I believe that for higher profits, all the aluminum profile manufacturers care much about the issue that how to reduce those unnecessary costs in the aluminum profile production process. Then, what is the unnecessary cost? It refers to those losses hat are avoidable in the production process. And as one of the major process, the casting process causes the casting loss technically often. Therefore, to tackle the issue, here we are going to take about how to effectively reduce the casting loss during the aluminum casting process.
Factors affecting the casting loss are:
1) liquid aluminum temperature; 2) the contact between aluminum liquid and oxygen; 3) the amount of aluminum in aluminum slag; 4) the aluminum liquid loss in the aluminum slag removal; 5) the amount of defective aluminum and large aluminum; 6) other losses.
Ways to reduce casting loss
1. Control the liquid aluminum temperature
Aluminum melting point is 660 ℃. In general, the pure aluminum casting temperature is controlled at 730 ℃or even lower, while because of the better flow ability, the aluminum alloy requires lower casting temperature correspondingly than the pure aluminum, about 710 ℃-730 ℃. For the aluminum manufacturers who directly use the aluminum liquid in electrolytic cell units, when put the hot aluminum liquid into the mixing furnace, it should be timely added the cold material in, that is, to add the defective aluminum, aluminum slag, etc., into the mixing furnace，or to add part of intermediate alloys (industrial silicon) in the furnace in advance, which can form a molten state, both to increase the actual yield and lower temperature. However, the surface of the cold material must be clean without any oil, or it may burn to combust resulting burning loss.
In short, the aluminum liquid temperature is effectively reduced to the corresponding casting temperature which can decrease the impact of the temperature on the casting loss.
2. Reduce contact between the aluminum liquid and air. The more frequent the contact, the more serious the oxidation burning, and the greater the loss of cast.
1) to reduce the contact time between the liquid aluminum and oxygen: ①Under the condition of meeting the needs of production, as soon as possible process the liquid aluminum in the furnace into the finished product; ②install the casting equipment at reasonable parts as far as possible to shorten the length of the launder to reduce the air exposure time of the liquid aluminum, and at the same time, cover the upper part of the launder with the aluminum silicate insulation, which can ensure a certain insulation and reduce the oxygen content in the launder.
In short, you should prevent a variety of causes that lead the liquid aluminum staying in the mixed furnace for a long time, in order to reduce the contact time between the aluminum liquid and oxygen to reduce the casting loss.
2) Control the mixing method of liquid aluminum: no matter the manned or mechanical mixing, both of them are operated in the opened oven, which not only will bring huge fluctuations in the liquid to increase the contact area with oxygen but also increase the oxygen content in the furnace, which is bound to accelerate the chemical reaction to intensify the burning loss. While the electromagnetic stirring can be carried out in a closed state and the fluctuation is very small effectively avoiding the corresponding disadvantage, but also can reduce the water within the air flow into the furnace, reducing the hydrogen absorption of the liquid aluminum.
3) Control the blowing height in liquid aluminum refining:
The general method of refining is to spray the refining agent directly into the furnace, and then to mix refining. But for some alloy production requiring blowing nitrogen to refine (refining time is long relatively up to 30 minutes), so there must be a certain degree of blowing height driving the huge fluctuations in liquid aluminum. Therefore, it is best to adjust the nitrogen pressure to control the blowing height at the 10-15mm.
3. Choose the right refining agent so that the full separation of slag aluminum can be done
In the aluminum and aluminum alloy smelting process, in addition to the inclusions in themselves, the aluminum and oxygen are easy to react to produce the alumina or hypophosphite, resulting in a layer of molten scum on aluminum surface which has sorts of infiltration with the aluminum melt. The aluminum slag is mixed with a considerable amount of melt so that a refining agent is needed to change the infiltration of both and increase the surface tension on the slag and aluminum interface to achieve the slag and aluminum separation.
Aluminum and aluminum alloy flux is usually made of alkali and alkaline earth metal chloride and fluoride composition, and the main components are KCl, NaCl, NaF, CaF₂, Na3AlF6, Na₂SiF6, etc. the different amount of content of components defers in effect. In addition to using the flux produced by the flux plant, it is preferable to adjust the proportion of the flux component according to the composition of the smelted aluminum alloy. At the same time, strictly control the refining process conditions, such as the amount of flux, the contact time and contact area of flux and melt, the mixing state and temperature, etc. The refining agent can effectively reduce the slag with aluminum to reduce casting losses.
4. Process the aluminum slag produced during the casting process
Aluminum slag is an inevitable part of the casting process, in spite of the relevant measures, there will be a certain amount of metal aluminum loss. So the aluminum slag needs to be effectively processed, rather than directly sold to other buyers. Most simply and economically, use the roller to grinding the aluminum slag repeatedly, and then screening, so as to effectively recycle part of the aluminum beans.
5. Lower the slag removal slope of the mixing furnace to removal the aluminum slag fully out of the furnace
The height of the slag removal slope of the mixed furnace directly affects the amount of the slag removal. The high slope makes it harder to removal the slag in the hidden part, resulting in the deposition of aluminum slag and aluminum. If the slag and the aluminum deposit can not be recovered in time, as far as possible to reduce the slag removal slope in the premise of ensuring the capacity of the mixing furnace.
6. Prevent the liquid aluminum brought out in slag removal.
The existing operation to remove the aluminum slag is basically manned slag removal with a rake aluminum slag. In addition to careful manned operation to avoid the aluminum liquid losses, the rake design also need to be considerable. Suggestively, the rake needs a few rows of small round hole on the surface through which the liquid aluminum in aluminum slag can flow back into the furnace.
7. Reduce the amount of defective aluminum and large pieces of aluminum
In the aluminum production process, as far as possible to avoid the defects of flash, burr, ripple, and unqualified weight, and at same time, process the liquid aluminum thoroughly into the qualified products before the end of production.
8. Process the produced defective aluminum
The varied defective aluminum, large aluminum, aluminum slag, and aluminum beans, etc. can be re-operation in the appropriate furnace so as to avoid unnecessary burning damage.
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