Balance spring for timekeeping movements

Abstract

To provide a spiral spring with chemical composition for eliminating fragile phases and reducing production times.SOLUTION: The invention relates to a spiral spring intended to form a balance of a horological movement. The spiral spring is made of an alloy comprising: Nb and Ti elements; at least one element selected from Zr and Hf; optionally at least one element selected from W and Mo; and optionally traces of other elements selected from O, H, Ta, C, Fe, N, Ni, Si, Cu and Al; where the content of Nb is 40-84 wt.%, the total content of Ti, Zr and Hf is 16-55 wt.%, the content of each of W and Mo is 0-2.5 wt.%, and the content of each of the elements selected from O, H, Ta, C, Fe, N, Ni, Si, Cu and Al is 0-1600 ppm with the total content of the trace elements being 0.3 wt.% or less. The invention relates also to a method for manufacturing such as a spiral spring.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a spiral spring intended to equip a balance of a timepiece movement. The present invention further relates to a method for manufacturing this balance spring.

Background Art

[0002] In the manufacture of spiral springs for portable timepieces (e.g., wristwatches, pocket watches), - High elastic limit - Easy production, especially stretching and rolling - Excellent fatigue resistance - Stable performance over a long period - Small cross-section one faces constraints that seem incompatible.

[0003] Also, the alloy selected for the spiral spring must have properties that ensure that a portable timepiece incorporating such a spiral spring maintains its chronometer performance even when used at various temperatures. Therefore, the thermal elastic coefficient (TEC) of the alloy is very important. To form a chronometer oscillator with a balance made of CuBe or silver brass, the thermal elastic coefficient needs to be within the range of ±10 ppm / °C. The equation relating the thermal elastic coefficient of the alloy to the expansion coefficient (α) of the spiral spring and the expansion coefficient (β) of the balance is as follows.

[0004]

Equation

[0005] Here, the variable M is the rate at s / d, the variable T is the temperature in °C, and E is the ​​​​​​​The Young's modulus of the spiral alloy is (1 / E)(dE / dT), and the thermoelastic coefficient of the spiral alloy is It is a number, and the coefficient of thermal expansion is °C -1 It is represented as follows.

[0006] In practice, TC is calculated as follows between 8°C and 38°C.

[0007]

number

[0008] This value must be between -0.6 and +0.6 s / d℃.

[0009] Spiral springs for the manufacture of portable watches are known to be made from conventional binary Nb-Ti alloys. In this alloy, the proportion of Ti is typically 40-60% by weight, and It is 47% by weight. Applying the deformation and heat treatment diagrams, this spiral spring is β-phase. It has a two-phase microstructure containing oats and titanium in the form of precipitates in the α phase. Cold-worked In alloys, the β phase has a strong positive thermoelastic modulus, and the α phase has a strong negative thermoelastic modulus. This allows the thermoelastic modulus of this two-phase alloy to approach zero, which is due to TC It is particularly preferable for this purpose.

[0010] However, there are several challenges when using a binary Nb-Ti alloy for spiral springs. be.

[0011] One of the challenges with binary Nb-Ti alloys is that they are mainly formed after the winding step during the fixing step. This is related to the deposition of titanium. In fact, the deposition time is very long, and in NbTi47 alloy In this case, the time is 8 to 30 hours, with an average of about 20 hours. This means that the production time The gap becomes very long.

[0012] Apart from the problem of long production time, if the proportion of titanium is too high, brittle martensite site phases may be formed, which can make the deformation of the material difficult or impossible, and thus not suitable for the production of spiral springs. Thus, it is recommended not to add excessive titanium to the alloy.

[0013] Even currently, there is still a need to develop a new chemical composition that meets various conditions such as having no brittle phases and shortening the production time for producing spiral springs.

Summary of the Invention

[0014] The present invention aims to propose a new chemical composition of a spiral spring that can solve the above problems.

