New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Ultrasonic magnetic abrasive finishing

Put forward a new kind of polishing method,ultrasonic magnetic abrasive fin-ishing(UMAF),and studied its mechanism of improving polishing efficiency.By analyzingall kind of forces acting on single abrasive particle in the polishing process and calculatingthe Size of the composition of forces,get the conclusion that UMAF will enhance the effi-ciency of the normal magnetic abrasive finishing(MAF)due to the ultrasonic vibration in-creases the cutting force and depth.At last the idea of designing the UMAF system basedon numerical control milling machine is put forward which is convenient to setup and willaccelerate the practical application of MAF.

Study of corrective abrasive finishing for plane surfaces using magnetic abrasive finishing processes

On the basis of ordinary plane magnetic abrasive finishing,a finishing method is proposed that can improve the flatness of a plane workpiece.In this method,the feed speed is varied during finishing according to the profile curve of the initial surface and the material removal efficiency,to control the effective finishing time in different areas and thereby improve the surface flatness.A small magnetic pole with an end face diameter of 1 mm is designed,and a ferromagnetic plate is placed under the workpiece to improve the uniformity of the magnetic field distribution near the magnetic pole.An experiment on an A5052 aluminum alloy plate workpiece shows that after 60 min of finishing using the proposed method,the extreme difference of the workpiece surface can be reduced from 14.317μm to 2.18μm,and the standard deviation can be reduced from 3.322μm to 0.417μm.At the same time,according to the measurement results,a similar flatness can be achieved at different positions on the finishing area.Thus,the proposed variable-speed finishing method leads to obvious improvements in flatness.

Investigation of the application of a magnetic abrasive finishing process using an alternating magnetic field for finishing micro-grooves

A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.

Hybrid post-processing effects of magnetic abrasive finishing and heat treatment on surface integrity and mechanical properties of additively manufactured Inconel 718 superalloys

Desired microstructure and surface integrity are critical to achieving the high performance of additively manufactured components.In the present work,the hybrid post-processes of magnetic abrasive finishing(MAF)and post-heat treatment(HT)were applied to the additively manufactured Inconel718 superalloys.Their hybrid effects and influencing mechanism on the surface quality and mechanical properties of the additively manufactured samples have been studied comparatively.The results show that the MAF process effectively reduces the surface roughness by more than an order of magnitude due to the flexibility and geometric consistency of the magnetic particles and abrasives with the finished surfaces.The proper sequence of MAF and HT obtains enhanced mechanical properties for the homogenized-MAF-aged sample with the yield strength of 1147 MPa,the ultimate tensile strength of 1334 MPa,and the elongation of 22.9%,which exceeds the standard wrought material.The surface integrity,compressive residual stress field,and grain refinement induced by the MAF and subsequent aging heat treatment increase the cracking resistance and delay the fracture failure,which significantly benefits the mechanical properties.The MAF process combined with proper post-heat treatment provides an effective pathway to improve the mechanical properties of additively manufactured materials.

利用双磁极平面磁力研磨法对单晶硅表面的抛光实验研究

为实现单晶硅表面平坦化,提出双磁极磁力研磨法(DMAF),并设计一套双磁极磁力研磨装置。探究双磁极磁力研磨法的加工机理,明确关键加工参数对单晶硅表面质量的影响,通过单因素对比实验对加工参数进行优化;利用ANSYS MAXWELL有限元软件,对传统平面磁力研磨法与双磁极磁力研磨法的磁场强度进行模拟仿真,对比两种方法在加工区域形成的磁感应强度,以实现定量分析磁性磨料粒子的研磨压力。基于单因素实验结果,确定了双磁极磁力研磨法对单晶硅片表面加工优化后的研磨参数:磨料组合为#200电解铁粉(Fe_(3)O_(4))+#8000白刚玉(White abrasive,WA),磁极间隙为12 mm,磁极转速为300 r/min,磨料质量比为3∶1。结果表明:在优化的研磨参数条件下,研磨60 min后的单晶硅片的平均表面粗糙度由初始的0.578μm降至8 nm,在研磨区域基本实现了镜面加工效果。仿真结果表明:与传统平面磁力研磨法相比,双磁极磁力研磨法可显著提高加工区域的磁感应强度,该研磨法所产生的磁场强度约为传统磁力研磨法的1.5倍。

