JP2007307596A - Core for forming and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core for forming and a manufacturing method therefor which has excellent proof pressure and can easily remove after casting or after forming. <P>SOLUTION: The core for forming is constituted of a core body combining granular bodies with binder and an infiltrating salt layer composed of the salt having higher melting point than that of the material of the forming body and forming on the surface layer of the core body. The core body is made to have a plurality of fine holes and the salt is made to get into the fine holes. The manufacturing method of the core for forming is constituted of a main body forming process for forming the core body and a fused salt filtrating process for filtrating the fused state of the salt on the surface layer portion of the core body under reduced pressure condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding core used when producing a hollow molded body and a method for producing the same.

  The molding core is a type of molding die used when molding a hollow molded body. A molding core is placed in a cavity in advance, a molding material such as a molten metal material (molten metal) or a molten resin is injected into the cavity, and the molding core is removed after the molding material is solidified. A hollow molded body such as a resin molded body can be manufactured. Hereinafter, in this specification, a hollow molded body is simply abbreviated as a molded body.

  By the way, as a forming core, it is common to use a material in which particles such as sand and ceramic are bonded together by a binder (so-called sand core). However, the molding material may enter the gaps between the granular bodies, and the surface of the molded body may not be smooth. For this reason, in recent years, a molding core in which a molding material does not easily enter the interior has been proposed (for example, see Patent Document 1). In the molding core introduced in Patent Document 1, a coating layer is formed on the surface of the core body in which the granular materials are bonded together by a binder. This coating layer includes a zircon flower as a powder refractory, a phenolic resin as a resin binder, mica as a lubricity-imparting material, and the like, and covers the surface of the core body. For this reason, it is thought that the surface of the molded object manufactured using this molding core is smooth.

  When removing the molding core introduced in Patent Document 1 from the molded body, it is considered that the core body may be collapsed by applying vibrations such as striking to the molded body. Further, it is considered that the coating layer remaining on the molded body can be removed by removing the collapsed core body from the molded body. However, when such a molding core is used, the operation of removing the coat layer from the molded body is complicated, and the manufacturing cost of the molded body is high. In addition, the molding core introduced in Patent Document 1 may be deformed when molded at high pressure because the pressure resistance of the coating layer is small. If the molding core is deformed at the time of molding, there is a problem that a molded body having excellent dimensional accuracy cannot be obtained.

  A technique for increasing the pressure resistance of a molding core has also been proposed (see, for example, Patent Document 2). The molding core introduced in Patent Document 2 is composed of a surface layer formed of a porous material having a melting point higher than the temperature of the molten metal, and a surface layer formed of a material having a melting point lower than the temperature of the molten metal. And a filling section that is filled. According to this molding core, if the molded body in which the molding core is contained is heated after the molding material is solidified, the low melting point material constituting the filling portion is melted and the molding core collapses. For this reason, the molding core can be easily removed from the molded body. Further, if a material having excellent pressure resistance such as salt is used as the low melting point material, the molding core will not be deformed during molding.

However, even when the molding core introduced in the cited document 2 is used, a heating step for melting the filling portion after obtaining the molded body is required. For this reason, in order to remove the molding core from the molded body, a large number of man-hours are still required, and it is still difficult to produce the molded body at low cost.
JP 2003-191048 A JP-A-2005-342751

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a molding core that is excellent in pressure resistance and can be easily removed after casting or molding, and a method for manufacturing the same.

  The molding core of the present invention that solves the above problems is a molding core for molding a hollow molded body, wherein a core body in which granular bodies are bonded together by a binder, and the molded body The core body has a osmotic salt layer formed of a salt having a melting point higher than that of the material and formed on the surface layer portion of the core body. The core body has a large number of pores, and the salt enters the pores. It is characterized by that.

The molding core according to the present invention preferably includes any of the following (1) to (2). It is desirable to have both (1) and (2).
(1) The mass of the salt is 25% to 45% when the mass of the core body is 100%.
(2) The salt comprises at least one selected from potassium chloride, sodium chloride, and sodium carbonate.

  A manufacturing method of a molding core of the present invention that solves the above problems is a molding core for molding a hollow molded body, wherein a core body in which granular bodies are bonded together by a binder, An osmotic salt layer formed on a surface layer portion of the core body, the core body having a large number of pores, and the salt in the pores. A method for producing an in-molding core, wherein a main body molding step for molding the core body in which the granules are bonded together by the binder, and a surface layer portion of the core body under reduced pressure conditions And a molten salt permeation step for allowing the molten salt to permeate.

