阅读说明：本技术 一种高纯钽锭及其制备方法 (High-purity tantalum ingot and preparation method thereof ) 是由 钟景明 白掌军 颉维平 焦红忠 牟东 石晓军 于 2020-06-29 设计创作，主要内容包括：本发明涉及一种高纯钽锭及其制备方法。其特点是,包括如下步骤：(1)将高熔点金属杂质含量较低的钽粉成型；(2)在真空下高温烧结制得钽棒、钽条或者钽块,采用同样纯度的钽丝制备真空电子束熔炼用的熔炼电极；(3)采用真空电子束熔炼炉进行至少两次熔炼,要求第一次熔炼采用水平进料或者垂直进料方式,在第二次或者第二次以后的熔炼均采用垂直进料方式；在进行第二次或者第二次以后的电极熔炼时要求电极旋转,控制旋转速度为0.3-0.8r/min。通过熔炼的工艺控制,其熔炼的钽铸锭纯度高,尤其间隙杂质元素C、O、N、H较低,其铸锭硬度低,气孔、疏松、缩孔等缺陷少,适于压力加工制备钽靶材等高端加工材。(The invention relates to a high-purity tantalum ingot and a preparation method thereof. The method is characterized by comprising the following steps: (1) forming tantalum powder with low content of high-melting-point metal impurities; (2) sintering at high temperature under vacuum to obtain tantalum rods, tantalum strips or tantalum blocks, and preparing a smelting electrode for vacuum electron beam smelting by adopting tantalum wires with the same purity; (3) smelting at least twice by using a vacuum electron beam smelting furnace, wherein the first smelting is required to adopt a horizontal feeding mode or a vertical feeding mode, and the second smelting or the later smelting adopts a vertical feeding mode; when the second or later electrode smelting is carried out, the rotation of the electrode is required, and the rotation speed is controlled to be 0.3-0.8 r/min. Through the control of the smelting process, the smelted tantalum cast ingot has high purity, particularly lower interstitial impurity element C, O, N, H, low hardness of the cast ingot and less defects of air holes, looseness, shrinkage cavities and the like, and is suitable for preparing high-end processing materials such as tantalum target materials and the like by pressure processing.)

1. A high-purity tantalum ingot is composed of Ta and impurities, wherein the Ta is more than or equal to 99.999% in percentage by mass.

2. The high purity tantalum ingot of claim 1, wherein: wherein Nb in the impurities is less than or equal to 2ppm, W is less than or equal to 1ppm, Mo is less than or equal to 1ppm, U is less than or equal to 0.001ppm, Th is less than or equal to 0.001ppm, S is less than 0.015ppm, Si is less than or equal to 0.08ppm, C is less than or equal to 10ppm, O is less than or equal to 15ppm, N is less than or equal to 15ppm, H is less than or equal to 2ppm, and other inevitable impurities, wherein the total amount of metal impurities is not more than 10ppm except.

3. The high purity tantalum ingot of claim 1, wherein: the hardness HV/9.8N of the cast ingot is less than or equal to 85.

4. The high purity tantalum ingot of claim 1, wherein: wherein the ingot is detected by ultrasonic flaw detection, the control interval is more than 50mm, and the wave height is more than

5. The high purity tantalum ingot of claim 1, wherein: wherein the density of the cast ingot is 16.5-16.6 g/cm³。

6. The preparation method of the high-purity tantalum ingot is characterized by comprising the following steps:

(1) forming tantalum powder with low content of high-melting-point metal impurities;

(2) sintering at high temperature under vacuum to obtain tantalum rods, tantalum strips or tantalum blocks, and preparing a smelting electrode for vacuum electron beam smelting by adopting tantalum wires with the same purity;

(3) smelting at least twice by using a vacuum electron beam smelting furnace, wherein the first smelting is required to adopt a horizontal feeding mode or a vertical feeding mode, and the second smelting or the later smelting adopts a vertical feeding mode;

when the second or later electrode smelting is carried out, the rotation of the electrode is required, and the rotation speed is controlled to be 0.3-0.8 r/min.

7. The method for preparing high purity tantalum ingots according to claim 6, wherein: and (3) operating the electron beams in an interval scanning mode to ensure the melting of the melting electrode and the maintenance of a molten pool, wherein the scanning track of the electron beams is controlled by taking the center of the crucible as an origin, the scanning tracks and the scanning residence time of different sizes are controlled, the maximum scanning track of a single gun is 9/10 of the radius of the crucible, and the maximum scanning track is sequentially decreased according to 1/10 of the radius of the crucible to form 8 scanning tracks in the molten pool, wherein the scanning residence time of the maximum scanning track is 100-140 ms.

