KR101772027B1 - Mold for Sand Casting and Dry Method for Preparing the Same - Google Patents
Mold for Sand Casting and Dry Method for Preparing the Same Download PDFInfo
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- KR101772027B1 KR101772027B1 KR1020150088660A KR20150088660A KR101772027B1 KR 101772027 B1 KR101772027 B1 KR 101772027B1 KR 1020150088660 A KR1020150088660 A KR 1020150088660A KR 20150088660 A KR20150088660 A KR 20150088660A KR 101772027 B1 KR101772027 B1 KR 101772027B1
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- KR
- South Korea
- Prior art keywords
- casting
- mold
- inorganic binder
- drying
- foundry sand
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/167—Mixtures of inorganic and organic binding agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
Abstract
The present invention relates to a casting mold for casting and a method for producing the casting mold, comprising: a first step of mixing a casting mold particle and an inorganic binder precursor to produce a mixed solution; A second step of drying the mixed solution to prepare a molding sand particle coated with an inorganic binder precursor; A third step of drying the coated foundry sand particles; A fourth step of mixing the foundry sand particles coated with the inorganic binder and the organic binder; A fifth step of drying a mixture of the foundry sand particles and the organic binder to form a molded body; And a sixth step of heat treating the formed body.
Description
BACKGROUND OF THE
In general, the conventional casting mold is an organic binder called resin. The mixture is poured into a mold to mold the casting mold and then cast into a molten metal. This mold casting process is simple and relatively low in production cost. It is widely used in industry.
However, such conventional casting molds are disadvantageous in that, due to the decomposition of the organic binder due to the high-temperature molten metal, the molds are collapsed during casting, defects are produced in the castings produced by the occurrence of blowholes, Stability and environmental pollution, and the thickness of the mold must be increased in order to maintain the shape of the mold at the time of casting.
Particularly, casting by casting method has a thickness limit of 5 mm, and shrinkage defect occurs in casting due to poor flowability of molten metal.
Precise casting techniques are therefore used to produce castings of thin wall (thin wall). However, since 8 to 10 coating processes and subsequent subsequent processes, i.e., drying processes for each coating, must be applied in the production of molds, There is a problem in that the productivity is low and the manufacturing cost is increased according to one manufacturing process, the size limitation of the casting product and the environmental pollution problem caused by the waste of the casting product.
Therefore, it is necessary to develop a new mold manufacturing process in order to simplify the process and enhance the price competitiveness by improving the performance.
The description of the mold for casting mold and the manufacturing method thereof as described above is described in detail in the following prior art documents, so that detailed description thereof will be omitted.
SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide an inorganic binder conversion process for a sand casting process, which increases the fluidity of a molten metal by heat treatment at a high temperature, And to provide a mold for casting molds having high dimensional stability and a method of manufacturing the same.
Another object of the present invention is to provide a casting die casting mold capable of increasing the firing strength according to the addition of an inorganic binder and a method for producing the same.
The above-mentioned object can be accomplished by a method for producing a mixed solution, comprising: a first step of mixing a foundry particle and an inorganic binder precursor to prepare a mixed solution; A second step of drying the mixed solution to prepare a molding sand particle coated with an inorganic binder precursor; A third step of drying the coated foundry sand particles; A fourth step of mixing the foundry sand particles coated with the inorganic binder and the organic binder; A fifth step of drying a mixture of the foundry sand particles and the organic binder to form a molded body; And a sixth step of heat treating the formed body.
The foundry sand may be made of any one of natural or artificial yarns having various particle sizes or a mixture thereof, and mullite-based particles having high heat resistance may be mixed with the foundry sand.
Further, the organic binder may be selected from water-soluble or oil-soluble polymers, and the inorganic binder may be a mixture of the metal alkoxide and the silica precursor.
The metal alkoxide of such an inorganic binder may be represented by MOR, M is an alkali metal or an alkaline earth metal, R may be hydrogen or an alkyl group, and the metal is selected from the group consisting of Na, Mg, K, Ca, And the alkyl group may be any one selected from the group consisting of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an isopropyl group, a hexyl group and a cyclohexyl group or a combination thereof have.
The silica precursor may be any one selected from the group consisting of silicates and siloxanes, or a combination thereof.
The drying of the organic binder may be performed at a temperature of 100 to 200 ° C, the drying of the inorganic binder may be performed at a temperature of 80 to 120 ° C, and the heat treatment may be performed at a temperature of 900 to 1000 ° C.
The casting mold for sand casting can be manufactured by the above-mentioned manufacturing method of sand casting casting mold.
According to the mold for casting mold of the present invention and the method for producing the mold, the inorganic binder is applied to the casting mold to manufacture the casting mold for casting mold, thereby improving the strength of the casting mold and reducing the production cost. Can be produced.
