Preparation method of tantalum sheet, tantalum sheet and application of tantalum sheet

Abstract

The invention relates to a preparation method of a tantalum sheet, the tantalum sheet and application of the tantalum sheet. The preparation method of the tantalum sheet comprises the following steps: 1) forging a tantalum ingot to obtain a forging stock; (2) the forging stock is subjected to heat treatment; and (3) the tantalum forging stock obtained in the step (2) is rolled to obtain a tantalum plate (the rolling machining rate is preferably larger than 65% and more preferably larger than 75%), and the tantalum plate is subjected to heat treatment.

Description

Technical Field

[0001] The present invention relates to a tantalum-based sheet material and a preparation method thereof, and more particularly to a tantalum-based sheet material for superconducting wire and a preparation method thereof. Background Art

[0002] Niobium tin (Nb3Sn) superconducting wires are widely used in the winding of high-field magnets with field strengths above 10T, such as magnets for magnetic confinement fusion reactors, nuclear magnetic resonance systems (NMR) and magnets for high-energy physics. For example, niobium tin (Nb3Sn) superconducting wires are mainly used in toroidal field (TF) coils and central solenoids (CS) in the ITER project. Since the TF coil will generate a magnetic field of up to 11.8T during operation, extremely high requirements are placed on the niobium tin superconducting wires, namely, moderate critical current density and sufficiently small hysteresis loss. Nb3Sn coils with higher operating parameters are an important component of the CFETR superconducting magnet system.

[0003] During the phase heat treatment of Nb3Sn, Sn may diffuse and react with Nb, and may also diffuse and contaminate the external stable body Cu and cause the RRR value of the Cu matrix to decrease. In order to avoid this defect, a barrier layer must be used in the Nb3Sn wire. The barrier layer is placed between the superconductor and the stable body Cu. Generally, Nb material or Ta material is used. After the two are processed into the finished Nb3Sn wire, they are used as a barrier layer with a thickness of about 10μm. Tantalum sheets (also known as tantalum-based sheets or tantalum plates, which can be used interchangeably in this article, both refer to tantalum metal or tantalum alloy in the form of sheets or plates) are often used to make barrier layer materials in Nb3Sn superconducting wires and are important basic materials. Ideally, in order to ensure good mechanical properties, tantalum sheets need to meet multiple conditions: such as complete recrystallization, grain size in ASTM 6-9 (preferably 6.5-7.5), hardness HV / 2.9N≤80, preferably ≤75, longitudinal and transverse elongation are ≥40%, etc. However, conventional tantalum sheet preparation methods can no longer meet all these requirements.

[0004] Common problems in the existing technology include:

[0005] -Tantalum sheets have poor isotropy, and processing plasticity and performance deviations in different directions are large;

[0006] - The microstructure of the tantalum sheet has large deviations. After heat treatment, the local grains of the tantalum sheet are coarse (ASTM grade 3-6) and the size is very different (such as the grain difference is more than 3 levels), there are banded structures, and the uniformity is poor;

[0007] - The elongation of tantalum sheets (lateral and longitudinal) is difficult to reach more than 40%; and the deviation between longitudinal and lateral elongation is too large, often greater than 15%;

[0008] -The hardness is not ideal, and machining (especially drawing) is difficult. Summary of the invention

[0009] According to a first aspect, the present invention relates to a method for preparing a tantalum-based sheet or a tantalum sheet. The preparation method comprises the following steps:

[0010] 1) Forging the tantalum ingot to obtain a forging blank;

[0011] 2) heat treating the forging blank;

[0012] 3) rolling the tantalum forging obtained in step (2) to obtain a tantalum plate, and heat treating the tantalum plate.

[0013] The main purpose of step 1) is to fully break the grains, and there is no restriction on the specific forging method, as long as the grains can be fully broken. However, after a large number of experiments, the inventors found that the following forging method can obtain optimized microstructure and mechanical properties. For example, from the perspective of optimizing the microstructure and mechanical properties, the tantalum ingot is preferably heated before forging, such as by heating it in a box-type resistance furnace. For example, it is preferably heated to 400-420°C. Preferably, the tantalum ingot used as the raw material in step 1) is cylindrical, and there is no restriction on the height-to-diameter ratio. However, the inventors found that from the perspective of processing convenience, the height-to-diameter ratio is preferably 1.8 to 2.2, and more preferably 1.9 to 2.1. In a preferred embodiment, the forging of step 1) includes a first processing in a first direction (e.g., axial direction) (preferably a processing rate of 30%-60%, more preferably 35% to 50%), a second processing in a second direction (e.g., radial direction) (preferably a processing rate of 20%-40%, more preferably 25% to 35%), and a third processing in a third direction (e.g., radial direction) (preferably a processing rate of 20-50%, more preferably 35% to 45%). Preferably, the second direction is different from the third direction. More preferably, the second direction is perpendicular to the third direction. Preferably, the forging also includes a fourth processing, the processing rate of which is preferably greater than 50%, more preferably greater than 65%. More preferably, the direction of the fourth processing is the same as the first processing.

