KR101287146B1 - A Bead, A Mold, A Product manufactured by A Mold, A Bead Manufacturing Method and A Mold Manufacturing Method by Dual-coating Process - Google Patents

Abstract

The present invention relates to a mold material, a mold, a method for producing a mold material and a method for producing a mold through a double coating process, the method of manufacturing a mold material, the composition is, by coating a starting powder consisting of alumina and silica with a metal alkoxide A first step of forming a first layer, a second step of forming a second layer by coating with a silica precursor and a third step of mixing the coated powder with an organic binder, and a fourth step of compressing the mixture into a molded body It may be configured to include a step, and five steps of heat-treating the molded body.

Description

A method for manufacturing mold materials, molds, mold products, molding materials through a double coating process and a method for manufacturing molds (A Bead, A Mold, A Product manufactured by A Mold, A Bead Manufacturing Method and A Mold Manufacturing Method by Dual-coating Process}

The present invention relates to a mold material, a mold, a method for manufacturing a mold material and a method for manufacturing a mold, and more particularly, by improving the existing mold manufacturing process, a double coating capable of producing a mold having a more efficient manufacturing process and excellent physical properties. It relates to a mold material, a mold, a method for producing a mold material and a method for producing a mold through the process.

Current molds are manufactured by a convert mold process with a relatively low heat treatment temperature (above 900), good mechanical properties and thermal stability, good disintegration and dimensional stability, and a relatively short process time. It is used to manufacture refractory molds for casting parts in the automobile and aviation industries. The convert mold process is divided into the following six main processes.

(1) Preparation of Starting Powder Coated with Organic Binder

(2) molding the starting powder of (1) into 200 starting mold

(3) immersion in precursor mixture (aqueous solution) containing inorganic binder

(4) primary mold drying of the above (3)

(5) secondary mold drying of the above (4)

(6) mold 1000 heat treatment of the above (5)

The convert mold process undergoes a hydrolysis reaction and a substitution reaction during the above process.

(1) hydrolysis reaction

NaOR + H ₂ O → ROH + NaOH

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

NaOR , ROH , NaOH , Si ( OR ) ₄ and SiO ₂ in the reaction Are named sodium alkoxides, alcohols, sodium hydroxide, alkyl silicates, silicates, respectively, and the sodium alkoxide used is one selected from alkali metal alkoxides. Sodium alkoxides and alkyl silicates are hydrolyzed by water to sodium hydroxide, silica and alcohols. In particular, alkyl silicates are condensation reactions of silanol (SiOH) molecules produced through hydrolysis simultaneously with hydrolysis. The gel reaction produces silicates.

(2) substitution reaction

2NaOH + SiO ₂ → Na ₂ OSiO ₂ + H ₂ O

Sodium silicate (silicate) is synthesized by reaction of sodium hydroxide with silica at about 1000 temperature. Sodium hydroxide used in the reaction was used as a network modifier to easily produce a glass phase. In addition, during the reaction, all of the organic binder coated on the surface of the starting powder (bead bead) consisting of silica sand and alumina is burned. Through this process, the organic binder is replaced with an inorganic binder to prepare a mold that can withstand the high temperature (1500-1600) melt casting.

However, the above-described prior art has the following problems.

The mold formed by the organic binder is immersed in the binder (inorganic binder) in which the metal alkoxide and the silica precursor are mixed, so that the inorganic binder is biased to one side of the mold, and the metal alkoxide and the silica precursor are uniformly mixed. Otherwise, not only the conversion efficiency to the inorganic binder is reduced, but also the glass phase is not uniformly coated on the mold surface, which causes defects. In addition, the conventional convert mold process is a process of replacing the inorganic binder by the combustion of the organic binder coated on the surface of the starting powder, the loss of the inorganic binder may occur in this combustion process.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and not only to make the precursor of the inorganic binder uniformly coated on the starting powder, but also to provide a mold having a high glass phase conversion efficiency and a low loss rate of the inorganic binder. It is to provide a mold material and a mold manufacturing method that can be produced.

According to a feature of the present invention for achieving the above object, the present invention provides a method for producing a mold material, the first step of forming a first layer by coating a starting powder consisting of alumina and silica with a metal alkoxide, and A second step of coating a precursor to form a second layer, a third step of mixing the coated powder with an organic binder, a fourth step of compressing the mixture into a molded body, and a five step of heat treating the molded body. Can be configured.

