Timepiece Resonator

Abstract

An antiferromagnetic alloy consisting of: between 10.0 and 30.0 wt.-% manganese, between 4.0 and 10.0 wt.-% chromium, between 5.0 and 15.0 wt.-% nickel, between 0.1 and 2.0 wt.-% titanium, the remainder being iron and residual impurities, the alloy being free of beryllium.

Claims

1. An antiferromagnetic alloy having a composition constituted of: 10.0% to 30.0% by weight manganese, 4.0% to 10.0% by weight chromium, 5.0% to 15.0% by weight nickel, 0.1% to 2.0% by weight titanium, the remainder being iron and residual impurities, the alloy being free of beryllium.

2. The alloy according to claim 1, wherein the manganese content is between 24% and 26% by weight.

3. The alloy according to claim 1, wherein the chromium content is between 7% and 9% by weight.

4. The alloy according to claim 1, wherein the nickel content is between 5.5% and 7.5% by weight.

5. The alloy according to claim 1, wherein the titanium content is between 0.3% and 1.2% by weight.

6. A timekeeping movement component at least partially constituted of an alloy according to claim 1.

7. The component according to claim 6, wherein the component is a resonator.

8. The component according to claim 6, wherein the component is a resonator in the form of a balance spring, or a flexible strip resonator, or a virtual pivot resonator.

9. A timekeeping movement component comprising at least one component according to claim 6.

10. A watch comprising a timekeeping movement according to claim 9.

11. A method for preparing an alloy according to claim 1, comprising the following successive steps: a step of melting the constituents of the alloy, carried out in one or more phases and at a temperature T.sub.melt, enabling the alloy containing the desired metals to be formed, a purification step, carried out in one or more phase(s), enabling the impurities from the constituents of the alloy to be removed while limiting the evaporation of manganese, and carried out at a temperature T.sub.pur and a pressure P greater than atmospheric pressure.

12. The method according to claim 11, wherein, at the end of the purification step, the alloy has a total impurities content of less than or equal to 1,500 ppm.

13. The method according to claim 11, wherein the purification step results in a variation in the manganese of less than or equal to 5% by weight, relative to the quantity of manganese resulting from the melting step.

14. The method according to claim 11, wherein the temperature T.sub.pur of the purification step is between 1250 C. and 1450 C., advantageously between 1300 C. and 1400 C., and in that the temperature T.sub.melt of the step of melting the constituents of the alloy is between 1250 C. and 1450 C., advantageously between 1300 C. and 1400 C.

15. The method according to claim 11, wherein the purification step is carried out at a pressure P greater than 10 bar, advantageously greater than 20 bar, the pressure P being advantageously lower than or equal to 50 bar.

16. The method according to claim 15, wherein the method of the purification step is an electro conducting slag pressure method.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0076] FIG. 1 shows the Young's modulus of the Nivarox alloy (38 to 41% nickel, 7.8 to 8% chromium, 1% titanium, 0.2% silicon, 0.4% manganese, 0.8 to 0.9% beryllium, and the remainder iron) as a function of temperature.

[0077] FIG. 2 illustrates the magnetic hysteresis cycle of the same Nivarox alloy.

[0078] FIG. 3 illustrates the evolution of the Young's modulus of an alloy as a function of temperature, after different thermal treatments.

[0079] FIGS. 4 to 15 illustrate the magnetic hysteresis cycles of an alloy as a function of temperature and thermal treatment time.

[0080] FIG. 16 corresponds to a simulation of the distribution diagram of the different phases of an alloy as a function of temperature.

DETAILED DESCRIPTION

[0081] Several examples of alloys have been made according to the described embodiments. (INV-1 to INV-12) have been prepared according to the following steps: [0082] melting constituents of the alloy, [0083] purification of the alloy, [0084] obtaining the alloy, [0085] mechanical treatment (preferably forging, but applicable also to drawing) and thermal treatment of the alloy.

[0086] Experimental conditions of the thermal treatment (carried out after the purification step) are specified in Table 1.