[0014] In an exemplary embodiment, the specific forging method is: ① axial upsetting first, with a processing rate of 30%-60%, preferably 35% to 50%; ② flattening along radial direction 1 (first time), with a processing rate of 20%-40%, preferably 25% to 35%; ③ rotating radial direction 1 by 90° and flattening along radial direction 2 (second time); processing rate 20-50%, more preferably 35% to 45%; ④ flattening and forging along radial direction 1 again, with a processing rate greater than 50%, more preferably greater than 65%. It should be understood that radial direction 1 is perpendicular to radial direction 2.

[0015] The main purpose of the heat treatment in steps 2) and 3) is to improve the internal structure, increase the cold working plasticity and toughness of the material, so as to achieve a refined and uniform structure of the tantalum sheet, a clean surface and low hardness.

[0016] Preferably, before the heat treatment in step 2), the step of pickling the forging blank is also included. The preferred pickling solution is a mixture of nitric acid, hydrofluoric acid (HF) and hydrochloric acid (HCl). More preferably, the concentration of nitric acid (HNO3) is 65% to 68%; the concentration of hydrofluoric acid (HF) is 40% to 45%; the concentration of hydrochloric acid (HCl) is 36% to 38%. More preferably, the volume ratio of these three acids is HNO3: HF: HCl = 3: 1: 2. In a preferred embodiment, before pickling, the forging blank is sawed (advantageously, clamped by turning jaws) and surface defects are turned (to clean the surface of the forging blank and increase the surface finish).

[0017] In a preferred embodiment, the heat treatment in steps 2) and 3) each includes heating the tantalum forging to 900 to 1050°C (preferably 950-1000°C) and keeping it warm for 60 to 120 minutes (preferably 80-100 minutes). Preferably, the heat treatment in steps 2) and 3) each includes two sub-steps. The first sub-step includes a first heating stage and a first insulation stage. The second sub-step includes a second heating stage and a second insulation stage. Preferably, the heating rate of the second sub-step (e.g., 25°C-30 / min) is greater than that of the first sub-step (e.g., 20-25°C / min). Most preferably, the heat treatment in steps 2) and 3) each consists of only the two sub-steps, that is, the heat treatment in steps 2) and 3) each includes only heating twice and insulation twice, and there is no further heating and insulation. It is easy for those skilled in the art to understand that it is generally necessary to cool down to room temperature after heat treatment so that the next step, such as pickling, can be carried out. Preferably, in the present invention, cooling is carried out by furnace cooling.

[0018] In a most preferred embodiment, the heat treatment in steps 2) and 3) is each completed by: heating from room temperature to 600°C at 20°C / min, and then keeping warm for 90 minutes; heating to 1000°C at 25°C / min, and keeping warm for 90 minutes.

[0019] In a preferred embodiment, the rolling processing rate in step (3) is greater than 65%, preferably greater than 75%.

[0020] In a preferred embodiment, step 3) is repeated 2-3 times. When step 3) is repeated for the second or third time, different process parameters may be used. For example, if the rolling processing rate of the first rolling is 80% and the heat treatment temperature is 980°C, the rolling processing rate of the second rolling may be 70% and the heat treatment temperature may be 1000°C. Preferably, if multiple rolling is performed, the tantalum material is pickled before and / or after each rolling, and the pickling solution may be the acid solution in step 2).

[0021] The heat treatment process conditions in steps 2) and 3), such as the heating rate, the temperature and the holding time, can be the same or different. Preferably, they are the same, so that the setting conditions of the furnace do not need to be changed, thereby achieving the purpose of simplifying the process.

[0022] Without being bound by general theory, the inventors believe that by adopting a unique forging method, combined with a unique heat treatment method (especially the heat treatment method after the second rolling), the obtained tantalum sheet is guaranteed to be substantially completely recrystallized, so that the microstructure is significantly optimized, ensuring good mechanical properties, especially ideal hardness and elongation, and a small longitudinal and transverse room temperature tensile property difference. The inventors unexpectedly found that the heating method plays an important role in improving the microstructure, especially when combined with the unique forging method.

