Preparation method of dummy ingot with low impurity content

Abstract

The invention relates to the technical field of pyrogenic purification of high-purity metal, in particular to a preparation method of a dummy ingot with low impurity content. The method comprises the steps that firstly, a certain amount of high-purity metal electrolytic plates are cleaned and then placed on an original common metal dummy bar of an electron beam, the stacking standard is that dummy ingots are covered and do not exceed the diameter of the dummy ingots, and then the high-purity metal electrolytic plates on the dummy bar are melted under the vacuum condition with low power; the process is repeated for many times until a cast ingot with the height being 5 cm or above is formed, then a normal feeding mode and an electron beam melting mode are adopted, the raw materials are scanned, melted and formed at high power under the vacuum condition, a compact metal cast ingot is formed, and the low-impurity-content dummy ingot is prepared. The process is simple, short in flow and environmentally friendly, and impurity introduction of the low-purity dummy ingot in the high-purity metal preparation process can be effectively controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-purity metal pyrogenic purification, and particularly relates to a preparation method of low-impurity-content starter ingot. BACKGROUND

[0002] High-purity metal is mainly used in electronic chemical materials and special alloy materials, and can be applied to high-tech fields such as preparation of magnetic recording materials, magnetic sensing materials, photoelectric materials and integrated circuits, hydrogenation catalysts, large-scale integrated circuits, biological materials, aircraft engines and low-expansion alloys. With the development of high-tech, many metals have become strategic materials for high-tech, and it is required to purify them to extremely high purity. The preparation, characteristics and application of high-purity and ultra-high-purity metals have been increasingly valued in the field of modern material science and engineering.

[0003] Among them, electron beam melting is one of the mainstream methods for preparing high-purity metal. Electron beam melting uses an electron beam to scan a starter ingot to form a molten pool, and a water-cooled copper crystallizer is used for cooling and forming. Therefore, there is no introduction of impurities from the medium of the smelting crucible and the forming mold. This is one of the advantages of electron beam melting for the preparation of high-purity metal. Therefore, after decades of development, this technology has become an important development direction of metallurgical science and metal, and is the main means for the purification, purification and forming of high-purity metals, especially active metals and high-melting-point metals, to be produced on a large scale in an economic way.

[0004] Among them, the starter ingot head is needed to form a molten pool for melting and downward cooling and forming during electron beam melting. Therefore, the starter ingot head metal and the high-purity metal raw material are fused with each other. This requires the starter ingot head to have the same or even higher purity as the high-purity metal being purified, so that the impurities in the starter ingot head will not be introduced into the high-purity metal ingot being purified and formed, causing pollution. At present, the preparation of many high-purity metals is still in the research stage, and it is difficult to obtain high-purity metal starter ingot rods with a purity of 5N or above. Therefore, when using an electron beam furnace to prepare high-purity metal, the starter ingot rod is generally made of ordinary and low-purity metal. High-purity metal raw materials need to be continuously melted and cast to dilute impurities, until the chemical purity of the starter ingot is the same as that of the high-purity metal raw material, so that the high-purity metal can be purified and prepared. This results in a large amount of consumption of expensive raw materials and time.

[0005] Therefore, there is a need to develop a preparation method of low-impurity-content starter ingot with less raw material consumption and rapidity. SUMMARY

[0006] In order to solve the problems in the prior art, the present application provides a preparation method of low-impurity-content starter ingot, and the specific steps are as follows:

[0007] Step 1: cleaning and blow-drying of high-purity metal electrolytic plate; the purity of the high-purity metal is 5N or above;

[0008] Step 2: Move the original metal bottom ingot in the electron beam furnace upward and above the upper edge of the crystallizer;

[0009] Step 3: Place high-purity metal electrolytic plates uniformly on the top end of the bottom ingot, and the placement standard is to cover the bottom ingot without exceeding its diameter;

[0010] Step 4: Lower the starter and make its upper end below the upper edge of the crystallizer, close the hatch, and vacuum to ≤10 -3 Pa;

