A method for producing a ingot of a nickel-titanium alloy containing a low melting point metal

Abstract

This invention discloses a method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal, comprising: Step 1: placing a first nickel rod vertically and making a hole to form a receiving hole; Step 2: filling the receiving hole with low-melting-boiling-point metal particles; Step 3: placing a second nickel rod on top of the first nickel rod and then welding them to obtain a binary alloy preform; Step 4: placing the binary alloy preform in a crucible, with the second nickel rod placed close to the bottom of the crucible; Step 5: placing the crucible containing the binary alloy preform in a vacuum induction melting furnace for melting to obtain a binary alloy body; Step 6: pressing sponge titanium, electrolytic nickel blocks, and the binary alloy body in a pressing machine to obtain an electrode. This invention does not require specialized equipment and does not incur additional equipment purchase costs. Compared with additive manufacturing and self-propagating high-temperature synthesis methods, it has advantages such as low cost, high efficiency, and high yield.

Description

Technical Field

[0001] This invention belongs to the field of alloy ingot smelting technology, and particularly relates to a method for preparing nickel-titanium alloy ingots containing low melting and boiling point metals. Background Technology

[0002] Since the 1960s, NiTi shape memory alloys have been widely used and researched in numerous fields, including physics and metallurgy. Currently, the extensive research on these alloys stems not only from their widespread applications in aerospace, biomedicine, and everyday life, but also from their numerous unexplored potential. These potentials include introducing third or even fourth components based on NiTi binary alloys to form NiTi-based shape memory alloys. In the industrial sector, alloys such as NiTiCu, NiTiV, NiTiNb, NiTiCr, and NiTiFe have played important roles in various scenarios and are gradually becoming standard application materials. The development of NiTiMg, NiTiAg, and NiTiZn alloys is currently in the academic research stage. Reports indicate that the addition of Mg can improve the corrosion resistance and compressive strength of NiTi alloys and inhibit the formation of the Ti₂Ni phase; the addition of Ag and Zn can improve the biocompatibility and antibacterial properties of NiTi alloys; these alloys have extremely high application value in the biomedical field.

[0003] The melting points of metallic Mg, Ag, Zn, Ni, and Ti are 649℃, 961℃, 419℃, 1453℃, and 1675℃, respectively, and their boiling points are 1090℃, 2213℃, 907℃, 2732℃, and 3530℃, respectively. The melting and boiling points of metallic Mg, Ag, and Zn are significantly lower than those of metallic Ni and Ti. The process of preparing nickel-titanium alloy ingots containing low-melting-point elements Zn, Ag, and Mg using conventional vacuum induction melting or vacuum arc melting methods faces the challenge that metallic Mg, Ag, and Zn have reached their melting or boiling points, while metallic Ni and Ti have not yet melted, increasing the difficulty of melting such alloys. Some researchers have prepared nickel-titanium alloys containing low-melting-point metals through additive manufacturing and self-propagating high-temperature synthesis methods. These methods all use metal powders as raw materials for alloy preparation, resulting in higher production costs. Based on a comprehensive analysis of preparation costs and practical value, this type of alloy cannot yet be widely studied and applied. In order to promote the utilization of the value of this type of alloy, it is urgent to solve the problems of high cost and low efficiency in smelting and accelerate the process of conventional application of this alloy. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing nickel-titanium alloy ingots containing low-melting-boiling-point metals, in order to solve the problem that ingots containing low-melting-boiling-point alloys can only be prepared by additive manufacturing or powder metallurgy, which leads to high preparation costs, low preparation efficiency and limited application of such products.

[0005] This invention employs the following technical solution: a method for preparing a nickel-titanium alloy ingot containing a low melting and boiling point metal, comprising:

[0006] Step 1: Place the first nickel rod vertically and make a hole along the axis of the first nickel rod from top to bottom to form a receiving hole.

[0007] Step 2: Fill the receiving hole with low melting and boiling point metal particles.

[0008] Step 3: Place the second nickel rod on top of the first nickel rod, ensuring that the axes of the second and first nickel rods coincide, and then weld them together to obtain a binary alloy preform.

[0009] Step 4: Place the binary alloy preform in the crucible, ensuring the second nickel rod is positioned close to the bottom of the crucible.

[0010] Step 5: Place the crucible containing the binary alloy preform into a vacuum induction melting furnace for melting to obtain the binary alloy body.

[0011] Step 6: Place the sponge titanium, electrolytic nickel block, and binary alloy body into a pressing machine and press them to obtain the electrode.

