1) Furnace Building Tools

①Whether the selection of the ramming machine for medium frequency furnace is appropriate also affects the furnace ramming quality. The electric vibratory rammer is used in the workshop. For electric vibratory rammers, the power, frequency and weight must all meet the specific requirements of the workshop, so as to avoid delamination during the ramming process and ensure a high-density furnace lining.

②The furnace ramming tools in the workshop include ramming forks, flattening hammers, etc. Ramming forks are used for ramming the furnace bottom and furnace wall, and flattening hammers are used to level the furnace bottom after it is rammed.

③There are several precautions for the manufacturing of the crucible mold: the exhaust holes shall be reasonably designed to facilitate the discharge of water vapor during the furnace drying process; the corners shall be designed as arc to avoid acute angles; the welding seams must be polished smooth; the wall thickness of the crucible mold shall ensure its stiffness, and reinforcement ribs can be welded inside the mold to prevent deformation during the ramming process.

2) Preparations before furnace ramming All necessary preparations shall be done before furnace ramming.

Check whether the coil is damaged, and take corresponding measures if there is any damage; prepare all kinds of furnace ramming tools, check whether there are loose screws on the ramming machine and whether the tines of the ramming fork are firm, so as to prevent foreign matters from falling into the furnace lining; prepare furnace ramming materials, cut the packaging bags straight along the flat side to avoid packaging paper falling into the furnace lining during feeding; prepare lighting tools for observing the specific situation during the furnace ramming process; prepare the crucible mold, check all its dimensions to see if it is deformed, replace the deformed crucible mold if necessary, polish off the rust on the surface of the crucible mold with emery cloth, clean it with a broom, block the exhaust holes with small firewood while keeping the surface of the crucible mold smooth, so as to prevent furnace lining sand from leaking out from the exhaust holes during ramming, and set it aside after preparation.  

3) Furnace Ramming Process

The quality of the furnace bottom and furnace wall directly affects the service life of the furnace, so this link is extremely important. For the medium frequency furnace, the thickness of the furnace bottom is 300 mm, and the thickness of the furnace wall is 110 mm. For ramming the furnace bottom, 16 bags of 25 kg packaged furnace lining sand are added, and tamped by three ramming machines for about 50 minutes, so as to ensure a compact and firm furnace bottom; after the furnace bottom is completed, put in the crucible mold, correct the wall thickness with a positioning ruler, require the error in all directions to be less than 5 mm, then fasten it with wooden wedges, put in pressed iron blocks to prevent the crucible from moving during ramming, then loosen 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 be compacted, the feeding amount of the first layer of the furnace wall should be smaller to avoid local incompaction or delamination, and the feeding amount of the first layer is 4 bags of furnace lining sand; the feeding amount of each layer from the 2nd layer to the 6th layer is 6 bags, and the ramming time of each layer is about 30 minutes. The feeding amount shall ensure that the ramming machine can compact the previous layer to avoid delamination, and the specific feeding amount shall be determined according to actual conditions; since the floating of coarse particles is inevitable during the ramming process, after each layer is completed, the coarse particles floating on the surface shall be removed to avoid delamination; after the furnace is capped, mix quartz sand with water glass and pave it on the top of the furnace and the outflow tank, tamp it tightly and trim it flat; after the furnace is built, cover it with an asbestos board, insert and position the thermocouple, and finish the preparations for furnace drying.