Titanium-Niobium Spiral Spring for High Elastic Limit Timekeeping
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Solution Overview
Problem
The manufacture of energy storage springs for horology faces challenges in achieving a high elastic limit, low modulus of elasticity, ease of manufacture, excellent fatigue resistance, durability, and temperature compensation, particularly in the production of balance springs which require a thermoelastic coefficient close to zero.
Innovation Solution
A spiral timepiece spring with a two-phase structure made from a titanium-based binary alloy containing niobium, where the alloy has a specific composition and undergoes deformation/precipitation heat treatment sequences to achieve a microstructure with a solid solution of β-phase and α-phase titanium, resulting in high elastic limit and low modulus of elasticity, and is processed to form coils suitable for mainsprings or balance springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional materials and methods are used to manufacture energy storage springs, then ease of manufacture is maintained, but the elastic limit is insufficient and the modulus of elasticity is too high
Solution Approach 1:
The patent changes the material parameters by using a titanium-based alloy with specific composition ranges (Ti: 60-85%, Nb: 15-40%) and controlled impurity levels. The deformation/precipitation heat treatment sequences transform the microstructure to achieve the desired combination of high elastic limit (≥1000 MPa) and low modulus of elasticity (60-80 GPa), resolving the contradiction between strength and manufacturability.
Solution Approach 2:
The patent employs a composite material system consisting of a titanium-niobium alloy with a two-phase microstructure (α-phase and β-phase). This composite microstructure, achieved through controlled heat treatment, provides both the high strength required for the elastic limit and the ductility needed for wire drawing, simultaneously addressing both requirements.
2Strength
If the alloy strength is improved, then the elastic limit increases, but the manufacturing complexity increases
Solution Approach 1:
The patent applies periodic deformation and heat treatment sequences during manufacturing. The alternating cycles of plastic deformation followed by precipitation heat treatment create the desired microstructure progressively, building up the high strength properties while keeping each individual step manageable and repeatable.
3Strength
If balance spring materials are optimized for mechanical strength, then the elastic limit improves, but temperature compensation capability deteriorates
Solution Approach 1:
The patent carefully controls the alloy composition parameters (Ti: 60-85%, Nb: 15-40%) and heat treatment parameters to achieve a two-phase microstructure where the α-phase provides temperature compensation (negative thermoelastic coefficient) and the β-phase provides mechanical strength. This parameter optimization simultaneously achieves high elastic limit and near-zero overall thermoelastic coefficient.
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 enables the production of springs with an elastic limit of at least 1000 MPa and a modulus of elasticity between 60 GPa and 80 GPa, ensuring chronometric performance and improved mechanical strength, while the thermoelastic coefficient is adjusted to near zero for temperature compensation.
Implementation Method 1
a two-phase microstructure containing β-phase body-centred cubic niobium and α-phase hexagonal close packed titanium
Implementation Method 2
deformation/precipitation heat treatment sequences
Implementation Method 3
the need to obtain a very high elastic limit
Data Source
AI summary
A spiral timepiece spring with a two-phase structure, made of a niobium and titanium alloy, and method for manufacturing this spring, including: producing a binary alloy containing niobium and titanium, with: niobium: the remainder to 100%; titanium: strictly greater than 60% and less than or equal to 85% by mass of the total, traces of components from among O, H, C, Fe, Ta, N, Ni, Si, Cu, Al; applying deformations alternated with heat treatments until a two-phase microstructure is obtained comprising a solid solution of niobium with β-phase titanium and a solid solution of niobium with α-phase titanium, the α-phase titanium content being greater than 10% by volume, wire drawing to obtain wire able to be calendered; calendering or insertion into a ring to form a mainspring, in a double clef shape before it is wound for the first time, or winding to form a balance spring.