Graphite-mold shell composite mold for casting reactor core of heat pipe reactor and preparation method of graphite-mold shell composite mold

Abstract

The invention particularly relates to a graphite-mold shell composite mold for casting a reactor core of a heat pipe reactor. The graphite-mold shell composite mold comprises an yttrium oxide surface layer mold shell, an upper graphite mold, a graphite rod, a middle graphite mold and a lower graphite mold, the yttrium oxide surface layer mold shell is inserted into the step-shaped through hole in the center of the graphite lower mold from bottom to top, and the outer surface of the yttrium oxide surface layer mold shell is connected with the step-shaped through hole in the center of the graphite lower mold in an attached mode; the graphite middle die is sleeved in an outer annular straight opening at the upper part of the graphite lower die from top to bottom to realize positioning; a graphite rod is inserted into a blind hole in the upper part of the graphite lower die from top to bottom for fixation; the graphite upper die is spliced and fixed at the top of the graphite middle die through a straight opening from top to bottom; and the bottom surface of the graphite upper die is pressed on the upper surface of the graphite rod. The invention further relates to a preparation method of the graphite-mold shell composite mold for casting the reactor core of the heat pipe reactor. According to the invention, sequential solidification of uranium-molybdenum alloy solution in the casting process of the reactor core of the heat pipe reactor is realized, and the exhaust capacity and the mold filling capacity of a dead angle position are improved.

Description

Technical Field

[0001] The invention relates to the technical field of heat pipe stack core moulds, and in particular to a graphite-shell composite mould for heat pipe stack core casting and a preparation method thereof. Background Art

[0002] With the rapid and vigorous development of my country's aerospace technology, nuclear energy is the preferred or even the only energy solution for interplanetary exploration, lunar missions and Mars missions. As a space reactor power source, the small heat pipe reactor has a simple system, compact structure, strong resistance to space debris and micrometeoroids, and high reliability. It can better meet the needs of my country's future aerospace industry for small-power space reactor power sources. The heat pipe reactor design uses metal fuel, and uranium-molybdenum alloy is designed as heat pipe reactor fuel because of its γ phase stability.

[0003] At present, the preparation and molding method of uranium-molybdenum alloy for heat pipe reactor is mainly casting. Due to the active chemical properties of uranium alloy, the mold materials applicable to the casting molding process are limited to graphite castings or yttria surface ceramic mold shells. These two casting molds have the following disadvantages in affecting the molding quality of castings:

[0004] 1. The graphite mold has a chilling effect, the solidification sequence of the uranium-molybdenum alloy melt is controllable, and graphite is easy to process and shape, which is convenient for making casting molds with different wall thicknesses. However, the wettability of the graphite mold to the uranium-molybdenum alloy melt is relatively poor, and the chilling effect of the added graphite reduces the melt fluidity. The filling ability of the uranium-molybdenum alloy melt in the graphite mold is relatively poor. In addition, the graphite mold has a large gas storage capacity and poor air permeability, which easily leads to pores and shrinkage holes inside the casting.

[0005] 2. The wettability and air permeability of yttria mold shell materials are relatively better. As a ceramic material, it has a small thermal conductivity and strong heat preservation ability, which is conducive to the filling and exhaust of uranium-molybdenum alloy melt. However, the ceramic shell is prepared by wax mold coating method, and the overall thickness of the mold tends to be consistent, which is not conducive to regulating the solidification sequence of oil-molybdenum alloy melt and is more likely to produce shrinkage defects. Summary of the invention

