Overview
SS440B (AISI 440B Stainless Steel) is a high-carbon martensitic stainless steel belonging to the 440 Series Stainless Steel Family. It offers an intermediate balance between SS440A and SS440C, providing higher hardness and wear resistance than SS440A while maintaining better toughness and corrosion resistance than SS440C.
SS440B is widely used in precision cutting tools, industrial knives, surgical instruments, valve components, bearings, wear-resistant parts, and high-strength mechanical assemblies where both hardness and corrosion resistance are required.
Compared with SS420, SS440B delivers significantly better wear resistance and edge retention. Compared with SS440C, it offers slightly improved toughness and machinability.
Material Specification
| Property | Value |
|---|---|
| Material Designation | AISI 440B |
| Material Family | High Carbon Martensitic Stainless Steel |
| UNS Number | S44003 |
| EN Grade | 1.4112 |
| 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) | 0.75–0.95 |
| 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 | 750–900 MPa |
| Yield Strength | ≥350 MPa |
| Elongation | ≥12% |
| Hardness | ≤269 HB |
| Elastic Modulus | 200 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 1200–1700 MPa |
| Yield Strength | 850–1350 MPa |
| Hardness | 56–60 HRC |
| Wear Resistance | Outstanding |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.74 g/cm³ |
| Melting Point | 1450–1510°C |
| Thermal Conductivity | 24.0 W/m·K |
| Electrical Resistivity | 0.60 μΩ·m |
| Thermal Expansion Coefficient | 10.2 × 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 |
SS440B offers corrosion resistance between SS440A and SS440C.
Its higher carbon content improves hardness but slightly reduces corrosion resistance compared with SS440A.
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 |
Proper heat treatment enables SS440B to achieve exceptional hardness and wear resistance.
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | 440B |
| UNS | S44003 |
| EN (Europe) | 1.4112 |
| DIN (Germany) | X90CrMoV18 |
| JIS (Japan) | SUS440B |
| GB/T (China) | 8Cr17Mo |
| ISO | X90CrMoV18 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Stainless Plate | Yes |
| Stainless Sheet | Yes |
| Forgings | Yes |
| Precision Machining Stock | Yes |
Typical Applications
Knife Manufacturing
- Premium Kitchen Knives
- Outdoor Knives
- Tactical Knives
- Industrial Blades
- Utility Cutters
Medical Industry
- Surgical Instruments
- Dental Instruments
- Precision Cutting Tools
- Medical Blades
Bearing Industry
- Bearing Components
- Bearing Races
- Roller Bearings
- Precision Rotating Parts
Industrial Machinery
- Wear Components
- Precision Shafts
- Guide Rails
- Mechanical Assemblies
Valve & Pump Industry
- Valve Seats
- Pump Components
- Mechanical Seals
- Wear Rings
Tooling Industry
- Cutting Tools
- Measuring Tools
- Precision Fixtures
- Mold Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Grinding | Outstanding |
| Heat Treatment | Outstanding |
| Polishing | Excellent |
| Forging | Excellent |
| Drilling | Moderate |
| Welding | Poor |
| Laser Cutting | Good |
Advantages
Very High Hardness
Can achieve up to 60 HRC after heat treatment.
Outstanding Wear Resistance
Suitable for abrasive and cutting applications.
Excellent Edge Retention
Maintains sharpness longer than SS420 and SS440A.
Good Corrosion Resistance
Better than many tool steels and carbon steels.
Excellent Polishability
Suitable for mirror-finished components.
Heat Treatable
Allows optimization of hardness and toughness.
Limitations
More Difficult to Machine
Higher hardness increases machining complexity.
Poor Weldability
Generally not recommended for welded structures.
Lower Toughness Than SS440A
Higher carbon content reduces impact resistance.
Not Ideal for Marine Service
SS316 provides superior corrosion resistance.
Comparison with Other Stainless Steels
| Property | SS440B | SS440A | SS440C | SS420 | SS304 |
|---|---|---|---|---|---|
| Hardness | Very High | High | Outstanding | High | Medium |
| Wear Resistance | Outstanding | Excellent | Outstanding | Excellent | Moderate |
| Corrosion Resistance | Good | Better | Moderate | Moderate | Excellent |
| Edge Retention | Excellent | Good | Outstanding | Good | Poor |
| Toughness | Good | Better | Lower | Better | Excellent |
| Heat Treatable | Yes | Yes | Yes | Yes | No |
Comparison with Common Blade Materials
| Material | Hardness (HRC) | Corrosion Resistance | Edge Retention |
|---|---|---|---|
| SS440B | 56–60 | Good | Excellent |
| SS440A | 54–58 | Better | 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 SS440B stainless steel?
SS440B is a high-carbon martensitic stainless steel offering a balanced combination of hardness, wear resistance, toughness, and corrosion resistance.
What is SS440B used for?
Typical applications include:
- Knife Blades
- Surgical Instruments
- Bearings
- Valve Components
- Industrial Cutting Tools
- Wear Parts
Is SS440B magnetic?
Yes. SS440B is magnetic in both annealed and hardened conditions.
Can SS440B be heat treated?
Yes. SS440B is specifically designed for hardening and tempering.
What is the difference between SS440A and SS440B?
| Property | SS440A | SS440B |
|---|---|---|
| Carbon Content | Lower | Higher |
| Hardness | Lower | Higher |
| Wear Resistance | Lower | Better |
| Toughness | Better | Slightly Lower |
What is the difference between SS440B and SS440C?
| Property | SS440B | SS440C |
|---|---|---|
| Hardness | High | Highest |
| Corrosion Resistance | Better | Lower |
| Toughness | Better | Lower |
| Machinability | Better | More Difficult |
Can SS440B rust?
Under normal conditions, SS440B provides good corrosion resistance. However, saltwater and harsh chemical exposure may cause corrosion.
Is SS440B suitable for knife manufacturing?
Yes. SS440B is frequently used for premium knife blades requiring excellent edge retention and corrosion resistance.
Why is SS440B used for bearings?
Because it combines:
- High Hardness
- Excellent Wear Resistance
- Good Corrosion Resistance
- Dimensional Stability
making it suitable for precision rotating components.
Does GCNOV provide custom manufacturing services for SS440B?
Yes. GCNOV provides:
- CNC Machining
- Precision Grinding
- Heat Treatment
- Knife Component Manufacturing
- Bearing Components
- Surgical Instrument Parts
- Surface Finishing
- Passivation
- Prototype Development
- Low-Volume Production
- Mass Production