Cleaning method for ultra-pure electrolytic iron

Abstract

The invention relates to an ultra-pure electrolytic iron cleaning method which comprises the following steps: (1) sequentially carrying out ultrasonic cleaning and drying on electrolytic iron to obtain primarily cleaned electrolytic iron; (2) carrying out acid pickling on the primarily cleaned electrolytic iron obtained in the step (1) to obtain secondarily cleaned electrolytic iron; and (3) sequentially carrying out vacuum ultrasonic cleaning and vacuum drying on the secondarily cleaned electrolytic iron obtained in the step (2) to obtain the cleaned electrolytic iron. According to the cleaning method provided by the invention, the ultra-pure electrolytic iron sheet can be quickly cleaned, the surface of the product is smooth and free of holes, and the product has silver metal luster.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic iron surface cleaning, and in particular to a method for cleaning ultra-high purity electrolytic iron. Background Art

[0002] In the semiconductor industry, zirconium-vanadium-iron (ZrVFe) alloy targets are mainly used as materials for the preparation of getter films, which are essential for semiconductor chip packaging. ZrVFe alloy targets are formed into thin films during the manufacturing process of semiconductor devices through magnetron sputtering technology, and their high gettering performance is used to absorb gas impurities inside the device, thereby improving the performance and reliability of semiconductor devices.

[0003] With the continuous improvement of semiconductor manufacturing processes, higher requirements are placed on the purity of ZrVFe alloy targets and high-purity metal raw materials. The oxide layer on the surface of high-purity electrolytic iron may increase the oxygen content of the alloy during the preparation of ZrVFe alloy ingots, affecting the uniformity of the alloy. In addition, the oxide layer may form solid or semi-solid inclusions in the melt, reducing the purity of the alloy and affecting the quality of the ZrVFe alloy target. Therefore, high-purity electrolytic iron needs to be cleaned before smelting as a basic element of the alloy to remove impurities remaining on the surface.

[0004] Ultra-high purity electrolytic iron, that is, high purity iron with a purity of ≥5N (99.999%), has excellent ductility, corrosion resistance, thermal conductivity, soft magnetism and high electrical conductivity. These characteristics make it widely used in aerospace, energy, chemical industry, marine engineering and semiconductor industries. Ultra-high purity electrolytic iron needs to be stripped and sheared after it is produced. Since the electrolytic environment for preparing ultra-high purity electrolytic iron is generally carried out at a high temperature of 40-80°C, there is still acidic electrolyte residue on the surface of the ultra-high purity electrolytic iron plate just out of the tank. Therefore, the process of stripping out of the tank is easy to cause oxidation of the electrolytic iron surface, and oil pollution may also appear on the electrolytic iron sheet during the shearing process. In addition, ultra-high purity electrolytic iron has better corrosion resistance than traditional pure iron and iron-based materials. The pickling effect of high-purity electrolytic iron sheets with 25% volume fraction hydrochloric acid is not good. Not only is the pickling time-consuming, requiring 12-14 hours to complete the cleaning of the electrolytic iron sheets, but pitting corrosion is also prone to occur on the surface of the iron sheets, seriously affecting production efficiency.

[0005] Therefore, how to quickly clean ultra-high purity electrolytic iron and avoid pitting on the surface of the electrolytic iron to improve the cleaning efficiency is a technical problem that needs to be solved in this field. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for cleaning ultra-high purity electrolytic iron. Compared with the prior art, the cleaning method provided by the present invention can quickly clean ultra-high purity electrolytic iron sheets, and the product surface is smooth and free of holes, presenting a silvery-white metallic luster.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for cleaning ultra-high purity electrolytic iron, the cleaning method comprising the following steps:

[0009] (1) subjecting the electrolytic iron to ultrasonic cleaning and drying in sequence to obtain the electrolytic iron after primary cleaning;

[0010] (2) pickling the primary cleaned electrolytic iron obtained in step (1) to obtain secondary cleaned electrolytic iron;

[0011] (3) subjecting the secondary cleaned electrolytic iron obtained in step (2) to vacuum ultrasonic cleaning and vacuum drying in sequence to obtain cleaned electrolytic iron.

