JPH11333545A - Manufacture of casting, and core used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a casting capable of preventing generation of uneven wall thickness or cavity and improving the production efficiency in manufacturing the casting having an enclosed part, and a core used therefor. SOLUTION: A circular flange part 51 is projected on a center part in the axial direction of a core 50, and a first forming part 52 and a second forming part 53 which are formed approximately symmetric are formed on both side thereof. A gas vent hole 51a is formed in an upper part of the flange part 51 to communicate an internal space 50a of the core 50 with the outer side. An opening part 50b is provided on an end part of the first forming part 52, and the opening part 50b is covered with a lid member 54. In a main mold 40, a first cavity 61 is formed around the first forming part 52, and a second cavity 62 is formed around the second forming part 53.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cast product and a core used for the same, and more particularly to a technique suitable for manufacturing a cast product having a closed portion.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a cast product having a closed part corresponding to a covered cylindrical lid part, a bowl-shaped bottom part, etc., as shown in FIG. The core 20 is accommodated in the main mold 10 having the core 10B, and a molding space (hereinafter, referred to as a cavity) 30 is formed around the molding part 21 corresponding to the molding part 21 of the core 20. Main mold 10
Is formed as a sand mold for each of the upper mold 10A and the lower mold 10B, and the core 20 is previously formed of various heat-resistant materials. The core 20 includes a supported portion (baseboard portion) 22 that is fixed by being sandwiched between the upper mold 10A and the lower mold 10B. In a cavity 30 of the main mold 10, a spout (gate) 11 connected to a molten metal introduction path (not shown).
Is provided. The molten metal is introduced into a pool (not shown) formed in the main mold 10, passes through a weir, and flows into a spout 11.
From the main mold 10 and the core 20 into the cavity 30.

[0003]

In the above-mentioned conventional casting method, when the molten metal is introduced from the spout 11, the molten metal is gradually filled from the lower portion of the cavity 30, and then the entire interior of the cavity 30 is filled. The molten metal is filled,
In the process of filling the molten metal, buoyancy is generated upward in the cavity 30 with respect to the molding portion 21 of the core 20 by the molten metal. There is a problem that it occurs. In order to prevent this uneven thickness, the supported portion 22 which is a part of the baseboard of the core 20 may be formed relatively large.
It is conceivable to extend the supported portion 22 as shown by a two-dot chain line. However, even in this case, the effect of eliminating uneven thickness is thin, and in this case, the mold volume becomes large and the production efficiency decreases. There is a problem.

[0004] In the structure shown in FIG.
Since the gas generated in the process of injecting the molten metal into the inside of the casting is hard to escape, there is also a problem that cavities are easily generated on the surface of the casting. In this case, the core 20 is made of a breathable material having a hollow structure (for example, a shell mold using resin sand), and an opening of the internal space is formed on the end face of the supported portion 22. Alternatively, a method of degassing from the opening may be considered. But,
In this case, the support of the supported portion 22 becomes more difficult, and the volume of the mold further increases.

Accordingly, the present invention is to solve the above-mentioned problems, and an object of the present invention is to prevent the occurrence of uneven thickness and burrs even in the production of a cast product having the above-mentioned closed portion. It is another object of the present invention to provide a method of manufacturing a casting that can improve production efficiency and a new core that can be used in the method.

[0006]

Means for solving the above-mentioned problems The present invention has been made to solve the above-mentioned problem in a method of manufacturing a cast product using a main mold and a core housed in the main mold. ,
The core includes a supported portion supported by the main mold, and first and second molding portions formed on both sides of the supported portion, and the main mold includes the first molding portion. A first molding space and a second molding space corresponding to each of the first molding portion and the second molding portion.
It is characterized in that a mold structure for guiding the molten metal to both the molding space and the second molding space is used. According to this means, the first molding portion and the second molding portion are provided on both sides of the supported portion of the core, and the first molding space and the first molding space are provided around the first molding portion and the second molding portion, respectively. Since the second molding space is configured to be defined, when the molten metal is introduced into the first molding space and the second molding space arranged on both sides of the supported portion of the core, the core is formed. Is subjected to stress from the molten metal from both sides, so that it is unlikely to assume an inclined posture due to stress from one side as in the related art, so that uneven thickness of the cast product can be reduced. Further, since the stress is reduced by receiving the stress from both sides, the volume of the supported portion can be reduced, so that the mold volume can be reduced. Further, since at least two castings can be manufactured at the same time, the productivity can be improved. Can be improved.

