Turning processes and mechanism of compacted graphite iron used for high performance engine

Abstract

Compacted graphite iron (CGI) represents a new material for high-performance diesel engines of next generation. Compared with gray cast iron (GCI), it can enhance the cylinder pressure while reducing the weight of the engine. However, not all of the tools and parameters used to process GCI are applicable to CGI. The tool life, which is characterized by the height of flank wear in machining GCI, is 10–20 times that of GCI. In order to deeply study the machining gap between CGI and GCI, the machined surface morphology of CGI-450 and GCI-280 with different surface roughness was investigated. In addition, tool wear and cutting temperature were also monitored. Finally, the chip morphology after the first cutting was analyzed. The results show that the primary surface defects, with Ra = 2.0 μm, of CGI-450 are graphite cavities and feed marks, while those of GCI-280 are plastic flow and graphite cavities. The tool wear patterns of turning CGI-450 and GCI-280 are the same, and the maximum flank face value reaches 133 μm and 102 μm, respectively. If Ra =1.6 μm is the tool failure criterion, the tool life for machining CGI-450 is 1.73 times that for cutting CGI-450. The serration depth and chip opening angle after machining CGI-450 are larger than those of GCI-280. The cutting temperature increases with the surface roughness within a certain range, and the temperature of CGI-450 is 20% higher than that of GCI-280.