STAINLESS STEEL - 440 Stainless Steel
Type 440A, 440B, and 440C
- Hardenable high-carbon chromium steels designed to provide stainless properties with maximum hardness
- Have maximum hardness together with high strength and corrosion resistance in the hardened and stress relieved condition
- Always used in the hardened or hardened and stress relieved conditions
- None of the alloys has its full corrosion resistance either in the annealed or in the hardened and tempered condition
- Wide applications where good corrosion resistance along with high hardness or abrasion resistance is required
- The following specifications are generally applicable:
Type 440A, 440B, and 440C
- ASTM A276-67
- ASTM A314-63
- ASTM A-580-67
In addition, Type 440 A is covered by spec AMS 5631 and Type 440C is covered by spec AMS 5630C.
Types 440A, 440B, and 440C Stainless Steels are available in:
- Used in numerous applications in areas where a very hard and abrasion resistant stainless is called for
- Applications include pivot pins, dental and surgical instruments, cutlery valve parts, ball bearings, nozzles, hardened steel balls and seats for oil well pumps, plus valve parts
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.
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. As these steels are strongly air-hardening, all parts should be furnace cooled after hot working to prevent cracking.
- 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.
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.
When forging, preheat to 1400-1500° F, then heat slowly and uniformly to 1900-2150° F. Do not forge below 1700° F.
Weldability: Because of their high hardenability, these steels are seldom welded. However, satisfactory welds are possible by preheating parts to 500° F before welding, followed by a 6- to 8-hour anneal at 1350 - 1400° F and air cooling. When weld rods are required, a composition similar to the parent metal should be used.