Low-cost preparation method of silicon nitride complex structural member

Abstract

The invention relates to a low-cost preparation method of a silicon nitride complex structural member, which belongs to the field of preparation of ceramic material lightweight members, and is characterized in that a low-temperature molten metal material is adopted as a mold, a silicon nitride complex structural member ceramic green body is prepared in a gel casting mode, and then the silicon nitride complex structural member ceramic green body is put into a sintering furnace to be sintered; the high temperature in the silicon nitride preparation process is utilized, the metal mold is molten into liquid, the metal liquid is collected again to prepare a new mold, the effect of recycling the mold is achieved, and the preparation cost is effectively reduced in the field of complex silicon nitride structural part preparation.

Description

Technical Field

[0001] The invention relates to the field of preparation of lightweight components made of ceramic materials, and in particular to a low-cost preparation method for complex silicon nitride structural parts. Background Art

[0002] Silicon nitride ceramics have unique physical and chemical properties, making them an excellent choice for high-temperature structural materials, tool ceramic materials, wear-resistant materials, and corrosion-resistant materials.

[0003] In the process of preparing complex silicon nitride structural parts, silicon nitride structural parts need to be formed in one piece. However, some silicon nitride structural parts are too complex in shape. In order to achieve the effect of uniform entry of raw materials into the mold, gel injection molding is often used to inject the raw materials into the complex structure. Under the gel injection molding process, in many cases the mold cannot be separated from the complex structural parts. The mold can only be melted and removed by the temperature of the sintering process, which makes the mold a consumable and generates higher production costs. Summary of the invention

[0004] The purpose of the present invention is to provide a low-cost preparation method for complex silicon nitride structural parts, using a relatively low-temperature molten metal material as a mold. During the sintering process, the molten liquid of the metal mold flows into a graphite mold, and the graphite mold is used to reuse the molten liquid to prepare a metal mold.

[0005] A low-cost method for preparing a complex silicon nitride structure, the steps of which are: S1. preparing an integrated molding die, wherein the shape and size of the cavity of the integrated molding die are the same as those of the silicon nitride complex structural part to be prepared; and the melting point of the integrated molding die is lower than 1600° C.; S2, adding silicon nitride powder and sintering aid into the gel system slurry and mixing evenly to obtain gel casting slurry; S3, injecting the gel casting slurry into the integrated molding mold, and waiting for the gel casting slurry to solidify to form a ceramic body of a complex structural part; S4, placing an integrated molding mold with a ceramic body of a complex structural part into the upper layer of the sintering furnace, placing a graphite mold in the lower layer of the sintering furnace, the shape and size of the cavity of the graphite mold being the same as those of the integrated molding mold; placing a special material component of the same shape and size as the ceramic body of the complex structural part in the graphite mold; the lower sintering furnace has a liquid collecting device made of graphite, and all liquids flowing out of the upper sintering furnace are collected by the liquid collecting device and enter the lower graphite mold; S5, close the sintering furnace, raise the temperature to 1700-1800°C for sintering, keep the temperature at 1700-1800°C in an inert gas environment for 2-6 hours, and then slowly cool down; S6. After the cooling is completed, the furnace is opened to take out the complex structural parts and the new mold in the lower graphite mold; the special material components in the new mold are crushed and removed to obtain a new integrated molding mold.

[0006] Furthermore, the material used for the integrated molding die is magnesium-aluminum alloy, aluminum alloy, or iron alloy.

[0007] Furthermore, the complex structural part has a planar supporting leg, which can be removed by processing; and the special material component has a planar supporting leg.

[0008] Furthermore, the material used for the special material component is graphite.

[0009] Furthermore, the special material component is a hollow structure.

[0010] Furthermore, the special material component is provided with an exhaust hole, the position of the exhaust hole is higher than the special material component, and the position of the exhaust hole is higher than the height of the integrated molding die.

[0011] The present invention utilizes the high temperature in the silicon nitride preparation process to melt the metal mold into liquid, and then collects the metal liquid to prepare a new mold, thereby achieving the effect of mold reuse. The present invention effectively reduces the preparation cost in the field of complex silicon nitride structural parts preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art are briefly introduced below.

[0013] Figure 1 This is a perspective view of a silicon nitride spiral aerospace structural component mold; Figure 2 This is a diagram of the positions of the integrated molding die and graphite die in the sintering furnace. DETAILED DESCRIPTION

[0014] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0015] This embodiment is to prepare a silicon nitride spiral aerospace structure, such as Figure 1 shown.

[0016] Preparation of integrated molding mold, integrated molding mold Figure 2As shown in the upper part, the material used for the integrated molding die is magnesium-aluminum alloy. There is a cavity structure in the shape of a silicon nitride spiral aerospace structural part in the integrated molding die, and the cavity structure in the shape of a silicon nitride spiral aerospace structural part is in an inverted state in the integrated molding die.

