Paramagnetic invar materials and mechanical watch hairs and uses, methods of manufacture

Abstract

The application provides a paramagnetic constant modulus alloy material, a mechanical watch hairspring and use and a preparation method. The paramagnetic constant modulus alloy material comprises 0.4wt%-0.8wt% N, 40wt%-50wt% Ti and 49.2wt%-59.6wt% Nb; or 0.4wt%-0.8wt% C, 40wt%-50wt% Ti and 49.2wt%-59.6wt% Nb; or 0.4wt%-0.8wt% N, 0.4wt%-0.8wt% C, 40wt%-50wt% Ti and 49.2wt%-59.6wt% Nb. At least one of nitrogen and carbon is used as a solid solution strengthening element, the strength and the elastic modulus of the alloy or the hairspring are improved, and the temperature coefficient of the elastic modulus of the alloy is controlled.

Description

Technical Field

[0001] This invention relates to the field of materials, and in particular to a paramagnetic constant elastic alloy material, a hairspring for mechanical watches, its uses, and a preparation method. Background Technology

[0002] For most metals or non-transformation alloys, the interatomic bonding forces gradually weaken with increasing temperature, leading to a decrease in the elastic modulus. This can negatively impact the accuracy of instruments and meters. Typically, the temperature coefficient of elastic modulus for metals and alloys is 10⁻⁶. -4 On the order of °C. However, for some alloys, the elastic modulus does not change with temperature or changes very little (generally ≤ ±20 × 10⁻⁶). -6 These alloys (with a temperature of / ℃) are also known as constant-elasticity alloys. Constant-elasticity alloys make accurate timekeeping possible in mechanical watches.

[0003] In mechanical watches, ferromagnetic alloys with Fe and Ni as basic components are widely used. These alloys have good machinability, high elastic modulus and strength. Through process and composition control, the temperature coefficient of mechanical watches can be made to be within 0.5 s / (d·℃). However, these ferromagnetic alloys are easily affected by magnetic fields, which can cause mechanical watches to keep inaccurate time.

[0004] Patent CN109116712B discloses a spiral watch spring made of a niobium-titanium alloy, comprising: 45.0% to 48.0% titanium, trace elements including O, H, C, Fe, Ta, N, Ni, Si, Cu, and Al, each at 0 to 1600 ppm by weight and totaling less than 0.3 wt%, and niobium to make up the balance of 100%. The alloy has an elastic limit higher than 1000 MPa and an elastic modulus higher than 60 GPa and less than 80 GPa. Patent CN109960132B discloses a balance spring made of a niobium and titanium alloy and its manufacturing method, wherein the alloy contains: 40 to 60 wt% titanium, trace elements including O, H, C, Fe, Ta, N, Ni, Si, Cu, and Al, each at 0 to 1600 ppm by weight and totaling less than 0.3 wt%, and niobium to make up to 100 wt%. The alloys disclosed in the aforementioned patents do not contain ferromagnetic elements. Hairsprings made from these paramagnetic alloys are unaffected by magnetic fields, but they have significant drawbacks, such as low elastic limit and elastic modulus, which affect the lifespan of the hairspring and the stability of the mechanical watch's timekeeping.

[0005] Precipitation strengthening is the main strengthening method for niobium-titanium alloys. The most common method in existing technology is to add an appropriate amount of aluminum to the alloy. The published technical document "Properties and Applications of Elastic Niobium Alloys" reports an alloy with the following composition: Nb -35～ 42 Ti -5～5.5A paramagnetic alloy of Al, which can be strengthened by precipitating (NbTi)3Al during heat treatment. Although the elastic modulus can reach 110 GPa, it is still relatively low. The temperature coefficient of elastic modulus of this alloy is (-32.2 to -54.5) × 10⁻⁶. -6 / ℃. The temperature coefficient c of a mechanical watch is determined by the temperature coefficient β of the elastic modulus of the hairspring and the coefficient of linear expansion α (approximately 8 × 10⁻⁶ for niobium-titanium alloys). -6 / ℃) and the linear expansion coefficient α′ of the balance wheel (the balance wheel material of a watch is generally 18×10 -6 The value of / ℃ is jointly determined and can be expressed by equation (1):

