JP6199018B2 - Precision casting mold manufacturing method - Google Patents

Description

The present invention relates to a cast-type production method for precision casting.

  As a casting method for producing a casting, there is a precision casting method used when producing a casting with high accuracy. As described in Patent Document 1, in the precision casting method, slurry is applied around a vanishing model (wax mold) having the same shape as the molded part, and then the first layer stucco (flower) is adhered and dried. Let Thereafter, the three steps of slurry application, stucco attachment, and drying are repeated to produce a mold (outer mold) that covers the outside of the casting.

Here, in the precision casting mold, a wax mold is attached to a slurry mainly composed of silica sol, and the slurry is attached to the surface of the wax mold and dried.
Since only a small amount of slurry can be deposited in one operation and only a thin slurry can be formed, the thickness is increased by repeating several times to several times. Also, coarse particles called stucco material are sprinkled on and adhered to the surface of the slurry in order to speed up drying or to ensure a quick wall thickness in order to prevent dry cracking. Therefore, the mold cross-sectional structure is a dense layer and a layer of coarse particles.
For example, silica sol is a liquid in which spherical silica particles having a particle diameter of about 20 nm are dispersed. The silica ultrafine particles adhere to the surface of relatively fine particles (several microns to several tens of microns) and coarse particles (stucco) (several hundred microns to several mm) such as zircon and alumina contained in the slurry during the drying process. By firmly bonding by drying and heat treatment, the shape of the mold is maintained, and at the same time, the strength is maintained and the mold can be used as a mold.

JP 2001-18033 A

  By the way, in general, a mold using the above-mentioned silica sol (a liquid in which ultrafine particles of silica are dispersed) is sufficient. For example, in manufacturing a unidirectional solidified blade, a molten metal is used to control the crystal precipitation direction. Hold. As a result, the holding time at a high temperature (for example, about 1550 ° C.) becomes longer. In this case, since it is held at a high temperature, there is a problem that silica as a binder is softened and the mold is deformed.

  Here, in the production of unidirectional solidified blades, the mold is placed in a heater in a vacuum, heated and held at a temperature above the melting point of the molten metal, the molten metal is injected into the mold, and the mold is moved downward from the heater. Generally, the molten metal is manufactured by cooling and solidifying from one direction below by pulling out while controlling the pulling down.

  Therefore, for example, in the production of unidirectionally solidified blades, the appearance of a mold that is prevented from being deformed even when held at a high temperature (for example, about 1550 ° C.) for a long time is eagerly desired.

The present invention was made in view of the above, and an object thereof is to provide a method of manufacturing a mold casting for precision casting which does not cause deformation even when held at a high temperature for a long time.

A first invention of the present invention for solving the above-mentioned problems is a method for producing a precision casting mold used for producing a casting, wherein a precision casting wax mold is formed with a grain size of 0.3 to 1.0 μm. It is composed of ultrafine alumina particles and silica sol, which are uniformly dispersed in a range of diameters, immersed in a precision casting mold slurry that becomes mullite at the time of firing, pulled up, dried, and then brazed. A first film forming step of forming a prime layer made of a slurry film on the surface, and a wax mold on which the prime layer is formed are immersed in the precision casting mold slurry and pulled up, and then a stucco material is sprinkled on the slurry surface, Then, a second film forming step for drying to form a backup layer and a step for forming a backup layer in the second film forming step are repeated a plurality of times, and a molded body forming step for obtaining a molded body having a multilayer backup layer formed thereon. Get A precision casting mold comprising: a dewaxing step for melting and removing wax-shaped wax from the molded product, and a mold firing step for firing the dewaxed molded product to obtain a mold. In the manufacturing method.

According to a second invention, in the first invention, a stucco layer is formed by attaching a stucco material to the slurry layer made of the precision casting mold slurry in the first film forming step, and then drying. It is in the manufacturing method of the mold for precision casting characterized by the above.

A third invention is the method for producing a precision casting mold according to the first or second invention, wherein the dispersant for the precision casting mold slurry is a polycarboxylic acid salt.

