S690Q and S690QL Structural Steel Plate
S690Q and S690QL are quenched and tempered high-yield structural steel plates manufactured in accordance with European standard EN 10025-6. As mainstream high-strength lightweight steel materials, they are widely applied in heavy engineering, offshore facilities, lifting machinery and construction projects in cold regions.
These two grades deliver identical yield strength (minimum 690 MPa for plate thickness ≤50 mm), tensile strength and baseline chemical composition. Their fundamental difference lies solely in low-temperature Charpy V-notch impact toughness. The suffix "L" in S690QL denotes enhanced low-temperature toughness performance.
S690Q vs S690QL High-Strength Structural Steel Plate Core Selection Principle
| Selection Dimension | Choose S690Q | Choose S690QL |
|---|---|---|
| Minimum Operating Temperature | Long-term minimum ambient temperature ≥ -20℃ | Long-term service temperature below -20℃ |
| Project Type | Temperate zone construction machinery, indoor steel structure, regular crane booms, quarrying equipment | Offshore wind power foundations, marine platforms, alpine mining vehicles, cold-region bridge main girders |
| Load Condition | Conventional static or quasi-static high-strength bearing | Cyclic fatigue load-bearing, thick-plate welded key components requiring anti-layer tearing |
| Budget Consideration | Tight material budget, controls raw material expenditure | Higher upfront cost but eliminates brittle fracture risks under cold shock load |
| Core Advantage | Meets conventional high-strength bearing requirements at lower cost | Ultra-low temperature toughness ensures structural safety in extreme cold environments |
Please provide our technical engineers with your project's operating temperature, maximum plate thickness and load conditions. We will offer a complimentary technical grade selection report and material consumption optimization plan for S690Q / S690QL, helping you prevent design defects caused by overspecified steel grades or insufficient low-temperature toughness.
S690Q vs S690QL High-Strength Structural Steel Plate Specification
| Product Name | S690Q S690QL High-Strength Structural Steel Plate |
| Standard | EN 10025-6 |
| Steel Type | High Yield Strength Quenched & Tempered Structural Steel |
| Manufacturing Process | Quenched and Tempered (Q&T) |
| Supply Thickness | 6–200 mm |
| Supply Width | 1,500–4,000 mm |
| Supply Length | 3,000–18,000 mm |
| Delivery Condition | Quenched & Tempered (Q) |
| Surface Finish | As Rolled, Shot Blasted & Painted |
| Edge Condition | Mill Edge (ME), Trimmed Edge (TE) |
S690Q vs S690QL High-Strength Plate Chemical Composition
| Element | C | Si | Mn | P | S | B | Cr | Mo | Ni | Cu |
|---|---|---|---|---|---|---|---|---|---|---|
| S690Q Max | 0.20 | 0.80 | 1.70 | 0.020 | 0.010 | 0.005 | 1.50 | 0.70 | 2.00 | 0.50 |
| S690QL Max | 0.20 | 0.80 | 1.70 | 0.020 | 0.010 | 0.005 | 1.50 | 0.70 | 2.00 | 0.50 |
S690Q vs S690QL High-Strength Plate Mechanical Property
| Parameter | S690Q (EN 10025-6) | S690QL / S690QL1 (EN 10025-6) |
|---|---|---|
| Minimum Yield Strength (ReH) | 690 MPa | 690 MPa |
| Tensile Strength (Rm) | 770 - 940 MPa | 770 - 940 MPa |
| Minimum Elongation (A5) | 14% | 14% |
| Impact Test Temperature | +20°C | -40°C (for QL1) / -60°C (for QL2) |
| Min. Impact Energy (KV) | Typically 30J (subject to thickness) | 40J at -40°C (QL1) / 30J at -60°C (QL2) |
S690Q vs S690QL High-Strength Steel Plate Weldability & Fabrication Performance Analysis
Common Characteristics of Both Grades
Both steel grades are supplied in quenched and tempered condition. Secondary overall heat treatment of finished structural components is prohibited. Low-hydrogen welding consumables (E11018-G, ER110S-G) shall be adopted for welding work. The plates are suitable for CNC flame cutting, plasma cutting, drilling, cold bending forming and surface sandblasting for anti-corrosion treatment. The low carbon equivalent design reduces hardening tendency in the heat-affected zone (HAZ).
Differentiated Welding Process Requirements
- Plate thickness ＜15 mm: Preheat temperature of 80–100°C;
- Plate thickness ≥15 mm: Preheat to 100–120°C, followed by post-weld hydrogen removal soaking for 1 to 2 hours. Applicable to conventional workshop fabrication with stable ambient temperature.
- Preheating above 120–150°C is mandatory for plates over 12 mm thick.
- Welding heat input shall be strictly controlled within the range of 0.8–1.5 kJ/mm.
- Slow cooling shall be implemented by covering weld joints with thermal insulation cotton after welding.
- For on-site welding under outdoor low-temperature conditions, temporary heated shelters are required to prevent low-temperature cracking at welded joints caused by excessive cooling rate.
Machining and Forming Performance
S690QL features a finer internal grain structure, leading to less tool wear during CNC finish machining. Both grades share the same minimum bending radius requirement for cold bending forming (≥ 3 times the plate thickness).
