A method for preparing NbTiTa alloy ingot for superconducting

Abstract

The present invention relates to the technical field of titanium alloy processing, and discloses a method for preparing a superconducting NbTiTa alloy ingot, comprising: mixing niobium powder and tantalum powder in a weight ratio of Nb:Ta=3:1, isostatically pressing and vacuum sintering the mixed material to obtain a NbTa sintered rod; subjecting the NbTa sintered rod to vacuum electron beam melting twice to obtain a Nb25Ta ingot; heating the Nb25Ta ingot to 300°C and holding the temperature for more than 2 hours to forge the Nb25Ta rod; determining the Nb content according to the measured composition of the Nb25Ta rod. The raw materials for the TiTa alloy and the NbTiTa alloy include at least: Nb25Ta rods, titanium sponge, and a TiTa mixed powder or a TiNb mixed powder. The titanium sponge and the TiTa mixed powder or the TiNb mixed powder are laid and pressed to form a titanium electrode block, wherein a groove is formed at the centerline of the upper surface of the titanium electrode block and runs through the opposite ends of the block. Multiple titanium electrode blocks and Nb25Ta rods are assembled and welded to form a rod-shaped consumable electrode. The consumable electrode is then subjected to three vacuum consumable arc melting processes to obtain a NbTiTa alloy ingot. This application achieves the purification of the alloy and the precision of its composition.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal processing, in particular to a method for preparing a NbTiTa alloy ingot for superconducting. Background Art

[0002] Since the discovery of superconductivity by Dutch physicist K. Onnes in 1911, dozens of metals and nearly 4,000 alloys and compounds have been found to exhibit superconductivity. Since its discovery, superconducting technology has rapidly developed and is now widely used in high-tech fields such as high-energy physics, controlled thermonuclear fusion, energy storage, magnetic levitation, and nuclear magnetic resonance. Superconducting materials are the foundation of superconducting technology, and the scope and applicability of superconducting technology are closely related to superconducting materials. NbTi alloy is currently the most widely used superconducting material due to its high mechanical properties and excellent superconducting properties. Based on the relationship between the spin-orbit scattering rate and the fourth power of the average atomic number of the alloy, adding the heavy-weight element Ta to the NbTi binary alloy can significantly improve its superconducting properties.

[0003] The melting point of Ta in NbTiTa alloy is as high as 3017℃ and the density is as high as 16.60g / cm3. The melting point of Nb is as high as 2469℃ and the density is as high as 8.57g / cm3. The melting point of active metal Ti is only 1668℃ and the density is only 4.50g / cm3. The melting points and densities of the three elements are very different. It is very easy to produce Ta and Nb non-melting blocks during vacuum consumable arc melting, and the ingot preparation technology is extremely difficult. When preparing titanium alloys containing refractory elements, the usual way is to first prepare the intermediate alloy by powder metallurgy or smelting method, and then prepare the titanium alloy containing refractory elements. However, the use of powder metallurgy to prepare intermediate alloys has the problem of difficult control of impurity elements, poor material purity, and high finished product quality. The use of traditional smelting methods to prepare intermediate alloy chips, on the one hand, has a greater risk of tantalum in the intermediate alloy not melting because the melting point of Ta is much higher than that of Ti. On the other hand, due to the high content of Ta and Nb elements in the alloy, if the proportion of intermediate alloy chips added is too large, it is easy for the block to fall off during the smelting process, which poses a great metallurgical risk. Summary of the Invention

[0004] In order to solve at least one of the problems existing in the above background technology, the present invention provides a method for preparing a NbTiTa alloy ingot for superconducting use.

[0005] The present invention provides a method for preparing a superconducting NbTiTa alloy ingot, comprising the following five steps:

[0006] Step 1: Niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta = 3:1, and after mixing, they are isostatically pressed and vacuum sintered to obtain NbTa sintered rods. The NbTa sintered rods are then subjected to two vacuum electron beam melting processes to obtain Nb25Ta ingots. The Nb25Ta ingots are heated to 300°C for more than 2 hours and forged using a multi-pass, small-pass forging method to obtain Nb25Ta rods of preset dimensions.

[0007] Step 2: Determine the raw materials of the NbTiTa alloy based on the measured composition of the Nb25Ta rod, the raw materials of the NbTiTa alloy at least including: Nb25Ta rod, titanium sponge, TiTa mixed powder or TiNb mixed powder;

[0008] Step 3: Sponge titanium and TiTa mixed powder or TiNb mixed powder are pressed to form a titanium electrode block, and a groove is formed at the center line of the upper surface of the titanium electrode block and passes through the opposite two ends thereof;

[0009] Step 4: Assemble and weld multiple titanium electrode blocks and Nb25Ta rods to form a rod-shaped consumable electrode, using non-tungsten electrode argon shielded welding;

[0010] Step 5: The consumable electrode is subjected to vacuum consumable arc melting three times to obtain a NbTiTa alloy ingot.

