Precision Machine Tool Bearing Microstructure Stabilization
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Solution Overview
Problem
The precision stability of machine tool bearings is compromised due to metastable microstructures and internal stresses resulting from conventional heat treatment processes, affecting the machining stability of precision tools.
Innovation Solution
A manufacturing method involving cold ring rolling, two liquid quenching, ultrasonic assisted cryo-tempering, stress ageing treatment, and magnetic treatment to stabilize microstructures and reduce internal stresses in bearing bodies, enhancing their precision stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional heat treatment processes are used, then the bearing body can be manufactured, but metastable microstructures and internal stresses are generated that damage precision stability
Solution Approach 1:
The patent applies cryogenic temperature treatment (−196℃ to −120℃) and controlled heating parameters (160℃ to 200℃ for 2-8 hours) to transform the microstructure from metastable to stable state, changing the physical parameters of the bearing body to eliminate retained austenite and stabilize the microstructure
Solution Approach 2:
The patent utilizes phase transition of austenite to martensite through cryogenic treatment, where the retained austenite transforms into stable martensite structure at low temperatures, and subsequent tempering further stabilizes the microstructure by transforming unstable martensite into stable tempered martensite
2Ease of manufacture
If conventional heat treatment processes are used, then the bearing body can be manufactured, but high internal stresses remain that affect precision stability
Solution Approach 1:
The patent applies controlled heating parameters (160℃ to 200℃ for 2-8 hours) during tempering to gradually reduce internal stresses through stress relief, changing the thermal parameters to allow stress relaxation without causing distortion or excessive hardening
Solution Approach 2:
The patent performs cryogenic treatment before final tempering to pre-stabilize the microstructure and reduce internal stresses in advance, preparing the bearing body for subsequent precision machining and assembly operations
3Stability of the object's composition
If multiple treatment steps are applied to stabilize microstructure and reduce stress, then precision stability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent combines cryogenic treatment, tempering, and stress relief operations into an integrated heat treatment process sequence, where multiple functions are achieved through a coordinated series of heating and cooling steps rather than separate independent operations
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 method significantly improves the thermal and mechanical stability of retained austenite, reduces internal stresses, and enhances the wear resistance of bearings, resulting in improved precision stability and machining performance.
Implementation Method 1
The bearing body is heated up to 820-840° C. in a protective atmosphere (such as nitrogen or argon) and held for 30-60 min. The quenched bearing body is obtained by oil quenched at 60-70° C. for 3-5 min, and then immersed in liquid nitrogen freezer at −190° C. for 4-10 min
Implementation Method 2
During the low temperature holding, the liquid nitrogen is vibrated by ultrasonic under vortex flow pressure of 2.5-3.5 MPa for 20-40 min
Implementation Method 3
After ultrasonic assisted multiple cryo-tempering treatment, stress ageing treatment is applied using a temperature and stress coupling loaded bearing body aging device
Implementation Method 4
Microstructure stabilized bearing body can be obtained by implementing stress ageing treatment with loading force ranged from 60-150N and aging temperature ranged from 80-150° C. for 3-6 hours
Data Source
AI summary
A manufacturing method of precision machine tool bearing with high precision stability includes the procedures: (1) microstructural stabilization of bearing body: by cold ring rolling, two liquid quenching, ultrasonic assisted multiple cryo-tempering treatment and stress ageing treatment, the bearing body with high microstructure stability can be obtained; (2) precision machining; (3) internal stress relaxation of bearing body: after precision machining, by executing magnetic treatment on the bearing body, bearing ring with high microstructure stability and low internal stresses can be obtained; and (4) bearing assembly: finally precision machine tool bearing with high precision stability can be obtained. Considering that the critical factors affecting the precision stability of bearing is the degree of microstructure stability and internal stresses, by improving the microstructure stability and reducing residual stress in multistage manufacture phase, precision stability of precision machine tool bearing should be promoted.