JPS63126638A - Water soluble core - Google Patents

Abstract

PURPOSE:To obtain a water soluble core which has excellent high-temp. strength and water solubility and permits easy recovery of sand particles by compounding a binder with refractory sand particles, kneading the mixture and drying and curing the kneaded mixture. CONSTITUTION:The binder consisting of a concd. soln. of potassium triphosphate and sodium aluminate is compounded as the binder with a base material consisting of the refractory sand particles such as alumina sand and the mixture is kneaded. The mixture is molded, dried and cured. Fine particles of aluminum hydroxide are added at need to said binder. The water soluble core obtd. by this method has high compressive strength and collapses completely in warm water. The core is adequately usable for molding of intricate die-cast products.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water-soluble core suitable for use in high-pressure casting such as die casting and molten metal forging.

[Conventional technology]

In general, metal cores are used in pressure casting such as die casting due to limitations on the strength of the core. Only cores with simple shapes are used in die casting, and there are only a few types of products to which it can be applied.

Therefore, research into water-soluble cores that can be removed by dissolving them in water after casting has been conducted since 1961, and many inventions have been made.

The purpose of these studies is to easily dissolve and remove the core of aluminum die-casting with water. As a result, die-cast products with complex shapes have become available.

However, when applying a water-soluble core to the Dikanut method,
Water-soluble cores are subjected to strong impact force, compressive stress, and thermal shock during molten metal injection, so they must have high-temperature strength to withstand these forces.

For this purpose, many studies have been made and many inventions have been made.

The current inventions each have their own characteristics, and although it is impossible to generalize them, they basically involve water-soluble salts. A water-soluble core is produced by melting it and casting it into a mold, or by molding it with salt powder under high pressure.

As is clear from the above method, strength is achieved by adding salts alone or in combination. Moreover, since this water-soluble core is required to have high strength, refractory particles are mixed as a reinforcing material into the salts that are the main raw materials. However, in order to increase the strength of these water-soluble cores, the salts must be densified or completely crystallized, resulting in slow water penetration and poor water solubility.

In this way, a water-soluble core is required to have contradictory properties.

From this point of view, Japanese Patent Publication No. 48-8368 and Japanese Patent Publication No. 48-1757 are examples of conventional water-soluble cores.
The one disclosed in Publication No. 0 is known.

The former is a core formed by using salts of Kcl and Nacl as main materials and adding a small amount of refractory particles such as alumina or zircon sand as a reinforcing material to the core by melting and casting into a mold.

The latter is a method in which salt powders of Kcl and Nacl are compression molded under high pressure.

However, these water-soluble cores have the following problems.

That is, when manufacturing the core, the process is complicated because salts are melted and poured into a mold, and it is difficult to manage the process. Therefore, productivity is low and it is not practical.

Furthermore, as is clear from the manufacturing method, water permeability is poor and the time for disintegration and elution of the core is relatively long.

Furthermore, since the main material is water-soluble salts, when the core is dissolved in water, it is difficult to post-process and reuse the solution.

[Problem that the invention seeks to solve]

The present invention has improved the above-mentioned problems, and aims to provide a new water-soluble core that has excellent high-temperature strength and water solubility, and in which the main material, heat-resistant sand particles, can be easily recovered. is its purpose.

[Means for solving problems]

That is, the present invention solves the above problems by molding a water-soluble core using alumina sand as a base material, adding a caking agent to the base material, and drying and hardening the mixture.

Next, the present invention will be explained in detail.

That is, alumina sand is used as the aggregate, a concentrated solution of tripotassium phosphate, which has a high melting point and high solubility in water, is used as the binding material, and sodium aluminate is added to increase the strength. A small amount was added.

Also, sodium aluminate increases the viscosity of the binder and improves its formability when mixed with alumina sand.

The molar ratio of sodium aluminate is preferably 165 or more. This is because when the aluminate ion concentration in the binder is high, alumina gel, which is poorly soluble in water, is precipitated during kneading, resulting in a significant deterioration of water solubility.

An example of the composition of the above binder is shown in Table 1.

