Beta Titanium Watch Spring for Magnetic and Torque Stability
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Solution Overview
Problem
Current watch spring materials, such as iron-nickel-based and Cobalt-Nickel-Chromium alloys, face challenges with high sensitivity to magnetic fields, limited miniaturization, and moderate power reserve, leading to torque and natural frequency drifts and reduced energy storage capacity.
Innovation Solution
A metastable β titanium alloy with a specific composition and crystallographic structure, comprising a mixture of austenitic, alpha, and omega phases, is developed, offering super-elastic properties, low Young's modulus, negligible magnetic susceptibility, and stability over temperature variations, along with a manufacturing process that includes work hardening and heat treatment to achieve optimal mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If iron-nickel-based alloys (Elinvar) are used for balance springs, then the alloy provides good elastic properties, but it exhibits high sensitivity to magnetic fields causing torque and natural frequency drift
Solution Approach 1:
The patent changes the material composition parameters by using titanium as the base metal instead of iron-nickel, and adjusts the alloying elements (Nb, Ta, V, Zr, Hf, Si, O) to achieve the desired balance between elastic properties and magnetic field resistance. This fundamental parameter change resolves the contradiction by selecting a different material system that inherently has lower magnetic susceptibility while maintaining the required mechanical properties.
2Stress or pressure
If cobalt-nickel-chromium alloys (Nivaflex) are used for mainsprings, then the alloy provides high elastic modulus, but it results in moderate power reserve and limited energy storage capacity
Solution Approach 1:
The patent changes the base metal parameter from cobalt to titanium, which has a lower density and different elastic properties. By adjusting the alloy composition (particularly the content of Nb, Ta, and other elements) and controlling the phase structure (beta phase with controlled alpha precipitates), the patent achieves an optimal balance between elastic modulus and energy storage capacity, resolving the contradiction between high stiffness and power reserve.
3Ease of manufacture
If standard forming processes are used for titanium-based alloys, then the manufacturing process is straightforward, but the miniaturization process results in decreased mechanical properties, irregularity in part size, or reduced surface finish quality
Solution Approach 1:
The patent changes the material parameters by controlling the phase composition (metastable beta phase with controlled alpha precipitates) and microstructure (grain size, phase distribution) through specific alloying and heat treatment parameters. This makes the titanium alloy more formable during miniaturization while maintaining mechanical properties and surface finish quality, resolving the contradiction between ease of manufacture and manufacturing precision.
4Strength
If the alloy composition is optimized for high elastic limit, then the energy storage capacity increases, but the manufacturing complexity and difficulty of achieving consistent mechanical properties increases
Solution Approach 1:
The patent optimizes the alloy composition parameters (base titanium with controlled amounts of Nb, Ta, V, Zr, Hf, Si, and O) and processing parameters (heat treatment temperature, time, and sequence) to achieve high elastic limit while maintaining manufacturing feasibility. The specific composition ranges and phase structure control provide a balance between performance and manufacturability, resolving the contradiction between strength and manufacturing complexity.
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 metastable β titanium alloy provides a clock spring with constant torque and natural frequency, enhanced energy storage capacity, and resistance to temperature and magnetic field variations, while maintaining mechanical strength and precision suitable for watchmaking applications.
Implementation Method 1
The metastable β-titanium alloy has a crystallographic structure comprising: a mixture of austenitic phase and alpha phase, and the presence of omega phase precipitates
Implementation Method 2
The mainspring is characterized by its elastic potential, which is directly proportional to its elastic limit and modulus of elasticity
Data Source
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AI summary
The invention relates to a metastable β titanium alloy comprising, by weight percent, between 24 and 45% niobium, between 0 and 20% zirconium, between 0 and 10% tantalum and/or between 0 and 1.5% silicon and/or less than 2% oxygen, said alloy being characterized in that it has a crystallographic structure comprising; - a mix of austenitic phase and alpha phase, and - a presence of omega phase precipitates the volume fraction of which is less than 10%. The invention also relates to a timepiece spring made from such an alloy and a method for producing such a spring.