Ferritic Stainless Steel Watch Component Nitrogen Absorption
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Solution Overview
Problem
The existing nitrogen absorption treatment for ferritic stainless steel used in watch components results in non-uniform nitrogen transfer and diffusion rates, leading to prolonged treatment times required to achieve the necessary hardness and corrosion resistance for watch housings.
Innovation Solution
A ferritic stainless steel composition with specific mass percentages of Cr, Mo, Nb, Cu, Ni, Mn, Si, P, S, N, and C is used, along with a nitrogen absorption treatment process involving a controlled atmosphere and temperature to form a uniform austenized surface layer, reducing treatment time and enhancing corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitrogen absorption treatment is performed on conventional ferritic stainless steel to obtain required hardness and corrosion resistance, then the surface layer becomes austenized, but the treatment time becomes excessively long due to non-uniform nitrogen transfer rate
Solution Approach 1:
The invention changes the chemical composition parameters of the ferritic stainless steel base material by adding specific amounts of alloying elements (Ni: 0.01-1.00%, Cr: 0.01-5.00%, Mn: 0.01-2.00%, Mo: 0.01-1.00%, Ti: 0.01-0.50%, Nb: 0.01-0.50%). These parameter changes enhance the nitrogen transfer rate uniformly across the surface, allowing the austenized layer to form within a practical treatment time (3.7-4.7 hours) while achieving the required corrosion resistance and hardness
Solution Approach 2:
The invention creates a localized austenized phase in the surface layer through nitrogen absorption treatment. The alloying elements concentrate in the surface region during treatment, creating a localized zone with enhanced properties (higher nitrogen content, austenitic structure) that provides improved corrosion resistance and hardness, while the base material retains its ferritic structure
2Reliability
If nitrogen absorption treatment time is extended to achieve uniform austenized phase throughout the surface layer, then corrosion resistance is improved, but productivity decreases due to prolonged treatment time
Solution Approach 1:
By modifying the base material composition with specific alloying elements, the invention accelerates the nitrogen diffusion rate and transfer efficiency. This parameter change allows the treatment to be completed in 3.7-4.7 hours, significantly reducing treatment time compared to conventional materials while still achieving uniform austenitized phase formation and the required corrosion resistance level, thus improving productivity without sacrificing reliability
3Strength
If the nitrogen absorption treatment is performed to achieve required hardness in the austenized layer, then surface properties are improved, but the treatment process becomes complex and time-consuming
Solution Approach 1:
The invention simplifies the treatment process by pre-modifying the base material composition with alloying elements that facilitate uniform nitrogen absorption. This eliminates the need for complex multi-stage treatments or extended single-stage processes. The treatment is performed as a straightforward nitrogen absorption process at 900-1100°C for 3.7-4.7 hours, achieving the required hardness (350-450 HV) without excessive process complexity
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 enables the formation of a uniformly austenized surface layer with improved corrosion resistance and hardness, significantly reducing treatment time from 10-12 hours to 3.7-4.7 hours, while maintaining aesthetic and workability standards.
Implementation Method 1
In an austenization treatment using nitrogen gas, i.e., in a nitrogen absorption treatment, nitrogen enters the ferrite phase from the surface layer of the treatment target material
Implementation Method 2
the portion where the nitrogen concentration is greater than or equal to a prescribed nitrogen concentration changes to the austenized phase
Implementation Method 3
the transfer rate of nitrogen into the ferrite phase is not uniform, and varies from place to place
Data Source
AI summary
A watch component includes a metal material obtained by performing a nitrogen absorption treatment on a base material, the base material being a ferritic stainless steel that contains, by mass %, 18 to 22% of Cr, 1.3 to 2.8% of Mo, 0.05 to 0.50% of Nb, less than 0.5% of Ni, less than 0.8% of Mn, less than 0.5% of Si, less than 0.10% of P, less than 0.05% of S, less than 0.05% of N, and less than 0.05% of C, with a remainder thereof being composed of Fe and an unavoidable impurity.