Thermocompensated Hairspring via Niobium Alloy Oxidation
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Solution Overview
Problem
Existing methods for manufacturing thermocompensated balance springs are costly and lack sufficient information on deformation and heat treatment steps required to achieve the desired crystallographic structure and properties.
Innovation Solution
A method involving a Niobium-Titanium, Niobium-Zirconium, or Niobium-Hafnium alloy blade, where the process includes oxidation of the surface, shaping by strapping, and a fixing heat treatment, allowing for a spiral spring with a near-zero coefficient of thermal expansion (CTE) to be achieved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple deformation and heat treatment steps are performed to achieve desired crystallographic structure, then Young's Modulus Thermal Coefficient is improved to +/- 10 ppm/°C, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The blade surface is oxidized before shaping and heat treatment operations. This preliminary oxidation creates a surface layer with specific thermal expansion characteristics that will compensate for temperature variations in the final product, eliminating the need for complex post-processing steps to achieve the desired thermal properties
Solution Approach 2:
The invention changes the physical-chemical state of the blade surface through controlled oxidation, creating a surface layer with different thermal expansion properties than the base material. By controlling oxidation depth and conditions, the thermal expansion characteristics can be precisely tuned to achieve near-zero CTE in the final hairspring
2Reliability
If multiple deformation and heat treatment steps are performed to achieve desired crystallographic structure, then thermocompensation properties are improved, but production time and cost increase
Solution Approach 1:
The invention combines multiple functions into the oxidation step: it creates the thermocompensation surface layer, prepares the surface for subsequent shaping operations, and establishes the foundation for achieving the desired crystallographic structure. This merging of functions reduces the total number of discrete manufacturing steps required
Solution Approach 2:
By performing oxidation before shaping and heat treatment, the invention establishes the thermal compensation characteristics early in the manufacturing process. Subsequent operations work with this pre-established surface layer, eliminating the need for additional specialized treatment steps that would otherwise be required to achieve temperature stability
3Manufacturing precision
If oxidation is performed after shaping, then surface treatment is complete, but thermocompensation cannot be optimized
Solution Approach 1:
The blade is oxidized while still in its blank state, before any shaping operations. This allows the oxidation process to penetrate and treat the entire surface area uniformly, and ensures that subsequent shaping operations deform the oxidized layer along with the base material, integrating the thermocompensation properties into the final geometry
Solution Approach 2:
The oxidation creates a surface layer with locally different properties (different thermal expansion characteristics) compared to the bulk material. By controlling the oxidation depth, a gradient structure is created where the surface layer provides thermocompensation while the bulk material provides structural integrity
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 allows for the easy implementation of conventional tools and devices, achieving a spiral spring with a CTE close to zero, which can be varied by modifying the oxidation rate, thus effectively compensating for temperature variations.
Implementation Method 1
carrying out an oxidation of the surface of said blade to a predetermined depth for example by thermal oxidation
Implementation Method 2
step d) is carried out by thermal oxidation, by heating said blade under the following conditions: temperature between 350°C and 700°C
Implementation Method 3
carrying out a fixing heat treatment in order to freeze the shape of said blade that it has taken during the stripping
Data Source
Figure 1a~1c
Figure 2
Figure 3~4
AI summary
Method for manufacturing a spiral spring (1) for a balance-spring oscillator, comprising the steps of: a) obtaining a blade (3) of Niobium-Titanium, Niobium-Zirconium or Niobium-Hafnium alloy having a predetermined height (H) and thickness (E); b) carrying out a slapping of said blade to put said blade into the shape of a spiral; c) carrying out a fixing heat treatment to fix the shape of said blade (3); d) carrying out an oxidation of the surface of said blade (3) to a predetermined depth (P).