[0011] Step 5: Use a low-power electron beam to scan the high-purity metal electrolytic plates on the bottom ingot, and stop scanning and close the smelting system immediately after the high-purity metal electrolytic plates are melted; the low power is not more than 40Kw;

[0012] Step 6: Keep the vacuum in the furnace ≤10 -3 Pa and open the hatch after cooling for at least 24h;

[0013] Step 7: Move the cooled metal starter upward above the upper edge of the crystallizer;

[0014] Step 8: Repeat steps 3-7 until the height of the metal ingot on the bottom ingot reaches more than 5cm, and then stop the above steps;

[0015] Step 9: Install the high-purity metal raw material in the feeding device, and lower the starter to its upper end at least 10cm below the upper edge of the crystallizer, close the hatch, and vacuum to ≤10 -3 Pa;

[0016] Step 10: Use a high-power electron beam of not less than 60Kw to melt the starter and form a molten pool, and scan the high-purity metal raw material, and the molten metal drips into the molten pool. When the liquid level approaches the upper edge of the crystallizer, start the ingot pulling system to lower and cool the starter. After the height of the dense ingot formed by melting and casting on the bottom ingot in this step is at least twice the metal ingot in step 8, stop the electron beam scanning and ingot pulling operation, and keep vacuum cooling for at least 24 hours to obtain a low-impurity high-purity metal starter.

[0017] Further, the thickness of the high-purity metal electrolytic plate placed in step 3 is 3±0.1cm.

[0018] Further, the upper end of the starter in step 4 is 2±0.1cm below the upper edge of the crystallizer.

[0019] Further, the diameter of the bottom ingot and the finally prepared low-impurity high-purity metal starter is the same, both being 80-400mm.

[0020] Further, the scanning power of the low-power electron beam in step 5 ranges from 10-40Kw.

[0021] Further, the distance between the top end of the dummy bar and the upper edge of the crystallizer in step 9 is at least twice the height of the metal ingot on the bottom dummy bar in step 8.

[0022] Further, the scanning power of the high-power electron beam in step 10 is in the range of 60-200Kw.

[0023] The preparation method of the present application first uses a low-power electron beam to scan the high-purity metal to melt the metal, so as to combine the high-purity metal with the original low-purity metal dummy bar (bottom dummy bar) in a manner of adhesion without full fusion, thereby inhibiting the diffusion between the high-purity metal and the low-purity metal, reducing the introduction of impurities and pollution of the high-purity metal layer by the original low-purity metal dummy bar, and effectively controlling the impurities and chemical purity of the buffer zone of the high-purity metal and the low-purity metal bottom dummy bar after several iterations; then a high-power electron beam is used for scanning in the later stage to scan the high-purity metal layer formed by adhesion on the bottom dummy bar and the continuous feed (high-purity metal), so that the high-purity metal on the bottom dummy bar and the feed (high-purity metal) are fully melted and fused with each other to form a dummy bar with high strength and chemical purity meeting the requirements of high-purity metal purification. Therefore, the dummy bar prepared by the method has high purity, and the purity of the head meets 5N, which can be used for preparing high-purity metal. The method is simple in process, short in flow, friendly to the environment, and can effectively control the introduction of impurities by the low-purity dummy bar during the preparation of high-purity metal. The preparation period of the high-purity metal bottom dummy bar can be shortened from at least one month (more than 30 furnace times) to 2-3 days by using the above method. Since the preparation of the bottom dummy bar requires a large amount of high-purity metal with high added value, the great shortening of the preparation period of the high-purity metal bottom dummy bar also greatly reduces the preparation cost of the bottom dummy bar. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail through specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0025] A preparation method of a low-impurity-content dummy bar, comprising the following steps:

[0026] Step 1: cleaning and drying the high-purity metal electrolytic plate; the purity of the high-purity metal is 5N or above;

[0027] Step 2: moving the original metal bottom dummy bar in the electron beam furnace upward by 5-10cm above the upper edge of the crystallizer;

[0028] Step 3: uniformly stacking the high-purity metal electrolytic plate with a thickness of 3±0.1cm on the top end of the bottom dummy bar, and the stacking standard is to cover the bottom dummy bar without exceeding its diameter;