[0023] Preferably, the obtained tantalum sheet is substantially completely recrystallized, with a grain size of ASTM 6-9 (preferably 6.5-7.5), a hardness of HV / 2.9N≤80 (preferably ≤75), and a longitudinal and transverse room temperature elongation of ≥40%. More preferably, the longitudinal and transverse room temperature elongation difference (or deviation) of the tantalum sheet is ≤15%. The tantalum sheet can be used for superconducting wires and / or fusion engineering test reactors.

[0024] The term “substantially completely recrystallized” herein means that more than 80% of the grains are recrystallized, preferably more than 85%, more preferably more than 90%, even more preferably more than 95%, and most preferably no unrecrystallized grains are detected.

[0025] The "longitudinal and transverse deviation" and the similar term "longitudinal and transverse elongation deviation" referred to herein refer to: (longitudinal value-transverse value) ÷ transverse value × 100%.

[0026] In this article, "min" and minute are used interchangeably.

[0027] According to a second aspect, the present invention relates to a tantalum-based sheet or tantalum sheet. Preferably, the tantalum-based sheet can be applied to Nb3Sn superconducting wire. Preferably, the tantalum sheet is fully recrystallized, with a grain size of ASTM 6-9 (preferably 6.5-7.5), a hardness of HV / 2.9N≤75, and a room temperature elongation of ≥40% (longitudinal and / or transverse). More preferably, the difference in room temperature elongation of the tantalum sheet in the longitudinal and transverse directions is ≤15%. The tantalum sheet can be used for superconducting wires and / or fusion engineering test reactors.

[0028] According to a third aspect, the present invention also relates to the use of the tantalum-based sheet or tantalum sheet in a superconducting wire and / or a fusion engineering test reactor.

[0029] According to the present invention, one or more of the following advantages can be obtained:

[0030] ① The grains of tantalum sheets are fully broken and refined, with improved deformation superplasticity;

[0031] ② Make the hardness of tantalum sheet more controllable and easier to achieve low hardness of tantalum sheet;

[0032] ③It is easier to achieve surface treatment and purification of tantalum sheets.

[0033] The tantalum sheet is obtained with a grain size of ASTM 6-9 (preferably 6.5-7.5), a hardness of HV / 2.9N≤80, preferably ≤75, and a room temperature elongation of ≥40% (longitudinal and / or transverse). BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 are optical microscope photographs of the microstructures of tantalum ingots obtained according to the embodiments and comparative examples of the present invention, wherein (a) is the microstructure of embodiment 1, (b) is the microstructure of embodiment 2, (c) is the microstructure of embodiment 3, (d) is the microstructure of comparative example 1, (e) is the microstructure of comparative example 2, and (f) is the microstructure of comparative example 3.

[0035] Figure 2 is a bar chart of the mechanical properties of tantalum ingots obtained in various embodiments and comparative examples, where a) is the yield strength (σ 0.2 ) and tensile strength (σ b ) is a bar graph, and b) is a bar graph of elongation.

[0036] Figure 3 It is a bar graph showing the hardness of the tantalum sheets obtained in Examples 1-3.

[0037] Figure 4 Schematic diagram of a specific forging process of step 1) according to an exemplary embodiment of the first aspect of the present invention.

[0038] In order to further understand the present invention, the preparation method of the tantalum-based sheet provided by the present invention is described in detail below in conjunction with the examples, and the protection scope of the present invention is not limited by the following examples.

[0039] These descriptions are only for further illustrating the features and advantages of the present invention, but are not intended to limit the present invention. If no specific conditions are specified in the examples, conventional conditions are used. If no manufacturer is specified for the reagents, raw materials or instruments used, they are all conventional products that can be obtained commercially.

[0040] For the purpose of this specification, all numbers indicating the amount of ingredients, reaction conditions, etc. in the specification and claims should be understood as being modified by the term "about" in all cases, unless otherwise specified. Accordingly, the numerical parameters given in the following specification and the appended claims are approximate values, which may vary according to the desired properties that the present invention attempts to obtain, unless otherwise indicated. At least, and without intending to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be interpreted at least in accordance with the number of reported significant figures and in accordance with conventional rounding techniques.

