DE112014002572T5 - Investment casting core, method for producing a investment casting core, and investment casting tool - Google Patents

Abstract

On a surface of a sintered silica core body (18a) containing mainly silica particles, a capping layer (19a) containing only silicon alkoxide or a mixed alkoxide of silicon alkoxide and aluminum alkoxide is formed to close holes (18c) formed in the surface. This makes it possible to prevent breakage of the core during potting.

Description

area

The present invention relates to a precision casting core, a method for producing a investment casting core, and a precision casting tool.

State of the art

As a precision cast product, for example, a turbine blade used in a gas turbine is known. In the gas turbine, a working fluid is heated by a burner to provide a high temperature / high pressure working fluid, and the working fluid rotates the turbine. That is, the working fluid compressed using a compressor is heated by the burner to increase the energy of the working fluid, the turbine recovers the energy to generate a rotational force, and the rotational force generates electrical energy. The turbine is provided with a turbine runner, and the outer edge region of the turbine runner is provided with at least one gas turbine blade.

Here, the gas turbine blade is exposed to high temperatures. To cool the gas turbine blade, a cooling medium flows through the gas turbine blade as a countermeasure. For this purpose, the gas turbine blade is provided with an internal cooling structure. To produce the inner cooling structure, a core is provided which has the same shape as a flow channel carrying the cooling medium, and the core is removed after casting. The core is removed by dissolution in an alkali solution (eg NaOH or KOH). As a result, for example, the inner cooling structure is generated for the turbine blade.

In the past, the core used was a ceramic particle-containing ceramic core (Patent Literature 1).

An investment casting core may be obtained by molding a silica material such as molten silica (SiO ₂ ) by injection molding or slip casting, and heat treating the same.

The injection molding method is a method in which a compact is obtained by kneading ceramic powder and wax, injecting a material obtained by heating and melting the wax into a metal mold, and cooling and curing the material.

The slip casting method further provides a method in which slurry is prepared by mixing ceramic powder with water or the like, the slurry is poured into a mold made of a solution absorbing material such as gypsum, and the slurry is dried to obtain a desired shaped body.

Bibliography

patent literature

• Patent Literature 1: Disclosed Japanese Patent Publication 6-340467

Summary

Technical problem

Incidentally, since the existing core is mainly made from the aspect of alkali solubility, there arises a problem that the core has low strength at high temperatures. Furthermore, in the injection molding process, a plurality of holes are formed in the surface of the core, which is sintered following the molding. This results in the problem of low strength, which is why the core may break from the holes as origin points during casting.

Accordingly, there has been a demand for an investment casting core having improved strength at high temperatures.

The invention has been made in consideration of the above-described circumstances, and has as its object to provide an investment casting core with improved strength at high temperatures, a process for producing a investment casting core, and a precision casting mold.

the solution of the problem

According to a first aspect of the invention for solving the above-described problems, there is provided an investment casting core which is obtained by forming an alkoxide-containing alkoxide coating layer on a surface of a sintered core casting containing mainly silica particles.

According to a second aspect, there is provided an investment casting core obtained by forming an alkoxide material and silica dust-containing alkoxide-silica dust cover layer on a surface of a sintered core casting containing mainly silica particles.

According to a third aspect, in the first or second aspect, there is provided an investment casting core in which the alkoxide material comprises only silicon alkoxide or a mixed alkoxide of silicon alkoxide and aluminum alkoxide.

According to a fourth aspect, there is provided a precision casting tool used to make a metal casting which has the investment casting core according to the first or second aspect in a shape corresponding to a cavity inside the metal casting, and an outside molding tool corresponding to the shape of the outer boundary surface of the casting metal , includes.

According to a fifth aspect, there is provided a method of manufacturing an investment casting core comprising immersing a sintered body of a fine casting core body containing mainly silica particles in an alkoxide material, drying the sintered body, and heating the sintered body to form a cover layer on the surface of the investment casting core.

According to a sixth aspect, there is provided a method of manufacturing a precision casting core which comprises immersing a sintered body of a fine casting core body containing mainly silica particles in an alkoxide-silica dust material consisting of an alkoxide material and silica dust, drying the sintered body, and heating the sintered body Sintered body for forming a cover layer on the surface of the investment casting core body comprises.

According to a seventh aspect, in the fifth or sixth aspect, there is provided a method of manufacturing an investment casting core in which the alkoxide material comprises only silicon alkoxide or a mixed alkoxide of silicon alkoxide and aluminum alkoxide.

