Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/06—Oscillators with hairsprings, e.g. balance
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B45/00—Time pieces of which the indicating means or cases provoke special effects, e.g. aesthetic effects
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/20—Compensation of mechanisms for stabilising frequency
  • G04B17/22—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature
  • G04B17/227—Compensation of mechanisms for stabilising frequency for the effect of variations of temperature composition and manufacture of the material used
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21F—WORKING OR PROCESSING OF METAL WIRE
  • B21F3/00—Coiling wire into particular forms
  • B21F3/02—Coiling wire into particular forms helically
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C14/00—Alloys based on titanium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/02—Alloys based on vanadium, niobium, or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
  • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/06—Oscillators with hairsprings, e.g. balance
  • G04B17/063—Balance construction
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/06—Oscillators with hairsprings, e.g. balance
  • G04B17/066—Manufacture of the spiral spring
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/32—Component parts or constructional details, e.g. collet, stud, virole or piton
  • G04B17/34—Component parts or constructional details, e.g. collet, stud, virole or piton for fastening the hairspring onto the balance
• • G—PHYSICS
  • G04—HOROLOGY
  • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
  • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials
  • G04D3/0002—Watchmakers' or watch-repairers' machines or tools for working materials for mechanical working other than with a lathe
  • G04D3/0035—Watchmakers' or watch-repairers' machines or tools for working materials for mechanical working other than with a lathe for components of the regulating mechanism
  • G04D3/0041—Watchmakers' or watch-repairers' machines or tools for working materials for mechanical working other than with a lathe for components of the regulating mechanism for coil-springs
• • G—PHYSICS
  • G04—HOROLOGY
  • G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
  • G04D3/00—Watchmakers' or watch-repairers' machines or tools for working materials
  • G04D3/0069—Watchmakers' or watch-repairers' machines or tools for working materials for working with non-mechanical means, e.g. chemical, electrochemical, metallising, vapourising; with electron beams, laser beams

Definitions

• the invention relates to a method of manufacturing a spiral spring intended to equip a balance of a timepiece movement and the spiral spring resulting from the method.
• spiral springs are also centered on the concern for thermal compensation, so as to guarantee regular chronometric performance. This requires obtaining a thermoelastic coefficient close to zero. We are also looking to produce spiral springs exhibiting limited sensitivity to magnetic fields.
• New balance springs have been developed from alloys of niobium and titanium.
• these alloys pose problems of sticking and seizing in the drawing or drawing dies and against the lamination rolls, which makes them almost impossible to transform into fine wires by the standard processes used, for example, for the production. 'steel.
• This copper layer on the wire has a disadvantage: it must be deposited in a thick layer (typically 10 microns for a diameter of Nb-Ti of 0.1 mm) to play its role of anti-sticking agent during the deformation steps. It does not allow fine control of the wire geometry during wire calibration and rolling. These dimensional variations of the Nb-Ti core of the wire result in significant variations in the torque of the balance springs.
• the present invention provides a method of manufacturing a spiral spring which makes it possible to facilitate shaping by deformation while avoiding the drawbacks associated with the copper layer.
• the blank As the blank undergoes a large number of deformation passes to bring it to specific dimensions and geometry, the blank must be coated with a layer preventing sticking in the successive dies thick enough not to be damaged during these successive deformations.
• the thickness of the copper layer for producing watch spiral springs is of the order of 10 microns. The Applicant has however observed that the external dimensions of the blank covered with the copper layer were well controlled during the successive deformation passes of the blank but on the other hand that the dimensions of the Nb-Ti core were not not mastered.
• the applicant therefore had the inventive idea which consists in coating the Nb-Ti blank with a thin layer (typically chosen between 800 nm and 1.2 microns when the blank has reached a diameter of between 15 and 50 microns) d '' a first anti-sticking material and preferably compatible with the thermoelastic coefficient (CTE) of the Nb-Ti core, before coating the blank with a layer of a second ductile material thicker than the layer of the first material to perform the first deformation steps and then to remove the "thick" layer of the second material before the final steps while retaining the "thin” layer of the first material.
• This “thin” layer will make it possible to carry out the final stages of deformation of the wire without sticking in the dies while perfectly controlling the dimensions of the Nb-Ti core.
