Method for suppressing stray crystal forming and growing at seed crystal starting end, and casting case construction thereof

Abstract

The invention relates to a technology for preparing a single crystal high-temperature alloy and especially provides a method for inhibiting stray crystal formation and growth in seed crystal initiating terminal and the shuttering structure. The preparing method based on seed crystal method comprises: preplacing the seed crystal in the shuttering, arranging a necking structure in the initiating terminal, forming stray crystal in the initiating terminal of inhibiting the seed crystal growth, and growing into the single crystal from the alloy melt on the unmelted interface of the seed crystal in the form of the epitaxial growth. The shuttering structure in the invention is the shuttering structure for preplacing the seed crystal, a necking structure is arranged on the bottom of the shuttering over the initiating terminal of seed crystal growth. The invention combines the seed crystal method initiating terminal design with the necking crystal-selecting device for inhibiting and removing the stray crystal in the process of the single crystal growth, controlling the crystal orientation, and improving the single crystal yield.

Description

technical field [0001] The invention relates to the preparation technology of single-crystal high-temperature alloys, and particularly provides a method for suppressing the formation and growth of miscellaneous crystals at the starting end of a seed crystal and a mold shell structure. Background technique [0002] In order to obtain a single crystal, a single crystal nucleus must first be formed in the metal melt, and a seed crystal or spontaneous nucleation can be introduced, and then a single crystal is continuously grown on the crystal nucleus-melt interface. There are usually two methods to obtain a single crystal nucleus, namely the selection method and the seed method. For single crystal superalloys, these two methods have their own advantages and disadvantages, and they complement each other and cannot be neglected. The crystal selection method does not require a tedious seed crystal preparation process, and the yield is high, so it has been widely used. It is based ...

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Problems solved by technology

When using the seed crystal method to grow a single crystal, when the seed crystal 2 is high but the melting part is small, an angle is formed between the seed crystal 2 and the mold shell 1, although the use of the corundum tube 3 at the starting end of the seed crystal 2 can ensure that the seed crystal The crystal 2 is in close contact with the corundum tube 3, but an angle or step is easily formed between the corundum tube 3 and the mold shell 1. According to the crystal nucleation theory, the nucleation work is the smallest at the angle or step, and the alloy liquid is easy to form here core and grow, destroying the integrity of the single crystal

When the seed crystal 2 is not preset, the gap between the seed crystal 2 and the mold shell 1 is too large, and it is easy to cause the alloy solution to flow down along the gap during pouring. The gap between seed crystal 2 and shell 1 nucleates and grows, thereby introducing miscellaneous crystals; when there is more alloy melt flowing down the gap, the gap between seed crystal 2 and shell 1 is larger at this time, and the friction is smaller. The alloy liquid easily lifts the seed crystal 2, the seed crystal 2 is separated from the crystallizer, and the heat dissipation path is cut off, resulting in the complete melting of the seed crystal 2, which loses the role of the single crystal nucleation core of the seed crystal, resulting in failure of the seed crystal growth

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