EN10025-6 S620Q Steel
EN10025-6 S620Q Steel: High-Strength Quenched & Tempered Structural Steel
In-depth material data for EN10025-6 S620Q carbon and low-alloy high-strength structural steel, including chemical composition, mechanical and thermal properties, and global equivalents.
Welding, Hot-Dip Galvanizing, Cutting, Cold Forming (restricted), Machining
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EN10025-6 S620Q Steel Introduction
S620Q is a high-strength, quenched and tempered structural steel grade defined by the European standard EN 10025-6. It features a minimum yield strength of 620 MPa, making it suitable for demanding structural applications where weight reduction is critical without compromising load-bearing capacity. The 'Q' in its designation signifies its delivery condition: quenched and tempered. This heat treatment gives the steel an excellent combination of high strength, good toughness, and weldability. Its typical applications are in heavy machinery like mobile cranes, offshore structures, and steel bridges.
EN10025-6 S620Q Steel Chemical Composition
The chemical composition of S620Q is precisely controlled to achieve its high strength and toughness after quenching and tempering. Key elements include carbon for strength, manganese for hardenability and toughness, and microalloying elements like niobium, vanadium, and titanium for grain refinement and precipitation strengthening. This results in a fine-grained microstructure with excellent mechanical properties.
| Element | Standard Value (max %) | Remarks |
|---|---|---|
| Carbon (C) | 0.20 | For nominal thickness ≤ 50 mm; For 50< t ≤100 mm, max is 0.22 |
| Silicon (Si) | 0.80 | Standard limit |
| Manganese (Mn) | 1.70 | Standard limit |
| Phosphorus (P) | 0.025 | For long products, max is 0.030 |
| Sulfur (S) | 0.015 | For long products, max is 0.017 |
| Aluminium (Al), total | 0.015 min | Minimum specified for fine grain practice |
| Niobium (Nb) | 0.06 | Optional grain-refining element |
| Vanadium (V) | 0.12 | Optional grain-refining element |
| Titanium (Ti) | 0.05 | Optional grain-refining element |
| Nitrogen (N) | 0.015 | Standard limit |
| Molybdenum (Mo) | 0.70 | Optional element for hardenability |
| Boron (B) | 0.0050 | Optional element for hardenability |
| Zirconium (Zr) | 0.15 | Optional element |
| Chromium (Cr) | 1.50 | Optional element for hardenability |
| Nickel (Ni) | 2.0 | Optional element for toughness |
| Copper (Cu) | 0.50 | Optional element |
EN10025-6 S620Q Steel Thermal and Electrical Physical Properties
These physical properties are typical for low-alloy, quenched and tempered steels at room temperature unless otherwise specified. They are essential for engineering calculations involving thermal loading, deformation, heat transfer, and electrical applications. Data is representative of the grade at 20°C unless a range is stated.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | kg/dm³ or g/cm³ | At 20°C |
| Modulus of Elasticity (E) | 205 | GPa | At 20°C, longitudinal |
| Shear Modulus (G) | 80 | GPa | At 20°C |
| Poisson's ratio (ν) | 0.29 | Dimensionless | At 20°C |
| Thermal Expansion Coefficient (α) | 11.5 x 10⁻⁶ | K⁻¹ or /°C | Between 20°C and 100°C |
| Thermal Expansion Coefficient (α) | 12.5 x 10⁻⁶ | K⁻¹ or /°C | Between 20°C and 200°C |
| Thermal Expansion Coefficient (α) | 13.5 x 10⁻⁶ | K⁻¹ or /°C | Between 20°C and 400°C |
| Thermal Conductivity (λ) | 35 | W/(m·K) | At 20°C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρe) | 0.25 x 10⁻⁶ | Ω·m | At 20°C |
EN10025-6 S620Q Steel Mechanical Properties
The mechanical properties of S620Q are guaranteed for the quenched and tempered (+QT) condition at ambient temperature. The values depend on the nominal product thickness, with thicker products generally having slightly lower strength. The Charpy impact test demonstrates the steel's ability to resist brittle fracture at low temperatures, with different quality grades (L, L1, M, etc.) specifying different testing temperatures.
