Method and device for homogenizing the solidified structure of a large ingot with a static magnetic field combined with a rotating magnetic field

Abstract

The invention discloses a method and device for homogenizing a large ingot solidification structure by combining a static magnetic field with a rotating magnetic field. Through the electromagnetic oscillation effect generated by a combined magnetic field and the rotational flow induction stirring effect of the rotating magnetic field, nucleation is promoted, dendritic crystal tips are crushed, crystal grains are refined, the solidification structure is homogenized, macroscopic segregation is reduced, and therefore the method and the device are used for the large ingot casting process. When metal melt is solidified, the static magnetic field and the rotating magnetic field are exerted to a heat preservation riser in a combined mode according to the characteristics that metal liquid at an ingot mould riser is solidified lastly, the riser wall and the metal liquid surface are easy to nucleate first, and the rotating magnetic field and the static magnetic field can easily permeate a riser material, the metal liquid in the heat preservation riser is effectively oscillated and stirred, and the metal liquid in the riser is delivered into the metal liquid at the center of an ingot mould through oscillating and rotational flow stirring; the dendritic crystal tips are crushed, the crystal grains are refined, the solidification structure is homogenized, macroscopic segregation is reduced, a compact, homogenized and crystal grain-refined large ingot is obtained, and therefore the subsequent machining performance and service performance of the large ingot are improved.

Description

technical field [0001] The invention relates to a metal solidification process and its device, in particular to a metal solidification process and its device intervened by an external magnetic field, which is applied in the technical field of metal solidification structure control. Background technique [0002] In machinery manufacturing, cast steel is widely used. In recent years, with the rapid development of modern industrial technology, large-scale is the development trend of modern forging production. To obtain large-scale forgings with good quality, high strength and large size, it is necessary to provide large-scale steel ingots with good quality. Therefore, the development of steel ingots also follows the trend of large-scale development, and the quality requirements are getting higher and higher. For example, the low-voltage rotor of a nuclear power plant with a power of 1300MW needs to be manufactured with a giant steel ingot weighing 600t. The production technol...

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Problems solved by technology

These methods solve the above problems to a certain extent, but there are more or less unavoidable defects

When the refiner of dissimilar materials is added, it is necessary to strictly control the amount of refiner added in order to achieve a better refinement effect, and in some fields that require high metal purity, the addition of refiner of dissimilar materials will also cause metal At present, it is also possible to see the method of increasing the number of crystal nuclei in the solidification system by adding the same metal in the form of filaments, strips, cakes or rods. However, due to the introduction of additional metal oxide scales, it is easy to have uneven melting. The problem of uneven distribution of newly formed crystal nuclei limits the application of this method; electromagnetic stirring has the advantage of not directly contacting the solidified metal, which avoids pollution to the solidified metal, but electromagnetic stirring has the problem of attenuation. The cross-sectional size of ingot or continuous casting slab increases, and the effect of electromagnetic stirring is greatly reduced

As for the metal ingot mold used for large steel ingots, due to its strong ferromagnetism and wall thickness of 80-150mm, even if a very low frequency or even DC magnetic field is used at the same time as a high-power electromagnetic generator, the electromagnetic field can hardly penetrate into the metal ingot mold inside the molten steel, resulting in no effect of electromagnetic stirring; similarly, ultrasonic stirring also has the problem of serious attenuation and the reaction between the probe and molten steel or alloy liquid, while the stirring paddle of ordinary mechanical stirring will be corroded by the metal melt, The service life of the agitator is short, and the corrosion of the agitator will also cause metal pollution. Improper agitation speed will also cause hazards such as slag rolling, and there is a risk of the agitator being solidified and bitten during the solidification process.

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