Preparation method of large-size alloy tantalum blank and prepared alloy tantalum blank

Abstract

The invention provides a preparation method of a large-size alloy tantalum blank, which belongs to the technical field of tantalum alloy processing, and comprises the following steps: firstly, selecting tantalum powder and doped powder, and fully and uniformly mixing to obtain alloy tantalum powder; then carrying out cold isostatic pressing molding on the alloy tantalum powder to obtain a square fillet alloy blank; the square fillet alloy blank is placed in a vacuum sintering furnace, direct current is introduced for vertical sintering, the vacuum degree ranges from 1.0 * 10 <-2 > Pa to 1.0 * 10 <-3 > Pa, the sintering temperature ranges from 2400 DEG C to 2600 DEG C, and the heat preservation time ranges from 2 h to 3 h; in the direct current sintering process, non-uniform heating of the interior of the sintered material caused by intermittence is avoided, and the grain structure in the blank is more uniform; and after sintering is completed, inert gas is firstly introduced for rapid cooling in a gradient cooling mode, non-uniformity of crystal grains in the blank caused by overgrowth of the crystal grains due to the fact that the blank is in a high-temperature stage for a long time can be avoided, and then the blank is naturally cooled to the room temperature, so that the large-specification alloy tantalum blank with the mass of 10-15 kg is obtained, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tantalum alloy processing, and particularly relates to a method for preparing a large-sized alloy tantalum billet and the obtained alloy tantalum billet. Background Art

[0002] Tantalum alloys play an irreplaceable role in multiple high-tech fields due to their unique physical and chemical properties. For example, tantalum alloys are mainly used in the electronics industry to manufacture capacitors, semiconductors, integrated circuits, and electronic packages. Among them, tantalum capacitors, with their excellent electrical conductivity and stable electrochemical properties, operate within a wide temperature range, have extremely low leakage current, and high reliability, making them very suitable for use in advanced communication equipment, military, and avionics systems. Therefore, the preparation of tantalum alloy billets is of great significance for improving material properties, expanding application fields, and promoting related technological progress.

[0003] Currently, in industrial production activities, the traditional method for preparing tantalum alloy billets is mainly powder metallurgy. It forms tantalum or tantalum alloy ingots through the processes of tantalum powder forming and vacuum vertical melting sintering. However, during the process of vertical melting and sintering the materials, enterprises all use a single-phase AC low-voltage high-current method to sinter the materials. Due to the periodic change of the current in the alternating current, the intermittent heating of the materials by the alternating current inevitably causes uneven heating inside the sintered materials, resulting in the quality of the tantalum billets obtained by traditional vertical melting sintering being between 4 kg and 6 kg, which cannot meet the high production efficiency requirements of production enterprises. Summary of the Invention

[0004] In view of this, in order to address the above deficiencies, it is necessary to propose a method for preparing a large-sized alloy tantalum billet, where the mass of the large-sized alloy tantalum billet is 10 kg - 15 kg, to improve the production efficiency of the alloy tantalum billet; It is also necessary to provide an alloy tantalum billet.

[0005] On the one hand, a method for preparing a large-sized alloy tantalum billet provided by the present invention includes the following steps: Step 1: Select tantalum powder and doping powder and mix them evenly to obtain alloy tantalum powder; Step 2: Cold isostatically press the alloy tantalum powder to form a square-round-corner alloy blank; Step 3: Place the square-round-corner alloy blank in a vacuum sintering furnace and conduct vertical melting sintering by passing direct current, where the vacuum degree is 1.0×10 -2 Pa - 1.0×10 -3 Pa, the sintering temperature is 2400°C - 2600°C, and the holding time is 2 h - 3 h; Step 4: After sintering is completed, adopt a gradient cooling method. First, introduce an inert gas for rapid cooling, and then naturally cool to room temperature to obtain a large-sized tantalum alloy blank.

[0006] Preferably, in the said Step 1, the doping powder is niobium powder or tungsten powder or rare earth oxide powder or metal nitrate powder.

[0007] Preferably, in the said Step 1, the loose bulk density of the tantalum powder is 3.0 g / cm 3 - 3.5 g / cm 3 , and the average particle size of the tantalum powder and the doping powder is 5.0 µm - 7.5 µm.

