JPS6092040A - Collapsible sand core for high-pressure casting - Google Patents

Abstract

PURPOSE:To obtain a sand core which is suitable for high-pressure casting and has a good thermocollapsing property by coating a prescribed mold coating material contg. powder of boron nitride as a base material for a sand core molding for which a thermosetting resin is used then drying the sand core molding at the temp. at which the collapsion of the core starts or below. CONSTITUTION:This invention relates to a thermocollapsible sand core to be used for high-pressure casting such as aluminum die casting or the like in which a mold coating material obtd. by compounding powder of boron nitride, methanol or ethanol as a solvent and a liquid resin is coated on or penetrated in a core molding obtd. by bonding and curing molding sand by a resin curable by chemical reaction or thermosetting resin. Such molding is thereafter dried at the temp. at which the collapsion of the sand core starts or below. The penetration of the molten metal into the sand core is thus eliminated in the stage of production and the removal of the sand core after casting is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-collapsible sand core used in high-pressure casting of aluminum die-casting and the like.

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 Since it is not possible to use a core, it is necessary to use a collapsible core instead, which can withstand constant pressure and has good collapsibility, which are completely contradictory properties.

However, this high pressure & 2f3i! Regarding the collapsible core used for i, various research and developments have been carried out and various proposals have been made. For example, there are those using a water-soluble molten salt, those using an alloy with a relatively low melting point, and those using a mixture of aggregate and processed starch. However, all of these cores cannot withstand the high pressure during casting and may break, or the molten metal may get inserted into the core, making it difficult to completely remove the core from the casting. It had drawbacks.

On the other hand, recently, molded sand cores have been developed to prevent the insertion of molten metal into the core during casting and core cracking as described above, and to facilitate the removal of core sand after mouth casting. Research into applying a coating agent, dipping, impregnating, etc. to the material and then using it as a core product.

Development is progressing, and various proposals regarding it have also been made. Regarding the method of using a mold coating agent for this core molded product, for example, (1) a mixture of aggregate powder, clay, and water is used.

(2) Alkali 11 aqueous solution a, which is a mixture of a powdered refractory and a water-soluble thermosetting resin, is used as a secondary coating agent, and a synthetic mica aqueous solution (including a finely powdered refractory made of metal powder) is used as a secondary coating agent. What I did.

(3) Those using acrylic resin or King Bogishi resin for direct application.

etc. However, the above 11? In the proposal (
In the case of method 1), it is necessary to perform baking after drying.

In the case of method (2), one culm needs to be coated and dried twice.

In the case of method (3), a high temperature drying step is required.

In addition, sand cores made by treating these mold coating agents cannot completely eliminate the penetration of molten metal between the sand particles on the surface of the core, and the core sand after casting. It was not easy to get rid of it. These drawbacks have made it substantially difficult to use collapsible sand cores in high-pressure casting.

The present invention eliminates and overcomes the above-mentioned drawbacks of the conventional technology, and provides a core molded product made by bonding and curing foundry sand with a chemical reaction hardening resin or a thermosetting resin, which has lubricity and is compatible with molten metal. Sexless and passionate.

After applying or penetrating a coating agent based on boron nitride powder, which is a substance that is chemically difficult to react with, it is dried at a predetermined temperature or lower, thereby creating an insertion layer without the need for firing a single culm. The object of the present invention is to provide a collapsed tel sand core for high-pressure casting, which facilitates the removal of core sand after casting.

The present invention will be explained in detail below.

Now, by aluminum die casting, the size shown in the figure is 1.
-If you are going to cast Lance Mission Case 1,
In order to form the cavity, it is necessary to insert If+I breakable sand core (referred to as a sand core) 2 having a diagonal shape into the mold. Then, to shape the sand core, the sand is bonded and hardened using a chemical reaction hardening resin or a thermosetting resin, and the sand core T2 molded in this way is coated with a molding agent. and the required core product to 1q.
It is something that

That is, in the case of molding a sand core using a chemical reaction hardening resin, the foundry sand forming the aggregate of the sand core 2 may be, for example, refractory crushed sand,
The organic binder as a binder and a hardening agent uses a chemical reaction curing resin (for example, different types of phenolic resin) as a constituent material, and a mixture of these is blown into a core mold with air and molded. Further, by blowing amine gas between the sand particles, the curing chemical reaction of the phenolic resin is carried out, and the core molded as required is heated.

Next, a mold coating agent is applied to or penetrated into the shape of the sand core 2 and the surface of the object. The mold coating agent in this case is a substance that has lubricating properties, has no affinity with molten metal, and is difficult to react thermally or chemically, such as boron nitride (I3 oron N).
(7) Add methanol or ethanol as a solvent to the powdered base material, and add liquid resin, such as resol with a relatively large molecular weight, to the base material with a large amount of metal hydroxide. It is a solution containing salts, etc. Also, this nitrogen! 111
A liquid resin can be applied to a base material made of a single powder as long as it has the same properties even if one type of compounded material is changed. When this mold coating agent based on nitride powder is applied to the sand core 2, nitride III gets into the spaces between the sand particles on the surface of the core and seals them. It will affect.

