[China Aluminum Network] The invention and development of industrial furnaces play a very important role in human advancement. China's Shang Dynasty presented a relatively complete copper furnace with a furnace temperature of 1200°C and a furnace internal diameter of 0.8 meters. During the Spring and Autumn Period and the Warring States Period, everyone further grasped the skill of improving the furnace temperature on the basis of the copper melting furnace and then produced the cast iron.
In 1794, the world presented a straight cylindrical cupola that melted cast iron. Then, in 1864, Martin Martin, the Frenchman, used British Siemens' principle of regenerative furnaces to create a front-side steelmaking open hearth heated with gaseous fuels. He used a regenerator to preheat the air and gas at high temperatures and then ensured temperatures above 1600°C for steelmaking. Around 1900, the supply of electrical energy became sufficient and various resistance furnaces, electric arc furnaces and cored induction furnaces began to be used.
In the 1950s, coreless induction furnaces were rapidly developed. The electron beam furnace was later presented. The use of an electron beam to impact the solid fuel can enhance the appearance of heating and the melting of high melting point data. The furnace used for casting and heating is a hand forging furnace earlier, and its working space is a concave groove. The groove is filled with coal, the incineration air is supplied from the lower part of the groove, and the workpiece is buried in the coal to be heated. This type of furnace has a low thermal efficiency, poor heating quality, and can only heat small parts. It can be used as a furnace for semi-enclosed or fully enclosed furnaces made of refractory bricks. Coal, gas or oil can be used as fuel. Electric energy can also be used as a heat source, and the workpiece is heated in the furnace.
In order to facilitate the heating of large workpieces, a trolley furnace suitable for heating steel ingots and slabs has also been presented, and pit furnaces have also been presented in order to heat the elongated rods. After the 1920s, various mechanized and automated furnaces that can improve furnace productivity and improve working conditions were presented.
The fuel of industrial furnaces also follows the development of fuel capital and the advancement of fuel conversion skills, and the use of solid fuels such as lump coal, coke, and pulverized coal has gradually shifted to gas and liquids such as producer gas, city gas, natural gas, diesel oil, and fuel oil. Fuels, and various incinerators adapted to the fuel used have been developed.
The structure, heating process, temperature control, and furnace atmosphere of the industrial furnace will directly affect the quality of the processed product. In casting furnaces, increasing the heating temperature of the metal can reduce the deformation resistance, but too high a temperature can cause grain growth, oxidation or over-burning, which will seriously affect the quality of the workpiece. In the heat treatment process, if the steel is heated to a point above the critical temperature and then suddenly cooled, the hardness and strength of the steel can be improved; if it is slowly cooled after being heated to a point below the critical temperature, it can also make the hardness of the steel. Decline to make patience progress.
In order to obtain accurate and clean-looking workpieces, or to reduce metal oxidation to reach the maintenance mold and reduce the machining allowance, various oxidation-free heating furnaces can be selected. In the non-oxidizing heating furnace of the open flame, the incomplete incineration of the fuel produces a regenerative gas, and heating the workpiece therein can reduce the oxidation loss rate to 0.3% or less.
Controlled atmosphere furnace is the use of artificially prepared atmosphere, into the furnace for gas carburizing, carbonitriding, bright quenching, normalizing, annealing and other heat treatment: in order to reach the changes in the metal arrangement, improve the mechanical properties of the workpiece. In the active particle furnace, the fuel incineration gas or other external fluidizing agent is forced to flow through the graphite particles or other lazy particle layers on the hearth, and the workpiece is buried in the particle layer to perform the enhanced heating. Carburizing, nitriding and other non-oxidation heating. In a salt bath furnace, molten salt solution is used as a heating medium to prevent oxidation and decarburization of the workpiece. The melting of cast iron in a cupola furnace is often affected by the quality of coke, air supply method, charging conditions, and air temperature, making it difficult for the smelting process to be stable and difficult to obtain high-quality molten iron. Hot air cupola can effectively improve the temperature of molten iron, reduce alloy burn, reduce the oxidation rate of hot metal, and then produce high-grade cast iron.
Following the presentation of coreless induction furnaces, cupolas have gradually been replaced. The melting furnace operation of this induction furnace is not limited by any cast iron grade. It can be used to convert one grade of cast iron and quickly convert to another grade of cast iron, which is beneficial for improving the quality of molten iron. Some special alloyed steels, such as ultra-low carbon stainless steels and steels for rolls and turbine rotors, require the molten steel smelted from open hearth furnaces or conventional electric arc furnaces to undergo vacuum degassing and argon agitation in the refining furnace to remove impurities and further refine the steel. High-purity, large-capacity high-quality molten steel.
The flame furnace has a wide range of fuel sources and offers a low price. It is easy to tailor fabrics to different structures, which is beneficial to reducing production costs. However, the flame furnace is difficult to achieve accurate control. It has serious environmental pollution and low thermal efficiency. The characteristics of the electric furnace are uniform furnace temperature and easy completion of active control, and the heating quality is good. According to energy conversion methods, electric furnaces can be further divided into resistance furnaces, induction furnaces and electric arc furnaces. The furnace heating capacity calculated by the furnace floor area per unit time is referred to as the furnace yield. The faster the furnace heats up and the greater the furnace load, the higher the furnace yield. Under normal conditions, the higher the furnace yield, the lower the unit calorie heat per kg of material. Therefore, in order to reduce energy consumption, production should be carried out at full capacity, the furnace output rate should be improved as much as possible, and the active sharing of fuel and combustion air should be implemented for the incineration equipment to prevent excess or lack of air volume. In addition, the heat storage and heat loss of the furnace wall, the heat loss of water-cooled components, the loss of radiant heat from various openings, and the loss of heat away from the flue gas are also reduced.
The ratio of the amount of heat that is absorbed when the metal or material is heated to the amount of heat that is supplied to the furnace is called the furnace thermal efficiency. The continuous furnace has higher thermal efficiency than the continuous furnace because of the high productivity of the continuous furnace and the non-continuous operation of the furnace. The thermal criteria of the furnace are in a stable state, there is no cyclical heat loss in the furnace wall, and there is a furnace interior. In the section of the preheated charge, some residual heat of the flue gas is due to a section of the preheated charge inside the hearth. Some residual heat of the flue gas is absorbed by the cold workpieces entering the furnace, which reduces the temperature of the flue gas from the furnace.
To complete the active control of furnace temperature, furnace atmosphere or furnace pressure.
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