基于Taguchi-GA协同的磁性磨料抛光性能预测及制备工艺参数寻优

通过改变黏结法磁性磨料的制备工艺参数来设计正交试验,制备不同系列规格的磁性磨料,并对其进行形貌和成分检测.以3D打印AlSi10Mg板为加工对象,通过平面磁力研磨试验,揭示磁性磨料制备工艺参数对磁力研磨质量的影响规律.基于回归分析,建立参数与响应之间的回归模型,通过遗传算法实现参数优化.结果表明,在SiC粒径为18~25µm,Fe与SiC的质量比为4.7,环氧树脂与聚酰胺的质量比为2,固化温度为100℃的条件下,材料去除率为1.7 mg/min,表面粗糙度由原始的3.90µm降低至0.27µm,降低率为93.1%.

电解辅助磁力研磨整体叶盘试验研究

针对航空发动机整体叶盘结构复杂和材料难以加工的特性,在磁力研磨技术的基础上引入电解作用作为辅助手段。通过电解作用产生易于处理的钝化膜,然后再引入磁力研磨加工技术,加快了对叶盘表面纹理的去除,同时使表面加工质量更加均匀。通过3D超景深电镜观测叶盘表面形貌,结果显示:经复合研磨20 min,叶盘表面纹理基本去除,表面更加细密、均匀。表面粗糙度值R_(a)由1.5μm降至0.4μm。

永磁交变磁场平面磁粒研磨试验研究

目的探究永磁交变磁场下平面磁粒研磨质量的影响因素,增强加工区域的磁场变化,使磁性磨粒的加工轨迹多样化,提高研磨效率和研磨效果。方法设计永磁交变磁场取代传统平面磁粒研磨中的恒定磁场源,并采用磁场模拟软件对永磁交变磁场进行仿真,对不同状态下磁场的分布进行分析,参考仿真结果选取实验参数;使用产生径向磁场的环形磁铁作为磁场发生源,导磁性良好的纯铁作为导磁骨架,通过磁路的开放和闭合实现磁场的交变;使用步进电机及脉冲发生器调节研磨磁场,进而调节磁极交变频率;通过试验对比不同参数下对SUS304不锈钢的研磨效果,在研磨间隙为1.5mm的条件下,对比不同研磨时间、不同磨粒目数、不同主轴转速对工件表面质量的影响,使用触针式表面粗糙度测量仪和超景深3D电子显微镜检测对比试验前后试件的表面质量并对仿真结果进行验证。结果对比永磁交变磁场不同磁场分布状态仿真图,发现永磁交变磁场研磨区域场强变化显著,场强峰值时磁感应强度较高;磁性磨粒随离心力与永磁交变磁极状态的变化做周期性运动,使研磨轨迹复杂化。在研磨时间为40min、主轴转速为245 r/min、磨粒粒径为60目条件下,SUS304不锈钢板经研磨后,表面粗糙度由原始的0.312μm降至0.060μm。结论永磁交变磁场在提高加工区域磁感应强度的同时,使磁场发生周期性变化进而使磁性磨粒在加工区域做周期性运动,复杂化研磨轨迹促进了磨粒的更新,相比于恒定磁场磁粒研磨工艺,永磁交变磁场提高了研磨效率与研磨效果。

结合ELID磨削与MAF工艺对复杂曲面的加工控制

在线电解修锐(electrolytic in-process dressing,ELID)磨削可以高效率地光整加工,而磁力研磨(magnetic abrasive finishing,MAF)具有柔性加工的特点。以三轴立式加工中心为平台,研发了一种结合ELID磨削与MAF的新型组合工艺。设计了ELID磨削工具和MAF工具头,提出了利用该组合工艺对复杂曲面进行加工的控制方法。分析了由于刀具磨损产生的工件形状误差,提出了误差补偿的措施,同时也讨论了避免加工干涉的方法。最后,开发出能同时适用于ELID磨削与MAF的复杂曲面光整加工控制与补偿软件。

