Bearing Ring Hardness Gradient for Roller Fatigue Life
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Solution Overview
Problem
Current techniques for improving the rolling fatigue life of roller bearings, such as carbonitriding, are costly and do not adequately address the high-load regions and rib breakage issues in roller bearings, leading to reduced lifespan.
Innovation Solution
A bearing ring design featuring an inner layer of tempered martensite or sorbite with a Vickers hardness of 450-550 HV and a surface layer with a raceway having varying compressive residual stress and hardness, including a high-hardness region for increased fatigue resistance and a rib with specific hardness to prevent breakage, manufactured using a heat treatment process that differentiates surface and internal temperatures for optimal hardness distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbonitriding heat treatment is used to increase surface hardness, then rolling fatigue life is improved, but manufacturing cost increases due to long treatment time
Solution Approach 1:
The patent applies different heat treatment conditions to different regions of the bearing ring. The raceway surface receives high-temperature treatment to achieve hardness of 700-800 HV for fatigue resistance, while the rib and other non-contact areas receive lower temperature treatment to maintain toughness and prevent breakage. This localized quality approach optimizes both fatigue life and manufacturing efficiency without requiring uniform expensive treatment throughout the entire component.
Solution Approach 2:
The patent applies heat treatment selectively only to the raceway surface and critical load-bearing areas rather than the entire bearing ring. By limiting the high-temperature treatment to the specific region where hardness is most needed (the raceway), the treatment time and energy consumption are reduced, thereby lowering manufacturing cost while still achieving the required rolling fatigue life improvement.
2Reliability
If uniform high hardness is applied throughout the bearing ring, then fatigue resistance is improved, but rib breakage occurs due to excessive brittleness
Solution Approach 1:
The patent creates a non-uniform hardness distribution where the raceway surface achieves high hardness (700-800 HV) for fatigue resistance, while the rib maintains lower hardness (50-60 HRC) to preserve toughness and prevent breakage. This spatial variation in material properties resolves the contradiction between fatigue resistance and rib strength by optimizing each region for its specific functional requirements.
Solution Approach 2:
The bearing ring is functionally segmented into different zones with distinct mechanical property requirements. The raceway zone is optimized for hardness and fatigue resistance, while the rib zone is optimized for toughness and impact resistance. This segmentation allows each part to have the appropriate hardness level for its specific role, preventing rib breakage while maintaining fatigue resistance.
3Reliability
If high compressive residual stress is applied to the entire raceway, then rolling fatigue life is improved, but distortion and manufacturing complexity increase
Solution Approach 1:
The patent applies compressive residual stress selectively to the raceway surface through localized heat treatment and cooling, rather than attempting to induce stress throughout the entire bearing ring. This localized stress application achieves the fatigue life improvement goal while minimizing distortion and simplifying the manufacturing process by concentrating the complex heat treatment operation only where needed.
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 significantly enhances the rolling fatigue life, shock resistance, and crushing strength of roller bearings while reducing manufacturing costs by creating a durable and long-lasting bearing ring structure.
Implementation Method 1
a heat treatment process that differentiates surface and internal temperatures for optimal hardness distribution
Implementation Method 2
The inner layer is made of tempered martensite or sorbite. The surface layer is made of tempered martensite
Implementation Method 3
The raceway includes a first raceway whose raceway surface is under a relatively high compressive residual stress, and a second raceway whose raceway surface is under a compressive residual stress lower than the compressive residual stress applied to the raceway surface of the first raceway
Data Source
AI summary
A raceway of a roller bearing includes a first raceway whose raceway surface is under a relatively high compressive residual stress, and a second raceway whose raceway surface is under a compressive residual stress lower than the compressive residual stress applied to the raceway surface of the first raceway. The raceway surface of the second raceway has a Vickers hardness of 700 HV or more but less than 800 HV. The raceway surface of the first raceway includes a portion that is harder than the raceway surface of the second raceway and that is to be in contact with at least one of axial ends of a rolling contact surface of a roller. A rib includes a rib surface having a Vickers hardness of 450 HV or more but less than 550 HV.