[0006]

[0007] To achieve good timekeeping in a mechanical watch, c is generally required to be within ±0.5, therefore β should be approximately within (+0.5~+23.5)×10⁻⁶ / ℃. Clearly, Nb -35～42 Ti -5～5.5 The temperature coefficient of the elastic modulus of Al does not meet the requirements for watch hairsprings. In addition, the addition of Al increases the brittleness of the alloy, making the drawing and rolling processes necessary for manufacturing watch hairsprings more difficult. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a paramagnetic constant elastic alloy material, a hairspring for mechanical watches, its applications, and a preparation method.

[0009] The technical solution proposed in this invention is as follows:

[0010] This invention proposes a paramagnetic constant elastic alloy material, comprising:

[0011] 0.4wt%–0.8wt% N, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or

[0012] 0.4wt%–0.8wt% C, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or

[0013] 0.4wt%–0.8wt% N, 0.4wt%–0.8wt% C, 40wt%–50wt% Ti and 49.2wt%–59.6wt% Nb.

[0014] The paramagnetic constant elastic alloy material of the present invention comprises 0.48wt% C, 0.62wt% N, 44wt% Ti, 54.8wt% Nb and 0.1wt% impurities.

[0015] This invention also proposes a method for preparing the paramagnetic constant elastic alloy material as described above, comprising the following steps:

[0016] Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering.

[0017] Step S2: The blank is processed into a blank through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations;

[0018] Step S3: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa.

[0019] Step S4: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa.

[0020] In the preparation method of the paramagnetic constant elastic alloy material of the present invention, in step S2, the single deformation amount of cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the forming process is 30%-90%.

[0021] In the preparation method of the paramagnetic constant elastic alloy material of the present invention, in the first heat treatment, the first heat treatment temperature is 700℃-1150℃, and the first heat treatment holding time is 1min-60min.

[0022] The present invention also proposes an application of the paramagnetic constant elastic alloy material as described above for the preparation of hairsprings for mechanical watches.

[0023] This invention also proposes a method for preparing a hairspring for a mechanical watch, comprising the following steps:

[0024] Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering.

[0025] Step S2: The billet is processed into a bar stock through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations;

[0026] Step S3: Coat the bar stock with a lubricating layer; then draw the bar stock coated with the lubricating layer into wires step by step, and then remove the lubricating layer to obtain wire;

[0027] Step S4: Roll the wire into a flat wire with a rectangular cross-section;

[0028] Step S5: Wind the flat wire into a blank inside the mold;

[0029] Step S6: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa.

[0030] Step S7: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa;

[0031] Step S8: Demold, trim, cut and assemble the blank after the third heat treatment to form the finished hairspring.

[0032] In the above-mentioned method for preparing the hairspring of a mechanical watch, in step S2, the single deformation amount of cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the molding process is 30%-90%.

[0033] In the above-mentioned method for preparing the hairspring of a mechanical watch, the first heat treatment temperature is 700℃-1150℃ and the first heat treatment holding time is 1min-60min.

[0034] In the above-mentioned method for preparing the hairspring of a mechanical watch, in step S4, the width of the flat wire is denoted as b, and the thickness is denoted as h, with the relationship being: 3h≤b≤5h.

[0035] Compared with the prior art, the present invention has the following technical advantages:

[0036] 1) In terms of composition, this invention uses at least one of nitrogen and carbon as a solid solution strengthening element. Compared with the prior art, it has a better strengthening effect and improves the strength and elastic modulus of the alloy or hairspring.

[0037] 2) In terms of process, the present invention introduces strengthening elements after the deformation process is completed. Compared with the existing processing technology, the material is subjected to less resistance during deformation processing and is easier to deform.

