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CN-122010541-A - Alumina-based paint capable of preventing crucible pollution in preparation process of high-purity aluminum and brushing method

CN122010541ACN 122010541 ACN122010541 ACN 122010541ACN-122010541-A

Abstract

The invention belongs to the technical field of high-purity aluminum, and discloses an alumina-based coating for preventing crucible pollution in the preparation process of high-purity aluminum and a brushing method. The coating method comprises the steps of cleaning a crucible, preheating, closing a heater after the preheating is completed, uniformly mixing an alumina-based coating, coating the inner wall of the crucible, drying the coating by using the waste heat of the crucible, repeatedly coating for 2-3 times to form 3-4 layers of coatings, heating to 98-102 ℃, carrying out heat preservation and solidification for 50-70min, wherein the preheating temperature is 78-82 ℃, and the preheating heat preservation time is 8-12min. The alumina-based paint consists of high purity alumina 50-70 wt%, BN powder 5-15 wt%, dispersant 1-5 wt% and water for the rest. The method is simple, the compact film layer is formed at low temperature, energy and time are saved, the safety is high, and the crucible pollution prevention effect is excellent in the preparation of high-purity aluminum.

Inventors

  • Jia Guilong
  • HUANG JUXIANG
  • CHEN XINRUI
  • Liu Zhaochuang
  • WU JIAN
  • HU CHUANBIN
  • LOU YUE
  • LI DONGRU
  • ZHANG YITONG
  • HOU XUJIE
  • DENG QUANHUA

Assignees

  • 广西广投高纯新材料有限公司

Dates

Publication Date
20260512
Application Date
20260109

Claims (8)

  1. 1. The alumina-based paint for preventing crucible pollution in the preparation process of high-purity aluminum is characterized by comprising, by mass, 50-70% of high-purity alumina, 5-15% of BN powder, 1-5% of BYK-110 dispersing agent and the balance of water; the purity of the high-purity alumina is more than or equal to 99.9 percent.
  2. 2. The aluminum oxide-based coating brushing method for preventing crucible pollution in the preparation process of high-purity aluminum is characterized by comprising the following steps of cleaning a crucible, preheating, closing a heater after the preheating is completed, uniformly mixing the aluminum oxide-based coating, brushing the inner wall of the crucible, drying the coating by using the residual heat of the crucible, repeatedly brushing the coating for 2-3 times to form 3-4 layers of coating, then raising the temperature, and carrying out heat preservation and solidification, wherein the preheating temperature is 78-82 ℃, the preheating heat preservation time is 8-12min, the raising temperature is 98-102 ℃, and the heat preservation and solidification time is 50-70min; The alumina-based coating is as defined in claim 1.
  3. 3. The method for brushing alumina-based paint for preventing crucible contamination in the process of preparing high purity aluminum according to claim 2, wherein: The alumina-based paint is prepared by uniformly mixing high-purity alumina and BN powder, adding BYK-110 dispersant and water, and stirring to paste; The crucible is a graphite crucible; the alumina-based paint is uniformly mixed, the thickness of each painting of the alumina-based paint painted on the inner wall of the crucible is 0.4-0.6mm, and the time for each painting and drying is 2-4min.
  4. 4. The method for coating alumina-based paint for preventing crucible contamination during the production of high purity aluminum according to claim 2, wherein the number of times of coating is 3.
  5. 5. The method for coating alumina-based paint for preventing crucible contamination in the process of preparing high purity aluminum according to claim 2, wherein the particle size of high purity alumina in the alumina-based paint is 200nm to 5 μm, and the particle size of BN powder is 100nm to 5. Mu.m.
  6. 6. The method for coating alumina-based paint for preventing crucible contamination according to claim 2, comprising the steps of: (1) Cleaning the crucible, namely cleaning the inner wall of the crucible, and removing old coatings and spalling; (2) Preheating, namely placing the crucible into a heating device for preheating, wherein the preheating temperature is 78-82 ℃, preserving heat for 8-12min, and closing the heating device after preserving heat; (3) Stirring and brushing, namely uniformly stirring an alumina-based coating, brushing a 1 st layer of coating on the inner wall of a crucible, wherein the thickness of the coating is 0.4-0.6mm, and then standing for 2-4min until the residual temperature is reached to dry the coating; (4) And (3) curing, namely starting a heating device, heating to 98-102 ℃, and preserving heat for 50-70min to thoroughly cure the 3-4 layers of coating to form a compact aluminum oxide cured film layer.
  7. 7. A crucible with a solidified film of alumina obtained by the method of any one of claims 2 to 6 for smelting high purity aluminum.
  8. 8. The method of claim 7, wherein the high purity aluminum has a purity of 4N6 or greater.

