High-matching easy-to-release ceramic core connecting rod for precision investment casting and preparation method thereof

Abstract

The application discloses a high-matching easy-to-extract core ceramic core connecting rod for investment precision casting and a preparation method of the connecting rod. The content of each substance in the ceramic core connecting rod is as follows: ceramic powder material 90-95 wt%, whisker component 1.5-5 wt%, and graphene 0.5-5 wt%. The preparation method comprises the following steps: a ceramic core connecting rod blank is prepared by using an extrusion forming method or a dry forming method, then low-temperature glue removal treatment and high-temperature sintering treatment are carried out, and finally the ceramic core connecting rod is prepared; the ceramic core connecting rod is sequentially subjected to pretreatment, post-treatment and heat treatment, and the high-matching easy-to-extract core ceramic core connecting rod is prepared. The application solves the problems of the traditional ceramic rod, such as difficult core extraction, poor matching, low strength, poor dimensional stability, easy breakage and the like, improves the investment precision casting process efficiency and the casting quality, and meets the production requirements of high-end manufacturing industry for complex structure castings.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of design and preparation of ceramic rod materials for investment precision casting, and particularly relates to a high-matching easy-to-core-out ceramic core connecting rod for investment precision casting and a preparation method thereof. The ceramic core connecting rod, namely ceramic rod, is particularly suitable for being used as an auxiliary part in the process of investment precision casting of key parts such as complex structure blades of an aero-engine or a gas turbine. BACKGROUND

[0002] In the process of investment precision casting, the ceramic core connecting rod plays an important role in connecting and supporting the ceramic core, and the performance of the ceramic core connecting rod determines the stability of the whole casting process and the quality of the castings. However, the traditional ceramic rod widely used at present has many technical problems that are difficult to overcome, which seriously restricts the production quality and production efficiency of high-precision and high-performance castings.

[0003] Firstly, the poor core-out performance is the primary problem faced by the traditional ceramic rod. The alumina ceramic rod is difficult to be effectively dissolved or decomposed by the core-out agent in the core-out process after the formation of the casting, because of its high chemical stability and dense structure, resulting in a time-consuming and labor-intensive core-out process, and the residual core in the inner cavity of the casting is extremely easy to occur. These residual cores not only damage the inner cavity structure of the parts such as blades and affect their performance, but also require additional manual or mechanical cleaning processes, which greatly increases the production cost and production cycle. Although the silica ceramic rod is slightly better than the alumina ceramic rod in terms of core-out performance, due to its low strength, the ceramic rod is prone to core breakage when the wax is injected into the mold at a certain pressure during the wax pressing process. The impact and pressure of the high-temperature alloy liquid during the pouring process also cause the silica ceramic rod to break, resulting in core leakage, which makes the casting scrap and causes great material waste and economic loss.

[0004] Secondly, the mismatch of the thermal expansion coefficient and a series of problems caused thereby are particularly prominent. The thermal expansion coefficient of the alumina ceramic rod is quite different from that of the silica-based ceramic core, and the shrinkage rates of the two are not synchronized during the sintering and forming process of the ceramic core. When the temperature decreases, due to the mismatch of the shrinkage, the connection between the ceramic rod and the ceramic core is prone to loosen, which leads to a decrease in the connection strength and the inability to effectively support the ceramic core. During the high-temperature pouring process, the difference in the thermal expansion coefficient will be further aggravated with the sharp rise in temperature and subsequent cooling, which will cause micro cracks between the ceramic rod and the ceramic core. During pouring, the high-temperature alloy liquid has extremely high fluidity and will easily flow into these micro cracks. When the alloy liquid cools and solidifies, it will form excess metal in the inner cavity of the blade, i.e., the so-called "metal deposition" phenomenon, which will seriously damage the inner cavity structure and performance of the blade, leading to the scrap of the whole batch of blades and causing great losses to the production.

[0005] Thirdly, traditional ceramic rods cannot achieve a harmonious match in terms of strength, dimensions, and friction with the ceramic core, ceramic shell, and molten alloy. During core making, the ceramic rod needs to be tightly connected to the ceramic core. Insufficient friction will cause the connection to loosen, and insufficient strength will easily lead to breakage during operation. In the mold and shell making stages, the ceramic rod needs to withstand the pressure and constraints of the mold and shell materials. Poor dimensional stability will result in the mold or shell exceeding dimensional accuracy standards, and insufficient strength and toughness will cause it to break during material solidification and shrinkage. During the casting process, the high-temperature molten alloy will generate enormous thermal shock and pressure on the ceramic rod. If the strength and toughness of the ceramic rod cannot withstand this impact, or if the friction with the molten alloy is mismatched, the connection will break, causing the ceramic core to lose support and ultimately affecting the molding quality of the casting.

[0006] The aforementioned technical bottlenecks of traditional ceramic rods have severely hindered the application and development of investment casting technology in high-end manufacturing. Therefore, developing a ceramic core connecting rod with excellent core removal performance, high matching performance, high strength and high dimensional stability is an urgent need in the field of investment casting. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides a high-matching, easily detachable ceramic core connecting rod for investment casting. The ceramic core connecting rod is composed of ceramic powder material, whisker component, and graphene. The mass percentage of each substance in the ceramic core connecting rod is 90-95 wt% ceramic powder material, 1.5-5 wt% whisker component, and 0.5-5 wt% graphene, with the sum of the contents of each substance being 100 wt%.

[0008] Preferably, the mass percentage of each substance in the ceramic powder material is 30-40 wt% alumina, 15-25 wt% silicon dioxide, 5-10 wt% magnesium oxide, 10-15 wt% zirconium oxide, 10-18 wt% mullite, and 5-12 wt% zirconium silicate.

[0009] In any of the above embodiments, it is preferred that the alumina, silicon oxide, and magnesium oxide each include three particle sizes: 56-75μm, 32-56μm, and 3-32μm, respectively. The mass percentage of each particle size in the alumina, silicon oxide, and magnesium oxide is as follows: 56-75μm accounts for 45-55wt%, 32-56μm accounts for 25-35wt%, and 3-32μm accounts for 20-30wt%.

[0010] Preferably in any of the above solutions, the zirconium oxide, the mullite, and the zirconium silicate each include two particle size ranges, 25-52 μm and 1-25 μm, and the mass percentage of each particle size range in the zirconium oxide, the mullite, and the zirconium silicate is 60-70 wt% and 30-40 wt%, respectively.

[0011] Preferably in any of the above solutions, the mass percentage of each substance in the whisker component in the whisker component is 18-30 wt% of mullite whisker, 15-26 wt% of aluminum oxide whisker, 8-18 wt% of silicon oxide whisker, 8-18 wt% of silicon carbide whisker, and 15-26 wt% of organic whisker; and the mass percentage of each substance in the organic whisker is 30-40 wt% of polyamide whisker and 60-70 wt% of chitin whisker.

