Purification method of high-purity chromium for target material

Abstract

The invention discloses a purification method of high-purity chromium for a target material, and belongs to the technical field of metal chromium purification, the purification method comprises the following steps: placing an original electroplated chromium sheet in a vacuum reduction furnace, vacuumizing the vacuum reduction furnace to 10Pa, filling 0-1atm of hydrogen, heating the vacuum furnace from room temperature to final temperature T DEG C according to a six-stage heating curve, keeping the temperature for 12-24 hours, and cooling to room temperature to obtain the high-purity chromium for the target material. And heating is stopped, hydrogen continues to be introduced into the vacuum reduction furnace, after the temperature in the vacuum reduction furnace is reduced to the room temperature, discharging is conducted, and the high-purity chromium is obtained. According to the purification method of the high-purity chromium for the target material, the high-purity chromium is prepared through purification of an original electroplated chromium sheet, the content of O in the chromium prepared through the purification method is smaller than or equal to 60 ppm, the content of N is smaller than or equal to 60 ppm, the content of C is smaller than or equal to 50 ppm, the content of S, Fe, Al and Si is smaller than or equal to 40 ppm, and the prepared high-purity chromium can be applied to the field of target materials.

Description

Technical Field

[0001] The invention belongs to the technical field of metal chromium purification, and in particular relates to a method for purifying high-purity chromium for target materials. Background Art

[0002] Magnetron sputtering coating can be used to sputter almost any material such as semiconductors, metals, insulators, etc. due to its high speed, low temperature, and low damage. It is widely used in the electronics industry, information storage industry, and other fields due to its advantages such as simple preparation, strong adhesion, large coating area, and easy control.

[0003] Magnetron sputtering high-purity chromium target is a new target material that has been newly developed and researched in recent years. The market scale and demand are still expanding. Therefore, improving the purity of chromium target has become a hot research and development direction.

[0004] The invention patent with application number 202110364732.9 discloses a method for preparing high-purity metal chromium blocks by wet mixing of metal powders. The invention first crushes the chromium block, then wet mixes it with a reducing agent such as sucrose, and then disperses it with distilled water. Finally, it is dried, pressed and vacuum sintered to obtain a high-purity metal chromium block. The oxygen content in the prepared metal chromium block is as low as 0.0293% to 0.0330%, and the carbon content is as low as 0.0011% to 0.0021%.

[0005] The invention patent with application number 202310390428.0 discloses a plasma purification method for metallic chromium. The invention uses the high-energy density arc of plasma melting technology to quickly melt metallic chromium, while maintaining the gas pressure in the furnace close to one atmospheric pressure. The oxygen content of the high-purity chromium finally prepared is as low as 16 to 32 ppm (0.0016% to 0.0032%).

[0006] The invention patent with application number 202311602611.9 discloses a method for purifying and controlling impurities in the preparation of high-purity metallic chromium. The invention first crushes the metallic chromium block, then adds additives and adhesives to it, and then sinters it in a vacuum after drying to obtain high-purity metallic chromium, wherein the additives are chromium trioxide and tin powder, and the adhesive is water glass, epoxy resin, phenolic resin or furfuryl alcohol resin. The purity of the high-purity metallic chromium block finally prepared reaches 99.99wt%, the carbon content is ≤0.02wt%, and the oxygen content is ≤0.03wt%.

[0007] The invention patent with application number 202311781885.9 discloses a method for purifying chromium. The invention can reduce the oxygen content in ordinary chromium (oxygen content 100ppm, N content 100ppm) to below 80ppm and the nitrogen content to below 20ppm after crushing, screening, mixing with carbon powder, briquetting and sintering to purify it, thus achieving the purity level of high-purity chromium and ultra-pure chromium.

