Homogenization of ductile iron using partial melting aided by modeling

Development of high Mo carbide free thick section nodular cast iron by partial melting homogenisation

“…In ductile iron, graphite promoting elements segregate around graphite nodules while carbide promoting elements segregate in the intercellular regions. [2][3][4][5][6][7][8] It has also been shown that the conventional solid state homogenisation does not effectively reduce alloying elements segregation even after a long period of high temperature austenitisation. 1,7,9,10 Purdy et al applied partial melting homogenisation (PMH) process successfully for homogenisation of NiSnCu alloys.…”

“…11 The same process was applied to different manganese content ductile iron, successfully homogenising the matrix with reasonable mechanical properties. 8,12,13 Partial melting heat treatment includes heating to PMH temperature and continuing the treatment isothermally for a period of specified duration. 8 Very little has been reported as far as the nature of Molybdenum eutectic carbides in ductile iron goes.…”

“…8,12,13 Partial melting heat treatment includes heating to PMH temperature and continuing the treatment isothermally for a period of specified duration. 8 Very little has been reported as far as the nature of Molybdenum eutectic carbides in ductile iron goes. Zeytin et al reported Fe 2 MoC and M 6 C carbides in high SiMo ductile iron alloyed with 2%Mo and 4-6%Si.…”

“…In case the homogenisation conditions are not well set, the liquid pool may form but may remain unchanged upon cooling to room temperature, it transforms to ledburite while the regions around the graphite nodules are left solid. 8 This is in fact an attempt to experience partial melting homogenisation (PMH) process on a high Mo ductile iron (1?24 wt-% Mo) to get a homogenised and carbide free austempered ductile iron. Special attention is paid to the characterisation of Mo rich as cast intercellular carbides and the carbides annihilation during the PMH process.…”

“…As more Mo or Mn or Cr is used, primary carbides form, and the size and fraction of carbides in the eutectic cell boundaries increase through the excessive segregation of the elements into the intercellular boundaries. In ductile iron, graphite promoting elements segregate around graphite nodules while carbide promoting elements segregate in the intercellular regions 2 – 8…”