According to an eighth aspect, in the third aspect, silicon ethoxide or silicon butoxide is used as the silicon alkoxide.

Advantageous Effects of the Invention

Since the invention is designed such that a cover layer of alkoxide material is formed on the surface of the sintered investment casting core body, the holes formed in the surface during sintering are sealed.

Accordingly, there is an effect that core breakage during casting is avoided by improving the strength of the core and closing the holes.

Brief description of the drawings

1 is a cross-sectional structure diagram of a investment casting core.

2 FIG. 10 is a flowchart exemplifying the flow of a casting method. FIG.

3 FIG. 4 is a flowchart exemplifying the flow of a method of manufacturing a molding tool. FIG.

4 is a schematic representation which a. Method of making a core illustrated.

5 FIG. 12 is a schematic perspective view illustrating a part of a metal mold. FIG.

6 Fig. 12 is a schematic diagram illustrating a method of producing a wax model.

7 Figure 3 is a schematic diagram illustrating one embodiment of the application of slurry to a wax model.

8th FIG. 12 is a schematic diagram illustrating a method of manufacturing an outer mold. FIG.

9 is a schematic diagram illustrating a sub-process of the method for producing a mold.

10 is a schematic representation illustrating a sub-process of the casting process.

Description of embodiments

In the following the invention will be described in more detail with reference to the drawings. Moreover, the invention is not limited to the following description. Furthermore, the components to be described below may comprise a component readily derivable by a person skilled in the art, a component having a substantially identical configuration, and a so-called equivalent component.

First Embodiment

1 is a cross-sectional structure diagram of a investment casting core.

An investment casting core according to the invention is made by forming a covering layer of two Types of silica materials having different particle diameters on a surface of a sintered, mainly silica particles containing investment casting core body (hereinafter referred to as "core body") obtained.

As in the upper part of the cross-sectional view of the functioning as a sintered body core body of 1 is illustrated, a plurality of holes during sintering 18c in a surface 18b a core body 18a educated.

As in the lower part of 1 Illustrated are the holes 18c in the context of the invention by coating the holes formed in the surface 18c with the topcoat 19a locked.

The core body 18a This includes mainly silica particles, such as molten silica (SiO ₂ ) such as quartz sand and quartz powder.

The core body 18a is prepared by a known method wherein wax is mixed by mixing silica particles such as quartz flour (for example, 800 mesh (10 to 20 μm)) and quartz sand (for example, 220 mesh (20 to 70 μm)) in a weight ratio of 1 : 1, prepared mixture, heated and kneaded, to obtain in this way a composite body.

By injection molding of the obtained composite body, a core compact is obtained.

The core body 18a is subsequently obtained by carrying out a degreasing treatment at, for example, 600 ° C and a sintering treatment at, for example, 1200 ° C.

The cover layer 19a is in the context of the invention on the surface 18b of the core body obtained as a sintered body 18a educated.

The alkoxide material is in the topcoat 19a used.

The alkoxide material herein comprises solely silicon alkoxide, or comprises a mixed alkoxide of silicon alkoxide and aluminum alkoxide.

As the silicon alkoxide, silicon ethoxide or silicon butoxide is used, and ethanol or butanol is used as the solvent.

In addition, when two kinds of alkoxides are mixed together, a mixed alkoxide material obtained by mixing silicon alkoxide and aluminum alkoxide is used, for example, using an alcoholic solvent such as butanol as a solvent.

When a mixed alkoxide is prepared, a mixed alkoxide consisting of silicon ethoxide and aluminum isopropoxide is dissolved in a butanolic solution.

The mixed alkoxide (silicon ethoxide + aluminum isopropoxide) is mixed in a molar ratio of 2: 3 so as to produce an organic mixed alkoxide.

The sample of the core is dipped in and withdrawn from the single alkoxide or mixed alkoxide product to thereby form a silicon layer or silicon aluminum alkoxide layer on the surface 18b of the core body 18a and a silicon component or silicon-aluminum alkoxide component even in the hole 18c to deposit the core surface.

Since the sole alkoxide or the mixed alkoxide dissolves in an alcoholic solution when immersed, the sole alkoxide or the mixed alkoxide penetrate easily into the core body, which is why a good cover layer 19a is trained.

After the drying process, a heat treatment at, for example, 1000 ° C is performed. If the surface with the topcoat 19a is provided, the heat treatment at, for example, 1000 ° C or less can be performed.

