CN116288091A

CN116288091A - Annealing process for preparing superfine grain tantalum sheet at low temperature

Info

Publication number: CN116288091A
Application number: CN202310309895.6A
Authority: CN
Inventors: 谭敦强; 熊伟龙
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2023-03-28
Filing date: 2023-03-28
Publication date: 2023-06-23

Abstract

The invention discloses an annealing process for preparing ultrafine grain tantalum sheets at low temperature, and relates to a process at annealing temperature based on a high strain tantalum plate. The method comprises the following steps: the tantalum ingot obtained by secondary electron beam smelting is subjected to multidirectional forging, the accumulated strain amount reaches more than 9.0, rolling deformation is carried out for 80-85% at the constant temperature of 600-950 ℃ for 50-80 min, then the tantalum sheet is subjected to constant temperature annealing for 50-80 min at the constant temperature of 500-600 ℃ and then rolling deformation for 90-93%, the tantalum sheet is placed in a tube furnace, heat treatment is sequentially carried out at the temperature of 450-550 ℃ and the temperature of 350-450 ℃ and the temperature of 900-1000 ℃, and finally cooling and taking out are carried out. According to the invention, after the tantalum ingot is subjected to plastic deformation, an annealing process is performed for 50-80 min at 500-600 ℃, the heat preservation temperature is far lower than the recrystallization temperature of tantalum, high deformation resistance of tantalum caused by plastic deformation is eliminated, the micro power of recrystallization is increased, and the preferred orientation advantage of tantalum grains can be effectively weakened, so that after a finished tantalum sheet is annealed on the basis of the same strain quantity, the grain size is finer, the crystal face orientation is more uniform, and the hardness and the plasticity of the tantalum sheet are greatly improved.

Description

Annealing process for preparing superfine grain tantalum sheet at low temperature

Technical Field

The invention relates to the technical field of heat treatment, in particular to an annealing process for preparing ultrafine grain tantalum chips.

Background

Tantalum (Ta) is a typical transition group refractory metal, which is a body-centered cubic crystal structure (Body Centered Cubic, BCC). Tantalum metal has higher melting point (2996 ℃) and density (16.6 g/cm < 3 >), extremely high corrosion resistance and excellent ductility. Based on the unique physical and chemical properties, tantalum and the alloy thereof are widely applied and deeply developed in the fields of electronics, military industry, medical instruments, aerospace and the like, and the specific application comprises a capacitor, a sputtering target material, a soft-shelled turtle material, a bone repair material, a high-temperature alloy, a corrosion-resistant application device and the like. Wherein the consumption of the electronic industrial products is maximum and accounts for more than 60 percent. Meanwhile, the development trend of the advanced equipment manufacturing industry is also towards intensive and miniature development, which directly leads to the trend of miniature manufacturing of various electronic components, so that the improvement of the mechanical properties of tantalum is an urgent research direction.

The tantalum capacitor is an important electronic component, has the characteristics of small volume, high energy storage, stable performance and the like, and is widely applied to the fields of mobile communication equipment, aerospace, various instruments and meters and the like. In particular in the field of aircraft systems, it may be said to be of great scope. This is mainly due to three major characteristics of tantalum capacitance: 1. the energy storage is more, and a plurality of tantalum capacitors are usually used in parallel; 2. the tantalum capacitor can effectively filter the cultural waves of the power supply and the like through the filtering function; 3. coupling, i.e. coupling and blocking of alternating signals. However, the working environment of the tantalum capacitor is generally bad, deformation and stress concentration caused by high-frequency vibration have great influence on the working stability of the tantalum capacitor, and the use safety and the service life of equipment are seriously threatened. Therefore, the improvement of the mechanical properties of the high-purity tantalum sheet becomes a key point. The main way to improve this performance is by obtaining tantalum flakes of fine and uniform grains.

The common mode for preparing the high-purity tantalum sheet is to prepare a high-purity tantalum ingot blank in a powder metallurgy and electron beam smelting mode, and then forge and roll the blank to prepare the tantalum sheet by combining a series of plastic processing and annealing processes such as forging and rolling. However, the crystal grain size of tantalum ingots obtained by electron beam melting is generally in the order of centimeters, so that a large deformation amount is required to break grain boundaries. However, the large deformation amount can lead to the rapid increase of the deformation resistance of tantalum, and cracks are easy to initiate, so that defects are generated inside the tantalum; the processing cost of warm deformation and thermal deformation is high, the operation process is complex, and the realization is not easy. At present, the average grain size of tantalum sheets used in the market is between 25 and 100 mu m, and the research on the grain size refinement is difficult to break through.

