KR101527356B1 - Ceramic core And Its Manufacturing Methode - Google Patents

Abstract

The present invention relates to a ceramic core and a manufacturing method thereof. The ceramic core of the present invention comprises ceramic particles; And a glassy metal silicate coating the ceramic particles, the method comprising: a first step of mixing a metal alkoxide, a silica precursor, ceramic particles and a solvent; A second step of filtering and drying the mixture obtained in the first step to produce ceramic particles coated with the metal alkoxide and the silica precursor; A third step of forming a molded body by compressing the ceramic particles produced in the second step; And a fourth step of heat-treating the molded body.
The ceramic core manufacturing method of the present invention dramatically improves the processes applied to the prior art and coating the ceramic particles, which are the starting materials of the ceramic core, with the glassy metal silicate to reduce the content of the low organic binder and the shrinkage and the shape change caused by the heat treatment And the mechanical strength such as high strength and high collapsibility can be improved.

Description

[0001] Ceramic core and its manufacturing method [0002]

The present invention relates to a ceramic core and a manufacturing method thereof. More particularly, the present invention relates to a ceramic core and a method for manufacturing the ceramic core, And a method of manufacturing the same.

Currently, Ceramic Core is an important component for forming the inner space in hollow casting production. It is required not only to directly contact with high temperature molten metal during casting, but also to have high temperature strength to withstand the weight of the molten metal, It is required to have a room temperature and a high temperature strength higher than a certain level.

Conventional ceramic cores are composed of ceramic particles such as zirconia and silica and a mixture of organic compounds such as a polymer material (wax or the like) or a surfactant for improving the compatibility with the ceramic particles or the ceramic particles, A sintering process is indispensably required for the development of strength. However, when sintering, the ceramic core tends to be twisted due to shrinkage, and pores in the core are formed due to vaporization of the organic material.

These problems lead to the breakage of the ceramic core during casting or directly to the failure of the casting product, and the provision of more than necessary strength results in a degradation of the collapsibility after casting. This results in different characteristics depending on the combination ratio of the starting materials, the manufacturing process parameters, and the heat treatment conditions, and thus it is not easy to acquire accurate data for producing the ceramic core suited to the required characteristics.

Therefore, in the present invention, a new ceramic core manufacturing process that overcomes the disadvantages of the conventional ceramic core manufacturing process has been developed, and a new concept of dimensionally stable ceramics having no shrinkage and shape change due to the heat treatment, We are going to make a ceramic core that has a variety of mechanical strengths through new process applications.

[Prior Art Literature]

Korean Patent Publication No. 10-2009-0068846

Korea Patent No. 10-2003-0014828

In view of the above problems of the prior art, the present invention has been made to solve the problems of the prior art by remarkably improving the processes applied to the ceramic core so as to more easily manufacture the ceramic core, and it has a low content of the organic binder and little shrinkage and shape change due to the heat treatment (sintering) Stable ceramic core exhibiting various mechanical strengths such as high strength and high disintegration property, and a process for producing the same.

Disclosure of the Invention The present invention has been made to solve the above-mentioned problems, And a glassy metal silicate coating the ceramic particles.

The ceramic particles may be selected from the group consisting of zirconia, silica and alumina.

The metal may be selected from the group consisting of Na, Mg, K, Ca, Li and Be.

The present invention also relates to a method for manufacturing a semiconductor device, comprising: a first step of mixing a metal alkoxide, a silica precursor, ceramic particles and a solvent; A second step of filtering and drying the product obtained in the first step to produce ceramic particles coated with the metal alkoxide and the silica precursor; A third step of forming a molded body by compressing the ceramic particles produced in the second step; And a fourth step of heat-treating the formed body.

The third step may further include mixing the ceramic particles produced in the second step with an organic binder.

Preferably, the metal alkoxide is represented by MOR, M is an alkali metal or alkaline earth metal, and R is hydrogen or an alkyl group.

The alkyl group may be selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, isopropyl, hexyl and cyclohexyl.

The metal may be selected from the group consisting of Na, Mg, K, Ca, Li and Be.

The content of the metal alkoxide is preferably 1 to 60 parts by weight based on 100 parts by weight of the solvent.

The silica precursor may be selected from the group consisting of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraisopropoxy silane, methoxytriethoxysilane, dimethoxydiethoxysilane, ethoxytrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane, tetramethoxyethylsilane, and tetra ≪ / RTI >

The content of the silica precursor is preferably 1 to 60 parts by weight based on 100 parts by weight of the solvent.

The ceramic particles may be selected from the group consisting of zirconia, silica and alumina.

The solvent may be selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol and cyclohexyl alcohol.

The organic binder may be selected from the group consisting of water-soluble polymers, oil-soluble polymers, or mixtures thereof.

