Gangsteel produces and exports EN 10025-6 S550QL quenched and tempered structural steel plate. S550QL belongs to a mid-range strength level of the EN 10025-6 steel plate family, with a minimum yield strength of 550 MPa for thicknesses up to 50 mm. It is used where a welded structure must carry high loads with less steel weight than ordinary structural grades.
S550QL is delivered in the quenched and tempered condition and has guaranteed Charpy impact energy at –40 °C, giving good toughness for outdoor and cold-climate service. For arctic or very low-temperature service, S550QL1 is tested at –60 °C.
Grade Designation
- S – Structural steel
- 550 – Minimum yield strength 550 MPa (thickness ≤ 50 mm)
- Q – Quenched and tempered delivery condition
- L – Guaranteed Charpy V-notch impact energy at –40 °C
Steel number: 1.8926
Key Advantages of S550QL Steel Plate
- Minimum yield strength of 550 MPa for lighter welded structures
- Guaranteed impact toughness at –40 °C
- Fine-grained quenched and tempered microstructure
- Weldable with a qualified welding procedure
- Specified over a wide thickness range in EN 10025-6
Chemical Composition (Heat Analysis, Maximum %)
| Element | C | Si | Mn | P | S | N | B | Cr | Cu | Mo | Nb | Ni | Ti | V | Zr |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| S550QL | 0.20 | 0.80 | 1.70 | 0.020 | 0.010 | 0.015 | 0.005 | 1.50 | 0.50 | 0.70 | 0.06 | 2.0 | 0.05 | 0.12 | 0.15 |
Note: The steel is fully killed and fine-grained. The producing mill chooses the actual alloy content within these limits, and the carbon equivalent (CEV) for each heat is shown on the mill certificate.
Mechanical Properties
| Thickness (mm) | Yield Strength ReH min (MPa) | Tensile Strength Rm (MPa) | Elongation A min (%) |
|---|---|---|---|
| 3 – 50 | 550 | 640 – 820 | 16 |
| > 50 – 100 | 530 | 640 – 820 | 16 |
| > 100 – 150 | 490 | 590 – 770 | 16 |
| Impact Test (Charpy V-notch) | 0 °C | –20 °C | –40 °C |
|---|---|---|---|
| Longitudinal, KV min (J) | 50 | 40 | 30 |
| Transverse, KV min (J), if agreed | 35 | 30 | 27 |
Note: Thickness rows follow the EN 10025-6:2004+A1 edition. The 2019 edition revised the thickness steps for thicker plates, so state the edition on your order. Guaranteed values depend on thickness and edition, and must be confirmed on the mill certificate for the ordered thickness.
Available Dimensions
- Thickness: to enquiry, within the EN 10025-6 range for S550 grades (from 3 mm; up to 150 mm in the 2004+A1 edition; confirm the maximum for the 2019 edition when ordering)
- Width and length: to enquiry
- Tolerances: EN 10029 unless otherwise agreed
- Delivery condition: Quenched and Tempered (Q+T)
Main Applications
- Welded high-strength structures and bridges
- Crane and lifting equipment components
- Heavy vehicle and trailer frames
- Construction and mining machinery parts
- Offshore and port structures
Equivalent Grades of S550QL
| Manufacturer / Standard | Equivalent Grade | Steel Number / Designation | Remarks |
|---|---|---|---|
| EN 10025-6 | S550QL | 1.8926 | Official European standard grade |
| EN 10137-2 (withdrawn) | S550QL | 1.8926 | Former European standard, replaced by EN 10025-6 |
| EN 10025-6 | S550QL1 | 1.8986 | Same strength, tested at –60 °C; can replace S550QL, not the reverse |
| GB/T 16270 (China) | Q550E | – | Approximate: similar strength class, impact tested at –40 °C; not identical limits |
Equivalents are for reference only. A grade from another standard is not a direct substitute unless the designer or project specification accepts it.
Related Products
Other grades in the EN 10025-6 steel plate range:
- EN 10025-6 S550Q steel plate
- EN 10025-6 S550QL1 steel plate
- EN 10025-6 S500QL steel plate
- EN 10025-6 S620QL steel plate
- Low alloy and high strength steel plate
Frequently Asked Questions (FAQ)
What is the difference between S550Q, S550QL and S550QL1?
All three have the same strength. They differ in impact test temperature: S550Q at –20 °C, S550QL at –40 °C and S550QL1 at –60 °C. QL and QL1 also have lower maximum phosphorus and sulfur than Q.
What is the carbon equivalent (CEV) of S550QL?
EN 10025-6 sets maximum CEV values that rise with plate thickness, up to 0.83 for the thickest plates. The limit for thinner plates is lower; check the table of the edition you order. The actual CEV of each heat is printed on the mill certificate. Use that value when you plan welding.
Is S550QL weldable?
Yes. S550QL is a weldable fine-grained steel, but it needs a qualified welding procedure (WPS) following EN 1011-2, low-hydrogen consumables and controlled heat input. The cold cracking risk increases with plate thickness.
Does the yield strength drop for thicker plates?
Yes. The minimum yield strength is 550 MPa up to 50 mm, 530 MPa above 50 mm to 100 mm, and 490 MPa for thicker plates. Design to the value for the actual thickness and check it on the mill certificate.
Can S550QL replace a lower-toughness quality?
Yes. S550QL has the same strength as S550Q, with impact energy guaranteed at a lower temperature, so it can normally replace them if the designer agrees. The reverse is not allowed.
Should I choose S550QL or S620QL?
S620QL gives a higher yield strength and may allow thinner plate, but welding and forming become more demanding. S550QL is often chosen as a balance between strength and fabrication. The designer should approve any change of grade.
Can S550QL be cold formed?
Yes, but it needs larger bending radii than ordinary structural steel. Hot forming is not recommended because it can destroy the quenched and tempered properties. Confirm forming limits for your thickness with the mill.
What information should I give when asking for a quotation?
Give the grade (EN 10025-6 S550QL), the standard edition, plate thickness, width, length, quantity, any extra tests (for example transverse impact or ultrasonic testing) and the inspection certificate type you need.
For a quotation or technical data for EN 10025-6 S550QL steel plate, please contact Gangsteel.