Development of a New Ultra-precision Finishing Process for Internal Surface by the Application of Magnetic Abrasive Machining Using Superconducting Coil

（1）在本实验室首次利用冷冻式超导电磁线圈实现了工作区3 T（30000 Gs）的高磁场强度。(2)在该超导线圈装置上，配备了非铁磁性细长管（SUS 304细长洁净管）的内光整装置。(3)通过分别用超微磨料和铁颗粒混合型磁流体对管件进行超精密内光整加工的实验结果，探讨了超精密内光整加工的机理。(4)通过实验，阐明了磁性磨粒直径（铁粒直径）和研磨压力对研磨压力的影响。用N-S磁极图确定磁场强度与梯度的乘积值。(5)通过采用常规直流电磁线圈和稀土永磁体的模拟实验装置，研究了磁场分布对抛光压力的影响。(6)用微机有限元法（FEM分析）对工作区磁场分布的分析结果与用特斯拉计传感器测得的结果一致。(7)通过有限元分析，讨论了N-S极排列与N-N（或S-S）极排列磁场分布的差异。(8)通过实验研究了N-N极排列方式对抛光特性的影响，并与N-S极排列方式进行了比较。(9)通过超导线圈的研究，在精密加工技术研究领域实际上获得了3 T的极高磁场强度。

The results obtained in this research during three years are summarized as follows :(1) High magnetic field strength of 3T (30000 Gs) in the working zone are first realized in our laboratory using freezing type superconducting electro-magnetic coil. (2) The internal finishing setup for non-ferromagnetic slender tubes (slender clean pipes of SUS304) was equipped on this supercoducting coil apparatus. (3) The mechanism of the internal ultra-precision finishing of a tube is discussed by the experimental results using mixed type magnetic fluid with ultra-micro abrasive grains and iron particles respectively. (4) From the experiments, it is clarified that the finishing pressur is infulenced by the both magnetic abrasive particle diameter (iron particle dia.) and the product value of the magnetic field strength and its gradient determined by N-S magnetic pole arrangemet. (5) The effect of magnetic field distribution on the finishing pressure by the modelling experimental setup using a conventional DC electromagnetic coil and rare earth permanent magnets. (6) The analytic results of the magnetic field distribution in the working zone by the Finite Element Method (FEM analysis) using a personal computer are equal to the measued value obtained using a tesla-meter sensor. (7) The difference between the magnetic field distribution of N-S pole arrangement and N-N (or S-S) pole arrangement is discussed by the FEM analysis. (8) The effects of N-N pole arrangement on the finishing characteristics are clarified experimentally, compared with N-S pole arrangement. (9) By this research using superconducting coil, very high magnetic field strength of 3T was actualy obtained in the research field of precision machining technology.