[0011] Furthermore, in the above-mentioned method for preparing a NbTiTa alloy ingot for superconducting use, in step one, niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta=3:1, including: mixing in a three-dimensional mixer for 5 to 10 hours; isostatic pressing after mixing to a static pressing strength of 120 to 200 MPa, and a holding time of 1 to 10 minutes; vacuum sintering temperature of 1300 to 1800°C, and a holding time of 3 to 15 hours.

[0012] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, in step 1, the NbTa sintered rod is subjected to vacuum electron beam melting twice to obtain a Nb25Ta ingot, and the vacuum before melting is less than 10 -2 Pa, with an input power of 180 to 300kW.

[0013] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, the Ti powder in the TiTa mixed powder in step 2 is 1.5 times that of the Ta powder, and the Ti powder in the TiNb mixed powder is 1.5 times that of the Nb powder; the TiTa mixed powder obtained by mixing the Ti powder and the Ta powder in a V-type mixer for 2 hours, and the TiNb mixed powder obtained by mixing the Ti powder and the Nb powder in a V-type mixer for 2 hours.

[0014] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, in step 3, the titanium sponge and TiTa mixed powder or TiNb mixed powder are spread and then pressed to form a titanium electrode block, including:

[0015] Pour 60% of the titanium sponge into the mold cavity, then sprinkle a small amount of powder evenly in the middle, and finally pour the remaining 40% of the titanium sponge into it. Use a hydraulic press to press it to form a titanium electrode block. The pressure strength of the hydraulic press is 25 to 28 MPa.

[0016] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, in step 4, assembling and welding a plurality of titanium electrode blocks and Nb25Ta rods to form a rod-shaped consumable electrode comprises:

[0017] Arrange multiple titanium electrode blocks in sequence to form a long groove, place Nb25Ta rods in the long groove, and then cover the arranged titanium electrode blocks with corresponding titanium electrode blocks to form a structure in which the titanium electrode blocks are wrapped on the outer circumference of the Nb25Ta rods. Weld the assembled titanium electrode blocks and Nb25Ta rods to form a consumable electrode;

[0018] The welding conditions are as follows: vacuuming to below 10Pa and filling with argon to 50,000Pa.

[0019] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, the crystallizer used in the first melting of the three vacuum consumable arc melting in step 5 has a specification of Φ360 mm, the vacuum degree before melting is ≤5.0 Pa, the leakage rate is ≤1.2 Pa / min, the melting voltage is 30 to 40 V, the melting current is 8 to 30 kA, the arc stabilization current is DC 3 to 18 A, and the cooling time after melting is greater than or equal to 3 hours;

[0020] Among them, the same brand of base pad is used for the first melting, and the upper end face of the base pad is turned into a "convex" shape; in the arc starting stage of the first melting, the lower end face of the consumable electrode is first contacted with the upper end face of the base pad, and the current is gradually increased from 2.5kA to 6kA in stages. After maintaining at 6kA for 3 to 5 minutes, the power is turned off, and the electrode rod is lifted 30 to 50mm before power is supplied to start arc melting.

[0021] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, the crystallizer specification used in the second melting of the three vacuum consumable arc melting in step five is Φ460 mm, the vacuum degree before melting is ≤2.0 Pa, the leakage rate is ≤1.0 Pa / min, the melting voltage is 30 to 45 V, the melting current is 10 to 30 kA, the arc stabilization current is AC 5 to 20 A, and the cooling time after melting is greater than or equal to 4 hours.

[0022] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, the crystallizer specification used in the third melting of the three vacuum consumable arc melting in step five is Φ520 mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained between 0.88 and 0.93, the vacuum degree before melting is 1.0 Pa, the leakage rate is 0.8 Pa / min, the melting voltage is 32 to 45 V, and the melting current is 8 to 30 kA; the arc stabilization current adopts AC of 8 to 25 A, the arc stabilization period is 10 to 60 s, and the cooling time after melting is greater than or equal to 5 hours.

[0023] Furthermore, in the above-mentioned method for preparing a superconducting NbTiTa alloy ingot, the specification of the NbTiTa alloy ingot in step five is Φ520 mm; the titanium content in the NbTiTa alloy ingot is 35 to 45 wt%, and the tantalum content is 8 to 15 wt%.

