目的 通常采用金刚线切割工艺批量生产NdFeB薄片，其表面粗糙度及表面线痕问题十分严重，提出超声水基切割液的金刚线切割新方法，以消除NdFeB薄片切割中的线痕，降低其表面粗糙度，并对超声辅助条件下的材料去除机理进行研究。方法 通过白光干涉仪和光学显微镜对样品表面形貌进行观察，通过激光位移传感器检测并分析了金刚线在各处的横向位移，分析其对切割表面线痕形成的影响因素。通过线激光测量方法量取超声辅助和纯水切2种条件下的线弓偏移，并分析线弓的形成机理，研究材料去除形式、排屑润滑之间的关系。综合分析线弓形成机制、线痕形成机制及表面形貌形成机制，揭示材料的去除机理。结果 实验结果表明，在进给速度0.2 mm/min下，可将水切的表面粗糙度Ra控制在0.4 μm以下，仅为油切的一半，而在超声辅助下的峰谷值(PV)仅为油切下的二分之一。在相同进给速度下超声辅助切割的线弓变形与水切的差值先增大后减小，在进给速度0.2 mm/min下达到0.5 mm。结论 水基切削液比油基切削液具有更好的排屑性能，能够有效降低切割表面的粗糙度，而在超声辅助下使金刚线在NdFeB表面进行微磨削，有效地消除了样品表面的线痕，超声辅助水基切割对NdFeB切割的表面质量具有很大的改善作用。

The waviness sawing mark as well as the high surface roughness is a huge problem that hinders the production rate of the NdFeB magnet. The work aims to propose a new ultrasonic vibration assisted water lubricated sawing method to improve the surface quality and reduce the surface roughness and research the material removal mechanism under ultrasonic vibration assistance. The formation mechanism of the linear bow was analyzed, and the relationship between material removal form and chip removal lubrication was studied. The formation mechanism of line bow, line mark and surface morphology was analyzed comprehensively, and the removal mechanism of materials was revealed. Several diamond wire sawing experiments were conducted under a feed rate of 0.1 and 0.2 mm/min, while the sawing condition was oil lubricated, water lubricated and ultrasonic vibration assisted with water lubrication. The surface roughness of the sawed surface from all groups was obtained under white light interferometer and so was the surface morphology. It was discovered that the surface roughness of the sample under three conditions was almost the same when the feed rate was only 0.1 mm/min. When the feed rate increased to 0.2 mm/min, the surface roughness Ra for the water lubricated group can be controlled below 0.4 μm, which was half of the oil lubricated group. And its PV value was also half of the oil lubricated group, which can effectively reflect the influence from waviness mark, was much lower for water lubricated group and even lower for the ultrasonic vibration assisted group. But the surface roughness Ra along the sawing direction for ultrasonic vibration assisted group was higher than the water lubricated group. The wire bow was measured under both water lubricated sawing and ultrasonic vibration assisted sawing using a linear laser displacement sensor. The lateral movement of the wire at different spots were measured by a linear laser displacement sensor. The lateral displacement for the diamond wire were as high as 0.55 mm at the wire releasing spot, and gradually decreased to 0.05 mm and then 0.01 mm after going through the tension wheel and the guiding wheel. The sawing part of the wire still had a 5-10 μm lateral displacement due to the large lateral gap on the guiding wheel. At the same feed speed, the difference line between ultrasonic vibration assisted bow deformation and water cutting decreases after increasing, and reaches 0.5 mm at the feed speed of 0.2 mm/min. It was discovered that the surface waviness mark was formed due to the lateral displacement of the diamond wire and it was originated from the spool lateral feed. After that the wire bow were measured for both water lubricated groups. The wire bow for ultrasonic vibration assisted groups were higher and it was discovered that the micro-grinding effect was responsible for the wire bow increase and the reduced surface mark. The ultrasonic vibration induced the wire to vibrate in vertical direction, hence having an intense micro grinding effect on the sawed surface. Such micro grinding effect effectively removed the sawing mark but at the same time increased the cutting force, hence the larger wire bow. Using a self-developed Matlab script, the total area of fracture zones on the microscope image of sawed surface can be identified and calculated. It was found that the fracture rate of the surface under oil lubrication was much higher than water lubrication, which shows that the chip transportation of the cutting fluid is very important for the wire sawing process. In conclusion, the ultrasonic vibration assisted diamond wire sawing under water lubrication can not only improve the surface quality, but also eliminate the surface waviness mark.