[0029] Step 4: Lower the starter and make its upper end 2±0.1 cm below the upper edge of the crystallizer, close the hatch and vacuumize to ≤10 -3 Pa;

[0030] Step 5: Scan the high-purity metal electrolytic plate on the bottom starter with a low-power electron beam of 10-40 kW, and stop scanning immediately after the high-purity metal electrolytic plate is melted and close the smelting system;

[0031] Step 6: Keep the vacuum in the furnace ≤10 -3 Pa and cool for at least 24 h before opening the hatch;

[0032] Step 7: Move the cooled metal starter up above the upper edge of the crystallizer;

[0033] Step 8: Repeat steps 3-7 until the height of the metal ingot on the bottom starter reaches more than 5 cm, and then stop the above steps;

[0034] Step 9: Install the high-purity metal raw material in the feeding device, and lower the starter to its upper end at least 10 cm below the upper edge of the crystallizer, close the hatch and vacuumize to ≤10 -3 Pa; The distance between the lower end of the starter and the upper edge of the crystallizer is at least twice the height of the metal ingot on the bottom starter in step 8;

[0035] Step 10: Melt the starter with a high-power electron beam of 60-200 kW and form a molten pool, and scan the high-purity metal raw material. The molten metal drips into the molten pool, and when the liquid level approaches the upper edge of the crystallizer, the ingot drawing system is started to lower and cool the starter. After the height of the dense ingot formed by melting and casting on the bottom starter in this step is at least twice the height of the metal ingot in step 8, the electron beam scanning and ingot drawing operations are stopped. After vacuum cooling for at least 24 hours, a low-impurity high-purity metal starter is prepared. The diameter of the bottom starter and the finally prepared low-impurity high-purity metal starter is the same, both being 80-400 mm.

[0036] Example 1

[0037] (1) Wash and dry the 5N and above high-purity metal electrolytic plate.

[0038] (2) Move the original 80 mm diameter metal bottom starter in the electron beam furnace up and above the upper edge of the crystallizer by 5-10 cm.

[0039] (3) Uniformly stack high-purity metal electrolytic plates with a thickness of about 3 cm on the upper end of the bottom starter. The stacking standard is to cover the starter without exceeding the diameter of the starter.

[0040] (4) Lower the starter and make its upper end about 2 cm from the upper edge of the crystallizer, close the hatch and vacuumize to ≤10 - 3 Pa.

[0041] (5) Adopt 12Kw electron beam to scan the high purity metal electrolytic plate on the bottom ingot, so that it is melted, then stop scanning and close the smelting system.

[0042] (6) Keep the vacuum in the furnace for 10 -3 Pa, and cool for 24h, then open the door.

[0043] (7) Move the cooled metal ingot above the upper edge of the crystallizer.

[0044] (8) Repeat steps 3-7 until the height of the metal ingot on the bottom ingot reaches 5cm, then stop the above steps.

[0045] (9) Install the high purity metal electrolytic plate or ingot as high purity metal raw material in the feeding device, and lower the ingot to about 10cm from the upper edge of the crystallizer, close the door and vacuum to ≤10 -3 Pa.

[0046] (10) Use 60Kw electron beam to melt the high purity metal ingot and form a molten pool, and scan the high purity metal raw material. The molten metal drips into the molten pool. When the liquid level approaches the upper edge of the crystallizer, start the ingot drawing system, and pull the ingot at a certain speed, cool it, and when the above process melts and casts a dense ingot about 5cm high, stop feeding, close the electron beam scanning and ingot drawing operation, and keep vacuum cooling for 24h. The high purity metal ingot with dense and required chemical purity is prepared, the purity of the high purity metal ingot is greater than or equal to 5N, and the purity of the head of the high purity metal ingot is equivalent to that of the high purity metal raw material.

[0047] Example 2

[0048] (1) Wash and dry the 5N and above high purity metal electrolytic plate.

