Metalworking fluids (MWFs) are crucial in the manufacturing industry, playing a key role in facilitating various production processes. As each machining operation comes with distinct requirements, the properties of the MWFs have to be tailored to meet these specific demands. Understanding the properties of different MWFs is fundamental for optimizing processes and improving performance. This study centered on characterizing the thermal behavior of various cutting oils and water-based cutting fluids over a wide temperature range and sheds light on the specific tribological behavior. The results indicate that water-based fluids exhibit significant shear-thinning behavior, whereas cutting oils maintain nearly Newtonian properties. In terms of frictional performance, cutting oils generally provide better lubrication at higher temperatures, particularly in mixed and full-fluid film regimes, while water-based fluids demonstrate greater friction stability across a wider range of conditions. Among the tested fluids, water-based formulations showed a phase transition from solid to liquid near 0 °C due to their high water content, whereas only a few cutting oils exhibited a similar behavior. Additionally, the thermal conductivity and heat capacity of water-based fluids were substantially higher than those of the cutting oils, contributing to more efficient heat dissipation during machining. These findings, along with the reported data, intend to guide future researchers and industry in selecting the most appropriate cutting fluids for their specific applications and provide valuable input for computational models simulating the influence of MWFs in the primary and secondary shear zones between cutting tools and the workpiece/chiplet.

To improve machining processes concerning the usage of lubricants, knowledge of the thermo-mechanical and thermo-fluid interactions at the cutting zone is of great importance. This study focuses on the description of the convective heat transfer which occurs during circular sawing when the lubricant is provided via an internal coolant supply. The highly complex flow field inside the cavity of the sawing process is separated into two distinct flow forms, an impingement and a channel flow. With the aid of experimental and numerical studies, the heat transfer characteristics of these two flow forms have been examined for water and a lubricant used in the circular sawing process. Studies have been conducted over a wide range of Reynolds numbers (impingement flow: $2\times {10}^3<\mathrm{Re}<17\times {10}^3$, channel flow: $1\times {10}^3<\mathrm{Re}<30\times {10}^3$). Additionally, the variation in the inlet temperature of the fluid, as well as the variation in heating power, has been studied. Overall, the impingement flow yields a significantly higher heat transfer than the channel flow with Nußelt-numbers ranging from 120 to 230, whereas the Nußelt-numbers in the case of the channel flow range from 20 to 160. For both flow forms, the use of the lubricant results in a better heat transfer compared with the usage of water. With the aid of these studies, correlations to describe the heat transfer have been derived. The provided correlations are to be used in a coupled numerical model of the chip formation process which also includes the effects of the heat transfer to the coolant lubricant.

Beim Sägen gelangt je nach Abschattung der Zerspanungszone durch das Bauteil, Werkzeug beziehungsweise anfallende Späne nur ein Bruchteil der eingesetzten KSS-Menge in die Zwischenräume von Span, Werkzeug und Werkstück. Eine innere Kühlschmiermittelzufuhr (IKZ) kann eine sichere KSS-Versorgung ermöglichen. Dieser Beitrag zeigt, wie erstmalig der Spanbildungsprozess in Interaktion mit einem Fluid im engen geschlossenen Schnittspalt beim Sägen sichtbar gemacht wird. Dies erlaubt die experimentelle Untersuchung thermischer und mechanischer Fluid-Festkörper-Wechselwirkungen im Sägeprozesses. In sawing, only a small amount of coolant reaches the spaces between the chip, tool and workpiece, depending on the shading of the cutting zone by the workpiece, tool or chips. An internal coolant supply (ICS) can enable a reliable coolant supply. For the first time, this paper shows how the chip formation process is made visible in interaction with a fluid in the narrow closed cutting gap during sawing. This enables the experimental investigation of thermal and mechanical fluid-solid interactions in the sawing process.