The organic binder may be selected from the group consisting of polyvinyl alcohol, epoxy resin, phenol resin and phenol isocyanate.

The content of the organic binder is preferably 5 to 15 parts by weight based on 100 parts by weight of the mixture of the ceramic particles produced in the second step and the organic binder.

The shaped body may be formed by a method selected from the group consisting of a uniaxial press, a cool isostatic press (CIP), and a hot isostatic press (HIP). More preferably, the molded article can be produced through uniaxial pressing followed by cold isostatic pressing.

The drying is preferably performed at a temperature of 80 to 120 ° C.

The heat treatment is preferably performed at a temperature of 900 to 1000 ° C.

The present invention also provides a ceramic core produced by the manufacturing method of the present invention.

The ceramic core manufacturing method according to the present invention dramatically improves the processes applied in the past and coating the ceramic particles, which are the starting materials of the ceramic cores, with the glassy metal silicate to obtain a low organic binder content, shrinkage and shape change due to heat treatment (sintering) And the mechanical strength such as high strength and high collapsibility can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart schematically showing a process flow of the ceramic core manufacturing method of the present invention. FIG.
2 is a graph showing the results of measurement of fracture strength for Example 1 and Comparative Example 1 in Test Example 1 of the present invention.
3 is a photograph before and after the experiment of dissolution of the ceramic core according to Example 1 in Test Example 2 of the present invention.

Hereinafter, the present invention will be described in detail. In the following description of the present invention, a detailed description of known configurations and functions will be omitted.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and should be construed in accordance with the technical meanings and concepts of the present invention.

The embodiments described in the present specification and the configurations shown in the drawings are preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention and thus various equivalents and modifications Can be.

A method of manufacturing a ceramic core of the present invention comprises: a first step of mixing a metal alkoxide, a silica precursor, ceramic particles and a solvent; A second step of filtering and drying the resultant mixture obtained in the first step to prepare ceramic particles coated with the inorganic metal alkaline compound; A third step of forming a molded body by compressing the ceramic particles produced in the second step; And a fourth step of heat-treating the molded body.

According to the ceramic core manufacturing method of the present invention, the metal alkoxide, the silica precursor, the ceramic particles and the solvent are mixed first.

The ceramic particles may be selected from the group consisting of zirconia, silica and alumina. The metal alkoxide and the silica precursor and the ceramic particles are mixed for about 1 to 60 minutes.

Preferably, the metal alkoxide is represented by MOR, M is an alkali metal or alkaline earth metal, and R is hydrogen or an alkyl group.

The alkyl group may be selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, isopropyl, hexyl and cyclohexyl.

The metal may be selected from the group consisting of Na, Mg, K, Ca, Li and Be.

The content of the metal alkoxide is preferably 1 to 60 parts by weight based on 100 parts by weight of the solvent. If the content of the metal alkoxide is less than the lower limit of the above range, the role as a network modifier is reduced to increase the glass transition temperature of the silica. If the content exceeds the upper limit of the above range, not only the formation of silica network structure is inhibited, Is not preferable because the mechanical strength of the ceramic core is not sufficiently manifested.

The silica precursor may be selected from the group consisting of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraisopropoxy silane, methoxytriethoxysilane, dimethoxydiethoxysilane, ethoxytrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane, tetramethoxyethylsilane, and tetra ≪ / RTI >

The content of the silica precursor is preferably 1 to 60 parts by weight based on 100 parts by weight of the solvent. When the content of the silica precursor is less than the lower limit of the above range, the vitrification reaction by silica hardly occurs. When the upper limit of the above range is exceeded, the glass transition temperature of the silica is increased to deteriorate the mechanical strength of the ceramic core I can not.

The solvent may be selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol and cyclohexyl alcohol.

Next, the ceramic particles mixed with the metal alkoxide and the silica precursor are filtered and dried to prepare a ceramic core coated with the metal alkoxide and the silica precursor.

The coating process of the ceramic particles is performed through a hydrolysis reaction and a condensation reaction as described below.

[Reaction Scheme 1] Hydrolysis reaction

MOR + H ₂ O → ROH + MOH

[Reaction Scheme 2] Condensation reaction

_{nSi (OR) 4 + 4nH 2} O → nSiO 2 + 4nROH

In the above reaction schemes 1 and 2, MOR, ROH, MOH, Si (OR) ₄ and SiO ₂ mean metal alkoxide, alcohol, metal hydroxide, alkyl silicate and silica, respectively. The metal alkoxide and the alkyl silicate are hydrolyzed with water, metal hydroxide, silica and alcohol. In particular, the alkyl silicate is subjected to a condensation reaction in which the silanol (SiOH) molecules generated through the hydrolysis reaction simultaneously with the hydrolysis reaction are reacted with each other, - Gel reaction to produce silica.

