KR20160150044A - Environmental casting mold, and method of fabricating of the same - Google Patents

Abstract

Provided is a method of manufacturing an environmentally friendly mold. The method of manufacturing the mold comprises: a step of preparing a base powder; a step of mixing the base powder and a water-soluble organic binder to prepare a preliminary mold; a step of coating the preliminary mold using an inorganic binder containing silicon and metal; and a step of preheating the preliminary mold where the inorganic binder is coated to prepare the mold where a metal silicate is coated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an environmentally friendly mold,

The present invention relates to an environmentally friendly mold and a manufacturing method thereof, and more particularly to a mold including a water-soluble organic binder and an inorganic binder, and a method of manufacturing the same.

Conventional casting molds mainly use resin-based binders. These resin-based binders are curable compounds and contain substances harmful to human body in the molecular structure. Therefore, the decomposition of the resin-based organic binder during casting causes toxic gas, which causes problems in the workplace and workers' health. In addition, hardening agents (eg, isocyanate) injected in gas form are very toxic and cause diseases such as skin diseases, rashes and dyspnea.

In addition, casting molds are accompanied by problems of blowhole formation, inability to heat treat at high temperature, and low dimensional stability due to decomposition of the organic binder during casting. Therefore, since the flowability of the molten metal causes shrinkage and solidification defects in the casting, the precision casting method is inevitable for manufacturing a thin-walled casting of complicated shape. However, precise casting requires 8-10 times of ceramic coating and drying process in the production of casting mold, resulting in low productivity due to long and complicated manufacturing process, increase of manufacturing cost, and limitation of size of casting product.

SUMMARY OF THE INVENTION The present invention provides an environmentally friendly mold and a manufacturing method thereof.

It is another object of the present invention to provide a mold capable of easily producing a cast product having a complicated shape and a method of manufacturing the same.

Another object of the present invention is to provide a mold having improved strength and dimensional stability at a high temperature and a method for producing the same.

It is another object of the present invention to provide a mold capable of high temperature heat treatment and a method of manufacturing the same.

Another object of the present invention is to provide a mold having a reduced manufacturing cost and a simplified manufacturing process, and a manufacturing method thereof.

The technical problem to be solved by the present invention is not limited to the above.

In order to solve the above technical problems, the present invention provides a method of manufacturing a mold.

According to one embodiment, a method of making a mold includes preparing a base powder, mixing the base powder and a water soluble organic binder to produce a preliminary mold, Coating an inorganic binder with an inorganic binder including silicon and a metal; and heat treating the preliminary mold coated with the inorganic binder to produce a metal silicate-coated mold.

According to one embodiment, the step of heat-treating the preform may be performed at a temperature higher than the glassfication temperature of the inorganic binder.

According to one embodiment, the inorganic binder may comprise a first material comprising silicon and a second material reducing the vitrification temperature of the first material and comprising a metal.

According to one embodiment, the method of manufacturing the mold may comprise sol-gel reaction of the first material and the second material in the inorganic binder to form silica and metal hydroxide.

According to one embodiment, in the step of heat-treating the preform, the silica and the metal hydroxide in the inorganic binder react to form the metal silicate.

According to one embodiment, the second material comprises a metal alkoxide, and the alcohol may be formed by a sol-gel reaction of the first material and the second material.

According to an embodiment, the method of manufacturing a mold may further include drying the preform before removing the alcohol before heat treatment of the preform.

According to one embodiment, the inorganic binder may further include a viscosity adjusting agent.

According to one embodiment, the water-soluble organic binder may not contain an aromatic functional group.

In order to solve the above technical problems, the present invention provides a mold.

According to one embodiment, the mold comprises a base powder and a water soluble organic binder, which may be coated with a metal silicate.

According to one embodiment, the metal silicate may be provided between the base powders.

According to an embodiment of the present invention, a preliminary mold is prepared by mixing a base powder and a water-soluble organic binder, and after the preliminary mold is coated with an inorganic binder, the preliminary mold is heat-treated to produce a mold having a glassy metal- .

Accordingly, it is possible to easily produce a complicated casting product, which can be subjected to a high-temperature heat treatment in an environmentally friendly manner without using a resin-based binder, to have a high molding strength by the water-soluble organic binder, A mold having strength and dimensional stability can be provided.