TABLE-US-00001 TABLE 1 preparation conditions of the alloys INV-1 to INV-12. INV-1 INV-2 INV-3 INV-4 INV-5 INV-6 Conditions: (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 and 4) and 5) and 6) and 7) and 8) and 9) time 30 min 60 min 30 min 60 min 30 min 60 min Fixing 500 C. 500 C. 550 C. 550 C. 600 C. 600 C. temperature INV-7 INV-8 INV-9 INV-10 INV-11 INV-12 Conditions: (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 (FIGS. 3 and 10) and 11) and 12) and 13) and 14) and 15) time 30 min 60 min 30 min 60 min 30 min 60 min Fixing 650 C. 650 C. 700 C. 700 C. 780 C. 780 C. temperature

[0087] FIGS. 4 to 15 illustrate the magnetic hysteresis cycles of the alloys according to examples INV-1 to INV-12. These alloys have the same composition, but they have been subjected to different treatments. FIGS. 4 to 15 therefore reflect the magnetic hysteresis cycles as a function of temperature and thermal treatment time. The influence of these two annealing factors is visible on the magnetic measurements (FIGS. 4 to 15). We can also see the influence of temperature and time on the evolution of the anomaly in the behavior of the measurement of the Young's modulus as a function of temperature (FIG. 3).

[0088] Magnetic measurements have been carried out on the examples INV-1 to INV-12. The mass and density measured as well as the sample volume are given in Table 2.

TABLE-US-00002 TABLE 2 mass, density and volume of samples. Examples Mass (mg) Density (g/cm.sup.3) Volume (cm.sup.3) INV-1 5.55 7.977 6.9575 .Math. 10.sup.4 INV-2 5.95 8.00725 7.43077 .Math. 10.sup.4 INV-3 3.87 7.8399 4.93629 .Math. 10.sup.4 INV-4 2.78 7.9478 3.49782 .Math. 10.sup.4 INV-5 2.71 8.0159 3.38078 .Math. 10.sup.4 INV-6 6.14 8.003 7.67212 .Math. 10.sup.4 INV-7 5.55 8.0059 6.93239 .Math. 10.sup.4 INV-8 2.99 7.9704 3.75138 .Math. 10.sup.4 INV-9 3.23 7.9798 4.04772 .Math. 10.sup.4 INV-10 5.78 7.9574 7.26368 .Math. 10.sup.4 INV-11 6.29 7.9319 7.93 .Math. 10.sup.4 INV-12 6.72 7.9897 8.41083 .Math. 10.sup.4

[0089] The measurement of the magnetic moment as a function of the applied magnetic field has been carried out in VSM mode (vibrating sample) with a frequency of 14 Hz and an amplitude of 3 mm.

[0090] The magnetic hysteresis cycles were measured over five quadrants (FIGS. 4 to 15), going from a minimum field of 2000 Oe (159 kA/m) to a maximum field of +2000 Oe (+159 kA/m), with a path of 20 Oe (1592 A/m).

[0091] The coercive field, residual field, saturated magnetization values are summarized in Table 3.

TABLE-US-00003 TABLE 3 properties of the samples Coercive Residual Saturated Susceptibility field magnetization magnetization dM/dH Examples (kA/m) (A/m) (kA/m) at M = 0 INV-1 1.66 5.8 non-saturated 0.00317 INV-2 0.73 1.7 non-saturated 0.00216 INV-3 0.70 1.8 non-saturated 0.00228 INV-4 1.17 2.8 non-saturated 0.00224 INV-5 0.56 1.4 non-saturated 0.00225 INV-6 0.78 2.1 non-saturated 0.00226 INV-7 0.25 0.6 non-saturated 0.00190 INV-8 1.25 5.9 non-saturated 0.00429 INV-9 0.10 0.5 non-saturated 0.00216 INV-10 0.16 0.5 non-saturated 0.00203 INV-11 0.10 0.34 non-saturated 0.00191 INV-12 0.48 1.2 non-saturated 0.00223

[0092] We see that the thermal treatments enable the residual magnetism to be clearly reduced. We can thus select the optimal thermal treatment for this specific alloy. A measurement at higher field (2T) has been carried out in order to find any saturation, but the linear behavior of M(H) is retained, indicating that the field saturation is probably located beyond the limits of this system.

[0093] FIG. 16 corresponds to a simulation illustrating the different phases of this alloy as a function of temperature, and more particularly the proportion of sigma phases (intermetallic phase), Laves phase, BCC (body centered cubic) and FCC (face centered cubic) structures, and liquid phase. This diagram also shows the solidification 1336 C.) and liquefaction or melting (1383 C.) temperatures of the alloy.