The rate of dissolution of sponge iron into molten steel has been studied. Reduced pellets from Midrex and HyL processes and pellets containing coal char were used. The dissolution of the pellets is accompanied by continuous gas evolution which is due mainly to the reduction of iron oxides remaining in the pellets by the carbon within the system. It was found that HyL pellets dissolved faster than Midrex and Midrex pellets dissolved faster than Sartenejas. The rate of heat transfer from the bath to the pellet was found to increase with increasing gas evolution. The melting process was simulated by a mathematical model by assuming heat transfer control. This model allowed the calculation of the heat transfer coefficient as a function of the instantaneous radius of the pellet.