Rare earth metal target material and preparation method thereof

Abstract

The invention provides a rare earth metal target material and a preparation method thereof. The preparation method comprises the following steps: providing a rare earth metal base material; the rare earth metal base material is placed in an electron beam cold bed smelting furnace to be smelted, and rare earth metal melt is formed; and cooling the rare earth metal melt to obtain the rare earth metal target material, wherein in the smelting treatment, a furnace body of the electron beam cold hearth smelting furnace and an electron gun chamber are vacuumized to be smaller than or equal to 2.0 * 10 <-3 > Pa, and the temperature of the cooling treatment is 10-55 DEG C. The preparation method of the rare earth metal target material can effectively reduce the inclusion content in the rare earth metal target material, the product purity is high, the oxygen and carbon content is low, crystal grains are fine, and the surface is free of nodulation.

Description

Technical Field

[0001] The present application relates to the technical field of rare earth metal material preparation, and in particular to a rare earth metal target material and a preparation method thereof. Background Art

[0002] At present, the fields involved in rare earth targets include thin film deposition, optical coating, semiconductor materials, integrated circuits, control rods and fuel elements for the nuclear industry, electronics, aerospace, medical equipment and other special fields. Rare earth targets are a type of sputtering target with rare earth metals as the main component. They are of great significance in the development of the entire target industry chain and will have broad market value in the fields of precision electronics, high-end equipment, new materials and so on in the future.

[0003] Since rare earth metal targets are highly active, poorly processable, and difficult to process during the preparation process, target smelting in traditional technologies usually uses medium frequency furnace smelting or suspension furnace smelting, induction melting furnace smelting, and arc melting furnace smelting. After smelting, rare earth metal target blanks are obtained by casting or pulling ingots, and then rare earth targets are obtained by forging, rolling, and other processes. However, this method has a long processing process, low yield, low purity, and requires repeated refining during smelting, making it difficult to mass produce.

[0004] Therefore, the traditional technology still needs to be improved. Summary of the invention

[0005] Based on this, the present application provides a rare earth metal target material and a preparation method thereof. The preparation method of the rare earth metal target material can effectively reduce the inclusion content in the rare earth metal target material, and the product has high purity, low oxygen and carbon content, and small grains and no tumors on the surface.

[0006] The technical solution of this application to solve the above technical problems is as follows:

[0007] In one aspect of the present application, a method for preparing a rare earth metal target is provided, comprising the following steps:

[0008] Providing rare earth metal substrates;

[0009] Placing the rare earth metal substrate in an electron beam cold hearth melting furnace for melting treatment to form a rare earth metal melt;

[0010] Cooling the rare earth metal melt to obtain the rare earth metal target;

[0011] In the smelting process, the furnace body and the electron gun chamber of the electron beam cold hearth smelting furnace are evacuated to a vacuum of less than or equal to 2.0×10 -3 Pa, the temperature of the cooling treatment is 10°C~55°C.

[0012] In one embodiment, the furnace body of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 7.7×10 -4 Pa;

[0013] And / or, the electron gun chamber of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 8.4×10 -4 Pa.

[0014] In one embodiment, the average cooling rate of the cooling process is 15°C / min~50°C / min;

[0015] And / or, the cooling treatment time is 30min~60min.

[0016] In one embodiment, the rare earth metal substrate includes at least one of metal gadolinium, metal terbium, metal dysprosium, metal erbium, metal lutetium, metal scandium and metal yttrium.

[0017] In one embodiment, the smelting process satisfies at least one of the following characteristics:

[0018] (1) During the smelting process, the voltage of the electron gun is 20kV~22KV;

[0019] (2) During the smelting process, the current of the electron gun is 1A~2A;

[0020] (3) During the smelting process, the power of the electron gun is 20 kW to 44 kW.

[0021] In one of the embodiments, the plane scanning state of the electron beam during the smelting process includes a horizontal scanning distribution and a vertical scanning distribution;

[0022] Optionally, the current of the coil in the horizontal scan is: 0~320mA;

[0023] Optionally, the current of the coil in the vertical scanning is: 0~120mA.