  According to the present invention, the heat-resistant temperature is improved with respect to the conventional use of silica sol by using alumina fine particles that become mullite having high heat resistance and silica sol, thereby increasing the heat-resistant temperature, for example, in the production of unidirectional solidified blades. Even when held for a long time at (° C.), there is an effect that a mold that does not deform is obtained.

FIG. 1 is a configuration diagram of a dry molded body serving as an outer mold. FIG. 2 is a configuration diagram of another dry molded body serving as an outer mold. FIG. 3 is a flowchart showing an example of the process of the casting method. FIG. 4 is a flowchart showing an example of steps of the mold manufacturing method. FIG. 5 is an explanatory view schematically showing a core manufacturing process. FIG. 6 is a perspective view schematically showing a part of the mold. FIG. 7 is an explanatory view schematically showing a wax mold manufacturing process. FIG. 8 is an explanatory diagram schematically showing a configuration in which slurry is applied to a wax mold. FIG. 9 is an explanatory view schematically showing a manufacturing process of the outer mold. FIG. 10 is an explanatory view schematically showing a part of the mold manufacturing method. FIG. 11 is an explanatory view schematically showing a part of the casting method.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description. In addition, constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range.

FIG. 1 is a configuration diagram of a dry molded body serving as an outer mold. FIG. 2 is a configuration diagram of another dry molded body serving as an outer mold.
As shown in FIG. 1, the precision casting mold is a precision casting mold used for manufacturing a casting, and corresponds to the shape of the core corresponding to the hollow portion inside the casting and the shape of the outer peripheral surface of the casting. An outer mold, and the outer mold is formed on the inner peripheral surface, and has a particle size of 1.0 μm or less (preferably 0.3 to 0.5 μm: described in the examples). A prime layer (first dry film) 101A made of a slurry film made of a precision casting mold slurry that is made of ultrafine alumina particles and silica sol, and becomes a mullite during firing, and the prime layer (first dry film). A first backup layer (second film) formed by drying a slurry layer 102 made of the precision casting mold slurry and a stucco layer 103 having a stucco material adhered to the slurry layer and dried. Dry film) The multi-layer backup layer 105 </ b> A is formed by forming 104-1 multiple times.

Here, the high-purity ultrafine alumina particles (alumina ultrafine particles), which are the binder for forming the slurry in the present invention, are monodispersed using, for example, a ball mill as a dispersing means.
Here, monodispersed means that, for example, when a slurry is formed using alumina fine particles having a particle size of about 0.5 μm, the result of the dispersion treatment is also monodispersed to 0.5 μm. State.
Here, the particle diameter of the alumina fine particles is 1.0 μm or less, more preferably in the range of 0.3 to 0.6 μm.

  In the present invention, the reason why the alumina fine particles are preferably 1.0 μm or less is that if it exceeds 1.0 μm, the result of the bending test strength is not preferable.

  Here, as a dispersing agent for monodispersing, for example, polycarboxylic acid salt (for example, ammonium salt) is used for dispersion.

  Moreover, as a dispersion | distribution means, although the ball mill using a 10-20 mm diameter ball can be illustrated, for example, if it is a means to carry out single dispersion | distribution, it will not be limited to this.

  In the present invention, it is important to obtain a good slurry in which alumina fine particles as a binder are monodispersed.

  In the present invention, it is important that mullite is uniformly formed when fired. Therefore, it is preferable that the blending ratio of alumina fine particles monodispersed in 0.5 μm, for example, is large.

Here, the alumina particle diameter is 1.0 μm or less, preferably 0.3 to 0.6 μm.
These blending ratios are preferably in the following ranges.
Al ₂ O ₃ / SiO ₂ = 1.5 (molar ratio)

  The silica sol is a uniform dispersion of 0.02 μm silica and is uniformly dispersed in the alumina slurry.

  In the present invention, the alumina fine particles having a predetermined particle diameter are made into a uniform dispersion, so that the reactivity with the silica sol in the baking process is good, and mullite can be formed at a lower temperature (for example, 1,000 ° C.). It becomes.

  If the alumina fine particles are used alone to form a casting slurry for precision casting, the price of the alumina fine particles is high, resulting in an increase in production cost. Therefore, as in the present invention, the production cost can be reduced by adding silica sol to the alumina fine particles to form mullite at the time of firing.

