S35VN Steel: Properties and Key Applications Explained
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Table Of Content
Table Of Content
S35VN steel, also known as CPM S35VN, is a high-performance stainless steel grade that falls under the category of martensitic stainless steels. It is primarily classified as a medium-carbon alloy steel, notable for its excellent balance of toughness, wear resistance, and corrosion resistance. The key alloying elements in S35VN include carbon (C), chromium (Cr), vanadium (V), and molybdenum (Mo), each contributing significantly to its overall properties.
Comprehensive Overview
S35VN steel is a product of the Crucible Particle Metallurgy (CPM) process, which enhances its microstructure and mechanical properties compared to traditional steel-making methods. The addition of vanadium improves wear resistance and toughness, while chromium provides corrosion resistance and contributes to the formation of a hard martensitic structure upon heat treatment. Molybdenum further enhances the steel's strength and resistance to pitting corrosion.
The most significant characteristics of S35VN include:
- High Wear Resistance: Ideal for applications requiring durability and longevity.
- Good Toughness: Offers resistance to chipping and cracking, making it suitable for demanding applications.
- Corrosion Resistance: Performs well in various environments, including humid and corrosive conditions.
Advantages and Limitations
| Pros | Cons |
|---|---|
| Excellent edge retention | More challenging to sharpen compared to softer steels |
| Good corrosion resistance | Higher cost compared to standard stainless steels |
| Enhanced toughness | Requires careful heat treatment to achieve optimal properties |
S35VN has gained popularity in the knife-making industry and high-performance tooling applications due to its unique combination of properties. Its historical significance lies in its development as an improvement over the earlier CPM S30V steel, addressing some of the limitations found in that grade.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S35VN | USA | Closest equivalent to AISI 440C with improved toughness |
| AISI/SAE | S35VN | USA | Enhanced version of S30V with better toughness |
| ASTM | A240 | USA | Standard specification for stainless steel plates |
| JIS | SUS440C | Japan | Similar properties but with different heat treatment requirements |
While S35VN is often compared to other stainless steels like AISI 440C and S30V, it is essential to note that S35VN's unique composition offers improved toughness and edge retention, making it a preferred choice for high-performance applications.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 1.40 - 1.50 |
| Cr (Chromium) | 14.00 - 15.00 |
| V (Vanadium) | 3.00 - 3.50 |
| Mo (Molybdenum) | 1.00 - 1.50 |
| Mn (Manganese) | 0.50 max |
| Si (Silicon) | 0.50 max |
| P (Phosphorus) | 0.03 max |
| S (Sulfur) | 0.03 max |
The primary role of the key alloying elements in S35VN includes:
- Carbon: Increases hardness and strength through the formation of carbides.
- Chromium: Enhances corrosion resistance and contributes to the formation of a hard martensitic structure.
- Vanadium: Improves wear resistance and toughness by refining the grain structure.
- Molybdenum: Enhances strength and resistance to pitting corrosion.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric - SI Units) | Typical Value/Range (Imperial Units) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Quenched & Tempered | Room Temp | 1,200 - 1,300 MPa | 174 - 188 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Quenched & Tempered | Room Temp | 1,100 - 1,200 MPa | 160 - 174 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | Room Temp | 5 - 7% | 5 - 7% | ASTM E8 |
| Hardness | Quenched & Tempered | Room Temp | 58 - 62 HRC | 58 - 62 HRC | ASTM E18 |
| Impact Strength | Quenched & Tempered | -20°C | 50 - 60 J | 37 - 44 ft-lbf | ASTM E23 |
The combination of these mechanical properties makes S35VN steel particularly suitable for applications that require high strength and toughness, such as knife blades and cutting tools. Its high tensile and yield strength ensure structural integrity under mechanical loading, while its hardness provides excellent wear resistance.
Physical Properties
| Property | Condition/Temperature | Value (Metric - SI Units) | Value (Imperial Units) |
|---|---|---|---|
| Density | Room Temp | 7.75 g/cm³ | 0.28 lb/in³ |
| Melting Point | - | 1,400 - 1,500 °C | 2,552 - 2,732 °F |
| Thermal Conductivity | Room Temp | 25 W/m·K | 14.5 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temp | 460 J/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.5 µΩ·m | 0.5 µΩ·in |
| Coeff. of Thermal Expansion | Room Temp | 11.5 x 10⁻⁶ /K | 6.4 x 10⁻⁶ /°F |
The practical significance of key physical properties for S35VN includes:
- Density: Affects the weight and balance of tools and knives, making it suitable for applications where weight is a consideration.
- Thermal Conductivity: Important for applications involving heat treatment processes, ensuring uniform heating and cooling.
