EN 10025-6 S960QL Ultra High Strength Structural Steel Plate

1. What is S550QL high-strength steel plate?

S960QL is a high-performance, cryogenic, high-strength structural steel defined by the EN 10025-6 standard, specifically developed for heavy machinery manufacturing in cold regions and large-scale steel structure projects in extreme environments.

Compared to conventional medium- and high-strength structural steels and the standard S960Q grade, S960QL employs a more refined low-carbon, low-sulfur, and low-phosphorus alloy composition along with stricter smelting processes. It features a fine, uniform grain structure and ultra-low impurity levels, delivering excellent low-temperature toughness while maintaining ultra-high strength, good weldability, formability, and fatigue resistance.

The superior strength-to-weight ratio of S960QL high-strength steel plates supports lightweight structural design, effectively reducing the dead weight of the steel, material consumption, and overall project costs. It is widely used in heavy industrial machinery and large-scale steel structure projects in high-altitude, high-latitude, and extremely low-temperature regions.

2. Grade Designation Meaning

S: Structural Steel

960: Minimum yield strength (ReH) 960 MPa

Q: Quenched and tempered

L: Low-temperature toughness level (Impact energy ≥ 30J, at -40℃, longitudinal)

Note: P and S are detrimental elements, strictly limited to avoid brittleness; alloying elements like Cr, Mo, Ni enhance strength and toughness; microalloying elements V, Nb, Ti refine the grain structure to optimize mechanical properties.

* Yield strength and tensile strength decrease as the thickness of the steel plate increases.

1. Ultra-high yield strength and outstanding load-bearing capacity

2. Extremely high strength-to-weight ratio, enabling lightweight design

3. Excellent low-temperature impact toughness, providing resistance to impact and fatigue

4. Good structural safety

5. Controllable weldability

6. Good machinability and formability

7. Uniform and stable material properties

8. Suitable for heavy-duty and demanding operating conditions

Due to its balance of high strength and toughness, S960QL is widely used in fields with demanding material performance requirements:

1. Lifting Equipment

1) Truck-mounted crane booms

2) Crawler crane booms

3) Telescoping booms

4) Crane outriggers

5) Load-bearing components for lifting equipment

6) High-strength connection and support components

Its high strength enables designers to reduce plate thickness and structural weight while meeting load-bearing requirements.

2. Construction Machinery

1) Excavator booms and dippers

2) Concrete pump truck booms

3) Structural components for loaders and heavy-duty construction vehicles

4) Road Construction Machinery

5) Heavy-Duty Equipment Chassis

6) High-Strength Support Structures

This type of equipment typically requires high resistance to bending, tensile stress, and fatigue; therefore, ultra-high-strength steel can be used to achieve high-load-bearing, lightweight structural designs.

3. Mining and Heavy Equipment

1) Large Mining Dump Truck Frames

2) Mining Transport Equipment

3) Structural Components for Excavation Equipment

4) Support Structures for Crushing and Conveying Equipment

5) Heavy-Duty Hydraulic Equipment

6) Mining Machinery Booms and Chassis

Particularly in large-scale mining equipment, reducing the structural weight can increase the payload capacity while maintaining high structural load-bearing capacity.

4. Heavy-Duty Transport Vehicles

1) Heavy-duty truck chassis

2) Dump truck bodies

3) Special-purpose transport vehicles

4) Heavy-duty trailers and semi-trailers

5) Load-bearing structures for large transport equipment

By using high-strength steel plates, it is possible to reduce the weight of certain structural components while meeting structural strength requirements, thereby increasing the payload capacity of transport equipment.

5. Bridges and Large Steel Structures

1) Bridges and bridge components

2) Large industrial steel structures

3) High-load support structures

4) Foundations and frames for large equipment

5) Special engineering structures

The advantage lies in the fact that higher strength allows for a reduction in the cross-sectional dimensions of certain components.

6. Wind Power, Marine, and Offshore Engineering

1) Wind turbine towers

2) Wind turbine frames

3) Marine engineering lifting equipment

4) Offshore operation equipment

5) Offshore engineering machinery

6) High-strength support structures

7) Offshore Engineering Lifting Equipment

The S960QL’s L-grade impact toughness at -40°C makes it suitable for load-bearing structures operating in certain low-temperature environments.

7. Agricultural Machinery

1) Large Agricultural Machinery Chassis

2) Agricultural Machinery Arms

3) Heavy-Duty Trailers

4) High-Strength Coupling Structures

5) Large Agricultural Machinery Load-Bearing Components

The primary value of high-strength steel in agricultural machinery lies in its ability to balance structural strength, equipment lightweighting, and load-bearing capacity.

Delivery and Processing Considerations:

Delivery Condition

Usually delivered in the "Quenched + Tempered" (Q+T) condition. The surface can be supplied as bare material, pickled, oiled, or painted based on requirements.

A Mill Test Certificate (MTC) provided by the steelmaker is required, containing compliance proof for chemical composition, mechanical properties, heat treatment records, etc.

Processing Recommendations

Cutting: Plasma cutting, laser cutting, or flame cutting can be used. Burrs and the heat-affected zone must be removed after cutting.

Welding: Use low-hydrogen electrodes (e.g., E11018-G) or wires (e.g., ER110S-G) is recommended. Strictly control preheat and interpass temperatures. Post-weld stress relief heat treatment (e.g., holding at 200-300°C) can be performed.

Forming: Cold bending or hot forming is possible. However, larger cold bending radii are required (to avoid cracking). Hot forming temperature is recommended to be controlled between 600-800°C.

Equivalent Materials

For a clearer understanding of its positioning, here is a comparison with high-strength steels from similar national standards:

Summary

EN 10025-6 S960QL is an ultra-high-strength, quenched and tempered structural steel offering an exceptional combination of minimum 960 MPa yield strength and high toughness at low temperatures. Its primary advantage is enabling lightweight, high-performance designs for demanding mechanical applications. However, its fabrication, particularly welding, demands strict adherence to specialized procedures to preserve its mechanical properties.