Zircon powder (for example, 350 mesh) is added as flour to the mixed slurry obtained by adding silica sol to the single dispersed alumina fine particle slurry to obtain a precision casting mold slurry.
In the present invention, it is acceptable to add no flour.

Next, a method for manufacturing a precision casting mold will be described with reference to FIGS.
(First film formation step)
First, in the first film forming step, a precision casting mold slurry (hereinafter referred to as “slurry”) composed of ultra-fine alumina particles having a particle size of 1.0 μm or less and silica sol, which becomes mullite during firing. ), The wax mold 30 is dipped, pulled up, and excess slurry is dropped. Thereafter, a slurry film (first dry film) is obtained on the surface of the wax mold 30 by drying.
This slurry film becomes a prime layer 101A in contact with the surface of the wax mold 30 in FIG.

(Second film formation step)
Next, after the wax mold 30 having the prime layer 101A is immersed in the slurry, it is pulled up and the excess slurry is dropped to form the slurry layer (second layer) 102. The wet slurry layer (second layer) 102 is sprinkled (stuccoed) with zircon stucco grains (average particle size 0.8 mm) as a stucco material, and the stucco layer (first layer) is attached. ) 103 is formed. The laminate of the slurry layer 102 and the stucco layer (first layer) 103 is dried to form the first backup layer (second dry film) 104-1 on the prime layer (first dry film) 101. .

(Molded body forming process)
The same operation as the second film forming step of the first backup layer 104-1 is repeated a plurality of times (for example, 6 to 10 times), and the slurry layer (n + 1 layer) 102 and the stucco layer (n layer) 103 are alternately arranged. A dry molded body 106A serving as an outer mold having a multilayer backup layer 105A having a predetermined thickness laminated on the substrate is obtained.

This dried molded body is put into an autoclave at 150 ° C., for example, and the wax constituting the wax mold 30 is melted and discharged.
Thereafter, this mold is heat-treated at 1,000 ° C. to obtain a precision casting mold in which the slurry constitutes mullite.

  The precision casting mold thus obtained was high in strength without deformation in a 1500 ° C. strength test, as shown in test examples described later. On the other hand, the softening behavior was confirmed using the conventional silica sol.

Further, as shown in FIG. 2, in the prime layer 101, a stucco material may be attached to the prime slurry layer 101a to form the prime stucco layer 101b, and then dried to form the prime layer 101B.
When a stucco material is attached as in the prime layer 101B, the number of times that the slurry layer of the multilayer backup layer 105B is stacked and the number of times that the stucco layer 103 is stacked are the same number (n layers). A dry molded body 106B serving as an outer mold having the layer backup layer 105B is obtained.

In the present invention, zircon powder was used as the flour, but in addition to zircon powder, alumina powder was used, and even if alumina stucco particles were used instead of zircon stucco particles, the same precision casting mold was obtained. Can do.
The relationship between the flour and the stucco material is not limited, and either zircon powder or alumina powder is used as the flour, and either zircon stucco particle or alumina stucco particle is used as the stucco material. Just do it.

  The particle size of the flour is 350 mesh, but the present invention is not limited to this. For example, it is preferable to use particles having a particle size of about 5 to 80 μm and an average particle size of, for example, 50 μm or less.

  The diameter of the stucco grains is 0.8 mm, but the present invention is not limited to this. For example, particles having a diameter of about 0.4 mm to 2 mm and an average diameter of 0.5 mm or more are used. Is preferred.

  Hereinafter, a casting method using the precision casting mold of the present invention will be described.

  FIG. 3 is a flowchart showing an example of the process of the casting method. Hereinafter, the casting method will be described with reference to FIG. Here, the processing shown in FIG. 3 may be executed fully automatically, or may be executed by an operator operating an apparatus that executes each process. The casting method of this embodiment produces a casting mold (step S1). The mold may be produced in advance or may be produced each time casting is performed.

  Hereinafter, the mold manufacturing method of the present embodiment executed in the step S1 will be described with reference to FIGS. FIG. 4 is a flowchart showing an example of steps of the mold manufacturing method. Here, the processing shown in FIG. 4 may be executed fully automatically, or may be executed by an operator operating an apparatus that executes each process.

