MECHANOCHEMICAL SUPERFINISHING OF OPTICAL GLASS – SCRATCHLESS SURFACE FINISHING PROCESS

光学玻璃的机械化学超精加工 – 无划痕表面精加工工艺 –

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发表时间：

2009

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作者：

N. Furushiro;M. Higuchi;Tomomi Yamaguchi;N. Matsumori;H. Ogura;S. Shimada

介绍了一种新研制的含CeO 2磨料的机械化学超硬磨料磨具。通过对光学玻璃的超精加工，评价了CeO 2磨料对光学玻璃超精加工性能的影响。结果发现，软CeO 2磨料摩擦光学玻璃的表面产生光滑的表面比金刚石磨料划痕少。CeO 2磨料的加入改善了光学玻璃的表面完整性，因为它减少了金刚石磨料产生的划痕。使用粘结磨料的研磨加工提供快速的材料去除和高尺寸精度。此外，使用与工件发生界面反应的机械化学石[1]，可以提供更好的表面。基于这种思维方式，已经开发出一些含有氧化铈CeO 2的机械化学宝石[2，3]。作者开发了含有磨料CeO 2的新型陶瓷结合超硬磨料磨具，并从理论和实验上研究了CeO 2和Fe之间的化学反应[4]。研磨剂CeO 2比光学玻璃软，但与它们发生化学反应[5]。使用这些石头，可以获得具有较少划痕的光滑表面，这在使用传统金刚石石头时是不可能的。通过光学玻璃的超精加工实验，对CeO 2石、金刚石、含CeO 2的金刚石磨料的性能进行了评价和比较。机械力化学超硬磨料试验石的性能研究为光学玻璃的超精加工研制了机械力化学超硬磨料试验石。它包括CeO 2 20000粒度与陶瓷结合剂。在本文中，这被称为CeO 2石。此外，还研制了一种由20000粒度的CeO 2和4000粒度的合成金刚石组成的机械化学超硬磨料磨具。本文将其称为SD/CeO 2石。同时制备了一种常规的陶瓷化SD石材，研究了CeO 2磨料对石材性能的影响。所有试验均在无心平面研磨机上进行。该机器如图1所示。工件的表面精加工是由一个旋转的杯形超级磨料石头与振荡运动。表1列出了所用的超精加工条件。图1.使用直杯形磨石的无心平面超精加工。结果与讨论CeO 2石材如果CeO 2磨料在超精加工过程中实际上与光学玻璃工件反应，则含有CeO 2磨料的石材的材料去除率将服从Arcidius方程，因为化学反应速率的温度依赖性。其中k是反应速率，A是指前因子，E是活化能，R是气体常数，T是绝对温度。在此基础上，分析了冷却剂温度为283 ~ 313 K时CeO 2结石的去除率。图2示出了去除速率的对数相对于图2的倒数的阿耳忒弥斯图。超精加工液温度对去除率的影响。图3.超精研液温度对精研比的影响。表1.超精加工条件。图4.超精加工液温度对粗糙度值的影响。温度氧化铈石的去除率随温度的升高几乎呈线性增加。从直线的斜率计算表观活化能，得到CeO 2石的表观活化能为10.9 kJ/mol。图3显示了精整比与温度的关系。随着温度的升高，CeO 2石材的抛光率几乎呈线性增加，这是由于去除量的增加和石材磨损量的减少。这些结果表明，CeO 2磨料在超精加工过程中与光学玻璃工件发生反应。图4示出了由CeO 2石产生的表面的粗糙度值Ra。CeO 2磨料由于其易碎性，几乎不刮擦光学玻璃表面，而仅摩擦光学玻璃表面。然而，CeO 2石有效地产生了更光滑的表面。图5示出了具有CeO 2石的BK 7的超精加工表面。表面的划痕比传统的钻石少。然而，在某些情况下，在超精加工过程中，金刚石磨料产生的划痕很少，仍然存在。温度（K）S ur fa ce roug ne ss（n m R a）280 290 310 320 300 1 10 5超精加工压力石速度工件速度振荡频率振幅超精加工液超精加工液温度超精加工时间工件材料0. 17 MPa 42 m/min 79 m/min 6. 7 Hz 0. 5 mm防锈剂在水中的稀释溶液浓度=1%

