Hot Machining: Utilisation of the Forging Heat for Efficient Turning at Elevated Temperatures

Abstract

The machining at elevated workpiece temperatures has many technological advantages and was intensively addressed in research within the last 20 years. Hot machining is foremost applied for difficult to cut materials, such as stainless steels. The key reason of the advantages of hot machining of steels is a reduction of the shear strength and a prevention of phase transformation in austenitic steels. The main disadvantage of hot machining remains the requirement for heating of the workpieces in connection with large energy consumption. An optional method to avoid this disadvantage is to machine the workpieces directly after the heat treatment at elevated temperatures. This method is in focus of hot machining research at the IWT Foundation Institute of Materials Science in Bremen within the cluster project Ecoforge. Within the current work the results of turning of the precipitation hardening ferrite-pearlite (AFP-) steel in two heat treated conditions with tungsten carbide inserts are presented. The cutting forces, tool wear and the chip formation are analysed due to turning of steel 38MnVS6 in the soft condition (ferrite-pearlite) and in the heat treated condition (bainite). The results show the potential of utilisation of the heat energy from the hot forming integrated heat treatment for hot turning of forge steels with bainite structure. The experimental results pave the way to shorten the process chain for the investigated materials within the cluster project Ecoforge and reveal correlations of machining at different workpiece temperatures.