A method of producing a single crystal blade by a seed crystal method

Abstract

The application discloses a method for preparing a single crystal blade by a seed crystal method, which comprises wax mold preparation, wax mold assembly, mold shell preparation, seed crystal loading and preheating and holding, and pouring and smelting; a removal channel is additionally arranged on the mold shell; during the pouring process, the top oxidation film of the seed crystal is pressed into the removal channel by using the molten metal liquid, and the oxidation film is removed from the seed crystal cavity, so that the seed crystal can grow smoothly by epitaxy, and thus the mixed crystal and strip crystal defects caused by the existence of the oxidation film are avoided; meanwhile, the removal channel is inclined upward and then bent downward to contact the quenching bottom disc, and the grains in the removal channel cannot grow into the seed crystal cavity to generate the mixed crystal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of single crystal preparation, and particularly relates to a method for preparing a single crystal blade by a seed crystal method. BACKGROUND

[0002] Currently, the methods for obtaining single crystals mainly include a selection method and a seed crystal method. The selection method is to obtain a single crystal by a competitive growth between crystal grains in a directional solidification process after a large number of nucleation at the bottom of a seed crystal section. The seed crystal method is to grow a single crystal in an epitaxial growth manner of a seed crystal by prepositioning a seed crystal with a desired orientation at the bottom of a casting, and the seed crystal method can accurately control the primary and secondary dendrite orientations of the single crystal casting. However, in the current seed crystal method, an oxidation film is generated at the top of the seed crystal loaded in the mold shell during a preheating process, which hinders the epitaxial growth of the seed crystal and causes the generation of mixed crystals and strip crystal defects (as shown in FIG. 1). Figure 1 SUMMARY

[0003] The main purpose of the application is to provide a method for preparing a single crystal blade by a seed crystal method, which aims to move the oxidation film at the top of the seed crystal out of the seed crystal cavity during pouring, so that the seed crystal can grow epitaxially smoothly, thereby achieving the purpose of solving the mixed crystal and strip crystal defects.

[0004] To this end, the method for preparing a single crystal blade by a seed crystal method provided by the application comprises the following steps.

[0005] S1, wax mold preparation

[0006] The blade wax mold, the base plate wax mold, the seed crystal cavity wax mold, the removal channel wax mold and the pouring system wax mold are made;

[0007] S2, wax mold assembly

[0008] The base plate wax mold, the seed crystal cavity wax mold, the blade wax mold and the pouring system wax mold are sequentially connected, one end of the removal channel wax mold is connected with the side of the seed crystal cavity wax mold, and the other end is extended upwardly and downwardly bent to be connected with the base plate wax mold, so as to form a wax tree;

[0009] S3, mold shell preparation

[0010] The corresponding ceramic mold shell is made by using the formed wax tree;

[0011] S4, seed crystal assembly and preheating

[0012] The seed crystal is assembled in the seed crystal cavity of the ceramic mold shell, and the top end of the seed crystal is located at the position where the seed crystal cavity is connected with the removal channel, and then the ceramic mold shell assembled with the seed crystal is loaded into a directional solidification furnace for preheating and heat preservation;

[0013] S5, pouring and smelting

[0014] ​The molten metal liquid is poured into the ceramic mold shell, and under the action of the pressure head, the oxidation film on the top of the seed crystal is pressed into the removal passage of the ceramic mold shell and falls along the removal passage to the chill base plate of the directional solidification furnace, and then is fixed by the rapidly solidified metal liquid.

[0015] Specifically, the seed crystal and the seed crystal cavity of the ceramic mold shell are designed as matching frustopyramidal shapes, and when the seed crystal and the ceramic mold shell are assembled, a support rod is matched and installed at the bottom end of the removal passage, and the lower ends of the seed crystal and the support rod are both extended to the outside of the ceramic mold shell. After the mold shell assembled with the seed crystal is installed on the chill base plate, the seed crystal and the support rod will support the entire ceramic mold shell, so that the ceramic mold shell does not contact the chill base plate, the weight of the ceramic mold shell is entirely pressed on the seed crystal and the support plate, the seed crystal cavity fully abuts against the seed crystal without gap, and the metal liquid cannot flow into the gap to form a gap, so that the gap crystal is not formed.

