Vacaero

Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services.

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Archives for April 2015

Hot Zone Repair, Re-build and Retrofit

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Besides catastrophic damage due to mechanical abuse, eutectic melting or braze alloy spillage, vacuum furnace hot zones will deteriorate over time as a result of the repeated thermal cycling to which they are exposed. 

The life of a hot zone may vary widely depending on operating conditions.  Furnaces that are operated constantly in aggressive environments (eg. sintering) or consistently at temperatures over 1370ºC (2500ºF) may require fairly major hot zone maintenance as often as once per year.  Hot zones in furnaces used for standard heat treating operations can be expected to last from 5 to 7 years. BY JEFF PRITCHARD

The Interlamellar Spacing of Pearlite

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The interlamellar spacing of pearlite is a very important microstructural parameter for steels containing pearlite, and becomes more important as the pearlite content increases towards a fully pearlitic microstructure. As the amount of pearlite in ferrite-pearlite microstructures increase, so does the strength, but toughness and ductility decrease. For a fully pearlitic steel, as the interlamellar spacing becomes finer, strength, toughness and ductility all increase. Consequently, in structure-property correlations it is important to measure the interlamellar spacing. This paper reviews procedures for performing such measurements. Due to the fineness of the spacing, either SEM images or TEM images of replicas or thin foils can be utilized. The range of spacings in a given specimen will be much narrower if the pearlite in the steel was formed isothermally rather than transformed over a range of temperatures, as in as-rolled or normalized steels.