Titanium-Niobium Spiral Spring Microstructure for Thermal Stability
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Solution Overview
Problem
The manufacture of watch springs faces challenges in achieving a high elastic limit, low modulus of elasticity, ease of production, excellent fatigue resistance, and thermal compensation, while balancing mechanical strength and fragility, particularly in the context of niobium-titanium alloys.
Innovation Solution
A method involving a binary titanium-based alloy with a two-phase microstructure comprising niobium and titanium, utilizing a coupled deformation-precipitation heat treatment process to achieve an elastic limit greater than 1000 MPa and a modulus of elasticity between 60 GPa and 80 GPa, with a thermoelastic coefficient close to zero, suitable for chronometric performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the mechanical strength of the alloy is improved, then the elastic limit increases, but the ease of processing deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the titanium content (60-85 mass%) and implementing a specific heat treatment regime (solution treatment at 700-900°C followed by aging at 400-500°C). These parameter adjustments optimize the microstructure to achieve high elastic limit while maintaining processability
Solution Approach 2:
The patent uses a composite material approach by creating a two-phase microstructure (α+β phases) through controlled alloying and heat treatment. This composite microstructure provides both high strength and improved ductility, resolving the contradiction between strength and ease of processing
2Manufacturing precision
If the cross-section is reduced, then the spring performance improves, but the fatigue resistance deteriorates
Solution Approach 1:
The patent changes material parameters by optimizing the alloy composition (60-85 mass% Ti) and heat treatment parameters (solution treatment temperature 700-900°C, aging temperature 400-500°C). These changes enable the production of thin-walled springs with excellent fatigue resistance by controlling the microstructure at the microscopic level
3Strength
If the alloy composition is optimized for strength, then the elastic limit increases, but the thermal compensation capability deteriorates
Solution Approach 1:
The patent simultaneously optimizes multiple parameters: titanium content (60-85 mass%), solution treatment temperature (700-900°C), and aging temperature (400-500°C). This multi-parameter optimization achieves both high elastic limit and thermoelastic coefficient close to zero, resolving the contradiction between strength and thermal compensation
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 method enables the production of watch springs with enhanced mechanical properties and thermal stability, ensuring high elastic limit and low modulus of elasticity, suitable for both mainsprings and hairsprings, maintaining chronometric performance across varying temperatures.
Implementation Method 1
coupled deformation-precipitation heat treatment sequences
Implementation Method 2
heat treatment at 475 °C for 10 minutes
Data Source
Figure 1~3
AI summary
Bi-phase spiral watch spring, made of niobium and titanium alloy, and manufacturing process of this spring, with: - preparation of a binary alloy comprising niobium and titanium, with: - niobium: balance at 100%; - titanium strictly greater than 60.0% and less than or equal to 85% by mass of the total, - traces of components among O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, between 0 and 1600 ppm of the total by mass individually, with cumulative less than 0.3% by mass; - application of alternating deformations to heat treatments to obtain a two-phase microstructure comprising a solid solution of niobium with titanium in the β phase and a solid solution of niobium with titanium in the a phase, the titanium content in the α phase being greater than 10% by volume, with a yield strength greater than 1000 MPa, and a modulus of elasticity less than 80 GPa; - drawing to obtain calenderable wire; - calendering or ring forming to form a barrel spring, in a treble clef before its first winding, or stretching to form a spiral spring.