Method for producing cu-ti alloy strip based on ultrasonic assisted solidification and liquid nitrogen cold rolling

Abstract

This invention relates to the technical field of high-end voice coil motor spring preparation methods, specifically to a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling. The specific process is as follows: ingredient preparation, determining the approximate content range of each element in the copper-titanium alloy; vacuum induction melting; ultrasonic vibration by applying ultrasonic fields of different power during alloy melting and solidification; solution treatment of the obtained copper-titanium alloy ingot, followed by water cooling; liquid nitrogen cold rolling, during which the copper-titanium alloy plate remains in a low-temperature environment to obtain a high-density nanotwinned structure; and aging treatment of the copper-titanium strip in a vacuum atmosphere furnace to obtain the final copper-titanium alloy strip. This invention solves the problem in existing methods where copper-titanium alloy ingots are prone to compositional segregation and coarse primary phase structures, leading to microstructural inheritance during subsequent deformation, thus hindering the synergistic improvement of the strength and conductivity of the copper-titanium alloy strip.

Description

Technical Field

[0001] This invention belongs to the technical field of high-end voice coil motor (VCM) spring preparation methods, specifically involving a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling. Background Technology

[0002] High-strength, high-elasticity copper alloys are highly favored in cutting-edge fields such as high-end electronic communications and aerospace due to their high strength, high elasticity, excellent electrical and thermal conductivity, and non-magnetic properties. Currently, beryllium copper alloys have long held a dominant position in the field of current-carrying conductive elastic materials, earning them the title of "King of Elastic Materials" due to their superior performance. However, beryllium, as a strategic metal, is scarce and extremely difficult to mine and utilize. With increasingly stringent environmental standards, the shortcomings of beryllium copper alloys are becoming increasingly apparent: in particular, the toxicity of beryllium poses a threat to the environment and human health; beryllium-containing dust and compounds that may be generated during smelting and processing are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC); under high-temperature environments, their stress relaxation resistance is poor and their electrical conductivity is insufficient, making it difficult to meet application requirements; furthermore, the long production cycle and low yield of beryllium copper alloys result in persistently high product prices. Therefore, the development of new, green, environmentally friendly copper alloys with high strength and high elasticity has become an urgent priority.

[0003] To address these issues, researchers have been searching for alternatives to beryllium copper alloys. Copper-titanium alloys, due to their similar excellent properties, such as good heat resistance, fatigue resistance, corrosion resistance, and high-temperature stress resistance, are considered one of the most promising alternatives. However, copper-titanium alloy strips produced using traditional processes do not meet the strength and conductivity requirements for high-end voice coil motor (VCM) springs and electrical connectors, becoming a key obstacle to their application. Therefore, solving the problem of synergistically improving the strength and conductivity of copper-titanium alloys is urgently needed.