[0012] In the cleaning method provided by the present invention, firstly, the oil stains on the surface of the electrolytic iron are removed by ultrasonic cleaning and drying, so as to ensure that the oil stains will not affect the cleaning effect in the subsequent pickling process; then, the electrolytic iron is pickled to remove the oxide layer and other impurities on the surface of the electrolytic iron, so as to reduce its oxygen content, which is beneficial to improving the composition and structural uniformity of the alloy obtained subsequently; finally, the acid liquid remaining on the surface of the electrolytic iron is completely removed by vacuum ultrasonic cleaning and vacuum drying, so as to avoid the acid liquid from polluting the alloy in the subsequent smelting process.

[0013] In the present invention, the ultra-high purity electrolytic iron refers to electrolytic iron with a purity of ≥5N (99.999%).

[0014] Preferably, the cleaning solution used in the ultrasonic cleaning in step (1) comprises isopropyl alcohol.

[0015] Preferably, the purity of the isopropanol is electronic grade.

[0016] Preferably, the purity of the electrolytic iron in step (1) is ≥99.999%, for example, it can be 99.9991%, 99.9992%, 99.9993%, 99.9994% or 99.9995%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, the ultrasonic cleaning time in step (1) is 3-4 min, for example, 3 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min or 4 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the frequency of the ultrasonic cleaning is 20-30 kHz, for example, 20 kHz, 22 kHz, 24 kHz, 26 kHz, 28 kHz or 30 kHz, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] In the present invention, by optimally controlling the time and frequency of ultrasonic cleaning, the ultrasonic wave can fully act on the surface of the electrolytic iron, thereby providing a good cleaning effect and reducing the energy consumption of cleaning.

[0020] Preferably, the drying temperature in step (1) is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the drying time is 3-4 min, for example, 3 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min or 4 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] In the present invention, the drying atmosphere in step (1) is not particularly limited, and for example, the drying can be carried out in a blast drying oven, that is, in an air atmosphere.

[0023] Preferably, the acid solution used for pickling in step (2) comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water.

[0024] Preferably, the volume fraction of hydrochloric acid in the mixed solution is 1-3%, for example, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the volume fraction of hydrogen peroxide in the mixed solution is 1-3%, for example, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the volume fraction of oxalic acid in the mixed solution is 1-3%, for example, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the hydrochloric acid is analytically pure.

[0028] Preferably, the purity of the hydrogen peroxide is analytical grade.

[0029] Preferably, the oxalic acid is analytically pure.

[0030] Preferably, benzotriazole is also added to the mixed solution.

[0031] Preferably, the amount of benzotriazole added to the mixed solution is 1-3 mg / L, for example, it can be 1 mg / L, 1.2 mg / L, 1.4 mg / L, 1.6 mg / L, 1.8 mg / L, 2 mg / L, 2.2 mg / L, 2.4 mg / L, 2.6 mg / L, 2.8 mg / L or 3 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, sodium dodecylbenzene sulfonate is also added to the mixed solution.

[0033] Preferably, the amount of sodium dodecylbenzenesulfonate added to the mixed solution is 0.05-0.15 g / L, for example, 0.05 g / L, 0.06 g / L, 0.08 g / L, 0.1 g / L, 0.12 g / L, 0.14 g / L or 0.15 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In the present invention, by using a mixed solution of hydrochloric acid, hydrogen peroxide and oxalic acid in the pickling process and controlling the volume fraction thereof within a specific range, the speed of removing the oxide layer can be further increased, the consumption of the acid solution can be reduced, and the cleaning efficiency can be improved. Furthermore, by preferably adding benzotriazole and sodium dodecylbenzene sulfonate to the acid solution and controlling the addition amount thereof, the cleaning effect can be further improved and the corrosion resistance of the metal can be enhanced.

[0035] Preferably, the pickling time is 25-35 min, for example, it can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In the present invention, by preferably controlling the pickling time within a specific range, it is possible to further ensure that oxides and impurities are completely removed, avoid excessive corrosion of electrolytic iron, and improve the cleaning efficiency.

[0037] Preferably, the cleaning solution used in the vacuum ultrasonic cleaning in step (3) comprises isopropanol.

[0038] Preferably, the vacuum ultrasonic cleaning time is 1-2 min, for example, 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min or 2 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the frequency of the vacuum ultrasonic cleaning is 35-45kHz, for example, it can be 35kHz, 36kHz, 37kHz, 38kHz, 39kHz, 40kHz, 41kHz, 42kHz, 43kHz, 44kHz or 45kHz, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the vacuum degree of the vacuum ultrasonic cleaning is ≤-0.08 MPa, for example, it can be -0.08 MPa, -0.09 MPa or -0.10 MPa, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] In the present invention, by adopting vacuum ultrasonic cleaning and controlling the cleaning frequency, vacuum degree and time within a specific range, the acid liquid remaining on the surface of the electrolytic iron can be further deeply removed, deep cleaning can be achieved, and the electrolytic iron can be prevented from being re-oxidized by contact with air, thereby improving the cleaning efficiency.

