JPH0768340A - Sand casting mold - Google Patents

Abstract

PURPOSE:To easily produce thin regardless of casting materials and to provide the sand casting mold having excellent thermal impact resistance by incorporating metallic chips at specific sizes and ratios into molding sand formed by kneading resins of an org. system in a sandy form. CONSTITUTION:This sand casting mold is used for casting to be executed by immersing the sand mold into, for example, molten metal and sticking the molten metal to the outer periphery thereof. The sand mold receives the heat quantity meeting the length of the immersion time and the metallic chips 3 having 5 to 20mm length, 0.2 to 0.6mm outside diameter at 1.4 to 3.0wt.% ratio to the molding sand 2 forming by kneading the resins of the org. system to sand grains. Crack is, therefore, prevented by the largeness of the heat capacity. The solidification of the molten metal progresses in a short period of time in a coating layer 4 consisting essentially of zirconia and iron powder and, therefore, the thin castings are stably formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand mold for producing a thin cast product, and more specifically, a sand mold is immersed in a molten metal to produce a predetermined thin cast product on the surface of the sand mold. For sand molds for.

[0002]

2. Description of the Related Art Generally, a casting method using a sand mold is performed by using an upper mold 10, a lower mold 11, and a core 12 as shown in FIG.
By molding, and by combining the respective molds, the molten metal 14 is filled in the cavity 13 with the tribe 15,
We manufacture castings with a specified wall thickness. In such a sand mold, since the cooling capacity that controls the directivity when the molten metal solidifies is small, small metal pieces (steel material cut pieces or steel balls) are mixed in the sand mold and directional solidification causes shrinkage cavities. It has been practiced to manufacture a cast product having no defects (Japanese Patent Laid-Open No. 63-1407).
39).

Further, as a casting method for producing a thin-walled cast product, a die (made of cast iron) formed in a cylindrical shape or a column shape is dipped in a molten metal, and a high thickness of a predetermined thickness is provided on the outer periphery of the die. A method for producing a thin cast product of a silicon-aluminum alloy has been considered (see JP-A-61-199568).

[0004]

However, with the casting method described in Japanese Patent Laid-Open No. 63-140739, it is possible to produce a thick cast product, but when producing a thin cast product, the molten metal is Since the thin portion of the cavity is easily solidified, there is a drawback that filling failure occurs. Empirically, cast iron has a thickness limit of about 3 mm and cast steel up to about 6 mm, and it has been impossible to manufacture cast products thinner than that.

Further, according to the casting method described in Japanese Patent Laid-Open No. 61-199568, it is possible to easily produce a thin-walled casting product if the casting product has a simple shape, but a casting product having a complicated shape is required. It could not be manufactured and was restricted by the product shape of the cast product. Further, in the material of the cast product, when casting cast iron, cast steel, etc., which are high melting point materials,
There is a problem that the mold is easily melted and cannot be cast.

Considering the above problems, those skilled in the art change the mold described in JP-A No. 61-199568 to a sand mold and immerse the sand mold in molten metal to manufacture a cast product. It's easy to think about how to do it.

However, in the casting method described in Japanese Patent Laid-Open No. 61-199568, even if the mold is simply changed to a sand mold for casting, the sand mold does not have the strength against thermal shock, and therefore, in the molten metal. When immersed in the sand mold, cracks were generated by the thermal shock of the molten metal, which sometimes caused the sand mold to collapse. Also, it becomes difficult to adjust the wall thickness of the product, and the molten metal adheres to parts other than the parts necessary for the product,
There is no point in carrying out the above method because the shape of the product part cannot be given in one step, that is, only by casting.

The present invention has been made in view of the above-mentioned various problems of the related art, and an object thereof is to make it possible to easily manufacture a thin-walled cast product regardless of the casting material and to have excellent thermal shock resistance. To provide a mold.

[0009]

In order to solve the above-mentioned problems, the sand mold of the present invention has a sand mold in which an organic resin is kneaded into sand grains and has a length of 5 to 20 mm and an outer diameter of 0.2 to 0.6
It is characterized in that a metal chip of mm is mixed at a ratio of 1.4 to 3.0 wt%.

Further, zirconia and 15 to 50 with respect to the zirconia are formed in a portion of the sand mold for forming a thin cast product.
It is characterized in that a coating layer containing iron powder mixed in a wt% ratio as a main component was formed.

[0011]

The sand mold of the present invention is used for casting, for example, by immersing the sand mold in the molten metal and adhering the molten metal to the outer periphery thereof. In that case, although it receives the amount of heat according to the length of the immersion time, the length of the metal tip is 5 to 20 mm and the outer diameter is 0.2 to
Since it contains 1.4 to 3.0 wt% of 0.6 mm, cracks are prevented due to its large heat capacity.