[0024] In some of the embodiments, the temperature of the smelting treatment is 1000° C. to 1600° C., and the time of the smelting treatment is 20 min to 60 min.

[0025] In some of the embodiments, after the step of cooling the rare earth metal melt, the process further includes turning over the product after the cooling treatment, and repeating the smelting treatment and the cooling treatment steps.

[0026] In some of the embodiments, after the step of cooling the rare earth metal melt, the method further includes the steps of sequentially performing surface treatment and machining treatment on the product after the cooling treatment.

[0027] In the method for preparing the above-mentioned rare earth metal target material, the rare earth metal substrate is subjected to electron beam melting treatment, and the furnace vacuum degree of a specific electron beam cold bed melting furnace and the vacuum degree of an electron gun chamber are controlled to minimize the oxygen and carbon content of the metal target blank to form a rare earth metal melt; the rare earth metal melt is then cooled, wherein the rare earth metal melt is controlled to be cooled at a specific temperature to block the slow growth of the grains, thereby obtaining a target blank with fine grains and good surface quality, and obtaining a rare earth metal target material. In this way, the absolute purity of the rare earth target material can be higher, the non-rare earth impurity content and the oxygen and carbon content can be reduced, and the grains can be smaller.

[0028] Furthermore, the above preparation method does not require subsequent forging and rolling processes, and realizes short-process large-scale preparation technology. Compared with traditional processes, it can achieve the preparation of high-purity, large-size, short-process, and fine-grained rare earth metal targets.

[0029] One aspect of the present application provides a rare earth metal target material, wherein the rare earth metal target material is prepared by the method for preparing the rare earth metal target material as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a physical picture of the rare earth metal target material of Example 1;

[0031] Figure 2 This is a physical picture of the rare earth metal target prepared in Comparative Example 1. DETAILED DESCRIPTION

[0032] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] The term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "comprising one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements. The indefinite articles "a kind of" and "one" before the elements or components of the present application are not restrictive to the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "one" or "a kind of" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the number obviously refers only to the singular form. The meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] The weight of the relevant components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also indicate the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, at% in the specification of the present application is the atomic percentage, which indicates the ratio of the number of atoms of an element to the total number of atoms, i.e., the molar percentage; the weight described in the specification of the embodiments of the present application can be mass units known in the chemical industry such as μg, mg, g, kg, etc.

[0036] Except as shown in the operating examples or otherwise indicated, all numbers used in the specification and claims to indicate the amount of ingredients, physicochemical properties, etc. are understood to be adjusted by the term "about" in all cases. For example, therefore, unless otherwise indicated, the numerical parameters listed in the above specification and the attached claims are approximate values, and those skilled in the art can use the teachings disclosed herein to seek to obtain the desired properties and appropriately change these approximate values. The use of numerical ranges expressed as endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0037] An embodiment of the present application provides a method for preparing a rare earth metal target, comprising steps S10 to S30.

[0038] Step S10: providing a rare earth metal substrate.

[0039] Step S20: placing the rare earth metal substrate in an electron beam cold hearth melting furnace for melting treatment to form a rare earth metal melt.

[0040] Step S30: Cooling the rare earth metal melt to obtain the rare earth metal target; wherein, during the smelting process, the furnace body and the electron gun chamber of the electron beam cold hearth smelting furnace are evacuated to a vacuum of less than or equal to 2.0×10 -3 Pa, the temperature of the above cooling treatment is 10℃~55℃.

[0041] In the method for preparing the above-mentioned rare earth metal target material, the rare earth metal substrate is subjected to electron beam melting treatment, and the furnace body vacuum and electron gun chamber vacuum of a specific electron beam cold hearth melting furnace are controlled to minimize the oxygen and carbon content of the metal target blank to form a rare earth metal melt; the rare earth metal melt is then cooled, wherein the rare earth metal melt is controlled to be cooled at a specific temperature to block the slow growth of the grains, thereby obtaining a target blank with fine grains and good surface quality, and obtaining a rare earth metal target material. In this way, the absolute purity of the rare earth target material can be higher, the non-rare earth impurity content and the oxygen and carbon content can be reduced, and the grains can be smaller.