[0004] To address the aforementioned challenges in preparing copper-titanium alloy strips, relevant research has been reported. Patent application number 202310778835.9 provides an ultra-high strength conductive copper-titanium alloy and its preparation method. The method is characterized by the following steps: (1) sequentially melting and casting the raw materials of the copper-titanium alloy to obtain a copper-titanium alloy ingot; (2) sequentially subjecting the copper-titanium alloy ingot obtained in step (1) to solution treatment, hot rolling, and a first aging treatment to obtain a copper-titanium alloy plate; (3) sequentially subjecting the copper-titanium alloy plate obtained in step (2) to a first cold rolling, a second aging treatment, and a second cold rolling to obtain an ultra-high strength conductive copper-titanium alloy. This invention uses Cu as the matrix and adds alloying elements Cr and Mg to effectively improve the strength and conductivity of the alloy. Mg is dissolved in the matrix, providing solid solution strengthening. Cr and Ti form Cr2Ti intermetallic compounds, reducing the dissolved Ti content and increasing the alloy's conductivity. Furthermore, these intermetallic compounds hinder dislocation movement during later rolling processes, increasing dislocation density and thus improving the alloy's strength and conductivity. Combined with aging treatment, the volume fraction of β-Cu4Ti precipitates can be increased while reducing production costs, significantly improving the alloy's conductivity. Furthermore, combining hot rolling and cold rolling facilitates the acquisition of a high-density, uniformly distributed β-Cu4Ti phase, thereby enhancing the strength and conductivity of the copper-titanium alloy. Patent application number 202280054776.4 provides a copper-titanium alloy, by weight, containing at least 90% copper, 5%-7% titanium, and 0.25%-0.5% iron. This copper-titanium alloy exhibits excellent ductility during solution annealing and tempering and high yield strength after aging treatment. The alloy according to this invention can replace Cu-Be alloys in any very high-strength alloy application requiring good mechanical properties but not necessarily good electrical conductivity, such as Bourdon tubes in high-pressure gauges, watch parts, ball bearings and bushings (especially for the aircraft and aerospace industry), and dies for plastic extrusion. Patent application number 202010620874.2 provides a method for preparing a copper-titanium alloy, specifically including the following steps: Step S1, obtaining a copper-titanium alloy ingot using an aluminothermic reaction; Step S2, rolling the copper-titanium alloy ingot obtained in Step S1, wherein the rolling reduction is 40%–80%; Step S3, solution treating the copper-titanium alloy after the rolling treatment in Step S2, wherein the solution temperature is 860°C, the holding time is 1 hour, and quenching is performed after the solution treatment; Step S4, aging the copper-titanium alloy after the solution treatment in Step S3. The method of this invention can not only obtain high titanium content copper-titanium alloys with higher strength, ductility and electrical conductivity, but also reduce manufacturing costs and improve production efficiency.Patent application number 202110203008.8 discloses a method for preparing a copper-titanium alloy, comprising the following steps: According to the designed composition, various metal raw materials are melted and cast to obtain an ingot; the ingot is hot-deformed and then subjected to a first solution treatment; after cold deformation, it undergoes a second solution treatment; and after the second solution treatment, it is aged to obtain a titanium-copper alloy. The second solution treatment can employ one of two processes: Process 1: The cold-deformed copper material undergoes high-temperature short-time annealing, with the copper material placed at 780–800℃ for less than 120–300 seconds followed by rapid cooling; Process 2: The cold-deformed copper material undergoes rapid heating and instantaneous annealing, with a heating rate greater than 50℃ / s, the optimal heating rate greater than 150℃ / s, heated to 650–800℃, followed by rapid cooling. The copper-titanium alloy prepared by this patent achieves a tensile strength of 1000 MPa and an elongation of 10%, meeting the requirements for high strength and high plasticity of copper and titanium, as well as the requirements for bending processes. Patent application number 202011537632.3 discloses a high-strength, high-conductivity, and high-toughness copper-titanium alloy for integrated circuits. The elements contained in the copper-titanium alloy and the weight percentage of each element are: titanium 2.9-3.4%, iron 0.17-0.23%, aluminum 0.15-0.20%, boron 0.03-0.10%, with the balance being copper and unavoidable impurities. The preparation method of the high-strength, high-conductivity, and high-toughness copper-titanium alloy includes the following steps: (1) batching; (2) vacuum melting to form a copper-titanium alloy melt; (3) casting to form an ingot; (4) cold rolling to obtain a sheet; and (5) aging treatment. This alloy has the advantages of high strength, good conductivity, and high toughness, and is mainly used in integrated circuits, especially large-scale and ultra-large-scale integrated circuit frames and various electronic product connectors. Patent application number 202010874363.3 discloses an elastic copper-titanium alloy and its preparation method. The preparation method of the elastic copper-titanium alloy includes the following steps: corresponding to the composition of the elastic copper-titanium alloy, the various metal raw materials are smelted and cast to obtain an ingot; the ingot is sequentially subjected to hot rolling, a first cold rolling, solution treatment, a third cold rolling, a second aging treatment, and annealing treatment to obtain the elastic copper-titanium alloy; the elemental composition of the elastic copper-titanium alloy, by mass percentage, includes Ti: 2.4~3.5%, Cr: 0.02~0.2%, Ni: 0.02~0.5%, Si: 0.05~0.1%, rare earth elements 0~0.05%, and the remainder being Cu. This invention, by changing the particle structure of the precipitated phase and coordinating the composition of the copper-titanium alloy, prepares an elastic copper-titanium alloy with high strength, high elongation, high electrical conductivity, low stress relaxation rate, and good bending resistance.