In the case of a mixed alkoxide, the silicon-aluminum alkoxide layer undergoes heat-treatment transformation into inorganic mullite (3Al ₂ O ₃ .2SiO ₂ ) which has a high melting point. That way, it's possible to get the core 18 to produce, whose core body 18a with the mullite topcoat 19a is covered.

Since the melting point of mullite is 1900 ° C and is therefore higher than the melting point of silicon dioxide (1600 ° C), this high casting temperatures can be handled.

In this way, since the plurality of holes formed in the surface are closed, it is possible to avoid the problem described in the prior art, according to which the core breaks from the holes as origin points during casting. Accordingly, the high-temperature strength of the investment casting core is improved.

<Test Example 1>

To verify the effect of the invention, a test example will be described below.

In the test example, a composite body was first obtained by adding wax to a mixture prepared by mixing quartz flour (800 mesh) and quartz sand (220 mesh) in a weight ratio of 1: 1, and heating and kneading the mixture. Here, "MCF-2000" (product name) manufactured by Tatsumori Ltd. was used as quartz flour, "RD-120" (product name) manufactured by Tatsumori Ltd. used as quartz sand, and "Cerita Wax F30-75" (product name ) manufactured by Paramelt Co. Ltd., used as wax.

Injection molding of the obtained composite obtained a compact.

As a test sample, a sample having a width of 30 mm, a length of 200 mm, and a thickness of 5 mm was obtained.

By carrying out a degreasing treatment at 600 ° C and a sintering treatment at 1200 ° C, a sample for a core body was subsequently obtained.

(Cover layer 1)

Subsequently, silicon ethoxide was dissolved in an ethanolic solution. The sample of the core body was dipped in and pulled out of the obtained silicon ethoxide around the alkoxide-formed overcoat layer 19a to train on their surface. Following the drying process, a heat treatment was carried out at 1000 ° C. around the covering layer consisting of inorganic silicon dioxide and comprising silicon ethoxide 19a on the surface 18b of the core body (sample 1).

(Cover layer 2)

Subsequently, a mixed alkoxide of silicon ethoxide and aluminum isopropoxide was dissolved in a butanolic solution. The mixed alkoxide (silicon ethoxide + aluminum isopropoxide) was mixed in a molar ratio of 2: 3 so as to prepare an organic mixed alkoxide.

The sample of the core body was dipped in and pulled out of the obtained mixed alkoxide around the overcoating layer made of mixed alkoxide 19a to train on their surface. After the drying process, a heat treatment was performed at 1000 ° C to obtain the overcoat layer from the mullite obtained by converting the mixed alkoxide of silicon ethoxide and aluminum isopropoxide 19a on the surface 18b of the core body (sample 2).

As a comparative example, a core body without a cover layer was prepared as a comparative sample.

The strength of each test sample was measured.

The strength test was conducted on the basis of "Bending strength of ceramic compositions (1981)" in accordance with JIS R 1601.

The strength of the comparative sample without the overcoat layer according to the conventional method was 20 MPa, whereas the strength of the sample 1 with the silica core covering layer 1 for the core body according to the method of the present invention was 22 MPa. As a result, it was found that the strength in the sample of the core body of the invention was increased by 10%.

Further, the strength of Sample 2 having the silica core cap layer 2 for the core body according to the method of the present invention was 24 MPa. As a result, it was found that the strength in the sample of the core body of the invention was increased by 20%.

According to sample 2 of the invention, since the high-temperature resistance of the core due to the mullite is improved, it is possible to provide a molding tool which does not undergo deformation even when the molding tool is exposed to a high temperature (for example, 1550 ° C.) for a long period of time. For example, when a one-side solidified turbine blade is made.

Hereinafter, a casting method will be described, which uses a molding tool with an investment casting core of the invention arranged therein.

2 FIG. 10 is a flowchart exemplifying a flow of the casting method. FIG. The casting method will be described below with reference to 2 described. The in 2 In this case, the illustrated process can be carried out completely automatically, or it can be performed by the persons operating the individual devices in a process-adapted manner. In the casting method of the embodiment, a molding tool is manufactured (step S1). The molding tool can be prepared in advance, or it can be made at every molding.