[0038] 3) In terms of performance, in existing technologies, the temperature coefficient of elastic modulus of the alloy is negative, ranging from (-32.2 to -54.5) × 10⁻⁶. -6 / ℃, while the present invention achieves the control of the temperature coefficient of the elastic modulus of the alloy, making it within (0~100)×10 -6 Within a certain temperature range (°C), and further by selecting the heat treatment temperature and holding time, the temperature coefficient of the alloy's elastic modulus can be controlled, making it within the range of (0~25)×10⁻⁶. -6 When used to make hairsprings for precision mechanical watches, temperatures within a certain range of ℃ can achieve a timekeeping temperature coefficient better than 0.5 s / (d·℃). Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0040] Figure 1 A micrograph of the paramagnetic constant elastic alloy material of Embodiment 1 of the present invention is shown;

[0041] Figure 2 A photograph of the finished hairspring of Embodiment 3 of the present invention is shown;

[0042] Figure 3 A metallographic photograph of the hairspring of a mechanical watch according to Embodiment 3 of the present invention is shown. Detailed Implementation

[0043] The technical objective of this application is to address the problems of existing paramagnetic constant elastic alloy materials having low elastic limit and elastic modulus, or negative temperature coefficient of elastic modulus, which do not meet the requirements of certain applications, especially watch hairsprings, or the introduction of strengthening elements that easily leads to processing difficulties. This application provides a paramagnetic constant elastic alloy material with high elastic limit and elastic modulus, a wide adjustable temperature coefficient of elastic modulus, and easy processing. It also provides a method for preparing the paramagnetic constant elastic alloy material, its applications, and a method for preparing a mechanical watch hairspring.

[0044] This invention proposes a paramagnetic constant elastic alloy material, comprising:

[0045] 0.4wt%–0.8wt% N, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or

[0046] 0.4wt%–0.8wt% C, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or

[0047] 0.4wt%–0.8wt% N, 0.4wt%–0.8wt% C, 40wt%–50wt% Ti and 49.2wt%–59.6wt% Nb.

[0048] Preferably, the paramagnetic constant elastic alloy material comprises 0.48 wt% C, 0.62 wt% N, 44 wt% Ti, 54.8 wt% Nb, and 0.1 wt% impurities.

[0049] Solid solution can strengthen niobium-titanium alloys. C, N, and B are all effective solid solution strengthening elements. However, in existing technologies, these elements are generally considered impurities because while increasing the alloy's strength and elastic modulus, they reduce its plasticity and toughness, hindering deformation processing. This invention solves the problem of difficulty in deformation processing after solid solution strengthening by introducing solid solution strengthening after deformation processing. In the alloy composition design, since solid solution strengthening is completed after deformation processing, C and N elements, which can be achieved through gas reactions, are selected as strengthening elements. If the C and N content is too low, the strengthening effect is limited; however, above 0.8%, C and N readily react with metallic elements in the alloy to form compounds. Therefore, this technical solution limits the C and N content to within 0.4% to 0.8%.

[0050] Furthermore, this invention proposes a method for preparing a paramagnetic constant elastic alloy material, comprising the following steps:

[0051] Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering.

[0052] In this step, Ti and Nb can be used in powder or block form.

[0053] Step S2: The blank is processed into a blank through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations;

[0054] Among them, the deformation amount of a single cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the forming process is 30%-90%.

[0055] In the first heat treatment, the temperature is 700℃-1150℃, and the holding time is 1min-60min.

[0056] The purpose of the first heat treatment is to form a full β phase in the billet, eliminate the internal stress caused by billet deformation, increase the plasticity of the alloy, and recrystallize the deformed grains, which is beneficial for deformation processing. Preferably, the first heat treatment temperature is 700℃-900℃.

[0057] Cold deformation, also known as cold working, refers to the deformation or processing of metal below its recrystallization temperature. In this embodiment, cold deformation is performed on the billet through one or more of the following methods: rotary forging, wire drawing, and rolling.

[0058] Step S3: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa.

[0059] In this step, the specific process of the second heat treatment is as follows: the blank is placed in the heat treatment furnace, and then the heat treatment furnace is evacuated to a vacuum of not less than 10°C. -3 Pa, then raise the temperature to 600℃-750℃ and hold for 5min-120min, during which nitrogen, ammonia or carbon monoxide is introduced into the heat treatment furnace.