[0042] Furthermore, the above preparation method does not require subsequent forging and rolling processes, and realizes short-process large-scale preparation technology. Compared with traditional processes, it can achieve the preparation of high-purity, large-size, short-process, and fine-grained rare earth metal targets.

[0043] It is understood that when a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0044] It should be noted that the temperature of the above cooling treatment is "10°C~55°C", that is, the minimum and maximum values ​​of the range of 10°C~55°C, and each value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C. Or a range consisting of any two of these values, for example, includes 10°C to 50°C.

[0045] In some embodiments, the furnace body of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 7.7×10 -4 Pa.

[0046] It is understandable that different materials have different requirements for the vacuum environment during the smelting process due to their own physical and chemical properties. In the smelting production of rare earth metal materials, a specific vacuum environment standard is usually set to ensure the stability of smelting quality and product performance. The smelting operation will only begin when the vacuum environment in the production equipment reaches this pre-set standard value. This is because a suitable vacuum environment can reduce the reaction between the molten metal and the gas, reduce the gas content in the molten metal, and avoid defects such as pores; it also helps to remove volatile impurities in the material and improve the purity of the material. If smelting begins when the vacuum environment does not meet the requirements, it may result in poor quality and unstable performance of the smelted material, affecting the final quality and performance of the product.

[0047] In some embodiments, the electron gun chamber of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 8.4×10 -4 Pa.

[0048] It can be understood that in the above-mentioned smelting process, due to the strong activity of rare earths and their easy reaction with oxygen, etc., it is necessary to carry out smelting in a higher vacuum environment to improve the quality of the entire smelting environment, control the furnace body and electron gun chamber of the electron beam cold hearth melting furnace within the above-mentioned specific vacuum range, and reduce the oxygen and carbon content of the metal target blank to the greatest extent. At the same time, combined with the characteristics of the electron beam cold hearth melting furnace, it has the effect of purifying, cleaning and controlling nitrogen, oxygen and carbon gas impurities, which can further improve the quality of the target material.

[0049] In some of the embodiments, the average cooling rate of the cooling treatment is 15°C / min to 55°C / min.

[0050] In some of the embodiments, the cooling treatment time is 30 min to 60 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min or 60 min. In some examples, it can be within the range formed by any two of these point values ​​as end values, the same below.

[0051] In some embodiments, the rare earth metal substrate includes at least one of metal gadolinium, metal terbium, metal dysprosium, metal erbium, metal lutetium, metal scandium and metal yttrium.

[0052] In some of the embodiments, the purity of the raw materials of the rare earth metal substrate is ≥99.9%, wherein the non-rare earth impurities are: Fe≤0.050%, Si≤0.010%, Ca≤0.080%, Ni≤0.010%; wherein the gas impurities are: O≤0.20%, C≤0.020%.

[0053] In some of the embodiments, during the above-mentioned smelting process, the voltage of the electron gun is 20 kV~22 KV, for example, it can be 20.0 kV, 20.1 kV, 20.2 kV, 20.3 kV, 20.4 kV, 20.5 kV, 20.6 kV, 20.7 kV, 20.8 kV, 20.9 kV, 21.0 kV, 21.1 kV, 21.2 kV, 21.3 kV, 21.4 kV, 21.5 kV, 21.6 kV, 21.7 kV, 21.8 kV, 21.9 kV or 22.0 kV.

[0054] In some embodiments, during the above smelting process, the current of the electron gun is 1 A to 2 A, for example, it can be 1.0 A, 1.1 A, 1.2 A, 1.3 A, 1.4 A, 1.5 A, 1.6 A, 1.7 A, 1.8 A, 1.9 A or 2.0 A.

