KR20080046169A - Mold, method for manufacture of the mold, and molded article using the mold - Google Patents

Abstract

Disclosed is a mold which hardly reacts with a molten alloy and is inexpensive. Also disclosed is a method for manufacture of the mold. Further disclosed is a molded article manufactured using the mold. A mold (40) for use in the manufacture of a molded article (60) composed of a titanium-aluminum alloy or a titanium alloy comprises a mold body (41). In the mold body (40), at least a first layer (44a) on the surface (43) of the cavity of the mold body (41) is made of a burned product of a slurry which comprises an aggregate composed mainly of cerous oxide and a binder composed mainly of silica sol.

Description

Mold, Method for Manufacture of Mold, and Molded Article Using the Mold

Field of technology

TECHNICAL FIELD This invention relates to the casting mold used for manufacture of a casting made from a titanium aluminum alloy or a titanium alloy, its manufacturing method, and the casting using the casting mold.

Background

Titanium aluminum alloy composed of titanium aluminide (TiAl), which is an intermetallic compound of Ti and Al, has characteristics such as light weight and high strength. Therefore, titanium aluminum alloys are considered to be promising in turbochargers of automobile engines, rotating members of gas turbine engines or jet engines for aircrafts.

In addition, titanium alloys are widely used in automobiles, motorcycles, sports and leisure products, artificial bones, artificial teeth, etc. because of their good corrosion resistance, light weight, and biocompatibility.

In order to apply a titanium aluminum alloy or a titanium alloy to these members, especially a commercial item, it is required to be a cast product because of cost problems. Molding is required to produce castings, and various molds have been proposed (see, for example, Patent Documents 1-4).

Patent Document 1: Japanese Patent Application Laid-Open No. 5-123820

Patent Document 2: Japanese Unexamined Patent Publication No. 2003-225738

Patent document 3: Unexamined-Japanese-Patent No. 5-277624

Patent document 4: Unexamined-Japanese-Patent No. 6-292940

Disclosure of the Invention

Problems to be Solved by the Invention

However, since titanium alloys have high activity, a needle-like altered layer (oxygen enriched layer, surface hardened layer) called α case may be formed in the surface layer portion of the obtained cast product. Such an α case is higher in hardness than the α phase in the parent phase and is a difficult material. Therefore, if the layer thickness of the α case is too thick, it takes a long time for chemical milling, mechanical cutting, etc., and there is a problem of causing an increase in product cost and a decrease in productivity.

In addition, the molds described in Patent Documents 1 to 4 described above are for titanium alloys, and these molds have often been useful as molds for titanium aluminum alloys.

Since the titanium aluminum alloy and the titanium alloy have high activity, it is necessary to consider the reaction between the molten alloy and the mold. In particular, since titanium aluminum alloy has a higher reactivity with a mold than titanium alloy, it becomes important to suppress reaction. This is due to the fact that Ti and Al are both active metals, but Al is more active than Ti, and in general the titanium aluminum alloy has a higher melting point than the titanium alloy.

Therefore, in the mold for titanium aluminum alloy and the titanium alloy, selection of the constituent material becomes an important factor. The mold is composed of a ceramic, and is mainly composed of aggregate (filler) and a binder for improving bonding between the aggregates. As a low reactivity constituent, aggregates include zirconium oxide (zirconia), yttrium oxide (yttria), calcium oxide (calcia), and the like, and zirconia sol and organic binders (for example, resins). .

By the way, zirconia and yttria are expensive to use industrially as aggregate. In addition, calcia is difficult to handle because it decomposes by reacting with water.

Zirconia sol is expensive to use industrially as a binder and has a weak strength near room temperature, and thus requires a different kind of binder to maintain room temperature strength. In addition, since the organic binder decomposes at a high temperature, another type of binder is required to maintain the high temperature strength, resulting in an increase in the mold cost.

SUMMARY OF THE INVENTION An object of the present invention devised in view of the above circumstances is to provide a mold which has little reaction with molten alloy and is inexpensive, a manufacturing method thereof, and a cast using the mold.