Table 1 The core is formed by blending 10 to 10 parts of the caking agent shown in Table 1 with alumina sand, and drying and curing the mixture. In addition, the suitable drying temperature is 300 to 3501:. 300°C is the lowest temperature required for tripotassium phosphate to decompose water of crystallization.

The caking materials shown in Table 1 have a moisture content of 30%,
As the moisture content of the binder increases, the wet strength of the core after molding decreases. If the wet strength is low, it will be difficult to release the mold and handle it after mold release.

Therefore, the binder according to the present invention has a moisture content of 30%.

[Example 1] The influence of aluminum hydroxide on the compressive strength and water solubility of the core was clarified.

Table-10 for aggregate alumina sand grain size 80 No. 100 parts
10 parts of caking agent A or B and 0.5 to 4 parts of 5 μm aluminum hydroxide powder were blended, and after kneading, the mixture was dried and hardened at 350° C. for 1 hour.

The compressive strength and water solubility of this water-soluble core were measured.

A disk-shaped sample with dimensions of 30 g x 20 mm was used.

The experimental results are shown in Figs. 1 and 2.

The addition of aluminum hydroxide has an effective effect on the compressive strength of the core, as shown in FIG.

Furthermore, the wet strength after molding was also improved. Moreover, as is clear from FIG. 2, if a small amount is added, the water solubility does not deteriorate. This is thought to be because aluminum hydroxide is soluble in alkaline solutions.

[Example 2] The influence of sodium aluminate on the compressive strength of the core was clarified.

To the alumina sand size 150 aggregate, 15 parts of a binder containing tripotassium phosphate as the main component and 0 to 257 degrees of sodium aluminate was mixed, dried and hardened at 350°C for 1 hour, and the core was compressed. The strength was measured.

A disk-shaped sample with dimensions of 30 f13 x 20H was used. The experimental results are shown in Figure 3.

As is clear from the figure, the content of sodium aluminate is
It has the effect of improving the compressive strength of the core.

[Example 3] Casting experiment-1 Alumina sand grain size 150, tripotassium phosphate 65%,
15 parts of a caking agent consisting of 3% sodium naluminate and 32% water content were mixed with 1 part of aluminum hydroxide powder, and after mixing, a disc-shaped core with a diameter of 30 mm was formed and heated at 350°C.
It was dried at h.

This core was placed inside the mold cavity and heated to 700℃ using a 250-piece cold chamber die-casting machine.
molten aluminum alloy was cast at a casting pressure of 800 f/cd.

After casting, the core was immersed in hot water at 60 to 70°C, and the core was completely eluted in 2 minutes.

The thus obtained die-cast product had good surface condition.

[Example 4] Casting experiment-2 Alumina sand grain size No. 80 was mixed with 10 parts of a binder consisting of 65% tripotassium phosphate, 3% sodium aluminate, and 32% water content, and 0.5 parts of aluminum hydroxide powder. After kneading, a disc-shaped core with a shoulder diameter of 30 parts was formed.
Dry at ℃Xlh.

This core was placed in the cavity of a mold, and cast using a 300T squeeze caston machine at a casting pressure cuff of 0019f/cd using molten aluminum alloy at 750°C. After casting, it was immersed in hot water at 60-70℃.3
It disintegrated in 0 seconds, and the core was completely eluted in 1 minute.

The finish and surface condition of the squeeze cast product thus obtained were good.

[Example 5] Casting experiment 1-3 Alumina sand grain size 150, tripotassium phosphate 60%,
After blending and kneading 20 parts of a binder consisting of 10% sodium aluminate and 30% water content, disk-shaped cores with a diameter of 30 were formed and dried at 350°C.

This core was placed in the cavity of a mold, and 720° C. molten aluminum alloy was cast at a casting pressure of 500A91:/i using a 3003 squeeze cast machine.

After casting, the core was immersed in hot water at 60 to 70°C, and the core was completely eluted in 4 minutes.

The finish and surface condition of the squeeze cast product thus obtained were good.

