DE112013004929T5 - Precision casting mold and process for its production - Google Patents

Abstract

Provided is a precision casting mold, which is to be used for the production of a cast product. The investment casting mold comprises a core having a shape corresponding to an inner hollow portion of the cast product and an outer shape corresponding to a shape of an outer peripheral surface of the cast product, the outer shape being composed of: a primary layer (first dried film) (101A) formed on an inner peripheral surface formed of a slurry film formed by drying slip for the investment casting mold, the monodispersed ultrafine zirconia particles having a particle size of 1.0 μm or smaller (preferably 0.3 to 0 5 μm, as disclosed in the examples); and a multilayer backing layer (105A) formed on the outside of the primary layer (first dried film) (101A) by repeatedly forming a backing layer (second dried film) (104-1) by molding and drying one of the slurry for the investment casting mold formed slip layer (102) and a stucco layer (103) in which a stucco material is applied to the slurry layer is formed.

Description

area

The present invention relates to a precision casting mold and a process for its production.

State of the art

For the production of high precision castings, a precision casting method is used as a casting method for producing a cast product. In the investment casting method disclosed in Patent Literature 1, slip is applied around a lost foam (wax pattern) casting model having the same shape as a molded component and then becomes applied thereto a first stucco layer (flour or dust layer) and subjected to a drying treatment. Subsequently, three operations are repeatedly carried out, namely the application of the slip, the application of the stucco and drying; Thus, a model for covering the outside (outer shape) of the cast product is produced.

The investment casting mold is formed in such a way that the wax model is placed in a slurry, which mainly comprises a silica sol, and the slurry is applied to the surface of the wax model, and the slurry is then dried.

Since the slip applied in a single operation is small and thin, the operation is repeated a few times up to ten times to achieve the desired thickness. In addition, coarse particles called stucco material are interspersed and applied to the surface of the slurry to perform rapid drying, to ensure the thickness rapidly, or to prevent drying cracks. For this reason, a dense layer and a coarse-grained layer are alternately provided in the cross-sectional structure of the mold.

The silica sol, for example, is a solution in which spherical silica particles having a particle size of about 20 nm are dispersed. When the ultrafine silica particles are applied to the surface of relatively fine particles (of several microns to higher microns) and coarse particles (several hundred microns to several millimeters), for example zirconium or alumina contained in the slurry, during drying and are firmly bonded together by the drying and heat treatment, the shape of the mold and also its strength is preserved, so that it can be used as a molding tool.

Citation list patent literature:

• Patent Literature 1: Japanese Patent Application Laid-Open No. 2001-18033 ,

Summary

Technical problem

However, it is generally enough to prepare a molding tool using the above-described silica sol (solution in which ultrafine silica particles are dispersed), but it is necessary to use a molten metal to have a crystal deposition direction, for example, in the production of a unidirectionally solidified blade. to control. It follows that a residence time at high temperature (for example, about 1550 ° C) is prolonged. In this case, there arises a problem that the silica serving as a binder softens because of the high temperature maintained, resulting in deformation of the mold.

In the unidirectionally solidified blade production shown here, the blade is generally produced by placing the mold in a vacuum oven and heating and maintaining it at a temperature higher than or equal to the melting point temperature of the molten metal, whereupon the molten metal flows into the molten metal the mold can be cast, and the mold is taken out of the oven and controlled for being drawn to a lower side, so that the molten metal is cooled and solidified from the lower side.

Accordingly, for example, in the production of the unidirectionally solidified blade, a mold is required which is not deformed even if it is kept at a high temperature (for example, about 1550 ° C.) for a long time.

The present invention has been made in consideration of the above-described problem, and an object thereof is to provide a precision casting mold which does not deform even when kept at a high temperature for a long period of time, such as the production of a unidirectionally consolidated blade, and a method for its production.

the solution of the problem

According to a first aspect of the present invention for solving the above-mentioned problems, there is provided a precision casting mold used for producing a cast product, comprising: a core having a shape corresponding to an inner hollow portion of the cast product; and an outer mold corresponding to a shape of an outer peripheral surface of the cast product, the outer mold being composed of: a primary layer formed on an inner peripheral surface formed of a slurry film prepared by drying slurry for the investment casting mold, which is monodispersed, ultrafine zirconia particles having a particle size of 1.0 μm or smaller is obtained; and a multilayer backing layer provided on the outside of the primary layer by repeatedly forming a backing layer formed by molding and drying a slurry layer formed from the slurry for the investment casting mold and a stucco layer in which a stucco material is coated on the slurry layer is, is formed.