Further, according to the present invention, in the coating layer containing zirconia and iron powder as the main components, solidification of the molten metal progresses in a short time, so that a thin cast product can be stably formed.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a sectional view of a sand mold showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a casting apparatus used in this embodiment.

In FIG. 1, reference numeral 1 is a sand mold for producing a liner made of cast steel which is wrapped in the exhaust port portion of the cylinder head, and comprises a casting sand 2 and a wire 3 in which an organic phenol resin is kneaded. Mixed and shaped. Here, reference numeral 4 is iron powder, zirconia (Zn2
O), a phenol resin, and a coating layer composed of alcohol. Further, reference numeral 5 is a coating layer containing alumina (Al2O3) powder and iron oxide as main components.

Further, in FIG. 2, reference numeral 6 is a molten metal holding furnace in which a molten metal 7 of stainless cast steel (SCH1) is placed. Reference numeral 8 is a holding jig for the sand mold 1, which is used for immersing the sand mold 1 in the melt 7 and for melting the melt 7.
It is designed to be taken out from inside.

Next, a method of manufacturing the sand mold will be described.
A molding sand 2 in which an organic phenolic resin is kneaded, and a mild steel wire 3 having an outer diameter of 0.35 mm and a length of 10 mm containing 3.0 wt% thereof (copper wire may be used as another material). .) And sand mold 1 is molded by the shell molding method. Then, a mold coat layer 4 made of iron powder, zirconia (Zn2O), phenol resin, and alcohol is formed on the sand mold 1 where the casting is to be formed by brush.
This mold coat layer 4 was formed by using iron powder having an average iron powder particle size of 100 mesh, and using a mold coat material containing 30 wt% of iron powder in zirconia (Zn2O), and having a mold coat thickness of 0.3 mm. . Next, a coating layer 5 containing alumina (Al2O3) powder and iron oxide as main components was formed on the non-product part in order to prevent adhesion of the molten metal.

Using the sand mold 1 manufactured as described above, a liner made of cast steel for casting in the exhaust port portion of the cylinder head is cast. That is, in FIG.
The sand mold 1 is held by a holding jig 8, immersed in a molten metal 7 of stainless cast steel (SCH1) heated to 1600 ° C. for 1 second, and then the sand mold 1 is taken out of the molten metal 7 to reduce the thickness. A cast product was manufactured. The time for dipping and removing the sand mold 1 was set to 5 seconds. Since the cast product manufactured in this manner was formed with a wall thickness of 1 mm only on the surface of the mold coating layer 4 of the sand mold 1, the sand mold 1 was taken out from the cast product and shot-blasted into the cast product. In this way, the liner that is cast in the exhaust port of the thin-walled cylinder head that requires heat resistance can be finished by casting. Therefore, by heat-sealing the aluminum alloy exhaust port portion with this cast steel liner, the exhaust port portion was able to obtain heat resistance up to 950 ° C. That is, in this embodiment, a thin cast product can be formed by one-time casting using a sand mold having a simple structure.

In this embodiment, a cast steel liner was manufactured in order to improve the heat resistance of the exhaust port portion. However, the invention is not limited to this embodiment, and a thin cast product of a portion where heat resistance is required is produced. Can be manufactured, and the component itself can be manufactured as a thin-wall cast product. Further, in this embodiment, the wire (wire) cut is added to the sand mold 1, but it is also possible to use cutting scraps and the like when cutting steel. Furthermore, in this example, using a sand mold, only the production of a thin-walled casting made of cast steel was described, but not limited to cast steel, thin-walled casting made of a high melting point material such as cast iron or a low melting point material such as an aluminum alloy. Goods can also be manufactured easily.

Further, in the sand mold 1 for immersion casting, the content of the metal chips 3 contained in the sand mold 1,
The diameter, the length, and the iron powder content of the mold coating layer 4 were examined, and will be described below with reference to FIGS. 3 to 5.

FIG. 3 is a diagram showing a crack generation time of the sand mold 1 with respect to the content of the metal tip 3. In FIG. 3, the metal tip 3 has an outer diameter of 0.35 mm and a length of 1
The experiment was carried out using a sand mold having a thickness of 0 mm and no mold coating layers 4 and 5. Here, the time required to immerse the sand mold in the molten metal 7 and take out the sand mold from the molten metal 7 was set to 5 seconds.
That is, in this casting method by immersion, it is difficult to immerse and remove the sand mold within 5 seconds, and the immersion condition of the sand mold also deteriorates.

