440 Stainless Steel
440 Stainless Steel, also as known as “razor blade steel,” is a hardenable high-carbon chromium steel.
Type 440 attains the highest hardness of all stainless steels. This lends itself to applications such as high quality knife blades, razor blade, high grade wood working tools such as chisels, surgical and dental instuments, valve components and ball bearings.
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440 Stainless Steel Bar Grinding Services
- 440 stainless steel is 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
Available Forms
Type 440 Stainless Steel is available in:
- Bar
- Wire
- Billets
Typical Applications
- Used in numerous applications in areas where a very hard & abrasion-resistant stainless is called for.
- Applications include pivot pins, dental and surgical instruments, cutlery valve parts, ball bearings, nozzles, hardened steel balls, seats for oil well pumps, and valve parts.
440 Stainless Steel Specifications
The following specifications are generally applicable:
Sheets and Plates
- AMS 5630C
- ASTM A276-67
- ASTM A314-63
- ASTM A-580-67
- QQ-2-763D
- MIL-S-862B
Composition & Properties
Property
Type 440C
Carbon
.95 – 1.2
Manganese
1.25 max
Silicon
1.00 max
Phosphorus
.04 max
Sulfur
.04 max
Chromium
16.5 – 18.0
Molybdenum
75 max
Nickel
NA
Mechanical Properties
Properties
Annealed
Hardened & Stress Relieved
Ultimate Tensile Strength (psi)
110,000
285,000
0.2% Yield Strength (psi)
65,000
275,000
Elongation (% in 2?)
14
2
Reduction in area (%)
25
10
Rockwell Hardness
B97
C57
Impact Strength (Izod, V-Notch) [ft-lbs]
NA
1-5
Machinability
- Because of the high carbon content, 440 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, 440 series alloys 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, Type 440C Stainless Steel can be moderately cold formed with only slightly more difficulty than the lower carbon, lower chromium grades of stainless steel.
- It 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.
Type 440 Stainless Steel 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.
Forging
- When forging, preheat to 1400-1500° F, then heat slowly and uniformly to 1900-2150° F.
- Do not forge below 1700° F.
Corrosion Resistance
- 440 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.
Welding
- 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.
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