Overview
SS420 (AISI 420 Stainless Steel) is a high-carbon martensitic stainless steel belonging to the 400 Series Stainless Steel Family. It is well known for its ability to achieve very high hardness through heat treatment while maintaining moderate corrosion resistance.
SS420 is commonly referred to as Cutlery Grade Stainless Steel because of its widespread use in knives, surgical instruments, scissors, blades, molds, wear-resistant components, and industrial tooling.
Compared with SS410, SS420 offers significantly higher hardness and wear resistance. Compared with SS440C, SS420 provides better toughness and easier machining, although with lower hardness.
Material Specification
| Property | Value |
|---|---|
| Material Designation | AISI 420 |
| Material Family | Martensitic Stainless Steel |
| UNS Number | S42000 |
| EN Grade | 1.4021 |
| Density | 7.75 g/cm³ |
| Magnetic Property | Magnetic |
| Standard Forms | Plate, Sheet, Bar, Rod, Tube, Forgings |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 12.0–14.0 |
| Carbon (C) | 0.15–0.40 |
| Manganese (Mn) | ≤1.00 |
| Silicon (Si) | ≤1.00 |
| Phosphorus (P) | ≤0.040 |
| Sulfur (S) | ≤0.030 |
| Nickel (Ni) | ≤0.75 |
| Molybdenum (Mo) | ≤0.60 |
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 650–850 MPa |
| Yield Strength | ≥345 MPa |
| Elongation | ≥15% |
| Hardness | ≤225 HB |
| Elastic Modulus | 200 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 900–1500 MPa |
| Yield Strength | 700–1200 MPa |
| Hardness | 48–56 HRC |
| Wear Resistance | Excellent |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.75 g/cm³ |
| Melting Point | 1450–1510°C |
| Thermal Conductivity | 24.9 W/m·K |
| Electrical Resistivity | 0.55 μΩ·m |
| Thermal Expansion Coefficient | 10.3 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Good |
| Atmospheric Exposure | Good |
| Fresh Water | Good |
| Industrial Environment | Moderate |
| Marine Environment | Poor |
| Chloride Environment | Poor |
| Chemical Processing Environment | Limited |
SS420 provides better corrosion resistance than ordinary carbon steels but lower corrosion resistance than SS304 and SS316.
For long-term corrosion protection, polishing, passivation, or coatings are often recommended.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 840–900°C |
| Cooling Method | Furnace Cool |
Hardening
| Parameter | Value |
|---|---|
| Temperature | 980–1065°C |
| Quenching | Oil or Air |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 150–650°C |
| Purpose | Adjust Hardness & Toughness |
SS420 can achieve hardness levels up to 56 HRC, making it one of the hardest standard martensitic stainless steels.
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | 420 |
| UNS | S42000 |
| EN (Europe) | 1.4021 |
| DIN (Germany) | X20Cr13 |
| JIS (Japan) | SUS420J1 |
| GB/T (China) | 20Cr13 |
| ISO | X20Cr13 |
Higher Carbon Variants
| Grade | Equivalent |
|---|---|
| SUS420J1 | Lower Carbon |
| SUS420J2 | Higher Carbon |
| 30Cr13 | Medium Carbon |
| 40Cr13 | High Carbon |
Available Forms
| Product Type | Availability |
|---|---|
| Stainless Steel Plate | Yes |
| Stainless Steel Sheet | Yes |
| Round Bar | Yes |
| Flat Bar | Yes |
| Forgings | Yes |
| Pipe | Yes |
| Tube | Yes |
| Machining Stock | Yes |
Typical Applications
Cutlery Industry
- Kitchen Knives
- Pocket Knives
- Scissors
- Razor Blades
- Cutting Tools
Medical Industry
- Surgical Instruments
- Forceps
- Scalpel Handles
- Dental Instruments
Industrial Tooling
- Molds
- Dies
- Punches
- Wear Components
Valve & Pump Industry
- Valve Components
- Pump Shafts
- Wear Rings
- Mechanical Seals
Automotive Industry
- Drive Components
- Precision Shafts
- Mechanical Assemblies
Consumer Products
- Multi-Tools
- Outdoor Equipment
- Sporting Goods
- 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 up to 56 HRC after heat treatment.