• the first material is preferably chosen from the set comprising niobium, gold, tantalum, vanadium, austenitic stainless steels, grade 316L steel
• the second material is chosen from the set comprising copper , silver, copper and nickel alloys, alpha single phase copper and zinc alloys (eg CuZn30).
• the first material is niobium and the second material is copper (ETP (electrolytic tough pitch), OF (oxygen-free) or OFE (oxygen free electronic) grade, for example).
• ETP electrolytic tough pitch
• OF oxygen-free
• OFE oxygen free electronic grade
• a preferred embodiment of the method of manufacturing the spiral spring according to the invention therefore comprises a step aimed at forming a thin layer of niobium coating the Nb-Ti core, then at forming a thick layer. of copper, partially deforming the coated core, removing the remaining Cu layer, and then completing the deformation of the Nb-Ti core simply coated with niobium.
• This niobium layer then forms the outer layer which is in contact with the dies and the rolling rolls. It is chemically inert and ductile and makes it easy to draw and roll the spiral wire. It has the other advantage of facilitating the separation between the hairsprings after the fixing step following the slipping step.
• the niobium layer is retained on the hairspring at the end of the manufacturing process. It is sufficiently thin with a thickness of between 50 nm and 5 ⁇ m and preferably 200 nm and 1.5 ⁇ m and more preferably between 800 nm and 1.2 ⁇ m, so as not to significantly modify the thermoelastic coefficient (CTE) of the hairspring.
• CTE thermoelastic coefficient
• Nb has a CTE similar to that of Nb-Ti, which makes it easier to obtain a balance spring.
• Nb-Ti core It is also perfectly adherent to the Nb-Ti core.
• These thicknesses of the niobium layer are typically suitable for Nb-Ti cores having diameters of between 15 and 100 ⁇ m.
• step d1) of the method of the invention consists in cold deforming by hammering and / or stretching and / or drawing the blank obtained in step c).
• a beta-type hardening step of said blank is carried out, so that the titanium of said alloy is essentially in the form of a solid solution with the niobium in beta phase and preferably, the ⁇ quenching step is a solution treatment, with a duration of between 5 minutes and 2 hours at a temperature between 700 ° C and 1000 ° C, under vacuum, followed by gas cooling.
• the step of removing the layer of the second material is carried out by etching.
• the final heat treatment of step g) is a treatment of precipitation of titanium in the alpha phase for a duration of between 1 hour and 80 hours at a temperature of between 350 ° C and 700 ° C, preferably between 5 hours and 30 hours between 400 ° C and 600 ° C.
• step g) consists of a heat treatment of precipitation of titanium in the alpha phase for a duration of between 1 hour and 80 hours at a temperature of between 350 ° C and 700 ° C, preferably between 5 hours and 30 hours between 400 ° C and 600 ° C.
• C and 600 ° C can also be carried out after each or certain sequences of the deformation step d1) and / or d2)
• the layer of the second material typically copper formed in step c
• each sequence of steps d1) and / or d2) is carried out with a strain rate of between 1 and 5, the global accumulation of strains over all the sequences leading to a total strain rate of between 1 and 14.
• the strain rate for each sequence g) corresponding to the classic formula 2ln (d0 / d), where d0 is the diameter of the last beta hardening, and where d is the diameter of the hardened wire
• step b) of forming the layer of the first material is carried out by winding a strip of the first material, for example. niobium, around the Nb-Ti core and step c) of forming the layer of the second material, typically a layer of copper, is carried out by introducing the blank obtained at after step b) in a tube of the second material, e.g. copper, followed by drawing and / or hammering and / or drawing of the entire tube and of the blank obtained at the end of step b).
• a tube of the second material e.g. copper
• the layer of the first material has a thickness between 300 nm and 1.5 ⁇ m and preferably between 400 nm and 800 nm.
• the first material is niobium.
• the Ti content is between 40 and 65% by weight, preferably between 40 and 49% by weight and more preferably between 46 and 48% by weight.
• the Nb-Ti core has a two-phase microstructure comprising niobium in the beta phase and titanium in the alpha phase.
• the spring has an elastic limit greater than or equal to 500 MPa, preferably 600 MPa, and an elastic modulus less than or equal to 120 GPa, preferably less than or equal to 100 GPa.
• the invention relates to a method of manufacturing a spiral spring intended to equip a balance of a timepiece movement.
