High-purity fine-grain tantalum target material and preparation method thereof

Abstract

The invention provides a high-purity fine-grain tantalum target material and a preparation method thereof, and relates to the technical field of preparation of refractory metal target materials, and the preparation method comprises the following steps: preparation of tantalum ingots, first forging of blanks, first heat treatment, second forging of blanks, second heat treatment, rolling, third heat treatment and machining. According to the preparation method, firstly, a tantalum strip is smelted into a tantalum cast ingot, then the tantalum cast ingot is sequentially subjected to forging, rolling, heat treatment and machining, the pure tantalum target material is finally obtained, crystalline grains in tantalum are fully crushed and refined through large-deformation forging and pressing deformation, the phenomenon that local crystalline grains are not uniform is further reduced, and therefore the equiaxed crystal tantalum target material with the crystalline grain size ranging from 15 micrometers to 25 micrometers is obtained; and the grains can be further refined while the structure uniformity is ensured, and the requirement of coating on the high-purity fine-grain tantalum target material is met.

Description

Technical Field

[0001] The invention relates to the technical field of refractory metal target material preparation, and in particular to a high-purity fine-grained tantalum target material and a preparation method thereof. Background Art

[0002] Sputtering coating technology uses high-energy ions to bombard the surface of the target material, so that the target material is evenly deposited on the surface of the substrate. This technology has been widely used in semiconductors, microelectronics, microwaves and other fields, and is one of the effective methods for preparing functional films. At present, the industry often combines metal materials with high conductivity with silicon substrates to form electronic component structures. However, at a certain temperature, the highly active metal layer material will diffuse into the Si substrate and react with it to form compounds, which will reduce the service life of the device.

[0003] Tantalum metal not only has high conductivity and high thermal stability, but also can effectively block atomic diffusion, making it an ideal material for a diffusion barrier layer. Therefore, tantalum metal targets have a large market demand. At present, the main methods for preparing tantalum targets include smelting and casting and powder metallurgy. The smelting and casting method refers to the use of high energy sources such as electron beams and arcs to melt tantalum metal and cool it at a certain rate to form an ingot. Compared with powder metallurgy, tantalum targets prepared by smelting and casting have lower gas impurity content, higher density, and higher performance consistency.

[0004] The performance of sputtered films is affected by many factors, including the target material's composition uniformity, grain size, and dimensional stability. Among them, the target material's grain size has an important influence on the film deposition rate and deposition uniformity. With the continuous improvement of the sophistication of integrated circuits, the target material grains also need to be more refined. The grain size of tantalum targets currently used in the market is mostly around 80 to 100 μm, and the uniformity is poor. To meet the development needs of ultrafine-grained targets in the future, it is necessary to further refine the grains while ensuring uniform organization. Therefore, researchers need to conduct more in-depth research on the preparation method of tantalum targets in order to obtain high-purity fine-grained tantalum targets for coating. Summary of the invention

[0005] The purpose of the present invention is to provide a high-purity fine-grained tantalum target material and a preparation method thereof. The present invention first melts tantalum bars into tantalum ingots, and then successively forges, rolls, heat treats, and machines to finally obtain a pure tantalum target material. The forging deformation with a large deformation amount allows the internal grains of the tantalum to be fully crushed and refined, and the phenomenon of local grain unevenness is further reduced, thereby obtaining an equiaxed tantalum target material with a grain size range of 15 to 25 μm. While ensuring uniform organization, the grains can be further refined, meeting the demand for high-purity fine-grained tantalum targets for coating.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a high-purity fine-grained tantalum target, comprising the following steps:

[0008] S1. Preparation of tantalum ingots: preparing tantalum ingots by smelting and casting;

[0009] S2, first forging of blank: the tantalum ingot is subjected to upsetting deformation to obtain a forged tantalum blank; the upsetting deformation includes at least three times, and in each upsetting deformation, the upsetting deformation amount is ≥40%, and the drawing deformation amount is ≥30%;