This paper describes a newly developed mechanochemical superabrasive stone containing CeO2 abrasive. The effect of CeO2 abrasive on their performances was evaluated through the superfinishing of optical glass. It was found that soft CeO2 abrasive rubs the surface of optical glass producing smooth surfaces with fewer scratches than diamond abrasive. The addition of CeO2 abrasive improves the surface integrity of optical glass because it reduces production of scratches by diamond abrasive. INTRODUCTION Abrasion machining using bonded abrasives provides rapid material removal and high dimensional accuracy. In addition, using mechanochemical stones [1], which have interfacial reaction with works, they provide better surfaces. On the basis of this way of thinking, some mechanochemical stones, containing cerium oxide, CeO2, have been developed [2, 3]. Authors have developed new vitrified-bonded superabrasive stones, which contains the abrasive CeO2, and have investigated the chemical reaction between CeO2 and Fe theoretically and experimentally [4]. The abrasive CeO2 is softer than the optical glass but reacts chemically with them [5]. Using these stones, it was possible to obtain a smooth surface with fewer scratches, which was not possible when using conventional diamond stones. In this paper, the performances of CeO2 stone, diamond stone, and diamond stone containing CeO2 abrasive are evaluated and compared through superfinishing experiments of optical glass. PERFORMANCE OF MECHANOCHEMICAL SUPERABRASIVE STONE Test Stones A Mechanochemical superabrasive stone was developed for superfinishing of optical glass. It consists of CeO2 20000-grit size with vitrified bond. In this paper, this is referred to as CeO2 stone. In addition, a mechanochemical superabrasive stone, which consists of CeO2 of 20000-grit size and synthetic diamond of 4000grit size with vitrified bond, was developed. This is referred to as SD/CeO2 stone in this paper. A conventional vitrified SD stone was also prepared to investigate the effect of the CeO2 abrasive on the performance of stone. Experimental Procedures All tests were performed on a centerless flat surface lapping machine. The machine is shown in Fig. 1. The workpiece was face-finished by a rotating cup-shaped superabrasive stone with oscillating motion. Table 1 tabulates the superfinishing conditions that were used. FIGURE 1. Centerless flat superfinishing using a straight cup-shaped abrasive stone. Results and Discussions CeO2 Stone If the CeO2 abrasive actually reacts on an optical glass workpiece in the superfinishing process, the material removal rate of the stone containing the CeO2 abrasive will obey the Arrhenius equation, because of the temperature dependence of chemical reaction rate. ⎟ ⎠ ⎞ ⎜ ⎝ ⎛− = RT E A k exp (1) where k is the reaction rate, A is the preexponential factor, E is the activation energy, R is the gas constant, and T is the absolute temperature. The removal rate of the CeO2 stone was analyzed based on this empirical law for coolant temperature from 283 K to 313 K. Fig. 2 shows the Arrhenius plot of the logarithm of the removal rate against the reciprocal of the FIGURE 2. Dependence of removal rate on temperature of the superfinishing fluid. FIGURE 3. Dependence of finishing ratio on temperature of the superfinishing fluid. TABLE 1. Superfinishing conditions. FIGURE 4. Dependence of roughness values on temperature of the superfinishing fluid. temperature. The removal rate of the CeO2 stone increase almost linearly as the temperature increases. Calculating the apparent activation energy from the slope of the straight line gives 10.9 kJ/mol for the CeO2 stone. Fig. 3 shows the finishing ratio against the temperature. The finishing ratio of the CeO2 stone increase almost linearly as the temperature increases because of the increase of the removal volume and the decrease of the stone wear volume. These results indicate that the CeO2 abrasive reacts on an optical glass workpiece in the superfinishing process. Fig. 4 shows the roughness values, Ra, of the surfaces generated by the CeO2 stone. The CeO2 abrasive hardly scratches the surface of optical glass but only rubs it, because of its friability. Nevertheless, the CeO2 stone effectively generates a smoother surface. Fig. 5 shows the superfinished surface of BK7 with the CeO2 stone. The surface has fewer scratches than conventional diamond stones. In some case, however, few scratches, which were generated with diamond abrasive during prefinishing process, remains after superfinishing. Temperature (K) S ur fa ce ro ug ne ss (n m R a) 280 290 310 320 300 1 10 5 Superfinishing pressure Stone speed Workpiece speed Frequency of oscillation Amplitude Superfinishing fluid Superfinishing fluid temperature Superfinishing time Workpiece material 0.17 MPa 42 m/min 79 m/min 6.7 Hz 0.5 mm Dilute solution of rust inhibitor in water, Concentration=1%

MECHANOCHEMICAL SUPERFINISHING OF OPTICAL GLASS – SCRATCHLESS SURFACE FINISHING PROCESS –

光学玻璃的机械化学超精加工 – 无划痕表面精加工工艺 –

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