In addition, another embodiment of the method for producing a mold of the present invention, the first step of forming a first layer by coating the starting powder with a silica precursor, the second step of forming a second layer by coating with a metal alkoxide and the And a third step of mixing the coated powder with an organic binder, a fourth step of compressing the mixture into a molded body, and a five step of heat treating the molded body.

Steps 1 and 2 may be characterized by having a mixing time of the silica precursor or the metal alkoxide with the starting powder within 1 minute to 1 hour.

The first step may be characterized in that it comprises a drying process for more than 0.5 hours at 80 to 200 ℃ or more.

The second step may be characterized by including a drying process for more than 0.5 hours at 80 to 200 ℃ or more.

The silica precursor may be characterized by including any one or more of a monomolecular silicate precursor and a polymer siloxane precursor. In more detail, the silica precursor may be composed of any one or more of polydimethyl siloxane (PDMS) or tetraethoxysilane (TEOS).

The metal alkoxide may be characterized by the following chemical formula.

M-O-R (M: alkali metal, R: hydrogen, alkyl group)

The organic binder of the three steps may be composed of a fat-soluble binder and a water-soluble binder.

In addition, after the three steps may be characterized by including a drying process for more than 0.5 hours at 80 to 200 ℃ or more.

The pressurization temperature of the molded body in the fourth step may be molded at all temperatures below the boiling point of the silica precursor, the metal alkoxide, or the organic binder.

Before the drying process of the first and second steps, any one of a method of leaving the molded body in the air for the hydrolysis reaction or a method of mixing water may be further added.

In the mold material, the mold, the mold manufacturing method and the manufacturing method of the mold according to the present invention has the following effects.

By coating the metal alkoxide and the silica precursor with different layers, the metal salt and silica can be uniformly coated on the surface of the mold, thereby reducing the occurrence of defects and the high glass phase conversion of the precursor compared to the casting products by the conventional mold making method. It is effective to make good quality castings with good physical properties with efficiency. In addition, it is possible to reduce the loss of the inorganic binder generated in the process of replacing the organic binder with the inorganic binder in the conventional mold fabrication process.

1 is a flow chart showing a first embodiment of a method for manufacturing a mold according to the present invention.
Figure 2 is a flow chart showing a second embodiment of a method of manufacturing a mold according to the present invention.
FIG. 3 is a diagram illustrating a fracture cross-section of a mold manufactured by a conventional mold manufacturing process and the mold manufacturing process according to the first and second embodiments of the present invention in the form of a scanning electron microscope. (As a silica precursor, tetraethyl orthosilicate (tetraethyl orthsilicate (TEOS) as the metal alkoxide using sodium methoxide (NaOMe).
Figure 4 is a graph showing the fracture strength of the mold produced by the existing mold manufacturing process and the mold manufacturing process of the first and second embodiments of the present invention.
5 is a diagram of a thread-shaped cast product using a mold produced by the existing mold manufacturing process and the mold manufacturing process of the first embodiment of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other It is to be understood that the present invention does not exclude the possibility of the presence or the addition of features, numbers, steps, operations, components, parts, or a combination thereof.

Hereinafter, a method of manufacturing a refractory mold material, a mold and a mold according to the present invention will be described in detail.

The method for manufacturing the refractory mold according to the present invention has various embodiments, but the present application describes a representative embodiment, and embodiments of various manufacturing processes can be manufactured based on the processes listed in the above-mentioned problem solving means. .

As shown in FIG. 1, the first embodiment includes a first step of forming a first layer by coating a starting powder composed of alumina and silica with a metal alkoxide, and coating with a silica precursor. A second step of forming a second layer and a third step of mixing the coated powder with an organic binder, a fourth step of compressing the mixture into a molded body, and a five step of heat treating the molded body. have.

In addition, as shown in FIG. 2, the second embodiment of the manufacturing process of the mold includes a first step of forming a first layer by coating a starting powder with a silica precursor and a second layer by coating with a metal alkoxide. It may comprise a second step of forming and a third step of mixing the coated powder with an organic binder, a fourth step of compressing the mixture into a molded body, and a five step of heat treatment of the molded body.

First, in order to manufacture the refractory mold according to the present invention, a mold material must be manufactured. In order to prepare the mold material, powder is required. The powder may be made of various materials, for example, bead of silica (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). Of course, it may be composed of beads of a composition in which silica and aluminum oxide are mixed in a proportion.