[0049] (2) Move the original 150mm diameter metal bottom ingot in the electron beam furnace and make it 5-10cm higher than the upper edge of the crystallizer.

[0050] (3) Uniformly stack high purity metal electrolytic plates with a thickness of about 3cm on the top of the bottom ingot. The stacking standard is to cover the ingot without exceeding the diameter of the ingot.

[0051] (4) Lower the ingot so that its upper end is about 2cm from the upper edge of the crystallizer, close the door and vacuum to ≤10 - 3 Pa.

[0052] (5) Adopt 18Kw electron beam to scan the high purity metal electrolytic plate on the bottom ingot, so that it is melted, then stop scanning and close the smelting system.

[0053] (6) Keep the vacuum in the furnace at 10 -3 Pa for 24 hours and then open the door.

[0054] (7) Move the cooled metal ingot up to be higher than the top edge of the crystallizer.

[0055] (8) Repeat steps 3-7 until the height of the metal ingot on the bottom ingot reaches 6 cm.

[0056] (9) Install high-purity metal electrolytic plates or ingots as high-purity metal raw materials in the feeding device, and lower the ingot to be about 12 cm away from the top edge of the crystallizer. Close the door and vacuum to ≤10 -3 Pa.

[0057] (10) Use an 80Kw electron beam to melt the high-purity metal ingot and form a molten pool, and scan the high-purity metal raw material. The molten metal drips into the molten pool. When the liquid level approaches the top edge of the crystallizer, start the ingot pulling system to pull the ingot at a certain speed and cool it down. After the above process melts and casts a dense ingot about 6 cm high, i.e. the height of the dense ingot formed on the bottom ingot is 12 cm, stop feeding, close the electron beam scanning and ingot pulling operation, and keep vacuum cooling for 24 hours. The high-purity metal ingot with dense and chemical purity meeting the requirements is prepared. The purity of the high-purity metal ingot is greater than or equal to 5N, and the purity of the head of the high-purity metal ingot is equivalent to that of the high-purity metal raw material.

[0058] Example 3

[0059] (1) Clean and dry 5N and above high-purity metal electrolytic plates.

[0060] (2) Move the original 200mm diameter metal bottom ingot in the electron beam furnace up to be 5-10 cm higher than the top edge of the crystallizer.

[0061] (3) Uniformly stack high-purity metal electrolytic plates with a thickness of about 3 cm on the top of the bottom ingot. The stacking standard is to cover the ingot without exceeding the diameter of the ingot.

[0062] (4) Lower the ingot so that its top is about 2 cm away from the top edge of the crystallizer. Close the door and vacuum to ≤10 - 3 Pa.

[0063] (5) Use a 22Kw electron beam to scan the high-purity metal electrolytic plates on the bottom ingot to melt them, then stop scanning and close the melting system.

[0064] (6) Keep the vacuum in the furnace at 10 -3 Pa for 24 hours and then open the door.

[0065] (7) Move the cooled metal ingot up to be higher than the top edge of the crystallizer.

[0066] (8) Repeat steps 3-7 until the height of the metal ingot on the dummy ingot reaches 5.5 cm.

[0067] (9) Install the high-purity metal electrolytic plate or ingot as a high-purity metal raw material in the feeding device, and lower the dummy ingot to about 11 cm from the upper edge of the crystallizer, close the hatch, and vacuumize to ≤10 -3 Pa.

[0068] (10) Use a 100Kw electron beam to melt the high-purity metal dummy ingot and form a molten pool, and scan the high-purity metal raw material. The molten metal drips into the molten pool, and when the liquid level approaches the upper edge of the crystallizer, start the ingot pulling system to pull the dummy ingot at a certain speed and cool it. After the above process melts and casts a dense ingot about 5.5 cm high, i.e. the dense ingot formed on the bottom ingot is 11 cm high, stop feeding, close the electron beam scanning and ingot pulling operation, and keep vacuum cooling for 24 hours. The high-purity metal dummy ingot with high density and chemical purity meeting the requirements is prepared, the purity of the high-purity metal dummy ingot is greater than or equal to 5N, and the purity of the head of the high-purity metal dummy ingot is equivalent to that of the high-purity metal raw material.

