Stainless Steel, Martensitic
440C Stainless Steel (S44004) Bar
A martensitic stainless steel with the highest carbon content in the 400 series.
440C stainless steel is a member of the 400 series of stainless steels. It has the highest carbon content among them. It is capable of attaining, after heat treatment, the highest strength, hardness and wear resistance of all the stainless alloys. Its very high carbon content is responsible for these characteristics, which make 440C particularly suited to such applications as ball bearings and valve parts.
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.
440C stainless steel is a high-carbon martensitic stainless steel known for its excellent hardness, superior wear resistance, and moderate corrosion resistance. It is the highest carbon content stainless steel in the 440 series, making it ideal for applications requiring high strength and edge retention.
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.
DOWNLOAD PDF
Range Enquiry
PLEASE NOTE
If you do not see what you are looking for, please contact your local service centre with your specific requirements.
Related Specifications
- S44096
- SUS 440C
- STS 440C
- S44004
- X105CrMo 17
- Z100CD17
- 1.4125
- 95Х18
Properties
Chemical Composition
1.4125 Steel
EN 10088-3
| Chemical Element | % Present |
| Carbon (C) | 0.95 - 1.20 |
| Chromium (Cr) | 16.00 - 18.00 |
| Manganese (Mn) | 0.00 - 1.00 |
| Silicon (Si) | 0.00 - 1.00 |
| Phosphorous (P) | 0.00 - 0.04 |
| Sulphur (S) | 0.00 - 0.03 |
| Molybdenum (Mo) | 0.40 - 0.80 |
| Iron (Fe) | Balance |
Mechanical Properties
Bar Up To 100mm Dia or Thickness
EN 10088-3
| Mechanical Property | Value |
| Proof Stress | 448-1900 MPa |
| Tensile Strength | 758-2030 MPa |
| Elongation A50 mm | 4-14 % |
General Physical Properties
| Physical Property | Value |
| Density | 7.65 g/cm³ |
| Thermal Expansion | 10.1 x 10-6/K |
| Modulus of Elasticity | 200 GPa |
| Thermal Conductivity | 24.2 W/m.K |
| Electrical Resistivity | 0.6 x 10-6 Ω .m |
Applications of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and good corrosion resistance. It is widely used for precision components, cutting tools, and high-strength applications.
1. Bearings and Precision Components
Ball bearings, roller bearings, and bearing races
Valve components and pump parts requiring high wear resistance
Precision mechanical parts in industrial machinery
2. Cutting Tools and Blades
Knives, scissors, and cutting tools
Surgical instruments and dental tools
High-wear industrial tooling
3. Aerospace and Automotive Applications
High-strength shafts and fasteners
Springs and precision components
Components requiring high hardness and wear resistance under stress
4. Industrial and Engineering Equipment
Wear-resistant gears and bushings
Components in machinery exposed to moderate corrosive environments
Die and mold parts requiring both hardness and dimensional stability
Summary
440C stainless steel is ideal for applications requiring high hardness, superior wear resistance, and moderate corrosion resistance. Its properties make it suitable for bearings, precision tools, cutting instruments, and high-strength mechanical components in industrial, automotive, and aerospace applications.
Applications of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and good corrosion resistance. It is widely used for precision components, cutting tools, and high-strength applications.
1. Bearings and Precision Components
Ball bearings, roller bearings, and bearing races
Valve components and pump parts requiring high wear resistance
Precision mechanical parts in industrial machinery
2. Cutting Tools and Blades
Knives, scissors, and cutting tools
Surgical instruments and dental tools
High-wear industrial tooling
3. Aerospace and Automotive Applications
High-strength shafts and fasteners
Springs and precision components
Components requiring high hardness and wear resistance under stress
4. Industrial and Engineering Equipment
Wear-resistant gears and bushings
Components in machinery exposed to moderate corrosive environments
Die and mold parts requiring both hardness and dimensional stability
Summary
440C stainless steel is ideal for applications requiring high hardness, superior wear resistance, and moderate corrosion resistance. Its properties make it suitable for bearings, precision tools, cutting instruments, and high-strength mechanical components in industrial, automotive, and aerospace applications.
Additional Information
Fabrication
Fabrication of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and good corrosion resistance. It is commonly used for cutting tools, bearings, and precision components. Its fabrication characteristics differ significantly from austenitic stainless steels due to its martensitic structure and high carbon content.