With reference to the 3 to 9 For example, the method of manufacturing a mold of the embodiment described by the process of step S1 will be described below. 3 FIG. 10 is a flowchart exemplifying the flow of the method of manufacturing a molding tool. FIG. The in 3 In this case, the illustrated process can be carried out completely automatically, or it can be performed by the persons operating the individual devices in a process-adapted manner.

In the method of manufacturing a molding tool, a core is manufactured (step S12). The core has a shape corresponding to the cavity inside the metal casting produced using the mold. Thus, since the core is disposed in a region corresponding to the cavity inside the metal casting, it is possible to prevent inflow of the metal functioning as casting metal during casting. Hereinafter, the method of manufacturing a core will be described with reference to FIG 4 described.

4 Fig. 12 is a schematic diagram illustrating the method of producing a core. As in 4 In the method of manufacturing a core, a metal mold is illustrated 12 manufactured (step S101). The metal mold 12 is formed such that an area corresponding to the core is formed as a cavity. A cavity-formed portion of the core is a convex portion 12a educated. Although it is in the cross-section of the metal mold 12 according to 4 is illustrated is the metal mold 12 moreover, shaped such that, in addition to an opening for injecting a material into a space or a hole for releasing air, basically another area, which includes the entire boundary surface of a region corresponding to the core, is formed as a cavity. In the method of casting a mold, over the opening for injecting a material into the gap of the metal mold 12 a ceramic slip 16 into the metal mold 12 injected, as with an arrow 14 is indicated. In particular, it becomes a core 18 produced by so-called injection molding, by the ceramic slip 16 into the metal mold 12 is injected. Following the production of the core 18 inside the metal mold 12 becomes the core 18 in the method of manufacturing a mold from the metal mold 12 separated, and the severed core 18 is in a combustion furnace 20 annealed. In this way, the core formed of ceramic 18 annealed and hardened (step S102). As material for the ceramic slurry 16 In this case, an "alkoxide" is used.

To make a topcoat on the surface of the core 18 form, became the sintered core 18 then in a with slip 19 filled storage area 17 dipped, and was pulled out therefrom for drying (step S103). Subsequently, the submerged core 18 taken and in the incinerator 20 annealed. In this way, the cover layer becomes 19a on the surface of the ceramic core 18 formed (step S104).

In the method of casting a mold, the one with the cover layer becomes 19a provided core 18 prepared as described above. In addition, the core becomes 18 made of a material which is removed after curing of the metal casting using a core removal process, such as a chemical treatment.

Following the production of the core 18 For example, in the method of manufacturing a mold, an outer metal mold is produced (step S14). The outer metal mold has a shape whose inner boundary surface corresponds to the outer boundary surface of the metal casting. The metal mold may be formed of metal or ceramic. 5 is a schematic perspective view illustrating a part of the metal mold. In the in 5 illustrated metal mold 22a corresponds to a formed on the inner boundary surface recess of the outer boundary surface of the metal casting. In addition, in 5 only the metal mold 22a illustrated; however, in addition, another, the metal mold 22a corresponding metal mold made in an orientation in which the recess formed on the inner boundary surface is covered so that it with the metal mold 22a matches. In the method of manufacturing a mold, when two metal molds are combined together, a mold is obtained whose inner boundary surface corresponds to the outer boundary surface of the metal mold.

Subsequent to the production of the outer metal mold, in the method of manufacturing a mold, a wax model (a wax mold) is prepared (step S16). Hereinafter, this method will be described with reference to 6 described. 6 Fig. 12 is a schematic diagram illustrating a method of producing a wax model. In the method of manufacturing a molding tool the core 18 at a predetermined location in the metal mold 22a arranged (step S110). After that, one covers the metal mold 22a corresponding metal mold 22b the recessed surface of the metal mold 22a while at the same time the boundary surface of the core 18 from metal mold tools 22a and 22b is enclosed, so the core 18 and the metal molds 22a and 22b a gap 24 form. In the process of making a mold, wax is then started 28 from one with the gap 24 connected line in the interspace 24 to inject, as with an arrow 26 is indicated (step S112). The wax 28 Here, a material, such as a wax, whose melting point is comparatively low, and which is heated and melted at a predetermined temperature or higher. In the method of manufacturing a mold, the wax becomes 28 in the entire area of the gap 24 filled (step S113). By curing the wax 28 then becomes a wax model 30 produced, in which the wax 28 the boundary surface of the core 18 encloses. The wax model 30 is shaped so that it is essentially made of wax 28 formed region which has the same shape as the metal casting to be produced is formed. In the process of making a metal casting, the wax model becomes 30 then from the metal molds 22a and 22b separated, and it becomes a sprue 32 attached thereto (step S114). The sprue 32 represents an opening through which molten metal functioning as a molten metal is introduced during casting. In the method of manufacturing a mold, the wax model becomes 30 which is the core 18 includes and from the same shape as the metal casting having wax 28 is formed as described above.