[0012] Preferably in any of the above solutions, the diameter of the mullite whisker, the aluminum oxide whisker, the silicon oxide whisker, and the silicon carbide whisker is controlled in the range of 1-5 μm, and the aspect ratio is controlled in the range of 15-25:1; and the diameter of the polyamide whisker and the chitin whisker is controlled in the range of 0.5-1 μm, and the aspect ratio is controlled in the range of 5-15:1.

[0013] The application also provides a preparation method of the high-matching easy-to-remove core ceramic core connecting rod for investment precision casting, which includes the following steps in sequence:

[0014] Step one: according to the designed process parameters, a ceramic core connecting rod blank is prepared by extrusion molding or dry molding, and then the ceramic core connecting rod blank is placed in a baking furnace for low-temperature glue removal treatment and high-temperature sintering treatment to obtain a ceramic core connecting rod;

[0015] Step two: the ceramic core connecting rod is pretreated to produce a frosted effect on the surface of the ceramic core connecting rod and form a large number of uniformly distributed etch pits or etch holes;

[0016] Step three: the ceramic core connecting rod is post-treated to cover the surface of the ceramic core connecting rod with a uniform coating;

[0017] Step four: the ceramic core connecting rod is heat treated to solidify the coating and tightly bond the coating with the surface of the ceramic core connecting rod, thereby obtaining a high-matching easy-to-remove core ceramic core connecting rod.

[0018] Preferably in step one, the ceramic core connecting rod blank is prepared by extrusion molding, which includes the following steps in sequence:

[0019] Step 1.1: each raw material is weighed according to the designed material ratio for standby use;

[0020] Step 1.2: Put all the alumina, silica, magnesium oxide, zirconium oxide, mullite and zirconium silicate in the V-type mixer, mix at room temperature for 20-30 min, the mixing speed is 100-200 r / min, so that the materials are uniformly mixed, and a composite powder material is prepared;

[0021] Step 1.3: Put water, binder and dispersant into the blender, stir at room temperature for 10-20 min, the stirring speed is 100-200 r / min, so that the materials are completely mixed, and a composite processing agent is prepared;

[0022] The adding amount of water, binder and dispersant is 5-10wt%, 1-3wt% and 1-3wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2-3:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate is 1-2:1:1;

[0023] Step 1.4: Put the composite powder material and the composite processing agent into the blender, stir at room temperature for 2-4 h, the stirring speed is 100-200 r / min, so that the materials are completely mixed;

[0024] Step 1.5: Put the mullite whiskers, alumina whiskers, silica whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers into the blender, continue to stir at room temperature for 4-6 h, the stirring speed is 100-200 r / min, so that the whiskers are uniformly dispersed;

[0025] Step 1.6: Put the graphene into the blender, continue to stir at room temperature for 3-4 h, the stirring speed is 100-200 r / min, so that the materials are uniformly mixed, and a ceramic slurry is prepared;

[0026] Step 1.7: Put the ceramic slurry into the extruder according to the designed shape and size, extrude at room temperature, the extrusion pressure is 10-20 MPa, and then dry at room temperature for 20-28 h, and a ceramic core connecting rod blank is prepared.

[0027] In any of the above schemes, preferably, in step one, the ceramic core connecting rod blank is prepared by dry forming method, which includes the following steps in order:

[0028] Step 2.1: Weigh each raw material according to the designed material ratio;

[0029] Step 2.2: Put all the alumina, silica, magnesia, zirconia, mullite and zirconium silicate in the V-type mixer, mix for 20-30 min at room temperature, and the mixing speed is 300-500 r / min, so that the materials are uniformly mixed;

[0030] Step 2.3: Put all the mullite whiskers, alumina whiskers, silica whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers in the V-type mixer, continue to mix for 5-8 h at room temperature, and the mixing speed is 300-500 r / min, so that the whiskers are uniformly dispersed;

[0031] Step 2.4: Put the graphene into the V-type mixer, continue to mix for 3-4 h at room temperature, and the mixing speed is 300-500 r / min, so that the materials are uniformly mixed;

[0032] Step 2.5: Put the water, binder and dispersant into the V-type mixer, continue to mix for 12-20 h at room temperature, and the mixing speed is 300-500 r / min, so that the materials are uniformly mixed, and the ceramic powder is prepared;

[0033] The adding amount of water, binder and dispersant is 1-3 wt%, 1-3 wt% and 1-3 wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2-3:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate to sodium dodecyl sulfate to sodium dodecyl benzene sulfonate is 1-2:1:1;

[0034] Step 2.6: Put the ceramic powder into the dry press machine according to the designed shape and size, and dry press form at room temperature, the pressure is 50-70 MPa, and the pressure holding time is 1-3 min, so that the ceramic core connecting rod blank is prepared.

[0035] In any of the above schemes, it is preferred that in step one, the process system of low-temperature glue removal treatment and high-temperature sintering treatment is: put the ceramic core connecting rod blank into the calcination furnace, first increase the temperature from room temperature to 400-600℃ at a rate of 5-10℃ / min, and keep the temperature for 10-20 h, that is, complete the low-temperature glue removal treatment; then increase the temperature from 400-600℃ to 1600-1700℃ at a rate of 3-5℃ / min, keep the temperature for 4-8 h, and cool to room temperature with the furnace, that is, complete the high-temperature sintering treatment; during the whole low-temperature glue removal treatment and high-temperature sintering treatment, no protective atmosphere is needed.

[0036] Preferably in any of the above solutions, in step two, the ceramic core connecting rod is pretreated, and the specific operation is as follows: the ceramic core connecting rod after high-temperature sintering treatment is immersed in an alkali solution or hydrofluoric acid, soaked for 3-6 hours at room temperature, then taken out from the alkali solution or hydrofluoric acid, and cleaned with deionized water, and naturally dried.

[0037] The preparation method of the alkali solution is as follows: sodium hydroxide and potassium hydroxide are mixed according to a mass ratio of 2:3, then put into deionized water to dissolve, and form an alkali solution with a concentration of 40-60%; the concentration of the hydrofluoric acid is 80-95%.

[0038] Preferably in any of the above solutions, in step three, the ceramic core connecting rod is post-treated, and the specific operation is as follows: the pretreated ceramic core connecting rod is immersed in silica sol or ceramic shell surface layer slurry, soaked for 10-20 minutes at room temperature, then taken out from the silica sol or ceramic shell surface layer slurry, and self-dried for 8-12 hours; the thickness of the coated layer is 2-5 microns.