According to a second aspect of the present invention, there is provided the precision casting mold according to the first aspect, wherein the slurry for the investment casting mold contains either zircon powder or alumina powder having an average particle size of 50 μm or smaller, and the stucco material is either zirconia stucco particles or alumina stucco particles having an average particle size of 0.5 mm or larger.

According to a third aspect of the present invention, the investment casting mold according to the first or second aspect is provided, wherein the primary layer comprises the stucco layer in which the stucco material is applied to the slurry layer formed from the slurry for the investment casting mold.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a precision casting mold used to make a cast product, the process comprising: a first film forming process in which a precision investment wax model is incorporated in the investment casting slip, the monodispersed, ultrafine Zirconia particles having a particle size of 1.0 μm or smaller are immersed, dipped and then subjected to a drying treatment, whereby a primary layer formed of a slurry film is formed on a surface of the wax pattern; a second film forming process in which a stucco material is scattered on a surface of the slurry after the wax pattern formed with the primary layer is dipped in and drawn out of the slurry for the investment casting mold, followed by a drying treatment, thereby forming a backing layer becomes; a molded body forming process in which the second film forming process for forming the backing layer is repeated more than once, thereby obtaining a molded article formed with a multilayer backing sheet; a wax removal process in which the wax of the wax model is melted and removed from the resulting molded body; and a mold firing process in which the molded body obtained after the wax removal is subjected to a firing treatment, thereby obtaining a molding die.

According to a fifth aspect of the present invention, there is provided the method of manufacturing the investment casting die according to the fourth aspect, wherein a stucco material is applied to the slurry layer formed from the slurry for the investment casting to form a stucco layer, and the stucco Layer is dried during the first film-forming process.

According to a sixth aspect of the present invention, there is provided a method for manufacturing the investment casting mold according to the fourth or fifth aspect, wherein a dispersant of the slurry for the investment casting mold is polycarboxylic acid salts.

Advantageous Effects of the Invention

According to the present invention, ultrafine zirconia particles having high heat resistance are used as the slurry, thereby providing a possibility of obtaining a molding tool which has higher heat resistance and is not deformed when used over a long period of time as compared with the conventional silica sol at a high temperature (eg, 1550 ° C), for example, in the production of a unidirectionally solidified blade.

Brief description of the drawings

1 FIG. 12 is a schematic diagram of a configuration of a dried molded article which is an outer mold. FIG.

2 Fig. 12 is a schematic representation of a configuration of another dried molded article which is an outer mold.

3 is a diagram illustrating the particle size distribution of fine zirconia particles.

4 is a diagram illustrating the particle size distribution of fine zirconia particles.

5 FIG. 10 is a flowchart illustrating an example of processes in a casting process. FIG.

6 FIG. 10 is a flowchart illustrating an example of processes in a method of manufacturing a molding tool. FIG.

7 Fig. 10 is an explanatory diagram schematically illustrating a process for producing a core.

8th FIG. 15 is a perspective view schematically illustrating a part of a metal mold. FIG.

9 Fig. 10 is an explanatory diagram schematically illustrating a process for producing a wax model.

10 is an explanatory diagram schematically illustrating a configuration in which slurry is applied to the wax model.

11 Fig. 10 is an explanatory diagram schematically illustrating a process for producing the outer mold.

12 Fig. 10 is an explanatory diagram schematically illustrating some processes in the method of manufacturing the molding tool.

13 is an explanatory diagram schematically illustrating some processes in a casting process.

Description of embodiments

Hereinafter, the present invention will be described in detail with reference to the drawings. Incidentally, the present invention is not limited to the following description. Further, in the following description, the components in the description below include those which are readily detectable by those skilled in the art, those which are substantially identical thereto, and those within a scope of so-called equivalents.

1 is a schematic representation of a configuration of a dried molded body of an outer mold. 2 is a schematic representation of a configuration of another dried shaped body of an outer mold.

