Paramagnetic constant-elasticity alloy material, hairspring of mechanical watch, and use thereof and preparation method therefor

Abstract

Disclosed in the present invention are a paramagnetic constant-elasticity alloy material, a hairspring of a mechanical watch, and the use thereof and a preparation method therefor. The paramagnetic constant-elasticity alloy material comprises: 0.4-0.8 wt% of N, 40-50 wt% of Ti and 49.2-59.6 wt% of Nb; or 0.4-0.8 wt% of C, 40-50 wt% of Ti and 49.2-59.6 wt% of Nb; or 0.4-0.8 wt% of N, 0.4-0.8 wt% of C, 40-50 wt% of Ti and 49.2-59.6 wt% of Nb. In the present invention, at least one of nitrogen and carbon is used as a solid solution strengthening element, thereby improving the strength and elastic modulus of the alloy or the hairspring, and achieving the regulation and control of the temperature coefficient of the elastic modulus of the alloy.

Description

Paramagnetic constant elastic alloy material and mechanical watch hairspring as well as uses and preparation methods Technical Field

[0001] The present invention relates to the field of materials, and in particular to a paramagnetic constant elastic alloy material and a mechanical watch hairspring as well as applications and preparation methods. Background Art

[0002] For general metals or alloys without phase change, as the temperature rises, the interatomic bonding force gradually weakens and the elastic modulus tends to decrease, which will have an adverse effect on the accuracy of instruments. Generally, the temperature coefficient of elastic modulus of metals and alloys is 10 -4 / ℃ order of magnitude. However, for some alloys, the elastic modulus does not change with temperature or changes very little (generally ≤±20×10 -6 / ℃), these alloys are also called constant elastic alloys. Constant elastic alloys make it possible for mechanical watches to accurately measure time.

[0003] Ferromagnetic alloys based on Fe and Ni are widely used in mechanical watches. These alloys offer excellent processing properties, high elastic modulus, and high strength. Through process and composition control, the temperature coefficient of mechanical watch travel can be reduced to within 0.5s / (d·°C). However, these ferromagnetic alloys are susceptible to magnetic fields, resulting in inaccurate timekeeping.

[0004] Patent CN109116712B discloses a spiral watch spring made of a niobium-titanium alloy, comprising: 45.0% to 48.0% titanium; trace elements, including trace elements such as O, H, C, Fe, Ta, N, Ni, Si, Cu, and Al, ranging from 0 to 1600 ppm by weight and less than 0.3% by weight in total; and niobium to make up the total to 100%. The alloy has an elastic limit exceeding 1000 MPa and an elastic modulus exceeding 60 GPa and less than 80 GPa. Patent CN109960132B discloses a balance spring made of a niobium-titanium alloy and a method for manufacturing the same. The alloy contains: 40 to 60% titanium; trace elements, including trace elements such as O, H, C, Fe, Ta, N, Ni, Si, Cu, and Al, ranging from 0 to 1600 ppm by weight and less than 0.3% by weight in total; and niobium to make up the total to 100% by weight. The alloy disclosed in the above patent does not contain ferromagnetic elements. The hairspring made of this type of paramagnetic alloy is not affected by the magnetic field, but it has obvious defects: the elastic limit and elastic modulus are relatively low, which affects the service life of the hairspring and the stability of the mechanical watch.

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

[0006] ...............................(1)

[0007] In order to make the mechanical watch run at a better level, c is generally required to be within ±0.5, and β should be within approximately (+0.5~+23.5)×10-6 / ℃. Technical issues

[0008] Obviously, Nb -35~42 Ti -5~5.5 The temperature coefficient of elastic modulus of aluminum doesn't meet the requirements for watch springs. Furthermore, the addition of aluminum increases the alloy's brittleness, making the wire drawing and rolling processes necessary for making watch springs more difficult. Technical Solutions

[0009] In response to the above technical problems, the present invention provides a paramagnetic constant elastic alloy material and a mechanical watch hairspring as well as their uses and preparation methods.

[0010] The technical solutions proposed in the present invention are as follows:

[0011] The present invention provides a paramagnetic constant elastic alloy material, comprising:

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

[0013] 0.4wt%-0.8wt% C, 40wt%-50wt% Ti and 49.2wt%-59.6wt% Nb; or

[0014] 0.4wt%~0.8wt% N, 0.4wt%~0.8wt% C, 40wt%~50wt% Ti and 49.2wt%-59.6wt% Nb.

