S960QL is a high-strength quenched and tempered structural steel grade defined by the European standard EN 10025-6, known for its exceptional mechanical properties and reliable performance under demanding conditions. With a minimum yield strength of 960 MPa and a tensile strength ranging from 980 to 1150 MPa, it belongs to the family of ultra-high-strength steels designed to reduce structural weight while maintaining superior load-bearing capacity. The material is produced through a controlled quenching and tempering process, which imparts excellent toughness, even at low temperatures, with typical impact energy values of at least 40 J at -40°C, and some variants capable of performing well at -60°C. Its low carbon equivalent and optimized chemical composition enhance weldability and formability, allowing it to be used in complex fabrications without compromising strength or durability. S960QL is widely applied in heavy machinery, mobile cranes, offshore structures, high-rise buildings, and transportation equipment where high strength, lightweight design, and resistance to fatigue and extreme environments are critical requirements.
Impact Properties
| Material | Min impact energy, Charpy V 10x10 mm tests specimens, transverse test, |
| S960QL | 40 J/ - 40 Degree C |
Maximum Carbon equivalent CET(CEV)
| Thickness | 4.0-34.9 | 35.0-120.0 |
| CET(CEV) | 0.38(0.58) | 0.41(0.67) |
S960 QL Steel Plate Chemical Composition
| % | |
|---|---|
| Si | 00.80 |
| C | 00.20 |
| Mn | 1.70 |
| P | 00.020 |
| S | 00.010 |
| N | 00.015 |
| B | 00.0050 |
| Cr | 1.50 |
| Cu | 00.50 |
| Mo | 00.70 |
| Nb | 00.06 |
| Ni | 2.0 |
| Ti | 00.05 |
| V | 00.12 |
| Zr | 00.15 |
Mechanical Properties
Thickness of material (mm) | Yield strength Rp0.2(min MPa) | Tensile strength Rm(MPa) | Elongation A5(min %) |
| 4.0 - 53.0 mm | 960 MPa | 980 - 1150 MPa | 12% |
| 53.1 - 120.0 mm | 850 MPa | 900 - 1100 MPa | 10% |
Quenched & Tempered S960QL Steel Plate Equivalent
| Material | SSAB Brand |
| S960QL | Strenx® 960 E |
processing
1. Welding
Welding is the most critical processing step. Excessive heat can soften the heat-affected zone (HAZ), reducing the steel's load-bearing capacity.
Processes: Suitable for MAG (GMAW), SMAW (stick), and SAW (submerged arc).
Preheating: Generally recommended at 80°C to 150°C for thicker sections to prevent cold cracking. Plates over 50mm may require preheating throughout the entire thickness.
Heat Input: Should be strictly limited (often < 1.0 kJ/mm) to avoid degrading the fine-grained martensite-bainite structure.
Consumables: Use filler materials with low hydrogen content. Options include "under-matched" fillers (lower strength than base metal) to improve joint toughness and reduce cracking risk.
2. Cutting
Thermal cutting methods are standard, but they create a heat-affected zone that may require edge preparation.
Methods: Laser cutting is preferred for high precision and minimal thermal distortion. Plasma and Oxy-fuel (flame) cutting are used for thicker plates, though oxy-fuel results in the largest HAZ.
Edge Quality: Thermal cut edges should be deburred or rounded via grinding before subsequent operations like bending to prevent fracture initiation.
3. Forming and Bending
S960QL offers good cold-formability despite its high hardness.
Minimum Bend Radius: High-strength steel requires larger radii than mild steel to avoid cracking. A general guideline is r = 1.5 to 2.5 times the plate thickness, though specific manufacturer guarantees (e.g., Strenx® Class B) may allow tighter bends.
Direction: Bending perpendicular to the rolling direction is recommended for tighter radii.
4. Post-Fabrication Treatment
Heat Treatment: Standard stress-relieving at high temperatures is generally not recommended, as it can impair the mechanical properties of the quenched-and-tempered steel.
Surface Preparation: Protective coatings (painting or galvanizing) are essential for corrosion protection in harsh environments.
Primary Industrial Applications
Lifting & Moving: Highly utilized in safety-critical components for mobile cranes, lifting booms, aerial platforms, and forest harvesters. Its high strength-to-weight ratio allows for longer reach and higher payloads.
Transportation: Used in chassis for heavy trucks, trailer frames, and specialized railway wagons. In 2026, the focus is on reducing vehicle dead weight to maximize fuel efficiency and payload capacity.
Earthmoving & Mining: Essential for heavy-duty machinery like excavators, dump trucks, and mining shovels. It is also found in dipper sticks and bucket parts that experience high stress.
Construction & Energy:
Infrastructure: Fabrication of high-rise buildings, long-span bridges, and offshore platforms.
Renewables: Increasingly used in wind turbine towers and hydraulic supports.
Industrial Plants: Applications include turbine scroll cases, penstocks, and unfired pressure vessels.
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What is the density of S960QL?
The density of S960QL is approximately 7.85 g/cm³, same as conventional carbon steels. This allows accurate weight calculation for structural design, ensuring optimal strength-to-weight ratio in engineering projects.
What is the typical application of S960QL?
S960QL is commonly used in heavy-duty equipment: crane booms, mining machinery, offshore platforms, and high-rise building steel structures. It also fits in military vehicles and pressure vessels requiring high strength-to-weight ratio.
Does S960QL require preheating before welding?
Yes, preheating is necessary for S960QL welding. The recommended preheating temperature is 80-150°C, depending on thickness. Preheating reduces the cooling rate, preventing martensite formation and cold cracking in the weld zone.
What is the impact toughness of S960QL?
S960QL has excellent impact toughness, typically ≥ 40 J at -20°C (Charpy V-notch test). This ensures it resists brittle fracture in low-temperature environments, suitable for outdoor and offshore applications.
What is the elongation at break of S960QL?
Its minimum elongation at break is 10% (for 16 mm thickness). This ductility ensures the steel can deform slightly before failure, absorbing energy and enhancing structural safety under unexpected loads.
Is S960QL a quenched and tempered steel?
Yes, S960QL is a quenched and tempered (Q&T) steel. Quenching heats it to high temperature then cools rapidly; tempering reheats it to lower temperature. This process creates a strong, tough microstructure for heavy-duty use.
Can S960QL be bent?
Bending S960QL is possible with proper procedures. Use slow bending speed, preheat if thickness exceeds 10 mm, and maintain a large bend radius (≥3× thickness) to avoid cracking. Post-bending inspection is recommended.
What is the modulus of elasticity of S960QL?
Its modulus of elasticity is approximately 206 GPa, same as most structural steels. This value is used in structural design calculations to predict deformation under load, ensuring structural stability and precision.
What is the maximum thickness of S960QL available?
S960QL is available in thicknesses up to 150 mm, depending on manufacturers. Thicker plates may need adjusted heat treatment to ensure uniform mechanical properties across the cross-section, meeting project-specific requirements.