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Notice before using graphite crucible

1. Transportation

When handling the crucible, special handling tools must be used, and the crucible cannot be rolled directly on the ground. Collision should be avoided when handling, so as not to damage the glaze layer, thereby affecting the service life of the crucible.

2. Storage

Crucibles must be kept in a dry, ventilated place, preferably on wooden racks. 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.

3. Specifications for product use

3.1. Preparations before installation:

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

3.1.2 Check whether there is residual slag in the furnace, and if so, remove it in time.

3.2. Choose the correct crucible base

3.2.1 The crucible base should be the same shape as the crucible bottom and slightly larger in size (about 2cm).

3.2.2 For different types of crucible furnaces, a crucible base with a suitable height should be selected.

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

3.3. Installation and fixing of crucible:

3.3.1 Install the crucible for gas or fuel oil: first place the crucible on the base, reserve a certain crucible expansion space between the crucible and the top of the furnace wall, and use wood blocks, cardboard and other materials to fix it. 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.

3.3.2 Installation of crucible for rotary furnace: Support bricks should be used to fix the crucible on both sides of the crucible nozzle to avoid wedging the crucible tightly. At the same time, a material such as cardboard of about 3-4mm is placed between the support brick and the crucible as a pre-expansion space for the crucible.

3.3.3 Install the 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 insulating cotton to seal between the crucible top and the furnace edge.

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

3.4. Crucible preheating:

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

3.4.1 According to different types of crucible furnaces, when using the crucible for the first time, without feeding the crucible, preheat the crucible to about 200°C for 30 minutes, and dry it for 60 minutes. The purpose is to volatilize moisture which was absorbed in the surface of the crucible . Prevent bursting in the initial stage of use.

3.4.2 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 easy-to-oxidize temperature region of the graphite crucible.

3.4.3 After the crucible has been preheated for the first time, it usually does not need to be preheated again, unless the crucible is damped again. (The crucible must be preheated again after each furnace shutdown.)

3.5. Feeding:

3.5.1 Metal materials must be dried before being added.

3.5.2 When feeding, it should be put down gently, and the metal ingot should not be thrown or poured into the crucible, so as not to damage the crucible.

3.5.3 Put the metal ingot vertically into the crucible, 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 not to swell the crucible due to the expansion of the metal ingot after heating.

3.5.4 Some small pieces of metal material can be added to the crucible first as a bedding for the large ingots.

3.5.5 During continuous melting, part of the metal solution can be kept in the crucible to speed up the melting speed. However, avoid adding large pieces of metal material to a small amount of solution, so as not to quench or solidify the solution, thereby damaging the crucible.

3.5.6 When adding liquid metal, avoid overfilling, generally not more than 80% of the crucible capacity.

3.6. Use of additives

When using additives, the instructions for use of the additives must be strictly followed.

3.6.1 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 crucible wall or outer edge, otherwise the crucible will be directly damaged.

3.6.2 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.

3.7. Use of crucible tongs

3.7.1 The size of the crucible tongs must match the size and shape of the crucible, and the upper edge of the crucible cannot be squeezed, so as not to damage the crucible or cause a safety accident.

3.7.2 The crucible clamp should be clamped in the middle and lower part of the crucible. If it is too high, it is easy to fall off or pinch the crucible, and if it is too low, it is not conducive to the operation during pouring.

3.7.3 When using crucible tongs to move the hot crucible, the crucible should be placed on a high temperature resistant plate or a transfer tool, and the hot crucible should not be placed on a cool surface to avoid damage to the bottom of the crucible.

3.8. 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.

3.8.1 When the metal solution reaches the predetermined casting temperature, it should be poured as soon as possible after slag removal and degassing.

3.8.2 When pouring, the heating should not be continued, so as not to cause inhalation, metal burning loss, and uneven corrosion of the crucible wall, thereby shortening the service life of the crucible.

3.8.3 When using the rotary crucible furnace, after completing a pouring operation, the crucible should be restored to its original position.

3.8.4 The metal solution should not be kept in the crucible for too long, otherwise the service life of the crucible will be shortened and the quality of the smelted metal will be reduced.

3.9. Empty the Crucible

3.9.1 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.

3.9.2 When the crucible is emptied, the molten metal in the crucible can be poured into the mold to form an ingot for later use.

3.9.3 If the molten metal remains in the crucible to solidify, it will directly swell the crucible due to expansion during the next heating.

3.10. Remove slag

During the smelting process, additives and impurities in the metal solution will form slag, which adheres to the crucible wall. Because the slag contains additives, it will corrode the crucible wall, so the slag should be cleaned once a day.

3.10.1 Special tools should be used to remove the slag, and the slag should be removed in time before it solidifies. The solidified slag will be difficult to remove.

3.10.2 Avoid scratching the crucible wall when removing slag.

3.10.3 When the multi-layer slag solidifies and remains on the crucible wall, it will corrode the crucible, affect the thermal conductivity of the crucible, and cause the crucible to crack during heating and expansion, thereby shortening the service life of the crucible.

4. How to get the best performance

During the use of the crucible, if the following items can be followed, the best performance of the crucible can be maintained and the service life of the crucible can be effectively extended.

4.1. For different smelting metals, the corresponding crucible should be selected.

4.2. When heating the crucible, pay attention to the following matters:

4.2.1. Heating the new crucible as required to remove the moisture in the crucible.

4.2.2. When heating, make the outer surface of the crucible heated evenly.

4.2.3. Use the crucible lid to seal the top of the crucible to reduce heat loss and oxidation of the crucible. But leave enough expansion space to avoid pressing on the top edge of the crucible.

When using gas or oil-fired crucible furnaces, use a lightly oxidizing flame and avoid direct flame jets on the bottom of the crucible. When adding additives, the metal solution should be stirred immediately, and the slag on the crucible should be removed in time. A bell jar should be used to immerse the flake or block additive when it is added.

4.3. During the pouring process, avoid tools such as crucible tongs and ladle colliding or knocking on the crucible.

4.4. When cleaning the crucible, use the special tools matched with the crucible to clean it while it is hot.

4.5. When the crucible is temporarily out of use, the following matters should be noted:

4.5.1. If a gas or oil furnace is used, all fans should be turned off to prevent the cold air from attacking the outer surface of the crucible and causing oxidation or even rupture.

4.5.2. Let the crucible cool to room temperature by itself. Speeding up or slowing down self-cooling may increase crucible oxidation or cause crucible rupture.

4.5.3. For crucibles that are not frequently used, they should be stored in a fixed area and kept in a dry storage environment.

4.6. The use of the crucible furnace should be checked frequently to ensure that the crucible furnace is working properly. The slag on the lining of the crucible furnace should be cleaned up in time.




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