[0041] Embodiment 1:

[0042] The Φ190mm tantalum ingot is first axially upset with a processing rate of 35%; flattened along radial 1 (first time) with a processing rate of 25%; rotate radial 1 90° and flattened along radial 2 (second time) with a processing rate of 35%; and then flattened and forged along radial 1 with a processing rate of 70%.

[0043] The obtained forging blank is sawn and turned to remove surface defects, and then pickled. The pickling solution is a mixture of HF:HCl:HNO3=1:2:3 mixed acid (volume ratio, HNO3 concentration is 65%; HF concentration is 40%; HCl concentration is 36%). Pickling can further remove surface impurities, and pickling is done until the tantalum metal luster is visible to the naked eye; then, the pickled tantalum forging blank is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min and keep it warm for 90min; then heat up to 1000℃ at 25℃ / min and keep it warm for 90min. Then cool to room temperature.

[0044] The tantalum forging billet obtained above is subjected to the first rolling (also known as billet rolling). Specifically, it is rolled from a thickness of δ=50mm to δ=6.5mm; then it is pickled with the same pickling solution to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled slab is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, and keep it warm for 90min; then heat up to 1000℃ at 25℃ / min, and keep it warm for 90min. Then it is cooled to room temperature to obtain a tantalum slab.

[0045] The tantalum slab is subjected to a second rolling process. Specifically, it is rolled from δ=6.5mm to δ=0.6mm; then it is pickled with the same pickling solution to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled slab is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, and keep it warm for 90min; then heat up to 1000℃ at 25℃ / min, and keep it warm for 90min. Then it is cooled to room temperature to obtain the product tantalum plate.

[0046] Embodiment 2:

[0047] The Φ190mm tantalum ingot is first axially upset with a processing rate of 45%; flattened along radial 1 (first time) with a processing rate of 30%; rotate radial 1 90° and flattened along radial 2 (second time) with a processing rate of 40%; and then flattened and forged along radial 1 with a processing rate of 70%.

[0048] The obtained forging blank is sawed and turned to remove surface defects, and then pickled. The pickling solution is a mixed acid of HF:HCl:HNO3=1:2:3 (volume ratio, HNO3 concentration is 65%; HF concentration is 40%; HCl concentration is 36%), which removes surface impurities and allows the tantalum metal luster to be visible by naked eye observation; the tantalum forging blank after pickling is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, keep warm for 90min; then heat up to 1000℃ at 25℃ / min, and keep warm for 90min. Then cool to room temperature.

[0049] The tantalum forging billet obtained above is rolled for the first time. Specifically, it is rolled from a thickness of δ=50mm to δ=6.5mm; then the same pickling solution is used to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled billet is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, keep warm for 90min; then heat up to 1000℃ at 25℃ / min, and keep warm for 90min. Then cool to room temperature.

[0050] The tantalum slab is subjected to a second rolling process. Specifically, it is rolled from δ=6.5mm to δ=0.6mm; then it is pickled with the same pickling solution to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled slab is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min and keep it warm for 90min (then heat up to 950℃ at 25℃ / min and keep it warm for 90min). Then it is cooled to room temperature to obtain the product tantalum plate.

[0051] Embodiment 3:

[0052] The Φ190mm tantalum ingot is first axially upset with a processing rate of 50%; flattened along radial 1 (first time) with a processing rate of 35%; rotate radial 1 90° and flattened along radial 2 (second time) with a processing rate of 45%; and then flattened and forged along radial 1 with a processing rate of 70%.

[0053] The obtained forging blank is sawed and turned to remove surface defects, and then pickled. The pickling solution is a mixed acid of HF: HCl: HNO3 = 1:2:3 (volume ratio, HNO3 concentration is 65%; HF concentration is 40%; HCl concentration is 36%), to further remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the tantalum forging blank after pickling is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, keep warm for 90min; then heat up to 1000℃ at 25℃ / min, and keep warm for 90min. Then cool to room temperature.

[0054] The tantalum forging billet obtained above is subjected to the first rolling (i.e., billet rolling). Specifically, it is rolled from a thickness of δ=50mm to δ=6.5mm; then, it is pickled with the same solution to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled slab is heat treated, and the specific heating system is to heat up to 600℃ at 20℃ / min, keep warm for 90min; then heat up to 950℃ at 25℃ / min, and keep warm for 90min. Then it is cooled to room temperature.