Means for Solving the Invention

In order to achieve the above object, the mold according to the present invention is a mold for producing a casting made of a titanium aluminum alloy or a titanium alloy, wherein at least an initial layer of the cavity surface of the mold main body is composed of an aggregate and a silica sol composed mainly of cerium oxide. It is formed from the baked material of the slurry comprised from the binder which has a main component.

Here, it is preferable to form the initial layer and the 2nd layer of the cavity surface of a mold main body by baking the slurry. Also, the mold is a shell mold or a solid mold.

On the other hand, the manufacturing method of the mold which concerns on this invention is a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, The aggregate and silica sol which have a cerium oxide as a main component on the surface of the wax model which is a burning model Forming an initial layer slurry film by attaching an initial layer slurry composed of a binder having a main component as a main component and drying the same, and sequentially forming a slurry film after a second layer on a surface of the initial layer slurry film, at least two layers Wax-coating a wax model coated with a slurry film of to form a mold precursor having a cavity inside the initial layer slurry film, and firing the mold precursor to solidify each slurry film to solidify each shell film. It will comprise the step of forming.

Here, as the step of forming the second layer slurry film, it is preferable to repeat the step of forming the initial layer slurry film again.

Moreover, the manufacturing method of the mold which concerns on this invention is a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, The aggregate and a silica-sol which have a cerium oxide as a main component on the surface of the wax model which is a burning-off model Forming a block body of the initial layer slurry by attaching an initial layer slurry composed of a binder having a main component as a main component and drying the same, and then performing a dewaxing treatment on the wax model having the block body. Forming a mold precursor having a cavity inside the block body, and forming a solid mold by subjecting the mold precursor to firing to solidify the block body.

Moreover, the manufacturing method of the mold which concerns on this invention is a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, The aggregate and a silica-sol which have a cerium oxide as a main component on the surface of the wax model which is a burning-off model Forming an initial layer slurry film, forming a block body of the final layer slurry around the initial layer slurry film, and attaching an initial layer slurry composed of a binder having a main component as a main component, and drying the initial layer slurry film. And dewaxing the wax model having the block body to form a mold precursor having a cavity inside the initial layer slurry film, and firing the mold precursor to form the initial layer slurry film and the block body. Solidifying to form a solid mold.

Here, after the formation of the initial layer slurry film, it is preferable to repeat the formation step of the initial layer slurry film again to form a block body of the final layer slurry around the initial layer slurry film of the two-layer structure.

Moreover, the titanium aluminum alloy casting which concerns on this invention is cast-formed using the above-mentioned shell casting or solid casting.

In addition, the titanium alloy casting according to the present invention is a titanium alloy casting formed by using the above-described shell mold or solid mold, and the layer thickness of the α case layer in the surface layer portion of the as-cast material is 300 μm. It is less than.

Effects of the Invention

According to the mold according to the present invention, the cast product made of titanium aluminum alloy having a good surface state even in the state of the raw casting material, and the cast product made of titanium alloy with less generation of α case in the surface layer portion can be obtained. .

Brief description of the drawings

1 is a cross-sectional view of a wax model used for producing a mold according to a preferred embodiment of the present invention.

FIG. 2 is a view showing a state after a slurry film is formed around a wax model in the manufacturing process of a mold according to a preferred embodiment of the present invention.

3 is a view showing a state after dewaxing in the manufacturing process of a mold according to a preferred embodiment of the present invention.

4 is a cross-sectional view of a mold according to one preferred embodiment of the present invention.

5 is a view showing a state in which molten metal is injected into the cavity of the mold of FIG.

FIG. 6 is a cross sectional view of a casting formed by casting using the mold of FIG.

Fig. 7 is a sectional view of a wax model used for producing a mold according to another suitable embodiment of the present invention.

FIG. 8 is a view showing a state after a slurry film is formed around a wax model in the process for producing a mold according to another preferred embodiment of the present invention.

Fig. 9 is a diagram when a slurry block body is formed around a slurry film in the manufacturing process of a mold according to another preferred embodiment of the present invention.

Fig. 10 is a view showing a state after the slurry block body is formed in the manufacturing process of the mold according to another preferred embodiment of the present invention.

