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The melting furnace in an aluminum plant is a melting equipment used in the casting workshop to melt aluminum ingots as well as various alloying ingots or intermediates, and to carry out processes such as mixing the ingredients for the final aluminum and aluminum alloys, maintaining the appropriate temperature, and removing slag. Aluminum smelting furnaces can be classified according to the type of energy used, including coal furnaces, oil furnaces, electric furnaces, and natural gas furnaces. Coal and oil furnaces cause significant environmental pollution; as environmental regulations become stricter, they will gradually be phased out. Natural gas furnaces are increasingly widely used due to their fast heating rate, high melting capacity, ability to enable clean production, and ease of automated control. Electric furnaces are widely used in static furnaces as they help reduce the reabsorption of hydrogen by the aluminum melt. With the rapid development of China’s aluminum processing industry, smelting furnaces are becoming larger in size, with furnaces of 30 tons, 50 tons, 70 tons, and even hundreds of tons now appearing. The proper use and maintenance of melting furnaces and holding furnaces are not only related to the safe production and product quality in a casting workshop, but the condition of these furnaces in terms of use and maintenance also reflects the level of management in that casting workshop. In 2007, an explosion caused by the spillage of molten aluminum occurred at a factory in Shandong. In addition to some design issues related to the furnaces, a lack of proper maintenance and monitoring of these furnaces was likely also a major contributing factor. Use and Maintenance of Aluminum Melting Furnaces in Aluminum Plants https://www.lyyhjn.com/news/industry/266.html For the design of aluminum melting furnaces, attention should first be paid to the design of the furnace itself. In terms of casting production, the following design factors need to be considered: (1) The thermal efficiency of the furnace; (2) The level of automated control of the furnace, such as control of furnace temperature, furnace pressure, automatic ignition, and alarm systems for shutting down the furnace; (3) The design and layout of the furnace door and openings. A larger furnace door is suitable for removing slag and refining, but it has poor insulation properties and lower thermal efficiency; (4) It is necessary to consider in advance whether manual or mechanical methods will be used for removing slag, as well as how the slag removal platform and slag container will be connected; (5) The method of feeding aluminum into the furnace – whether to use electrolytically produced aluminum melt or remelted aluminum ingots. Different raw materials require different furnace structures and pre-heating methods. (6) Design the necessary dust collection equipment. Baking schedule: Once the melt in the furnace has been poured, a proper baking schedule should be established. A furnace drying system should be established during the installation of new furnaces, during repairs and overhauls of existing furnaces, as well as during short-term and long-term shutdowns of furnaces. The following points should be taken into account when establishing such a system. (1) Develop a reasonable furnace heating curve, paying attention to controlling the heating rate and holding time. Especially for new furnaces, the heating rate during the low-temperature phase of heating is generally controlled between 15°C and 30°C; otherwise, not only will the service life of the furnace be shortened, but serious accidents such as furnace explosions can also occur. The heating rate of old furnaces can be faster, generally kept between 15°C and 30°C. (2) Special attention should be paid to maintaining an appropriate temperature within the three temperature ranges of 100°C–150°C (phase of removing adsorbed water), 350°C–450°C (phase of removing crystalline water), and 600°C–650°C (phase of removing chemical water). The temperature range of 100°C to 150°C corresponds to the drying stage, during which a large amount of water is removed. The temperature should not be increased too quickly, as otherwise water will be removed too rapidly. In this case, the rate at which residual water inside diffuses is slower than the rate of surface evaporation, and the heat applied to this internal water causes it to turn into steam, leading to expansion that results in cracking of the cast material. This reduces the bonding strength and weakens the structure of the furnace. Therefore, the temperature should not be raised too fast during this stage; an increase rate of less than 10°C is advisable. Additionally, the temperature should be maintained at 150°C for a certain period of time to ensure that the furnace is fully dried. The second stage, namely the heating stage, is primarily aimed at completing the phase transformation of the refractory materials and eliminating stresses. After the first dehydration step, the furnace chamber still requires multiple further dehydration processes in order to complete the polymerization associated with crystal structure transformation, and it must be heated gradually to achieve sintering strength. (3) During baking, the temperature inside the furnace should be made as uniform as possible. Temperature control should be based on the highest point when heating the furnace; the actual temperature should be maintained within ±20°C of the set temperature. Depending on the size of the furnace, three or more temperature measurement points should be selected at different locations for monitoring. The larger the furnace size, the greater the temperature difference between various points; the smaller the furnace size, the smaller the temperature difference between those points. The