Means for Solving the Problems

[0015] In such a situation, the present invention relates to a spiral spring of a portable watch made of at least a ternary alloy based on niobium and titanium. According to the present invention, Ti is partially replaced by Zr and / or Hf. This can also form α-phase precipitation. By partially replacing Ti with Zr and / or Hf, the precipitation during fixation can be accelerated, and the

[0016] production time can be shortened. Specifically, the present invention relates to a spiral spring intended to equip a balance of a timepiece movement, and the spiral spring - If present, at least one element selected from W and Mo, and - If present, selected from O, H, Ta, C, Fe, N, Ni, Si, Cu and Al Other trace elements Made from at least three alloys, - The Nb content is 40-84% by weight. - The total content of Ti, Zr, and Hf is 16-55% by weight, preferably containing Ti The amount is at least 15% by weight, - The W and Mo content is 0-2.5% by weight, - Each element selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al The content ranges from 0 to 1600 ppm, and the total amount of the aforementioned trace elements is 0.3% by weight or less.

[0017] The present invention further relates to a method for manufacturing this portable watch spiral spring, the method being , - A step of creating or preparing a blank made of at least three alloys, - The titanium in the alloy is substantially in the form of a solid solution, containing niobium in the β phase, and zirconium The β of the blank is such that the β and / or hafnium also substantially form a solid solution. Steps to perform a type quench, - A series of deformation sequences are performed on the alloy, followed by an intermediate heat treatment. Top, - The steps of winding to form a spiral spring, and - The final heat treatment step, also known as fixing, is performed. The aforementioned alloy is - Elements Nb and Ti, and at least one element selected from Zr and Hf, - If present, at least one element selected from W and Mo, - If present, select from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al. It consists of other trace elements, - The Nb content is 40-84% by weight. - The total content of Ti, Zr, and Hf is 16-55% by weight, preferably containing Ti The amount is at least 15% by weight, - The W and Mo content is 0-2.5% by weight, - Each element selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al The content ranges from 0 to 1600 ppm, and the total amount of the aforementioned trace elements is 0.3% by weight or less.

[0018] Preferably, the precipitation of titanium, zirconium and / or hafnium is ultimately carried out. The final heat treatment step is performed at a holding temperature of 400°C to 600°C for a duration of 4 to 8 hours. It can be done.

[0019] In addition to shortening the setting time, titanium is partially replaced with zirconium. This reduces secondary errors, as explained below. [Modes for carrying out the invention]

[0020] The present invention relates to a ternary element comprising at least niobium, titanium, and one or more additional elements. This concerns the spiral spring in a portable watch made of alloy.

[0021] According to the present invention, this alloy is - Elements Nb and Ti, and at least one element selected from Zr and Hf, - If present, at least one element selected from W and Mo, and - If present, selected from O, H, C, Ta, Fe, N, Ni, Si, Cu and Al It consists of other trace elements, - The Nb content is 40-84% by weight. - The total content of Ti, Zr, and Hf is 16-55% by weight. - The W and Mo content is 0-2.5% by weight, - Each element selected from O, H, C, Ta, Fe, N, Ni, Si, Cu, and Al The content ranges from 0 to 1600 ppm, and the total amount of the aforementioned trace elements is 0.3% by weight or less.

[0022] Preferably, the Nb content is greater than 45% by weight, and more preferably 50% by weight or more. This allows us to obtain a sufficient proportion of the β phase having a strong positive thermoelastic coefficient. The coefficient of elasticity is intended to be compensated for by the negative thermoelastic moduli of the α phases of Ti, Zr, and Hf. It is being done.

[0023] Preferably, the Ti content is maintained at a minimum of 15% by weight or more. This is because, Because Ti is more economical than Zr or Hf. Also, Ti has a lower melting point than Zr or Hf. It has the advantage of being lower and easier to mold.

[0024] The proportion of oxygen is less than 0.10% by weight of the total, and even less than 0.085% by weight of the total. ru.

[0025] The proportion of hydrogen should be 0.01% by weight or less of the total, especially 0.0035% by weight or less of the total, and furthermore It accounts for less than 0.0005% by weight of the total.

[0026] The proportion of carbon should be 0.04% by weight or less of the total, especially 0.020% by weight or less of the total, and further This is less than 0.0175% by weight of the total.

[0027] The proportion of tantalum is 0.10% by weight or less of the total.

[0028] The proportion of iron should be 0.03% by weight or less of the total, especially 0.025% by weight or less of the total, and furthermore It is less than 0.020% by weight of the total.

