JP2964371B2 - Release agent for mold casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a casting method in which the speed of injecting molten metal is low and the molten metal is easy to cool, such as squeeze die casting, among aluminum die castings. The present invention relates to a release agent having good heat insulating properties (heat retention properties) and good releasability, which can be suitably used in cases where mold release properties are strictly required, such as in casting of complicated shapes.

[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.
For parts with long shapes or large and complicated shapes,
Due to shrinkage during solidification, the releasability deteriorates, and the product may be distorted or the product may not be released. Conventional release agents have high thermal conductivity and are suitable for small parts with simple shapes where casting defects are relatively difficult to appear.However, in the case of large and 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, the present invention has a heat insulating property (heat retention property) that has an effect that a molten metal is hardly cooled, does not cause a quality defect in a low-speed casting method, and has a good separation even in a large part. It is an object of the present invention to provide a release agent having moldability.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, a mold release agent for mold casting according to the present invention comprises a wax and a porous material as release agent particles suspended in water containing a dispersant. It is characterized by using synthetic silicate compound particles having a specific surface area of 40 m ² / g or more. In this case, the wax is at least one of wood wax, beeswax, rice wax, carnauba wax, wool wax, paraffin wax, microcrystalline wax and polyethylene wax, and the synthetic silicate compound is magnesium aluminate silicate, metasilicate It is characterized in that it is at least one of magnesium aluminate, aluminum silicate, magnesium silicate, magnesium bismuth silicate and calcium silicate. Further, in addition to the wax and the release agent particles composed of the synthetic silicate compound, talc, sericite, rock, boron nitride, molybdenum disulfide, tungsten disulfide, mica, enstatite having a solid content of less than 90% by weight, Calcium carbonate, fluorinated graphite, PT
It is characterized by containing at least one of FE, melamine cyanurate and graphite. Further, the release agent suspension is characterized by containing water glass or colloidal silica.

The above waxes include animal and plant waxes such as beeswax used for cosmetics, mineral waxes such as paraffin wax used for food packaging, and synthetic waxes such as polyethylene wax. Among the synthetic waxes, for example, polyethylene wax is produced by high-pressure polymerization of ethylene, low-pressure (Ziegler-type catalyst) polymerization, or thermal decomposition of high-molecular-weight polyethylene. The above-mentioned eight types of waxes are relatively easily available at present, but it is presumed that various derivatives similar to these have similar functions and effects.

[0006] The above-mentioned synthetic silicate compound is a compound that is chemically synthesized similarly to the one used as an acid adsorbent for pharmaceuticals, and is porous and has a specific surface area of 40 m ² / m ² .
g or more, the particle size is about 0.01 to 30 μm. For example, in the case of magnesium silicate, this synthetic silicate compound is obtained 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 an acidic aqueous solution of a bismuth salt is added thereto for reaction. Let
It can be prepared by combining a basic aluminum magnesium salt with bismuth hydroxide. Further, the above-mentioned six types of synthetic silicate compounds are substances that are easily available at present,
It is presumed that various derivatives similar to these have similar actions and effects.

[0007] 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.

[0008] Among the release agents of the present invention, the release agent composed of wax and silicate compound particles has relatively poor film-forming properties on a mold, but has good lubricity and heat insulation properties, so that a cast product is simple. It is suitable for a wide range of products from various shapes to long shapes having a large shrinkage rate during solidification. When the casting has a complicated shape, solid lubricant particles such as talc, sericite, boron nitride, graphite fluoride, etc. are added rather than a release agent consisting of only wax and silicate compound particles to improve lubricity. It is suitable that the film forming property on the mold is improved while maintaining the above. 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. The amount of the wax is preferably 0.1 to 20% by weight as a solid content. If the amount is less than 0.1% by weight, the lubricating property is not significantly improved. If the amount exceeds 20% by weight, the amount of generated gas increases, and casting defects due to entrainment of gas into the casting are liable to occur. In addition, among the solid lubricant particles, graphite and molybdenum disulfide are black-gray, so that when they are used, it is preferable to use a small amount.

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.

The release agent suspension according to the present invention has a high solid content at the time of preparation, and usually has an appropriate concentration of water at the time of use according to the size, shape and application conditions of the mold. Dilute with and use.

[0011]

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 made 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. Getting worse. 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. When wax is added to the wax, the wax that has entered between the synthetic silicate compounds is liquid or evaporates during casting to improve the fluidity between the synthetic silicate compound particles, and has substantially good lubricity and releasability. It becomes a release agent. Further, since the synthetic silicate compound and the wax are white or pale yellow substances, they do not deteriorate the working environment.

