S350GD Steel: Properties and Key Applications
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Table Of Content
Table Of Content
S350GD steel is a hot-dip galvanized steel grade primarily used in the automotive and construction industries. It falls under the category of low-carbon steel, specifically designed for applications requiring good formability and corrosion resistance. The primary alloying elements in S350GD include iron (Fe), carbon (C), and zinc (Zn), with zinc being crucial for its galvanization process, which enhances its corrosion resistance.
Comprehensive Overview
S350GD steel is classified as a low-carbon steel, notable for its excellent balance of strength, ductility, and corrosion resistance. The primary alloying element is zinc, which is applied through a hot-dip galvanization process, providing a protective layer that significantly enhances the steel's durability in corrosive environments. The carbon content is typically low, which contributes to its good weldability and formability.
Key Characteristics:
- High Strength: S350GD exhibits a minimum yield strength of 350 MPa, making it suitable for structural applications.
- Good Ductility: The low carbon content allows for significant deformation without fracture.
- Corrosion Resistance: The zinc coating provides excellent protection against rust and corrosion, extending the lifespan of components made from this steel.
Advantages:
- Cost-Effective: The galvanization process is economical, providing long-lasting protection without the need for additional coatings.
- Versatile Applications: Suitable for various applications, including automotive parts, building components, and appliances.
Limitations:
- Temperature Sensitivity: The mechanical properties can degrade at elevated temperatures.
- Limited High-Strength Applications: While strong, it may not be suitable for applications requiring ultra-high strength materials.
S350GD has gained popularity in the market due to its balance of performance and cost, making it a preferred choice in many engineering applications.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S350GD | International | Closest equivalent to EN 10346 |
| EN | S350GD | Europe | Commonly used in automotive applications |
| ASTM | A653 | USA | Similar properties but different coating specifications |
| JIS | G3302 | Japan | Minor compositional differences to be aware of |
The table above highlights the various standards and equivalents for S350GD steel. While these grades may be considered equivalent, subtle differences in composition and coating processes can affect their performance in specific applications. For instance, ASTM A653 may have different coating thickness requirements, which can influence corrosion resistance.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| Fe (Iron) | Balance |
| C (Carbon) | 0.06 - 0.12 |
| Zn (Zinc) | 0.5 - 1.5 |
| Mn (Manganese) | 0.3 - 0.8 |
| P (Phosphorus) | ≤ 0.04 |
| S (Sulfur) | ≤ 0.03 |
The primary alloying elements in S350GD steel play crucial roles:
- Zinc (Zn): Provides corrosion resistance through galvanization.
- Carbon (C): Enhances strength but must be kept low to maintain ductility.
- Manganese (Mn): Improves hardenability and strength.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|
| Yield Strength (0.2% offset) | Hot-Dip Galvanized | 350 MPa | 50.8 ksi | ASTM E8 |
| Tensile Strength | Hot-Dip Galvanized | 450 MPa | 65.3 ksi | ASTM E8 |
| Elongation | Hot-Dip Galvanized | 22% | 22% | ASTM E8 |
| Hardness (Brinell) | Hot-Dip Galvanized | 120 HB | 120 HB | ASTM E10 |
| Impact Strength | - | 27 J (at -20°C) | 20 ft-lbf (at -4°F) | ASTM E23 |
The mechanical properties of S350GD steel make it suitable for structural applications where strength and ductility are critical. Its yield strength of 350 MPa ensures it can withstand significant loads, while its elongation percentage indicates good formability.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | - | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | 20 °C | 50 W/m·K | 34.5 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | - | 0.46 kJ/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | - | 0.0000017 Ω·m | 0.0000017 Ω·in |
The density and melting point of S350GD steel indicate its suitability for high-temperature applications. The thermal conductivity and specific heat capacity suggest it can effectively dissipate heat, which is advantageous in automotive applications.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3% | 25 °C | Fair | Risk of pitting |
| Sulfuric Acid | 10% | 20 °C | Poor | Not recommended |
| Sodium Hydroxide | 5% | 25 °C | Good | Limited exposure acceptable |
S350GD steel demonstrates good resistance to atmospheric corrosion and moderate resistance to chlorides. However, it is susceptible to corrosion in acidic environments, which can lead to rapid degradation. Compared to other grades like S235 and S355, S350GD offers superior corrosion resistance due to its galvanization, making it a preferred choice in environments prone to moisture and corrosive agents.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 200 °C | 392 °F | Above this, properties may degrade |
| Max Intermittent Service Temp | 250 °C | 482 °F | Short-term exposure acceptable |
| Scaling Temperature | 300 °C | 572 °F | Risk of oxidation increases |
At elevated temperatures, S350GD steel maintains its mechanical properties up to a certain limit. Beyond 200 °C, the risk of oxidation and loss of strength increases, making it unsuitable for high-temperature applications without special considerations.