Following the production of the wax model 30 In the method of manufacturing a molding tool, slurry application (dipping) is performed (step S18). 7 Figure 3 is a schematic diagram illustrating one embodiment of the application of slurry to a wax model. 8th FIG. 12 is a schematic diagram illustrating a method of manufacturing an outer mold. FIG. As in 7 is illustrated, the wax model 30 in the process of making a mold into a slurry 40 filled storage area 41 dipped, and is withdrawn therefrom for drying (step S19). In this way, a primary layer 101A on the surface of the wax model 30 be formed.

The slip applied in step S18 is in this case a slip which directly onto the wax model 30 is applied. As a slip 40 For example, a slurry obtained by dispersing only ultrafine alumina particles is used. In the slip 40 For example, it is desirable to use refractory microparticles, such as about 350 mesh zirconia, as flour. Further, it is desirable to use a polycarboxylic acid as a dispersant. Further, it is desirable to the slurry 40 Add a small amount, for example 0.01%, of defoamer (a silicon material) or of a wettability enhancing agent. If the wettability enhancing agent is added to the slip, it is possible to increase the adhesive property of the slip 40 to the wax model 30 to improve.

As in 7 is illustrated, the application of slurry (dipping) is carried out on the primary layer (the first dried film) 101A wax model in the process of making a mold by applying and drying the slurry 40 (Step S20). As in 8th is then stuccoed, consisting of zirconia stucco grains (with a mean particle diameter of 0.8 mm) as stucco material 54 are sprinkled on the surface of the wet slurry (step S21). Following this is a layer of moist slurry, on the surface of which is the stucco material 54 adheres, dried, to thereby form a first backing layer (a second dried film) 104-1 on the primary layer (the first dried film) 101A form (step S22).

It is determined whether or not to form the first supporting layer (the second dried film) 104-1 used process is repeated several times (for example, n: 6 to 10 times) (step S23). The nth support layer 104-n is laminated in a predetermined number (n) (step S23: Yes), so that a dried compact acting as an outer mold becomes 106A which is the thickness of a multilayer backing layer 105A of for example 10 mm.

Following the preparation of one with a plurality of layers consisting of the primary layer 101A and the multilayer support layer 105A provided dried compact 106A becomes the dried compact 106A in the process for producing a molding tool, subjected to a heat treatment (step S24). Specifically, the wax between the outer mold and the core is removed, and the outer mold and the core are sintered. This will be explained below with reference to 9 described. 9 is a schematic representation illustrating a sub-process of the method for producing a molding tool. As illustrated in step S130, the one acting as an outer mold becomes a plurality of layers consisting of the primary layer 101A and the multilayer support layer 105A provided dried compact 106A in the process of making a mold in an autoclave 60 heated. The autoclave 60 heats the wax model 30 inside the dried compact 106A by introducing pressurized steam into the latter. In this way, this becomes the wax model 30 forming wax melted, leaving molten wax 62 from one of the dried compact 106A enclosed space 64 is dissipated.

Because the melted wax 62 from the gap 64 is discharged, is in the process for producing a mold, a molding tool 72 generated, in which the gap 64 in a wax filled area between the core 18 and the dried molding acting as the outer mold 106A is formed as illustrated in step S131. As illustrated in step S132, in the method of manufacturing a molding tool, the space is subsequently used 64 between the core 18 and the dried molding acting as the outer mold 106A provided mold 72 by means of a combustion furnace 70 heated. This way, out of the mold 72 one in the acting as an outer mold dried compact 106A removed superfluous component or moisture component, and the mold is used to form the outer mold 61 sintered and hardened. In the method of producing a metal casting, the molding tool becomes 72 prepared as described above.

The casting method is described with reference to 2 to 10 described throughout. 10 is a schematic representation illustrating a sub-process of the casting process. Following the manufacture of the mold in step S1, the mold is preheated in the casting process (step S2). Here, the mold is placed, for example, in a furnace (a vacuum furnace and a combustion furnace) and heated to a range of 800 ° C to 900 ° C. Due to the preheating treatment, it is possible to avoid breaking of the mold when molten metal (molten metal) is injected into the mold to make a metal mold.