[0012]

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 an inorganic powder suspension. Next, 10% by weight of an emulsifier (polyoxyethylene alkyl ether)
Was added with 20% by weight of various waxes, followed by thorough stirring. 70% by weight of water was gradually added thereto, and the mixture was sufficiently stirred and dispersed by a homogenizer to prepare a wax emulsion.
The two liquids were mixed at a required ratio and stirred to obtain a sample. Table 1 shows the types of the inorganic powders and the respective specific surface areas. Table 1
Talc, sericite, boron nitride and graphite are inorganic powders contained in conventional mold release agents, while magnesium silicate, aluminum silicate and magnesium silicate are synthetic silicate compounds according to the present invention. Also,
Tables 2 and 3 show that the total amount of inorganic powder and wax is 1
The amounts of the respective materials to be set to 00% by weight and the results of tests on the heat insulating properties and the coefficient of friction of the coating applied with the release agent are shown.
In Tables 2 and 3, "Material Silicate Al
“g”, “Al silicate” and “Mg silicate” represent E, F, and G in Table 1, that is, synthetic magnesium aluminate, synthetic aluminum silicate, and synthetic magnesium silicate, respectively.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[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.

The lubricity of the release agent film was evaluated based on the coefficient of friction obtained by the ring compression test method. The mold is 60m in diameter
m, height 50 mm, the material is SKD61, and two of them are used. The mold was heated to about 160 ° C., and each suspension sample diluted 10-fold with water was sprayed on the mold surface to uniformly form a coating film having a thickness of about 5 μm. Thereafter, the test piece (material AC4C, outer diameter 20) heated to 400 ° C.
mm, inner diameter 10 mm, height 5 mm) between the coating surfaces of the two molds, and a compression ratio of 40 using an Amsler type testing machine.
% Compressed. The friction coefficient was calculated from the compressibility and the change in inner diameter of the test piece.

As shown in Table 2, Samples 1-4 containing only boron nitride, talc, sericite and graphite had a solidification time of 1
20 seconds or less, the heat insulation effect is low. Samples 5 to 7 using porous particles of magnesium aluminate, aluminum silicate, and magnesium silicate show a solidification time of about 190 seconds and have an excellent heat insulating effect, but have a friction coefficient of 0.40 or more. It shows a high value, indicating that the lubricity is slightly inferior. In contrast, Samples 9 to 14 of the present invention, in which a synthetic silicate compound and a wax were combined, had a solidification time of 180
It shows good heat insulation of ~ 191 seconds, and friction coefficient is 0.03
It can be seen that the lubricating property is good, being as low as about 0.10. Samples 15 to 15 obtained by adding a conventional inorganic powder to the components of the present invention
20 also shows that both the heat insulation effect and the lubricity show good values. The relationship between the mixing ratio of magnesium aluminate silicate and wax and the heat insulating properties and the coefficient of friction can be found by comparing Samples 5, 9, 10 and 11. That is, the sample 5 containing only magnesium aluminate silicate has the best heat insulating property, but has a high friction coefficient and poor lubricity. By adding the wax to 5, 10 and 15% by weight (samples 9, 10 and 11, respectively), the friction coefficient is greatly reduced and the lubricity is improved without greatly impairing the heat insulating effect. You can see that.

[0019]

As described above, the release agent of the present invention is excellent in heat insulation and lubricity, so that the cooling rate of the aluminum melt filled in the mold can be slowed, so that low-speed injection can be achieved. If the present invention is applied to casting, the flow of the molten metal and the flowability of the molten metal are improved, and the coefficient of friction can be reduced. With the above effects, it is possible to produce a high-quality aluminum casting having a complicated shape.

Claims (5)

(57) [Claims] 1. A mold casting mold release agent characterized in that wax and a release agent particle comprising a porous synthetic silicate compound having a specific surface area of 40 m ² / g or more are suspended in water containing a dispersant. Mold. 2. The wax according to claim 1, wherein the wax is at least one of wood wax, beeswax, rice wax, carnauba wax, wool wax, paraffin wax, microcrystalline wax and polyethylene wax. Release agent for mold casting. 3. The synthetic silicate compound comprises at least one of magnesium silicate, magnesium metasilicate, magnesium silicate, aluminum silicate, magnesium silicate, magnesium bismuth silicate and calcium silicate.
The mold release agent for mold casting according to claim 1 or 2, which is a seed. 4. The release agent particles wherein the solid content is less than 90% by weight of talc, sericite, rock, boron nitride, molybdenum disulfide, tungsten disulfide, mica, enstatite, calcium carbonate, graphite fluoride. The mold release agent according to any one of claims 1 to 3, comprising at least one of PTFE, PTFE, melamine cyanurate and graphite. 5. The release agent for mold casting according to claim 1, wherein the suspension of the release agent particles contains water glass or colloidal silica.