11 is a view showing a state after dewaxing in the manufacturing process of the mold according to another preferred embodiment of the present invention.

12 is a cross sectional view of a mold according to another suitable embodiment of the present invention.

FIG. 13 is a view showing a state in which molten metal is injected into the cavity of the mold of FIG.

FIG. 14 is a cross sectional view of a casting formed by casting using the mold of FIG. 12; FIG.

Fig. 15 is a plan view of a part of a titanium aluminum alloy casting formed by casting using a mold according to a preferred embodiment of the present invention.

FIG. 16 is an enlarged view of the main part 16 of FIG.

Fig. 17 is a plan view of a part of a titanium aluminum alloy casting formed by casting using a conventional mold.

FIG. 18 is an enlarged view of the main part 18 of FIG.

Fig. 19 is a cross-sectional view showing the adhesion state between the wax model and the initial layer slurry when the filler / binder ratio of the initial layer slurry is 1.8.

Fig. 20 is a cross-sectional view showing the state of adhesion between the wax model and the initial layer slurry when the filler / binder ratio of the initial layer slurry is 2.0.

Fig. 21 is a cross-sectional view showing the adhesion state between the wax model and the initial layer slurry when the filler / binder ratio of the initial layer slurry is 3.0.

Fig. 22 is a cross-sectional view of a titanium alloy casting formed by casting using a shell mold according to a preferred embodiment of the present invention.

Fig. 23 is a cross-sectional observation diagram of a titanium alloy casting formed by casting using a conventional shell mold.

24 is a cross-sectional view of a titanium alloy casting formed by casting using a solid mold according to another suitable embodiment of the present invention.

Fig. 25 is a cross-sectional view of a titanium alloy casting formed by casting using a conventional solid mold.

* Description of Major Symbols in Drawings *

40: shell mold (mold) 41: mold body

43: cavity surface 44a: initial layer

60: casting

Best Mode for Carrying Out the Invention

In the casting molds for Ni-based alloys, Co-based alloys, and Fe-based alloys, colloidal silica (silica sol) is used as a binder. Silica sol has the advantages of being chemically stable (low activity), industrially inexpensive, and high in strength from room temperature to high temperature. However, such silica sol has a property of reacting strongly with titanium aluminum alloy or titanium alloy. Therefore, it has conventionally been considered that silica sol cannot be used as a binder of a titanium aluminum alloy or a template for titanium alloys.

However, as a result of earnest research by the present inventors, it was found that by adjusting the composition of the aggregate of the titanium aluminum alloy or the mold for the titanium alloy, a strong reaction with the titanium aluminum alloy or the titanium alloy does not occur even when a silica sol is used as the binder. .

EMBODIMENT OF THE INVENTION Below, one preferred embodiment of this invention is described based on an accompanying drawing.

4 is a cross sectional view of a mold according to a preferred embodiment of the present invention.

As shown in FIG. 4, the mold (shell mold) 40 which concerns on this embodiment is the at least initial layer of the surface (henceforth a cavity surface) 43 which contact | connects the cavity 32 of the mold main body 41. As shown in FIG. In Fig. 4, the two layers of the initial layer 44a and the second layer 44b of the cavity surface 43 are calcined from a slurry composed of an aggregate composed mainly of cerium oxide and a binder composed mainly of silica sol. It is formed of water (hereinafter referred to as cerium oxide-silica sol fired product).

The mold main body 41 includes an initial layer (most outer layer) 44a, a second layer 44b, and a third layer 44c. It is a multilayer structure. The slurry fired material constituting the third layer 44c and subsequent layers may be any of the same kind or different types as the cerium oxide-silica sol fired products constituting the initial layer 44a and the second layer 44b. It is possible. The third layer 44c and subsequent layers are slurry firings of a different kind from the cerium oxide-silica sol firings, which are similar to those of ordinary molds (for example, zirconia, alumina, silica, mullite, A fired product of a slurry composed of aggregate composed of at least one member selected from zircon or yttria as a main component and a binder composed mainly of zirconia sol).