[0024] The beneficial effects of the present invention are as follows: 1. By combining powder metallurgy and vacuum electron beam melting methods, the present invention achieves preliminary alloying and purification of Nb and Ta, resulting in a Nb25Ta ingot with a lowered melting point and reduced impurity element content; 2. Due to the high vacuum and high power of a vacuum electron beam furnace, it is difficult to precisely control the composition of the Nb25Ta rod. According to the measured composition of the Nb25Ta rod, a small amount of TiTa mixed powder or TiNb mixed powder is added, which ensures both precise control of the composition and a low content of impurity elements. The mixed powder is distributed in the middle of the titanium sponge to prevent the formation of Nb and Ta non-melting blocks due to powder leakage; 3. By rationally arranging the relative positions of the NbTa rod, mixed powder, and titanium sponge, pressing special-shaped titanium electrode blocks, and first short-circuiting heating to increase the temperature of the NbTa rod during the primary smelting, and rationally designing the primary smelting process, the problem of Ta and Nb non-melting blocks is solved, and the alloy is purified, the composition is precisely determined, and preliminary alloying is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic flow chart of a method for preparing a superconducting NbTiTa alloy ingot provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of the titanium electrode block after titanium sponge is pressed and formed;

[0028] Figure 3Schematic diagram of the consumable electrode structure after assembly welding;

[0029] Figure 4 This is a schematic diagram of short-circuit heating during the first smelting;

[0030] Figure 5 This is the X-ray test result of Φ520mm NbTiTa ingot;

[0031] Figure 6 This is a comparison chart of the critical current density of NbTi and NbTiTa alloy ingots with the same specifications. DETAILED DESCRIPTION

[0032] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Figure 1 The present invention provides a schematic flow chart of a method for preparing a superconducting NbTiTa alloy ingot.

[0035] The present invention provides a method for preparing a superconducting NbTiTa alloy ingot, Figure 1 , including five steps from S101 to S105:

[0036] S101: Niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta=3:1, and after mixing, they are isostatically pressed and vacuum sintered to obtain NbTa sintered rods. The NbTa sintered rods are subjected to two vacuum electron beam melting processes to obtain Nb25Ta ingots; the Nb25Ta ingots are heated to 300°C and kept warm for more than 2 hours, and are forged using a multi-pass, small-pass deformation forging method to obtain Nb25Ta rods of preset dimensions.

[0037] Specifically, in Example S101 of the present application, niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta=3:1, including: mixing in a three-dimensional mixer for 5 to 10 hours; isostatic pressing after mixing to a static pressing strength of 120 to 200 MPa, and a holding time of 1 to 10 minutes; vacuum sintering temperature of 1300 to 1800°C, and a holding time of 3 to 15 hours. The conditions for obtaining Nb25Ta ingots by vacuum electron beam melting of NbTa sintered rods in S101 are that the vacuum before melting is less than 10 -2 Pa, with an input power of 180 to 300kW.

[0038] It should be understood that in this application, by combining the methods of powder metallurgy and vacuum electron beam melting, preliminary alloying and purification of Nb and Ta are achieved, and Nb25Ta ingots with lowered melting point and reduced impurity element content are obtained.

[0039] S102: Determine the raw materials of the NbTiTa alloy according to the measured composition of the Nb25Ta rod. The raw materials of the NbTiTa alloy include at least: Nb25Ta rod, titanium sponge, TiTa mixed powder or TiNb mixed powder.

[0040] Specifically, in the TiTa mixed powder in Example S102 of the present application, the Ti powder is 1.5 times that of the Ta powder, and in the TiNb mixed powder, the Ti powder is 1.5 times that of the Nb powder; the TiTa mixed powder obtained by mixing the Ti powder and the Ta powder in a V-type mixer for 2 hours, and the TiNb mixed powder obtained by mixing the Ti powder and the Nb powder in a V-type mixer for 2 hours.

[0041] It should be understood that the high vacuum and high power required by the vacuum electron beam furnace in this application make precise control of the composition of the Nb25Ta rod difficult. Adding a small amount of TiTa mixed powder or TiNb mixed powder based on the measured composition of the Nb25Ta rod ensures precise control of the composition while also minimizing the level of impurities. Placing the mixed powder in the center of the titanium sponge prevents powder leakage and the formation of unmelted Nb and Ta lumps.

[0042] S103: Sponge titanium and TiTa mixed powder or TiNb mixed powder are spread and pressed to form a titanium electrode block, and a groove penetrating the opposite two ends of the titanium electrode block is formed at the center line of the upper surface of the titanium electrode block.

[0043] Figure 2 This is a schematic diagram of the titanium electrode block structure after titanium sponge is pressed and formed.

[0044] Combine Figure 2 The figure shows the schematic diagram of the structure of the titanium electrode block after titanium sponge is pressed and formed.

[0045] S104: Assembling and welding a plurality of titanium electrode blocks and Nb25Ta rods to form a rod-shaped consumable electrode, wherein the welding method is non-tungsten electrode argon shielded welding.

[0046] Figure 3 Schematic diagram of the consumable electrode structure after assembly welding.

