Stainless Steel, Martensitic
420 Stainless Steel (S42000) Bar
A martensitic machining bar with machinability enhanced through the addition of sulphur.
As with most other free-machining stainless steels the improvement in machinability is achieved by addition of sulphur which forms manganese sulphide inclusions; this sulphur addition also lowers the corrosion resistance, weldability and formability to below that of its non-free machining equivalent Grade 410.
420 stainless steel is a high-carbon martensitic stainless steel known for its high hardness, good wear resistance, and moderate corrosion resistance. It is commonly used in applications that require cutting edges, wear resistance, and the ability to be hardened.
Martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised. Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment. Corrosion resistance is lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures.
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Related Specifications
- S42020
- SUS 420J1
- STS 420J1
- S42000
- X20Cr 13
- Z20C 13
- 1.4021
- 420S37
Properties
Chemical Composition
1.4021 Steel
EN 10088-3
| Chemical Element | % Present |
| Carbon (C) | 0.16 - 0.25 |
| Chromium (Cr) | 12.00 - 14.00 |
| Manganese (Mn) | 0.00 - 1.50 |
| Silicon (Si) | 0.00 - 1.00 |
| Phosphorous (P) | 0.00 - 0.04 |
| Sulphur (S) | 0.00 - 0.03 |
| Iron (Fe) | Balance |
Mechanical Properties
Bar Up to 160mm Dia / Thickness
EN 10088-3
| Mechanical Property | Value |
| Proof Stress | 500 - 600 MPa |
| Tensile Strength | 700 - 950 MPa |
| Elongation A | 12 - 13 % |
General Physical Properties
| Physical Property | Value |
| Density | 7.75 g/cm³ |
| Thermal Expansion | 10.3 x 10-6/K |
| Modulus of Elasticity | 200 GPa |
| Thermal Conductivity | 24.9 W/m.K |
| Electrical Resistivity | 0.55 x 10-6 Ω .m |
Applications of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its excellent hardness, good wear resistance, and moderate corrosion resistance. It is widely used in applications requiring cutting performance, precision, and durability.
1. Cutting Tools and Blades
Knives, scissors, and surgical instruments
Razors and trimming tools
Industrial cutting and shaping tools
2. Mechanical and Industrial Components
Gears, shafts, and bushings
Bearings and valve components
Dies, molds, and wear-resistant parts
3. Automotive and Aerospace Applications
High-strength fasteners and pins
Springs and precision components
Components requiring wear resistance under stress
4. Household and Decorative Applications
Kitchen knives and utensils
Tools and hardware exposed to moderate wear and moisture
Decorative fittings requiring moderate corrosion resistance
Summary
420 stainless steel combines high hardness, good wear resistance, and moderate corrosion resistance, making it ideal for cutting tools, precision mechanical components, industrial parts, and household items. It is particularly suitable for applications requiring sharp edges, durability, and dimensional stability.
Characteristics of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and moderate corrosion resistance. It is widely used in applications requiring cutting performance, durability, and dimensional stability.
1. Chemical Composition
Carbon: 0.15–0.40% – provides high hardness and wear resistance
Chromium: 12–14% – gives corrosion resistance and hardenability
Minor elements such as manganese, silicon, and nickel enhance mechanical properties
2. Hardness and Mechanical Properties
Can be hardened to 50–55 HRC after heat treatment
Excellent tensile strength and wear resistance
Moderate ductility and toughness, designed primarily for hard, wear-resistant applications
3. Corrosion Resistance
Moderate resistance to oxidation and mild corrosive environments
Better than carbon steels but lower than austenitic stainless steels (e.g., 304, 316)
Suitable for kitchen tools, industrial components, and precision parts exposed to mild moisture or chemical exposure
4. Machinability and Fabrication
Machinable in annealed condition
Can be polished to a bright finish for aesthetic or functional applications
Welding is possible but may reduce hardness in the heat-affected zone; post-weld heat treatment is recommended
5. Applications
Knives, scissors, and cutting tools
Gears, shafts, bearings, and wear-resistant mechanical components
Springs, dies, molds, and precision engineering parts
Kitchen utensils and decorative hardware
Summary
420 stainless steel is characterized by high hardness, excellent wear resistance, and moderate corrosion resistance. Its combination of properties makes it ideal for cutting tools, precision mechanical components, industrial parts, and household items requiring durability and dimensional stability.
Additional Information
Fabrication
Fabrication of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its good hardness, wear resistance, and moderate corrosion resistance. Fabrication requires careful handling due to its high carbon content and potential for hardening during processing.
1. Forming
Hot Working:
Best performed in the annealed condition.
