基于多层均质钎焊砂轮在线电解修整技术的超细晶硬质合金高效精密磨削研究

It is aimed at developing a new technology to realize high efficiency and precision grinding of ultrafine cemented carbides based on electrolytic in-process dressing of multilayer homogeneous brazing wheel. It is hoped that this new technology can overcome the shortages of the machined surface instability and the abrasives falling off the wheel prematurely during the traditional grinding due to the high hardness and high strength of the ultrafine cemented carbides. The multilayer homogeneous brazing wheel which has more excellent grinding properties and longer tool life was prepared using powder injection molding and vacuum brazing.The powder injection molding can overcome the shortages of inhomogeneous density and the abrasive wear in the mould pressing, and the vacuum brazing can increase holding strength between the diamonds and brazing alloy due to the presence of the chemical bonding. The electrolytic in-process dressing will be introduced to remove the brazing alloy to get enough chip-pocket space and increase dressing efficiency, and to keep the balance between effective dressing rate and wear rate of abrasive during the grinding. A further study on the grinding performance and grinding mechanism of the ultrafine cemented carbides will be carried out to establish some related basic theory. This research is expected to promote the widespread use of multilayer homogeneous brazing wheels, and also to promote the development of high efficiency and precision machining technology of difficult-to-cut materials.

本项目主要针对超细晶硬质合金的高强度、高硬度的“双高”特性引起的加工表面质量不稳定、砂轮磨粒磨钝/脱落严重等机械加工问题，提出了一种基于多层均质钎焊砂轮在线电解修整技术的超细晶硬质合金高效精密磨削方法。利用粉末注射成型及真空钎焊技术制备出磨粒把持力大且多层分布、组织均匀的多层均质钎焊砂轮，粉末注射成型技术有效避免了传统模压工艺存在的密度不均匀、金刚石易挤压磨损的不足，而真空钎焊技术则有效提高了磨粒把持强度；采用在线电解修整技术解决多层均质钎焊砂轮修整困难和频繁间断修整效率低下的问题，实现砂轮金属基体去除速度与磨粒磨耗速度的动态平衡，使其在磨削过程中始终保持锋利性和理想的容屑空间。深入开展基于多层均质钎焊砂轮在线电解修整技术的超细晶硬质合金磨削性能和磨削机理研究，建立其高效精密磨削基础理论。本项目的研究成果将对多层均质钎焊砂轮的推广应用及难加工材料高效精密加工技术的发展起到积极推动作用。

项目主要针对超细晶硬质合金的高强度、高硬度的“双高”特性引起的加工表面质量不稳定、砂轮磨粒磨钝/脱落严重等机械加工问题，提出了一种基于多层钎焊砂轮在线电解修整技术的超细晶硬质合金高效精密磨削方法。通过采用模压成型和真空钎焊技术制备了一种磨粒把持力大、磨粒多层分布、组织均匀的多层钎焊金刚石砂轮；并配制了一种含碳纳米管电解液以用于多层钎焊砂轮的电解修整。研究结果表明，碳纳米管能显著提高电解液的电解能力，电解氧化膜厚度增大了56.3%-80.2%，这有利于磨损磨粒的顺利脱落，保证了钎焊砂轮的锋利性和理想的容屑空间；螺旋卷曲状的碳纳米管在电解过程中能吸附、分布于氧化膜中，氧化膜的粘附强度增大了30%-50%，这能充分发挥氧化膜的研磨、抛光效果，这对提高钎焊砂轮的磨削性能是极为有利的。磨削结果也表明，含碳纳米管电解液电解修整多层钎焊金刚石砂轮的磨削力降低了30%以上；超细晶硬质合金的磨削表面粗糙度小，且增长幅度相对平缓，即使当进给速度为30mm/s，磨削深度为16μm时，表面粗糙度也仅为0.15μm左右；磨削加工表面完整性较好，没有出现破碎、裂纹等加工缺陷，可有效实现超细晶硬质合金等难加工材料的高效精密磨削加工。本项目研究成果将为多层钎焊砂轮电解修整磨削技术的推广应用提供技术支持，具有十分重要的研究意义和应用价值。