[0008] The invention patent with application number 202410093524.3 discloses a method for preparing metallic chromium by electrodeposition. The invention patent adds sulfuric acid, a reducing agent (one or more of methanol, ethanol, formaldehyde and hydrazine hydrate) and pure water to chromium salt (chromic anhydride / sodium dichromate) to prepare an electrodeposition solution, and then obtains metallic chromium sheets after electrodeposition with a purity of 99.999%. Summary of the invention

[0009] Ordinary metallic chromium is reduced by aluminotherm, and its purity is 99.5% (2N5), its oxygen content is about 1000ppm, its nitrogen content is about 200ppm, and impurity elements such as Fe, Al, and Si are all above 1000ppm. Electrolytic chromium sheets are produced by electrolysis. Since the effect of chemical purification is much higher than physical purification, its purity is above 99.95% (3N5), wherein the oxygen content is about 5000ppm, and the nitrogen content is about 100ppm. Only high-purity chromium with a purity of more than 99.95% can be applied to the field of target materials. However, the oxygen content in the electrolytic chromium sheet is too high, and it is necessary to reduce the oxygen content from 5000ppm to below 60ppm, while ensuring that the content of impurity elements such as Fe, Al, and Si is less than 100ppm. This is the technical problem that the present invention aims to solve. To this end, the present invention provides a method for purifying high-purity chromium for target materials.

[0010] The purpose of the present invention can be achieved by the following technical solutions: A method for purifying high-purity chromium for a target material comprises the following steps: The original electroplated chromium sheet is placed in a vacuum reduction furnace, and the vacuum degree in the vacuum reduction furnace is evacuated to 10Pa, and then filled with 0-1atm hydrogen. The vacuum furnace is heated from room temperature to the final temperature T℃ according to a six-stage heating curve, and the temperature is kept constant for 12-24h. The heating is stopped, and hydrogen is continued to be introduced into the vacuum reduction furnace. After the temperature in the vacuum reduction furnace drops to room temperature, it is taken out of the furnace to obtain high-purity chromium.

[0011] Furthermore, the average thickness of the original electroplated chrome sheet is 1.2 mm.

[0012] Furthermore, the original electroplated chromium sheet has an average mass percentage content of oxygen of 0.52%, an average mass percentage content of nitrogen of 0.024%, and an average mass percentage content of carbon of 0.015%.

[0013] Furthermore, the purity of the hydrogen is 99.99%.

[0014] Furthermore, the six-stage heating curve is as follows: The first stage: from room temperature to 395-420℃, the heating rate is 230-300℃ / h; The second stage: from 395-420℃ to 690-720℃, the heating rate is 180-210℃ / h; The third stage: from 690-720℃ to 890-910℃, the heating rate is 150-180℃ / h; The fourth stage: from 890-910℃ to 1040-1155℃, the heating rate is 110-130℃ / h; The fifth stage: from 1040-1155°C to 1295-1310°C, the heating rate is 90-100°C / h; The sixth stage: from 1295-1310℃ to the final temperature T℃, the heating rate is 50-55℃ / h.

[0015] Furthermore, the six-stage heating curve is as follows: The first stage: from room temperature to 400°C, the heating rate is 250°C / h; The second stage: from 400℃ to 700℃, the heating rate is 200℃ / h; The third stage: from 700℃ to 900℃, the heating rate is 170℃ / h; The fourth stage: from 900℃ to 1045℃, the heating rate is 125℃ / h; The fifth stage: from 1045℃ to 1300℃, the heating rate is 95℃ / h; The sixth stage: from 1300℃ to the final temperature T℃, the heating rate is 50℃ / h.

[0016] Furthermore, the relationship between the final temperature T and the impurity content and thickness of the original electroplated chromium sheet is: T=X1×[16sin(O×100)+26sin((N+C)×100)] / sin1+X2×ln(1200); Wherein, T is the final temperature; O is the average mass percentage content of oxygen; N is the average mass percentage content of nitrogen; C is the average mass percentage content of carbon; and t is the thickness of the original electroplated chrome sheet.

[0017] Furthermore, the value of X1 is 100; the value range of X2 is 50-100.

[0018] Furthermore, the value range of X2 is 60-80.

[0019] Furthermore, the high-purity chromium has an average O content of 58-44 ppm, an average N content of 60-58 ppm, an average C content of 53-40 ppm, an average S content of 31-25 ppm, an average Fe content of 30-23 ppm, an average Al content of 20-15 ppm, and an average Si content of 17-15 ppm.