However, by drying the sand core 2 coated with or impregnated with this mold coating agent 112, a desired core product 19 is obtained. In this case, the quality of drying is as follows: If the core collapses beyond the drying limit, the core will break 1111 times during drying.
Although it is necessary to dry at a lower temperature, it is actually desirable to dry at room temperature, which is below the deterioration temperature of the sand core.

During this erosion, the sand core 2 obtained as described above was set in a mold, and the aluminum alloy was heated to a plunger injection pressure of -8.
Die-casting was carried out under the conditions of 0 kg/cm to 2801+ (1/Cn+, lagoon dryness: 670'C.) After this T8 construction, the lagoon mouth was cut, and then the sand was blasted to the sand core 2 by sand blasting. When the sand particles were removed, an insertion layer formed by the aluminum and sand particles mixed in between the sand particles was generated. When the above 19-hole cut 1 is sand fired in a furnace for the required time, the 1/gin in the sand core 2 is thermally decomposed, and when sandblasting is performed in the same manner as above, the core sand and the insert layer are removed. can be done more easily,
I have a very good die casting product! ? I was able to

In addition, in the tenth embodiment, a core molded article made of 1 g using a chemical reaction hardening resin as a binder by the cold box method was coated with 61 coats of a coating agent containing 1all nitride powder as a base and dried. Although the case where the required core product is manufactured by 1!7 has been described, the present invention is not limited to this, and the present invention is not limited to this. Even when a core product is obtained by applying a coating agent based on this boron nitride powder to a 1q core molded product, thermal decay 41. It can achieve the same effect as a sand core.

As is clear from the above description, the present invention provides a core molded product made by using a chemical reaction hardening resin or a thermosetting resin as a binder in foundry sand, which has lubricating properties and is compatible with the molten metal. A liquid coating agent is applied by blending boron nitride powder, which is a strong substance that is inert and thermally and chemically reactive, with methanol or ethanol as a solvent, and further with liquid resin. C1. By infiltrating the sand core and drying it below the temperature at which the sand core begins to collapse, the required core product can be produced (7). A sand core of 1!l- is one that can be properly disintegrated.

That is, in the sand core made according to the present invention, the boron nitride in the coating agent component penetrates between the sand particles on the surface of the sand core during application and acts to close the eyes, while this boron nitride Since it has no affinity with molten metal, the synergistic effect of the above-mentioned sealing action will lead to the insertion of molten metal between the surface sand particles of the sand core. This made it possible to use a collapsible sand core.

As a result of preventing the molten metal from being inserted between the surface sand particles of the sand core, it is possible to obtain a casting with a clean casting surface and excellent dimensional accuracy and surface roughness.

In addition, in the sand core made according to the present invention, after the coating agent is applied or permeated, the drying time is below the collapse starting temperature.
Since it is not necessary to perform baking or high-temperature drying as with conventional sand cores, it is possible to coat the sand core without affecting the components of the coating agent that has penetrated into the mouth. There is no need for extensive equipment for those processes, and the manufacturing process can be greatly simplified, making a significant contribution to reducing costs to 1.

Roughly speaking, the shape of the sand core is maintained during casting by the action of the liquid resin in the mold coating agent, and most of its components are decomposed by the high-temperature residual heat of the aluminum after casting. The core has good disintegration properties, making it easy to remove sand and cast iron.
lI = 1 Since it becomes easy to remove the deposited coating agent layer, the post-process is simplified and a good 4T casting can be produced at low cost.

4. Drawing No. rIrI11x<=Il Light Drawing (J A schematic cross-sectional view of a product for explaining an embodiment of the present invention.

In the drawing, 1 is an aluminum alloy lance transmission case, and 2 is a sand core.

Patent applicant Tokyo Light Alloy Seisakusho Co., Ltd. Procedural amendment (voluntary) Chief examiner of the Patent Office Patent Office Examining Palace 1, Case indication 1151- Patent Application No. 14109 2, Name of the invention High f [Casting Use of collapsible sand core 3, relationship with amendment case No. 1 Patent applicant postal code @ 361 (1-location 1-2 Fujimi-cho, Saiko Sogyo M-shi IWi 1 Showa-11/11-15, Column for detailed explanation of the invention in the specification subject to amendment (1) Page 6, line 17 of the specification [l) j Output pressure 80k
(]/Cl1l to 280kg/cmJ will be corrected to [Injection pressure・80kg/cm2 to 280ka/cm”J.

Continuing amendment (spontaneous) May 24, 1980 Examiner of the Patent Office 1, Indication of the case 1981 Patent application No. 14109 Bow 2, Name of the invention High pressure t#f Zoida 1i It I Ura 1i Sand core 3, correction J
Related to the case Patent applicant's postal number 1 361 Showa - 1st month 1st month 5th, subject of amendment 1, Mei II, page 6, line 1 "Nitrogen side 1 is changed to "boron nitride"
I will correct it.

that's all

Claims (1)

[Claims] Converting foundry sand into chemical reaction hardening resin or thermosetting resin J:
After applying or infiltrating the core molded product obtained by bonding and curing, a coating agent made by blending boron nitride powder, methanol or ethanol as a solvent, and liquid resin is applied or infiltrated. LIilyA sand core for high-pressure casting, which is obtained by drying the sand core at a temperature below the collapse starting temperature of the sand core.