Method and device for restraining macrosegregation of cast aluminum alloy cast ingots in direct chill (DC) casting

Abstract

The invention discloses a method and device for restraining macrosegregation of cast aluminum alloy cast ingots in direct chill (DC) casting. The method includes the steps that an electromagnetic stirrer is arranged over a crystallizer, and in the casting process, the included angle alpha of the magnetic line of force of the electromagnetic stirrer and the slope of a liquid cave is adjusted to be greater than or equal to 90 degrees until the DC casting process is finished. An additional flow field formed by the electromagnetic stirrer in aluminum alloy melt can weaken or eliminate an aluminum alloy melt flow field caused by heat convection of aluminum alloy melt in the crystallizer, the aluminum alloy melt in the crystallizer and solute atoms at a solidification front of the liquid cave are promoted to be distributed evenly, macrosegregation of the aluminum alloy cast ingots is restrained, meanwhile, the slope of the solidification front of the liquid cave and the depth of the liquid cave are reduced, the temperature field in the aluminum alloy melt in the liquid cave is promoted to be even, and thus the structure and property homogeneity of subsequent processed products of oversized aluminum alloy cast ingots is remarkably improved. Compared with the prior art, relative macrosegregation of alloy elements of the cast ingots can be reduced from 10-17% to be within 5%, the problem of poor structure and property homogeneity of the oversized aluminum alloy cast ingots and the subsequent processed products of oversized aluminum alloy cast ingots in DC casting is solved, and the method and device are suitable for being applied to industries.

Description

technical field [0001] The invention discloses a method and device for suppressing the macro-segregation of DC casting (DC casting is DirectChillCasting, direct water-cooled semi-continuous casting) aluminum alloy ingot, especially a method and device for suppressing the macro-segregation of DC casting super-large aluminum alloy ingot , belonging to the field of non-ferrous metal material processing. Background technique [0002] Aluminum alloy processing products for aerospace structures have a high degree of alloying. When DC casting super-large aluminum alloy ingots, there is significant heat convection in the aluminum alloy melt in the crystallizer, such as Figure 2a As shown, it is easy to cause serious macro-segregation, and the relative macro-segregation of main alloy elements reaches 10-17%, resulting in uneven composition, structure and performance of aluminum processed products. As the specification of DC casting aluminum alloy ingots increases, the degree of macr...

AI Technical Summary

Problems solved by technology

[0004] (1) At present, when the electromagnetic stirring of the mold or other external fields are not used to intervene in the alloy element flow field caused by the convection of the aluminum alloy melt in the mold, the DC cast aluminum alloy ingot is prone to macro segregation. As the size of the ingot increases, the macro segregation is particularly significant. The DC cast high-alloyed large-scale aluminum alloy ingot may have serious macro segregation, and the relative macro segregation is 10-17%.

Due to severe macro-segregation, the content of alloy elements in local parts (such as the center) of the ingot is higher than the maximum limit of the nominal composition of the alloy, while at the same time, the content of alloy elements in the local part (such as the edge) of the ingot is lower than the minimum limit of the nominal composition of the alloy, such as image 3 and Figure 4 As shown, resulting in poor microstructure and performance uniformity of the final aluminum processed product, the design performance index must be reduced, and even the design use requirements cannot be met.

[0005] (2) The existing fixed electromagnetic stirrer above the crystallizer and the fixed electromagnetic stirrer under the water jacket of the crystallizer, since the positions of the electromagnetic stirrer and the crystallizer are fixed, the additional aluminum alloy melt flow generated by electromagnetic stirring cannot be adjusted field and the solidification front of the aluminum alloy melt liquid cavity in the mold, that is, the direction of the additional flow field of the aluminum alloy melt in the mold cannot be adjusted, and the effect of inhibiting the macro segregation of the DC casting aluminum alloy ingot is limited

[0006] (3) The existing fixed electromagnetic stirrer under the crystallizer water jacket is limited by the space of the fixed electromagnetic stirrer under the crystallizer water jacket, the size of the electromagnetic inductor is limited, the electromagnetic induction magnetic field strength and the additional aluminum alloy melt flow field The strength is small, the effect is affected, or in the case of the same electromagnetic induction magnetic field strength and additional aluminum alloy melt flow field strength, a higher power DC power supply is required, and the specifications of DC casting aluminum alloy ingots are limited, making it difficult to effectively suppress Macro-segregation of super-sized aluminum alloy ingots in DC casting

[0007] The existing method of fixing the electromagnetic stirrer above the crystallizer and the electromagnetic stirrer under the water jacket of the mold controls the stability of the electromagnetic induction magnetic field strength, and thus ensures the process stability and the stability of the ingot structure in the entire DC casting process The difficulty is greater, the direction of the induction magnetic field cannot be adjusted, and the economy is also poor

[0008] (4) The existing method of circulating the aluminum alloy melt in the crystallizer with a mechanical pump is easy to damage the oxide film on the surface of the aluminum alloy melt in the crystallizer, and the oxide film is involved in the melt to form secondary inclusions. It is also easy to cause local coarse grains in DC casting aluminum alloy ingots, and the risk of various casting defects is high, and the quality of DC casting high-alloyed super-large aluminum alloy ingots with high requirements cannot be guaranteed.

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