8. The method for preparing high purity tantalum ingots according to claim 6, wherein: the smelting electrode for vacuum electron beam smelting prepared in the step (2) specifically adopts a binding or welding mode.

9. The method for preparing high purity tantalum ingots according to claim 6, wherein: in the tantalum powder with low content of high-melting-point metal impurities in the step (1), Nb is less than or equal to 0.001 percent, W is less than or equal to 0.0005 percent, and Mo is less than or equal to 0.0005 percent according to weight percentage.

10. The method for preparing high purity tantalum ingots according to claim 6, wherein: the forming in the step (1) specifically adopts isostatic pressing forming or compression molding forming, and the forming pressure is controlled to be more than or equal to 200 MPa.

11. The method for preparing high purity tantalum ingots according to claim 6, wherein: in the step (2), the high-temperature sintering temperature is controlled to be more than or equal to 1800 ℃, the sintering heat preservation time is more than or equal to 6 hours, and the relative density after sintering is more than or equal to 70 percent.

12. The method for preparing high purity tantalum ingots according to claim 6, wherein: the vacuum degree of the smelting chamber is required to be more than or equal to 1.0 multiplied by 10 in the smelting process of the step (3)^-2Pa, the specific electric energy during smelting, namely the ratio of smelting power to smelting speed, is not less than 4, the cooling water temperature during smelting is controlled at 20-30 ℃, and tantalum ingots formed after smelting are cooled in a vacuum cooling chamber for not less than 6 hours.

Technical Field

The invention relates to a high-purity tantalum ingot and a preparation method thereof.

Background

Tantalum is an important metal material in industry, has high melting point and good corrosion resistance, is applied to wide fields, is mainly used as tantalum powder and tantalum wires of a sintering anode of an electrolytic capacitor, and is used for manufacturing structural materials such as a heating body and an insulating layer of a high-temperature vacuum furnace, chemical anti-corrosion materials, high-temperature alloy, hard alloy and super alloy. Tantalum metal has excellent dielectric property, chemical stability, thermal conductivity and special corrosion resistance, so that the target material can be used as an electronic material, a sputtering film material and a corrosion-resistant material and is widely applied to the aspects of microelectronic industry, flat panel displays, optical disks, magnetic head disks and the like. The application of high-purity refractory metal Ta as a wiring material, a sputtering target material, and the like to a large-scale integrated circuit has attracted attention from various countries, and is considered to be a microelectronic material with great future.

The preparation technology of the target material can be divided into two technical routes of smelting and thermal mechanical treatment and powder sintering and thermal mechanical treatment according to the main processing process, wherein the preparation of the tantalum target material mainly adopts the smelting and thermal mechanical treatment method to carry out the microstructure control and blank forming on the tantalum cast ingot by the thermal mechanical treatment technologies such as forging, rolling and thermal treatment. The high-purity tantalum foil is used for manufacturing a shell of a tantalum capacitor, is used for packaging the full-tantalum capacitor, is mainly applied to high-reliability military tantalum capacitors, and requires the stamping performance and the higher purity of the tantalum foil, and the defects of microcrack prevention and the like of the tantalum foil are the primary requirements. At present, tantalum ingots in different forms are mainly produced by taking tantalum as a smelting electrode and smelting by one or a combination of vacuum consumable arc, vacuum electron beam, vacuum plasma beam and plasma arc.

Regardless of the melting method, the casting quality of the ingot is the most critical. The production of high-quality tantalum ingots is the primary link in metal pressure processing production and is also an indispensable component. It not only supplies raw material-ingot necessary for processing part, but also influences the quality and technological performance of the processed product to a great extent. Therefore, the fusion casting and ingot casting production provides the high-quality ingot casting meeting the pressure processing production requirement. The casting task mainly comprises the following aspects of 1) obtaining metal with uniform chemical components and purity meeting the use requirement, 2) casting the metal into an ingot with the shape and the size suitable for pressure processing, wherein the ingot has small processing resistance and is suitable for deformation processing, 3) controlling the crystal structure, the shape and the distribution of the ingot, 4) the inner part of the ingot has no structural defects such as air holes, cracks and the like, and the crystal structure of the ingot is fine and can reach the theoretical density.