• This spiral spring is made of a binary type alloy comprising niobium and titanium. It also relates to the spiral spring resulting from this process.
• niobium as a first material and copper as a second material.
• the method of the invention further comprises a step h) consisting in removing said copper layer formed in step c), at a time in step c) at which the blank has reached a diameter such that one can still pass said blank at least through one die and preferably through two dies with an elongation rate of the blank of about 10% at each die before the first rolling step d2) or at the latest before the last pass of step d2).
• the core is made from an Nb-Ti alloy comprising between 5 and 95% by weight of titanium.
• the alloy used in the present invention comprises by weight between 40 and 60% titanium.
• it comprises between 40% and 49% by weight of titanium, and more preferably between 46% and 48% by weight of titanium.
• the percentage of titanium is sufficient to obtain a maximum proportion of Ti precipitates in the form of alpha phase while being reduced to avoid the formation of a martensitic phase causing problems of fragility of the alloy during its use.
• the Nb-Ti alloy used in the present invention does not comprise other elements except for possible and inevitable traces. This makes it possible to avoid the formation of fragile phases.
• the oxygen content is less than or equal to 0.10% by weight of the total, or even less than or equal to 0.085% by weight of the total.
• the tantalum content is less than or equal to 0.10% by weight of the total.
• the carbon content is less than or equal to 0.04% by weight of the total, in particular less than or equal to 0.020% by weight of the total, or even less than or equal to 0.0175% by weight of the total.
• the iron content is less than or equal to 0.03% by weight of the total, in particular less than or equal to 0.025% by weight of the total, or even less than or equal to 0.020% by weight of the total.
• the nitrogen content is less than or equal to 0.02% by weight of the total, in particular less than or equal to 0.015% by weight of the total, or even less than or equal to 0.0075% by weight of the total.
• the hydrogen content is less than or equal to 0.01% by weight of the total, in particular less than or equal to 0.0035% by weight of the total, or even less than or equal to 0.0005% by weight of the total.
• the silicon content is less than or equal to 0.01% by weight of the total.
• the nickel content is less than or equal to 0.01% by weight of the total, in particular less than or equal to 0.16% by weight of the total.
• the content of ductile material, such as copper, in the alloy is less than or equal to 0.01% by weight of the total, in particular less than or equal to 0.005% by weight of the total.
• the aluminum content is less than or equal to 0.01% by weight of the total.
• the Nb-Ti core of the blank in step a) is coated with a layer of niobium.
• the addition of the niobium layer around the core can be achieved galvanically, by PVD, CVD or mechanically. In the latter case, a niobium tube is fitted to a bar of the Nb-Ti alloy. The assembly is deformed by hammering, stretching and / or wire drawing to thin the bar and form the blank which was made available in step a).
• the thickness of the niobium layer is chosen so that the niobium area / area ratio of the Nb-Ti core for a given wire section is less than 1, preferably less than 0.5, and more preferably between 0.01 and 0.4. For example, the thickness is preferably between 1 and 500 micrometers for a wire having a total diameter of 0.2 to 1 millimeter.
• the niobium layer can be produced by winding a niobium strip around the Nb-Ti core, the niobium strip / Nb-Ti core assembly then being deformed by hammering, stretching and / or wire drawing. to thin the bar and form the blank which was made available at the end of step a).
• the Nb-Ti core of the blank obtained in step b) is coated with a layer of copper during step c) .
• the addition of the copper layer around the core can be achieved galvanically, by PVD, CVD or mechanically. In the latter case, a copper tube is fitted to a bar of the Nb-Ti alloy coated with the niobium layer. The assembly is deformed by hammering, stretching and / or wire drawing to thin the bar and form the blank which was made available at the end of step b).
• the thickness of the copper layer is chosen so that the ratio of copper surface / surface area of the Nb-Ti core covered with the niobium layer for a given wire section is less than 1, preferably less than 0.5 , and more preferably between 0.01 and 0.4.
• the thickness is preferably between 1 and 500 micrometers for a wire having a total diameter of 0.2 to 1 millimeter.
• the copper layer can be produced by winding a copper strip around the Nb-Ti core covered with the niobium layer, the niobium strip / Nb-Ti core assembly then being deformed by hammering. , stretching and / or wire drawing to thin the bar and form the blank which was made available at the end of step b).