1. Forming
Hot Working:
Hot forging is possible in the annealed condition at temperatures of 980–1150°C (1800–2100°F).
Avoid overheating to prevent grain growth, which can reduce toughness.
Cold Working:
Limited cold forming is possible but may lead to cracking or high internal stresses due to high hardness.
Preferred to perform forming in the annealed condition.
2. Machining
440C has high hardness, which makes machining challenging in the hardened condition.
Best machined in the annealed or softened state.
Requires sharp carbide tooling, slower cutting speeds, and adequate coolant to avoid excessive tool wear.
3. Welding
Not typically recommended due to high carbon content and susceptibility to cracking and distortion.
If welding is necessary, preheating and post-weld heat treatment are required to reduce stresses.
4. Heat Treatment Considerations
Fabrication is usually done before hardening.
After forming or machining, 440C can be hardened via heat treatment to achieve maximum strength and wear resistance.
5. Surface Finishing
Can be polished to a high finish to enhance corrosion resistance.
Passivation may be applied to further improve corrosion resistance, especially in moist or corrosive environments.
6. Applications
Ball and roller bearings
Cutlery and knives
Valve components and precision instruments
Wear-resistant mechanical parts
Summary
Fabrication of 440C stainless steel is best performed in the annealed condition due to its high carbon content and martensitic structure. It can be hot worked, machined, and formed before hardening. Post-fabrication heat treatment imparts high hardness and wear resistance, making 440C ideal for cutting tools, bearings, and precision components.
Weldability
Weldability of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and good corrosion resistance. However, its weldability is limited due to the high carbon content, which increases the risk of cracking and distortion during welding.
1. Welding Challenges
High carbon content leads to martensite formation in the heat-affected zone, increasing the risk of brittle welds and cracking.
Hardness in the as-hardened condition makes welding difficult or inadvisable.
Residual stresses can cause distortion or dimensional changes.
2. Welding Recommendations
Preheating: Heat parts to 150–300°C (300–570°F) to reduce thermal stress.
Filler Material: Use matching low-carbon martensitic stainless steel filler rods/wires (e.g., 410 or 420 types).
Controlled Cooling: Slow cooling after welding reduces the risk of cracking.
Post-Weld Heat Treatment: Required to relieve stresses and restore toughness.
3. Welding Methods
TIG (GTAW) or SMAW: Preferred for precise control and minimal heat input.
MIG (GMAW): Can be used with appropriate preheating and controlled cooling.
Avoid welding in the fully hardened condition whenever possible.
4. Practical Considerations
For critical applications, mechanical fastening or brazing may be preferred over welding.
Post-weld machining or polishing may be required to restore surface finish and dimensional accuracy.
Welding is generally limited to small repairs or non-critical areas.
5. Applications
Small repairs of bearings or valve components
Non-critical joining of precision components where welding cannot be avoided
Summary
440C stainless steel has limited weldability due to its high carbon content and martensitic structure. Welding requires careful preheating, filler selection, controlled cooling, and post-weld heat treatment. For critical applications, alternative joining methods may be preferred to maintain strength, hardness, and corrosion resistance.
Machinability
Machinability of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its excellent hardness, wear resistance, and moderate corrosion resistance. Its high carbon and hardness make machining more challenging compared to austenitic stainless steels.
1. Machining Characteristics
Difficult to machine in the hardened condition due to high hardness (up to 60 HRC after heat treatment).
Better machinability in the annealed condition, which is recommended for forming and shaping before hardening.
Tends to produce short, stiff chips, reducing the risk of entanglement.
2. Tooling Recommendations
Tool materials: Use carbide or high-speed steel (HSS) tools, preferably coated for heat resistance.
Cutting speed: Low to moderate; higher speeds generate heat that can reduce tool life.
Feed rate: Moderate to maintain surface finish and avoid tool chatter.
Coolant: Adequate cutting fluid is essential to reduce heat and improve tool life.
3. Machining Operations
Turning, milling, and drilling: Best performed in the annealed condition. Hardened 440C requires specialized carbide tooling.
Grinding: Often used after hardening for precision dimensions and surface finish.
EDM (Electrical Discharge Machining): Can be employed for hardened parts with complex shapes.
4. Advantages
Can achieve high precision and wear-resistant surfaces after machining and heat treatment.