[0006] The purpose of the present invention is to provide a graphite-shell composite mold for heat pipe reactor core casting and a preparation method thereof, so as to give full play to the respective advantages of the graphite casting mold and the yttria surface layer ceramic shell, realize the sequential solidification of the uranium-molybdenum alloy solution during the heat pipe reactor core casting process, and improve the exhaust capacity and filling capacity of the dead corner position.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A graphite-mold composite mold for casting a heat pipe reactor core, comprising an yttrium oxide surface mold, a graphite upper mold, a graphite rod, a graphite middle mold and a graphite lower mold; a stepped through hole is arranged at the center of the graphite lower mold; the yttrium oxide surface mold is a stepped structure, and a bottom opening blind hole is arranged at the center; the yttrium oxide surface mold is inserted from bottom to top into the stepped through hole at the center of the graphite lower mold, and the outer surface of the yttrium oxide surface mold is fitted and connected with the stepped through hole at the center of the graphite lower mold ; The upper part of the graphite lower mold is provided with an outer ring side straight mouth, and the graphite middle mold is sleeved from top to bottom in the outer ring straight mouth of the upper part of the graphite lower mold to achieve positioning; the upper part of the graphite lower mold is provided with a blind hole, and the graphite rod is inserted from top to bottom into the blind hole of the upper part of the graphite lower mold to achieve fixation; the graphite upper mold is a stepped structure with a through hole in the center and a straight mouth at the bottom; the graphite upper mold is fixed to the top of the graphite middle mold through the straight mouth from top to bottom, and the bottom surface of the graphite upper mold is pressed against the upper surface of the graphite rod.

[0009] The present invention also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0010] Step 1: Open a through hole in the middle of the aluminum alloy blank by mechanical processing to make a wax block forming mold;

[0011] Step 2, placing the wax block forming mold on the platform in a manner that one end face is vertical, taking the medium-temperature casting wax paste and pouring it into the middle through hole of the wax block forming mold, and taking it out after the medium-temperature casting wax paste solidifies to make a wax block;

[0012] Step 3, machining the wax block into stepped blind holes by mechanical processing to make a wax mold;

[0013] Step 4, using an investment casting shell making process to make an yttria surface layer mold shell on the inner surface of the wax mold;

[0014] Step 5: Use graphite blank to make graphite upper mold, graphite rod, graphite middle mold and graphite lower mold, and splice and assemble the yttrium oxide surface layer mold shell, graphite upper mold, graphite rod, graphite middle mold and graphite lower mold into a heat pipe core graphite-mold shell composite casting mold.

[0015] As one of the feasible methods, step 1, mechanical processing is used to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, make cylindrical wax block molding mold.

[0016] As one of the achievable methods, step 2, placing the cylindrical wax block molding mold on the platform in a manner that one end face is vertical, taking (58-62)°C medium temperature casting wax paste, pouring it into the middle through hole of the cylindrical wax block molding mold, and taking it out after the medium temperature casting wax paste solidifies to make Cylindrical wax block.

[0017] As one of the feasible methods, step 3, a mechanical processing method is used to Cylindrical wax blocks are processed as well as The stepped blind holes are made into wax models.

[0018] As one of the feasible methods, an investment casting shell making process is used to make an yttria surface layer mold shell on the inner surface of the wax mold, including the following steps:

[0019] Step 31, mixing nano yttrium oxide powder and silica sol evenly to prepare yttrium oxide refractory coating; applying the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model, and sprinkling yttrium oxide sand on the inner surface of the stepped blind hole of the wax model to form a coating and drying;

[0020] Step 32, repeating step 31 multiple times to continuously increase the total thickness of the coating; when the total thickness of the coating exceeds a certain thickness, step 31 is stopped to form an yttrium oxide surface layer mold shell attached to the wax mold;

[0021] Step 33, placing the yttrium oxide surface layer mold shell attached to the wax mold in a steam dewaxing kettle to complete dewaxing, so that the yttrium oxide surface layer mold shell is separated from the wax mold;

[0022] Step 34: Place the yttria surface layer mold shell in a box furnace for sintering.

[0023] As one of the feasible methods, in step 31, nano yttrium oxide powder and silica sol are mixed uniformly in a mass ratio of (2.8-3.2):1 to prepare yttrium oxide refractory coating; the yttrium oxide refractory coating is applied on the inner surface of the stepped blind holes of the wax model, and 300 mesh yttrium oxide sand is sprinkled on the inner surface of the stepped blind holes of the wax model to form a coating; the wax model is placed in an environment with a temperature of (25-26)°C and a humidity of (53-55)% for 8 hours to dry the coating.

[0024] As one of the feasible methods, step 32, step 31 is repeated (15 to 20) times to continuously increase the total coating thickness; when the total coating thickness exceeds 10 mm, step 31 is stopped to form an yttrium oxide surface layer mold shell attached to the wax mold.