[0012] Step 7: Prepare multiple electrodes, weld the electrodes together, and melt them in a vacuum arc furnace to obtain a nickel-titanium alloy ingot containing low melting and boiling point metals.

[0013] Furthermore, the low melting and boiling point metals are Zn, Ag, or Mg.

[0014] Furthermore, the mass ratio of nickel to low-melting-boiling-point metal in the binary alloy preform is 4:1.

[0015] Furthermore, the sum of the heights of the second nickel rod and the first nickel rod is less than or equal to... The depth of the inner hole of the crucible, and the height of the second nickel rod is 10-30 mm.

[0016] Furthermore, the diameter of the second nickel rod is the same as that of the first nickel rod, and when the low melting point metal is Mg, the wall thickness of the receiving hole of the first nickel rod is ≥5mm.

[0017] Furthermore, the diameter of the second nickel rod is the same as that of the first nickel rod, and when the low melting and boiling point metal is Zn or Ag, the wall thickness of the receiving hole of the first nickel rod is ≥20mm.

[0018] Furthermore, the smelting method in step 5 is as follows:

[0019] Stop evacuating the furnace when the vacuum level is ≤0.1Pa. Then, introduce argon gas into the furnace until the pressure inside the furnace reaches 0.03~0.09MPa. Start energizing the induction coil with an initial power of 5KW. Gradually increase the power at a rate of 1KW / min. When the first nickel rod of the binary alloy preform begins to melt, reduce the power by 1~5KW and continue energizing for 10~30min. Then, pour the solution in the crucible into the graphite mold and allow the solution to solidify and cool to room temperature.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention uses a combination of vacuum induction melting and vacuum consumable melting technologies to prepare nickel-titanium alloy ingots containing low-melting-point metals in the range of 150-1000 kg, which can meet the needs of industrial production. The equipment used is a typical vacuum induction melting furnace and a vacuum consumable melting furnace. No special equipment is required, and no additional equipment purchase costs are incurred. Compared with additive manufacturing and self-propagating high-temperature synthesis methods, it has the advantages of low cost, high efficiency, and high yield.

[0022] 2. In this invention, Ni metal with a relatively low melting and boiling point is first alloyed with a low melting and boiling point metal to prepare a binary alloy body. Then, the binary alloy body is alloyed and smelted with Ti metal and the balance Ni. This largely avoids the low melting and boiling point metal from coming into contact with the Ti metal solution with an excessively high melting point before alloying. During the alloying and smelting process of the alloyed binary alloy body with Ti metal and the balance Ni, the low melting and boiling point metal elements will not undergo significant volatilization, effectively reducing the volatilization of the low melting and boiling point metal during the smelting process.

[0023] 3. This invention uses a first nickel rod with a receiving hole to fill the receiving hole with a low-melting-point metal element. Then, a second nickel rod is used to seal the opening of the first nickel rod to obtain a binary alloy preform. Finally, the binary alloy preform is placed in the crucible of a vacuum induction melting furnace for melting to obtain a binary alloy body. During the melting process, the power supply is gradually increased to ensure that the binary alloy preform heats up slowly. During the heating process, the sealed low-melting-point metal melts first. Then, after the metal Ni reaches its melting point, the gaseous and liquid low-melting-point metals begin to melt into the metal Ni solution. The melting process is carried out under an argon protective atmosphere to prevent the pressure difference between the gas in the receiving hole of the first nickel rod and the gas pressure difference in the furnace cavity from being too large, which would cause a large amount of gaseous low-melting-point metal to volatilize into the furnace environment. This ensures that the low-melting-point metal is fully melted into the metal Ni solution, thus achieving the alloying of the two elements.

[0024] 4. In this invention, since the melting and boiling points of low-melting-boiling-point metals are lower than those of metal Ni, a large number of pores will be formed in the prepared binary alloy body. This invention uses the prepared binary alloy body, metal Ti and the balance Ni to prepare finished ingots by vacuum consumable electrode melting. This can ensure that the porosity defects in the binary alloy body are eliminated in the consumable melting process, and finally obtain a high-quality nickel-titanium alloy ingot with no obvious shrinkage cavities or pores except at the riser.

[0025] 5. The present invention uses a second metallic nickel rod to seal the opening of the first metallic nickel rod. In this process, only simple argon arc welding is required to complete the operation. The overall process is simple and easy to operate, and can be mass-produced. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the material arrangement inside the crucible in this invention.

