High temperature vacuum furnace structure, temperature control, heating process and furnace atmosphere, etc., will directly affect the quality of vacuum furnace after the production of products. In the forging furnace, increasing the temperature of the metal can reduce the melting resistance, but too high temperature will cause the oxidation of grains or overburning, seriously affecting the quality of products in the vacuum furnace. In the process of heat treatment, if the steel is heated to a certain point above the critical temperature, and then suddenly used cooling hair cooling, can improve the hardness and strength of steel; If heated to a point below the critical temperature and then slowly cooled, it can make the steel more ductile. In order to obtain a smooth surface and accurate size of the workpiece, or in order to reduce metal oxidation to achieve the purpose of protecting the mold, reduce the processing allowance, can be used in a variety of less oxidation furnace. In the less oxidation furnace with open flame, reducing gas is produced by incomplete combustion of fuel, in which the burning loss rate can be reduced to less than 0.6% by heating workpiece.