Fe-Mn Alloy for Timepiece Hairsprings with Low Magnetic Susceptibility
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Solution Overview
Problem
Precision timekeeping devices are exposed to stronger magnetic fields due to increased use of magnets in electronic devices, necessitating components with low magnetic susceptibility and high impact resistance, while existing materials like glass and silicon are brittle.
Innovation Solution
An Fe—Mn alloy with specific compositions and crystal structures, including γ-Fe and β-Mn phases, is produced through hot and cold working, followed by hardening heat treatment to achieve low magnetic susceptibility and excellent workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ferromagnetic alloys (iron and cobalt based) are used for hairsprings, then excellent workability and toughness are achieved, but magnetic susceptibility increases making the component sensitive to magnetic fields
Solution Approach 1:
The invention changes the compositional parameters by incorporating specific amounts of manganese (10-30 wt%), chromium (4-10 wt%), nickel (5-15 wt%), and titanium (0.1-2 wt%) into the iron-based alloy. These parameter changes transform the magnetic properties from ferromagnetic to antiferromagnetic while preserving the base iron matrix that provides good workability and toughness.
Solution Approach 2:
The invention creates a composite alloy system where multiple elements (Fe-Mn-Cr-Ni-Ti) are combined to achieve synergistic effects. The manganese and chromium form antiferromagnetic phases that reduce overall magnetic susceptibility, while the iron base and nickel maintain workability and mechanical properties, resulting in a composite material with balanced properties.
2Object-affected harmful factors
If non-metallic materials (glass and silicon) are used for hairsprings, then magnetic susceptibility is reduced, but impact resistance deteriorates due to brittleness
Solution Approach 1:
The invention changes the material class from non-metallic to metallic by developing an iron-based alloy with specific compositional parameters. The controlled addition of manganese (10-30 wt%) and other alloying elements creates an antiferromagnetic metallic structure that provides both low magnetic susceptibility and high impact resistance through the ductile nature of the iron matrix.
Solution Approach 2:
The invention replaces fragile, expensive non-metallic materials (glass and silicon) with a more durable, cost-effective metallic alloy system. The Fe-Mn-Cr-Ni-Ti alloy provides comparable or superior performance in terms of impact resistance and durability while maintaining the desired low magnetic susceptibility property.
3Object-affected harmful factors
If high manganese content (10-30 wt%) is added to achieve antiferromagnetic properties, then magnetic susceptibility decreases, but alloy complexity and manufacturing difficulty increase
Solution Approach 1:
The invention establishes specific parameter ranges for each alloying element to achieve antiferromagnetic properties: manganese (10-30 wt%), chromium (4-10 wt%), nickel (5-15 wt%), and titanium (0.1-2 wt%). These defined parameters provide a clear manufacturing guideline that balances magnetic performance with production feasibility, avoiding excessive complexity while achieving the desired low magnetic susceptibility.
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 Fe—Mn alloy exhibits low magnetic susceptibility and excellent workability, making it suitable for hairsprings in timepieces, with a method that ensures the alloy's properties are maintained throughout the production process.
Implementation Method 1
As a crystal structure, the Fe—Mn alloy has a γ-Fe phase or a β-Mn phase, and the sum of the area fractions of the γ-Fe and β-Mn phases is 50% or more
Implementation Method 2
A method for producing an Fe—Mn alloy includes a hot working step to obtain a hot-worked product by hot-working an ingot, a cold working step to obtain a cold-worked product by cold-working the hot-worked product
Implementation Method 3
a hardening heat treatment step to obtain an Fe—Mn alloy by subjecting the cold-worked product to hardening heat treatment
Data Source
AI summary
An Fe—Mn alloy includes, by mass, more than 30.0% but not more than 35.0% manganese (Mn), 1.0% to 8.0% aluminum (Al), 0.5% to 1.5% carbon (C), 5.0% to 10.0% chromium (Cr), and 2.5% to 5.0% nickel (Ni) in terms of composition, the remainder being iron (Fe). As a crystal structure, the Fe—Mn alloy has a γ-Fe phase or a β-Mn phase. The sum of the area fractions of the γ-Fe and β-Mn phases being 50% or more.