  The mold manufacturing method produces a core (core) (step S12). A core is a shape corresponding to the cavity inside the casting produced with a casting_mold | template. That is, the core is arranged in a portion corresponding to the cavity inside the casting, thereby suppressing the metal that becomes the casting from flowing in at the time of casting. Hereafter, the manufacturing process of a core is demonstrated using FIG. FIG. 5 is an explanatory view schematically showing a core manufacturing process. In the mold manufacturing method, a mold 12 is prepared as shown in FIG. 5 (step S101). The mold 12 has a hollow area corresponding to the core. The portion that becomes the cavity of the core becomes the convex portion 12a. In FIG. 5, the cross section of the mold 12 is shown, but the mold 12 basically covers the entire circumference of the region corresponding to the core except for an opening for injecting material into the space and a hole for extracting air. It is hollow. In the mold casting method, the ceramic slurry 16 is injected into the mold 12 through an opening for injecting material into the space of the mold 12 as indicated by an arrow 14. Specifically, the core 18 is produced by so-called injection molding in which the ceramic slurry 16 is injected into the mold 12. In the mold manufacturing method, when the core 18 is produced inside the mold 12, the core 18 is removed from the mold 12, and the removed core 18 is placed in the firing furnace 20 and fired. Thereby, the core 18 made of ceramic is baked and hardened (step S102). In the mold casting method, the core 18 is produced as described above. The core 18 is formed of a material that can be removed by a decore process such as a chemical process after the casting is solidified.

  In the mold manufacturing method, after the core 18 is manufactured, an external mold is manufactured (step S14). The outer mold has a shape in which the inner peripheral surface corresponds to the outer peripheral surface of the casting. The mold may be made of metal or ceramic. FIG. 6 is a perspective view schematically showing a part of the mold. In the mold 22a shown in FIG. 6, the recess formed on the inner peripheral surface corresponds to the outer peripheral surface of the casting. In FIG. 6, only the mold 22 a is shown, but a mold corresponding to the mold 22 a and corresponding to the mold 22 a is also produced so as to close the concave portion formed on the inner peripheral surface. In the mold manufacturing method, two molds are combined to form a mold whose inner peripheral surface corresponds to the outer peripheral surface of the casting.

  After producing the external mold, the mold manufacturing method produces a wax mold (wax mold) (step S16). Hereinafter, a description will be given with reference to FIG. FIG. 7 is an explanatory view schematically showing a wax mold manufacturing process. In the mold manufacturing method, the core 18 is installed at a predetermined position of the mold 22a (step S110). Thereafter, a mold 22b corresponding to the mold 22a is placed on the surface of the mold 22a where the recess is formed, the core 18 is surrounded by the molds 22a and 22b, and the core 18 and the molds 22a and 22b are separated. A space 24 is formed therebetween. The mold manufacturing method starts injection of WAX 28 from the pipe connected to the space 24 toward the inside of the space 24 as indicated by an arrow 26 (step S112). WAX 28 is a substance having a relatively low melting point, such as wax, which melts when heated above a predetermined temperature. In the mold manufacturing method, the entire space 24 is filled with the WAX 28 (step S113). Thereafter, the wax 28 is solidified to form the wax mold 30 in which the WAX 28 surrounds the core 18. The wax mold 30 basically has the same shape as the casting for which the part formed by the WAX 28 is manufactured. Thereafter, in the casting manufacturing method, the wax mold 30 is separated from the molds 22a and 22b, and the gate 32 is attached (step S114). The gate 32 is a port into which molten metal, which is a metal melted during casting, is charged. As described above, the mold manufacturing method produces the wax mold 30 including the core 18 inside and formed of the WAX 28 having the same shape as the casting.