[0029] The nitrogen content should be 0.02% by weight or less of the total, especially 0.015% by weight or less of the total, and furthermore This is less than 0.0075% by weight of the total.

[0030] The nickel content is less than 0.01% by weight of the total.

[0031] The proportion of silicon is 0.01% by weight or less of the total.

[0032] The proportion of copper is 0.01% by weight or less of the total, and especially 0.005% by weight or less of the total.

[0033] The proportion of aluminum is less than 0.01% by weight of the total.

[0034] According to the present invention, Ti is partially replaced by Zr and / or Hf, which is Ti This is how α precipitates are formed, accelerating precipitation during fixation and thus shortening production time. This is possible. Preferably, the total content of Zr and Hf is 1-40% by weight. The total content of Zr and Hf is 5-25% by weight, more preferably 10-25% by weight. More preferably, it is 15-25% by weight.

[0035] Preferably, Ti is replaced by at least Zr. This results in two points The curvature of the rate is generally approximated by a straight line passing through (8°C and 38°C). This can reduce certain secondary errors. The effects of Ti and Zr on secondary errors are shown. Therefore, a binary alloy Nb-Ti (NbTi47) with a Ti content of 47 wt%, and Zr Tests were performed with Nb-Zr at concentrations ranging from 0% to 70% by weight. Secondary errors were measured at 23°C. The secondary error is 23 for the straight line connecting the rate at 8°C and the rate at 38°C. This is the difference in rates at different temperatures. For example, the rates at 8°C, 23°C, and 38°C are shown in the image. Measurements can be taken using a Witschi chronoscope-type device.

[0036] Table 1 below shows the weight percentage of pure Nb, NbTi47 alloy, and Nb-Zr The data for the alloy is shown. Pure Nb has a secondary error of -6.6 s / at 23°C. d. The precipitation of Ti in the NbTi47 alloy compensates for the negative effect of Nb, but 4.5s It increases excessively with positive values ​​reaching / d. On the other hand, Nb-Zr alloys are more than 0 wt% There is a negative secondary error in the case of a large Zr content, and in the case of a Zr content of 45% by weight or more. It can even become zero. Therefore, in ternary alloys, Ti is partially replaced by Zr. This allows us to compensate for the excessively strong positive effect of Ti on secondary errors. By adding a certain percentage of Zr, the secondary error is brought closer to zero than in the binary NbTi47 alloy. It can be reduced to a certain value. Therefore, preferably, the Zr content is at least 5 times It is a percentage.

[0037] [Table 1]

[0038] The alloy may further contain W and Mo in amounts of 0 to 2.5% by weight, respectively. This increases the Young's modulus of the alloy, and the given torque of the spring is proportional to the thickness of the spiral. Making it thinner makes the spiral lighter.

[0039] Preferably, the spiral spring according to the present invention has a central cubic β-phase niobium and a single It has a multiphase microstructure containing α-phase titanium and zirconium and / or hafnium.

[0040] In order to obtain such a microstructure, the manufacturing method involves heat treatment when fixing the spring. The α phase precipitation requires a finishing treatment. This manufacturing method is as follows: Perform the steps sequentially. - Steps to create or prepare a blank For example, the blank is made by melting elements in an electric arc or electron gun furnace to make a billet or It can be made by forming an ingot. This billet or ingot is The blank is hot forged, cold deformed, and heat-treated during the deformation stage. - Elements Nb and Ti, and at least one element selected from Zr and Hf, - If present, at least one element selected from W and Mo, - If present, select from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al. Other trace elements Made from at least three alloys, - The Nb content is 40-84% by weight. - The total content of Ti, Zr, and Hf is 16-55% by weight. - The W and Mo content is 0-2.5% by weight, - Each element selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al The content ranges from 0 to 1600 ppm, and the total amount of the aforementioned trace elements is 0.3% by weight or less. - The titanium in the alloy is substantially in the form of a solid solution, containing niobium in the β phase, and zirconium The β of the blank is such that the β and / or hafnium also substantially form a solid solution. Steps to perform a type quench - A series of deformation sequences are performed on the alloy, followed by an intermediate heat treatment step. P Here, deformation refers to deformation due to stretching and / or rolling. In stretching, Therefore, it is necessary to use one or more dies in the same sequence or in different sequences. There may be a need for this. Stretching is carried out until a wire with a round cross-section is obtained. Rolling is similar to stretching. This can be done during the same transformation sequence or during another sequence. Preferably, The final sequence performed on the alloy is rolling, preferably at the entrance of the winding pin. Use a rectangular profile that aligns with the section. - Steps to wind and form a spiral spring - Final heat treatment step