[0042] Preferably, the vacuum drying temperature in step (3) is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the vacuum drying time is 3-4 min, for example, 3 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min or 4 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the vacuum degree of the vacuum drying is ≤-0.08 MPa, for example, it can be -0.08 MPa, -0.09 MPa or -0.10 MPa, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, after the vacuum drying in step (3), the electrolytic iron is also vacuum packaged to obtain cleaned electrolytic iron.

[0046] In the present invention, by vacuum drying and vacuum packaging the electrolytic iron, oxidation and contamination of the electrolytic iron can be effectively prevented, the quality of the electrolytic iron is guaranteed, and the purity and composition uniformity of the subsequent alloy are improved.

[0047] As a preferred technical solution of the present invention, the cleaning method comprises the following steps:

[0048] (1) using electronic grade isopropyl alcohol to ultrasonically clean electrolytic iron with a purity of ≥99.999% for 3-4 minutes at a frequency of 20-30 kHz, and then drying at 40-50° C. for 3-4 minutes to obtain electrolytic iron after one cleaning;

[0049] (2) subjecting the electrolytic iron obtained in step (1) to pickling for 25-35 min, wherein the pickling solution comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water, wherein the volume fraction of hydrochloric acid in the mixture is 1-3%, the volume fraction of hydrogen peroxide is 1-3%, and the volume fraction of oxalic acid is 1-3%, and benzotriazole is added in an amount of 1-3 mg / L and sodium dodecylbenzene sulfonate is added in an amount of 0.05-0.15 g / L to obtain electrolytic iron after secondary cleaning;

[0050] (3) The electrolytic iron after secondary cleaning obtained in step (2) is subjected to vacuum ultrasonic cleaning for 1-2 min using electronic grade isopropyl alcohol at a frequency of 35-45 kHz and a vacuum degree of ≤-0.08 MPa, and then vacuum dried for 3-4 min at a temperature of 40-50° C. and a vacuum degree of ≤-0.08 MPa, and then vacuum packaged to obtain the cleaned electrolytic iron.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The cleaning method provided by the present invention removes oil stains on the surface of electrolytic iron by ultrasonic cleaning and drying, ensuring that the oil stains will not affect the cleaning effect in the subsequent pickling process; removes the oxide layer and other impurities on the surface of electrolytic iron by pickling, and reduces its oxygen content; thoroughly removes the acid solution remaining on the surface of electrolytic iron by vacuum ultrasonic cleaning and vacuum drying, and adopts vacuum packaging to prevent it from being oxidized again. The present invention can quickly and effectively clean ultra-high purity electrolytic iron, and the surface of the obtained product is smooth and free of holes, presenting a silvery white metallic luster, which is conducive to ensuring the purity and composition uniformity of the subsequent alloy. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0054] Example 1

[0055] This embodiment provides a method for cleaning ultra-high purity electrolytic iron, the cleaning method comprising the following steps:

[0056] (1) using electronic grade isopropyl alcohol to ultrasonically clean electrolytic iron with a purity of ≥99.999% at a frequency of 25 kHz for 3.5 minutes, and then drying at 45° C. for 3.5 minutes to obtain electrolytic iron after one cleaning;

[0057] (2) pickling the electrolytic iron after the primary cleaning obtained in step (1) for 30 minutes, wherein the pickling solution comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water, wherein the volume fraction of hydrochloric acid in the mixture is 2%, the volume fraction of hydrogen peroxide is 2%, and the volume fraction of oxalic acid is 2%, and benzotriazole is added in an amount of 2 mg / L and sodium dodecylbenzene sulfonate is added in an amount of 0.1 g / L to obtain the electrolytic iron after the secondary cleaning;

[0058] (3) The electrolytic iron after secondary cleaning obtained in step (2) is subjected to vacuum ultrasonic cleaning for 1.5 min using electronic grade isopropyl alcohol at a frequency of 40 kHz and a vacuum degree of -0.08 MPa, and then vacuum dried for 3.5 min at a temperature of 45° C. and a vacuum degree of -0.08 MPa, and then vacuum packaged to obtain the cleaned electrolytic iron.