[0060] During the second heat treatment and holding process, carbon and nitrogen atoms in the second heat treatment atmosphere will diffuse and dissolve into the β(Nb,Ti) phase lattice. Typically, this diffusion process is affected by the atmosphere pressure, temperature, and holding time. Therefore, the pressure, temperature, and holding time must be controlled to reduce the formation of TiC, TiN, and Ti(C,N). Based on the process range in this technical solution, the formation of TiC, TiN, and Ti(C,N) can be effectively avoided.

[0061] Step S4: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa.

[0062] In this step, the purpose of the third heat treatment is to induce the precipitation of the α phase from the metastable β phase. By selecting the temperature and holding time of the third heat treatment, the precipitation ratio of the α phase can be controlled, thereby enabling the regulation of the temperature coefficient of the alloy's elastic modulus, keeping it within the range of (0~100)×10⁻⁶. -6 / ℃ or less.

[0063] Furthermore, this invention also proposes the use of a paramagnetic constant elastic alloy material for manufacturing the hairspring of a mechanical watch. Preferably, the temperature coefficient of the elastic modulus of the paramagnetic constant elastic alloy material used for the hairspring of a mechanical watch is controlled by selecting the temperature and holding time of the third heat treatment, keeping it within (0~25)×10⁻⁶. -6 / ℃ or less.

[0064] Furthermore, the present invention also proposes a method for preparing a hairspring for a mechanical watch, comprising the following steps:

[0065] Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering.

[0066] In this step, Ti and Nb can be used in powder or block form.

[0067] Step S2: The billet is processed into a bar stock through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations;

[0068] Among them, the deformation amount of a single cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the forming process is 30%-90%.

[0069] In the first heat treatment, the temperature is 700℃-1150℃, and the holding time is 1min-60min.

[0070] The purpose of the first heat treatment is to form a full β phase in the billet, eliminate the internal stress caused by billet deformation, increase the plasticity of the alloy, and recrystallize the deformed grains, which is beneficial for deformation processing. Preferably, the first heat treatment temperature is 700℃-900℃.

[0071] Cold deformation, also known as cold working, refers to the deformation or processing of metal below its recrystallization temperature. In this embodiment, cold deformation is performed on the billet through one or more of the following methods: rotary forging, wire drawing, and rolling.

[0072] The diameter of the bar stock section is 6mm-8mm.

[0073] Step S3: Coat the bar stock with a lubricating layer; then draw the bar stock coated with the lubricating layer into wires step by step, and then remove the lubricating layer to obtain wire;

[0074] During the progressive wire drawing process, the lubricated bar stock can undergo a first heat treatment to reduce processing difficulty. Before the first heat treatment, the lubricating layer needs to be removed, either by heating, mechanical removal, or chemical removal. After the first heat treatment, before proceeding to the next stage of wire drawing, the lubricating layer needs to be coated again.

[0075] Step S4: Roll the wire into a flat wire with a rectangular cross-section;

[0076] In this step, the width of the flat wire is denoted as b, and the thickness is denoted as h. The relationship is: 3h≤b≤5h, preferably 3.5h≤b≤4.5h.

[0077] Step S5: Wind the flat wire into a blank inside the mold;

[0078] Step S6: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa.

[0079] In this step, the specific process of the second heat treatment is as follows: the blank is placed in the heat treatment furnace, and then the heat treatment furnace is evacuated to a vacuum of not less than 10°C. -3 Pa, then raise the temperature to 600℃-750℃ and hold for 5min-120min, during which nitrogen, ammonia or carbon monoxide is introduced into the heat treatment furnace.

[0080] During the second heat treatment and holding process, carbon and nitrogen atoms in the second heat treatment atmosphere will diffuse and dissolve into the β(Nb,Ti) phase lattice. Typically, this diffusion process is affected by the atmosphere pressure, temperature, and holding time. Therefore, the pressure, temperature, and holding time must be controlled to reduce the formation of TiC, TiN, and Ti(C,N). Based on the process range in this technical solution, the formation of TiC, TiN, and Ti(C,N) can be effectively avoided.

[0081] Step S7: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa.

[0082] In this step, the purpose of the third heat treatment is to induce the precipitation of the α phase from the metastable β phase. By selecting the temperature and holding time of the third heat treatment, the precipitation ratio of the α phase can be controlled, thereby enabling the regulation of the temperature coefficient of the alloy's elastic modulus, keeping it within the range of (0~100)×10⁻⁶. -6 / ℃ or less.

