S700 Steel: Properties and Key Applications in Construction
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Table Of Content
Table Of Content
S700 steel is a high yield structural steel grade that falls under the category of low-alloy high-strength steel. It is primarily characterized by its high yield strength, which makes it suitable for various structural applications where weight reduction and strength are critical. The primary alloying elements in S700 steel include carbon (C), manganese (Mn), silicon (Si), and small amounts of other elements such as chromium (Cr) and nickel (Ni). These elements contribute to the steel's overall mechanical properties and performance.
Comprehensive Overview
S700 steel is classified as a low-alloy high-strength structural steel, designed to provide superior strength while maintaining good weldability and formability. Its high yield strength, typically around 700 MPa (101.5 ksi), allows for thinner sections in structural applications, which can lead to weight savings and reduced material costs. The steel's composition is optimized for structural integrity, making it a preferred choice in construction, heavy machinery, and transportation sectors.
Key Characteristics:
- High Yield Strength: Enables the use of thinner sections without compromising structural integrity.
- Good Weldability: Suitable for various welding processes, facilitating ease of fabrication.
- Excellent Toughness: Maintains performance in low-temperature environments.
Advantages (Pros):
- Weight Efficiency: Thinner sections reduce overall weight, beneficial for transport and construction.
- Cost-Effectiveness: Less material usage can lead to lower costs in large-scale applications.
- Versatility: Applicable in various industries, including construction, automotive, and shipbuilding.
Limitations (Cons):
- Corrosion Resistance: May require protective coatings in aggressive environments.
- Cost Variability: Prices can fluctuate based on alloying elements and market demand.
Historically, S700 steel has gained prominence in modern engineering due to its ability to meet the demands of high-performance applications while providing a balance of strength and ductility.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| EN | S700MC | Europe | Closest equivalent to S700QL |
| ASTM | A572 Grade 50 | USA | Similar yield strength but different composition |
| JIS | SM490A | Japan | Minor compositional differences |
| DIN | S690QL | Germany | Higher yield strength, suitable for similar applications |
| ISO | 10025-6 | International | General standard for structural steels |
The table above highlights various standards and equivalent grades for S700 steel. Notably, while grades like S690QL offer higher yield strengths, they may not possess the same balance of ductility and weldability as S700, making S700 a more versatile choice for certain applications.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.12 - 0.20 |
| Mn (Manganese) | 1.00 - 1.60 |
| Si (Silicon) | 0.10 - 0.50 |
| Cr (Chromium) | 0.00 - 0.30 |
| Ni (Nickel) | 0.00 - 0.30 |
| Mo (Molybdenum) | 0.00 - 0.10 |
| P (Phosphorus) | ≤ 0.025 |
| S (Sulfur) | ≤ 0.015 |
The primary alloying elements in S700 steel play crucial roles in its performance:
- Manganese (Mn): Enhances hardenability and tensile strength.
- Silicon (Si): Improves strength and oxidation resistance.
- Chromium (Cr): Increases hardness and corrosion resistance.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|
| Yield Strength (0.2% offset) | Quenched & Tempered | 700 - 900 MPa | 101.5 - 130.5 ksi | ASTM E8 |
| Tensile Strength | Quenched & Tempered | 770 - 950 MPa | 111.5 - 137.5 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | 14 - 20% | 14 - 20% | ASTM E8 |
| Reduction of Area | Quenched & Tempered | 40 - 50% | 40 - 50% | ASTM E8 |
| Hardness (Brinell) | Quenched & Tempered | 235 - 300 HB | 235 - 300 HB | ASTM E10 |
| Impact Strength | -40°C | 27 J | 20 ft-lbf | ASTM E23 |
The mechanical properties of S700 steel make it suitable for applications requiring high strength and toughness. Its yield strength allows for efficient load-bearing structures, while its elongation and reduction of area indicate good ductility, essential for forming processes.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | - | 7850 kg/m³ | 490 lb/ft³ |
| Melting Point | - | 1420 - 1540 °C | 2590 - 2810 °F |
| Thermal Conductivity | 20 °C | 50 W/m·K | 34.5 BTU·in/h·ft²·°F |
| Specific Heat Capacity | - | 460 J/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | - | 0.0000017 Ω·m | 0.0000017 Ω·ft |
The density of S700 steel contributes to its weight efficiency in structural applications. Its thermal conductivity and specific heat capacity are important for applications involving heat treatment or exposure to varying temperatures.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-5 | 20-60 °C (68-140 °F) | Fair | Risk of pitting |
