Steel for wind power gear with improved purity and reliability, and smelting method therefor

A smelting method for producing purified steel, comprising the following steps:

• a primary smelting step S1, comprising
• adding raw materials of molten iron and scrap steel to a converter in a predetermined ratio for primary smelting to obtain primary molten steel;
• a refining step S2, comprising
• hanging a molten iron ladle containing the primary molten steel obtained in step S1 into a refining furnace, and
• adding premelted refining slag to the primary molten steel and performing refining,
• wherein components in the premelted refining slag, which include primarily Al2O3 and CaF2, are selected in amounts and proportions to obtain a refined molten steel having predetermined inclusion characteristics;
• a vacuum degassing step S3, comprising
• subjecting the refined molten steel obtained in step S2 to a vacuum degassing treatment to remove hydrogen and oxygen from the refined molten steel;
• a continuous casting step S4, comprising
• after vacuum degassing the refined molten steel in step S3, hanging the molten iron ladle into a continuous casting ladle,
• performing slag discharge detection, and
• performing a continuous casting process,
• wherein during said continuous casting process,
• long nozzle inert gas protection and submerged nozzle protection are implemented,
• tundish inert gas protection is implemented,
• tundish covering slag is utilized,
• continuous temperature measurement is implemented,
• casting protection with a crystallizer pre-melted slag is implemented,
• automatic liquid level control is implemented,
• crystallizer electromagnetic stirring is implemented,
• water dynamic control is implemented in a secondary cooling zone,
• end section electromagnetic stirring is implemented, and
• a continuous casting blank is obtained at a constant temperature falling within the range of 1500-1600° C. and at a constant pulling rate falling within the range of 0.20˜0.28 m/min;
• wherein the tundish covering slag is a tundish covering agent and its main components include magnesium oxide, silicon dioxide, and silicon oxide;
• and
• wherein the continuous casting step S4 is performed in a manner such that a shrinkage cavity of the continuous casting blank obtained in the step S4 is not greater than 1.0 grade;
• and
• an electroslag remelting step S5, comprising
• placing the continuous casting blank obtained in step S4 into a gas-shielded electroslag furnace having a gas protection device,
• charging a protective gas from the gas protection device,
• adding a slag charge, and
• igniting, smelting, and feeding after slag melting so as to obtain said purified steel;
• wherein
• a melting rate of the smelting in step S5 is in the range of 12-15 kg/min;
• the slag charge added during said electroslag remelting in the step S5 is a binary slag system composed of Ca compounds and Al compounds;
• and
• the protective gas charged in the step S5 is argon gas or nitrogen gas;
• the steps S1 through S5 being conducted such that the chemical components of the purified steel, in terms of mass percentage, are C:
• 15˜0.19%, Si≤0.4%, Mn:
• 0.5˜0.7%, P≤0.012%, S≤0.006%, Cr:
• 1.5˜1.8%, Mo:
• 0.28˜0.35%, Ni:
• 1.4˜1.7%, Al:
• 0.02˜0.04%, and the balance is Fe and unavoidable impurities.