Patent ID: 11137721

Abstract:
A balance spring for a balance with a blank containing: niobium: the remainder to 100 wt %, titanium: between 40 and 60 wt %, traces of elements selected from the group formed of O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, between 0 and 1600 ppm by weight individually, and less than 0.3 wt % combined, a step of β-quenching the blank with a given diameter, such that the titanium of the alloy is essentially in solid solution form with β-phase niobium, the α-phase titanium content being less than or equal to 5% by volume, at least one deformation step of the alloy alternated with at least one heat treatment step such that the niobium and titanium alloy obtained has an elastic limit higher than or equal to 600 MPa and a modulus of elasticity lower than or equal to 100 GPa, a winding step to form the balance spring being performed prior to the final heat treatment step, prior to the deformation step, a step of depositing, on the alloy blank, a surface layer of a ductile material such as copper, the surface layer of ductile material being retained on the balance spring, the thermoelastic coefficient of the niobium and titanium alloy being adapted accordingly.