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440-C Stainless UNS S44004
440-C stainless steel is a high carbon chromium steel. It is designed to provide maximum hardness with stainless properties. It has been used primarily as a bearing steel, used in the hardened and tempered condition. When heat treated 440-C can be hardened to Rockwell C 60 which is the highest hardness of any stainless steel.
Applications: 440-C stainless steel was originally used in bearing assembles, including ball bearings and races. It is widely used in cutlery, valve seats, needle valves, ball valves, pump parts, bushings and textile machinery.
| Carbon | 0.95-1.20% | Manganese | 1.00% |
| Phosphorus | 0.040% | Sulfur | 0.030% |
| Silicon | 1.0% | Chromium | 16.00 - 18.00% |
| Iron | 77.98-80.23% | Molybdenum | 0.75% |
Heat Treatment
Annealing: typical Heat uniformly, 1550/1600f (843/871c) Soak and cool very slow in furnace, brinell hardness approximately 223. Process anneal, heat uniformly to 1350/1400 (732/760c), air cool brinell hardness aprox 255.
Before tempering make sure parts are to room temperature after hardening. This will complete the transformation of martensite, which is necessary to prevent non-uniform structures and hardness.
Hardening: Heat to 1850/1950f (1010/1066c) soak, quench in warm oil or air cool. Do not over heat, when overheated maximum hardness cannot be obtained. Take care to minimize temperature time at 2000f (1099c) to avoid excessive grain growth. For best corrosion resistance, temper below or around 800f (427c).
Tempering: Hardened 1900 f (1038c) oil quench and tempered one hour (1” rd)
| Tempering temperature F | Tempering temperature C | Brinell Hardness |
|---|---|---|
| 300 | 149 | 60 |
| 400 | 204 | 59 |
| 500 | 260 | 57 |
| 600 | 316 | 56 |
| 700 | 371 | 56 |
| 800 | 427 | 56 |
Corrosion Resistance
The following table is for reference only, many factors can affect the corrosive resistance, a corrosion test for each application should be applied.
| Phosphoric acid | Restricted | Acetic Acid | Good |
| Sodium Hydroxide | Moderate | ||
| Salt Spray | Restricted | Nitric Acid | Moderate |
| Sulfuric Acid | Restricted | Humidity | Good |
Typical Room Temperature Tensile Properties
| 0.2% Yield Strength | Ultimate Tensile Strength | % Elongation in 2” (50.8mm) | % Reduction of area | Brinell Hardness | ||
|---|---|---|---|---|---|---|
| ksi | Mpa | ksi | Mpa | ksi | ||
| 275 | 1896 | 285 | 1965 | 2 | 10 | 580 |
- Machinability:
- 440C machines best in the annealed condition. Because of the high carbon it machines like high speed steel. The chips will be tough and string so a chip curler or breaker should be used. If polishing, use care in the tempered condition no to overheat as hardness will be compromised. If polishing is important an individually forged product will polish best.
- Shapes Manufactured:
- Flat Bars, Square Bars, Round Bars, Rings, Hollows, Discs, Blocks and special Shapes. Send us a drawing to see how we can save you material and Machining time!
The information in this data sheet is for information only and should not be used for engineering.
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