Inclusion engineering of steels for high speed machining

CIM Bulletin, Vol. 91, No. 1021, 1998

S.V. Subramanian, H.O. Gekonde, X.Zhang and J.Gao
Departement of Materials Science and Engineering
McMaster University, Hamilton, Ontario

The functional role of inclusions at low cutting speeds is to promote ductile fracture in chip formation process, whereas the role of inclusions at high cutting speeds is to prevent tool crater wear by surpressing the tribological phenomenon of seizure at the tool-chip interface at high cutting speeds. The viscous layer lubricates the tool-chip interface to prevent the seizure. In comparison with the large volume fraction of inclusions needed for promoting ductile fracture at low cutting speeds, the amount of inclusions required for lubricating the tool-chip interface at high cutting speeds is very small and is in the range that is typical ofr clean steels. The chip fracture process at high cutting speed machining involves the control of the rheology and composition of inclusions to meet target viscosity at the tool-chip interface. The application of thermodynamic models in controlled production of inclusions in steels designed for high speed machining is discussed.

Keywords: Metallurgy, Steel, Inclusion engineering, High speed machining