[0010] S3, first heat treatment: loading the forged tantalum blank into a heat treatment furnace, performing stress relief heat treatment, and obtaining a first heat-treated tantalum blank;

[0011] S4, forging the blank for the second time: using a fast forging machine to continue forging the first heat-treated tantalum blank to form a square blank;

[0012] The forging includes: pressing into a slab after upsetting once; wherein the pressing deformation ratio is 50% to 60%; in the upsetting, the upsetting deformation is 40% to 50%, and the drawing deformation is 45% to 65%;

[0013] S5, second heat treatment: placing the square billet into a heat treatment furnace, performing stress relief heat treatment, and obtaining a second heat-treated tantalum billet;

[0014] S6, rolling: rolling the second heat-treated tantalum blank by a cross-rolling process to obtain a tantalum plate blank;

[0015] S7, third heat treatment: loading the tantalum slab into a heat treatment furnace, performing recrystallization heat treatment, and obtaining a tantalum target slab with an internal structure of equiaxed crystals;

[0016] S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target.

[0017] Furthermore, step S1 specifically includes the following steps: melting the sintered tantalum bar in an electron beam melting furnace, and then casting to obtain a tantalum ingot;

[0018] And / or, the purity of the tantalum ingot is 99.99%;

[0019] And / or, in step S2, the tantalum ingot is subjected to surface polishing and segment cutting before the upsetting deformation;

[0020] The length of the tantalum ingot segment before upsetting and drawing is 100 to 150 mm.

[0021] Furthermore, the melting power of the electron beam melting furnace is 200-220KW, and the vacuum degree of the gun chamber is 1×10 -3Pa~3×10-3Pa, the vacuum degree of the melting furnace chamber is 3×10 -3Pa ~8×10 -3Pa .

[0022] Further, in step S2, three upsetting deformations are performed using forging dies with diameters of 120 mm, 100 mm and 80 mm, respectively;

[0023] And / or, in step S2, in each upsetting deformation, the upsetting deformation amount is 40% to 50%; and the stretching deformation amount is 40% to 65%.

[0024] Furthermore, in step S3, the conditions of the first heat treatment include: a heat treatment temperature of 800 to 1000° C. and a heat preservation time of 1 to 3 hours.

[0025] Furthermore, in step S5, the conditions of the second heat treatment include: a heat treatment temperature of 800 to 1200° C. and a heat preservation time of 1 to 3 hours.

[0026] Furthermore, in step S6, the rolling is cold rolling, and the rolling method is cross rolling;

[0027] And / or, the deformation amount of the single rolling pass is 10% to 30%.

[0028] Furthermore, in step S7, the conditions of the third heat treatment include: a heat treatment temperature of 950 to 1100° C. and a heat preservation time of 1 to 3 hours.

[0029] The present invention also provides a high-purity fine-crystalline tantalum target material obtained by the method for preparing the high-purity fine-crystalline tantalum target material as described above.

[0030] Furthermore, the grain size of the high-purity fine-grained tantalum target material is in the range of 15 to 25 μm.

[0031] The present invention provides a high-purity fine-grained tantalum target material and a preparation method thereof, and the beneficial effects are as follows:

[0032] 1. The present invention first melts tantalum bars into tantalum ingots, and then sequentially forges, rolls, heat treats, and machines to finally obtain pure tantalum targets. The large deformation amount of forging deformation allows the internal grains of tantalum to be fully broken and refined, further reducing the phenomenon of local grain non-uniformity, thereby obtaining equiaxed tantalum targets with a grain size of 15 to 25 μm, ensuring uniform organization while further refining the grains, meeting the demand for high-purity fine-grained tantalum targets for coating.