Disclosure of Invention

The invention aims to at least solve one of the technical problems in the prior art, provides a heat treatment process of a high-purity tantalum sheet, can effectively reduce the average grain size under the condition of the same deformation, has high-efficiency product production rate compared with the traditional annealing mode, and is suitable for popularization.

The technical scheme of the invention is as follows:

an annealing process for preparing ultra-fine grain tantalum chips at low temperature comprises the following steps:

step 1, placing the tantalum sheet after forging into a heat treatment furnace, heating the tantalum sheet to 600-950 ℃ and carrying out constant temperature treatment for 50-80 min;

step 2, cooling the tantalum sheet subjected to the heat treatment in the step 1 to room temperature along with a furnace, and taking out;

step 3, rolling the tantalum sheet in the step 2, wherein the rolling deformation is 80% -85%;

step 4, placing the tantalum sheet in the step 3 into a heat treatment furnace, heating the tantalum sheet to 500-600 ℃, and carrying out constant temperature treatment for 50-80 min;

step 5, rolling and deforming the tantalum sheet in the step 4, wherein the rolling deformation is 90% -93%;

step 6, placing the tantalum sheet in the step 5 into a heat treatment furnace, heating the tantalum sheet to 450-550 ℃, and heating the tantalum sheet at constant temperature for 50min;

step 7, reducing the heat treatment temperature in the step 6 by 100-200 ℃, and continuously heating the tantalum sheet at constant temperature for 50-80 min;

step 8, raising the heat treatment temperature in the step 7 to 900-1000 ℃, and continuously heating the tantalum sheet at constant temperature for 50-90 min;

and 9, cooling the tantalum sheet subjected to the heat treatment in the step 7 to room temperature along with a furnace, and taking out.

Preferably, in the step 1, the purity of the tantalum flake is not less than 99.9%.

Preferably, the plastic deformation treatment before the step 1 comprises forging the electron beam melting tantalum ingot for a plurality of times, annealing after each forging, and the total equivalent strain generated in the forging process is 9.0-10.8.

Preferably, in the step 3, the rolling treatment is performed on the forged tantalum ingot, and the strain amount of the rolling is controlled to be 1.6.

In the preferred embodiment, in the steps 1 to 9, the heat treatment process of the high-purity tantalum plate is performed under the protection of argon atmosphere, and the heating rate of the heat treatment furnace is 10 ℃/min.

In the step 4, the constant temperature heat treatment temperature is 600 ℃;

in the step 4, the constant temperature heat treatment temperature is 450-550 ℃; in the step 5, the constant temperature heat treatment temperature is 350-450 ℃; in the step 6, the constant temperature heat treatment temperature is 900-1000 ℃.

By adopting the annealing process for preparing the ultra-fine grain tantalum sheet at the low temperature, the average grain size of the obtained tantalum sheet is between 14 and 26 mu m.

The invention has at least one of the following beneficial effects: the invention provides a low-temperature annealing process of a high-purity tantalum sheet, which can reduce the deformation resistance of the tantalum sheet after plastic processing while reducing the annealing temperature and saving the energy consumption and the time cost, so that the subsequent processing of the tantalum sheet can not crack due to stress concentration caused by overlarge deformation resistance, and the intermediate annealing process has obvious effect of refining grains for finally preparing the tantalum sheet. The grain size of the tantalum sheet prepared by the common heat treatment process is thinned by 10-25%. The tantalum sheet prepared by the method has more uniform texture, and the (222) crystal face texture coefficient is reduced by 20-25% compared with that of the tantalum sheet prepared by the common heat treatment process. The invention has important practical value for preparing tantalum sheets with excellent plasticity.

Drawings

FIG. 1 is a golden phase diagram of a Transverse (TD) -plate Normal (ND) plane of a high purity tantalum plate after treatment in examples and comparative examples, wherein (a) is a golden phase diagram of comparative example 1, (b) is a golden phase diagram of example 1, and (c) is a golden phase diagram of example 2;

FIG. 2 is a bar graph of average grain size of the treated high purity tantalum flake of examples and comparative examples;

fig. 3 is an XRD pattern of the rolled face of tantalum flake after the treatment of example 1 and comparative example 1.

Detailed Description

The invention provides an annealing process for preparing ultrafine grain tantalum chips at a low temperature.

Step 1, forging a rod-shaped tantalum ingot in three directions under a 75Kg air hammer, wherein the forging directions are along three directions of x, y and z of the tantalum ingot (x and y are two radial directions of the tantalum ingot which are mutually perpendicular, and z is the axial direction of the tantalum ingot), the three directions are respectively forged twice for one forging period, and the total true strain of deformation of each forging period is controlled to be 1.6-2.0. After forging, the tantalum ingot is placed in a tube furnace and annealed in an argon atmosphere, and a forging annealing cycle is taken up. The above steps are repeated for a plurality of cycles, and the total strain amount during forging is 9.0-10.8.