[0055] In some of the embodiments, during the above-mentioned smelting process, the power of the electron gun is 20 kW~44 kW, for example, it can be 20 kW, 21 kW, 22 kW, 23 kW, 24 kW, 25 kW, 26 kW, 27 kW, 28 kW, 29 kW, 30 kW, 31 kW, 32 kW, 33 kW, 34 kW, 35 kW, 36 kW, 37 kW, 38 kW, 39 kW, 40 kW, 41 kW, 42 kW, 43 kW or 44 kW.

[0056] It can be understood that by regulating the above-mentioned voltage, current and power, the energy output of the electron beam can be accurately controlled, and then the melting speed, temperature and melting area of ​​the rare earth metal can be accurately controlled, which is conducive to achieving fine control of the rare earth metal smelting process and improving the consistency and stability of product quality.

[0057] In some of the embodiments, during the smelting process, the planar scanning state of the electron beam during the smelting process includes a horizontal scanning distribution and a vertical scanning distribution.

[0058] In some of these embodiments, the horizontal scanning mode and the vertical scanning mode are described above.

[0059] It can be understood that the above-mentioned alternating horizontal distribution scanning and vertical distribution scanning is one periodic scanning, and the number of periodic scanning can be multiple times, such as two or three times.

[0060] In some of the embodiments, the current of the coil in the horizontal scanning mode is 0-320 mA.

[0061] In some of the embodiments, the current of the coil in the vertical scanning mode is 0-120 mA.

[0062] It can be understood that through this horizontal and vertical scanning, the electron beam can act evenly on the surface of the rare earth metal target blank, avoiding local overheating or uneven melting, ensuring that the entire target blank can be fully and evenly melted, and improving the quality and performance uniformity of the target blank.

[0063] In some embodiments, the temperature of the smelting treatment is 1000° C. to 1600° C., and the time of the smelting treatment is 20 min to 60 min.

[0064] In some of the embodiments, after the step of cooling the rare earth metal melt, the process further includes turning over the product after the cooling process, and repeating the smelting process and the cooling process.

[0065] It can be understood that by smelting the other side of the rare earth metal target blank according to the same principle, it can ensure that the quality and performance of both sides of the entire rare earth metal target blank are consistent, meeting the requirements for the overall quality of the target blank in practical applications.

[0066] In some embodiments, the cooling process is performed in a water-cooled copper crucible crystallizer.

[0067] In some of the embodiments, the size of the water-cooled copper crucible crystallizer can be designed according to requirements, and its shape can be square or round.

[0068] In some of the embodiments, after the step of cooling the rare earth metal melt, the method further includes the steps of sequentially performing surface treatment and machining treatment on the product after the cooling treatment.

[0069] In some of the embodiments, a vertical milling machine is used to perform surface treatment on the product after the cooling treatment, and the accuracy tolerance of the milling machine is controlled to be ±0.05 mm.

[0070] In some of the embodiments, the machining process is performed to obtain a rare earth metal target of a desired size, and the machining accuracy is controlled within ±0.01 mm.

[0071] In some of the embodiments, the purity of the rare earth target material is ≥99.9%; the non-rare earth impurities are: Fe≤0.015%, Si≤0.0028%, Ca≤0.0048%, Ni≤0.0041%; and the gas impurities are O≤0.0033%, C≤0.022%.

[0072] An embodiment of the present application further provides a rare earth metal target material, which is prepared by the above-mentioned method for preparing the rare earth metal target material.

[0073] The rare earth metal target material prepared by the preparation method has low inclusion content, high purity, low oxygen and carbon content, fine grains and no tumor on the surface.

[0074] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, technical personnel in the field should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0075] Example 1

[0076] (1) Providing rare earth metal substrate: Prepare 19.51 kg of metallic yttrium with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into 1-2 mm blocks.

