JP2000140993A - Manufacture of mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mold which can prevent the occurrence of defective casting caused by lowering of the strength of a coating shell. SOLUTION: In a method for producing the mold 1, with which a wax pattern 22 with a sprue having many annular recessed grooves 22a and the same shape as the casting shape is formed and successively, ceramic coating treatment is repeatedly applied on the wax pattern 22 to form the shell 2 and thereafter, the shell 2 is fired and also, the wax pattern 22 is melted out, on the way of forming of the shell 2, after forming the shell coating layer 2a with the ceramic coating treatment on the wax pattern 22 except the sprue 1a, filling material 3 which can remove after solidifying on the inside of the shell coating layer 2a in the annular recessed grooves 22a, is poured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold suitable for producing a mold by, for example, a ceramic shell method.

[0002]

2. Description of the Related Art In general, a lost wax casting method is known as a typical precision casting method capable of casting a thin part having high dimensional accuracy. In such a lost wax casting method, when casting a cast part made of an iron-based casting material, a mold manufactured by a ceramic shell method is often used. This has a space portion having the same shape as that of the casting inside, and is composed of a number of ceramic layers (shell coating layers).

[0003] Incidentally, such a mold is required to have a sufficient strength to withstand the pressure of the molten metal at the time of casting of a casting, and to have a property of being easily removed (broken) after casting.

Conventionally, this type of mold manufacturing method includes a method shown in FIG.
One that produces a mold through the steps shown in (a) to (c) is employed. FIG. 2 shows the method of manufacturing this mold.
This will be described with reference to (a) to (c). First, as shown in FIG. 2A, a casting 31 having an annular concave groove 31a shown in FIG.
Groove (annular groove) 22a having the same shape as the shape of
To form an attached wax mold 22.

[0005] Next, as shown in FIG.
After the spigot 23 is attached to the shell 24, the wax mold 22 is coated with a ceramic so as to form a shell 24.
To form At this time, a coating layer of a slurry in which fine silicone or ceramic is mixed is formed in the wax mold 22, and a coating layer of ceramic powder is formed on the coating layer and dried. further,
The coating process using the slurry, the coating process using the ceramic powder, and the drying process are repeated to obtain a shell 24 having a predetermined thickness on the wax mold 22.

Thereafter, as shown in FIG. 1C, the shell 24 is fired and the wax mold 2 inside the shell 24 is baked.
Dissolve 2 and discharge. In this manner, the mold 32 having the space 32a having the same shape as that of the casting 31 inside can be cast.

[0007]

However, in the conventional method of manufacturing a mold, a casting 31 having a large number of annular concave grooves 31a having a narrow groove width and a large groove depth is cast by a ceramic shell method. As shown in FIG. 4, the coating material 41 is attached so as to swell between two adjacent grooves 22a (tips of the convex portions in the wax mold 22).

As a result, the entrance of the groove 22a is closed or narrowed by the coating material 41 during the ceramic coating process, and the cavity 41a is formed in the coating material 41 in the groove 22a after the coating process. Or the coating material 4 is formed in the groove 22a.
For example, there is a problem in that casting is not performed due to a decrease in the strength of the ceramic shell, for example, due to insufficient filling of the ceramic shell with a sufficient density.

Prior arts are disclosed in Japanese Patent Application Laid-Open Nos. 9-094631 and 10-156484 as a "single-crystal precision casting mold" and a "precision casting mold", respectively. Has not been resolved.

[0010] The present invention has been made in view of such circumstances, and by injecting a filler into the inside of the shell coating layer in the wax-shaped recess, the gap between the inside of the shell coating layer in the wax-shaped recess is formed. It is an object of the present invention to provide a method for manufacturing a mold, into which a filler can be poured, thereby preventing casting defects due to a reduction in the strength of a coating shell.

[0011]

According to a first aspect of the present invention, there is provided a method for manufacturing a mold, comprising: a plurality of recesses which are open to the outside; A method of manufacturing a mold by forming a wax mold with a gate and then repeatedly applying a ceramic coating process to the wax mold to form a shell, and then firing and melting the wax mold to form a mold. In the process of forming, after forming a shell coating layer by a ceramic coating process except for the sprue in the wax mold, a filler material that can be removed after solidification inside the shell coating layer in the concave portion of the shell coating layer. There is a method of injection. Therefore, the filler flows into the inner space of the shell coating layer in the wax-shaped recess when the filler is injected.

According to a second aspect of the present invention, there is provided a method of manufacturing a mold according to the first aspect, wherein a reinforcing member is disposed inside the shell coating layer in the recess before the filling material is injected. Therefore, the durability of the mold against the pressure of the molten metal during casting can be obtained by the reinforcing member.

