JPS6352745A - Core for pressure casting and its production - Google Patents

Abstract

PURPOSE:To eliminate the development of cracking and to obtain a core restraining insertion of molten metal by forming a first coating layer containing refractory and metallic oxide on the outer surface of core main body and a second coating layer containing refractory salt grain. CONSTITUTION:On the outer surface of the core main body 4 for core 1 or core 2, liquid slurry containing powdery refractory, metallic oxide, etc., is coated and dried, to form the first coating layer 5 having about 300-350 mum thickness. Next, as necessity requires, solution containing grains of graphite, mica, etc., is coated and dried, to form the intermediate coating layer 6. In succession, solution containing refractory salt grain of carboxylic acid lithium salt, etc., is coated and dried, to form the second coating layer 7 having about 5-15 mum thickness. In this way, the core having the prevention effect of insertion of molten metal into the core main body 4 is effectively produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a core used for pressure casting such as die casting and a method for manufacturing the same.

(Prior art) Generally, when casting a casting having a hollow part by a pressure casting method such as a die casting method, the molten metal is inserted into the shell core by the hot water pressure, so the inner wall of the hollow part of the casting after casting is There is a risk that some of the core sand that makes up the core may get caught. If a casting with part of this core sand entrapped is used as a product, the core sand will separate from the inner wall of the hollow part during use and mix with liquids such as oil and water flowing inside the hollow part. Therefore, in order to prevent such a situation from occurring, for example, the
As disclosed in the above publication, a first coating layer is formed by coating and drying a slurry liquid containing a mixture of powdered refractories and colloidal silica on the surface of a shell core, and then
By applying a mica aqueous solution on the first coating layer to form a second coating layer, the surface of the shell core is smoothed by the first coating layer, and hot water pressure acts on the core surface. It is known that the shell core is made uniform, and the second coating layer is used to suppress the penetration of molten metal into the shell core.

(Problems to be Solved by the Invention) However, the outermost surface layer (second coating layer) of the shell core formed as described above is coated in a mica aqueous solution (
Due to the poor dispersibility of mica particles, it is difficult for the mica particles to be uniformly distributed in the layer, and since the IJlle-C particles are large, the liquid dripping phenomenon makes the distribution of mica particles even more uneven in the layer. .

If the distribution of mica particles in the outermost surface layer (second coating layer) becomes uneven in this way, the degree of shrinkage caused by heating during layer formation, that is, during drying, will vary throughout the layer. There is a risk that cracks may occur in the layer, and if a shell core with cracks generated is used for casting, the molten metal will be inserted from the cracked area into the shell core, that is, the core body made of resin-textured sand. A problem may occur.

In addition, because the core body shrinks due to the liquid that acts during casting, or because the mica layer, which is the outermost surface layer, is difficult to shrink, it is particularly important to It is easy for this to occur, and the molten metal is often inserted into the core body from the cracked area.

The present invention has been made in view of these points, and its purpose is to identify the components constituting the outermost surface layer of the core, and to determine the distribution state of the components in the layer. uniformly, and also to minimize the effect of shrinkage of the core body on the outermost surface layer during casting, thereby reducing the heating of the outermost surface layer of the core during layer formation, that is, during drying. This eliminates the occurrence of cracks due to variations in layer shrinkage I and the cracks that occur in parts of the core during casting, and prevents the molten metal from entering the core body during casting. An object of the present invention is to provide a pressure casting core that can reliably suppress insertion.

Furthermore, the present invention is directed to providing a manufacturing method for efficiently manufacturing the core.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides a core body with a powdery refractory material, metal oxide, etc. on the outer surface of the core body. - form a coating layer. Further, a second coating layer made of hardly soluble salt particles is formed on the first coating layer.

Furthermore, the present invention provides a manufacturing method for manufacturing the core, in which a slurry liquid containing powdered refractories, metal oxides, etc. is first applied to the outer surface of the core body, and then a drying process is performed. A first coding layer is thereby formed. Next, a solution containing hardly soluble salt particles is coated on the first coating layer and then dried through a T culm to form a second coating layer.

