Untersuchung der Reaktionen an der Schnittstelle Korn - Bindung für Sol-Gel-Korund

摘要

In the early 1990ths grinding wheels of Sol-Gel-Corundum were introduced for the finishing of metallic materials. Sol-Gel-Corundum wheels represent a flexible, efficient and economical alternative to the high-hard abrasives CBN and diamond. Likewise high-speed grinding technique was established in the 1990ths as efficient finishing technology. Previous developments are concentrated on the technical systems grinding wheel and grinding machine. Little attention found the system grinding wheel structure, which consist of the components grain and bond. Although new grain and bond materials were introduced, systematic investigations of the grain bond compounds are missing. Questions about real geometry of the grains and the bond bridges or the reactions at the interface grain/bond remained unanswered. Target of this work was, to examine systematically the chemical reactions of the grinding grain materials Sol-Gel-Corundum compared with White Corundum with a ceramic bond material and to discuss the effects of the reaction zones at the interface grain/bond for a grinding wheel structure. The perceptions should be brought into connection with the mechanical data from bending strength investigations and grain outbreak tests as well as be examined in relation to the real grinding wheel structure.Within the methodology a special attention was turned to the interdisciplinary approach, which connects the systematic mode of operation of product development with the approaches of the engineering sciences and analytics of the natural sciences. It were used Design of Experiments for mixture quantity experiments, the Inductive coupled plasma (ICP) for the chemical analysis, the heating microscopy for determination of the flow behaviour, the Differential Scanning Calorimetry Analysis (DSC) for the analysis of the phase formation under temperature supply, the light microscopy and the raster electron microscopy analysis (REM) for the investigation of the two-dimensional grinding wheel structures, bending break test for the determination of the flexural strength and youngs-modulus, grain break out experiments for the determination of the grain break out behaviour, electron beam micro probe analysis (EPMA) for the phase analysis as well as the microcomputer tomographic investigation of a grinding wheel structure, whose results were transferred as three-dimensional geometry model into a CAD system.It could be shown that the simplifications of the models according to Frenkel, Pietsch and Rumpf will not be able to represent the structure of a grinding wheel. Both the simplifications of the effective forces at the interface grain/bond and of the description of geometry of the grains and the bond bridges are too large, than that the model could illustrate the grinding wheel structure with sufficient accuracy. As well it is not possible to determine the number of bond bridges, which connect the grains. Therefore a further technique was used, in order to illustrate the three-dimensional geometry of a grinding wheel structur and make it possible to analys a grinding wheel by numerical simulations. The priority target of further investigations must be the analysis of the phases occurring at the boundary surface of the interface grain/bond. The detailed knowledge of the mechanical characteristic values of the grains and the bond bridges as well as crystallites in the burned status are elementary conditions for the accurate numeric simulation of the grinding process. Therefore special attention must be put to the develop methods for the determination of the mechanical characteristic values of a burned grinding wheel and adequate material models for their representation in future research projects in order to prepare the way from the empirical to the systematical product development. The knowledge of the processes running between grain and bond have been deepened and the fundamental connections between the chemical raw material and the resulting physical and mechanical characteristics at the boundary surface at the interface grain/bond in a grinding wheel have been determined. Thus the basis is given to detect and understand the working mechanisms as well as the causes and effects of the reactions between grain and ceramic bond. With this work the foundation was created to use the determined findings of the reactions at the interface grain/bond from Sol-Gel-Corundum for the process understanding and the grinding process design.