Interface bonding mechanism and heat treatment of the composite roll manufactured by electroslag remelting cladding method

Abstract

The Cr5/42CrMo and 45#/45# composite rolls had been produced by the electroslag remelting cladding (ESRC) method. The interface bonding mechanism was revealed according to grain and dendrite growth. The dendrites of cladding started an epitaxial growth on the partially melted grains and the grains boundaries of cladding grew following the orientation of the partially melted grains of the roll core, ensuring reliable metallurgical bonding between the cladding and the roll core. The heat treatment included the normalizing, annealing, quenching, and tempering process. During the annealing process, the ferrite zone formed on the roll core side because the C atoms diffused from the roll core of low C content to the cladding of high C content for the activity difference. During the quenching process, C atoms diffused from the cladding to the roll core, and the ferrite zone disappeared which ensured the continuous microhardness. The gradient of elements contents on both sides of the interface led to the distinctive difference in microstructure and properties. After the heat treatment, from the cladding to the roll core, the microstructures changed from martensite + carbides to pearlite + ferrite. Accordingly, the values of the Rockwell hardness (HRC) 53.6 and 25.7, the tensile strength (MPa) 1657 and 879, and the impact toughness (J/cm2) 5 to 54 were achieved in the cladding and roll core, respectively. The composite rolls had the cladding of high hardness and roll core of superior impact toughness that could satisfy the requirement for backup rolls of hot strip mills.