1. Direct heating furnace: a furnace that directly contacts the high-temperature gas or flame produced by combustion with the heating object. Direct heating furnaces are characterized by high heat transfer efficiency and fast heating speed. Common direct heating furnaces include flame furnaces and high-frequency induction furnaces.vacuum-brazing-repair-method-for-cracks Flame furnace: directly heats objects through the heat of the combustion flame, often used in metal heating, glass melting and other processes. -High-frequency induction furnace: It uses high-frequency electromagnetic fields to generate eddy currents to generate heat inside objects. It is often used for metal heating and smelting.Vacuum brazing of ceramic and metal materials ⒉Indirect heating furnace: heat is transferred to the object through a medium or heat transfer device, and the object is heated through indirect contact with the high-temperature gas or flame generated by combustion through the heat transfer device. The indirect heating furnace is characterized by uniform and stable temperature, and is suitable for processes with higher temperature requirements. Common indirect heating furnaces include hot blast furnaces and resistance heating furnaces.Atmospheric Pressure and Vacuum Sintering of High Purity Dense MgO Ceramics -Hot blast stove: generates high-temperature flue gas through combustion, and transfers heat to objects in the industrial furnace through a heat exchanger. It is often used in processes such as drying and baking.Applied Crack Repair Technology of Vacuum Brazing