超声振动辅助磁粒研磨技术的研究进展

超声振动辅助磁粒研磨技术是在磁粒研磨的基础上增加了超声波振动功能,可以在短时间内将表面抛光至纳米级别,因其具有辅助研磨效果佳、可控性和适用性好等优点,在越来越多的领域得到了应用。首先对超声辅助磁粒研磨加工技术的发展概况进行了简要介绍,分别从表面粗糙度、材料去除率、显微组织和残余应力等方面进行了重点分析和总结。其次,超声振动工艺参数是影响研磨效果的重要因素,优化选取振幅、振动频率、主轴转速以及磨料粒径等工艺参数可以明显提高研磨效果。此外还要考虑合适的加工时间和加工间隙,从而对复杂曲面进行精密研磨。最后,提出了超声振动辅助磁粒研磨加工技术研究中存在的一些缺陷,并对其未来的发展趋势进行了展望。

基于PSO-ELM的316L不锈钢细长管磁粒研磨内表面粗糙度预测模型

针对316L不锈钢细长管磁粒研磨加工过程中,最佳工艺参数难以选择,以及加工后对工件内表面粗糙度(Ra)的预测问题,将影响磁粒研磨316L不锈钢细长管内表面粗糙度的四个工艺参数作为输入值,内表面粗糙度作为输出值,构建粒子群(PSO)优化极限学习机(ELM)模型来预测316L不锈钢细长管内表面粗糙度,利用PSO对工艺参数进行全局寻优,获得最佳工艺参数组合,最后通过试验与预测结果进行对比。构建的PSO-ELM表面粗糙度预测模型拟合优度R2为0.9848,绝对误差(MAE)为0.0134,均方根误差(RMSE)为0.0214。得到的最佳工艺参数组合为:主轴转速2389.011r/min,进给速度3.167 mm/s,磨料粒径216.185μm,加工时间35.856 min,预测Ra为0.178μm。对工艺参数进行调整,试验得到的Ra为0.182μm,与预测值相比误差为2.24%。基于PSO-ELM方法构建316L不锈钢细长管内表面粗糙度预测模型,实现对工件内表面粗糙度的精确预测,应用粒子群方法得到最佳工艺参数组合,提高了磁粒研磨316L不锈钢细长管的加工效率。

基于多轴刀路轨迹的自由曲面磁粒研磨试验

目的通过自由曲面的磁粒研磨试验,使工件曲面经研磨后能够获得较好的表面形貌,降低工件的表面粗糙度。方法使用UG生成曲面三维模型,利用后处理功能,生成包含刀具位置和姿态的刀位文件,提取刀位文件中原始的刀路轨迹点,分析刀路轨迹,利用曲率的临界值提取轨迹的特征点。采用积累弦长参数化法对提取的轨迹特征点进行三次B样条插值,对比插值前后轨迹点拟合曲线在z轴的误差,再根据刀轴矢量计算机械臂末端姿态。选择磁极的不同开槽方式,并在Ansoft Maxwell软件里进行仿真模拟和分析,选定理论上较优的球形开槽磁极形式。通过试验加工铝合金自由曲面,对比研磨前后的表面形貌和表面粗糙度。结果使用积累弦长参数法进行3次B样条插值,获得了步长较为均匀的轨迹点,优化了原始刀位轨迹。在球形磁极上进行开槽,使均匀磁场变为非均匀磁场,同时使最大磁感应强度由0.556 T增至0.727 T,增大了磁粒研磨过程中的研磨力。对铝合金曲面的部分区域进行60 min的研磨,其表面平均粗糙度从原始的Ra 8.71μm降至Ra 0.56μm。结论将磁粒研磨与六自由度机械臂结合,进行曲面的光整加工,可以有效改善工件的表面质量,降低其表面粗糙度。

弹性磁极磨头磁力研磨TC4钛合金的工艺优化

尽管磁力研磨具有随形加工特性,但使用小磨头磁力研磨大扭曲度工件时,磨头在工件不同位置处的间隙差异,给磁力研磨加工带来了挑战。为了改善磁力研磨的加工表面质量,进一步减小工件间隙差异对表面粗糙度的影响,设计了一种以聚氨酯弹性体为磁极载体的弹性磁极磨头,对其磁场进行仿真分析并验证。在试验中使用黏结法制备的金刚石磁性磨料,比较不同加工间隙下聚氨酯弹性磁极磨头与普通磁极磨头的研磨加工性能,探索主轴转速、进给速度和磨料粒度对钛合金表面粗糙度的影响规律。结果表明:在工艺参数相同的情况下,聚氨酯弹性磁极磨头的加工性能优于普通磁极磨头的;使用聚氨酯弹性磁极磨头,在主轴转速为800 r/min,加工间隙为2.0 mm,进给速度为5 mm/min,磨料粒径范围为62~90μm时,磁力研磨加工效果最优,经过12 min的研磨加工,TC4钛合金的表面粗糙度R_(a)从最初的0.350μm降至0.039μm,表面粗糙度改善率达到89%。试验结果验证了聚氨酯弹性层的弹性及仿形特性对TC4钛合金加工表面质量的提升作用。

