Means to Improve Machinability of Sintered PM Steels
Powder metallurgy (PM) is a method known for producing components of great complexity i.e. to near net shape and to very close tolerances. Nevertheless, some components require at least some type of machining operation to fully obtain the definitive shape and geometry, e.g. holes perpendicular to powder pressing direction, bevels, slots and threads. Machining operations are also used to fulfil the demands of higher surface quality and to further improve tolerances. Once the decision to carry out a machining operation of a PM steel component has been made the need to understand the characteristic of machinability will be inevitable. However, machinability of PM steel will not be influenced by the material properties alone but by all parameters concerning the machining operation, i.e. tool grade and geometry, cutting speed and machine stability. This paper describes how machinability for some sintered PM steels can be improved by optimizing different parameters, e.g. tool material, additives and cutting fluid.