[0077] (2) Place the cut yttrium metal raw material in a φ350 mm crucible in an electron beam cold-bed melting furnace. The water-cooled copper crucible is 10 mm thick. Start the cooling water pump and evacuate the furnace body of the melting equipment to a vacuum of ≤7.5×10 -4 Pa; gun vacuum ≤ 2.0×10 -3 Pa; after the vacuum meets the smelting requirements, adjust the high voltage voltage of the electron beam gun in the smelting chamber to 22 KV; the high voltage current is adjusted to 2 A; the electron gun power is adjusted to: 44 kW; set the current of the coil in the horizontal scanning mode to: 320 mA; the current of the coil in the vertical scanning mode is: 120 mA, and the material is scanned horizontally and vertically by adjusting the speed of the electron gun stepper motor, and the temperature zone formed between the electron gun and the material is observed through the observation hole. The temperature is monitored by an infrared thermometer and the smelting temperature is controlled at 1400℃~1600℃. After smelting for 25 minutes, stop smelting; after one side is smelted, re-smelt the other side according to the above method.

[0078] (3) After both sides are melted, they are cooled in a water-cooled copper crucible. The cooling temperature of the water-cooled copper crucible is monitored by a thermometer and the water temperature is controlled at 35°C by the water flow rate. The average cooling rate is 24.8°C / min. After cooling for 1 hour, the metal yttrium target blank can be taken out. The obtained metal yttrium target blank is surface treated by a milling machine and then machined using machining equipment to obtain a metal yttrium target of the required size and smooth surface.

[0079] Example 2

[0080] (1) Providing rare earth metal substrate: Prepare 18.76 kg of scandium metal with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into 1-4 mm blocks.

[0081] (2) Place the cut scandium metal raw material in a φ350 mm crucible in an electron beam cold-bed melting furnace. The water-cooled copper crucible is 10 mm thick. Start the cooling water pump and evacuate the furnace body of the melting equipment to a vacuum of ≤7.8×10 -4 Pa; the gun vacuum is evacuated to ≤1.5×10 -3 Pa; after the vacuum meets the smelting requirements, adjust the high voltage voltage of the electron beam gun in the smelting chamber to 10 KV; the high voltage current is adjusted to 1.6 A; the electron gun power is adjusted to 16 kW; the current of the coil in the horizontal scanning mode is set to 320 mA; the current of the coil in the vertical scanning mode is set to 60 mA, and the material is scanned horizontally and vertically by adjusting the speed of the electron gun stepper motor, and the temperature zone formed between the electron gun and the material is observed through the observation hole. The temperature is monitored by an infrared thermometer and the smelting temperature is controlled at 1450℃~1550℃. After smelting for 20 minutes, stop smelting; after one side is smelted, re-smelt the other side according to the above method.

[0082] (3) After both sides are melted, they are cooled in a water-cooled copper crucible. The cooling temperature of the water-cooled copper crucible is monitored by a thermometer and controlled at 37°C by the water flow rate. The average cooling rate is 25°C / min. After cooling for 1 hour, the metal scandium target blank can be taken out. The obtained metal scandium target blank is surface treated by a milling machine and then machined using machining equipment to obtain a metal scandium target of the required size and smooth surface.

[0083] Example 3

[0084] (1) Providing rare earth metal substrate: Prepare 10.275 kg of metallic erbium with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into blocks of 1-6 mm.

[0085] (2) Place the cut erbium metal raw material in a φ350mm crucible in an electron beam cold-bed melting furnace. The water-cooled copper crucible is 10mm thick. Start the cooling water pump and evacuate the furnace body of the melting equipment to a vacuum of ≤9.0×10 -4 Pa; the gun vacuum is evacuated to ≤1.5×10 -3 Pa; after the vacuum meets the smelting requirements, adjust the high voltage voltage of the electron beam gun in the smelting chamber to 9.8 KV; the high voltage current is adjusted to 1.6 A; the electron gun power is adjusted to 15.68 kW; set the current of the coil in the horizontal scanning mode to 80 mA; the current of the coil in the vertical scanning mode is 60 mA, and the material is scanned horizontally and vertically by adjusting the speed of the electron gun stepper motor, and the temperature zone formed between the electron gun and the material is observed through the observation hole. The temperature is monitored by an infrared thermometer and the smelting temperature is controlled at 1500℃~1600℃. After smelting for 18 minutes, stop smelting; after one side is smelted, re-smelt the other side according to the above method.

