S690QL is a high‑strength quenched and tempered structural steel offering good toughness, weldability, and formability. It is used in heavy‑duty applications where strong, durable, and relatively lightweight structural components are required.
Chemical Composition
| Element | Percentage % | Element | Percentage % |
| C | 0.20 | Cu | 0.50 |
| Si | 0.80 | Mo | 0.70 |
| Mn | 1.70 | Nb* | 0.06 |
| P | 0.025 | Ni | 2.0 |
| S | 0.015 | Ti* | 0.05 |
| N | 0.015 | V* | 0.12 |
| B | 0.0050 | Zr* | 0.15 |
| Cr | 1.50 |
Mechanical Properties
| Designation | Mechanical Properties (ambient temperature) | |||||||
| Steel Name | Steel Number | Min. Yield Strength Reh MPa | Tensile Strength Rm MPa | Min. % elongation after fracture | ||||
| Nominal thickness (mm) | Nominal thickness (mm) | |||||||
| ≥3 ≤50 | ≥50 ≤100 | ≥100 ≤150 | ≥3 ≤50 | ≥50 ≤100 | ≥100 ≤150 | |||
| S690QL | 1.8931 | 690 | 650 | 630 | 770/940 | 760/930 | 710/900 | 14 |
S690QL - V Notch Impact Testing
| Grade | Sample Orientation | @ 0°C | @-20°C | @-40°C | @-60°C |
| S690QL | Longitudinal | 50 J | 40 J | 30 J | ¨C¨C |
| Traverse | 35 J | 30 J | 27 J | ¨C¨C |
Processing Characteristics
Despite its high strength, S690QL exhibits excellent workability, with key processing features as follows:
Weldability: As a core processing feature, it can avoid cold cracking and maintain stable joint strength with proper preheating and post-weld heat treatment, compatible with common welding techniques like arc welding and gas shielded welding.
Formability: It performs well in shaping, allowing bending, rolling, and pressing into complex shapes under controlled temperature conditions without damaging structural integrity.
Machinability: Though sharp tools and appropriate parameters are needed to handle its hardness, its consistent material quality ensures stable processing results and reduces production errors.
Main Applications
Its applications span multiple heavy-duty industries, mainly including:
Construction industry: Widely used in large-scale structures such as bridge supports, crane booms, and high-rise building frameworks, where high load-bearing capacity and light weight are critical requirements.
Automotive and transportation sector: Applied to truck frames, trailer components, and railway vehicle parts, it enhances product durability while reducing overall weight to improve fuel efficiency.
Offshore and mining fields: Essential for offshore platforms and mining machinery components, as it can withstand harsh environments like corrosion and low temperatures.
Core Advantages
S690QL boasts prominent core advantages, which are reflected in the following aspects:
Outstanding strength-to-weight ratio: Compared to conventional steel, it can reduce structural weight by 20%-30% under the same load requirements, effectively cutting material and transportation costs.
Excellent environmental adaptability: It possesses remarkable toughness and low-temperature performance, maintaining stable performance even in cold climates and expanding its application scope.
Reliable mechanical properties: Its quenched and tempered structure ensures uniform mechanical properties, enabling reliable performance during long-term service.
High economic value: The combination of good workability and durability simplifies the manufacturing process, extends product service life, and brings significant economic benefits to engineering projects.
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What is the density of S690QL?
The density of S690QL is approximately 7.85 g/cm³, the same as most carbon and low-alloy steels, facilitating weight calculation in designs.
Is S690QL magnetic?
Yes, S690QL is ferromagnetic due to its iron-based composition. This property is irrelevant for most structural applications but should be noted in magnetic environments.
What is the maximum operating temperature of S690QL?
Its maximum safe operating temperature is around 200°C. Beyond this, its mechanical strength and toughness may decrease significantly.
Does S690QL come in different surface finishes?
Yes, common surface finishes include hot-rolled, pickled and oiled, or shot-blasted. The finish depends on application requirements and corrosion protection needs.
Can S690QL be used in cold environments?
Yes, its low-temperature toughness (down to -20°C) makes it suitable for cold regions, such as northern construction and refrigeration equipment.
What is the weight of a 10mm thick S690QL plate per square meter?
A 10mm thick S690QL plate weighs about 78.5 kg per square meter, calculated by density × thickness × area.
Is S690QL a low-alloy steel?
Yes, S690QL is a low-alloy high-strength steel. It contains small amounts of alloying elements to improve strength without sacrificing weldability.
What is the delivery condition of S690QL?
It is delivered in quenched and tempered (Q&T) condition, which imparts its high yield strength and excellent toughness.
Can S690QL be used for crane booms?
Absolutely, S690QL is ideal for crane booms. Its high strength reduces boom weight while ensuring load-bearing capacity and operational safety.
What is the elongation of S690QL?
The minimum elongation of S690QL is 14% (for thickness ≤16mm). This ensures sufficient ductility for structural deformation under load.
Does S690QL require post-weld heat treatment?
It is recommended for thick sections or high-stress applications. Post-weld heat treatment relieves residual stress and improves joint toughness.