[0025] As one of the feasible methods, in step 33, the yttrium oxide surface layer mold shell attached to the wax mold is placed in a steam dewaxing kettle, and dewaxing is completed in a high temperature and high pressure steam environment of (175-177)°C and (0.75-0.8)MPa, so that the yttrium oxide surface layer mold shell is separated from the wax mold.

[0026] As one of the feasible ways, in step 34, the yttrium oxide surface layer mold shell is placed in a box furnace and sintered at (950-960)°C for 2 hours.

[0027] Beneficial technical effects of the present invention:

[0028] The graphite-shell composite mold for casting the heat pipe reactor core of the present invention realizes a unified combination of two casting mold materials, namely, the graphite mold and the yttria surface layer ceramic mold, and gives full play to the respective advantages of the graphite mold and the yttria surface layer ceramic mold. It has the advantages of good sequential solidification of the uranium-molybdenum alloy solution of the graphite mold and good wettability and good exhaust performance of the yttria surface layer ceramic mold. In the casting process of the heat pipe reactor core, the sequential solidification of the uranium-molybdenum alloy solution is realized, and at the same time, the exhaust capacity and filling capacity of the dead corner position are improved, which is beneficial to improving the material yield and qualified rate of the heat pipe reactor core castings.

[0029] The method for preparing the graphite-shell composite mold for heat pipe stack core casting of the present invention does not involve the design and production of a special wax pressing mold, but mainly involves basic mechanical processing work, which is beneficial to shortening the process cycle of the graphite-shell composite mold for heat pipe stack core casting and reducing the production cost of the graphite-shell composite mold for heat pipe stack core casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an embodiment of a wax block forming mold;

[0031] Figure 2 It is a structural schematic diagram of an embodiment of a wax model;

[0032] Figure 3 The present invention is a schematic structural view of an embodiment of a graphite-shell composite mold for casting a heat pipe stack core according to the present invention.

[0033] In the figure, 1. wax block molding mold; 2. wax mold; 3. yttria surface layer mold shell; 4. graphite upper mold; 5. graphite rod; 6. graphite middle mold; 7. graphite lower mold. DETAILED DESCRIPTION

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0035] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0037] refer to Figure 3 The present invention provides a graphite-mold composite mold for casting a heat pipe reactor core, comprising an yttrium oxide surface mold shell 3, a graphite upper mold 4, a graphite rod 5, a graphite middle mold 6 and a graphite lower mold 7; a stepped through hole is provided at the center of the graphite lower mold 7; the yttrium oxide surface mold shell 3 is a stepped structure, and a bottom opening blind hole is provided at the center; the yttrium oxide surface mold shell 3 is inserted from bottom to top into the stepped through hole at the center of the graphite lower mold 7, and the outer surface of the yttrium oxide surface mold shell 3 is in contact with the stepped through hole at the center of the graphite lower mold 7. The upper part of the graphite lower mold 7 is provided with an outer ring side straight mouth, and the graphite middle mold 6 is sleeved in the outer ring straight mouth of the upper part of the graphite lower mold 7 from top to bottom to achieve positioning; the upper part of the graphite lower mold 7 is provided with a blind hole, and the graphite rod 5 is inserted into the blind hole of the upper part of the graphite lower mold 7 from top to bottom to achieve fixation; the graphite upper mold 4 is a stepped structure, with a through hole in the center and a straight mouth at the bottom; the graphite upper mold 4 is fixed to the top of the graphite middle mold 6 from top to bottom through the straight mouth splicing, and the bottom surface of the graphite upper mold 4 is pressed tightly against the upper surface of the graphite rod 5.

[0038] In the present invention, as one of the feasible ways, there are 10 graphite rods, 10 blind holes are provided on the upper part of the graphite lower mold 7, and the 10 graphite rods are inserted into the 10 blind holes on the upper part of the lower mold 7 from top to bottom to achieve fixation.

