JPS6092039A - Mold coating material for collapsible sand core for high pressure casting - Google Patents

Abstract

PURPOSE:To enable use of a collapsible sand core in high-pressure casting by using powder of boron nitride as a base material for a mold coating material, adding methanol or ethanol as a solvent thereto and compounding further a liquid resin therewith. CONSTITUTION:A mold coating material prepd. by using powder of boron nitride as a base material, adding methanol or ethanol as a solvent thereto and compounding further a liquid resin therewith is used as a mold coating material for a thermocollapsible sand core to be used in high-pressure casting such as aluminum die casting. Such mold coating material does not require calcining stage after coating and is dried at an ordinary temp. The penetration of a molten metal into the sand core in the stage of production is thus eliminated and the removal of the sand core after casting is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold coating agent for heat-collapsible sand cores used in high-pressure TJ construction such as aluminum die casting.

Conventionally, high-pressure casting such as aluminum die-casting has been widely used to improve productivity, but when casting a casting with a complex cavity or undercut in a part of the shape, it is necessary to use high-pressure casting as a core during drawing. Since it is not possible to use a core, a collapsible sand core is used instead, which has the contradictory functions of being able to withstand constant pressure and having good collapsibility.

With regard to the molding of the collapsible sand core used in this high-pressure casting, it is necessary to prevent the core from cracking during casting and from inserting molten metal between the sand particles, and to facilitate the removal of the core sand after casting. Various studies have been conducted on the coating agent for the purpose of
A variety of proposals have been made. For example, (1) A mixture of aggregate powder, clay, and water.

(2) An alkaline aqueous solution containing a powdered refractory and a water-soluble thermosetting resin is used as the primary coating agent, and a synthetic sea urchin aqueous solution (including a finely divided refractory made of metal powder) is used as the secondary coating agent.

<3) Acrylic resin or J-
Made using boxy resin.

However, in the above proposal, In the case of method (1) It needs to be fired after drying.

In the case of method (2) Two application and drying steps are required.

In the case of method (3) A high temperature drying process is required.

In addition, even when these methods are used, it is not possible to completely eliminate melting and intrusion between the sand particles, and it is not easy to remove the core sand after casting.

These drawbacks have made it substantially difficult to use collapsible sand cores in high-pressure casting.

The present invention eliminates the above-mentioned conventional drawbacks by using boron nitride, which has lubricating properties, has no affinity with molten metal, and is difficult to react thermally or chemically. Collapsible sand for high-pressure casting that prevents the formation of an intercalation layer without requiring a firing process and facilitates the removal of core sand after casting by applying or permeating the core sand. The present invention provides a coating agent for cores.

The present invention will be explained in detail below.

Now, by aluminum die casting I
- When trying to cast the Lance Mission Case 1,
A collapsible sand core with a diagonal shape (
A sand core (hereinafter referred to as a sand core) 2 is required, but it may be shaped by any conventionally known method. Here, a case will be described in which a chemical reaction hardenable sand core molded by, for example, a cold box method is used as the sand core 2, and a mold coating agent is applied to the sand core.

Regarding the molding of this chemical reaction hardening sand core, please refer to Sand Core 2.
The foundry sand that makes up the aggregate is, for example, refractory silica sand, and the organic binder used as the caking agent and hardening agent is a chemical reaction curing resin (e.g., a phenolic resin with a different class of wires) as a constituent material, and these are mixed. is blown into the core mold with air, and then amine gas is blown between the sand particles)
By reducing the Δ value, the phenolic resin can be cured by the curing chemical reaction, and the desired shape of 3i! This is to obtain an i-type product.

Next, a mold coating agent is applied or permeated onto the surface of the molded article of the sand core 2. The mold coating agent in this case is a powder of a substance that has lubricating properties, has no affinity with molten metal, and is difficult to react thermally or chemically, such as boron nitride (Boron N 1TR).
irle powder as a base material, methanol or ethanol is added as a solvent to the base material, and a liquid resin such as a resol with a relatively large molecular weight made into a water-soluble salt with a large amount of metal hydroxide is added to the base material. This is the solution. It should be noted that liquid resin can be applied to this base material made of nitrogen (2) element, as long as it has the same properties even if the nine types of materials to be mixed are changed.

When this mold coating agent having boron nitride as a base material is applied to the sand core 2, the boron nitride enters between the surface sand particles of the core and acts to seal them.

After that, sand core 2 coated with or impregnated with this coating agent.
Dry. Dry smallpox in this case is ll1l of the core.
If the temperature exceeds the temperature limit, the core will collapse during drying, so it is necessary to dry the core at a temperature lower than that level, or it may be dried at room temperature. After that, as shown below, set the sand core 2 in the mold and apply aluminum 18 alloy to the plunger injection pressure of 80kg/allz to 280kg/
cm", tf [3m!'lJ ・670℃). After this casting, a lagoon cut was performed, and then the sand was removed from the sand core 2 by sandblasting, and the sand was mixed between the sand particles. There was little occurrence of an insertion layer formed by sand particles and aluminum, and it was possible to completely remove the core sand quickly.Furthermore, after cutting the sprue mentioned above, sand baking was performed in a furnace for the required time. When this was done, the resin in the sand core 2 was thermally decomposed, and when sandblasting was performed in the same manner as above, the core sand and the insert layer could be removed even more easily, and an extremely good die-casting product could be obtained. .

