Sintering Atmospheres

Atmospheres used for sintering must perform several functions (Ref 1, 2). During sintering, atmospheres must:

• Prevent air from entering the furnace

• Delube or dewax the parts

• Reduce surface oxides on the powder particles

• Control carbon on the surface and in the core of steel parts

• Remove carbon in special applications

• Provide controlled oxidation during cooling in special applications

• Convey or remove heat efficiently and uniformly

Because furnace atmospheres affect the sintering process and the material being treated, sintering is never performed in air or in an oxygen-rich atmosphere. A basic function of a sintering atmosphere is to protect metal parts from the effects of contact with air. Atmospheres must be maintained at a sufficient pressure and flow rate to prevent infiltration of air through furnace openings. In addition to protecting the part, atmospheres provide sufficient conduction convection for uniform heat transfer to ensure even heating or cooling within the various furnace zones (Fig. 7).

Fig. 7 Typical furnace schematic for sintering steel
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