-G |
| FCAW | E81T1-Ni1, E91T1-G |
| SAW | Matching high-strength wire and flux combinations |
Preheating is generally required, especially for thicker plates. Interpass temperature control and, in some cases, post-weld heat treatment are recommended for critical applications.
Equivalent Material Grades
| Grade | Standard | Remarks |
|---|---|---|
| S550Q | EN 10025-6 | Primary designation |
| 1.8904 | EN | Material number |
| Q550D / Q550E | GB/T 1591 | Closest Chinese equivalents |
| Selected A514 / A517 grades | ASTM | Similar quenched & tempered concept |
| StE 550 V | Former DIN | Historical related grade |
Applications
EN 10025-6 S550Q is selected when higher strength than the S460 series is required. Typical applications include:
| Application Area | Typical Components / Keywords |
|---|---|
| Heavy Construction | Crane booms, heavy frames, high-load columns – S550Q Structural Steel |
| Bridge Engineering | Main girders, support structures – S550Q Bridge |
| Mining & Earthmoving Equipment | Chassis, boom structures – S550Q Mining |
| Offshore & Marine | Platform components, lifting equipment – S550Q Offshore |
| Energy & Power | Wind turbine components, heavy fabrications – S550Q Energy |
| General Heavy Fabrication | High-strength welded assemblies – S550Q Fabrication |
Why Choose SHH STEEL
SHH STEEL is a China Mill-Direct Exporter. We maintain long-term strategic cooperation with major Chinese steel mills and act as a first-level agent. This direct supply model allows us to offer competitive mill-direct pricing, shorter lead times, consistent quality and full Mill Test Certificates (EN 10204 3.1 / 3.2) for EN 10025-6 S550Q Steel Plate.
Our experienced export and technical teams provide support on material selection, welding procedures, cutting and processing. Customers benefit from reliable supply and professional service for high-strength quenched and tempered steel projects worldwide.
FAQ
- What does “Q” mean in S550Q?“Q” indicates the quenched and tempered condition and impact testing at –20°C.
- What is the difference between S550Q and S550QL?Both grades have the same strength level. S550Q is impact tested at –20°C, while S550QL is tested at –40°C and offers higher toughness for colder service.
- What is the material number of S550Q?1.8904
- Can SHH STEEL supply S550Q with Z-direction testing?Yes. Z15, Z25 and Z35 testing can be arranged according to project requirements.
Conclusion
EN 10025-6 S550Q (1.8904) quenched and tempered steel plate from SHH STEEL provides a high yield strength of 550 MPa combined with reliable toughness at –20°C. As a China Mill-Direct Exporter, we offer competitive pricing, consistent quality and full technical support. Contact SHH STEEL today for stock availability, pricing or processing services.
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