Watch Movement Pivot Axis With Non-Magnetic Surface Hardening
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Solution Overview
Problem
Existing watch pivot shaft materials, such as martensitic carbon steels, are magnetic, prone to corrosion, and have insufficient hardness for wear resistance, leading to potential disruption of watch operations and limited machinability.
Innovation Solution
A non-magnetic copper alloy pivot shaft with a selectively hardened external surface to a depth of 5-40% of the diameter, achieving a hardness greater than 600 HV, combined with a manufacturing process that includes ion implantation and diffusion treatment to enhance toughness and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If martensitic carbon steel is used for pivot shafts, then hardness and wear resistance are improved, but magnetic sensitivity and corrosion resistance deteriorate
Solution Approach 1:
The invention changes the material composition parameters by using a copper-based alloy with specific element concentrations (Ni: 10-20%, Zn: 5-15%, Mn: 2-10%, Pb: 0.5-5%, S: 0.01-0.5%) to achieve non-magnetic properties while maintaining machinability. This compositional parameter change resolves the contradiction between hardness and magnetic sensitivity.
Solution Approach 2:
The invention creates a composite structure with a copper-based alloy core and a hardened surface layer containing diffused atoms. This composite material approach provides both the non-magnetic properties of the copper alloy core and the high hardness of the surface layer, resolving the contradiction between magnetic sensitivity and hardness.
2Object-affected harmful factors
If austenitic stainless steel is used for pivot shafts, then magnetic sensitivity is improved, but hardness and wear resistance deteriorate
Solution Approach 1:
The invention changes the hardness parameter by creating a hardened surface layer with hardness greater than 600 HV through diffusion treatment, while maintaining the non-magnetic austenitic structure of the core. This resolves the contradiction between magnetic sensitivity and hardness.
Solution Approach 2:
The invention applies local quality by hardening only the external surface layer (depth of 5-40% of diameter) where wear resistance is needed, while the core remains soft and non-magnetic. This localized treatment resolves the contradiction between surface hardness and bulk magnetic properties.
3Strength
If hard layers are deposited on pivot shafts, then hardness is improved, but reliability deteriorates due to delamination risk
Solution Approach 1:
The invention merges the core material and surface layer into a single integrated structure through diffusion treatment, where atoms are diffused into the surface layer of the copper-based alloy. This eliminates the interface between separate layers, removing the delamination risk while maintaining high surface hardness.
Solution Approach 2:
The invention creates a metallurgically bonded composite structure through diffusion, where the hardened surface layer is chemically integrated with the copper-based alloy core. This composite approach provides high hardness without the delamination problems of conventional coatings.
4Object-affected harmful factors
If non-magnetic copper alloy is used for pivot shafts, then magnetic sensitivity is improved, but hardness deteriorates
Solution Approach 1:
The invention applies local quality by maintaining the soft, non-magnetic copper-based alloy core while creating a hardened surface layer through diffusion treatment. The surface layer has hardness greater than 600 HV, while the core remains machinable and non-magnetic, resolving the contradiction between bulk hardness and surface wear resistance.
Solution Approach 2:
The invention changes the local parameters of the surface layer through diffusion treatment, achieving hardness greater than 600 HV in the surface layer while maintaining the non-magnetic properties of the copper-based alloy core. This parameter change resolves the contradiction between magnetic sensitivity and hardness.
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 provides a pivot shaft with low magnetic sensitivity, high hardness, and improved corrosion resistance, maintaining toughness and machinability, thus ensuring reliable watch operation and longevity.
Implementation Method 1
at least the external surface of said at least one pivot is hardened in depth relative to the core of the axis according to a predetermined depth
Implementation Method 2
a manufacturing process that includes ion implantation and diffusion treatment
Data Source
Figure 1~2
AI summary
The invention relates to a pivot axis comprising at least one metal pivot (3) at at least one of its ends. The metal is a non-magnetic copper alloy to limit its sensitivity to magnetic fields, and at least the external surface (5) of one of the two pivots (3) is hardened to a predetermined depth relative to the rest of the axis in order to harden the pivot(s) (3). The invention relates to the field of watch movements.