Both 431 and 431A are martensitic stainless steels, hardenable by heat treatment. They exhibit higher corrosion resistance and fatigue properties than Cr types. These stainless steels care commonly used in:
- Valve parts
- Pump shafts
- Propeller shafts
They offer one of the highest corrosion resistance among martensitic stainless steels, meaning that they do well in marine/moist environments.