In the mold manufacturing method, when the wax mold 30 is produced, slurry application (dipping) is performed (step S18). FIG. 8 is an explanatory diagram schematically showing a configuration in which slurry is applied to a wax mold. In the mold manufacturing method, as shown in FIG. 8, the wax mold 30 is immersed in the storage portion 41 in which the slurry 40 is stored, and is taken out and then dried (step S19). Thereby, the prime layer 101 </ b> A can be formed on the surface of the wax mold 30.
Here, the slurry applied in step S <b> 18 is a slurry applied directly to the wax mold 30. The slurry 40 is composed of ultrafine alumina particles and silica sol, and uses a casting slurry for precision casting that becomes mullite during firing. In the slurry 40, it is preferable to use refractory fine particles of about 350 mesh, such as zirconia, as flour. Further, it is preferable to use a polycarboxylic acid salts as a dispersant. Further, it is preferable to add a small amount, for example, 0.01%, of an antifoaming agent (silicon-based substance) or a wettability improving agent to the slurry 40. By adding the wettability improving agent, the adhesion of the slurry 40 to the wax mold 30 can be improved.

As shown in FIG. 9, in the mold manufacturing method, slurry application is performed with the slurry 40, and the solder mold having the prime layers (first dry films) 101A and 101B is further dried (dipping) (step dipping). S20). Stuccoing is performed by sprinkling zircon stucco grains (average particle diameter 0.8 mm) as the stucco material 54 on the surface of the wet slurry (step S21). Thereafter, the surface of the slurry layer with the stucco material attached is dried, and the first backup layer (second dry film) 104-1 is formed on the prime layers (first dry film) 101A, 101B (step S22). ).
The first backup layer of this (second dry film) 104-1 the same operation a plurality of times and forming process (e.g., n: 6 to 10 times) is performed repeatedly (step S23). A predetermined number (n) of the n-th backup layers 104-n are stacked (step S23: Yes) to obtain a dry molded body 106A which is an outer mold having a thickness of, for example, 10 mm on which the multilayer backup layer 105A is formed.

In the mold manufacturing method, after obtaining the dry molded body 106A on which a plurality of layers of the prime layer 101A and the multilayer backup layer 105A are obtained, the dry molded body 106A is subjected to heat treatment (step S24). Specifically, WAX between the outer mold and the core is removed, and the outer mold and the core are further fired. Hereinafter, a description will be given with reference to FIG. FIG. 10 is an explanatory view schematically showing a part of the mold manufacturing method. In the mold manufacturing method, as shown in step S130, a dry molded body 106 serving as an outer mold in which a plurality of layers of a prime layer 101A and a multilayer backup layer 105A is formed is placed in the autoclave 60 and heated. The autoclave 60 heats the wax mold 30 in the dry molded body 106 by filling the interior with pressurized steam. As a result, the wax forming the wax mold 30 is melted and the molten wax 62 is discharged from the space 64 surrounded by the dry molded body 106.
In the mold manufacturing method, the melted WAX 62 is discharged from the space 64, so that, as shown in step S131, the space 64 is filled in the region filled with WAX between the dry molded body 106 serving as the outer mold and the core 18. A mold 72 in which is formed is produced. Thereafter, in the mold manufacturing method, as shown in step S132, the mold 72 in which the space 64 is formed between the dry molded body 106 serving as the outer mold and the core 18 is heated in the firing furnace 70. As a result, the mold 72 is cured by firing by removing water components and unnecessary components contained in the dry molded body 106 serving as the outer mold, and the outer mold 61 is formed. In the casting manufacturing method, the mold 72 is produced as described above.

  The description of the casting method will be continued with reference to FIGS. FIG. 11 is an explanatory view schematically showing a part of the casting method. In the casting method, when the mold is produced in step S1, the mold is preheated (step S2). For example, the mold is placed in a furnace (vacuum furnace, firing furnace) and heated to 800 ° C. or higher and 900 ° C. or lower. By performing preheating, it is possible to prevent the mold from being damaged when molten metal (melted metal) is injected into the mold at the time of casting production.

  In the casting method, when the mold is preheated, pouring is performed (step S3). That is, as shown in step S <b> 140 of FIG. 11, a molten metal 80, that is, a molten casting material (for example, steel) is injected between the outer mold 61 and the core 18 from the opening of the mold 72.

  In the casting method, after the molten metal 80 poured into the mold 72 is solidified, the outer mold 61 is removed (step S4). That is, as shown in step S141 in FIG. 11, when the molten metal hardens into the casting 90 inside the mold 72, the outer mold 61 is crushed and removed from the casting 90 as a broken piece 61a.