The aggregate of the initial layer is, for example, at least one selected from, for example, at least 75 wt%, preferably at least 80 wt%, of cerium oxide, and the remainder selected from zirconia, alumina, silica, mullite, zircon or yttria. It consists of an oxide of Of course, the aggregate may consist only of cerium oxide (cerium oxide is 100 wt%).

In addition, the binder is, for example, silica sol (20-50% silica sol aqueous solution) of 10 to 100wt%, preferably 50 to 100wt% of the total, the remainder is zirconia sol, yttria sol, alumina sol or organic It consists of a binder and the like.

The viscosity of the initial layer slurry is adjusted to a filler (g) / binder (g) ratio and is at least 2-4, preferably in the range of 2.5-3.5. When the viscosity of the slurry is low, the slurry does not remain in the mold (wax model 10 described later) or peeling occurs. As shown in Fig. 19, when the filler / binder ratio is 1.8, peeling occurs, and when the filler / binder ratio is 2.0, it is understood that peeling is about to occur. As shown in Fig. 21, when the filler / binder ratio was 3.0, no peeling occurred, and it was confirmed that a uniform film was formed. In addition, if the viscosity of the slurry is too high, the slurry film adheres too thick, which takes a long time to dry or does not dry uniformly, resulting in "uniformity". Therefore, the filler / binder ratio is up to 4.0.

In the shell mold 40 which concerns on this embodiment, although the case where the mold main body 41 has a three-layered structure was demonstrated, it is not specifically limited to this. For example, the mold main body 41 may have a two-layer structure or a four-layer or more structure.

In addition, in the shell mold 40 which concerns on this embodiment, the case where the initial layer 44a and the 2nd layer 44b were comprised from the cerium oxide-silica sol baking material (the same material) was demonstrated, Especially It is not limited to this. For example, when the layer thickness of the initial layer 44a is sufficiently thick (for example, when the layer thickness of the initial layer 44a is 500 μm or more), only the initial layer 44a is formed of a cerium oxide-silica sol fired product. After the second layer, it is preferable to use the same material as that of a normal mold (for example, a fired product of a slurry composed of an aggregate mainly composed of zirconium oxide and a binder mainly composed of zirconia sol). In consideration of this, a slurry in which the filler / binder ratio is lowered to lower the viscosity than the initial layer may be used.

Next, the manufacturing method of the mold which concerns on this embodiment is demonstrated based on an accompanying drawing.

First, as shown in FIG. 1, the wax model 10 of the same shape and the same size as the target precision casting product (refer FIG. 6 mentioned later) is produced previously.

Next, after applying an initial layer slurry around the said wax model 10, an initial layer stucco is apply | coated and then dried, and as shown in FIG. 2, an initial layer slurry film 24a is shown. ) Is formed. Subsequently, after apply | coating a 2nd layer slurry around the initial layer slurry film 24a, a 2nd layer starco is apply | coated and then dried, and the 2nd layer slurry film 24b is formed. The initial layer slurry and the second layer slurry are the same kind of slurry. In other words, the initial layer slurry film 24a and the second layer slurry film 24b have a two-layer structure of the initial layer slurry film 24a.

Here, an initial layer slurry and a 2nd layer slurry mix the aggregate which has a cerium oxide as a main component in the ratio of 2-4 kg with respect to 1 kg of binders which have a silica sol as a main component, for example. In addition, as a starco (refractory particles to be attached to the surface of the slurry to be attached to the slurry surface) of the initial layer and the second layer, for example, selected from zirconia, alumina, silica, mullite, or yttria of about # 60 to 160 mesh Although at least 1 sort (s) can be used, particle size and a material are not specifically limited. Examples of the method for attaching the slurry include a dipping method, a spraying method, and a coating method, but a dipping method is preferable.

Next, after apply | coating a 3rd layer slurry around the 2nd layer slurry film 24b, a 3rd layer starco is apply | coated and then dried, and the 3rd layer slurry film 24c is formed. Here, the formation process of the slurry film after a 3rd layer is performed repeatedly suitably as needed, and the film thickness of the whole slurry film is controlled to desired thickness by this. The constituent materials of the third layer slurry and the slurry after the third layer and the third layer starco and the third layer after the third layer are not particularly limited, and any one can be used as long as it is conventionally used as a shell molding slurry and starco. .

