Influence de la température sur l'usinabilité du Ti-5-5-5-3
Résumé
The realization of aeronautic parts with strong mechanical properties requires the use of high performance materials. That's why, some new materials are used for landing gears as refractory titanium (as Ti-5-5-5-3). The machining of this material leads to high cutting forces and temperatures. So, it is necessary to use low cutting conditions on the industrial machining process. In order to increase the productivity, it is possible to increase the initial temperature of the workpiece. Hot machining is a new research track. The principle consists in heating material before machining it, in order to take advantage of its mechanical properties reduction. First, studying the state of the art permit us to determine all heating instruments used and the thermal alleviation that exists on conventional materials. A heating by induction was chosen and a system capable to maintain a constant temperature into the workpiece during machining (turning) was conceived. The measure of the temperature is achieved in the setup of the workpiece by thermocouples and by thermography camera. Trails permit to identify the variation of cutting forces according to the initial temperature of the workpiece, with fixed cutting conditions according to the TMP (Tool- Material-Pair) methodology at ambient temperature. Tool life and deterioration type are identified notably. The results analysis shows a low reduction of specific cutting forces for a temperature area compatible with industrial process. The reduction is more important at elevated temperature. However, it has bad consequences on quality of the workpiece surface (oxidation, problem on surface integrity and mechanical properties degradation). In perspective, different ways of heating are studied to permit a localized and more effective heath compatible with the industrial application.
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