Alexander Sahm

Wear Mechanism when Machining Compacted Graphite Iron

Abstract The industrial application of compacted graphite iron in the automotive industry is taking a rather long time due to its uneconomic machinability, because of a significant decrease in tool life. After six years of holistic research of the PTW in cooperation with foundries, manufactures and material scientists, the wear mechanism was understood and clarified: Sulphur in the microstructure of compacted graphite iron has direct influence on the formation of a manganese-sulphur layer on the cutting edge. For machining gray cast iron this layer protects the cutting edge against abrasive wear. Therefore the design of cutting tools for the machining of CGI must consider the absence of manganese-sulphur layer.

Material aspects of chip formation in HSC machining

Abstract Investigations in the past have shown, that chip formation changes by increasing cutting speed, because most of the experimental work had been carried out in the original material stage. In contrary to this new machining investigations were made on an aluminium alloy at different heat treatment states. This investigations confirm that precipitation hardening is the key in changing from continuous to segmented chip formation and not only the cutting parameters. By applying this new knowledge, the relationship between chip formation and cutting forces was examined.

Machining of Compacted Graphite Iron (CGI)

The industrial application of compacted graphite iron in the automotive industry is taking a rather long time due to its uneconomic machinability, because of a significant decrease in tool life. After six years of holistic research of the PTW in cooperation with foundries, manufactures and material scientists, the wear mechanism was understood and clarified: Sulphur in the microstructure of cast iron has direct influence on the formation of a manganese-sulphur layer on the cutting edge. For machining gray cast iron this layer protects the cutting edge against abrasive wear. In case of CGI no layer formation occurs. Against the abrasive wear new cutting materials and tools for the machining of CGI must be developed.