Following the preheating of the molding tool, potting is performed in the casting process (step S3). As in step S140 of FIG 10 is illustrated, this means that molten metal 80 ie, a raw material (eg steel) of a molten cast metal, from the opening of the mold 72 in a gap between the outer mold 61 and the core 18 is injected.

Following the solidification of the in the mold 72 poured molten metal 80 In the casting process, the outer mold becomes 61 removed (step S4). As in step S141 of FIG 10 is illustrated, this means that the outer mold 61 after the metal casting 90 by solidifying the molten metal inside the mold 72 was obtained, is crushed, as a fragment 61a from metal casting 90 to be disconnected.

Following the separation of the outer mold 61 from metal casting 90 In the casting method, the core removal process is performed (step S5). As in step S142 of FIG 10 is illustrated, this means that by introducing the metal casting 90 in an autoclave 92 a core removal process is performed. The core 18 inside the metal casting 90 is then melted, and a molten core 94 is from inside the metal casting 90 dissipated. This is the metal casting 90 inside the autoclave 92 immersed in an alkali solution and repeatedly subjected to pressure increase and pressure lowering around the molten core 94 from the metal casting 90 dissipate.

Subsequent to performing the core removal process, a post-treatment is performed in the casting process (step S6). This means that an aftertreatment of the surface or the interior of the metal casting 90 he follows. Furthermore, in the casting process during the aftertreatment, the quality of the metal casting is checked. As in step S143 of FIG 10 can be illustrated in this way a metal casting 100 getting produced.

In the casting method of the embodiment, the metal casting is produced by producing the molding tool by the above-described lost wax casting method using a wax. In the method of manufacturing a mold, the casting method, and the mold of the embodiment, the outer mold functioning as the outer portion of the mold is hereby formed as a multi-layered structure in which the primary layer (the first dried film functioning as the primary layer) 101A formed as an inner boundary surface due to the use of a slurry of ultrafine alumina particles and the multilayer support layer 105A on the outside of the primary layer 101A is trained.

In the molding method of the embodiment, since the cover layer is formed on the surface of the core, the dimensional accuracy improves, thus improving the durability even at high molding temperatures.

Moreover, since a core having high strength is provided, the freedom of potting design (for example, a low pull-down speed or the like) increases even with a long casting time.

Moreover, it is possible to provide a precision cast product, such as a turbine blade, which is thin and has good thermal efficiency.

As the investment casting product according to the invention, besides the gas turbine blade, there may be exemplified a gas turbine nozzle, a gas turbine combustor, a gas turbine pipe ring, or the like.

Second Embodiment

Since the embodiment has the same configuration as the investment casting core of the first embodiment, description will be made with reference to the drawings. 1 and 2 ) of the first embodiment.

1 is a cross-sectional structure diagram of the investment casting core.

An investment casting core according to the invention is obtained by forming a covering layer of two kinds of silica materials having different particle diameters on a surface of a sintered main casting core body mainly containing silica particles (hereinafter referred to as "core body").

As in the upper part of the cross-sectional view of the functioning as a sintered body core body of 1 is illustrated, a plurality of holes during sintering 18c in a surface 18b a core body 18a educated.

As in the lower part of 1 Illustrated are the holes 18c in the context of the invention by coating the holes formed in the surface 18c with a cover layer 19a locked.

The core body 18a This includes mainly silica particles, such as molten silica (SiO ₂ ) such as quartz sand and quartz powder.

The core body is produced by a known method wherein wax is mixed by mixing silica particles such as quartz flour (for example, 800 mesh (10 to 20 μm)) and quartz sand (for example, 220 mesh (20 to 70 μm)) in a weight ratio 1: 1 mixture is added, heated and kneaded to obtain a composite body in this way.

By injection molding of the obtained composite body, a core compact is obtained.

The core body 18a is subsequently obtained by carrying out a degreasing treatment at, for example, 600 ° C, and a sintering treatment at, for example, 1200 ° C.

The cover layer 19a is in the context of the invention on the surface of the core body obtained as a sintered body 18a educated.

The cover layer 19a includes an alkoxide-silica dust material formed from an alkoxide material and silica dust.

The alkoxide material herein comprises solely silicon alkoxide, or comprises a mixed alkoxide of silicon alkoxide and aluminum alkoxide.