Next, the wax precursor 10 is de-waxed using steam, so that the mold precursor 30 is obtained as shown in FIG. The mold precursor 30 has a cavity 32 inside the precursor body 31 composed of three layers of slurry films 24a, 24b, and 24c.

Next, by firing the mold precursor 30, as shown in FIG. 4, the mold (shell mold) 40 according to the present embodiment is obtained. The shell mold 40 has a cavity 32 inside a mold main body 41 composed of three layers of an initial layer 44a, a second layer 44b, and a third layer 44c.

Next, as shown in FIG. 5, the molten metal 50 of a titanium aluminum alloy or a titanium alloy is injected into the cavity 32 of the said shell mold 40, and casting is performed. Thereafter, by cooling the shell mold 40, the molten metal 50 is solidified and casting is completed. As a result, a cast body is formed in the shell mold 40.

Thereafter, the shell mold 40 is immersed in a high temperature alkaline bath or the like, the shell, that is, the mold body 41 is dissolved and removed, and the mold is removed. As shown in FIG. 6, a cast made of a titanium aluminum alloy or a titanium alloy is shown. (60) is obtained. As removal of the mold, a physical method (eg blast cleaning) is used. As blast cleaning, any of sand blast, shot blast, or water jet (injection of high pressure water) is possible. In addition, the shake out may be used as a physical method other than blast cleaning.

Next, the operation of the mold 40 according to the present embodiment will be described.

In the mold (shell mold) 40 according to the present embodiment, the initial layer 44a and the second layer of the cavity surface 43 of the mold body 41 in direct contact with the molten metal 50 of titanium aluminum alloy ( 44b) is formed of a cerium oxide-silica sol fired product.

Here, cerium oxide used as a main component of the aggregate of the shell mold 40 cannot be called an especially stable oxide compared with zirconia and yttria. This is also apparent through the comparison of free energy.

However, cerium oxide shows excellent stability with respect to Ti and hardly reacts directly with Ti or is reduced by the molten metal 50 of the titanium aluminum alloy injected into the cavity 32 of the shell mold 40. The inventors have focused on this property of cerium oxide. That is, by using cerium oxide as a main component of the aggregate of the mold main body 41, there is little possibility that the molten metal 50 of the titanium aluminum alloy reacts with or oxidizes in the cavity 32.

In addition, the silica sol used as a main component of the binder of the mold main body 41 generally reacts strongly with the molten metal 50 of a titanium aluminum alloy. However, like the shell mold 40 according to the present embodiment, by using cerium oxide as the main component of the aggregate, there is no fear that the silica sol and the titanium aluminum alloy react strongly even when the silica sol is used as the binder. In addition, since the silica sol is chemically stable (low activity), industrially inexpensive, and high in strength from room temperature to high temperature, by using a silica sol, the strength can be maintained with only a single sol, and the binder As a result, no other type of sol or organic binder is required.

Moreover, since cerium oxide is cheaper than zirconia and yttria, by using cerium oxide as a main component of the aggregate of the shell mold 40, the raw material cost of a mold can be reduced. On the other hand, since the silica sol is used as a binder of an ordinary mold (for example, a Ni-based alloy mold or the like), by using the silica sol as the main component of the binder of the shell mold 40, a wide range due to common binders is achieved. Cost reduction can also be expected. Thereby, the low cost shell mold 40 can be obtained.

From the above, the initial layer 44a and the second layer 44b of the cavity surface 43 of the mold main body 41 are formed of a cerium oxide-silica sol fired product, thereby oxidizing the titanium aluminum alloy and silica sol and titanium aluminum. The reaction of the alloy can be reliably (or almost certainly) controlled, and the formation of oxygen-rich layers on the surface of the casting 60 is controlled, and the mold body 41 with respect to the surface of the casting 60 is controlled. Adhesion is suppressed.