[0047] Specific, combined Figure 3 As shown, in Example S104 of the present application, multiple titanium electrode blocks and Nb25Ta rods are assembled and welded to form a rod-shaped consumable electrode. Referring to the figure, multiple titanium electrode blocks are arranged in sequence to form a long strip groove, and the Nb25Ta rod is placed in the long strip groove. Then, the arranged titanium electrode blocks are covered with the corresponding titanium electrode blocks to form a structure in which the titanium electrode blocks are wrapped on the outer peripheral surface of the Nb25Ta rod. The assembled titanium electrode blocks and Nb25Ta rod are welded to form a consumable electrode; wherein, the welding conditions are to evacuate to below 10Pa and fill with argon to 50000Pa.

[0048] It should be understood that in this application, by rationally arranging the relative positions of Nb25Ta rods, mixed powder and sponge titanium, pressing special-shaped titanium electrode blocks, short-circuiting heating to increase the temperature of the NbTa rods during a single smelting, and rationally designing a single smelting process, the problem of Ta and Nb non-melting blocks is solved, and the purification of the alloy, the precision of the composition and the preliminary alloying are achieved.

[0049] S105: The consumable electrode is subjected to vacuum consumable arc melting three times to obtain a NbTiTa alloy ingot.

[0050] Figure 4 This is a schematic diagram of short-circuit heating during the first smelting.

[0051] Specific, combined Figure 5 In Example S105 of the present application, the crystallizer specification used in the first melting of the three vacuum consumable arc meltings is Φ360mm, the vacuum degree before melting is ≤5.0 Pa, the leakage rate is ≤1.2Pa / min, the melting voltage is 30 to 40 V, the melting current is 8 to 30 kA, the arc stabilization current is DC 3 to 18A, and the cooling time after melting is greater than or equal to 3 hours; wherein, the same brand of bottom pad is used for the first melting, and the upper end surface of the bottom pad is turned to a "convex" shape; in the arc starting stage of the first melting, the lower end surface of the consumable electrode is first contacted with the upper end surface of the bottom pad, and the current is gradually increased from 2.5kA to 6kA in stages, and the power is turned off after maintaining 6kA for 3 to 5 minutes, and the electrode rod is lifted 30 to 50mm before power is turned on to start arc melting.

[0052] Specifically, the crystallizer specification used in the second melting of the three vacuum consumable arc melting in Example S105 of the present application is Φ460mm, the vacuum degree before melting is ≤2.0 Pa, the leakage rate is ≤1.0Pa / min, the melting voltage is 30 to 45V, the melting current is 10 to 30 kA, the arc stabilization current is AC 5 to 20A, and the cooling time after melting is greater than or equal to 4 hours.

[0053] Specifically, the crystallizer specification used in the third of the three vacuum consumable arc melting in Example S105 of the present application is Φ520 mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained between 0.88 and 0.93, the vacuum degree before melting is 1.0 Pa, the leakage rate is 0.8 Pa / min, the melting voltage is 32 to 45 V, and the melting current is 8 to 30 kA; the arc stabilization current adopts AC of 8 to 25 A, the arc stabilization period is 10 to 60 s, and the cooling time after melting is greater than or equal to 5 hours.

[0054] Specifically, the specification of the NbTiTa alloy ingot in Example S105 of the present application is Φ520 mm; the titanium content in the NbTiTa alloy ingot is 35 to 45 wt%, and the tantalum content is 8 to 15 wt%.

[0055] Figure 6 This is a comparison chart of the critical current density of NbTi and NbTiTa alloy ingots with the same specifications.

[0056] Specifically, through theoretical calculation, the NbTiTa alloy ingot in this application is a Nb40Ti12Ta alloy ingot, combined with Figure 6 , Nb40Ti12Ta alloy ingots greatly improve the performance of superconducting wires.

[0057] A method for preparing a superconducting NbTiTa alloy ingot is described below with reference to three embodiments.

[0058] Example 1

[0059] This embodiment provides a method for preparing a superconducting NbTiTa alloy and an ingot thereof, and the specific steps are as follows:

[0060] Step 1: Select niobium powder and tantalum powder that meet the requirements, and mix them in a three-dimensional mixer at a weight ratio of Nb:Ta=3:1 for 5 hours; then the powder mixture is isostatically pressed and vacuum sintered to obtain NbTa sintered rods, with an isostatic pressing strength of 150MPa and a holding time of 3min; the vacuum sintering temperature is 1600℃ and the holding time is 5h; after two vacuum electron beam melting, Nb25Ta ingots are obtained, and the vacuum before melting is less than 10 -2Pa, input power is 180 to 300kW. The Nb25Ta ingot is heated to 300℃ and kept at this temperature for more than 2 hours. The Nb25Ta rod with a diameter of 140mm is obtained by forging with multiple passes and small deformation and machining.