[0055] The tantalum slab is subjected to a second rolling process. Specifically, it is rolled from δ=6.5mm to δ=0.6mm; then, it is pickled with the same solution to remove surface impurities, and the tantalum metal luster can be seen by naked eye observation; the pickled slab is heat treated, and the specific heating system is to heat it to 600℃ at 20℃ / min, keep it warm for 90min; then heat it to 950℃ at 25℃ / min, and keep it warm for 90min. Then it is cooled to room temperature to obtain the product tantalum plate.

[0056] Comparative Example 1:

[0057] Other conditions are the same as in Example 1.

[0058] The only difference is

[0059] The specific heating system for heat treatment of the tantalum forging billet after the second rolling is: heating from room temperature to 500°C at a heating rate of 10°C / min, keeping warm for 30 minutes; then heating to 800°C at 10°C / min, keeping warm for 30 minutes; then heating to 1000°C at 10°C / min, keeping warm for 90 minutes. Then cooling to room temperature to obtain the product tantalum plate.

[0060] Comparative Example 2:

[0061] Other conditions are the same as in Example 1.

[0062] The only difference is

[0063] The specific heating system for heat treatment of the tantalum forging billet after the first rolling is: heating from room temperature to 500°C at a heating rate of 10°C / min, and keeping warm for 30 minutes; then heating to 800°C at 10°C / min, and keeping warm for 30 minutes; then heating to 1050°C at 10°C / min, and keeping warm for 90 minutes.

[0064] The specific heating system for heat treatment of the tantalum forging billet after the second rolling is: heating from room temperature to 500°C at a heating rate of 10°C / min, keeping warm for 30 minutes; then heating to 800°C at 10°C / min, keeping warm for 30 minutes; then heating to 1000°C at 10°C / min, keeping warm for 90 minutes. Then cooling to room temperature to obtain the product tantalum plate.

[0065] Comparative Example 3:

[0066] Other conditions are the same as in Example 1.

[0067] The only difference is that the specific heating system for heat treatment of the tantalum forging billet after the second rolling is: heating from room temperature to 500°C at a heating rate of 10°C / min, keeping warm for 30 minutes; then heating to 1000°C at 25°C / min, keeping warm for 90 minutes. Then cooling to room temperature to obtain the product tantalum plate.

[0068] The test methods and results of the grain size, room temperature tensile properties, and hardness of the tantalum plates in the examples and comparative examples are summarized as follows:

[0069] 1. The microstructures of the rolled surfaces of the tantalum materials in Examples 1 to 3 and Comparative Examples 1 to 3 were observed using an optical microscope. The results are as follows: Figure 1 According to the "Method for Determination of Average Grain Size of Metals" (GB / T6394-2017), the average grain size of the tantalum plates in Examples 1 to 3 was calculated from Figure 1 The grain sizes are: (a) 6.5, (b) 7.0, and (c) 7.0; the average grain sizes of the tantalum plates produced in Comparative Examples 1-3 are (d) 3.0, (e) 3.0, and (f) 4.0.

[0070] 2. The room temperature tensile properties of the tantalum plates in Examples 1 to 3 and Comparative Examples 1 to 3 were tested according to "Tensile Test of Metal Materials: Room Temperature Test Method" (GB / T228.1-2021). Figure 2 ).

[0071] Among them, the longitudinal tensile strength of the tantalum plate product in Example 1 is 254.4MPa, the yield strength is 143.7MPa, and the elongation after fracture is 56.8%; the transverse tensile strength is 256.3MPa, the yield strength is 148.7MPa, and the elongation after fracture is 51.2%; the deviation between the longitudinal and transverse elongation is 10.93%.

[0072] The longitudinal tensile strength of the rolled tantalum plate of the product in Example 2 is 254.0 MPa, the yield strength is 168.5 MPa, and the elongation after fracture is 60.4%; the transverse tensile strength is 256.6 MPa, the yield strength is 179.0 MPa, and the elongation after fracture is 54.8%; the deviation between the longitudinal and transverse elongations is 10.22%.

[0073] The longitudinal tensile strength of the tantalum plate of Example 3 is 248.7 MPa, the yield strength is 170.1 MPa, and the elongation after fracture is 55.6%; the transverse tensile strength is 252.2 MPa, the yield strength is 169.5 MPa, and the elongation after fracture is 49.6%; the deviation between the longitudinal and transverse elongations is 12.10%.