The mold for casting molds manufactured as in the present invention has the effect of improving properties such as high strength, dimensional stability, and high efficiency.
Further, according to the present invention, it is possible to manufacture a casting product having a complicated shape, and thus it is possible to manufacture various industrial device parts.
FIG. 1 is a process drawing of a mold casting mold by a dry process according to the present invention.
Fig. 2 shows the size and shape of the foundry sand used in the casting mold for casting according to the present invention.
3 is a graph showing the fracture strength for Comparative Example 1 of the present invention.
4 is a graph showing the results of measurement of fracture strength in Example 1 in Test Example 1 of the present invention.
Fig. 5 is a view showing a fractured section of a mold specimen according to the first embodiment of the present invention as seen from a scanning microscope. Fig.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The terms used in the present invention are defined in consideration of the functions of the present invention and may vary depending on the intention or custom of the user or the operator. Therefore, the definitions of these terms are meant to be in accordance with the technical aspects of the present invention As well as the other.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention and are incorporated in and constitute a part of this specification. Embodiments that include components replaceable as equivalents in the components may be included within the scope of the present invention.
In addition, optional terms in the following embodiments are used to distinguish one element from another element, and the element is not limited by the terms. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of related arts which may unnecessarily obscure the gist of the present invention will be omitted.
As shown in FIG. 1, the casting mold for casting mold according to the present invention comprises a first step (S100) of mixing a foundry particle and an inorganic binder precursor to prepare a mixed solution, a step of drying the mixed solution to form an inorganic binder precursor A second step S200 of producing a molding sand particle, a third step S300 of drying the foundry sand particles, a fourth step S400 of mixing the foundry particle coated with the inorganic binder and the organic binder, A fifth step (S500) of drying a mixture of particles and an organic binder to form a molded article, and a sixth step (S600) of heat-treating the formed article.
In the mold for casting molds produced by the dry process according to the present invention, since the loss of the inorganic binder due to the vaporization of the organic binder is reduced by coating the foundry sand with the inorganic binder first and then forming the molded body with the organic binder, Strength and dimensional stability can be imparted.
That is, the mold for sand casting by the wet process is a step of impregnating the inorganic binder with a molding body made of a molding sand and an organic binder, and a step of impregnating the inorganic binder coated with the organic binder by burning the organic binder coated on the surface of the foundry sand, In this embodiment, in order to reduce the loss of the inorganic binder, a dry process is performed in which a foundry sand is first coated with an inorganic binder, and then an organic binder is mixed to produce a formed body. The loss of the inorganic binder due to the vaporization of the organic binder can be reduced. Therefore, it may be effective to manufacture a small casting by a wet process and a large casting by a dry process.
The above-mentioned foundry sand particles (starting particles) are silica-based foundry sand having different particle sizes. Any of natural or artificial yarns having various particle sizes may be used singly, as in FIG. 2, Can be used.
In addition, mullite-based particles having high heat resistance may be mixed with the foundry sand particles as described above. Thus, the mullite-based particles mixed with the foundry sand are much superior in mechanical strength to casting sand, and have lower production cost than the casting process for precision casting and have a high competitive power.
On the other hand, the inorganic binder used for imparting plasticity strength and dimensional stability is an inorganic alkali metal mixture, which is synthesized as a metal alkoxide and a silica precursor, and is subjected to a hydrolysis reaction and condensation reaction as described below, .
(1) Hydrolysis and condensation reaction
[Reaction Scheme 1]
MOR + H 2 O → ROH + MOH
[Reaction Scheme 2]
nSi (OR) 4 + 4nH 2 O →
In this reaction, MOR, ROH, MOH, Si (OR) 4 and SiO 2 are named metal alkoxide, alcohol, metal hydroxide, alkyl silicate and silica, respectively. The metal alkoxide and alkyl silicate are hydrolyzed by water to metal hydroxide, silica and alcohol. In particular, the alkyl silicate is subjected to a condensation reaction in which silanol (SiOH) molecules generated through hydrolysis and reaction simultaneously react with each other, Gel reaction to produce silica.
The generated silica and hydroxide metal are generated on the surface of the ceramic core particles by the vitreous of the metal silicate through a heat treatment at a high temperature (over 900 ° C.), and the plastic strength of the ceramic core is expressed by the vitreous do.
(2) vitrification reaction
SiO 2 + 2MOH SiO 2 M 2 O + H 2 O
The mold starting particles mixed with the inorganic binder and molding sand are preferably mixed for about 1 to 60 minutes.
Preferably, the metal alkoxide is represented by MOR, M is an alkali metal or an alkaline earth metal, R is hydrogen or an alkyl group, and the metal is selected from the group consisting of Na, Mg, K, Ca, And the alkyl group may be any one selected from the group consisting of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an isopropyl group, a hexyl group and a cyclohexyl group or a combination thereof have.
