Horological Spiral Spring Alloy for Faster Precipitation Control
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Solution Overview
Problem
Current binary Nb-Ti alloys used for watch spiral springs face challenges such as long production times due to titanium precipitation and the formation of fragile martensitic phases, which hinder deformation and increase production costs.
Innovation Solution
A ternary alloy composition replacing part of the titanium with Zr and/or Hf, which accelerates precipitation and reduces production times, while maintaining a favorable thermo-elastic coefficient, comprising niobium, titanium, and additional elements like Zr and Hf, with specific weight percentages to achieve a stable microstructure and reduced secondary error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If binary Nb-Ti alloy is used for spiral spring, then high elastic limit and zero TEC can be achieved, but production time increases significantly due to long precipitation times (8-30 hours)
Solution Approach 1:
The patent changes the chemical composition parameters by introducing Zr and/or Hf elements to replace part of Ti, which fundamentally alters the precipitation kinetics and microstructure formation, enabling faster precipitation (4-8 hours) while maintaining the desired TEC properties
Solution Approach 2:
The patent creates a composite alloy system by combining Nb, Ti, and Zr/Hf elements, where each component contributes specific properties: Nb provides the base structure, Ti contributes to TEC control, and Zr/Hf accelerate precipitation, achieving synergistic effects that resolve the time-performance contradiction
2Reliability
If high percentage of titanium is used in Nb-Ti alloy, then TEC close to zero can be achieved, but fragile martensitic phases form making deformation difficult or impossible
Solution Approach 1:
The patent modifies the alloy composition by introducing Zr and/or Hf elements that change the phase transformation behavior and suppress martensitic phase formation, allowing Ti content to be optimized for TEC control without sacrificing deformability during manufacturing
Solution Approach 2:
The Zr and Hf elements act as intermediary elements that mediate between Ti's TEC-control function and the alloy's deformability requirement, preventing harmful martensitic transformations while preserving the beneficial effects of Ti precipitation
3Device complexity
If binary Nb-Ti alloy is used, then simple composition can be maintained, but precipitation time increases and fragile phases form
Solution Approach 1:
The patent transitions from a binary to a ternary/quaternary alloy system, where the additional Zr and Hf elements provide specific functions (accelerated precipitation, suppressed martensite) that more than compensate for the increased compositional complexity, achieving net productivity improvement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The ternary alloy significantly reduces production times, minimizes secondary errors, and maintains a high elastic limit and zero thermo-elastic coefficient, making it suitable for chronometric performance in watchmaking applications.
Implementation Method 1
the precipitation of the alpha phase which has a strongly negative TEC allows the two-phase alloy to be brought to a TEC close to zero
Implementation Method 2
Ti is partly replaced by Zr and/or Hf which are also able to form alpha phase precipitates
Implementation Method 3
The cold-worked alloy in the beta phase has a strongly positive TEC and the precipitation of the alpha phase which has a strongly negative TEC allows the two-phase alloy to be brought to a TEC close to zero
Implementation Method 4
With an adapted deformation and heat treatment diagram, this spiral spring has a two-phase microstructure including niobium in the beta phase and titanium in the form of precipitates in the alpha phase
Data Source
AI summary
A spiral spring intended to equip a balance of a horological movement, wherein the spiral spring is made of an alloy consisting of Nb, Ti and at least one element selected from Zr and Hf, optionally at least one element selected from W and Mo, possible traces of other elements selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, Al, with the following weight percentages: a content of Nb comprised between 40 and 84%, a total content of Ti, Zr and Hf comprised between 16 and 55%, a content for W and Mo respectively comprised between 0 and 2.5%, a content for each of said elements selected from O, H, Ta, C, Fe, N, Ni, Si, Cu, Al comprised between 0 and 1600 ppm with the sum of said traces less than or equal to 0.3% by weight. The method for manufacturing the spiral spring is also disclosed.