S690 Steel: Properties and Key Applications Overview
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Table Of Content
Table Of Content
S690 steel, classified as a high yield structural steel, is part of the European standard EN 10025-6. It is primarily characterized by its high strength and excellent weldability, making it suitable for a variety of demanding applications in construction and engineering. The primary alloying elements in S690 steel include carbon (C), manganese (Mn), and silicon (Si), with small amounts of other elements such as chromium (Cr), nickel (Ni), and molybdenum (Mo) that enhance its mechanical properties.
Comprehensive Overview
S690 steel is known for its high yield strength, typically ranging from 690 MPa to 960 MPa, which allows for thinner sections in structural applications without compromising strength. This characteristic not only reduces the weight of structures but also leads to cost savings in materials and transportation. The steel exhibits good toughness and ductility, which are critical for applications subjected to dynamic loads.
Advantages of S690 Steel:
- High Strength-to-Weight Ratio: Enables the design of lighter structures.
- Excellent Weldability: Suitable for various welding processes, facilitating fabrication.
- Good Toughness: Maintains performance in low-temperature environments.
Limitations of S690 Steel:
- Cost: Higher than conventional structural steels due to alloying elements.
- Brittleness at Low Temperatures: Requires careful consideration in cold environments.
- Limited Corrosion Resistance: May require protective coatings in aggressive environments.
S690 steel has gained significant traction in the market due to its performance in heavy construction, mining, and offshore applications. Its historical significance lies in its development to meet the increasing demands for stronger and more efficient materials in modern engineering.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S690QL | USA | Closest equivalent to EN 10025-6 |
| ASTM | A572 Grade 65 | USA | Minor compositional differences |
| EN | S690QL | Europe | Commonly used in structural applications |
| DIN | 1.8928 | Germany | Equivalent to S690QL |
| JIS | SM490YB | Japan | Similar yield strength but different composition |
| ISO | 10025-6 | International | Standard for high yield strength structural steels |
The differences between these grades can significantly affect performance. For instance, while S690QL and A572 Grade 65 may have similar yield strengths, their chemical compositions and toughness characteristics can vary, influencing their suitability for specific applications.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.10 - 0.20 |
| Mn (Manganese) | 1.20 - 1.60 |
| Si (Silicon) | 0.10 - 0.50 |
| Cr (Chromium) | 0.30 max |
| Ni (Nickel) | 0.30 max |
| Mo (Molybdenum) | 0.10 - 0.15 |
The primary alloying elements in S690 steel play crucial roles:
- Carbon (C): Increases strength and hardness but can reduce ductility.
- Manganese (Mn): Enhances hardenability and toughness.
- Silicon (Si): Improves deoxidation and increases strength.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Yield Strength (0.2% offset) | Quenched & Tempered | Room Temp | 690 - 960 MPa | 100 - 139 ksi | ASTM E8 |
| Tensile Strength | Quenched & Tempered | Room Temp | 770 - 1100 MPa | 112 - 160 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | Room Temp | 12 - 20% | 12 - 20% | ASTM E8 |
| Hardness (Brinell) | Quenched & Tempered | Room Temp | 200 - 300 HB | 200 - 300 HB | ASTM E10 |
| Impact Strength (Charpy) | Quenched & Tempered | -20°C | 27 J | 20 ft-lbf | ASTM E23 |
The combination of high yield and tensile strength makes S690 steel suitable for applications that require significant load-bearing capacity while maintaining structural integrity. Its elongation and impact strength ensure that it can withstand dynamic loads without fracturing.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | - | 7850 kg/m³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | 20 °C | 50 W/m·K | 34.5 BTU·in/h·ft²·°F |
| Specific Heat Capacity | 20 °C | 460 J/kg·K | 0.11 BTU/lb·°F |
| Coefficient of Thermal Expansion | 20 - 100 °C | 12 x 10⁻⁶ /K | 6.67 x 10⁻⁶ /°F |
The density of S690 steel contributes to its weight, which is an important factor in structural design. The thermal conductivity and specific heat capacity are critical for applications involving heat transfer, while the coefficient of thermal expansion must be considered in environments with temperature fluctuations.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-5 | 20-60 | Fair | Risk of pitting corrosion |
| Sulfuric Acid | 10-20 | 20-40 | Poor | Not recommended |
| Sea Water | - | 20-30 | Fair | Requires protective coating |
S690 steel exhibits moderate resistance to corrosion, particularly in marine environments where chlorides are present. However, it is susceptible to pitting and stress corrosion cracking (SCC) in aggressive environments, necessitating protective measures such as coatings or cathodic protection.