As in 1 1, an investment casting is an investment casting used to make a cast product and having a core whose shape corresponds to an inner cavity of the cast product and an outer shape corresponding to a shape of an outer peripheral surface of the cast product; wherein the outer shape is composed of: a primary layer (first dried film) 101A formed on an inner peripheral surface formed of a slip film formed by drying slip for the investment casting mold, the monodispersed ultrafine zirconia particles having a particle size of 1.0 μm or smaller (preferably 0.3 to 0 5 μm, as disclosed in the examples); and a multilayer support layer 105A on the outside of the primary layer (first dried film) 101A by repeatedly forming a first support layer (second dried film) 104-1 formed by molding and drying a slip layer formed from the slip for the investment casting mold 102 and a stucco layer 103 in which a stucco material on the slip layer 102 is applied, is formed, is formed.

The zirconia fine particles (ultrafine zirconia particles) of ultrapure ultrafine particles which have been monodispersed using, for example, a ball mill as a dispersing agent are used as a binder which constitutes the slurry in the present invention.

Yttrium-stabilized zirconia (YSZ) can be used as fine zirconia particles.

The term "monodispersion" as used herein means a state of being monodispersed to 0.3 μm due to a dispersion treatment upon formation of the slurry using, for example, zirconia fine particles having a particle size of about 0.5 μm.

The particle size of the zirconia fine particles is 1.0 μm or smaller, and more preferably, it may be in the range of 0.3 to 0.6 μm.

In the present invention, the reason that the zirconia fine particles are preferably 1.0 μm or smaller in size is that the results of a flexural strength test are undesirable when the zirconia fine particles exceed 1.0 μm in size ,

Zirconium powder (for example, having a size of 350 mesh) is added to the binder of the monodispersed zirconia fine particles as a flour or dust, thereby obtaining the slurry for the investment casting mold.

Also, in the present invention, a case where the flour or dust is not added may be acceptable.

Here, polycarboxylic acid salts (for example, ammonium salts) are used to be monodispersed as a dispersant.

In addition, a ball mill using, for example, balls having a diameter of 10 to 20 mm can be listed as an example of a dispersant; however, the dispersant is not limited thereto as long as it is an agent which is monodispersed.

In the present invention, it is important to obtain a good slip by monodispersing the zirconia fine particles serving as a binder.

3 and 4 are diagrams illustrating the particle size distribution of the zirconia fine particles.

It is required that the monodispersion be carried out so that the particle size distribution is narrow, and it is preferable that dispersing as in 3 is performed so that the distribution is set to the range of 0.8 d (0.24) to 1.07 d (0.32) from an average particle size (d: 0.3 μm) when the average particle size is 0.3 μm.

In addition, the dispersing, as in 4 is preferably performed so that the distribution is set in the range of 0.8 d (0.48) to 1.2 d (0.72) starting from an average particle size (d: 0.6 μm), when the average particle size is 0.6 μm.

The particle size distribution was measured herein using the apparatus below.

A laser scattering / diffraction type particle size distribution measuring apparatus "CILAS 850B" was used, manufactured by Aishin Nano Technologies, Co., Ltd.

Next, a method of manufacturing the investment casting mold will be described with reference to FIGS 1 and 2 described.

(First film-making process)

First, in the first film-forming process, a wax model becomes 30 into the slurry for the investment casting mold (hereinafter referred to as "slurry") containing the ultrafine zirconia particles, and then pulled out therefrom, and excess slip is shaken off. Thereafter, by a drying treatment, a slurry film (first dried film) is formed on the surface of the wax model 30 receive.

In 1 the slurry film is the primary layer 101A that match the surface of the wax model 30 comes into contact.

(Second film-making process)

Next is the wax model 30 with the primary layer 101A immersed in the slurry and then pulled out of this, and the excess slip is shaken off, whereby the slip layer (second layer) 102 is formed. Zircon stucco particles (with an average particle size of 0.8 mm) are applied as stucco material to the moist slip layer (second layer) 102 strewn (stuccoed), whereby the stucco layer (first layer) 103 is formed, to which the stucco material adheres. A laminated structure of the slurry layer 102 and the stucco layer (first layer) 103 is dried so that the first backing layer (second dried film) 104-1 on the primary layer (first dried film) 101A is formed.