[0083] Step S8: Demold, trim, cut and assemble the blank after the third heat treatment to form the finished hairspring.

[0084] Let the diameter of the wire be d1. d1 can be corrected using the following formula (2):

[0085]

[0086] In the formula, k is a trimming coefficient, which is mainly related to the thickness of the lubricating layer.

[0087] The values ​​of b and h mentioned above can be determined by the following formula (3) and the combination of 3h≤b≤5h:

[0088]

[0089] In the above formula, E is the elastic modulus of the finished hairspring;

[0090] T0 is the oscillation period of the clock;

[0091] J b Let be the moment of inertia of the balance wheel;

[0092] L is the length of the hairspring.

[0093] After the pre-processing and third heat treatment, the blank has formed a fixed shape, allowing it to be removed from the mold while maintaining that shape. The hairspring is then shaped and excess material is trimmed to form the finished hairspring.

[0094] Compared with the prior art, the present invention has the following technical advantages:

[0095] 1) In terms of composition, this invention uses at least one of nitrogen and carbon as a solid solution strengthening element. Compared with the prior art, it has a better strengthening effect and improves the strength and elastic modulus of the alloy or hairspring.

[0096] 2) In terms of process, the present invention introduces strengthening elements after the deformation process is completed. Compared with the existing processing technology, the material is subjected to less resistance during deformation processing and is easier to deform.

[0097] 3) In terms of performance, in existing technologies, the temperature coefficient of elastic modulus of the alloy is negative, ranging from (-32.2 to -54.5) × 10⁻⁶. -6 / ℃, while the present invention achieves the control of the temperature coefficient of the elastic modulus of the alloy, making it within (0~100)×10 -6 Within a certain temperature range (°C), and further by selecting the heat treatment temperature and holding time, the temperature coefficient of the alloy's elastic modulus can be controlled, making it within the range of (0~25)×10⁻⁶. -6 When used to make hairsprings for precision mechanical watches, temperatures within a certain range of ℃ can achieve a timekeeping temperature coefficient better than 0.5 s / (d·℃).

[0098] To make the technical objectives, technical solutions, and technical effects of the present invention clearer, and to enable those skilled in the art to understand and implement the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0099] Example 1

[0100] First, the materials were prepared according to a ratio of 40 wt% Ti and 60 wt% Nb, where both Ti and Nb were metal powders. The average particle size of the titanium powder was 3 μm, and the average particle size of the niobium powder was 5 μm. The powders were then loaded into a ball mill with grinding balls at a ratio of 15:1, and 1.5% by weight of ethanol was added. The milling process lasted for 24 hours.

[0101] The powder obtained from ball milling is mixed with a forming agent and pressed into a blank using a molding press. In this embodiment, the blank is a simple block shape. After removing the forming agent, the blank is vacuum sintered to form a niobium-titanium alloy blank. The sintering temperature is 1600℃ and the sintering time is 120 minutes.

[0102] The niobium-titanium alloy billet was cold-worked by rotary forging, with a deformation of 50%. After deformation, it underwent a first heat treatment at 850℃ for 45 minutes. After the first heat treatment, it was subjected to two more cold deformations, each with a deformation of 15% to 20%.

[0103] Next, a second heat treatment is performed. The temperature of the second heat treatment is 600℃, the holding time is 60 minutes, the atmosphere of the second heat treatment is a nitrogen-containing atmosphere, and the atmosphere pressure is 50 MPa.

[0104] The second heat treatment process is as follows: First, the heat treatment furnace is evacuated to a vacuum level of not less than 10°C. -3 Pa, then raise the temperature to 600℃ and hold, then introduce nitrogen gas to make the atmosphere pressure reach 50MPa, and hold for 60min.

[0105] Then, the third heat treatment is carried out, which involves evacuating the heat treatment furnace to a vacuum of 2×10⁻⁶. -3 Pa, then raise the temperature to 450℃, hold for 300 minutes, and then cool in the furnace.