Here, it is preferable that the core is made of a gas-permeable material having a hollow structure, and is provided with a gas vent hole for communicating the inside and the outside of the supported portion. According to this means, since the gas that has penetrated into the air-permeable core can be released to the outside through the gas vent by making the core hollow, the occurrence of nests due to gas accumulation can be reduced. In this case, it is desirable for the core to be provided with an opening in the hollow portion and a lid member for closing the opening. In these cases, the core is preferably manufactured by a shell mold method using a resin sand.

In each of the above means, it is preferable that the first molding space and the second molding space are formed substantially symmetrically on both sides of the supported portion. According to this means, since the first molding space and the second molding space are formed substantially symmetrically on both sides of the supported portion, it is possible to substantially balance the stress applied to the core by the molten metal from both sides, The occurrence of uneven thickness can be more strictly suppressed, and the accuracy of the formed shape can be improved.

Next, in a core housed in a main mold used for casting, a supported portion supported by the main mold and surface shapes for casting formed on both sides of the supported portion are defined. It is characterized in that a first forming portion and a second forming portion provided are provided.

Preferably, the core is made of a gas-permeable material having a hollow structure, and is provided with a gas vent hole for communicating the inside and the outside at the supported portion. It is desirable to have a part and a lid member for closing the opening. In these cases, the core is preferably manufactured by a shell mold method using a resin sand.

In each of the above means, the cast product has a closed portion such as a covered cylinder or a bowl, and corresponds to a closed portion such as a covered tube-shaped lid or a bowl-shaped bottom. Preferably, the part is cast such that it is molded at the end of the core remote from the supported part. Further, it is preferable to form a convex portion or a concave portion to be fitted to the main mold on the supported portion of the core in order to enhance the stability and the positioning accuracy of the core, and in particular, the second It is formed in a circular shape over the entire circumference between the first molding part and the second molding part (for example,
An annular convex portion (flange portion) or an annular groove is desirable.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for manufacturing a casting according to the present invention and a core used for the same will be described with reference to the accompanying drawings. In this embodiment, a case where a sand casting method is used will be described. In this embodiment, a mold composed of a main mold 40 and a core 50 housed therein is used. The main mold 40 includes an upper mold 40A and a lower mold 40, each of which is a sand mold formed by a model.
B. The core 50 is a hollow cylindrical air-permeable shell mold whose end face is closed, and its axis is installed substantially horizontally. At the center of the core 50 in the axial direction, a circular flange portion 51 is formed so as to protrude. On both sides of the flange portion 51, a first forming portion 52 and a second forming portion 53 which are a pair of substantially symmetrically formed forming portions are formed.

A gas vent hole 51a is formed in the upper part of the flange portion 51 which protrudes in an annular shape.
0a is communicated to the outside. An opening 50b is provided at an end of the first molding portion 52, and the opening 50b is covered by a cover member 54. The first molding section 52 is designed to be symmetrical with the second molding section 53 when the lid member 54 is mounted.

