Purification method of high-temperature alloy powder return scrap

Abstract

The invention provides a method for purifying high-temperature alloy powder return scraps, which comprises the following steps: placing the high-temperature alloy powder return scraps at the bottom of a crucible, covering the powder with an alloy block with the same brand and the same size as the crucible, and refining by adopting an electron beam refining process to obtain a high-temperature alloy ingot. The method provided by the invention solves the problem that the high-temperature alloy powder return scrap, especially the coarse-particle-size powder return scrap, is difficult to directly remelt and purify, or the impurity content is high after remelting. By utilizing the characteristics of high temperature, high vacuum, cleanness and no pollution of the electron beam melting technology, O, N and other impurities in the high-temperature alloy powder return scrap are effectively removed.

Description

Technical Field

[0001] The present invention relates to the technical field of powder return material purification, and in particular to a method for purifying high-temperature alloy powder return material. Background Art

[0002] At present, the international mainstream aircraft engine turbine discs are all prepared by powder metallurgy. Compared with the traditional deformation process, the turbine discs produced by powder metallurgy have a series of advantages such as fine grains, good uniformity of structure and high strength. The preparation of powder high-temperature alloy turbine discs first adopts vacuum gas atomization, electrode induction gas atomization or plasma rotating electrode atomization to prepare high-temperature alloy powder, and then prepares the ingot through powder metallurgy process (such as hot pressing, hot isostatic pressing, forging). The maximum particle size of powder used in existing powder metallurgy turbine discs does not exceed 106μm, and the powder size used for important parts is even ≤45μm.

[0003] The particle size of powders prepared by argon atomization or plasma rotating electrode process is log-normally distributed, which makes the coarse-particle powder produced unusable, resulting in a decrease in the yield of finished powder by about 60%. With the development and application of advanced aero-engines in my country, the demand for high-temperature alloy powder is increasing, which also leads to a large amount of coarse-particle high-temperature alloy powder return materials being idle and wasted. How to achieve efficient reuse of high-temperature alloy powder return materials is a major problem that needs to be solved at present.

[0004] At present, the vacuum induction process is widely used in China to remelt the powder return material to achieve the reuse of the powder return material. This process is to add powder to the melt during the vacuum induction melting process, so that the powder gradually melts. Since the maximum temperature of the vacuum induction melting process is only 1600℃, the maximum vacuum degree during melting is 10 -1 Pa, so it is difficult to remove the N element and high melting point inclusions in the powder return material, resulting in a significant gap between the purity of the returned ingot and the purity of the new ingot, and it can only be downgraded for use. If the powder is smelted directly, there will be problems such as difficulty in melting and powder scattering causing damage to the vacuum system of the equipment. Chinese patent CN117583595A uses a cold isostatic pressing process to press the high-temperature alloy powder return material into blocks, and then uses a vacuum smelting process to smelt and prepare alloy ingots. This method is only applicable to powder return materials with smaller particle sizes. When the powder particle size is larger (the average particle size is greater than 70μm), it is difficult to press the powder return material into shape using the cold isostatic pressing process. Summary of the invention

[0005] According to the technical problems raised above, a purification method for high-temperature alloy powder return material is provided. The present invention does not need to pre-treat the high-temperature alloy powder return material before smelting. The high-temperature alloy powder return material is first placed at the bottom of the crucible, and then an alloy block of the same grade and size as the crucible is covered on top of the powder. At the same time, the high temperature, high vacuum and clean and pollution-free characteristics of electron beam refining are utilized to effectively remove impurities such as O and N in the high-temperature alloy powder return material.

[0006] The technical means adopted by the present invention are as follows:

[0007] A method for purifying high-temperature alloy powder return material, comprising:

[0008] Step 1: Processing the high-temperature alloy raw material of the same grade as the high-temperature alloy powder return material into an alloy block of a specific size, wherein the size of the alloy block is determined by the size and shape of the crucible;

[0009] Step 2, pretreatment: grinding the alloy block processed in step 1;

[0010] Step 3: Clean the sample: clean and dry the polished alloy block for later use;

[0011] Step 4: Clean the electron beam melting equipment: Grind and clean the crucible and furnace for electron beam melting;