[0086] (3) After both sides are melted, they are cooled in a water-cooled copper crucible. The cooling temperature of the water-cooled copper crucible is monitored by a thermometer and the water temperature is controlled at 32°C by the water flow rate. The average cooling rate is 23°C / min. After cooling for 1 hour, the metal erbium target blank can be taken out. The obtained metal erbium target blank is surface treated by a milling machine and then machined using machining equipment to obtain a metal erbium target of the required size and smooth surface.

[0087] Comparative Example 1

[0088] This comparative example is based on the comparison between Implementation Example 1 and Implementation Example 4 of the existing preparation method using a medium frequency induction melting furnace.

[0089] (1) Providing rare earth metal substrate: Take 19.51 kg of metallic yttrium with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into 1-2 mm blocks.

[0090] (2) Place the cut yttrium metal raw material in a 15 kg medium frequency induction melting furnace tungsten crucible with a diameter of 240 mm and a height of 380 mm. Prepare a rectangular cast iron mold with a width of 250 mm and a length of 400 mm for casting after smelting. Start the cooling water pump, start the mechanical pump and valve, start the molecular pump, and when the molecular pump R: 21000r, start the molecular pump valve until the vacuum reaches ≤3×10 -3Pa, close the vacuum valve and vacuum system, use 99.999% high-purity argon to fill the furnace with argon, and when the rough vacuum reaches 0.04 Mpa, increase the power from 10kw to 40kw in a step-by-step manner, and heat for 30-40min. Observe the melt surface through the observation hole, it is bright and luminous, and there is no visible gray gas volatilization. Use an infrared electron gun to measure the temperature, and control the temperature at 1400℃~1600℃. After keeping warm for 10 min, stop heating.

[0091] (3) Casting into the prepared cast iron mold, cooling for 1 hour, and then machining the metal yttrium ingot target blank to obtain the metal yttrium target of the required size.

[0092] Comparative Example 2

[0093] Comparative Example 2 is substantially the same as Example 1, except that the furnace body and the electron gun chamber of the electron beam cold hearth melting furnace are evacuated differently during the smelting process, as follows:

[0094] (1) Providing rare earth metal substrate: Prepare 19.51 kg of metallic yttrium with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into 1-2 mm blocks.

[0095] (2) Place the cut yttrium metal raw material in a φ350 mm crucible in an electron beam cold-bed melting furnace. The thickness of the crucible is 10 mm. Start the cooling water pump and evacuate the furnace body of the melting equipment to a vacuum of ≤5.0X10 -3 Pa; gun vacuum ≤5.8×10 -2 Pa; after the vacuum meets the smelting requirements, adjust the high voltage voltage of the electron beam gun in the smelting chamber to 22 KV; the high voltage current is adjusted to 2 A; the electron gun power is adjusted to: 44 kW; set the current of the coil in the horizontal scanning mode to: 320 mA; the current of the coil in the vertical scanning mode is: 120 mA, and the material is scanned horizontally and vertically by adjusting the speed of the electron gun stepper motor, and the temperature zone formed between the electron gun and the material is observed through the observation hole. The temperature is monitored by an infrared thermometer and the smelting temperature is controlled at 1400℃~1600℃. After smelting for 25 minutes, stop smelting; after one side is smelted, re-smelt the other side according to the above method.

[0096] (3) After both sides are melted, they are cooled in a water-cooled copper crucible. The cooling temperature of the water-cooled copper crucible is monitored by a thermometer and the water temperature is controlled at 35°C by the water flow rate. The average cooling rate is 24.8°C / min. After cooling for 1 hour, the metal yttrium target blank can be taken out. The obtained metal yttrium target blank is surface treated by a milling machine and then machined using machining equipment to obtain a metal yttrium target of the required size and smooth surface.

