Effect of Melting Rate of Electroslag Rapid Remelting on the Microstructure and Carbides in a Hot Work Tool Steel

The microstructure and primary carbides in the steel billets produced by an industrial-scale electroslag rapid remelting (ESRR) at different melting rates were studied. The amount and size of primary carbides MC and M2C at the center of the remelted ingots is larger than that at the mid-radius of the remelted ingots. The amount of primary carbides and secondary dendrite arm spacing of the ingot increase with the increase in the melting rates of ESRR, caused by the increase in the local solidification time. The microsegregation of Mo in the remelted ingots after annealing is most serious among the carbide-forming elements. The microsegregation of Mo and Cr increases linearly with increasing the melting rate, and the microsegregation of V keeps nearly constant with further increasing the melting rate from 400 to 500 kg/h. Increasing the melting rate of ESRR do not change the types of primary carbides until 500 kg/h, at which another type of primary carbide M7C3 is formed. The amount of the primary carbides and the microsegregation degree of Mo, V and Cr in the ESRR billets at the melting rate of 400 kg/h is nearly same as that produced by same-scale conventional ESR.