Scrap melting in the steelmaking process has recently attracted considerable attention. This study developed a mathematical model to investigate the effects of sizes, initial temperatures and carbon contents of scrap, and bath flow on its melting behaviors. The results showed that the volume of the solidified shell on the melting interface could be decreased or eliminated by increasing the initial temperature of the scrap. The initial carbon content also significantly influenced the melting behavior. The completion melting time decreased from 253 to 80 s when the carbon content increased from 0.10% to 0.30%. Importantly, the natural convection or driven flow formed in the bath significantly influenced the melting behaviors. Moreover, the dominating factors changed as the melting proceeded. Therefore this study provides more insights into the melting behavior of the scrap during the steelmaking process at different operating conditions.