The main mold 40 has a first molding portion 52 around the first molding portion 52.
A cavity 61 is formed, and is molded so that a second cavity 62 is formed around the second molding portion 53.
In the center of the main mold 40, the flange 5 of the core 50 is provided.
1, a fitting groove 41 is formed in the fitting groove 41, and an exhaust hole 40a communicating with the gas vent hole 51a is formed in the fitting groove 41.
Are formed. On both sides of the fitting groove 41, cylindrical support surfaces 42 abutting on both outer peripheral surfaces of the flange portion 51 of the core 50,
43 are formed. The flange portion 51 of the core 50 and the outer peripheral surfaces on both sides thereof constitute a baseboard portion (supported portion) supported by the main mold 40. Upper side 40 of main mold 40
A pair of grooves are formed by a pair of grooves respectively formed on the butting surface of A and the butting surface of the lower mold 40B, and these weirs are formed by the spouts 40b and 40c which are opened in the first cavity 61 and the second cavity 62, respectively. It has.

The molten metal is introduced into the first and second cavities 61 and 62 from the spouts 40b and 40c via a pool (not shown), a weir, and the like by the mold having the above structure, and casting is performed. And the second
In each of the cavities 62, a bowl-shaped casting (for example, a valve cylinder or the like) is formed. The casting method according to the present embodiment is particularly suitable when applied to a casting having a closed portion, for example, a cast having a cylindrical shape or a bowl shape. However, the cast product may be a closed tubular shape or a bowl shape as a whole. For example, a cast product in which a through hole needs to be formed after casting in a closed portion is similarly effective.

Next, a method of manufacturing the core 50 will be described. The core 50 is usually formed by a method called a shell mold method. As shown in FIG.
The (metal mold) is heated to 250 to 300 ° C. in advance, and a resin sand (for example, sand in which 3 to 7% of phenolic synthetic resin powder is mixed) is blown into the interior of the model 70 through the opening 70 a to form the resin sand. After adhering and solidifying on the inner surface of the model 70 and leaving it in that state for a certain period of time, sand that has not adhered and solidified on the inner surface of the model 70 is discharged from the opening 70a.
Thereafter, the whole is further heated and cured, and the core is released to take out the core body 50 '. On the other hand, the lid member 54 is formed by the same shell molding method, and the core body 50 ′ is formed.
When the lid member 54 is fitted to the end so as to cover the opening 50b, the core 50 shown in FIG. 1 is completed. Here, the pins 71 inserted into the model 70 are for forming the gas vent holes 51a.

As shown in FIG. 1, the top surface 51b and the two (both sides) side surfaces 51 of the flange portion 51 of the core 50 are provided.
c is configured to be fitted almost exactly into the fitting groove 41 of the main mold 40, and has a top surface 51b and a side surface 51c.
Corner 51d of the main mold fitting groove 41.
When the core 50 is incorporated into the main mold 40 (the upper mold 40A and the lower mold 40B), the main mold sand is shaved, and this sand is formed between the corners and the corners. The misalignment of the core 50 due to being bitten is prevented.

In the above embodiment, the center flange portion 51 of the core 50 and the outer peripheral surfaces on both sides thereof constitute a baseboard portion (supported portion), and two molding portions (first molding portions) are formed on both sides thereof. The main mold 40 supports the flange portion 51 of the core 50 and the outer peripheral surfaces on both sides thereof, and also has cavities (first and second portions) around the two formed portions. Since the cavity 61 and the second cavity 62) are configured to define the cavity, when the molten metal is introduced from the pouring ports 40b and 40c, the two molded portions receive stress (buoyancy) from both sides by the molten metal. Therefore, the change in the posture of the core is reduced as compared with the conventional case where the stress is applied only from one side, so that the cast product is less likely to have uneven thickness.

Further, since the core 50 has air permeability and is formed in a hollow shape, the gas generated in the first cavity 61 and the second cavity 62 is used for the core 50.
The gas can be permeated into the inside and can be discharged from the gas vent hole 51a, so that the occurrence of nests due to gas accumulation can be reduced and prevented. At this time, an exhaust device may be connected to the exhaust hole 40a communicating with the gas vent hole 51a to positively suck the gas.

