Deep clean smelting process for preparing high-purity aluminum

Abstract

The invention relates to a deep clean smelting process for preparing high-purity aluminum, and aims to improve the purity of molten aluminum through multi-step purification and refining treatment. The process comprises the key steps of aluminum ingot selection and pretreatment, smelting, refining, degassing, filtering, stirring, casting and the like. According to the method, coarse slag inclusion is removed by adopting an immersed closed structure, a high-purity graphite crucible is used, high-purity argon is introduced for protection, and a mixed refining agent of AlCl3 and NaCl is used for refining for multiple times, so that the content of impurities in molten aluminum can be remarkably reduced. And further, through ceramic filtration, rotary jet degassing and electromagnetic stirring, it is ensured that molten aluminum components are uniform and clean. The final product is smooth and flawless in surface after being polished and ultrasonically cleaned, and is suitable for the high-tech field with strict requirements on material purity. The process is simple and efficient, the preparation quality of the high-purity aluminum can be greatly improved, and the method has wide application prospects.

Description

Technical Field

[0001] The present invention relates to a process for preparing aluminum, and more particularly to a deep clean smelting process for preparing high-purity aluminum. Background Art

[0002] In the modern industrial field, high-purity aluminum, as an important basic material, is widely used in high-tech fields such as aerospace, electronics, semiconductors, and optoelectronics. These fields have extremely strict requirements on the purity of materials. The purity of aluminum directly affects its key properties such as electrical conductivity, thermal conductivity, mechanical properties, and corrosion resistance. Therefore, how to prepare high-purity aluminum materials has become an important topic of research and development in related fields.

[0003] Traditional aluminum smelting processes usually use simple smelting and refining methods. However, these methods often cannot effectively remove non-metallic inclusions such as oxides, nitrides, carbides, and gas impurities in the aluminum liquid, making it difficult to obtain high-purity aluminum materials. Especially during high-temperature smelting, aluminum liquid is very likely to react with oxygen, nitrogen, carbon and other elements in the air, resulting in an increase in impurity content, which affects the final performance of the material. In addition, aluminum liquid is prone to form pores and inclusions during the casting process, which will also reduce the mechanical properties and chemical stability of the material. Therefore, the existing technology is difficult to meet the strict requirements for the preparation of high-purity aluminum. Summary of the invention

[0004] In order to solve the shortcomings of the existing technology, a deep clean smelting process for the preparation of high-purity aluminum is provided. The specific scheme is as follows:

[0005] A deep clean smelting process for preparing high purity aluminum, the smelting process comprising the following steps:

[0006] S1: Select aluminum ingots with a purity of not less than 99.9%;

[0007] S2: After removing the coarse slag inclusions through the immersion closed structure, the aluminum liquid is transferred to the melting furnace, and the aluminum ingot is melted by using a high-purity graphite crucible and placed in an induction melting furnace;

[0008] S3: When the aluminum liquid temperature reaches 690-750°C, electromagnetic stirring is performed and the surface slag is cleaned;

[0009] S4: adding appropriate amount of AlCl3 and NaCl mixed refining agent, spraying covering agent for secondary refining;

[0010] S5: introducing high-purity nitrogen for degassing;

[0011] S6: filtering the aluminum liquid using a ceramic filter with a pore size of 10 μm;

[0012] S7: an electromagnetic stirring device is set outside the smelting furnace, an alternating magnetic field is applied, the frequency is 50 Hz, and the stirring time is 10 minutes;

[0013] S8: preheat the casting mold to 300°C to prevent the aluminum liquid from cooling too quickly during the casting process;

[0014] S9: The casting is lightly mechanically polished to remove surface scale and other defects, and ultrasonically cleaned.

[0015] Furthermore, in S2, the heating rate of the aluminum ingot is set to 10°C / min, and the aluminum ingot is gradually heated to 700°C.

[0016] Furthermore, during the smelting process, high-purity argon gas protection was introduced, and the argon gas flow rate was 2 L / min.

[0017] Furthermore, the mass ratio of AlCl3 and NaCl in S4 is 1:1, and the added amount is 1% of the weight of the aluminum liquid.

[0018] Furthermore, the S5 filtration process is to filter the aluminum liquid once through a ceramic filter at 800° C., and the filtration rate is controlled at 0.5 L / min.

[0019] Furthermore, the degassing treatment in S5 uses a rotary jet degasser with a rotation speed of 400 RPM, a flow rate of high-purity nitrogen of 0.5 L / min, and a duration of 15 minutes.