For example, as shown in Figs. 15 and 16, the titanium aluminum alloy casting 150 formed by casting using the shell mold 40 according to the present embodiment has almost no sticking of the mold body to the surface thereof. . That is, the titanium aluminum alloy casting 150 had a beautiful surface appearance and a smooth surface. On the other hand, as shown in Figs. 17 and 18, the titanium aluminum alloy cast article 160 formed by casting zirconia as the main component of the aggregate of the mold and silica sol as the main component of the binder is pressed on the surface of the mold body. There were many stickings (161). That is, the titanium aluminum alloy cast product 160 had a poor surface appearance, a rough surface, and a poor surface state.

Therefore, since the titanium-aluminum alloy casting goods 150 cast-molded using the shell mold 40 which concerns on this embodiment hardly adhere | attach the mold main body on the surface, it is favorable surface state through simple blast cleaning. Can be obtained. For example, the titanium aluminum alloy cast product 150 has an average surface roughness of 200 탆 or less, preferably 50 탆 or less. Accordingly, the titanium aluminum alloy casting 150 has a sufficiently good surface even in the state of a raw casting material, and does not need to finish the surface such as chemical milling or mechanical cutting (or is finished with a slight surface finish). ). Therefore, the titanium aluminum alloy casting 150 can reduce the number of manufacturing processes compared with the conventional titanium aluminum alloy casting 160, and can aim at reducing product cost and improving productivity.

In addition, the shell mold 40 which concerns on this embodiment is manufactured only by changing the formation process of the initial layer slurry film 24a and the 2nd layer slurry film 24b (or only the initial layer slurry film 24a). It is possible. Therefore, the shell mold 40 which concerns on this embodiment can be manufactured, without largely changing the manufacturing line of the conventional shell mold which already exists, and also can suppress a raise of manufacturing cost.

In addition, by performing casting using the molten metal 50 of the titanium alloy to the shell mold 40 according to the present embodiment, it is to produce a hardened layer (α case) containing a lot of oxygen in the surface layer portion of the cast product 60 Suppressed. The layer thickness of the α case produced in the surface layer portion of the cast product 60 obtained is as thin as less than 300 µm, preferably less than 250 µm.

For example, as shown in FIG. 22, the titanium alloy cast product 220 cast by using the shell mold 40 according to the present embodiment had a layer thickness of about 220 µm formed in the surface layer portion. On the other hand, as shown in FIG. 23, the titanium alloy cast product 230 formed by casting zirconia as the main component of the aggregate of the mold and silica sol as the main component of the binder has a weak layer thickness of the α case formed at the surface layer portion. 500 μm. Accordingly, it can be seen that the layer thickness of the α case is less than half of that of the titanium alloy cast product 220 as compared with the titanium alloy cast product 230.

Therefore, the titanium alloy cast product 220 cast by using the shell mold 40 according to the present embodiment has less surface area than the conventional titanium alloy cast product 230 because there is little generation of α case in the surface layer portion. The time required for processing (chemical milling, mechanical cutting, etc.) is shortened. Furthermore, the productivity of the titanium alloy casting 220 may be improved while reducing the product cost of the titanium alloy casting 220. Further, in order to obtain the final product, it is not necessary to perform surface treatment on the titanium alloy casting 220 so much, and because the dimensional difference between the titanium alloy casting 220 and the final product is small, the material yield is good, and the titanium alloy casting ( The raw material cost of 220 can be reduced.

 The mold 40 according to the present embodiment is suitable for a mold for precision casting, and is, for example, a titanium aluminum alloy precision casting, such as a rotating member of a turbocharger, a gas turbine engine or an jet engine for an automobile, a heat resistant jig, or the like. Can be mentioned. Examples of the titanium alloy precision casting products include automobiles, motorcycle parts, sports and leisure products, artificial bones, artificial teeth, heat exchangers, and the like.

Next, another embodiment of this invention is described based on an accompanying drawing.

12 is a cross sectional view of a mold according to another suitable embodiment of the present invention.

As shown in FIG. 12, the mold (solid mold) 120 according to the present embodiment includes at least an initial layer (in FIG. 12) of the cavity surface 123 of the mold body 121. Two layers of layer 44a and second layer 44b) are formed of a cerium oxide-silica sol fired product.

