Low-alloyed ferritic heat resisting grade with improved scaling resistance. Uncritical regarding embrittlement at service temperatures. Applied for e.g. furnace equipment, thermal boiler components, grids, burner nozzles, conveying parts, thermowells.
The high temperature (HT) ferritic stainless steels complement GNEE austenitic heat and creep portfolio. The main alloying element in the ferritic grades is chromium. Its positive effect on the scaling resistance is enhanced by silicon and aluminium. The characteristic properties are excellent resistance to oxidising and reducing sulphur containing atmospheres, good resistance to oxidation and high thermal conductivity with low thermal expansion.
1.4713 does not form brittle phases but should only be exposed to moderately corrosive atmospheres owing to its low chromium content.
1.4724 is a truly stainless high temperature grade with 13% chromium. It is not critical in terms of embrittlement. 1.4742 shows better scaling resistance than 1.4724 and can be subjected to reducing sulphur environments without risk. It is subject to 475°C embrittlement and grain coarsening at temperatures above 950°C. σ-phase may form after long time exposures to temperatures around 650°C.
1.4762 - with the highest chromium content- is the most resistant to reducing sulphurous gases. It is susceptible to the same embrittlement phenomena as 1.4742 whilst σ-phase forms during long exposures in the range 600°C to 800°C.
The characteristic temperatures for the different grades are shown in the table below.
|Steel grade||Maximum service temperature in dry air,ºC||Hot forming1,ºC||Annealing2,ºC|
1 Cooling still air 2 Cooling forced air or water
Creep properties of 47XX, Rp0,1 N/mm2 (mean values) are shown in the table below.
GNEE Stainless ferritic high temperature steels are mostly used in high temperature applications with sulphurous atmospheres and/or low tensile loads such as for installations within:
Thermal boiler components
Chemical industry (drums)
Power industry (coal burners)
Metalworking industry (heat treatment boxes)