[0033] 2. The deformation method adopted by the present invention is cold deformation, which is more convenient and quick; the organizational structure is optimized only by annealing heat treatment during the whole process, and no heating is required during deformation; secondly, the target material prepared by this method has finer grains, and the grain size can reach 15 to 25 μm, which is more advantageous for later use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 A process flow chart of a method for preparing a high-purity fine-grained tantalum target provided by the present invention;

[0036] Figure 2 The metallographic image of the rolled surface of the tantalum target prepared in Example 1 provided by the present invention;

[0037] Figure 3 This is a schematic diagram of the tantalum target prepared in Example 1 provided by the present invention observed from a to d;

[0038] Figure 4 The metallographic image of the rolled cross section of the tantalum target material corresponding to the region a prepared in Example 1 provided by the present invention;

[0039] Figure 5 The metallographic image of the rolled cross section of the tantalum target material corresponding to the region b prepared in Example 1 provided by the present invention;

[0040] Figure 6 The metallographic image of the rolled cross section of the tantalum target material corresponding to the c region prepared in Example 1 provided by the present invention;

[0041] Figure 7 The metallographic image of the rolled cross section of the tantalum target material corresponding to the d region prepared in Example 1 provided by the present invention;

[0042] Figure 8 is a metallographic image of the tantalum target prepared in Comparative Example 1;

[0043] Fig. 9 This is the metallographic image of the tantalum target prepared in Comparative Example 2. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0045] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0046] According to the following Figure 1 The process flow chart shown describes a high-purity fine-grained tantalum target material and a preparation method thereof provided by the present invention:

[0047] According to a first aspect of the present invention, there is provided a method for preparing a high-purity fine-grained tantalum target, comprising the following steps:

[0048] S1. Preparation of tantalum ingots: preparing tantalum ingots by smelting and casting;

[0049] S2, first forging of blank: the tantalum ingot is subjected to upsetting deformation to obtain a forged tantalum blank; the upsetting deformation includes at least three times, and in each upsetting deformation, the upsetting deformation amount is ≥40%, and the drawing deformation amount is ≥30%;

[0050] S3, first heat treatment: loading the forged tantalum blank into a heat treatment furnace, performing stress relief heat treatment, and obtaining a first heat-treated tantalum blank;

[0051] S4, forging the blank for the second time: using a fast forging machine to continue forging the first heat-treated tantalum blank to form a square blank;

[0052] The forging includes: pressing into a slab after upsetting once; wherein the pressing deformation ratio is 50% to 60% (such as 52%, 54%, 56%, 58%, etc.); in the upsetting, the upsetting deformation is 40% to 50% (such as 42%, 44%, 46%, 48%, etc.), and the drawing deformation is 45% to 65% (such as 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, etc.);

[0053] S5, second heat treatment: placing the square billet into a heat treatment furnace, performing stress relief heat treatment, and obtaining a second heat-treated tantalum billet;

[0054] S6, rolling: rolling the second heat-treated tantalum blank by a cross-rolling process to obtain a tantalum plate blank;

[0055] S7, third heat treatment: loading the tantalum slab into a heat treatment furnace, performing recrystallization heat treatment, and obtaining a tantalum target slab with an internal structure of equiaxed crystals;

[0056] S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target.

[0057] The deformation method adopted by the present invention is cold deformation, which is more convenient and quick; the organizational structure is optimized only by annealing heat treatment during the whole process, and no heating is required during deformation; secondly, the target material prepared by this method has finer grains, and the grain size range can reach 15 to 25 μm, which is more advantageous for later use.

[0058] The present invention first melts tantalum bars into tantalum ingots, and then sequentially forges, rolls, heat treats, and machines to finally obtain pure tantalum target materials. Through large deformation forging deformation, the internal grains of tantalum are fully broken and refined, and the phenomenon of local grain unevenness is further reduced, thereby obtaining a tantalum target material with a grain size range of 15 to 25 μm, which meets the coating requirements.

[0059] As an optional embodiment of the present invention, in the step of preparing the tantalum ingot, the sintered tantalum bar is melted in an electron beam melting furnace, and then cast to obtain the tantalum ingot;

[0060] The smelting process of the present invention can ensure that the purity of the obtained tantalum ingot reaches 99.99%.