The mold main body 121 is composed of a block-shaped main body portion 124 and a layer portion 125 in contact with the cavity 112. The layer portion 125 has a two-layer structure of the initial layer 44a and the second layer 44b. The slurry fired product constituting the main body portion 124 can be of the same kind or different types as the cerium oxide-silica sol fired products constituting the initial layer 44a and the second layer 44b. The main body portion 124 is a slurry composition of a different kind from the cerium oxide-silica sol fired product, which is the same as a conventional mold (for example, at least selected from zirconia, alumina, silica, mullite, zircon or yttria). A fired product of a slurry composed of an aggregate composed mainly of one species and a binder composed mainly of a zirconia sol).

The cavity surface 123 of the mold main body 121 in the shell mold 120 according to the present embodiment may be a single layer structure or a structure of three or more layers.

When the layer thickness of the initial layer 44a in the solid mold 120 according to the present embodiment is sufficiently thick, only the initial layer 44a is formed of a cerium oxide-silica sol fired product, and the second layer 44b is formed. ) May be formed of the same material as the body portion 124.

Next, the manufacturing method of the mold which concerns on this embodiment is demonstrated based on FIGS. In addition, the same code | symbol is attached | subjected to the member same as FIGS. 1-6, and description is abbreviate | omitted about these members.

First, as shown in Fig. 7, a wax model of the same shape and the same size as the target precision casting product (see Fig. 14 to be described later) is produced in advance.

Next, after apply | coating an initial layer slurry around the said wax model 70, an initial layer starco is apply | coated and then dried, and the initial layer slurry film 24a is formed as shown in FIG. do. Subsequently, after apply | coating a 2nd layer slurry around the initial layer slurry film 24a, a 2nd layer starco is apply | coated and then dried, and the 2nd layer slurry film 24b is formed. The initial layer slurry and the second layer slurry are the same kind of slurry. In other words, the initial layer slurry film 24a and the second layer slurry film 24b have a two-layer structure of the initial layer slurry film 24a.

Next, as shown in FIG. 9, after arranging the wax model 70 in which each slurry film 24a, 24b was formed in the space part 92 of the casting mold 91, the space 92 The final layer slurry 93 is injected. The final layer slurry 93 is naturally cured over time, and may appropriately contain an organic compound (for example, a phenol resin), a curing agent, a refractory material, or the like. As shown in FIG. 10 by the natural hardening of the said final layer slurry 93, the block body of the final layer slurry 93 around the wax model 70 which formed each slurry film 24a, 24b. 103 is formed.

Next, the wax precursor 70 is dewaxed using steam, so that the mold precursor 110 is obtained as shown in FIG. The mold precursor 110 has a cavity 112 inside the precursor body 111. The precursor body 111 is composed of a block body 103 which is a body portion and slurry films 24a and 24b in contact with the cavity 112.

Next, by firing on the mold precursor 110, as shown in FIG. 12, the mold (solid mold) 120 according to the present embodiment is obtained. The solid mold 120 has a cavity 112 inside the mold body 121 composed of the body portion 124 and the layer portion 125.

Next, as shown in FIG. 13, the molten metal 50 of a titanium aluminum alloy or a titanium alloy is injected into the cavity 112 of the said solid mold 120, and casting is performed. Thereafter, by cooling the solid mold 120, the molten metal 50 is solidified and casting is completed. As a result, a cast is formed in the solid mold 120.

Thereafter, as shown in FIG. 14, the cast product is taken out of the solid mold 120 to obtain a cast article 140 made of a titanium aluminum alloy or a titanium alloy.

In the manufacturing method of the mold 120 which concerns on this embodiment, although the case where the block body 103 of the final layer slurry 93 was formed around the slurry film 24a, 24b of a two-layer structure was demonstrated, It is not specifically limited to this. For example, a block body may be formed directly around the wax model 70 in one manufacturing process. That is, after arranging the wax model 70 in the space portion 92 of the mold frame 91, the final layer slurry 93 is injected into the space portion 92, and around the wax model 70, It is also possible to form a block body consisting of a single final layer slurry monolith. The final layer slurry 93 is equivalent to the initial layer slurry.