Typical hot working temperature: 900–1050°C (1650–1920°F).
Avoid overheating to prevent grain growth and loss of toughness.
Cold Working:
Possible in the annealed state.
Cold deformation increases strength through strain hardening, but excessive deformation can cause cracking.
Suitable for bending, stamping, and rolling thin sections.
2. Machining
Machining is easier in the annealed condition.
Hardened 420 is difficult to machine, requiring carbide tooling and proper cooling.
Use cutting fluids to reduce heat and maintain tool life.
3. Welding
Welding is limited due to high carbon content.
Preheating and post-weld stress relief are recommended to prevent cracking.
Use matching or low-carbon filler materials for better corrosion resistance and strength.
4. Heat Treatment
Annealing is used before fabrication to soften the steel for forming or machining.
Hardening followed by tempering is applied after fabrication to achieve desired hardness and wear resistance.
5. Surface Treatment
Polishing or passivation can improve corrosion resistance and appearance.
Surface finishing is particularly important for cutlery, surgical instruments, and precision components.
6. Applications Benefiting from Fabrication
Cutlery and knives
Surgical instruments and medical tools
Industrial tooling and valve components
Precision mechanical parts requiring wear resistance
Summary
420 stainless steel fabrication is typically performed in the annealed condition to allow hot or cold forming, machining, and limited welding. Post-fabrication heat treatment and surface finishing ensure optimal hardness, wear resistance, and moderate corrosion resistance, making 420 ideal for cutting tools, surgical instruments, and precision mechanical components.
Weldability
Weldability of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its good hardness, wear resistance, and moderate corrosion resistance. Welding this steel requires care due to its high carbon content and tendency to harden, which can lead to cracking if not properly managed.
1. General Considerations
High carbon content increases the risk of cracking during welding.
Preferred welding in the annealed or soft condition to reduce brittleness.
Preheating and post-weld heat treatment are recommended to minimize residual stresses and prevent martensitic hardening.
2. Preheating
Preheat to 150–250°C (300–480°F) before welding.
Helps reduce thermal stress and the risk of cracking in the heat-affected zone (HAZ).
3. Welding Methods
TIG (GTAW) and MIG (GMAW) are commonly used for precision welds.
Stick welding (SMAW) is possible but requires skilled control.
Use low-hydrogen electrodes to reduce the risk of cracking.
4. Filler Materials
Use matching 420 filler metal for best corrosion resistance and mechanical properties.
Lower carbon or martensitic stainless fillers can be used to reduce cracking risk.
5. Post-Weld Heat Treatment
Stress relief or tempering after welding is critical to restore toughness.
Avoid quenching immediately after welding unless specifically required.
Typical post-weld tempering: 150–250°C (300–480°F) for 1–2 hours.
6. Limitations
Welding in the hardened condition is not recommended.
Not suitable for applications requiring high corrosion resistance in welded joints without proper post-weld treatment.
Careful control of heat input is necessary to prevent distortion and cracking.
7. Applications
Welded components in cutlery and knives (annealed condition)
Light-duty industrial components
Mechanical parts requiring moderate corrosion resistance after welding
Summary
420 stainless steel is weldable with caution, preferably in the annealed condition. Proper preheating, controlled welding, low-hydrogen filler, and post-weld tempering are essential to prevent cracking and ensure good mechanical properties. While weldability is limited compared to austenitic stainless steels, it can be effectively welded for cutlery, tools, and moderate-duty mechanical applications.
Machinability
Machinability of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its good hardness, wear resistance, and moderate corrosion resistance. Its machinability depends heavily on its heat treatment condition, with the annealed state being much easier to machine than the hardened state.
1. General Characteristics
Annealed condition:
Machinable with standard high-speed steel (HSS) or carbide tools.
Provides good surface finish and dimensional control.
Hardened condition:
Machining is difficult due to high hardness (up to ~50 HRC).
Requires carbide tooling, slow cutting speeds, and ample coolant.
Strain hardening: High-carbon content may cause work hardening during machining.
2. Recommended Cutting Parameters
Cutting Speed: Lower speeds compared to mild steels to prevent tool wear.
Feed Rate: Moderate, to balance surface finish and tool life.
Depth of Cut: Shallow cuts in hardened material to avoid excessive tool stress.
Coolant: Use water-soluble oil or cutting fluid to reduce heat and friction.
3. Tooling
Hardened 420: Best machined with carbide or ceramic tools.
Annealed 420: Can be machined with high-speed steel (HSS) tools.
Threading and tapping: Use slow speeds and sharp tooling to prevent galling.
4. Advantages
Achieves good surface finish in the annealed condition.