[0039] Preferably in any of the above solutions, in step four, the ceramic core connecting rod is heat treated, and the specific operation is as follows: the post-treated ceramic core connecting rod is put into a heat treatment furnace, heated from room temperature to 600-900℃ at a heating rate of 5-8℃ / min, kept for 1-3 hours, and cooled to room temperature with the furnace, without the need of introducing a protective atmosphere.

[0040] In the present application, the V-shaped mixer, the stirrer, the extruder, the dry press, the calcination furnace, the heat treatment furnace and the like used are all conventional equipment, and there is no special requirement for the equipment structure and model. The alumina, the silicon oxide and the magnesium oxide all include three grades of particle size, which are particle size 56-75 microns, particle size 32-56 microns and particle size 3-32 microns, i.e. 56 microns≤particle size≤75 microns, 32 microns≤particle size<56 microns and 3 microns≤particle size<32 microns; the zirconium oxide, the mullite and the zirconium silicate all include two grades of particle size, which are particle size 25-52 microns and particle size 1-25 microns, i.e. 25 microns≤particle size≤52 microns and 1 micron≤particle size<25 microns; for each grade of particle size, the material obtained after the material passes through the upper and lower two screen holes in turn has a particle size between the upper and lower two screen holes, such as the particle size 32-56 microns, i.e. the material obtained after the material passes through the 56 micron screen hole and the 32 micron screen hole in turn has a particle size between 32-56 microns.

[0041] In the components of the ceramic core connecting rod, the alumina can improve the strength and hardness of the connecting rod, the silicon oxide can improve the core removal performance of the connecting rod, so that the connecting rod can be removed together with the silicon oxide-based ceramic core; the magnesium oxide and the zirconium oxide can adjust the thermal expansion coefficient of the connecting rod and improve the dimensional stability of the connecting rod; the mullite and zirconium silicate can enhance the high-temperature performance and chemical stability of the connecting rod; the addition of the whisker can significantly improve the toughness and fracture resistance of the connecting rod; and the addition of the graphene can improve the toughness and strength of the connecting rod.

[0042] The extrusion molding method is suitable for preparing connecting rods with relatively complex shapes and small diameters, such as round rods with diameters of 0.5-2.5 mm, square rods with side lengths of 1 mm*1 mm, rectangular rods with side lengths of 2 mm*1 mm, etc. The dry molding method is suitable for preparing connecting rods with relatively simple shapes and large diameters.

[0043] The ceramic core connecting rod blank is placed in a low-temperature environment for degassing treatment to remove the organic binder therein, so as to avoid defects such as pores caused by combustion of organic matter in the subsequent high-temperature sintering process; and the ceramic core connecting rod blank is placed in a high-temperature environment for sintering treatment, so that the particles in the blank diffuse and fuse with each other to form a dense ceramic structure.

[0044] The purpose of the pretreatment of the ceramic core connecting rod is to improve the physical properties of the surface of the connecting rod. The alkali solution or hydrofluoric acid can chemically react with part of the components on the surface of the connecting rod, corrode the surface, produce a frosted effect on the surface of the connecting rod, and form a large number of uniformly distributed corrosion pits or corrosion holes. Such a surface structure can increase the contact area between the connecting rod and the subsequent impregnated material and improve the bonding strength therebetween.

[0045] The purpose of the post-treatment of the ceramic core connecting rod is to further optimize the performance of the connecting rod. The pretreated connecting rod is immersed in a silica sol or a ceramic shell surface layer slurry, so that the surface of the connecting rod is covered with a uniform coating. There are many materials for the surface layer slurry used for preparing the ceramic shell, and as long as the slurry can be used for preparing the surface layer of the ceramic shell, it can be used for the post-treatment of the ceramic core connecting rod.

[0046] The purpose of the heat treatment of the ceramic core connecting rod is to solidify the coating and make the coating tightly combined with the surface of the connecting rod, so as to improve the matching property and the bonding strength of the connecting rod with the ceramic core and the ceramic shell.

[0047] The high-matching easy-core-removal ceramic core connecting rod for investment precision casting and the preparation method have the following beneficial effects:

[0048] (1) has excellent core removal effect. Because the connecting rod contains appropriate amount of silicon oxide component, and is subjected to special pretreatment and post-treatment, its chemical property matches that of the silicon oxide based ceramic core, the erosion rate in 80℃, 5% NaOH solution for 24 hours can reach 40±5%, and it can be effectively eroded by the core removal agent. In the core removal process, the core removal agent can act on the connecting rod and the ceramic core at the same time, so that the connecting rod is smoothly removed together with the silicon oxide based ceramic core, without any residue, which not only saves the cumbersome residue cleaning process, but also avoids the influence of the residue on the performance of the casting, and improves the production efficiency and the casting quality.

[0049] (2) has extremely high matching property. Through reasonable component design, the thermal expansion coefficient of the connecting rod matches the expansion and contraction characteristics of the silicon oxide based ceramic core, the shell and the alloy liquid at different temperatures, and the shrinkage matching property and the physical compatibility are realized. In the core making process, the connecting rod and the ceramic core at the connecting position can be tightly combined without gap and looseness, and the overall structural stability of the ceramic core is ensured; in the melting and pouring process, even if experiencing severe temperature change, the connecting rod and the ceramic core will not produce shrinkage gap, and the phenomenon of metal deposition in the inner cavity of the blade caused by the alloy liquid immersed in the gap is effectively avoided, and the rejection rate of the casting is greatly reduced.

[0050] (3) has high strength, good toughness and excellent surface friction. The addition of whiskers and reasonable sintering process make the connecting rod have high strength and high toughness, the room temperature bending strength is not less than 320MPa, and the high temperature bending strength at 1540℃ is not less than 230MPa, which can withstand various external force impact and pressure in the core making, mold making, shell making and pouring process. At the same time, the frosted surface and the corrosion pits or holes formed after pretreatment increase the friction of the connecting rod surface, so that the connecting position will not loosen due to insufficient friction, and will not break due to insufficient strength, which ensures the stability and reliability of the entire casting process.