In particular, as described above, the content of the metal alkoxide constituting the inorganic binder is preferably 50 to 60 parts by weight based on 100 parts by weight of the solvent, that is, the inorganic binder (see Table 2). When the content of the metal alkoxide is below the lower limit of the above range, the function as a network modifier is reduced to increase the glass transition temperature of the silica. When the upper limit of the above range is exceeded, the silica network structure And the mechanical strength of the mold is not sufficiently developed due to the whitening phenomenon, which is not preferable.
The silica precursor may be selected from the group consisting of silicate and siloxane series, or a combination thereof.
The content of the silica precursor is preferably 30 to 40 parts by weight based on 100 parts by weight of the solvent, that is, the inorganic binder (see Table 2). 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 increase the mechanical strength Which is undesirable.
Next, the molding sand mixed with the inorganic binder (starting powder) is filtered, dried and coated with a binder.
At this time, drying of the inorganic binder is carried out at 80 to 120 DEG C for 0.5 to 3 hours, and this drying includes a step of drying the alcohol produced during the hydrolysis reaction.
When the drying temperature of the inorganic binder is less than the lower limit of the above range, the alcohol does not sufficiently volatilize and the drying time becomes longer than necessary. On the other hand, when the drying temperature exceeds the upper limit of the above range, The silica precursor is vaporized or decomposed to reduce the vitrification reaction efficiency.
The molecular weight and content of the organic binder may be selected in accordance with the type of the casting sand (starting powder) to increase the strength of the mold, and the organic binder may be selected from the group consisting of water- It is preferable to use them differently. For example, the content of the organic binder is preferably 2.34 wt% (wt%) based on the sum of the foundry particles and the organic binder as shown in Table 1.
Particularly, when the content of the organic binder is more or less than the optimal content, the contact surface between the foundry sand (starting powder) particles decreases, and the formation of vitreous between particles adversely affects. The contact between the particles is caused by the entanglement of the polymer chains, which are organic binders, and the contact surface varies depending on the molecular weight.
If the drying temperature of the organic binder is less than the lower limit of the above range, the drying time becomes longer than necessary. On the other hand, the upper limit of the above range It is not preferable because the vitrification reaction efficiency is decreased.
The dried product is heat-treated. The heat treatment process is a process for producing a glassy metal silicate on the surface of a casting sand (starting powder), and the strength of the mold is expressed by vitrification through vitrification. Here, the vitreous is a product obtained through the reaction of a metal alkoxide and a silica precursor with a metal silicate.
If the heat treatment temperature is below the lower limit of the above range, the conversion of the glassy metal silicate to the vitreous may be reduced. If the upper limit of the above range is exceeded, The vaporization and decomposition of the glassy metal silicate is promoted and the vitrification efficiency is reduced, which is not preferable.
The metal of the vitreous metal silicate may be selected from the group consisting of Na, Mg, K, Ca, Li, and Be, but is not limited thereto.
Hereinafter, embodiments of the present invention will be described in detail. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention in more detail and that the scope of the present invention is not limited by these embodiments in accordance with the gist of the present invention .
Example 1
(Starting powder) particles were mixed with the composition shown in the following Table 1 and mixed with an inorganic binder composed of a metal alkoxide (sodium methoxide) and a silica precursor (tetraethylorthosilicate) as shown in Table 2, And dried at 100 ° C. for 1 hour to prepare mold powder particles coated with an inorganic binder and then mixed with an organic binder (PVA) (0.58 wt%, 2.34 wt%, 9.36 wt%) to prepare a ceramic core compact. The molded product is heat-treated at 1000 ° C for 1 hour to prepare a test piece for mold for casting mold (dry process).
[Table 1] Composition table (drying process) according to type of casting mold casting (starting powder), organic binder molecular weight and content
[Table 2] Composition of inorganic binder
Comparative Example 1
A molded body was formed from a mixture of foundry sand and resin-based organic binder blended with the composition shown in Table 3, and heat treated at 1000 ° C for 1 hour to prepare a mold for casting molds.
[Table 3] Composition for existing casting mold casting
Test Example 1: Fracture strength measurement test and microstructure of mold section
The fracture strength of the test pieces of molds for casting moldings prepared in Examples 1 and 2 and Comparative Example 1 was measured and shown in FIG. 3 to FIG.
The fracture strength is the average value measured five times 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. 3, the mold test piece prepared by the existing sand mold casting process using the resin of Comparative Example 1, the plastic strength after immersion in the inorganic binder was measured at 1 MPa.
