Nb-Ti Alloy Spiral Spring for Chronometric Stability
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Solution Overview
Problem
The production 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 maintaining mechanical strength and avoiding local fragility and complexity in composition and manufacturing.
Innovation Solution
A clockwork spiral spring with a two-phase structure is developed using a binary alloy of niobium and titanium, with a specific composition range and a manufacturing process involving coupled deformation-precipitation heat treatment to achieve a microstructure of beta niobium and alpha titanium, ensuring high elastic limit and low modulus of elasticity, and thermal compensation through precise control of the thermoelastic coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high elastic limit is obtained through material improvement, then mechanical strength is improved, but the modulus of elasticity increases which is not desirable
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition (Ti: 45-48%, Nb: balance) and heat treatment parameters (temperature ranges, holding times, cooling rates) to achieve a two-phase microstructure that provides both high elastic limit (>1000 MPa) and low modulus of elasticity (60-80 GPa), resolving the contradiction between strength and stiffness
Solution Approach 2:
The patent uses composite materials by creating a two-phase microstructure consisting of alpha-Ti and beta-Nb phases within the alloy. This composite structure at the microstructural level allows the material to simultaneously exhibit high elastic limit and low modulus of elasticity, as the different phases contribute different mechanical properties that complement each other
2Stability of the object's composition
If thermal compensation is achieved through alloy composition, then chronometric performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent achieves thermal compensation by optimizing the alloy composition parameters (Ti content between 45-48%) and heat treatment parameters (solutioning temperature 700-900°C, aging temperature 400-600°C) to obtain a thermoelastic coefficient close to zero, while keeping the manufacturing process systematic and controllable rather than overly complex
Solution Approach 2:
The patent applies local quality by creating a specific microstructural distribution of alpha-Ti and beta-Nb phases through controlled heat treatment. The local microstructural arrangement and phase distribution are optimized to achieve thermal compensation at the microstructural level, ensuring chronometric performance stability without requiring complex overall system design
3Volume of moving object
If small sections are used to reduce size, then the spring becomes more compact, but mechanical strength and fatigue resistance decrease
Solution Approach 1:
The patent uses parameter changes by optimizing the alloy composition (adding Nb to Ti base) and heat treatment parameters to achieve superior mechanical properties that allow small cross-section dimensions while maintaining high strength and fatigue resistance. The controlled microstructure enables small sections to perform as if they were larger
Solution Approach 2:
The patent employs composite materials at the microstructural level with a two-phase structure of alpha-Ti and beta-Nb. This composite microstructure provides enhanced strength-to-weight ratio and fatigue resistance, enabling the spring to use smaller sections while maintaining or improving mechanical performance and fatigue life
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 results in a spiral spring with an elastic limit greater than 1000 MPa and a modulus of elasticity between 60 GPa and 80 GPa, suitable for maintaining chronometric performance across temperature variations, and facilitates the production of high-quality barrel and hairsprings with improved mechanical properties.
Implementation Method 1
coupled deformation-precipitation heat treatment to achieve a microstructure of beta niobium and alpha titanium
Implementation Method 2
two-phase structure... microstructure of beta niobium and alpha titanium
Implementation Method 3
thermal compensation through precise control of the thermoelastic coefficient... maintaining chronometric performance across temperature variations
Data Source
Figure 1~3
AI summary
A bi-phase spiral watch spring, made of niobium and titanium alloy, and a manufacturing process for this spring, comprising: - preparation of a binary alloy containing niobium and titanium, with: - niobium: 100% balance; - titanium between 45.0% and 48.0% by mass of the total, - traces of components including O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, between 0 and 1600 ppm of the total by mass individually, with a cumulative total of less than 0.3% by mass; - application of alternating deformations to heat treatments to obtain a bi-phase microstructure comprising beta niobium and alpha titanium, with a yield strength greater than 1000 MPa and a modulus of elasticity less than 80 GPa; - drawing to obtain calenderable wire; - calendering or ringing to form a barrel spring, in a treble clef before its first winding, or stretching to form a spiral spring.