<a https://www.aluminum-furnace.com/news_detail/1798892991992135680.html>aluminium ingot making machine is an efficient automation equipment. It has a wide range of applications in the waste aluminum recycling industry.
During the aluminum ingot casting process, more or less "water ripples" are formed on the surface of the aluminum ingot when it condenses, which affects the appearance quality in severe cases, and then affects its selling price. Products with serious ripples are often returned and forced to go back to the furnace for re-melting, causing huge economic losses to the manufacturer and seriously affecting the reputation of the manufacturer.
For this reason, we need to fully study the causes and solutions of the ripples on the surface of aluminum ingots.
Common Corrugations on the Surface of Aluminum Ingots
The ingot belongs to flat die casting. Ideally, the solidification direction of the molten aluminum is from bottom to top, and the upper middle is finally solidified, leaving a normal groove-shaped depression.
Slight corrugation is inevitable and does not affect the quality of the ingot, it is allowed. In the following, only the more serious surface ripples are analyzed.
Common surface corrugations of aluminum ingots have three states: concentric circles, bubbles and grooves at both ends.
Concentric Water Ripples
A corrugation formed after liquid aluminum enters the aluminum ingot mold through a flow divider to cool and solidify. It is centered at a certain point on the surface of the aluminum ingot, and it has a shape that spreads to all sides in a corrugated manner.
The liquid aluminum flowing out of the furnace enters the casting mold through the chute. Since the surface of the high-temperature aluminum liquid is oxidized in the air, a large amount of oxide film slag is formed, which flows into the mold with the aluminum liquid, so that a layer of scum mainly composed of alumina is formed on the surface of the aluminum water in the mold.
When the slag is picked up from the mold, the surface of the molten aluminum is disturbed by stirring the liquid aluminum in the mold, so that concentric circles are formed when the molten aluminum solidifies.
Bubble Water Ripple
It is a raised or floating block-shaped corrugation formed on the surface of the aluminum ingot after the liquid aluminum is cooled and formed. After the corrugation is formed, the surface of the aluminum ingot is uneven. Seen from the cross-section, the bubbly water ripples sometimes make the aluminum ingot form a sandwich.
During the casting process of the aluminum ingot, the upper surface is exposed to the air for direct cooling, and the other surfaces are indirectly cooled by water through the casting mold.
If there is residual moisture in the casting mold, water vapor will inevitably be generated after the high-temperature molten aluminum is injected into the casting mold. During the solidification process of the molten aluminum, the gas escapes from the inside to the surface and bubbles to form bubble-shaped water ripples.
In addition, when the aluminum water flowing out of the holding furnace contains a large amount of hydrogen, a large amount of hydrogen gas escapes to form bubbles during the solidification process, and foamy water ripples will also be formed.
Grooved Corrugations at Both Ends
During the cooling process of the liquid aluminum in the casting mold, due to the vibration of the casting mold, ripples appear on the surface of the formed aluminum ingot. Its shape is to form deep groove-like corrugations on the surface of the aluminum ingot, and the middle is the deepest, and the ends are shallower. This kind of water ripple has the greatest influence on the appearance quality of aluminum ingots, and the ripple amplitude is the largest.
In the chain drive, because the chain moves in a polygonal shape, the chain speed and the instantaneous transmission ratio fluctuate periodically, which causes the transmission to be unstable.
At the same time, the relative speed at the moment of meshing between the chain link and the gear teeth will also cause the vibration of the ingot mold. The mold vibrates to shake the liquid aluminum.
Because the temperature near the inner wall of the mold is relatively low, the liquid aluminum at this position solidifies first. The crest of the vibration wave of the unsolidified aluminum water will solidify and form every time it approaches the solidified aluminum, so that the aluminum ingot will form a deep groove with the middle part as the boundary.
Improvements
Improvement Measures of Concentric Corrugation
(1) Strengthen the refining of molten aluminum in the holding furnace, and the slag removal process should be as clean and thorough as possible to reduce the impact on subsequent slag removal;
(2) Minimize the length of the chute to reduce the contact time with the air during the flow of molten aluminum, thereby reducing the oxidation slag formed by surface oxidation.
Bubble Water Ripple Improvement Measures
(1) Strictly control the quality of aluminum ingot casting molds, and avoid installing molds with defects such as blisters and cracks on the unit;
(2) Regularly inspect the casting molds, and promptly replace the casting molds that have cracks or defects due to various reasons such as high temperature;
(3) The casting temperature of liquid aluminum must be strictly controlled below 720°C to avoid excessive temperature;
(4) The storage time of liquid aluminum in the holding furnace is controlled within a reasonable range.
Improvement Measures for Grooved Water Ripples at Both Ends
From the above analysis, it can be known that in order to make the chain transmission stable and reduce the fluctuation of operation, it is necessary to reduce the speed unevenness of the mold and optimize the chain transmission to reduce the impact of the chain transmission on the aluminum ingot casting process.
(1) Improve the structure and process of the chain to improve the stability of operation
Because the chain roller changes from rolling to sliding. Therefore, a self-lubricating copper sleeve can be added between the shaft and the inner hole of the roller.
This type of bearing has the characteristics of small friction coefficient, good wear resistance and corrosion resistance, and oil-free lubrication.
(2) Changing the chain pitch
Through the previous analysis of the polygonal effect of the chain drive, the instantaneous speed of the chain drive used in the aluminum ingot casting machine is not constant, and the vibration cannot be eliminated. However, by adjusting the chain pitch, the variation of speed can be reduced and the stability can be greatly improved.
Summarize
After adopting the above measures, the surface of aluminum ingots produced by most aluminum ingot casting manufacturers is relatively smooth and flat. The "water ripple" problem on the surface of aluminum ingots has been greatly improved.