Disclosure of Invention

The invention aims to provide a large-size, high-purity, low-defect and low-hardness high-purity metal tantalum cast ingot which is suitable for preparing a tantalum target material for sputtering and other tantalum processing materials with special purposes.

A high-purity tantalum ingot is composed of Ta and impurities, wherein the Ta is more than or equal to 99.999% in percentage by mass.

Wherein Nb in the impurities is less than or equal to 2ppm, W is less than or equal to 1ppm, Mo is less than or equal to 1ppm, U is less than or equal to 0.001ppm, Th is less than or equal to 0.001ppm, S is less than 0.015ppm, Si is less than or equal to 0.08ppm, C is less than or equal to 10ppm, O is less than or equal to 15ppm, N is less than or equal to 15ppm, H is less than or equal to 2ppm, and other inevitable impurities, wherein the total amount of metal impurities is not more than 10ppm except.

The hardness HV/9.8N of the cast ingot is less than or equal to 85.

Wherein the ingot is detected by ultrasonic flaw detection, the control interval is more than 50mm, and the wave height is more thanEquivalent weight, defect rate less than or equal to 1 percent

In which the casting is carried outThe density of the ingot is 16.5-16.6 g/cm³。

The preparation method of the high-purity tantalum ingot is characterized by comprising the following steps:

(1) forming tantalum powder with low content of high-melting-point metal impurities;

(2) sintering at high temperature under vacuum to obtain tantalum rods, tantalum strips or tantalum blocks, and preparing a smelting electrode for vacuum electron beam smelting by adopting tantalum wires with the same purity;

(3) smelting at least twice by using a vacuum electron beam smelting furnace, wherein the first smelting is required to adopt a horizontal feeding mode or a vertical feeding mode, and the second smelting or the later smelting adopts a vertical feeding mode;

when the second or later electrode smelting is carried out, the rotation of the electrode is required, and the rotation speed is controlled to be 0.3-0.8 r/min.

And (3) operating the electron beams in an interval scanning mode to ensure the melting of the melting electrode and the maintenance of a molten pool, wherein the scanning track of the electron beams is controlled by taking the center of the crucible as an origin, the scanning tracks and the scanning residence time of different sizes are controlled, the maximum scanning track of a single gun is 9/10 of the radius of the crucible, and the maximum scanning track is sequentially decreased according to 1/10 of the radius of the crucible to form 8 scanning tracks in the molten pool, wherein the scanning residence time of the maximum scanning track is 100-140 ms.

The smelting electrode for vacuum electron beam smelting prepared in the step (2) specifically adopts a binding or welding mode.

In the tantalum powder with low content of high-melting-point metal impurities in the step (1), Nb is less than or equal to 0.001 percent, W is less than or equal to 0.0005 percent, and Mo is less than or equal to 0.0005 percent according to weight percentage.

The forming in the step (1) specifically adopts isostatic pressing forming or compression molding forming, and the forming pressure is controlled to be more than or equal to 200 MPa.

In the step (2), the high-temperature sintering temperature is controlled to be more than or equal to 1800 ℃, the heat preservation time is more than or equal to 6 hours, and the relative density after sintering is more than or equal to 70 percent.

The vacuum degree of the smelting chamber is required to be more than or equal to 1.0 multiplied by 10 in the smelting process of the step (3)^-2Pa, the specific electric energy during smelting, namely the ratio of smelting power to smelting speed is more than or equal to 4, and the cooling water temperature during smelting is controlledAnd cooling the tantalum ingot formed after smelting in a vacuum cooling chamber for more than or equal to 6 hours at the temperature of between 20 and 30 ℃.

The high-purity tantalum ingot has the following advantages: through the control of the smelting process, the smelted tantalum cast ingot has high purity, particularly lower interstitial impurity element C, O, N, H, low hardness of the cast ingot and less defects of air holes, looseness, shrinkage cavities and the like, and is suitable for preparing high-end processing materials such as tantalum target materials and the like by pressure processing.

Drawings

FIG. 1 is a flow chart of a production process of a high-purity tantalum ingot;

FIG. 2 is a schematic diagram showing electron beam scanning trajectory of a high-purity tantalum ingot molten pool.

Detailed Description

The invention is further illustrated with reference to the figures and examples.

The following examples were produced according to the process flow of FIG. 1.