Enquiry
Martensitic Stainless Steel 440A, B, C
Grade 440C 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.
Applications
Corrosion Resistance
These stainless steels have good corrosion resistance in the hardened and stress relieved conditions. Hence, they should, usually, be used only in that condition. These steels are resistant to such conditions as fresh water, steam, crude oil, gasoline, perspiration, and alcohol.
| Composition | |||
|---|---|---|---|
| Property | Type 440A | Type 440B | Type 440C |
| Carbon | .60 - .75 | .75 - .95 | .95 - 1.2 |
| Manganese | 1.00 max | 1.00 max | 1.25 max |
| Silicon | 1.00 max | 1.00 max | 1.00 max |
| Phosphorus | .04 max | .04 max | .04 max |
| Sulfur | .03 max | .03 max | .04 max |
| Chromium | 16.0 - 18.0 | 16.0 - 18.0 | 16.5 - 18.0 |
| Molybdenum | .75 max | .75 max | .75 max |
| Nickel | .50 max | NA | NA |
| Mechanical Properties | ||||||
|---|---|---|---|---|---|---|
| Property | Annealed | Type 440A Hardened & Stress Relieved | Annealed | Type 440B Hardened & Stress Relieved | Annealed | Type 440C Hardened & Stress Relieved |
| Ultimate tensile strength, psi | 105,000 | 260,000 | 107,000 | 280,000 | 110,000 | 285,000 |
| 0.2% Yield strength, psi | 60,000 | 240,000 | 62,000 | 270,000 | 65,000 | 275,000 |
| Elongation, % in 2? | 20 | 5 | 18 | 3 | 14 | 2 |
| Reduction of area, % | 45 | 20 | 35 | 15 | 25 | 10 |
| Rockwell hardness | B95 | C51 | B96 | C55 | B97 | C57 |
| Impact strength Izod V-Notch, ftlbs | NA | 3-6 | NA | 2-5 | NA | 1-5 |
Machinability
Because of the high carbon content, these alloys have an abrasive action on cutting tools. In the annealed condition, their machinability rating is about 40% compared to Bessemer oven stock (AISI B1112). As heat treated, the 440 series are difficult to machine because of their high hardness. For parts that require extensive machining, the free-machining versions, Type 440F or Type 440F Se, offer improved machining properties.
Formability
If annealed for maximum softness, Types 440A, 440B, and 440C Stainless Steels can be moderately cold formed with only slightly more difficulty than the lower carbon, lower chromium grades of stainless steel. They can also be hot headed. Preheating in the range of 1400 - 1500° F insures the best results in hot working. Parts should be furnace cooled after hot working to prevent cracking.
Heat Treatment
PROCESS ANNEAL: Heat at 1350-1450° F then cool very slowly in the furnace. FULL ANNEAL: Heat uniformly at 1550-1600° F soak and cool slowly in furnace to 1000-1250° F at a rate of 20-50° F per hour, then cool in air, oil, or water.
HARDENING: Preheat slowly to 1450° F and soak, then raise temperature to 1850-1950° F, quench in warm oil or air. Products hardness of C55-58 Rockwell. STRESS RELIEVE: Heat to 300-800° F for 1 to 3 hours, air cool.
