Stainless Steel 422
| Chemical Analysis | |
|---|---|
| C | Carbon 0.20 – 0.25 |
| Mn | Manganese 1.00 max |
| P | Phosphorus 0.040 max |
| S | Sulfur 0.030 max |
| Si | Silicon 1.00 max |
| Cr | Chromium 11.50 – 13.50 |
| Ni | Nickel 0.50 – 1.00 |
| Mo | Molybdenum 0.75 – 1.25 |
| V | Vanadium 0.20 – 0.50 |
| W | Tungsten 0.75 – 1.25 |
General Characteristics of Stainless 422
Stainless type 422 is a hardenable steel good for service temperatures to 1200ºF (650ºC), and capable of heat treatment to high mechanical property values.
Applications of Stainless 422
Buckets and blades in compressors and steam turbines, forged high-temperature bolting, compressor and turbine wheels, valves and valve trim and aircraft parts
Forging Stainless 422
Large sections should be preheated to 1200/1400ºF (650/760ºC), then to 1900/2150ºF (1040/1175ºC). Forgings should be slow cooled and annealed or tempered as soon as possible after reaching room temperature.
Hardening should not be attempted without an inter anneal or preheat in the range 1200/1400ºF (650/760ºC.)
Heat Treatment
Annealing
Heat to 1350/1430ºF (730/780ºC) and soak for 4 hours, then furnace or air cool. The resulting hardness will be Rc21-25 and the microstructure tempered martensite. Or isothermal anneal by heating to 1900ºF (1040ºC), cooling to 1275ºF (690ºC) and holding for 24-48 hours and air cooling. This treatment will give a hardness of Rb90-95 and a structure of ferrite plus carbide. Following an iso anneal the part must be re-hardened (1900/1950ºF (1040/1065ºC) and tempered to required mechanical properties.
Hardening
Heat to 1900ºF (1040ºC), soak and oil quench to a resulting hardness of Rc45/50. Intricate shapes may be marquenched to 650ºF (340ºC) and air cooled. Parts should not be air cooled to the Ms temperature and quenched as this will likely cause cracking.
Parts should be cooled to room temperature before tempering. Complete transformation to martensite is necessary to prevent non-uniform structures and hardness after tempering.
Tempering
Past experience should be used to determine tempering temperatures required to attain desired mechanical properties. It is preferable to temper straight after parts reach room temperature from hardening.
Machinability
The alloy is readily machined in the annealed condition: it machines as 420 stainless steel.
Weldability
Welding of this alloy is difficult, due to cracking. Preheating, and a post-weld stress relief of the welded areas at 1100/1400ºF (590/760ºC) for 4 hours are recommended.
Best corrosion resistance is obtained in the hardened and tempered condition.
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