[0051] (4) has good dimensional stability. The synergistic effect of various components in the connecting rod makes it have excellent thermal shock resistance and dimensional stability. In different temperature environments, the size change of the connecting rod is very small, which can not only accurately ensure the size precision of the key positions such as the dust removal hole and the process hole of the blade, but also maintain good matching property with the alloy liquid and the core / shell in size, to ensure that the size precision of the casting meets the design requirements. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The flow chart of a preferred embodiment of the high-matching easy-core-removal ceramic core connecting rod for investment precision casting and the preparation method according to the application;

[0053] Figure 2 The connecting rod is used for connecting the silicon oxide based ceramic core and the shell, and is used for connecting the silicon oxide based ceramic core and the shell. Figure 1The photo of the ceramic core connecting rod of the shown embodiment is adopted extrusion molding and high temperature sintering treatment;

[0054] Figure 3 For Figure 1 The photo of the ceramic core connecting rod of the shown embodiment after pretreatment (immersed in alkali solution), wherein: the left photo is the ceramic core connecting rod after high temperature sintering treatment, and the right photo is the ceramic core connecting rod after pretreatment;

[0055] Figure 4 For Figure 1 The photo of the ceramic core connecting rod of the shown embodiment after post-treatment (immersed in coating), wherein: the left photo is the ceramic core connecting rod after high temperature sintering treatment, and the right photo is the ceramic core connecting rod after post-treatment;

[0056] Figure 5 For Figure 1 The photo of the high matching easy-to-release core ceramic core connecting rod finally prepared in the shown embodiment;

[0057] Figure 6 For Figure 1 The photo of the application effect of the high matching easy-to-release core ceramic core connecting rod prepared in the shown embodiment. DETAILED DESCRIPTION

[0058] In order to further understand the inventive content of the present application, the present application will be described in detail below in combination with specific embodiments.

[0059] Embodiment one:

[0060] According to a preferred embodiment of the high matching easy-to-release core ceramic core connecting rod for investment precision casting of the present application, the ceramic core connecting rod is compounded by ceramic powder material, whisker component and graphene, and the mass percentage of each substance in the ceramic core connecting rod is 93wt% of ceramic powder material, 3.5wt% of whisker component and 3.5wt% of graphene.

[0061] The mass percentage of each substance in the ceramic powder material is 35wt% of aluminum oxide, 20wt% of silicon oxide, 8wt% of magnesium oxide, 13wt% of zirconium oxide, 15wt% of mullite and 9wt% of zirconium silicate.

[0062] The aluminum oxide, the silicon oxide and the magnesium oxide all include three grades of particle sizes, which are 56-75μm, 32-56μm and 3-32μm respectively, and the mass percentage of each grade of particle size in the aluminum oxide, the silicon oxide and the magnesium oxide is 50wt% of particle size 56-75μm, 30wt% of particle size 32-56μm and 20wt% of particle size 3-32μm respectively.

[0063] The zirconium oxide, the mullite, and the zirconium silicate each include two grades of particle sizes, 25-52 μm and 1-25 μm, and the mass percentage of each grade of particle size in the zirconium oxide, the mullite, and the zirconium silicate is 65 wt% for the particle size 25-52 μm and 35 wt% for the particle size 1-25 μm.

[0064] The mass percentage of each substance in the whisker component in the whisker component is 26 wt% for the mullite whisker, 22 wt% for the aluminum oxide whisker, 15 wt% for the silicon oxide whisker, 15 wt% for the silicon carbide whisker, and 22 wt% for the organic whisker; and the mass percentage of each substance in the organic whisker in the organic whisker is 35 wt% for the polyamide whisker and 65 wt% for the chitin whisker.

[0065] The diameter of each of the mullite whisker, the aluminum oxide whisker, the silicon oxide whisker, and the silicon carbide whisker is controlled in the range of 1-5 μm, and the aspect ratio of each of the mullite whisker, the aluminum oxide whisker, the silicon oxide whisker, and the silicon carbide whisker is controlled in the range of 15-25:1; the diameter of each of the polyamide whisker and the chitin whisker is controlled in the range of 0.5-1 μm, and the aspect ratio of each of the polyamide whisker and the chitin whisker is controlled in the range of 5-15:1.

[0066] As shown in Figure 1 The embodiment also provides a preparation method of the high-matching easy-to-remove core ceramic core connecting rod for investment precision casting, and the preparation method includes the following steps in the order:

[0067] Step one: according to the designed process parameters, a ceramic core connecting rod blank is prepared by using an extrusion molding method or a dry molding method, and then the ceramic core connecting rod blank is placed into a baking furnace for low-temperature glue removal treatment and high-temperature sintering treatment to obtain a ceramic core connecting rod;

[0068] Step two: the ceramic core connecting rod is pretreated to produce a frosted effect on the surface of the ceramic core connecting rod and form a large number of uniformly distributed etching pits or etching holes;

[0069] Step three: the ceramic core connecting rod is post-treated to cover the surface of the ceramic core connecting rod with a uniform coating layer;

[0070] Step four: the ceramic core connecting rod is heat-treated to solidify the coating layer and tightly combine the coating layer with the surface of the ceramic core connecting rod, thereby obtaining the high-matching easy-to-remove core ceramic core connecting rod.

[0071] In step one, the ceramic core connecting rod blank is prepared by using the extrusion molding method, and the preparation method includes the following steps in the order:

[0072] Step 1.1: each raw material is weighed according to the designed material ratio for standby;

[0073] Step 1.2: Put all the alumina, silica, magnesia, zirconia, mullite and zirconium silicate in the ceramic powder material into a V-type mixer, mix at room temperature for 25 min, the mixing speed is 150 r / min, so that the materials are uniformly mixed, and a composite powder material is prepared;

[0074] Step 1.3: Put water, binder and dispersant into a blender, stir at room temperature for 15 min, the stirring speed is 150 r / min, so that the materials are completely integrated, and a composite treatment agent is prepared;

[0075] The addition amount of water, binder and dispersant is 8wt%, 2wt% and 2wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2.5:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate is 1.5:1:1;

[0076] Step 1.4: Put the composite powder material and the composite treatment agent into a blender, stir at room temperature for 3h, the stirring speed is 150 r / min, so that the materials are completely integrated;

[0077] Step 1.5: Put the mullite whiskers, alumina whiskers, silica whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers in the whisker component into a blender, continue to stir at room temperature for 5h, the stirring speed is 150 r / min, so that the various whiskers are uniformly dispersed;

[0078] Step 1.6: Put graphene into the blender, continue to stir at room temperature for 3.5h, the stirring speed is 150 r / min, so that the materials are uniformly mixed, and a ceramic slurry is prepared;

[0079] Step 1.7: According to the designed shape and size, put the ceramic slurry into an extruder, extrude at room temperature, the extrusion pressure is 15 MPa, and then dry at room temperature for 24h, to obtain a ceramic core connecting rod blank, the diameter is 2.5mm.

