Abstract: Particularly important properties required for exterior protective members for sheathing heaters are resistance to oxidation, anti-stress corrosion properties and weldability. An austenitic stainless steel for the exterior protective members has been developed from the findings that, firstly, the resistance to oxidation can be remarkably improved by increasing the Cr content together with a combined addition of Al and rare earth metals. Secondly, a small amount of Co addition is effective to enhance alloy ability to withstand stress corrosion cracking in the environment to which sheathing heaters are subjected, and that the weldability of such members can be made superior by maintaining the content of Si and Ti within a specified region.

Abstract: An alloy prepared by reducing the sulfur content of ASTM UNS N06600 (Trademark Inconel Alloy 600) to an extremely small value and adding specified amounts of Nb and N, and an alloy prepared by reducing the oxygen content of Inconel Alloy 600 and adding specified amounts of Nb, N, B and Mg show a mechanical strength equivalent or superior to that of Inconel Alloy 600 and excellent hot workability, and further has intergranular corrosion resistance and integranular stress corrosion cracking resistance which are far more excellent than those of Inconel Alloy 600.