selection of temperature measurement points should be representative. (4) Keep furnace drying records. It is best to use a temperature measuring instrument with continuous recording capability, one that can plot temperature variation curves. To properly use and maintain the melting furnace, a comprehensive system for adding waste materials, a system for purifying the furnace interior, and a regular furnace cleaning system must be established. (1) Strengthen ingredient management, reduce defective materials in the ingredients, increase the speed of ingredient preparation, and raise the first-time qualification rate for ingredient preparation; where possible, use computers for ingredient preparation to minimize human errors. (2) Establish a reasonable furnace cleaning system. The melting furnace should be cleaned once per shift; currently, there are mechanical and manual methods for cleaning it. When cleaning the furnace, a portion of cleaning agent can be spread in advance to facilitate the process. When cleaning the furnace, the electric furnace should have its power turned off first, and for gas furnaces, the burners must be shut off before cleaning can take place, in order to avoid danger. When cleaning the furnace, it is necessary to remove the slag accumulated at the bottom and walls of the furnace, as well as the slag on the top of the furnace. (3) Establish an appropriate waste addition system. The sequence and method of loading the charge not only affect the melting time, metal loss, and heat consumption, but also influence the quality of the molten metal and the service life of the furnace. The principles for charging the furnace are as follows: the sequence of charging materials should be reasonable; the correct method of charging depends on the properties and state of the materials, and it is also necessary to take into account the fastest melting speed, minimal loss due to burning, and accurate control of chemical composition. During loading, small pieces or thin sheets of scrap should be placed first, aluminum ingots and large pieces in the middle, and finally the master alloys. The easily oxidizable intermediate alloys with low melting points are placed in the middle and lower layers, while those with high melting points are placed in the top layer. The charged charge should be evenly distributed in the molten pool to prevent localized accumulation of a certain type of charge. Small pieces or thin sheets are placed in the lower layer; this helps to reduce burning damage, and it also protects the furnace from being damaged by larger pieces. Some master alloys have high melting points; for example, the melting points of Al Ni and Al Mn alloys range from 750°C to 800°C. These alloys are placed in the upper layer, where the high temperature facilitates their melting. They also have sufficient time to diffuse, resulting in a uniform distribution of the master alloys, which helps in controlling the composition of the melt. The charge is leveled so that the melting rate is similar throughout, which helps to prevent localized overheating of the metal. The charge should be fed into the furnace at once; adding it in two or more batches will increase the amount of non-metallic inclusions and gas content. For products with high quality requirements (including forgings, die forgings, hollow beams, and beam profiles), in addition to the aforementioned loading requirements, 20 kg to 30 kg of powdered flux must be scattered into the molten pool before loading. During the loading process, the powdered flux should be applied to the charge in layers; this helps to improve the purity of the melt and also reduces burnout. (4) Establish an appropriate in-furnace purification system; in-furnace purification is primarily aimed at removing gases and inclusions from the aluminum melt. Depending on the chemical composition and properties of the alloy, corresponding refining agents and coating agents are used. When using argon or nitrogen for powder spraying refining, pay attention to the pressure of argon or nitrogen. If the pressure is too low, it can cause blockages in the refining tubes; if the pressure is too high, the aluminum melt will splash, leading to secondary contamination of the aluminum melt and the accumulation of aluminum on the furnace roof, which affects heating. Currently, some manufacturers use permeable bricks at the bottom of the furnace for in-furnace refining, along with automated control; this approach yields good refining results and is energy-efficient and environmentally friendly, making it worthy of further research and promotion. Pay attention to the application of new technologies: (1) Use electromagnetic stirring. Electromagnetic stirring not only makes the composition of the melt more uniform but also reduces the number of times manual stirring is required. This lowers the workload on workers, reduces heat loss, and helps save energy. (2) By using advanced furnace automation technologies to effectively control parameters such as temperature and pressure inside the furnace, it not only facilitates the implementation and stability of the manufacturing process but also prevents sudden fluctuations in furnace temperature. This reduces deformation stresses on the furnace, thereby significantly extending its service life. (3) Reasonably design the furnace structure to improve energy efficiency. At present, the thermal efficiency of melting furnaces in domestic aluminum plants is generally low; more research should be conducted to reduce energy consumption. Here, our company recommends the energy-saving melting furnaces (gas melting furnaces) or electric radiation melting furnaces produced by Luoyang Yanhao Energy-Saving Technology Co., Ltd. These furnaces are energy-efficient and highly effective, making them the ideal choice in today’s environmentally conscious context!