Bearing Ring Intermediate Member for Heat-Treatment Roundness Control
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Solution Overview
Problem
Rolling bearings face challenges in maintaining roundness and rotational accuracy due to elliptical deformation from heat treatment and subsequent polishing, leading to increased manufacturing costs and potential torque loss in applications like automobile transmissions.
Innovation Solution
A bearing ring intermediate member with a surface-hardened layer is developed, where the residual stress gradient from the surface to the core is made gentle, and the average residual stress is controlled between 0 to 191 MPa, achieved through specific heat treatment conditions and rapid cooling after quenching, to minimize deformation during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If quenching treatment is performed to achieve high hardness, then the bearing ring gains required hardness, but elliptical deformation occurs reducing roundness
Solution Approach 1:
The patent applies preliminary action by performing a first quenching treatment to achieve high hardness, then performing a second quenching treatment after surface hardening to adjust the structure and reduce residual stress. This preliminary second quenching prepares the bearing ring for subsequent polishing by reducing elliptical deformation, thereby maintaining roundness while preserving the hardness achieved in the first quenching.
2Reliability
If surface hardening treatment by carburizing or carbonitriding is performed to compensate for reduced thickness, then durability is improved, but elliptical deformation increases during subsequent quenching
Solution Approach 1:
The patent performs surface hardening treatment (carburizing or carbonitriding) as a preliminary action before the second quenching treatment. The second quenching is specifically designed to adjust the structure and reduce residual stress generated by the surface hardening, thereby minimizing elliptical deformation while maintaining the improved durability from the surface hardening layer.
Solution Approach 2:
The patent changes the quenching parameters by performing a second quenching treatment with controlled cooling conditions after surface hardening. This parameter change allows adjustment of the microstructure and residual stress distribution, reducing elliptical deformation while preserving the hard surface layer for durability.
3Reliability
If repeated quenching is performed to adjust structure after surface hardening, then durability is maintained, but elliptical deformation is promoted
Solution Approach 1:
The patent optimizes the parameters of the second quenching treatment by controlling the cooling rate and temperature conditions. This parameter optimization allows the second quenching to adjust the microstructure and reduce residual stress without causing excessive elliptical deformation, thereby maintaining durability while improving roundness compared to conventional repeated quenching.
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 results in a bearing ring with high roundness and improved rotational accuracy, reducing the need for excessive polishing and associated costs, while maintaining low residual stress levels, thus enhancing the performance and efficiency of rolling bearings.
Implementation Method 1
a gradient of a residual stress from a surface to a core portion is gentle
Implementation Method 2
after heat treatment in a step for manufacturing a bearing ring
Implementation Method 3
carburizing or carbonitriding is performed to increase the amount of retained austenite on a bearing ring surface
Implementation Method 4
carburizing or carbonitriding is performed to increase the amount of retained austenite on a bearing ring surface
Data Source
AI summary
A method for manufacturing a bearing ring of a rolling bearing includes a series of steps of cutting out an annular member from a material, forming a surface-hardened layer on the annular member, quenching and tempering the annular member, and polishing inner and outer diameter surfaces of the annular member. The method includes, after the quenching, rapidly cooling the ring member such that the ring member has a surface temperature of 50° C. or lower to form a bearing ring intermediate member, and after the tempering, polishing inner and outer diameter surfaces of the bearing ring intermediate member.