The method for producing a molding core according to the present invention preferably includes any of the following (3) to (4). It is desirable to have both (3) and (4).
(3) In the molten salt infiltration step, 25% to 45% of the salt is infiltrated when the mass of the core body is 100%.
(4) The salt comprises at least one selected from potassium chloride, sodium chloride, and sodium carbonate.

  The molding core of the present invention can be easily removed from the molded body. That is, in the molding core of the present invention, since the core body is composed of a granular body and a binder, the core body collapses if vibration such as striking is applied to the molded body, as in the conventional molding core. To do. Therefore, the core body can be easily removed from the molded body. Moreover, since the osmotic salt layer formed on the surface layer portion of the core body is made of salt, it easily dissolves in water. Therefore, the osmotic salt layer can be easily removed by washing the hollow part of the molded body with warm water.

  Moreover, since the molding core of the present invention is excellent in pressure resistance, it is difficult to be deformed even when the molded body is molded at a high pressure. That is, in the molding core of the present invention, the osmotic salt layer formed on the surface layer portion of the core body is made of salt and has excellent pressure resistance. Therefore, excellent pressure resistance derived from the permeation salt layer is imparted to the molding core of the present invention. In the molding core of the present invention, the osmotic salt layer not only covers the surface of the core body, but also enters the pores of the core body. The share is large. In other words, the thickness of the osmotic salt layer is large. Therefore, the molding core of the present invention sufficiently exhibits the pressure resistance effect derived from the osmotic salt layer. Therefore, according to the molding core of the present invention, a molded article having excellent dimensional accuracy can be obtained.

  The molding core according to the present invention having the above (1) is more excellent in pressure resistance and can be easily taken out from the molded body. This is because the proportion of the osmotic salt layer in the molding core is large enough to sufficiently exert the pressure-resistant effect derived from the osmotic salt layer, and small enough that the osmotic salt layer is easily dissolved in warm water or the like. is there.

  The molding core according to the present invention having the above (2) is more excellent in pressure resistance and can be taken out from the molded body more easily. Since potassium chloride, sodium chloride, and sodium carbonate are all excellent in strength when solid and easily dissolved in water, they can be easily taken out from the molded body by washing with warm water or the like.

  In the method for producing a molding core according to the present invention, the salt is infiltrated into the surface layer portion of the core body in the molten salt infiltration step. Therefore, according to the molding core manufacturing method of the present invention, it is possible to manufacture a molding core that is excellent in pressure resistance and can be easily removed after casting or molding. In the production method of the present invention, in the molten salt infiltration step, the salt is infiltrated into the surface layer portion of the core body under reduced pressure. Therefore, the salt easily penetrates not only to the surface of the core body but also to the surface layer portion of the core body, that is, the inside. Further, since a molten salt, that is, a high-concentration salt is infiltrated into the core body, a desired amount of salt can be rapidly infiltrated into the core body. Therefore, according to the manufacturing method of the present invention, the molding core can be manufactured easily and inexpensively.

  As described above, the method for producing a molding core of the present invention comprising the above (3) can produce the molding core of the present invention which is more excellent in pressure resistance and can be easily taken out from the molded body.

  As described above, the method for producing a molding core according to the present invention comprising the above (4) can produce the molding core according to the present invention which is more excellent in pressure resistance and can be easily taken out from the molded body.

  The molding core of the present invention can be used when molding (casting) a cast body or molding a resin molded body.

  The blending ratio of the binder in the molding core of the present invention may be such that the particles can be bonded to each other and pores are formed in the core body. In addition, the pore of the core body in the present invention refers to a gap between granular bodies, a gap between granular bodies and a binder, a gap between binders, and the like. When a porous body is selected as the granular body, the pores of the granular body itself also become the pores of the core body.

  As the granular material in the molding core of the present invention, a granular material used in a conventional sand core may be used, but a granular material having a higher melting point than the molding material is preferable. This is to prevent deformation of the molding core when molding the molded body. Moreover, it is desirable to use a granular material made of a material having a melting point higher than that of the salt.

  In the molding core of the present invention, the osmotic salt layer may be formed by allowing a salt dissolved in a solvent such as water to penetrate into the core body and evaporating the solvent. Alternatively, the molten salt may be penetrated into the core body, and the salt may be cooled and solidified. In any case, the osmotic salt layer in the molding core is composed of a solid salt. In the case where the molten salt is infiltrated into the core body, there is an advantage that the process of manufacturing the molding core is further simplified.

