Thin Bearing Ring Heat Treatment for Hoop-Stress Crack Suppression
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Solution Overview
Problem
Conventional methods fail to effectively impart compressive residual stress to the raceway surface of thin bearing rings, making them susceptible to cracking from hoop stress due to inadequate surface hardening conditions.
Innovation Solution
A method involving a ring-shaped steel member with a quench-hardened layer on either the radially inner or outer surface, where the heat treatment temperature and cooling rate are controlled to satisfy specific conditions, ensuring the quench-hardened layer forms only on one surface and not the other, thereby inducing compressive residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface hardening is performed on a thin bearing ring, then compressive residual stress can be imparted to suppress cracking, but both surfaces are easily hardened making it difficult to harden only one surface
Solution Approach 1:
The invention applies local quality by creating different thermal conditions on opposite surfaces of the bearing ring. The raceway surface receives intensive induction heating to achieve austenitization and subsequent quenching for hardening, while the opposite surface is shielded or cooled to prevent hardening. This selective local treatment imparts compressive residual stress at the raceway without hardening the opposite surface, resolving the contradiction between achieving crack suppression and maintaining manufacturing precision.
Solution Approach 2:
The invention utilizes parameter changes by controlling the heating temperature, heating time, and cooling rate to achieve differential hardening. By adjusting these parameters, the raceway surface reaches austenitization temperature for quench hardening while the opposite surface remains below the transformation temperature. This parameter control enables selective single-surface hardening, simultaneously achieving crack suppression through compressive stress and precise manufacturing control.
2Strength
If conventional heat treatment is applied to thin bearing rings, then both surfaces are hardened, but this prevents imparting compressive residual stress to the raceway surface
Solution Approach 1:
The invention applies local quality by creating different thermal conditions on opposite surfaces of the bearing ring. The raceway surface receives intensive induction heating to achieve austenitization and subsequent quenching for hardening, while the opposite surface is shielded or cooled to prevent hardening. This selective local treatment imparts compressive residual stress at the raceway without hardening the opposite surface, resolving the contradiction between achieving crack suppression and maintaining manufacturing precision.
Solution Approach 2:
The invention utilizes parameter changes by controlling the heating temperature, heating time, and cooling rate to achieve differential hardening. By adjusting these parameters, the raceway surface reaches austenitization temperature for quench hardening while the opposite surface remains below the transformation temperature. This parameter control enables selective single-surface hardening, simultaneously achieving crack suppression through compressive stress and precise manufacturing control.
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 by creating a compressive residual stress on the bearing component, enhancing its structural integrity.
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
quenching and tempering
Implementation Method 3
austenitizing only a surface layer of the raceway
Implementation Method 4
quench-hardened layer
Data Source
Figure 1~2
Figure 3
Figure 4
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 (1) having a radially inner surface (12), a radially outer surface (11), and a thickness which is a distance between the radially inner surface and the radially outer surface (S10); 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 (S20), the method satisfying S ≥ 930/(0.3477W2 - 1.594W - 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).