Tribological relationships of high-pressure grinding of casted steel slabs
The machining of casted steel slabs with high-pressure grinding enables uniform stock removal with a high metal removal rate in order to produce a defect-free surface for further processing in the subsequent rolling process.
During the high-pressure grinding, constant process parameter values (grinding force, cutting speed, feed rate, and wheel angle), in conjunction with the behavior and influencing variables of the abrasive, are used to achieve a resulting stock removal on the workpiece (slab). It is necessary to achieve a specified and defined stock removal value in a reliable and reproducible manner for all types of material to be machined ("Werksmarken"). Since the influence of the different material parameters of the material to be machined changes both the material removal rate and the surface quality of the workpiece, these process parameters described here must be determined by empirical test series and stored in the machine control system.
The motivation and objective of this work are to close current knowledge gaps and to obtain a general fundamental basis of process understanding for machining with geometrically indeterminate cutting edge (grinding) of continuous casted slabs. This is of enormous importance in order to be able to use this machining variant in an economically optimal way and to prevent failures due to slab breakages.
This work is divided into a theoretical and an experimental part. Extensive experimental analysis before and after machining is used to correlate the evolution of the friction coefficient and the processes taking place under dry friction with the surface topography and microstructural properties. The accumulated knowledge from these investigations of the tribological system will lead to a comprehensive understanding of the process and will be incorporated into a simulation model that serves as the basis for further optimization in the form of a predictive model. This knowledge will enable a quantitative prediction for optimizing the removal result at the surface-near boundary layer zones. Furthermore, machine and tool parameters can be selected in such a way that cracks and fractures of casted steel slabs are prevented by the residual stresses contained in the workpiece, thus enabling quality-assured and economical machining.