[0016] Specifically, the diameter of the wax mold of the seed crystal cavity is 5-8 mm, and the diameter of the wax mold of the removal passage is 4-6 mm.

[0017] Specifically, the included angle between the inclined section of the wax mold of the seed crystal cavity and the wax mold of the removal passage is 50-60°.

[0018] Specifically, the preheating temperature of the ceramic mold shell is 1500-1600 °C, and the holding time is 10-20 min.

[0019] Compared with the prior art, at least one embodiment of the present application has the following beneficial effects: by additionally arranging the removal passage on the mold shell, in the pouring process, the oxidation film on the top of the seed crystal is pressed into the removal passage by the molten metal liquid, the oxidation film is removed from the seed crystal cavity, so that the seed crystal can grow smoothly, and the existence of the oxidation film will not cause the defects of the mixed crystal and the strip crystal; meanwhile, the removal passage is inclined outward and upward and then is bent downward to contact the chill base plate, so that the grains in the removal passage will not grow into the seed crystal cavity to produce the mixed crystal. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0021] Figure 1 is a schematic diagram of the assembly of the seed crystal and the seed crystal cavity in the prior art seed crystal method;

[0022] Figure 2 is a schematic diagram of the assembly of the seed crystal and the seed crystal cavity involved in embodiment 1 of the present application;

[0023] Figure 3 is a schematic diagram of the pouring and smelting involved in embodiment 1 of the present application;

[0024] Figure 4 is a schematic diagram of the casting smelting involved in embodiment 2 of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] In the description of the present application, it should be understood that the terms “center”, “longitudinal”, “transverse”, “length”, “width”, “thickness”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0027] In addition, the terms “first” and “second” are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with “first” and “second” can include one or more of the features explicitly or implicitly. In the description of the present application, the meaning of “multiple” is two or more, unless otherwise specifically limited.

[0028] Embodiment 1

[0029] Referring to Figure 2 and Figure 3 A method for preparing a single crystal blade by a seed crystal method, comprising:

[0030] S1, wax mold preparation

[0031] The blade wax mold, the base plate wax mold, the seed crystal cavity wax mold, the removal channel wax mold and the pouring system wax mold are made;

[0032] S2, wax mold assembly

[0033] The base plate wax mold, the seed crystal cavity wax mold, the blade wax mold and the pouring system wax mold are sequentially connected, one end of the removal channel wax mold is connected with the side of the seed crystal cavity wax mold, and the other end is inclined upward and then bent downward to connect with the base plate wax mold, to form a wax tree;

[0034] S3, shell preparation

[0035] The wax tree is used to make a corresponding ceramic shell;

[0036] S4, seed crystal and preheating

[0037] The seed crystal is assembled in the seed crystal cavity of the ceramic shell, and the top end of the seed crystal is located at the connection position of the seed crystal cavity and the removal passage. Then the ceramic shell with the seed crystal is placed on the chill base of the directional solidification furnace, and the ceramic shell is raised into the hot chamber of the directional solidification furnace for preheating and holding. The preheating temperature is 1600°C, and the holding time is 10 minutes.

[0038] S5, pouring and smelting

[0039] The 1600°C molten metal liquid is poured into the ceramic shell, and the metal liquid enters the seed crystal cavity along the pouring system and the blade cavity. Under the action of the metal liquid pressure head, the oxidation film at the top of the seed crystal is pressed into the removal passage of the ceramic shell and falls onto the chill base along the removal passage. Then the chill base is lowered to lower the shell into the cold chamber, and the seed crystal grows epitaxially to form a single crystal blade. The metal liquid in the removal passage is rapidly solidified under the action of the chill base to fix the oxidation film.

[0040] In this embodiment, by adding a removal passage on the shell, the top oxidation film of the seed crystal is pressed into the removal passage by the molten metal liquid during pouring, and the oxidation film is removed from the seed crystal cavity, so that the seed crystal can grow epitaxially smoothly, and thus the defects of mixed crystals and strip crystals caused by the existence of the oxidation film are avoided. At the same time, the removal passage is inclined outward and extends upward and then bends downward to contact the chill base. The grains in the removal passage will not grow into the seed crystal cavity to produce mixed crystals. After the shell is completed, the removal passage part can also play a role in reinforcing the strength of the shell in the seed crystal section.

