PURPOSE: To effectively utilize the sensible heat of waste gas, reduce the mixing ratio of molten pig iron, and raise its yield by recovering waste gas generated after being utilized for preheating scraps prior to charge into the converter.

CONSTITUTION: A scraps preheating box 2 is placed in duct 1 through an entrance 1a by using a roller table 4. The scraps 3 are preheated directly by high-temperature waste gas. The preheating box 2 is made of a material obtained by coating a heatresistant steel plate with a refractory, and also each roller of the roller table is made of a water-cooled hollow material. Thus, the amount of iron ore to be charged can be increased with lesser amounts of molten pig iron and therefore its yield can be raised.