Preparation method of low-carbon high-purity niobium cast ingot

Abstract

The invention relates to the technical field of high-purity metal, and provides a preparation method of a low-carbon high-purity niobium cast ingot. The preparation method comprises the following steps: sintering niobium oxide powder into blocks, heating and melting the blocks, carrying out gas atomization treatment on the melted niobium oxide by using oxygen as a powder spraying medium to obtain carbon-removed niobium oxide powder with high purity and good fluidity, and preparing the carbon-removed niobium oxide powder with high purity and good fluidity by using the carbon-removed niobium oxide powder as a raw material. The low-carbon high-purity niobium cast ingot is prepared by combining vacuum aluminothermic reduction and electron beam melting, so that the residual resistivity of the low-carbon high-purity niobium cast ingot can be effectively improved, and the unit consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity metal preparation, and in particular to a method for preparing a low-carbon high-purity niobium ingot. Background Art

[0002] Superconducting radio frequency (SRF) technology is one of the core supporting technologies for advanced scientific research platforms such as high-energy particle accelerators, free electron laser devices, and nuclear physics experiments. Its operating principle is to leverage the zero-resistance properties of superconducting materials at extremely low temperatures (typically around 2 Kelvin) to establish a high-intensity radio frequency electromagnetic field within a metal cavity, enabling contactless acceleration of high-energy particles. To achieve high acceleration gradients and ultra-high quality factors (Q values), the metal materials used in RF superconducting cavities must possess exceptional electrical, magnetic, and mechanical properties. Niobium (Nb), due to its high superconducting critical temperature (9.25 K), excellent electrical conductivity, moderate mechanical strength, and excellent machinability, is currently the only pure metal material widely used in the manufacture of RF superconducting cavities, holding an irreplaceable position.

[0003] The key to high-purity niobium materials for RF superconductors lies in their extremely high purity requirements and strict control of impurity elements. The residual resistivity (RRR) is typically required to be no less than 300, with high-quality products reaching over 400. This means that impurity levels in the material must be kept to extremely low levels, such as oxygen, nitrogen, and carbon below 20 ppm, and hydrogen below 10 ppm. Metallic impurities such as iron, tantalum, and titanium must also be strictly controlled. These impurities can cause superconducting performance degradation, increase resistance, enhance magnetic flux penetration, and even lead to the "Q disease" effect, seriously affecting the acceleration efficiency and stability of the RF superconducting cavity. Therefore, the preparation of high-purity niobium, from raw material selection and reduction to subsequent purification, must be carried out under highly clean and controlled conditions to ensure that the final product meets the stringent purity requirements for superconducting materials.

[0004] Currently, high-purity niobium is typically produced from niobium oxide using vacuum aluminothermic reduction to produce an aluminum-niobium alloy. This alloy is then purified through multiple electron beam melting (EBM) cycles to produce high-purity niobium ingots. The EBM process involves heating the niobium ingot with a directed electron beam under ultra-high vacuum conditions to effectively evaporate and remove high-vapor-pressure impurities (such as oxygen, nitrogen, and hydrogen). This process is the most critical step in improving RRR values. While EBM is highly effective at removing gaseous impurities such as oxygen, nitrogen, and hydrogen, as well as low-melting-point metals, its ability to remove carbon, which significantly impacts RRR values, is very limited. Furthermore, niobium is lost due to evaporation during the EBM process. Removing carbon by increasing the number of EBM cycles increases the unit cost of producing high-purity niobium ingots, resulting in higher costs.

