【作者】 张桂香；

【导师】 左敦稳； 赵东标；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2012， 博士

【摘要】 磁力光整加工技术，作为一种先进的光整加工工艺，在航空、航天、机械、仪器、仪表、医疗器械等精密光整加工的许多领域具有广泛的应用前景。在磁力光整加工技术中，磁性磨料起着至关重要的作用，甚至决定着加工零件的表面质量。然而，目前制备的磁性磨料，存在着形状不规则、加工效率低、使用寿命短、工艺复杂、成本高等问题，已经成为磁力光整加工技术亟待解决的瓶颈问题。为此，本文提出一种新的磁性磨料制备方法——雾化快凝磁性磨料制备方法。通过改进气体雾化快速凝固制粉系统，使高压雾化气体与陶瓷硬质磨料粉末预先混合后，再雾化熔融态的铁磁性合金基体液流，然后快速凝固的方法制备球形复合磁性磨料，并将其应用于导磁和非导磁材料的磁力光整加工中。本文的主要研究工作和创新点如下：（1）深入研究金属及其合金粉末气体雾化快速凝固制备系统的结构组成，基于磁性磨料的性能要求，研制雾化快凝球形复合磁性磨料制备系统。该系统能够解决传统陶瓷/铁基合金复合材料体系中陶瓷相与铁基体相很难相容的技术难题，使磁性磨料粉末制备工艺简单，成本低，产量高，可实现规模化工业生产。（2）基于磁性磨料的理想微观形貌和性能要求，对陶瓷/铁基合金复合材料制备工艺、铁磁性合金磁性能和雾化快凝工艺特点进行研究，确定适合该工艺条件下球形复合材料的组成配比；成功制备符合磁性磨料性能要求和理想结构模型的Al2O3/铁基合金球形复合磁性磨料和SiC/铁基合金球形复合磁性磨料。（3）借助扫描电镜、能谱仪和X射线衍射仪，试验研究雾化快凝工艺条件下球形复合磁性磨料的形成机理、影响因素和界面微结构。结果表明，只有对雾化快凝工艺参数、铁基体成分合金化和流体动力学效应影响因素的综合控制，才能制备出符合性能要求的球形复合磁性磨料；其界面微观结构：Al2O3/铁基合金球形复合磁性磨料是机械结合、溶解与润湿结合的混合结合；SiC/铁基合金球形复合磁性磨料是冶金反应润湿结合。（4）研究磁力光整加工系统的技术特点，根据磁通量连续原理和安培环路定理，设计并研制Nd-Fe-B稀土永磁磁极的开路磁场磁力光整加工系统。在该系统上，进行不导磁材料316L不锈钢和导磁材料S136模具钢的磁力光整加工性能试验。结果表明，Al2O3/铁基合金球形复合磁性磨料和SiC/铁基合金球形复合磁性磨料都可实现高效率和纳米级表面粗糙度水平的光整加工，工件的表面质量得到明显改善，表面粗糙度最低可达Ra10nm以下。（5）通过磁力光整加工试验研究所制备球形复合磁性磨料的磨损特征和使用寿命。结果显示，Al2O3/铁基合金球形复合磁性磨料和SiC/铁基合金球形复合磁性磨料在磁力光整加工过程中其使用寿命均达140分钟以上，磨损形式都是正常的磨耗磨损，未发现陶瓷磨粒脱落现象。这表明，在本文研制的制备系统上通过雾化快凝工艺实现了铁磁性基体相与陶瓷硬质磨粒相的牢固结合，使得磁性磨料的使用寿命得以显著提高。博士课题研究工作将为球形复合磁性磨料的规模化工业制备提供依据与指导。更多还原