[0059] Example 2

[0060] This embodiment provides a method for cleaning ultra-high purity electrolytic iron, the cleaning method comprising the following steps:

[0061] (1) using electronic grade isopropyl alcohol to ultrasonically clean electrolytic iron with a purity of ≥99.999% for 4 minutes at a frequency of 20 kHz, and then drying at 40° C. for 4 minutes to obtain electrolytic iron after one cleaning;

[0062] (2) pickling the electrolytic iron after the primary cleaning obtained in step (1) for 25 minutes, wherein the pickling solution comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water, wherein the volume fraction of hydrochloric acid in the mixture is 1%, the volume fraction of hydrogen peroxide is 3%, and the volume fraction of oxalic acid is 1%, and benzotriazole is added in an amount of 3 mg / L and sodium dodecylbenzene sulfonate is added in an amount of 0.05 g / L to obtain electrolytic iron after secondary cleaning;

[0063] (3) The electrolytic iron after secondary cleaning obtained in step (2) is subjected to vacuum ultrasonic cleaning for 1 min using electronic grade isopropyl alcohol at a frequency of 45 kHz and a vacuum degree of -0.08 MPa, and then vacuum dried for 3 min at a temperature of 50° C. and a vacuum degree of -0.08 MPa, and then vacuum packaged to obtain cleaned electrolytic iron.

[0064] Example 3

[0065] This embodiment provides a method for cleaning ultra-high purity electrolytic iron, the cleaning method comprising the following steps:

[0066] (1) using electronic grade isopropyl alcohol to ultrasonically clean electrolytic iron with a purity of ≥99.999% for 3 min at a frequency of 30 kHz, and then drying at 50° C. for 3 min to obtain electrolytic iron after one cleaning;

[0067] (2) subjecting the electrolytic iron obtained in step (1) to pickling for 25 minutes, wherein the pickling solution comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water, wherein the volume fraction of hydrochloric acid in the mixture is 3%, the volume fraction of hydrogen peroxide is 1%, and the volume fraction of oxalic acid is 3%, and benzotriazole is added in an amount of 1 mg / L and sodium dodecylbenzene sulfonate is added in an amount of 0.15 g / L to the mixture, thereby obtaining electrolytic iron after secondary cleaning;

[0068] (3) The electrolytic iron after secondary cleaning obtained in step (2) is subjected to vacuum ultrasonic cleaning for 2 min using electronic grade isopropyl alcohol at a frequency of 35 kHz and a vacuum degree of -0.08 MPa, and then vacuum dried for 4 min at a temperature of 40° C. and a vacuum degree of -0.08 MPa, and then vacuum packaged to obtain cleaned electrolytic iron.

[0069] It can be seen from the cleaned electrolytic iron obtained in Examples 1-3 that the surface of the obtained product has a silvery white metallic luster, a smooth surface without holes, and a total cleaning time of less than 47 minutes (excluding the time for vacuum packaging), which can effectively remove impurities and oxides on the surface of the electrolytic iron while ensuring a high cleaning efficiency.

[0070] Example 4

[0071] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the volume fraction of hydrochloric acid is 0.5%.

[0072] Example 5

[0073] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the volume fraction of hydrochloric acid is 4%.

[0074] Compared with Example 1, from the situation of the electrolytic iron after the cleaning obtained, it can be seen that Example 4 cannot completely remove the oxide on the surface of the electrolytic iron under the same pickling time as Example 1, and the pickling time needs to be extended to at least 200min before the oxide layer can be removed; and the amount of hydrochloric acid added in Example 5 is too much, resulting in the problem of pitting corrosion on the surface of the electrolytic iron, affecting the quality of the electrolytic iron, and resulting in a high cost of pickling, increasing the difficulty of subsequent removal of the acid solution, and if the acid solution cannot be completely removed, it will cause pollution to the subsequent production of alloys. It can be seen that the present invention can further improve the pickling effect while avoiding affecting the quality of the product and reducing production costs by preferably controlling the volume fraction of hydrochloric acid.

[0075] Example 6

[0076] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the volume fraction of hydrogen peroxide is 0.5%.

[0077] Example 7

[0078] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the volume fraction of hydrogen peroxide is 4%.