(For Ink) With the above configuration, in the present invention, the outer surface of the core body (
First, from powdered refractories, metal oxides, etc.]
-Ting layer, second TZ consisting of slightly soluble and 1 (1) salt particles
l-=T-ing layers are sequentially laminated 4'. On this occasion,
- Said second] - As the slightly soluble salt particles constituting the coating layer, ultrafine particles of, for example, 0.1 μm are used. In other words, fine particles or flat particles such as the mica mentioned above can only be crushed to a size of 1 μm at most, but hardly soluble salt particles can be crystallized to the order of 0.1 μm. There is a method C that utilizes this feature.

Therefore, when a solution containing these poorly soluble salt particles is applied to the first coating layer 1 of the core body, the salt particles are fine particles and cannot be uniformly dispersed in the solution. The second layer is formed through a subsequent drying process.
] - There are no cracks in the ding layer during heating (due to variations in shrinkage and adhesion of the ζ layer).Moreover, as mentioned above, the salt particles are characteristic particles and therefore have an almost spherical shape, so external forces can be avoided. The free deformation due to the action of
・τ+:) ε: collection if! ? 1 (according to JT - (casting due to the deformation of the second doting layer) j5 [In particular, the crank is applied to a part of the core plate, etc. / I does not exist, so 1) is 3
When making 4 (J), the insertion of the molten metal into the core body will be reliably suppressed.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIGS. 1 and 2 show a pressure casting medium according to an embodiment of the present invention, which is a two-part type consisting of a first core 1 and a second core 2, which is applied when casting a rotor for a rotary engine of an automobile. The above plan 1 and 2 of the core 3 are shown below.
Since the cores 1 and 2 have the same structure except for their different shapes, the first core 1 will be explained below, and the second core will be explained below.
Regarding the core 2, the same constituent parts are given the same reference numerals and detailed explanation thereof will be omitted.

4 is a core body of the first core 1;
For example, about 250 pieces of resin-coated sand, which is made by mixing 200 meshes of sand with phenolic resin as a binder, is used.
It is molded by filling it into a core mold (not shown) heated and maintained at .degree.

Further, a first coating layer 5 is provided on the outer surface of the core body 4.
is formed, and the first coating layer 5 has a thickness of, for example, 100 to 350 μm by applying a slurry liquid containing powdered refractories, metal oxides, etc. to the outer surface of the core body 4 and then going through a drying process. Formed to the thickness of the tiles. This first
The reason why the thickness of the coating layer 5 is set in the above range is that if it is less than 100 μm, cracks may occur due to the pressure of the hot metal during casting, while if it exceeds 350 μm, it will be proportional to the increase in the layer thickness of the molten metal relative to the core body 4. This is because the effect of preventing infiltration cannot be expected, and on the contrary, the dimensional accuracy of the first core 1 is adversely affected. The composition of the slurry liquid is, for example, S! O257.5% by weight, Aβ2032.0% by weight, Fe203 4.0% by weight, Ca00.5% by weight, Mg025. O weight%, Z
ro20.5% by weight, C6.0% by weight, others 4.5
The weight percentage was diluted to 50% with ethyl alcohol.

Further, an intermediate coating layer 6 is formed on the first coating layer 5 of the core body 4, and the intermediate coating layer 6 is formed by applying a solution containing fine particles or flat particles of graphite, mica, etc., and then drying it. For example, in the case of a graphite layer, an average particle size of 0.5 to 10 μm is reduced to a layer thickness of 10 to 50 μm, and in the case of a mica layer, an average particle size of 2
Each layer is formed to a layer thickness of 50 to 150 μm with a thickness of ~10 μm. The reason why the particle diameters of the graphite and mica particles constituting the intermediate coating layer 6 are set in the above range is that the lower limit is a manufacturing problem, and the upper limit is difficult to densify the layer and prevent molten metal from penetrating. This is because there is a risk. The reason for setting the layer thickness of graphite and mica within the above range is that if the thickness of the graphite layer is less than 10 μm, there is a risk of cracks occurring due to the pressure of hot water during casting, while if it exceeds 50 μm, the molten metal will This is because an infiltration prevention effect proportional to the increase in layer thickness cannot be expected, and in the case of a mica layer, similarly to the graphite layer described above, if the thickness is less than 50 μm, cracks may occur due to the hot water pressure during casting.
If the thickness exceeds .mu.m, the effect of preventing the molten metal from penetrating into the core body 4 in proportion to the increase in layer thickness cannot be expected. And the graphite mentioned above.