1 is a flowchart illustrating a method of manufacturing a mold according to an embodiment of the present invention.
2 is a graph showing FT-IR analysis results of a molded article according to a comparative example of the present invention.
3 is a graph of FT-IR analysis results of a molded article according to an embodiment of the present invention.
4 is a graph for explaining fracture strengths of the molded bodies according to Examples and Comparative Examples of the present invention.
5 is an SEM photograph of a fracture surface of a molded article according to an embodiment of the present invention.
6 is a SEM photograph of a fracture surface of a molded article according to a comparative example of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Also, while the terms first, second, third, etc. in the various embodiments of the present disclosure are used to describe various components, these components should not be limited by these terms. These terms have only been used to distinguish one component from another. Thus, what is referred to as a first component in any one embodiment may be referred to as a second component in another embodiment. Each embodiment described and exemplified herein also includes its complementary embodiment. Also, in this specification, 'and / or' are used to include at least one of the front and rear components.

The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the terms such as " comprises "or" having "are intended to specify the presence of stated features, integers, Should not be understood to exclude the presence or addition of one or more other elements, elements, or combinations thereof.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a flowchart illustrating a method of manufacturing a mold according to an embodiment of the present invention.

Referring to FIG. 1, a base powder is prepared (S110). According to one embodiment, the base powder may be sand. For example, the base powder may be artificial yarn, natural yarn, or a mixture thereof.

A preliminary mold may be prepared by mixing the base powder and the water soluble organic binder (S120). The water-soluble organic binder may be an eco-friendly binder. In other words, the water-soluble organic binder can be selected from polymer compounds having a molecular structure in which toxic gases or carcinogens generated by decomposition at a high temperature in a subsequent heat treatment process or casting process are minimized. According to one embodiment, the water soluble organic binder may not contain an aromatic functional group. For example, the water soluble organic binder may be PVA (polyvinyl alcohol).

According to one embodiment, curing may occur due to the entanglement of the polymer chain of the water-soluble organic binder, whereby the strength of the mold described below can be controlled according to the molecular weight and content of the water-soluble organic binder.

The preform may be dried. According to one embodiment, the preform may be dried at 100 ° C to 200 ° C.

The preliminary mold may be coated with an inorganic binder including silicon and metal (S130). According to one embodiment, the preform may be immersed in the inorganic binder.

The inorganic binder may comprise a first material comprising silicon, a second material comprising a metal, and a viscosity modifier.

The first material may be a silica precursor. The heat treatment of the preliminary mold described later turns the first material into a glassy material, and the strength of the mold can be improved. According to one embodiment, the first material may be a silicate-based or siloxane-based material. For example, the first material may be selected from the group consisting of tetraethylorthosilicate, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraisopropoxy silane, methoxytriethoxysilane, But are not limited to, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, methyldiethoxysilane, Methyl silane, tetramethoxyethyl silane, or tetraethoxymethyl silane.

According to one embodiment, the content of the first material in the inorganic binder may be 60 parts by weight or less. If the content of the first material in the inorganic binder is higher than 60 parts by weight, the temperature of the vitrification reaction described later may increase, and the mechanical strength of the mold may be lowered. However, as described above, according to one embodiment, the content of the first material in the inorganic binder is controlled to 60 parts by weight or less, so that a mold having improved mechanical strength can be manufactured.

The second material may reduce the vitrification temperature of the first material. According to one embodiment, the second material may be a metal alkoxide represented by the following formula (1).

However,

MOR

M is an alkali metal (for example, lithium, sodium, potassium or the like) or an alkaline earth metal (for example, beryllium, magnesium or calcium), R is hydrogen or an alkyl group For example, methyl group, ethyl group, propyl group, butyl group, pentyl group, isopropyl group, hexyl group, cyclohexyl group).

According to one embodiment, the content of the second material in the second material may be 60 parts by weight or less. If the inorganic binder does not include the second material, as described later, the vitrification temperature of the first material may be increased to increase the process temperature and process cost. If the content of the second material in the inorganic binder is higher than 60 parts by weight, the formation of the silica network structure may be inhibited and the whitening phenomenon may be caused, thereby reducing the strength of the mold. However, as described above, according to one embodiment, the content of the second material in the inorganic binder is controlled to 60 parts by weight or less, so that a mold having improved mechanical strength can be manufactured.