As is clear from the above description, the present invention provides a mold coating agent for sand cores used in high-pressure casting, which has lubricating properties as a base material, has no affinity with molten metal, and is thermally and chemically reactive. By using methanol or ethanol as a solvent and adding liquid resin to make the 1k) powder of boron nitride, which is a substance that is difficult to dissolve, to make it liquefied and make it stick to the sand core, thermal collapse in high-pressure VF manufacturing, which was difficult in the past, has been avoided. This made it possible to use sand cores of different sizes.

That is, while the boron nitride in the mold coating agent of the present invention penetrates between the surface sand particles of the sand core during coating and acts to close the eyes, it does not have any affinity for molten aluminum aluminum during casting. Due to the synergistic effect with
This prevents the formation of an intercalation layer due to aluminum and sand particles mixed between sand particles, making it possible to use heat-collapsible sand cores in high-pressure casting.

When this coating agent penetrates into the inside of the sand core, the sand particles are more firmly bonded in the internal structure, increasing the pressure resistance of the sand core and preventing the core from cracking during casting. It acts in a certain way. Furthermore, although the liquid resin in this mold coating is thermally decomposed by the high temperatures during casting, the sand core maintains its shape without collapsing during casting, and its components are decomposed by high-temperature heating after casting. Since it is completely decomposed, the disintegrability of the sand core is good, and it is suitable for sand removal and casting.
The deposited mold coating layer can be easily removed.

In the above embodiments, a mold coating agent based on boron nitride was used in a chemical reaction hardening sand core using a cold box method, but the pot box method and the shell mold method can also be used.

It can be commonly applied to sand cores molded by other methods, and greatly contributes to producing 1 q of good-quality castings at low cost.

[Brief explanation of drawings]