That is, in the present invention, in order to increase the strength of the binder after drying without impeding water solubility, fine particles are blended to improve the strength by dispersion strengthening. That is, a small amount of aluminum hydroxide powder of about 5 μm is added to the binder. When this dispersion reinforcing material is added, an excellent core having both compressive strength capable of withstanding die casting and good water solubility can be obtained. For example, the core of the present invention has a compressive strength of 1.50 to 1.
．． 80 Soil/CWI completely disintegrates in about 10 seconds in warm water at 60-70°C.

〔Effect of the invention〕

As explained above, since the water-soluble core according to the present invention is molded, it has high strength and good water solubility, so it is suitable for use in molding die-cast FF products with complex internal shapes. Since the core is of a dry hardening type, the sand can be easily reused, resulting in cost savings.

In addition, due to its high heat resistance, it can be applied to molding die-cast products made from high-melting point metals, and it also requires more man-hours to manufacture the core compared to known water-soluble cores for die-casting. It has advantages such as being excellent in mass production and easy to industrialize.

[Brief explanation of the drawing]

Figures 1 and 2 show the relationship between the aluminum hydroxide content and compressive strength, the aluminum hydroxide distribution bone, and water solubility, respectively, in the experimental results of Example 1 of the water bathable core according to the present invention. The graphs shown in FIG. 3 are graphs showing the relationship between the amount of sodium aluminate blended and the compressive strength in the experimental results of Example 2 of the same water-soluble core. Water Solubility (Sec) Compressive Strength (Residue/Residue Figure 3 Sodium Anopenate Amount (%) Name: Water-soluble core 3, Relationship with the case of the person making the amendment Patent applicant address: 762 Mezaki-cho, Fuchu-shi, Hiroshima Prefecture Voluntary amendment 5, Subject of amendment (1) "Claims" column in the specification ( 2) "Detailed Description of the Invention" column in the specification (3) Contents of amendment to the "Brief Description of Drawings" column in the specification 1) Amend the "Claims" column in the specification as follows: do. (1) A water-soluble core characterized in that it is formed by using refractory sand particles as a base material, adding a caking agent to the base material, and drying and curing the mixture. (2) The water-soluble core according to claim 1, wherein the binder comprises a concentrated solution of tripotassium phosphate and sodium aluminate. (3) The water-soluble core according to claim 1, wherein the binder is formed by adding aluminum hydroxide to a concentrated solution of tripotassium phosphate and sodium aluminate. (4) The water-soluble core according to claim 1, wherein the binder is made by adding aluminum hydroxide to tripotassium phosphate. 2) The column "Detailed Description of the Invention" in the specification is amended as follows. (1) In the 12th line of page 2, the phrase ``Easily removed by dissolving with water'' should be corrected to ``Easily removed by dissolving with water.'' (2) In the first line of page 3, the phrase "currently" is corrected to "these." (3) In the third line of page 3, the word "melt" should be corrected to "melt." (4) 1 refractory particle on page 3, line 9 and page 4, line 1.”
The statement has been corrected to "refractory sand particles." (5) On page 3, line 11, the phrase “or completely” should be amended to read “or.” (6) rKC waist Na on page 3, line 19 and page 4, line 3
Correct clJ to rKcI and NaC1. (7) On page 4, line 19, "heat resistance" is corrected to "refractory." (8) In the 2nd and 7th lines of page 5, ``1 alumina sand'' should be corrected to ``refractory sand particles such as alumina sand, silica sand, zircon sand, etc.''. (9) In the 10th line of page 5, the word "to" is corrected to "zarani." (10) "Alumina sand" in line 13 of page 5 and line 5 of page 6 is corrected to "refractory sand particles." (11) On page 5, line 20, the phrase “shown in Table 1” should be replaced with “shown in Table 1.” However, the number B column shows the composition when only tripotassium phosphate is used as the binder. Yes,” he corrected. (12) Change “Table-1” to “Table-1” in the first line of page 6.
Composition of caking agent (%)” (13) On page 6, lines 10 to 11, “Table-1...