The first material and the second material in the inorganic binder may undergo a sol-gel reaction to produce silica, metal hydroxide, and alcohol. More specifically, for example, when the first material is tetraethylorthosilicate and the second material is sodium methoxide, the hydrolysis and condensation reaction is performed according to the following formulas (2) and (3) , Sodium hydroxide, and ethanol may be produced. In Formula 3, n may be a rational number of 1 or more.

(2)

NaOMe + H ₂ O -> MeOH + NaOH

(3)

_{nSi (OEt) 4 + 4nH 2} O -> (n + 1) SiO 2 + 4nEtOH

The viscosity modifier may control the hydrolysis of the first material and the second material and the viscosity of the inorganic binder. For example, the viscosity modifier may include at least one of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an isopropyl group, a hexyl group or a cyclohexyl group.

The preform may be dried. The preliminary mold is dried so that the alcohol produced by the sol-gel reaction of the first substance and the second substance in the inorganic binder can be removed. According to one embodiment, the preform may be dried at a temperature of 80 ° C to 120 ° C for 30 minutes to 3 hours. If the alcohol is not sufficiently removed, the silica and the metal hydroxide in the inorganic binder may be vaporized or decomposed to reduce the efficiency of the vitrification reaction described below.

The preliminary mold coated with the inorganic binder may be thermally treated to form a metal silicate coated mold (S140). The metal silicate may be glassy. The metal silicate is provided between the base powders so that the strength of the mold can be improved. In other words, the metal silicate is provided between the particles and the particles, so that the bonding force at the interface between the particles and the particles can be improved.

As described above, the inorganic binder may comprise the silica and the metal hydroxide produced by the sol-gel reaction of the first material and the second material. The preliminary mold coated with the inorganic binder containing silica and the metal hydroxide is subjected to heat treatment to react the silica and the metal hydroxide, whereby the metal silicate can be formed.

For example, as described above, when the first material is tetraethylorthosilicate, the second material is sodium methoxide, and the silica and sodium hydroxide are produced by the following formula 2 and formula 3, The sodium silicate can be produced by reacting, as shown in the following formula (4).

≪ Formula 4 >

_{2NaOH + SiO 2 -> Na 2} OSiO 2 + H 2 O

According to one embodiment, the step of heat-treating the preform may be performed at a temperature higher than a glassfication temperature at which the inorganic binder is converted into glassy. For example, if the vitrification temperature of the inorganic binder is 860 캜, the preform may be heat treated at a temperature of 900 캜 to 1000 캜, higher than 860 캜 for 30 minutes to 2 hours. If the heat treatment of the preform is performed at a temperature lower than the vitrification temperature of the inorganic binder, the metallic silicate of vitreous may not be easily produced. Also, when the heat treatment of the preform is performed at a temperature higher than 1000 ° C., the vaporization and decomposition of the metal silicate of the vitreous may be promoted and the vitrification efficiency may be reduced. However, as described above, according to one embodiment, the heat treatment of the preliminary mold is performed at a temperature higher than the vitrification temperature of the inorganic binder and lower than 1000 deg. C, so that vitrification efficiency is improved and the metal silicate is easily produced .

According to an embodiment of the present invention, the preliminary mold is prepared by mixing the base powder and the water-soluble organic binder, and the preliminary mold is coated with the inorganic binder, and then the preliminary mold is heat-treated, Coated molds can be produced. Accordingly, it is possible to easily produce a complicated casting product, which can be subjected to a high-temperature heat treatment in an environmentally friendly manner without using a resin-based binder, to have a high molding strength by the water-soluble organic binder, A mold having strength and dimensional stability can be provided.

According to another embodiment of the present invention, there is provided a method of manufacturing a mold, comprising the steps of immersing a base powder in an inorganic binder, obtaining and drying the base powder impregnated in the inorganic binder, Preparing a base powder coated with an inorganic binder, preparing a preliminary mold using the base powder coated with the inorganic binder and a water-soluble organic binder, heat treating the preliminary mold to form a glassy metal silicate- To form a mold.

