1.4006, designated as SUS410 in Japanese Industrial Standards (JIS), is a martensitic stainless steel known for its combination of moderate corrosion resistance, good mechanical strength, and the ability to be hardened by heat treatment. It is one of the most widely used martensitic grades, valued for its versatility in applications requiring both strength and basic corrosion resistance.
Basic Information
Definition: 1.4006 (SUS410) is a chromium-based martensitic stainless steel with low carbon content, allowing it to be heat-treated to achieve high hardness. Unlike austenitic grades (e.g., 304, 316), it is magnetic and offers better strength but lower corrosion resistance.
Corresponding Standards: Conforms to EN 10088-1 (European) and JIS G4303 (Japanese). International equivalents include:
American: AISI 410
Chinese: 1Cr13 (GB/T 1220)
Key Characteristics: Heat-treatable to high hardness, good wear resistance, moderate corrosion resistance, and magnetic properties, making it suitable for both structural and cutting applications.
Chemical Composition
The composition of 1.4006 (SUS410) is optimized for martensitic transformation and balanced performance:
Element Content Range Role in the Steel
Chromium (Cr) 11.5–13.5% Primary element for corrosion resistance, forming a protective oxide layer; enables martensitic transformation.
Carbon (C) 0.08–0.15% Controls hardenability and strength; higher carbon increases hardness after heat treatment but may reduce corrosion resistance.
Silicon (Si) ≤0.60% Acts as a deoxidizer; improves oxidation resistance at high temperatures.
Manganese (Mn) ≤1.00% Enhances hardenability and strength; aids in hot workability.
Phosphorus (P) ≤0.040% Limited to prevent brittleness, especially in welded joints.
Sulfur (S) ≤0.030% Minimized to avoid hot cracking during welding and reduce toughness loss.
Iron (Fe) Balance Base metal providing structural integrity.
Physical Properties
Density: ~7.75 g/cm³ (slightly lower than austenitic stainless steels).
Melting Point: ~1480–1530°C.
Thermal Conductivity: ~25 W/(m·K) at room temperature.
Coefficient of Thermal Expansion: ~10.5×10⁻⁶/°C (20–100°C), lower than austenitic grades, reducing thermal distortion.
Elastic Modulus: ~200 GPa at room temperature.
Magnetic Properties: Magnetic in all conditions (due to martensitic/ferritic microstructure), unlike austenitic stainless steels.
Mechanical Properties
1.4006 (SUS410) exhibits significant property variations with heat treatment, allowing customization for specific applications:
Property Annealed State Quenched & Tempered (300°C)
Tensile Strength (Rm) 450–600 MPa 1000–1300 MPa
Yield Strength (Rp0.2) ≥205 MPa ≥800 MPa
Elongation (A) ≥20% ≥12%
Hardness ≤200 HB 38–45 HRC
Impact Toughness (Akv) ~60 J ~30–40 J (varies with tempering)
Heat Treatment Effect: Quenching (from 950–1000°C) forms hard martensite, while tempering adjusts strength-toughness balance. Higher tempering temperatures (e.g., 600°C) reduce hardness but improve toughness.
Wear Resistance: Excellent after hardening, suitable for cutting tools and abrasive environments.
Heat Treatment
Heat treatment is critical to unlocking 1.4006 (SUS410)’s full potential:
Annealing
Purpose: Soften the steel for machining, reduce internal stress, and improve ductility.
Process: Heat to 650–750°C, hold 2–4 hours, then cool slowly. Results in hardness ≤200 HB.
Quenching
Temperature: 950–1000°C (austenitization), held 1–2 hours.
Cooling: Oil or air quenching to form martensite, achieving as-quenched hardness of 50–55 HRC.
Tempering
Temperature Range: 200–700°C (adjusted for desired properties).
Common Practice: Temper at 300–400°C for high strength (38–45 HRC) or 600–700°C for improved toughness (25–30 HRC).
Corrosion Resistance
1.4006 (SUS410) offers moderate corrosion resistance, suitable for non-aggressive environments:
Atmospheric Resistance: Resists rust in dry or moderately humid air; may corrode in industrial or coastal environments with high pollutants or salt.
Water Resistance: Tolerates fresh water but is susceptible to pitting in saltwater or chlorinated water (inferior to 304/316).
Chemical Resistance: Resists mild acids and alkalis but is attacked by strong acids (e.g., sulfuric, hydrochloric) and chloride-rich solutions.
Passivation: Can be passivated (with nitric acid) to enhance the chromium oxide layer, improving corrosion resistance in mild environments.
Processing Performance
Weldability: Moderate—requires preheating (200–300°C) and post-weld annealing to prevent cracking, due to martensite formation in the heat-affected zone (HAZ).
Machinability: Good in the annealed state (≤200 HB) with high-speed steel or carbide tools. Hardened 1.4006 (HRC ≥38) is more challenging, requiring sharp tools and slow speeds.
Formability: Fair in the annealed state for bending, stamping, or forging. Poor formability in the hardened state due to high strength.
Polishability: Can be polished to a smooth finish but not to the mirror quality of austenitic grades.
Application Fields
1.4006 (SUS410) is widely used in applications requiring heat-treatable strength and moderate corrosion resistance:
Cutting Tools & Blades: Knives, scissors, and surgical instruments (hardened for sharpness and wear resistance).
Automotive Components: Exhaust manifolds, valve stems, and pump shafts (resist moderate heat and corrosion).
Mechanical Hardware: Bolts, nuts, and fasteners requiring high strength and basic rust resistance.
Industrial Equipment: Valves, pumps, and shafts for non-aggressive fluid handling; turbine blades for low-temperature applications.
Household Goods: Kitchen knives, appliance parts, and decorative items (magnetic properties may be advantageous).
Advantages and Limitations
Advantages
Heat-Treatable: Can be hardened to high levels (up to 55 HRC) for wear resistance and cutting performance.
Cost-Effective: Lower cost than austenitic grades (304/316) due to no nickel content.
Magnetic: Useful in applications requiring magnetic properties (e.g., sensors, magnetic clamps).
Good Strength: Higher tensile strength than ferritic grades (e.g., 430) after heat treatment.
Limitations
Limited Corrosion Resistance: Inferior to austenitic stainless steels; not suitable for saltwater or aggressive chemicals.
Welding Complexity: Requires pre- and post-weld heat treatment, increasing production costs.
Low-Temperature Toughness: May become brittle at sub-zero temperatures, limiting use in cold environments.
Comparison with Related Steels
Steel Grade Type Tensile Strength (Quenched/Tempered) Corrosion Resistance Key Use Case
1.4006 (410) Martensitic 1000–1300 MPa Moderate Cutting tools, exhaust parts
1.4016 (430) Ferritic 450–600 MPa Moderate Appliances, architectural trim
1.4301 (304) Austenitic 500–700 MPa High Food processing, marine use
1.4021 (420) Martensitic 1200–1500 MPa Moderate High-hardness tools (e.g., dies)
In summary, 1.4006 (SUS410) is a versatile martensitic stainless steel that balances strength, wear resistance, and cost-effectiveness. Its ability to be heat-treated for high hardness makes it indispensable in applications requiring cutting performance or structural strength in moderately corrosive environments.