[0061] As an optional embodiment of the present invention, in the first forging step of the blank: before the upsetting deformation, the tantalum ingot is also subjected to surface polishing and segment cutting;

[0062] The length of the tantalum ingot segment before upsetting and drawing is 100 to 150 mm (eg, 110 mm, 120 mm, 130 mm, 140 mm, etc.).

[0063] As an optional embodiment of the present invention, the melting power of the electron beam melting furnace is 200-220KW (such as 205KW, 210KW, 215KW, etc.), and the vacuum degree of the gun chamber is 1×10 -3 Pa~3×10 -3 Pa (e.g. 1.5×10 -3 Pa, 2×10 - 3 Pa, 2.5×10-3 Pa, etc.), the vacuum degree of the melting furnace chamber is 3×10 -3 Pa~8×10 -3 Pa (e.g. 4×10 -3 Pa, 5×10 -3 Pa, 6×10 -3 Pa, 7×10 -3 Pa, etc.

[0064] As an optional embodiment of the present invention, in the first forging step of the blank: forging dies with diameters of 120 mm, 100 mm and 80 mm are used in sequence to perform upsetting deformation three times;

[0065] In the present invention, one-time upsetting and drawing deformation means: upsetting once and then drawing once;

[0066] In step S2, in each upsetting deformation, the upsetting deformation amount is 40% to 50% (for example, 42%, 44%, 46%, 48%, etc.); the stretching deformation amount is 40% to 65% (for example, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, etc.).

[0067] Specifically, the purpose of using dies with different diameters for upsetting deformation is to ensure the upsetting deformation amount, so that the upsetting deformation amount reaches more than 40%, and the drawing deformation amount reaches more than 30%.

[0068] Furthermore, as the diameter of the die continues to decrease, the larger upsetting deformation and stretching deformation cause the grains to be subjected to external forces and produce dislocation defects, which cause the dislocations to slip, resulting in the grains being fully broken and refined.

[0069] Furthermore, the upsetting operation can be performed by using a fast forging machine or by replacing a deformation die.

[0070] As an optional embodiment of the present invention, in the first heat treatment step:

[0071] The conditions of the first heat treatment include: a heat treatment temperature of 800-1000° C. (such as 850° C., 900° C., 950° C., etc.) and a heat preservation time of 1-3 h (such as 1.5 h, 2 h, 2.5 h, etc.).

[0072] As an optional embodiment of the present invention, in the second heat treatment step:

[0073] The conditions of the second heat treatment include: a heat treatment temperature of 800-1200°C (such as 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, etc.), and a holding time of 1-3h (such as 1.5h, 2h, 2.5h, etc.).

[0074] As an optional embodiment of the present invention, in the rolling step:

[0075] The rolling is cold rolling, and the rolling method is cross rolling;

[0076] The cross rolling is to change the rolling direction during the rolling process, for example, after rolling once in the width direction, the rolling direction is adjusted by 90° before rolling again.

[0077] The deformation amount of the single rolling pass is 10% to 30% (eg, 15%, 20%, 25%, etc.).

[0078] As an optional embodiment of the present invention, in the third heat treatment step:

[0079] The conditions of the third heat treatment include: a heat treatment temperature of 950-1100°C (such as 980°C, 1000°C, 1020°C, 1040°C, 1060°C, 1080°C, etc.), and a holding time of 1-3h (such as 1.5h, 2h, 2.5h, etc.).

[0080] Specifically, the present invention limits the temperature of the third heat treatment to 950-1100°C because if the temperature is too high, the grain size is likely to grow and cannot meet the use requirements; if the temperature is too low, the grains cannot complete recrystallization and cannot form equiaxed crystals.

[0081] Specifically, the first heat treatment and the second heat treatment are stress relief annealing, which mainly play the role of eliminating residual stress. Too low or too high temperature will affect the stress relief effect; the third heat treatment is recrystallization annealing, which plays the role of optimizing grains.

[0082] As an optional embodiment of the present invention, the grain size of the high-purity fine-grained tantalum target is 15 to 25 μm (such as 18 μm, 20 μm, 22 μm, 24 μm, etc.).

