EN 10025EN 10025-6 S690QL
EN 10025-6 S690QL Quenched and Tempered High Strength Structural Steel
Comprehensive data sheet for S690QL steel: chemical composition, mechanical properties, thermal and electrical properties, international equivalents, and application guide.
Thermo-mechanically rolled or heat-treated by quenching and tempering
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EN 10025EN 10025-6 S690QL Introduction
S690QL is a high-strength, quenched and tempered structural steel designated in EN 10025-6. The 'S' indicates structural steel, '690' the minimum yield strength of 690 MPa for thin gauges, 'Q' the quenching and tempering delivery condition, and 'L' Charpy impact testing at -50°C with a minimum energy of 27 J. This steel combines high strength with excellent toughness and good weldability, making it suitable for heavy-loaded welded structures operating in low-temperature environments. It is widely used in mobile crane booms, offshore platforms, bridges, and earthmoving equipment.
EN 10025EN 10025-6 S690QL Chemical Composition
The chemical requirements for S690QL ensure a balanced alloy design that achieves high strength through quenching and tempering while maintaining weldability and toughness. Maximum values are provided unless otherwise stated. Alloying elements such as Cr, Ni, and Mo are controlled to obtain hardenability and strength. Micro-alloying elements (V, Nb, Ti) refine grain size and improve toughness. Note: The actual carbon equivalent (CEV) is typically restricted to ≤0.52–0.54 depending on thickness.
| Chemical Element | Specified Value (max %) | Remarks |
|---|---|---|
| C | 0.20 | Maximum for ≤50 mm; lower for thicker gauges |
| Si | 0.80 | Deoxidizer and strength contributor |
| Mn | 1.70 | Enhances hardenability and strength; maximum for ≤50 mm |
| P | 0.025 | Maximum; low to avoid temper embrittlement |
| S | 0.015 | Maximum; minimizes sulfide inclusions |
| Al | 0.015 min (total) | Fine grain practice; required for quenched & tempered steels |
| Cr | 1.50 | Improves hardenability; may be lower for thin gauges |
| Ni | 2.0 | Enhances toughness at low temperatures; maximum value |
| Mo | 0.70 | Increases hardenability and reduces temper embrittlement |
| Cu | 0.50 | Residual element from scrap; minor precipitation strengthening |
| Nb | 0.06 | Grain refiner; optional, typical micro-alloying addition |
| V | 0.12 | Precipitation strengthening; optional |
| Ti | 0.05 | Grain refinement and nitrogen binding; optional |
| N | 0.015 | Maximum; lower for improved toughness |
| B | 0.005 (if added) | Trace hardenability element; not always present |
EN 10025EN 10025-6 S690QL Thermal and Electrical Physical Properties
Physical properties are provided as typical values for quenched and tempered structural steel at room temperature unless otherwise indicated. These may vary slightly with exact chemical composition and heat treatment condition.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | 20 °C |
| Elastic Modulus (E) | 210 | GPa | 20 °C, tension |
| Shear Modulus (G) | 81 | GPa | Calculated, G ≈ E / (2(1+ν)) |
| Poisson's Ratio (ν) | 0.3 | – | Typical for steels |
| Thermal Expansion Coefficient (α) | 11.1 | 10⁻⁶·K⁻¹ | 20–100 °C |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶·K⁻¹ | 20–200 °C |
| Thermal Expansion Coefficient (α) | 13.0 | 10⁻⁶·K⁻¹ | 20–300 °C |
| Thermal Conductivity (λ) | 46 | W/(m·K) | At 20 °C, typical for low alloy steel |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρe) | 0.25 | µΩ·m | At 20 °C, typical for structural steel |
EN 10025EN 10025-6 S690QL Mechanical Properties
Mechanical properties are guaranteed for quenched and tempered condition. Values depend on nominal thickness (t) and specimen orientation. The table lists minimum requirements according to EN 10025-6. Note: Bend test is performed to 180° with no cracks. Impact energy relates to Charpy-V specimens (longitudinal or transverse) at -50°C.