As a solution containing fine particles or flat particles such as mica, for example, in the case of graphite, 50% by weight of graphite particles to 5% water
In the case of mica, a mixture of water glass (sodium silicate > 20% by weight) is used with respect to 80% by weight of mica particles.

Further, as a feature of the present invention, a second coating layer 7 is formed on the intermediate coding layer 6 of the core body 4,
The second coating layer 7 has an average particle size of 0.1 to 1, for example.
A layer thickness of, for example, 5 to 15 μm is formed by applying a solution containing sparingly soluble salt particles of a lithium carboxylic acid salt having a thickness of 5 μm and then passing through a drying process. The reason why the particle size of the salt particles constituting the second coating layer 7 is set in the above range is that it is difficult to manufacture non-vortexed particles of 0.1 μm, whereas if the size exceeds 1 μm, the shape of the salt particles will change. This is because the nearly spherical shape may reduce the effect of preventing infiltration of molten metal. The reason for setting the layer thickness of the salt particles within the above range is that if it is less than 5 μm, cracks may occur due to the pressure of the hot metal during casting, while if it exceeds 15 μm, the layer thickness of the molten metal relative to the core water body 4 may increase. Proportional ingress protection tl=
fjjJ results can be expected. Further, a weak option of forming the second coating layer 7 directly on the first coating layer 5 when forming the intermediate coding layer 6 is as follows:
The layer thickness of the second coating layer 7 is 10 to 100 νm.

to form. The reason for setting it in this range is the same reason as in the case of forming the intermediate coating layer 6. As the sparingly soluble salt particles, barium sulfate, calcium sulfate, calcium carbonate, calcium silicate, etc., other than sodium carboxylate salt, can also be used with a particle size of 1 μm or less.

In addition, the above 1. The drying conditions for forming the intermediate d'3 and the second coated ink layers 5 to 7 are, for example, a drying temperature of 150'C and a drying time of 20 minutes, but are not limited thereto. For each of No. 5 to No. 7, the drying temperature and drying time may be set as long as they can evaporate the volatile components in the covering solution.

Next, the pressure VI manufacturing process 3 according to the above embodiment will be explained.

After filling the resin rowat nand into the mold 1, it is fired to form the T-water body 4 in each of the C1d5 and the second cores 1 and 2. After that, repeat the operation of immersing each core water body 4 in a slurry solution mixed as described above several times to dip-coat the outer surface of the core water body 4 with the slurry solution.
After the first drying, the core body 4 coated with the slurry liquid is carried into a drying process, and the drying humidity is set to 150'C1, for example.
By drying under the condition of 20 minutes drying time, a 150 μm first co-lining layer 5 is formed on the outer surface of each of the core water bodies 4.

Next, a solution containing graphite particles blended as described above is applied to this first coating layer 57 by spraying J-1~, or the core on which the first coating layer 5 is formed is coated with a solution containing graphite particles as described above. Immerse the main body in the above solution, and
By drying under the same drying conditions as when forming the coating layer 5, the first coating layer 51 has a thickness of 10μ.
middle of m] --7-, form layer 6.