Description

Alumina-based paint capable of preventing crucible pollution in preparation process of high-purity aluminum and brushing method Technical Field The invention relates to the field of high-temperature protective coatings, in particular to an alumina-based coating for preventing crucible pollution in the preparation process of high-purity aluminum and a brushing method. Background In the smelting process of high-purity aluminum (purity is more than or equal to 99.99%), the crucible is used as a core container directly contacting molten aluminum liquid, and the pollution control of the inner wall is a key for determining the purity of the final product. The high purity aluminum has very low tolerance to impurities, while the traditional graphite or clay crucible can continuously release impurities to the aluminum liquid due to thermochemical corrosion at high temperature, and meanwhile, the high activity of the molten aluminum liquid can aggravate the interface reaction with the crucible substrate, so that the impurities in the aluminum liquid are increased. High-end application scenes such as semiconductors, sputtering targets and the like require that the purity of aluminum reaches more than 4N6 (99.996%), and any micron-sized crucible spalling or interface reaction layer can seriously influence the purity of products, so that the yield is greatly reduced. In order to avoid pollution of the crucible to the molten aluminum, the high-temperature protective coating is coated on the surface of the crucible, and the commonly used and effective coating is an alumina-based coating at present. The Chinese patent application CN 104845413A discloses a crucible anti-pollution coating formula and a coating method thereof, wherein powdery aluminum oxide and aluminum dihydrogen phosphate solution are mixed into paste according to the mass ratio of 1.4:1, the coating mode is that a first layer (0.4-0.8 mm) is coated after the crucible is preheated at 198-202 ℃, then the temperature is kept for 1 hour at 500 ℃, the temperature is reduced to 198-202 ℃ after the coating of the first layer is completed, and then the steps of coating, heat preservation and temperature reduction are repeated for 1 time. The coating method has the advantages of high crucible preheating temperature and heat preservation temperature, long heat preservation time, high energy consumption, long downtime (> 4 h) and low efficiency. The methods of brushing alumina-based coatings other than CN 104845413A are not disclosed. The invention aims at the defects and provides the alumina-based paint and the painting method for preventing crucible pollution, which realize simple operation, energy saving, time saving and excellent protection effect through the combination of a paint formula and a low-temperature painting process. Disclosure of Invention Aiming at the defects of the existing painting process, the invention aims to provide an alumina-based paint for preventing crucible pollution in the preparation process of high-purity aluminum and a painting method. According to the invention, the paint is cured at a low temperature by optimizing the paint formula and the painting process, so that the high-efficiency protection is realized in the preparation process of high-purity aluminum. In order to achieve the above purpose, the technical scheme of the invention is as follows: the alumina-based paint for preventing crucible pollution in the preparation process of high-purity aluminum consists of high-purity alumina (purity is greater than or equal to 99.9%) 50-70%, BN powder 5-15%, dispersant 1-5% and water in balance. The dispersing agent is BYK-110 dispersing agent. The alumina-based paint is prepared by uniformly mixing high-purity alumina and BN powder (boron nitride powder), adding BYK-110 dispersant and water, and stirring to paste. The method for brushing the alumina-based paint for preventing crucible pollution in the preparation process of high-purity aluminum comprises the following steps of preheating a crucible after cleaning, closing a heater after preheating, uniformly mixing the alumina-based paint, brushing the mixture on the inner wall of the crucible, drying the paint by using the residual heat of the crucible, repeatedly brushing the paint for 2-3 times to form 3-4 layers of coatings, then raising the temperature, and carrying out heat preservation and solidification. The crucible is a graphite crucible. The preheating temperature is 78-82 ℃, and the preheating heat preservation time is 8-12min. The alumina-based paint is uniformly mixed and coated on the inner wall of the crucible, the thickness of each coating of the alumina-based paint is 0.4-0.6mm, and the drying time of each coating is 2-4min. The number of the brushing is 3. The elevated temperature means that the temperature is raised to 98-102 ℃. The heat preservation time is 50-70min. The alumina-based paint brushing method for preventing crucible pollution in the preparation proces