Aiming at the quality problems such as segregation, porosity and shrinkage cavities that are difficult to eliminate due to the size effect of large die-cast steel ingots as large forging blanks, the idea of layered casting of large steel ingots is proposed. The transient heat transfer process and cladding path of the ingot core and cladding layer under different molten steel casting temperatures, different ingot core diameters and different ingot core preheating temperatures were studied by combining numerical simulation and thermal experiments. The research results show that the cladding path has a certain functional relationship with the diameter of the ingot core and the preheating temperature of the ingot core. Obviously, the interfacial melting rate can be significantly improved. The thermal scaling experiment was carried out on the cladding path under the condition of a casting temperature of 1,560°C and no preheating of the ingot core. The microhardness of the interface is higher than that of the clad steel ingot, and the metallurgical bond of the interface is good.