Stainless Steel SUS440C
Introduction to Stainless Steel SUS440C: A High-Carbon Martensitic Alloy with Superior Hardness
Stainless Steel SUS440C is a high-carbon martensitic stainless steel known for its exceptional hardness, wear resistance, and moderate corrosion resistance. With a carbon content of 0.95%–1.20%, SUS440C offers excellent strength and hardness after heat treatment. It is ideal for applications where high wear resistance and durability are crucial, such as in tooling, bearings, and high-performance machinery. This alloy is particularly suitable for environments where strength and resistance to abrasive wear are required, but the material's corrosion resistance is moderate compared to austenitic stainless steels.
SUS440C can achieve a hardness of up to 58 HRC, making it one of the hardest stainless steels. It is commonly used to produce cutting tools, ball bearings, and valve components. CNC machining of SUS440C requires special attention due to its hardness, but it can be efficiently machined with carbide tooling and proper cooling techniques. At Neway, CNC-machined SUS440C parts are produced to meet strict tolerances and surface quality standards for demanding applications.
SUS440C Stainless Steel: Key Properties and Composition
SUS440C Stainless Steel Chemical Composition
Element | Composition (wt%) | Role/Impact |
|---|---|---|
Carbon (C) | 0.95–1.20% | High carbon content provides high hardness and wear resistance after heat treatment. |
Manganese (Mn) | 0.60–1.00% | Improves toughness and strength, especially at low temperatures. |
Chromium (Cr) | 16.0–18.0% | Provides resistance to corrosion and oxidation, enhancing durability. |
Nickel (Ni) | ≤0.75% | Improves formability and ductility, though lower than in austenitic grades. |
Phosphorus (P) | ≤0.04% | Reduces sulfur contamination and improves machinability. |
SUS440C Stainless Steel Physical Properties
Property | Value | Notes |
|---|---|---|
Density | 7.75 g/cm³ | Similar to other martensitic stainless steels, ensuring durability. |
Melting Point | 1,400–1,530°C | Suitable for both cold and hot working, ideal for high-temperature applications. |
Thermal Conductivity | 26.3 W/m·K | Moderate heat dissipation, suitable for high-heat applications. |
Electrical Resistivity | 7.4×10⁻⁷ Ω·m | Low electrical conductivity, ideal for non-electrical applications. |
SUS440C Stainless Steel Mechanical Properties
Property | Value | Testing Standard/Condition |
|---|---|---|
Tensile Strength | 750 MPa | ASTM A240/A240M standard |
Yield Strength | 500 MPa | Suitable for high-strength applications |
Elongation (50mm gauge) | 10% | Lower ductility, ideal for structural components. |
Brinell Hardness | 500–550 HB | Achieved after heat treatment, offering superior wear resistance. |
Machinability Rating | 45% (vs. 1212 steel at 100%) | Suitable for machining, though it requires careful tool selection and slower speeds. |
Key Characteristics of SUS440C Stainless Steel: Benefits and Comparisons
SUS440C stainless steel is known for its exceptional hardness and wear resistance. Below is a technical comparison highlighting its unique advantages over similar materials like SUS304 Stainless Steel, SUS410 Stainless Steel, and SUS420 Stainless Steel.
1. High Hardness and Wear Resistance
Unique Trait: SUS440C achieves a hardness of up to 58 HRC after heat treatment, offering excellent wear resistance for tools and components subjected to friction.
Comparison:
vs. SUS304 Stainless Steel: SUS304 has much lower hardness and wear resistance than SUS440C, making it unsuitable for high-wear applications.
vs. SUS410 Stainless Steel: SUS440C offers superior hardness, while SUS410 is more suited for general-purpose applications with lower wear resistance.
vs. SUS420 Stainless Steel: SUS440C has higher hardness and wear resistance than SUS420, making it better suited for high-performance components.
2. Corrosion Resistance
Unique Trait: SUS440C offers moderate corrosion resistance, which is suitable for applications that do not require extensive protection from harsh environments.
Comparison:
vs. SUS304 Stainless Steel: SUS304 offers much better corrosion resistance, especially in highly corrosive environments like those found in the food and chemical industries.
vs. SUS410 Stainless Steel: SUS440C has better corrosion resistance than SUS410, which is prone to oxidation in some environments.
vs. SUS420 Stainless Steel: SUS440C has superior corrosion resistance compared to SUS420, making it more suitable for harsh environments.
3. Strength and Toughness
Unique Trait: With a tensile strength of 750 MPa, SUS440C provides high mechanical strength for demanding applications such as bearings, valves, and tooling.
Comparison:
vs. SUS304 Stainless Steel: SUS304 has better ductility and toughness but lower strength and hardness compared to SUS440C.
vs. SUS410 Stainless Steel: SUS440C is stronger and harder, making it more suitable for wear-resistant components.
vs. SUS420 Stainless Steel: SUS440C offers superior strength and hardness, which is critical for parts requiring high wear resistance.