[0015] The paramagnetic constant elastic alloy material of the present invention includes 0.48wt% C, 0.62wt% N, 44wt% Ti, 54.8wt% Nb and 0.1wt% impurities.

[0016] The present invention also provides a method for preparing the paramagnetic constant elastic alloy material as described above, comprising the following steps:

[0017] Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming a blank by melting or powder sintering;

[0018] Step S2, processing the blank 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;

[0019] Step S3, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600° C.-750° C., the second heat treatment holding time is 5 min-120 min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000 Pa-50 MPa;

[0020] Step S4, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450℃-500℃, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum degree is not less than 2×10 -3 Pa.

[0021] In the method for preparing 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%.

[0022] In the method for preparing the paramagnetic constant elastic alloy material of the present invention, in the first heat treatment, the first heat treatment temperature is 700° C.-1150° C., and the first heat treatment holding time is 1 min-60 min.

[0023] The present invention also proposes a use of the paramagnetic constant elastic alloy material as described above, which is used to prepare a hairspring for a mechanical watch.

[0024] The present invention also provides a method for preparing a hairspring for a mechanical watch, comprising the following steps:

[0025] Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming a blank by melting or powder sintering;

[0026] Step S2, processing the blank into a bar 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;

[0027] Step S3, coating a lubricating layer on the rod; then drawing the rod coated with the lubricating layer step by step, and then removing the lubricating layer to obtain a wire material;

[0028] Step S4, rolling the wire into a flat wire with a rectangular cross section;

[0029] Step S5, winding the flat wire into a blank in a mold;

[0030] Step S6, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600°C-750°C, the second heat treatment holding time is 5min-120min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000Pa-50MPa;

[0031] Step S7, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450℃-500℃, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum degree is not less than 2×10 -3 Pa;

[0032] Step S8: demoulding, trimming, cutting and assembling the blank after the third heat treatment to form a finished hairspring.

[0033] In the method for preparing the hairspring of a mechanical watch 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%.

[0034] In the method for preparing the hairspring of a mechanical watch of the present invention, in the first heat treatment, the first heat treatment temperature is 700° C.-1150° C., and the first heat treatment holding time is 1 min-60 min.

[0035] In the method for preparing a hairspring for a mechanical watch of the present invention, in step S4 , the width of the flat wire is denoted as b, and the thickness is denoted as h, and the relationship is: 3h≤b≤5h. Beneficial effects

[0036] Compared with the prior art, the present invention has the following technical advantages:

[0037] 1) In terms of composition, the present invention uses at least one of nitrogen and carbon as a solid solution strengthening element. Compared to existing technologies, this has a better strengthening effect, increasing the strength and elastic modulus of the alloy or hairspring.

[0038] 2) In terms of process, the present invention introduces strengthening elements after the deformation process is completed. Compared with the processing technology of the prior art, the material is subjected to less resistance during the deformation process and is easier to deform.

[0039] 3) In terms of performance, in the existing technology, the temperature coefficient of elastic modulus of the alloy is negative, ranging from (-32.2 to -54.5)×10 -6 / ℃, and the present invention realizes the regulation of the temperature coefficient of elastic modulus of the alloy, making it (0~100)×10 -6 / ℃, and further through the selection of heat treatment temperature and holding time, the temperature coefficient of elastic modulus of the alloy can be regulated to be within (0~25)×10 -6 / ℃, and after being used to make hairsprings for precision mechanical watches, the temperature coefficient of travel time can reach a level better than 0.5 s / (d·℃). BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0041] FIG1 shows a micrograph of the paramagnetic constant elastic alloy material of Example 1 of the present invention;

[0042] FIG2 shows a photograph of a finished balance spring according to Example 3 of the present invention;

[0043] FIG3 shows a metallographic photograph of a hairspring of a mechanical watch according to Example 3 of the present invention. Modes for Carrying Out the Invention

[0044] The technical purpose of the present application is to provide a paramagnetic constant elastic alloy material with high elastic limit and elastic modulus, a wide adjustable range of elastic modulus temperature coefficient, and easy processing, in order to address the problems in the prior art of paramagnetic constant elastic alloy materials, such as low elastic limit and elastic modulus, or negative elastic modulus temperature coefficient, which do not meet the requirements of certain occasions, especially watch hairsprings, or the introduction of strengthening elements that easily lead to processing difficulties. A preparation method and use of the paramagnetic constant elastic alloy material and a preparation method for a mechanical watch hairspring are also provided.

