JPH10211543A - Method for molding integral core for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a core having complicated shape without any damaging on the way of a process and any missing of the size by molding a part of the core for casting with shell molding method and molding with a beta-set method so as to integrate the above core part with a part or the whole of the remained part of the core. SOLUTION: A part 6 of the core for casting is molded with the shell molding method. This part 6 of the core is inserted into molding parts 2, 3 in a metallic mold. Successively, molding sand mixing water soluble phenol resin, etc., is injected into space parts 2b, 3b of the molding parts 2, 3 in the metallic mold from feeding holes 2c, 3c and methyl formate, etc., on a hardening agent is injected and the molding sand is hardened. The core is molded so as to integrate the core part 6 with the remained part of the core, i.e., the part corresponding to the space part 2b, 3b with the beta-set method. The molding parts 2, 3 in the metallic mold are unnecessary to heat and this work is easily executed. Further, the core having characteristics excellent in the reproductiveness of the molding sand and collapsibility after casting, is obtd. with this beta-set method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for casting a metal casting such as a copper alloy casting, and more particularly to a mold for a casting core.

[0002]

2. Description of the Related Art A casting method for casting a metal casting usually comprises a matrix and a core. Cores are generally complicated in shape, and many of them cannot be molded at once with a two-part mold. In this case, the core is often divided into several parts, separately molded, and inserted or bonded to assemble into a complicated shape.

[0003] However, when inserting or laminating, these cores, which are usually made of sand, are liable to peel off or crack in the sand, which is troublesome to handle and requires many man-hours. In addition, the quality of the casting may be adversely affected by causing the casting to be out of dimension or shape, or causing sand to grind.

[0004] These core portions are often made by a shell mold method which has relatively high precision and strength and is excellent in disintegration after casting. In particular, most cores of mass-produced products are made by the shell mold method. Nevertheless, the fact is that the above problems cannot be avoided.

[0005] In addition, when the core portion is bonded, more man-hours are required for applying the adhesive, and irregularities in the size and shape due to the sticking out or sandwiching of the adhesive adversely affect the precision of the casting. Also, heat may generate gas from the adhesive due to heat, causing defects in the casting.

The invention described in Japanese Patent Publication No. 5-73500 has a problem in that the above-described core is divided into several parts, separately manufactured, and inserted or bonded. It is for solving the point, charging the core part molded by the shell mold method into the molding die,
The remaining part or all of the core is formed by a shell molding method so as to be integrated with this part.

FIGS. 2, 3 and 4 are views shown in the above-mentioned publication, and FIG. 2 shows a machine of a body of a bronze screw-type gate valve made by an embodiment of the molding method of the invention. FIG. 3 is a longitudinal sectional view of a finished product after processing, FIG. 3 is a longitudinal sectional view of an integral core formed by a conventional molding method for casting a casting of the body, and FIG. 4 is a molding method of the invention described above. It is a longitudinal cross-sectional view of the one-piece core made by.

[0010] Annular sheet portions 21 and 22 project into the body 20 having the shape shown in FIG. 2 so as to face each other. The sheet portions 21 and 22 have a smaller diameter than the threaded portions 23 and 24 for piping. It has holes 21a and 22a. For this reason,
The cores 30 and 40 shown in FIGS. 3 and 4 have recesses 31 and 32 for forming the sheet portions 21 and 22 described above.
And 41, 42 must be formed.

[0009] Such recesses 31, 32 or 41, 4
Forming a core having an outer shape of 2 at a time with a two-part molding mold requires removing the molding die from the molded core regardless of the position of the dividing surface of the molding die at any position. It is impossible because it cannot. For this reason, in this case, in the core 30, the parts 33, 34 and 35 are
In the above, the part 43, 44 and 45 are made separately.

The integral core 30 shown in FIG.
3, 34 and 35 are separately formed by a shell molding method or the like, and the three parts 33, 34 and 35 are assembled by inserting or bonding as shown in the figure. For this reason, as described above, the integral core 30 is troublesome to handle and requires a lot of man-hours. There is a problem in that a bad influence is exerted, and a gas is generated from the adhesive by heat during casting to cause defects in the casting.

In the above invention for solving such a problem, in FIG. 4, a portion 43 of the integral core 40 is formed by a shell molding method, and
The molds 4 and 45 are inserted into separate or simultaneous molding molds for molding, and are molded by a shell molding method so that the core portions 44 and 45 are integrated with 43.

