Al_2O_3纤维砂轮的开发及其磨削特性

DEVELOPMENT OF Al_2O_3 FIBER WHEEL AND ITS GRINDING PERFORMANCES

细磨粒砂轮用于高精度磨削。然而 ,由于细磨粒具有较小的结合面积和强度 ,即使在正常的磨削条件下 ,磨粒易于从砂轮表面上脱落 ,导致加工精度与效率低下。近年来 ,由于Al2 O3 纤维具有优良的机械与物理化学性能如高强度、高弹性模量、耐磨损、耐高温氧化及耐酸、耐碱等 ,与基质材料具有良好的相容性 ,因而被广泛地用于FRP、FRC和FRM等的强化材料。Al2 O3 纤维的平均直径和长度分别为 3～ 5 μm和数百 μm ,比相同直径的细磨粒具有较大的结合面积和强度。因此 ,1998年以来 ,日本山口胜美、洞口严教授和中国魏源迁教授使用Al2 O3 纤维替代磨粒作为磨料 ,与酚醛树脂结合剂结合 ,成功地开发了一种Al2 O3 纤维砂轮[1] ,能克服磨粒砂轮的缺陷。该砂轮中的纤维排列方向与磨削面相垂直 ,纤维的端部可用作为切削刃 ,而且纤维砂轮比磨粒砂轮细密 ,使用纤维砂轮可实现干磨削和纳米加工。为了考察Al2 O3 纤维砂轮的磨削特性 ,本文对难加工材料如模具钢SKD11(HRC60 )进行了大量的磨削试验 ,试验结果表明能获得纳米级加工表面 (Ra2 .1nm/Ry2 2nm)。

Fine grain wheels are used to fulfill high precision grinding. However, fine grain wheels have a common weakness, that is, the grains are easily torn loose from the wheel surfaces even under normal grinding conditions because of their small bonding areas and strength, resulting in bad machining precision and low efficiency. With recent advances, Al 2O 3 fibers have been extensively used as reinforcing materials of FRP, FRC and FRM due to their excellent mechanical, physical and chemical properties such as high tensile strength, high modulus of elasticity, wear resistance, heat resistant temperature, acid base resistance, and good compatibility. The average diameter of Al 2O 3 fibers is about 3～5μm and their length in the range of several hundred μm, thus have relatively larger bonding areas and strength. As a result, a phenol resin bonded Al 2O 3 fiber grinding wheel has been developed. In this new wheel, the fibers are directionally aligned and uniformly set normal to the grinding wheel surface, and their ends are served as cutting edges or tips. Such fiber wheel can overcome the common shortcoming of grain wheels and have a closer texture in comparison with grain wheels. Owing to good properties of fibers, the Al 2O 3 fiber wheel can be applied to dry grinding and nano grinding. To examine the grinding performances of the new Al 2O 3 fiber wheel, a large number of grinding experiments of difficult to cut materials such as hardened die steel SKD11 (HRC60) have been carried out in this paper. The investigations showed that a nanometer level ground surface with roughness values of Ra2.1nm and Ry22nm can be achieved.