Excellent Wear Resistance
Ideal for cutting and friction applications.
Good Strength
Suitable for high-load mechanical components.
Heat Treatable
Mechanical properties can be customized.
Good Polishability
Produces highly polished surfaces.
Cost Effective
More affordable than many tool steels.
Limitations
Lower Corrosion Resistance Than SS304
Not suitable for highly corrosive environments.
Poor Weldability
Heat treatment is often required after welding.
Reduced Toughness at High Hardness
Higher hardness can decrease impact resistance.
Not Suitable for Marine Applications
SS316 is preferred for saltwater environments.
Comparison with Other Stainless Steels
| Property | SS420 | SS410 | SS416 | SS440C | SS304 |
|---|---|---|---|---|---|
| Hardness | Very High | High | High | Extremely High | Medium |
| Wear Resistance | Excellent | Good | Good | Outstanding | Moderate |
| Corrosion Resistance | Moderate | Moderate | Moderate | Good | Excellent |
| Heat Treatable | Yes | Yes | Yes | Yes | No |
| Weldability | Poor | Fair | Poor | Poor | Excellent |
| Toughness | Good | Better | Moderate | Lower | Excellent |
Comparison with Common Engineering Metals
| Material | Density (g/cm³) | Hardness | Wear Resistance | Corrosion Resistance |
|---|---|---|---|---|
| SS420 | 7.75 | Very High | Excellent | Moderate |
| SS410 | 7.75 | High | Good | Moderate |
| SS440C | 7.70 | Outstanding | Outstanding | Good |
| Tool Steel D2 | 7.70 | Outstanding | Outstanding | Fair |
| Carbon Steel 1095 | 7.85 | High | Good | Poor |
| Aluminum 7075 | 2.81 | Medium | Moderate | Fair |
Available Surface Finishes
Mill Finishes
- Hot Rolled Finish
- Cold Rolled Finish
- Ground Finish
- Bright Finish
Decorative Finishes
- Mirror Polish
- Satin Finish
- Brushed Finish
- Hairline Finish
Functional Finishes
- Passivation
- Electropolishing
- Hard Chrome Plating
- Black Oxide Coating
- Nitriding
- PVD Coating
Frequently Asked Questions (FAQ)
What is SS420 stainless steel?
SS420 is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and heat-treatable properties.
What is SS420 used for?
Typical applications include:
- Knives
- Surgical Instruments
- Scissors
- Molds
- Valve Components
- Precision Mechanical Parts
Is SS420 magnetic?
Yes. SS420 is fully magnetic in both annealed and hardened conditions.
Can SS420 be heat treated?
Yes. SS420 is specifically designed for heat treatment and can achieve hardness levels up to 56 HRC.
What is the difference between SS420 and SS410?
| Property | SS420 | SS410 |
|---|---|---|
| Carbon Content | Higher | Lower |
| Hardness | Higher | Lower |
| Wear Resistance | Better | Lower |
| Toughness | Slightly Lower | Better |
What is the difference between SS420 and SS440C?
| Property | SS420 | SS440C |
|---|---|---|
| Hardness | Up to 56 HRC | Up to 60 HRC |
| Toughness | Better | Lower |
| Machinability | Better | More Difficult |
| Cost | Lower | Higher |
Can SS420 rust?
Yes. Although corrosion resistant, SS420 can rust if exposed to saltwater, acids, or poor maintenance conditions.
Is SS420 suitable for knife manufacturing?
Yes. SS420 is one of the most widely used stainless steels for knife blades and cutting tools.
Why is SS420 used for surgical instruments?
Because it combines:
- High Hardness
- Good Corrosion Resistance
- Excellent Polishability
- Sterilization Resistance
making it ideal for medical tools.
Does GCNOV provide custom manufacturing services for SS420?
Yes. GCNOV provides:
- CNC Machining
- CNC Turning
- Precision Grinding
- Heat Treatment
- Surgical Instrument Components
- Mold Components
- Surface Finishing
- Passivation
- Prototype Development
- Low-Volume Production
- Mass Production