JP2964369B2 - Release agent for mold casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating material which can be suitably used in a casting method in which a molten metal is easily injected and a molten metal is easily cooled, such as squeeze die casting, among aluminum die castings. The present invention relates to a mold release agent having good heat retaining properties.

[0002]

2. Description of the Related Art In a mold casting method in which a molten metal is injected at a low speed (low-speed casting), a high-strength cast product can be obtained without involving gas in the cast product. Therefore, such castings are widely used in the production of aluminum parts accompanying the trend toward reducing the weight of automobiles. Conventionally, graphite has been mainly used as a mold release agent at the time of mold casting. However, since it is black and stains the surroundings, natural minerals such as talc, sericite, and limestone, or boron nitride, PTFE (polyethylene) are used. White release agents such as tetrafluoroethylene) are often used. These release agent particles are made of carboxymethylcellulose (CM
The composition is applied to a heated mold in the form of a paint suspended in water containing a dispersant such as C) to form a film.

[0003]

SUMMARY OF THE INVENTION
If the temperature of the molten metal drops before the molten metal is completely filled in the mold,
There is a potential drawback that the running of the hot water deteriorates and quality defects such as hot water lines, hot water borders, and underfill are easily caused.
Conventional release agents have good thermal conductivity, so they were suitable for small parts with simple shapes where casting defects are relatively difficult to appear, but in the case of large, complicated shapes or thin parts,
There is a problem that quality defects due to poor running of the molten metal easily occur. In view of the circumstances described above, an object of the present invention is to provide a release agent that has heat insulation properties (warming properties) showing an effect that a molten metal is hardly cooled, and does not cause quality defects in a low-speed casting method. It is assumed that.

[0004]

In order to solve the above-mentioned problems, a mold release agent for mold casting according to the present invention is a porous and specific surface area release agent particle which is suspended in water containing a dispersant. Is characterized by using synthetic silicate compound particles of 40 m ² / g or more. In this case, the synthetic silicate compound is characterized in that it is at least one of magnesium silicate, magnesium metasilicate, aluminum silicate, magnesium silicate, magnesium bismuth silicate and calcium silicate. Further, in addition to the release agent particles composed of the above-mentioned synthetic silicate compound, talc, sericite, rock, boron nitride, molybdenum disulfide, tungsten disulfide, mica, enstatite, fluoride having a solid content of less than 90% by weight. It is characterized by containing at least one of graphite, PTFE, melamine cyanurate and graphite. Furthermore, in these release agent suspensions,
It is characterized by containing water glass or colloidal silica.

[0005] The above-mentioned synthetic silicate compound is a compound which is chemically synthesized similarly to those conventionally used as an acid adsorbent for pharmaceuticals and the like, and is porous and has a specific surface area of 40 m.
² / g or more, the particle size is about 0.01 to 3 μm. For example, in the case of magnesium silicate aluminate, this synthetic silicate compound is produced by metathesis of sodium silicate, sodium aluminate and magnesium chloride. In the case of magnesium bismuth aluminate silicate, a basic aluminum salt is precipitated by adding a dilute solution of a basic magnesium compound such as magnesium carbonate to an aqueous solution of an aluminum salt, and ammonia water is added to add the basic aluminum magnesium salt. The precipitate can be prepared by adding an acidic aqueous solution of a bismuth salt to the precipitate, reacting the precipitate, and combining the basic aluminum magnesium salt with bismuth hydroxide. In addition, although the above-mentioned six kinds of synthetic silicate compounds are easily available at present, it is presumed that various derivatives similar to these have similar functions and effects.

[0006] The above-mentioned porous material means that the surface of the particle or the whole particle is porous, and that the fine primary particles are about 1%.
Includes those that are formed into porous particles by forming aggregated particles of about μm. According to the result of the heat insulation test, the synthetic silicate compound having a specific surface area of less than 40 m ² / g is inferior in heat insulation. In addition, a material having a large specific surface area is industrially about 400 m ² / g, which can be used as a matter of course.

[0007] Among the release agents of the present invention, the release agent composed of silicate compound particles alone has a relatively low lubricating property, but has good heat insulating properties, and thus is suitable for a case where the cast product has a simple shape. When the casting has a complicated shape, the lubricating property is improved by adding solid lubricant particles such as talc, boron nitride, and fluorinated graphite, rather than the release agent containing only the silicate compound particles. Are suitable. In this case, the amount of the synthetic silicate compound particles is 10% by weight or more as a solid content. If the amount of the synthetic silicate compound particles is less than this, the heat insulating properties are not significantly improved. Further, among the solid lubricant particles described above, graphite is black, and therefore it is preferable to use a small amount of graphite when used.

[0008] When adhesion of the release agent coating to the mold surface is required depending on the shape and size of the cast article, water glass or colloidal silica can be added to the suspension.
The amount is preferably about 2 to 15% by weight as a solid content.

In the release agent suspension according to the present invention, the concentration of the solid content is increased at the time of preparation, and usually the concentration is adjusted to an appropriate concentration at the time of use according to the size, shape, application conditions and the like of the mold. Use diluted with water.