【Abstract】 Magnetic abrasive finishing (MAF), as an advanced finishing method, can be widely used inmany field, such as aeronautics, astronautics, medical apparatus and instruments etc. And magneticabrasives play a very important role in MAF, further more directly determines the surface quality ofparts finished. However, the irregular shape, low processing efficiency, short service life, complexprocess, high cost exist in the commercial magnetic abrasives which are prepared by traditionalmethods, so the preparation of magnetic abrasives becomes a bottleneck problem urgently to besolved in MAF.Therefore, a new method, that combines gas atomization and rapid solidification, is proposed toprepare spherical composite magnetic abrasive in this paper. Depending on improving the system ofpreparation powder, the high-pressure atomizing gas and ceramic hard abrasive powder werebeforehand mixed uniformly, it makes the molten ferromagnetic alloy matrix atomize into tinydroplets, and the tiny droplets were rapidly cooled down and solidified, and then the sphericalcomposite magnetic abrasive powder was obtained. Subsequently this spherical composite magneticabrasive was used in MAF to process non-conductive magnetic material and conductive magneticmaterial.The main work and the results obtained in this dissertation are as follows:(1) The system equipment which fabricates powder of metal or its alloy by gas atomization andrapid solidification was studied and analyzed firstly. And a special equipment to prepare sphericalcomposite magnetic abrasive through a process that combines gas atomization and rapid solidificationwas developed based on performance requirement of magnetic abrasives. This equipment can solvethe technical conundrum for the system of ceramic/Fe-based composite in which the compatibility ofFe-based phase and ceramics phase is very bad, and make the preparation process simple, cost low,productivity high. And this method can realize the large-scale industrial manufacturing of magneticabrasives.(2) The study was carried out on composite materials preparation theory of ceramic/Fe-basedsystem, magnetic property of ferromagnetic alloys and process characteristics of gas atomization andrapid solidification. The composition of spherical composite magnetic abrasive under the condition ofgas atomization and rapid solidification was investigated according to ideal micro-morphology andperformance requirement of magnetic abrasive. Al2O3/Fe-based and SiC/Fe-based sphericalcomposite magnetic abrasive, which conform to the ideal structural model and requirements of mechanical and soft magnetic properties of the magnetic abrasive, were successfully obtained.(3) The formation mechanism, interfacial microstructure and influencing factors of sphericalcomposite magnetic abrasive under different conditions of gas atomization and rapid solidificationwere detected by means of scanning electron microscope(SEM), energy dispersion spectrometer(EDS)and X-ray diffraction(XRD). The results demonstrate that three factors, i.e. process parameters for gasatomization and rapid solidification, alloying of the ferromagnetic matrix and the hydrodynamic effectare effectively controlled at the same time, the magnetic abrasive which conforms to the idealstructural model and requirements of mechanical and soft magnetic properties of the magneticabrasive can be obtained. The interfacial microstructure of Al2O3/Fe-based is joining mixed withmechanical, dissolved and wetted combined; the interfacial microstructure of SiC/Fe-based ismetallurgy reaction wetting joining.(4) The MAF system of open magnetic field of Nd-Fe-B rare earth permanent magnetic poleswas developed according to the magnetic flux continuous principle and Amp loop theorem based onMAF theory. The investigation were carried out on the processing performance of magnetic abrasivefor316L stainless steel and S136mold steel based on this MAF system developed. During machining,not only Al2O3/Fe-based and SiC/Fe-based spherical composite magnetic abrasive under differentconditions could realize high efficiency and nanometer level surface roughness finishing, but also thesurface quality of the machined parts could be observably improved.(5) The tests were carried out on wearing characteristics and service life of the magneticabrasives. During tests, the abrasion wear is the dominating wear behavior for the Al2O3/Fe-based andSiC/Fe-based spherical composite magnetic abrasive. The disadvantageous phenomenon of the fallout of Al2O3and SiC grains have never happened, their service life reaches to more than140minutesin the tests. This indicates that between the ferromagnetic matrix phase and abrasive phase of thismagnetic abrasive had been realized strong joining through gas atomization and rapid solidification inthis special equipment developed. And this process can make the service life of magnetic abrasiveimprove significantly.This work can provide basis and guidance for the large-scale industrial manufacturing ofspherical composite magnetic abrasives.更多还原