Energy efficient heat-treating furnace system

Abstract

A method and apparatus are disclosed for heat-treating parts in a furnace system which uses a minimum total amount of energy. The self-contained, continuous heat-treating system includes components such as a carburizer, a tempering furnace, and a part cooler. Energy transfer between these and other components operable at different temperatures and/or energy requirements are used to maximize thermal efficiency of the system. Furnace components are provided and interconnected so that combustion air for radiant tube heaters supplying thermal energy to parts in a high temperature furnace such as a carburizer is preheated by exchanging heat in a part cooler and by recuperation of the carburizer exhaust; combustion products from the carburizer supply energy for reheating parts in a lower temperature furnace such as a tempering furnace; the tempering furnace exhaust is used for preheating parts prior to their entry into the carburizer; and energy transferred by the parts to a quench medium is used to heat water for subsequent washing of the parts. In one arrangement of components a tempering furnace is mounted on top of a carburizer as part of a compact multi-level configuration. In another arrangement the components form a single level system with energy transfer features and high thermal efficiencies similar to those of the multi-level system.