(Process for Forming the Shaped Body)

The same operation as the second film formation process for forming the first support layer 104-1 is repeated more than once (for example, 6 to 10 times), whereby a dried molded article 106A which is the outer shape having a predetermined thickness of the multilayer support layer 105A in which the slip layer is ((n + 1) th layer) 102 and the stucco layer (nth layer) 103 are laminated alternately.

The dried shaped body is placed, for example, in an autoclave at 150 ° C, so that the wax, which is the wax model 30 forms, is melted and then excreted.

Thereafter, the model is subjected to a heat treatment at 1000 ° C, whereby the investment casting mold is obtained.

The obtained investment mold was not deformed even in a strength test at 1500 ° C, as shown in a test example to be described below, which had high strength. In contrast, in the case of using the conventional silica sol, a softening behavior was confirmed.

In addition, as in 2 illustrated in a primary layer one with the stucco Material afflicted primary stucco layer 101b on a primary slip layer 101 formed and then dried, creating a primary layer 101B is formed.

As in the primary layer 101B If the stucco material is applied, there is also the possibility of a dried molded body 106B an outer shape with the multilayer support layer 105B in which the slip layer and the stucco layer 103 the multilayer support layer 105B have the same number of laminates (n layers).

Although zirconia powder was used as a flour or dust in the present invention, it is possible to use the same investment casting mold even when using alumina powders instead of zircon powders as flour, and alumina stucco particles instead of the zirconia stucco particles as stucco To get material.

In addition, the ratio between the flour or dust and the stucco material is not limited; Rather, both the zirconium powders and the alumina powders may be used as the flour and both the zirconium stucco particles and the alumina stucco particles may be used as the stucco material.

Although the particle size of the flour is 350 mesh, the present invention is not limited thereto but preferably uses particles of, for example, about 5 to 80 μm and particles having an average particle size of, for example, 50 μm or smaller.

Although the particle size of the stucco particles is 0.8 mm, the present invention is not limited thereto, but preferably uses particles of, for example, about 0.4 mm to 2 mm and particles having an average particle size of, for example, 0.5 mm or larger.

Hereinafter, a casting method using the investment casting mold according to the present invention will be described.

5 FIG. 10 is a flowchart illustrating an example of processes in the casting process. FIG. The casting method will be described below with reference to FIG 5 described. In the 5 In this case, illustrated processes can be carried out fully automatically or in such a way that an operator actuates each of the devices for executing the respective processes. In the casting method of the present embodiment, a molding tool is manufactured (step S1). The molding tool may be produced in advance, or may be produced each time a casting process is performed.

The manufacturing method of the molding tool of the present embodiment to be executed in step S1 will be described below with reference to FIGS 6 to 12 described. 6 FIG. 10 is a flowchart illustrating an example of processes in the method of manufacturing the molding tool. FIG. In the 6 In this case, illustrated processes can be carried out fully automatically or in such a way that an operator actuates each of the devices for executing the respective processes.

In the method of manufacturing the molding tool, a core is manufactured (step S12). The shape of the core corresponds to an internal cavity of a cast product to be produced with the mold. This means that the core is placed in a part corresponding to the internal cavity of the cast product and prevents the inflow of a metal, which is a material for the cast product, during the casting process. Hereinafter, a process for producing the core will be described with reference to FIG 7 described. 7 is an explanatory diagram schematically illustrating the process of making the core. In the method of manufacturing the molding tool as shown in FIG 7 is illustrated, is a metal mold 12 manufactured (step S101). The metal mold 12 has a hollow area corresponding to the core. The hollow portion of the core is a convex portion 12a , Furthermore, in 7 the metal mold 12 illustrated in cross section; however, the metal forming tool forms 12 basically, the cavity for covering an entire outer circumference of the core corresponding portion except for an opening through which a material is poured into a space and a hole through which air is discharged. In the process of casting the mold, as indicated by the arrow 14 is hinted about the opening through which the material in the space of the metal mold 12 is poured, ceramic slip 16 into the interior of the metal mold 12 cast. In particular, so-called injection molding becomes a core 18 produced, wherein the ceramic slip 16 into the interior of the metal mold 12 is sprayed. In the method of manufacturing the molding tool, the core becomes 18 after the core 18 inside the metal mold 12 has been made of the metal mold 12 separated, and the severed core 18 gets into a kiln 20 placed and burned. In this way, the core formed of a ceramic material 18 fired and cured (step S102). In the method of casting the mold becomes the core 18 made in the manner described above. Further, the core becomes 18 formed of a material that can be removed by a core removal treatment, such as by a chemical treatment after curing of the cast product.