[0106] The paramagnetic constant elastic alloy material obtained according to this embodiment includes 0.8 wt% N, 39.6 wt% Ti, 59.3 wt% Nb, and 0.1 wt% impurities. After testing, the alloy achieved an elastic limit of 1126 MPa, an elastic modulus of 146 GPa, and a temperature coefficient of elastic modulus of 68 × 10⁻⁶. -6 / ℃. Micrographs of paramagnetic constant elastic alloy materials, such as... Figure 1 As shown.

[0107] Example 2

[0108] First, the materials were batched and smelted according to the ratio of 48wt%Ti and 52wt%Nb to obtain niobium-titanium alloy ingot billets;

[0109] The niobium-titanium alloy ingot blanks are cold-worked using methods including rotary forging and rolling. Specifically, two cold working processes are performed first, each with a deformation of 15%, followed by a first heat treatment at 1150℃ for 1 minute. After the first heat treatment, a second cold deformation with a deformation of 30% is performed.

[0110] Next, a second heat treatment is performed. The temperature of the second heat treatment is 750℃, the holding time is 5 minutes, the atmosphere of the second heat treatment is CO, and the atmosphere pressure is 2000 Pa.

[0111] Then, a third heat treatment is performed. The temperature of the third heat treatment is 500℃, the holding time is 600 min, and the vacuum degree is 1.2×10⁻⁶. -3 Pa, then the furnace cooled.

[0112] The paramagnetic constant elastic alloy material obtained according to this embodiment includes 0.52 wt% C, 47.8 wt% Ti, 51.6 wt% Nb, and 0.08 wt% impurities. After testing, the elastic limit of the paramagnetic constant elastic alloy material reached 1180 MPa, the elastic modulus reached 128 GPa, and the temperature coefficient of elastic modulus was 43 × 10⁻⁶. -6 / ℃.

[0113] Example 3

[0114] First, the materials were prepared according to a ratio of 42 wt% Ti and 58 wt% Nb, where both Ti and Nb were metal powders. The average particle size of the titanium powder was 3 μm, and the average particle size of the niobium powder was 5 μm. The powders were then loaded into a ball mill with grinding balls at a ratio of 15:1, and 1.5% by weight of ethanol was added. The milling process lasted for 24 hours.

[0115] The powder obtained from ball milling is injection molded into a billet. In this embodiment, the billet is rod-shaped. The billet is then vacuum sintered to form a niobium-titanium alloy material. The sintering temperature is 1400℃, and the sintering time is 60 minutes. The niobium-titanium alloy material is then melted to form a niobium-titanium alloy ingot billet. Sintering followed by melting yields a more uniform material.

[0116] The niobium-titanium alloy ingot billet is cold-deformed using a combination of rotary forging and rolling to achieve a width of 40mm × 40mm. It then undergoes a first heat treatment at 700℃ for 60 minutes. It is then rolled into a φ8 coil. This is followed by another first heat treatment to obtain the billet. Finally, copper plating is applied to the surface of the billet.

[0117] The copper-plated blank is cold-drawn. The drawing process is divided into several stages: φ8mm-φ4mm-φ0.8mm. Each stage gradually reduces the surface area. A first heat treatment is interspersed between each stage. Before the first heat treatment, the wire is pickled to remove the surface copper plating. After the first heat treatment and before the next drawing stage, the wire is copper-plated again. After drawing to φ0.8mm, the surface copper plating is removed by pickling, and the first heat treatment is performed. The wire is then gradually cold-drawn to a diameter d1 of 0.062mm.

[0118] The wire is rolled at least once on a precision rolling mill. To reduce dimensional deviations caused by springback during rolling, this embodiment involves two rolling processes, ultimately forming a flat wire with a rectangular cross-section, a thickness h of 0.028 mm, and a width b of 0.1 mm. Cleaning the wire is necessary during the rolling process.

[0119] Then, according to the calculated length, the aforementioned filament is wound to form the Archimedean spiral required for the hairspring. The winding process is carried out in a specific mold, where the filament has high elasticity and needs to be fixed in shape with the assistance of the mold.

