Partial Carbonitriding Stainless Steel Ferrule
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing partial heat treatment methods for stainless steel ferrules result in uneven hardness distribution, leading to increased rotational torque and compromised corrosion resistance, particularly when high hardness is required only on specific portions, and traditional carbonitriding processes use harmful cyanide compounds.
Innovation Solution
A partially carbonitriding heat treatment process using a molten salt solution with a nitrogen-based organic compound like uric acid, which decomposes at low temperatures to supply nitrogen and carbon, creating a multilayer structure with a nitrogen-rich surface layer and a carbon-rich deeper layer, preventing chromium precipitation and maintaining corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional carbonitriding heat treatment is applied to the entire ferrule surface, then hardness is improved, but corrosion resistance deteriorates due to chromium precipitation
Solution Approach 1:
The patent applies carbonitriding heat treatment only to specific portions of the ferrule surface that require high hardness (such as the swaging surface), while leaving other portions untreated to maintain corrosion resistance. This selective heat treatment creates local quality differentiation where different regions of the ferrule have different surface properties optimized for their specific functional requirements.
2Strength
If partial heat treatment is applied to achieve selective hardening, then hardness distribution becomes uneven, but rotational torque increases
Solution Approach 1:
The patent carefully controls the extent and location of heat treatment to achieve uniform enough hardness distribution that prevents excessive rotational torque, while still providing sufficient hardness in critical areas. The heat treatment parameters and duration are optimized to balance local hardening needs with overall rotational performance.
3Ease of manufacture
If traditional cyanide-based carbonitriding is used, then carbonitriding effect is achieved, but harmful factors increase due to cyanide toxicity
Solution Approach 1:
The patent replaces harmful cyanide-based carbonitriding reagents with safer alternative materials that achieve the same carbonitriding effect without cyanide toxicity. This substitution eliminates the harmful factors while maintaining the manufacturing process effectiveness, turning a harmful traditional method into a safe modern process.
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 process achieves selective hardening of specific ferrule portions with enhanced corrosion resistance and reduced manufacturing costs, preventing rotational torque increase and maintaining the ferrule's strength and corrosion resistance.
Implementation Method 1
A partially carbonitriding heat treatment process using a molten salt solution with a nitrogen-based organic compound like uric acid, which decomposes at low temperatures to supply nitrogen and carbon
Implementation Method 2
causes the chemical component of a base metal to change to achieve surface hardening. In a typical chemical surface hardening method, heat treatment is performed by bringing a workpiece into contact with a gas or molten salt solution for carburizing or nitriding at high temperature to thus diffuse the carbon or nitrogen atoms to the surface of the workpiece
Implementation Method 3
heat treatment is performed by bringing a workpiece into contact with a gas or molten salt solution for carburizing or nitriding at high temperature
Implementation Method 4
A partially carbonitriding heat treatment process using a molten salt solution with a nitrogen-based organic compound
Implementation Method 5
creating a multilayer structure with a nitrogen-rich surface layer and a carbon-rich deeper layer, preventing chromium precipitation and maintaining corrosion resistance
Data Source
AI summary
This invention relates to a partially carbonitriding heat treated stainless steel ferrule, having a first region with a first hardness and a second region with a second hardness, wherein the first region includes a nitrogen layer having a nitrogen concentration higher than a carbon concentration, and a carbon layer formed under the nitrogen layer and having a carbon concentration higher than a nitrogen concentration, so that the first hardness is greater than the second hardness. Thereby, partial heat treatment is effective at preventing rotational torque of the region, except for the portion to be heat treated, from increasing due to the total hardening.