Q620F High-Strength Quenched & Tempered Steel Plate (GB/T 16270)
Q620F High-Strength Structural Steel Plate (GB/T 16270) - Properties & Equivalents
Comprehensive material data for Q620F steel plate according to GB/T 16270: chemical composition, mechanical and physical properties, international equivalents, and typical applications in heavy machinery and structural engineering.
Hot rolling, quenching and tempering, welding, cutting, cold forming (limited), machining
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Q620F High-Strength Quenched & Tempered Steel Plate Introduction
Q620F is a low-alloy high-strength structural steel plate produced to the Chinese standard GB/T 16270, supplied in the quenched and tempered condition. With a minimum yield strength of 620 MPa and excellent low-temperature toughness down to -60°C, it is designed for heavy welded structures subjected to high static and dynamic loads. The 'F' designation guarantees Charpy V-notch impact energy of at least 27 J at -60°C. Key characteristics include:
- High strength-toughness balance, enabling weight reduction without sacrificing safety
- Good weldability using appropriate preheating and low-hydrogen processes
- Consistent through-thickness properties for thick sections
- Available in plate form for structural fabrication
Typical applications span construction machinery, bridges, offshore platforms, pressure vessels, and mining equipment.
Q620F High-Strength Quenched & Tempered Steel Plate Chemical Composition
The chemical composition of Q620F steel is strictly controlled to achieve high strength and superior low-temperature toughness. Maximum limits for impurities and alloying elements ensure reliable weldability and hardenability. The heat analysis values conform to GB/T 16270-2009; product analysis tolerances may apply.
| Element | Value (max, unless range) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.15 | |
| Silicon (Si) | ≤0.50 | |
| Manganese (Mn) | 1.00 – 1.60 | For thickness ≤50 mm; may be adjusted for heavier plates |
| Phosphorus (P) | ≤0.020 | |
| Sulfur (S) | ≤0.010 | |
| Niobium (Nb) | ≤0.06 | Optional grain refiner |
| Vanadium (V) | ≤0.08 | Optional strengthening element |
| Titanium (Ti) | ≤0.05 | Optional grain refiner |
| Chromium (Cr) | ≤0.50 | |
| Nickel (Ni) | ≤1.00 | Improves toughness |
| Copper (Cu) | ≤0.50 | |
| Molybdenum (Mo) | ≤0.50 | Enhances hardenability |
| Boron (B) | ≤0.005 | Minor addition for hardenability |
Q620F High-Strength Quenched & Tempered Steel Plate Thermal and Electrical Physical Properties
Physical properties are representative for low-alloy quenched and tempered steels and vary slightly with exact chemical composition and heat treatment. These data serve as general engineering references and are not mandatory values per GB/T 16270.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Modulus of Elasticity (E) | 210 | GPa | Tensile modulus |
| Shear Modulus (G) | 81 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | — | Elastic range |
| Thermal Expansion Coefficient (α) | 11.5 – 13.0 | ×10⁻⁶/K | Between 20°C and 200°C |
| Thermal Conductivity (λ) | 40 – 45 | W/(m·K) | At 20°C; decreases with temperature |
| Specific Heat Capacity | 460 – 500 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρₑ) | 0.25 – 0.35 | μΩ·m | At 20°C |
Q620F High-Strength Quenched & Tempered Steel Plate Mechanical Properties
The mechanical properties are guaranteed for quenched and tempered plates as specified in GB/T 16270-2009. Values vary with plate thickness. Transverse tensile specimens are used for thickness ≥3 mm. Impact tests are performed on Charpy V-notch specimens at -60°C.
