Heating specialists Kanthal, a product area of Sandvik Materials Technology, has introduced a new material grade for radiant and protection tubes for furnace applications.
Designated Kanthal APMT, the new iron-chromium-aluminium (FeCrAl) tube grade is a development of Kanthal's Advanced Powder Metallurgy (APM) technology, which has been used successfully for many years in both gas and electrically heated furnaces. Used mainly in the heat treatment, steel and aluminium industries, Kanthal radiant and protection tubes combine strength and corrosion resistance with high temperature operation.
The key benefit of the new grade is improved hot strength, at temperatures up to 1250°C. This makes it suitable for use in demanding, horizontal radiant and protection tube applications, where form stability is needed and where sagging deformation may be a problem. As well as high strength, Kanthal APMT tubes have excellent, high temperature corrosion resistance.
The chemical composition of Kanthal APMT is slightly modified, compared to Kanthal APM. It has the same FeCrAl (iron-chromium-aluminium) base as Kanthal APM but with added molybdenum.
When heated, all Kanthal PM materials form an aluminium oxide that protects tubes from corrosion and therefore, extends service life. The surface oxide also provides good protection in carburising and sulphidising atmospheres. It is practically non-spalling which means that there is no scaling within the tube to contaminate the heating element or gas burner. Similarly, there is no scaling on the outside of the tube to affect goods in the furnace.
Compared to nickel-chrome (NiCr) and iron-nickel-chrome (FeNiCr) alloys, Kanthal PM materials have a higher loading potential. At a furnace temperature of 1000°C, the loading can be more than double. Fewer tubes are, therefore, needed for the same power rating. Kanthal PM tubes also offer a weight advantage, weighing less than the equivalent NiCr and FeNiCr tubes of the same dimension.
Produced by the extrusion process, the new Kanthal APMT tubes are available in a size range from 26.67mm up to 198mm outside diameter.
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