Chemical Composition
| Grade Symbol |
UNS Number |
Alloy |
Elements |
Composition % |
| F91 |
K90901 |
9% chromium, 1% molybdenum, 0.2% vanadium plus columbium and nitrogen |
Carbon |
0.08 - 0.12 |
| Manganese |
0.30 - 0.60 |
| Phosphorus |
0.020 max |
| Sulfur |
0.010 max |
| Silicon |
0.20 - 0.50 |
| Nickel |
0.40 max |
| Chromium |
8.0 - 9.5 |
| Molybdenum |
0.85 - 1.05 |
| Columbium |
0.06 - 0.10 |
| Nitrogen |
0.03 - 0.07 |
| Aluminium |
0.02 max |
| Vanadium |
0.18 - 0.25 |
| Titanium |
0.01 max |
| Zirconium |
0.01 max |
Mechanical Properties
| Property | Value |
|---|
| Tensile Strength, min, ksi [MPa] |
90 [620] |
| Yield Strength, min, ksi [MPa] |
60 [415] |
| Elongation in 2 in. [50mm] or 4D, min, % |
20 |
| Reduction or Area, min, % |
40 |
| Brinell Hardness Number, HBW |
190-248 |
Heat Treatment
After hot working, forgings shall be cooled to a temperature below 1000 °F [538 °C] prior to heat treating in accordance with the requirements.