[0097] Comparative Example 3

[0098] Comparative Example 3 is substantially the same as Example 1, except that the temperature of the cooling treatment is different, as follows:

[0099] (1) Providing rare earth metal substrate: Prepare 19.51 kg of metallic yttrium with a purity of ≥99.9%. After weighing it using an electronic scale, use a vertical extruder equipped with a non-standard tool mold to shear the raw material into 1-2 mm blocks.

[0100] (2) Place the cut yttrium metal raw material in a φ350 mm crucible in an electron beam cold-bed melting furnace. The water-cooled copper crucible is 10 mm thick. Start the cooling water pump and evacuate the furnace body of the melting equipment to a vacuum of ≤7.5×10 -4 Pa; gun vacuum ≤ 2.0×10 -3 Pa; after the vacuum meets the smelting requirements, adjust the high voltage voltage of the electron beam gun in the smelting chamber to 22 KV; the high voltage current is adjusted to 2 A; the electron gun power is adjusted to: 44 kW; set the current of the coil in the horizontal scanning mode to: 320 mA; the current of the coil in the vertical scanning mode is: 120 mA, and the material is scanned horizontally and vertically by adjusting the speed of the electron gun stepper motor, and the temperature zone formed between the electron gun and the material is observed through the observation hole. The temperature is monitored by an infrared thermometer and the smelting temperature is controlled at 1400℃~1600℃. After smelting for 25 minutes, stop smelting; after one side is smelted, re-smelt the other side according to the above method.

[0101] (3) After both sides are melted, they are cooled in a water-cooled copper crucible. The cooling temperature of the water-cooled copper crucible is monitored by a thermometer and the water temperature is controlled at 65°C by the water flow rate. The average cooling rate is 24.3°C / min. After cooling for 1 hour, the metal yttrium target blank can be taken out. The obtained metal yttrium target blank is surface treated by a milling machine and then machined using machining equipment to obtain a metal yttrium target of the required size and smooth surface.

[0102] test:

[0103] 1. Observe the surface quality of the rare earth metal targets prepared in the examples and comparative examples.

[0104] 2. The impurity content of the rare earth metal target materials prepared in the embodiments and comparative examples is detected. Specifically, the ICP method is used to detect the non-rare earth metals in the rare earth metal targets prepared in the above embodiments and comparative examples; the oxygen and nitrogen gas elements in the rare earth are analyzed and detected by an oxygen, nitrogen and hydrogen analyzer; the carbon gas element in the rare earth is detected by a carbon and sulfur analyzer; and the proportion of the target rare earth metal to the total amount and distribution content of all rare earth metals is detected; the diameter size of the rare earth metal target materials prepared in the above embodiments is detected using a calibrated vernier caliper; and the grain size is detected using the naked eye or metallographic microscopy method.

[0105] Table 1 Chemical element composition analysis results of the embodiments and comparative examples (%)

[0106]

[0107] The traditional smelting process uses a medium frequency furnace induction melting furnace or a suspension melting furnace, and the vacuum degree is low, resulting in a high content of gas impurities. Repeated refining is required to obtain the best purity of the metal yttrium target blank, but repeated refining can easily lead to the volatilization of raw materials, seriously affecting the yield. During casting, due to the influence of thermodynamics and kinetics, the casting in the cast iron cools slowly, resulting in the slow growth of the grains, which is prone to serious cold shut. After machining, the ingot under casting has large grains visible to the naked eye, and unreasonable pouring ports or casting methods will lead to metal tumors. Only through forging and hot / cold rolling can the problem of coarse grains be solved. In view of the single deformation of rare earth materials during hot / cold rolling processing of about 5-7%, only through multiple processing and more than 50% of the total deformation can the coarse grains be solved. During cold processing, due to work hardening, annealing is required between passes, which prolongs the entire metal yttrium target processing process, and the purity of the metal yttrium is reduced under the long process flow.

