精密机床轴承套圈冷环轧-热处理协同调控组织稳定性与强韧性技术基础研究

The precision maintenance and reliability of precision machine tool bearing during operating are depend on the microstructures stability and strength-toughness of bearing ring, and further to determine the machining accuracy of spindle system. However, the current research about microstructures stability and strength-toughness of bearing ring was limited to the influence of single heat treatment process, which neglected the microstructures genetic evolution from ring-forming to heat treatment and both collaborative effect. This project proposed a novel pre-thermomechanical treatment, which is based on the integrated manufacturing idea of bearing ring by combining cold ring rolling and heat treatment (martensite pre-quenching + bainite transformation). By using the cold-rolled deformation degree of bearing ring as independent variable, to research the quantitative rule between microstructures evolution and cold-rolled deformation degree, the effect of cold-rolled deformation degree on phase transformation temperature and the mechanism of carbides dissolution from cold ring rolling to heat treatment. Finally, the improvement of microstructures stability and strength-toughness of bearing ring were realized by using novel pre-thermomechanical treatment through multiple strengthening mechanism, such as solution strengthening, grain refinement and refining microstructures. Meanwhile, the microstructures evolution law and technical principle were clarified and to reveal the regulation and control mechanism of microstructures stability and strength-toughness. This study is not only beneficial to provide novel research approach and technology for manufacture precision machine tool bearing, but also provide scientific basis for the breakthrough of key core technology of manufacture precision machine tool bearing.

精密机床轴承服役条件下的精度保持性和可靠性取决于轴承套圈基体组织稳定性和强韧性，并决定了机床主轴系统的加工精度。当前对套圈基体组织稳定性和强韧性的研究局限于单一热处理工艺的影响，忽视了套圈成形-热处理过程中微观组织遗传演变及二者的协同作用。本项目基于轴承套圈冷环轧-热处理一体化制造思路，提出套圈冷环轧成形和热处理(马氏体预淬火+贝氏体相变)相结合的预形变热处理新工艺，以套圈冷轧变形量为自变量，研究套圈冷轧变形量与微观组织演变定量关系规律、对热处理相变温度影响规律以及冷环轧-热处理过程中碳化物溶解机理。进而通过预形变热处理新工艺，耦合固溶强化、细晶强化和组织细化等多种强化机制提高套圈基体组织稳定性与强韧性，阐明预形变热处理微观组织遗传演变规律及工艺原理，揭示其组织稳定性和强韧性调控机理。本项目有望为精密机床轴承制造提供新的研究思路和技术方法，为突破精密机床轴承制造关键核心技术提供科学依据。

本项目以制约我国高档数控机床自主发展的主轴轴承为研究对象，针对影响主轴轴承可靠性和精度保持性的轴承套圈基体组织稳定性和强韧性开展研究，通过冷环轧-热处理相结合实现组织和性能调控。研究成果总结如下：1、以B7008C为原型，结合有限元模拟分析实现套圈轧制成形参数优化及套圈成形制造。以轧制变形量为变量，建立了轧制变形量与金属流线、残余应力、位错密度、织构和碳化物等微观组织演变定量关系规律。2、冷变形明显降低Ms温度和细化奥氏体晶粒，为热处理调控组织和性能提供有利前提。变形量为0%，15%，30%和45%的样品Ms温度分别为232℃、210℃、206℃和198℃，奥氏体晶粒分别为14.5μm、11.7μm、10.3μm和9.2μm。3、冷变形加速热处理过程中球状碳化物溶解并提高传统QT热处理后残余奥氏体稳定性。4、冷变形抑制贝氏体形核和长大，细化贝氏体束内铁素体片间距，与传统QT热处理相比，冲击韧性得到进一步提高。5、冷变形结合马氏体预淬火和贝氏体相变，在保证硬度大于60HRC的前提下，冲击韧性和残余奥氏体稳定性明显提高。项目揭示了轴承套圈冷环轧-热处理过程微观组织遗传演变规律，通过套圈冷环轧成形工艺参数和热处理工艺参数匹配优化，达到了提高组织稳定性和强韧性的研究目的。本项目研究成果发表学术论文5篇，其中SCI论文4篇，1篇中文核心，授权中国发明专利7项，协助其他导师培养博士2人和硕士研究生1人，培养自己名下研究生1人。研究结果为发展精密机床主轴轴承制造技术提供了新的思路和方法，能够为开发其他高端装备用轴承制造技术提供借鉴。