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How Should Aluminium Ingot Rust be Handled?

Apr. 02, 2020

Will 99.85% aluminum ingot rust? Many friends have doubts. I have seen copper rust and iron rust, but I have never seen aluminum rust. Is n’t aluminum rust? In fact, aluminum products such as aluminum powder and aluminum grains will of course rust, but aluminum does not rust like iron until it finishes rusting.

Oxidation of metal by oxygen in the air is rust. Aluminum ingot chemically reacts with oxygen to form alumina, which is aluminum rust. Aluminum rust is very thin, its thickness is only one ten thousandth of a millimeter, but it is very hard and very wear-resistant. It clings to the surface of aluminum, so that the aluminum inside can not contact the outside air, preventing the aluminum from continuing to rust.

Alumina films also have "busters": one is alkali and the other is acid. When alumina meets them, a chemical reaction occurs to generate compounds, which will cause the aluminum oxide film on the surface of the aluminum ingot to fall off easily.

In daily life, dishes often contain acid and alkali components. Therefore, do not put dishes and wine in aluminum utensils to avoid corrosion and damage to the aluminum pan. In addition, do not rub the surface of the aluminum pan with sand because it is embarrassed. Although the aluminum pan is brighter, the aluminum pan also loses the protective film on the surface, and the aluminum pan continues to oxidize, affecting its service life.

crack. The reason is that the temperature of the molten aluminum is too high and the speed is too fast, which increases the residual stress. The aluminum in the aluminum solution contains more than 0.8% silicon, which generates an aluminum-silicon co-melt, and then generates a certain amount of free silicon, which increases the thermal crackability of the metal. Or insufficient cooling water. When the surface of the mold is rough or no lubricant is used, cracks may also occur on the surface and corners of the aluminum ingot.

Aluminum Ingot

Aluminum Ingot

Stomata. The pores mentioned here refer to small pores with a diameter of less than 1㎜. The reason for this is that the casting temperature is too high and the condensation is too fast, so that the gas contained in the aluminum liquid cannot escape in time. After solidification, small bubbles are accumulated in the ingot to form air holes.

Cold partition. The formation of cold insulation is mainly caused by excessive fluctuations in the level of aluminum liquid in the mold, lower casting temperature, slow speed of aluminum ingot casting, or uneven vibration and lowering of the casting machine.

What is the common cleaning method for aluminum ingots?

There are many residues in the aluminum liquid in the electrolytic cell, so Tianjin aluminum ingots must be filtered before forging die-casting aluminum ingots, common methods, organic solvents, vapors, and clean discharge methods. The following briefly shows the organic solvent cleaning method and gas purification method.

First, the organic solvent cleaning method refers to the use of an organic solvent in an aqueous solution. The organic solvent has the characteristics of small relative density, large specificity, and strong work ability. According to the absorption of the compounds in the aqueous solution, a new liquid is generated and rises to the surface layer. Scum is produced after water cooling.

Second, gas purification, common hydrogen, hydrogen or chlorine-nitrogen mixed gas, is this key primary aluminum cleaning method.

Hydrogen clean. The hydrogen gas introduced into the aluminum liquid is converted into many cat fever blisters, which are sufficiently mixed in the aluminum liquid, and the melting hydrogen, as well as certain mechanical equipment impurities, can be absorbed on the small bubbles. The aluminum ingots in Tianjin rose to the surface of the molten aluminum and were discharged.

Hydrogen cleaning method. Because hydrogen is harmful and costly, hydrogen cleaning has emerged. Alumina balls (418 mm) were used as the media. N2 immediately passed into the molten aluminum. The molten aluminum is continuously sent into the cleaning furnace, and the die-casting aluminum ingot is sold. The company considers the layer according to the alumina ball, and is subject to hydrogen cleaning. Therefore, the non-metallic material impurities in the molten aluminum and the dissolved hydrogen are enough to be eliminated, and then continuously discharged , So that the minute hydrogen bubbles are distributed in the solution of the aluminum solution to have a cleaning effect.

Mixed gas purification method. Tianjin aluminum ingots use hydrogen and hydrogen compounds to clean the aluminum liquid. Its effect is not only to remove chlorine and separate compounds, but also to remove some metal material residues (such as magnesium) in aluminum. The common composition is 95% hydrogen + 12% hydrogen. Also select 12% hydrogen + 12% co2 + 90% hydrogen. That way, the actual effect is stronger. Co2 can make hydrogen and hydrogen diffuse very well, which can reduce the actual operation time.

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