选区激光熔化TC4钛合金表面磁力光整加工的表面质量

为了研究磁力光整加工工艺对SLM制备的TC4钛合金表面完整性的影响,采用响应曲面法对钛合金试样进行三因素三水平的响应曲面分析试验。首先使用数控成形磨床对SLM制备的TC4钛合金试样进行磨削加工,磨削加工将钛合金试样表面粗糙度从6μm(SLM成形后)下降到约0.6μm,使带有球状体和凹坑等缺陷的粗糙表面演化为有划痕和孔隙的细表面。然后在不同的磁力光整加工工艺参数下,利用XK7136C数控铣床改造的磁力光整加工系统,采用雾化法制备的新型Al_(2)O_(3)/铁基球形磁性磨料对钛合金试样进行磁力光整加工,分析加工后钛合金试样的粗糙度、表面形貌以及残余应力,并确定最佳工艺参数。结果表明:当磁力光整加工工艺参数分别为主轴转速1 000.00 r/min,加工间隙1.50 mm,进给速度15.00 mm/min时,磁力光整加工效果最好,钛合金试样表面粗糙度由初始的0.6μm降低到0.065μm,试样表面均匀,划痕和表面缺陷被有效去除,达到接近镜面效果。试样表面的残余应力由最初的拉应力+297.4MPa转变为压应力-237.8MPa。利用磨削加工和磁力光整加工技术对SLM制备的TC4钛合金试样进行光整加工,可有效改善工件表面完整性,提高工件表面质量。

基于WOA–LSSVM的磁粒研磨表面粗糙度预测及工艺参数优化

目的实现磁粒研磨过程中表面粗糙度值的准确预测,同时获得提高材料表面质量的最优工艺参数组合。方法通过自由降落气固两相流双级雾化快凝法制备CBN/Fe基磁性磨料,用于磁粒研磨试验。将316L不锈钢作为实验材料,以磁极转速n、加工间隙δ、进给速度v和磁性磨料粒径d为输入值,以表面粗糙度Ra为输出值,设计L25(54)正交试验。同时借助Matlab软件引入鲸鱼优化算法(WOA)与最小二乘支持向量机(LSSVM),基于正交试验结果构建WOA–LSSVM的磁粒研磨表面粗糙度预测模型,并将输出值表面粗糙度Ra作为适应度,再次调用WOA对工艺参数进行全局寻优,获得最优工艺参数组合。使用优化得到的工艺参数组合进行试验,并与模型预测结果进行对比。结果根据正交试验构建的WOA–LSSVM表面粗糙度预测模型的均方根误差(RMSE)为0.003373,平均绝对百分比误差(MAPE)为2.814%。通过WOA寻优得到了最佳工艺参数组合,n、δ、v、d分别为1526.6907 r/min、1.527414 mm、1.0767327 mm/min、114.26052μm,此时获得的最佳表面粗糙度为0.063512μm。对寻优所得的工艺参数组合微调后进行试验,得到的表面粗糙度Ra为0.062μm,与模型预测值的相对误差约为2.44%。结论基于WOA–LSSVM的表面粗糙度预测模型拟合性能优良,可实现磁粒研磨的可控加工。使用磁粒研磨技术结合WOA的寻优结果可获得更优的表面质量。