| Property | Standard Requirement Value | Unit | Test Condition |
|---|---|---|---|
| Minimum yield strength (ReH) | 620 | MPa | Nominal thickness (t) ≤ 50 mm |
| Minimum yield strength (ReH) | 580 | MPa | 50 mm < Nominal thickness (t) ≤ 100 mm |
| Minimum yield strength (ReH) | 560 | MPa | 100 mm < Nominal thickness (t) ≤ 150 mm |
| Tensile strength (Rm) | 700 - 890 | MPa | Nominal thickness (t) ≤ 50 mm |
| Tensile strength (Rm) | 650 - 830 | MPa | 50 mm < Nominal thickness (t) ≤ 100 mm |
| Tensile strength (Rm) | 620 - 800 | MPa | 100 mm < Nominal thickness (t) ≤ 150 mm |
| Minimum elongation after fracture (A) | 14 | % | Gauge length L0 = 5.65√S0 on longitudinal specimens, t ≤ 100 mm |
| Minimum elongation after fracture (A) | 13 | % | Gauge length L0 = 5.65√S0 on longitudinal specimens, 100 < t ≤ 150 mm |
| Charpy impact energy (KV2) | 30 | J | Test temp: 0°C (For quality grades S620QL/QL1) |
| Charpy impact energy (KV2) | 27 | J | Test temp: -20°C (For quality grades S620Q/Q1) |
| Charpy impact energy (KV2) | 27 | J | Test temp: -40°C (For quality grades S620QL1/Q) |
| Charpy impact energy (KV2) | 27 | J | Test temp: -60°C (For quality grade S620QL1) |
EN10025-6 S620Q Steel Completely Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (ISO) | ISO 4951-2 | S620Q | Completely equivalent designation and technical requirements. |
| China (CN) | GB/T 16270 | Q620D | Chemical composition and properties are equivalent, D indicates impact test at -20°C. |
| China (CN) | GB/T 16270 | Q620E | Chemical composition and properties are equivalent, E indicates impact test at -40°C. |
| Germany (DE) | DIN EN 10025-6 | S620Q | Adoption of European standard, technical requirements are identical. |
EN10025-6 S620Q Steel Application Introduction
S620Q steel is the material of choice for dynamically and statically loaded structures that demand extremely high yield strength, superior toughness, and good weldability. Its high strength-to-weight ratio allows engineers to design lighter structures, reducing fabrication and transportation costs while enhancing payload capacity. The quenching and tempering (+QT) process ensures a fine grain structure, essential for low-temperature toughness and resistance to brittle fracture. It is predominantly used in the fabrication of mobile cranes, heavy-duty vehicles, and complex offshore structures where service, safety, and performance are critical.
Product Applications: All-terrain and crawler crane telescopic booms, Heavy truck chassis frames and outrigger beams, Offshore platform modules, jack-up rig legs, and crane pedestals, Highway and railway bridge girders and arches, Large-diameter high-pressure penstocks and spiral cases for hydropower plants, Mine haul truck bodies and loader arms
Processed into products: Welded box-section booms, High-strength pins and bushings, Complex welded nodes and chord sections for trusses, Bending-resistant flange plates for girders, Cold-formed structural hollow sections (with restricted forming ratios), Machined load-bearing blocks and supports
Application industries: Heavy Lifting and Transport Engineering, Offshore and Marine Engineering, Civil Engineering and Steel Bridge Construction, Mining and Earth-moving Machinery, Pressure Vessel and Boiler Manufacturing (when specified)
EN10025-6 S620Q Steel Similar/Comparable Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A514/A517 | Grade S | A quenched and tempered alloy steel plate with similar 620 MPa yield strength, typically used in similar structural applications. Note tighter sulfur limits in EN. |
| USA | ASTM A709 | HPS 100W | High-Performance Steel with 690 MPa yield, offering superior weldability and toughness compared to S620Q, but at a higher strength level. |
| China (CN) | GB/T 1591 | Q690D | A high-strength structural steel with a min. 690 MPa yield strength. Slightly higher strength, but can be a suitable alternative if design allows. |
| Japan | JIS G 3128 | SHY 685N | A high yield strength steel plate for welded structures. The tensile strength is comparable to S620Q. |
Notes:
Weldability: S620Q has good weldability and can be welded using all conventional processes. However, strict adherence to the manufacturer's welding procedure specification (WPS) is mandatory. The heat input and preheat/interpass temperatures must be controlled to avoid softening in the heat-affected zone (HAZ). Low-hydrogen consumables are essential to prevent cold cracking.
Cold Forming: Due to its high strength and limited ductility compared to mild steel, cold forming requires larger bending radii. Hot forming is possible but will alter the quenched and tempered microstructure; a subsequent re-heat treatment may be necessary to restore the original properties.
Corrosion Protection: The material is not inherently weather-resistant. For exposed applications, protective coatings such as painting or hot-dip galvanizing are standard. The high silicon content can sometimes lead to thicker, more brittle zinc layers during galvanizing, a known effect for silicon-killed steels.
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