Purifying method for ultra-pure aluminum

Abstract

The invention relates to a purifying method for ultra-pure aluminum. The purifying method specifically comprises the following steps: injecting molten aluminum with purity being 4N6 into a cast iron crucible, and heating the molten aluminum by a heating wire on the outer wall of the cast iron crucible for preserving the temperature of the molten aluminum to be 680-700 DEG C; stretching seed crystals above the cast iron crucible into a position 2-3cm under the liquid level of the molten aluminum, and introducing cooling gas to the other ends of the seed crystals to cool and crystallize the molten aluminum; spirally rotating the seed crystals in the cast iron crucible, thereby enabling the molten aluminum to carry out rotary motion in the cast iron crucible; and after the crystallizing is ended, quickly pulling out the seed crystals with crystallized ingots, and finally enabling the crystal seeds and the formed crystallized ingots to be in shape of inverted mushroom. The purifying method has the advantages of greatly reducing the purifying cost, and greatly improving the purifying efficiency and the purifying purity, and is suitable for industrial production.

Description

technical field [0001] The invention relates to a method for purifying metal aluminum, in particular to a method for purifying ultra-high-purity aluminum. Background technique [0002] With the continuous progress and development of science and technology, ultra-high-purity aluminum (aluminum products with a purity of more than 5N are called ultra-high-purity) are widely used in electronics, aviation, navigation, chemical and defense industries, and their consumption is increasing year by year. However, there are very few domestic companies that can produce 5N5 ultra-high-purity aluminum to meet the needs of users, and there are only a handful of R&D units. Therefore, most of the ultra-high-purity aluminum required in China needs to be imported. How to solve the above problems is the top priority of domestic demand. [0003] Although some domestic enterprises are already in trial production or large-scale production of ultra-high-purity aluminum, there is a big gap compared ...

AI Technical Summary

Problems solved by technology

[0003] Although some domestic enterprises have been in trial production or large-scale production of ultra-high-purity aluminum, there is a big gap compared with similar foreign enterprises, and there are many deficiencies: 1. The equipment and process are relatively complicated, and it uses multi-disciplinary technology to make The investment cost is too large, and it is inconvenient to control; 2. The efficiency of impurity discharge is not ideal, and no qualified products can be produced; 3. The energy consumption is high, reaching more than 15000KWH / ton, which is contrary to the national energy saving and emission reduction policy. 4. Although the products are produced, the quality is still unstable, making it impossible for domestic users to use

[0004] After searching the literature of the prior art, it was found that Chinese Patent No. 200910045029.0 proposed a method for ultrasonic purification of high-purity aluminum. The method is specifically to melt the aluminum in the crucible after passing an inert protective gas into the heating furnace cavity; the aluminum liquid is heated to 660°C-750°C, insert the seed crystal under the liquid surface of the aluminum melt, turn on the ultrasonic generator, and the other end of the seed crystal is forced to cool by water cooling to ensure a temperature gradient of 100-300K / cm at the front of the interface; put the melt The temperature is controlled near the melting point. After the crystallization starts, slowly pull up the seed crystal or slowly pull down the crucible containing the aluminum melt, and control the crystallization speed at 5-25cm / h, and keep the pulling speed and crystallization speed consistent; control the ultrasonic The power is between 0.2kw-10kw, and the final formed aluminum ingot is cylindrical; this method can make the purified solid phase purity more than 5N, and the average grain size is below 200μm; but the graphite crucible used in this method makes The carbon content in the aluminum ingot is relatively high, so the purity is relatively low

[0005] During the search, it was also found that Chinese Patent No. 200910309668 proposed a method for purifying ultra-high-purity aluminum. This method selects refined aluminum with a purity of at least 4N6, and wherein Mg<6ppm, Ti<0.2ppm, and Zr<0.2ppm. , and cleaned and dried; put the selected raw material refined aluminum into the purification furnace, and the purification furnace is sealed, vacuumized, and the purification furnace heated to 680°C-750°C with a gas furnace is moved into the crystallization furnace, and the crystallization furnace is heated Heater to keep the constant temperature in the crystallization furnace at 660°C, and the liquid aluminum in the purification furnace rotates in the heater of the crystallization furnace. By controlling the heat dissipation of the crystallization furnace, the liquid aluminum in the purification furnace maintains a crystallization speed of 5-10cm / h, After 4-6 hours, the crystallization ends; the crystallized purification furnace is cooled, the crystallized ingot is taken out, and 25%-35% of the weight of the crystallized ingot is removed from the tail of the crystallized ingot to obtain the first purified aluminum ingot; the first time The purified aluminum ingots are then put into the purification furnace, and the purification is repeated until the aluminum ingots that meet the purity requirements are obtained; this method improves the purity of the crystallized aluminum liquid, but the purification efficiency is low

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