[0008] Preferably, in the said Step 1, the content of the doping powder in the tantalum alloy powder is 100 ppm - 500 ppm.

[0009] Preferably, the said Step 1 is specifically: put the tantalum powder and the doping powder into a "V"-type mixer and first perform forward pre-mixing for 30 min - 60 min. After the pre-mixing is completed, then perform reverse secondary mixing for 30 min - 60 min to obtain tantalum alloy powder.

[0010] Preferably, the said Step 2 is specifically: put the tantalum alloy powder into a cylindrical square-rounded rubber sleeve, after kneading and forming and sealing, place it in a cold isostatic pressing machine, pressurize to a predetermined pressure and hold the pressure for a predetermined time, and then release the pressure and demold to complete cold isostatic pressing and forming to obtain a square-rounded alloy blank.

[0011] Preferably, the said predetermined pressure is 150 MPa - 250 MPa, and the said predetermined time is 10 min - 20 min.

[0012] Preferably, in the said Step 3, the voltage of the direct current is 20 V - 30 V, and the current is 700 A - 850 A.

[0013] Preferably, the said Step 4 is specifically: S41: After sintering is completed, introduce an inert gas to cool the tantalum alloy blank at a cooling rate of 100 - 200 °C per minute to 750 °C - 800 °C, wherein the inert gas is argon or helium; S42: Stop introducing the inert gas and evacuate to 1.0×10 -2 Pa - 1.0×10 -3 Pa; S43: Naturally cool to room temperature to obtain a large-sized tantalum alloy blank.

[0014] On the other hand, the present invention provides a tantalum alloy blank, which is prepared by the preparation method of the large-sized tantalum alloy blank described in the above aspect.

[0015] As can be seen from the above technical solutions, a method for preparing a large-sized tantalum alloy billet provided by the present invention first selects tantalum powder and doping powder and mixes them evenly to obtain tantalum alloy powder; then, the tantalum alloy powder is cold isostatically pressed into a square-round-corner alloy billet. The square-round-corner alloy billet is convenient for the effective fixation of the sintering chuck in a vacuum sintering furnace, increasing the contact area between the billet and the chuck, thereby reducing the bar-drop rate during sintering; then, the square-round-corner alloy billet is placed in a vacuum sintering furnace and subjected to vertical melting sintering by passing direct current. Among them, the vacuum degree is 1.0×10 -2 Pa - 1.0×10 -3 Pa, the sintering temperature is 2400°C - 2600°C, and the holding time is 2h - 3h, so that the square-round-corner alloy billet generates heat due to its own resistance. At the same time, during the process of using direct current sintering, the intermittent heating caused by alternating current is avoided, ensuring the continuous and stable heat inside the billet, and further making the grain structure inside the billet more uniform; after sintering, a gradient cooling method is adopted. First, an inert gas is introduced for rapid cooling, which can avoid the uneven growth of grains inside the billet caused by the billet being in the high-temperature stage for a long time, and then natural cooling to room temperature can gradually reduce the internal stress of the billet to prevent the billet from cracking or deforming, thereby obtaining a large-sized tantalum alloy billet with a mass of 10 kg - 15 kg to improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of the method for preparing a large-sized tantalum alloy billet provided by the embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of the fixation of the square-round-corner alloy billet and the sintering chuck obtained by the embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram of the fixation of the circular compact and the sintering chuck obtained by the comparative example of the traditional method.

[0019] Figure 4 It is a metallographic picture of the core part of the large-sized tantalum alloy billet obtained by the embodiment of the present invention.

[0020] Figure 5 It is a metallographic picture of the periphery of the large-sized tantalum alloy billet obtained by the embodiment of the present invention.

[0021] Figure 6 It is a metallographic picture of the core part of the rod-shaped sintered tantalum alloy billet obtained by the comparative example of the traditional method.