[0017] like Figure 2 As shown, the middle support plate is a graphite plate, and the graphite plate has a hollow structure.

[0018] like Figure 2 As shown, the lower part is a graphite mold, and the effective cavity part of the graphite mold is the same size and shape as the integrated molding mold, and the rest of the graphite mold is only used to support the graphite plate and collect the molten liquid. A silicon nitride spiral aerospace structural part graphite cavity mold is placed in the effective cavity structure in the graphite mold, and the silicon nitride spiral aerospace structural part graphite cavity mold is in an upright state. The graphite cavity mold has a horizontal base, and the horizontal base has a single cavity L-tube that bypasses the silicon nitride spiral aerospace structural part to the top, and the cavity L-tube is used for the overall exhaust of the silicon nitride spiral aerospace structural part graphite cavity mold.

[0019] Adding silicon nitride powder and sintering aid into the gel system slurry and mixing evenly to obtain gel casting slurry; Injecting the gel casting slurry into the integrated molding mold, and waiting for the gel casting slurry to solidify to form a ceramic body of a complex structural part; Ceramic green bodies with complex structures Figure 2 Place the device into the sintering furnace and ensure that the base of the sintering furnace is level; The sintering furnace is closed, and the temperature is raised to 1750℃ for sintering. At the same time, nitrogen is introduced. When the temperature in the sintering furnace reaches 700 degrees, as the temperature in the sintering furnace gradually increases, the magnesium-aluminum alloy is slowly dissolved into liquid, flows through the graphite plate, and flows into the effective cavity structure of the graphite mold along the inner wall of the graphite mold. After all the magnesium-aluminum alloy is melted, the liquid level in the graphite mold is always kept horizontal under the action of gravity. After keeping warm at 1750 degrees Celsius and in an inert gas environment for 4 hours, the temperature is slowly lowered to ensure that all the molten metal liquid has flowed into the graphite mold and the sintering of complex silicon nitride structural parts is completed.

[0020] After the cooling is completed, the furnace is opened to take out the complex structural parts and the new mold in the lower graphite mold; the special material components in the new mold are crushed and removed to obtain a new integrated molding mold.

Claims

1. A low-cost preparation method for complex silicon nitride structural parts, characterized in that: The steps are: S1. preparing an integrated molding die, wherein the shape and size of the cavity of the integrated molding die are the same as those of the silicon nitride complex structural part to be prepared; and the melting point of the integrated molding die is lower than 1600° C.; S2, adding silicon nitride powder and sintering aid into the gel system slurry and mixing evenly to obtain gel casting slurry; S3, injecting the gel casting slurry into the integrated molding mold, and waiting for the gel casting slurry to solidify to form a ceramic body of a complex structural part; S4, placing an integrated molding mold with a ceramic body of a complex structural part into the upper layer of the sintering furnace, placing a graphite mold in the lower layer of the sintering furnace, the shape and size of the cavity of the graphite mold being the same as those of the integrated molding mold; placing a special material component of the same shape and size as the ceramic body of the complex structural part in the graphite mold; the lower sintering furnace has a liquid collecting device made of graphite, and all liquids flowing out of the upper sintering furnace are collected by the liquid collecting device and enter the lower graphite mold; S5, close the sintering furnace, raise the temperature to 1700-1800°C for sintering, keep the temperature at 1700-1800°C in an inert gas environment for 2-6 hours, and then slowly cool down; S6. After the cooling is completed, the furnace is opened to take out the complex structural parts and the new mold in the lower graphite mold; the special material components in the new mold are crushed and removed to obtain a new integrated molding mold.

2. A low-cost method for preparing complex silicon nitride structures according to claim 1, characterized in that: The material used for the integrated molding die is magnesium-aluminum alloy, aluminum alloy, and iron alloy.

3. A low-cost method for preparing complex silicon nitride structures according to claim 1, characterized in that: The complex structural part has a planar support leg, which can be removed by processing; the special material component has a planar support leg.

4. A low-cost method for preparing complex silicon nitride structures according to claim 1, characterized in that: The material used for the special material component is graphite.

5. A low-cost method for preparing complex silicon nitride structures according to claim 1, characterized in that: The special material component is a hollow structure.

6. A low-cost method for preparing complex silicon nitride structures according to claim 4, characterized in that: The special material component is equipped with an exhaust hole, the position of the exhaust hole is higher than the special material component, and the position of the exhaust hole is higher than the height of the integrated molding mold.

7. A low-cost method for preparing complex silicon nitride structures according to claim 1, characterized in that: The inert gas in step S5 is argon or nitrogen.

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