[0079] Compared with Example 1, from the situation of the electrolytic iron after cleaning obtained in Example 6-7, it can be seen that in Example 6, the corrosion rate of the oxide layer is slower under the same pickling time as that in Example 1, and the pickling time needs to be extended to at least 120 minutes to remove the oxide layer; while in Example 7, the amount of hydrogen peroxide added is too much, resulting in a too fast corrosion rate, which may cause uneven local corrosion and ultimately affect the quality of the product. It can be seen that the present invention can further improve the pickling effect while avoiding affecting the quality of the product and reducing production costs by preferably controlling the volume fraction of hydrogen peroxide.

[0080] Example 8

[0081] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that benzotriazole is not added to the mixed solution.

[0082] Example 9

[0083] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that sodium dodecylbenzene sulfonate is not added to the mixed solution.

[0084] Example 10

[0085] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the amount of benzotriazole added to the mixed solution is 4 mg / L.

[0086] Embodiment 11

[0087] This embodiment provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method is different from that of Embodiment 1 only in that the amount of sodium dodecylbenzene sulfonate added to the mixed solution is 0.2 g / L.

[0088] Compared with Example 1, it can be seen from the situation of the electrolytic iron after the obtained cleaning that in Example 8, benzotriazole is not added, which will lead to too fast corrosion rate, rough surface of electrolytic iron, and obvious corrosion pits; the amount of benzotriazole added in Example 10 is not within the preferred range of the present invention, resulting in an increase in the content of elements such as C, N, and H on the surface of electrolytic iron, further resulting in an increase in the content of C, N, and H in the alloy gas elements after smelting, and the production requirements of subsequent targets cannot be met; and in Example 9, sodium dodecylbenzene sulfonate is not added, which will lead to too slow removal of the oxide layer on the surface of electrolytic iron, and it is necessary to extend the pickling time to remove it; in Example 11, the amount of sodium dodecylbenzene sulfonate added is not within the preferred range of the present invention, resulting in excessive elements such as C, H, O, Na, and S, and also unable to meet the requirements of alloy smelting and subsequent preparation of targets. It can be seen that the present invention can further improve the pickling effect by preferably controlling the addition of benzotriazole and sodium dodecylbenzene sulfonate and the amount added, and avoid introducing too many impurities into the alloy to meet the purity requirements of subsequent production targets.

[0089] Comparative Example 1

[0090] This comparative example provides a method for cleaning ultrahigh-purity electrolytic iron. The cleaning method differs from Example 1 only in that the ultrasonic cleaning and drying in step (1) are not performed, and the electrolytic iron after one cleaning is directly subjected to step (2) instead of the electrolytic iron after one cleaning.

[0091] Comparative Example 2

[0092] This comparative example provides a method for cleaning ultrahigh-purity electrolytic iron. The cleaning method is different from that of Example 1 only in that no acid washing is performed, and the electrolytic iron after the first cleaning is directly subjected to step (3) instead of the electrolytic iron after the second cleaning.

[0093] Comparative Example 3

[0094] This comparative example provides a method for cleaning ultra-high purity electrolytic iron. The cleaning method differs from Example 1 only in that vacuum ultrasonic cleaning, vacuum drying and vacuum packaging are not performed, and the electrolytic iron after secondary cleaning is ultrasonically cleaned in an air environment at a frequency of 40 kHz for 1.5 minutes, and then dried in an air environment at a temperature of 45°C for 3.5 minutes.

[0095] Compared with Example 1, in Comparative Examples 1-3, ultrasonic cleaning and drying in step (1) are not performed in Comparative Example 1, and the oil stain on the surface of the electrolytic iron cannot be removed in advance. The oil stain is insoluble in acid solution, resulting in the inability to effectively remove the oxide layer covered by the oil stain during the subsequent pickling process; in Comparative Example 2, pickling is not performed, and the oxide layer on the surface of the electrolytic iron cannot be removed, resulting in the formation of solid or semi-solid inclusions in the melt during the subsequent alloy preparation process, reducing the purity of the alloy, and reducing the composition uniformity of the alloy, thereby affecting the quality of the target material; in Comparative Example 3, cleaning and drying in an air atmosphere are adopted, and vacuum ultrasonic cleaning, vacuum drying and vacuum packaging are not adopted, resulting in the risk of re-oxidation of the surface of the electrolytic iron after pickling after being left for a long time, and the smelting requirements of subsequent alloy preparation cannot be met.

[0096] In summary, the cleaning method provided by the present invention can quickly clean ultra-high purity electrolytic iron sheets, and the product surface is smooth without holes and presents a silvery white metallic luster.