  In the casting method, when the outer mold 61 is removed from the casting 90, a core removal process is performed (step S5). That is, as shown in step S142 of FIG. 11, the casting 90 is put into the autoclave 92 and the core removal process is performed by melting the core 18 inside the casting 90, and the molten core 94 is dissolved in the casting 90. Drain from inside. Specifically, the casting 90 is put into an alkaline solution inside the autoclave 92, and the melting core 94 is discharged from the casting 90 by repeating pressurization and decompression.

  In the casting method, after the core removal process is performed, a finishing process is performed (step S6). That is, a finishing process is performed on the surface and inside of the casting 90. In the casting method, the casting is inspected together with the finishing process. Thereby, as shown to step S143 of FIG. 11, the casting 100 can be manufactured.

As described above, the casting method of the present embodiment produces a casting by using a lost wax casting method using WAX (wax) to produce a casting. Here, the mold manufacturing method, the casting method, and the mold according to the present embodiment include an outer mold, which is an outer portion of the mold, and a prime layer (first layer that is the first layer) that becomes an inner peripheral surface using zirconia ultrafine particles as a slurry. (Dry film) 101A is formed, and a plurality of backup layers 105A are formed outside the prime layer 101A to form a multilayer structure.
As described above, the prime layer 101B including the slurry layer 101a to which the stucco material is added and the stucco layer 101b may be used as the prime layer (see FIG. 2).

Example 1
Hereinafter, the mold manufacturing method and the casting method of the present embodiment will be described using examples. In the following examples, the wax mold before the outer mold is formed is a member having a width of 30 mm, a thickness of 8 mm, and a length of 300 mm, and this wax mold has a prime layer (first dry film) made of a slurry layer, A mold was prepared by forming a multilayer backup layer of slurry and stucco material.

A slurry of high-purity ultrafine alumina (Al ₂ O ₃ , specific surface area of 10 m ² / g, particle size of about 0.5 μm) is kneaded for 24 hours using a ball mill using ammonium polycarboxylate as a dispersant. Turned into. The solid content concentration of the obtained alumina slurry is 30 wt%.
In the alumina slurry, as a result of the dispersion treatment, it was confirmed that the alumina particles were monodispersed to 0.5 μm.
Further, silica sol (SiO ₂ , particle size 0.02 μm, solid content concentration 30%) was prepared.
At the time of firing, alumina slurry: silica sol = 306: 120 (the molecular weight of 3Al ₂ O ₃ is 3 × 102 = 306, the molecular weight of 2SiO ₂ is 2 × so as to have a composition of mullite (3Al ₂ O ₃ .2SiO ₂ ). 60 = 120) The slurry was blended in advance.
At this time, no precipitation was observed even when mixed.
To this blended slurry, 350 mesh zircon powder was added as flour to obtain a precision casting mold slurry.
At the same time, 0.01% silicon-based antifoaming agent and 0.01% wettability improving agent were added to prepare slurry for use.

  Prepare a wax body with a width of 30 mm, a thickness of 8 mm, and a length of 300 mm, immerse the wax body in the resulting slurry, pull it up and attach the used slurry to the wax surface, then drop the excess used slurry and dry it Thus, a slurry prime layer (first dry film) was obtained on the surface of the wax body.

Next, in order to obtain a second dry film, a wax body having a prime layer was immersed in the slurry, and then the excess used slurry was dropped.
Zircon stucco grains having an average grain size of 0.8 mm were adhered to the wet slurry and then dried to form a second dry film (first backup layer).

An operation equivalent to the formation of the second dry film (first backup layer) was repeated 6 times to obtain a molded body having a thickness of about 10 mm having a multilayer backup layer.
The obtained dried molded body was put in an autoclave at 150 ° C. to melt and discharge the wax.
Next, this mold was heat-treated at 1000 ° C. to obtain a mold of Example 1.

[Comparative example]
For comparison, a slurry using a conventional silica sol (a liquid in which spherical silica particles having a particle diameter of about 20 nm are dispersed) was used, and the same procedure as in the example was performed, and a template of a comparative example was also prototyped.