[0080] In step one, the process system of low-temperature glue removal treatment and high-temperature sintering treatment is as follows: put the ceramic core connecting rod blank into a calcination furnace, first increase the temperature from room temperature to 500℃ at a rate of 8℃ / min, and keep the temperature for 15h, which completes the low-temperature glue removal treatment; then increase the temperature from 500℃ to 1650℃ at a rate of 4℃ / min, keep the temperature for 6h, and cool to room temperature with the furnace, which completes the high-temperature sintering treatment; no protective atmosphere is needed during the whole low-temperature glue removal treatment and high-temperature sintering treatment.

[0081] In step two, the ceramic core connecting rod is pretreated, and the specific operation is as follows: the ceramic core connecting rod after high-temperature sintering treatment is immersed in an alkali solution or hydrofluoric acid, soaked at room temperature for 4.5 hours, then taken out from the alkali solution or hydrofluoric acid, and cleaned with deionized water, and naturally dried.

[0082] The preparation method of the alkali solution is as follows: sodium hydroxide and potassium hydroxide are mixed according to a mass ratio of 2:3, then put into deionized water to dissolve, and form an alkali solution with a concentration of 50%; the concentration of the hydrofluoric acid is 88%.

[0083] In step three, the ceramic core connecting rod is post-treated, and the specific operation is as follows: the pretreated ceramic core connecting rod is immersed in silica sol or ceramic shell surface layer slurry, soaked at room temperature for 15 minutes, then taken out from the silica sol or ceramic shell surface layer slurry, and self-dried for 10 hours; the thickness of the coated layer is 3.5 microns.

[0084] In step four, the ceramic core connecting rod is heat treated, and the specific operation is as follows: the post-treated ceramic core connecting rod is put into a heat treatment furnace, heated from room temperature to 750℃ at a heating rate of 6.5℃ / min, kept for 2 hours, and cooled to room temperature with the furnace, without the need of introducing a protective atmosphere.

[0085] In this embodiment, the ceramic core connecting rod blank is prepared by extrusion molding, and the ceramic core connecting rod obtained after high-temperature sintering treatment of the blank is as shown in Figure 2 The morphology of the ceramic core connecting rod after pretreatment (immersion in alkali solution) is as shown in Figure 3 The left picture is the ceramic core connecting rod after high-temperature sintering treatment, and the right picture is the pretreated ceramic core connecting rod; the morphology of the ceramic core connecting rod after post-treatment (immersion in coating) is as shown in Figure 4 The left picture is the ceramic core connecting rod after high-temperature sintering treatment, and the right picture is the post-treated ceramic core connecting rod. The high-matching easy-to-release core ceramic core connecting rod finally prepared in this embodiment is as shown in Figure 5 The application effect is as shown in Figure 6

[0086] The high-matching easy-to-release core ceramic core connecting rod and the preparation method of this embodiment have excellent core releasing effect and extremely high matching property, and at the same time, have high strength, good toughness, excellent surface friction property, and good dimensional stability. The connecting rod prepared in this embodiment is used in the investment precision casting production of a certain type of vane, and the results show that: the core releasing process is smooth, and no residual core is left; the connecting rod is connected closely with the ceramic core, and no loosening and fracture phenomenon occurs at the connecting part during the core making, mold making, shell making and pouring processes; the dimensional precision of the dust removal hole and the process hole of the vane completely meets the design requirements, and no alloy liquid metal phenomenon occurs, and the vane qualification rate reaches more than 90%.​

[0087] Embodiment two:

[0088] Another preferred embodiment of the high-matching easy-to-extract core ceramic core connecting rod for precision investment casting according to the present application has basically the same raw material selection and proportioning, preparation process and process parameters, technical principle, beneficial effects, etc. as Embodiment one, except that:

[0089] The ceramic core connecting rod is compounded from ceramic powder material, whisker component and graphene, and the mass percentage of each substance in the ceramic core connecting rod is 90wt% of ceramic powder material, 5wt% of whisker component and 5wt% of graphene.

[0090] The mass percentage of each substance in the ceramic powder material is 30wt% of alumina, 25wt% of silicon oxide, 5wt% of magnesium oxide, 15wt% of zirconium oxide, 13wt% of mullite and 12wt% of zirconium silicate. The alumina, the silicon oxide and the magnesium oxide all include three grades of particle sizes, i.e. 56-75μm, 32-56μm and 3-32μm, and the mass percentage of each grade of particle size in the alumina, the silicon oxide and the magnesium oxide is 45wt% of particle size 56-75μm, 25wt% of particle size 32-56μm and 30wt% of particle size 3-32μm.

[0091] The zirconium oxide, the mullite and the zirconium silicate all include two grades of particle sizes, i.e. 25-52μm and 1-25μm, and the mass percentage of each grade of particle size in the zirconium oxide, the mullite and the zirconium silicate is 60wt% of particle size 25-52μm and 40wt% of particle size 1-25μm.

[0092] The mass percentage of each substance in the whisker component is 22wt% of mullite whisker, 26wt% of alumina whisker, 13wt% of silicon oxide whisker, 18wt% of silicon carbide whisker and 21wt% of organic whisker; and the mass percentage of each substance in the organic whisker is 30wt% of polyamide whisker and 70wt% of chitin whisker.

[0093] The diameter of the mullite whisker, the alumina whisker, the silicon oxide whisker and the silicon carbide whisker is controlled within the range of 1-5μm, and the aspect ratio is controlled within the range of 15-25:1; and the diameter of the polyamide whisker and the chitin whisker is controlled within the range of 0.5-1μm, and the aspect ratio is controlled within the range of 5-15:1.

[0094] In step one, the ceramic core connecting rod blank is prepared by extrusion molding method, including the following main parameters: step 1.2: the ceramic powder material is put into a V-type mixer, mixed at room temperature for 20 min, and the mixing speed is 200 r / min, to prepare the composite powder material; step 1.3: water, binder and dispersing agent are put into a stirrer, stirred at room temperature for 10 min, and the stirring speed is 200 r / min, to prepare the composite treatment agent; the adding amount of water, binder and dispersing agent is 5wt%, 1wt% and 1wt% of the ceramic powder material respectively, the mass ratio of polyvinyl alcohol and starch in the binder is 2:1, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate in the dispersing agent is 1:1:1; step 1.4: the composite powder material and the composite treatment agent are put into a stirrer, stirred at room temperature for 2h, and the stirring speed is 200 r / min; step 1.5: the whisker component is added into the stirrer, and continues to stir at room temperature for 4h, and the stirring speed is 200 r / min; step 1.6: the graphene is added into the stirrer, and continues to stir at room temperature for 3h, and the stirring speed is 200 r / min, to prepare the ceramic slurry; step 1.7: the ceramic slurry is put into an extruder, and is extruded at room temperature, the extrusion pressure is 10 MPa, and then is self-dried at room temperature for 28h, to prepare the ceramic core connecting rod blank.