  In order to infiltrate the molten salt into the core body, it is necessary to use a granular material made of a material having a melting point higher than that of the salt. Furthermore, the granular material is preferably a porous material. The granular material made of a porous material is easily penetrated by the binder and salt, and is firmly bonded to the binder and salt, so that the pressure resistance of the molding core is increased. Examples of the material preferably used as the granular material include silica sand, alumina, mullite, zircon, chromite and the like.

  In the molding core of the present invention, an osmotic salt layer is formed on the surface layer portion of the core body. In other words, the surface layer portion of the core body is hardened with salt. Therefore, the pressure resistance required for the core body is relatively small, and the pressure resistance required for the binder is also relatively small. In the molding core of the present invention, the salt constituting the osmotic salt layer has a higher melting point than the molding material. Therefore, the pressure resistance of the molding core at the time of molding is sufficiently ensured by the osmotic salt layer. Therefore, a binder having a melting point lower than that of the molding material or a material that burns below the melting point of the molding material can be used as the binder. For this reason, a phenol resin, an isocyanate resin, a furan resin, etc. can be used as a binder in the molding core of this invention.

  The salt in the molding core of the present invention has a higher melting point than the molding material. Therefore, the salt may be appropriately selected according to the molding material. Potassium chloride, sodium chloride, sodium carbonate, and the like are preferably used because they have a high melting point, excellent pressure resistance when solid, and are easily dissolved in water.

  Hereinafter, the molding core of the present invention and the manufacturing method thereof will be described with reference to the drawings.

(Example)
The molding core of the example includes the above (1) to (2). Moreover, the manufacturing method of the molding core of an Example is provided with said (3)-(4). FIG. 1 is a cross-sectional view schematically showing the molding core of the example. FIG. 2 shows an enlarged view of the main part of FIG. FIG. 3 is an explanatory diagram schematically showing the molten salt permeation step in the method for manufacturing a molding core of the example. FIG. 4 to FIG. 7 are explanatory views schematically showing how a molded body is manufactured using the molding core of the example.

  As shown in FIG. 1, the molding core 1 of the embodiment has a core body 2 and an osmotic salt layer 3 formed on the surface layer portion of the core body 2. The core body is made of silica sand as the granular material 20 and phenol resin as the binder 21. The mass ratio of the granular material 20 and the binder 21 is 97: 3. An osmotic salt layer 3 is formed on the surface layer portion of the core body 2. In the molding core 1 of the example, the salt constituting the osmotic salt layer 3 is potassium chloride. As shown in FIG. 1, the osmotic salt layer 3 is formed on the entire surface layer portion of the core body 2. As shown in FIG. 2, the granular materials 20 are joined together by a binder 21. In the osmotic salt layer 3, the salt 30 enters the pores of the core body 2. The mass of the salt is 30% when the mass of the core body 2 is 100%.

  The manufacturing method of the core 1 for a shaping | molding of an Example is as follows.

(1. Main body forming process)
AV coated sand (coated with silica sand with phenolic resin) manufactured by Asahi Organic Materials Co., Ltd. was used as a mixed material, and this mixed material was poured into a mold for the core body. At this time, in order to increase the filling rate of the mixed material into the mold, the mold was vibrated with a vibrator. The mold filled with the mixed material was heated to 250 ° C. After the heating, the mold was cooled to obtain a core body in which the granular materials are bonded together by a binder.

(2. Molten salt infiltration process)
A salt bath 40 containing the salt 30 and a core immersion device 41 containing the core body 2 were disposed in the chamber 42. A heater is attached to the salt bath 40, and salt can be heated. Further, since the core immersion device 41 can move up and down with respect to the salt bath 40, the core accommodated in the core immersion device 41 can enter and exit the salt bath 40. A decompression device (not shown) for decompressing the interior of the chamber 42 is attached to the chamber 42 (FIG. 3).

  First, the heater was driven, the salt bath 40 was heated to 850 ° C., and the salt 30 was heated and melted. Next, the decompression device was driven to decompress the inside of the chamber 42 to 80 mmHg (about 106.7 hPa). After decompression, the core immersion device 41 was moved down, and the core body 2 obtained in the body formation step was immersed in the molten salt 30. Since the inside of the chamber 42 was depressurized, the molten salt 30 entered the pores formed in the surface layer portion of the core body 2. After several seconds after the start of the immersion, the core immersion device 41 was moved up, and the core body 2 was pulled up from the molten salt 30. The core body 2 was cooled and dried to obtain the molding core 1 of the example.

