Overview
SS440A (AISI 440A Stainless Steel) is a high-carbon martensitic stainless steel belonging to the 440 Series Stainless Steel Family. It is known for its excellent hardness, good wear resistance, moderate corrosion resistance, and ability to achieve high strength through heat treatment.
SS440A contains less carbon than SS440B and SS440C, providing a better balance between corrosion resistance, toughness, and hardness. It is widely used in knife blades, surgical instruments, valve components, bearing parts, cutting tools, and precision mechanical components.
Compared with SS420, SS440A offers higher hardness and wear resistance. Compared with SS440C, SS440A provides better corrosion resistance and toughness but slightly lower hardness.
Material Specification
| Property | Value |
|---|---|
| Material Designation | AISI 440A |
| Material Family | High Carbon Martensitic Stainless Steel |
| UNS Number | S44002 |
| EN Grade | 1.4109 |
| Density | 7.70–7.75 g/cm³ |
| Magnetic Property | Magnetic |
| Standard Forms | Bar, Rod, Plate, Sheet, Forgings |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 16.0–18.0 |
| Carbon (C) | 0.60–0.75 |
| Manganese (Mn) | ≤1.00 |
| Silicon (Si) | ≤1.00 |
| Phosphorus (P) | ≤0.040 |
| Sulfur (S) | ≤0.030 |
| Molybdenum (Mo) | ≤0.75 |
| Nickel (Ni) | ≤0.75 |
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 700–850 MPa |
| Yield Strength | ≥350 MPa |
| Elongation | ≥15% |
| Hardness | ≤255 HB |
| Elastic Modulus | 200 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 1000–1600 MPa |
| Yield Strength | 750–1300 MPa |
| Hardness | 54–58 HRC |
| Wear Resistance | Excellent |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.74 g/cm³ |
| Melting Point | 1450–1510°C |
| Thermal Conductivity | 24.2 W/m·K |
| Electrical Resistivity | 0.60 μΩ·m |
| Thermal Expansion Coefficient | 10.1 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Excellent |
| Atmospheric Exposure | Good |
| Fresh Water | Good |
| Food Contact Applications | Good |
| Industrial Environment | Moderate |
| Marine Environment | Fair |
| Chloride Environment | Limited |
SS440A offers better corrosion resistance than SS440B and SS440C because of its lower carbon content.
It performs well in:
- Humid Environments
- Freshwater Exposure
- Food Processing Equipment
- Household Applications
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 850–900°C |
| Cooling Method | Furnace Cool |
Hardening
| Parameter | Value |
|---|---|
| Temperature | 1010–1065°C |
| Quenching | Oil or Air |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 150–370°C |
| Purpose | Improve Toughness & Stability |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | 440A |
| UNS | S44002 |
| EN (Europe) | 1.4109 |
| DIN (Germany) | X65CrMo14 |
| JIS (Japan) | SUS440A |
| GB/T (China) | 7Cr17 |
| ISO | X65CrMo14 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Stainless Plate | Yes |
| Stainless Sheet | Yes |
| Forgings | Yes |
| Machining Stock | Yes |
Typical Applications
Knife Manufacturing
- Kitchen Knives
- Outdoor Knives
- Folding Knives
- Utility Blades
- Hunting Knives
Medical Industry
- Surgical Instruments
- Medical Cutting Tools
- Dental Instruments
- Precision Medical Components
Bearing Industry
- Bearing Races
- Ball Bearings
- Roller Components
Valve Industry
- Valve Seats
- Valve Components
- Flow Control Parts
Industrial Machinery
- Wear Components
- Precision Shafts
- Mechanical Components
- Pump Parts
Consumer Products
- Scissors
- Multi-Tools
- Sporting Equipment
- Precision Hardware
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Grinding | Outstanding |
| Heat Treatment | Outstanding |
| Polishing | Excellent |
| Forging | Excellent |
| Drilling | Good |
| Welding | Poor |
| Laser Cutting | Good |
Advantages
High Hardness
Can achieve hardness levels up to 58 HRC.
