Thin Bearing Ring Surface Hardening for Hoop Stress Cracking
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Solution Overview
Problem
Conventional methods struggle to impart compressive residual stress to the raceway surface of thin bearing rings, making it difficult to suppress cracking caused by hoop stress, as appropriate conditions for surface hardening have not been clarified.
Innovation Solution
A bearing component with a quench-hardened layer formed on either the radially inner or outer surface of a ring-shaped steel member, where the heat treatment temperature and cooling rate are controlled to satisfy a specific relationship, ensuring that the quench-hardened layer is only formed on one surface and not the other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface hardening is performed on a thin bearing ring, then compressive residual stress can be imparted to the raceway surface, but the opposite surface also becomes hardened making it difficult to achieve selective surface hardening
Solution Approach 1:
The invention applies local quality by creating different material properties at different locations of the bearing ring. Specifically, the raceway surface receives compressive residual stress through controlled surface hardening, while the opposite surface maintains its original properties. This is achieved by carefully controlling heating temperature and cooling rate to harden only the targeted surface.
Solution Approach 2:
The invention utilizes parameter changes by adjusting the heating temperature and cooling rate to achieve selective surface hardening. By controlling these parameters within specific ranges, the process enables compressive residual stress to be imparted to one surface while preventing hardening of the opposite surface, thereby resolving the contradiction between achieving sufficient stress and maintaining selective control.
2Reliability
If conventional surface hardening conditions are used on thin bearing rings, then both surfaces become hardened, but this prevents effective suppression of cracking from hoop stress
Solution Approach 1:
The invention changes the processing parameters (heating temperature and cooling rate) to achieve the desired outcome. By controlling the heating temperature to be sufficiently high and the cooling rate to be sufficiently fast, the process selectively hardens only the raceway surface, imparting compressive residual stress that suppresses cracking while avoiding hardening of the opposite surface.
Solution Approach 2:
The invention applies periodic action through the controlled heating and cooling cycles. The rapid heating and cooling process creates thermal gradients that result in compressive residual stress on the raceway surface during specific phases of the cycle, while the opposite surface remains unaffected due to the brief duration and controlled parameters of the treatment.
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
This approach effectively suppresses cracking caused by hoop stress through the application of compressive residual stress, enhancing the durability of the bearing component.
Implementation Method 1
a heat treatment step of performing a heat treatment to locally heat one of the radially inner surface and the radially outer surface to a heat treatment temperature and subsequently cool the one of the radially inner surface and the radially outer surface
Implementation Method 2
The ring-shaped member has a quench-hardened layer in only one of the radially inner surface and the radially outer surface
Implementation Method 3
subsequently cool the one of the radially inner surface and the radially outer surface
Implementation Method 4
it is effective to previously impart compressive residual stress to a raceway surface of the bearing ring
Data Source
AI summary
In one aspect of the present invention, a method for manufacturing a bearing component includes: a preparation step of preparing a ring-shaped member of steel having a radially inner surface, a radially outer surface, and a thickness which is a distance between the radially inner surface and the radially outer surface; and a heat treatment step of performing a heat treatment to locally heat one of the radially inner surface and the radially outer surface to a heat treatment temperature and subsequently cool the one of the radially inner surface and the radially outer surface, the method satisfying S≥930/(0.3477 W2−1.594 W−0.804), where S represents an average temperature increasing rate (unit: ° C./sec) applied when the surface is heated and W represents the thickness (unit: mm).