TABLE 7-6. THERMAL; TREATMENT FOR HARDENING AND TEMPERING TOOL STEEL - GENERAL (CONT)
For large tools and tools having intricate sections, preheating at 1050 to 1200 is recommended.
Use moderately oxidizing atmosphere in furnace or a suitable neutral salt bath.
Use protective pack, from which volatile matter has been removed, carefully balanced neutral salt bath or atmosphere controlled furnaces. In the latter
case, the furnace atmosphere should be in equilibrium with the carbon content of the steel being treated. Furnace atmosphere dew point is considered a
reliable method of measuring and controlling this equilibrium.