[test]
A strength test piece of 10 mm × 50 mm and a thickness of 5 mm was processed from the obtained mold of Example 1 and the comparative mold, and a high-temperature strength test was performed.
In the strength test at 1500 ° C., the softening behavior was confirmed using the conventional silica sol.
As a result, the test piece of the comparative example was not clearly cut and bent.
On the other hand, the test piece using the slurry (zircon grains as the stucco material) blended as mullite (3Al ₂ O ₃ .2SiO ₂ ) of the present example was not deformed and fractured at 100 MPa.
Here, the strength test was performed according to “Bending strength of ceramics (1981)” according to JIS R 1601.

  From this test result, the conventional silica sol is used by making the binder into a slurry that becomes mullite (melting point: 1,885 ° C.) with high heat resistance during firing and stucco material as zircon grains (melting point: 2,715 ° C.). As a result, the heat resistant temperature was improved, and a mold that did not deform even when kept at a high temperature (1550 ° C.) for a long time in the production of a unidirectionally solidified blade could be obtained.

(Example 2)
In Example 1, 350 mesh alumina powder was added as flour instead of zircon powder to obtain a precision casting mold slurry.
Further, a mold of Example 2 was obtained in the same manner as in Example 1 except that alumina stucco particles having an average particle diameter of 0.8 mm were used as the stucco material.

[test]
A strength test piece of 10 mm × 50 mm and a thickness of 5 mm was processed from the obtained mold of Example 2 and the mold of Comparative Example, and the same high-temperature strength test as in Example 1 was performed.
The test piece using the slurry (alumina particles as the stucco material) serving as the mullite of this example was not deformed and was broken at 100 MPa.

  From this test result, the conventional silica sol is used by making the binder into a slurry that becomes mullite (melting point 1,885 ° C.) with high heat resistance during firing and the stucco material as alumina particles (melting point 2,070 ° C.). As a result, the heat resistant temperature was improved, and a mold that did not deform even when kept at a high temperature (1550 ° C.) for a long time in the production of a unidirectionally solidified blade could be obtained.

  From the above, the binder is made of ultra-fine alumina particles with a particle size of 1.0 μm or less and silica sol, and the mold slurry for precision casting that becomes mullite with high heat resistance at the time of firing is used as the slurry. Or by using a stucco material of alumina powder, the heat resistance temperature of the obtained mold is improved compared to the case of using conventional silica sol, and the mold is kept at a high temperature (1,550 ° C.) for a long time in the production of a unidirectional solidified blade. In some cases, a mold that does not deform was obtained.

12, 22a, 22b Mold 12a Convex 14, 26 Arrow 16 Ceramic slurry 18 Core (core)
20, 70 Firing furnace 24, 64 Space 28 WAX
30 Wax mold 32 Gate 40 Slurry 60, 92 Autoclave 61 Outer mold 61a Debris 62 Molten WAX
72 Mold 80 Melt 90, 100 Casting 94 Melting core 101A, 101B Prime layer 102 Slurry layer 103 Stucco layer 104-1 First backup layer 104-n nth backup layer 105A, 105B Multi-layer backup layer

Claims (3)

A method for manufacturing a precision casting mold used for manufacturing a casting,
For precision casting, which consists of ultrafine particles of alumina and silica sol, which is a uniform dispersion obtained by mono-dispersing a precision casting wax mold in the particle size range of 0.3-1.0 μm. A first film forming step of immersing in a mold slurry, lifting and drying to form a prime layer made of a slurry film on the surface of the wax mold;
A second film forming step in which the wax mold in which the prime layer is formed is dipped in the precision casting mold slurry, pulled up, sprinkled with a stucco material on the slurry surface, and then dried to form a backup layer;
The step of forming the backup layer of the second film formation step is repeated a plurality of times, and a molded body forming step for obtaining a molded body in which the multilayer backup layer is formed,
A dewaxing step of melting and removing wax-type wax from the obtained molded body,
And a mold firing step of firing the dewaxed molded body to obtain a mold, and a method for producing a precision casting mold. In claim 1,
A method for producing a precision casting mold, wherein a stucco layer is formed by adhering a stucco material to a slurry layer made of the precision casting mold slurry during the first film forming step, followed by drying. In claim 1 or 2,
A precision casting mold manufacturing method, wherein the precision casting mold slurry dispersant is a polycarboxylate.

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