The drying is carried out by allowing the ceramic particles to stand at 80 to 120 DEG C for 0.5 to 3 hours. The drying includes a step of drying the alcohol produced during the solvent or the hydrolysis reaction.

If the temperature is below the lower limit of the above range, there is a problem that the alcohol does not sufficiently volatilize and the drying time becomes longer than necessary. When the upper limit of the above range is exceeded, the metal alkoxide and the silica precursor are vaporized or decomposed The vitrification reaction efficiency is reduced, which is not preferable.

The method may further include mixing the ceramic particles with an organic binder.

The organic binder may be selected from the group consisting of a water-soluble polymer, a liposoluble polymer, or a mixture thereof. Specific examples of the organic binder include polyvinyl alcohol, epoxy resin, phenol resin and phenol isocyanate.

The content of the organic binder is preferably 5 to 15 parts by weight based on 100 parts by weight of the mixture of the ceramic particles produced in the second step and the organic binder.

If the content of the organic semi-binder is below the lower limit of the above range, there is a problem in the formability of the ceramic core. If the content exceeds the upper limit of the above range, pores in the core are formed due to vaporization of the organic material.

Next, the formed mixture is compressed to form a formed body.

The molding of the mixture for forming the molded body in this step may be carried out by a method selected from the group consisting of uniaxial press, cool isostatic press (CIP) and hot isostatic press (HIP) More preferably, the uniaxial pressing is followed by cold pressing to produce a molded body.

Finally, the molded body is heat-treated.

The heat treatment process is a process for forming a vitreous metal silicate on the surface of the ceramic particles, and the strength of the ceramic core is expressed through vitrification. Wherein the glassy metal silicate is the product obtained through the vitrification of the metal alkoxide and the silica precursor.

[Reaction Scheme 3]

SiO ₂ + 2MOH SiO ₂ M ₂ O + H ₂ O

The heat treatment is preferably performed at a temperature of 900 to 1000 ° C.

If the temperature is below the lower limit of the above range, there is a problem that the conversion of the glassy metal silicate to the glassyiness decreases. If the temperature exceeds the upper limit of the above range, the vaporization and decomposition of the glassy metal silicate is promoted, Which is undesirable.

The metal of the vitreous metal silicate may be selected from the group consisting of Na, Mg, K, Ca, Li and Be, for example, as an alkali metal or an alkaline earth metal. However, it is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for explaining the present invention in more detail. According to the gist of the present invention,

It will be apparent to those skilled in the art that the scope of the invention is not limited by these examples.

Example  One

The starting ceramic particles were mixed with the composition shown in Table 1 below and mixed with an alkali metal compound consisting of a silica precursor (tetraethylorthosilicate) and a metal alkoxide (sodium methoxide) as shown in Table 2, For 1 hour to prepare ceramic particles coated with a glassy metal silicate. Then, the surface-coated ceramic particles were added with 10wt% of polyvinyl alcohol (PVA) used as an organic binder, uniaxially pressed, And the formed body is heat-treated at 1000 캜 for one hour to prepare a ceramic core test piece.

Composition table according to starting ceramic particle size Starting ceramic particles content ( wt %) Zircon Flour 2 10 Zircon Flour 3 10 Fused silica 10 Silica powder (25 탆) 10 Silica powder (45 탆) 25 Silica powder (149 탆) 25 Silica powder (100 ~ 200㎛) 10

Composition ratio of inorganic coating Tetraethylorthosilicate
( wt % ( mol  %)) Sodium methoxide
( wt % ( mol  %)) Isobutyl alcohol
( wt % ( mol  %)) 38 (0.18) 56 (1.5) 6 (0.08)

Comparative Example  One

The mixture of the starting ceramic particles mixed with the composition of Table 1 and the organic compound of Table 3 is uniaxially pressed and then pressed by cold or the like to form a molded body and heat treated at 1000 ° C for 1 hour to prepare an existing ceramic core specimen.

Organic Compound Composition Ratio for Making Conventional Ceramic Core Conventional binder Rate  ( wt . %) Paraffin Wax (solid) 80 ~ 85 Micro Crystal Was (solid) 7 ~ 9 Oleic Acid (liquid) 5 ~ 7 Stearic Acid (solid) 1-3 Total 100

Test Example  1: Fracture strength test

The fracture strength of the ceramic core specimens prepared in Example 1 and Comparative Example 1 was measured and shown in Fig. Here, the numerals 1 and 2 in FIG. 2 indicate before and after the heat treatment, respectively.

The fracture strength is a mean value of five measurements at room temperature at a rate of 0.5 mm / min in a 4-point bending mode using a universal testing machine.

