S235JR Steel: Properties and Key Applications
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Table Of Content
Table Of Content
1.0037 Steel (S235JR) is a low-carbon structural steel grade that is widely used in construction and engineering applications. Classified under the European standard EN 10025, S235JR is known for its good weldability, machinability, and overall structural integrity. The primary alloying element in S235JR is carbon, with a maximum carbon content of 0.20%, which contributes to its strength and ductility. This steel grade is often used in the fabrication of structural components such as beams, columns, and plates.
Comprehensive Overview
S235JR is categorized as a low-carbon mild steel, which makes it suitable for a variety of structural applications. Its chemical composition primarily consists of iron (Fe) with a small percentage of carbon and other alloying elements such as manganese (Mn) and silicon (Si). The presence of these elements enhances its mechanical properties, making it a versatile choice for engineers and fabricators.
Key Characteristics:
- Strength: S235JR exhibits a minimum yield strength of 235 MPa, which is adequate for many structural applications.
- Ductility: The steel's low carbon content allows for good elongation and reduction of area, making it easy to form and shape.
- Weldability: S235JR is known for its excellent weldability, allowing for easy joining processes without the need for preheating.
Advantages:
- Cost-effective for large-scale construction projects.
- Readily available in various forms and sizes.
- Good mechanical properties for structural integrity.
Limitations:
- Limited corrosion resistance compared to higher alloy steels.
- Not suitable for high-temperature applications due to lower strength at elevated temperatures.
Historically, S235JR has been a staple in the construction industry, often used in the manufacturing of bridges, buildings, and other infrastructure projects due to its favorable balance of strength, ductility, and cost.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | K02401 | USA | Closest equivalent to S235JR |
| AISI/SAE | - | USA | - |
| ASTM | A36 | USA | Similar properties, but with different chemical composition |
| EN | S235JR | Europe | Standard designation |
| DIN | St37-2 | Germany | Similar properties, minor compositional differences |
| JIS | SS400 | Japan | Comparable, but with different yield strength |
| GB | Q235 | China | Equivalent grade with similar applications |
| ISO | S235JR | International | Standard designation |
The table above highlights various standards and equivalent grades for S235JR. Notably, while grades like ASTM A36 and DIN St37-2 are often considered equivalent, they may have subtle differences in chemical composition and mechanical properties that can affect performance in specific 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 S235JR is to enhance its strength and hardness. Manganese contributes to improved hardenability and tensile strength, while silicon helps in deoxidation during steelmaking and enhances strength. The low levels of phosphorus and sulfur are crucial for ensuring good ductility and weldability.
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) | Hot Rolled | Room Temp | 235 MPa | 34.1 ksi | EN 10002-1 |
| Tensile Strength | Hot Rolled | Room Temp | 360 - 510 MPa | 52.2 - 73.8 ksi | EN 10002-1 |
| Elongation | Hot Rolled | Room Temp | ≥ 20% | ≥ 20% | EN 10002-1 |
| Reduction of Area | Hot Rolled | Room Temp | ≥ 40% | ≥ 40% | EN 10002-1 |
| Hardness (Brinell) | Hot Rolled | Room Temp | ≤ 160 HB | ≤ 160 HB | EN 10003-1 |
| Impact Strength | Charpy V-notch | -20°C (-4°F) | ≥ 27 J | ≥ 20 ft-lbf | EN 10045-1 |
The mechanical properties of S235JR make it suitable for a variety of structural applications. Its yield strength allows it to withstand significant loads, while its elongation and reduction of area indicate good ductility, making it ideal for forming and welding processes. The impact strength at low temperatures ensures that it can perform well 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 | 0.0000175 Ω·m | 0.000011 Ω·in |
| Coefficient of Thermal Expansion | Room Temp | 11.0 x 10⁻⁶/K | 6.1 x 10⁻⁶/°F |
The density of S235JR indicates that it is a relatively heavy material, which is typical for structural steels. Its melting point range shows that it can withstand high temperatures before transitioning to a liquid state. The thermal conductivity and specific heat capacity suggest that S235JR can effectively dissipate heat, making it suitable for applications where thermal management is critical.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Atmospheric | - | - | Fair | Susceptible to rust without protective coatings |
| Chlorides | - | - | Poor | Risk of pitting corrosion |
| Acids | - | - | Poor | Not recommended for acidic environments |
| Alkalis | - | - | Fair | Moderate resistance, but protective measures recommended |
| Organics | - | - | Good | Generally resistant to organic solvents |
S235JR exhibits moderate corrosion resistance, making it suitable for many applications but requiring protective measures in harsh environments. Its susceptibility to rust in atmospheric conditions necessitates the use of coatings or galvanization for outdoor applications. Compared to higher alloy steels like S355 or stainless steels, S235JR's corrosion resistance is limited, particularly in chloride-rich environments where pitting can occur.