| Property | Specified Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | 690 | MPa | t ≤ 50 mm |
| Yield Strength (ReH) | 650 | MPa | 50 < t ≤ 100 mm |
| Yield Strength (ReH) | 630 | MPa | 100 < t ≤ 150 mm |
| Tensile Strength (Rm) | 770–940 | MPa | t ≤ 50 mm |
| Tensile Strength (Rm) | 760–930 | MPa | 50 < t ≤ 100 mm |
| Tensile Strength (Rm) | 710–900 | MPa | 100 < t ≤ 150 mm |
| Elongation after fracture (A) | 14 | % | t ≤ 50 mm, gauge length 5.65√So |
| Elongation after fracture (A) | 14 | % | 50 < t ≤ 100 mm |
| Elongation after fracture (A) | 14 | % | 100 < t ≤ 150 mm |
| Charpy Impact Energy (KV, Long.) | 27 (min) | J | -50 °C, longitudinal specimen |
| Charpy Impact Energy (KV, Trans.) | 27 (min) | J | -50 °C, transverse specimen |
| Bend Test (180°) | D = 3a | – | t ≤ 16 mm, no cracks; D = mandrel diameter, a = thickness |
EN 10025EN 10025-6 S690QL Completely Equivalent Material Standards and Replacement Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (ISO) | ISO 4950-2 | E690QL | Fully equivalent, thickness ranges aligned |
| China | GB/T 16270 | Q690E (Q690QL1?) | Q690E at -40°C; for -50°C check Q690D or special agreement |
| USA | ASTM A514 / A709 | Grade B, H, F, etc. (not exact) | A514 grades have comparable strength but different chemical restrictions and no designated -50°C impact |
EN 10025EN 10025-6 S690QL Application Introduction
S690QL is designed for demanding structural applications requiring high strength-to-weight ratio and reliable impact toughness at very low temperatures. It is extensively used in welded constructions where weight saving and safety are critical. Typical industries and products include:
Product Applications: Mobile crane telescopic booms, lattice booms, and outriggers, Offshore platform legs, chords, and spudcans, Long-span highway and railway bridge girders, Load-carrying frames for mining trucks, High-pressure hydraulic cylinders and valve bodies, Wind turbine tower sections (bottom segments)
Processed into products: Crane boom sections, jib sections, and turntable frames, Jack-up rig leg chords and rack chocks, Bridge deck plates, stiffeners, and crossbeams, Dump body liners and wear plates (combined with abrasion-resistant steels), Welded box-shaped hollow sections for structural nodes, Thick-walled pressure vessels heads and shells
Application industries: Lifting and transportation equipment (mobile and crawler cranes), Offshore and marine engineering (jack-up rig legs, platform structures), Bridge construction (orthotropic decks, box girders), Mining and earthmoving machinery (dump truck bodies, excavator booms), Pressure vessels and storage tanks (subject to stress and low temperature), Civil engineering and heavy structural columns
EN 10025EN 10025-6 S690QL Recommended Similar or Substitute Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| EU | EN 10025-6 | S690Q | Same strength but impact at 0°C or -20°C, lower toughness |
| EU | EN 10025-6 | S690QL1 | Impact at -20°C, otherwise similar |
| EU | EN 10025-6 | S890QL | Higher strength (890 MPa min yield), for weight-critical designs |
| USA | ASTM A517 | Grade B, H, etc. | Quenched and tempered with 690 MPa yield, some grades have -45°C impact; check chemical composition |
| Japan | JIS G 3128 | SHY 685 | High yield strength steel with low temperature toughness, similar mechanical properties |
Notes:
Welding: Preheating (typically 100–200 °C) and interpass temperature control are required depending on thickness and hydrogen levels. Low-hydrogen consumables are recommended. Post-weld heat treatment (PWHT) may be necessary for thick components but must be carefully designed to avoid loss of temper. Cold forming: The material can be cold formed; minimum bending radii of 3t (t ≤ 8 mm) to 4t for thicker sections are suggested. Delivery conditions: Products are usually supplied shot-blasted and primed. Certificates according to EN 10204-3.1 are standard.
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