S690Q vs S690QL Plate Life Cycle Cost (LCC) Comparison
Life cycle cost covers initial material purchase, processing & welding cost, operation maintenance, failure loss and service life, the core indicator for large long-cycle projects.
| Cost Item | S690Q | S690QL |
|---|---|---|
| Upfront Raw Material Cost | Baseline | +12%~15% premium |
| Welding Processing Cost | Standard processing expense | +8%~10% (higher preheating & heat preservation energy consumption, stricter welding procedure qualification PQR) |
| In-Service Failure Risk | High cold brittle fracture risk below -20℃, sudden structural failure leads to equipment shutdown & maintenance loss | Near-zero brittle fracture risk in cold environment, stable fatigue performance reduces overhaul frequency |
| Service Life (Cold Region) | 5~7 years for outdoor cold service | Extend service life to 10~13 years |
| Overall LCC (Temperate Zone) | Lower total cost | Unnecessary premium, higher comprehensive cost |
| Overall LCC (Cold/Offshore Zone) | High hidden failure cost | Balanced total cost, obvious economic advantage in full life cycle |
S690Q vs S690QL Plate Direct Market Price Comparison
Ex-factory price of S690Q: Calculated on conventional thickness (10~60 mm), the prevailing export spot price serves as the bottom cost benchmark.
Ex-factory price of S690QL: 12%–15% higher per metric ton than S690Q. The price premium comes from high-standard production procedures including clean steel smelting, low-temperature impact testing, stringent inclusion control and comprehensive finished product inspection.
Price fluctuation note: For heavy plates over 80 mm, the price gap widens to 18% due to heightened difficulties in uniform quenching and tempering (Q&T) heat treatment required to guarantee stable low-temperature toughness.
Get in touch with our sales team to obtain the latest FOB breakbulk quotations for Tianjin Port and Shanghai Port, spot stock lists and custom rolling quotations for heavy-gauge plates of S690Q and S690QL. Volume discounts are available for orders exceeding 50 metric tons.
S690Q vs S690QL High-Strength Structural Plate Typical Application Scenarios
Primary Applications of S690Q (Temperate Climate, Service Temperature ≥ -20°C)
- Telescopic booms for truck-mounted cranes and mobile wheeled cranes supplied to European markets;
- Crusher frames for quarry operations and support structures for stationary mine conveyors;
- Steel columns, steel beams and load-bearing platforms for indoor heavy-duty factory buildings;
- Main girders of conventional highway steel bridges in mid-latitude regions;
- Structural components for fixed container spreaders at large container yards.
Primary Applications of S690QL (Low-temperature, Offshore and Fatigue-prone Service Conditions)
- Transition pieces for offshore wind turbine foundations and main load-bearing beams of offshore platforms;
- Chassis for open-pit mining dump trucks in frigid zones and snow removal engineering equipment for cold regions;
- Transnational railway bridges in cold climates and temporary emergency steel bridges at high latitudes;
- Main beams of hydraulic supports for northern coal mines and reinforcement plates for low-temperature pressure pipelines;
- Chassis of polar engineering equipment and reinforcement structural parts for ship decks.
One-Stop Service Support from GNEE Steel
As a professional supplier specializing in EN-standard high-strength structural steel plates with 18 years of export experience, GNEE delivers full-chain supporting services for projects adopting S690Q and S690QL steel.
We supply Mill Test Certificates complying with EN 10204 3.1/3.2, CE certificates, classification society approvals from DNV, BV and ABS, Z-direction property certificates, ultrasonic testing reports, and a full set of documents required for customs clearance and project acceptance.
Both containerized shipment and breakbulk vessel transportation are available, along with door-to-door delivery services covering major ports. Professional steel-specific packaging is adopted to avoid rusting and deformation during ocean transportation.
Services including surface shot blasting, anti-rust paint coating and tailor-made nesting cutting plans are available to elevate material utilization rate and reduce raw material wastage.
FAQ
Can S690Q be directly replaced by S690QL for cost reduction?
No, replacing S690Q with S690QL will not reduce costs. S690QL is a higher-grade material that costs roughly 10% to 15% more per ton because it undergoes stricter processing and testing to guarantee impact toughness down to -40°C, whereas S690Q is only rated down to -20°C.
Can S690QL be used in all working conditions of S690Q?
Yes. S690QL can be used in all working conditions where S690Q is used, and it can also handle colder environments. The letter "L" stands for low temperature, meaning S690QL has stricter impact toughness testing at -40°C, while S690Q is tested at -20°C or 0°C. Both share the same minimum yield strength of 690 MPa.
Do S690Q and S690QL require post-weld stress relief annealing?
No, S690Q and S690QL do not generally require post-weld stress relief annealing. In fact, standard post-weld heat treatment (PWHT) is often discouraged because high heat can ruin the quenched and tempered microstructure, causing a severe drop in tensile strength and toughness.
What are the differences between S690QL and S690 steel?
The primary difference is that S690QL is specifically impact-tested at low temperatures (the "L" stands for low temperature, down to -40°C), whereas base S690 (often referred to as S690Q) is rated for standard or moderate temperature conditions. Both share a minimum yield strength of 690 MPa.