The silica precursors described above include, but are not limited to, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraisopropoxy silane, methoxytriethoxysilane, dimethoxydiethoxysilane, Methyltrimethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyidethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane, and the like. Tetramethoxyethylsilane, tetraethoxymethylsilane, and the like are used. As the polysiloxane compound of the polymer form newly used in the present invention, diorganodichlorosilane, dimethyldichlorosilane, ethylmethyldichlorosilane, diethyldichlorosilane, di-n -Propyl dichlorosilane, di-i-propyldichlorosilane, hexylmethyldichlorosilane, di-n-butyldichlorosilane, di-i-butyldichlorosilane, di-t-butyldichlorosilane and n-butylmethyldichlorosilane Any one or combination of linear hydroxy terminated polyorganosiloxanes selected from the group. In addition, the terminal group includes one such as hydroxy, alkyl, vinyl, hydrogen, etc. Among them, a compound suitable for the required properties and properties can be selected and used, and the content is in the range of 1-100% by weight.

In particular, the silica precursor in the present invention may be used alone or mixed with a specific weight ratio of polysiloxane in the form of a polymer. In particular, the silicate precursor in the form of polysiloxane may be used by mixing precursors having different molecular structures such as viscosity and chain length.

As a solvent for dissolving the silica precursor, an alcohol solvent is generally used. For example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol, cyclohexyl alcohol, and the like are contained. Let it be by weight%.

The metal alkoxide is represented by the general formula MOR, M represents an alkali metal, R represents hydrogen or an alkyl group, specifically, one of methyl, ethyl, propyl, butyl, isopropyl, hexyl and cyclohexyl groups Select and use 1-100% by weight.

As the solvent for dissolving the metal alkoxide, an alcohol solvent is generally used. For example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol, cyclohexyl alcohol, and the like are contained. Let it be by weight%.

A powder coated with an inorganic binder precursor is prepared by coating a silica precursor (based on Example 1) or a metal alkoxide (based on Example 2) on a starting powder composed of alumina and silica.

Then, a drying step of drying the powder coated with the silica precursor (based on Example 1) or the metal alkoxide (based on Example 2) is performed. The drying step consists of leaving the powder in a dryer of 80 or more for 0.5 hours or more. The drying step includes a step of drying the alcohol mixed in the silica precursor and the metal alkoxide.

Next, a double coating powder is prepared by coating a metal alkoxide (based on Example 1) or a silica precursor (based on Example 2) on the dried powder.

Then, a drying step of drying the powder coated with the metal alkoxide and the silica precursor is performed. As described above, the drying step is allowed to stand for at least 0.5 hours in a dryer of 80 or more. The drying step includes a step of drying the alcohol mixed in the metal alkoxide and the silica precursor.

Before the drying step of the first and second steps, in order to sufficiently hydrolyze the inorganic binder, a method such as leaving the coated powder in the air or mixing water may be used. However, the present invention includes a step of drying the alcohol produced during the hydrolysis reaction or the alcohol mixed in the precursor with the hydrolysis reaction of the inorganic binder precursor in a step of drying for about 0.5-2 hours in an 80-100 dryer. Therefore, a separate process is not required for the hydrolysis reaction, which shortens the process time. The casting material is produced by the above process.

Meanwhile, a mold is manufactured using the mold material, and a third step of mixing the mold material with an organic binder is performed. Thereafter, a fourth step of forming the molded body by compression molding is performed. The mold is manufactured by the above-described process, and a preferred method of manufacturing the mold may include a fifth step of heat-treating the mold coated by the binder, as shown in FIGS. 1 and 2. The heat treatment process may be performed by leaving at 900 or more for 0.5 hours or more.

In addition, the present invention includes a step of heat-treating the molded body and drying the alcohol mixed with the precursor or the alcohol produced during the hydrolysis reaction together with the hydrolysis reaction of the inorganic binder precursor.

Hydrolysis and condensation reactions (sol-gel reaction) generated during the drying process are as follows.

NaOMe + H ₂ O → MeOH + NaOH

nSi (OEt) ₄ + ₄ nH ₂ O → (n + 1) SiO ₂ + 4 nEtOH

The heat treatment of the molded body is preferably performed at 900 or more as described above. At this time, a high strength cast molded product is produced by the following vitrification reaction.