In the method of manufacturing the molding tool, after the core 18 has been made, an outer metal mold produced (step S14). The outer metal mold has a shape in which an inner peripheral surface thereof corresponds to the outer peripheral surface of the cast product. The metal mold may be formed of a metal or a ceramic material. 8th is a perspective view in which a part of the metal mold is illustrated schematically. A metal mold 22a as it is in 8th is configured such that a concave portion formed on the inner peripheral surface corresponds to the outer peripheral surface of the molded product. Furthermore, in 8th only the metal mold 22a illustrated; however, in analogy to the metal mold 22a in one direction also a metal forming tool 22a corresponding metal mold is made to close the concave portion formed on the inner peripheral surface. The method of manufacturing the mold is such that the inner peripheral surface corresponds to the outer peripheral surface of the cast product when two metal molds are set together.

In the method of manufacturing the mold, after the production of the outer metal mold, a wax model is produced (step S16). The following description will be made with reference to FIG 9 , 9 Fig. 10 is an explanatory diagram schematically illustrating a process for producing the wax model. In the method of manufacturing the molding tool, the core becomes 18 at a predetermined position of the metal mold 22a installed (step S110). After that, cover the metal mold 22a corresponding metal mold 22b a surface on which the concave portion of the metal mold 22a is formed, so that the metal molds 22a and 22b the outer circumference of the core 18 enclose, and between the core 18 and the metal molds 22a and 22b a gap 24 is trained. In the process of making the mold, as indicated by the arrow 26 implied, a wax 28 from one with the gap 24 connected pipe in the interior of the space 24 poured (step S112). The wax 28 For example, a wax is a relatively low melting point material that melts when heated to a predetermined temperature or higher. In the method of manufacturing the mold, the entire area of the gap becomes 24 with the wax 28 filled (step S113). By subsequently solidifying the wax 28 encloses the wax 28 the core 18 , making the wax model 30 is formed. The wax model 30 is a wax model in which one out of the wax 28 formed portion basically has the same shape as the cast product of the manufacturing object. Thereafter, in the process for producing the cast product, the wax model 30 from metal mold tools 22a and 22b separated, and then the wax model is a sprue 32 attached (step S114). The sprue 32 is a mouth into which a molten metal, which is a molten metal during casting, is introduced. In the process of making the mold, the wax becomes 28 formed wax model 30 made in the manner described above so that it has the same shape as the cast product and the core 18 contained therein.

In the method of manufacturing the mold, after the production of the wax model 30 Slip applied (dipped) (step S18). 10 is an explanatory diagram schematically illustrating a configuration in which the slurry is applied to the wax model. In the method of manufacturing the molding tool as shown in FIG 10 is illustrated, the wax model 30 in a storage section 41 dipped, in the slip 40 is stored, and then, after being taken out therefrom, dried (step S19). Thus, the primary layer 101A on the surface of the wax model 30 be formed.

The slip applied in step S18 is a slip directly onto the wax model 30 is applied. For the slip 40 For example, a slurry is used in which the ultrafine zirconia particles are monodispersed. In the slip 40 For example, zirconia with refractory fine particles of about 350 mesh is preferably used as the flour. In addition, polycarboxylic acid salts are preferably used as a dispersant. In addition, it is preferable that a trace of a defoaming agent (a silicon-based substance) or a wettability-improving agent in an amount of, for example, 0.01% of the slurry 40 added. By adding the wettability improving agent, the sticking property of the slurry can be improved 40 in terms of the wax model 30 be improved.

In the method of manufacturing the molding tool as shown in FIG 10 is illustrated with the slip 40 a slip application is performed, and the applied slurry is dried, leaving on the wax model 30 with the primary layer (first dried film) 101A in addition, the slurry is applied (dipped) (step S20). As in 11 is illustrated, the Stucco process of scattering zirconium stucco particles (with an average particle size of 0.8 mm) as stucco material 54 on the surface of the wet slurry (step S21). Thereafter, the stuck on the surface of the slurry layer stucco material is dried, whereby the first support layer (second dried film) 104-1 on the primary layer (first dried film) 101A is formed (step S22).