On the other hand, as shown in FIG. 4, in the case of the mold test piece manufactured by artificial yarn No. 7 of the dry process, since the inorganic binder is coated on the foundry particle, the high coating efficiency on the particle surface and the glass phase (See FIG. 5). After heat treatment at 1000 占 폚 for 1 hour, the strength was improved to about 6.5 MPa, which is the strength of the mold made of beads which are heat resistant particles.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the present invention. It is obvious that the modification or improvement is possible.
It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
S100: first step S200: second step
S300: third step S400: fourth step
S500: fifth step S600: sixth step
Claims (13)
A second step of drying the mixed solution to prepare a molding sand particle coated with an inorganic binder precursor;
A third step of drying the coated foundry sand particles;
A fourth step of mixing the foundry sand particles coated with the inorganic binder and the organic binder;
A fifth step of drying a mixture of the foundry sand particles and the organic binder to form a molded body; And
And a sixth step of heat-treating the formed body,
Wherein the inorganic binder precursor is a mixture of 50 to 60 parts by weight of a metal alkoxide and 30 to 40 parts by weight of a silica precursor based on 100 parts by weight of the inorganic binder precursor.
Wherein the molding sand is made of any one of natural or artificial yarns having various particle sizes or a mixture thereof.
A method for manufacturing a mold for casting dry sand casting which mixes mullite-based particles having a high heat resistance with a foundry sand.
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.
Wherein the silica precursor comprises any one selected from the group consisting of silicates and siloxanes, or a combination thereof.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020150088660A KR101772027B1 (en) | 2015-06-22 | 2015-06-22 | Mold for Sand Casting and Dry Method for Preparing the Same |
| PCT/KR2015/006795 WO2016208795A1 (en) | 2015-06-22 | 2015-07-02 | Sand casting mold and dry preparation method for same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
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| KR1020150088660A KR101772027B1 (en) | 2015-06-22 | 2015-06-22 | Mold for Sand Casting and Dry Method for Preparing the Same |
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| KR20160150529A KR20160150529A (en) | 2016-12-30 |
| KR101772027B1 true KR101772027B1 (en) | 2017-08-28 |
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| WO (1) | WO2016208795A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102183487B1 (en) | 2019-07-08 | 2020-11-26 | 성보공업주식회사 | Continuous vertical type centrifugal casting |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101995007B1 (en) * | 2017-11-22 | 2019-07-02 | 창원대학교 산학협력단 | Fabricating method for ceramic core using double coating process |
| KR102156549B1 (en) * | 2018-07-02 | 2020-09-16 | 창원대학교 산학협력단 | Alumina sintered body and manufacturing method thereof |
| KR102107521B1 (en) * | 2019-07-19 | 2020-05-07 | 창원대학교 산학협력단 | Method for manufacturing ceramic core having high-strength by combining dry and photopolymerization processes |
| KR102242823B1 (en) * | 2019-07-26 | 2021-04-21 | 천지산업주식회사 | Casting method for high temperature parts having single crystal using ceramic core applied inorganic binder |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008307566A (en) * | 2007-06-14 | 2008-12-25 | Japan Steel Works Ltd:The | Casting sand and mold for casting |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000271698A (en) * | 1999-03-29 | 2000-10-03 | Ritsumeikan | Binder for molding sand and manufacture thereof, regenerate-recovering method, molding sand and manufacture thereof and mold and molding method and shake-out method thereof |
| GB0026902D0 (en) * | 2000-11-03 | 2000-12-20 | Foseco Int | Machinable body and casting process |
| KR100942924B1 (en) | 2007-12-28 | 2010-02-22 | 한국생산기술연구원 | Method and apparatus for manufacturing mold for sand casting |
| KR101298840B1 (en) * | 2009-07-10 | 2013-08-23 | 창원대학교 산학협력단 | A Mold and A Mold Manufacturing Method |
| JP5755911B2 (en) * | 2010-03-18 | 2015-07-29 | 花王株式会社 | Binder composition for mold making |
| KR101287146B1 (en) * | 2011-01-20 | 2013-07-17 | 현대메티아 주식회사 | A Bead, A Mold, A Product manufactured by A Mold, A Bead Manufacturing Method and A Mold Manufacturing Method by Dual-coating Process |
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- 2015-06-22 KR KR1020150088660A patent/KR101772027B1/en active IP Right Grant
- 2015-07-02 WO PCT/KR2015/006795 patent/WO2016208795A1/en active Application Filing
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008307566A (en) * | 2007-06-14 | 2008-12-25 | Japan Steel Works Ltd:The | Casting sand and mold for casting |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102183487B1 (en) | 2019-07-08 | 2020-11-26 | 성보공업주식회사 | Continuous vertical type centrifugal casting |
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| KR20160150529A (en) | 2016-12-30 |
| WO2016208795A1 (en) | 2016-12-29 |
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