| Acids | 10-20 | 20-40 °C (68-104 °F) | Poor | Not recommended |
| Alkaline | 5-10 | 20-60 °C (68-140 °F) | Fair | Risk of stress corrosion |
| Atmospheric | - | - | Good | Requires protective coating |
S700 steel exhibits moderate corrosion resistance, particularly in atmospheric conditions. However, it is susceptible to pitting in chloride environments and should be protected in acidic or alkaline conditions. Compared to stainless steels, S700's corrosion resistance is limited, necessitating protective measures in harsh environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400 °C | 752 °F | Suitable for structural applications |
| Max Intermittent Service Temp | 500 °C | 932 °F | Short-term exposure only |
| Scaling Temperature | 600 °C | 1112 °F | Risk of oxidation beyond this temp |
| Creep Strength Considerations | 400 °C | 752 °F | Begins to lose strength |
S700 steel maintains good mechanical properties at elevated temperatures, making it suitable for applications where heat exposure is a factor. However, care must be taken to avoid prolonged exposure to temperatures above 400 °C, as this can lead to significant strength loss.
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 | Excellent for precision work |
| Stick | E7018 | - | Suitable for outdoor work |
S700 steel is known for its good weldability, making it suitable for various welding processes. Preheating may be required to avoid cracking, especially in thicker sections. Post-weld heat treatment can enhance the mechanical properties of the weld.
Machinability
| Machining Parameter | S700 Steel | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Moderate machinability |
| Typical Cutting Speed (Turning) | 50 m/min | 80 m/min | Adjust based on tooling |
S700 steel has moderate machinability compared to benchmark steels like AISI 1212. Optimal conditions include using sharp tools and appropriate cutting speeds to minimize tool wear.
Formability
S700 steel exhibits good formability, allowing for cold and hot forming processes. However, due to its high strength, care must be taken to avoid excessive work hardening. Recommended bend radii should be adhered to in order to prevent cracking during forming.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Normalizing | 900 - 950 °C (1652 - 1742 °F) | 1 - 2 hours | Air | Refine grain structure |
| Quenching | 850 - 900 °C (1562 - 1652 °F) | 1 hour | Water/Oil | Increase hardness |
| Tempering | 500 - 700 °C (932 - 1292 °F) | 1 hour | Air | Reduce brittleness |
Heat treatment processes such as normalizing and tempering significantly affect the microstructure of S700 steel, enhancing its toughness and ductility while maintaining high strength.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Construction | High-rise buildings | High yield strength, good weldability | Structural integrity |
| Automotive | Chassis components | Lightweight, high strength | Weight reduction |
| Shipbuilding | Hull structures | Toughness, corrosion resistance | Durability in marine environments |
| Heavy Machinery | Load-bearing frames | High tensile strength | Safety and reliability |
Other applications include:
- Bridges and infrastructure
- Offshore platforms
- Rail vehicles
S700 steel is chosen for these applications due to its ability to provide strength without excessive weight, which is crucial in structural engineering.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | S700 Steel | S690QL | SM490A | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High yield strength | Higher yield strength | Moderate yield strength | S700 is more versatile for various applications |
| Key Corrosion Aspect | Fair resistance | Good resistance | Fair resistance | S690QL may be better for corrosive environments |
| Weldability | Good | Moderate | Good | S700 is easier to weld than S690QL |
| Machinability | Moderate | Moderate | Good | S700 is less machinable than SM490A |
| Formability | Good | Moderate | Good | S700 offers better formability than S690QL |
| Approx. Relative Cost | Moderate | Higher | Lower | S700 offers a balance of cost and performance |
| Typical Availability | Common | Less common | Common | S700 is widely available in the market |
When selecting S700 steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. Its balance of strength, ductility, and weldability makes it a preferred choice in many structural applications. However, for environments with high corrosion risks, alternative grades may be more appropriate.
In summary, S700 steel is a high-performance material that meets the demands of modern engineering applications, providing a combination of strength, versatility, and cost-effectiveness.