[0045] The present invention provides a paramagnetic constant elastic alloy material, comprising:

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

[0047] 0.4wt%-0.8wt% C, 40wt%-50wt% Ti and 49.2wt%-59.6wt% Nb; or

[0048] 0.4wt%~0.8wt% N, 0.4wt%~0.8wt% C, 40wt%~50wt% Ti and 49.2wt%-59.6wt% Nb.

[0049] Preferably, the paramagnetic constant elastic alloy material includes 0.48 wt % C, 0.62 wt % N, 44 wt % Ti, 54.8 wt % Nb and 0.1 wt % impurities.

[0050] Solid solution can strengthen niobium-titanium alloys, and C, N, and B are all very effective solid solution strengthening elements. However, in the prior art, these elements, while increasing the strength and elastic modulus of the alloy, reduce the plasticity and toughness of the alloy, which is not conducive to deformation processing. Therefore, in the prior art, these elements are generally regarded as impurity elements. The present invention can solve the problem of being difficult to deform after solid solution strengthening by introducing solid solution strengthening after deformation processing. In the design of the alloy composition, because the introduction of solid solution strengthening is completed after deformation processing, C and N elements that can be achieved through gas reaction are used in the selection of strengthening elements. If the C and N content is too low, the strengthening effect is limited; but after exceeding 0.8%, C and N are easy to react with the metal elements in the alloy to form compounds. Therefore, the present technical solution limits the content of C and N to within 0.4~0.8%.

[0051] Furthermore, the present invention provides a method for preparing a paramagnetic constant elastic alloy material, comprising the following steps:

[0052] Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming a blank by melting or powder sintering;

[0053] In this step, Ti and Nb can be in powder form or in block form.

[0054] Step S2, processing the blank 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;

[0055] Among them, the single deformation of cold deformation is 15%-50%; the cumulative deformation of multiple cold deformations in the forming process is 30%-90%;

[0056] In the first heat treatment, the first heat treatment temperature is 700° C.-1150° C., and the first heat treatment holding time is 1 min-60 min;

[0057] The purpose of the first heat treatment is to form a full β phase in the blank, eliminate the internal stress caused by the deformation of the blank, 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℃.

[0058] Cold deformation is also called cold working, which refers to the deformation or processing of metal below the recrystallization temperature. In this embodiment, cold deformation is performed on the blank by one or more of swaging, wire drawing, and rolling.

[0059] Step S3, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600° C.-750° C., the second heat treatment holding time is 5 min-120 min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000 Pa-50 MPa;

[0060] In this step, the specific process of the second heat treatment is: put the blank into the heat treatment furnace, and then evacuate the heat treatment furnace to a temperature not less than 10 -3 Pa, then heat to 600℃-750℃ and keep warm for 5min-120min, during which nitrogen, ammonia or carbon monoxide is introduced into the heat treatment furnace.

[0061] During the second heat treatment and holding process, the carbon atoms and nitrogen atoms in the second heat treatment atmosphere will diffuse and dissolve into the lattice of the β (Nb, Ti) phase. Usually, 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). According to the process range in this technical solution, the formation of TiC, TiN, and Ti (C, N) can be effectively avoided.

[0062] Step S4, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450℃-500℃, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum degree is not less than 2×10 -3 Pa.

[0063] In this step, the purpose of the third heat treatment is to promote the precipitation of α phase in the metastable β phase. By selecting the temperature and holding time of the third heat treatment, the precipitation ratio of α phase can be controlled, and the temperature coefficient of elastic modulus of the alloy can be regulated to be within the range of (0~100)×10 -6 / ℃ or less.

[0064] Furthermore, the present invention also proposes a use of a paramagnetic constant elastic alloy material for preparing a mechanical watch hairspring. Preferably, the temperature coefficient of elastic modulus of the paramagnetic constant elastic alloy material used for the mechanical watch hairspring is controlled by selecting the temperature and holding time of the third heat treatment to be within the range of (0 to 25) × 10 -6 / ℃ or less.