[0020] Beneficial effects of the present invention: The invention provides a method for purifying high-purity chromium for target materials. The invention utilizes an original electroplated chromium sheet to purify and prepare the high-purity chromium. The chromium prepared by the purification method of the invention has an O content of ≤60ppm, an N content of ≤60ppm, a C content of ≤60ppm, and an S, Fe, Al and Si content of ≤40ppm. The prepared high-purity chromium can be applied to the field of target materials.

[0021] The difference between the purification method provided by the present invention and the prior art is that the present invention is committed to the research and control of parameters in the high-temperature negative pressure hydrogen reduction process. First of all, the present invention strictly controls the temperature rise curve to ensure the uniformity and consistency of the purification of the original electroplated chromium sheet. Too fast temperature rise will form local purification or uneven purification, too long temperature rise time, and too high production cost. The present invention adopts a temperature rise rate that is first fast and then slow and a temperature rise interval that is first wide and then narrow, and improves the temperature rise process into six stages. After testing, the purity of the chromium finally prepared is significantly improved. At the same time, the present invention studies the final temperature of the heating stage, and accidentally finds that the final temperature is closely related to the thickness of the raw material and the content of impurities oxygen, nitrogen and carbon. In this regard, the present invention provides the associated carrier, that is, the relationship, and through detection, the temperature is set using the relationship of the present invention, and the purity of the chromium finally prepared is significantly improved.

[0022] Finally, the present invention aims to fully disclose the relevant results of the above-mentioned research on the parameters in the high-temperature negative pressure hydrogen reduction process. The above-mentioned research content has also been fully studied, and the data table clearly shows that it has outstanding and significant effects and progress in purifying and preparing high-purity chromium from electroplated chromium sheets. The purification method of this application is worthy of promotion and reference. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for purifying high-purity chromium for a target material comprises the following steps: The original electroplated chrome sheet was purified. After testing, the average thickness of the original electroplated chrome sheet was 1.2 mm, the average mass percentage content of oxygen in the original electroplated chrome sheet was 0.52%, the average mass percentage content of nitrogen was 0.024%, and the average mass percentage content of carbon was 0.015%; First, the original electroplated chromium sheet is placed in a vacuum reduction furnace, the vacuum reduction furnace is closed, and the vacuum degree in the vacuum reduction furnace is evacuated to ≤10Pa. In this embodiment, the vacuum degree is 10Pa, and then 0.2atm of hydrogen with a purity of 99.99% is filled. The vacuum furnace heats the electroplated chromium sheet from room temperature to the final temperature T°C according to a six-stage heating curve, and the temperature is kept constant for 12 hours. Specifically, the six-stage heating curve is as follows: The first stage: from room temperature to 395°C, the heating rate is 230°C / h; The second stage: from 395℃ to 690℃, the heating rate is 180℃ / h; The third stage: from 690℃ to 890℃, the heating rate is 150℃ / h; The fourth stage: from 890℃ to 1040℃, the heating rate is 110℃ / h; The fifth stage: from 1040℃ to 1295℃, the heating rate is 90℃ / h; Stage 6: From 1295℃ to final temperature T℃, heating rate 50℃ / h: Among them, the relationship between the final temperature T and the impurity content and thickness of the original electroplated chrome sheet is: T=X1×[16sin(O×100)+26sin((N+C)×100)] / sin1+X2×ln(1200); Wherein, T is the final temperature; O is the value of the average mass percentage content of oxygen; N is the value of the average mass percentage content of nitrogen; C is the value of the average mass percentage content of carbon; t is the value of the thickness of the original electroplated chromium sheet; X1 is the weight factor of the impurity content of the original electroplated chromium sheet to the final temperature, and X1 is 100; X2 is the weight factor of the thickness of the original electroplated chromium sheet to the final temperature, and X2 is in the range of 50 to 100. It has been verified that when X2 is in the range of 60 to 80, the effect is better, that is, the weight ratio of the impurity content of the original electroplated chromium sheet to the final temperature is relatively increased, and the purity of the high-purity chromium finally prepared is higher. In this embodiment, X2 is 60. According to the above formula, the final temperature T is 1434.8°C; Then, after the constant temperature is ended, the heating is stopped, and hydrogen with a purity of 99.99% is continued to be introduced into the vacuum reduction furnace. After the temperature in the vacuum reduction furnace drops to room temperature, the furnace is taken out to obtain high-purity chromium. After testing, the average O content in the prepared high-purity chromium is 58ppm, the average N content is 60ppm, the average C content is 53ppm, the average S content is 31ppm, the average Fe content is 30ppm, the average Al content is 20ppm, and the average Si content is 17ppm.

