St 37 Steel Properties and Key Applications Overview
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Table Of Content
St 37 Steel, also known as S235JR, is a low-carbon structural steel grade widely used in construction and engineering applications. Classified as a non-alloy structural steel, it primarily consists of iron with a small percentage of carbon, typically around 0.17% to 0.20%. The low carbon content contributes to its excellent weldability and machinability, making it a preferred choice for various structural components.
Comprehensive Overview
St 37 steel is characterized by its good mechanical properties, including moderate tensile strength and yield strength, which make it suitable for a variety of structural applications. The primary alloying elements in St 37 steel include manganese, which enhances hardenability and strength, and silicon, which improves resistance to oxidation. The steel's inherent properties include good ductility, toughness, and weldability, allowing it to be easily formed and shaped into various structural components.
| Advantages (Pros) | Limitations (Cons) |
|---|---|
| Excellent weldability | Limited corrosion resistance |
| Good machinability | Lower strength compared to higher-grade steels |
| Cost-effective | Not suitable for high-temperature applications |
| Versatile applications | Susceptible to pitting in corrosive environments |
Historically, St 37 steel has been a staple in the construction industry, particularly in Europe, due to its balance of strength and ductility. Its common applications range from beams and columns in buildings to frames for machinery and vehicles. The steel's market position remains strong due to its widespread availability and cost-effectiveness.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| EN | S235JR | Europe | Closest equivalent to St 37 |
| DIN | St 37 | Germany | Historical designation |
| ASTM | A36 | USA | Similar properties, but with different chemical composition |
| JIS | SS400 | Japan | Comparable, but may have different yield strength |
| ISO | S235 | International | General equivalent, similar applications |
While St 37 and its equivalents like S235JR and A36 are often considered interchangeable, subtle differences in chemical composition and mechanical properties can affect performance in specific applications. For instance, A36 may have slightly higher yield strength, making it more suitable for certain structural applications.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.12 - 0.20 |
| Mn (Manganese) | 0.30 - 0.60 |
| Si (Silicon) | 0.10 - 0.40 |
| P (Phosphorus) | ≤ 0.045 |
| S (Sulfur) | ≤ 0.045 |
The primary role of carbon in St 37 steel is to enhance strength and hardness. Manganese improves hardenability and toughness, while silicon contributes to oxidation resistance. The low levels of phosphorus and sulfur help maintain ductility and weldability.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Annealed | Room Temp | 370 - 510 MPa | 54 - 74 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | Room Temp | 235 MPa | 34 ksi | ASTM E8 |
| Elongation | Annealed | Room Temp | 20% | 20% | ASTM E8 |
| Hardness (Brinell) | Annealed | Room Temp | 120 - 160 HB | 120 - 160 HB | ASTM E10 |
| Impact Strength | Charpy V-notch | -20°C (-4°F) | ≥ 27 J | ≥ 20 ft-lbf | ASTM E23 |
The combination of moderate tensile and yield strength, along with good ductility, makes St 37 steel suitable for structural applications where load-bearing capacity and flexibility are essential. Its impact strength at low temperatures ensures performance in colder environments.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | Room Temp | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1420 - 1540 °C | 2590 - 2810 °F |
| Thermal Conductivity | Room Temp | 50 W/m·K | 34.5 BTU·in/h·ft²·°F |
| Specific Heat Capacity | Room Temp | 0.49 kJ/kg·K | 0.12 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.0000017 Ω·m | 0.0000017 Ω·in |
The density of St 37 steel indicates its weight, which is crucial for structural calculations. The thermal conductivity suggests good heat dissipation properties, while the specific heat capacity indicates how much energy is required to raise its temperature, relevant in applications involving temperature fluctuations.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Atmospheric | Varies | Ambient | Fair | Susceptible to rust |
| Chlorides | Varies | Ambient | Poor | Risk of pitting |
| Acids | Varies | Ambient | Poor | Not recommended |
| Alkaline | Varies | Ambient | Fair | Moderate resistance |
St 37 steel exhibits limited corrosion resistance, particularly in chloride-rich environments where pitting can occur. Compared to stainless steels like AISI 304, which offer excellent corrosion resistance, St 37 is less suitable for applications exposed to harsh environments. In comparison to other carbon steels, it performs adequately but requires protective coatings or treatments in corrosive settings.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400 °C | 752 °F | Limited oxidation resistance |
| Max Intermittent Service Temp | 450 °C | 842 °F | Risk of scaling |
| Scaling Temperature | 600 °C | 1112 °F | Begins to lose strength |
At elevated temperatures, St 37 steel can experience oxidation and scaling, which can compromise its structural integrity. Its performance diminishes beyond 400 °C, making it unsuitable for high-temperature applications such as pressure vessels or heat exchangers.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 mix | Good results with proper technique |
| TIG | ER70S-2 | Argon | Excellent for thin sections |
| SMAW | E7018 | - | Requires preheat for thick sections |
St 37 steel is known for its excellent weldability, making it suitable for various welding processes. Preheating may be necessary for thicker sections to avoid cracking. Post-weld heat treatment can enhance the mechanical properties of the welds.
Machinability
| Machining Parameter | St 37 Steel | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 70% | 100% | Good for general machining |
| Typical Cutting Speed (Turning) | 80 m/min | 120 m/min | Adjust for tool wear |
St 37 steel offers good machinability, although it is not as easily machined as some higher-carbon steels. Optimal cutting speeds and tooling should be employed to achieve the best results.
Formability
St 37 steel exhibits good formability, allowing for cold and hot forming processes. It can be bent, stamped, and shaped without significant risk of cracking. The work hardening effect should be considered during extensive forming operations.
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 | Refined grain structure |
| Quenching | 800 - 850 °C / 1472 - 1562 °F | 30 minutes | Water or oil | Increased hardness |
Heat treatment processes such as annealing and normalizing can significantly alter the microstructure of St 37 steel, enhancing its mechanical properties. Annealing softens the steel, while normalizing refines the grain structure, improving strength and toughness.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Construction | Structural beams | Good strength, weldability | Cost-effective and versatile |
| Automotive | Chassis components | Ductility, machinability | Lightweight and strong |
| Machinery | Frames and supports | Toughness, formability | Easy to fabricate |
| Shipbuilding | Hull structures | Corrosion resistance (with coatings) | Durable and reliable |
Other applications include:
-
- Bridges and overpasses
-
- Industrial equipment frames
-
- Agricultural machinery
St 37 steel is chosen for these applications due to its balance of strength, ductility, and cost-effectiveness, making it ideal for structural components that require reliable performance.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | St 37 Steel | A36 Steel | S235JR Steel | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | Moderate | Moderate | Moderate | Similar performance across grades |
| Key Corrosion Aspect | Fair | Fair | Fair | All require protective measures |
| Weldability | Excellent | Good | Excellent | St 37 and S235JR excel in welding |
| Machinability | Good | Excellent | Good | A36 is easier to machine |
| Formability | Good | Good | Good | All grades are formable |
| Approx. Relative Cost | Low | Low | Low | Cost-effective options |
| Typical Availability | High | High | High | Widely available |
When selecting St 37 steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. While it offers good mechanical properties, its limited corrosion resistance may necessitate protective coatings in certain environments. Additionally, its weldability and machinability make it a versatile choice for various engineering applications.
In summary, St 37 steel is a reliable and widely used structural steel grade, offering a balance of strength, ductility, and cost-effectiveness. Its applications span multiple industries, making it a fundamental material in modern engineering and construction.