[0020] Furthermore, the electromagnetic stirring in S7 is performed while the aluminum liquid temperature is maintained at 700°C.

[0021] Furthermore, the casting mold in S8 is made of high-purity graphite material.

[0022] Furthermore, the surface treatment in S9 was performed by grinding using sandpaper with a particle size of 200 mesh.

[0023] Furthermore, after S9, the finished casting is subjected to ultrasonic cleaning for 10 minutes.

[0024] Beneficial effects:

[0025] The deep clean smelting process for preparing high-purity aluminum provided by this patent has the following beneficial effects:

[0026] (1) By adopting an immersion closed structure to remove coarse slag inclusions, using a high-purity graphite crucible for smelting, and multiple electromagnetic stirring and refining treatments, the impurity content in the aluminum liquid, especially oxides and non-metallic slag inclusions, is significantly reduced, the purity of the aluminum liquid is greatly improved, and the high quality of the final product is ensured.

[0027] (2) During the entire smelting and refining process, high-purity argon and nitrogen are introduced as protective and degassing gases to prevent oxidation and gas contamination of the aluminum liquid under high temperature conditions. At the same time, the use of ceramic filters effectively removes fine particle impurities, further improving the cleanliness of the aluminum liquid. By using a refining agent combination of AlCl3 and NaCl and a covering agent, the refining effect is enhanced, so that impurities in the aluminum liquid can float up and be removed more effectively, and the refining efficiency is significantly improved.

[0028] (3) Multiple electromagnetic stirring processes not only help to float and remove impurities, but also make the composition of the aluminum liquid more uniform, reducing defects caused by unevenness during the casting process.

[0029] (4) By preheating the mold and controlling the temperature of the molten aluminum, the rapid cooling of the molten aluminum due to low temperature during the casting process is effectively avoided, the formation of pores and inclusions inside the casting is reduced, and the quality of the casting is improved. DETAILED DESCRIPTION

[0030] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0031] Example:

[0032] This embodiment provides a deep clean smelting process for the preparation of high-purity aluminum to ensure the high purity of aluminum materials, which is suitable for the strict requirements of material purity in high-tech fields. The following are specific implementation steps and detailed explanations:

[0033] S1: Selection and pretreatment of aluminum ingots

[0034] Aluminum ingot selection: Aluminum ingots with a purity of not less than 99.9% are selected as raw materials to reduce the introduction of impurities during the smelting process.

[0035] Aluminum ingot pretreatment: The surface of the aluminum ingot is cleaned with deionized water to remove the oil and oxide layer on the surface. Then the aluminum ingot is dried in an oven at 120°C for 1 hour to ensure that there is no moisture on the surface to avoid unnecessary water vapor or oxidation reaction during the smelting process.

[0036] S2: Preliminary purification and smelting

[0037] Removal of coarse slag inclusions: Removal of coarse slag inclusions in the aluminum ingot through the fore furnace aluminum outlet with an immersion-type closed structure. This step helps to reduce the impurity content of the molten aluminum before it enters the smelting furnace.

[0038] Melting operation: The purified aluminum liquid is transferred to the melting furnace, and a high-purity graphite crucible is used to prevent chemical reaction between the aluminum liquid and the crucible. During the melting process, the heating rate is set at 10℃ / minute, and the aluminum ingot is gradually heated to 700℃ to ensure that the temperature of the aluminum liquid is uniform and stable.

[0039] S3: Electromagnetic stirring and surface cleaning

[0040] Temperature control: When the aluminum liquid temperature reaches 690-750℃, start the electromagnetic stirring device. The frequency of the electromagnetic stirring is set to 50Hz and the duration is 10 minutes to ensure that the fine impurities in the aluminum liquid are evenly distributed and slag is formed on the surface of the aluminum liquid.

[0041] Scum cleaning: After stirring, use special tools to clean the scum on the surface of the aluminum liquid in time. This step is crucial to reduce the impurity content in the aluminum liquid and improve the effect of subsequent refining.

[0042] S4: Refining and coating treatment

[0043] First refining: add appropriate amount of AlCl3 and NaCl mixed refining agent, configure in a mass ratio of 1:1, and the added amount is 1% of the weight of the aluminum liquid. These refining agents absorb and remove impurities in the aluminum liquid through chemical reactions.

[0044] Covering agent treatment: Under the action of the refining agent, a layer of covering agent is evenly sprayed on the surface of the aluminum liquid to further protect the aluminum liquid from contact with the air and reduce oxidation.

[0045] Secondary refining: After the aluminum liquid is initially refined, it is stirred again using an electromagnetic stirring device for 20 minutes to ensure that the impurities float further. The scum on the surface is then cleaned again.

