420 - UNS S42000:
AISI Type 420 is a martensitic stainless steel that provides increased strength and hardness relative to Type 410, with moderate corrosion resistance. It is magnetic in both the annealed and hardened conditions. Maximum corrosion resistance is attained in the fully hardened or fully hardened and stress relieved condition. High carbon content results in the formation of chromium carbide compounds, providing excellent wear resistance and edge retention when hardened. The alloy is not normally used at temperatures exceeding 800°F (427°C) due to rapid softening and loss of corrosion resistance.
A higher carbon variant, Type 420HC, can be used when higher hardness is desired.
- Melting Point: 2649 - 2750°F (1454 – 1510°C)
- Density: 0.2790 lbs/in3 / 7.73 g/cm3
- Modulus of Elasticity in Tension: 29 X 106 psi / 200 GPa
- Tensile Strength Minimum (psi): 85,000
- Yield Strength Minimum 0.2% offset (psi): 40,000
- % Elongation in 2” Typical: 25%
- Hardness: Rockwell B88
Temper: Hardened + 350°F
- Tensile Strength Typical (psi): 230,000
- Yield Strength Typical 2% offset (psi): 195,000
- % Elongation in 2": 8%
- Hardness: Rockwell C55
All values specified are approximate minimums unless otherwise specified. Values are derived from the applicable AMS and ASTM specifications.
- Carbon: 0.15 max
- Manganese: 1.00 max
- Phosphorus: 0.040 max
- Sulfur: 0.030 max
- Silicon: 1.00 max
- Chromium: 12.00 - 14.00
- Iron: Balance
All values are maximum values unless otherwise specified. Values derived from applicable AMS and ASTM specifications.
- Heat slowly to 1500-1650°F (816-899°C), cool slowly in furnace.
- Heat to 1350-1450°F (732-788°C), air cool.
- Preheat to 1800 - 1950°F (982 - 1066°C), air cool or oil quench.
- Follow by stress-relief or temper.
- Heat at 300 - 800°F (149 - 427°C) for 1 to 3 hours, air cool.
Low Temperature Tempering:
- Heat to 300 - 500°F (150 - 260°C) for 0.5 to 1 hours, air cool.
AISI Type 420 provides full corrosion resistance only in the hardened or hardened and stress relieved conditions. In these conditions, its corrosion resistance is similar to Type 410. Type 420 resists corrosion by the atmosphere, fresh water, mine water, steam, carbonic acid, crude oil, gasoline, perspiration, alcohol, ammonia, mercury, sterilizing solutions, soaps and other similar corrosive media.