Allows precise machining of complex shapes before hardening.
Hardened 420 retains shape and wear resistance after final machining and polishing.
5. Limitations
High carbon content reduces machinability in hardened condition.
Excessive heat during machining may cause tool wear or surface discoloration.
Requires careful cooling and cutting control in hardened condition.
6. Applications Benefiting from Machining
Cutlery and knives
Surgical instruments
Precision components such as valve parts and industrial tools
Summary
420 stainless steel is moderately machinable in the annealed condition and difficult to machine when hardened. Proper tool selection, cutting speeds, feed rates, and coolant use are essential to achieve accurate dimensions, good surface finish, and tool longevity, making it ideal for cutlery, surgical instruments, and precision industrial components.
Corrosion Resistance
Corrosion Resistance of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its good hardness and wear resistance. Its corrosion resistance is moderate, higher than ordinary carbon steels but lower than austenitic stainless steels such as 304 or 316.
1. General Corrosion Properties
Provides moderate resistance to atmospheric corrosion and mild oxidizing environments.
Susceptible to pitting and rusting in chloride-rich or marine environments.
Polished surfaces improve corrosion resistance by reducing surface roughness.
2. Factors Affecting Corrosion Resistance
Carbon content: Higher carbon improves hardness but slightly reduces corrosion resistance.
Surface finish: Smooth, polished, or passivated surfaces significantly improve resistance.
Heat treatment: Hardened 420 may be more prone to corrosion due to microstructural changes.
Environment: Best suited for dry or mildly corrosive environments; avoid prolonged exposure to saltwater or acidic conditions.
3. Enhancing Corrosion Resistance
Polishing: Reduces surface roughness, minimizing sites for corrosion initiation.
Passivation: Treatment with nitric or citric acid forms a protective oxide layer.
Proper maintenance: Regular cleaning prevents accumulation of corrosive agents.
4. Applications Benefiting from Corrosion Resistance
Cutlery, knives, and surgical instruments in low-corrosion environments
Industrial tools and precision components exposed to mild conditions
Valve components and fittings in non-marine environments
5. Limitations
Not suitable for marine or highly acidic environments without protective coatings.
Prolonged exposure to moisture can lead to rust and pitting.
Welding without proper care may reduce corrosion resistance in the heat-affected zone.
Summary
420 stainless steel offers moderate corrosion resistance, suitable for cutlery, surgical instruments, and industrial tools in mild environments. Its corrosion resistance can be enhanced through polishing, passivation, and careful maintenance, but it is not recommended for prolonged exposure to aggressive or marine environments.
Cold Working
Cold Working of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its good hardness, wear resistance, and moderate corrosion resistance. Cold working is a key process for shaping and strengthening this steel, but it must be performed with care due to its high carbon content and work-hardening tendency.
1. General Characteristics
Cold working increases strength and hardness through strain hardening.
Excessive cold working can lead to cracking, especially in hardened or heat-treated conditions.
Suitable for bending, rolling, stamping, and drawing in the annealed state.
2. Recommended Practices
Perform cold working in the annealed condition to reduce brittleness.
Use gradual deformation rather than aggressive forming to prevent fractures.
Lubrication during forming helps reduce surface defects and tool wear.
Intermediate annealing may be necessary for extensive deformation to restore ductility.
3. Effects of Cold Working
Increased hardness and strength proportional to the amount of deformation.
Reduced ductility as work hardening progresses.
Enhanced surface finish and dimensional precision in certain forming processes.
4. Applications Benefiting from Cold Working
Cutlery and knives (pre-hardening shaping)
Surgical instruments
Springs and small mechanical components
Precision tools and industrial fittings
5. Limitations
Hardened or overworked 420 is difficult to form and prone to cracking.
Requires careful temperature control and potential intermediate annealing for large deformations.
Cold working alone cannot achieve final maximum hardness—post-working heat treatment is usually required.
Summary
Cold working of 420 stainless steel is most effective in the annealed condition, allowing shaping through bending, rolling, stamping, and drawing. It increases strength and hardness but reduces ductility, so careful control of deformation and intermediate annealing is essential. After cold working, heat treatment is typically applied to achieve final hardness and wear resistance, making it ideal for cutlery, surgical instruments, springs, and precision mechanical components.
Heat Treatment
Heat Treatment of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. Heat treatment is essential to achieve optimal hardness, strength, and dimensional stability.
1. Annealing
Purpose: Softens the steel for forming, machining, or cold working.
Process:
Heat to 800–900°C (1470–1650°F).
Hold at temperature to allow uniform microstructure.
Slow cooling in the furnace or in still air.
Result: Steel becomes soft, ductile, and machinable.