Referring to FIG. 2, in the case of the ceramic core test piece prepared in Example 1, the inorganic binder was coated on the base particles, and the coating efficiency of the inorganic binder on the surface of the base particles and the glass phase well formed on the particle interface Of 16 MPa, which is the strength of 4 MPa or more, which is the fracture strength of the ceramic core.

2, the strength of the ceramic core test piece before the heat treatment was maintained only with the organic binder, but the strength rapidly increased due to the glass phase converted from the inorganic binder after the heat treatment.

Test Example  2: Elution property  exam

FIG. 3 shows a photograph of a dissolution test (concentration of 40 wt%) in the sodium hydroxide solution of the ceramic core test piece of Example 1 prepared according to the production method of the present invention. Here, it means (a) before the elution test and (b) after 3 hours of the elution test.

As a result of the degradability of the ceramic core made by the inorganic coating agent in the sodium hydroxide solution, it was found that the glassy substance of the sodium silicate produced by drying and heat treatment was completely decomposed in the sodium hydroxide solution.

For the ceramic core, a large amount of organic binder should be used at room temperature and sintering at high temperature in order to exhibit strength at room temperature and high temperature. The ceramic cores are impregnated with a sodium hydroxide solution after casting to decompose them, and hollow cavities can be made using the space of the disassembled ceramic core. From the above results, it was found that a ceramic core having excellent mechanical strength and excellent elution was produced.

Therefore, by coating the surface of the ceramic particles with a glassy metal silicate in place of the organic binder added for maintaining the shape of the conventional ceramic core, an environmentally friendly ceramic core having a low organic binder content and high heat resistance can be produced at a low production cost .

As described above, preferred embodiments of the present invention have been disclosed in the present specification and drawings, and although specific terms have been used, they have been used only in a general sense to easily describe the technical contents of the present invention and to facilitate understanding of the invention , And are not intended to limit the scope of the present invention.

It is to be understood by those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

Claims (21)

delete delete delete A first step of mixing the metal alkoxide, the silica precursor, the ceramic particles and the solvent;
A second step of filtering and drying the product obtained in the first step to produce ceramic particles coated with the metal alkoxide and the silica precursor;
A third step of forming a molded body by compressing the ceramic particles produced in the second step; And a fourth step of heat-treating the formed body,
The third step may further include mixing the ceramic particles produced in the second step with an organic binder,
Wherein the content of the organic binder is 5 to 15 parts by weight based on 100 parts by weight of the mixture of the ceramic particles produced in the second step and the organic binder.
delete 5. The method of claim 4,
Wherein the metal alkoxide is represented by MOR, M is an alkali metal or an alkaline earth metal, and R is hydrogen or an alkyl group.
The method according to claim 6,
Wherein the alkyl group is selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, isopropyl, hexyl and cyclohexyl.
The method according to claim 6,
Wherein the metal is selected from the group consisting of Na, Mg, K, Ca, Li and Be.
5. The method of claim 4,
Wherein the content of the metal alkoxide is 1 to 60 parts by weight based on 100 parts by weight of the solvent.
5. The method of claim 4,
The silica precursor may be selected from the group consisting of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraisopropoxy silane, methoxytriethoxysilane, dimethoxydiethoxysilane, ethoxytrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane, tetramethoxyethylsilane, and tetra ≪ RTI ID = 0.0 > ethoxymethyl < / RTI > silane.
5. The method of claim 4,
Wherein the content of the silica precursor is 1 to 60 parts by weight based on 100 parts by weight of the solvent.
5. The method of claim 4,
Wherein the ceramic particles are selected from the group consisting of zirconia, silica, and alumina.
5. The method of claim 4,
Wherein the solvent is selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol and cyclohexyl alcohol.
5. The method of claim 4,
Wherein the organic binder is selected from the group consisting of water-soluble polymers, oil-soluble polymers, and mixtures thereof.
5. The method of claim 4,
Wherein the organic binder is selected from the group consisting of polyvinyl alcohol, epoxy resin, phenolic resin, and phenol isocyanate.
delete 5. The method of claim 4,
Wherein the shaped body is formed by a method selected from the group consisting of a uniaxial press, a cool isostatic press (CIP), and a hot isostatic press (HIP).
18. The method of claim 17,
Wherein the shaped body is compressed and formed by cold pressing after uniaxial pressing.
5. The method of claim 4,
Wherein the drying is performed at a temperature of 80 to 120 ° C.
5. The method of claim 4,
Wherein the heat treatment is performed at a temperature of 900 to 1000 占 폚.
A ceramic core produced by the manufacturing method of any one of claims 4, 6 to 15, and 17 to 20.

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