STAINLESS STEEL - 420 Stainless Steel
Type 420
- Hardenable, martensitic stainless steel with corrosion resistance similar to Type 410
- Higher carbon content to increase strength and hardness over Type 410
- Maximum corrosion resistance only in the fully hardened condition or fully hardened and stress relieved condition
- Never used in the annealed condition
Composition
Property |
Type 420 |
| Carbon | .15 max |
| Manganese | 1.00 max |
| Silicon | 1.00 max |
| Phosphorus | .040 max |
| Sulfur | .030 max |
| Chromium | 12.0 - 14.0 |
Specifications
Type 420 Stainless Steel (bar, wire and billets) is covered by the following specifications:
| QQ-W-423A |
| MIL-S-862B |
| MIL-S-8142 |
| MIL-W-17481A |
| AMS 5621 |
| ASTM A276-67 |
| ASTM A314-63 |
| ASTM A580-67 |
| QQ-S-763D |
Mechanical Properties
| Property | Condition | ||
| Annealed | Hardened | Stress Relieved | |
| Ultimate tensile strength, psi | 95,000 |
|
230,000 |
| 0.2% Yield strength, psi | 50,000 |
|
195,000 |
| Elongation, % in 2" | 25 | 8 |
|
| Rockwell hardness | B92 | C54 | C50 |
| Reduction of area, % | 55 |
|
25 |
| Impact strength Izod, V-Notch, ft-lbs | 30 |
|
5-15 |
Typical Applications
- Specified for a wide variety of applications where good corrosion and hardness in the range of C50 to C54 is requiredApplications include cutlery, surgical and dental instruments, scissors, tapes and straight edges, gauges, needle valves, ball check valves, gear shafts, cams, pivots, ball bearings and hand toolsNot normally used at temperatures exceeding 800° F due to rapid softening and loss of corrosion resistance
Formability
- If annealed for maximum softness, Type 420 can be moderately cold formed, and cold headed. It can be readily forged and hot-headed. Preheating prior to hot working insures the best results. Because this steel is air hardening, all hot worked parts should be furnace cooled to prevent cracking.
Machinability
Type 420 Stainless Steel machines like a high carbon steel. Chips are tough and stringy. Carbide cutting tools are recommended because this alloy has an abrasive action on tools. For parts that require extensive machining, the two free-machining versions, Type 430 and Type 430F Se offer fabrication economies.
Corrosion Resistance
-
Type 420 has its 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.
Heat Treatment
ANNEALING: For maximum softness heat to 1550-1650° F hold for sufficient time, and furnace cool slowly to 1100° F. For cold forming operations, uniformly heat to 1350-1450° F, hold for sufficient time and air cool.
HARDEN: Heat to 1700-1850° F, hold for sufficient time, and air cool.
STRESS RELIEF: Heat to 300-800° F, hold for sufficient time and air cool.
TEMPER: Heat to 1100-1400° F, hold for sufficient time and air cool
Weldability
Because of the air hardening characteristics of Type 420, it has only fair weldability and is seldom welded.