[0065] Furthermore, the present invention also proposes a method for preparing a hairspring for a mechanical watch, comprising the following steps:

[0066] Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming a blank by melting or powder sintering;

[0067] In this step, Ti and Nb can be in powder form or in block form.

[0068] Step S2, processing the blank into a bar 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;

[0069] Among them, the single deformation of cold deformation is 15%-50%; the cumulative deformation of multiple cold deformations in the forming process is 30%-90%;

[0070] In the first heat treatment, the first heat treatment temperature is 700° C.-1150° C., and the first heat treatment holding time is 1 min-60 min;

[0071] The purpose of the first heat treatment is to form a full β phase in the blank, eliminate the internal stress caused by the deformation of the blank, 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℃.

[0072] Cold deformation is also called cold working, which refers to the deformation or processing of metal below the recrystallization temperature. In this embodiment, cold deformation is performed on the blank by one or more of swaging, wire drawing, and rolling.

[0073] The cross-sectional diameter of the bar is 6mm-8mm.

[0074] Step S3, coating a lubricating layer on the rod; then drawing the rod coated with the lubricating layer step by step, and then removing the lubricating layer to obtain a wire material;

[0075] During the stage-by-stage wire drawing process, the lubricating layer-coated bar stock can undergo a first heat treatment to reduce processing difficulty. Before the first heat treatment, the lubricating layer needs to be removed by heating, mechanical removal, or chemical removal. After the first heat treatment, the lubricating layer needs to be reapplied before the next stage of wire drawing.

[0076] Step S4, rolling the wire into a flat wire with a rectangular cross section;

[0077] In this step, the width of the flat wire is recorded as b, and the thickness is recorded as h, and the relationship is: 3h≤b≤5h, preferably, 3.5h≤b≤4.5h.

[0078] Step S5, winding the flat wire into a blank in a mold;

[0079] Step S6, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600°C-750°C, the second heat treatment holding time is 5min-120min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000Pa-50MPa;

[0080] In this step, the specific process of the second heat treatment is: put the blank into the heat treatment furnace, and then evacuate the heat treatment furnace to a temperature not less than 10 -3 Pa, then heat to 600℃-750℃ and keep warm for 5min-120min, during which nitrogen, ammonia or carbon monoxide is introduced into the heat treatment furnace.

[0081] During the second heat treatment and holding process, the carbon atoms and nitrogen atoms in the second heat treatment atmosphere will diffuse and dissolve into the lattice of the β (Nb, Ti) phase. Usually, 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). According to the process range in this technical solution, the formation of TiC, TiN, and Ti (C, N) can be effectively avoided.

[0082] Step S7, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450℃-500℃, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum degree is not less than 2×10 -3 Pa.

[0083] In this step, the purpose of the third heat treatment is to promote the precipitation of α phase in the metastable β phase. By selecting the temperature and holding time of the third heat treatment, the precipitation ratio of α phase can be controlled, and the temperature coefficient of elastic modulus of the alloy can be regulated to be within the range of (0~100)×10 -6 / ℃ or less.

[0084] Step S8: demoulding, trimming, cutting and assembling the blank after the third heat treatment to form a finished hairspring.

[0085] The wire diameter is recorded as d1, which can be corrected by the following formula (2):

[0086]

[0087] Where k is the dressing coefficient, which is mainly related to the thickness of the lubricating layer.

[0088] The above b and h can be determined by the following formula (3) and 3h≤b≤5h:

[0089]

[0090] In the above formula, E is the elastic modulus of the finished balance spring;

[0091] T0 is the vibration period of the clock;

[0092] J b is the moment of inertia of the balance wheel;

[0093] L is the length of the hairspring.

[0094] After the pre-processing and third heat treatment, the blank has a fixed shape, allowing it to be removed from the mold without changing its fixed shape. The hairspring is then trimmed and the excess is removed to form the finished hairspring.

[0095] Compared with the prior art, the present invention has the following technical advantages:

[0096] 1) In terms of composition, the present invention uses at least one of nitrogen and carbon as a solid solution strengthening element. Compared to existing technologies, this has a better strengthening effect, increasing the strength and elastic modulus of the alloy or hairspring.

[0097] 2) In terms of process, the present invention introduces strengthening elements after the deformation process is completed. Compared with the processing technology of the prior art, the material is subjected to less resistance during the deformation process and is easier to deform.

