Ways to Reduce Casting Losses
Control the temperature of liquid aluminum
The melting point of aluminum is 660℃. Generally speaking, the casting temperature of primary aluminum is controlled at about 730℃ or even lower. The fluidity of aluminum alloy is correspondingly lower than that of primary aluminum, about 710℃-730℃. For direct use In the unit of liquid aluminum in the electrolytic cell, when the high-temperature aluminum liquid enters the mixing furnace, it should be mixed with cold material in time, that is, add inferior aluminum, aluminum slag, etc. to the mixing and holding furnace, or part of the intermediate alloy can be added to the furnace in advance. A pressure-melted state is formed, which not only increases the actual yield but also reduces the temperature. At the same time, the surface of the cold material added should be clean and free of oil stains, otherwise it may burn and release heat and promote burning. In short, effectively reducing the temperature of the molten aluminum to the corresponding casting temperature can reduce the great influence of temperature on casting loss.
Reduce the contact strength between liquid aluminum and air. The greater the contact strength between liquid aluminum and oxygen, the more serious the oxidation burning loss and the greater the casting losses.
1) Reduce the contact time between liquid aluminum and oxygen: ①Under the conditions of meeting the production requirements, turn the liquid aluminum in the furnace into finished products as quickly as possible. It is best to produce on-duty ingredients and do not make the liquid aluminum stay in the furnace for too long; ② Reasonably arrange the melting and casting equipment to shorten the length of the launder as much as possible to reduce the exposure time of liquid aluminum in the air. At the same time, the upper part of the launder can be covered with an aluminum silicate insulation board, which has a certain insulation effect and can reduce the oxygen content in the casting launder.
In a word, avoid the long-term storage of molten aluminum in the mixing furnace due to various reasons, so as to reduce the contact time between molten aluminum and oxygen to reduce casting losses.
2) Control the mixing method of liquid aluminum: whether it is manual mixing with a large rake or mechanical mixing, it is carried out with the furnace door open, which will not only bring about huge fluctuations in the liquid level, increase the contact area with oxygen, but also increase the oxygen content in the furnace It is bound to accelerate the above-mentioned chemical reaction and increase the burning loss. The electromagnetic stirring can be carried out in a closed state and the liquid level fluctuation is small, which effectively avoids the corresponding disadvantages. At the same time, it can also reduce the moisture in the air into the furnace and reduce the probability of hydrogen absorption by the liquid aluminum.
3) Control the blowing height during liquid aluminum refining: The general refining method is to manually sprinkle the refining agent into the furnace, and then perform stirring and refining, but for some alloy production, nitrogen blowing refining is required (the refining time is longer, up to 30 minutes Left and right), there will inevitably be a certain bubble height, horizontal to the side and vertical to the head, which will drive the huge fluctuation of the liquid aluminum. Therefore, it is best to adjust the nitrogen pressure to control the bubble height to 10-15mm.