Chromium additive for producing aluminum alloy and preparation method of chromium additive

Abstract

The invention belongs to the field of additives for aluminum alloy and discloses a chromium additive for producing aluminum alloy and a preparation method of the chromium additive. The chromium additive for producing aluminum alloy is formed by mainly pressing chromium powder, aluminum powder and a fluxing agent and is in the shape of a cake or a football. The chromium powder and the aluminum powder are broken under the protection of inert gases. The chromium additive for producing aluminum alloy further comprises a surface active agent. Specifically, the chromium additive for producing aluminum alloy comprises, by mass, 90%-97% of the chromium powder, 2%-9.39% of the aluminum powder, 0.01%-5% of the fluxing agent and 0.5%-2% of the surface active agent. The density of the chromium agent formed by pressing all the components ranges from 2.8g / cm <3> to 5.0 g / cm <3>. The chromium content of the additive can be as high as 97%. According to the chromium agent, the melting temperature is low, an aluminum melt can melt at the temperature as low as 670 DEG C, the melting time is short, the aluminum melt can melt in ten to fifteen minutes, and the recovery rate of chromium metal can be as high as 95%.

Description

technical field [0001] The invention belongs to the field of aluminum alloy additives, and in particular relates to an aluminum alloy chromium additive and a preparation method thereof. Background technique [0002] With the continuous development of aluminum processing and aluminum alloy industry, the development of aluminum alloy is listed as a key development technology, and alloying is an important part of the aluminum alloy production process. The dissolution of alloying elements in molten aluminum is an important process of alloying. The dissolution of elements is closely related to their properties, and is controlled by the destruction of the bonding force of the solid-state structure of the added elements and the diffusion speed of atoms in the aluminum liquid. Alloying elements commonly used in aluminum alloys are: silicon, iron, copper, magnesium, nickel, zinc, vanadium, etc. Some alloying elements with low melting point or high solubility, such as magnesium and ...

AI Technical Summary

Problems solved by technology

In addition, due to the low content of alloy elements contained in the master alloy, the amount of master alloy used will be relatively large in the calculation of weighing. In order to ensure the temperature of the molten master alloy, the amount of master alloy added each time should not be too much. If the amount is too much, the temperature of the aluminum melt will drop, and the intermediate alloy cannot be melted. Therefore, when producing the same type of aluminum alloy, it is necessary to add a small amount of the intermediate alloy to the aluminum melt many times, so that it will The following problems are caused: 1. The time required to melt the intermediate alloy is too long; 2. The amount of impurities generated by the reaction of the aluminum melt with oxygen, hydrogen, carbon, moisture and other substances in the atmosphere for a long time increases, resulting in an increase in the amount of impurities in the aluminum alloy. The quality is reduced; 3. Long melting time will increase energy consumption, which will increase the burning loss and air absorption of aluminum melt

However, this method needs a large amount of flux to realize, so in each additive product, the content of manganese, iron and chromium can only reach about 85%. If the content of manganese, iron and chromium in the additive product is increased to If it is above 90%, the amount of the corresponding flux will be reduced. After the product is added to the molten aluminum, the manganese, iron, and chromium in the additive cannot be completely melted; , content ratio, etc. have special requirements

Taking chromium as an example, the particle size distribution of iron powder with a chromium content of 80% is: greater than 60 mesh requires less than 5%, 60-80 mesh is 30%-35%, 80-100 mesh is 15% -20%, 100-325 mesh is 35%-45%, less than 325 mesh requires less than 10%; the above-mentioned particle size is mainly between 60-325 mesh, it can be seen that the particle size distribution is very narrow, usually in the crushing process, the particle size distribution The narrower it is, the higher the crushing process requirements are, so the chromium powder with the above particle size distribution has very high requirements on the crushing process, and the processing cost is also very high. For example, in the crushing stage, we need more than 85% of the chromium powder particle size It should not be larger than 60 mesh and not smaller than 325 mesh, but the existing crushing process often cannot meet such a strict particle size distribution range, so the qualified rate of the produced chromium agent is usually lower than 60%.

Furthermore, because the overall average particle size of the chromium powder in the existing chromium-based aluminum alloy additives is relatively large, after adding the aluminum liquid, due to the small specific surface area and small surface energy of the relatively large chromium powder, the melting is relatively slow. Moreover, the casting and melting temperature is required to be high, usually around 710°C

In addition, in order to avoid loosening of the additive product during transportation, the additive product is usually pressed into a cake or ball with a higher density, and the density is usually greater than 5.0g / cm 3 , but for additive products with higher density, after adding molten aluminum, on the one hand, the melting time is relatively slow, and the melting time is usually 15-20min, which is long; At the bottom, the melting speed of the chromium powder will slow down, and it will lead to uneven dispersion of the chromium powder after dissolution; on the other hand, a denser additive product will form a dense protective film on the surface during the melting process, resulting in the inability to continue melting inside. This will make the recovery rate low, the highest can only reach about 90%

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