[0097] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for cleaning ultra-high purity electrolytic iron, characterized in that: The cleaning method comprises the following steps: (1) subjecting the electrolytic iron to ultrasonic cleaning and drying in sequence to obtain the electrolytic iron after primary cleaning; (2) pickling the primary cleaned electrolytic iron obtained in step (1) to obtain secondary cleaned electrolytic iron; (3) subjecting the secondary cleaned electrolytic iron obtained in step (2) to vacuum ultrasonic cleaning and vacuum drying in sequence to obtain cleaned electrolytic iron.

2. The cleaning method according to claim 1, characterized in that: The washing liquid used in the ultrasonic cleaning in step (1) includes isopropanol; Preferably, the purity of the isopropanol is electronic grade.

3. The cleaning method according to claim 1 or 2, characterized in that: The purity of the electrolytic iron in step (1) is ≥99.999%.

4. The cleaning method according to any one of claims 1 to 3, characterized in that: The ultrasonic cleaning time in step (1) is 3-4 minutes; Preferably, the frequency of the ultrasonic cleaning is 20-30 kHz.

5. The cleaning method according to any one of claims 1 to 4, characterized in that: The drying temperature in step (1) is 40-50° C. Preferably, the drying time is 3-4 minutes.

6. The cleaning method according to any one of claims 1 to 5, characterized in that: The acid solution used for pickling in step (2) includes a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water; Preferably, the volume fraction of hydrochloric acid in the mixed solution is 1-3%; Preferably, the volume fraction of hydrogen peroxide in the mixed solution is 1-3%; Preferably, the volume fraction of oxalic acid in the mixed solution is 1-3%; Preferably, the hydrochloric acid is analytically pure; Preferably, the purity of the hydrogen peroxide is analytically pure; Preferably, the purity of the oxalic acid is analytically pure; Preferably, benzotriazole is also added to the mixed solution; Preferably, the amount of benzotriazole added to the mixed solution is 1-3 mg / L; Preferably, sodium dodecylbenzene sulfonate is also added to the mixed solution; Preferably, the amount of sodium dodecylbenzene sulfonate added to the mixed solution is 0.05-0.15 g / L; Preferably, the pickling time is 25-35 minutes.

7. The cleaning method according to any one of claims 1 to 6, characterized in that: The cleaning solution used in the vacuum ultrasonic cleaning in step (3) includes isopropanol; Preferably, the vacuum ultrasonic cleaning time is 1-2 min; Preferably, the frequency of the vacuum ultrasonic cleaning is 35-45kHz; Preferably, the vacuum degree of the vacuum ultrasonic cleaning is ≤-0.08MPa.

8. The cleaning method according to any one of claims 1 to 7, characterized in that: The vacuum drying temperature in step (3) is 40-50°C; Preferably, the vacuum drying time is 3-4 minutes; Preferably, the vacuum degree of the vacuum drying is ≤-0.08MPa.

9. The cleaning method according to any one of claims 1 to 8, characterized in that: After the vacuum drying in step (3), the electrolytic iron is also vacuum packaged to obtain cleaned electrolytic iron.

10. The cleaning method according to any one of claims 1 to 9, characterized in that: The cleaning method comprises the following steps: (1) using electronic grade isopropyl alcohol to ultrasonically clean electrolytic iron with a purity of ≥99.999% for 3-4 minutes at a frequency of 20-30 kHz, and then drying at 40-50° C. for 3-4 minutes to obtain electrolytic iron after one cleaning; (2) pickling the electrolytic iron after the primary cleaning obtained in step (1) for 25-35 min, wherein the pickling solution comprises a mixture of hydrochloric acid, hydrogen peroxide, oxalic acid and water, wherein the volume fraction of hydrochloric acid in the mixture is 1-3%, the volume fraction of hydrogen peroxide is 1-3%, and the volume fraction of oxalic acid is 1-3%, and benzotriazole is added in an amount of 1-3 mg / L and sodium dodecylbenzene sulfonate is added in an amount of 0.05-0.15 g / L to obtain the electrolytic iron after the secondary cleaning; (3) The electrolytic iron after secondary cleaning obtained in step (2) is subjected to vacuum ultrasonic cleaning for 1-2 min using electronic grade isopropyl alcohol at a frequency of 35-45 kHz and a vacuum degree of ≤-0.08 MPa, and then vacuum dried for 3-4 min at a temperature of 40-50° C. and a vacuum degree of ≤-0.08 MPa, and then vacuum packaged to obtain the cleaned electrolytic iron.