[0026] Example 2

[0027] A method for purifying high-purity chromium for a target material comprises the following steps: The original electroplated chrome sheet was purified. After testing, the average thickness of the original electroplated chrome sheet was 1.2 mm, the average mass percentage content of oxygen in the original electroplated chrome sheet was 0.52%, the average mass percentage content of nitrogen was 0.024%, and the average mass percentage content of carbon was 0.015%; First, the original electroplated chromium sheet is placed in a vacuum reduction furnace, the vacuum reduction furnace is closed, and the vacuum degree in the vacuum reduction furnace is evacuated to ≤10Pa, and the vacuum degree in this embodiment is 5Pa, and then 0.15atm of hydrogen with a purity of 99.99% is filled. The vacuum furnace heats the electroplated chromium sheet from room temperature to the final temperature T℃ according to a six-stage heating curve, and the temperature is kept constant for 24 hours. Specifically, the six-stage heating curve is as follows: The first stage: from room temperature to 400°C, the heating rate is 250°C / h; The second stage: from 400℃ to 700℃, the heating rate is 200℃ / h; The third stage: from 700℃ to 900℃, the heating rate is 170℃ / h; The fourth stage: from 900℃ to 1045℃, the heating rate is 125℃ / h; The fifth stage: from 1045℃ to 1300℃, the heating rate is 95℃ / h; Stage 6: From 1300℃ to final temperature T℃, heating rate 50℃ / h: Among them, the relationship between the final temperature T and the impurity content and thickness of the original electroplated chrome sheet is: T=X1×[16sin(O×100)+26sin((N+C)×100)] / sin1+X2×ln(1200); Wherein, T is the final temperature; O is the value of the average mass percentage content of oxygen; N is the value of the average mass percentage content of nitrogen; C is the value of the average mass percentage content of carbon; t is the value of the thickness of the original electroplated chromium sheet; X1 is the weight factor of the impurity content of the original electroplated chromium sheet to the final temperature, and X1 is 100; X2 is the weight factor of the thickness of the original electroplated chromium sheet to the final temperature, and X2 is in the range of 50 to 100. It has been verified that when X2 is in the range of 60 to 80, the effect is better, that is, the weight ratio of the impurity content of the original electroplated chromium sheet to the final temperature is relatively increased, and the purity of the high-purity chromium finally prepared is higher. In this embodiment, X2 is 70. According to the above formula, the final temperature T is 1505.7°C; Then, after the constant temperature is ended, the heating is stopped, and hydrogen with a purity of 99.99% is continued to be introduced into the vacuum reduction furnace. After the temperature in the vacuum reduction furnace drops to room temperature, the furnace is taken out to obtain high-purity chromium. After testing, the average O content in the prepared high-purity chromium is 40ppm, the average N content is 53ppm, the average C content is 37ppm, the average S content is 22ppm, the average Fe content is 22ppm, the average Al content is 12ppm, and the average Si content is 13ppm.

