Stainless Steel SUS309
Introduction to Stainless Steel SUS309: High-Temperature Resistant Austenitic Alloy
Stainless Steel SUS309 is an austenitic stainless steel alloy known for its excellent resistance to high temperatures and oxidation, making it ideal for applications in industries such as petrochemicals, power generation, and furnace components. With a composition of 24–26% chromium and 13–15% nickel, SUS309 exhibits outstanding strength and oxidation resistance at elevated temperatures, making it suitable for parts that must perform in extreme environments.
SUS309 provides good resistance to scaling at temperatures up to 1,100°C and retains its mechanical properties even in high-heat applications. CNC machining of SUS309 requires specialized techniques due to its high strength and toughness, but it can be efficiently machined with carbide tooling and proper cooling. At Neway, CNC-machined SUS309 parts are produced to ensure tight tolerances and high-quality finishes for demanding high-temperature applications.
SUS309 Stainless Steel: Key Properties and Composition
SUS309 Stainless Steel Chemical Composition
Element | Composition (wt%) | Role/Impact |
|---|---|---|
Carbon (C) | ≤0.20% | Low carbon content improves weldability and prevents carbide precipitation. |
Manganese (Mn) | 2.00% | Enhances strength and toughness at high temperatures. |
Chromium (Cr) | 24.0–26.0% | Provides resistance to oxidation and corrosion at high temperatures. |
Nickel (Ni) | 13.0–15.0% | Improves formability, ductility, and resistance to oxidation in high-temperature environments. |
Phosphorus (P) | ≤0.045% | Improves machinability and helps reduce the formation of surface defects during machining. |
SUS309 Stainless Steel Physical Properties
Property | Value | Notes |
|---|---|---|
Density | 7.90 g/cm³ | Similar to other austenitic stainless steels, ensuring durability. |
Melting Point | 1,400–1,450°C | Suitable for high-temperature applications with excellent resistance to oxidation. |
Thermal Conductivity | 16.2 W/m·K | Moderate heat dissipation, suitable for applications with fluctuating temperatures. |
Electrical Resistivity | 7.4×10⁻⁷ Ω·m | Low electrical conductivity, suitable for non-electrical applications. |
SUS309 Stainless Steel Mechanical Properties
Property | Value | Testing Standard/Condition |
|---|---|---|
Tensile Strength | 520–720 MPa | ASTM A240/A240M standard |
Yield Strength | 205 MPa | Suitable for high-temperature and structural applications |
Elongation (50mm gauge) | 35% | Good ductility, allowing for easier forming and welding. |
Brinell Hardness | 150–190 HB | Achieved in a solution-treated state, offering moderate hardness. |
Machinability Rating | 55% (vs. 1212 steel at 100%) | Suitable for machining with carbide tools and low cutting speeds. |
Key Characteristics of SUS309 Stainless Steel: Benefits and Comparisons
SUS309 stainless steel is known for its excellent high-temperature strength and oxidation resistance. Below is a technical comparison highlighting its unique advantages over similar materials like SUS304 Stainless Steel, SUS310 Stainless Steel, and SUS316 Stainless Steel.
1. High-Temperature Resistance
Unique Trait: SUS309 provides exceptional resistance to oxidation and scaling at high temperatures (up to 1,100°C), making it ideal for furnace parts and industrial equipment exposed to heat.
Comparison:
vs. SUS304 Stainless Steel: SUS309 has higher temperature resistance compared to SUS304, which performs well only up to 870°C.
vs. SUS310 Stainless Steel: SUS310 offers even better high-temperature performance than SUS309 but at a higher cost.
vs. SUS316 Stainless Steel: SUS316 provides good corrosion resistance but is less effective than SUS309 at high temperatures.
2. Corrosion Resistance
Unique Trait: SUS309 offers good corrosion resistance in high-temperature environments, though not as high as that of austenitic grades like SUS316.
Comparison:
vs. SUS304 Stainless Steel: SUS309 has better high-temperature oxidation resistance, while SUS304 offers superior resistance in aqueous environments.
vs. SUS310 Stainless Steel: SUS310 offers superior oxidation resistance compared to SUS309, making it ideal for extreme temperatures.
vs. SUS316 Stainless Steel: SUS316 provides better corrosion resistance in acidic environments but does not handle high temperatures as well as SUS309.
3. Machinability
Unique Trait: SUS309 is relatively easy to machine compared to other high-temperature stainless steels, but it requires carbide tooling and slower machining speeds due to its strength.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is easier to machine than SUS309 but offers lower performance at high temperatures.
vs. SUS310 Stainless Steel: SUS310 is harder to machine than SUS309 due to its higher alloy content and higher strength.
vs. SUS316 Stainless Steel: SUS316 is easier to machine than SUS309 but unsuitable for high-temperature applications.
4. Cost-Effectiveness
Unique Trait: SUS309 balances high-temperature performance and cost, making it a more affordable option than other high-performance alloys like SUS310.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is less expensive but unsuitable for high-temperature environments.
vs. SUS310 Stainless Steel: SUS310 is more expensive than SUS309 due to its higher resistance to extreme temperatures.
vs. SUS316 Stainless Steel: SUS316 is more expensive than SUS309, though it offers better corrosion resistance in chemical environments.
CNC Machining Challenges and Solutions for SUS309 Stainless Steel
Machining Challenges and Solutions
Challenge | Root Cause | Solution |
|---|---|---|
Work Hardening | Low work hardening rate | Use carbide tools with TiN coatings to improve tool life. |
Surface Roughness | Low carbon content and ductility | Optimize feed rates and use high-speed tools for smoother finishes. |
Tool Wear | Abrasive nature of stainless steel | Use high-performance tool coatings like TiAlN for reduced wear. |
Dimensional Inaccuracy | Stresses from machining | Perform stress-relief annealing to reduce dimensional variations and improve precision. |
Chip Control Issues | Long, stringy 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 SUS309 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 SUS309 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 SUS309 Stainless Steel Parts
Automotive Industry
Exhaust Systems: SUS309’s high temperature resistance makes it ideal for exhaust components and catalytic converters.
Power Generation Industry
Furnace Components: SUS309 is commonly used for furnace parts exposed to extreme heat, such as furnace tubes and kilns.
Chemical Processing
Heat Exchangers: SUS309’s high-temperature resistance makes it suitable for heat exchangers and other critical components in chemical plants.
Technical FAQs: CNC Machined SUS309 Stainless Steel Parts & Services
How does SUS309 compare to SUS304 in high-temperature environments?
What are the best welding techniques for SUS309 stainless steel?
How does SUS309 perform in acidic environments compared to other stainless steels?
What are the recommended heat treatment processes for SUS309?
How does SUS309 perform in aerospace applications compared to other high-temperature alloys?
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