View Sample Alloy Digest Data Sheet (PDF)Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.ACI Type HP is an iron-chromium-nickel alloy with a combination of elements that makes it resistant to both oxidizing and carburizing atmospheres at high temperatures. The alloy has good creep-rupture properties in the 1800-2000 F temperature range. It has an austenitic structure at all temperatures, thus it is not susceptible to embrittlement from sigma phase formation. Type HP was developed for rugged steel-mill furnace-roll service; no comparable wrought alloy exists.