[0012] Step 5. Place the raw materials: Pour the high-temperature alloy powder return material evenly into the crucible, then cover the alloy block on the high-temperature alloy powder return material, and close the furnace door after making sure it is ready;

[0013] Step 6: Turn on the electron beam melting equipment, preheat the diffusion pump, and evacuate the electron gun and the furnace to the target vacuum state;

[0014] Step 7: After the vacuum degree reaches the target state, turn on the electron gun filament for preheating;

[0015] Step 8: After preheating, turn on the electron gun high voltage, adjust the beam spot size and focusing current, start the spindle spinning mechanism, and increase the power to the melting power to melt the raw materials;

[0016] Step 9: After the raw materials are completely melted, the power is adjusted to the required refining power for refining, and the refining is immediately completed, and the high voltage of the electron gun is turned off to obtain an alloy ingot;

[0017] Step 10: Continue to cool the alloy ingot in the vacuum environment. After the alloy ingot is completely cooled, release the vacuum in the furnace and take out the alloy ingot.

[0018] Furthermore, the high-temperature alloy raw material is a nickel-based high-temperature alloy rod or ingot; the high-temperature alloy powder return material is a nickel-based high-temperature alloy powder return material, and its average particle size is >60μm.

[0019] Furthermore, when the alloy raw material is of inappropriate size or irregular shape, it is melted into a primary ingot using an electron beam in a crucible of the same size for use in powder melting.

[0020] Furthermore, in the step three, the polished alloy block is ultrasonically cleaned with deionized water and alcohol, and is cleaned three times with deionized water and alcohol respectively, and then dried for standby use.

[0021] Furthermore, in step 4, the crucible is a water-cooled copper crucible, and the cleaning method is: polish the inner wall, the bottom of the crucible and the furnace with sandpaper, wipe them with alcohol after polishing, and dry them.

[0022] Furthermore, in step 6, the preheating time of the diffusion pump is 30 min to 120 min, and the vacuum degree of the electron gun and the furnace body is required to be higher than 5×10 -3 Pa.

[0023] Furthermore, in step seven, the preheating time of the filament is 5 min to 20 min, the filament voltage is 80 V to 160 V, the filament current is 1 A to 5 A, the cathode voltage is 100 V to 400 V, and the cathode current is 5 A to 10 A.

[0024] Furthermore, in the step eight, the beam spot diameter is 5 mm to 20 mm, the rotation speed of the crucible is 1 rpm to 10 rpm; the melting power is 4 kW to 20 kW, and the melting time is 5 min to 30 min.

[0025] Furthermore, in step nine, the refining power is 6 kW to 30 kW, and the refining time is 10 min to 60 min.

[0026] Furthermore, in the step 10, the cooling time of the alloy ingot under vacuum state is more than 2 hours.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention uses alloy blocks of the same grade as the powder as the top covering layer to melt the high-temperature alloy powder return material, which will not change the chemical composition of the high-temperature alloy.

[0029] 2. The present invention does not require the high-temperature alloy powder return material to be pre-treated by adding a binder and cold isostatic pressing to press the powder return material into ingots before smelting.

[0030] 3. The present invention uses electron beam melting to refine the powder return material, and the vacuum degree during refining is less than 5×10 -3 Pa, the refining temperature is above 1600K, which can effectively remove impurities such as O and N in the powder return material.

[0031] Based on the above reasons, the present invention can be widely promoted in the field of powder return material purification and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 Flow chart of the purification method of the present invention.

[0034] Figure 2 This is a schematic diagram of the placement of alloy blocks and high-temperature alloy powder return materials in one embodiment of the present invention.

[0035] In the figure: 1. Crucible for electron beam melting; 2. Alloy block; 3. High-temperature alloy powder return material. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0040] The present invention provides a method for purifying high-temperature alloy powder return materials, firstly placing the high-temperature alloy powder return materials at the bottom of a crucible, then covering the powder with an alloy block of the same grade and size as the crucible, and then refining the powder using a specific electron beam refining process to obtain a high-temperature alloy ingot. The method of the present invention solves the problem that high-temperature alloy powder return materials, especially coarse-grained powder return materials, are difficult to directly remelt and purify, or have a high impurity content after remelting. By utilizing the high temperature, high vacuum, clean and pollution-free characteristics of electron beam melting technology, impurities such as O and N in high-temperature alloy powder return materials are effectively removed, wherein the O content can be reduced to below 6ppm, and the N content can be reduced to below 2ppm.