[0083] According to a second aspect of the present invention, there is provided a high-purity fine-crystalline tantalum target material, which is prepared by the above-mentioned method for preparing a high-purity fine-crystalline tantalum target material.

[0084] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0085] It should be noted that the grain size is measured using the intercept method in the metal average grain size measurement method.

[0086] Example 1

[0087] S1. Preparation of tantalum ingots: Sintered tantalum bars were melted in an electron beam melting furnace with a melting power of 220KW and a chamber vacuum of 1.0×10 -3Pa, the vacuum degree of the melting furnace chamber is 3.0×10 -3 Pa, smelted twice to obtain a high-purity tantalum ingot with a specification of 155×1200mm (diameter×length), and the purity of the tantalum ingot is 99.99%.

[0088] S2. First forging of billet: Use a general lathe to polish the surface of the high-purity tantalum ingot to obtain a tantalum ingot with a diameter of 150 mm, and use a sawing machine to cut the high-purity tantalum ingot into high-purity tantalum ingot segments with a length of 120 mm.

[0089] First, the high-purity tantalum ingot segment with a length of 120 mm is forged using a forging die with a diameter of 120 mm, and upsetting and deforming is performed once to obtain a tantalum ingot with a size of 120×190 mm (diameter×length);

[0090] Then, the tantalum ingot with the specification of 120×190 mm is deformed by upsetting once using a forging die with a diameter of 100 mm to obtain a tantalum ingot with a size of 100×270 mm (diameter×length);

[0091] Finally, the tantalum ingot is upset and deformed once more using a forging die with a diameter of 80 mm to obtain a tantalum ingot with a specification of 80×420 mm (diameter×length).

[0092] Among them, in each upsetting deformation, the upsetting deformation is 50%; the three stretching deformations are 64%, 45%, and 45% respectively.

[0093] S3, first heat treatment: the tantalum ingot with a specification of 80×420 mm after forging is placed into a heat treatment furnace, and subjected to stress relief heat treatment at 900° C. for 1 hour;

[0094] S4. Second forging of blank: The tantalum ingot after the above heat treatment is cut into 3 sections, each with a specification of 80×140 mm. After being upset and drawn once by a fast forging machine, it is pressed into a square plate blank of 35×144×140 mm (thickness×width×length); during the upsetting and drawing, the upsetting deformation is 50%, the drawing deformation is 50%, and the pressing deformation ratio is 56%.

[0095] S5. Second heat treatment: Place the square slab with the specification of 35×144×140 mm into a heat treatment furnace and perform stress relief heat treatment at 800° C. for 1 hour;

[0096] S6. Rolling: The tantalum billet after the above heat treatment is cold rolled along the width direction by cross rolling process, the deformation of a single pass is 30%, the width is rolled to 230 mm and then adjusted, the thickness is rolled to 9 mm, and the size of the semi-finished product after rolling is 9×230×340 mm.

[0097] S7, third heat treatment: the rolled tantalum plate blank is loaded into a heat treatment furnace, and recrystallized at 950°C for 1 hour to obtain a tantalum target slab with an internal structure of equiaxed crystals, a grain size of 20 μm, and a grain range of 15 to 25 μm;

[0098] S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target finished product.

[0099] The grain size of the tantalum target prepared by the existing preparation method is basically 80-100 μm, and there is often a problem of large local grain size in grain distribution. However, the grain size of the tantalum target prepared by the present invention is within the range of 15-25 μm: Figure 2 As shown, it is a metallographic image of the rolled surface of the tantalum target prepared in Example 1, and it can be seen that the grain size is small and evenly distributed;

[0100] like Figure 3 As shown in the figure, the metallographic specimen is observed from regions a to d, and region a corresponds to the metallographic image of the rolled section of the tantalum target. Figure 4 As shown; area b corresponds to the metallographic diagram of the rolled section of the tantalum target, as shown Figure 5 As shown; the c area corresponds to the metallographic diagram of the rolled section of the tantalum target, as shown Figure 6 As shown; the d area corresponds to the metallographic diagram of the rolled section of the tantalum target, as shown Figure 7 As shown; the grain size in each area a~d is small and evenly distributed, and the grain size is measured to be in the range of 15~25μm.