(Manufacture of molded body using core 1 for molding)
A method for producing a molded body (cast body) using the molding core 1 of the embodiment will be described below. In this method for producing a molded body, aluminum ADC12 for die casting was used as a molding material.

(1. Molding process)
First, the molding core 1 was placed in the cavity 51 of the casting mold 50 (FIG. 4). Next, a molding material 53 in a molten state was injected from the injection plunger 52 toward the cavity 51. The molding material temperature (molten metal temperature) at this time was 680 ° C., the molding pressure (casting pressure) was 20 MPa, and the injection speed was 2.0 m / s.

(2. Core decay process)
By the molding process described above, a molded body in which the molding core 1 was integrated (hereinafter referred to as an intermediate molded body 54) was obtained (FIG. 5). A baseboard portion 55 of the intermediate molded body 54 (a portion exposed to the outside in the molding core 1) was beaten with a hammer. Subsequently, the intermediate molded body 54 was knocked by the knockout machine, and the core body 2 was collapsed. The knock pressure at this time was 0.2 MPa, and the knock time was 30 seconds. The core body 2 collapsed by the core collapse process, and most of the fragments of the granular material 20 and the binder 21 dropped out of the intermediate molded body 54 due to their own weight. Part of the osmotic salt layer 3 dropped out of the intermediate molded body 54 together with the granular body 20 and the like, and part of the osmotic salt layer 3 remained inside the intermediate molded body 54 (FIG. 6).

(3. Cleaning process)
After the core collapse step, the inside of the intermediate molded body 54 was washed with hot water at 60 ° C. The salt 30 remaining inside the intermediate molded body 54 was dissolved by the hot water and dropped out of the intermediate molded body 54. By this washing step, a hollow molded body 56 was obtained (FIG. 7).

  The inner surface of the obtained molded body 56 was smooth, and insertion of the molding material 53 into the molding core 1 was not observed. Moreover, since the obtained molded object 56 was excellent in dimensional accuracy, it turned out that the shaping | molding core 1 of an Example does not deform | transform even if it shape | molds by high pressure.

  The molding core 1 of the embodiment can be removed from the intermediate molded body simply by knocking and folding the baseboard, knocking the intermediate molded body, and washing the osmotic salt layer remaining inside the intermediate molded body. Therefore, the molding core 1 of the embodiment can be easily removed from the molded body.

  In addition, the molding core 1 of the example is excellent in pressure resistance and hardly deforms even when the molded body is molded at a high pressure. Therefore, according to the molding core 1 of the embodiment, a molded body having excellent dimensional accuracy can be obtained.

It is sectional drawing which represents the core for shaping | molding of an Example typically. It is a principal part enlarged view of FIG. It is explanatory drawing which represents typically the molten salt osmosis | permeation process in the manufacturing method of the molding core of an Example. It is explanatory drawing which represents typically a mode that the molded object is manufactured using the molding core of an Example. It is explanatory drawing which represents typically a mode that the molded object is manufactured using the molding core of an Example. It is explanatory drawing which represents typically a mode that the molded object is manufactured using the molding core of an Example. It is explanatory drawing which represents typically a mode that the molded object is manufactured using the molding core of an Example.

Explanation of symbols

1: Molding core, 2: Core body, 3: Penetration salt layer, 20: Granular body, 21: Binder, 30: Salt

Claims (6)

A molding core for molding a hollow molded body,
A core body formed by bonding particles together with a binder, and a permeation salt layer formed of a salt having a melting point higher than the material of the molded body and formed on a surface layer portion of the core body;
The core for molding has a large number of pores, and the salt penetrates into the pores.   2. The molding core according to claim 1, wherein the mass of the salt is 25% to 45% when the mass of the core body is 100%.   The molding core according to claim 1, wherein the salt comprises at least one selected from potassium chloride, sodium chloride, and sodium carbonate. A molding core for molding a hollow molded body, comprising a core body in which granular bodies are bonded together by a binder, and a salt having a melting point higher than the material of the molded body. The core body has a large number of pores, and the salt is a method for producing a molding core that has entered the pores.
A main body molding step of molding the core main body formed by bonding the granular materials with the binder;
And a molten salt permeation step for infiltrating the molten salt into the surface layer portion of the core body under reduced pressure conditions.   5. The method for manufacturing a molding core according to claim 4, wherein, in the molten salt infiltration step, 25% to 45% of the salt is infiltrated when the mass of the core body is 100%.   The method for producing a molding core according to claim 4, wherein the salt comprises at least one selected from potassium chloride, sodium chloride, and sodium carbonate.

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