[0005] Although the aforementioned patents have made improvements in optimizing the processing methods and heat treatment processes of copper-titanium alloy strips, which is beneficial to improving the performance of copper-titanium alloy strips, they have not yet solved the bottleneck problem of the difficulty in synergistically improving the electrical conductivity and strength of copper-titanium alloy strips. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling. This method addresses the problem in existing methods where copper-titanium alloy billets are prone to compositional segregation and coarse primary phase microstructure, leading to microstructural inheritance during subsequent deformation and hindering the synergistic improvement of the strength and electrical conductivity of the copper-titanium alloy strip.

[0007] Another object of the present invention is to provide a copper-titanium alloy strip obtained by the above preparation method.

[0008] This invention relates to a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling, specifically implemented according to the following steps:

[0009] Step 1, ingredient preparation: the element content of the titanium bronze alloy, by mass percentage, is: Ti 3-6%, Cu 96-97%;

[0010] Step 2: Perform vacuum induction melting by placing the raw materials into a vacuum melting equipment for melting.

[0011] Step 3: Apply ultrasonic fields of different powers to the alloy from Step 2 during melting and solidification to induce ultrasonic vibration;

[0012] Step 4: The obtained copper-titanium alloy ingot is subjected to solution treatment, followed by water cooling;

[0013] Step 5, liquid nitrogen cold rolling: First, the copper-titanium alloy is cooled, and the rolls are also cooled to a certain temperature before rolling. During the rolling process and after each pass, there are corresponding cooling operations until the required deformation is achieved to obtain the cold-rolled billet.

[0014] Step 6: Place the copper-titanium strip into a vacuum atmosphere furnace for aging treatment to obtain the final copper-titanium alloy strip.

[0015] Preferably, the specific process of step 1 is as follows: Ingredients: The content of each element in the titanium bronze alloy is as follows, by mass percentage: Ti 3-6%, Cu 96-97%.

[0016] Preferably, the specific process of step 2 is as follows: Vacuum induction melting: The raw materials weighed in step (1) are placed in a vacuum melting device for vacuum melting, with a vacuum degree of 5×10 -3 - 8×10 -3 Pa, smelting current 22A-26A.

[0017] Preferably, the specific process of step 3 is as follows: the alloy in step (2) is subjected to ultrasonic fields of different powers during melting and solidification to perform ultrasonic oscillation. The ultrasonic amplitude changes with the power. The frequency of the applied ultrasound is 20-25KHz and the ultrasonic power is 0-2700W to obtain copper-titanium alloy ingots.

[0018] Preferably, the specific process of step 4 is as follows: solution treatment: the copper-titanium alloy ingot obtained in step (3) is subjected to solution heat treatment at a temperature of 750℃-900℃. The sample is heated with the furnace and the solution time is 1-12h. After the solution treatment is completed, it is cooled with water.

[0019] Preferably, the specific process of step 5 is as follows: Before preparing for liquid nitrogen rolling, the copper-titanium alloy obtained in step (4) is placed in a container filled with liquid nitrogen and cooled for 40-70 minutes. After the copper-titanium alloy has been fully cooled, the rolling mill is started, and the rolls are sprayed with liquid nitrogen for 5-10 minutes to cool the rolls to a certain temperature. During the rolling process, the linear speed of the rolls is 60-240 mm / s, and the reduction rate per pass is 15%-25%. After each pass of rolling is completed, the copper-titanium alloy strip is cooled in liquid nitrogen for 10-30 minutes. The above rolling process is repeated until the copper-titanium alloy plate reaches the required deformation amount, with a total reduction rate of 60%-85%, to obtain a cold-rolled copper-titanium alloy billet. During the rolling process, the copper-titanium alloy plate is always in a low-temperature environment to suppress the dislocation movement of the copper-titanium alloy plate during the rolling process and obtain a high-density nanotwin structure.