2NaOH + SiO ₂ → Na ₂ OSiO ₂ + H ₂ O

The conventional convert mold process causes the loss of the inorganic binder due to the replacement of the organic binder with the inorganic binder. However, the cast article produced by the process according to the embodiment has the advantage that the substitution reaction is not generated to increase the conversion rate of the inorganic binder to the glass phase to increase the efficiency of the inorganic binder precursor.

In addition, the metal alkoxide and the silica precursor are coated with different layers, respectively, so that the metal salt and the silica can be uniformly applied to the mold surface compared to the existing mold manufacturing method using a mixture of the metal alkoxide and the silica precursor together. There is an effect of making a high-strength mold with reduced generation and high glass phase conversion efficiency of the precursor.

FIG. 3 is a view comparing a fractured cross section of a mold manufactured by a conventional mold fabrication process by a convert mold process with a fabrication process according to the first and second embodiments of the present invention using a scanning electron microscope. FIG. TEOS was used as the prepared silica precursor, and NaOMe was used as the metal alkoxide. It can be seen that a uniform glass phase is coated on the surface of the mold in a process in which the metal alkoxide and the silica precursor are coated with different layers, respectively, compared to the mold by the conventional mold process showing a local glass phase.

Figure 4 is a graph showing the breaking strength of the mold produced by the existing mold manufacturing process and the mold manufacturing process of the first and second embodiments of the present invention. As seen from the electron scanning microscope, the strength of the mold according to Example 1 (type B) is higher than that of Example 2 (type C). In addition, the strength of the molds produced by the first and second embodiments according to the present invention was higher than that of the molds manufactured by the existing mold process, because of the uniformly formed glass phase on the mold surface and the high conversion rate.

FIG. 5 is a view comparing the existing mold manufacturing process with the actual cast product cast into the mold manufactured according to the first embodiment of the present invention, and showed high collapsibility of the mold regardless of the manufacturing process.

Claims (16)

A first step of forming a first layer by coating a silicate precursor on the powder, and
A method of manufacturing a mold material through a double coating process comprising a second step of forming a second layer by coating a metal alkoxide. A first step of forming a first layer by coating a metal alkoxide to the powder, and
A method of manufacturing a mold material through a double coating process prepared by a method comprising a second step of coating a silicate precursor to form a second layer. 3. The method according to claim 1 or 2,
In the first step,
Method of producing a mold material through a double coating process, characterized in that it further comprises the step of drying after the coating of the first layer. 3. The method according to claim 1 or 2,
In the second step,
Method of producing a mold material through a double coating process, characterized in that it further comprises a step of drying after the coating of the second layer. 3. The method according to claim 1 or 2,
The silicate precursor,
A method for producing a mold material through a double coating process, characterized in that it comprises any one or more of a single molecule silicate precursor and a polymer siloxane precursor. 3. The method according to claim 1 or 2,
The silicate precursor,
Method for producing a mold material through a double coating process, characterized in that composed of any one or more of PDMS or TEOS. 3. The method according to claim 1 or 2,
The metal alkoxide,
Method for producing a mold material through a double coating process, characterized in that consisting of the following formula.
MOR (M: alkali metal, R: hydrogen, alkyl group) The method of claim 3, wherein
The drying step,
Method for producing a mold material through a double coating process, characterized in that the drying for 0.5 to 2 hours at 80 ℃ or more. 5. The method of claim 4,
The drying step,
Method for producing a mold material through a double coating process, characterized in that the drying for 0.5 to 2 hours at 80 ℃ or more. The third step of mixing the organic binder to the mold material produced by the manufacturing method of claim 1 or 2,
A method of manufacturing a mold through a double coating process comprising a fourth step of heat-treating the mold material mixed with the binder. The method of claim 10,
Before the third and fourth steps,
Method for producing a mold through a double coating process, characterized in that any one of the method of leaving the mold material in the air for the hydrolysis reaction or a method of mixing water is further added. The method of claim 10,
The binder is a mold manufacturing method through a double coating process, characterized in that consisting of a fat-soluble binder. The method of claim 10,
The binder is a method of manufacturing a mold through a double coating process, characterized in that consisting of a water-soluble binder. Mold material through a double coating process prepared by the manufacturing method of claim 1 or 2. Mold through a double coating process prepared by the method of claim 10. A casting manufactured by a mold manufactured by the manufacturing method of claim 1.

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