[0041] In these combined deformation-heat treatment sequences, each deformation is a given deformation of 1 to 5 This is done using a shape quantity, and this deformation quantity corresponds to the traditional formula 2ln(d0 / d). Here, d0 is The last β quench is the diameter, and d is the diameter of the wire being cold-worked. The global accumulation of deformations across the entire scale results in a total deformation of 1 to 14. Each of the combined deformation-heat treatment sequences involves Ti, Zr, and / or Hf each time. This includes performing heat treatment to precipitate the α phase.

[0042] The β-quench before the deformation and heat treatment sequence is performed at a temperature of 700°C to 1000°C under vacuum. This dissolution process is carried out for a duration of 5 minutes to 2 hours, after which it is cooled under gas.

[0043] Furthermore, this β-quench is a dissolution process that is sustained at 800°C for 1 hour under vacuum, and Later, it is cooled under gas.

[0044] To return to the combined deformation-heat treatment sequence, the heat treatment is performed at temperatures of 300°C to 700°C. This is a precipitation treatment performed at a temperature of 1 to 200 degrees Celsius for a duration of 1 to 200 hours. In particular, at 400°C to 600°C. The test is conducted at a temperature that lasts for 3 to 30 hours.

[0045] In particular, this method involves a number of combined deformation-heat treatment sequences ranging from one to five.

[0046] In particular, the first combined deformation-heat treatment sequence reduces the cross-section by at least 30%. This includes the processing of the first transformation.

[0047] In particular, each of the combined deformation-heat treatment sequences that is not the first deformation treatment is This includes one deformation treatment between the two heat treatments, reducing the cross-section by at least 25%.

[0048] In particular, after the alloy blank is made and before the deformation-heat treatment sequence, additional In the typical steps, copper, nickel, cupronickel, cupromanganese, gold, silver, Table of ductile materials selected from nickel-phosphorus (Ni-P) and nickel-boron (Ni-B), etc. A surface layer is added to the blank, making it easier to form into a wire shape during deformation. After the heat treatment sequence, or after the winding step, especially by chemical attack, the wire Then the ductile material layer is removed.

[0049] Instead, the surface layer of the ductile material is spyed such that the pitch is not a multiple of the blade thickness. It is deposited to form a ral spring. In another variant, the surface layer of the ductile material is made py The material is deposited in such a way that it forms a spring with variable tension.

[0050] Therefore, in a specific timekeeping application, a ductile material or copper is used at a given time. By adding this, the wire shape is easily formed, thereby achieving a thickness of 10 to 500 μm. The material remains on the wire, and the final diameter is 0.3-1 mm. From the wire, especially chemically Through targeted attack, the ductile material or copper layer is removed, rolled and flattened, and then wi By doing so, the actual springs are manufactured.

[0051] The installation of ductile materials or copper can be galvanic or mechanical. In this case, it is a ductile material or a copper jacket or tube, which is a large diameter alloy It is adjusted on the rod and then thinned during the deformation steps of the composite rod.

[0052] Layer removal is particularly achieved through chemical attacks using cyanide or acid-based solutions, such as nitric acid. It can be done by shooting.

[0053] The final heat treatment is carried out at a temperature of 300°C to 700°C for a duration of 1 to 200 hours. In particular, the duration is 3 to 30 hours at temperatures of 400°C to 600°C. Furthermore, it is maintained at a temperature of 400°C to 600°C, and the duration is 4 to 8 hours. During the heat treatment, the deposition of α-phase titanium, hafnium, and / or zirconium is completed.

[0054] Through a series of appropriate deformations and heat treatments, β-niobium, titanium, and hafnium are produced. A very fine, especially nanometer-scale, micro, containing the α phase of zirconium. A structure can be obtained. This alloy is very high, at least greater than 500 MPa. It possesses both an elastic limit and an elastic modulus of 100 GPa or higher, preferably 110 GPa or higher. This combination of properties is suitable for spiral springs. Furthermore, this according to the present invention is less Both ternary niobium-titanium-hafnium and / or zirconium alloys are ductile materials or copper. It can be easily covered, and this significantly promotes deformation due to stretching. Cut.