In this case, the organic binder is coated on the inorganic binder, and the loss of the inorganic binder may be reduced by the combustion of the organic binder. Accordingly, the vitrification efficiency of the inorganic binder can be improved during the heat treatment of the preform. In addition, the metal silicate is easily provided between the base powders, so that the bonding force between the particles and the interface of the particles can be improved. As a result, the strength of the mold can be improved.

Hereinafter, the evaluation results of the characteristics of the mold according to the embodiment of the present invention described above will be described.

Production of a molded article according to an embodiment

PVA having a molecular weight of 89,000 to 98,000 was prepared as a base powder by Artificial Yarn No. 7 and a water-soluble organic binder. A preform was prepared by mixing PVA No. 7 and 2.34 wt% of PVA, and dried at 100 ° C for 1 hour.

As the first material containing silicon, tetraethylorthosilicate, sodium methoxide as a second material containing sodium and reducing the vitrification temperature, and isobutyl alcohol as a viscosity modifier were prepared. (0.18 mol%) tetraethylorthosilicate, 56 wt% (1.5 mol%) sodium methoxide and 6 wt% (0.08 mol%) isobutyl alcohol were mixed to prepare an inorganic binder.

The preform was immersed in the inorganic binder, and the preform with the inorganic binder coated thereon was heat-treated at 1000 캜 for 1 hour to prepare a molded body according to an embodiment coated with sodium silicate.

Production of a molded article according to a comparative example

Resin No. 7 coated with a resin and hexaamine were used to prepare a preform. The preform was immersed in the inorganic binder described in the above-described embodiment, and the preform with the inorganic binder coated thereon was heat-treated at 1000 占 폚 for 1 hour to prepare a molded article according to a comparative example.

Hazardous gas analysis

The noxious gas components produced in the process of manufacturing the molded article according to the above-described embodiment and the above-described comparative example were measured, and the measurement results are shown in Table 1 below.

division carbon
(wt%, C) Hydrogen
(wt%, H) nitrogen
(wt%, N) Sulfur
(S) Example 0.36 0.07 0.13 - Comparative Example (after heat treatment) 1.93 0.06 0.13 - Comparative Example (Before heat treatment) 0.03 0.05 0.12 -

As can be seen from Table 1, the carbon content in the noxious gas was 0.03 wt% before the heat treatment after coating the inorganic binder with the preform by using the resin according to the comparative example. However, the heat treatment process was performed It can be confirmed that the carbon content in the noxious gas rapidly increases to 1.93 wt% when the molded article is produced. On the other hand, according to the comparative example, when a preform is produced using PVA as a water-soluble polymer without using a resin, and the molded body is manufactured by applying heat treatment to the inorganic binder after coating, 0.36 wt% of carbon is generated as a harmful gas component.

In other words, in the case of producing a molded article using a resin according to a comparative example, it can be confirmed that the carbon content in the noxious gas is 5.36 times larger than that in the case of forming a molded article using PVA according to the embodiment. That is, according to the embodiment of the present invention, it can be confirmed that a mold is manufactured using a water-soluble polymer without using a resin, which is an environmentally friendly process for producing a mold.

Analysis of FT-IR results

FIG. 2 is a graph of FT-IR analysis results of a molded article according to a comparative example of the present invention, and FIG. 3 is a FT-IR analysis result of a molded article according to an embodiment of the present invention.

2 and 3, FT-IR (Fourier Transform Infrared Spectrometry) analysis of the molded body according to the above-described embodiment and the above-described comparative example was performed. 2 and 3 are FT-IR analysis results of the molded bodies according to the comparative example and the example, respectively.

As can be seen from FIGS. 2 and 3, it can be confirmed that the benzolic cycle (aromatic group) peak was measured when a molded article was prepared using a resin according to a comparative example. On the other hand, when a molded article is produced using PVA according to the embodiment, no benzolic cycle (aromatic group) peak is observed. Accordingly, it can be confirmed that, in accordance with the embodiment of the present invention, a mold is manufactured using a water-soluble polymer without using a resin, which is an environmentally friendly process for producing a mold.