[0010]

The natural minerals such as talc and boron nitride which are conventionally used are composed of single crystalline particles, and the particles themselves have good thermal conductivity. When a mold release agent of such a material is applied to the mold surface to form a coating and the molten metal is poured, the heat of the molten metal is easily transmitted to the mold and radiated. Worsens. Since the synthetic silicate compound is a porous particle, when a coating film is formed, it exhibits excellent heat insulating properties due to finely dispersed voids in the coating film, thereby suppressing cooling of the molten metal. Is improved.
Further, since the synthetic silicate compound is a white substance, it does not deteriorate the working environment. Synthetic silicate compound particles are porous, and the powder is more susceptible to external force than natural minerals, and apparently exhibit cleavage properties similar to solid lubricants such as molybdenum disulfide. Similar lubrication effects can be expected.

[0011]

Embodiments will be described below with reference to embodiments. To a liquid in which 2% by weight of CMC was dissolved in water as a dispersant, 20% by weight of various inorganic powders were gradually added so as not to cause agglomerates,
The mixture was sufficiently stirred to prepare a release agent sample. Table 1 shows the types of the inorganic powders and the respective specific surface areas. The talc, sericite, pyroxene, boron nitride and graphite in Table 1 are inorganic powders contained in the conventional release agent, while magnesium silicate, aluminum silicate and magnesium silicate according to the present invention are used in the present invention. It is a synthetic silicate compound. Tables 2 and 3 show the blending amounts of the respective materials with the total amount of the inorganic powder being 100% by weight, and the results of tests on the heat insulating properties of the coating applied with the release agent. In Tables 2 and 3, “Al-Mg Silicate”, “Al Silicate” and “Mg Silicate” in the material column are F, G, and H in Table 1, respectively, that is, synthetic magnesium aluminate silicate and synthetic aluminum silicate. And synthetic magnesium silicate.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

The heat insulating property of the release agent film was evaluated by the solidification time of the molten metal according to the following method. The mold is 20mm x 200
mm cavity with a depth of 200 mm and a thickness of 20 mm
mm. Further, a gate and a thermocouple for measuring the temperature at the center of the cavity are provided at the upper part, and the structure is divided vertically into two parts and assembled by bolts. The mold was disassembled and heated to about 150 ° C., and each of the suspension samples was diluted with water for 1 hour.
Spray the solution diluted 0-fold onto the inner surface of the mold to obtain a thickness of about 5μ.
After forming a coating film of m and assembling a mold, the temperature was raised to 240 ° C., a molten aluminum (AC4C) at a temperature of 720 ° C. was poured, and the time until solidification was measured.

As shown in Table 2, Samples 1 to 5 containing only boron nitride, limestone, talc, sericite and graphite had a solidification time of 120 seconds or less, whereas magnesium aluminate silicate and aluminum silicate The samples 6 to 8 of the present invention using porous particles of magnesium silicate have a solidification time of 1
It shows around 90 seconds, which indicates that the heat insulating effect is excellent. In particular, magnesium silicate aluminate has the best heat insulation at 195 seconds. Also, from Tables 2 and 3,
Samples 9 to 10 obtained by adding magnesium silicate, aluminum silicate or magnesium silicate to conventional inorganic powder
20 also shows that the heat insulating effect is significantly improved. Regarding the relationship between the mixing ratio of sericite and magnesium aluminate silicate and the heat insulating property, samples 2, 6,
It can be known by comparing 9, 10, 11, and 12.
That is, the sample containing only magnesium aluminate has the highest heat insulating property, and the heat insulating property gradually decreases as the ratio of magnesium aluminate decreases to 70, 50, 30, and 10% by weight, and the sample containing only sericite ( Sample 2)
It turns out that the heat insulation is much lower.

[0017]

As described above, since the release material of the present invention has excellent heat insulating properties, the cooling rate of the molten aluminum filled in the mold can be reduced, so that the present invention can be applied to low-speed injection casting. If the hot water and hot water flow,
It is possible to produce a high quality aluminum casting having a complicated shape.

Claims (4)

(57) [Claims] 1. A mold release agent for mold casting, wherein release agent particles made of a porous synthetic silicate compound having a specific surface area of 40 m ² / g or more are suspended in water containing a dispersant. . 2. The synthetic silicate compound is at least one of magnesium aluminate silicate, magnesium metasilicate aluminate, aluminum silicate, magnesium silicate, magnesium bismuth aluminate silicate and calcium silicate.
The release agent for mold casting according to claim 1, which is a seed. 3. The method according to claim 1, wherein the release agent particles have a solid content of less than 90% by weight of talc, sericite, pyroxene, boron nitride, molybdenum disulfide, tungsten disulfide, mica, enstatite, fluorinated graphite, PTFE, The mold release agent for mold casting according to claim 1 or 2, comprising at least one of melamine cyanurate and graphite. 4. The release agent for mold casting according to claim 1, wherein the suspension of the release agent particles contains water glass or colloidal silica.