Special handling tools must be used to transport the crucible, and the crucible must not be rolled directly on the ground. Avoid collisions during transportation, so as not to damage the glaze layer, thereby affecting the service life of the crucible.
The crucible must be stored in a dry and ventilated place, preferably on a wooden bracket. Avoid placing the crucible directly on the brick, soil or cement floor. Moisture of the crucible will damage the glaze layer and reduce the melting efficiency and service life of the crucible. In severe cases, the bottom may even fall off.
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(1) Preparation before installation
① Check whether the inner wall and bottom of the crucible furnace are intact.
② Check whether there is residual slag in the graphite crucible furnace, if there is, remove it in time.
(2) Choose the right crucible base
① The base of the crucible should have the same shape and size as the bottom of the crucible (about 2cm).
② For different types of crucible furnaces, a crucible base with a suitable height should be selected.
③ Avoid using waste crucible base, otherwise it will greatly shorten the service life of the crucible.
(3) Installation and fixing of crucible
① Install the crucible for gas or fuel oil: first place the crucible on the base, reserve a certain expansion space between the crucible and the top of the furnace wall, and fix it with wood blocks, cardboard and other materials. Adjust the position of the burner and nozzle so that the flame is aimed at the combustion chamber, not directly at the bottom of the crucible.
② Install the crucible for the rotary furnace: support bricks should be used to fix the crucible on both sides of the crucible spout to avoid wedging the crucible. At the same time, a cardboard and other materials of about 3 to 4mm are inserted between the supporting brick and the crucible as the pre-expansion space of the crucible.
③ Installation of crucible for electric furnace: The crucible should be placed in the center of the resistance furnace, and the bottom of the crucible should be higher than the bottom row of heating elements. At the same time, use insulation cotton to seal between the top of the crucible and the edge of the furnace.
④ Install the crucible for the induction furnace: ensure that the crucible is placed in the center of the induction coil to avoid local overheating and cracks in the crucible.
(4) Crucible preheating
Preheating the crucible in the correct way can greatly extend the service life of the crucible.
① According to different types of crucible furnaces, when the crucible is used for the first time, without adding materials, take 30 minutes to preheat the crucible to about 200°C and dry it for 60 minutes. The purpose is to make the surface of the crucible absorb water and volatilize and to prevent bursting in the early stage of use.
② After preheating, the crucible should be heated to 900°C to 1000°C (about 2 hours) as soon as possible, which should be kept for 20 to 30 minutes, and then raised or lowered to the working temperature. The purpose is to quickly pass through the easy oxidation temperature area of the graphite crucible.
③ The crucible usually does not need to be preheated after the first preheating, unless the crucible is damp again. (The crucible must be preheated again after each shutdown.)
(5) Adding materials
① The metal material must be dried before being added.
② The material should be put down gently when feeding, and metal ingots should not be thrown or poured into the crucible, so as not to damage the crucible.
③ Put the metal ingot into the crucible vertically, and there should be enough expansion space between the metal ingot and the crucible wall. Do not place the metal ingot horizontally in the crucible, so as to prevent the metal ingot from expanding and breaking the crucible after heating.
④ Some small pieces of metal can be added to the crucible first, as a bedding for the large ingots.
⑤ During continuous smelting, part of the metal solution can be kept in the crucible to speed up the melting speed. However, it is necessary to avoid adding large metal materials to a small amount of solution, so as to avoid the solution's sudden cooling or solidification, which may damage the crucible.
⑥ When adding liquid metal, avoid overfilling. Generally, it should not exceed 80% of the crucible capacity.
(6) Use of additives
When using additives, you must strictly follow the instructions for use of the additives.
① Additives can only be put in after the metal material is completely dissolved. Do not put additives in the empty crucible or solid metal materials, and do not allow the additives to directly contact the wall or outer edge of the crucible, otherwise the crucible will be directly damaged.
② When using additives, they must be added in strict accordance with the prescribed dosage. Excessive use of additives will greatly shorten the service life of the crucible.
(7) The use of crucible tongs
① The size of the crucible tongs must match the size and shape of the crucible, and the upper edge of the crucible must not be squeezed to avoid damage to the crucible or cause safety accidents.
② The crucible tongs should be clamped in the middle and lower part of the crucible. Crucible tongs clamped in a too higher position will easily fall off or damage the crucible, while it is not conducive to the operation during pouring when tongs are clamped in a too lower position.
③ When using the crucible to move the hot crucible, place the crucible on a high-temperature resistant plate or transfer tool. Do not place the hot crucible on the surface of a cold object to avoid damage to the bottom of the crucible.
When using the crucible for pouring, it should be carried out in strict accordance with the operating specifications to avoid damage to the crucible.
① When the molten metal reaches the predetermined casting temperature, pouring should be carried out as soon as possible after slagging and degassing.
② When pouring, heating should not be continued, so as not to cause air inhalation, produce metal burnout, and at the same time cause uneven corrosion of the crucible wall, thereby shortening the service life of the crucible.
③ When using a rotating crucible furnace, after completing a pouring operation, the crucible should be restored to its original position.
④ Do not keep the metal solution in the crucible for too long, otherwise it will shorten the service life of the crucible and reduce the quality of the molten metal.
(9) Empty the crucible
① When it is necessary to temporarily stop using the crucible due to slag removal or maintenance of the crucible furnace, the molten metal in the crucible should be emptied.
② When emptying the crucible, the molten metal in the crucible can be poured into the mold (trough) to form an ingot for later use.
③ If the molten metal is kept in the crucible for solidification, it will directly swell the crucible due to expansion during the next heating.
(10) Remove slag
During the smelting process, additives and impurities in the metal solution will form slag and adhere to the crucible wall. Because the slag contains additives that will corrode the crucible wall, the slag should be removed once a day.
① Special tools should be used to remove the slag, and the slag should be removed in time when the slag is not solidified. The solidified slag will be difficult to remove.
② Avoid scratching the crucible wall when removing slag.
③ When multiple layers of slag solidify and remain on the wall of the crucible, it will corrode the crucible and affect the thermal conductivity of the crucible. It will also cause the crucible to crack during thermal expansion, thereby shortening the service life of the crucible.