Authors: Varun Nayyar, Uta Klement, Lars Nyborg, Peter Sotkovszki, Buelnt Tasdelen and Jacek Kaminski
Dry and Semi-Dry machining has gained interest in the last years because of the new environmental legislations and the possibility to decrease the machining cost. However, the role of cutting media such as emulsion, compressed air and Minimum Quantity Lubrication (MQL) on the chip formation has not been understood yet. The mechanical and thermo dynamical conditions in the cutting zone affects the properties of work piece material under cutting and these conditions change with the application of cutting media. In this work medium alloyed forged steel was machined with assistance of emulsion, MQL and only compressed air and the results were compared to dry machining in terms of chip color, micro structure, white-etching band and contact area between chip and the insert rake face. It was observed that white-etching band, which is believed to be ferrite, forms both on the chip upper free side and chip back side for all conditions. In emulsion cutting, this band has finest grains and with dry cutting it has largest grains proving a slower cooling with dry cutting. Not a big difference was observed on white-etching band when MQL, compressed air and dry machining were compared. However, it was observed that thermo-mechanical effect of air in MQL and compressed air supply has affected the contact area when the media was applied on rake face.
white-etching band; chip micro structure; MQL; compressed air; emulsion; dry; turning.