[0061] Step 2: The weight percentage contents of Ta in the head, middle and tail of the Nb25Ta rod obtained in step 2 are 24.1%, 25.2% and 26.2% respectively; according to the measured composition of the Nb25Ta alloy, the raw materials of the NbTiTa alloy are selected as Nb25Ta rod, sponge titanium, and a small amount of TiNb mixed powder; the ratio of the TiNb mixed powder is 1.5 times that of the Nb powder, and the mixture is mixed in a V-type mixer for 2 hours.

[0062] Step 3: Pour 60% of the titanium sponge prepared in step 3 into the mold cavity, then sprinkle a small amount of powder evenly in the middle. Finally, pour the remaining 40% of the titanium sponge into the mold cavity and use a hydraulic press to press the titanium electrode block. The hydraulic press press pressure is 25 to 28 MPa. A groove is formed on the centerline of the upper surface of the titanium electrode block, running through its two opposite ends.

[0063] Step 4: Assemble and weld the 12 titanium electrode blocks pressed in step 4 and the Nb25Ta rod to form a rod-shaped consumable electrode. The structure of the consumable electrode is to wrap the titanium electrode block around the outer periphery of the Nb25Ta rod. The welding process adopts non-tungsten electrode argon shielded welding. The welding conditions are vacuuming less than 10Pa and filling argon to more than 50,000Pa.

[0064] Step 5: The consumable electrode obtained in step 4 is subjected to three vacuum consumable arc melting processes:

[0065] First smelting: The crystallizer used is Φ360mm, the vacuum degree before smelting is ≤5.0Pa, the leakage rate is ≤1.2Pa / min, the smelting voltage is 30 to 40V, the smelting current is 8 to 30kA, the arc stabilization current is DC 3 to 18A, and the cooling time after smelting is greater than or equal to 3 hours; the same brand of bottom pad is used for the first smelting, and the upper end surface of the bottom pad is turned into a "convex" shape. During the arc starting stage of the smelting, the lower end surface of the consumable electrode is first brought into contact with the upper end surface of the bottom pad. The current is gradually increased from 3kA to 4kA to 5kA to 6kA. After maintaining it at 6kA for 3 minutes, the power is turned off. The electrode rod is raised 35mm before the power is turned on to start the arc melting.

[0066] Second smelting: The crystallizer used is Φ460mm, the vacuum degree before smelting is ≤2.0 Pa, the leakage rate is ≤1.0Pa / min, the smelting voltage is 30 to 45V, the smelting current is 10 to 30 kA, the arc stabilization current is AC 5 to 20A, and the cooling time after smelting is greater than or equal to 4 hours;

[0067] The third smelting: the crystallizer specification used is Φ520mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained at 0.88 to 0.93, the vacuum degree before smelting is 1.0Pa, the leakage rate is 0.8Pa / min, the smelting voltage is 32 to 45V, and the smelting current is 8 to 30kA; the arc stabilization current adopts AC 8 to 25A, the arc stabilization period is 10 to 60s, and the cooling time after smelting is greater than or equal to 5 hours.

[0068] The NbTiTa alloy ingot with a diameter of 520 mm melted in this embodiment was analyzed. The contents of the main elements Ti, Ta and impurity elements at three longitudinal points are shown in Table 1:

[0069] Table 1 Longitudinal three-point sampling results of Φ520mm Nb40Ti12Ta alloy ingot

[0070]

[0071] As shown in Table 1, the Ti and Ta elemental compositions of the NbTiTa ingot at three longitudinal points are uniform, and the impurity element contents are all less than 0.04%. X-ray inspection of the middle part of the ingot shows no Ta or Nb non-melting block phenomenon. Figure 5 shown.

[0072] Example 2

[0073] This embodiment provides a method for preparing a superconducting NbTiTa alloy and an ingot thereof, and the specific steps are as follows:

[0074] Step 1: Select niobium powder and tantalum powder that meet the requirements, and mix them in a three-dimensional mixer at a weight ratio of Nb:Ta=3:1 for 5 hours; then the powder mixture is isostatically pressed and vacuum sintered to obtain NbTa sintered rods, with an isostatic pressing strength of 150MPa and a holding time of 3min; the vacuum sintering temperature is 1600℃ and the holding time is 5h; after two vacuum electron beam melting, Nb25Ta ingots are obtained, and the vacuum before melting is less than 10 -2 Pa, with an input power of 180 to 300kW. The ingot is heated to 300℃ and kept at this temperature for more than 2 hours. The Nb25Ta rod with a diameter of 140mm is obtained by forging with multiple passes and small deformation and machining.