[0101] Example 2

[0102] S1. Preparation of tantalum ingots: Sintered tantalum bars were melted in an electron beam melting furnace with a melting power of 220KW and a chamber vacuum of 3.0×10 -3 Pa, the vacuum degree of the melting furnace chamber is 8.0×10 -3 Pa, smelted twice to obtain a high-purity tantalum ingot with a specification of 155×1200mm (diameter×length).

[0103] S2. First forging billet: Use a general lathe to polish the surface of the high-purity tantalum ingot to a diameter of 150 mm, and use a saw to cut the high-purity tantalum ingot into high-purity tantalum ingot segments with a length of 150 mm.

[0104] First, the high-purity tantalum ingot segment with a length of 150 mm is forged using a forging die with a diameter of 120 mm, and upsetting and drawing is performed once to obtain a tantalum ingot with a size of 120×240 mm (diameter×length);

[0105] Then, the tantalum ingot with the specification of 120×240 mm is upset and deformed once by using a forging die with a diameter of 100 mm to obtain a tantalum ingot with a size of 100×345 mm (diameter×length);

[0106] Finally, the tantalum ingot is upset and deformed once more using a forging die with a diameter of 80 mm to obtain a tantalum ingot with a specification of 80×540 mm (diameter×length).

[0107] Among them, in each upsetting deformation, the upsetting deformation is 50%; the three stretching deformations are 64%, 45%, and 45% respectively.

[0108] S3, first heat treatment: the forged tantalum ingot with a specification of 80×540 mm is placed into a heat treatment furnace, and subjected to stress relief heat treatment at 900° C. for 2 hours;

[0109] S4. Second forging blank: The tantalum ingot after the above heat treatment is cut into 3 sections, each with a specification of 80×180mm. After being upset and drawn once by a fast forging machine, the height is upset short and then pressed into a square plate blank of 35×160×160mm (thickness×width×length); during the upsetting and drawing, the upsetting deformation is 50%, the drawing deformation is 50%, and the pressing deformation ratio is 56%.

[0110] S5, second heat treatment: the square slab with the specification of 35×160×160 mm is placed in a heat treatment furnace, and subjected to stress relief heat treatment at 1100° C. for 2 hours;

[0111] S6. Rolling: The tantalum billet after the heat treatment is cold rolled along the width direction by cross rolling process, the deformation of a single pass is 30%, the width is rolled to 230mm and then the direction is adjusted, the thickness is rolled to 9mm, and the size of the semi-finished product after rolling is 9×230×340mm

[0112] S7, third heat treatment: the rolled tantalum plate blank is loaded into a heat treatment furnace, and recrystallized at 1100°C for 1 hour to obtain a tantalum target blank with an internal structure of equiaxed crystals; the grain size range is 15 to 25 μm;

[0113] S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target finished product.

[0114] Example 3

[0115] S1. Preparation of tantalum ingots: Sintered tantalum bars were melted in an electron beam melting furnace with a melting power of 220KW and a chamber vacuum of 1.0×10 -3 Pa, the vacuum degree of the melting furnace chamber is 5.0×10 -3 Pa, smelted twice to obtain a high-purity tantalum ingot with a specification of 155×1200mm (diameter×length).

[0116] S2. First forging billet: Use a general lathe to polish the surface of the high-purity tantalum ingot to a diameter of 150 mm, and use a saw to cut the high-purity tantalum ingot into high-purity tantalum ingot segments with a length of 150 mm.

[0117] First, the high-purity tantalum ingot segment with a length of 150 mm is forged using a forging die with a diameter of 120 mm, and upsetting and drawing is performed once to obtain a tantalum ingot with a size of 120×240 mm (diameter×length);

[0118] Then, the tantalum ingot with the specification of 120×240 mm is upset and deformed once by using a forging die with a diameter of 100 mm to obtain a tantalum ingot with a size of 100×345 mm (diameter×length);

[0119] Finally, the tantalum ingot is upset and deformed once more using a forging die with a diameter of 80 mm to obtain a tantalum ingot with a specification of 80×540 mm (diameter×length).