Suitable for bearings, cutting tools, and precision components when proper machining practices are followed.
5. Limitations
Machining in the hardened condition is slow and tool-intensive.
Work hardening can occur if machining is attempted in partially hardened areas.
6. Applications Benefiting from Machinability
Bearings and rollers
Cutlery, knives, and blades
Precision valves and mechanical components
Wear-resistant parts for industrial machinery
Summary
440C stainless steel has challenging machinability due to its high carbon content and hardness. Machining is best performed in the annealed condition with proper tooling, speed, feed, and cooling. After machining and heat treatment, it offers excellent wear resistance, strength, and dimensional precision, making it ideal for cutting tools, bearings, and precision components.
Corrosion Resistance
Corrosion Resistance of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and moderate corrosion resistance. Its corrosion resistance is good for martensitic stainless steels but lower than that of austenitic types like 304 or 316.
1. General Corrosion Resistance
Resists mild oxidizing environments, including air and mildly corrosive atmospheres.
Performs well in dry conditions and is suitable for components with occasional exposure to moisture.
Not suitable for continuous exposure to chlorides or harsh chemical environments, where pitting and crevice corrosion may occur.
2. Effect of Carbon Content
High carbon content increases hardness and wear resistance, but may reduce corrosion resistance compared to low-carbon martensitic or austenitic steels.
Proper heat treatment and tempering help balance hardness and corrosion resistance.
3. Surface Treatment
Polishing or passivation can significantly improve corrosion resistance.
Coatings, such as oil or plating, may be applied in severe environments to protect against rust.
4. Applications Benefiting from Corrosion Resistance
Bearings and rollers used in controlled environments
Precision mechanical parts exposed to moderate moisture
Cutlery, knives, and surgical instruments in dry or lightly humid conditions
Valve components and small industrial tools
5. Limitations
Not recommended for marine environments or exposure to strong acids and chlorides.
Requires careful maintenance and protection to prevent rust in aggressive conditions.
Summary
440C stainless steel offers moderate corrosion resistance, suitable for industrial, mechanical, and precision applications in controlled or mildly corrosive environments. While not as corrosion-resistant as austenitic stainless steels, its combination of hardness, wear resistance, and reasonable corrosion resistance makes it ideal for bearings, cutting tools, and precision components.
Cold Working
Cold Working of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. Its ability to be cold worked is limited due to its high carbon content and hardenability, requiring careful processing.
1. Cold Working Characteristics
Cold working is difficult in the hardened condition because 440C is brittle and prone to cracking.
Most forming operations are performed in the annealed condition, where the steel is softer and more ductile.
Cold deformation increases strength and hardness through strain hardening but reduces ductility.
2. Techniques
Bending and shaping: Limited in the annealed state; avoid sharp bends in hardened steel.
Drawing and stamping: Possible for thin sections in the annealed condition.
Rolling or pressing: Should be done cautiously to avoid cracks in partially hardened material.
3. Advantages
Cold working in the annealed condition allows for shaping complex or precision components before final hardening.
Can improve surface finish and dimensional precision when done correctly.
4. Limitations
Cold working in the hardened condition is not recommended due to brittleness.
Excessive deformation may lead to cracking, distortion, or residual stresses.
Requires subsequent heat treatment to achieve final hardness and wear resistance.
5. Applications Benefiting from Cold Working
Precision components such as bearings and valve parts
Cutlery and knife blanks before final hardening
Industrial components requiring dimensional accuracy
Summary
440C stainless steel has limited cold working capability, best performed in the annealed condition to shape components before hardening. Cold working increases strength and hardness but can reduce ductility, so careful control and subsequent heat treatment are required to produce durable, wear-resistant, and corrosion-resistant components.
Heat Treatment
Heat Treatment of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, excellent wear resistance, and moderate corrosion resistance. Heat treatment is essential to achieve its maximum hardness, strength, and wear properties.
1. Annealing
Purpose: Softens the steel for machining or forming before final hardening.
Process:
Heat to 815–845°C (1500–1550°F).
Hold long enough for uniform temperature.
Slow cool in furnace to minimize residual stresses.
Produces a soft, ductile condition for fabrication.
2. Hardening
Purpose: Develops high hardness and wear resistance.
Process:
Austenitize at 1010–1075°C (1850–1970°F).
Quench in oil or air (depending on part size) to form martensite.