Excellent Wear Resistance
Ideal for cutting and abrasive applications.
Better Corrosion Resistance Than SS440C
Offers improved rust resistance.
Good Edge Retention
Popular for premium knife blades.
Excellent Polishability
Can achieve mirror-finish surfaces.
Heat Treatable
Mechanical properties can be optimized through heat treatment.
Limitations
Lower Corrosion Resistance Than SS304
Not suitable for aggressive marine environments.
Poor Weldability
Generally not recommended for welded structures.
Reduced Toughness Compared to SS420
Higher hardness may reduce impact resistance.
More Difficult to Machine After Hardening
Requires grinding and precision finishing.
Comparison with Other Stainless Steels
| Property | SS440A | SS420 | SS440B | SS440C | SS304 |
|---|---|---|---|---|---|
| Hardness | High | High | Very High | Outstanding | Medium |
| Corrosion Resistance | Good | Moderate | Moderate | Moderate | Excellent |
| Wear Resistance | Excellent | Excellent | Outstanding | Outstanding | Moderate |
| Toughness | Good | Better | Moderate | Lower | Excellent |
| Heat Treatable | Yes | Yes | Yes | Yes | No |
| Magnetic | Yes | Yes | Yes | Yes | No |
Comparison with Common Blade Materials
| Material | Hardness (HRC) | Corrosion Resistance | Edge Retention |
|---|---|---|---|
| SS440A | 54–58 | Good | Excellent |
| SS420 | 48–56 | Moderate | Good |
| SS440C | 58–62 | Moderate | Outstanding |
| AUS-8 | 57–59 | Good | Good |
| VG10 | 60–61 | Excellent | Outstanding |
| D2 Tool Steel | 58–62 | Fair | Outstanding |
Available Surface Finishes
Mill Finishes
- Ground Finish
- Bright Finish
- Cold Finished Surface
Decorative Finishes
- Mirror Polish
- Satin Finish
- Hairline Finish
- Brushed Finish
Functional Finishes
- Passivation
- Electropolishing
- Black Oxide Coating
- PVD Coating
- DLC Coating
Frequently Asked Questions (FAQ)
What is SS440A stainless steel?
SS440A is a high-carbon martensitic stainless steel offering excellent hardness, wear resistance, and corrosion resistance for cutting and precision applications.
What is SS440A used for?
Typical applications include:
- Knife Blades
- Surgical Instruments
- Bearings
- Valve Components
- Precision Mechanical Parts
Is SS440A magnetic?
Yes. SS440A is magnetic in both annealed and hardened conditions.
Can SS440A be heat treated?
Yes. SS440A is designed to achieve high hardness through heat treatment.
What is the difference between SS440A and SS440C?
| Property | SS440A | SS440C |
|---|---|---|
| Carbon Content | Lower | Higher |
| Corrosion Resistance | Better | Lower |
| Hardness | Lower | Higher |
| Toughness | Better | Lower |
What is the difference between SS440A and SS420?
| Property | SS440A | SS420 |
|---|---|---|
| Hardness | Higher | Lower |
| Wear Resistance | Better | Lower |
| Edge Retention | Better | Lower |
| Corrosion Resistance | Slightly Better | Moderate |
Can SS440A rust?
Under normal conditions, SS440A provides good corrosion resistance, but it may corrode in saltwater or harsh chemical environments.
Is SS440A good for knives?
Yes. SS440A is widely used for high-quality knife blades because it balances hardness, corrosion resistance, and toughness.
Why is SS440A used for surgical instruments?
Because it combines:
- High Hardness
- Good Corrosion Resistance
- Excellent Polishability
- Wear Resistance
making it suitable for precision medical tools.
Does GCNOV provide custom manufacturing services for SS440A?
Yes. GCNOV provides:
- CNC Machining
- Precision Grinding
- Heat Treatment
- Knife Component Manufacturing
- Surgical Instrument Components
- Surface Finishing
- Passivation
- Prototype Development
- Low-Volume Production
- Mass Production