[0039] See also Figure 1-2 The present invention also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0040] Step 1: A through hole is opened in the middle of the aluminum alloy blank by mechanical processing to form a wax block forming mold 1;

[0041] Step 2, placing the wax block forming mold 1 on the platform in a manner of vertically placing one end face thereof, pouring the medium-temperature casting wax paste into the middle through hole of the wax block forming mold 1, and taking out the medium-temperature casting wax paste after solidification to form a wax block;

[0042] Step 3, machining the wax block into stepped blind holes by mechanical processing to form a wax model 2;

[0043] Step 4, using an investment casting shell making process to form an yttria surface layer mold shell 3 on the inner surface of the wax mold 2;

[0044] Step 5: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7; splice and assemble yttria surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0045] In the present invention, as one of the achievable methods, step 1, using mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, make cylindrical wax block molding mold 1.

[0046] In the present invention, as one of the achievable methods, in step 2, a cylindrical wax block forming mold 1 is placed on a platform in a manner that one end face is vertical, a (58-62)°C medium-temperature casting wax paste is taken out and poured into the middle through hole of the cylindrical wax block forming mold 1, and the medium-temperature casting wax paste is taken out after solidification to form a Cylindrical wax block.

[0047] In the present invention, as one of the achievable methods, step 3, using a mechanical processing method to Cylindrical wax blocks are processed as well as A wax model 2 is made by forming a stepped blind hole.

[0048] In the present invention, as one of the achievable methods, an investment casting shell making process is used to make an yttria surface layer mold shell 3 on the inner surface of the wax mold 2, comprising the following steps:

[0049] Step 31, mixing nano yttrium oxide powder and silica sol evenly to prepare yttrium oxide refractory coating; applying the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating and drying;

[0050] Step 32, repeating step 31 multiple times to continuously increase the total thickness of the coating; when the total thickness of the coating exceeds a certain thickness, step 31 is stopped to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0051] Step 33, placing the yttria surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle to complete dewaxing, so that the yttria surface layer mold shell 3 is separated from the wax mold 2;

[0052] Step 34: Place the yttria surface layer mold shell 3 in a box-type furnace for sintering.

[0053] In the present invention, as one of the feasible methods, step 31, nano yttrium oxide powder and silica sol are mixed evenly according to a mass ratio of (2.8-3.2): 1 to prepare an yttrium oxide refractory coating; the yttrium oxide refractory coating is applied to the inner surface of the stepped blind holes of the wax model 2, and 300 mesh yttrium oxide sand is sprinkled on the inner surface of the stepped blind holes of the wax model 2 to form a coating; the wax model 2 is placed in an environment of temperature (25-26) ° C and humidity (53-55)% for 8 hours to dry the coating.

[0054] In the present invention, as one of the feasible methods, step 32, step 31 is repeated (15 to 20) times to continuously increase the total thickness of the coating; when the total thickness of the coating exceeds 10 mm, step 31 is stopped to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2.

[0055] In the present invention, as one of the feasible methods, step 33, the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 is placed in a steam dewaxing kettle, and dewaxing is completed in a high temperature and high pressure steam environment of (175~177)℃ and (0.75~0.8)MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2.

[0056] In the present invention, as one of the achievable methods, in step 34, the yttria surface layer mold shell 3 is placed in a box furnace and sintered at (950-960)°C for 2 hours.

[0057] Example 1

[0058] This embodiment provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0059] Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, to form a cylindrical wax block molding mold 1;

[0060] Step 2: Place the cylindrical wax block forming mold 1 on the platform in a vertical manner, take 58°C medium-temperature casting wax paste, pour it into the middle through hole of the cylindrical wax block forming mold 1, and take it out after the medium-temperature casting wax paste solidifies to make Cylindrical wax block;

[0061] Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax mold 2 is made by forming a stepped blind hole;

[0062] Step 4, mixing nano yttrium oxide powder and silica sol in a mass ratio of 2.8:1 to prepare yttrium oxide refractory coating; brushing the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling 300 mesh yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating; placing the wax model 2 at a temperature of 25°C and a humidity of 53% for 8 hours to dry the coating;