[0041] It can be understood that in actual design, the diameter of the wax mold of the seed crystal cavity can be designed as 6mm, the height is 35mm, the diameter of the wax mold of the removal passage can be designed as 4mm, and the included angle of the inclined section of the wax mold of the seed crystal cavity and the wax mold of the removal passage is designed as 55°. When pouring the molten metal liquid, the metal liquid will press part of the molten seed crystal and the metal film into the right Ф4mm removal passage under the action of gravity, thereby preventing the oxidation film from cutting or pulling the normal growth of the seed crystal section dendrite, and eliminating the large-angle grain boundary caused by the metal film to cause the casting to be scrapped.

[0042] Example 2

[0043] Reference Figure 4Unlike Example 1, in this example, the seed crystal cavity of the seed crystal and the ceramic mold shell are designed as matching frustoconical shapes. When the seed crystal and the ceramic mold shell are assembled, a support rod is installed at the bottom of the removal channel. At the same time, the lower ends of the seed crystal and the support rod extend outside the ceramic mold shell. After the mold shell with the seed crystal is installed on the chilling base, the seed crystal and the support rod will support the entire ceramic mold shell, so that the ceramic mold shell does not contact the chilling base. The weight of the ceramic mold shell is entirely pressed on the seed crystal and the support plate. The seed crystal cavity and the seed crystal are fully fitted without gaps. Therefore, during pouring, the molten metal will not enter between the seed crystal and the seed crystal cavity to form a gap, and thus no gap impurities will be formed.

[0044] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0045] Furthermore, if the present invention discloses or relates to mutually fixedly connected components or structural parts, then unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured using a casting process) (except where it is obviously impossible to use an integral molding process).

[0046] Furthermore, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in this invention include states or shapes that are similar to, analogous to, or close to those states or shapes. Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured using a one-piece molding process.

[0047] The above embodiments are merely illustrative examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing single-crystal blades using a seed crystal method, characterized in that, include: S1. Wax Model Preparation Make wax models of blades, chassis, seed crystal cavity, removal channel, and gating system; S2, Wax Model Tree The base wax model, seed crystal cavity wax model, blade wax model and gating system wax model are connected in sequence. One end of the exit channel wax model is connected to the side of the seed crystal cavity wax model, and the other end is tilted outward, extended upward and then bent downward to connect with the base wax model to form a wax tree. S3, Mold Preparation The corresponding ceramic mold shells are made using the wax tree components; S4, loading seed crystals and preheating / insulating the temperature. The seed crystal is assembled in the seed crystal cavity of the ceramic mold shell, and the top of the seed crystal is located at the connection position between the seed crystal cavity and the removal channel. Then the ceramic mold shell with the seed crystal is placed in the directional solidification furnace for preheating and heat preservation. S5, Casting and Melting Molten metal is poured into a ceramic mold. Under the action of the pressure head, the oxide film on the top of the seed crystal is pressed into the removal channel of the ceramic mold and falls down along the removal channel onto the cooling base of the directional solidification furnace, where it is then fixed by the rapidly solidified molten metal. The diameter of the seed crystal cavity wax model is 5-8mm, the diameter of the exit channel wax model is 4-6mm, and the angle between the inclined sections of the seed crystal cavity wax model and the exit channel wax model is 50-60°.

2. The method according to claim 1, characterized in that: The seed crystal cavity of the seed crystal and the ceramic mold shell are designed to match in a frustoconical shape. When the seed crystal and the ceramic mold shell are assembled, a support rod is installed at the bottom of the removal channel. At the same time, the lower ends of the seed crystal and the support rod extend outside the ceramic mold shell. After the mold shell with the seed crystal is installed on the quenching base, the seed crystal and the support rod will support the entire ceramic mold shell, so that the ceramic mold shell does not contact the quenching base. The weight of the ceramic mold shell is entirely pressed on the seed crystal and the support plate. The seed crystal cavity and the seed crystal are fully fitted without gaps, and the molten metal will not flow in to form a burr, thus preventing the formation of burr impurities.

3. The method according to claim 1 or 2, characterized in that: The preheating temperature of the ceramic mold shell is 1500-1600℃, and the holding time is 10-20 minutes.

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