Since the core 50 is constituted by the core body 50 'having the opening 50b and the cover member (cap) 54, the hollow structure can be easily manufactured. Further, a cover member 54 is provided in the opening 50b of the core body 50 '.
Is attached to form one forming part (first forming part 52), so that the structure can be simplified.

The above effect is obtained, for example, by using the method shown in FIG. 3 in the related art, where the defective product occurrence rate is close to 50%, but in the present embodiment, the non-defective product rate is almost 100%. Proven by being able to do it. Further, in the present embodiment, a pair of castings can be manufactured at once, so that productivity is remarkably improved. Especially,
In the present embodiment, the flange portion 51 corresponding to the central baseboard
And the vicinity thereof (supported portion) can position and support the two molded portions at a time, so that the occupied volume ratio of the portion corresponding to the baseboard in the mold can be greatly reduced. At this time, the volume of the supported portion is increased because the effect of fixing the core is enhanced by the balance between the two molded portions.
It is even possible to make it smaller than the core skirting board used in the conventional method shown in FIG.

In the above-described embodiment, the pair of molded portions has
Although an example in which three castings are manufactured is shown, it is also possible to arrange three or more moldings substantially evenly around the central supported portion and manufacture three or more castings at a time. . Further, although the stability and positioning accuracy of the core are improved by providing a flange portion which is a convex portion on the supported portion, a concave portion such as an annular groove may be provided on the core.

[0023]

As described above, the first molding portion and the second molding portion are provided on both sides of the supported portion of the core, and the first molding portion and the second molding portion are respectively provided around the first molding portion and the second molding portion. Since the first molding space and the second molding space are configured to define the molten metal, the molten metal is guided into the first molding space and the second molding space arranged on both sides of the supported portion of the core. In this case, since the core receives stress from the molten metal from both sides, it is difficult for the core to assume an inclined posture due to stress from one side as in the related art, so that uneven thickness of the cast product can be reduced. Further, since the stress is reduced by receiving the stress from both sides, the volume of the supported portion can be reduced, so that the volume of the mold can be reduced. Further, since at least two castings can be manufactured at the same time,
Productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a mold showing an embodiment of a method for manufacturing a casting according to the present invention and a structure of a core used in the method.

FIG. 2 is an explanatory view showing a method of manufacturing the core of the embodiment.

FIG. 3 is a schematic sectional view of a mold showing a conventional method for producing a cast product.

[Explanation of symbols]

 40 Main die 40A Upper die 40B Lower die 41 Fitting groove 41a Corner 50 Core 50a Internal space 50b Opening 51 Flange 51a Gas vent 51b Top 51c Side 51d Corner 52 First forming 53 Second forming 54 Lid member 61 First cavity (first molding space) 62 Second cavity (second molding space)

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[Procedure amendment]

[Submission date] August 9, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

Claims (6)

[Claims] 1. A method of manufacturing a cast product using a main mold and a core housed in the main mold, wherein the core includes a supported portion supported by the main mold, A first forming part and a second forming part formed on both sides of the supported part, and the main mold is provided with a first forming part around the first forming part and the second forming part corresponding to each of the first forming part and the second forming part. A method for manufacturing a cast product, comprising a mold structure configured to define a molding space and a second molding space, and using a mold structure for guiding a molten metal to both the first molding space and the second molding space. 2. The method according to claim 1, wherein the core is made of a gas-permeable material having a hollow structure, and has a gas vent hole in the supported portion for communicating the inside and the outside. . 3. The method according to claim 1, wherein the first molding space and the second molding space are substantially symmetrically formed on both sides of the supported portion. . 4. A core housed in a main mold used for casting, a supported portion supported by the main mold, and surface shapes formed on both sides of the supported portion for casting. A core, comprising: a first molding portion and a second molding portion provided. 5. The core according to claim 4, wherein the core is made of a gas-permeable material having a hollow structure, and has a gas vent hole for communicating the inside and the outside in the supported portion. 6. The core according to claim 5, further comprising an opening in the hollow portion, and a lid member for closing the opening.