[0027] Wherein: 1. First nickel rod; 2. Second nickel rod; 3. Receiving hole. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0030] This invention discloses a method for preparing nickel-titanium alloy ingots containing low-melting-boiling-point metals, such as... Figure 1 As shown, including

[0031] Step 1: Place the first nickel rod 1 vertically, and make a hole 3 along the axis of the first nickel rod 1 from top to bottom.

[0032] Step 2: Fill the receiving hole 3 with low melting and boiling point metal particles.

[0033] Step 3: Place the second nickel rod 2 on top of the first nickel rod 1, ensuring that the axes of the second nickel rod 2 and the first nickel rod 1 coincide, and then weld them together to obtain a binary alloy preform.

[0034] Step 4: Place the binary alloy preform in the crucible, ensuring the second nickel rod 2 is positioned close to the bottom of the crucible.

[0035] Step 5: Place the crucible containing the binary alloy preform into a vacuum induction melting furnace for melting to obtain the binary alloy body.

[0036] Step 6: Place the sponge titanium, electrolytic nickel block, and binary alloy body into a pressing machine and press them to obtain the electrode.

[0037] Step 7: Prepare multiple electrodes, weld the electrodes together, and melt them in a vacuum arc furnace to obtain a nickel-titanium alloy ingot containing low melting and boiling point metals.

[0038] The low-melting-point boiling point metal is Zn, Ag, or Mg.

[0039] The mass ratio of nickel to low-melting-boiling-point metal in the binary alloy preform is 4:1.

[0040] Wherein, the sum of the heights of the second nickel rod 2 and the first nickel rod 1 is less than or equal to The depth of the inner hole of the crucible, and the height of the second nickel rod 2 is 10-30 mm.

[0041] Wherein, the diameter of the second nickel rod 2 is the same as the diameter of the first nickel rod 1, and when the low melting point metal is Mg, the wall thickness of the receiving hole 3 of the first nickel rod 1 is ≥5mm.

[0042] Wherein, the diameter of the second nickel rod 2 is the same as the diameter of the first nickel rod 1, and when the low melting point metal is Zn or Ag, the wall thickness of the receiving hole 3 of the first nickel rod 1 is ≥20mm.

[0043] The smelting method in step 5 is as follows:

[0044] Stop evacuating the furnace when the vacuum level is ≤0.1Pa. Then, introduce argon gas into the furnace until the pressure inside the furnace reaches 0.03~0.09MPa. Start energizing the induction coil with an initial power of 5KW. Gradually increase the power at a rate of 1KW / min. When the first nickel rod 1 of the binary alloy preform begins to melt, reduce the power by 1~5KW and continue energizing for 10~30min. Then, pour the solution in the crucible into the graphite mold and allow the solution to solidify and cool to room temperature.

[0045] Because low-melting-point metals have low melting points (Mg: 649℃, Zn: 419℃, Ag: 961℃) and low boiling points (Mg: 1090℃, Zn: 907℃, Ag: 2213℃), while nickel has a melting point of 1435℃.

[0046] In the existing preparation process, the low-melting-boiling-point metal may melt or even vaporize before the nickel melts, making it impossible to control the content of low-melting-boiling-point metal in the finished product. The present invention fills the first nickel rod 1 with low-melting-boiling-point metal and seals it. Even if the low-melting-boiling-point metal melts or vaporizes before the temperature reaches the melting point of the nickel during the smelting process, it can be sealed in the first nickel rod 1. The low-melting-boiling-point metal solution or gas is alloyed with the nickel solution before overflowing from the first nickel rod 1 to prepare a binary alloy body.

[0047] Because low-melting-point metals have low melting points, they melt and vaporize first during the initial stage of induction melting as induced heat is generated. After vaporization, a large amount of low-melting-point metal vapor will be present in the receiving hole 3 of the first nickel rod 1. As melting continues, the first nickel rod 1 gradually heats up and melts, and some of the low-melting-point metal vapor alloys with nickel. If the melting power is not properly controlled during this process, some low-melting-point metal vapor will splash out of the solution. To prevent the solution from splashing out of the crucible during melting, the sum of the heights of the first nickel rod 1 and the second nickel rod 2 must be less than the depth of the inner hole of the crucible.

