SCM435 Steel: Properties and Key Applications
Bagikan
Table Of Content
Table Of Content
SCM435 steel, classified as a medium-carbon alloy steel, is primarily composed of chromium (Cr) and molybdenum (Mo) as its key alloying elements. This steel grade is known for its excellent hardenability, strength, and toughness, making it suitable for a variety of engineering applications. The addition of chromium enhances corrosion resistance and hardenability, while molybdenum contributes to improved strength and resistance to wear at elevated temperatures.
Comprehensive Overview
SCM435 steel is widely recognized for its balance of strength, ductility, and toughness, which are critical for components subjected to high stress and fatigue. Its primary alloying elements, chromium and molybdenum, play significant roles in defining its mechanical properties. Chromium increases the steel's hardness and resistance to oxidation, while molybdenum enhances its strength and stability at high temperatures.
Advantages of SCM435 Steel:
- High Strength and Toughness: Suitable for high-load applications.
- Good Hardening Capability: Can be heat-treated to achieve desired mechanical properties.
- Excellent Wear Resistance: Ideal for components subjected to friction and wear.
Limitations of SCM435 Steel:
- Weldability Issues: Requires careful consideration during welding due to potential cracking.
- Cost: Higher alloy content can lead to increased material costs compared to lower-grade steels.
Historically, SCM435 has been utilized in various industries, including automotive and machinery, for manufacturing gears, shafts, and other critical components. Its market position remains strong due to its versatility and reliability in demanding applications.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | SCM435 | USA | Closest equivalent to AISI 4135 |
| AISI/SAE | 4135 | USA | Minor compositional differences |
| ASTM | A29/A29M | USA | General specification for alloy steels |
| EN | 34CrMo4 | Europe | Similar properties, used in Europe |
| JIS | SCM435 | Japan | Equivalent designation in Japan |
| DIN | 1.7220 | Germany | Closely related grade with similar properties |
The differences between equivalent grades, such as AISI 4135 and EN 34CrMo4, may include variations in carbon content and specific alloying elements, which can affect the steel's performance in specific applications. Understanding these nuances is crucial for selecting the appropriate grade for a given application.
Key Properties
Chemical Composition
| Element (Symbol) | Percentage Range (%) |
|---|---|
| Carbon (C) | 0.28 - 0.34 |
| Chromium (Cr) | 0.90 - 1.20 |
| Molybdenum (Mo) | 0.15 - 0.25 |
| Manganese (Mn) | 0.60 - 0.90 |
| Silicon (Si) | 0.15 - 0.40 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.030 |
The primary alloying elements in SCM435 steel, chromium and molybdenum, significantly enhance its properties. Chromium improves hardenability and corrosion resistance, while molybdenum increases strength and stability at elevated temperatures, making this steel suitable for high-performance applications.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|
| Tensile Strength | Quenched & Tempered | 800 - 1100 MPa | 1160 - 160 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Quenched & Tempered | 600 - 900 MPa | 87 - 130 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | 15 - 20% | 15 - 20% | ASTM E8 |
| Hardness (HRC) | Quenched & Tempered | 28 - 34 HRC | 28 - 34 HRC | ASTM E18 |
| Impact Strength (Charpy, -20°C) | Quenched & Tempered | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The mechanical properties of SCM435 steel make it particularly suitable for applications requiring high strength and toughness. Its ability to withstand significant loads and resist deformation under stress is essential for components such as gears and shafts in machinery.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | Room Temperature | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | Room Temperature | 45 W/m·K | 31 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temperature | 460 J/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | Room Temperature | 0.000001 Ω·m | 0.0000001 Ω·in |
The density and melting point of SCM435 steel indicate its suitability for high-temperature applications, while its thermal conductivity and specific heat capacity suggest effective heat dissipation in mechanical systems.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-5 | 20-60 | Fair | Risk of pitting corrosion |
| Sulfuric Acid | 10-20 | 20-40 | Poor | Not recommended |
| Atmospheric | - | - | Good | Generally resistant |
SCM435 steel exhibits moderate corrosion resistance, particularly in atmospheric conditions. However, it is susceptible to pitting in chloride environments and should be avoided in acidic conditions. Compared to stainless steels, SCM435's corrosion resistance is limited, making it less suitable for applications in highly corrosive environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400 | 752 | Suitable for high-temperature applications |
| Max Intermittent Service Temp | 500 | 932 | Short-term exposure only |
| Scaling Temperature | 600 | 1112 | Risk of oxidation at high temps |
| Creep Strength considerations begin around | 400 | 752 | Critical for long-term applications |
SCM435 steel maintains its strength and toughness at elevated temperatures, making it suitable for applications such as automotive components and machinery parts that experience high thermal loads. However, care must be taken to avoid prolonged exposure to temperatures exceeding its maximum service limits.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 | Preheat recommended |
| TIG | ER80S-Ni1 | Argon | Requires post-weld heat treatment |
| Stick | E7018 | - | Careful control of heat input |
SCM435 steel can be welded using various processes, but preheating and post-weld heat treatment are essential to prevent cracking. The choice of filler metal is crucial to ensure compatibility and maintain mechanical properties in the weld zone.
