(AISI 440C)
| Typical Chemistry | |
| Carbon | 1.00% |
| Manganese | 0.50% |
| Silicon | 0.30% |
| Chromium | 17.50% |
| Molybdenum | 0.50% |
| Typical Applications | ||
| Bearings | Mold Inserts | |
| Knives | Surgical Tools | |
- Hardening
Preheat: 1100/1250F, equalize, 1400/1450F, equalize.
High Heat: 1850/1900F, hold 30/45 minutes at temperature.
Quench: Air, positive pressure vacuum, interrupted oil. Cool to 150F.
Temper: 400-800F, hold 1 hour/inch of thickness, 2 hours minimum.
Tempering between 800 and 1100F should be avoided, due to a decrease in both toughness and corrosion resistance.
Cryogenic Treating: Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.
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| AQ | 59 |
| 212 | 59 |
| 400 | 56 |
| 600 | 54 |
| 800 | 55 |
| 1000 | 51 |
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Nitriding decreases the corrosion resistance of stainless steels, and is not generally recommended for this grade. Because of the limitations of tempering between 800 and 1100F, surface treatments for 440C should be limited to those compatible with tempering temperatures under 800F.
Annealing
A. Heat to 1650F, hold two hours, cool slowly (25F/hour maximum) to 1200F, then air cool.
Or
B. Heat to 1600F, hold two hours, cool to 1300F, hold 4 hours, then air cool.
Typical annealed hardness: 217/255 BHN.
Stress Relieving
Annealed Material: Heat to 1200/1250F, hold two hours, cool in still air.
Hardened Material: Heat to 25F below original tempering temperature, hold two hours, cool in still air.
Welding
Use type 440C or 420 filler material.
Annealed Material: Preheat to 600/800F. Maintain above 600F during welding. Reanneal or temper 1300F 4 hours.
Hardened Material: Preheat to 25F below original tempering temperature (400F minimum). Maintain above 400F during welding. Cool to 150F after welding. Temper 25F below original tempering temperature (400F) minimum.
Physical Properties
Modulus of Elasticity ..............................................................30 psi x 106
Density .......................................................................................0.278 lb/in3
Thermal Conductivity ...................200F............................ 14 BTU/hr/ft/°F
Thermal Expansion
RT-200F ..................................................................5.7 X 10-6 in./in./°F
RT-600F ................................................................. 6.0 X 10-6 in./in./°F