In inorganic silica dust, for example, a spherical material having a particle diameter of 0.15 μm is used.

Here, it is desirable that the silica dust has a particle diameter of 0.05 to 0.5 μm.

The dispersion content of silica dust is adjusted to 5 to 40% by weight, and is approximately 20% by weight.

As the silicon alkoxide, silicon ethoxide or silicon butoxide is used, and ethanol or butanol is used as the solvent.

When two kinds of alkoxides are mixed together, a mixed alkoxide material obtained by mixing silicon alkoxide and aluminum alkoxide is used, for example, using an alcoholic solvent such as butanol as a solvent.

When a mixed alkoxide is produced, one of silicon ethoxide and Aluminum isopropoxide existing mixed alkoxide dissolved in a butanolic solution.

The mixed alkoxide (silicon ethoxide + aluminum isopropoxide) is mixed in a molar ratio of 2: 3 to thereby produce an organic mixed alkoxide.

The sample of the core is dipped in and withdrawn from the silica-dust-containing silicon layer or silicon-aluminum alkoxide layer in the product consisting of the sole alkoxide or mixed alkoxide and silica dust dispersed therein 18b of the core body 18a and a silicon dioxide-containing silicon layer or silicon-aluminum alkoxide component even in the hole 18c to deposit the core surface.

Since the sole alkoxide or the mixed alkoxide dissolves in an alcoholic solution when immersed, the sole alkoxide or the mixed alkoxide penetrate easily into the core body, which is why a good cover layer 19a is trained.

After the drying process, for example, a heat treatment at 1000 ° C is performed. If the surface with the topcoat 19a is provided, the heat treatment may be carried out, for example, at 1000 ° C or less.

Following the drying process has a deposition of the alkoxide and silica dust components even in the hole 18c the surface of the core body 18a occurred. Here, a mixed layer is formed from a silica particle layer having a large particle size and a fine and dense alkoxide layer.

Since an inorganic ceramic material is generated in the alkoxide layer due to the heat treatment at 1000 ° C., voids in the large particle size silica dust layer are filled by means of a dense ceramic layer, and therefore, the adhesion strength between the particles improves.

In the case of a mixed alkoxide, the silicon dioxide dust-containing silicon aluminum alkoxide layer undergoes heat-treatment transformation into inorganic mullite (3Al ₂ O ₃ .2SiO ₂ ) which has a high melting point. Since the voids in the large particle size silica dust layer are filled with a dense mullite layer, it is possible to fill the core 18 to get its core body 18a with the improved adhesion between the particles effecting cover layer 19a is covered.

Since the melting point of mullite is 1900 ° C and is therefore higher than the melting point of silicon dioxide (1600 ° C), this high casting temperatures can be handled.

In this way, since the plurality of holes formed in the surface are closed, it is possible to avoid the problem described in the prior art, according to which the core breaks from the holes as origin points during casting. Accordingly, the high-temperature strength of the investment casting core is improved.

Moreover, since silica dust has a large particle size, even a heat treatment at 1000 ° C. is associated with a low heat shrinkage.

<Test Example 2>

To verify the effect of the invention, a test example will be described below.

In the test example, a composite body was first obtained by adding wax to a mixture prepared by mixing quartz flour (800 mesh) and quartz sand (220 mesh) in a weight ratio of 1: 1, and heating and kneading the mixture. Herein, "MCF-200C" (product name) manufactured by Tatsumori Ltd. was used as quartz flour, "RD-120" (product name) manufactured by Tatsumori Ltd. used as quartz sand, and "Cerita Wax F30-75" (product name ) manufactured by Paramelt Co. Ltd., used as wax.

Injection molding of the obtained composite obtained a compact.

As a test sample, a sample having a width of 30 mm, a length of 200 mm, and a thickness of 5 mm was obtained.

By carrying out a degreasing treatment at 600 ° C and a sintering treatment at 1200 ° C, a sample for a core body was subsequently obtained.

(Cover layer 3)

Subsequently, silicon ethoxide was dissolved in an ethanolic solution. 20% by weight of silica dust (for example having a particle diameter of 0.15 μm, spherical material) was mixed with the silicon ethoxide produced, to obtain in this way a silicon ethoxide slurry in admixture with silica dust.

