Precautions before using graphite crucible

1. Handling


Special handling tools must be used to carry the crucible, and the crucible cannot 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.

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2. storage


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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3.Product specification


1. Preparations before installation:


1.1 Check whether the inner wall and bottom of the crucible furnace are intact.


1.2 Check whether there is residual slag in the furnace, if there is, remove it in time.


2. Choose the right crucible base


2.1 The base of the crucible should have the same shape and size as the bottom of the crucible (about 2cm).


2.2 For different types of crucible furnaces, crucible bases of appropriate height should be selected.


2.3 Avoid using waste crucible base, otherwise it will greatly shorten the life of the crucible.


3. Installation and fixing of crucible:


3.1 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.


3.2 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 wedge the crucible. At the same time, between the support brick and the crucible, a cardboard and other materials of about 3-4mm are inserted as the pre-expansion space of the crucible.


3.3 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.


3.4 Install the crucible for induction furnace: make sure the crucible is placed in the center of the induction coil to avoid local overheating and cracks in the crucible.

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4. Crucible preheating:


Preheating the crucible in the correct way can greatly extend the service life of the crucible.


4.1 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. Prevent bursting in the early stage of use.


4.2 After preheating, the crucible should be heated to 900°C-1000°C (about 2 hours) as soon as possible, and kept for 20-30 minutes, and then raised or lowered to the working temperature. The purpose is to quickly pass through the oxidation temperature zone of the graphite crucible.


4.3 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:


5.1 The metal material must be dried before being added.


5.2 Put down gently when adding materials, and do not throw or pour metal ingots into the crucible to avoid damage to the crucible.


5.3 Put the metal ingot into the crucible vertically, and keep 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 crucible from swelling due to the expansion of the metal ingot after heating.


5.4 You can add some small pieces of metal into the crucible first, as a bedding for the large ingots.


5.5 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 pieces of metal to a small amount of solution to avoid sudden cooling or solidification of the solution, thereby damaging the crucible.


5.6 When adding liquid metal, avoid overfilling, generally not exceeding 80% of the crucible capacity.


6. Use of additives


When using additives, you must strictly follow the instructions for use of the additives.


6.1 Additives can only be put in after the metal material is completely dissolved. Do not put additives in empty crucibles or solid metal materials, and do not allow additives to directly contact the walls or outer edges of the crucible, otherwise the crucible will be directly damaged.


6.2 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.

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7. The use of crucible tongs


7.1 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.


7.2 The crucible clamp should be clamped in the middle and lower part of the crucible. Too close to the top side will easily fall off or pinch the crucible, and too close to the bottom is not conducive to the pouring operation.


7.3 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.

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8. Pouring


When using the crucible for pouring, it should be carried out in strict accordance with the operating specifications to avoid damage to the crucible.


8.1 When the metal solution reaches the predetermined casting temperature, pouring should be carried out as soon as possible after removing slag and gas.


8.2 When pouring, heating should not be continued, so as not to cause air inhalation, produce metal burnout, and cause uneven corrosion of the crucible wall, thereby shortening the service life of the crucible.


8.3 When using a rotating crucible furnace, after finishing a pouring operation, the crucible should be restored to its original position.


8.4 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


9.1 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.


9.2 When emptying the crucible, the molten metal in the crucible can be poured into the mold (trough) to form an ingot for later use.


9.3 If the molten metal remains 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, the additives and impurities in the metal solution will form slag and adhere to the crucible wall. Because the slag contains additives which will corrode the crucible wall, the slag should be removed once a day.


10.1 Special tools should be used to remove the slag, and the slag should be removed in time when it is not solidified. The solidified slag will be difficult to remove.


10.2 Avoid scratching the crucible wall when removing slag.


10.3 When multiple layers of molten slag solidify and remain on the crucible wall, it will corrode the crucible and affect the thermal conductivity of the crucible. It will also cause the crucible to crack when heated and expand, thereby shortening the life of the crucible.

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Post time: Oct-24-2020

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