Alloys of the Heat Resistant Group are characterized by substantial additions of Chromium and Nickel alloy to stabilize their structure at temperatures approaching their melting point. Both Iron and Nickel base alloys are included in this group. Alloying of specific grades address oxidation resistance, carburization, high temperature creep resistance and stress rupture properties through balancing of the alloy content. The microstructures run from fully ferritic to fully austenitic.
Melting and casting characteristics are generally good. Proper alloy content is critical to the performance of the castings and as such require attention that they are not contaminated with other alloys. Contamination from Copper is a specific example. They also must be melted with additions to maintain their oxidizable elements such as Carbon and Silicon. Alloys are generally used in the as cast condition and cannot be strengthened by heat treatment.
Applications for alloys in this group include many heating applications for various industries. Selection of specific alloys should include considerations of thermal cycling, impact loading, maximum temperature and specific service environment to mention a few. The design and ability to feed a casting to soundness must be considered for maximum performance life.