- Coefficient of Thermal Expansion: Critical for applications where dimensional stability under temperature changes is necessary.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3.5% | 25°C/77°F | Good | Risk of pitting corrosion |
| Acids (Sulfuric) | 10% | 25°C/77°F | Fair | Susceptible to localized corrosion |
| Alkaline Solutions | 10% | 25°C/77°F | Good | Generally resistant |
| Atmospheric | - | - | Excellent | Performs well in humid environments |
S35VN exhibits good corrosion resistance in various environments, including atmospheric conditions, chlorides, and alkaline solutions. However, it is susceptible to pitting corrosion in chloride-rich environments, which is a common concern for stainless steels. Compared to other grades like AISI 440C and S30V, S35VN offers improved toughness and resistance to chipping, making it a better choice for applications where both corrosion resistance and mechanical performance are critical.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 300°C | 572°F | Suitable for high-temperature applications |
| Max Intermittent Service Temp | 400°C | 752°F | Can withstand short-term exposure to higher temperatures |
| Scaling Temperature | 600°C | 1,112°F | Begins to lose properties at elevated temperatures |
At elevated temperatures, S35VN maintains its mechanical properties well, making it suitable for applications that may experience thermal cycling. However, prolonged exposure to temperatures above 300°C can lead to a reduction in hardness and strength, necessitating careful consideration in high-temperature applications.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| TIG | ER 316L | Argon | Requires preheating to avoid cracking |
| MIG | ER 308L | Argon/CO2 | Post-weld heat treatment recommended |
S35VN can be welded using conventional methods, but care must be taken to avoid cracking due to its high carbon content. Preheating and post-weld heat treatment can help mitigate these issues, ensuring the integrity of the weld.
Machinability
| Machining Parameter | S35VN | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | More challenging to machine than softer steels |
| Typical Cutting Speed (Turning) | 30-40 m/min | 60-80 m/min | Use carbide tooling for best results |
Machining S35VN requires specialized tools and techniques due to its hardness. Carbide tools are recommended, and slower cutting speeds can help achieve better surface finishes.
Formability
S35VN is not particularly suited for extensive forming processes due to its high hardness and strength. Cold forming is possible but may lead to work hardening, requiring careful control of bending radii and forming techniques.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 1,000 - 1,100°C / 1,832 - 2,012°F | 1-2 hours | Air cool | Reduce hardness, improve machinability |
| Quenching | 1,050 - 1,100°C / 1,922 - 2,012°F | 30 minutes | Oil or air | Achieve hardness and strength |
| Tempering | 400 - 600°C / 752 - 1,112°F | 1 hour | Air cool | Reduce brittleness, enhance toughness |
The heat treatment processes for S35VN involve austenitizing, quenching, and tempering to achieve the desired balance of hardness and toughness. The metallurgical transformations during these treatments significantly impact the microstructure, resulting in a fine distribution of carbides that enhance wear resistance.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Knife Manufacturing | High-end kitchen knives | High wear resistance, edge retention | Preferred for premium cutlery |
| Tooling | Cutting tools | Toughness, hardness | Suitable for demanding machining applications |
| Medical Devices | Surgical instruments | Corrosion resistance, strength | Essential for sterile environments |
Other applications include:
-
- Aerospace components
-
- Automotive parts
-
- Industrial machinery
S35VN is chosen for these applications due to its unique combination of properties, particularly its ability to maintain sharp edges and resist wear in demanding environments.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | S35VN | AISI 440C | S30V | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength, toughness | High hardness | Good edge retention | S35VN offers a balance of toughness and wear resistance |
| Key Corrosion Aspect | Good resistance | Moderate resistance | Good resistance | S35VN performs better in humid environments |
| Weldability | Moderate | Poor | Moderate | Requires care to avoid cracking |
| Machinability | Challenging | Easy | Moderate | S35VN needs specialized tooling |
| Formability | Limited | Moderate | Limited | Not ideal for extensive forming |
| Approx. Relative Cost | Higher | Moderate | Higher | Cost reflects performance benefits |
| Typical Availability | Moderate | High | High | S35VN is less common than 440C |
When selecting S35VN, considerations include its cost-effectiveness, availability, and specific application requirements. While it may be more expensive than some alternatives, its superior performance in edge retention and toughness often justifies the investment. Additionally, its availability may vary, so sourcing from reputable suppliers is essential for consistent quality.
In summary, S35VN steel stands out as a versatile and high-performance material, particularly suited for applications demanding a combination of strength, toughness, and corrosion resistance. Its unique properties, derived from its composition and processing, make it a preferred choice in various industries, particularly in high-end knife manufacturing and tooling applications.
