Solid-state phase transformation of ductile cast iron during electroslag remelting cladding

ABSTRACT A bimetallic composite roll with the cladding layer of high-speed steel (HSS) and the roll core of ductile cast iron (DCI) was manufactured by the electroslag remelting cladding (ESRC) technology, and the changes in the graphite morphology, matrix structure, and mechanical properties of the DCI core before and after the ESRC process were compared. The DCI core was first heated to a very high temperature and then cooled down to room temperature during ESRC which led to a deteriorative graphite morphology with a low spheroidisation rate, a large size, and a nonuniform distribution and also caused a solid-state phase transformation of the matrix structure from lamellar pearlite + few carbides to bainite + large amounts of carbides. Based on the changes of graphite sphericity, matrix structure, carbides content, the tensile strength and impact toughness of DCI before and after the ESRC process changed from 458 MPa, 3.02 J/cm2 to 417 MPa, 5.74 J/cm2, respectively.