St 35 Steel: Properties and Key Applications Overview
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Table Of Content
Table Of Content
St 35 Steel, classified as a low-carbon mild steel, is primarily utilized in the manufacturing of pipes and tubes, particularly in the German engineering sector. This steel grade is characterized by its excellent weldability, moderate strength, and good ductility, making it suitable for various applications where these properties are essential. The primary alloying element in St 35 is carbon, with a typical carbon content of around 0.05% to 0.15%. This low carbon content contributes to its malleability and ease of fabrication, while also providing sufficient strength for structural applications.
Comprehensive Overview
St 35 steel is widely recognized for its balance of strength and ductility, which is crucial in applications requiring both toughness and the ability to withstand deformation. Its low carbon content results in a material that is easy to weld and form, making it a preferred choice in the construction of pipelines and structural components.
Advantages:
- Weldability: St 35 can be easily welded using conventional methods, which is a significant advantage in pipe manufacturing.
- Ductility: The steel exhibits good elongation properties, allowing it to be formed into complex shapes without cracking.
- Cost-Effectiveness: As a low-carbon steel, it is generally more affordable than higher alloyed steels.
Limitations:
- Strength: While adequate for many applications, St 35 does not possess the high strength characteristics of medium or high-carbon steels.
- Corrosion Resistance: It is more susceptible to corrosion compared to stainless steels or alloyed grades, necessitating protective coatings in certain environments.
Historically, St 35 has been significant in the development of the German steel industry, particularly in the production of seamless pipes and tubes for various engineering applications. Its market position remains strong due to its versatility and reliability in structural applications.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| DIN | St 35 | Germany | Closest equivalent to AISI 1020 |
| EN | S235JR | Europe | Similar properties but higher yield strength |
| UNS | G10350 | USA | Minor compositional differences |
| ASTM | A106 Gr. B | USA | Used for high-temperature service |
| JIS | STK 400 | Japan | Comparable in mechanical properties |
The table above highlights several standards and equivalents for St 35 steel. Notably, while S235JR offers higher yield strength, St 35's lower carbon content provides better ductility, making it more suitable for applications requiring extensive forming.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.05 - 0.15 |
| Mn (Manganese) | 0.30 - 0.60 |
| Si (Silicon) | 0.10 - 0.40 |
| P (Phosphorus) | ≤ 0.035 |
| S (Sulfur) | ≤ 0.025 |
The primary alloying elements in St 35 steel include carbon, manganese, and silicon. Carbon is crucial for enhancing strength and hardness, while manganese improves hardenability and tensile strength. Silicon serves as a deoxidizer during steel production and contributes to overall strength.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric - SI Units) | Typical Value/Range (Imperial Units) | Reference Standard for Test Method |
|---|---|---|---|---|
| Tensile Strength | Annealed | 350 - 450 MPa | 51 - 65 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | 200 - 250 MPa | 29 - 36 ksi | ASTM E8 |
| Elongation | Annealed | 20 - 25% | 20 - 25% | ASTM E8 |
| Hardness (Brinell) | Annealed | 120 - 160 HB | 120 - 160 HB | ASTM E10 |
| Impact Strength | -40°C (-40°F) | 27 J | 20 ft-lbf | ASTM E23 |
The mechanical properties of St 35 steel indicate its suitability for applications requiring moderate strength and good ductility. The combination of tensile and yield strength makes it ideal for structural components that undergo dynamic loading.
Physical Properties
| Property | Condition/Temperature | Value (Metric - SI Units) | Value (Imperial Units) |
|---|---|---|---|
| Density | Room Temperature | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | Room Temperature | 50 W/m·K | 34.5 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temperature | 0.49 kJ/kg·K | 0.12 BTU/lb·°F |
| Coefficient of Thermal Expansion | Room Temperature | 11.5 x 10⁻⁶ /K | 6.4 x 10⁻⁶ /°F |
The density and melting point of St 35 steel indicate its robustness, while its thermal conductivity and specific heat capacity are relevant for applications involving thermal processing. The coefficient of thermal expansion is critical in applications where temperature fluctuations occur.