[0075] Step 2: The weight percentage contents of Ta in the head, middle and tail of the Nb25Ta alloy rod obtained in step 1 are 23.5%, 24.3% and 25.1% respectively; according to the measured composition of the Nb25Ta alloy, the raw materials of the NbTiTa alloy are selected as Nb25Ta rod, sponge titanium, and a small amount of TiTa mixed powder; the ratio of the TiTa mixed powder is 1.5 times that of the Ta powder, and the mixture is mixed in a V-type mixer for 2 hours.

[0076] Step 3: Pour 60% of the titanium sponge from step 2 into the mold cavity, then sprinkle a small amount of powder evenly in the middle, and finally pour the remaining 40% of the titanium sponge into the mold cavity. Use a hydraulic press to press the titanium electrode block to form a titanium electrode block with a pressure strength of 25 to 28 MPa. A groove is formed on the center line of the upper surface of the titanium electrode block, running through its two opposite ends.

[0077] Step 4: Assemble and weld the 12 titanium electrode blocks pressed in step 3 and the NbTa rod to form a rod-shaped consumable electrode. The structure of the consumable electrode is to wrap the titanium electrode block around the outer periphery of the NbTa rod. The welding process adopts non-tungsten electrode argon shielded welding, pre-vacuuming less than 10Pa, and filling with argon to more than 50,000Pa.

[0078] Step 5: The consumable electrode obtained in step 4 is subjected to three vacuum consumable arc melting processes:

[0079] First smelting: The crystallizer used is Φ360mm, the vacuum degree before smelting is ≤5.0 Pa, the leakage rate is ≤1.2Pa / min, the smelting voltage is 30 to 40 V, the smelting current is 8 to 30 kA, the arc stabilization current is DC 3 to 18A, and the cooling time after smelting is greater than or equal to 3 hours; the same brand of bottom pad is used for the first smelting, and the upper end face of the bottom pad is turned into a "convex" shape. During the arc starting stage of the smelting, the lower end face of the consumable electrode is first brought into contact with the upper end face of the bottom pad. The current is gradually increased from 3kA to 4kA to 5kA to 6kA. After maintaining it at 6kA for 3 minutes, the power is turned off. The electrode rod is raised 35mm before the power is turned on to start the arc melting.

[0080] Second smelting: The crystallizer used is Φ460mm, the vacuum degree before smelting is ≤2.0 Pa, the leakage rate is ≤1.0Pa / min, the smelting voltage is 30 to 45V, the smelting current is 10 to 30 kA, the arc stabilization current is AC 5 to 20A, and the cooling time after smelting is greater than or equal to 4 hours;

[0081] The third smelting: the crystallizer specification used is Φ520mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained at 0.88 to 0.93, the vacuum degree before smelting is 1.0Pa, the leakage rate is 0.8Pa / min, the smelting voltage is 32 to 45V, and the smelting current is 8 to 30kA; the arc stabilization current adopts AC 8 to 25A, the arc stabilization period is 10 to 60s, and the cooling time after smelting is greater than or equal to 5 hours.

[0082] The NbTiTa alloy ingot with a diameter of 520 mm melted in this embodiment was analyzed. The contents of the main elements Ti, Ta and impurity elements at three longitudinal points are shown in Table 2:

[0083] Table 2 Longitudinal three-point sampling results of Φ520mm Nb40Ti12Ta alloy ingot

[0084]

[0085] Table 2 shows that the resulting NbTiTa ingot exhibits excellent uniformity of Ti and Ta elemental composition at three longitudinal points, with impurity content below 0.04%. X-ray analysis of a sample taken from the center of the ingot revealed no unmelted Ta or Nb mass.

[0086] Example 3

[0087] This embodiment provides a method for preparing a superconducting NbTiTa alloy and an ingot thereof, and the specific steps are as follows:

[0088] Step 1: Select niobium powder and tantalum powder that meet the requirements, and mix them in a three-dimensional mixer at a weight ratio of Nb:Ta=3:1 for 5 hours; then the powder mixture is isostatically pressed and vacuum sintered to obtain NbTa sintered rods, with an isostatic pressing strength of 150MPa and a holding time of 3min; the vacuum sintering temperature is 1600℃ and the holding time is 5h; after two vacuum electron beam melting, Nb25Ta ingots are obtained, and the vacuum before melting is less than 10 -2 Pa, input power is 180 to 300kW. The Nb25Ta ingot is heated to 300℃ and kept at this temperature for more than 2 hours. The Nb25Ta rod with a diameter of 140mm is obtained by forging with multiple passes and small deformation and machining.

[0089] Step 2: The weight percentage contents of Ta in the head, middle and tail of the Nb25Ta rod obtained in step 1 are 23.3%, 24.3% and 25.2% respectively; according to the measured composition of the Nb25Ta alloy, the raw materials of the NbTiTa alloy are selected as Nb25Ta rod, sponge titanium, and a small amount of TiTa mixed powder; the ratio of the TiTa mixed powder is 1.5 times that of the Ta powder, and the mixture is mixed in a V-type mixer for 2 hours.