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 | Limited use at elevated temperatures |
| Scaling Temperature | 600 °C | 1112 °F | Risk of oxidation at high temperatures |
| Creep Strength Considerations | 300 °C | 572 °F | Creep may become a concern at elevated temperatures |
S235JR performs adequately at elevated temperatures, but its mechanical properties can degrade significantly above 400 °C (752 °F). This limitation makes it less suitable for applications involving high thermal loads or prolonged exposure to elevated temperatures. The risk of oxidation and scaling at high temperatures necessitates careful consideration in design and material selection.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 mixture | Good for thin sections |
| TIG | ER70S-2 | Argon | Excellent for precision welding |
| SMAW | E7018 | - | Suitable for thicker sections |
S235JR is known for its excellent weldability, making it a preferred choice for various welding processes. Preheating is generally not required, but post-weld heat treatment may be beneficial to relieve stresses. Common defects include porosity and undercutting, which can be minimized with proper technique and filler selection.
Machinability
| Machining Parameter | S235JR | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 70% | 100% | Good machinability for structural applications |
| Typical Cutting Speed (Turning) | 80 m/min | 120 m/min | Adjust based on tooling and setup |
S235JR exhibits good machinability, allowing for efficient processing in various machining operations. Optimal conditions include using sharp tooling and appropriate cutting speeds to minimize wear and achieve desired surface finishes.
Formability
S235JR is highly formable, making it suitable for cold and hot forming processes. Its low carbon content allows for significant deformation without cracking. The steel can be bent, rolled, and shaped into various forms, with recommended bend radii typically being 2-3 times the material thickness.
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 | Improve ductility and reduce hardness |
| Normalizing | 850 - 900 °C / 1562 - 1652 °F | 1 - 2 hours | Air | Refine grain structure and enhance strength |
| Quenching & Tempering | 850 - 900 °C / 1562 - 1652 °F | 1 hour | Oil or water | Increase hardness and strength |
Heat treatment processes such as annealing and normalizing can significantly alter the microstructure of S235JR, enhancing its mechanical properties. Annealing improves ductility, while normalizing refines the grain structure, leading to improved 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 | High yield strength, good weldability | Essential for load-bearing structures |
| Automotive | Chassis components | Ductility, machinability | Lightweight and strong materials needed |
| Manufacturing | Machinery frames | Strength, formability | Custom shapes and high strength required |
| Shipbuilding | Hull structures | Corrosion resistance, weldability | Durable and strong for marine environments |
In construction, S235JR is often selected for its balance of strength and ductility, making it ideal for structural applications. In the automotive industry, its machinability and formability allow for the production of complex shapes while maintaining strength.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | S235JR | S355 | A36 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | Yield Strength: 235 MPa | Yield Strength: 355 MPa | Yield Strength: 250 MPa | S355 offers higher strength but at a higher cost |
| Key Corrosion Aspect | Fair | Good | Fair | S355 has better corrosion resistance due to higher alloy content |
| Weldability | Excellent | Good | Good | All grades are weldable, but S235JR is the easiest |
| Machinability | Good | Fair | Good | S235JR is easier to machine than S355 |
| Formability | Excellent | Good | Good | S235JR is more formable due to lower carbon content |
| Approx. Relative Cost | Low | Medium | Low | S235JR is cost-effective for large projects |
| Typical Availability | High | Medium | High | S235JR is widely available in various forms |
When selecting S235JR, considerations include cost-effectiveness, availability, and the specific mechanical properties required for the application. While S355 offers higher strength, S235JR remains a popular choice for many structural applications due to its balance of properties and lower cost. Its excellent weldability and machinability make it a versatile option for engineers and fabricators alike.
In summary, S235JR is a widely used low-carbon structural steel that offers a combination of strength, ductility, and cost-effectiveness, making it suitable for a variety of applications in construction, manufacturing, and automotive industries.