Fracture strength analysis and breaking analysis

4 is a graph for explaining fracture strengths of the molded bodies according to the embodiments of the present invention and comparative examples, FIG. 5 is a SEM photograph of a fracture surface of the molded body according to the embodiment of the present invention, FIG. Fig. 3 is a SEM photograph of a fracture surface of a molded article according to a comparative example of Fig.

4 to 6, the molded body according to the above-described embodiment and the molded body according to the comparative example were measured at a speed of 0.5 mm / min in a 4 point bending mode using a universal testing machine at a rate of 5 The mean value of the measured values is calculated and shown in FIG. SEM photographs of the fractured surfaces of the molded body according to the embodiment and the molded body according to the comparative example are shown in Figs. 5 and 6, respectively.

As can be seen from Fig. 4, the molding strength (2-1 in Fig. 4) and the plasticity strength (2-2 in Fig. 4) of the molded article produced using the resin according to the comparative example were measured to be 2.68 MPa and 1.56 MPa, respectively . In addition, the molding strength (1-1 in FIG. 4) and the plasticity strength (1-2 in FIG. 4) of the molded article produced using PVA according to the examples were measured to be 3.85 MPa and 2.74 MPa, respectively. In the case of the molding strength, it can be confirmed that the molded body according to the embodiment is improved by about 143% as compared with the molded body according to the comparative example. In addition, in the case of the plastic strength, it can be confirmed that the molded body according to the embodiment is improved by about 175% as compared with the molded body according to the comparative example. In other words, according to the embodiment of the present invention, it can be confirmed that the production of a mold using a water-soluble polymer without using a resin is an efficient method of producing a mold having improved molding strength and plasticity strength.

5 and 6, the mixing of PVA, a water-soluble organic binder, and an artificial yarn, which is a base powder, in a molded article according to the embodiment is more uniform than that of a synthetic resin and a base powder in a molded article according to the comparative example Can be confirmed. In other words, according to the embodiment of the present invention, it can be confirmed that mixing with the base powder using a water-soluble organic binder is an efficient method of improving the uniformity of the mixing of the binder and the base powder.

In addition, in the case of the molded body coated with the sodium silicate prepared by performing the heat treatment process after coating the inorganic binder, it can be confirmed that the sodium silicate is penetrated and provided between the artificial yarns as the base powder. In other words, according to an embodiment of the present invention, it is possible to manufacture a mold coated with a metal silicate by coating a preliminary mold prepared using a base powder onto an inorganic binder and heat-treating a preliminary mold coated with an inorganic binder, It is an effective method for improving the strength and the high-temperature stability of the catalyst.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. It will also be appreciated that many modifications and variations will be apparent to those skilled in the art without departing from the scope of the invention.

Claims (11)

Preparing a base powder;
Mixing the base powder and the water soluble organic binder to produce a preliminary mold;
Coating the preform with an inorganic binder comprising silicon and metal; And
And heat treating the preliminary mold coated with the inorganic binder to produce a metal silicate coated mold.
The method according to claim 1,
Wherein the heat treatment of the preform is performed at a temperature higher than a glassfication temperature of the inorganic binder.
The method according to claim 1,
Wherein the inorganic binder comprises:
A first material comprising silicon; And
And reducing the vitrification temperature of the first material and comprising a second material comprising a metal.
The method of claim 3,
Wherein the first material and the second material in the inorganic binder are sol-gel reacted to form silica and a metal hydroxide.
5. The method of claim 4,
Wherein in the step of heat-treating the preform, the silica and the metal hydroxide in the inorganic binder react to form the metal silicate.
5. The method of claim 4,
Wherein the second material comprises a metal alkoxide,
Wherein the alcohol is formed by sol-gel reaction of the first material and the second material.
The method according to claim 6,
Further comprising drying the preliminary mold prior to heat treatment of the preliminary mold to remove the alcohol.
The method of claim 3,
Wherein the inorganic binder further comprises a viscosity adjusting agent.
The method according to claim 1,
Wherein the water soluble organic binder does not contain an aromatic functional group.
A base powder and an organic binder, wherein the mold is coated with a metal silicate.
11. The method of claim 10,
Wherein the metal silicate is provided between the base powders.

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