Hairspring Alloy Composition for Temperature Stability
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Solution Overview
Problem
Existing hairspring materials for mechanical timepieces exhibit variations in Young's modulus with temperature changes, affecting the accuracy of timekeeping and requiring adjustments in the balance wheel's moment of inertia.
Innovation Solution
A hairspring material with a specific composition of 37.5 to 39.5% Ni, 9.2 to 9.9% Cr, 0.35 to 0.55% Ti, and 0.6 to 0.9% Be, with limited amounts of unavoidable impurities like C, Mn, and Al, where Ti and C form TiC inclusions less than 5 µm, reducing microcracks and stabilizing Young's modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional hairspring materials with elinvar effect are used, then temperature stability of Young's modulus is improved, but variation in Young's modulus at ordinary temperature increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the alloy, specifically limiting C to 0.003-0.03%, Mn to 0.05-0.5%, and Al to 0.003-0.03%, while setting Ni at 37.5-39.5% and Cr at 9.2-9.9%. This compositional parameter optimization resolves the contradiction by achieving both temperature stability and minimal variation in Young's modulus at ordinary temperature.
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy system combining Fe, Ni, Cr, Ti, Be, with controlled impurities of C, Mn, and Al. This composite alloy structure achieves synergistic effects where the specific combination and ratios of elements provide both temperature compensation (elinvar effect) and consistent mechanical properties at ordinary temperatures.
2Temperature
If alloy composition is optimized for temperature stability, then elinvar effect is improved, but manufacturing precision of hairspring varies
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing narrow compositional ranges for each element. The carbon content is limited to 0.003-0.03%, manganese to 0.05-0.5%, and aluminum to 0.003-0.03%, while nickel is set at 37.5-39.5% and chromium at 9.2-9.9%. These controlled parameters ensure both temperature stability and manufacturing precision by minimizing compositional variations that could lead to property inconsistencies.
3Strength
If cold drawing process is applied to achieve proper strength, then mechanical strength is improved, but die life decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition to include controlled amounts of carbon (0.003-0.03%), manganese (0.05-0.5%), and aluminum (0.003-0.03%), along with nickel (37.5-39.5%) and chromium (9.2-9.9%). This compositional parameter optimization enables the material to achieve proper mechanical strength through cold drawing while reducing die wear, thereby extending die 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 hairspring with minimal variation in Young's modulus (0 to 2.44 GPa), improved mechanical strength, and enhanced temperature stability, reducing the need for frequent adjustments and extending die life during cold drawing.
Implementation Method 1
Ti and C are contained as TiC and the size of TiC is not more than 5 μm
Implementation Method 2
The alloy disclosed in this patent literature 1 is slightly distorted by magnetostriction due to self magnetization, and a change that the interatomic distance is decreased by reduction of magnetization with temperature increase and a change that the interatomic distance is increased by thermal expansion are compensated each other
Implementation Method 3
a change that the interatomic distance is decreased by reduction of magnetization with temperature increase and a change that the interatomic distance is increased by thermal expansion are compensated each other
Data Source
Figure 1
Figure 2~3
AI summary
[Problem] To provide a hairspring material for a mechanical timepiece, a variation in Young's modulus of which can be made smaller than that of conventional ones. [Solution] The hairspring material for a mechanical timepiece of the present invention comprises an alloy which contains 37.5 to 39.5% by mass of Ni, 9.2 to 9.9% by mass of Cr, 0.35 to 0.55% by mass of Ti and 0.6 to 0.9% by mass of Be, based on the total amount of the alloy, and contains a remainder including Fe and unavoidable impurities, said alloy being an alloy containing, as the unavoidable impurities, C (carbon), Mn in an amount of more than 0% by mass but not more than 0.5% by mass and Al in an amount of more than 0% by mass but less than 0.03% by mass, the amount of said C (carbon) being limited to not more than 0.03% by mass.