[0063] Step 5, repeat step 4 15 times to continuously increase the total thickness of the coating; when the total thickness of the coating reaches 12 mm, stop repeating step 4 to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0064] Step 6: Place the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle, and complete dewaxing in a high-temperature and high-pressure steam environment of 175° C. and 0.75 MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2;

[0065] Step 7, placing the yttrium oxide surface layer mold shell 3 in a box furnace and sintering it at 950° C. for 2 hours;

[0066] Step 8: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7, and splice and assemble yttrium oxide surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0067] Example 2

[0068] This embodiment also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0069] Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, to form a cylindrical wax block molding mold 1;

[0070] Step 2: Place the cylindrical wax block forming mold 1 on the platform in a manner that one end face is vertical, take 62°C medium-temperature casting wax paste, pour it into the middle through hole of the cylindrical wax block forming mold 1, and take it out after the medium-temperature casting wax paste solidifies to make Cylindrical wax block;

[0071] Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax mold 2 is made by forming a stepped blind hole;

[0072] Step 4, mixing nano yttrium oxide powder and silica sol in a mass ratio of 3.2:1 to prepare yttrium oxide refractory coating; applying the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling 300 mesh yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating; placing the wax model 2 at a temperature of 26°C and a humidity of 55% for 8 hours to dry the coating;

[0073] Step 5, repeat step 4 20 times to continuously increase the total thickness of the coating; when the total thickness of the coating reaches 12 mm, stop repeating step 4 to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0074] Step 6: Place the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle, and complete dewaxing in a high-temperature and high-pressure steam environment of 177° C. and 0.8 MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2;

[0075] Step 7, placing the yttrium oxide surface layer mold shell 3 in a box furnace and sintering it at 960° C. for 2 hours;

[0076] Step 8: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7, and splice and assemble yttrium oxide surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0077] Example 3

[0078] This embodiment also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0079] Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, to form a cylindrical wax block molding mold 1;

[0080] Step 2: Place the cylindrical wax block forming mold 1 on the platform in a manner that one end face is vertical, take 60°C medium-temperature casting wax paste, pour it into the middle through hole of the cylindrical wax block forming mold 1, and take it out after the medium-temperature casting wax paste solidifies to make Cylindrical wax block;

[0081] Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax mold 2 is made by forming a stepped blind hole;

[0082] Step 4, mixing nano yttrium oxide powder and silica sol in a mass ratio of 3:1 to prepare yttrium oxide refractory coating; applying the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling 300 mesh yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating; placing the wax model 2 at a temperature of 25°C and a humidity of 55% for 8 hours to dry the coating;

[0083] Step 5, repeating step 4 16 times to continuously increase the total thickness of the coating; when the total thickness of the coating reaches 12 mm, stop repeating step 4 to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0084] Step 6: Place the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle, and complete dewaxing in a high-temperature and high-pressure steam environment of 176° C. and 0.8 MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2;

[0085] Step 7, placing the yttrium oxide surface layer mold shell 3 in a box furnace and sintering it at 951° C. for 2 hours;

[0086] Step 8: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7, and splice and assemble yttrium oxide surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0087] Example 4

[0088] This embodiment also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0089] Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, to form a cylindrical wax block molding mold 1;

[0090] Step 2: Place the cylindrical wax block forming mold 1 on the platform in a vertical manner, take 59°C medium-temperature casting wax paste, pour it into the middle through hole of the cylindrical wax block forming mold 1, and take it out after the medium-temperature casting wax paste solidifies to make Cylindrical wax block;

[0091] Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax mold 2 is made by forming a stepped blind hole;

[0092] Step 4, mixing nano yttrium oxide powder and silica sol in a mass ratio of 3.1:1 to prepare yttrium oxide refractory coating; applying the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling 300 mesh yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating; placing the wax model 2 at a temperature of 25°C and a humidity of 55% for 8 hours to dry the coating;

[0093] Step 5, repeating step 4 16 times to continuously increase the total thickness of the coating; when the total thickness of the coating reaches 13 mm, stop repeating step 4 to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0094] Step 6: Place the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle, and complete dewaxing in a high-temperature and high-pressure steam environment of 177° C. and 0.8 MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2;

[0095] Step 7, placing the yttrium oxide surface layer mold shell 3 in a box furnace and sintering it at 954° C. for 2 hours;