Also in the mold 120 which concerns on this embodiment, the effect similar to the mold 40 which concerns on embodiment mentioned above can be acquired.

In addition, casting is performed using the molten metal 50 of a titanium alloy on the solid mold 120 according to the present embodiment, so that the cured layer (α case) containing a lot of oxygen in the surface layer also in the cast product 140. Production is suppressed, and the layer thickness of the α case is thin, less than 300 µm. For example, as shown in FIG. 24, in the titanium alloy cast product 240 formed by casting using the solid mold 120 according to the present embodiment, the layer thickness of the α case formed on the surface layer portion was about 280 µm. On the other hand, as shown in FIG. 25, the titanium alloy cast product 250 formed by casting zirconia as the main component of the aggregate of the mold and silica sol as the main component of the binder has a weak layer thickness of the α case formed at the surface layer portion. 500 μm. Accordingly, it can be seen that the titanium alloy casting 240 is about half the layer thickness of the α case compared to the titanium alloy casting 250.

Moreover, the mold 120 which concerns on this embodiment is suitable as a casting mold of a super large casting, an ornament, an artificial tooth, an artificial bone, etc. rather than the casting for precision casting products. Since the mold 120 is durable and has fewer laminations, the manufacturing process is simplified, so the mold 120 is excellent in cost performance.

As mentioned above, this invention is not limited to embodiment mentioned above, Needless to say, various things are assumed other than that.

Claims (11)

As a mold for producing a casting made of titanium aluminum alloy or titanium alloy, A mold, characterized in that at least an initial layer of the cavity surface of the mold body is formed of a fired product of a slurry composed of an aggregate containing cerium oxide as a main component and a binder containing silica sol as a main component. The mold according to claim 1, wherein the initial layer and the second layer of the cavity surface of the mold body are formed of a fired product of the slurry. The mold according to claim 1 or 2, wherein the mold is a shell mold. The mold according to claim 1 or 2, wherein the mold is a solid mold. As a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, Forming an initial layer slurry film by adhering an initial layer slurry composed of an aggregate composed mainly of cerium oxide and a binder mainly composed of a silica sol on the surface of the wax model, which is a burning model, and drying the same; Sequentially forming a slurry film after the second layer on the surface of the initial layer slurry film; Dewaxing the wax model coated with at least two layers of slurry film to form a mold precursor having a cavity inside the initial layer slurry film; And Calcining the mold precursor to solidify each slurry film to form a shell mold; Method for producing a mold comprising a. 6. The method for producing a mold according to claim 5, wherein the forming of the slurry film of the second layer is repeated again. As a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, Forming a block body of the initial layer slurry by attaching an initial layer slurry composed of an aggregate composed mainly of cerium oxide and a binder containing silica sol as a main component on the surface of the wax model, which is the burner model, and drying the same; Dewaxing the wax model having the block body to form a mold precursor having a cavity inside the block body; And Calcining the mold precursor to solidify the block to form a solid mold; Method for producing a mold comprising a. As a manufacturing method of the mold for manufacturing the casting made from a titanium aluminum alloy or a titanium alloy, Forming an initial layer slurry film by adhering an initial layer slurry composed of an aggregate composed mainly of cerium oxide and a binder mainly composed of a silica sol on the surface of the wax model, which is a burning model, and drying the same; Forming a block of final layer slurry around the initial layer slurry film; Dewaxing the wax model having the initial layer slurry film and the block body to form a mold precursor having a cavity inside the initial layer slurry film; And Calcining the mold precursor to form a solid mold by solidifying the initial layer slurry film and the block body; Method for producing a mold comprising a. The mold according to claim 8, wherein after the initial layer slurry film forming step, the initial layer slurry film forming step is repeated to form a block body of the final layer slurry around the initial layer slurry film of the two-layer structure. Method of preparation. A cast aluminum titanium alloy casting formed using the mold of claim 3 or 4. A titanium alloy casting formed by casting using the mold according to claim 3 or 4, wherein the layer thickness of the α case layer in the surface layer portion of the raw casting material is less than 300 µm.

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