[0041] A method for purifying high-temperature alloy powder return material of the present invention specifically comprises the following steps:

[0042] Step 1: Process the nickel-based high-temperature alloy raw material of the same grade as the nickel-based high-temperature alloy powder return material 3 into an alloy block 2 of a specific size, the size of which is determined by the size and shape of the crucible; if the alloy raw material size is not appropriate or the shape is irregular, it can be melted into a primary ingot using an electron beam in a crucible of the same size for use in powder melting;

[0043] Step 2: Pretreatment: Grind the surface of the alloy block with an angle grinder to avoid introducing external contamination;

[0044] Step 3: Clean the sample: Use deionized water and alcohol to ultrasonically clean the polished alloy block for three times, and then dry it for later use.

[0045] Step 4. Clean the electron beam melting equipment: Grind and clean the water-cooled copper crucible (electron beam melting crucible 1) and the furnace for electron beam refining (grind the inner wall, bottom of the crucible and the furnace with sandpaper, wipe with alcohol and dry after grinding), ensure that the crucible is clean and pollution-free, clean the furnace body and furnace wall to avoid introducing external pollution.

[0046] Step 5. Place the raw materials: Pour the high-temperature alloy powder return material evenly into the polished and cleaned crucible, try to ensure that the surface is smooth, then cover the alloy block on the high-temperature alloy powder return material, make sure the furnace body is clean and close the furnace door.

[0047] Step 6: Turn on the electron beam melting equipment, preheat the diffusion pump, and pump the vacuum of the electron gun and the furnace to the target vacuum state. After the vacuum is pumped to the target vacuum state, turn on the electron gun filament for preheating. After the preheating is completed, turn on the high voltage, adjust the beam spot size and focusing current, turn on the ingot spinning mechanism, and increase the power to the melting power to melt the raw materials. After the raw materials are completely melted, increase the power to the target refining power, refine for a period of time at the refining power, turn off the high voltage after the refining is completed, obtain the alloy ingot, continue to keep the alloy ingot cooling in a vacuum environment, and after the alloy ingot is completely cooled, turn off the vacuum and take out the alloy ingot.

[0048] When implemented, the average particle size of the nickel-based high-temperature alloy powder return material is >60μm.

[0049] During implementation, in step six, the preheating time of the diffusion pump is 30 minutes to 120 minutes.

[0050] During implementation, in step 6, the vacuum degree of the electron gun and the furnace body is required to be higher than 5×10 -3 Pa.

[0051] During implementation, in step six, the preheating time of the filament is 5 minutes to 20 minutes, the filament voltage is 80V to 160V, the filament current is 1A to 5A, the cathode voltage is 100V to 400V, and the cathode current is 5A to 10A.

[0052] During implementation, in step six, the beam spot diameter is 5 mm to 20 mm.

[0053] During implementation, in step 6, the melting power is 4 kW to 20 kW, the melting time is 5 min to 30 min, the refining power is 6 kW to 30 kW, and the refining time is 10 min to 60 min.

[0054] During implementation, in step six, the cooling time of the alloy ingot under vacuum state is more than 2 hours.

[0055] During implementation, in step six, the rotation speed of the crucible is 1 rpm-10 rpm.

[0056] Example 1

[0057] The high-temperature alloy powder return material targeted by this embodiment has an average particle size of >60 μm, an O content of 51 ppm, and a N content of 4 ppm. The purification method of the high-temperature alloy powder return material is as follows:

[0058] Step 1: Place the irregularly shaped alloy block (weighing about 984g) after pretreatment in the electron beam melting crucible, make sure the furnace is clean and close the furnace door. Open the slide valve pump and start preheating the diffusion pump for 80 minutes. While preheating the diffusion pump, you can start the Roots pump, the electron gun mechanical pump and the molecular pump. After the diffusion pump is preheated, pump the furnace and the electron gun to the target vacuum state (higher than 5×10 -3 Pa). After the vacuum is drawn to the target state, turn on the filament for preheating. After preheating for 12 minutes, the cathode current rises to 7.8A. Turn on the high voltage, increase the power to 6kW, adjust the beam spot diameter to 15mm, focus I current to 100mA, and focus II current to 50mA. Turn on the ingot spinning mechanism and set the crucible speed to 3rpm. At the beginning of smelting, the beam spot is located in the center of the crucible. Observe the smelting situation from the observation window. Adjust the beam spot position to 1 / 2 of the crucible radius to evenly scan the sample surface. Smelt for 20 minutes, the alloy is completely melted, reduce the power to 0, turn off the high voltage and ingot spinning mechanism, continue to keep the alloy ingot cooling under vacuum for 2 hours, turn off the vacuum after cooling and solidification, and obtain a primary ingot with a diameter of 120mm and a height of about 10mm.

[0059] Step 2: Place 1000g of high-temperature alloy powder return material in the electron beam melting crucible, and then cover the above-mentioned primary ingot on the high-temperature alloy powder return material. After ensuring that the furnace body is clean, close the furnace door. Open the slide valve pump and start preheating the diffusion pump for 80 minutes. While preheating, you can start the Roots, electron gun mechanical pump and molecular pump. After the diffusion pump is preheated, pump the furnace body and electron gun vacuum to the target state (higher than 5×10 -3 Pa). After the vacuum is drawn to the target state, turn on the filament for preheating. Preheat for 15 minutes and the cathode current is increased to 8A. Turn on the high voltage, increase the power to 6kW, adjust the beam spot diameter to 15mm, focus I current to 100mA, and focus II current to 50mA. Turn on the spindle mechanism and set the crucible speed to 3rpm. At the beginning of smelting, the beam spot is located in the center of the crucible. Observe the smelting situation from the observation window. Adjust the beam spot position to 1 / 2 of the crucible radius to evenly scan the sample surface. Smelt for 20 minutes and the alloy is completely melted; increase the power to 8kW and refine for 15 minutes. After the refining is completed, turn off the high voltage and spindle mechanism, and continue to keep the alloy ingot cooling under vacuum for 2 hours. After cooling, turn off the vacuum and take out the alloy ingot.

[0060] Step 3: sampling the refined alloy ingot for O and N testing, wherein the O content is reduced to 6.29 ppm, and the N content is reduced to 1.63 ppm.

[0061] Example 2

[0062] The high-temperature alloy powder return material targeted by this embodiment has an average particle size of >60 μm, an O content of 51 ppm, and a N content of 4 ppm. The purification method of the high-temperature alloy powder return material is as follows:

[0063] Step 1: Place the irregularly shaped alloy block (weight about 991g) after pretreatment in the electron beam melting crucible, make sure the furnace is clean and close the furnace door. Open the slide valve pump and start preheating the diffusion pump for 90 minutes. While preheating the diffusion pump, you can start the Roots, electron gun mechanical pump and molecular pump. After the diffusion pump is preheated, pump the furnace and electron gun vacuum to the target state (higher than 5×10 -3 Pa). After the vacuum is drawn to the target state, turn on the filament for preheating. Preheat for 10 minutes and the cathode current is increased to 7A. Turn on the high voltage, increase the power to 6kW, the beam spot diameter is 15mm, the focusing I current is 100mA, and the focusing II current is 50mA. Turn on the ingot spinning mechanism and set the crucible speed to 3rpm. At the beginning of smelting, the beam spot is located in the center of the crucible. Observe the smelting situation from the observation window, adjust the beam spot position to 1 / 2 of the crucible radius and evenly scan the sample surface. Smelt for 20 minutes, the alloy is completely melted, reduce the power to 0, turn off the high voltage and ingot spinning mechanism, continue to keep the alloy ingot cooling under vacuum for 2 hours, turn off the vacuum after cooling, and obtain a primary ingot with a diameter of 120mm and a height of about 10mm.