[0095] In step one, the process system of low-temperature glue removal treatment and high-temperature sintering treatment is as follows: the ceramic core connecting rod blank is put into a calcining furnace, first heated from room temperature to 400℃ at a rate of 5℃ / min, and kept for 20h, to complete the low-temperature glue removal treatment; then heated from 400℃ to 1600℃ at a rate of 3℃ / min, kept for 8h, and cooled to room temperature in the furnace, to complete the high-temperature sintering treatment.

[0096] In step two, the ceramic core connecting rod is pretreated, and the specific operation is as follows: the ceramic core connecting rod after high-temperature sintering treatment is immersed in an alkali solution or hydrofluoric acid at room temperature for 3h, and then cleaned and naturally dried. The concentration of the alkali solution is 40%; the concentration of the hydrofluoric acid is 80%.

[0097] In step three, the ceramic core connecting rod is post-treated, and the specific operation is as follows: the pretreated ceramic core connecting rod is immersed in silica sol or ceramic shell surface layer slurry at room temperature for 10 min, and then self-dried for 8h; the thickness of the coated layer is 2μm.

[0098] In step four, the ceramic core connecting rod is heat treated, and the specific operation is as follows: the post-treated ceramic core connecting rod is put into a heat treatment furnace, heated from room temperature to 600℃ at a rate of 5℃ / min, kept for 3h, and cooled to room temperature in the furnace.

[0099] Example three:

[0100] According to another preferred embodiment of the high-matching easy-to-extract core ceramic core connecting rod for precision investment casting and the preparation method, the raw material selection and proportioning, the preparation process and process parameters, the technical principle, and the beneficial effects are basically the same as those of the first embodiment, except that:

[0101] The ceramic core connecting rod is compounded by a ceramic powder material, a whisker component, and graphene, and the mass percentage of each substance in the ceramic core connecting rod is 95wt% of the ceramic powder material, 3wt% of the whisker component, and 2wt% of the graphene.

[0102] The mass percentage of each substance in the ceramic powder material is 40wt% of aluminum oxide, 15wt% of silicon oxide, 10wt% of magnesium oxide, 10wt% of zirconium oxide, 18wt% of mullite, and 7wt% of zirconium silicate.

[0103] The aluminum oxide, the silicon oxide, and the magnesium oxide all include three grades of particle sizes, which are 56-75μm, 32-56μm, and 3-32μm, respectively, and the mass percentage of each grade of particle size in the aluminum oxide, the silicon oxide, and the magnesium oxide is 48wt% of the particle size 56-75μm, 32wt% of the particle size 32-56μm, and 20wt% of the particle size 3-32μm.

[0104] The zirconium oxide, the mullite, and the zirconium silicate all include two grades of particle sizes, which are 25-52μm and 1-25μm, respectively, and the mass percentage of each grade of particle size in the zirconium oxide, the mullite, and the zirconium silicate is 70wt% of the particle size 25-52μm and 30wt% of the particle size 1-25μm.

[0105] The mass percentage of each substance in the whisker component is 30wt% of mullite whisker, 15wt% of aluminum oxide whisker, 18wt% of silicon oxide whisker, 11wt% of silicon carbide whisker, and 26wt% of organic whisker, and the mass percentage of each substance in the organic whisker is 40wt% of polyamide whisker and 60wt% of chitin whisker.

[0106] The diameters of the mullite whisker, the aluminum oxide whisker, the silicon oxide whisker, and the silicon carbide whisker are all controlled within the range of 1-5μm, and the aspect ratios are all controlled within the range of 15-25:1; the diameters of the polyamide whisker and the chitin whisker are both controlled within the range of 0.5-1μm, and the aspect ratios are both controlled within the range of 5-15:1.

[0107] In step one, the ceramic core connecting rod blank is prepared by extrusion molding method, including the following main parameters: step 1.2: the ceramic powder material is put into a V-type mixer, mixed at room temperature for 30 min, and the mixing speed is 100 r / min, to prepare the composite powder material; step 1.3: water, binder and dispersing agent are put into a stirrer, stirred at room temperature for 20 min, and the stirring speed is 100 r / min, to prepare the composite treatment agent; the adding amount of water, binder and dispersing agent is 10wt%, 3wt% and 3wt% of the ceramic powder material respectively, the mass ratio of polyvinyl alcohol and starch in the binder is 3:1, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate in the dispersing agent is 2:1:1; step 1.4: the composite powder material and the composite treatment agent are put into a stirrer, stirred at room temperature for 4 h, and the stirring speed is 100 r / min; step 1.5: the whisker component is added into the stirrer, and continues to stir at room temperature for 6 h, and the stirring speed is 100 r / min; step 1.6: the graphene is added into the stirrer, and continues to stir at room temperature for 4 h, and the stirring speed is 100 r / min, to prepare the ceramic slurry; step 1.7: the ceramic slurry is put into an extruder, and is extruded at room temperature, the extrusion pressure is 20 MPa, and then is self-dried at room temperature for 20 h, to prepare the ceramic core connecting rod blank.

[0108] In step one, the process system of low-temperature glue removal treatment and high-temperature sintering treatment is as follows: the ceramic core connecting rod blank is put into a calcining furnace, first heated from room temperature to 600℃ at a rate of 10℃ / min, and kept for 10 h, to complete the low-temperature glue removal treatment; then heated from 600℃ to 1700℃ at a rate of 5℃ / min, kept for 4 h, and cooled to room temperature in the furnace, to complete the high-temperature sintering treatment.

[0109] In step two, the ceramic core connecting rod is pretreated, and the specific operation is as follows: the ceramic core connecting rod after high-temperature sintering treatment is immersed in an alkali solution or hydrofluoric acid at room temperature for 6 h, and then cleaned and naturally dried. The concentration of the alkali solution is 60%; the concentration of the hydrofluoric acid is 95%.

[0110] In step three, the ceramic core connecting rod is post-treated, and the specific operation is as follows: the pretreated ceramic core connecting rod is immersed in a silica sol or a ceramic shell surface layer slurry at room temperature for 20 min, and then self-dried for 12 h; the thickness of the coated layer is 5μm.

[0111] In step four, the ceramic core connecting rod is heat treated, and the specific operation is as follows: the post-treated ceramic core connecting rod is put into a heat treatment furnace, heated from room temperature to 900℃ at a rate of 8℃ / min, kept for 1 h, and cooled to room temperature in the furnace.

