EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate
S690QL High-Strength Quenched & Tempered Steel Plate | EN 10025-6 Properties & Composition
Explore the comprehensive technical data for EN 10025-6 S690QL, a 690 MPa yield strength quenched and tempered structural steel. Chemical composition, mechanical properties, thermal and electrical characteristics, equivalent grades, and application guide.
Cutting, cold forming (limited), hot forming (with re-quenching and tempering), welding (with proper precautions), machining
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EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Introduction
S690QL is a high-strength structural steel grade defined by the European standard EN 10025-6 for hot-rolled products of structural steels. Delivered in the quenched and tempered condition, it offers a minimum yield strength of 690 MPa at room temperature, making it suitable for weight-saving, heavy-load applications. The 'Q' denotes quenched and tempered, 'L' indicates low-temperature impact testing at -40°C. Typical uses include crane booms, heavy machinery, bridges, and offshore structures. It provides excellent weldability when using appropriate procedures and a balance of high strength with moderate toughness.
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Chemical Composition
The chemical composition of S690QL is precisely controlled to achieve the required mechanical properties after quenching and tempering. Key elements include carbon for strength, manganese and chromium for hardenability, molybdenum to resist temper embrittlement, and micro-alloying elements like niobium and titanium for grain refinement. Maximum limits are specified for harmful elements such as phosphorus and sulfur to ensure toughness.
| Element | Typical Value (max unless range given) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.20% | According to EN 10025-6, for thicknesses ≤ 50 mm; for >50 mm ≤100 mm: ≤0.22% |
| Silicon (Si) | ≤ 0.80% | Deoxidizer, improves strength |
| Manganese (Mn) | ≤ 1.70% | Enhances hardenability |
| Phosphorus (P) | ≤ 0.020% | Max limit for low-temperature toughness |
| Sulfur (S) | ≤ 0.010% | Max limit to avoid hot shortness |
| Chromium (Cr) | ≤ 1.50% | Optional alloying element, hardenability |
| Nickel (Ni) | ≤ 2.0% | Optional, improves toughness |
| Molybdenum (Mo) | ≤ 0.70% | Optional, hardenability and tempering resistance |
| Copper (Cu) | ≤ 0.50% | Residual limit |
| Nitrogen (N) | ≤ 0.015% | Limited to prevent strain ageing |
| Titanium (Ti) | ≤ 0.05% | Micro-alloying for grain refinement |
| Niobium (Nb) | ≤ 0.06% | Micro-alloying element |
| Vanadium (V) | ≤ 0.12% | Optional micro-alloying |
| Boron (B) | ≤ 0.005% | Optional, strongly increases hardenability |
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Thermal & Electrical Physical Properties
The following physical properties are typical for quenched and tempered low-alloy high-strength steel at room temperature, unless otherwise noted. They are not part of the mandatory EN 10025-6 delivery requirements but are essential for design calculations involving heat transfer, thermal stress, and electrical conductivity.
| Property | Typical Value | Unit | Test Conditions |
|---|---|---|---|
| Density (ρ) | ~ 7.85 | g/cm³ | At 20°C |
| Elastic Modulus (E) | ~ 210 | GPa | At 20°C |
| Shear Modulus (G) | ~ 81 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | ~ 0.3 | — | At 20°C |
| Thermal Expansion Coefficient (α) | ~ 11.5 × 10⁻⁶ | K⁻¹ | 20–100°C |
| Thermal Expansion Coefficient (α) | ~ 12.5 × 10⁻⁶ | K⁻¹ | 20–200°C |
| Thermal Expansion Coefficient (α) | ~ 13.5 × 10⁻⁶ | K⁻¹ | 20–300°C |
| Thermal Conductivity (λ) | ~ 42 | W/(m·K) | At 20°C |
| Specific Heat Capacity (cp) | ~ 460 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | ~ 0.25 × 10⁻⁶ | Ω·m | At 20°C |
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Mechanical Properties
The mechanical properties of S690QL are guaranteed for products in the quenched and tempered condition. The yield strength and tensile strength decrease with increasing product thickness, as specified in the standard. Impact toughness is tested at -40°C (designated by 'L'). Bending requirements ensure adequate ductility for fabrication.