[0108] The present application adopts electron beam cold bed melting furnace combined with water-cooled copper crucible melting, and the metal yttrium target blank obtained after cooling for 1 hour is machined, such as Figure 1 As shown, no obvious grains can be seen on the surface with the naked eye, and the surface quality is better than the target blank cast by traditional medium frequency furnace melting cast iron. Large-sized metal targets can be prepared according to different crucibles. Figure 2 The metal yttrium target material prepared in Comparative Example 1 has large grains visible to the naked eye after machining in the metal yttrium target blank prepared in a medium frequency induction melting furnace. Experiments on target ingots in water-cooled crucibles at different cooling temperatures in Example 1 and Comparative Example 3 show that excessively high water temperature will cause the grains to grow finely and also produce grains visible to the naked eye.

[0109] In summary, the rare earth metal target material prepared in the embodiment of the present application has high purity, low non-rare earth impurity content and low oxygen and carbon content, and small grains.

[0110] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be based on the attached claims.

Claims

1. A method for preparing a rare earth metal target, characterized in that: The steps include: Providing rare earth metal substrates; Placing the rare earth metal substrate in an electron beam cold hearth melting furnace for melting treatment to form a rare earth metal melt; Cooling the rare earth metal melt to obtain the rare earth metal target; In the smelting process, the furnace body and the electron gun chamber of the electron beam cold hearth smelting furnace are evacuated to a vacuum of less than or equal to 2.0×10 -3 Pa, the temperature of the cooling treatment is 10°C~55°C.

2. The method for preparing a rare earth metal target according to claim 1, characterized in that: The furnace body of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 7.7×10 -4 Pa; And / or, the electron gun chamber of the electron beam cold hearth melting furnace is evacuated to a vacuum less than or equal to 8.4×10 -4 Pa.

3. The method for preparing a rare earth metal target according to claim 1, characterized in that: The average cooling rate of the cooling treatment is 15°C / min~50°C / min; And / or, the cooling treatment time is 30 min to 60 min.

4. The method for preparing a rare earth metal target according to claim 1, characterized in that: The rare earth metal substrate includes at least one of metal gadolinium, metal terbium, metal dysprosium, metal erbium, metal lutetium, metal scandium and metal yttrium.

5. The method for preparing a rare earth metal target according to any one of claims 1 to 4, characterized in that: The smelting process satisfies at least one of the following characteristics: (1) During the smelting process, the voltage of the electron gun is 20 kV~22 KV; (2) During the smelting process, the current of the electron gun is 1 A to 2 A; (3) During the smelting process, the power of the electron gun is 20 kW to 44 kW.

6. The method for preparing a rare earth metal target according to claim 5, characterized in that: The plane scanning state of the electron beam during the smelting process includes a horizontal scanning distribution and a vertical scanning distribution; Optionally, the current of the coil in the horizontal scan is: 0~320 mA; Optionally, the current of the coil in the vertical scanning is: 0~120 mA.

7. The method for preparing a rare earth metal target according to any one of claims 1 to 4 and 6, characterized in that: The temperature of the smelting treatment is 1000° C. to 1600° C., and the time of the smelting treatment is 20 min to 60 min.

8. The method for preparing a rare earth metal target according to any one of claims 1 to 4 and 6, characterized in that: After the step of cooling the rare earth metal melt, the method further includes turning over the product after the cooling treatment, and repeating the smelting treatment and the cooling treatment steps.

9. The method for preparing a rare earth metal target according to any one of claims 1 to 4 and 6, characterized in that: After the step of cooling the rare earth metal melt, the method further includes the steps of sequentially performing surface treatment and machining treatment on the product after the cooling treatment.

10. A rare earth metal target, characterized in that: The rare earth metal target is prepared by the method for preparing the rare earth metal target as described in any one of claims 1 to 9.

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