[0120] Among them, in each upsetting deformation, the upsetting deformation is 50%; the three stretching deformations are 64%, 45%, and 45% respectively.

[0121] S3, first heat treatment: the forged tantalum ingot with a specification of 80×540 mm is placed into a heat treatment furnace, and subjected to stress relief heat treatment at 900° C. for 2 hours;

[0122] S4. Second forging blank: The tantalum ingot after the above heat treatment is cut into 3 sections, each with a specification of 80×180mm. After being upset and drawn once by a fast forging machine, the height is upset short and then pressed into a square plate blank of 35×160×160mm (thickness×width×length); during the upsetting and drawing, the upsetting deformation is 50%, the drawing deformation is 50%, and the pressing deformation ratio is 56%.

[0123] S5, second heat treatment: the square slab with the specification of 35×160×160 mm is placed in a heat treatment furnace, and subjected to stress relief heat treatment at 1200° C., and kept at this temperature for 1 hour;

[0124] S6. Rolling: The tantalum billet after the above heat treatment is cold rolled along the width direction by cross rolling process, the deformation of a single pass is 30%, the width is rolled to 230 mm and then adjusted, the thickness is rolled to 9 mm, and the size of the semi-finished product after rolling is 9×230×340 mm.

[0125] S7, third heat treatment: the rolled tantalum plate blank is loaded into a heat treatment furnace, and recrystallized at 950°C for 3 hours to obtain a tantalum target slab with an equiaxed crystal structure and a grain size of 15 to 25 μm;

[0126] S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target finished product.

[0127] Comparative Example 1

[0128] In this comparative example, except that the third heat treatment temperature in step S7 is 900° C., other processes and parameters are the same as those in Example 1.

[0129] like Figure 8 As shown, it is the metallographic structure diagram of the third heat treatment at 900°C. Due to the low temperature, the grains are not completely recrystallized and equiaxed crystals cannot be formed, so the grain size of the target material cannot be measured.

[0130] Comparative Example 2

[0131] In this comparative example, except that the third heat treatment temperature in step S7 is 870° C., other processes and parameters are the same as those in Example 1.

[0132] like Fig. 9 As shown, it is the metallographic structure diagram of the third heat treatment at 870°C. Due to the low temperature, the grains are not completely recrystallized and equiaxed crystals cannot be formed, so the grain size of the target material cannot be measured.

[0133] Comparative Example 3

[0134] In this comparative example, except that the section of the high-purity tantalum ingot before the upsetting deformation in step S2 is 180 mm, other processing parameters are the same as those in Example 1. The measured target grain size range is 31-42 μm.

[0135] Compared with Example 1, the comparative example has different tantalum ingot segments before upsetting deformation, so the length after forging is different, which will affect the final grain size and uniformity. The longer the length, the longer the length after forging, which has the problem of insufficient grain crushing, and the ingot is prone to tilt when upsetting after the length is increased, with irregular shapes and larger grain sizes.

[0136] Comparative Example 4

[0137] The main difference between this comparative example and Example 1 is that in step S2, the upsetting deformation is 20% during each upsetting process, and the other processes and parameters are the same as those of Example 1. The measured target grain size is 32-45 μm.

[0138] Compared with Example 1, in this comparative example, the upsetting deformation amount is relatively small during each upsetting process, resulting in that the grains are not fully broken and refined, resulting in a relatively large grain size of the target material.

[0139] Comparative Example 5

[0140] The main difference between this comparative example and Example 1 is that in step S2, the three elongation deformations are all 20%, and the other processes and parameters are the same as those in Example 1. The measured target grain size is 37-50 μm.

[0141] Compared with Example 1, in this comparative example, the amount of elongation deformation during each upsetting process is relatively small, resulting in insufficient crushing and refinement of the grains, resulting in a relatively large grain size of the target material.