Result: Achieves high hardness (up to 60 HRC).
3. Tempering
Purpose: Reduces brittleness and relieves stresses while maintaining hardness.
Process:
Heat to 150–370°C (300–700°F) depending on desired balance of hardness and toughness.
Hold and then air cool.
Multiple tempering cycles may be applied for dimensional stability and toughness.
4. Stress Relief
Optional stress-relief treatments may be applied after machining or welding to minimize distortion.
Typical stress-relief temperature: 150–370°C (300–700°F).
5. Surface Treatment Post Heat-Treatment
Polishing, passivation, or coating may be applied to improve corrosion resistance and surface finish.
6. Applications Benefiting from Heat Treatment
Bearings, rollers, and valve components
Cutlery and knives
Wear-resistant mechanical parts
Precision industrial tools
Summary
Heat treatment of 440C stainless steel involves annealing for machining, hardening for maximum strength and wear resistance, and tempering for toughness and dimensional stability. Proper heat treatment allows 440C to reach its optimum hardness, wear resistance, and moderate corrosion resistance, making it ideal for bearings, precision tools, and high-wear components.
Heat Resistance
Heat Resistance of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. While it excels in mechanical strength and wear properties, its heat resistance is limited compared to austenitic stainless steels like 304 or 316.
1. Temperature Limits
Continuous service: Up to approximately 150–200°C (300–390°F).
Intermittent exposure: Can tolerate slightly higher temperatures for short periods.
Prolonged exposure to higher temperatures may cause softening, loss of hardness, or tempering effects, reducing wear resistance.
2. Oxidation Resistance
Resists mild oxidation at low to moderate temperatures.
Not suitable for high-temperature oxidizing environments.
Surface scaling can occur if exposed to temperatures above recommended limits.
3. Effect on Mechanical Properties
Elevated temperatures can reduce hardness and tensile strength due to tempering of the martensitic structure.
Care must be taken to avoid prolonged exposure above the tempering range to maintain wear resistance.
4. Applications
Bearings and rollers in moderate-temperature environments
Precision components in industrial machinery
Cutlery and knives not exposed to high cooking or industrial heat
Valve and mechanical parts with limited heat exposure
5. Practical Considerations
440C is primarily designed for wear resistance and high hardness, not high-temperature applications.
For applications involving elevated temperatures, consider martensitic or austenitic stainless steels specifically designed for heat resistance (e.g., 410, 420, 309, or 310).
Post-fabrication polishing and surface treatment help reduce oxidation at moderately elevated temperatures.
Summary
440C stainless steel has limited heat resistance, suitable for moderate-temperature applications where hardness and wear resistance are critical. It is ideal for bearings, cutting tools, and precision components operating below approximately 200°C, but prolonged high-temperature exposure can soften the steel and reduce performance.
Hot Working
Hot Working of 440C Stainless Steel
440C stainless steel is a high-carbon martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. Hot working is possible, but due to its high carbon content and martensitic structure, it requires careful temperature control to avoid cracking or excessive grain growth.
1. Hot Working Characteristics
Hot working is generally performed in the annealed condition before hardening.
Allows forging, rolling, extrusion, and shaping of components with large deformations.
Reduces work hardening compared to cold working, making shaping easier.
2. Recommended Temperature Range
Hot working (forging/rolling): 980–1150°C (1800–2100°F).
Avoid overheating above 1150°C to prevent grain growth that can reduce toughness and wear resistance.
Controlled cooling is essential to maintain desired properties.
3. Advantages
Facilitates the formation of large or complex parts.
Reduces residual stresses compared to cold working.
Provides a uniform microstructure when followed by proper heat treatment.
4. Limitations
Surface scaling may occur at high temperatures, requiring descaling or polishing after processing.
Not suitable for strengthening by heat treatment alone; final hardness requires subsequent hardening and tempering.
Requires skilled control of temperature and deformation rates to avoid cracking or distortion.
5. Applications
Forged or rolled parts requiring precision and strength
Bearings, valve components, and industrial tooling
Cutlery and knives (pre-hardened shaping)
Wear-resistant components in machinery
Summary
440C stainless steel can be hot worked effectively in the annealed condition to form complex or large components. Proper temperature control and post-processing heat treatment are essential to achieve its maximum hardness, wear resistance, and dimensional accuracy, making it ideal for bearings, cutting tools, and high-wear precision components.
