NOVELTY - Iron ore is sintered and smelted using a blast furnace to reduce and obtain molten iron. After dephosphorization and desulfurization, molten iron is injected into an intermediate frequency induction furnace. Waste steel and foundry returns are added to smelt, and the components of molten iron are regulated. Nodulizing and inoculating treatments are carried out, and molten iron is cast to obtain a cast with thick and large section for wind power equipment.    USE - Casting of wind power equipment.    ADVANTAGE - The method is short and productive. The method uses an intermediate frequency induction furnace to replace cupola furnace. Hence, the impurities in molten iron and the temperature of molten iron are precisely controlled to enable environmental protection and energy-saving function. In dephosphorizing, desulfurizing, nodulizing and inoculating treatments, alloy cored wires are used to make the treatments have quick effect and high efficiency, so that the graphite spheres are effectively increased so as to obtain cast with thick and large section.    DETAILED DESCRIPTION - Fine iron powder is prepared by crushing and magnetically separating iron ore, and sintered into a sintered ore. The sintered ore is fed into a blast furnace to be reduced into melted iron through hot air and coke. The molten iron is added to a heat preserving ladle and the ladle is conveyed to a wire feeding machine. An alloy cored wire covered by a dephosphorizing agent is fed into the ladle, in which the additional amount of dephosphorizing agent is 2-5 %mass. The dephosphorizing agent is a powder prepared using (in %mass) calcium oxide (42-45), ferrous oxide (44-46), and calcium fluoride (9-14). Nitrogen is blown-in into the bottom of ladle to form a whirl to stir molten iron for dephosphorization. The alloy cored wire covered by dephosphorizing agent is fed to the ladle, in which the additional amount of dephosphorizing agent is 0.8-2 %mass. Nitrogen is blown-in into the bottom of ladle to form whirl for stirring to dephosphorize molten iron in the ladle, and then molten iron is slagged off. The molten iron is injected after dephosphorization and desulfurization into an intermediate frequency induction furnace for smelting. After spectrometric detection to analyze the ingredients of molten iron, waste steel and foundry returns are added to regulate the ingredients of molten iron to adjust carbon and silicon content to 3.45-3.55 %mass and 0.6-0.7 %mass, respectively. The additional amount of molten iron is 75-80 %mass, foundry returns is 10-12.5 %mass, and waste steel is 10-12.5 %mass. Molten iron, foundry returns, and waste steel are smelted together, in which foundry returns are unqualified casts need to be re-smelted. Smelted molten iron is injected into a pouring ladle and conveyed to wire feeding machine. The alloy cored wire covered by yttrium-based heavy rare-earth composite nodulizing agent powder is fed into molten iron, while blowing-in nitrogen into the bottom of pouring ladle for nodulizing treatment, in which the additional amount of nodulizing agent is 1.5-1.6 %mass. The alloy cored wire covered with inoculating agent is then fed into molten iron, while blowing-in nitrogen into the bottom of pouring ladle for inoculating treatment, in which the additional amount of inoculating agent is 1.25-1.35 %mass, and then molten steel is slagged off. The yttrium-based heavy-rare-earth composite nodulizing agent is a powder comprising magnesium (6.5-8.5), rare-earth element (2-3.5), silicon (45-50), calcium (1-2), barium (1-2), and iron (remainder). Yttrium takes 50-60% of rare-earth element. The inoculating agent is a powder comprising silicon (70-75), barium (1-3), calcium (0.75-1.5), and iron (remainder). Molten iron is directly pour-formed into a cast with thick and large section for wind power equipment. The final chemical components of the cast are carbon (3.4-3.5), silicon (1.9-2), manganese (0.25 or less), sulfur (0.015 or less), phosphorus (0.035 or less), titanium (0.035 or less), rare-earth element (0.015 or less), magnesium (0.045-0.06), and iron (remainder).