[0005] Niobium oxide is the primary raw material for producing high-purity niobium ingots. Due to the characteristics of the wet process for producing niobium oxide, the carbon content cannot be kept low, making it difficult to remove the carbon after the niobium ingots are produced. Therefore, removing carbon from the niobium oxide raw material used in producing high-purity niobium ingots and reducing the carbon content at the raw material end is an urgent problem in the field. Summary of the Invention

[0006] In light of this, the present invention provides a method for preparing a low-carbon, high-purity niobium ingot. This method efficiently removes carbon from niobium oxide powder, producing a decarbonized niobium oxide powder with high purity and good fluidity. Using this decarbonized niobium oxide powder as a raw material, a low-carbon, high-purity niobium ingot with a high RRR value can be produced.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A method for preparing a low-carbon, high-purity niobium ingot comprises the following steps: Sintering niobium oxide powder in an oxygen atmosphere to obtain a niobium oxide sintered block; heating and melting the niobium oxide sintered block in an oxygen atmosphere to obtain a niobium oxide melt; Using oxygen as a powder spraying medium, the niobium oxide melt is subjected to gas atomization treatment to obtain carbon-removed niobium oxide powder; performing vacuum aluminothermic reduction on the decarbonized niobium oxide powder and aluminum particles to obtain an aluminum-niobium alloy; The aluminum-niobium alloy is electron beam melted to obtain a low-carbon high-purity niobium ingot; the low-carbon high-purity niobium ingot has a carbon content of ≤0.0004wt% and a purity of ≥99.99%.

[0008] Preferably, the chemical composition of the niobium oxide powder includes: Nb2O5≥99.7wt%, Ta≤0.005wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%, and C≤0.003wt%.

[0009] Preferably, the bulk density of the niobium oxide powder is ≥0.65 g / cm 3 .

[0010] Preferably, the sintering temperature is 1350-1400° C., and the sintering time is 1.5-2.5 hours; the material of the mold used for sintering is magnesia brick or corundum brick.

[0011] Preferably, the size of the niobium oxide sintered block is 30-100 mm×30-100 mm×30-100 mm.

[0012] Preferably, the heating and melting method is heating in a high-temperature resistance furnace, and the heating and melting temperature is 1550-1650°C.

[0013] Preferably, the conditions of the gas atomization treatment include: an oxygen pressure of 0.5-1.5 MPa, and a flow rate of the niobium oxide melt of 0.35-0.8 L / min.

[0014] Preferably, the purity of the oxygen used in the sintering, heating melting and gas atomization treatment is 90-94%.

[0015] Preferably, the chemical composition of the aluminum particles includes: Ta≤0.003wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%, C≤0.002wt%, and Al≥99.9wt%.

[0016] Preferably, the electron beam melting is performed 4 to 5 times, and the melting rate of each time is 25 to 30 kg / h.

[0017] The present invention provides a method for preparing a low-carbon, high-purity niobium ingot, comprising the following steps: sintering niobium oxide powder in an oxygen atmosphere to obtain a niobium oxide sintered block; heating and melting the niobium oxide sintered block in an oxygen atmosphere to obtain a niobium oxide melt; atomizing the niobium oxide melt using oxygen as a powder spraying medium to obtain decarbonized niobium oxide powder; performing vacuum aluminothermic reduction on the decarbonized niobium oxide powder and aluminum particles to obtain an aluminum-niobium alloy; and electron beam melting the aluminum-niobium alloy to obtain a low-carbon, high-purity niobium ingot. The low-carbon, high-purity niobium ingot has a carbon content of ≤0.0004wt% and a purity of ≥99.99%. The present invention sintered niobium oxide powder into blocks and then heated and melted the blocks, removing carbon from the niobium oxide by oxidizing the carbon at high temperature, thereby improving the purity of the niobium oxide powder. In addition, the present invention uses oxygen as a powder spraying medium to perform a gas atomization treatment on the melted niobium oxide, thereby obtaining decarbonized niobium oxide powder with good fluidity. The carbon content of the niobium oxide powder treated by the method of the present invention is significantly reduced, and the fluidity is greatly improved. The decarbonized niobium oxide powder is used as a raw material, combined with vacuum aluminothermic reduction and electron beam melting, to prepare a low-carbon, high-purity niobium ingot, which can effectively improve the residual resistivity of the low-carbon, high-purity niobium ingot while reducing unit consumption. DETAILED DESCRIPTION

