Abstract: This invention relates to heat and corrosion resistant alloys for structural parts in industrial furnaces and similar installations requiring hot strength, long life and resistance to hot gas corrosion, carburization and thermal fatigue, and to master alloys to aid in the production of these alloys. The alloys consist of additions of less than one percent by weight each of the components tungsten, zirconium, molybdenum, columbium, titanium and one or more rare earth elements to base alloys of the types standardized by the Alloy Castings Institute Division of the Steel Founders Society of America or to similar base alloys. The master alloys consist of all of these components, with the possible exception of Mo, combined together in the desired proportions, possibly along with some combination of iron, nickel or chromium in total content of up to about half of the master alloys by weight as partial diluents. The resultant master alloys are always denser than molten baths of the base heat resistant alloys.