[0074] The longitudinal tensile strength of the tantalum plate product in Comparative Example 1 is 235.4 MPa, the yield strength is 146.3 MPa, and the elongation after fracture is 35.1% in the longitudinal direction; the transverse tensile strength is 237.4 MPa, the yield strength is 144.3 MPa, and the elongation after fracture is 29.2%; the deviation between the longitudinal and transverse elongations is 20.21%.

[0075] The longitudinal tensile strength of the tantalum plate product in Comparative Example 2 is 242.4 MPa, the yield strength is 156.1 MPa, and the elongation after fracture is 34.9%; the transverse tensile strength is 233.0 MPa, the yield strength is 148.6 MPa, and the elongation after fracture is 28.8%; the deviation between the longitudinal and transverse elongations is 21.18%.

[0076] The longitudinal tensile strength of the tantalum plate product in Comparative Example 3 is 261.3 MPa, the yield strength is 167.2 MPa, and the elongation after fracture is 42.3%; the transverse tensile strength is 257.4 MPa, the yield strength is 162.4 MPa, and the elongation after fracture is 35.4%; the deviation between the longitudinal and transverse elongations is 19.49%.

[0077] It can be seen from these embodiments and comparative examples that the mechanical properties of the embodiments of the present invention are significantly better than those of the comparative examples. In particular, the longitudinal and transverse elongation after fracture of the comparative examples are not as good as those of the embodiments, and the longitudinal and transverse elongation after fracture deviation is significantly greater than that of the embodiments, which cannot meet the high requirements in the industry.

[0078] 3. The Vickers hardness of the tantalum plates in Examples 1 to 3 was tested in accordance with "Metallic Materials Vickers Hardness Test Part 1: Test Method" (GB / T4340.1-2009); the hardness HV / 2.9N (2.9N load) ≤ 75; see Figure 3 ( Figure 3 In HV2.9, the 1st, 2nd and 3rd points represent three different areas on the surface of the test sample).

[0079] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a tantalum sheet, comprising the following steps: 1) Forging the tantalum ingot to obtain a forging blank; 2) heat treating the forging blank; 3) The tantalum forging obtained in step (2) is rolled to obtain a tantalum plate (the rolling processing rate is preferably greater than 65%, more preferably greater than 75%), and the tantalum plate is heat treated.

2. The method according to claim 1, wherein in step 1), the tantalum ingot is heated before forging, for example, by a box-type resistance furnace, preferably heated to 400-420°C.

3. The method according to claim 1 or 2, wherein: The forging in step 1) includes a first processing in a first direction (preferably a processing rate of 30%-60%, more preferably 35% to 50%), a second processing in a second direction (preferably a processing rate of 20%-40%, more preferably 25% to 35%), and a third processing in a third direction (preferably a processing rate of 20-50%, more preferably 35% to 45%), and optionally, also includes a fourth processing (preferably the direction of the fourth processing is the same as the first processing), and its processing rate is preferably greater than 50%, more preferably greater than 65%.

4. The method according to claim 1, 2 or 3, wherein: The temperature of the heat treatment in steps 2) and 3) is respectively 900 to 1050° C. (preferably 950-1000° C.), and the holding time of the heat treatment is 60 to 120 minutes (preferably 80-100 minutes).

5. According to the method of claim 1 or 2 or 3 or 4, the heat treatment in step 2) and 3) each comprises two sub-steps, and preferably, the heating rate of the second sub-step is greater than the heating stage of the first sub-step.

6. The method according to claim 1 or 2 or 3 or 4 or 5, wherein step 3) is repeated 2-3 times, and preferably, the tantalum material is pickled before and / or after each rolling, and the pickling solution is the acid solution in step 2).

7. The method according to claim 1 or 2 or 3 or 4 or 5 or 6, wherein the heat treatment in steps 2) and 3) is each completed by the following method: heating from room temperature to 600°C at 20°C / min, and then keeping the temperature for 90 minutes; then heating to 1000°C at 25°C / min, keeping the temperature for 90 minutes, and then cooling to room temperature.

8. A tantalum sheet having a longitudinal and / or transverse room temperature elongation of ≥40%, and optionally: The grain size is in the ASTM 6-9 range (preferably 6.5-7.5).

9. The tantalum sheet according to claim 8, wherein the tantalum sheet satisfies: The difference between the room temperature tensile properties in the longitudinal and transverse directions is ≤ 15%, and / or Hardness HV / 2.9N ≤ 80, preferably ≤ 75, and / or The tantalum sheet is substantially fully recrystallized.

10. The tantalum sheet according to claim 8 or 9, which is used for superconducting wires and / or fusion engineering test reactors.

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