When compared to other high-strength steels like S355 and S460, S690 offers superior strength but may require more rigorous corrosion protection strategies due to its lower inherent resistance.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400 | 752 | Suitable for structural applications |
| Max Intermittent Service Temp | 500 | 932 | Limited oxidation resistance |
| Scaling Temperature | 600 | 1112 | Risk of scaling at elevated temperatures |
At elevated temperatures, S690 steel maintains its strength but may experience oxidation, which can affect its performance in high-temperature applications. Careful consideration of service conditions is essential to avoid degradation.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 | Good for thin sections |
| TIG | ER70S-2 | Argon | Suitable for precision work |
| SMAW | E7018 | - | Requires preheat |
S690 steel is highly weldable, making it suitable for various welding processes. Preheating may be necessary to avoid cracking, especially in thicker sections. Post-weld heat treatment can enhance the mechanical properties of the weld.
Machinability
| Machining Parameter | [S690 Steel] | [AISI 1212] | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Requires high-speed tooling |
| Typical Cutting Speed (Turning) | 30 m/min | 50 m/min | Use carbide tools for efficiency |
S690 steel presents challenges in machining due to its high strength. Optimal conditions and tooling are essential to achieve desired surface finishes and tolerances.
Formability
S690 steel can be cold and hot formed, but its high yield strength requires careful consideration of bend radii and work hardening effects. Cold forming may lead to increased hardness, while hot forming can improve ductility.
Heat Treatment
| Treatment Process | Temperature Range (°C) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Quenching | 850 - 900 | 30 min | Air or Oil | Increased hardness and strength |
| Tempering | 500 - 700 | 1 - 2 hours | Air | Improved toughness and ductility |
Heat treatment processes significantly influence the microstructure of S690 steel, enhancing its mechanical properties. Quenching increases hardness, while tempering reduces brittleness, making the steel more ductile.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
|---|---|---|---|
| Construction | High-rise buildings | High yield strength, weldability | Reduces structural weight |
| Mining | Excavator buckets | Toughness, impact resistance | Handles heavy loads |
| Offshore | Oil rigs | Corrosion resistance, strength | Endures harsh environments |
| Transportation | Bridges | High strength-to-weight ratio | Enhances load capacity |
Other applications include:
- Heavy machinery components
- Structural frames for industrial buildings
- Crane booms and supports
S690 steel is chosen for these applications due to its ability to withstand significant loads while maintaining structural integrity, making it ideal for demanding environments.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | [S690 Steel] | [S355 Steel] | [S460 Steel] | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Yield Strength | 690 MPa | 355 MPa | 460 MPa | Higher strength in S690 |
| Corrosion Aspect | Fair | Good | Fair | S355 offers better corrosion resistance |
| Weldability | Excellent | Good | Fair | S690 is easier to weld |
| Machinability | Moderate | Good | Poor | S690 requires specialized tooling |
| Approx. Relative Cost | High | Moderate | High | Cost considerations for projects |
| Typical Availability | Moderate | High | Moderate | S355 is more commonly available |
When selecting S690 steel, factors such as cost, availability, and specific application requirements must be considered. While it offers superior strength, its higher cost and potential challenges in machining and corrosion resistance may influence the decision.
In summary, S690 steel is a versatile and robust material that excels in high-strength applications, making it a preferred choice in modern engineering and construction. Its unique properties and fabrication characteristics provide significant advantages, although careful consideration of its limitations is essential for optimal performance.