[0069] Example 4

[0070] (1) Wash and dry the 5N and above high-purity metal electrolytic plate.

[0071] (2) Move the original 300mm diameter metal bottom ingot in the electron beam furnace to be 5-10 cm higher than the upper edge of the crystallizer.

[0072] (3) Uniformly stack high-purity metal electrolytic plates with a thickness of about 3 cm on the top of the bottom ingot, and the stacking standard is to cover the dummy ingot without exceeding the diameter of the dummy ingot.

[0073] (4) Lower the dummy ingot so that its upper end is about 2 cm from the upper edge of the crystallizer, close the hatch, and vacuumize to ≤10 - 3 Pa.

[0074] (5) Use a 30Kw electron beam to scan the high-purity metal electrolytic plate on the bottom ingot to melt it, then stop scanning and close the melting system.

[0075] (6) Keep the vacuum in the furnace at 10 -3 Pa for 24 hours and open the hatch.

[0076] (7) Move the cooled metal dummy ingot up to be higher than the upper edge of the crystallizer.

[0077] (8) Repeat steps 3-7 until the height of the metal ingot on the dummy ingot reaches 6.5 cm.

[0078] (9) high purity metal electrolytic plate or ingot is installed as high purity metal raw material in the feeding device, the dummy bar is lowered to about 13 cm from the upper edge of the crystallizer, the hatch is closed and vacuum is extracted to ≤10 -3 Pa.

[0079] (10) 140Kw electron beam is used to melt the high purity metal dummy bar and form a molten pool, and the high purity metal raw material is scanned, the molten metal is dropped into the molten pool, when the liquid level approaches the upper edge of the crystallizer, the ingot drawing system is started, the dummy bar is drawn at a certain speed, and after the above process is melted and cast to form a dense ingot about 6.5 cm high, i.e. the dense ingot formed by melting and casting on the bottom ingot is 13 cm high, the feeding is stopped, the electron beam scanning and ingot drawing operation are closed, and after 24 hours of vacuum cooling, the dense and chemically pure high purity metal dummy bar is prepared, the purity of the high purity metal dummy bar is greater than or equal to 5N, and the purity of the head of the high purity metal dummy bar is equivalent to that of the high purity metal raw material.

[0080] Example 5

[0081] (1) The 5N and above high purity metal electrolytic plate is cleaned and dried.

[0082] (2) The original diameter 400mm metal bottom ingot in the electron beam furnace is moved up and is 5-10cm higher than the upper edge of the crystallizer.

[0083] (3) The high purity metal electrolytic plate with a thickness of about 3cm is uniformly placed on the top of the bottom ingot, and the placement standard is to cover the dummy bar without exceeding the diameter of the dummy bar.

[0084] (4) The dummy bar is lowered and the upper end is about 2cm from the upper edge of the crystallizer, the hatch is closed and vacuum is extracted to ≤10 - 3 Pa.

[0085] (5) 39Kw electron beam is used to scan the high purity metal electrolytic plate on the bottom ingot, and after melting, the scanning is stopped and the melting system is closed.

[0086] (6) The vacuum in the furnace is maintained at 10 -3 Pa for 24h and the hatch is opened.

[0087] (7) The cooled metal dummy bar is moved up and is higher than the upper edge of the crystallizer.

[0088] (8) Steps 3-7 are repeated until the height of the metal ingot on the dummy bar reaches 5cm, and the above steps are stopped.

[0089] (9) high purity metal electrolytic plate or ingot is installed as high purity metal raw material in the feeding device, the dummy bar is lowered to about 13 cm from the upper edge of the crystallizer, the hatch is closed and vacuum is extracted to ≤10 -3 Pa.