[0098] 3) In terms of performance, in the existing technology, the temperature coefficient of elastic modulus of the alloy is negative, ranging from (-32.2 to -54.5)×10 -6 / ℃, and the present invention realizes the regulation of the temperature coefficient of elastic modulus of the alloy, making it (0~100)×10 -6 / ℃, and further through the selection of heat treatment temperature and holding time, the temperature coefficient of elastic modulus of the alloy can be regulated to be within (0~25)×10 -6 / ℃, and after being used to make hairsprings for precision mechanical watches, the temperature coefficient of travel time can reach a level better than 0.5 s / (d·℃).

[0099] In order to make the technical objectives, technical solutions and technical effects of the present invention clearer and to facilitate 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.

[0100] Example 1

[0101] First, prepare the materials according to a ratio of 40wt% Ti and 60wt% Nb, with both Ti and Nb being metal powders. The average particle size of the titanium powder is 3μm, and the average particle size of the niobium powder is 5μm. Each powder is loaded into a ball mill at a ball-to-powder ratio of 15:1, loaded with grinding balls, and then milled for 24 hours in 1.5% by weight ethanol.

[0102] The powder obtained by ball milling is mixed with a forming agent and pressed into a green body using a molding press. In this embodiment, the green body is in the form of a simple block. After the green body is removed from the forming agent, it is vacuum sintered to form a niobium-titanium alloy green body. The sintering temperature is 1600°C and the sintering time is 120 minutes.

[0103] 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°C for 45 minutes. Following this initial heat treatment, it was cold-formed twice, with deformations ranging from 15% to 20%.

[0104] The second heat treatment was then performed at a temperature of 600° C., a holding time of 60 minutes, a nitrogen-containing atmosphere, and a pressure of 50 MPa.

[0105] The second heat treatment process is: first, evacuate the heat treatment furnace to a temperature not lower than 10 -3 Pa, then heat to 600℃ and keep warm, then introduce nitrogen to make the atmosphere pressure reach 50MPa, and keep warm for 60min.

[0106] Then, the third heat treatment is carried out, that is, the heat treatment furnace is evacuated to 2×10 -3 Pa, then heated to 450 ° C, kept at this temperature for 300 min, and then furnace cooled.

[0107] The paramagnetic constant elastic alloy material obtained according to this embodiment includes 0.8wt% N, 39.6wt% Ti, 59.3wt% Nb and 0.1wt% impurities. After testing, the elastic limit of the alloy reaches 1126MPa, the elastic modulus reaches 146 GPa, and the temperature coefficient of elastic modulus is 68×10 -6 / ℃. A micrograph of the paramagnetic constant elastic alloy material is shown in Figure 1.

[0108] Example 2

[0109] First, a niobium-titanium alloy ingot was obtained by mixing and smelting the ingredients according to a ratio of 48wt% Ti and 52wt% Nb;

[0110] The niobium-titanium alloy ingot was cold worked using rotary forging and rolling. Specifically, two cold working steps were performed, each with a 15% deformation, followed by a first heat treatment at 1150°C for 1 minute. After the first heat treatment, a further cold deformation step of 30% was performed.

[0111] Then, a second heat treatment is performed at a temperature of 750° C., a holding time of 5 minutes, a CO atmosphere, and a pressure of 2000 Pa.

[0112] Then the third heat treatment is carried out. The temperature of the third heat treatment is 500℃, the holding time is 600min, and the vacuum degree is 1.2×10 -3 Pa, then the furnace is cooled.

[0113] The paramagnetic constant elastic alloy material obtained according to this embodiment includes 0.52wt% C, 47.8wt% Ti, 51.6wt% Nb and 0.08wt% impurities. After testing, the elastic limit of the paramagnetic constant elastic alloy material reaches 1180MPa, the elastic modulus reaches 128 GPa, and the temperature coefficient of elastic modulus is 43×10 -6 / ℃.

[0114] Example 3

[0115] First, the materials were prepared according to a ratio of 42wt% Ti and 58wt% Nb, with both Ti and Nb being metal powders. The average particle size of the titanium powder was 3μm, and the average particle size of the niobium powder was 5μm. The powders were loaded into a ball mill at a ball-to-powder ratio of 15:1, with grinding balls installed. 1.5wt% ethanol was added and the milling process continued for 24 hours.