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 | Requires preheat for thick sections |
S350GD steel is generally considered weldable, but care must be taken to avoid issues such as hydrogen-induced cracking. Preheating may be necessary for thicker sections to ensure proper fusion and minimize residual stresses.
Machinability
| Machining Parameter | S350GD | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Moderate machinability |
| Typical Cutting Speed (Turning) | 90 m/min | 150 m/min | Use sharp tools for best results |
S350GD exhibits moderate machinability, which can be improved with proper tooling and cutting conditions. It is essential to use sharp tools and appropriate cutting speeds to achieve optimal results.
Formability
S350GD steel is well-suited for both cold and hot forming processes. Its low carbon content allows for significant deformation without cracking, making it ideal for applications requiring complex shapes. The recommended bend radius is typically three times the material thickness to avoid cracking during forming.
Heat Treatment
| Treatment Process | Temperature Range (°C) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 600 - 700 | 1 - 2 hours | Air | Improve ductility and reduce hardness |
| Normalizing | 850 - 900 | 1 - 2 hours | Air | Refine grain structure |
Heat treatment processes such as annealing and normalizing can significantly alter the microstructure of S350GD steel, enhancing its ductility and reducing residual stresses. These treatments are crucial for applications requiring improved formability.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Automotive | Body panels | High strength, good formability | Lightweight and durable |
| Construction | Structural components | Corrosion resistance, weldability | Long-lasting performance |
| Appliances | Washing machines | Good machinability, aesthetic finish | Cost-effective and reliable |
- Automotive: Used for body panels and structural components due to its strength and corrosion resistance.
- Construction: Ideal for structural applications where durability is essential.
- Appliances: Commonly used in manufacturing washing machines and other household appliances.
S350GD is chosen for these applications due to its excellent balance of mechanical properties, corrosion resistance, and cost-effectiveness.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | S350GD | S235 | S355 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Yield Strength | 350 MPa | 235 MPa | 355 MPa | Higher strength in S355 |
| Corrosion Resistance | Good | Fair | Fair | Superior due to galvanization |
| Weldability | Good | Excellent | Good | S235 has better weldability |
| Machinability | Moderate | Good | Moderate | S235 is easier to machine |
| Formability | Good | Excellent | Good | S235 offers better formability |
| Approx. Relative Cost | Moderate | Low | High | S350GD is cost-effective |
| Typical Availability | Common | Very Common | Common | S235 is widely available |
When selecting S350GD steel, considerations include its mechanical properties, corrosion resistance, and cost-effectiveness. While S235 offers better weldability and formability, S350GD's galvanization provides superior corrosion resistance, making it a preferred choice for many applications. Additionally, its moderate cost and availability make it an attractive option for manufacturers.
In conclusion, S350GD steel is a versatile material that balances strength, ductility, and corrosion resistance, making it suitable for a wide range of applications in the automotive, construction, and appliance industries. Its unique properties and cost-effectiveness position it favorably in the market, ensuring its continued relevance in modern engineering.