And 2, respectively carrying out constant-temperature annealing on the forged tantalum ingot at 600-950 ℃ for 50-80 min, carrying out rolling deformation treatment on the annealed tantalum ingot, wherein the rolling deformation strain is 1.6, and carrying out constant-temperature annealing on the rolled tantalum sheet at 500-600 ℃ for 50min. And rolling and deforming the annealed tantalum sheet again, wherein the rolling deformation strain is 2.3.

And 4, placing the finally prepared tantalum sheet into a heat treatment furnace, heating to 450-550 ℃ and preserving heat for 50min, reducing the temperature to 350-450 ℃ and preserving heat for 50min, heating to 900-1000 ℃ and preserving heat for 80min, and then cooling to room temperature along with the furnace and taking out.

The tantalum flake obtained by the heat treatment process has fine and uniform crystal grains and average crystal grain size smaller than 26 mu m.

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to the following specific embodiments.

Comparative example 1

(1) Plastic deformation of tantalum plate: the rod-shaped tantalum ingot is subjected to three-way forging under a 75Kg air hammer, the forging direction is along the x, y and z directions of the tantalum ingot (x and y are two radial directions of the tantalum ingot which are perpendicular to each other, and z is the axial direction of the tantalum ingot), the three directions are respectively forged twice for one forging period, and the total true strain of deformation in each forging period is controlled to be 1.6-2.0. After forging, the tantalum ingot is placed in a tube furnace and annealed in an argon atmosphere, and a forging annealing cycle is taken up. Repeating the steps for a plurality of periods, wherein the total strain amount during forging is 9.0-10.8;

(2) Annealing the forged tantalum ingot at 950 ℃ for 80min at a temperature rising rate of 10k/min; rolling the tantalum ingot with deformation of 80%, and then placing the tantalum sheet at 925 ℃ for 80min at a heating rate of 5k/min; and (3) carrying out secondary rolling treatment on the annealed tantalum sheet, wherein the deformation is 90%, then placing the tantalum sheet in a heat treatment furnace, heating to 550 ℃ and preserving heat for 50min, then cooling to 450 ℃ and preserving heat for 50min, then heating to 1000 ℃ and preserving heat for 80min, and then cooling to room temperature along with the furnace and taking out.

Example 1

(2) Annealing the forged tantalum ingot at 600 ℃ for 50min at a constant temperature, wherein the heating rate is 10k/min; then rolling the tantalum ingot with the deformation of 80%, and then placing the tantalum sheet at 600 ℃ for 50min at the temperature rising rate of 10k/min; and (3) carrying out secondary rolling treatment on the annealed tantalum sheet, wherein the deformation is 90%, then placing the tantalum sheet in a heat treatment furnace, heating to 550 ℃ and preserving heat for 50min, then cooling to 450 ℃ and preserving heat for 50min, then heating to 1000 ℃ and preserving heat for 80min, and then cooling to room temperature along with the furnace and taking out.

Example 2

(1) Plastic deformation of tantalum plate: the rod-shaped tantalum ingot is subjected to three-way forging under a 75Kg air hammer, the forging direction is along the x, y and z directions of the tantalum ingot (x and y are two radial directions of the tantalum ingot which are perpendicular to each other, and z is the axial direction of the tantalum ingot), the three directions are respectively forged twice for one forging period, and the total true strain of deformation in each forging period is controlled to be 1.6-2.0. After forging, the tantalum ingot is placed in a tube furnace and annealed in an argon atmosphere, and a forging annealing cycle is taken up. Repeating the steps for a plurality of periods, wherein the total strain amount during forging is 9.0-10.8; (2) Annealing the forged tantalum ingot at 950 ℃ for 80min at a temperature rising rate of 10k/min; then rolling the tantalum ingot with the deformation of 80%, and then placing the tantalum sheet at 600 ℃ for 50min at the temperature rising rate of 10k/min; and (3) carrying out secondary rolling treatment on the annealed tantalum sheet, wherein the deformation is 90%, then placing the tantalum sheet in a heat treatment furnace, heating to 550 ℃ and preserving heat for 50min, then cooling to 450 ℃ and preserving heat for 50min, then heating to 1000 ℃ and preserving heat for 80min, and then cooling to room temperature along with the furnace and taking out.

Comparative examples and examples the grain size and grain orientation of the tantalum flake after preparation was completed, and the test methods and test results were as follows:

the microstructure of the rolling surface of comparative example 1 and examples 1 and 2 was observed with an optical microscope, and the results are shown in fig. 1, wherein (a) is the microstructure of comparative example 1, (b) is the microstructure of example 1, and (c) is the microstructure of example 2;

the average grain size of the tantalum flake of comparative example 1 and examples 1 and 2 shown in FIG. 1 was calculated according to the method for measuring average grain size of metals (GB/T6394-2017), and the results are shown in FIG. 2.

