Austenitic Stainless Steel Mainspring for Thin Timepiece Applications
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Solution Overview
Problem
Timepiece springs, particularly mainsprings, face challenges with fatigue resistance and longevity due to sensitivity to corrosion and permanent deformations, and existing high-carbon steel alloys are expensive and difficult to produce in small dimensions required for watchmaking.
Innovation Solution
A stainless steel alloy with a face-centered cubic structure, comprising iron, chromium, manganese, and nitrogen, with a specific composition of chromium (15-25%), manganese (5-25%), nitrogen (0.10-0.90%), and carbon (0.10-1.00%), optimized for improved ductility and reduced nitrogen content to facilitate industrial production of springs with thicknesses less than 0.20 mm and radii of curvature below 2.15 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high carbon steel alloys are used to achieve desired elasticity characteristics, then elasticity is improved, but corrosion resistance deteriorates and fatigue resistance worsens
Solution Approach 1:
The invention changes the chemical composition parameters of the steel alloy by strictly limiting carbon content to maximum 0.10% and nitrogen content to maximum 0.05%, while optimizing chromium (17-25%), manganese (10-20%), and nickel (8-18%) contents. This parameter adjustment resolves the contradiction by achieving the required elasticity through controlled alloying rather than high carbon content, thereby maintaining corrosion and fatigue resistance.
Solution Approach 2:
The invention creates a composite alloy system combining multiple elements (Cr, Mn, Ni, Mo, N) in specific proportions to achieve the desired mechanical properties. The synergistic interaction between these elements provides both elasticity and corrosion/fatigue resistance, resolving the contradiction that exists in conventional high-carbon steels.
2Strength
If nitrogen content is increased to improve mechanical properties, then strength is improved, but ductility deteriorates and the alloy becomes difficult to process
Solution Approach 1:
The invention dramatically reduces nitrogen content from conventional levels (0.75-1.00%) to a maximum of 0.05%, which restores ductility and processability while maintaining mechanical properties through optimized chromium, manganese, and nickel contents. This parameter change resolves the contradiction between strength and ease of manufacture.
3Reliability
If complex production methods are used to achieve desired alloy characteristics, then material performance is improved, but production cost increases
Solution Approach 1:
The invention simplifies production by establishing clear compositional parameters (low C and N, optimized Cr, Mn, Ni) that can be achieved through conventional steelmaking processes without complex treatments. This resolves the contradiction by achieving high material performance through compositional control rather than complex processing.
4Duration of action of moving object
If spring thickness is reduced to less than 0.20 mm to increase power reserve, then power reserve is improved, but manufacturing precision requirements worsen
Solution Approach 1:
The invention changes the material parameters (low carbon and nitrogen content, optimized alloying elements) to improve ductility and reduce brittleness, enabling the manufacture of ultra-thin springs with thickness less than 0.20 mm and small radii of curvature (below 2.15 mm) while maintaining adequate manufacturing precision through controlled deformation behavior.
Data Source
AI summary
A timepiece spring, as a mainspring, made of austenitic stainless steel including a base formed of iron and chromium, thickness of the spring being less than 0.20 mm, and the spring including, by mass: chromium: minimum value 15%, maximum value 25%; manganese: minimum value 5%, maximum value 25%; nitrogen: minimum value 0.40%, maximum value 0.75%; carbon: minimum value 0.10%, maximum value 1.00%; the total (C+N) carbon and nitrogen content between 0.40% and 1.50% by mass; the carbon-to nitrogen ratio (C/N) by mass between 0.125 and 0.550; impurities and additional metals with the exception of iron: minimum value 0%, maximum value 12.0%; iron: the complement to 100%.