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% | 20-40°C (68-104°F) | Poor | Susceptible to general corrosion |
| Alkaline Solutions | 5-10% | 20-60°C (68-140°F) | Fair | Risk of stress corrosion cracking |
St 35 steel exhibits moderate corrosion resistance, particularly in environments with chlorides and alkaline solutions. It is prone to pitting and stress corrosion cracking, especially in high-stress applications. Compared to stainless steels, such as AISI 304, which offer excellent corrosion resistance, St 35 requires protective coatings or treatments in corrosive environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400 °C | 752 °F | Suitable for moderate temperatures |
| Max Intermittent Service Temp | 500 °C | 932 °F | Short-term exposure only |
| Scaling Temperature | 600 °C | 1112 °F | Risk of oxidation beyond this temp |
St 35 steel maintains its mechanical properties at elevated temperatures, but prolonged exposure above 400 °C can lead to oxidation and scaling. It is essential to consider these limits in applications involving heat.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 mix | Good penetration |
| TIG | ER70S-2 | Argon | Clean welds, low distortion |
| SMAW | E7018 | - | Suitable for thicker sections |
St 35 steel is highly weldable, making it suitable for various welding processes. Preheating may be necessary for thicker sections to avoid cracking. Post-weld heat treatment can enhance the properties of the weld zone.
Machinability
| Machining Parameter | St 35 Steel | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 70 | 100 | Good machinability, but care needed to avoid work hardening |
| Typical Cutting Speed (Turning) | 80 m/min | 120 m/min | Use sharp tools for best results |
St 35 steel offers good machinability, though it can work-harden if not handled properly. Optimal cutting speeds and tool selection are critical for achieving desired surface finishes.
Formability
St 35 steel is suitable for both cold and hot forming processes. Its low carbon content allows for significant deformation without cracking, making it ideal for applications requiring intricate shapes. However, care must be taken to avoid excessive work hardening during cold forming.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 600 - 700 °C / 1112 - 1292 °F | 1 - 2 hours | Air or water | Softening, improved ductility |
| Normalizing | 850 - 900 °C / 1562 - 1652 °F | 1 - 2 hours | Air | Refine grain structure |
| Quenching | 800 - 850 °C / 1472 - 1562 °F | 30 minutes | Oil or water | Increase hardness |
Heat treatment processes such as annealing and normalizing are essential for enhancing the mechanical properties of St 35 steel. These treatments refine the microstructure, improving toughness and ductility.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Oil & Gas | Pipeline construction | Good weldability, moderate strength | Essential for safe transport |
| Automotive | Chassis components | Ductility, formability | Allows for complex shapes |
| Construction | Structural beams | Strength, cost-effectiveness | Economical and reliable |
St 35 steel is widely used in various industries, including oil and gas, automotive, and construction. Its combination of properties makes it a versatile choice for applications requiring strength, ductility, and ease of fabrication.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | St 35 Steel | S235JR | AISI 1020 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | Moderate Strength | Higher Yield Strength | Lower Strength | S235JR offers better load-bearing capacity |
| Key Corrosion Aspect | Fair | Good | Poor | S235JR has better resistance to corrosion |
| Weldability | Excellent | Good | Good | All grades are weldable, but St 35 is preferred for ease |
| Machinability | Good | Fair | Excellent | AISI 1020 is easier to machine |
| Formability | Excellent | Good | Fair | St 35 is superior for forming |
| Approx. Relative Cost | Moderate | Moderate | Low | Cost varies with market conditions |
| Typical Availability | High | High | High | All grades are commonly available |
When selecting St 35 steel, considerations include its mechanical properties, corrosion resistance, and fabrication characteristics. While it is cost-effective and widely available, its limitations in strength and corrosion resistance compared to alternative grades should be evaluated based on specific application requirements.
In summary, St 35 steel is a reliable choice for various engineering applications, particularly where moderate strength and excellent weldability are required. Its historical significance and continued relevance in modern manufacturing underscore its value in the materials science landscape.