[0090] (10) using 190Kw electron beam to melt high purity metal starter and form a molten pool, and scanning high purity metal raw material, molten metal drops into the molten pool, when the liquid level approaches the upper edge of the crystallizer, start the ingot drawing system, the starter is drawn down and cooled at a certain speed, after the above process of melting and casting forms a dense ingot about 5cm high, i.e. the height of the dense ingot formed by melting and casting on the bottom ingot is 10cm, the feeding can be stopped, the electron beam scanning and the ingot drawing operation are closed, and after 24 hours of vacuum cooling, the preparation of the dense high purity metal starter which meets the requirements of chemical purity is completed, the purity of the high purity metal starter is greater than or equal to 5N, and the purity of the head of the high purity metal starter is equivalent to that of the high purity metal raw material.

[0091] The above describes some exemplary embodiments of the present application, and it can be understood that the above embodiments are only used to explain the present application and do not constitute a limitation on the protection scope of the present application. The features in these embodiments can be recombined in a suitable manner, and the schemes obtained thereby are still within the protection scope required by the present application. Based on the above embodiments, all other embodiments obtained by those skilled in the art without creative labor, i.e. all modifications, equivalent replacements and improvements, etc. made within the spirit and principles of the present application, are within the protection scope required by the present application.

Claims

1. A method for preparing a low-impurity ingot, characterized in that: The following steps are involved: Step 1: Clean and dry the high-purity metal electrolytic plate; the purity of the high-purity metal is 5N or above; Step 2: Move the original metal bottom ingot in the electron beam furnace upward and above the upper edge of the crystallizer; Step 3: Evenly stack high-purity metal electrolytic plates on the top of the bottom ingot. The stacking standard is to cover the bottom ingot and not exceed its diameter. Step 4: Lower the ingot so that its upper end is lower than the upper edge of the crystallizer, close the hatch and evacuate to ≤10 -3 Pa; Step 5: Scanning the high-purity metal electrolytic plate on the bottom ingot with a low-power electron beam, stopping scanning immediately after the high-purity metal electrolytic plate is melted and shutting down the smelting system; the low power is no more than 40Kw; Step 6: Maintain the vacuum in the furnace ≤10 -3 Pa and cool for at least 24 hours before opening the hatch; Step 7: Move the cooled metal ingot up to the upper edge of the crystallizer; Step 8: Repeat steps 3 to 7 until the height of the metal ingot on the bottom ingot reaches more than 5 cm, then stop the above steps; Step 9: Install the high-purity metal raw material in the feeding device, and lower the ingot until its upper end is at least 10 cm below the upper edge of the crystallizer, close the hatch and evacuate to ≤10 -3 Pa; Step 10: Use a high-power electron beam of not less than 60Kw to melt the ingot and form a molten pool, and scan the high-purity metal raw material. The molten metal drips into the molten pool. When the liquid level approaches the upper edge of the crystallizer, start the ingot pulling system to pull the ingot down and cool it. After the height of the dense ingot cast on the bottom ingot in this step is at least twice that of the metal ingot described in step 8, turn off the electron beam scanning and ingot pulling operations, maintain vacuum cooling for at least 24 hours, and prepare a low-impurity high-purity metal ingot.

2. The method for preparing a low-impurity ingot according to claim 1, characterized in that: The thickness of the high-purity metal electrolytic plates stacked in step 3 is 3±0.1 cm.

3. The method for preparing a starter ingot with low impurity content according to claim 1, characterized in that: In step 4, the upper end of the dummy ingot is 2±0.1 cm lower than the upper edge of the crystallizer.

4. The method for preparing a starter ingot with low impurity content according to claim 1, characterized in that: The base ingot and the finally prepared low-impurity high-purity metal starter ingot have the same diameter, both of which are 80-400 mm.

5. The method for preparing a starter ingot with low impurity content according to claim 1, characterized in that: The scanning power range of the low-power electron beam in step 5 is 10-40Kw.

6. The method for preparing a starter ingot with low impurity content according to claim 1, characterized in that: In step 9, the distance between the upper end of the dummy ingot and the upper edge of the crystallizer is at least twice the height of the metal ingot on the bottom ingot in step 8.

7. The method for preparing a starter ingot with low impurity content according to claim 1, characterized in that: The scanning power range of the high-power electron beam in step 10 is 60-200Kw.