Pre-oxidation treatment to increase the service life of heat treatment furnace conveyor belts made of AISI 330Cb Industrial application

Tuesday, April 19, 2016: 3:30 PM
Ballroom BC (Hyatt Regency Savannah)
Mrs. CECILE COMBE , CETIM, SAINT ETIENNE, France
Mr. PIERRE FRANCOIS CARDEY , CETIM, SAINT ETIENNE, France
Dr. HENRI BUSCAIL , LVEEM, LE PUY EN VELAY, France
C. Issartel , LVEEM, LE PUY EN VELAY, France
F. Riffard , LVEEM, LE PUY EN VELAY, France
R. Rolland , LVEEM, LE PUY EN VELAY, France
Lifetime optimization of the 330Cb conveyor belts in carburizing atmosphere

 

The conveyor belts used in the heat treatment furnaces in 330Cb steel have a limited lifetime.

The alloy 330Cb (Fe-34Ni-23Cr-1Nb-1.55Si) is generally used in high temperature carburizing and carbonitriding conditions. These environments induce severe conveyor units degradation due to a quick alloy weakening.

To improve the alloy carburization resistance it is assumed that the presence of an adherent oxide scale acts as a carbon and nitrogen diffusion barrier. The 330Cb oxidation leads to a chromium oxide which is a good diffusion barrier under isothermal conditions. The external manganese chromite can limit the chromium oxide evaporation at temperatures higher than 1000 °C. Important oxide layer degradation occurred after cooling to room temperature.

Recent search has shown that silica acts like a protective/adherent oxide and improves the carburizing resistance.

Formation of the protective silica layer (amorphous or crystallized) is promoted by:

-alloys with silicon content (1.00-2.00%),

-alcaline conditions (a low NaOH concentration)

-and low oxygen containing gaseous environments.

This paper concerns the application of the pre oxidation treatment on an industrial conveyor belt.