Stainless Steel SUS431
Introduction to Stainless Steel SUS431: A High-Strength Martensitic Alloy
Stainless Steel SUS431 is a martensitic stainless steel that offers superior strength, hardness, and moderate corrosion resistance compared to other martensitic alloys like SUS410. This alloy contains 16–18% chromium, giving it good oxidation and corrosion resistance in moderate environments. With a carbon content ranging from 0.20% to 0.30%, SUS431 is designed for applications requiring high strength, wear resistance, and the ability to withstand harsh environments, such as in the automotive, aerospace, and tooling industries.
SUS431 is particularly well-suited for applications where high hardness and wear resistance are critical. After heat treatment, SUS431 can achieve a hardness of up to 50 HRC, making it ideal for components that are subject to wear and need to maintain sharpness or strength over time. CNC machining of SUS431 requires special attention due to its hardness, but it can be efficiently machined with proper tooling and techniques. At Neway, CNC-machined SUS431 parts are carefully produced to meet tight tolerances and surface finish requirements for demanding applications.
SUS431 Stainless Steel: Key Properties and Composition
SUS431 Stainless Steel Chemical Composition
Element | Composition (wt%) | Role/Impact |
|---|---|---|
Carbon (C) | 0.20–0.30% | High carbon content increases hardness and wear resistance after heat treatment. |
Manganese (Mn) | 0.60–1.00% | Improves strength and toughness, especially at lower temperatures. |
Chromium (Cr) | 16.0–18.0% | Provides resistance to corrosion and oxidation, enhancing durability. |
Nickel (Ni) | ≤0.60% | Improves formability and ductility, though lower than in austenitic grades. |
Phosphorus (P) | ≤0.04% | Reduces sulfur contamination and improves machinability. |
SUS431 Stainless Steel Physical Properties
Property | Value | Notes |
|---|---|---|
Density | 7.80 g/cm³ | Slightly denser than 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. |
SUS431 Stainless Steel Mechanical Properties
Property | Value | Testing Standard/Condition |
|---|---|---|
Tensile Strength | 700 MPa | ASTM A240/A240M standard |
Yield Strength | 500 MPa | Suitable for high-strength applications |
Elongation (50mm gauge) | 15% | Moderate ductility for shaping and forming. |
Brinell Hardness | 450–500 HB | Achieved after heat treatment, offering excellent wear resistance. |
Machinability Rating | 55% (vs. 1212 steel at 100%) | Suitable for machining, though it requires slow speeds to manage hardness. |
Key Characteristics of SUS431 Stainless Steel: Benefits and Comparisons
SUS431 stainless steel is known for its excellent hardness and wear resistance. Below is a technical comparison highlighting its unique advantages over similar materials like SUS410 Stainless Steel, SUS430 Stainless Steel, and SUS440C Stainless Steel.
1. High Hardness and Wear Resistance
Unique Trait: The high carbon content in SUS431 allows it to achieve a hardness of up to 50 HRC, making it ideal for wear-resistant applications.
Comparison:
vs. SUS410 Stainless Steel: SUS431 offers significantly higher hardness and wear resistance, making it more suitable for tooling and cutting applications.
vs. SUS430 Stainless Steel: SUS430 provides good corrosion resistance but is not as hard as SUS431, limiting its use in high-wear environments.
vs. SUS440C Stainless Steel: SUS440C offers similar hardness to SUS431 but is more difficult to machine due to its high hardness.
2. Corrosion Resistance
Unique Trait: While SUS431 offers better corrosion resistance than some other martensitic steels, its performance is still lower than that of austenitic stainless steels.
Comparison:
vs. SUS410 Stainless Steel: SUS431 offers better corrosion resistance due to its higher chromium content.
vs. SUS430 Stainless Steel: SUS431 has improved resistance to oxidation compared to SUS430, though not as much as austenitic grades.
vs. SUS440C Stainless Steel: SUS440C has higher corrosion resistance than SUS431 but is generally more brittle.
3. Strength and Toughness
Unique Trait: SUS431 provides high strength, making it suitable for structural components that must withstand high mechanical loads.
Comparison:
vs. SUS410 Stainless Steel: SUS431 has higher strength and toughness, allowing it to handle heavier loads and resist wear more effectively.
vs. SUS430 Stainless Steel: SUS430 provides lower strength than SUS431 but offers better formability.
vs. SUS440C Stainless Steel: SUS440C is stronger than SUS431 but is harder to machine and prone to brittleness.
4. Cost-Effectiveness
Unique Trait: SUS431 offers a good balance of performance and cost-effectiveness, making it a preferred material for a wide range of applications.
Comparison:
vs. SUS410 Stainless Steel: SUS431 is more expensive than SUS410 but offers significantly better performance in high-wear applications.
vs. SUS430 Stainless Steel: SUS430 is more affordable but lacks the hardness and strength offered by SUS431.
vs. SUS440C Stainless Steel: SUS440C is more expensive than SUS431 but provides better corrosion resistance, especially in high-temperature environments.
CNC Machining Challenges and Solutions for SUS431 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 SUS431 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 SUS431 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 SUS431 Stainless Steel Parts
Automotive Industry
Cutting Tools: SUS431’s high hardness makes it ideal for precision cutting tools used in automotive manufacturing.
Aerospace Industry
Turbine Blades: SUS431’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 SUS431 Stainless Steel Parts & Services
How does SUS431 compare to SUS440C in terms of hardness and wear resistance?
What are the optimal machining parameters for CNC machining SUS431?
How does SUS431 perform in high-temperature environments compared to other martensitic stainless steels?
What post-processing techniques are best for enhancing the corrosion resistance of SUS431?
How does SUS431 perform in aerospace applications compared to other stainless steels?
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