Can occasional Tool Steel Heat Treatment be performed in Air Furnace?
No. Heating High Carbon Tool Steel in Air Furnace will cause decarburization (loss of surface carbon) that will substantially reduce thesurface hardness obtained upon quenching. Oxidation too is generallyobjectionable. In fact the higher the carbon content, the most significant thedecarburization process will be, and tool steels generally contain high carbon. For occasional heat treatment of tool steels in an air furnace one can use air tight bags manufactured of stainless steel foil. These are made bymultiple folds at the overlapping edges or by seam welding. The tool isintroduced in the bag, most of the air is then removed by enveloping the tool astightly as possible in the bag. A tiny hole must be left in the closed bag,usually by putting in the last fold a fine nail that is later withdrawn, for theresidual hot air to find a way out. The bag will then protect the tool from oxidation and decarburization duringheat treatment in the air furnace.