According to a third aspect of the present invention, in the method for manufacturing a mold according to the second aspect, the reinforcing member is formed of the same material as the material of the shell. Therefore,
During casting, the heat distribution in the reinforcing member becomes identical to the heat distribution in the shell.

According to a fourth aspect of the present invention, in the method for producing a mold according to the first, second or third aspect, the filler has water solubility after solidification. Therefore, by removing the filler by dissolving it in water after casting, removal in the concave portion of the mold is simplified.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a mold according to any one of the first to fourth aspects, wherein the filler has heat resistance after solidification. Therefore,
Heat resistance to the molten metal poured into the mold during casting is obtained in the filler.

According to a sixth aspect of the present invention, there is provided the method for manufacturing a mold according to any one of the first to fifth aspects, wherein the filler comprises gypsum dissolved in water. Therefore, a filler having sufficient strength to withstand the pressure of the molten metal poured into the mold at the time of casting and having characteristics that can be easily removed after casting can be obtained.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a method for manufacturing a mold according to the first embodiment of the present invention.
2, the same reference numerals are given to the wax molds shown in FIGS. 2 and 4, and the castings shown in FIG. 3 are used for the description of the castings in the embodiment. FIG. 1 shows a mold before the wax mold is melted out. Before explaining the method of manufacturing the mold in the present embodiment, the mold will be described with reference to FIG. In the figure, a mold denoted by reference numeral 1 is a bottomed cylindrical body having a gate 1a for molten metal injection opening upward, and includes a shell 2, a filler 3, and a reinforcing member 4.

The shell 2 has a large number of shell coating layers 2a (two layers in FIG. 1), and is entirely formed of, for example, a ceramic material. On the inner peripheral surface of the shell 2,
Recess 2 extending in the circumferential direction and alternately arranged in the axial direction
A and the convex portion 2B are formed.

The filler 3 has heat resistance and water solubility in a solidified state, and is made of a material in which gypsum or the like which can be broken after solidification is dissolved in water. The filler 3 is provided inside the shell coating layer 2a in the annular groove 22a. Is filled. Thereby, the heat resistance to the molten metal and the strength sufficient to withstand the pressure of the molten metal at the time of casting in the filler 3 are obtained. The casting 31 having the same shape as that of the wax mold 22 is taken out by dissolving and removing the mold 1 in water after casting, or by breaking the mold 1 by applying an external force.

The reinforcing member 4 is embedded in the filler 3 and is formed by two semi-annular plates (only one is shown) made of, for example, a ceramic material. As a result, the pressure of the molten metal during casting can
And the heat distribution is the same as the heat distribution in the shell 2. The reinforcing member 4 may be formed by solidifying a slurry mixed with silicone or ceramic powder into a predetermined shape.

Next, a method for manufacturing a mold according to the first embodiment of the present invention will be described with reference to FIG. First, a wax mold 22 having a large number of annular concave grooves 22a which are open to the outside and are arranged in parallel at a predetermined interval in the axial direction, and which has the same shape as a cylindrical casting 31 (shown in FIG. 3). Form.
Next, a shell coating layer 2a is formed except for the gate 1a by performing a coating process using a ceramic with the gate 1a and the like attached to the outer peripheral surface of the wax mold 22. At this time, the shell coating layer 2a is also formed on the inner surface of the annular groove 22a of the wax mold 22.

After that, the reinforcing member 4 is disposed inside the shell coating layer 2a in the annular groove 22a of the wax mold 22. In this case, the reinforcing member 4 is formed of the same or equivalent material as that of the shell 2 and fired in advance. The gap between the reinforcing member 4 and the shell coating layer 2a is set to a small size so that the influence of thermal expansion during casting of the filler 3 and the shell coating layer 2 is reduced.

Thereafter, the shell coating layer 2a in the annular groove 22a of the shell coating layer 2a
The filling material 3 which can be removed in a solidified state is injected into the inside. At this time, the filler 3 flows into the space inside the shell coating layer 2a in the annular groove 22a of the wax mold 22. In this case, as the filler 3, a gypsum or the like which has solubility in water after solidification and can be broken by an external force is used. Thereby, the reinforcing member 4 when the mold 1 is destroyed after casting and the casting 31 is taken out to the outside.
Removal is easier.

The shell coating layer 2a is repeatedly subjected to a ceramic coating process so as to cover the filler 3, whereby the shell coating layer 2a is formed.
The shell 2 having a predetermined thickness including a is formed. In this case, the shell 2 has a large number of ceramic layers (shell coating layers) so that the shell 2 has sufficient strength to withstand the pressure of the molten metal during casting of the casting 31 and has a characteristic of being easily removed (broken) after casting.
And Thereafter, the shell 2 is fired and the wax mold 2 is fired.
Dissolve 2 and drain.