[0018] The present invention provides a method for preparing a low-carbon high-purity niobium ingot, comprising the following steps: Sintering niobium oxide powder in an oxygen atmosphere to obtain a niobium oxide sintered block; heating and melting the niobium oxide sintered block in an oxygen atmosphere to obtain a niobium oxide melt; Using oxygen as a powder spraying medium, the niobium oxide melt is subjected to gas atomization treatment to obtain carbon-removed niobium oxide powder; performing vacuum aluminothermic reduction on the decarbonized niobium oxide powder and aluminum particles to obtain an aluminum-niobium alloy; The aluminum-niobium alloy is electron beam melted to obtain a low-carbon high-purity niobium ingot; the low-carbon high-purity niobium ingot has a carbon content of ≤0.0004wt% and a purity of ≥99.99%.

[0019] The present invention sintered niobium oxide powder in an oxygen atmosphere to obtain a niobium oxide sintered block. In the present invention, the chemical composition of the niobium oxide powder preferably includes: Nb2O5 ≥ 99.7wt%, Ta ≤ 0.005wt%, Ti ≤ 0.002wt%, W ≤ 0.0005wt%, Mo ≤ 0.0005wt%, Cr ≤ 0.005wt%, Mn ≤ 0.005wt%, Fe ≤ 0.005wt%, Ni ≤ 0.005wt%, Si ≤ 0.005wt%, Cu ≤ 0.005wt%, Zr ≤ 0.003wt%, Co ≤ 0.005wt%, and C ≤ 0.003wt%. Specifically, the C content in the niobium oxide powder may be 0.0012-0.0015wt%. The bulk density of the niobium oxide powder is preferably ≥ 0.65g / cm 3 The sintering temperature is preferably 1350-1400°C, specifically 1350°C, 1370°C, or 1400°C. The sintering time is preferably 1.5-2.5 hours, specifically 1.5 hours, 2 hours, or 2.5 hours. The mold used for sintering is preferably made of magnesia brick or corundum brick. The purity of the oxygen atmosphere used for sintering is preferably 90-94%. In a specific embodiment of the present invention, niobium oxide powder is loaded into a sintering mold for sintering. The size of the sintering mold is selected based on the size of the target niobium oxide sintered block.

[0020] In the present invention, the size of the niobium oxide sintered block is preferably 30-100 mm×30-100 mm×30-100 mm, specifically 30×30×30 mm, 50×50×50 mm, or 100×100×100 mm.

[0021] After obtaining the niobium oxide sintered mass, the present invention heats and melts the niobium oxide sintered mass in an oxygen atmosphere to obtain a niobium oxide melt. In the present invention, the heating and melting method is preferably heating in a high-temperature resistance furnace. The heating and melting temperature is preferably 1550°C to 1650°C, specifically 1550°C, 1600°C, or 1650°C. The purity of the oxygen atmosphere used for the heating and melting is preferably 90% to 94%.

[0022] After obtaining the niobium oxide melt, the present invention uses oxygen as a powder spraying medium to subject the niobium oxide melt to a gas atomization treatment to obtain decarbonized niobium oxide powder. In the present invention, the gas atomization treatment preferably comprises: an oxygen pressure of 0.5 to 1.5 MPa, specifically 0.5 MPa, 1 MPa, or 1.5 MPa; a niobium oxide melt flow rate of 0.35 to 0.8 L / min, specifically 0.35 L / min, 0.6 L / min, or 0.8 L / min; and the purity of the oxygen used in the gas atomization treatment is preferably 90 to 94%.

[0023] In the present invention, after decarbonization using the method of the present invention, the carbon content of the niobium oxide powder can be reduced by 30-50% by weight, and the residual resistivity of the high-purity niobium ingot produced using the powder as raw material can be increased by 5-10%. In a specific embodiment of the present invention, the carbon content of the decarbonized niobium oxide powder is ≤0.0009% by weight.