A process for determining whether the same operation as the first support layer formation process (second dried film) 104-1 is repeated several times (for example, n = six to ten times) is performed (step S23). An nth support layer 104-n is laminated by a predetermined number of times (n) (step S23: yes), whereby the dried molded article 106A which is the outer molding tool associated with the multilayer backing layer 105A is formed with a thickness of, for example, 10 mm.

In the process for producing the molding tool, the dried molded article becomes 106A after the dried shaped body 106A with the from the primary layer 101A and the multilayer support layer 105A was subjected to a heat treatment (step S24). In particular, the wax is removed between the outer mold and the core, and the outer mold and the core are further fired. The following description will be made with reference to FIG 12 , 12 Fig. 10 is an explanatory diagram schematically illustrating some processes of the method of manufacturing the molding tool. In the method of manufacturing the molding tool, as illustrated in step S130, the dried molded article becomes 106A , which is the outer shape with that of the primary layer 101A and the multilayer support layer 105A formed multilayer structure, in an autoclave 60 put and then heated. The interior of the autoclave 60 is filled with pressurized steam, creating the wax model 30 inside the dried shaped body 106A is heated by the pressurized vapor. Thus, this becomes the wax model 30 forming wax melted, and the melted wax 62 is made from the dried shaped body 106A surrounded gap 64 excreted.

In the process of making the mold, when the molten wax 62 from the gap 64 has been discharged, as illustrated in step S131, a mold 72 made in which the gap 64 in a region filled with the wax between the dried shaped body 106A , which is the outer shape, and the core 18 is formed. Thereafter, in the method of manufacturing the molding tool, as illustrated in step S132, the molding tool is used 72 with the between the dried shaped body 106A , which is the outer shape, and the core 18 formed gap 64 by means of a kiln 70 heated. In this way, in the mold 72 a water component, or one in the dried molding 106A , which is the outer mold, removed unnecessary component contained, and is the outer shape by further firing and curing 61 educated. In the process of making the cast product, the mold becomes 72 made in the manner described above.

The casting method will be further described with reference to FIGS 5 and 13 described. 13 is an explanatory diagram schematically illustrating some processes of the casting process. In the casting method, after the molding tool is manufactured in step S1, the molding tool is preheated (step S2). For example, the mold is placed in an oven (vacuum oven, kiln) and heated to 800 ° C or higher and 900 ° C or lower. By the preheating, it is possible to prevent damage to the mold when the molten metal is poured into the mold at the time of manufacturing the cast product.

In the casting method, the molten metal is poured after the mold has been preheated (step S3). As in step S140 of FIG 13 is illustrated, thereby becomes a molten metal 80 Thus, a dissolved raw material (for example steel) of the cast product, over the opening of the mold 72 between the outer shape 61 and the core 18 cast.

In the casting process, the outer shape becomes 61 removed after that into the mold 72 cast, molten metal 80 has solidified (step S4). As in step S141 of FIG 13 is illustrated, the outer shape 61 after the molten metal 80 inside the mold 72 is cured and become a cast product 90 is crushed, and then as a fragment 61a from the cast product 90 away.

After the outer shape 61 from the cast product 90 has been removed, a core removal treatment is performed in the casting process (step S5). As in step S142 of FIG 13 is illustrated, the cast product 90 while in the autoclave 92 put and subjected to the core removal treatment, so that the core 18 inside the cast product 90 dissolves and the dissolved core 94 from the inside of the cast product 90 is excreted. In particular, this becomes an alkaline solution inside the autoclave 92 inlaid cast product 90 repeatedly pressurized and depressurized, leaving the dissolved core 94 from the cast product 90 is excreted.

In the casting process, after performing the core removal treatment, a finishing treatment is performed (step S6). The final treatment is at the surface or inside the cast product 90 carried out. Further, in the casting process, in addition to the final treatment, a check of the cast product is performed. As in step S143 of FIG 13 can thus be a cast product 100 getting produced.

