Bearing Element Carbonitriding Nitrogen Control
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Solution Overview
Problem
Bearing parts face inadequate durability and dimensional stability issues, even when the carbonitriding process is applied, and it can lead to increased secular dimensional changes, affecting the bearing's performance in harsh environments.
Innovation Solution
A bearing part made of steel with specific carbon, silicon, manganese, and chromium content, featuring a surface layer with controlled nitrogen concentration and carbide distribution, combined with a carbonitriding and diffusing process to optimize nitrogen distribution and prevent incompletely quenched structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the carbonitriding process is applied to improve durability, then the rolling fatigue life is improved, but the rate of secular dimensional change increases deteriorating dimensional stability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitrogen concentration in the surface layer (0.03-0.6 mass%) and the carbon concentration (0.8-1.3 mass%), along with specific heat treatment temperatures (850-950°C) and times, to achieve both high durability and dimensional stability. This resolves the contradiction by optimizing the chemical composition parameters within specific ranges.
Solution Approach 2:
The patent implements local quality by creating a nitrogen-rich surface layer with specific nitrogen concentration (0.03-0.6 mass%) that differs from the base material, providing enhanced durability at the surface while maintaining dimensional stability in the core. The surface layer structure is locally optimized with carbides and retained austenite in controlled amounts.
2Strength
If the carbon concentration in the surface layer is increased to enhance static load capacity, then the hardness is improved, but the rate of secular dimensional change increases affecting dimensional stability
Solution Approach 1:
The patent applies parameter changes by controlling the carbon concentration within the range of 0.8-1.3 mass% in the surface layer, along with specific heat treatment parameters (temperature: 850-950°C, time: controlled duration). This optimized parameter combination achieves high hardness and static load capacity while minimizing secular dimensional changes to maintain dimensional stability.
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 ensures high durability and dimensional stability of the bearing part, even in harsh environments, by maintaining an appropriate nitrogen concentration and carbide distribution, thereby enhancing its static load capacity and resistance to foreign matter intrusion.
Implementation Method 1
a carbonitriding process of introducing carbon and nitrogen into a surface layer portion of a bearing part prior to quenching
Implementation Method 2
a process in which a bearing part made of a steel is heated to a temperature range of the A 1 transformation temperature or more in an atmosphere containing ammonia, carbon monoxide, carbon dioxide, and hydrogen, to thereby introduce carbon in a surface layer portion of the bearing part, or introduce nitrogen in the surface layer portion
Implementation Method 3
prior to quenching
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
An outer ring (11), an inner ring (12), and a ball (3) each serving as a bearing part is made of a steel containing 0.95 mass% or more and 1.10 mass% or less of carbon, 0.05 mass% or more and less than 0.3 mass% of silicon, 0.10 mass% or more and 0.50 mass% or less of manganese, and 1.30 mass% or more and 2.00 mass% or less of chromium, with the rest made up of iron and an impurity. A surface layer region (11B, 12B, 13B) defined as a region extending to a depth of not more than 20 µm from an outer ring raceway surface (11A), an inner ring raceway surface (12A), and a ball rolling surface (13A), which are each a surface where the bearing part is in rolling contact with another part, has an average nitrogen concentration of 0.2 mass% or more and 0.7 mass% or less. Five or more carbides with a diameter of 0.5 µm or less are present per 100 µm2 in the surface layer region (11B, 12B, 13B).