Abstract: Disclosed is a method of controlling the atmosphere of a heat-treating furnace whose atmosphere consists essentially of a carrier gas of CO, H.sub.2 and N.sub.2 produced from a mixture of methanol and nitrogen. In accordance with the present invention, the ratio of flow of methanol to flow of nitrogen is varied to maintain the CO content of the furnace atmosphere at a predetermined value. This renders more effective the control by conventional means of the flow of additive gases to maintain the carbon potential of the furnace atmosphere at a predetermined value. The flows of methanol and nitrogen may be controlled based on monitored CO content only, or their control may be interrelated to monitored carbon potential as well.

Abstract: Disclosed are a method and apparatus for clean, low loss melting of aluminum using heat transfer by convection and radiation in separate stages. Heat input to a melter stage is provided by silicon carbide tubes into which gas-fueled burners fire so that the tubes radiate heat to a molten aluminum bath. Combustion products exiting the silicon carbide tubes pass through recuperators, preheating burner combustion air. The combustion products then are piped to a preheater stage and formed into jets of hot gases. The jets are directed into convective contact with solid aluminum stock as the stock is transported along a conveyor, preheating the stock to a temperature of about 1,000.degree. F. The solid stock then is fed to the charge zone of the melter stage and melted by contact with the molten bath.

Abstract: Heat-treating apparatus which includes an insulated furnace compartment through which stock to be heat-treated is passed. Perforated tubes are arranged in the furnace and they are heated to radiance by burners which also generate products of combustion which are ejected through the perforations at high velocity to impinge upon a surface or surfaces of the stock being heat-treated. The combination of radiation and convection enhanced by the impingement of the jets upon a surface of the stock provides highly efficient primary heat transfer. The burners are designed to insure that rapid combustion takes place at a point removed from the perforations to avoid flame issuing from the perforations. The tubes are sized and spaced to enhance secondary heat transfer from gases in the furnace compartment and from the walls of the compartment to the stock.

Abstract: A ceramic tube recuperator for recovering energy from hot flue gases, in which a multiplicity of heat exchange elements connected to a cold air inlet manifold and a hot air outlet chamber extend upwardly into a flow passage for hot flue gases. Each heat exchanger comprises an inner open ended tube extending into the cold air inlet manifold, and an outer ceramic tube having a closed upper end and an open lower end communicating with the hot air chamber. An essential feature of the invention is that the lower end of the ceramic tube is sealed solely as a result of resting on an annular seal, so that the ceramic tube may be removed and replaced simply by lifting and lowering through an access opening in the flue passage.

Abstract: The invention relates to controlled atmosphere heat treating furnaces and particularly to furnaces for bright annealing of copper or its alloys. A new concept is proposed for conserving energy uses by first having a separate atmosphere producing system that fires constantly, independent of the temperature control and secondly having a cooling system that only extracts the excess heat produced by the combustion for atmosphere. In this way the furnace may be maintained at the desired operating temperatures regardless of variation of the work load, yet all of the heat generated by the atmosphere producing device is released within the furnace thereby eliminating unnecessary heat losses.

Abstract: A crucible furnace for high-temperature melting of metals or other materials which includes a capped vessel for serving as a crucible to hold a charge of material to be melted, a solid baffle surrounding and closely spaced from the vessel to form a restricted passageway and a refractory wall surrounding and widely spaced from the baffle to form a combustion chamber. Fuel is supplied at the base of the combustion chamber and mixed with air preheated by a compact internal recuperator operative from exhaust gases exiting the restricted passageway. The fuel is burned in the combustion chamber, heating the baffle which in turn radiates heat to the vessel containing the charge. Several of the elements forming the combustion and heat transfer system also serve as structural elements providing rigid support to internal components when the furnace is upright and when it is tilted to pour off melt.

Abstract: A furnace for receiving continuously advancing stock in linear array is assembled from a number of independent furnace units. In each unit, a furnace chamber surrounds the advancing stock with a radiative wall. Each chamber is fired by gas burners which surround the stock at the chamber exit. The burners include a series of gas jets which feed the fuel, with or without air, radially into the chamber toward the stock and a series of air jets which are paired with the gas jets to feed combustion air axially into the chamber.

Abstract: The invention relates to a recuperator having an improved core within the primary heat transfer surface. This core, by its unique construction, achieves a combination of reradiative and convective heat transfer which outperforms either of these separate modes while maintaining a low pressure loss. The core consists of a series of radial plates between which are a series of triangular baffles arranged at an angle with the horizontal of 45.degree. to 70.degree.. The baffles intercept the flow of flue gas and gently channel the flow of gas into a swirling pattern, thereby enhancing convective heat transfer while maintaining low pressure loss. The staggered triangular baffles also tend to reflect radiation that would otherwise be lost back to the primary heat transfer surface.

Abstract: Apparatus and method for carburizing and carbonitriding ferrous metal work in a continuous furnace having aligned heating, carburizing and diffusing zones. Each zone is provided with fan means in at least one side wall of the furnace, with both the inlet and the outlet of the fan at a level below the work trays which are conveyed through the furnace so that the gas atmosphere is pulled downwardly through the work at one or more pier positions within a processing zone and pushed upwardly through the work at the remaining pier positions within the zone. By proper refractory design and fan locations a more uniform and controllable flow pattern is provided throughout the length and width of each processing zone.