Further, a solution containing the lithium carboxylate blended as described above is applied to the intermediate coating layer 6+ by spray coating, or the core body 4 on which the first and intermediate coating layers 5 and 6 have been formed is placed in the solution. A second coating layer 7 of 5 μm is formed on the intermediate ink layer G by immersing it in the ink layer G and drying it under the same drying and operating conditions as when forming the first and intermediate ink layers 5 and 6. Form.

In this way, the outer surfaces of the rain core water bodies 4, 4 are coated with the first water.
As shown in FIG. 3, the first and second cores 1 and 2 in which the intermediate and second core layers 5 to 7 are laminated are placed on top of the first core 1 with a reinforcing material 8 interposed therebetween. Then, a core 3 is formed by assembling the second core 2 at the bottom, and this core 3 is placed in a mold 11 that is located above the upper mold 9 and the upper mold 10.
The molten metal A of, for example, an aluminum alloy is poured into the mold '11 at a pressure of, for example, 700 to 3/cnf by the operation of the brange dispenser 12.
By injecting it into the tank, the 1-tar 13 of the engine shown in FIG. 4 is cast. At this time a
The relationship between the penetration depth of the molten metal into the core 3 and the casting pressure (1) is shown in Figure 5. A comparative example in which a second coding layer 6 made of graphite particles with a layer thickness of 10 μm was provided on the 1-1-1-ting layer 5 without providing a layer with a width of lithium carboxylate (
I), -The one shown by the dotted chain line -C is a comparative example in which a layer of lithium carboxylate width is not provided [This is a comparative example in which a second coating layer 6 made of graphite particles with a layer thickness of 15 μm 7 is provided on the first coating layer 5 ( ■) On the dashed-double line, - (In the case of knife 5, a layer 6 having a layer thickness of 1100 μm made of mica particles is provided in the first coating layer 57 while also providing a layer with a width of lithium carboxylate). In the comparative example (■), the one shown by the solid line is the second layer of Calcibo Sunami Liboum J with a layer thickness of 5μrrL on the middle layer of graphite particles with a layer thickness of 1+ourrL. This implementation 1! IJ (I) 7 was set, and -5 shown by the solid line is the I-ting layer 5 L H inside [Lυ) 1
- This is the present embodiment (n) in which a flying layer (5) is provided, and a second coating layer 7 of a lithium salt of 1/l-acid is provided, having a layer thickness of 100 mm and a u-plane surface. The first coating layer 5 is set to have the same layer thickness of 150 μm on each side. According to this data, in the above comparative example (1), the casting pressure was approximately 750 μm.
When it becomes 'J/crtt, the penetration depth of molten metal A is 0.16 mm in thickness of the first and graphite coating layer.
It can be seen that the molten metal A has reached the core body 4 beyond . In addition, in the above comparative example (II), the casting pressure was 800
Kg/ci, the penetration depth of the molten metal A becomes 0.20 mm, and the molten metal A reaches the core body 4 beyond the i-1 tal layer thickness of 0.165# of the first and graphite coating layers. I know that there is. Furthermore, in the above comparative example (III>), it can be seen that 2 mA of melt permeates into the core body 4 when the casting pressure exceeds 600 3/cni.
In this example (1), no insertion of molten IA into the core body 4 was observed up to 1000Kg/cm, and up to 1000Kg/cm
The insertion of molten metal A into the third coating layer 7 is started at the point when it exceeds ut, and about 116QK91/c is poured into the core body 4.
It can be seen that insertion of molten metal A cannot be seen unless ri is reached. In addition, this example (n
), a comparative example (III
) The molten metal A begins to penetrate at a higher casting pressure J, and has almost the same characteristics as a graphite coating layer.

As described above, in this example, since the second coating layer 7, which is the outermost surface layer of the core body 4, is made of ultrafine particles of lithium carboxylate than graphite particles,
The lithium carboxylate salt is uniformly dispersed in the solution, and the second coating layer 7 formed through the subsequent drying process becomes a layer in which the lithium carboxylate salt is uniformly dispersed. Therefore, there are no cracks in the second coating layer 7 due to variations in the degree of layer shrinkage caused by heating, and as mentioned above, the salt particles are extremely fine and therefore have a substantially spherical shape. Therefore, even if the core body 4 contracts due to the molten metal pressure during casting, the second coating layer 7 deforms in response to this contraction, so that some core corners etc. are deformed during casting. Therefore, insertion of the molten metal A into the core body 4 during casting can be reliably suppressed.