[0024] After obtaining the decarbonized niobium oxide powder, the present invention mixes the decarbonized niobium oxide powder with aluminum granules and performs vacuum aluminothermic reduction to obtain an aluminum-niobium alloy. In the present invention, the chemical composition of the aluminum granules preferably includes: Ta ≤ 0.003 wt%, Ti ≤ 0.002 wt%, W ≤ 0.0005 wt%, Mo ≤ 0.0005 wt%, Cr ≤ 0.005 wt%, Mn ≤ 0.005 wt%, Fe ≤ 0.005 wt%, Ni ≤ 0.005 wt%, Si ≤ 0.005 wt%, Cu ≤ 0.005 wt%, Zr ≤ 0.003 wt%, Co ≤ 0.005 wt%, C ≤ 0.002 wt%, and Al ≥ 99.9 wt%. The vacuum degree of the vacuum aluminothermic reduction is preferably 20 to 200 Pa.

[0025] In the present invention, the niobium content in the aluminum-niobium alloy is preferably 88-91 wt%, specifically 90 wt%.

[0026] After obtaining the aluminum-niobium alloy, the present invention performs electron beam melting on the aluminum-niobium alloy to produce a low-carbon, high-purity niobium ingot. In the present invention, the electron beam melting temperature is preferably 2800-3200°C, the number of electron beam melting passes is preferably 4-5, and the melting rate for each pass is preferably 25-30 kg / h. Electron beam melting removes low-melting-point impurities, such as aluminum, from the aluminum-niobium alloy to produce a low-carbon, high-purity niobium ingot.

[0027] In the present invention, the carbon content of the low-carbon high-purity niobium ingot is ≤0.0004wt%, and the purity is ≥99.99%; the residual resistivity of the low-carbon high-purity niobium ingot is ≥450.

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] The chemical composition of the niobium oxide powder used in the following examples and comparative examples is as follows: Nb2O5≥99.7wt%, Ta≤0.005wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%; the C content is shown in the specific examples.

[0030] The chemical composition of the aluminum particles used in the following examples and comparative examples is as follows: Ta≤0.003wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%, C≤0.002wt%, Al≥99.9wt%.

[0031] Example 1 (1) 1000 kg of niobium oxide powder was loaded into sintering molds. The size of each sintering mold was 30 × 30 × 30 mm. (2) Sintering the niobium oxide powder in an oxygen atmosphere at a sintering temperature of 1350°C for 2.5 hours to obtain a niobium oxide sintered block; (3) Place the niobium oxide sintered block into a crucible and heat it to 1550°C in an oxygen atmosphere; (4) After all the niobium oxide sintered blocks in the crucible are melted, the oxygen pressure is adjusted to 0.5 MPa and the flow rate of the niobium oxide melt is adjusted to 0.35 L / min for gas atomization treatment; (5) After the atomization is completed, the obtained carbon-removed niobium oxide powder is sampled and tested; (6) Using decarbonized niobium oxide powder as raw material, adding aluminum particles, and preparing an aluminum-niobium alloy with a niobium content of 90 wt% by vacuum aluminothermic reduction; (7) Electron beam melting the aluminum-niobium alloy in step (6) was performed four times using an EB furnace at a melting temperature of 3000°C and a melting rate of 25 kg / h each time to obtain a low-carbon, high-purity niobium ingot; (8) The carbon content, purity and residual resistivity (RRR) of low carbon high purity niobium ingots were tested.

[0032] The test results of the carbon content of niobium oxide before and after decarbonization, as well as the carbon content, purity, and residual resistivity of the low-carbon high-purity niobium ingot in this embodiment are shown in Table 1. At the same time, the unit consumption for preparing the low-carbon high-purity niobium ingot was calculated, and the results are shown in Table 1.

[0033] Table 1 Test results

[0034] The test results in Table 1 indicate that the carbon content of the treated niobium oxide powder is significantly reduced. Low-carbon, high-purity niobium ingots prepared using the treated niobium oxide powder exhibit low carbon content, high purity, and high residual resistivity, while also requiring minimal production costs. Furthermore, the treated niobium oxide powder significantly improved its fluidity during the experiment.

