F11 / P11 Flange Steels are chromium-molybdenum alloy steels specifically developed for high-temperature and pressure applications in power plants, refineries, petrochemical plants, and industrial process systems. Under ASTM International specifications, F11 generally refers to forged alloy steel flanges (ASTM A182 F11), while P11 refers to alloy steel pipes and pressure components used in elevated temperature service. These alloy steels are widely valued for their excellent mechanical strength, creep resistance, and long-term thermal stability.