Instructions for Use of the Crucible

Instructions for Use of the Crucible

Crucible storage
1. The EPS or polystyrene foam must be stored in a dry environment, placed on a wooden pallet and kept ventilated; 2. The crucible can be placed on top of each other when placed upside down;
3. Do not expose the crucible to a humid environment, otherwise the glaze layer of the crucible after absorbing moisture will easily peel off during the crucible preheating process, causing the graphite to be oxidized and the thermal conductivity of the crucible to gradually decrease, resulting in a reduction in the service life of the entire crucible.
Transportation of the crucible
In order to better protect the glaze layer of the crucible, you must be very careful when transporting the crucible to avoid knocking, collision or falling, and do not roll the crucible horizontally on the ground. Once the glaze layer of the crucible is damaged, the crucible will be prone to oxidation and aging during use. Crucibles should be handled carefully using a padded trolley (or other suitable transport tool).

Crucible installation
1. Before installing the crucible, you must first check the inside of the furnace: the furnace walls and bottom should be intact, with no metal or slag attached. If cement or slag adheres to the furnace walls or bottom, it must be cleaned. Otherwise, the advancement of the flame will be hindered and the direction of the flame will be deflected, resulting in local overheating of the crucible, oxidation or small holes on the crucible wall.
2. Bottom support of crucible:
1. When installing the crucible, the bottom support of the crucible must use a large enough cylindrical base. The diameter of the base must be at least the same as the bottom of the crucible, which should be slightly larger by 2-3cm, and the height of the base should be slightly higher than the fire outlet, thereby preventing The flame burns directly to the bottom of the crucible. As a result, the bottom material is quickly eroded, the crucible becomes tapered, or the crucible cracks due to uneven stress on the bottom of the crucible.
2. To prevent the crucible and the base from adhering, a layer of spacer (such as fine refractory sand or cardboard) can be placed between the crucible and the base.
3. When using a falcon base in a tilting furnace, it must be ensured that the protrusions of the base and the groove of the crucible match each other. If the protrusion of the base is too high or too large, the bottom of the crucible will be squeezed, which will inevitably cause the bottom to break, and the crucible cannot be effectively fixed after tipping.
4. When installing a tilting furnace crucible with a long spout, a base with a suitable height should be provided and the crucible support should be fixed. If the base support is not suitable, this type of crucible will "hang" in the furnace only by the spout. The crucible will break off from the top.
3. The gap between the crucible and the supporting bricks:
1. The gap between the crucible and the support brick is too small, and the crucible will be blocked and cracked after thermal expansion. You can place combustibles (insert small wood chips or cardboard) directly between the crucible and the support brick at the top of the furnace wall. After the crucible is heated, the combustibles will Will burn away leaving enough space.
2. For furnaces that exhaust exhaust gas on the side, the space between the crucible and the furnace wall can be sealed with insulation cotton and then fixed with high-temperature-resistant cement. This can not only prevent the top of the crucible from being oxidized and cracked due to incomplete sealing of the furnace top, but also prevent cracking from being blocked when the crucible is heated and expands upward, and also protects the heating wire.
(Note: It is recommended to use a furnace rim cover to prevent oxidation, cracking and corrosion of the top of the crucible. The inner edge of the furnace rim cover should cover 100mm of the inner surface of the crucible, which can better prevent the crucible from being impacted by external forces and oxidized.)
3. In the tilting furnace, there should be one or two supporting bricks at half the height of the crucible under the pouring spout to fix the crucible. Cardboard should be placed between the crucible and the support brick to leave enough space to prevent the crucible from being blocked when it expands.