基于混合粒径的TC4钛合金低粗糙度磁力研磨研究

目的获得更低粗糙度的TC4钛合金零件表面。方法采用黏结法制备不同粒径的磁性磨料,依次运用粒径为150~250μm和63~106μm的磁性磨粒以及这两种粒径的混合磨料进行磁力研磨对比实验,分析基于混合粒径的TC4钛合金低粗糙度磁力研磨可行性。基于磁性颗粒动力模型,根据最小能量原理分析了混合粒径磁力链的微结构,并利用体式显微镜对单粒径和混合粒径磁力链进行对比分析。结果单粒径和混合粒径磁力研磨在12 min时钛合金工件表面粗糙度均约为0.11μm,此时单一粒径趋于平衡,而混合粒径磁力研磨的表面粗糙度继续下降,在16 min左右达到最低,为0.084μm,比单一粒径降低了20%,工件表面初始划痕和凹坑得到了更好的去除,加工后表面纹理更为致密。大粒径磁力链颗粒能量最小,约为‒3.6×10^(‒13)J,其次是混合粒径磁力链结构,颗粒能量约为‒2.1×10^(‒13)J,而小粒径磁力链结构颗粒能量约为‒0.45×10^(‒13)J,是大粒径和混合粒径磁力链的5~9倍,这说明小粒径颗粒不易形成单独磁力链。结论混合粒径磁力链中,小粒径颗粒不易形成单独磁力链,而是吸附在大粒径磁力链间隙中,提高了磁力刷的刚性和密度,不同粒径的磨粒同时参与研磨,从而在混合粒径磁力研磨TC4钛合金中能够有效的降低表面粗糙度。

渐开线槽磁极改进磁粒研磨毛刺效果的试验研究

目的改善传统磁粒研磨去除毛刺时磁感应强度变化率小、磨粒飞溅损耗严重等问题,设计带渐开线槽的磁极,通过优化磁场分布和逆渐开线展开转动的方式提高毛刺去除的效率和质量。方法基于渐开线原理,设计不同基圆直径的磁极沟槽,仿真了磁感应强度云图及磁感应强度曲线,并与传统磁极进行平面研磨对比试验,通过综合分析优选磁极槽类型。对镍基高温合金GH3128螺旋铣孔板开展磁粒研磨孔切出毛刺的试验研究,分析主轴转速、磨粒填充量和磨粒粒径对孔缘毛刺去除的影响,得到渐开线槽磁极磁粒研磨孔切出毛刺的较佳工艺参数方案。结果使用基圆直径为8mm的渐开线槽磁极研磨平面时,其有效研磨面积更大,在主轴转速为1600 r/min、磁性磨粒平均粒径为250μm、进给速度为0.05 mm/s、磁性磨粒填充量为30 g、加工间隙为2 mm的工艺条件下研磨镍基高温合金GH3128孔板18 min后,孔切出毛刺平均高度由原始的29.6μm降至10.2μm,毛刺的平均宽度从原始的288.6μm降至169.4μm。结论带渐开线槽的磁极改善了磁感应强度变化梯度,抑制了磁性磨粒的飞溅损耗,加速了磨粒切削刃的更新,使研磨效率和研磨均匀性都得到提高。此外,该加工方案可为其他类型毛刺的去除提供参考。

航空发动机铣削叶片抛磨技术研究现状及其发展趋势

叶片是航空发动机的核心部件,其苛刻的工况对其加工精度和表面完整性提出了更高要求。针对铣削叶片现有成性技术,阐述了叶片典型结构及抛磨前的表面状态,归纳了叶片抛磨技术关键共性难点。以表面完整性为评价指标,从手工抛磨、砂轮抛磨、砂带抛磨、磨粒流抛磨、柔性工具抛磨、磁力辅助抛磨、滚磨光整加工等方面介绍了航空发动机叶片抛磨的国内外研究进展,对比了各种抛磨技术的优缺点及适用范围。

基于响应曲面法的磁力研磨310S不锈钢参数优化

采用磁力研磨光整加工技术(MAF)提高310S不锈钢工件的表面质量,探讨3种工艺参数对其表面粗糙度的影响规律。通过主轴改造后的XK7136C数控铣床作为加工平台,基于响应曲面方法,采用雾化快凝法制备的Al_(2)O_(3)球形磁性磨料对310S不锈钢进行研磨实验研究。以磁力研磨后的表面粗糙度值(R_(a))为响应值,对实验过程中的主轴转速、进给速率和加工间隙进行优化,在主轴转速为1720 r/min,进给速度为16 mm/min,加工间隙为1.8 mm的条件下恒定研磨30 min,工件的表面粗糙度值由初始的0.350μm下降至0.039μm,表面粗糙度模型预测值为0.044μm,实验实际值与预测值误差为11.3%。残余压应力由初始的-289 MPa增加至-391 MPa,结果表明:磁力研磨后工件表面凹坑、毛刺和划痕均被去除,表面质量得到极大地改进。