[0048] In addition, to prevent the outer wall of the corresponding receiving hole 3 in the first nickel rod 1 from melting prematurely and causing the low melting point metal vapor to escape through the nickel solution before alloying or before most of the low melting point metal vapor has been alloyed, the wall thickness of the receiving hole 3 of the first nickel rod 1 is set to ≥5mm or ≥20mm. This ensures that the wall thickness of the first nickel rod 1 is large enough to prevent the volatilization of low melting point metal gas to the greatest extent.

[0049] The binary alloy pre-body is placed in the crucible, and the second nickel rod 2 is placed close to the bottom of the crucible, that is, the second nickel rod 2 is in contact with the bottom of the crucible. This is to ensure that the welding position is downward. Since the gas after the metal vaporizes will rise, this can prevent the gas from rising and contacting the parts that have not been welded. This can greatly prevent the low melting point metal from escaping after the welding part melts.

[0050] In the smelting method, the heating rate is increased by 1 kW / min. Gradually increasing the power ensures a stable heating rate. During the heating process, the low-melting-boiling-point metal melts or even vaporizes first. Some of the low-melting-boiling-point metal gas or liquid will gradually begin to alloy with the liquid nickel during the slow heating process until the second nickel rod 2 and the first nickel rod 1 are completely melted, after which the low-melting-boiling-point metal has been melted into the nickel solution. After the first nickel rod 1 of the binary alloy preform begins to melt, the power is reduced by 1-5 kW to ensure that the solution temperature does not become too high after the nickel melts, preventing the solution from boiling and causing the unalloyed low-melting-boiling-point metal distributed in the solution to volatilize out of the nickel solution. Continuing to apply power for 10-30 minutes ensures that the unalloyed low-melting-boiling-point metal in the solution is fully alloyed with the nickel. Vacuum refining is not performed during the smelting process because the unalloyed low-melting-boiling-point metal in the solution is more likely to volatilize after vacuuming.

[0051] The solution in the crucible is poured into a graphite mold. After the solution solidifies and cools to room temperature, the binary alloy body is removed. The oxide scale and impurities on the surface of the binary alloy body and the riser are cleaned. Multiple binary alloy bodies are prepared in the same way.

[0052] The weight of sponge titanium, metallic nickel, and low-melting-point metal required to press one electrode is calculated based on the nominal composition of the nickel-titanium alloy ingot. The weight of one electrode is 30-100 kg. The materials are then proportioned according to the calculation results. The required weight of the binary alloy body is 5 times the required weight of the low-melting-point metal, and the required weight of the electrolytic nickel block is 0.8 times the calculated weight of metallic nickel minus the weight of the binary alloy body.

[0053] Five to ten electrode blocks are repeatedly obtained and welded using argon arc welding or other alternative welding methods to obtain consumable electrodes, with a total weight of 150 to 1000 kg. The consumable electrodes are then melted into ingots using a vacuum consumable arc furnace. After melting, the risers are removed to obtain nickel-titanium alloy ingots. Consumable melting can completely eliminate defects such as shrinkage cavities left over from unrefined binary alloys, and the product will not have defects caused by the introduction of elements with low melting and boiling points. However, vacuum consumable arc melting has the characteristic of simultaneous melting and solidification; to ensure the compositional uniformity of the entire ingot, the volume of the molten pool must be greater than or equal to the volume of a single electrode block.

[0054] Example 1

[0055] Taking the smelting of 150kg nickel-titanium-magnesium ingots as an example, the specific procedure is as follows:

[0056] The nominal component of the NiTiMg product is Ni. 51.0 Ti 44.2 Mg 4.8(by mass percentage) If an electrode weighs 30kg, then the required materials for one electrode are 13.26kg of sponge titanium, 15.30kg of metallic nickel, and 1.44kg of metallic magnesium.

[0057] A first nickel rod 1 with a diameter of 140 mm, a height of 170 mm, and a weight of 23.28 kg was selected and machined to form a receiving hole 3. The hole was cylindrical, with a depth of 160 mm and a diameter of 130 mm. After machining, the first nickel rod 1 weighed 4.39 kg. A second nickel rod 2 with a diameter of 140 mm, a height of 10 mm, and a weight of 1.37 kg was selected.

[0058] Metal Mg is inserted into the receiving hole 3 of the first metal nickel rod 1, and the second metal nickel rod 2 is placed on top of the receiving hole 3 of the first metal nickel rod 1, so that the center lines of the first metal nickel rod 1 and the second metal nickel rod 2 coincide. Finally, the first metal nickel rod 1 and the second metal nickel rod 2 are welded together using argon arc welding to obtain a 7.20kg binary alloy preform with a height of 180mm.