[0116] The powder obtained by ball milling is injection molded into a green body. In this example, the green body is rod-shaped. The green body is vacuum sintered to form a niobium-titanium alloy material. The sintering temperature is 1400°C and the sintering time is 60 minutes. The niobium-titanium alloy material is then melted to form a niobium-titanium alloy ingot. Sintering first, followed by melting, produces a more uniform material.

[0117] The niobium-titanium alloy ingot was cold-deformed by rotary forging and rolling to a width of 40 mm x 40 mm. The ingot then underwent a first heat treatment at 700°C for 60 minutes. The ingot was then rolled into a φ8 coil. The ingot then underwent another first heat treatment to obtain a blank. The surface of the blank was then copper-plated.

[0118] The copper-plated blank is cold-drawn. The drawing process is divided into several stages: φ8mm, φ4mm, and φ0.8mm. Each stage is completed with gradual surface reduction. A first heat treatment is performed 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 surface-coated with copper. After drawing to φ0.8mm, the wire is pickled to remove the surface copper plating and undergo the first heat treatment. The wire is then gradually cold-drawn to a diameter d1 of 0.062mm.

[0119] The wire was rolled at least twice on a precision rolling mill to reduce dimensional deviations caused by springback during the rolling process. This embodiment was rolled twice to form a rectangular flat wire with a thickness h of 0.028 mm and a width b of 0.1 mm. During the rolling process, it was necessary to clean the wire.

[0120] The wire is then wound to the calculated length to form the Archimedean spiral required for the hairspring. This winding process takes place in a specialized mold, where the wire, while still highly elastic, needs to be fixed in shape.

[0121] Then put the mold with the wire into the heat treatment furnace for the second heat treatment. The temperature of the second heat treatment is 650℃, the holding time is 20min, the heat treatment atmosphere is a mixture of CO and N2, where the ratio of CO and N2 is 20:80, and the atmosphere pressure is 60000Pa. Before heating, evacuate the furnace to a temperature of not less than 10 -3 Pa.

[0122] The mold containing the wire was then subjected to a third heat treatment at a temperature of 460°C, a holding time of 30 minutes, and a vacuum degree of 0.8×10 -3 After the third heat treatment, the parts are removed, the wire is demoulded and trimmed to form a finished balance spring, as shown in Figure 2.

[0123] In this embodiment, all process parameters of the first heat treatment are the same. In other embodiments, within the scope of the present invention, it is also feasible to change the process parameters of the first heat treatment in each step.

[0124] The mechanical watch hairspring prepared according to this embodiment has a material composition of 0.44wt% C, 0.80wt% N, 41.5wt% Ti, 57.2wt% Nb and 0.06wt% impurities. The elastic limit of the material is 1203MPa, the elastic modulus is 156GPa, and the temperature coefficient of elastic modulus is 17×10 -6 / ℃, and after being installed in a 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. A metallographic photograph of a mechanical watch hairspring is shown in Figure 3.

[0125] Example 4

[0126] The difference from Example 3 is that the raw material ratio is 50 wt% Ti and 50 wt% Nb, and Ti and Nb are metal powders.

[0127] Unlike Example 3, the blank preparation process is as follows: the powders are charged into a ball mill at a ball-to-powder ratio of 15:1, milling balls are added, and 1.5% by weight of ethanol is added for 24 hours. The milled powder is then mixed with a forming agent and pressed into a blank using a molding press. In this example, the blank is a simple block. After removing the forming agent from the blank, vacuum sintering is performed to form a niobium-titanium alloy blank. The sintering temperature is 1600°C and the sintering time is 120 minutes.

[0128] Unlike Example 3, the first heat treatment temperature was 700°C and the holding time was 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 decomposing it through heating, and then heat treatment was repeated at 700°C with a holding time of 60 minutes. The lubricating layer was then applied, and the wire was drawn to a diameter d1 of 0.086 mm, after which the lubricating layer was removed.

[0129] Different from Example 3, the round wire is rolled by precision rolling, and the rolling is performed twice. The second rolling is performed to a thickness h of 0.0383 mm and a width b of 0.1586 mm.

[0130] Different from Example 3, the second heat treatment process is performed at a temperature of 600° C., a holding time of 120 minutes, an ammonia atmosphere, and a pressure of 0.1 MPa.

[0131] The difference from Example 3 is that the temperature of the third heat treatment is 450°C, the holding time is 120 minutes, and the vacuum degree is 0.8×10 -3 Pa.

