Hydrogen-Enriched Nb-Ti Hairspring for Thermal Stability
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Solution Overview
Problem
Existing watchmaking spiral springs made from binary NB-Ti alloys face challenges in maintaining low secondary error and thermal coefficient while ensuring chronometric performance across varying temperatures.
Innovation Solution
A spiral spring manufactured from a niobium, titanium, and hydrogen alloy, where hydrogen is added through thermochemical treatment under controlled atmosphere, resulting in a microstructure with a single beta phase and hydrogen mainly in the form of interstitials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If binary Nb-Ti alloy is used to achieve low thermal coefficient, then thermal coefficient is improved, but secondary error worsens
Solution Approach 1:
The patent uses a composite microstructure consisting of two distinct phases: a beta phase matrix and alpha phase precipitates. This composite structure allows the material to simultaneously achieve low thermal coefficient (through the beta phase) and low secondary error (through the alpha phase precipitates), resolving the contradiction between these two performance parameters.
Solution Approach 2:
The invention introduces localized alpha phase precipitates within the beta phase matrix. These precipitates are distributed specifically within the alloy structure to correct the secondary error, while the overall beta phase structure maintains the low thermal coefficient. This local modification approach allows independent optimization of different performance characteristics.
2Manufacturing precision
If binary Nb-Ti alloy is used to achieve low secondary error, then secondary error is improved, but thermal coefficient worsens
Solution Approach 1:
The patent employs a composite microstructure with beta phase matrix and alpha phase precipitates. The beta phase provides low thermal coefficient while the alpha phase precipitates provide low secondary error, achieving both performance targets simultaneously through material composition design.
Solution Approach 2:
The invention changes the microstructural parameters of the alloy by controlling the size, distribution, and volume fraction of alpha phase precipitates within the beta phase matrix. By adjusting these microstructural parameters through heat treatment and alloy composition, both thermal coefficient and secondary error are optimized to acceptable ranges.
3Temperature
If alloy composition is optimized for low thermal coefficient, then thermal coefficient is improved, but breaking load worsens
Solution Approach 1:
The patent creates a composite microstructure where alpha phase precipitates are distributed within the beta phase matrix. This composite structure simultaneously achieves low thermal coefficient and high breaking load, as the alpha phase precipitates act as reinforcement that strengthens the material while the beta phase maintains the desired thermal properties.
Solution Approach 2:
The invention introduces localized alpha phase precipitates that provide strengthening effect in specific regions of the alloy. These precipitates are strategically distributed to enhance breaking load without significantly affecting the overall thermal coefficient, which is primarily determined by the beta phase matrix composition.
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 solution achieves a secondary error close to zero and a thermal coefficient close to zero, while maintaining a high charge at rupture (RM) and elasticity module, thereby enhancing the chronometric performance and stability of the spiral spring across temperature variations.
Implementation Method 1
hydrogen is added to the Nb-Ti alloy by thermochemical treatment under a controlled atmosphere during the manufacturing process
Implementation Method 2
The spiral spring thus produced contains hydrogen mainly or exclusively in the form of interstitials
Data Source
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AI summary
The present invention relates to a balance spring for use in a clockwork movement, characterized in that the balance spring is made of an alloy consisting of: - Nb, Ti, H, and possible traces of other elements selected from O, C, Fe, N, Ni, Si, Cu, and Al, with the following weight percentages: - a Ti content between 1 and 80%, - an H content between 0.17 and 2%, - a total content for all other elements less than or equal to 0.3% by weight, - the remaining 100% being Nb. The present invention also relates to its manufacturing process, comprising a thermochemical treatment step of a blank made of an Nb-Ti alloy in an atmosphere containing hydrogen, so as to enrich the Nb-Ti alloy with hydrogen in the form of interstitials.