30% is the appropriate moisture content of the binder, as shown in Table F-1. ” he corrected. (14) On page 6, lines 12 to 14, [... Wet strength was set to 30% moisture. "The wet strength decreases, making release from the mold and handling after release difficult.Next, we will discuss the effects of aluminum hydroxide.In order to roughly increase the strength of the core, the composition shown in Table 1 is used. 1 to 5 parts of fine aluminum hydroxide powder is added to the binder. As a result, the strength is significantly increased and a good core is obtained. It is characterized by a composite blend of sodium aluminate in the core to increase its strength, and it also contains fine particles to increase the strength of the binder after drying without significantly inhibiting its water solubility. It is characterized by improving strength through dispersion strengthening. In other words, a small amount of aluminum hydroxide powder is added to the caking agent. When this dispersion strengthening agent is added, the core has a compressive strength that can withstand die casting. An excellent core with good water solubility can be obtained.For example, the core of the present invention with a compressive strength of 150 to 180'j/cm has a compressive strength of 60 to 7
It completely disintegrates in about 10 seconds in warm water at 0°C. Examples of the water-soluble core of the present invention will be described below. ” he corrected. (15) In the 15th line of page 6, [Example 1] is corrected to [Example 2]. (16) "30φ" in the 4th line of page 7 and the 1st line of page 8 is corrected to [φ30sJ. (17) In the 6th and 7th lines of page 7, "Figure 1" should be corrected to "Figure 2." (18) In the 6th line of page 7, "Figure 2" is corrected to "Figure 3." (19) On page 7, lines 9 and 10, “Improving results...
・The phrase ``a small amount'' was replaced by ``a small amount,'' which tended to make molding easier. Figure 3 shows the time it takes for the core to disintegrate after being immersed in water. "is a small amount" is corrected. (20) In the 14th line of page 7, the text "Example 2" is corrected to "Example 1". (21) In the second line of page 8, "Figure 3" is corrected to "Figure 1." (22) On page 8, lines 4 and 5, after "...has the effect of improving..." [[Example 3] Silica sand and zircon sand were also used under the same conditions as in Examples 1 and 2. A sample was prepared and its compressive strength was measured, and the compressive strength was the same as that of alumina sand, and the water solubility was also good. ” to join. (23) In the 6th line of page 8, ``Example 3'' is corrected to ``Example 4''. (24) On page 8, line 9, "sodium nalmate" should be corrected to "sodium aluminate." (25) On page 9, line 1, [Example 4] is corrected to [Example 5]. (26) Page 9, line 16, [Example 5] is corrected to [Example 6]. (27) From page 10, line 11 to line 20 of the same page, the statement ``In other words, the present invention...is destroyed.'' is deleted. (28) On page 11, lines 2 and 3, “The water-soluble core is...
・Correct the phrase ``because it is a water-soluble core'' to ``because it is a water-soluble core.'' 3) The column "Brief explanation of drawings" in the specification should be amended as follows. (1) From page 11, line 15 to page 12, line 1, “Fig.
Figure 2 is a graph. [Figure 1 is a graph showing the relationship between the amount of sodium aluminate blended and the compressive strength in the experimental results of Example 1 of the same water-soluble core.
Figures 2 and 3 show the relationship between the aluminum hydroxide content and compressive strength, and the relationship between the aluminum hydroxide content and water solubility, respectively, in the experimental results of Example 2 of the water-soluble core according to the present invention. These are each graph. ” he corrected. 4) Correct only the drawing numbers from drawing 1 to drawing 2, drawing 2 to drawing 3, and drawing 3 to drawing 1.

Claims (4)

[Claims] (1) A water-soluble core characterized in that it is formed by using alumina sand as a base material, adding a caking agent to the base material, and drying and curing the mixture. (2) The water-soluble core according to claim 1, wherein the binder comprises a concentrated solution of tripotassium phosphate and sodium aluminate. (3) The water-soluble core according to claim 1, wherein the binder is formed by adding aluminum hydroxide to a concentrated solution of tripotassium phosphate and sodium aluminate. (4) The water-soluble core according to claim 1, wherein the binder is made by adding aluminum hydroxide to tripotassium phosphate.