In summary, the smelting, refining, and casting of iron and steel are the processes for extracting iron from ore, removing useless and harmful elements and adding necessary elements, and obtaining clean and homogeneous materials of required shape, respectively. These results are achieved by making use of chemical reactions among the substances involved. The scientific principles that deal with chemical reactions are those of thermodynamics and reaction kinetics. The former deals with the direction in which a reaction proceeds and reaches the equilibrium state, and the latter considers the mechanism and rate of the reaction to reach the equilibrium. A prerequisite for the application of these principles is that the structure of the substances participating in the reactions and the values of physical properties based on their structure should be known in as much detail as possible. For better understanding, it is necessary to have a knowledge of statistical mechanics and statistical thermodynamics. The most important feature of the smelting, refining, and casting processes for iron and steel is their ability to handle large amounts of liquid materials such as hot metal, molten steel, and molten slag. Consequently, it is imperative to have a thorough knowledge of the scientific principles underlying the transfer of heat, momentum, and mass, and the movement of fluids at elevated temperatures. Good castings without segregation of solute elements or cracks can be achieved by studying (i) the nucleation, growth and phase transformation of crystals growing from molten steel, (ii) associated heat transfer, and stress and strain in the crystals, (iii) changes in the concentration of the solute elements, and (iv) the mechanical behavior of materials at elevated temperatures. Advances in computer technology enable desk experiments by combining physical and mathematical models with computer simulation. Recent progress in this approach includes analysis and design of iron and steel manufacturing processes and construction of phase diagrams for designing new alloys. As the data base for this area of science and technology accumulates and our understanding on the processes improves, this approach will further develop to enhance the progress of the processing of iron and steelmaking. Further progress in all of these related studies is required to ensure that smelting, refining, and casting techniques continue to improve in the future.