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Showing 1 results for Partial Austenitising
Mohsen Sabzalipour, Ali Mohammad Rashidi,
Volume 24, Issue 8 (7-2024)
Abstract
The main goal of present work is to identify the appropriate austenitising category to achieve the austempered ductile irons with dual matrix structure having the best possible machinability. In this regard, specimens of low-alloyed ferritic spheroidal graphite cast iron were prepared by casting process. In order to obtain a mixed ferrite-austenite structures having different volume fraction of austenite phase, samples were subjected to one of two processes: a) partial austenitising at 870 oC for various times (5 to 60 min) or b) intercritical austenitising at various temperatures (750, 765, 780 and 800 oC) for 60 minutes. After that they were austempered in molten salt at a temperature of 350 oC for one hour. During turning with a lathe equipped with a force dynamometer, the cutting forces of the workpieces were measured as a general adopted criterion for machinability investigation. According to the obtained results, with the increase of partial austenitising time or intercritical austenitising temperature, the volume fraction of the ausferrite phase increased, but the cutting force decreased initialy and then increased. For a certain percentage of the ausferrite phase, the turning of samples prepared with partial austenitising process was associated with lower cutting force, compared to the samples obtained by the intercritical austenitising process. In general, it can be concluded that the maximum machinability of dual matrix ductile iron austempered at 350 oC is achieved when the selected austenitising temperature and time results to creation dual matrix structure containing 39 ± 3 Vol% ausferrite phase
