As fuel resources are developed and fuel conversion technology advances, the fuel for the trolley-type annealing furnace has gradually shifted from solid fuels like lump coal, coke, and coal powder to gaseous and liquid fuels such as blast furnace gas, town gas, natural gas, diesel, and fuel oil. Various incineration equipment suitable for the used fuels have also been developed.
The structure, heating technology, temperature control, and furnace atmosphere of the car-type annealing furnace directly affect the quality of the processed product. In the casting heating furnace, increasing the heating temperature of the metal can reduce deformation resistance, but excessive temperature can lead to grain growth, oxidation, or overburning, severely impacting the quality of the workpiece. During the heat treatment process, if the steel is heated to a point above the critical temperature and then rapidly cooled, it can increase the hardness and strength of the steel; if it is heated to a point below the critical temperature and cooled slowly, the hardness of the steel can be reduced while its toughness is improved.
To achieve precise dimensions and a smooth finish on workpieces, or to reduce metal oxidation for purposes such as mold protection and minimizing machining allowances, various low or no-oxidation heating furnaces can be selected. Inside the open flame of a low or no-oxidation heating furnace, reductive gases are produced from the incomplete combustion of fuel, and heating the workpiece in these gases can lower the oxidation burn rate to below 0.3%.
Controlled atmosphere furnaces utilize artificially prepared atmospheres that are introduced into the furnace for processes such as gas carburization, carbonitriding, bright quenching, normalizing, and annealing, all of which aim to alter the microstructure and improve the mechanical properties of workpieces. In an active particle furnace, the combustion gases of the fuel or other fluidizing agents applied externally are forced to flow through a layer of graphite particles or other inert particles on the furnace bed. Workpieces buried in this particle layer can undergo intensive heating and various non-oxidizing heat treatments, such as carburization and nitriding. In a salt bath furnace, the molten salt acts as the heating medium, preventing oxidation and decarburization of the workpieces. In a cupola furnace, melting cast iron is typically affected by factors such as coke quality, blowing method, furnace charge conditions, and air temperature, making the smelting process difficult to stabilize and resulting in the difficulty of obtaining molten iron. A hot blast cupola can effectively increase the temperature of the molten iron, reduce alloy burn loss, and lower the oxidation rate of the molten iron, thus enabling the production of cast iron.