Stainless Steel SUS420
Introduction to Stainless Steel SUS420: A High-Strength Martensitic Alloy
Stainless Steel SUS420 is a martensitic stainless steel known for its high strength, hardness, and moderate corrosion resistance. With a carbon content ranging from 0.15% to 0.40%, SUS420 is primarily used in applications that require wear resistance and strength, such as cutlery, surgical instruments, and tools. Although it offers better hardness than austenitic stainless steel, its corrosion resistance is lower, making it more suitable for environments with mild corrosion conditions.
Thanks to its high carbon content, SUS420 can achieve a hardness of up to 50 HRC after heat treatment, allowing it to maintain sharp edges and durability in harsh conditions. CNC machining of SUS420 stainless steel requires specific techniques to minimize tool wear due to its hardness, but it can be machined to tight tolerances and fine finishes. At Neway, CNC-machined SUS420 parts undergo stringent quality control processes to ensure precision and surface quality for critical applications.
SUS420 Stainless Steel: Key Properties and Composition
SUS420 Stainless Steel Chemical Composition
Element | Composition (wt%) | Role/Impact |
|---|---|---|
Carbon (C) | 0.15–0.40% | High carbon content provides hardness and wear resistance after heat treatment. |
Manganese (Mn) | 0.60–1.00% | Improves toughness and increases strength at lower temperatures. |
Chromium (Cr) | 12.0–14.0% | Provides corrosion resistance and improves hardness and strength at elevated temperatures. |
Nickel (Ni) | ≤0.60% | Enhances ductility and formability, though lower than in austenitic stainless steels. |
Molybdenum (Mo) | ≤0.75% | Increases resistance to pitting and crevice corrosion in chloride environments. |
SUS420 Stainless Steel Physical Properties
Property | Value | Notes |
|---|---|---|
Density | 7.75 g/cm³ | Similar to other martensitic stainless steels, providing strength and durability. |
Melting Point | 1,400–1,530°C | Suitable for both cold and hot working, especially in high-temperature applications. |
Thermal Conductivity | 25.4 W/m·K | Moderate heat dissipation capacity, ideal for high-wear applications where heat buildup is an issue. |
Electrical Resistivity | 6.9×10⁻⁷ Ω·m | Suitable for non-electrical applications, with low electrical conductivity. |
SUS420 Stainless Steel Mechanical Properties
Property | Value | Testing Standard/Condition |
|---|---|---|
Tensile Strength | 600 MPa | ASTM A240/A240M standard |
Yield Strength | 450 MPa | Suitable for high-strength applications |
Elongation (50mm gauge) | 12–15% | Moderate ductility, suitable for moderate-forming processes. |
Brinell Hardness | 450–500 HB | Achieved after heat treatment, offering excellent wear resistance. |
Machinability Rating | 45% (vs. 1212 steel at 100%) | Suitable for machining, though it requires sharp tools and slow speeds. |
Key Characteristics of SUS420 Stainless Steel: Benefits and Comparisons
SUS420 stainless steel is a high-strength material often used for wear-resistant components. Below is a technical comparison highlighting its unique advantages over similar materials like SUS304 Stainless Steel, SUS316 Stainless Steel, and SUS440C Stainless Steel.
1. High Hardness
Unique Trait: The high carbon content in SUS420 allows it to achieve a hardness of up to 50 HRC after heat treatment, making it ideal for cutting tools and wear-resistant applications.
Comparison:
vs. SUS304 Stainless Steel: SUS304 has a much lower hardness and is better suited for applications requiring higher corrosion resistance rather than wear resistance.
vs. SUS316 Stainless Steel: SUS316 has superior corrosion resistance but cannot match SUS420's hardness for wear-resistant applications.
2. Moderate Corrosion Resistance
Unique Trait: While SUS420 offers better corrosion resistance than some other high-carbon steels, its performance is not as robust as austenitic grades like SUS304 or SUS316.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is more resistant to oxidation and corrosion, particularly in acidic environments.
vs. SUS316 Stainless Steel: SUS316 offers superior corrosion resistance in marine and chloride-rich environments compared to SUS420.
3. High Strength
Unique Trait: With a tensile strength of 600 MPa, SUS420 can withstand high mechanical loads and is suitable for high-strength applications.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is less strong than SUS420 but offers better ductility and toughness for forming and welding.
vs. SUS440C Stainless Steel: SUS440C has similar strength and hardness but is harder to machine than SUS420.
4. Wear Resistance
Unique Trait: Due to its high hardness, SUS420 offers excellent wear resistance, making it suitable for cutting tools, dies, and bearings.
Comparison:
vs. SUS304 Stainless Steel: SUS304 is not as wear-resistant and is better suited for applications requiring corrosion over wear resistance.
vs. SUS440C Stainless Steel: SUS440C provides similar wear resistance but has a higher chromium content, which enhances its corrosion resistance but makes it harder to machine.
5. Post-Processing Flexibility
Unique Trait: SUS420 is compatible with various heat treatments to achieve the desired hardness and wear resistance.
Comparison:
vs. SUS304 Stainless Steel: SUS304 does not require heat treatment for most applications, whereas SUS420 requires heat treatment to achieve its high hardness.
vs. SUS316 Stainless Steel: SUS316’s superior corrosion resistance allows for less post-processing in most applications.
CNC Machining Challenges and Solutions for SUS420 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 | High hardness leading to wear | Slow feed rates and sharp tools will minimize surface roughness. |
Tool Wear | Abrasiveness of the material | Use high-performance coatings like TiAlN to reduce friction and tool wear. |
Dimensional Inaccuracy | Stresses from machining | Use low-speed cutting and adequate cooling to reduce thermal distortion. |
Chip Control Issues | Hard, stringy chips | High-pressure coolant and chip breakers on tools can improve chip formation. |
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 SUS420 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 SUS420 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 SUS420 Stainless Steel Parts
Automotive Industry
Cutting Tools: SUS420’s high hardness makes it ideal for producing precision cutting tools used in automotive assembly.
Medical Industry
Surgical Instruments: The material’s strength and corrosion resistance make it suitable for surgical instruments that require durability and cleanliness.
Tooling Industry
Ball Bearings: The hardness of SUS420 ensures excellent wear resistance in high-stress applications like bearings.
Technical FAQs: CNC Machined SUS420 Stainless Steel Parts & Services
How does SUS420 compare to other martensitic stainless steels regarding hardness and wear resistance?
What are the optimal machining strategies for minimizing tool wear when CNC machining SUS420?
Can SUS420 be used in marine applications, and how does it perform compared to other stainless steels?
What are the common surface treatments for improving the corrosion resistance of SUS420 in harsh environments?
How does heat treatment affect the hardness and machinability of SUS420 steel?
Explore Related Blogs