[0020] Preferably, the specific process of step 6 is as follows: the copper-titanium strip obtained in step (5) is placed in a vacuum atmosphere furnace and kept at 400℃-500℃ for 1-24h to obtain the final copper-titanium alloy strip.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The beneficial effects of this invention are:

[0023] (1) This invention is based on a method for preparing CuTi alloy strip using ultrasonic-assisted solidification and liquid nitrogen cold rolling. It employs induction melting and ultrasonic-assisted solidification. Existing technologies typically rely on hot rolling and subsequent multiple cold rolling processes to achieve grain refinement. However, this patent innovatively proposes applying an ultrasonic field during the alloy solidification stage. Through the cavitation and acoustic flow effects of the ultrasonic field, it promotes solute homogeneity, equiaxed refinement of α-Cu, and improves alloy composition segregation. This allows the sample grains to gradually refine during solidification, thereby obtaining a high-performance billet and enabling the sample to achieve preliminary grain refinement before cold rolling. This enhances the grain refinement effect obtained by cold rolling and significantly improves process efficiency.

[0024] (2) Liquid nitrogen cold rolling is used instead of room temperature rolling. At room temperature, the stacking fault energy of materials is high, and dislocation slip is the main deformation mechanism, making twinning deformation difficult to occur. Therefore, room temperature rolling mainly improves the strength of materials by dislocation slip and grain refinement, forming fine equiaxed crystals or fibrous structures, rather than nanotwins. However, ordinary grain boundaries strongly scatter electrons due to the disordered atomic arrangement and lattice distortion, increasing electrical resistance. The number of grain boundaries in fine-grained reinforced materials increases significantly, thus leading to a significant decrease in electrical conductivity. Liquid nitrogen cold rolling is a cold rolling process carried out at extremely low temperatures, namely the liquid nitrogen temperature (approximately -196°C). At extremely low temperatures, the stacking fault energy of materials decreases, and twinning deformation is more likely to occur. During the low-temperature plastic deformation process, strips generate a large number of nanograins, dislocation structures, and nanotwins. This high-density nanotwins and dislocation structures can significantly improve the strength of materials; at the same time, the scattering effect of nanotwin boundaries on electrons is very small, thus maintaining the electrical conductivity of the material. Furthermore, the alloy cold-rolled with liquid nitrogen exhibits faster phase transformation kinetics and smaller nucleation barriers during subsequent aging treatment, which helps to form finer and more uniformly distributed precipitates, further synergistically improving the strength, plasticity, and electrical conductivity of the copper-titanium alloy.

[0025] (3) Thirdly, the process is simplified. Compared with the traditional room temperature multiple rolling and long-term heat treatment preparation method, the preparation process proposed in this patent is simple, time-saving, and does not require multi-stage deformation aging heat treatment to achieve the purpose of synergistic improvement of strength and conductivity. Detailed Implementation

[0026] This invention relates to a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling, specifically implemented according to the following steps:

[0027] The specific process of step 1 is as follows: Ingredients: The content of each element in the titanium bronze alloy is as follows, by mass percentage: Ti 3-6%, Cu 96-97%;

[0028] Furthermore, the specific process of step 2 is as follows:

[0029] Vacuum induction melting: The raw materials weighed in step (1) are placed in a vacuum melting equipment for vacuum melting, with a vacuum degree of 5×10⁻⁶. -3 - 8×10 -3 Pa, melting current 22A-26A;

[0030] Further, the specific process of step 3 is as follows: when the alloy in step (2) is melted and solidified, ultrasonic fields of different powers are applied to perform ultrasonic oscillation. The ultrasonic amplitude changes with the power. The frequency of the applied ultrasound is 20-25KHz and the ultrasonic power is 0-2700W.

[0031] Further, the specific process of step 4 is as follows: solution treatment: the copper-titanium alloy ingot obtained in step (3) is subjected to solution heat treatment at a temperature of 750℃-900℃. The sample is heated with the furnace and the solution time is 1-12h. After the solution treatment is completed, it is cooled by water.

[0032] Further, the specific process of step 5 is as follows: Before preparing for liquid nitrogen rolling, the copper-titanium alloy obtained in step (4) is placed in a container filled with liquid nitrogen and cooled for 40-70 minutes. After the copper-titanium alloy has been fully cooled, the rolling mill is started and the rolls are sprayed with liquid nitrogen for 5-10 minutes to cool the rolls to a certain temperature. During the rolling process, the linear speed of the rolls is 60-240 mm / s, and the reduction rate per pass is 15%-25%. After each pass of rolling is completed, the copper-titanium alloy strip is cooled in liquid nitrogen for 10-30 minutes. The above rolling process is repeated until the copper-titanium alloy plate reaches the required deformation amount, with a total reduction rate of 60%-85%, to obtain a cold-rolled copper-titanium alloy billet. During the rolling process, the copper-titanium alloy plate is always in a low-temperature environment. The purpose is to suppress the dislocation movement of the copper-titanium alloy plate during the rolling process and obtain a high-density nanotwin structure.

