Method of manufacturing balance spring of timepiece movement

Abstract

A method for manufacturing a balance spring intended to equip a balance of a horological movement, including a step of producing a blank made of a Nb-Zr alloy including between 10 and 30 wt % Zr, a step of annealing and cooling the blank, at least one step of deforming the annealed blank in order to form a wire, wherein, before the deformation step, a step of depositing, on the blank, a layer of aductile material chosen from copper, nickel, cupronickel, cupro-manganese, gold, silver, nickel-phosphorus Ni-P and nickel-boron Ni-B, in order to facilitate the wire shaping operation, the thicknessof the ductile material layer deposited being chosen such that the ratio of the area of ductile material to the area of the alloy for a given wire cross-section is less than 1, preferably less than 0.5, and more preferably lies in the range 0.01 to 0.4.

Description

technical field [0001] The invention relates to a method of manufacturing a balance spring to be fitted to a balance wheel of a timepiece movement. Background technique [0002] The manufacture of balance springs for timepieces is subject to constraints that often seem incompatible at first glance: [0003] - need to obtain high yield strength, [0004] - ease of manufacture, especially drawing and rolling operations, [0005] - excellent fatigue strength, [0006] - performance level stability over time, [0007] -Small cross section. [0008] The manufacture of the hairspring also focuses on temperature compensation to ensure a consistent level of timekeeping performance. This requires obtaining a thermoelastic coefficient close to 0. Hairsprings with limited sensitivity to magnetic fields were also pursued. [0009] Hairsprings have been developed using niobium and zirconium alloys. However, these alloys cause problems related to sticking and seizure in the drawin...

AI Technical Summary

Problems solved by technology

However, these alloys cause problems related to sticking and seizure in the drawing or wire drawing die (diamond or hard metal) and on the roll (hard metal or steel), so that it is almost impossible to use standard methods such as for steel. They transform into filaments