Furthermore, the above manufacturing method only uses a lithium carboxylic acid salt as the second coating layer 7 constituting the outermost surface of the core 3, and there is no need to adopt any special means for forming the second coating layer 7. Insertion of the molten metal Δ into the core water body 4 can be efficiently suppressed.

In the above embodiment, the intermediate coating layer 6 was formed of graphite particles, and the second coating layer 7 was formed of lithium carboxylic acid salt, but the present invention is not limited to this. For example, the intermediate coating layer 6 may be formed of mica particles, alumina particles, etc. It is also possible to form the second coating layer 7 with barium sulfate, calcium carbonate, etc., or to form the second coating layer 7 of salt particles on the first coating layer 5 without providing the intermediate coating layer 6.
The coating layer 7 may also be applied directly.

Further, in the above embodiment, the core bodies 4, 4 are made of resin-coated sand, but they are not limited to this, and may be made of hard white sand such as cement sand, or fine-grained gypsum. It can be adopted, and in general, the core 3 does not need to be limited to the split type.

Further, in the above embodiment, the rotor 13 of a rotary engine of a car is cast, but the application is not limited to this, and can also be applied to casting products other than cylinder blocks, cylinder heads, and other mountain vehicle parts. It goes without saying that it is possible.

(Effects of the Invention) As explained above, according to the present invention, a solution containing hardly soluble salt particles is applied onto the first coating layer, and the outermost surface layer of the core is coated with the layer of salt particles. I configured it with
When salt particles are coated on the first coating layer, the salt particles can be made into ultrafine particles, so if ultrafine salt particles are used, they will be uniformly dispersed in the solution and the subsequent drying process will be difficult. The second coating layer formed through this process is a layer in which salt particles are uniformly dispersed, and therefore the second coating layer is a layer in which salt particles are uniformly dispersed.
] - There are no cracks in the ding layer due to variations in the degree of layer shrinkage during heating, and as mentioned above, the salt particles are extremely fine particles and therefore have a nearly spherical shape, so there is a high degree of freedom in deformation due to the action of external force. is large, and therefore, even if the core body contracts due to the molten metal pressure J during casting, the second coating layer deforms in response to this contraction, so there is no chance of cracks occurring in parts of the core corners etc. during casting. Therefore, it is possible to reliably suppress the insertion of the molten metal into the core body during casting.

Further, according to the manufacturing method of the present invention, a core having the above-mentioned effect of preventing insertion of molten metal into the core body can be efficiently manufactured without using any special means.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a two-part type pressure casting core according to an embodiment of the present invention applied to the casting of rotors for rotary engines of automobiles; FIG. 2 is an enlarged longitudinal sectional front view of the core; The figure is a longitudinal sectional front view showing the casting state of the rotor.
FIG. 4 is a perspective view of the cast rotor, and FIG. 5 is data showing the penetration depth of molten metal into the core during casting. 4... Core body, 5... First coding layer, 7.
...Second coding layer. Figure 3 Figure 1 Figure 4 Figure 5 Casting pressure (C1/Cm') Figure 2

Claims (2)

[Claims] (1) A core body, a first coating layer formed on the outer surface of the core body consisting of a powdered refractory, metal oxide, etc., and a hardly soluble coating layer formed on the first coating layer. A pressure casting core comprising a second coating layer made of salt particles. (2) A first coating layer is formed by applying a slurry liquid containing powdered refractories, metal oxides, etc. to the outer surface of the core body, and then performing a drying process.
A method for producing a pressure casting core, which comprises applying a solution containing hardly soluble salt particles onto the coating layer and then performing a drying process to form a second coating layer.