[0142] Comparative Example 6

[0143] The main difference between this comparative example and Example 1 is that in step S4, the pressing deformation ratio is 30%, and the other processes and parameters are the same as those of Example 1. The measured target grain size is 45-65 μm.

[0144] Compared with Example 1, in this comparative example, the pressing deformation ratio is relatively small during each forging process, resulting in that the grains are not sufficiently crushed and refined, resulting in a relatively large grain size of the target material.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-purity fine-grained tantalum target, characterized in that: The steps include: S1. Preparation of tantalum ingots: preparing tantalum ingots by smelting and casting; S2, first forging of blank: the tantalum ingot is subjected to upsetting deformation to obtain a forged tantalum blank; the upsetting deformation includes at least three times, and in each upsetting deformation, the upsetting deformation amount is ≥40%, and the drawing deformation amount is ≥30%; S3, first heat treatment: loading the forged tantalum blank into a heat treatment furnace, performing stress relief heat treatment, and obtaining a first heat-treated tantalum blank; S4, forging the blank for the second time: using a fast forging machine to continue forging the first heat-treated tantalum blank to form a square blank; The forging includes: pressing into a slab after upsetting once; wherein the pressing deformation ratio is 50% to 60%; in the upsetting, the upsetting deformation is 40% to 50%, and the drawing deformation is 45% to 65%; S5, second heat treatment: placing the square billet into a heat treatment furnace, performing stress relief heat treatment, and obtaining a second heat-treated tantalum billet; S6, rolling: rolling the second heat-treated tantalum blank by a cross-rolling process to obtain a tantalum plate blank; S7, third heat treatment: loading the tantalum slab into a heat treatment furnace, performing recrystallization heat treatment, and obtaining a tantalum target slab with an internal structure of equiaxed crystals; S8. Machining: machining the tantalum target slab to obtain a high-purity fine-grained tantalum target.

2. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: Step S1 specifically includes the following steps: melting the sintered tantalum bars in an electron beam melting furnace, and then casting to obtain tantalum ingots; And / or, the purity of the tantalum ingot is 99.99%; And / or, in step S2, the tantalum ingot is subjected to surface polishing and segment cutting before the upsetting deformation; The length of the tantalum ingot segment before upsetting and drawing is 100 to 150 mm.

3. The method for preparing a high-purity fine-grained tantalum target according to claim 2, characterized in that: The melting power of the electron beam melting furnace is 200-220KW, and the vacuum degree of the gun chamber is 1×10 -3 Pa~3×10 -3 Pa, the vacuum degree of the melting furnace chamber is 3×10 - 3 Pa~8×10 -3 Pa.

4. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: In step S2, three upsetting deformations are performed using forging dies with diameters of 120 mm, 100 mm and 80 mm respectively; And / or, in step S2, in each upsetting deformation, the upsetting deformation amount is 40% to 50%; and the stretching deformation amount is 40% to 65%.

5. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: In step S3, the conditions of the first heat treatment include: a heat treatment temperature of 800 to 1000° C. and a heat preservation time of 1 to 3 hours.

6. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: In step S5, the conditions of the second heat treatment include: the heat treatment temperature is 800-1200° C., and the heat preservation time is 1-3 hours.

7. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: In step S6, the rolling is cold rolling, and the rolling method is cross rolling; And / or, the deformation amount of the single rolling pass is 10% to 30%.

8. The method for preparing a high-purity fine-grained tantalum target according to claim 1, characterized in that: In step S7, the conditions of the third heat treatment include: the heat treatment temperature is 950-1100° C., and the heat preservation time is 1-3 hours.

9. A high-purity fine-crystalline tantalum target material obtained by the method for preparing a high-purity fine-crystalline tantalum target material as described in any one of claims 1 to 8.

10. The high-purity fine-grained tantalum target according to claim 9, characterized in that: The grain size of the high-purity fine-grained tantalum target material is in the range of 15 to 25 μm.

Images