[0028] Example 3

[0029] A method for purifying high-purity chromium for a target material comprises the following steps: The original electroplated chrome sheet was purified. After testing, the average thickness of the original electroplated chrome sheet was 1.2 mm, the average mass percentage content of oxygen in the original electroplated chrome sheet was 0.52%, the average mass percentage content of nitrogen was 0.024%, and the average mass percentage content of carbon was 0.015%; First, the original electroplated chromium sheet is placed in a vacuum reduction furnace, the vacuum reduction furnace is closed, and the vacuum degree in the vacuum reduction furnace is evacuated to ≤10Pa. In this embodiment, the vacuum degree is 10Pa, and then 0.3atm of hydrogen with a purity of 99.99% is filled. The vacuum furnace heats the electroplated chromium sheet from room temperature to the final temperature T℃ according to a six-stage heating curve, and the temperature is kept constant for 24 hours. Specifically, the six-stage heating curve is as follows: The first stage: from room temperature to 420℃, the heating rate is 300℃ / h; The second stage: from 420℃ to 720℃, the heating rate is 210℃ / h; The third stage: from 720℃ to 910℃, the heating rate is 180℃ / h; The fourth stage: from 910℃ to 1155℃, the heating rate is 130℃ / h; The fifth stage: from 1155°C to 1310°C, the heating rate is 100°C / h; Stage 6: From 1310℃ to final temperature T℃, heating rate 55℃ / h: Among them, the relationship between the final temperature T and the impurity content and thickness of the original electroplated chrome sheet is: T=X1×[16sin(O×100)+26sin((N+C)×100)] / sin1+X2×ln(1200); Wherein, T is the final temperature; O is the value of the average mass percentage content of oxygen; N is the value of the average mass percentage content of nitrogen; C is the value of the average mass percentage content of carbon; t is the value of the thickness of the original electroplated chromium sheet; X1 is the weight factor of the impurity content of the original electroplated chromium sheet to the final temperature, and the value of X1 is 100; X2 is the weight factor of the thickness of the original electroplated chromium sheet to the final temperature, and the value range of X2 is 50 to 100. It has been verified that when the range of X2 is 60 to 80, the effect is better, that is, the weight ratio of the impurity content of the original electroplated chromium sheet to the final temperature is relatively increased, and the purity of the high-purity chromium finally prepared is higher. In this embodiment, X2 is 80. According to the above formula, the value of the final temperature T is 1576.6°C; Then, after the constant temperature is ended, the heating is stopped, and hydrogen with a purity of 99.99% is continued to be introduced into the vacuum reduction furnace. After the temperature in the vacuum reduction furnace drops to room temperature, the furnace is taken out to obtain high-purity chromium. After testing, the average O content in the prepared high-purity chromium is 44ppm, the average N content is 58ppm, the average C content is 40ppm, the average S content is 25ppm, the average Fe content is 23ppm, the average Al content is 15ppm, and the average Si content is 15ppm.

[0030] Comparative Example 1 to Comparative Example 6 Comparative Examples 1 to 6 are control groups of Example 2. The heating rates in Example 2 are fixedly set to 250°C / h, 200°C / h, 170°C / h, 1125°C / h, 95°C / h and 50°C / h, respectively. The remaining purification methods remain the same as in Example 2, and high-purity chromium is finally obtained. After testing, the test results shown in Table 1 are obtained: Table 1 Test results project Example 2 Comparative Example 1 Comparative Example 2 Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Heating rate℃ / h Six stages 250 200 170 125 95 50 Average O content / ppm 40 108 82 65 51 40 34 Average N content / ppm 53 135 107 85 67 55 48 Average C content / ppm 37 89 70 56 45 38 35 Total heating time / h 12.1 6.0 7.5 8.8 12.0 15.8 30.1 It can be seen from Table 1 that according to the six-stage heating rate in Example 2 of the present invention, the temperature can be raised to the target final temperature in about 12 hours, and the impurity content of the high-purity chromium finally prepared is effectively reduced. Compared with Comparative Examples 1 to 6, the heating curve of Example 2 can achieve a comprehensive improvement in production efficiency and purity.