[0090] Step 3: Pour 60% of the titanium sponge from step 2 into the mold cavity, then sprinkle a small amount of powder evenly in the middle, and finally pour the remaining 40% of the titanium sponge into the mold cavity. Use a hydraulic press to press the titanium electrode block to form a titanium electrode block with a pressure strength of 25 to 28 MPa. A groove is formed on the center line of the upper surface of the titanium electrode block, running through its two opposite ends.

[0091] Step 4: Assemble and weld the 12 titanium electrode blocks pressed in step 3 and the NbTa rod to form a rod-shaped consumable electrode. The structure of the consumable electrode is to wrap the titanium electrode block around the outer periphery of the NbTa rod. The welding process adopts non-tungsten electrode argon shielded welding. The welding conditions are vacuuming less than 10Pa and filling argon to more than 50,000Pa.

[0092] Step 5: The consumable electrode obtained in step 4 is subjected to three vacuum consumable arc melting processes:

[0093] First smelting: The crystallizer used is Φ360mm, the pre-smelting vacuum is ≤5.0Pa, the gas leakage rate is ≤1.2Pa / min, the melting voltage is 30 to 40V, the melting current is 8 to 30kA, the arc stabilization current is DC 3 to 18A, and the cooling time after melting is greater than or equal to 3 hours. The same brand of bottom pad is used for the first smelting, and the upper end of the bottom pad is turned into a "convex" shape. During the arc starting stage of the smelting, the lower end of the consumable electrode is first brought into contact with the upper end of the bottom pad. The current is gradually increased from 3kA to 4kA to 5kA to 6kA. After maintaining it at 6kA for 3 minutes, the power is turned off. The electrode rod is raised 35mm before the power is turned on to start the arc melting.

[0094] Second smelting: The crystallizer used is Φ460mm, the vacuum degree before smelting is ≤2.0Pa, the leakage rate is ≤1.0Pa / min, the smelting voltage is 30 to 45V, the smelting current is 10 to 30kA, the arc stabilization current is AC 5 to 20A, and the cooling time after smelting is greater than or equal to 4 hours;

[0095] The third smelting: the crystallizer specification used is Φ520mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained at 0.88 to 0.93, the vacuum degree before smelting is 1.0Pa, the leakage rate is 0.8Pa / min, the smelting voltage is 32 to 45V, and the smelting current is 8 to 30kA; the arc stabilization current adopts AC 8 to 25A, the arc stabilization period is 10 to 60s, and the cooling time after smelting is greater than or equal to 5 hours.

[0096] The NbTiTa alloy ingot with a diameter of 520 mm melted in this embodiment was analyzed. The contents of the main elements Ti, Ta and impurity elements at three longitudinal points are shown in Table 3:

[0097] Table 3 Longitudinal three-point sampling results of Φ520mm Nb40Ti12Ta alloy ingot

[0098]

[0099] Table 3 shows that the resulting NbTiTa ingot exhibits excellent uniformity of Ti and Ta elements at three longitudinal points, with impurity content less than 0.04%. X-ray analysis of a sample taken from the center of the ingot revealed no unmelted Ta or Nb lumps.

[0100] The above results indicate that the Ti and Ta elemental compositions of the NbTiTa ingot are uniform at three points along its longitudinal direction, with impurity content below 0.04%. X-ray analysis of a sample taken from the center of the ingot revealed no unmelted Ta or Nb lumps.

[0101] Those skilled in the art will appreciate that although some embodiments described herein include some features and not others included in other embodiments, the combination of features from different embodiments is intended to be within the scope of the invention and to form different embodiments.

[0102] Those skilled in the art will understand that the description of each embodiment has its own focus, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0103] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for preparing a superconducting NbTiTa alloy ingot, characterized in that: It includes the following five steps: Step 1: Niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta=3:1, and after mixing, they are isostatically pressed and vacuum sintered to obtain NbTa sintered rods. The NbTa sintered rods are subjected to vacuum electron beam melting twice to obtain Nb25Ta ingots; the Nb25Ta ingots are heated to 300°C and kept at this temperature for more than 2 hours, and forged using a multi-pass, small-pass deformation forging method to obtain Nb25Ta rods of preset dimensions; Step 2: Determine the raw materials of the NbTiTa alloy according to the measured composition of the Nb25Ta rod, wherein the raw materials of the NbTiTa alloy include at least: Nb25Ta rod, titanium sponge, TiTa mixed powder or TiNb mixed powder; Step 3: The titanium sponge and TiTa mixed powder or TiNb mixed powder are pressed to form a titanium electrode block, wherein a groove penetrating two opposite ends of the titanium electrode block is formed at the center line of the upper surface of the titanium electrode block; Step 4: Assembling and welding a plurality of titanium electrode blocks and Nb25Ta rods to form a rod-shaped consumable electrode, the welding method being non-tungsten electrode argon shielded welding; Step 5: subjecting the consumable electrode to vacuum consumable arc melting three times to obtain a NbTiTa alloy ingot.

2. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, characterized in that: In the step 1, niobium powder and tantalum powder are mixed in a weight ratio of Nb:Ta=3:1, including: mixing in a three-dimensional mixer for 5 to 10 hours; isostatically pressing after mixing to a static pressing strength of 120 to 200 MPa and a holding time of 1 to 10 minutes; and vacuum sintering at a temperature of 1300 to 1800°C and a holding time of 3 to 15 hours.

3. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, wherein: The condition for obtaining Nb25Ta ingot by vacuum electron beam melting twice in step 1 is that the vacuum before melting is less than 10 -2 Pa, with an input power of 180 to 300kW.

4. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, wherein: In the TiTa mixed powder in step 2, the Ti powder is 1.5 times that of the Ta powder, and in the TiNb mixed powder, the Ti powder is 1.5 times that of the Nb powder; the TiTa mixed powder obtained by mixing the Ti powder and the Ta powder in a V-type mixer for 2 hours, and the TiNb mixed powder obtained by mixing the Ti powder and the Nb powder in a V-type mixer for 2 hours.

5. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, wherein: In step 3, the titanium sponge and TiTa mixed powder or TiNb mixed powder are pressed and then formed into a titanium electrode block, including: 60% of the titanium sponge is poured into the mold cavity, and then a small amount of powder is evenly sprinkled in the middle. Finally, the remaining 40% of the titanium sponge is poured in and pressed using a hydraulic press to form a titanium electrode block. The pressure strength of the hydraulic press is 25 to 28 MPa.

6. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, characterized in that: In the fourth step, a plurality of titanium electrode blocks and Nb25Ta rods are assembled and welded to form a rod-shaped consumable electrode, including: Arrange multiple titanium electrode blocks in sequence to form a long groove, place the Nb25Ta rod in the long groove, and then cover the arranged titanium electrode blocks with corresponding titanium electrode blocks to form a structure in which the titanium electrode blocks are wrapped on the outer circumference of the Nb25Ta rod, and weld the assembled titanium electrode blocks and Nb25Ta rod to form a consumable electrode; The welding conditions are as follows: vacuuming to below 10Pa and filling with argon to 50,000Pa.

7. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, characterized in that: The crystallizer used in the first of the three vacuum consumable arc melting processes in step 5 has a specification of Φ360 mm, a vacuum degree before melting of ≤5.0 Pa, a gas leakage rate of ≤1.2 Pa / min, a melting voltage of 30 to 40 V, a melting current of 8 to 30 kA, a DC arc stabilization current of 3 to 18 A, and a cooling time after melting of ≥3 hours; Among them, the same brand of base pad is used for the first melting, and the upper end face of the base pad is turned into a "convex" shape; in the arc starting stage of the first melting, the lower end face of the consumable electrode is first contacted with the upper end face of the base pad, and the current is gradually increased from 2.5kA to 6kA in stages. After maintaining at 6kA for 3 to 5 minutes, the power is turned off, and the electrode rod is lifted 30 to 50mm before power is supplied to start arc melting.

8. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, characterized in that: The crystallizer specification used in the second melting of the three vacuum consumable arc melting in the step 5 is Φ460mm, the vacuum degree before melting is ≤2.0 Pa, the leakage rate is ≤1.0Pa / min, the melting voltage is 30 to 45V, the melting current is 10 to 30 kA, the arc stabilization current is AC 5 to 20A, and the cooling time after melting is greater than or equal to 4 hours.

9. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, wherein: The crystallizer specification used in the third of the three vacuum consumable arc melting in the step 5 is Φ520 mm, the ratio of the outer diameter of the consumable electrode to the inner diameter of the crystallizer is maintained between 0.88 and 0.93, the vacuum degree before melting is 1.0 Pa, the leakage rate is 0.8 Pa / min, the melting voltage is 32 to 45 V, and the melting current is 8 to 30 kA; the arc stabilization current adopts AC of 8 to 25 A, the arc stabilization period is 10 to 60 s, and the cooling time after melting is greater than or equal to 5 hours.

10. The method for preparing a superconducting NbTiTa alloy ingot according to claim 1, characterized in that: The specification of the NbTiTa alloy ingot in step 5 is Φ520 mm; the titanium content of the NbTiTa alloy ingot is 35 to 45 wt %, and the tantalum content is 8 to 15 wt %.

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