In the casting method of the present embodiment, as described above, the molding tool is manufactured by means of an investment casting process using wax, thereby producing the cast product. In the method of manufacturing the mold, the casting method, and the mold of the present embodiment, the outer mold having the multilayer structure which is the outside of the mold is formed such that the primary layer (first dried film as a first layer) 101A serving as an inner peripheral surface formed by using the zirconia ultrafine particles as a slurry, and the multilayer supporting layer 105A on the outside of the primary layer 101A is formed.

In addition, as described above, the primary layer may be the primary layer 101B which is the slip layer 101 with the added stucco material and the stucco layer 101b includes (see 2 ).

(Example 1)

The method of manufacturing the molding die and the casting method of the present embodiment will be described below by way of examples. In the following examples, a front wax model formed with an outer mold was a member having a width of 30 mm, a thickness of 8 mm and a length of 300 mm, and is composed of a slurry layer and a multilayer support layer of slurry and formed a stucco material primary layer (first dried film) formed in a wax model, whereby a mold is produced.

High purity, ultrafine zirconia particles (having a specific surface area of 10 m ² / g and a particle size of about 0.3 μm) were kneaded with a ball mill for 24 hours using polycarboxylic acid salts as a dispersant, thereby forming a slurry Zirconia slurry was obtained. The solids concentration of the resulting zirconia slurry is 50% by weight.

It was confirmed that the zirconia particles resulting from dispersion treatment in the zirconia slurry were monodispersed to 0.3 μm.

350 mesh zircon powder was added to the zirconia slurry as a flour or dust, thereby forming a slurry for a precision casting mold.

At the same time, a silicon-based substance as a defoaming agent in an amount of 0.01% and a wettability-improving agent in an amount of 0.01% were added to prepare a ready-to-use slurry.

A wax body having a width of 30 mm, a thickness of 8 mm and a length of 300 mm was prepared after the wax body was immersed in and pulled out of the resulting slurry, whereby the ready-to-use slurry was applied to the surface of the wax; excess ready-to-use slip was shaken off, and by a drying treatment, a primary layer (first dried film) of the slurry was obtained on the surface of the wax body.

Next, to obtain a second dried film, the wax body having the primary layer was dipped in the ready-to-use slurry and then pulled out therefrom, and excess ready-to-use slurry was shaken off.

Zircon stucco particles having an average particle size of 0.8 mm were applied to the wet slurry and then dried to form a second dried film (first backing layer).

A similar operation as the second dried film formation process (first backing layer) was repeated six times to obtain a molded article having a multilayer backing layer having a thickness of about 10 mm.

The obtained dried molded article was placed in an autoclave at 150 ° C, so that the wax was melted and then precipitated.

Thereafter, the wax model was subjected to a heat treatment at 1000 ° C, whereby the molding tool of Example 1 was obtained.

(Comparative Example)

For the purpose of comparison, in a similar operation as in the example, a trial production of a mold of a comparative example was conducted by using conventional silica sol slurry (solution in which spherical silica particles having a particle size of about 20 nm were dispersed).

(Test)

A test piece for testing the strength having a size of 10 mm × 50 mm and a thickness of 5 mm was produced from the mold obtained in Example 1 and the mold obtained in Comparative Example, and was subjected to a high-temperature strength test.

In a strength test at 1500 ° C, a softening behavior was observed in the case of using the conventional silica sol.

In addition, as a result, the cutting of the test piece according to the comparative example was not clear but bent.

On the other hand, the test piece broke using the zirconia slip (zircon particle as a stucco material) according to the present example at 100 MPa without deformation.

The strength test was carried out on the basis of "Bending strength of ceramics" (1981) according to JIS R 1601.

From this test result, when a slurry of ultrafine zirconia particles (melting point: 2715 ° C) having high heat resistance as a binder and a stucco material of zirconium particles (melting point: 2715 ° C) is used instead of conventional silica sol, a mold is obtained can be, which has an increased heat resistance and is not deformed even if it is kept at a high temperature (1550 ° C) for a long time in the production of a unidirectional, solidified blade.

(Example 2)

Slip obtained by adding 350 mesh alumina powders as flour instead of the zirconia powders of Example 1 was used as a slip for a precision casting mold.