[0031] Comparative Example 7 to Comparative Example 11 Comparative Examples 7 to 11 are all control groups of Example 2. The final temperature T in Example 2 is set to 1400° C., 1450° C., 1500° C., 1550° C. and 1600° C. in sequence, and the remaining purification methods remain the same as in Example 2, and finally high-purity chromium is obtained. After testing, the test results shown in Table 2 are obtained: Table 2 Test results project Comparative Example 7 Comparative Example 8 Comparative Example 9 Example 2 Comparative Example 10 Comparative Example 11 Final temperature T / ℃ 1400 1450 1500 1505.7 1550 1600 Average O content / ppm 61 42 40 40 43 46 Average N content / ppm 65 58 53 53 55 61 Average C content / ppm 64 48 42 37 40 42 From the data in Table 2, it can be obtained that: according to the relationship between the final temperature and the thickness of the raw material and the content of impurities oxygen, nitrogen and carbon provided in Example 2 of the present invention, by measuring the parameters of the raw material, the range of the optimal final purification temperature can be quickly narrowed, thereby greatly improving production efficiency.

[0032] It should be noted that, in this article, terms such as "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment.

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for purifying high-purity chromium for a target material, characterized in that: The following steps are involved: The original electroplated chromium sheet is placed in a vacuum reduction furnace, and the vacuum degree in the vacuum reduction furnace is evacuated to 10Pa, and then filled with 0-1atm hydrogen. The vacuum furnace is heated from room temperature to the final temperature T℃ according to a six-stage heating curve, and the temperature is kept constant for 12-24h. The heating is stopped, and hydrogen is continued to be introduced into the vacuum reduction furnace. After the temperature in the vacuum reduction furnace drops to room temperature, it is taken out of the furnace to obtain high-purity chromium.

2. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The average thickness of the original electroplated chrome sheet is 1.2 mm.

3. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The original electroplated chromium sheet has an average oxygen content of 0.52%, an average nitrogen content of 0.024%, and an average carbon content of 0.015%.

4. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The purity of the hydrogen is 99.99%.

5. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The six-stage heating curve is as follows: The first stage: from room temperature to 395-420℃, the heating rate is 230-300℃ / h; The second stage: from 395-420℃ to 690-720℃, the heating rate is 180-210℃ / h; The third stage: from 690-720℃ to 890-910℃, the heating rate is 150-180℃ / h; The fourth stage: from 890-910℃ to 1040-1155℃, the heating rate is 110-130℃ / h; The fifth stage: from 1040-1155°C to 1295-1310°C, the heating rate is 90-100°C / h; The sixth stage: from 1295-1310℃ to the final temperature T℃, the heating rate is 50-55℃ / h.

6. The method for purifying high-purity chromium for target material according to claim 5, characterized in that: The six-stage heating curve is as follows: The first stage: from room temperature to 400°C, the heating rate is 250°C / h; The second stage: from 400℃ to 700℃, the heating rate is 200℃ / h; The third stage: from 700℃ to 900℃, the heating rate is 170℃ / h; The fourth stage: from 900℃ to 1045℃, the heating rate is 125℃ / h; The fifth stage: from 1045℃ to 1300℃, the heating rate is 95℃ / h; The sixth stage: from 1300℃ to the final temperature T℃, the heating rate is 50℃ / h.

7. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The relationship between the final temperature T and the impurity content and thickness of the original electroplated chromium sheet is: T=X1×[16sin(O×100)+26sin((N+C)×100)] / sin1+X2×ln(1200); Wherein, T is the final temperature; O is the average mass percentage content of oxygen; N is the average mass percentage content of nitrogen; C is the average mass percentage content of carbon; and t is the thickness of the original electroplated chrome sheet.

8. The method for purifying high-purity chromium for target material according to claim 7, characterized in that: The value of X1 is 100; the value range of X2 is 50-100.

9. The method for purifying high-purity chromium for target material according to claim 8, characterized in that: The value range of X2 is 60-80.

10. The method for purifying high-purity chromium for target material according to claim 1, characterized in that: The high-purity chromium has an average O content of 58-44 ppm, an average N content of 60-58 ppm, an average C content of 53-40 ppm, an average S content of 31-25 ppm, an average Fe content of 30-23 ppm, an average Al content of 20-15 ppm, and an average Si content of 17-15 ppm.