[0046] S5: Degassing

[0047] Degassing operation: The aluminum liquid is transferred to a static furnace and degassed using a rotary jet degasser. The speed of the degasser is set to 400RPM, and high-purity nitrogen is introduced at a flow rate of 0.5L / min for 15 minutes. This process can effectively remove hydrogen and other gas impurities in the aluminum liquid, further improving the purity of the aluminum liquid.

[0048] S6: Ceramic filtration

[0049] Filtration operation: Use a ceramic filter with a pore size of 10μm to filter the aluminum liquid. During filtration, the aluminum liquid temperature is controlled at 800℃ and the filtration rate is 0.5L / min. This step is to remove tiny particle impurities in the aluminum liquid to ensure the high purity of the final product.

[0050] S7: Electromagnetic stirring homogenization

[0051] Stir again: Set up an electromagnetic stirring device outside the melting furnace, apply an alternating magnetic field again, with a frequency of 50Hz and a stirring time of 10 minutes. This step can further homogenize the aluminum liquid and reduce the residual trace impurities.

[0052] S8: Casting preparation

[0053] Mold preparation: Preheat the mold to 300°C to prevent the aluminum liquid from cooling too quickly during the casting process. Choose high-purity graphite as the mold material to avoid contaminating the aluminum liquid.

[0054] Casting operation: Pour the purified aluminum liquid slowly into the mold at 700℃ to ensure that there are no bubbles or inclusions inside the casting. The casting is cooled naturally at room temperature and demolded after it is completely solidified.

[0055] S9: Finished product handling and cleaning

[0056] Surface treatment: The casting is lightly mechanically polished, using sandpaper with a particle size of 200 mesh to remove the surface oxide scale and other defects to make the casting surface smooth and defect-free.

[0057] Ultrasonic cleaning: The polished castings are ultrasonically cleaned for 10 minutes to remove the tiny particles of impurities remaining on the surface of the castings and further improve the cleanliness of the finished product.

[0058] This embodiment uses a multi-step smelting, purification and casting process to ultimately produce a high-purity aluminum product. The fine operation and strict parameter control in each step ensure that the aluminum liquid is minimally contaminated throughout the process, meeting the requirements of high-purity aluminum materials.

[0059] As a further improvement, the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep clean smelting process for preparing high purity aluminum, characterized in that: The smelting process comprises the following steps: S1: Select aluminum ingots with a purity of not less than 99.9%; S2: After removing the coarse slag inclusions through the immersion closed structure, the aluminum liquid is transferred to the melting furnace, and the aluminum ingot is melted by using a high-purity graphite crucible and placed in an induction melting furnace; S3: When the aluminum liquid temperature reaches 690-750°C, electromagnetic stirring is performed and the surface slag is cleaned; S4: adding appropriate amount of AlCl3 and NaCl mixed refining agent, spraying covering agent for secondary refining; S5: introducing high-purity nitrogen for degassing; S6: filtering the aluminum liquid using a ceramic filter with a pore size of 10 μm; S7: an electromagnetic stirring device is set outside the smelting furnace, an alternating magnetic field is applied, the frequency is 50 Hz, and the stirring time is 10 minutes; S8: preheat the casting mold to 300°C to prevent the aluminum liquid from cooling too quickly during the casting process; S9: The casting is lightly mechanically polished to remove surface scale and other defects, and ultrasonically cleaned.

2. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: In S2, the heating rate of the aluminum ingot is set to 10°C / min, and the aluminum ingot is gradually heated to 700°C.

3. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: During the smelting process, high-purity argon gas protection was introduced with an argon flow rate of 2L / min.

4. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The mass ratio of AlCl3 and NaCl in S4 is 1:1, and the added amount is 1% of the weight of the aluminum liquid.

5. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The S5 filtration process is to filter the aluminum liquid once through a ceramic filter at 800°C, and the filtration rate is controlled at 0.5L / min.

6. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The degassing process in S5 used a rotary jet degasser with a rotation speed of 400 RPM and a flow rate of high-purity nitrogen of 0.5 L / min for a duration of 15 minutes.

7. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The electromagnetic stirring in S7 is performed while the aluminum liquid temperature is maintained at 700°C.

8. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The casting mold in S8 is made of high-purity graphite material.

9. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: The surface preparation in S9 was performed by sanding with 200-grit sandpaper.

10. A deep clean smelting process for preparing high purity aluminum according to claim 1, characterized in that: After S9, the finished castings were ultrasonically cleaned for 10 minutes.