Therefore, the molding method according to the invention of the core 40 shown in FIG. 4 solves most of the above-mentioned problems with the conventional molding method of the core 30 shown in FIG.
However, since the core parts 44 and 45 are formed integrally with the part 43 by the shell molding method, the molding die must be heated to a required temperature, which is troublesome, and the molding is difficult. The core portion 43 may be damaged by the thermal deformation of the core. Further, when the coated sand for shell molding is blown into the molding die, the coated sand is blown out from a gap between the core portion 43 and the molding die, which hinders the operation or removes the core having a poor shape. There is a risk of making.

[0013]

A core having a complicated shape which cannot be molded at a time with a two-part molding mold is divided into several parts and separately molded and inserted or pasted. In the conventional core molding method of assembling together, handling is cumbersome and requires a lot of man-hours, causing dimensional and shape irregularities in the casting and sanding, adversely affecting the quality of the casting. In addition, there is a problem that a gas is generated from the adhesive due to heat during casting, causing defects in the casting.

Further, a core portion for solving the above problem is formed by a shell molding method, and this portion is charged into a molding die, and the remaining core is integrated with this portion. In the method of forming an integral core by molding a part or the whole of the core by a shell mold method, the molding die must be heated, and this work is troublesome, and the core is deformed by thermal deformation of the mold. There is a possibility that the part may be damaged, and when the coated sand is blown, the coated sand blows out from a gap between the core part and the molding die, which hinders the work or makes an integral core having a poor shape. There is a fear. The present invention is to solve these problems.

[0015]

In order to achieve the above-mentioned object, the present invention provides a method of forming a casting core portion by a shell mold method, and charging this portion into a molding die. The remaining part or all of the core is molded by the beta set method so as to be integrated with this part. in this case,
It is preferable that the above-mentioned casting core is a casting core of a valve part.

Further, it is preferable that the casting core is inserted into the molding die so as to abut and seal at a cylindrical step having a reduced diameter. In this case, the remaining part or all of the casting core may be formed by a shell molding method so as to be integrated with the casting core.

In the method of forming a one-piece core according to the present invention, the following operation is performed. First, since the casting core is formed by the shell molding method, this portion has relatively high dimensional accuracy and high strength. Therefore, it is easy to insert this into a molding die for molding the remaining part or all of the core, and it is less likely to be damaged.

The surface of the surface of the casting core formed by the shell molding method is clean, the molding speed is high, and the production cost is low.

Next, the molding method in the present invention when the remaining part or the whole of the core is molded by the above-mentioned molding die is performed by using a water-soluble phenol resin as a binder and methyl formate as a curing gas. Because it is an organic gas curing method generally called a beta set method, there is no need to heat the molding die, and therefore, this work is easy, and the core portion charged by thermal deformation of the die is used. The core is not damaged, and the size and shape of the integral core are not changed.

The above-mentioned beta-setting method is economical because it has excellent characteristics such as excellent recyclability of molding sand and good disintegration after casting.

Further, in the molding method of the integral core according to the present invention, a portion of the casting core made by the shell molding method is brought into contact with a molding die for charging the same at a cylindrical step portion having a different diameter and sealed. As a result, even if molding sand is blown into this molding die, it does not blow out from the joint between the core portion and the molding die. For this reason, there is no possibility that work is hindered by blow-off or an integral core having a defective shape is formed.

With such a structure of the core and the molding die, even if the molding is performed by the shell mold method instead of the beta set method, the operation is hindered, and an integral core having a defective shape is produced. Or not.

As described above, the molding method of the integral core for casting according to the present invention requires relatively little man-hours for a core having a complicated shape for casting a metal casting, and damages the core during the process. It is an economical molding method that can be molded without causing irregularities in dimensions and shapes without any inconvenience.The casting cast using this one-piece core has no irregularities in dimensions and shapes, and has few defects It is a cheap casting.

[0024]

FIG. 1 is a longitudinal sectional view showing a molding die in one embodiment of a molding method of an integral core for casting according to the present invention. The molding die is made of bronze as shown in FIG. This is a core molding die for casting the body of the screw-in type gate valve.

This molding die 1 has four parts 2, 3, 4
6 is a part of a casting core formed by the shell molding method, and the cylindrical parts 6a and 6b of the core part 6 having different diameters are respectively provided with molding dies 2 and 3 respectively. The core portion 6 is inserted into the molding dies 2 and 3 so that the cylindrical step portions 2a and 3a having different diameters are brought into contact with each other and sealed.

