NbZr Balance Spring Manufacturing via Ductile Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of balance springs for horological movements faces challenges in achieving high yield strength, ease of manufacture, excellent fatigue strength, stability over time, and temperature compensation, particularly with niobium and zirconium alloys that tend to stick and seize during wire drawing and rolling operations.
Innovation Solution
A method involving the production of a niobium and zirconium alloy blank with controlled impurities, followed by annealing, deformation, and the deposition of a thin ductile material layer to facilitate wire shaping, combined with multiple deformation and heat treatment steps to achieve the desired properties and prevent sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If niobium and zirconium alloys are used for balance springs, then high yield strength and excellent fatigue strength are achieved, but sticking and seizing occurs during wire drawing and rolling operations
Solution Approach 1:
A ductile material layer is deposited on the surface of the NbZr alloy blank to act as an intermediary between the alloy and the drawing/rolling tools. This layer prevents direct contact and sticking between the NbZr alloy and the tooling, enabling wire drawing and rolling operations to proceed without seizing while maintaining the high strength properties of the core NbZr alloy material.
Solution Approach 2:
The invention creates a composite structure consisting of a NbZr alloy core with a ductile material coating layer. This composite structure combines the high strength properties of the NbZr alloy with the ease of deformation and anti-sticking properties of the ductile coating, resolving the contradiction between strength and manufacturability.
2Ease of manufacture
If a thick layer of ductile material is deposited on the NbZr alloy blank, then sticking during deformation is prevented, but clogging issues in the drawplate occur and wire shape control becomes difficult
Solution Approach 1:
The thickness of the ductile material layer is precisely controlled and optimized within specific parameters. By maintaining the layer thickness within the range of 0.01 to 0.4 times the wire cross-sectional area ratio, the invention achieves the optimal balance between preventing sticking during deformation and avoiding clogging in the drawplate, while maintaining proper wire shape control.
3Manufacturing precision
If the ductile material layer is made thinner, then wire shape control is improved, but sticking during deformation may occur
Solution Approach 1:
The invention establishes specific parameter ranges for the ductile material layer thickness (0.01 to 0.4 times the wire cross-sectional area ratio) that simultaneously satisfy both requirements: preventing sticking during deformation while maintaining adequate wire shape control. This optimized parameter range resolves the contradiction between thickness-related benefits and drawbacks.
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
This method enables the efficient manufacturing of balance springs with high yield strength, low modulus of elasticity, and a thermoelastic coefficient close to zero, suitable for horological applications, while minimizing sticking issues during processing.
Implementation Method 1
a step of depositing, on the blank, a layer of a ductile material chosen from the group consisting of copper, nickel, cupronickel, cupro-manganese, gold, silver, nickel-phosphorus Ni—P and nickel-boron Ni—B
Implementation Method 2
a step of annealing and cooling said blank followed by a step of deforming the annealed blank to form a wire
Data Source
AI summary
A method for manufacturing a balance spring intended to equip a balance of a horological movement, including a step of producing a blank made of a Nb—Zr alloy including between 10 and 30 wt % Zr, a step of annealing and cooling the blank, at least one step of deforming the annealed blank in order to form a wire, wherein, before the deformation step, a step of depositing, on the blank, a layer of a ductile material chosen from copper, nickel, cupronickel, cupro-manganese, gold, silver, nickel-phosphorus Ni—P and nickel-boron Ni—B, in order to facilitate the wire shaping operation, the thickness of the ductile material layer deposited being chosen such that the ratio of the area of ductile material to the area of the alloy for a given wire cross-section is less than 1, preferably less than 0.5, and more preferably lies in the range 0.01 to 0.4.