4. Cost-Effectiveness
Unique Trait: SUS440C is cost-effective when compared to high-end alloys like SUS316, offering good wear resistance and strength at a lower price point.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is more expensive due to higher nickel content and superior corrosion resistance.
vs. SUS410 Stainless Steel: SUS440C is more cost-effective than SUS410 while offering superior wear resistance.
vs. SUS420 Stainless Steel: SUS440C is more expensive than SUS420, but its superior hardness and wear resistance justify the price in high-performance applications.
CNC Machining Challenges and Solutions for SUS440C Stainless Steel
Machining Challenges and Solutions
Challenge | Root Cause | Solution |
|---|---|---|
Work Hardening | High carbon content and hardness | Use carbide tools with TiN coatings to improve tool life. |
Surface Roughness | Brittle material causing "tearing" | Optimize feed rates and use sharp, high-speed tools for smoother finishes. |
Tool Wear | High hardness and abrasiveness | Use high-performance coatings like TiAlN to reduce friction and tool wear. |
Dimensional Inaccuracy | Stresses from machining | Perform stress-relief annealing to reduce dimensional variations and improve precision. |
Chip Control Issues | Hard, continuous chips | Use high-pressure coolant and optimize tool geometry to break chips. |
Optimized Machining Strategies
Strategy | Implementation | Benefit |
|---|---|---|
High-Speed Machining | Spindle speed: 1,200–1,800 RPM | Increases productivity and reduces heat buildup. |
Climb Milling | Cutting in the direction of tool rotation | Improves surface finish (Ra 1.6–3.2 µm). |
Toolpath Optimization | Use trochoidal milling for deep pockets | Reduces cutting forces, minimizing part deflection. |
Stress-Relief Annealing | Preheat to 650°C for 1 hour per inch | Minimizes residual stress and improves machining accuracy. |
Cutting Parameters for SUS440C Stainless Steel
Operation | Tool Type | Spindle Speed (RPM) | Feed Rate (mm/rev) | Depth of Cut (mm) | Notes |
|---|---|---|---|---|---|
Rough Milling | 4-flute carbide end mill | 1,000–1,500 | 0.15–0.25 | 2.0–4.0 | Use coolant to prevent work hardening. |
Finish Milling | 2-flute carbide end mill | 1,500–2,000 | 0.05–0.10 | 0.5–1.0 | Climb milling for smoother finishes (Ra 1.6–3.2 µm). |
Drilling | 135° split-point HSS drill | 600–800 | 0.10–0.15 | Full hole depth | Peck drilling for precise hole formation. |
Turning | CBN or coated carbide insert | 500–700 | 0.20–0.30 | 1.5–3.0 | Dry machining is acceptable with air blast cooling. |
Surface Treatments for CNC Machined SUS440C Stainless Steel Parts
Electroplating: Adds a corrosion-resistant metallic layer, extending part life in humid environments and improving strength.
Polishing: Enhances the surface finish, providing a smooth, shiny appearance ideal for visible components.
Brushing: Creates a satin or matte finish, masking minor surface defects and improving aesthetic quality for architectural components.
PVD Coating: Boosts wear resistance, increasing tool life and part longevity in high-contact environments.
Passivation: Creates a protective oxide layer, enhancing corrosion resistance in mild environments without altering dimensions.
Powder Coating: Offers high durability, UV resistance, and a smooth finish, ideal for outdoor and automotive parts.
Teflon Coating: Provides non-stick and chemical-resistant properties, ideal for food processing and chemical handling components.
Chrome Plating: Adds a shiny, durable finish that enhances corrosion resistance, commonly used in automotive and tooling applications.
Black Oxide: Provides a corrosion-resistant black finish, ideal for parts in low-corrosion environments like gears and fasteners.
Industry Applications of CNC Machined SUS440C Stainless Steel Parts
Automotive Industry
Cutting Tools: SUS440C’s high hardness makes it ideal for producing precision cutting tools used in automotive manufacturing.
Aerospace Industry
Turbine Blades: SUS440C’s wear resistance makes it suitable for parts that must endure high pressures and temperatures.
Industrial Equipment
Valves and Pump Components: The material’s high strength ensures durability in heavy-duty machinery.
Technical FAQs: CNC Machined SUS440C Stainless Steel Parts & Services
How does SUS440C compare to SUS420 in terms of wear resistance and machinability?
What are the recommended machining parameters for CNC machining SUS440C?
How does SUS440C perform in high-temperature applications compared to other martensitic stainless steels?
What are the best surface treatments for enhancing the corrosion resistance of SUS440C in harsh environments?
How does SUS440C perform in aerospace applications compared to other stainless steels?
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