The drawing is a schematic sectional view of a product for explaining one embodiment of the present invention. In the drawing, 1 is an aluminum alloy transmission case, and 2 is a sand core. Patent Applicant Tokyo Light Alloy Seisakusho Co., Ltd. 1 Procedural Amendment (Voluntary) March 19, 1980 Chief Examiner of the Japan Patent Office Examiner of the Japan Patent Office 1, Indication of Case 1982 Patent Application No. 199463 3 , Relationship with the case of the person making the amendment Patent applicant 5, Specification to be amended Document 1, Title of the invention High pressure tR) Coating agent for heavy-duty disintegrating sand cores 2, Claims (1) Nitrided III cord A molding agent for a collapsible sand core for high-pressure casting, which is made by using a powder of the following as a base material, adding methanol or ethanol as a solvent to the cough base material, and further blending these with a liquid resin. 3. Detailed Description of the Invention The present invention relates to a mold coating agent for heat-collapsible sand cores used in high-pressure casting of aluminum die-casting and the like. Hitherto, high-pressure casting such as aluminum die casting has been widely used to improve productivity. Since it is not possible to use a handling core, a collapsible sand core is used instead, which has the contradictory functions of being able to withstand constant pressure and having good collapsibility. By the way, regarding the collapsible sand core used for this high-pressure casting, in order to prevent core cracking during casting and insertion of molten lagoon between sand particles, and to facilitate the removal of core sand after casting, In contrast to using the core molded product directly for casting, research and development is progressing on applying treatments such as coating, dipping, and impregnating the molded core with a molding agent and then using it as a core product. Various proposals have also been made regarding the coating agent. For example, (1) A mixture of aggregate powder, clay, and water. (2) An alkaline aqueous solution containing a powdered refractory and a water-soluble thermosetting resin is used as the primary coating agent, and a synthetic sea urchin aqueous solution (including a finely divided refractory made of metal powder) is used as the secondary coating agent. (3) Those using acrylic resin or epoxy resin for direct application. However, in the above proposal, in the case of method (1), it is necessary to perform baking after drying. In the case of method (2), the steps of coating and drying are required twice. In the case of method (3), a high temperature drying step is required. In addition to requiring extra steps such as these, even if these methods are used, it is not possible to completely eliminate the insertion of molten metal between the sand particles on the surface of the core during casting, and it is also easy to remove the core sand after casting. It wasn't. These drawbacks have made it substantially difficult to use collapsible sand cores in high-pressure tR construction. The present invention eliminates the above-mentioned drawbacks of the conventional technology by using boron nitride, which is a substance that has lubricating properties, has no affinity with molten metal, and is difficult to react thermally or chemically. By coating or permeating the core, no firing process is required, the generation of an insertion layer is prevented, and El, 3
The present invention provides a coating agent I2 for use in a collapsible sand core for high-pressure casting, which facilitates the removal of core sand after m. The present invention will be explained in detail below. Now, when trying to cast a transmission case 1 as shown in the figure by aluminum die casting, a collapsible sand core (hereinafter referred to as a sand core) 2 shaped like a diagonal line is placed in the mold to form a cavity. Although it is necessary to insert it into the container, a conventionally well-known method may be used for its shaping. Here, a case will be described in which a chemical reaction hardenable sand core molded by, for example, a cold box method is used as the sand core 2, and a mold coating agent is applied to the sand core. Regarding the molding of this chemical reaction hardening sand core, please refer to Sand Core 2.
The foundry sand that makes up the aggregate is, for example, refractory silica sand, and the organic binder that serves as the caking agent and hardening agent is a chemical reaction curing resin (such as a type of phenolic resin) that is used as a constituent material, and these are mixed together. The material is blown into a core mold using air, and then amine gas is blown between the sand particles to cause the phenolic resin to harden through a curing chemical reaction, resulting in a core molded product having the desired shape. Next, a mold coating agent is applied or permeated onto the surface of the molded product of the sand core 2. The coating agent in this case is a substance that has no affinity with the molten metal and is difficult to react thermally or chemically, such as boron nitride (13oron N 1tr
icle) powder as a base material, methanol or ethanol is added as a solvent to the base material, and a liquid resin, such as a resol with a relatively large molecular weight, is made into a water-soluble salt with a large number of metal hydroxides. This is a mixed solution. It should be noted that liquid resin can be applied to the base material made of nitrogen-boron powder even if the nine types of materials mixed therein are changed as long as they have similar properties. A mold coating agent using this nitrided 1-strand powder as a base material has a sand core of 2.
When the boron nitride is applied to the surface of the core, the boron nitride enters between the sand particles on the surface of the core and acts as a sealant. After that, sand core 2 coated with or impregnated with this coating agent.
Dry. In this case, if the drying temperature exceeds the core collapse @ temperature, the core will collapse during drying, so it is necessary to dry at a temperature lower than that, but in reality, the deterioration temperature of the sand core is It is desirable to dry at room temperature below. After that, the sand core 2 obtained as described above was set in a mold, and the aluminum alloy was heated to 80
day/cm” to 280kg/cm2-, Note?Q'a
Die-casting was performed under h-polishing and 670°C conditions. After this casting, sprue cutting is performed, and then Sandplus 1-
When the sand was removed from the sand core 2, an insertion layer was formed between the sand particles by crystallized aluminum and sand particles (the core sand could be quickly and completely removed). In addition, if sand baking is performed in a furnace for the required time after the above sprue cutting, the resin deposited in the sand core 2 (1) will be thermally decomposed, and if Sand Plus 1 ~ is performed in the same manner as above, the core sand and the insert layer will be removed. can be done more easily and is very good
We were able to obtain a die-cast product. As is clear from the above description, the present invention provides a mold coating agent for sand cores used in high-pressure casting.
Boron nitride powder, which is a substance that has no affinity with molten metal and does not react thermally or chemically, is made into a liquid by using methanol or ethanol as a solvent and adding liquid resin. By introspecting the sand core, it has become possible to use a heat-collapsible sand core in high-pressure casting, which has been difficult in the past. When applied, boron nitride penetrates between the surface sand particles of the sand core and acts to close the eyes, but during casting it has no affinity with molten aluminum, so due to the synergistic effect with the sealing effect described above,
This prevents the formation of an intercalation layer due to aluminum and sand particles mixed between sand particles, making it possible to use heat-collapsible sand cores in high-pressure construction. In addition, when this coating agent penetrates into the core, the sand particles in the internal structure become more firmly bonded, increasing the pressure resistance of the sand core and effectively preventing core cracking during casting. It acts on Furthermore, although the liquid resin in this mold coating is thermally decomposed by the high temperature during casting, the sand core retains its shape without collapsing during casting, and the high-temperature residual heat of the aluminum after casting allows it to maintain its shape. Since most of the components are decomposed, the disintegrability of the sand core is improved, making it easier to remove the sand and remove the mold coating layer that has adhered to the casting. In the above example, a case was explained in which a coating agent based on boron nitride powder was used for a chemical reaction hardening sand core. It can be commonly applied to hardenable sand cores, and greatly contributes to obtaining castings with good θT at low cost. 4. Brief description of the drawings The drawings are schematic sectional views of products for explaining one embodiment of the present invention. In the drawings, 1 is a transmission case made of aluminum 911 alloy, 2 is a sand core. Patent applicant: Tokyo Light Alloy Manufacturing Co., Ltd. Procedural Amendment (Voluntary) May 24, 1980 1, Inc.'1 Indication 1981F Patent Application No. 199463 2, Name of the invention: Molding agent for collapsible sand cores for high-pressure casting 3, Person making the amendment 1'] Patent applicant Postal code: 361 Address: Saitama Motoyuki 11 1-21, Ichitomijuji-cho, 1-15
, Subject of correction: "March 19, 1980, I1 submission, 1, 1ffl't!l," page 5, line 7, "nitrogen boron" will be corrected to "boron nitride."I"2

Claims (1)

[Claims] (1) A molding agent for a collapsible sand core for high-pressure casting, which uses a powder of nitrided Ill as a base material, adds methanol or ethanol as a solvent to the base material, and further mixes liquid resin with the base material.