In addition, with the exception of the use of aluminum oxide stucco particles having an average particle size of 0.8 mm as a stucco material, a mold of Example 2 was obtained by a similar operation as in Example 1.

(Test)

A test piece for testing the strength having a size of 10 mm × 50 mm and a thickness of 5 mm was produced from the mold obtained in Example 2 and the mold obtained in Comparative Example, and was subjected to a similar high-temperature strength test as in Example 1.

The test piece for which the zirconia slurry (alumina particle as a stucco material) according to the present example was used broke at 100 MPa without deformation.

From this test result, when a slurry of ultrafine zirconia particles (melting point: 2715 ° C) having high heat resistance as a binder and alumina particles (melting point: 2070 ° C) is used as a stucco material instead of conventional silica sol, a mold is obtained can, which has an increased heat resistance and is not deformed even if it is kept at a high temperature (1550 ° C) for a long time in the production of a unidirectionally solidified blade.

Thus, if the binder is the slurry obtained by monodispersing the slurry of ultrafine zirconia particles having high heat resistance, and the stucco material is the zirconia powder or the alumina powder, then compared with the use of conventional silica sol, there is the possibility of to obtain a molding tool in which the heat resistance of the obtained molding die is increased and which is not deformed even when it is kept at a high temperature (1550 ° C) for a long time in the production of a unidirectionally solidified blade.

LIST OF REFERENCE NUMBERS

12, 22a, 22b

Metal mold

12a

Convex section

14, 26

arrow

16

Ceramic slip

18

core

20, 70

kiln

24, 64

gap

28

wax

30

wax model

32

sprue

40

Schlicker

60, 92

autoclave

61

external form

61a

fragment

62

Dissolved wax

72

mold

80

Molten metal

90, 100

casting product

94

Dissolved core

101A, 101B

primary layer

102

slip

103

Stucco layer

104-1

First support layer

104-n

nth support layer

105A, 105B

Multilayer support layer

Claims (6)

Investment casting mold used to make a cast product comprising: a core having a shape corresponding to an inner hollow portion of the cast product; and an outer shape corresponding to a shape of an outer circumferential surface of the cast product, wherein the outer mold is composed of: a primary layer formed on an inner peripheral surface formed of a slurry film obtained by drying slurry for the investment casting mold, the monodispersed ultrafine zirconia particles having a particle size of 1.0 μm or less is obtained; and a multilayer backing layer provided on the outside of the primary layer by repeatedly forming a backing layer formed by molding and drying a slurry layer formed from the slurry for the investment casting mold and a stucco layer in which a stucco material is coated on the slurry layer is, is formed. Investment casting mold according to claim 1, wherein the slurry for the investment casting mold either zirconium powder or alumina powder having an average particle size of 50 microns or smaller, and wherein the stucco material either zirconium stucco particles or alumina stucco particles having an average particle size of 0.5 mm or larger. Investment casting mold according to claim 1 or 2, wherein the primary layer has a stucco layer in which the stucco material is applied to the slip layer formed from the slurry for the investment casting mold. A method of making a precision casting mold used to make a cast product, the method comprising: a first film-forming process in which a precision investment wax model is immersed in and drawn out of slurry for the investment casting mold containing monodispersed zirconia ultrafine particles having a particle size of 1.0 μm or smaller and then subjected to a drying treatment, thereby forming a primary layer formed of a slurry film on a surface of the wax model; a second film forming process in which a stucco material is scattered on a surface of the slurry after the wax pattern formed with the primary layer is dipped in and drawn out of the slurry for the investment casting mold, and then a drying treatment is performed, thereby forming a backing layer becomes; a molded body forming process in which the second film forming process for forming the backing layer is repeated more than once, thereby obtaining a molded article formed with a multilayer backing sheet; a wax removal process in which the wax of the wax model is melted and removed from the resulting molded body; and a mold firing process in which the molded body obtained after the wax removal is subjected to a firing treatment, thereby obtaining a molding die. A method of manufacturing the investment casting mold according to claim 4, wherein a stucco material is applied to a slurry layer formed from the slurry for the investment casting mold to form a stucco layer, and the stucco layer is dried during the first film forming process. A method for producing the investment casting mold according to claim 4 or 5, wherein a dispersant of the slurry for the investment casting mold are polycarboxylic acid salts.

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