[0022] Figure 7 It is a metallographic picture of the periphery of the rod-shaped sintered tantalum alloy billet obtained by the comparative example of the traditional method. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] For a better understanding of the present invention, the following describes the present invention in further detail in conjunction with embodiments. However, the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0024] Please refer to Figure 1 , on the one hand, a method for preparing a large-sized tantalum alloy blank provided by the present invention includes the following steps: Step 1: Select tantalum powder and doping powder and mix them evenly to obtain tantalum alloy powder; Step 2: Cold isostatically press the tantalum alloy powder to form a square-round-corner alloy blank; Step 3: Place the square-round-corner alloy blank in a vacuum sintering furnace and conduct vertical melting sintering by passing direct current, wherein the vacuum degree is 1.0×10 -2 Pa - 1.0×10 -3 Pa, the sintering temperature is 2400°C - 2600°C, and the holding time is 2h - 3h; Step 4: After sintering, adopt a gradient cooling method, first pass in an inert gas for rapid cooling, and then naturally cool to room temperature to obtain a large-sized tantalum alloy blank.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for preparing a large-sized tantalum alloy blank provided by the present invention first selects tantalum powder and doping powder and mixes them evenly to obtain tantalum alloy powder; then cold isostatically presses the tantalum alloy powder to form a square-round-corner alloy blank, please refer to Figure 2 and Figure 3 , wherein the square-round-corner alloy blank is convenient for the effective fixation of the sintering chuck in the vacuum sintering furnace, increases the contact area between the blank and the chuck, and thus reduces the bar-drop rate during sintering; then place the square-round-corner alloy blank in a vacuum sintering furnace and conduct vertical melting sintering by passing direct current, wherein the vacuum degree is 1.0×10 -2 Pa - 1.0×10 -3Pa, the sintering temperature is 2400°C - 2600°C, and the heat preservation time is 2h - 3h, so that the square-round alloy blank generates heat due to its own resistance. At the same time, during the process of sintering with direct current, the intermittent heating caused by alternating current is avoided, ensuring uniform heat inside the sintered material and continuous and stable heat inside the blank. As a result, the grain structure inside the blank is more uniform. After sintering, a gradient cooling method is adopted. First, an inert gas is introduced for rapid cooling, which can prevent the grains from overgrowing due to the blank being in the high-temperature stage for a long time, resulting in non-uniform grains inside the blank. Then, natural cooling to room temperature can gradually reduce the internal stress of the blank to prevent the blank from cracking or deforming, thereby obtaining a large-sized alloy tantalum blank with a mass of 10kg - 15kg, improving production efficiency. For example, in the prior art, vacuum alternating current vertical melting sintering takes 4 hours for 6kg, while the vacuum direct current vertical melting sintering of the present invention takes 4 hours for 12kg. With the same sintering time, the mass of the alloy tantalum blank has doubled, the sintering efficiency has been significantly improved, and the cost is significantly lower.

[0026] In one embodiment, in the step 1, the doped powder is niobium powder or tungsten powder or rare earth oxide powder or metal nitrate powder.

[0027] In one embodiment, the loose bulk density of the tantalum powder is 3.0g / cm 3 - 3.5g / cm 3 and the average particle size of the tantalum powder and the doped powder is 5.0µm - 7.5µm.

[0028] In one embodiment, in the step 1, the content of the doped powder in the alloy tantalum powder is 100ppm - 500ppm.

[0029] In one embodiment, the step 1 is specifically: first, the tantalum powder and the doped powder are pre-mixed in the forward direction for 30min - 60min, and after the pre-mixing is completed, reverse secondary mixing is carried out for 30min - 60min to obtain alloy tantalum powder.

[0030] In one embodiment, the step 2 is specifically: the alloy tantalum powder is loaded into a cylindrical square-round rubber sheath, kneaded and formed, sealed, then placed in a cold isostatic press, pressurized to a predetermined pressure and held for a predetermined time, and then depressurized and demolded to complete cold isostatic pressing and forming, obtaining a square-round alloy blank.

[0031] In this application, isostatic pressing forming is to place the sample to be pressed in a high-pressure container and uniformly press the sample from all directions by using the incompressible property of the liquid medium and the property of uniform pressure transmission. When the liquid medium is injected into the pressure vessel through a pressure pump, its pressure remains unchanged and is uniformly transmitted to all directions. Cold isostatic pressing is an isostatic pressing method for forming workpieces at room temperature.

[0032] In one embodiment, in order to make the structure of the square-rounded alloy blank uniform, with high density and small shrinkage rate, the predetermined pressure is 150 MPa - 250 MPa, and the predetermined time is 10 min - 20 min.

