Refractory steels and alloys - Production

Refractory steels and alloys are generally used for the manufacture of parts characterized primarily by their resistance to the effects of hot gases and combustion products at temperatures above 550°C. At higher temperatures, refractory steels and alloys can only be used to a limited extent, as their properties of use disappear.

The main parameters to bear in mind when choosing a refractory steel or alloy are as follows:

• corrosion resistance is essentially linked to the selective oxidation of chromium and certain minor elements (Si, Al, etc.). A good refractory alloy must therefore have a high chromium content and, often, an addition of Si or Al ;

• Nickel, which does not combine with carbon, is suitable for reducing atmospheres, but has the disadvantage of not withstanding sulfurous atmospheres. The addition of elements with highly stable oxides (Si, Al) will improve resistance in these environments;

• creep resistance is strongly influenced by alloy structure. The ferritic structure has little or no resistance above 800°C. The austenitic structure is the most resistant.