[0120] Next, the mold containing the filament is placed in a heat treatment furnace for a second heat treatment. The temperature of the second heat treatment is 650℃, the holding time is 20 minutes, the heat treatment atmosphere is a mixture of CO and N2 gas with a ratio of CO:N2 of 20:80, and the atmosphere pressure is 60000 Pa. Before heating, the furnace is evacuated to a vacuum level of not less than 10°C. -3 Pa.

[0121] The mold containing the filament is then subjected to a third heat treatment at a temperature of 460℃ for 30 minutes, with a vacuum degree of 0.8×10⁻⁶. -3 Pa. After the third heat treatment, the part is removed, and the wire is demolded and trimmed to form the finished hairspring, such as... Figure 2 As shown.

[0122] In this embodiment, the process parameters for all first heat treatments are the same. In other embodiments, within the scope of protection claimed by this invention, it is also feasible to change the process parameters for the first heat treatment in each step.

[0123] The mechanical watch hairspring produced according to this embodiment has the following material composition: 0.44 wt% C, 0.80 wt% N, 41.5 wt% Ti, 57.2 wt% Nb, and 0.06 wt% impurities. The material has an elastic limit of 1203 MPa, an elastic modulus of 156 GPa, and a temperature coefficient of elastic modulus of 17 × 10⁻⁶. -6 / ℃, after being installed in the watch movement, the temperature coefficient of the watch was measured to be 0.16-0.44s / (d·℃), which can well meet the requirements of a precision chronograph. Metallographic photograph of the balance spring of a mechanical watch is shown below. Figure 3 As shown.

[0124] Example 4

[0125] Unlike Example 3, the raw material ratio used is 50 wt% Ti and 50 wt% Nb. Ti and Nb are metal powders.

[0126] Unlike Example 3, the preparation process of the billet is as follows: The powders are loaded into a ball mill at a powder-to-ball ratio of 15:1, and 1.5% by weight of ethanol is added. The milling process lasts for 24 hours. The resulting powder is then mixed with a forming agent and pressed into a billet using a molding press. In this example, the billet shape is a simple block. After removing the forming agent, the billet is vacuum sintered to form a niobium-titanium alloy billet. The sintering temperature is 1600°C, and the sintering time is 120 minutes.

[0127] Unlike Example 3, the first heat treatment was performed at 700°C for 60 minutes. After the first heat treatment, an organic coating was applied, and the wire was drawn to a diameter of 0.8 mm. The lubricating layer was removed by heating to decompose it, followed by another heat treatment at 700°C for 60 minutes. Then, a lubricating layer was applied, and the wire was drawn to a diameter d1 of 0.086 mm before the lubricating layer was removed.

[0128] Unlike Example 3, the round wire is rolled by precision rolling in two stages. The second rolling is performed until the thickness h is 0.0383 mm and the width b is 0.1586 mm.

[0129] Unlike Example 3, the second heat treatment process is performed at a temperature of 600°C, a holding time of 120 minutes, a heat treatment atmosphere of ammonia, and a pressure of 0.1 MPa.

[0130] Unlike Example 3, the third heat treatment was performed at a temperature of 450°C, a holding time of 120 minutes, and a vacuum degree of 0.8 × 10⁻⁶. -3 Pa.

[0131] The mechanical watch hairspring produced according to this embodiment has a material composition of 0.42 wt% N, 49.75 wt% Ti, 49.73 wt% Nb, and 0.1 wt% impurities. The material has an elastic limit of 1158 MPa, an elastic modulus of 128 GPa, and a temperature coefficient of elastic modulus of 25 × 10⁻⁶. -6 / ℃, after being installed in the watch movement, the temperature coefficient of the watch was measured to be 0.20-0.46s / (d·℃), which can well meet the requirements of a precision timekeeping watch.

[0132] Example 5

[0133] Unlike Example 4, the raw material ratio used was 44 wt% Ti and 56 wt% Nb.

[0134] Unlike Example 4, the raw materials were smelted according to the specified ratio to obtain niobium-titanium alloy ingot billets;

[0135] Unlike Example 4, the wire was drawn to d1 of 0.074 mm.

[0136] Unlike Example 4, the round wire is rolled by precision rolling in two stages. The second rolling is performed to a thickness h of 0.0363 mm and a width b of 0.1783 mm.

