Method for manufacturing large ingot through electromagnetically-controlled self-inoculation treatment

Abstract

The invention relates to a method for manufacturing a large ingot through electromagnetically-controlled self-inoculation treatment. The method comprises the steps as follows: (1) a Y-shaped double-phase conveying nozzle is adopted for molten metal casting, and an electromagnetic device I is arranged on the outer side of the straight section of the double-phase conveying nozzle; an electromagnetic device II is arranged on the outer side of an ingot mold riser; (2) an ingot mold and the double-phase conveying nozzle are preheated before casting; (3) argon shielding is performed during casting, an inoculant is added when the liquid level of molten metal rises to 1/2-2/3 of the height of an inner cavity of the ingot mold, meanwhile, the electromagnetic device I is started, and the electromagnetic device II is started when the liquid level of molten metal rises to the height of the ingot mold riser line; and both the electromagnetic device I and the electromagnetic device II run at the low frequency; (4) after casting is completed, the electromagnetic device I is shut down, the electromagnetic device II s adjusted to run at the intermediate frequency from the low frequency, and heat insulation is performed on the ingot mold riser part by the aid of the Joule heating effect of the intermediate-frequency magnetic field until the ingot is solidified. With the method, the solidification structure of the steel ingot can be refined, the center segregation can be reduced, the center porosity can be reduced, and thus the inner and outer quality of the ingot can be improved.

Description

technical field [0001] The invention relates to the technical field of metal casting, in particular to the technical field of large ingot solidification structure and segregation control. Background technique [0002] Large castings and forgings are the basis for the development of the equipment manufacturing industry, and are widely used in important fields such as metallurgy, shipbuilding, national defense, electric power, nuclear energy, high-rise buildings, petrochemicals, etc. It has irreplaceable advantages in the production. Large-scale castings and forgings are mostly used in extreme and special environments. Therefore, steel not only requires high strength and plasticity, but also has extremely strict requirements on microstructure, composition uniformity, and defects such as segregation and cracks. [0003] Liquid metal solidification forming is one of the most important links in the ingot production process. The solidification structure is hereditary to the subse...

AI Technical Summary

Problems solved by technology

However, for steel castings with large cross-sectional dimensions, it is difficult to achieve rapid solidification through interface heat transfer. The ingot is cooled by increasing the external cooling intensity, and the temperature gradient of the ingot cross-section cannot be too large, otherwise crack defects will occur

Step cooling is beneficial for forming a positive temperature gradient from outside to inside, ensuring sequential solidification, and forming shrinkage cavities in the riser, but the cooling gradient and its dynamic control are not very operable

Electromagnetic stirring water-cooled mold casting steel ingot under the action of electromagnetic field strengthens the temperature uniformity in the steel ingot mold, and enhances heat transfer through the water-cooled mold, but it still only transfers heat through the mold wall interface, and the cooling intensity is difficult to achieve rapid cooling

[0005] Some technicians have explored the method of combining accelerated cooling with nucleation promotion, promoting the supercooling of molten steel in the mold by adding chilled iron, and reducing the heat transfer at the interface. Segregation large-scale steel ingot manufacturing method", the Chinese patent No. CN101406937 discloses "a kind of internal cooling method for suppressing macro-segregation of large steel ingots", and the Chinese patent No. CN104259441A discloses "built-in cold core and top electromagnetic field casting large steel ingot method” etc.; by adding chilling body and cold core casting, solidification can be achieved in both directions, increasing the cooling intensity and improving the central structure, but the uniformity of the distribution of the chilling body in the melt and the uniformity of the interface structure between the cold core and the ingot and stress problems are difficult to control

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