[0035] Example 2 (1) 1000 kg of niobium oxide powder was loaded into sintering molds. The size of each sintering mold was 50 × 50 × 50 mm. (2) Sintering the niobium oxide powder in an oxygen atmosphere at a sintering temperature of 1370°C for 2 hours to obtain a niobium oxide sintered block; (3) Place the niobium oxide sintered block into a crucible and heat it to 1650°C in an oxygen atmosphere; (4) After all the niobium oxide sintered blocks in the crucible are melted, the oxygen pressure is adjusted to 1.5 MPa and the flow rate of the niobium oxide melt is adjusted to 0.8 L / min for gas atomization treatment; (5) After the atomization is completed, the obtained carbon-removed niobium oxide powder is sampled and tested; (6) Using decarbonized niobium oxide powder as raw material, adding aluminum particles, and preparing an aluminum-niobium alloy with a niobium content of 90 wt% by vacuum aluminothermic reduction; (7) Electron beam melting the aluminum-niobium alloy in step (6) was performed four times using an EB furnace at a melting temperature of 3000°C and a melting rate of 25 kg / h each time to obtain a low-carbon, high-purity niobium ingot; (8) The carbon content, purity and residual resistivity (RRR) of low carbon high purity niobium ingots were tested.

[0036] The test results of the carbon content of niobium oxide before and after decarbonization, as well as the carbon content, purity, and residual resistivity of the low-carbon high-purity niobium ingot in this embodiment are shown in Table 2. At the same time, the unit consumption for preparing the low-carbon high-purity niobium ingot was calculated, and the results are shown in Table 2.

[0037] Table 2 Test results

[0038] The test results in Table 2 indicate that the carbon content of the treated niobium oxide powder is significantly reduced. Low-carbon, high-purity niobium ingots prepared using the treated niobium oxide powder exhibit low carbon content, high purity, and high residual resistivity, while also requiring minimal production costs. Furthermore, the treated niobium oxide powder significantly improved its fluidity during the experiment.

[0039] Example 3 (1) 1000 kg of niobium oxide powder was loaded into sintering molds. The size of each sintering mold was 100 × 100 × 100 mm. (2) Sintering the niobium oxide powder in an oxygen atmosphere at a sintering temperature of 1400°C for 1.5 hours to obtain a niobium oxide sintered block; (3) The sintered niobium oxide agglomerate is placed in a crucible and heated to 1600°C in an oxygen atmosphere; (4) After the niobium oxide in the crucible is almost completely melted, the oxygen pressure is adjusted to 1 MPa and the flow rate of the niobium oxide melt is adjusted to 0.6 L / min for gas atomization treatment; (5) After the atomization is completed, the obtained carbon-removed niobium oxide powder is sampled and tested; (6) Using decarbonized niobium oxide powder as raw material, adding aluminum particles, and preparing an aluminum-niobium alloy with a niobium content of 90 wt% by vacuum aluminothermic reduction; (7) Electron beam melting the aluminum-niobium alloy in step (6) was performed four times using an EB furnace at a melting temperature of 3000°C and a melting rate of 25 kg / h each time to obtain a low-carbon, high-purity niobium ingot; (8) Perform residual resistivity (RRR) test on low carbon high purity niobium ingots.

[0040] The test results of the carbon content of niobium oxide before and after decarbonization, as well as the test results of the carbon content, purity and residual resistivity of the low-carbon high-purity niobium ingot in this embodiment are shown in Table 3. At the same time, the unit consumption of preparing the low-carbon high-purity niobium ingot was calculated, and the results are shown in Table 3.

[0041] Table 3 Test results

[0042] The test results in Table 3 indicate that the carbon content of the treated niobium oxide powder is significantly reduced. Low-carbon, high-purity niobium ingots prepared using the treated niobium oxide powder exhibit low carbon content, high purity, and high residual resistivity, while also requiring minimal production costs. Furthermore, the treated niobium oxide powder significantly improved its fluidity during the experiment.