The sample of the core body was dipped in and pulled out of the mixture of the silicon-ethoxide slurry and the silica dust around the coating layer made of alkoxide and the silica dust contained therein 19a to train on the surface. After the drying process, a heat treatment was performed at 1000 ° C to obtain the overcoat layer from the inorganic silica obtained from silicon ethoxide and the silica dust contained therein 19a on the surface 18b of the core body (sample 3).

(Cover layer 4)

Subsequently, a mixed alkoxide of silicon ethoxide and aluminum isopropoxide was dissolved in a butanolic solution. The mixed alkoxide (silicon ethoxide + aluminum isopropoxide) was mixed in a molar ratio of 2: 3 so as to prepare an organic mixed alkoxide.

20% by weight of silica dust (for example, having a particle diameter of 0.15 μm, spherical material) was mixed with the obtained mixed alkoxide so as to obtain a slurry of the mixed alkoxide in admixture with silica dust.

The sample of the core body was dipped in and pulled out of the mixture composed of the mixed alkoxide and silica dust slurry around the mixed alkoxide coating layer 19a to train on their surface. After the drying process, a heat treatment was performed at 1000 ° C. to remove the overcoat layer from the silica dust-containing mullite containing the mixed alkoxide of silicon ethoxide and aluminum isopropoxide 19a on the surface 18b of the core body (sample 4).

As a comparative example, a core body without a cover layer was prepared as a comparative sample.

The strength of each test sample was measured.

The strength test was conducted on the basis of "Bending strength of ceramic compositions (1981)" in accordance with JIS R 1601.

The strength of the comparative sample without the overcoat layer according to the conventional method was 20 MPa, whereas the strength of the sample 3 with the overcoat layer formed as the silica overcoat layer 3 for the core body according to the method of the invention was 23 MPa. As a result, it was found that the strength in the sample of the core body of the invention was increased by 15%.

Further, the strength of the sample 4 having the silica core cap layer 4 for the core body according to the method of the present invention was 25 MPa. As a result, it was found that the strength in the sample of the core body of the invention was increased by 25%.

According to the sample 4 of the invention, since the high temperature resistance of the core due to the mullite is improved, it is possible to provide a molding tool which does not undergo deformation even if the molding tool is exposed to a high temperature (for example, 1550 ° C.) for a long period of time, For example, when a one-side solidified turbine blade is made.

The casting method using the molding die provided with the investment casting core of the embodiment has the following other than the "alkoxide material" used in the method of the first embodiment as the material of the ceramic slurry 16 is used, the "alkoxide material and silica dust comprising alkoxide-silica dust material" is used, the same configuration, and therefore no description thereof.

LIST OF REFERENCE NUMBERS

12, 22a, 22b

Metal mold

12a

Convex area

14, 26

arrow

16

Ceramic slip

18

core

18a

core body

18b

surface

18c

hole

19

Schlicker

19a

topcoat

20, 70

incinerator

24, 64

gap

28

wax

30

wax model

32

sprue

40

Schlicker

60, 92

autoclave

61

outer mold

61a

fragment

62

melted wax

72

mold

80

molten metal

90, 100

metal casting

94

melted core

101A

primary layer

Claims (7)

An investment casting core obtained by forming an alkoxide-containing alkoxide cover layer on a surface of a sintered core casting containing mainly silica particles. Investment casting core, which is obtained by forming an alkoxide and silica dust containing alkoxide-silica dust cover layer on a surface of a sintered, mainly silicon dioxide particles containing investment casting core body. Investment casting core according to claim 1 or 2, wherein the alkoxide material comprises only silicon alkoxide or a mixed alkoxide of silicon alkoxide and aluminum alkoxide. Precision casting tool used to make a metal casting comprising: the investment casting core according to claim 1 or 2, which has a shape corresponding to a cavity in the interior of the metal casting; and an outer mold which corresponds to the shape of the outer boundary surface of the metal casting. Method for producing a investment casting core, comprising: Immersing a sintered body of a fine casting core body mainly containing silica particles into an alkoxide material; Drying the sintered body; and Heating the sintered body to form a covering layer on the surface of the investment casting core body. Method for producing a investment casting core, comprising: Immersing a sintered body of a fine casting core body mainly containing silica particles in an alkoxide-silica dust material consisting of an alkoxide material and silica dust; Drying the sintered body; and Heating the sintered body to form a covering layer on the surface of the investment casting core body. A method of manufacturing a refining core according to claim 5 or 6, wherein the alkoxide material comprises solely silicon alkoxide or a mixed alkoxide of silicon alkoxide and aluminum alkoxide.

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