[0132] The mechanical watch hairspring prepared according to this embodiment has a material composition of 0.42wt% N, 49.75wt% Ti, 49.73wt% Nb and 0.1wt% impurities, an elastic limit of 1158MPa, an elastic modulus of 128GPa, and a temperature coefficient of elastic modulus of 25×10 -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 better meet the requirements of precision chronograph watches.

[0133] Example 5

[0134] Different from Example 4, the raw material ratio is 44wt% Ti and 56wt% Nb.

[0135] Different from Example 4, the raw materials are smelted according to the proportions to obtain niobium-titanium alloy ingots;

[0136] The difference from Example 4 is that the wire drawing is performed until d1 is 0.074 mm.

[0137] Different from Example 4, the round wire is rolled by precision rolling, and the rolling is performed twice. The second rolling is performed to a thickness h of 0.0363 mm and a width b of 0.1783 mm.

[0138] Different from Example 4, the second heat treatment process is performed at a temperature of 700° C., a holding time of 45 min, and a heat treatment atmosphere of ammonia at 1 MPa.

[0139] The difference from Example 4 is that the third heat treatment temperature is 480°C, the holding time is 60 min, and the vacuum degree is 0.6×10 -3 Pa.

[0140] The mechanical watch hairspring prepared according to this embodiment has a material composition of 0.48wt% C, 0.62wt% N, 43.5wt% Ti, 55.3wt% Nb and 0.1wt% impurities. The elastic limit of the material is 1210MPa, the elastic modulus is 142GPa, and the temperature coefficient of elastic modulus is 12×10 -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 better meet the requirements of precision chronographs.

[0141] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A paramagnetic constant elastic alloy material, characterized in that: 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.

2. The paramagnetic constant elastic alloy material according to claim 1, characterized in that: Comprises 0.48wt% C, 0.62wt% N, 44wt% Ti, 54.8wt% Nb and 0.1wt% impurities.

3. A method for preparing the paramagnetic constant elastic alloy material as claimed in claim 1, characterized in that: The following steps are involved: Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming them into a blank by smelting or powder sintering; Step S2, processing the blank 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, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600°C-750°C, the second heat treatment holding time is 5min-120min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000Pa-50MPa; Step S4, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450°C-500°C, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum is not less than 2×10 -3 Pa.

4. The method for preparing the paramagnetic constant elastic alloy material according to claim 3, characterized in that: 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%.

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

6. A use of the paramagnetic constant elastic alloy material as claimed in claim 1, characterized in that: Used to prepare hairsprings for mechanical watches.

7. A method for preparing a hairspring for a mechanical watch, characterized in that: The following steps are involved: Step S1, preparing 40wt%-50wt% Ti and 50wt%-60wt% Nb and forming them into a blank by smelting or powder sintering; Step S2, processing the blank into a bar 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, coating a lubricating layer on the rod material; then drawing the rod material coated with the lubricating layer step by step, and then removing the lubricating layer to obtain a wire material; Step S4, rolling the wire into a flat wire with a rectangular cross section; Step S5, winding the flat wire into a blank in a mold; Step S6, performing a second heat treatment on the blank; in the second heat treatment, the second heat treatment temperature is 600°C-750°C, the second heat treatment holding time is 5min-120min, the second heat treatment atmosphere is a nitrogen-containing atmosphere and / or a carbon-containing atmosphere, and the second heat treatment atmosphere pressure is 2000Pa-50MPa; Step S7, performing a third heat treatment on the blank; in the third heat treatment, the third heat treatment temperature is 450°C-500°C, the third heat treatment holding time is 30min-600min, and the third heat treatment vacuum is not less than 2×10 -3 Pa; Step S8, demoulding, trimming, cutting and assembling the blank after the third heat treatment to form a finished hairspring.

8. The method for preparing a hairspring for a mechanical watch according to claim 7, characterized in that: 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%.

9. The method for preparing a hairspring for a mechanical watch according to claim 7, characterized in that: In the first heat treatment, the first heat treatment temperature is 700° C.-1150° C., and the first heat treatment holding time is 1 min-60 min.

10. The method for preparing a hairspring for a mechanical watch according to claim 7, characterized in that: In step S4, the width of the flat wire is recorded as b, and the thickness is recorded as h, and the relationship is: 3h≤b≤5h.

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