What S890QL Steel Plate Is
S890QL is an extra high strength structural steel plate covered by EN 10025-6 and supplied in the quenched and tempered condition. Its specified minimum yield strength is 890 MPa in the standard thickness range, and the QL suffix identifies a Charpy V-notch impact class tested at -20 °C. That toughness level is what separates S890QL from the basic S890Q grade and is the reason the material is widely used in equipment that has to keep working through winter conditions and in cold coastal environments.
For designers replacing conventional structural steel the weight saving is substantial: a minimum yield strength of 890 MPa is about 224 % higher than the 275 MPa minimum of S275JR, so a component can often be made thinner and lighter while carrying the same load, which in turn raises the payload capacity of the finished machine or structure.
Chemical Composition
Chemistry is controlled to a low carbon, low impurity window so that the quenched and tempered microstructure delivers both strength and toughness.
| Element | Limit (%) | Function |
|---|---|---|
| C | 0.20 max | Strength, kept low for weldability and toughness |
| Si | 0.80 max | Deoxidation |
| Mn | 1.70 max | Hardenability and solid solution strengthening |
| P | 0.020 max | Impurity control for toughness |
| S | 0.010 max | Impurity control for toughness |
| Cr | 1.50 max | Hardenability |
| Ni | 2.0 max | Matrix toughness at low temperature |
| Mo | 0.70 max | Hardenability and tempering resistance |
| Cu | 0.50 max | Residual control |
| N | 0.015 max | Free nitrogen control |
| B | 0.005 max | Hardenability at low addition level |
| Nb / V / Ti / Zr | 0.06 / 0.12 / 0.05 / 0.15 max | Grain refinement and microalloy control |
Carbon equivalent is calculated as CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. Ladle refining and vacuum degassing are used to reduce sulfur, oxygen and hydrogen before casting, since cleanliness is what converts the high strength microstructure into a material that still absorbs energy in the Charpy V-notch test at -20 °C.
Mechanical Properties and Low Temperature Service Behaviour
| Property | 6-50 mm | >50-100 mm |
|---|---|---|
| Minimum yield strength ReH | 890 MPa | 830 MPa |
| Tensile strength Rm | 940-1100 MPa | 880-1100 MPa |
| Minimum elongation A | 11 % | 11 % |
| Impact test temperature | -20 °C | -20 °C |
| Minimum absorbed energy (Charpy V, longitudinal) | 30 J | 30 J |
| Delivery condition | Quenched and tempered | |
The tensile range above 940 MPa means the plate is roughly three times stronger than ordinary structural steel in tension as well as in yield, which is why a single plate can replace a built up section and reduce both fabrication hours and weld volume.
Impact class is a fracture behaviour property, not a strength property. At low service temperature the risk is brittle fracture, and the Charpy V-notch test at -20 °C verifies that the plate still absorbs a defined minimum energy at that temperature. That is the practical difference between S890Q and S890QL:
S890Q: impact class at 0 °C, suitable for temperate service.
S890QL: impact class at -20 °C, suitable for cold region and offshore service, and the grade most often specified for winter operated equipment.
S890QL1: impact class at -40 °C, used for severe cold and arctic service.
Because all three share the same 890 MPa yield requirement, the suffix never changes the strength calculation; it only changes the temperature at which the toughness is guaranteed.
Fabrication and Welding Notes
Cutting: plasma, laser, waterjet or abrasive methods are all used; thermally cut edges should be cleaned of oxide and any micro-cracked layer before welding.
Forming: bending radii must be generous relative to thickness, and cold forming at high strain is followed by a decision on stress relief, since overheating above the tempering range destroys the 890 MPa level.
Welding: low hydrogen consumables, controlled heat input, adequate preheat governed by combined thickness and carbon equivalent, and a qualified welding procedure. Heat input that is too high softens the heat affected zone, while excessive restraint plus hydrogen causes delayed cracking.
Post-weld heat treatment: normally avoided; where required by the construction code, it must be qualified below the original tempering temperature.
Testing: ultrasonic inspection to EN 10160, dimensional tolerances to EN 10029, and inspection documents to EN 10204 3.1 with heat number traceability.
Typical Applications
Mobile and tower cranes, booms and lattice structures
Mining, earthmoving and agricultural machinery where payload and fuel efficiency depend on dead weight
Trailers, heavy transport equipment and lifting frames
Bridge components, long span steel structures and high rise steelwork where self weight governs the design
Offshore equipment, wind energy structures and cold climate construction
Special structures and rescue equipment that must remain reliable at low temperature
In every one of these cases the engineering logic is the same: reduce section thickness without losing load capacity, and verify that the new thinner section still has the low temperature toughness the application demands.
Frequently Asked Questions
Q: What does the QL suffix mean in S890QL?
It defines the Charpy V-notch impact class: QL means the plate is tested at -20 °C with a minimum absorbed energy of 30 J.
Q: How much weight can S890QL save compared with S275JR?
The minimum yield strength is about 224 % higher, so a strength driven component can often be reduced to roughly one third of the original section thickness, subject to stiffness constraints.
Q: Is S890QL the same as S890QL1?
No. Both have 890 MPa minimum yield strength, but S890QL is tested at -20 °C and S890QL1 at -40 °C, so the latter is used where the design temperature is lower.
Q: What is the maximum thickness with guaranteed 890 MPa yield?
The 890 MPa minimum applies up to 50 mm. From 50 mm to 100 mm the minimum yield level is 830 MPa, and heavier sections are supplied against agreed property levels.
Q: Can S890QL be welded without preheat?
Thin sections may be welded with modest preheat, but thicker plates and higher combined carbon equivalent require preheat and controlled heat input under a qualified procedure to avoid hydrogen cracking.
Q: Is ultrasonic testing normal for this grade?
Yes. Plates for critical lifting, offshore and structural duty are usually ordered with ultrasonic testing to EN 10160, plus dimensional and surface inspection before dispatch.
Q: Does stress relief after welding reduce the strength?
It can. Heat treatment above the original tempering temperature lowers both yield and tensile strength, so any mandatory stress relief must be carried out below that range and validated by testing.