[0064] Step 2: Place 1000g of high-temperature alloy powder return material in the electron beam melting crucible, make sure the furnace body is clean and close the furnace door. Open the slide valve pump and start preheating the diffusion pump for 80 minutes. While preheating the diffusion pump, you can start the Roots, electron gun mechanical pump and molecular pump. After the diffusion pump is preheated, pump the furnace body and electron gun vacuum to the target state (higher than 5×10 -3 Pa). Turn on the filament for preheating. Preheat for 15 minutes and the cathode current is increased to 8A. Turn on the high voltage and increase the power to 6kW. The beam spot diameter is 15mm, the focus I current is 100mA, and the focus II current is 50mA. Turn on the spindle mechanism and set the crucible speed to 3rpm. At the beginning of smelting, the beam spot is located in the center of the crucible. Observe the smelting situation from the observation window. Adjust the beam spot position to 1 / 2 of the crucible radius to evenly scan the sample surface. Smelt for 20 minutes. When the alloy is completely melted, increase the power to 8kW and refine for 30 minutes. After refining, turn off the high voltage and spindle mechanism. Continue to keep the alloy ingot cooling under vacuum for 2 hours. After cooling, turn off the vacuum and take out the alloy ingot.

[0065] Step 3: sampling the refined alloy ingot for O and N testing, wherein the O content is reduced to 4.2ppm, and the N content is reduced to 1.33ppm.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying high-temperature alloy powder return material, characterized in that: include: Step 1: Processing the high-temperature alloy raw material of the same grade as the high-temperature alloy powder return material into an alloy block of a specific size, wherein the size of the alloy block is determined by the size and shape of the crucible; Step 2, pretreatment: grinding the alloy block processed in step 1; Step 3: Clean the sample: clean and dry the polished alloy block for later use; Step 4: Clean the electron beam melting equipment: Grind and clean the crucible and furnace for electron beam melting; Step 5. Place the raw materials: Pour the high-temperature alloy powder return material evenly into the crucible, then cover the alloy block on the high-temperature alloy powder return material, and close the furnace door after making sure it is ready; Step 6: Turn on the electron beam melting equipment, preheat the diffusion pump, and evacuate the electron gun and the furnace to the target vacuum state; Step 7: After the vacuum degree reaches the target vacuum state, turn on the electron gun filament for preheating; Step 8: After preheating, turn on the electron gun high voltage, adjust the beam spot size and focusing current, start the spindle spinning mechanism, and increase the power to the melting power to melt the raw materials; Step 9: After the raw materials are completely melted, the power is adjusted to the required refining power for refining, and the refining is immediately completed, and the high voltage of the electron gun is turned off to obtain an alloy ingot; Step 10: Continue to cool the alloy ingot in the vacuum environment. After the alloy ingot is completely cooled, release the vacuum in the furnace and take out the alloy ingot.

2. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: The high-temperature alloy raw material is a nickel-based high-temperature alloy rod or ingot; the high-temperature alloy powder return material is a nickel-based high-temperature alloy powder return material, and its average particle size is >60μm.

3. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: When the alloy raw material is of unsuitable size or irregular shape, it is melted into a primary ingot using an electron beam in a crucible of the same size for use in powder melting.

4. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step three, the polished alloy block is ultrasonically cleaned with deionized water and alcohol, and is cleaned with deionized water and alcohol three times respectively. After cleaning, it is dried for standby use.

5. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step 4, the crucible is a water-cooled copper crucible, and the cleaning method is: polish the inner wall, the bottom of the crucible and the furnace with sandpaper, wipe them with alcohol after polishing, and dry them.

6. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In step 6, the preheating time of the diffusion pump is 30 min to 120 min, and the vacuum degree of the electron gun and the furnace body is required to be higher than 5×10 -3 Pa.

7. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step seven, the preheating time of the filament is 5 minutes to 20 minutes, the filament voltage is 80V to 160V, the filament current is 1A to 5A, the cathode voltage is 100V to 400V, and the cathode current is 5A to 10A.

8. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step eight, the beam spot diameter is 5 mm to 20 mm, the crucible rotation speed is 1 rpm to 10 rpm, the melting power is 4 kW to 20 kW, and the melting time is 5 min to 30 min.

9. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step nine, the refining power is 6 kW to 30 kW, and the refining time is 10 min to 60 min.

10. The method for purifying high temperature alloy powder return material according to claim 1, characterized in that: In the step 10, the cooling time of the alloy ingot under vacuum state is more than 2 hours.

Images