| Property | Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥620 | MPa | Plate thickness 3–50 mm |
| Yield Strength (ReH) | ≥600 | MPa | Plate thickness >50–100 mm |
| Yield Strength (ReH) | ≥580 | MPa | Plate thickness >100–150 mm |
| Tensile Strength (Rm) | 700 – 890 | MPa | Plate thickness 3–50 mm |
| Tensile Strength (Rm) | 690 – 880 | MPa | Plate thickness >50–100 mm |
| Tensile Strength (Rm) | 680 – 880 | MPa | Plate thickness >100–150 mm |
| Elongation after Fracture (A) | ≥15 | % | L0=5.65√S0, transverse, thickness 3–50 mm |
| Elongation after Fracture (A) | ≥15 | % | Thickness >50–100 mm |
| Elongation after Fracture (A) | ≥14 | % | Thickness >100–150 mm |
| Bend Test (180°) | D = 3a | — | Thickness ≤16 mm, a = specimen thickness |
| Bend Test (180°) | D = 4a | — | Thickness >16–50 mm |
| Bend Test (180°) | D = 5a | — | Thickness >50–100 mm |
| Charpy V-notch Impact Energy (KV2) | ≥27 | J | Longitudinal, at -60°C, average of 3 tests |
Q620F High-Strength Quenched & Tempered Steel Plate Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-6:2019 | S620QL1 | Direct equivalent – Q+T, guaranteed impact at -60°C, similar chemical limits |
| International | ISO 4950-2:1995 (Withdrawn) | S620Q (or FeE620Q) | Closest match; lower toughness classification unless modified |
| China | GB/T 16270-2009 | Q620F | Original specification |
| Japan | JIS G 3128 (SHY 685) | SHY 685 | Approximate – yield 685 MPa, toughness class must be specified for -60°C |
| USA | ASTM A514/A514M | Multiple grades (B, H, F, Q) | Approximate – min. yield 690 MPa, toughness at -18°C or lower; not identical to -60°C unless supplementary requirement specified |
| Germany (historical) | DIN EN 10025-6 (former) | S620QL1 | Same as current EN |
Q620F High-Strength Quenched & Tempered Steel Plate Application Introduction
Q620F is primarily used in applications requiring a combination of high strength, excellent toughness, and good weldability. Its guaranteed impact energy at -60°C makes it particularly suitable for arctic environments and structures subject to dynamic loads. The steel is supplied in the quenched and tempered condition and is typically fabricated by welding, with controlled preheating and interpass temperatures to avoid cold cracking.
Product Applications: Mobile crane telescopic booms and lattice sections, Excavator booms, arms, and buckets, Heavy-duty structural frames for mining trucks, Bridge box girders, arch ribs, and pylon components, Offshore platform lift legs and nodes, Penstocks and high-pressure pipelines, Wind turbine tower flanges and transition pieces (where high strength is needed)
Processed into products: Welded steel plates cut and formed into box sections, Machined and bolted joints for crane connections, Fatigue-critical weldments in bridges and offshore structures, Heavy plate components subject to multi-axial loads, Wear-resistant attachments (using overlay or specialized inserts)
Application industries: Heavy machinery and mobile equipment (crane booms, excavator arms, bulldozer blades), Bridge construction (orthotropic decks, main girders, high-load bearing members), Offshore engineering (jack-up rigs, platform structures, ice-breaker hulls), Mining and earthmoving machinery (dump truck bodies, buckets, crusher housings), Pressure vessels and penstocks (thick-walled cylinders requiring high strength and toughness), Shipbuilding (special vessels, ice-class ships)
Q620F High-Strength Quenched & Tempered Steel Plate Similar and Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 16270 | Q550F | Lower strength class but identical toughness guarantees (-60°C); may be considered where 550 MPa yield suffices |
| China | GB/T 16270 | Q690F | Higher strength class (690 MPa) with same -60°C toughness; for weight-sensitive designs |
| Europe | EN 10025-6 | S620Q | Same strength, but guaranteed impact at -20°C; use where low-temperature requirement is less severe |
| Europe | EN 10025-6 | S690QL1 | Higher strength (690 MPa) with -60°C toughness; an upgrade alternative |
| USA | ASTM A514 | Grade H | Minimum yield 690 MPa; typically used in structural applications; supplementary toughness tests can improve cryogenic performance |
| Japan | JIS G 3106 | SM570 | Rolled steel with lower strength (~570 MPa), not Q+T; used where strength demands are moderate |
Notes:
- Q620F plates are typically produced with a thickness range of 3 to 150 mm, wider widths available from major mills.
- Welding procedures should follow recommendations for high-strength quenched and tempered steels (e.g., AWS D1.1, ISO 15614). Low-hydrogen electrodes and appropriate preheat (typically 75–150°C) are essential to avoid hydrogen-induced cracking.
- Strain aging sensitivity is low; however, post-weld stress relief (if required) should be performed below the tempering temperature to avoid strength loss.
- This steel is not intended for hot forming above the tempering temperature; cold forming is possible with large radii and springback compensation.
- Third-party certification (e.g., DNV, ABS, CCS) is often available for marine and offshore applications upon request.
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