According to the broken line A in FIG. 3, the sand mold must contain 1.4 to 3.0 wt% of metal chips 3 with respect to the molding sand 2. When the content of the metal tip 3 is less than 1.4 wt%, cracks are generated by the thermal shock of the molten metal 7 during casting, and it is impossible to manufacture a thin cast product. Further, when the content of the metal chips 3 exceeds 3.0 wt%, it becomes difficult to knead and mold the sand mold, and it is impossible to manufacture a thin cast product.

This cast product is a thin cast product,
When the sand mold is taken out of the molten metal 7, the molten metal 7 adhering to the surface of the sand mold solidifies at about the same time, so even if cracks occur in the sand mold after 5 seconds, there is no adverse effect on the casting. Further, the content of the metal tip 3 was tested by fixing the diameter and the length of the metal tip 3, but it was 1.4 wt% or more from the viewpoint of giving the cooling ability to the sand mold 1 regardless of the size. It is necessary to contain the metal chip 3.

Next, FIG. 4 and FIG. 5 are diagrams showing the crack generation time of the sand mold with respect to the length and outer diameter of the metal tip 3. At the broken lines B and C in each figure, the metal chip 3
The mixing amount was set to 3.0 wt%, and the relationship between the length and the outer diameter of the metal chip 3 with respect to one fixed value of the outer diameter of 0.35 mm and the length of 10 mm was tested. Based on these results, the length of the metal tip 3 is 5 to 20 mm.
Is required, and the outer diameter of the metal tip 3 is 0.2 to
A diameter of 0.6 mm is required. Below these lower limits, cracks occur in the sand mold 1 during immersion in the molten metal 7, and thin-walled cast products cannot be manufactured. Further, it has been found that when the upper limit values are exceeded, it becomes difficult to mold the sand mold 1.

Next, FIG. 6 is a diagram showing the relationship between the amount of iron powder mixed in the mold coating layer 4 and the product thickness. The sand mold containing the metal chips 3 can form a thin cast product without coating the mold coating layer 4. However, although the cast product is not unusable as a product, the thickness varied and the stability of the thickness was lacking. Therefore, the metal tip 3.0
A coating thickness of 0.3 mm was formed on a sand mold containing wt%, and an experiment was conducted by changing the iron powder content of an iron powder average particle size of 100 mesh. The immersion and removal time is 5 seconds.

According to the broken line D in FIG. 6, the product thickness is
It is found that the particles are uniformly formed according to the amount of iron powder. However, when the amount of the iron powder mixed is less than 15 wt%, the solidified layer due to the adhesion of the molten metal 7 becomes too thin. Further, when the amount of the iron powder mixed exceeds 50 wt%, the solidified layer due to the adhesion of the molten metal becomes thick. Therefore, when a thin cast product is manufactured by this method, iron powder is added to zirconia (Zn2
It is usually necessary to mix 15 to 50 wt% with respect to O). By performing dip casting using the sand mold of this example, it is possible to easily cast a thin cast product with a minimum wall thickness of 0.5 mm that can be used as a product.

[0026]

As described above, according to the present invention, it is possible to provide a sand mold capable of easily manufacturing a cast product having a complicated shape to a desired thickness. Therefore, as compared with the conventional mold and the sand mold, there is an advantage that the manufacturing cost of the sand mold of the present invention and the manufacturing cost of the product by the sand mold of the present invention can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a sand mold showing an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a casting apparatus used in this embodiment.

FIG. 3 is a diagram showing a crack generation time of a sand mold with respect to a metal chip content.

FIG. 4 is a diagram showing a crack generation time of a sand mold with respect to a length of a metal tip.

FIG. 5 is a diagram showing the time taken for cracks to occur in the sand mold with respect to the diameter of the metal tip.

FIG. 6 is a diagram showing the relationship between the amount of iron powder mixed in the mold coating layer 4 and the product thickness.

FIG. 7 is a sectional view of a mold in a conventional casting method.

[Explanation of symbols]

 1 Sand Mold 2 Foundry Sand 3 Metal Chip 4 Coat Layer (Main Component: Iron Powder, Zirconia) 5 Coat Layer (Main Component: Alumina Powder, Iron Oxide Iron Powder)

Claims (2)

[Claims] 1. Metal sand having a length of 5 to 20 mm and an outer diameter of 0.2 to 0.6 mm is mixed at a ratio of 1.4 to 3.0 wt% into foundry sand in which sand particles are kneaded with an organic resin. A sand mold. 2. Zirconia in a portion of the sand mold for forming a thin cast product and 15 to 50 wt% of the zirconia.
The sand mold according to claim 1, wherein a mold coating layer containing iron powder mixed in a proportion of 10% as a main component is formed.