Incidentally, the molding dies 2 and 3 each have a sectional surface shown in FIG. Therefore, in the figures, the molding dies 2 and 3 are also roughly hatched, but this is not to show the cross section, but to make their shapes easy to see.

The molding die 4 is for holding the core portion 6 and the dies 2 and 3, and 5 is a plate for preventing the core portion 6 from falling. Therefore, the molding dies 2 and 3
It is necessary to make it with a material suitable for the molding die such as abrasion resistance,
The molding dies 4 and 5 may be made of an appropriate material such as cast iron or carbon steel sheet.

Next, with reference to FIG. 1, a method of molding an integral core according to the present invention and its operation will be described. Core part 6 for casting
Is molded by a shell mold method, and therefore has relatively high dimensional accuracy and high strength. For this reason, the core part 6 is inserted into the molding dies 2 and 3, and in fact, the molding dies 2
The work of mounting the core 3 and the core 3 on the core part 6 is easy, and the core part 6 is hardly damaged.

The core portion 6 formed by the shell molding method has a beautiful surface skin, a high molding speed, and a low production cost.

Next, in the spaces 2b and 3b for molding the remaining portion of the core in FIG. 1, casting sand sprinkled with a water-soluble phenol resin as a binder is supplied to the inlets 2c and 3b.
The remaining part (corresponding to the space portions 2b and 3b in the figure) of the core is made into a core portion 6 by a so-called beta-set method in which the resin is blown from c, and is blown with methyl formate as a hardener to cure and mold. Mold so that they become one.

For this reason, there is no need to heat the molding dies 2 and 3 and the work is easy, and the inserted core 6 may be damaged due to the thermal deformation of the dies, and the size and size of the integrated core may be reduced. It does not cause shape irregularities. The beta set method is economical because it has excellent characteristics such as excellent reproducibility of casting sand and good collapse after casting.

In FIG. 1, a cylindrical step 6a is formed on a core step 6a of the core 2 formed by the shell molding method, a cylindrical step 2a is formed on the cylindrical step 2a of the forming mold 2, and a cylindrical step 6b is formed on the forming mold 3 by the shell mold method.
The molding dies 2 and 3 are inserted in such a manner that the molding dies 2 and 3 are brought into contact with each other and sealed at the cylindrical step 3a, so that the inlets 2c and 3c are inserted into the spaces 2b and 3b of these molding dies 2 and 3. Even if the molding sand is blown from above, it does not blow out from the seam between the core portion 6 and the molding dies 2 and 3 (the contact portion of the cylindrical step portion). For this reason, the blowing does not hinder the work and does not produce an integral core having a defective shape.

With the configuration of the core portion 6 and the molding dies 2 and 3 as shown in FIG. 1, even if the molding is performed by the shell molding method instead of the beta set method, the operation may be hindered. Also, there is no possibility of forming an integral core having a defective shape.

[0034]

As is apparent from the above, according to the present invention, the molding method of the integral core for casting requires a relatively small number of man-hours for a core having a complicated shape for casting a metal casting. ,
It is an economical molding method that can be molded without any damage during the process and without any irregularities in the dimensions and shape.The castings cast using this one-piece core have irregular dimensions and shapes. It is possible to obtain an inexpensive casting with few defects.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a molding die in one embodiment of a molding method of an integral core for casting according to the present invention.

FIG. 2 is a longitudinal sectional view of a finished product after machining of a body of a bronze threaded gate valve.

FIG. 3 is a longitudinal sectional view of an integrated core made by a conventional molding method for casting the body casting shown in FIG. 2;

FIG. 4 is a longitudinal sectional view of an integral core produced by a molding method obtained by improving the molding method of the integral core shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2, 3 Molding die part 2a, 3a Cylindrical step part of molding die 6 Core part for casting 6a, 6b Cylindrical step part of core part

Claims (4)

[Claims] 1. A part of a casting core is formed by a shell molding method, and this part is charged into a molding die, and a part or all of the remaining part of the casting core is integrated with this part. A molding method of an integral core for casting, characterized by being molded by a beta set method. 2. The molding method for an integral casting core according to claim 1, wherein said casting core is a casting core for a valve part. 3. The casting core according to claim 1, wherein the casting core is inserted into the molding die so as to abut and seal at a cylindrical step having a reduced diameter. Molding method. 4. The integral casting core according to claim 3, wherein the remaining part or all of the casting core is formed by a shell molding method so as to be integrated with the casting core. Molding method.