[0043] Comparative Example 1 The niobium oxide powder is not pre-treated and high-purity niobium ingots are directly prepared. The specific steps are as follows: (1) Using raw niobium oxide powder as raw material, aluminum particles were added and an aluminum-niobium alloy with a niobium content of 90 wt% was prepared by vacuum aluminothermic reduction; (2) using an EB furnace to electron beam melt the aluminum-niobium alloy prepared in step (1) four times at a melting temperature of 3000°C and a melting rate of 25 kg / h each time to obtain a high-purity niobium ingot; (3) Perform residual resistivity (RRR) test on high purity niobium ingots.

[0044] The test results of carbon content, purity, residual resistivity and unit consumption of the high-purity niobium ingot prepared in Comparative Example 1 are shown in Table 4.

[0045] Table 4 Test results

[0046] The test results in Table 4 show that when high-purity niobium ingots are prepared using niobium oxide powder without decarbonization, the resulting ingots have a high carbon content, low residual resistivity, and high unit consumption. The above results indicate that although electron beam melting has a certain carbon removal ability, the removal effect is poor. The present invention reduces the carbon content at the raw material end and then uses the decarbonized niobium oxide to prepare niobium ingots. This can effectively reduce the carbon content in the niobium ingots, improve the RRR value of the niobium ingots, and reduce the unit consumption.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a low-carbon high-purity niobium ingot, characterized in that: The following steps are involved: Sintering niobium oxide powder in an oxygen atmosphere to obtain a niobium oxide sintered block; heating and melting the niobium oxide sintered block in an oxygen atmosphere to obtain a niobium oxide melt; Using oxygen as a powder spraying medium, the niobium oxide melt is subjected to gas atomization treatment to obtain carbon-removed niobium oxide powder; performing vacuum aluminothermic reduction on the decarbonized niobium oxide powder and aluminum particles to obtain an aluminum-niobium alloy; The aluminum-niobium alloy is electron beam melted to obtain a low-carbon high-purity niobium ingot; the low-carbon high-purity niobium ingot has a carbon content of ≤0.0004wt% and a purity of ≥99.99%.

2. The preparation method according to claim 1, characterized in that The chemical composition of the niobium oxide powder includes: Nb2O5≥99.7wt%, Ta≤0.005wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%, and C≤0.003wt%.

3. The preparation method according to claim 1, characterized in that The bulk density of the niobium oxide powder is ≥0.65 g / cm 3 .

4. The preparation method according to claim 1, characterized in that The sintering temperature is 1350-1400° C., and the sintering time is 1.5-2.5 hours. The material of the mold used for sintering is magnesia brick or corundum brick.

5. The preparation method according to claim 1, characterized in that The size of the niobium oxide sintered block is 30-100 mm×30-100 mm×30-100 mm.

6. The preparation method according to claim 1, characterized in that The heating and melting method is heating in a high-temperature resistance furnace, and the heating and melting temperature is 1550-1650°C.

7. The preparation method according to claim 1, characterized in that The conditions of the gas atomization treatment include: an oxygen pressure of 0.5-1.5 MPa, and a flow rate of the niobium oxide melt of 0.35-0.8 L / min.

8. The preparation method according to claim 1, characterized in that The purity of the oxygen used in the sintering, heating melting and gas atomization treatment is 90-94%.

9. The preparation method according to claim 1, characterized in that The chemical composition of the aluminum particles includes: Ta≤0.003wt%, Ti≤0.002wt%, W≤0.0005wt%, Mo≤0.0005wt%, Cr≤0.005wt%, Mn≤0.005wt%, Fe≤0.005wt%, Ni≤0.005wt%, Si≤0.005wt%, Cu≤0.005wt%, Zr≤0.003wt%, Co≤0.005wt%, C≤0.002wt%, and Al≥99.9wt%.

10. The preparation method according to claim 1, characterized in that The electron beam melting is performed 4 to 5 times, and the melting rate of each time is 25 to 30 kg / h.

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