Nonscale Heating Furnace

a gas flame furnace for heating metal to a high temperature before forging, pressing, rolling, or heat treating in an atmosphere consisting of the incomplete combustion products of the gas.

Gas with a high heat of combustion is burned in the heating chamber with an excess air ratio of α = 0.5, thus obtaining a gas with a ratio of CO/CO₂ = 2.5 to 3.2 and of H₂/H₂O = 1.2 to 1.3, which protects the metal from oxidation. The required temperature in the working space is achieved by preheating the air to between 800 and 1000° C using heat obtained from the afterburning of the incompletely burned gas products or through the use of oxygen.

There are nonscale heating furnaces that operate periodically (reverberatory) and continuously (holding and rotary). The periodic reverberatory types are subdivided into the recuperative in which gas is burned in the heating chamber with air that may or may not be enriched with oxygen preheated to 600–800° C; the recuperative in which the heat is transmitted through the crown; and the regenerative. The holding furnace for the nonscale reheating of metal is a continuously operating type of furnace.