[0033] In one embodiment, in step 3, the voltage of the direct current is 20 V - 30 V, and the current is 700 A - 850 A.

[0034] In one embodiment, step 4 is specifically as follows: S41: After sintering is completed, an inert gas is introduced, and the tantalum alloy blank is cooled to 750 °C - 800 °C at a cooling rate of 100 - 200 °C per minute, where the inert gas is argon or helium; S42: Stop introducing the inert gas and evacuate to 1.0×10 -2 Pa - 1.0×10 -3 Pa; S43: Naturally cool to room temperature to obtain a large-sized tantalum alloy blank.

[0035] On the other hand, the present invention provides a tantalum alloy blank prepared by the preparation method of the large-sized tantalum alloy blank described in the above aspect.

[0036] The preparation process and test results of the large-sized tantalum alloy blank are shown through the examples of the method of the present invention and the comparative examples of the traditional method.

[0037] Example: Produce 34 tantalum alloy blanks with a single weight of 12 kg. Take metallurgical-grade tantalum powder and niobium powder. The loose bulk density of the metallurgical-grade tantalum powder is 3.3 g / cm 3 , the average particle sizes of the metallurgical-grade tantalum powder and niobium powder are both 6.5 µm, and the content of niobium powder is 200 ppm. Put the tantalum powder and niobium powder into a "V"-shaped mixer and first perform forward pre-mixing for 30 min. After the pre-mixing is completed, perform reverse secondary mixing for 30 min to obtain tantalum alloy powder. Put the tantalum alloy powder into a cylindrical square-rounded rubber sheath, and after kneading, forming, and sealing, place it in a cold isostatic press. After pressurizing to 240 Mpa, hold the pressure for 15 min, and then release the pressure and demold to complete cold isostatic pressing and forming to obtain a square-rounded alloy blank. Place the square-rounded alloy blank in a vacuum sintering furnace. Please refer to Figure 2 , after fixing the square-rounded alloy blank through a sintering chuck, introduce direct current for vertical melting sintering. Among them, the vacuum degree is 1.0×10 -2 Pa, the voltage is 25 V, the current is 800 A, it is heated to 2450 °C in 45 minutes, after holding the temperature for 2.5 hours, introduce argon with a flow rate of 50 L / min, and cool the tantalum alloy blank to 800 °C at a cooling rate of 150 °C per minute. Then stop introducing argon and evacuate to 1.0×10-2 Pa, and it is naturally cooled to room temperature to obtain a large-sized tantalum alloy blank.

[0038] Comparative example: 34 tantalum alloy blanks with a single weight of 12 kg are prepared. Metallurgical-grade tantalum powder and niobium powder, -100 mesh 100%, with a bulk density of 4.02 g / cm, are loaded into a circular rubber sheath. A rubber plug is inserted at the opening of the sheath. After the air in the sheath is discharged, the latex sheath at the rubber plug part is tied tightly with iron wire. The sheathed blank bars are kneaded evenly, clamped with two clamping plates, and then the clamping plates and the blank bars are fixed together with rubber bands. Then, they are placed in a cold isostatic pressing machine, and the maximum pressure holding pressure is controlled at 250 MPa for a pressure holding time of 15 min to complete cold isostatic pressing and forming. Finally, the mold is removed to obtain a circular green compact. The circular green compact is placed in a vacuum sintering furnace. Please refer to Figure 3 , after fixing the circular green compact through a sintering chuck, alternating current is passed through, where the voltage of the alternating current is 20 V - 30 V and the current is 800 A - 1000 A. First, vacuum pre-sintering is carried out with a vacuum degree of 2.0×10 -4 Pa, heated to 800 °C at a rate of 15 °C per minute, held for 5 hours, then heated to 1300 °C at a rate of 15 °C per minute and held for 2 hours; cooled to room temperature, and then vacuum vertical sintering is carried out with a vacuum degree of 1.0×10 -4 Pa, heated to 2200 °C in 60 minutes, held for 3 hours and then naturally cooled to room temperature to obtain a rod-shaped sintered tantalum alloy blank.