Machinability
| Machining Parameter | SCM435 | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | SCM435 is more challenging to machine |
| Typical Cutting Speed (Turning) | 40 m/min | 80 m/min | Use carbide tools for best results |
SCM435 has moderate machinability, requiring appropriate tooling and cutting speeds to achieve optimal results. It is advisable to use carbide tools and maintain proper cooling to prevent overheating during machining operations.
Formability
SCM435 steel exhibits good formability in both cold and hot conditions. Cold forming can lead to work hardening, which may require subsequent heat treatment to restore ductility. The steel can be bent with appropriate radii, but care should be taken to avoid excessive strain that could lead to cracking.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 600 - 700 / 1112 - 1292 | 1 - 2 hours | Air | Softening, improving ductility |
| Quenching | 850 - 900 / 1562 - 1652 | 30 minutes | Oil/Water | Hardening |
| Tempering | 500 - 650 / 932 - 1202 | 1 hour | Air | Reducing brittleness, improving toughness |
The heat treatment processes for SCM435 steel significantly influence its microstructure and mechanical properties. Quenching increases hardness, while tempering is essential to reduce brittleness and enhance toughness, making the steel suitable for high-stress applications.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
|---|---|---|---|
| Automotive | Gears | High strength, toughness | Critical for performance under load |
| Machinery | Shafts | Wear resistance, hardenability | Essential for durability and reliability |
| Aerospace | Fasteners | High-temperature strength | Required for safety and performance |
| Oil & Gas | Valve components | Corrosion resistance, toughness | Necessary for harsh environments |
Other applications include:
- - Structural components in heavy machinery
- - Tooling and dies
- - High-stress fasteners
SCM435 steel is chosen for these applications due to its excellent mechanical properties, which ensure reliability and performance under demanding conditions.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | SCM435 | AISI 4140 | 4340 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength | Moderate strength | High toughness | SCM435 offers a balance of strength and toughness |
| Key Corrosion Aspect | Fair resistance | Good resistance | Moderate resistance | SCM435 is less resistant than stainless steels |
| Weldability | Moderate | Good | Fair | Requires careful handling to avoid cracking |
| Machinability | Moderate | Good | Fair | SCM435 is more challenging to machine than AISI 4140 |
| Formability | Good | Moderate | Good | SCM435 can be formed but may require heat treatment |
| Approx. Relative Cost | Moderate | Moderate | Higher | Cost-effective for high-performance applications |
| Typical Availability | Common | Common | Less common | SCM435 is widely available in various forms |
When selecting SCM435 steel, considerations such as cost-effectiveness, availability, and specific mechanical properties are crucial. Its balance of strength, toughness, and moderate corrosion resistance makes it suitable for a wide range of applications, particularly in industries where reliability and performance are paramount. Understanding the trade-offs with alternative grades can guide engineers in making informed material choices for their projects.