[0055] This alloy has a similar effect to "Elinvar" and is commonly used in portable watches. The thermoelastic coefficient is virtually zero in the temperature range in which it is used, and it is a spiral with a self-compensating function. It is suitable for the manufacture of [product name].

Claims

1. A spiral spring intended to equip a timekeeping movement with balance, wherein the spiral spring is The elements Nb and Ti, and at least one element selected from Zr and Hf, Optionally, at least one element selected from W and Mo, and Other trace elements selected from O, H, Ta, C, Fe, N, Ni, Si, Cu and Al Made from an alloy consisting of, The Nb content is 50-75% by weight. The total content of Ti, Zr, and Hf is 25-50% by weight, the Ti content is 15% or more by weight, and the total content of Zr and Hf is 10-25% by weight. The W and Mo content is 0-2.5% by weight, The content of each element selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al is 0 to 1600 ppm, and the total amount of the trace elements is 0.3% by weight or less. The spiral spring has a microstructure comprising β-phase Nb, α-phase Ti, and Zr and / or Hf. A spiral spring characterized by the following features.

2. The total content of Zr and Hf is 15-25% by weight. The spiral spring according to claim 1.

3. Contains at least 5% by weight of Zr The spiral spring according to claim 1.

4. Includes Zr and Hf The spiral spring according to claim 1.

5. The elastic limit is 500 MPa or higher, and the elastic modulus is 100 GPa or higher. The spiral spring according to claim 1.

6. The modulus of elasticity is 110 GPa or higher. The spiral spring according to feature 5.

7. A method for manufacturing a spiral spring intended to equip a timekeeping movement with a balance, The steps include preparing a blank using at least a ternary alloy, The steps include performing a β-type quench on the blank such that the titanium of the alloy is substantially in the form of a solid solution, contains β-phase niobium, and the zirconium and / or hafnium are also substantially in the form of a solid solution, The process involves performing a series of deformation sequences on the alloy, followed by an intermediate heat treatment, The steps include winding to form a spiral spring, and The final heat treatment step is performed. The aforementioned alloy is The elements Nb and Ti, and at least one element selected from Zr and Hf, Optionally, at least one element selected from W and Mo, It consists of O, H, Ta, C, Fe, N, Ni, Si, Cu, and other trace elements selected from Al. The Nb content is 50-75% by weight. The total content of Ti, Zr, and Hf is 25-50% by weight, the Ti content is 15% or more by weight, and the total content of Zr and Hf is 10-25% by weight. The W and Mo content is 0-2.5% by weight, The content of each element selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, and Al is 0 to 1600 ppm, and the total amount of the trace elements is 0.3% by weight or less. A method characterized by the following:

8. The aforementioned β-type quench is a dissolution process, which is carried out under vacuum at a temperature of 700°C to 1000°C for a duration of 5 minutes to 2 hours, followed by cooling under gas. The method according to feature 7.

9. The aforementioned β-type quench is a dissolution process performed at 800°C for 1 hour under vacuum, followed by cooling under gas. The method according to 7 or 8, characterized by the features described above.

10. The intermediate and final heat treatments in each sequence are precipitation treatments of α-phase Ti, Zr, and / or Hf, performed at a holding temperature of 300°C to 700°C for a duration of 1 to 200 hours. The method according to 7 or 8, characterized by the features described above.

11. The aforementioned final heat treatment is performed at a holding temperature of 400°C to 600°C for a duration of 4 to 8 hours. The method according to 7 or 8, characterized by the features described above.

12. After the step of preparing the blank with the alloy, and after performing the series of deformation sequences, and before the step of performing intermediate heat treatment, a surface layer of a ductile material selected from copper, nickel, cupronickel, cupromanganese, gold, silver, nickel-phosphorus (Ni-P), and nickel-boron (Ni-B) is added to the blank to facilitate its formation into a wire shape. Before or after the step of winding to form a spiral spring, the layer of ductile material is removed by chemical attack. The method according to any one of claims 7 or 8, characterized by the features described herein.

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