Fired mold precision casting method for improving solidification heat dissipation conditions of directional solidification casting

Abstract

The invention belongs to the technical field of precision casting of directional solidification column crystal or single crystal test bars, and relates to a fired mold precision casting method for improving solidification heat dissipation conditions of a directional solidification casting. In the directional column crystal or single crystal test bar manufacturing process, selected mold shell materials are the same as universal mold shell materials. The shape of a mold shell is changed, the equal-distance variable cross section is increased, and a plurality of equal-distance rectangular grooves are formed. When the directional solidification test bars and the mold shell move to the position below a heat insulation plate together, mechanical expansion rings arranged in a directional solidification furnace are inlaid in the equal-distance rectangular grooves of the mold shell; the mechanical expansion rings expand downwards to remove the part, below the grooves, of the mold shell; the lower end of the directional solidification casting is in direct contact with cooling media, so that the heat exchange conditions of the directional solidification test bars and the cooling media are improved; and therefore, the cooling speed of the directional solidification casting and the temperature gradient of a solid-liquid interface are greatly improved, the dendritic crystal structure of the directional solidification casting is refined, dendritic segregation is reduced, and the mechanical property of the casting is remarkably improved.

Description

technical field [0001] The invention belongs to the technical field of precision casting of directional solidification castings, and in particular provides an investment precision casting method for improving directional solidification heat dissipation conditions. Background technique [0002] In the casting process of directional solidification castings, the precision mold shell casting method is commonly used at present. The heat exchange between the casting and the environment has four control links, which are: the interface heat transfer between the casting and the chilled plate (heat transfer coefficient h C ); the radiation heat transfer between the casting and the inner surface of the mold shell (heat transfer coefficient h gap ); heat conduction through the formwork (heat conduction coefficient h sheel ); the heat transfer between the shell and the ambient cooling medium (heat transfer coefficient h r ). The total heat transfer coefficient between the casting and...

AI Technical Summary

Problems solved by technology

[0004] Generally speaking, the interface heat transfer coefficient h between the casting and the chilled plate C Larger, about 1500W / (m 2 k) or so, while the other three items have poor thermal conductivity due to the shell material, the heat transfer coefficient h gap 、h sheel 、h r than h C An order of magnitude smaller, resulting in the total heat transfer coefficient H of the casting and the environment b Very low, unable to guarantee the high temperature gradient of the solidification interface of the casting and the optimization of the microstructure and properties of the casting

At present, the Bridgman method, LMC method, GCC and FBQ method that have been researched and developed in the world all only improve the conditions for heat dissipation from the surface of the mold shell to the surrounding environment, and do not fundamentally change the huge thermal resistance brought by the mold shell itself during the solidification process of the casting. Therefore, it is impossible to fundamentally improve the temperature gradient at the solidification interface of the casting.

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