1) Furnace building tools
① Whether the medium frequency furnace building machine is properly selected also affects the quality of furnace building. Electric vibrators are used in the workshop. As far as the electric vibrator is concerned, the power, frequency and weight of the furnace building machine should meet the specific requirements of the workshop. It is necessary to ensure that layering is avoided in the process of furnace building, and at the same time, it is necessary to ensure that the furnace lining with high density is obtained.
② The furnace building tools in the workshop include tamping forks, flat hammers, etc. the tamping forks are used to pound the furnace bottom and furnace wall, and the flat hammers are used to pound the furnace bottom after it is pounded.
③ There are several precautions for the manufacture of crucible mold: the exhaust hole should be reasonably designed to facilitate the discharge of water vapor during the drying process; The corners should be circular arcs to avoid sharp corners; The weld must be polished smooth; The wall thickness of the crucible mold should ensure its rigidity. Stiffeners can be welded in the mold to prevent deformation in the process of pounding the furnace.
2) Work preparation before furnace building work preparation shall be made before furnace building.
Check whether the coil is damaged. If yes, take measures to deal with it; Prepare various furnace building tools, and check whether the screws of the furnace building machine are loose and whether the tamping fork is firm, so as to prevent foreign matters from falling into the furnace lining; Prepare the furnace building materials and cut the bag open. It is required to cut the bag flat to avoid the wrapping paper falling into the furnace lining during the charging process; Prepare lighting tools to observe the specific situation in the process of furnace building; Prepare the crucible mold, check its various dimensions to see whether it is deformed. If it is deformed, replace the crucible mold, polish the rust on the surface of the crucible mold with emery cloth, sweep it clean with a broom, and block the exhaust hole with small firewood, but the surface of the crucible mold should be smooth to prevent the furnace lining sand from discharging from the exhaust hole when it is pounding the furnace. It can be used after it is ready.
3) Furnace building process
The quality of furnace bottom and furnace wall directly affects the service life of the furnace, so this link is very important. The thickness of the bottom of the medium frequency furnace is 300 mm, and the thickness of the furnace wall is 110 mm. When building the furnace bottom, add 16 bags of 25 kg furnace lining sand, which is tamped by three furnace building machines for about 50 minutes to ensure a solid furnace bottom; After the furnace bottom is built, put in the crucible mold, correct the wall thickness with a positioning ruler, and the error in each direction is required to be less than 5 mm, then fasten it with a wooden wedge, and put in the furnace pressing iron block to prevent the crucible from moving during the furnace flushing process, and then shovel the quartz sand between the crucible and the asbestos cloth with a flat shovel; Since the inclined part of the crucible mold is not easy to tamp, the charging of the first layer of the furnace wall needs to be less to avoid local looseness or layering. The charging of the first layer is 4 bags of furnace lining sand; From the second layer to the sixth layer, each layer is charged with 6 bags, and the tamping time is about 30 minutes. The feeding amount should ensure that the furnace can be tamped to the first layer to avoid layering. The feeding amount should be determined according to the specific situation; Due to the inevitable floating phenomenon of coarse particles in the process of furnace flushing, after each layer is completed, the coarse particles floating on it should be separated to avoid stratification; After the furnace is capped, use quartz sand mixed with water glass to lay it on the top of the furnace and the water outlet tank, tamp it tightly and level it; The thickness of furnace bottom and lining shall be adjusted according to the size of furnace body. After the furnace is built, cover the asbestos board, insert the thermocouple and position it, and prepare for oven drying.