Christophe Lescalier

EXPERIMENTAL ANALYSIS OF TEMPERATURE IN GRINDING AT THE GLOBAL AND LOCAL SCALES

The purpose of the article is the experimental estimation of the global and local heat fluxes and the corresponding energy partition to the workpiece for regular grinding of 100Cr6 steel with aluminium oxide wheel. By using a grindable thermocouple, the temperature and the real contact length allow determination of the global heat flux and the partition ratio at the wheel scale. The high frequency analysis of the signal has shown maximum flash temperatures of about 1000°C corresponding to the local temperature under the chip-grain unit with very high heating speed of about 100°C/µs. The comparison between theoretical temperature decay and experimental cooling has demonstrated that the time response of the sensor is fast enough for the estimation of the local temperature and power due to the sliding of grain and to the plastic strain of ground materials.

Influence of material structure on deep hole machinability of super high strength steels : application to crankshaft manufacturing

The gain of productivity in machining is generally sought through tools and/or cutting conditions optimisation however an increase in productivity is achievable too through the work-material optimisation. The metallurgical structure as well as the chemical composition of steels widely influences their ability to be machined. Mittal Steel Europe Research and Development (R&D) develops new steel grades such as the Super High Strength Steels whose tensile stresses may reach 1000 or 1200 MPa. A cooperative research programme between Mittal Steel Europe R&D and ENSAM tends to propose a methodology able to sort the steel grades in terms of ability to be manufactured (in forging and machining). This study focuses on such an industrial application: the heavy vehicles crankshaft manufacturing. The operation investigated consists in deep hole drilling of the crankshaft lubrication holes. This paper proposes some relevant criteria to compare the different steel grades and/or structures. Some experimental results are proposed.

Influence of material structure on deep hole machinability of Super High Strength Steels

The gain of productivity in machining is generally sought through tools and/or cutting conditions optimisation however an increase in productivity is achievable too through the work-material optimisation. The metallurgical structure as well as the chemical composition of steels widely influences their ability to be machined. Mittal Steel Europe Research and Development (R&D) develops new steel grades such as the Super High Strength Steels whose tensile stresses may reach 1000 or 1200 MPa. A cooperative research programme between Mittal Steel Europe R&D and ENSAM tends to propose a methodology able to sort the steel grades in terms of ability to be manufactured (in forging and machining). This study focuses on such an industrial application: the heavy vehicles crankshaft manufacturing. The operation investigated consists in deep hole drilling of the crankshaft lubrication holes. This paper proposes some relevant criteria to compare the different steel grades and/or structures. Some experimental results are proposed.