[0059] The weight ratio of Mg metal to the sum of the weights of the first and second nickel rods is 1:4. The binary alloy preform is placed inside the crucible, ensuring the second nickel rod is in contact with the bottom. The furnace is evacuated to 0.1 Pa, then evacuation is stopped. Argon gas is introduced into the furnace until the pressure reaches 0.09 MPa. The induction coil is then energized with an initial power of 5 kW, gradually increasing by 1 kW / min. When melting of the binary alloy preform is observable, the power is reduced by 1 kW, and energization continues for 15 minutes. The solution in the crucible is then poured into a graphite mold. After solidification and cooling to room temperature, the binary alloy body is obtained. The above steps are repeated to prepare five binary alloy bodies, and the oxide scale and impurities on the surface and riser of each body are cleaned.

[0060] Weigh 13.26 kg of sponge titanium, 9.54 kg of metallic nickel, and 7.20 kg of binary alloy body. Mix the prepared materials evenly and pour them into the mold cavity of the press to press them into electrodes. Repeat this process to obtain 5 electrode blocks. Weld the electrode blocks by argon arc welding to obtain a 150 kg consumable electrode. Use a vacuum consumable arc furnace to melt the consumable electrode into an ingot. During the melting process, ensure that the volume of the molten pool is greater than or equal to the volume of a single electrode. After melting is completed, remove the riser to obtain a 150 kg NiTiMg alloy ingot.

[0061] Samples were taken from the NiTiMg alloy ingot at a distance of 50 mm from the riser end and 50 mm from the bottom end face, and were marked as 1# and 2# respectively. The metals Ni and Mg were tested, and the test results are shown in Table 1. As can be seen from the table, Mg has been melted into the finished ingot, and no obvious volatilization phenomenon occurred during the smelting process.

[0062] Table 1

[0063] Sample number Ni content (wt.%) Mg content (wt.%) 1# 51.32 4.62 2# 50.98 4.58

[0064] Example 2

[0065] Taking the smelting of 1000kg nickel-titanium-zinc ingots as an example, the operation steps in this embodiment are the same as in Embodiment 1, except that:

[0066] The nominal component of the NiTiZn product is Ni. 52 Ti 44.0 For Zn4 (mass percentage), if one electrode weighs 100kg, then one electrode requires 44kg of sponge titanium, 52kg of metallic nickel, and 4kg of metallic zinc.

[0067] Select a first nickel rod 1 with a diameter of 240 mm, a height of 220 mm, and a weight of 88.53 kg. The depth of the receiving hole 3 is 180 mm and the diameter is 200 mm. After the hole is removed, the weight of the first nickel rod 1 is 38.23 kg. Select a second nickel rod 2 with a diameter of 240 mm, a height of 20 mm, and a weight of 8.05 kg. Prepare 4 kg of granular Zn metal.

[0068] The binary alloy pre-body weighs 50.28 kg and has a height of 240 mm.

[0069] Argon gas was introduced into the furnace until the furnace pressure reached 0.03 MPa; once the binary alloy preform could be observed to begin melting, the power was reduced by 5 kW, and the power was continued for 30 minutes. The above steps were repeated to prepare 10 binary alloy bodies.

[0070] Weigh 44 kg of sponge titanium, 5.72 kg of metallic nickel, and 50.28 kg of binary alloy body. Mix the prepared materials evenly and pour them into the mold cavity of the press to press into electrodes. Repeat this process to obtain 10 electrode blocks. Weld the electrode blocks by argon arc welding to obtain a 1000 kg consumable electrode. After melting in a vacuum consumable arc furnace, obtain a 1000 kg NiTiZn alloy ingot.

[0071] Samples were taken from the NiTiZn alloy ingot at a distance of 50 mm from the riser end and 50 mm from the lower end face, and were marked as 3# and 4# respectively. The metals Ni and Zn were tested, and the test results are shown in Table 2. It can be seen from the table that the Zn element has been melted into the finished ingot, and no obvious volatilization phenomenon of Zn occurred during the smelting process.

[0072] Table 2

[0073] Sample number Ni content (wt.%) Zn content (wt.%) 3# 52.18 3.85 4# 52.05 3.91

[0074] Example 3

[0075] Taking the smelting of 300kg nickel-titanium-silver ingots as an example, the operation steps in this embodiment are the same as in Embodiment 1, except that:

[0076] The nominal component of the NiTiAg product is Ni. 53.7 Ti 44.0 Ag 2.3 (by mass percentage) If an electrode weighs 30kg, then the required materials for one electrode are: 13.20kg of sponge titanium, 16.11kg of metallic nickel, and 0.69kg of metallic silver.

