Eder Silva Costa

Burr produced on the drilling process as a function of tool wear and lubricant-coolant conditions

This work shows the resulting height and shape of the burrs produced by drilling holes with ratio L/D = 3. The tool used in the tests was the solid twist HSS drill coated with TiAlN, with diameter of 10 mm, to drill the microalloyed steel DIN 38MnS6. The height of the burr was studied under different lubricant/coolant systems, namely: dry machining, use of Minimum Quantity Lubrication (MQL) at the flow rate of 30 ml/h, and fluid applied in the conventional way (flooding). The following cutting fluids were used: vegetable oil (MQL), mineral oil (MQL and flooding) and semi-synthetic oil (flooding). The trials were carried out at two cutting speeds (45 and 60 m/min) and the criterion adopted for the end of the test was the catastrophic failure of the drill. The results showed that the height of the burr increases primarily with the wear of the tool and that this increase is almost exponential after 64% and 84% of drills life, for the speeds of 45 and 60 m/min, respectively. Furthermore, the results generally showed that the smallest burr height was obtained for the dry machining and the largest for the MQL systems.

Influence of tellurium addition on drilling of microalloyed steel (DIN 38MnS6)

Purpose – This paper seeks to evaluate the influence of tellurium content on the machinability of the microalloyed pearlitic steel (DIN 38MnS6). Two grades of steels were used, one with high (27 times greater) tellurium content and one with a low tellurium content. Machinability of the steel was determined by the number of holes drilled by the tool before undergoing severe deformation. The drilling test matrix was prepared using a fractional factorial design with five input variables studied at two levels (25‐1). Other variables investigated include cutting speed (45 and 60 m/min), feed rate (0.15 and 0.25 mm/rev), geometry of the twist drills and use of minimum quantity lubrication (MQL) at the flow rates of 30 and 100 ml/h. Statistical analysis of the results revealed that composition of the work material was most influential on tool performance. Addition of tellurium to the steel significantly improved machinability, increasing the number of drilled holes by over 100 per cent. The MQL flow rate was the...