The grain orientations of comparative example 1 and example 1, 2 tantalum flakes were tested by X-ray diffraction (XRD) and the test results are shown in fig. 3;

as shown in FIG. 1, it can be seen that the grain size is largest in FIG. 1 (a), sub-FIG. 1 (b), and smallest in FIG. 1 (c). It can be seen that the use of an intermediate annealing process during forging and rolling significantly reduces the grain size of the finally produced tantalum flake.

The average grain size of comparative example 1 and examples 1 and 2 is shown in fig. 2. As can be seen from the graph, the average grain size of the tantalum flake prepared in comparative example 1 was 29.54 μm, the average grain size of the tantalum flake prepared in example 1 was 25.93 μm, and the average grain size of the tantalum flake prepared in example 2 was 22.93. Mu.m. Example 1 reduced the average grain size by 12.3% compared to comparative example 1 and example 2 reduced the average grain size by 22.4% compared to comparative example 1.

FIG. 3 shows X-ray diffraction patterns of comparative example 1 and examples 1 and 2. As can be seen from the graph, the (222) crystal plane diffraction peak intensities of comparative example 1 are significantly higher than those of examples 1 and 2, while the (200) and (110) diffraction peak intensities are lower than those of examples 1 and 2; calculated by the crystal plane texture coefficient (TC value), the (222) crystal plane TC value of example 1 was 21.4% lower than that of comparative example 1, and the (222) crystal plane TC value of example 2 was 24.3% lower than that of comparative example 1.

In summary, compared with the traditional annealing process, the low-temperature annealing process is added in the plastic deformation process, so that the annealing time and energy consumption in the plastic deformation process are saved, and most importantly, the influence of the annealing process on the grain refinement and crystal face orientation homogenization of the finished product is reduced, and the mechanical properties such as the hardness, the tensile strength and the like of the product can be greatly improved.

The above is merely exemplary embodiments of the present invention, and the scope of the present invention is not limited in any way. All technical schemes formed by adopting equivalent exchange or equivalent substitution fall within the protection scope of the invention.

Claims

1. An annealing process for preparing ultra-fine grain tantalum chips at low temperature is characterized by comprising the following steps:

s1, forging tantalum sheets to perform plastic deformation treatment;

s2, carrying out constant-temperature heat treatment and preliminary rolling deformation: performing constant temperature heat treatment at 600-950 ℃, cooling to room temperature along with a furnace, and performing rolling deformation treatment, wherein the rolling deformation is 80-85%;

s3, heat treatment at constant temperature and secondary rolling deformation: carrying out constant-temperature heat treatment at 500-600 ℃, and carrying out rolling deformation treatment on the tantalum sheet after annealing, wherein the rolling deformation is 90% -93%;

s4, sectional type constant temperature heat treatment, namely adopting a mode of firstly reducing temperature and then increasing temperature in a heat treatment furnace, carrying out the heat treatment in stages at different heat treatment temperatures, and finally cooling to room temperature along with the furnace and taking out.

2. The annealing process for preparing ultra-fine grain tantalum chips at low temperature according to claim 1, wherein: the step S1 specifically comprises the steps of forging an electron beam smelting tantalum ingot for a plurality of times, annealing after each forging, wherein the sum of equivalent strains generated in the forging process is 9.0-10.8; the purity of the prepared tantalum sheet is not less than 99.9%.

3. The annealing process for preparing ultra-fine grain tantalum chips at low temperature according to claim 1, wherein: the heat treatment processes in the steps S2 to S4 are all carried out under the protection of argon atmosphere, and the heating rate of the heat treatment is 10 ℃/min.

4. The annealing process for preparing ultra-fine grain tantalum chips at low temperature according to claim 1, wherein: in the steps S2 and S2, the constant temperature heat treatment time is 50-80 min.

5. The annealing process for preparing ultra-fine grain tantalum chips at low temperature according to claim 1, wherein: in the step S4, the temperature of the heat treatment in stages is 450-550 ℃, 350-450 ℃ and 900-1000 ℃ respectively; wherein the constant temperature heating is carried out for 50min at the stage of 450-550 ℃; heating at constant temperature for 50-80 min at the temperature of 350-450 ℃; heating at constant temperature for 50-90 min at 900-1000 deg.c.

6. An ultra-fine grain tantalum flake produced by the annealing process of any one of claims 1 to 5.

7. The ultra-fine grain tantalum flake of claim 6, wherein: the average grain size of the superfine grain tantalum sheet is between 14 and 26 mu m.