In this way, it is possible to manufacture the mold 1 having an internal shape conforming to the shape of the casting 31. That is, in order to manufacture the mold 1 in the present embodiment, a sprue mold 22 having a number of annular concave grooves 22a opened to the outside and having the same shape as the casting 31 is formed. In a method of manufacturing the mold 1 by repeatedly applying the ceramic coating process to the wax mold 22 to form the shell 2 and then firing the shell 2 and dissolving the wax mold 22, in the process of forming the shell 2, After the shell mold layer 2a is formed on the wax mold 22 by the ceramic coating process except for the gate 1a, the shell coat layer 2a can be removed after solidification inside the shell coat layer 2a in the annular groove 22a. This is performed by injecting the filler 3.

Therefore, in the present embodiment, the reinforcing member 4 is arranged in the annular groove 22a of the wax mold 22, and then the filler 3 is injected. A cavity is not formed in the coating material in the coating material 22a, and the coating material is not buried at a sufficient density in the annular groove 22a.

In this embodiment, since the filler 3 is made of gypsum dissolved in water, when the casting 31 is taken out, the shell 2 including a portion corresponding to the annular groove 22a of the wax mold 22 is formed. Removal can be easily performed.

In order to cast the casting 31 using the casting mold 1 of the present embodiment, a molten metal is poured into the casting mold 1 from a gate 1a, and after cooling, the casting mold 31 is broken and the casting 31 is taken out. Do. In this case, the shell 2 and the filler 3 including the inside of the annular groove 22a can be easily broken, and the casting can be simplified.

In this embodiment, the reinforcing member 4 is provided inside the shell coating layer 2a in the annular groove 22a.
Has been described, the case where the filler 3 that can be removed in the solidified state is injected is described. However, the present invention is not limited to this, and the filler 3 has characteristics necessary for the mold in the solidified state. No reinforcing member is required as long as it can be easily removed after solidification of 3.

In addition, in the present embodiment, a case has been described in which a casting mold for casting a casting 31 having an annular concave groove 31a is manufactured. However, the present invention is not limited to this. The same effect as that of the embodiment can be obtained in the case of manufacturing a casting mold, that is, a casting mold for casting a casting having a narrow and deep concave portion.

[0031]

As described above, according to the present invention, after the shell coating layer is formed by the ceramic coating process except for the sprue in the middle of forming the shell, the concave portion of the shell coating layer is formed. Since the filler which can be removed after solidification is injected into the inside of the shell coating layer in the inside, the filler flows into the inside space of the shell coating layer in the wax-shaped recess when the filler is injected.

Therefore, a cavity may be formed in the coating material in the concave portion after the coating process as in the related art,
Since the coating material is not buried at a sufficient density in the concave portion, a mold can be obtained that can prevent the occurrence of casting defects due to a decrease in the strength of the ceramic shell.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for manufacturing a mold according to a first embodiment of the present invention.

2 (a) to 2 (c) are cross-sectional views for explaining a conventional method for manufacturing a mold.

FIG. 3 is a perspective view showing a casting cast using a mold according to a conventional method of manufacturing a mold.

FIG. 4 is a cross-sectional view for explaining an example of a defect due to a conventional mold manufacturing method.

[Explanation of symbols]

 Reference Signs List 1 mold 1a gate 2 shell 2a shell coating layer 2A concave portion 2B convex portion 3 filler 4 reinforcing member 22 wax type 22a annular concave groove 31 casting 31a annular concave groove

Claims (6)

[Claims] 1. A wax mold with a sprue having a number of recesses opening to the outside and having the same shape as that of a casting is formed, and then a ceramic coating process is repeatedly performed on the wax mold to form a shell. A method of manufacturing a mold by sintering the shell and dissolving the wax mold, and then forming a shell coating layer by a ceramic coating process on the wax mold except for the sprue. A method of manufacturing a mold, comprising, after forming, injecting a filler that can be removed after solidification into the inside of the shell coating layer in the concave portion of the shell coating layer. 2. The method according to claim 1, wherein a reinforcing member is disposed inside the shell coating layer in the recess before the filling material is injected. 3. The method according to claim 2, wherein the reinforcing member is formed of the same material as the material of the shell. 4. The method according to claim 1, wherein said filler has water solubility after solidification. 5. The method according to claim 1, wherein said filler has heat resistance after solidification. 6. The method according to claim 1, wherein the filler is made of gypsum dissolved in water.