2. Hardening (Quenching)
Purpose: Increases hardness and wear resistance.
Process:
Heat to 980–1050°C (1800–1920°F) until fully austenitized.
Quench in air, oil, or water depending on section size.
Result: Martensitic structure is formed, producing high hardness (~50 HRC).
3. Tempering
Purpose: Relieves stresses and improves toughness while maintaining hardness.
Process:
Heat quenched steel to 150–250°C (300–480°F).
Hold for 1–2 hours, then air cool.
Effect: Reduces brittleness, enhances wear resistance, and stabilizes the martensitic structure.
4. Effects of Heat Treatment
Annealed 420: Soft, ductile, suitable for forming and machining.
Hardened 420: High hardness and wear resistance, suitable for cutting tools and knives.
Tempered 420: Balanced hardness and toughness, less prone to cracking during service.
5. Applications of Heat-Treated 420 Stainless Steel
Cutlery and knives
Surgical instruments
Industrial tools and precision components
Wear-resistant parts
6. Limitations
Excessive tempering may reduce hardness and wear resistance.
Overheating during quenching can cause distortion or cracking.
Heat-treated 420 should be handled carefully to maintain dimensional accuracy.
Summary
The heat treatment of 420 stainless steel involves annealing, hardening, and tempering to achieve the desired combination of hardness, wear resistance, and toughness. Proper control of temperatures and times is critical, making it suitable for cutlery, surgical instruments, industrial tools, and precision wear-resistant components.
Heat Resistance
Heat Resistance of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. Its heat resistance is limited compared to austenitic stainless steels such as 304 or 316.
1. General Properties
Can withstand intermittent exposure to temperatures up to 315°C (600°F) without significant loss of mechanical properties.
Continuous exposure to high temperatures may lead to oxidation, scaling, and loss of hardness.
Retains moderate mechanical strength at moderately elevated temperatures but is not suitable for high-temperature service.
2. Effects of High Temperature
Loss of hardness: Martensitic structure may soften if exposed to high heat.
Oxidation and scaling: Occurs at elevated temperatures, particularly in air or oxidizing atmospheres.
Dimensional changes: Extended exposure to heat can cause minor distortion.
3. Practical Considerations
Best used in ambient to moderately elevated temperatures.
Not recommended for continuous service above 315°C (600°F).
Can be heat treated to optimize hardness and wear resistance, but high service temperatures will reduce hardness over time.
4. Applications
Cutlery and knives (not exposed to extreme heat)
Surgical instruments and tools
Industrial tooling where high wear resistance is more critical than heat resistance
5. Summary
420 stainless steel has limited heat resistance, suitable for moderate-temperature applications. It is ideal for cutting tools, knives, surgical instruments, and industrial components where hardness, wear resistance, and corrosion resistance are important, but it is not recommended for high-temperature or continuous heat applications.
Hot Working
Hot Working of 420 Stainless Steel
420 stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. Hot working is an important process to shape the steel before it is hardened, as it improves ductility and reduces the risk of cracking.
1. General Guidelines
Hot working should be performed in the annealed condition to prevent cracking.
Typical hot working temperature: 900–1050°C (1650–1920°F).
Avoid overheating, which can cause grain growth, reducing toughness.
2. Common Hot Working Processes
Hot rolling: Used to form sheets, plates, and bars.
Hot forging: Shapes parts such as blades, tools, and industrial components.
Hot extrusion: Produces complex profiles and precision components.
3. Advantages of Hot Working
Reduces strength and hardness temporarily, allowing easier forming.
Minimizes the risk of cracking or brittleness.
Promotes homogeneous microstructure throughout the workpiece.
4. Post-Hot Working Considerations
Annealing: May be necessary after hot working to relieve stresses.
Machining: Typically easier after hot working in the annealed condition.
Heat treatment: Hardening and tempering applied afterward to achieve final hardness and wear resistance.
5. Limitations
High-carbon content limits hot working compared to lower-carbon martensitic steels.
Requires careful temperature control to avoid surface oxidation or scaling.
Not suitable for shaping in the fully hardened condition.
6. Applications Benefiting from Hot Working
Industrial knives and blades
Surgical instruments
Wear-resistant tooling and components
Precision mechanical parts before final hardening
Summary
Hot working of 420 stainless steel is performed in the annealed condition at temperatures of 900–1050°C (1650–1920°F). It allows shaping through rolling, forging, or extrusion, reduces brittleness, and produces a homogeneous microstructure. After hot working, annealing, machining, and final heat treatment are applied to achieve the desired hardness, wear resistance, and mechanical properties for applications such as cutlery, surgical instruments, and industrial tools.