[0112] In addition, the ceramic core connecting rod blank of the three embodiments above can also be prepared by a dry forming method, which comprises the following steps in order:

[0113] Step 2.1: weigh each raw material according to the designed material ratio for standby;

[0114] Step 2.2: put all the alumina, silicon oxide, magnesium oxide, zirconium oxide, mullite and zirconium silicate of each size range of the ceramic powder material into a V-type mixer, mix at room temperature for 20-30 min, and the mixing speed is 300-500 r / min, so that each substance is uniformly mixed;

[0115] Step 2.3: add mullite whiskers, alumina whiskers, silicon oxide whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers in the whisker component into the V-type mixer, continue to mix at room temperature for 5-8 h, and the mixing speed is 300-500 r / min, so that various whiskers are uniformly dispersed;

[0116] Step 2.4: add graphene into the V-type mixer, continue to mix at room temperature for 3-4 h, and the mixing speed is 300-500 r / min, so that each substance is uniformly mixed;

[0117] Step 2.5: add water, binder and dispersant into the V-type mixer, continue to mix at room temperature for 12-20 h, and the mixing speed is 300-500 r / min, so that each substance is uniformly mixed, and the ceramic powder is prepared; the adding amount of water, binder and dispersant is 1-3 wt%, 1-3 wt% and 1-3 wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2-3:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate is 1-2:1:1;

[0118] Step 2.6: according to the designed shape and size, put the ceramic powder into a dry press machine, dry press at room temperature, the pressure is 50-70 MPa, and the pressure holding time is 1-3 min, and the ceramic core connecting rod blank is prepared.

[0119] Comparative Example One:

[0120] A pure alumina ceramic rod is prepared. An alumina powder with a purity of 95% is used to prepare a blank with a diameter of 5 mm by dry forming at a pressure of 25 MPa, and is fired at 1650°C for 4 hours. No pretreatment, post-treatment and heat treatment is performed.

[0121] The prepared pure alumina ceramic rod is used in a certain type of vane casting, the core removal is difficult, the residual core rate is more than 40%, the thermal expansion coefficient of the ceramic rod and the silica-based ceramic core does not match, the loose rate of the connection is more than 35%, the alloy liquid metal phenomenon occurs at a rate of more than 25%, and the qualified rate of the casting is only 50%.

[0122] Comparative Example Two:

[0123] A pure silica ceramic rod is prepared. The silica powder with a purity of 98% is extruded into a green body with a diameter of 6 mm, and after low-temperature degassing, it is sintered at 1550 DEG C for 3 hours. No pretreatment, post-treatment and heat treatment is performed.

[0124] The prepared pure silica ceramic rod is applied to the casting of a certain gas turbine vane, the core breaking rate during the wax pressing step is more than 45%, the fracture rate during the pouring process is more than 30%, and the qualified rate of the casting is only 40%.

[0125] The high-matching easy-core-removal ceramic core connecting rods prepared in the above three examples and the pure alumina ceramic rods and the pure silica ceramic rods prepared in the two comparative examples are subjected to performance testing, and the test results are shown in Table 1.

[0126] Table 1 Performance test results of the ceramic rods of the three examples and the two comparative examples

[0127]

[0128] As can be seen from the performance test results, the high-matching easy-core-removal ceramic core connecting rods prepared in the three examples have excellent core removal effect and extremely high matching, and at the same time, have high strength and high toughness, the core removal rate is smooth, no residual core is left, the connecting rod is connected closely with the ceramic core, no loose and fracture phenomenon occurs at the connection during the core making, mold making, shell making and pouring process, no alloy liquid metal phenomenon occurs, and the vane qualified rate reaches more than 90%.

[0129] The ceramic powder materials, whisker components and graphene and other raw materials used in the above examples are purchased from Aladdin Reagent Co., Ltd. and Sinopharm Chemical Reagent Co., Ltd.

[0130] Special note: The technical solution of the present application involves many parameters, which need to be considered comprehensively to obtain the beneficial effects and significant progress of the present application. Moreover, the value range of each parameter in the technical solution is obtained through a large number of tests, and the inventors have recorded a large number of test data for each parameter and the mutual combination of each parameter. Due to the limited space, the specific test data is not disclosed here.

[0131] It is understood by those skilled in the art that the present application encompasses any combination of the parts shown in the summary and detailed description of the application and the drawings, which have not been described one by one in order to limit the description and make it concise. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A high matchability easy-to-die ceramic core connecting rod for precision investment casting, characterized by, The ceramic core connecting rod is compounded by ceramic powder material, whisker component and graphene, and the mass percentage of each substance in the ceramic core connecting rod is as follows: ceramic powder material 90-95wt%, whisker component 1.5-5wt%, and graphene 0.5-5wt%, and the sum of the content of each substance is 100wt%. The mass percentage of each substance in the ceramic powder material is as follows: alumina 30-40wt%, silicon oxide 15-25wt%, magnesium oxide 5-10wt%, zirconium oxide 10-15wt%, mullite 10-18wt%, and zirconium silicate 5-12wt%. The mass percentage of each substance in the whisker component is as follows: mullite whisker 18-30wt%, alumina whisker 15-26wt%, silicon oxide whisker 8-18wt%, silicon carbide whisker 8-18wt%, and organic whisker 15-26wt%, and the mass percentage of each substance in the organic whisker is as follows: polyamide whisker 30-40wt%, and chitin whisker 60-70wt%.

2. The high match easy-to-die ceramic core print bar for investment precision casting according to claim 1, characterized in that, The alumina, the silicon oxide and the magnesium oxide all include three grades of particle size, which are 56μm≤particle size≤75μm, 32μm≤particle size<56μm and 3μm≤particle size<32μm, and the mass percentage of each grade of particle size in the alumina, the silicon oxide and the magnesium oxide is as follows: 56μm≤particle size≤75μm accounts for 45-55wt%, 32μm≤particle size<56μm accounts for 25-35wt%, and 3μm≤particle size<32μm accounts for 20-30wt%. The zirconium oxide, the mullite and the zirconium silicate all include two grades of particle size, which are 25μm≤particle size≤52μm and 1μm≤particle size<25μm, and the mass percentage of each grade of particle size in the zirconium oxide, the mullite and the zirconium silicate is as follows: 25μm≤particle size≤52μm accounts for 60-70wt%, and 1μm≤particle size<25μm accounts for 30-40wt%.

3. The high match easy-to-die ceramic core print bar for investment precision casting according to claim 2, characterized by, The diameter of the mullite whisker, the alumina whisker, the silicon oxide whisker and the silicon carbide whisker is controlled in the range of 1-5μm, and the aspect ratio is controlled in the range of 15-25:1; the diameter of the polyamide whisker and the chitin whisker is controlled in the range of 0.5-1μm, and the aspect ratio is controlled in the range of 5-15:

1.

