The invention relates to a
smelting method for high-strength thick and large
ductile iron. Steel
scrap is added into a medium-frequency induction electric furnace to be smelted, then
foundry returns are added, heat preservation is performed for 5 min to 10 min when the temperature of molten iron in the furnace reaches 1500 DEG C to 1520 DEG C, meanwhile,
quenching and
tempering treatment is performed, and base iron is formed; a spheroidizing agent is added into a spheroidizing reaction pit of a spheroidizing
tundish, then the spheroidizing agent is covered with an inoculant, and finally the inoculant is covered with a 0
silicon steel sheet; when the temperature of the base iron reaches 1430 DEG C to 1460 DEG C, the base iron is discharged out of the furnace to enter the spheroidizing
tundish, when a spheroidizing reaction breaks out and begins, the inoculant is added into the spheroidizing
tundish again, and after spheroidizing, final molten iron is formed; and after spheroidizing ends, the final molten iron is subjected to pouring and
casting at the temperature of 1320 DEG C to 1340 DEG C within 10 min, meanwhile, a third-time inoculant is added, after pouring, when a
casting is cooled to 830 DEG C to 880 DEG C, a box is opened for
air cooling, and a
ductile iron pearlite is obtained. The
smelting method has the beneficial effects that the
smelting method can prevent burning losses of crystallizing
nucleation in molten iron, the molten iron quality is improved, and strength can also be substantially improved.