440C Stainless Steel Plate - UNS S44004
Type 440C (UNS S44004) is a martensitic stainless steel with high carbon and chromium content. Molybdenum improves the steel's deep hardening and toughness. It also enhances wear resistance. After heat treatment, it is capable of attaining the highest strength, hardness and wear resistance of all stainless alloys. 440C stainless steel derives its corrosion resistance from the inclusion of chromium and is comparable to grade 304. This material is commonly used in the medical industry for surgical instruments and is used for household utensils such as cutlery and measuring instruments. Other applications for this grade include nozzles, valve parts, hardened steel balls and seats for oil well pumps, separating screens and strainers, springs, shears, and wear surfaces.
- Inventory & Specs
- Chemical Composition
- Physical Properties
- Mechanical Properties
- Datasheet
- Additional Info
- FAQs
Inventory Size Ranges for 440C
| Type | Thickness | AMS Standards | ASTM | Get a Quote |
|---|---|---|---|---|
| Plate | 0.1875" - 2.500" | AMS 5630 (Chem Only) | ASTM A 276, ASTM A 480, ASTM F 899 | Get a Quote |
Characteristics of 440C
Highest resistance can be achieved through hardening and polishing, and the properties of 440C steel make it ideal for knives and cutting instruments like surgical blades. It maintains good corrosion resistance to fresh water, foods, and mild acids. Once hardened, this material holds a sharp edge and resists corrosion, and it can be polished to a near mirror finish. Its toughness and ability to resist wear makes 440C stainless steel a good choice for tools like chisels and ball bearings. This alloy exhibits good corrosion resistance to atmospheric corrosion, potable water, and to mildly corrosive chemical environments because of its ability to form a tightly adherent oxide film which protects its surfaces from further attack. Its exposure to chlorides in everyday type activities (e.g., food preparation, sport activities...) is generally satisfactory when proper cleaning is performed after exposure to use.
Working with 440C
440C typically is harden by heating to high austenitizing temperatures, followed by oil or aid quenching depending on the section size, then tempered to desired hardness. The final hardness can reach 56-60+ HRC. Cryogenic treatment is also sometimes used to reduce retained austenite. Machining 440C can prove to be difficult due to the fact it work-hardens aggressivity and in the annealed state is still quite hard compared to 410 and 416 stainless steel grades. Welding 440C is generally not recommended due to its high carbon content which poses a cracking risk. Additionally, welding 440C can lead to heat-affected zones losing their corrosion resistance and hardness levels drops unless post-weld heat treatment is performed. If welding is necessary, it is important to preheat and post-weld tempered. 440C also has poor formability and low ductility due to its high carbon content. 440C is best used for machined or ground parts as opposed to formed components.
Other industry standards we comply with:
- DFARS Compliant
Common Trade Names
- 440C Surgical Steel Plate
Industry Applications for 440C
- Cutting Instruments
- Knife Blades
- Surgical Instruments
- Chisels
- Measuring instruments
- Ball Bearings and Valves
Chemical Composition
Percent maximum unless a range is specified
| Element | Min | Max | |
|---|---|---|---|
| C | Carbon | - | 1.20 |
| Cr | Chromium | - | 18.0 |
| Mn | Manganese | - | 1.0 |
| Mo | Molybdenum | - | 0.75 |
| P | Phosphorus | - | 0.04 |
| Si | Silicon | - | 1.0 |
| S | Sulfur | - | 0.030 |
Physical Properties
| Property | Value |
|---|---|
| Density | 7650 kg/cm3 |
| Thermal Conductivity at 212°F (100°C) | 24.2 |
| Electrical Resistivity | 600 |
| Elastic Modulus | 200 GPa |
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength 0.2% Proof | 448 Mpa |
| Tensile Strength | 75 MPa |
| Elongation Percent in 50mm | 14 |
| Hardness (HB) | 269 max |
Datasheet
Additional Info
A Brief History of 440C
440C is part of the martensitic 400‑series stainless steels, known for high carbon and high hardness. It became recognized as the hardest and most wear‑resistant of the 440 family (440A, 440B, 440C) due to its elevated carbon content (0.95–1.20%). Historical research on stainless steels shows that the 440 series evolved as metallurgy advanced and industries demanded stainless alloys capable of both corrosion resistance and high edge retention.
How 440C Was Developed
440C was developed to fill a performance gap. Scientists looked to create a stainless alloy with exceptional hardness and wear resistance—especially for cutlery and precision machinery. Advances in heat‑treatable martensitic stainless steels allowed metallurgists to push carbon content higher while maintaining chromium levels for corrosion resistance. The 440 series was refined into A, B, and C variants, with 440C representing the high‑carbon, high‑hardness end of the spectrum. Metallurgists Increased carbon to ~1% to enable martensitic transformation and high hardness after heat treatment. They also optimized heat treatment to achieve 58–60 HRC, which was high for stainless steels at the time.
Early Applications of 440C
Early uses centered on industries that needed both corrosion resistance and high hardness, including rolling-contact bearings, high end cutlery and knives, precision mechanical components, and aerospace instruments.
How 440C is Used Today
Despite newer “super steels,” 440C remains widely used because of its balance of hardness, corrosion resistance, and cost. Today, 440C is used for knife blades, ball and roller bearings, valve and pump parts, medical instruments, industrial tooling, and firearm components.
Your Trusted Provider of 440C Stainless
United Performance Metals carries 440C plate sizes 0.1875" - 2.500". This material is commonly used in the medical industry for surgical instruments and is used for household utensils such as cutlery and measuring instruments. Other applications for this grade include nozzles, valve parts, hardened steel balls and seats for oil well pumps, separating screens and strainers, springs, shears, and wear surfaces.
Product FAQs
440C stainless steel has moderate corrosion resistance. It performs better than carbon steel but is not as corrosion resistant as 304 or 316 stainless. 440C performs best in mild, clean environments. Its corrosion resistance decreases slightly at maximum hardness because more chromium is tied up in carbides.
In the annealed state, it machines reasonably well. After hardening, 440C becomes very difficult to machine due to high hardness.
To preserve the life of 440C, keep it dry and clean and apply light oil to avoid staining. Make sure to avoid prolonged exposure to saltwater and always sharpen with a ceramic or diamond stone.