| Property | Required Value | Unit | Test Conditions / Thickness Range |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 690 | MPa | Thickness ≤ 50 mm |
| Yield Strength (ReH) | ≥ 670 | MPa | Thickness > 50 mm ≤ 100 mm |
| Yield Strength (ReH) | ≥ 630 | MPa | Thickness > 100 mm ≤ 150 mm |
| Tensile Strength (Rm) | 770 – 940 | MPa | Thickness ≤ 50 mm |
| Tensile Strength (Rm) | 740 – 900 | MPa | Thickness > 50 mm ≤ 100 mm |
| Tensile Strength (Rm) | 700 – 880 | MPa | Thickness > 100 mm ≤ 150 mm |
| Elongation after fracture (A) | ≥ 14 | % | Longitudinal, L0 = 5.65√S0, thickness ≤ 50 mm |
| Elongation after fracture (A) | ≥ 14 | % | Longitudinal, thickness > 50 mm ≤ 100 mm |
| Elongation after fracture (A) | ≥ 14 | % | Longitudinal, thickness > 100 mm ≤ 150 mm |
| Impact energy (KV) | ≥ 27 | J | At -40°C, longitudinal, min. avg. value |
| Bend test (bending angle / mandrel diameter) | Crack-free at 180° bend | — | Mandrel diameter 3× thickness (t ≤ 16 mm); increase as per standard for thicker sections |
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Exact Equivalent Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10025-6:2019 | S690QL | Original designation, direct replacement |
| Germany | DIN EN 10025-6 | S690QL | Identical adoption of EN standard |
| United Kingdom | BS EN 10025-6 | S690QL | Identical; formerly BS 7191 690QL |
| France | NF EN 10025-6 | S690QL | Identical European standard |
| Italy | UNI EN 10025-6 | S690QL | Identical |
| Spain | UNE EN 10025-6 | S690QL | Identical |
| Sweden | SS-EN 10025-6 | S690QL | Identical; previously SS 2142, SS 2144 |
| Finland | SFS-EN 10025-6 | S690QL | Identical |
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Application Introduction
S690QL is engineered for structural applications where high strength permits weight and material reduction, while still providing good weldability and adequate toughness at low temperatures. Typical applications demand a combination of static and dynamic loading resistance. Due to its quenched and tempered condition, careful welding heat input control and preheating guidance are essential to preserve heat-affected zone properties.
Product Applications: Mobile crane telescopic booms, Heavy-duty truck chassis frames, Girder bridges and box bridges, Heavy-lift ships and offshore platform components, Mining excavator buckets and booms, Hydraulic cylinders, Wind turbine tower wall sections (in thicker sections)
Processed into products: Welded structural hollow sections (fabricated from plate), Cut-into-shapes for heavy machinery brackets, Flanges and webs in plate girders, Pump and compressor housings (when weight is critical), Load-bearing shafts and pins (when alternative to forgings), Reinforcement ribs and stiffeners in large structures
Application industries: Crane and lifting equipment manufacturing, Heavy transport and mobile machinery, Bridge engineering, Offshore and marine structures, Mining and earth-moving machinery, Pressure vessel and boiler construction (within applicable pressure codes), Hydroelectric penstocks and gates
EN 10025-6 S690QL High-Strength Quenched & Tempered Steel Plate Similar or Comparable Alternative Grades
| Country/Region | Standard | Grade | Remarks / Features |
|---|---|---|---|
| USA / International | ASTM A514 / A517 | Grade F, H, Q, etc. | Quenched and tempered alloy steel plate with 690 MPa yield but different composition. Equivalent to S690Q (without low-temp guarantee). Use only if impact at -40°C not required. |
| Japan | JIS G 3128 | SHY 685N / SHY 685NS | High yield strength steel for welded structures; similar strength, but check impact test temperature (N: -50°C may exceed S690QL requirement). |
| China | GB/T 16270 | Q690D | Hight-strength quenched and tempered steel; impact at -20°C, slightly lower toughness than QL. Q690E requires -40°C and is closer equivalent. |
| ISO | ISO 4950-2 | ISO E690QL | Earlier international standard, now superseded but technically similar. Composition ranges may vary. |
| Germany (older) | DIN EN 10137-2 (withdrawn) | S690QL | Predecessor standard; same designation but check for updated requirements. |
Notes:
Welding: S690QL requires low-hydrogen welding consumables and control of heat input (typically 1.5 – 3.5 kJ/mm) to avoid softening in the heat-affected zone. Preheating temperatures up to 150°C are common, depending on plate thickness. Post-weld heat treatment is generally not recommended due to risk of strength reduction.
Cold Forming: Limited cold bending is possible; the minimum bending radius should be at least 3 times the plate thickness for transverse bends. Hot forming above Ac1 requires re-quenching and tempering.
Corrosion Resistance: Not inherently corrosion resistant; protection such as painting or galvanizing is required for outdoor applications. Consult the specific EN 10025-6 delivery addendum for testing, tolerances, and inspection.
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