• the Nb-Ti core covered with the niobium strip can be introduced into a copper tube, the assembly being hot co-extruded at a temperature of the order of 600 to 900 degrees through a pathway.
• Beta-type quenching consisting of a solution treatment is carried out at least before the subsequent deformation steps.
• This treatment is carried out so that the titanium of the alloy is essentially in the form of a solid solution with the niobium in the beta phase.
• it is carried out for a period of between 5 minutes and 2 hours at a temperature of between 700 ° C and 1000 ° C, under vacuum, followed by cooling under gas.
• this beta quench is a dissolving treatment at 800 ° C. under vacuum for 5 minutes to 1 hour, followed by cooling under gas.
• Deformation step d) is carried out in several sequences.
• deformation is meant a deformation by wire drawing and / or rolling.
• the deformation step comprises at least successively sequences of deformation, preferably cold, by hammering and / or stretching and / or calibration drawing designated by step d1 ).
• Step d1) makes it possible to bring the blank obtained at the end of step c) to a determined diameter called the wire calibration diameter.
• the method further comprises a step h) which consists in removing the copper layer formed in step c), when during step d1), the blank has reached a diameter such that one can still pass said blank at least through a die with a degree of elongation of the blank of about 10% before the first subsequent rolling step d2).
• This step of removing the copper layer is carried out by chemical attack in a solution based on cyanides or acids, for example in a nitric acid bath at a concentration of 53% by mass in water.
• a sequence of rolling operations preferably with a rectangular profile compatible with the entry section of a stepping spindle is then carried out, this sequence forming step d2 ).
• Each sequence of steps d1) and d2) is carried out with a given strain rate between 1 and 5, this strain rate corresponding to the classic formula 2ln (d0 / d), where d0 is the diameter of the last beta hardening, and where d is the diameter of the hardened wire.
• the global accumulation of deformations over the whole of this succession of sequences leads to a total rate of deformation between 1 and 14.
• the niobium layer coating the Nb-Ti core to a thickness between 20 nm and 10 ⁇ m, preferably between 300 nm and 1.5 ⁇ m, more preferably between 400 and 800 nm .
• the laminated wire strip obtained at the end of step d2) is then cut to a length determined during step e) .
• Step f) of slipping to form the spiral spring is followed by step g) of final heat treatment on the spiral spring.
• This final heat treatment is a precipitation treatment of Ti in the alpha phase lasting between 1 and 80 hours, preferably between 5 and 30 hours, at a temperature between 350 and 700 ° C, preferably between 400 and 600. ° C.
• the process can also comprise, between each sequence or between certain sequences of the deformation steps d1) and / or d2), an intermediate heat treatment for precipitation of titanium in the alpha phase for a duration of between 1 hour and 80 minutes. hours at a temperature between 350 ° C and 700 ° C, preferably between 5 hours and 30 hours between 400 ° C and 600 ° C.
• this intermediate treatment is carried out in step d1) between the first wire drawing sequence and the second calibration wire drawing sequence.
• the spiral spring produced according to this process has an elastic limit greater than or equal to 500 MPa, preferably greater than 600 MPa, and more precisely between 500 and 1000 MPa.
• it has a modulus of elasticity less than or equal to 120 GPa, and preferably less than or equal to 100 GPa.
• the spiral spring comprises an Nb-Ti core coated with a layer of niobium, said layer having a thickness between 50 nm and 5 ⁇ m, preferably between 200 nm and 1.5 ⁇ m, more preferably between 800 nm and 1.2 ⁇ m .
• the spiral spring core has a two-phase microstructure comprising niobium in the beta phase and titanium in the alpha phase.
• the spiral spring produced according to the invention has a thermoelastic coefficient, also called CTE, allowing it to guarantee the maintenance of chronometric performance despite the variation in the temperatures of use of a watch incorporating such a spiral spring.
• the method of the invention allows the production, and more particularly the shaping, of a balance spring for a balance in a niobium-titanium type alloy, typically containing 47% by weight of titanium (40-60%).
• This alloy has high mechanical properties, by combining a very high elastic limit, greater than 600 MPa, and a very low modulus of elasticity, of the order of 60 Gpa to 80 GPa. This combination of properties is well suited for a spiral spring.
• such an alloy is paramagnetic.

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• 2019
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