[0096] Step 8: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7, and splice and assemble yttrium oxide surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0097] Example 5

[0098] This embodiment also provides a method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, comprising the following steps:

[0099] Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through hole, to form a cylindrical wax block molding mold 1;

[0100] Step 2: Place the cylindrical wax block forming mold 1 on the platform in a vertical manner, take 61°C medium-temperature casting wax paste, pour it into the middle through hole of the cylindrical wax block forming mold 1, and take it out after the medium-temperature casting wax paste solidifies to make Cylindrical wax block;

[0101] Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax mold 2 is made by forming a stepped blind hole;

[0102] Step 4, mixing nano yttrium oxide powder and silica sol in a mass ratio of 2.8:1 to prepare yttrium oxide refractory coating; brushing the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model 2, and sprinkling 300 mesh yttrium oxide sand on the inner surface of the stepped blind hole of the wax model 2 to form a coating; placing the wax model 2 at a temperature of 25°C and a humidity of 55% for 8 hours to dry the coating;

[0103] Step 5, repeating step 4 16 times to continuously increase the total thickness of the coating; when the total thickness of the coating reaches 14.5 mm, stop repeating step 4 to form an yttrium oxide surface layer mold shell 3 attached to the wax mold 2;

[0104] Step 6: Place the yttrium oxide surface layer mold shell 3 attached to the wax mold 2 in a steam dewaxing kettle, and complete dewaxing in a high-temperature and high-pressure steam environment of 175° C. and 0.79 MPa, so that the yttrium oxide surface layer mold shell 3 is separated from the wax mold 2;

[0105] Step 7, placing the yttrium oxide surface layer mold shell 3 in a box furnace and sintering it at 951° C. for 2 hours;

[0106] Step 8: Use graphite blank to make graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7, and splice and assemble yttrium oxide surface layer mold shell 3, graphite upper mold 4, graphite rod 5, graphite middle mold 6 and graphite lower mold 7 into a heat pipe core graphite-mold shell composite casting mold.

[0107] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A graphite-shell composite mold for heat pipe reactor core casting, characterized in that: It comprises an yttria surface layer mold shell (3), a graphite upper mold (4), a graphite rod (5), a graphite middle mold (6) and a graphite lower mold (7); The center of the graphite lower mold (7) is provided with a stepped through hole; the yttrium oxide surface layer mold shell (3) is a stepped structure, and the center is provided with a bottom opening blind hole; the yttrium oxide surface layer mold shell (3) is inserted from bottom to top into the stepped through hole in the center of the graphite lower mold (7), and the outer surface of the yttrium oxide surface layer mold shell (3) is fitted and connected with the stepped through hole in the center of the graphite lower mold (7); The upper part of the graphite lower mold (7) is provided with an outer ring side straight opening, and the graphite middle mold (6) is sleeved from top to bottom in the outer ring straight opening of the upper part of the graphite lower mold (7) to achieve positioning; A blind hole is provided on the upper part of the graphite lower mold (7), and the graphite rod (5) is inserted from top to bottom into the blind hole on the upper part of the graphite lower mold (7) to be fixed; The graphite upper mold (4) is a stepped structure with a through hole in the center and a straight opening at the bottom. The graphite upper mold (4) is fixed to the top of the graphite middle mold (6) from top to bottom through the straight opening, and the bottom surface of the graphite upper mold (4) is pressed tightly against the upper surface of the graphite rod (5).

2. A method for preparing a graphite-shell composite mold for casting a heat pipe reactor core, characterized in that: The steps include: Step 1, using mechanical processing to open a through hole in the middle of the aluminum alloy blank to make a wax block forming mold (1); Step 2, placing the wax block forming mold (1) on a platform in a manner such that one end face thereof is vertical, taking the medium-temperature casting wax paste and pouring it into the middle through hole of the wax block forming mold (1), and taking it out after the medium-temperature casting wax paste solidifies to form a wax block; Step 3, machining the wax block into stepped blind holes by mechanical processing to form a wax model (2); Step 4, using an investment casting shell making process to form an yttria surface layer mold shell (3) on the inner surface of the wax mold (2); Step 5: Use graphite blanks to make graphite upper molds (4), graphite rods (5), graphite middle molds (6) and graphite lower molds (7); splice and assemble the yttrium oxide surface layer mold shell (3), graphite upper mold (4), graphite rods (5), graphite middle mold (6) and graphite lower mold (7) into a heat pipe core graphite-mold composite casting mold.