[0033] Further, the specific process of step 6 is as follows: the copper-titanium alloy strip obtained in step (5) is placed in a vacuum atmosphere furnace and kept at 400℃-500℃ for 1-24h to obtain the final copper-titanium alloy strip.

[0034] Example 1

[0035] This invention relates to a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling, specifically implemented according to the following steps:

[0036] Step 1: Ingredients: By weight percentage, the percentage content of each element in the raw materials is: Ti 3%, Cu 97%;

[0037] Step 2: Cleaning: Remove the oxide scale from step (1), put it into a beaker containing alcohol, put the beaker into an ultrasonic cleaner at 40°C, clean for 15 minutes, and prepare to start smelting.

[0038] Step 3: Vacuum induction melting: Place the raw materials weighed in step (2) into a vacuum induction melting device for vacuum melting, with a vacuum degree of 8.0 × 10⁻⁶. -3 MPa, melting times are 5 times, melting repeatedly from top to bottom, each melting time is 15 minutes, and the current is controlled at 26A during the melting process;

[0039] Step 4: Solution treatment: After removing the head and tail of the alloy in step (3), place it in a vacuum atmosphere furnace and perform a solution treatment at 850°C for 4 hours, followed by water quenching.

[0040] Step 5: Liquid nitrogen rolling deformation: Place the alloy billet from step (4) in a container filled with liquid nitrogen and cool for 60 minutes. After the copper-titanium alloy has cooled sufficiently, start the rolling mill and spray the rolls with liquid nitrogen for 10 minutes to cool the rolls to a certain temperature. During the rolling process, the linear speed of the rolls is 60 mm / s, and the reduction rate is 25% per pass. After each pass is completed, the copper-titanium alloy strip is immersed in liquid nitrogen for 10 minutes to cool. Repeat the above rolling process until the copper-titanium alloy plate reaches the required deformation amount. The total reduction rate is 80%, and a cold-rolled copper-titanium alloy billet is obtained. During the rolling process, the copper-titanium alloy plate is always in a low-temperature environment. The purpose is to suppress the dislocation movement of the copper-titanium alloy plate during the rolling process and obtain a high-density nanotwin structure.

[0041] Step 6: Aging treatment: Place the copper-titanium strip obtained in step (5) into a vacuum atmosphere furnace and keep it at 450°C for 4 hours to obtain the final copper-titanium alloy strip.

[0042] Step 7: Test its mechanical and electrical properties. The final test results are: electrical conductivity 11.69% IACS, tensile strength 912.14 MPa.

[0043] Example 2

[0044] This invention relates to a method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling, specifically implemented according to the following steps:

[0045] Step 1: Ingredients: By weight percentage, the percentage content of each element in the raw materials is: Ti 3%, Cu 97%;

[0046] Step 2: Cleaning: Remove the oxide scale from step (1), put it into a beaker containing alcohol, put the beaker into an ultrasonic cleaner at 40°C, clean for 15 minutes, and prepare to start smelting.

[0047] Step 3: Vacuum induction melting: Place the raw materials weighed in step (2) into a vacuum induction melting device for vacuum melting, with a vacuum degree of 8.0 × 10⁻⁶. -3 MPa, melting 5 times, melting repeatedly from top to bottom, each melting time is 15 minutes, and the current is controlled at 22A during the melting process;

[0048] Step 4: Applying an ultrasonic field: The frequency of the ultrasonic field applied during the melting and solidification of the alloy in step (3) is 20KHz and the ultrasonic power is 1800W;

[0049] Step 5: Solution treatment: After removing the head and tail of the alloy in step (4), place it in a vacuum atmosphere furnace and perform a solution treatment at 850°C for 4 hours, followed by water quenching.