[0137] Unlike Example 4, the second heat treatment process is performed at a temperature of 700°C, a holding time of 45 minutes, and a heat treatment atmosphere of ammonia at 1 MPa.

[0138] Unlike Example 4, the third heat treatment temperature was 480°C, the holding time was 60 min, and the vacuum degree was 0.6 × 10⁻⁶. -3 Pa.

[0139] The mechanical watch hairspring produced according to this embodiment has the following material composition: 0.48 wt% C, 0.62 wt% N, 43.5 wt% Ti, 55.3 wt% Nb, and 0.1 wt% impurities. The material has an elastic limit of 1210 MPa, an elastic modulus of 142 GPa, and a temperature coefficient of elastic modulus of 12 × 10⁻⁶. -6 / ℃, after being installed in the watch movement, the temperature coefficient of the watch was measured to be 0.13-0.36s / (d·℃), which can well meet the requirements of a precision timekeeping watch.

[0140] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a paramagnetic constant elastic alloy material, characterized in that, Paramagnetic constant elastic alloy materials include: 0.4wt%–0.8wt% N, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or 0.4wt%–0.8wt% C, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; or 0.4wt%–0.8wt% N, 0.4wt%–0.8wt% C, 40wt%–50wt% Ti, and 49.2wt%–59.6wt% Nb; The preparation method of paramagnetic constant elastic alloy materials includes the following steps: Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering. Step S2: The blank is processed into a blank through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations; Step S3: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa. Step S4: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa.

2. The method for preparing the paramagnetic constant elastic alloy material according to claim 1, characterized in that, In step S2, the deformation amount of a single cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the forming process is 30%-90%.

3. The method for preparing the paramagnetic constant elastic alloy material according to claim 1, characterized in that, In the first heat treatment, the temperature is 700℃-1150℃ and the holding time is 1min-60min.

4. The method for preparing the paramagnetic constant elastic alloy material according to claim 1, characterized in that, Paramagnetic constant elastic alloy material, comprising 0.48wt% C, 0.62wt% N, 44wt% Ti, 54.8wt% Nb and 0.1wt% impurities.

5. The use of a paramagnetic constant elastic alloy material prepared by the preparation method as described in claim 1, characterized in that, Used to manufacture hairsprings for mechanical watches.

6. A method for preparing a hairspring for a mechanical watch, characterized in that, Includes the following steps: Step S1: Prepare 40wt%~50wt% Ti and 50wt%~60wt% Nb and form them into billets by melting or powder sintering. Step S2: The billet is processed into a bar stock through a forming process; the forming process includes a first heat treatment and multiple cold deformations; the first heat treatment is completed between the multiple cold deformations; Step S3: Coat the bar stock with a lubricating layer; then draw the bar stock coated with the lubricating layer into wires step by step, and then remove the lubricating layer to obtain wire; Step S4: Roll the wire into a flat wire with a rectangular cross-section; Step S5: Wind the flat wire into a blank inside the mold; Step S6: Perform a second heat treatment on the blank; in the second heat treatment, the temperature is 600℃-750℃, the holding time is 5min-120min, the atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the pressure is 2000Pa-50MPa. Step S7: Perform a third heat treatment on the blank; in the third heat treatment, the temperature is 450℃-500℃, the holding time is 30min-600min, and the vacuum degree is not less than 2×10 -3 Pa; Step S8: Demold, trim, cut and assemble the blank after the third heat treatment to form the finished hairspring.

7. The method for preparing a mechanical watch hairspring according to claim 6, characterized in that, In step S2, the deformation amount of a single cold deformation is 15%-50%; the cumulative deformation amount of multiple cold deformations in the forming process is 30%-90%.

8. The method for preparing a mechanical watch hairspring according to claim 6, characterized in that, In the first heat treatment, the temperature is 700℃-1150℃ and the holding time is 1min-60min.

9. The method for preparing a mechanical watch hairspring according to claim 6, characterized in that, In step S4, the width of the flat wire is denoted as b, and the thickness is denoted as h, with the relationship being: 3h≤b≤5h.

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