3. The method for preparing the graphite-shell composite mold for heat pipe stack core casting according to claim 2, characterized in that: Step 1: Use mechanical processing to The cylindrical 6061 aluminum alloy billet is cut in the middle Through holes are formed to form a cylindrical wax block molding mold (1).

4. The method for preparing the graphite-shell composite mold for heat pipe reactor core casting according to claim 3, characterized in that: Step 2, placing the cylindrical wax block forming mold (1) on a platform in a manner that one end face is vertical, taking (58-62)°C medium temperature casting wax paste, pouring it into the middle through hole of the cylindrical wax block forming mold (1), and taking it out after the medium temperature casting wax paste solidifies, to make Cylindrical wax block.

5. The method for preparing the graphite-shell composite mold for heat pipe reactor core casting according to claim 4, characterized in that: Step 3: Use mechanical processing method to Cylindrical wax blocks are processed as well as A wax model (2) is made by forming a stepped blind hole.

6. The method for preparing the graphite-shell composite mold for heat pipe reactor core casting according to claim 5, characterized in that: An yttrium oxide surface layer mold shell (3) is formed on the inner surface of a wax mold (2) by using an investment casting shell making process, comprising the following steps: Step 31, mixing nano yttrium oxide powder and silica sol uniformly to prepare yttrium oxide refractory coating; brushing the yttrium oxide refractory coating on the inner surface of the stepped blind hole of the wax model (2), and sprinkling yttrium oxide sand on the inner surface of the stepped blind hole of the wax model (2) to form a coating and drying; Step 32, repeating step 31 multiple times to continuously increase the total coating thickness; When the total coating thickness exceeds a certain thickness, step 31 is stopped and repeated to form an yttrium oxide surface layer mold shell (3) attached to the wax mold (2); Step 33, placing the yttrium oxide surface layer mold shell (3) attached to the wax mold (2) in a steam dewaxing kettle to complete dewaxing, so that the yttrium oxide surface layer mold shell (3) is separated from the wax mold (2); Step 34: placing the yttria surface layer mold shell (3) in a box-type furnace for sintering.

7. The method for preparing the graphite-shell composite mold for heat pipe stack core casting according to claim 6, characterized in that: Step 31, mixing nano yttrium oxide powder and silica sol in a mass ratio of (2.8-3.2):1 to form an yttrium oxide refractory coating; applying the yttrium oxide refractory coating to the inner surface of the stepped blind hole of the wax model (2), and sprinkling 300 mesh yttrium oxide sand to the inner surface of the stepped blind hole of the wax model (2) to form a coating; The wax model (2) is placed in an environment with a temperature of (25-26)°C and a humidity of (53-55)% for 8 hours to dry the coating.

8. The method for preparing the graphite-shell composite mold for heat pipe reactor core casting according to claim 6, characterized in that: Step 32, repeating step 31 (15 to 20) times to continuously increase the total coating thickness; when the total coating thickness exceeds 10 mm, stop repeating step 31 to form an yttrium oxide surface layer mold shell (3) attached to the wax mold (2).

9. The method for preparing a graphite-shell composite mold for heat pipe reactor core casting according to claim 6, characterized in that: Step 33, placing the yttrium oxide surface layer mold shell (3) attached to the wax mold (2) in a steam dewaxing kettle, and completing dewaxing in a high temperature and high pressure steam environment of (175-177)°C and (0.75-0.8) MPa, so that the yttrium oxide surface layer mold shell (3) is separated from the wax mold (2).

10. The method for preparing the graphite-shell composite mold for heat pipe reactor core casting according to claim 6, characterized in that: Step 34, placing the yttrium oxide surface layer mold shell (3) in a box-type furnace and sintering it at (950-960)°C for 2 hours.

Images