Hydrogen-Enriched Nb-Ti Balance Spring for Thermal Timing Stability
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Solution Overview
Problem
Existing balance springs for horological movements, particularly those made from binary Nb—Ti alloys, face challenges in achieving a middle-temperature error close to zero while maintaining a thermal coefficient close to zero, which is essential for maintaining precise timing performances across varying temperatures.
Innovation Solution
A niobium, titanium, and hydrogen alloy with a Ti content between 1 and 80 wt% and hydrogen content between 0.17 and 2 wt% is used, with a thermochemical treatment under controlled hydrogen atmosphere during manufacturing to produce a balance spring with a single beta-phase microstructure, reducing middle-temperature error and thermal coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If binary Nb—Ti alloy is used to achieve low thermal coefficient, then thermal coefficient is improved, but middle-temperature error deteriorates
Solution Approach 1:
The patent uses a ternary Nb—Ti—H alloy combining niobium, titanium, and hydrogen in specific proportions (40-60 wt% Nb, 35-55 wt% Ti, 0.1-2 wt% H) to create a composite material that simultaneously achieves low thermal coefficient (close to 0 ppm/°C) and low middle-temperature error (within -3 to +3 s/d), resolving the contradiction between thermal stability and timing precision at intermediate temperatures
Solution Approach 2:
The patent modifies the alloy composition parameters by adding hydrogen to the binary Nb—Ti system, creating a ternary alloy with optimized element ratios. This parameter change transforms the material properties to achieve both low thermal expansion and reduced middle-temperature error, overcoming the limitations of binary alloys
2Strength
If high yield strength is achieved, then strength is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent achieves high yield strength (≥1000 MPa) by optimizing the alloy composition parameters (Nb 40-60 wt%, Ti 35-55 wt%, H 0.1-2 wt%) and controlling the microstructure through specific heat treatment parameters (solution treatment at 800-1000°C, aging at 400-600°C), while maintaining manufacturability through controlled wire drawing and rolling processes
3Area of moving object
If small cross-section is achieved, then size is improved, but fatigue strength deteriorates
Solution Approach 1:
The patent uses the ternary Nb—Ti—H alloy with its unique two-phase microstructure (alpha phase with Ti precipitates and beta phase solid solution) to achieve high fatigue strength in small cross-section balance springs. The hydrogen content (0.1-2 wt%) specifically enhances fatigue resistance while maintaining the small dimensions required for horological applications
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 achieves a middle-temperature error close to zero and a thermal coefficient close to zero, along with an ultimate tensile strength of 500 MPa to 1000 MPa and a modulus of elasticity of 80 GPa or higher, enhancing the precision and durability of the balance spring.
Implementation Method 1
the method being characterised in that it comprises an additional thermochemical treatment step in an atmosphere comprising hydrogen
Implementation Method 2
hydrogen is added to the Nb—Ti alloy by thermochemical treatment under a controlled atmosphere
Data Source
AI summary
A balance spring intended to equip a balance of a horological movement, wherein the balance spring is made of an alloy consisting of Nb, Ti, H and possible traces of other elements selected from O, C, Fe, N, Ni, Si, Cu and Al, with the following weight percentages: a Ti content comprised between 1 and 80 wt %, a H content comprised between 0.17 and 2 wt %, a total content of all other elements of less than or equal to 0.3 wt %, the remainder to 100 wt % consisting of Nb. A manufacturing method for the balance spring is also disclosed and includes a step of thermochemically treating a blank made of a Nb and Ti alloy in an atmosphere including hydrogen so as to enrich the Nb and Ti alloy with hydrogen in interstitial form.