[0077] The first nickel rod 1 weighs 23.28 kg. The depth of the receiving hole 3 is 150 mm and the diameter is 100 mm. After the hole is removed, the first nickel rod 1 weighs 12.80 kg. A second nickel rod 2 with a height of 20 mm is selected. The second nickel rod 2 weighs 2.74 kg. 0.69 kg of granular Ag metal is prepared. The binary alloy pre-body weighs 16.23 kg and has a height of 190 mm.

[0078] Argon gas was introduced into the furnace until the furnace pressure reached 0.05 MPa; when the binary alloy preform could be observed to begin melting, the power was reduced by 2 kW, and the power was continued for 10 minutes. The above steps were repeated to prepare 10 binary alloy bodies.

[0079] Weigh 13.20 kg of sponge titanium, 0.57 kg of metallic nickel, and 16.23 kg of binary alloy block. Mix the prepared materials evenly and pour them into the mold cavity of the press to press them into electrodes. Repeat this process to obtain 10 electrode blocks. Weld the electrode blocks by argon arc welding to obtain a 300 kg consumable electrode. After melting in a vacuum consumable arc furnace, obtain a 300 kg NiTiAg alloy ingot.

[0080] Samples were taken from the NiTiAg alloy ingot at 50mm from the riser end and 50mm from the bottom end face, and were marked as 5# and 6# respectively. The metals Ni and Ag were tested, and the test results are shown in Table 3. As can be seen from the table, Ag has been melted into the finished ingot, and no obvious volatilization of Ag occurred during the smelting process. The ingot meets the usage requirements.

[0081] Table 3

[0082] Sample number Ni content (wt.%) Ag content (wt.%) 5# 53.74 2.40 6# 53.82 2.36

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal, characterized in that, include: Step 1: Place the first nickel rod (1) vertically and make holes along the axis of the first nickel rod (1) from top to bottom to form a receiving hole (3). Step 2: Fill the receiving hole (3) with low melting and boiling point metal particles. Step 3: Place the second nickel rod (2) on top of the first nickel rod (1), ensuring that the axes of the second nickel rod (2) and the first nickel rod (1) coincide, and then weld them together to obtain a binary alloy preform. Step 4: Place the binary alloy preform in the crucible, with the second nickel rod (2) positioned close to the bottom of the crucible. Step 5: Place the crucible containing the binary alloy preform into a vacuum induction melting furnace for melting to obtain the binary alloy body. Step 6: Place the sponge titanium, electrolytic nickel block, and binary alloy body into a pressing machine and press them to obtain the electrode. Step 7: Prepare multiple electrodes, weld the electrodes together, and melt them in a vacuum arc furnace to obtain a nickel-titanium alloy ingot containing low melting and boiling point metals.

2. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The low melting and boiling point metal is Zn, Ag, or Mg.

3. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The mass ratio of nickel to low-melting-boiling-point metal in the binary alloy preform is 4:

1.

4. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The sum of the heights of the second nickel rod (2) and the first nickel rod (1) is less than or equal to The depth of the inner hole of the crucible and the height of the second nickel rod (2) are 10-30 mm.

5. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The diameter of the second nickel rod (2) is the same as that of the first nickel rod (1). When the low melting point metal is Mg, the wall thickness of the receiving hole (3) of the first nickel rod (1) is ≥5mm.

6. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The diameter of the second nickel rod (2) is the same as that of the first nickel rod (1). When the low melting point metal is Zn or Ag, the wall thickness of the receiving hole (3) of the first nickel rod (1) is ≥20mm.

7. The method for preparing a nickel-titanium alloy ingot containing a low-melting-boiling-point metal according to claim 1, characterized in that, The smelting method in step 5 is as follows: Stop evacuating the furnace when the vacuum level is ≤0.1Pa. Then introduce argon gas into the furnace until the pressure inside the furnace reaches 0.03~0.09MPa. Start energizing the induction coil with an initial power of 5KW. Gradually increase the power at a rate of 1KW / min. When the first nickel rod (1) of the binary alloy preform begins to melt, reduce the power by 1~5KW and continue energizing for 10~30min. Then pour the molten liquid in the crucible into the graphite mold. Allow the molten liquid to solidify and cool to room temperature.

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