4. A method for producing a high-matching ceramic core print rod for investment precision casting according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps in the order: Step one: according to the designed process parameters, a ceramic core connecting rod blank is prepared by using extrusion molding method or dry molding method, and then the ceramic core connecting rod blank is put into a calcining furnace for low-temperature glue removal treatment and high-temperature sintering treatment to obtain a ceramic core connecting rod; Step two: the ceramic core connecting rod is pretreated to produce a frosted effect on the surface of the ceramic core connecting rod and form a large number of uniformly distributed corrosion pits or corrosion holes; Step three: the ceramic core connecting rod is post-treated to cover the surface of the ceramic core connecting rod with a uniform coating. Step four: heat treatment is conducted on the ceramic core connecting rod, so that the coating is solidified and tightly combined with the surface of the ceramic core connecting rod, i.e. a high-matching easy-to-release core ceramic core connecting rod is prepared.

5. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 4, characterized in that, In step one, the ceramic core connecting rod blank is prepared by using the extrusion molding method, which comprises the following steps in sequence: Step 1.1: each raw material is weighed according to the designed material ratio for standby; Step 1.2: all the alumina, silicon oxide, magnesium oxide, zirconium oxide, mullite and zirconium silicate of various particle sizes in the ceramic powder material are put into a V-type mixer, mixed at room temperature for 20-30 min, and the mixing speed is 100-200 r / min, so that each substance is uniformly mixed, and a composite powder material is prepared; Step 1.3: water, binder and dispersant are all put into a stirrer, stirred at room temperature for 10-20 min, and the stirring speed is 100-200 r / min, so that each substance is completely fused, and a composite treatment agent is prepared; The adding amount of water, binder and dispersant is 5-10wt%, 1-3wt% and 1-3wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2-3:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate is 1-2:1:1; Step 1.4: the composite powder material and the composite treatment agent are all put into a stirrer, stirred at room temperature for 2-4 h, and the stirring speed is 100-200 r / min, so that each substance is completely fused; Step 1.5: mullite whiskers, alumina whiskers, silicon oxide whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers in the whisker component are all added into the stirrer, and continue to stir at room temperature for 4-6 h, and the stirring speed is 100-200 r / min, so that various whiskers are uniformly dispersed; Step 1.6: graphene is added into the stirrer, and continue to stir at room temperature for 3-4 h, and the stirring speed is 100-200 r / min, so that each substance is uniformly mixed, and a ceramic slurry is prepared; Step 1.7: the ceramic slurry is put into an extruder according to the designed shape and size, and is extruded at room temperature, the extrusion pressure is 10-20 MPa, and then is self-dried at room temperature for 20-28 h, i.e. a ceramic core connecting rod blank is prepared.

6. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 4, characterized by, In step one, the ceramic core connecting rod blank is prepared by using the dry molding method, which comprises the following steps in sequence: Step 2.1: each raw material is weighed according to the designed material ratio for standby; Step 2.2: all the alumina, silicon oxide, magnesium oxide, zirconium oxide, mullite and zirconium silicate of various particle sizes in the ceramic powder material are put into a V-type mixer, mixed at room temperature for 20-30 min, and the mixing speed is 300-500 r / min, so that each substance is uniformly mixed; Step 2.3: Put the mullite whiskers, alumina whiskers, silicon oxide whiskers, silicon carbide whiskers, polyamide whiskers and chitin whiskers in the whisker component into a V-type mixer, and continue to mix at room temperature for 5-8 hours at a mixing speed of 300-500 r / min, so that the various whiskers are uniformly dispersed; Step 2.4: Put the graphene into the V-type mixer, and continue to mix at room temperature for 3-4 hours at a mixing speed of 300-500 r / min, so that the various substances are uniformly mixed; Step 2.5: Put the water, binder and dispersant into the V-type mixer, and continue to mix at room temperature for 12-20 hours at a mixing speed of 300-500 r / min, so that the various substances are uniformly mixed, and a ceramic powder material is prepared; The adding amounts of the water, binder and dispersant are 1-3 wt%, 1-3 wt% and 1-3 wt% of the ceramic powder material respectively; the binder is composed of polyvinyl alcohol and starch, and the mass ratio of polyvinyl alcohol to starch is 2-3:1; the dispersant is composed of sodium stearate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the mass ratio of sodium stearate to sodium dodecyl sulfate to sodium dodecyl benzene sulfonate is 1-2:1:1; Step 2.6: According to the designed shape and size, the ceramic powder material is put into a dry press machine for dry pressing at room temperature, and the pressure is 50-70 MPa and the pressure holding time is 1-3 minutes, so that a ceramic core connecting rod blank is prepared.

7. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 6, characterized in that, In step one, the process system of low-temperature glue removal treatment and high-temperature sintering treatment is as follows: the ceramic core connecting rod blank is put into a sintering furnace, first heated from room temperature to 400-600℃ at a heating rate of 5-10℃ / min, and kept for 10-20 hours, so that the low-temperature glue removal treatment is completed; then heated from 400-600℃ to 1600-1700℃ at a heating rate of 3-5℃ / min, and kept for 4-8 hours, and then cooled to room temperature in the furnace, so that the high-temperature sintering treatment is completed; during the whole low-temperature glue removal treatment and high-temperature sintering treatment, no protective atmosphere is needed to be introduced.

8. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 7, characterized in that, In step two, the ceramic core connecting rod is pretreated, and the specific operation is as follows: the ceramic core connecting rod after high-temperature sintering treatment is immersed in an alkali solution or hydrofluoric acid at room temperature for 3-6 hours, then taken out from the alkali solution or hydrofluoric acid, and cleaned with deionized water, and then naturally air-dried; The preparation method of the alkali solution is as follows: sodium hydroxide and potassium hydroxide are mixed according to a mass ratio of 2:3, and then put into deionized water to dissolve, so that an alkali solution with a concentration of 40-60% is formed; the concentration of the hydrofluoric acid is 80-95%.

9. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 8, characterized in that, In step three, the ceramic core connecting rod is post-treated, and the specific operation is as follows: the pretreated ceramic core connecting rod is immersed in a silica sol or a ceramic shell surface layer slurry at room temperature for 10-20 minutes, then taken out from the silica sol or the ceramic shell surface layer slurry, and then air-dried for 8-12 hours; the thickness of the coated layer is 2-5 μm.

10. The method of producing a high-matching ceramic core print rod for investment precision casting according to claim 9, characterized in that, In step four, the ceramic core connecting rod is heat treated, and the specific operation is as follows: the ceramic core connecting rod after the post-treatment is put into a heat treatment furnace, and is heated from room temperature to 600-900℃ at a heating rate of 5-8℃ / min, is kept for 1-3h, and is cooled to room temperature with the furnace, without needing to introduce a protective atmosphere.

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