furnaces help the ageing process
November 1st 2003

Two custom-built Carbolite furnaces with provision for protective atmospheres are providing Howmet Exeter Castings with precisely controlled facilities for heat-treating industrial gas turbine blades. The furnaces are used for long-term ageing of components to increase their strength and creep resistance before final finishing. This takes place for up to 24h at 700 to 1100C, depending on size and specification. Large components are aged individually; smaller items can be processed in batches of more than 100. Furnaces are heated by heavy-gauge wire spiral elements located in the roof and below the hearth, where they are protected from damage by silicon carbide tiles. Temperature control is provided by a Eurotherm 2416 programmer with one programme and eight segments. Temperature uniformity is better than 10C, and over-temperature protection is provided. To avoid surface contamination of the blades, furnaces have specially designed Inconel retorts suitable for protective atmospheres, with a sand seal providing a gas-tight fit between base and lid.

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