[0050] Step 6: Liquid nitrogen rolling deformation: Place the alloy billet from step (5) in a container filled with liquid nitrogen and cool for 60 minutes. After the copper-titanium alloy has cooled sufficiently, start the rolling mill and spray the rolls with liquid nitrogen for 10 minutes to cool the rolls to a certain temperature. During the rolling process, the linear speed of the rolls is 60 mm / s, and the reduction rate is 25% per pass. After each pass is completed, the copper-titanium alloy strip is immersed in liquid nitrogen for 10 minutes to cool. Repeat the above rolling process until the copper-titanium alloy plate reaches the required deformation amount. The total reduction rate is 80%, and a cold-rolled copper-titanium alloy billet is obtained. During the rolling process, the copper-titanium alloy plate is always in a low-temperature environment. The purpose is to suppress the dislocation movement of the copper-titanium alloy plate during the rolling process and obtain a high-density nanotwin structure.

[0051] Step 7: Aging treatment: Place the copper-titanium strip obtained in step (6) into a vacuum atmosphere furnace and hold it at 450℃ for 4 hours. The final copper-titanium alloy strip is obtained.

[0052] Step 8: Test its mechanical and electrical properties. The final test results are: electrical conductivity 12.13% IACS, tensile strength 1008.09 MPa.

Claims

1. A method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling, characterized in that, The specific steps are as follows: Step 1, ingredient preparation: by mass percentage, the element content of titanium bronze alloy is: Ti 3-6%, Cu 96-97%; Step 2: Perform vacuum induction melting by placing the raw materials into a vacuum melting equipment for melting. Step 3: Apply ultrasonic fields of different powers to the alloy from Step 2 during melting and solidification to perform ultrasonic vibration, thereby obtaining a copper-titanium alloy ingot. Step 4: The obtained copper-titanium alloy ingot is subjected to solution treatment, followed by water cooling; Step 5, liquid nitrogen cold rolling: First, the copper-titanium alloy is cooled, and the rolls are also cooled to a certain temperature before rolling. During the rolling process and after each pass, there are corresponding cooling operations until the required deformation is achieved to obtain the cold-rolled billet. Step 6: Place the copper-titanium strip into a vacuum atmosphere furnace for aging treatment to obtain the final copper-titanium alloy strip.

2. The method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling according to claim 1, characterized in that, The specific process of step 2 is as follows: Vacuum induction melting: The raw materials weighed in step (1) are placed in a vacuum melting equipment for vacuum melting, with a vacuum degree of 5×10 -3 - 8×10 -3 Pa, smelting current 22A-26A.

3. The method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling according to claim 1, characterized in that, The specific process of step 3 is as follows: When the alloy in step (2) is melted and solidified, ultrasonic fields with different powers are applied to perform ultrasonic oscillation. The ultrasonic amplitude changes with the power. The frequency of the applied ultrasound is 20-25kHz and the ultrasonic power is less than or equal to 2700W.

4. The method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling according to claim 1, characterized in that, The specific process of step 4 is as follows: Solution treatment: The copper-titanium alloy ingot obtained in step (3) is subjected to solution heat treatment. The solution temperature is 750℃-900℃. The sample is heated with the furnace. The solution time is 1-12h. After the solution is completed, it is water-cooled.

5. The method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling according to claim 1, characterized in that, The specific process of step 5 is as follows: Before preparing for liquid nitrogen rolling, the copper-titanium alloy obtained in step (4) is placed in a container filled with liquid nitrogen and cooled for 40 to 70 minutes. After the copper-titanium alloy has been fully cooled, the rolling mill is started and the rolls are sprayed with liquid nitrogen for 5 to 10 minutes to cool the rolls to a certain temperature. During the rolling process, the linear speed of the rolls is 60 to 240 mm / s, and the reduction rate is 15% to 25% per pass. After each pass is completed, the copper-titanium alloy strip is cooled in liquid nitrogen for 10 to 30 minutes. The above rolling process is repeated until the copper-titanium alloy plate reaches the required deformation amount. The total reduction rate is 60% to 85%, and a cold-rolled copper-titanium alloy billet is obtained.

6. The method for preparing CuTi alloy strip based on ultrasonic-assisted solidification and liquid nitrogen cold rolling according to claim 1, characterized in that, The specific process of step 6 is as follows: the copper-titanium strip obtained in step (5) is placed in a vacuum atmosphere furnace and kept at 400℃-500℃ for 1-24h to obtain the final copper-titanium alloy strip.