High Performance Turning of Austempered Ductile Iron (ADI) with adapted Cutting Inserts

Heat treated Ductile Iron with austenitic-ferritic matrix (ADI) has a high potential for the substitution of forged steel and conventional Ductile Iron. Advantages of ADI compared to steel are good castability and lower density. In comparison to conventional Ductile Iron, the increased ratio of tensile strength/ductility with higher resistance against abrasive wear and durability are of advantage. In the industrial applications, the material sided advantages are counterbalanced by the higher costs of the demanding machining, especially in rough turning operations. In this presentation, the development of cutting inserts for high performance turning operations, which are adapted on the specific requirements of the machining of ADI 900, are described. In the first step, the particular machinability, which can be traced back to the metallic matrix, was specified. The characteristic, discontinuous chip formation in combination with the strong tendency of hardening of the austenitic− ferritic matrix was identified as a major wear mechanism, resulting in extreme peaks of cutting forces and high specific mechanical load on the insert edge. For an enhanced evaluation of chip formation and the resultant thermomechanical tool load, a 3D FEM simulation model was developed. By using this 3D simulation model of the longitudinal external turning process, the maximum cutting forces were specified in addition to the influence of the chip segment formation frequency. The obtained results from the simulation have been used to develop an optimised insert geometry. By using the optimised tool, an increased tool life of 70% could be observed. The shown results are part of the PhD Thesis authors Dissertation “Werkzeug− und Prozessauslegung zur Drehbearbeitung von austenitisch-ferritischem Gusseisen mit Kugelgraphit”