[0039] The cores and peripheries of the large-sized tantalum alloy blank and the rod-shaped sintered tantalum alloy blank are photographed through a metallurgical microscope, and the metallographic pictures of the core of the large-sized tantalum alloy blank are as shown in Figure 4 , the metallographic pictures of the periphery of the large-sized tantalum alloy blank are as shown in Figure 5 , the metallographic pictures of the core of the rod-shaped sintered tantalum alloy blank are as shown in Figure 6 , the metallographic pictures of the periphery of the rod-shaped sintered tantalum alloy blank are as shown in Figure 7 .

[0040] Table 1 Performance of tantalum alloy blanks obtained in the examples and comparative examples

[0041] Thus, it can be seen that, please refer to Figures 4 - 7As well as Table 1, for the large-sized tantalum alloy billets obtained in the examples, on the one hand, since the direct current used in sintering has the stability of not generating intermittence, the billets are heated evenly as a whole during the sintering process, with uniform shrinkage and consistent deformation. On the other hand, due to the use of gradient cooling, an inert gas is first introduced for rapid cooling, which can avoid the uneven growth of grains inside the billets caused by the billets staying at a high temperature for a long time. Then, natural cooling to room temperature can gradually reduce the internal stress of the billets to prevent the billets from cracking or deforming. The density of the core and periphery of the sintered large-sized tantalum alloy billets is uniform. At the same time, the strip loss rate of the sintered large-sized tantalum alloy billets is increased from about 1.5% to about 0.5%, improving the product yield. The sintering actual recovery rate of the large-sized tantalum alloy billets is increased from about 92.1% to about 93.6%, enhancing the product quality.

[0042] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand the whole or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for preparing a large-size tantalum alloy billet, characterized in that: The following steps are involved: Step 1: Select tantalum powder and doping powder and mix them thoroughly to obtain tantalum alloy powder; Step 2: cold isostatically pressing the tantalum alloy powder to obtain a square rounded corner alloy billet; Step 3: Place the square rounded alloy billet in a vacuum sintering furnace and pass direct current for vertical melting sintering. The vacuum degree is 1.0×10 -2 Pa-1.0×10 -3 Pa, sintering temperature is 2400℃-2600℃, holding time is 2h-3h; Step 4: After sintering, a gradient cooling method is adopted. First, an inert gas is introduced for rapid cooling, and then naturally cooled to room temperature to obtain a large-sized tantalum alloy billet.

2. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: In the step 1, the doped powder is niobium powder, tungsten powder, rare earth oxide powder or metal nitrate powder.

3. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: In step 1, the bulk specific gravity of the tantalum powder is 3.0 g / cm 3 -3.5g / cm 3 The average particle size of the tantalum powder and the doped powder is 5.0µm-7.5µm.

4. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: In the step 1, the content of the doped powder in the tantalum alloy powder is 100ppm-500ppm.

5. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: The step 1 is specifically as follows: the tantalum powder and the doped powder are placed in a "V" type mixer for forward premixing for 30 minutes to 60 minutes, and after the premixing is completed, reverse secondary mixing is performed for 30 minutes to 60 minutes to obtain tantalum alloy powder.

6. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: The step 2 is specifically as follows: the tantalum alloy powder is loaded into a cylindrical square rounded corner rubber sheath, after being kneaded into shape and sealed, it is placed in a cold isostatic pressing machine, pressurized to a predetermined pressure and maintained for a predetermined time, then the pressure is released and demolded to complete the cold isostatic pressing and forming, and a square rounded corner alloy billet is obtained.

7. The method for preparing large-size tantalum alloy billet according to claim 4, characterized in that: The predetermined pressure is 150MPa-250MPa, and the predetermined time is 10min-20min.

8. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: In step 3, the voltage of the direct current is 20V-30V, and the current is 700A-850A.

9. The method for preparing large-size tantalum alloy billet according to claim 1, characterized in that: The step 4 is specifically as follows: S41: after sintering is completed, an inert gas is introduced to cool the tantalum alloy billet to 750° C.-800° C. at a cooling rate of 100-200° C. / min, wherein the inert gas may be argon or helium; S42: Stop the inert gas flow and evacuate to 1.0×10 -2 Pa-1.0×10 -3 Pa; S43: Cool naturally to room temperature to obtain a large-sized tantalum alloy billet.

10. A tantalum alloy billet, prepared by the method for preparing a large-size tantalum alloy billet according to any one of claims 1 to 9.

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