Crucible preheating
1. The crucible is a ceramic product. There are a certain number of pores in the crucible wall, which are easy to absorb moisture. Therefore, before using the crucible without adding materials, the crucible must be preheated to ensure that no moisture remains in the crucible wall: it should be placed Bake in a warm furnace for more than 24 hours. During this period, the crucible should be rotated several times to heat it evenly and remove moisture in the crucible wall to prevent the crucible from heating up too quickly, causing thermal expansion of the crucible and causing the bottom to fall. Delamination or bursting.
Note: Moisture generally evaporates quickly at 75 to 100 degrees, so the temperature rise must be slow at this temperature; after 2 hours, preheat the crucible to 150 to 200 degrees and keep it warm for one hour, and then increase the temperature by 150 degrees every hour. Since the crucible wall will undergo rapid oxidation in the temperature range of 315 to 650 degrees, oxidation will not only shorten the life of the crucible, but also affect its performance due to reduced thermal conductivity, so the crucible does not need to stay in this temperature range for too long. .
2. After the crucible has been preheated, it usually does not need to be preheated again if it is used continuously, unless the crucible is exposed to a humid environment again.
3. After the crucible is preheated, the operator needs to quickly raise the temperature to 850~950 degrees without adding materials, keep it warm for half an hour, then lower it to the normal operating temperature, and then add materials. (Heating the crucible to a temperature higher than the normal operating temperature will extend the service life of the crucible.) Usually heating the crucible to 815~930 degrees will help protect the glaze of the crucible. If possible, this high temperature heating can be done every week Do it all once

Crucible charging
1. Put the crucible into the furnace and wait for it to turn red. First put some small metal scraps at the bottom of the crucible, and then put the metal ingot (the metal ingot must be placed on the edge of the furnace for baking before being put into the crucible) to avoid cold ingots. Put it directly into the crucible, causing the crucible to explode when exposed to cold. It is also necessary to ensure that these materials have enough room to expand when heated in the crucible, otherwise the crucible will easily be squeezed and cracked.
2. The baked metal ingot must be slowly put vertically into the pot. If it is placed horizontally, the thermal expansion of the metal ingot will easily crush the crucible. Be very careful when adding materials to the crucible. Use clamps to carefully place ingots and heavier materials into the crucible. Never add materials by pouring, as the edges of the ingot may crack the crucible.
3. During use, if there is too little metal water in the crucible, do not add too much material at one time. This will easily cause the metal water in the crucible to solidify when it is cold. Then when the temperature rises again, the metal will thermally expand and burst the crucible.

Crucible handling
1. The size of the crucible clamp must match the size of the crucible, and the entire inside of the clamp must contact the crucible.
2. When the clamp is holding the crucible, the handle cannot squeeze the upper edge of the crucible.
3. Use the clamp to clamp the lower middle part of the crucible so that the entire crucible is evenly stressed.
If you do not pay attention to the above points, it is easy to damage the crucible prematurely or cause an accident.
control of flame
1. The height of the flame should be level with the base, enter along the tangent direction of the base, first go around the base, and then spiral up around the crucible.
2. In order to protect the crucible glaze layer and avoid oxidation of the crucible, the flame should be a slightly oxidizing atmosphere (the flame head of the oil furnace appears light green).
3. To ensure uniform heating of the entire crucible and avoid overheating of certain parts, appropriate burners and combustion nozzles should be used, and the firepower should not be too large.

Use of additives
1. Additives must be added in strict accordance with the prescribed amount. Excessive additives will shorten the life of the crucible.
2. Additives cannot be put into empty crucibles or solid metal. They should be added to the middle of the molten metal after the metal is completely dissolved, and stirred slowly and evenly to avoid direct contact of the additives with the crucible body.
Removing slag from crucible
1. The additives remaining in the crucible will penetrate the crucible wall and corrode the crucible, thus shortening the crucible life.
2. You must insist on using a flat-bottomed steel shovel every day to carefully scrape off the residue on the inner wall of the crucible.

Empty the crucible
1. After the hot crucible is lifted out of the furnace, it should be placed on a high-temperature resistant plate or hung on a transfer tool. Do not place it directly on the sand, otherwise the sand will react with the glaze layer of the crucible to form slag.
2. After the crucible is shut down, the metal liquid in the crucible must be poured out and cleaned. Never let the metal liquid solidify in the crucible, otherwise the metal expansion will burst the crucible the next time it is heated and used.
3. If production is interrupted for some reason, the metal liquid should be poured into the mold (it should be a small ingot mold) to form an ingot for easy use next time.