JPH0573500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a casting technique for casting copper alloy castings, iron castings, steel castings, etc., and metal castings.
In particular, this article relates to the shell mold manufacturing method, which is widely used because the dimensional accuracy of the casting is high, the casting surface is clean, the molding speed is fast, and the manufacturing cost of the casting is low. This invention relates to a method for molding a casting core with a complex shape that cannot be molded in one go.

Therefore, the mold making method of the present invention is a mold making method that is particularly useful for making casting cores for valve casting parts, in which high quality metal castings of complex shapes are often used.

(Prior art) Molds made by the shell mold making method have high dimensional accuracy, relatively high strength, and excellent disintegration properties after casting, and are often used for casting cores. It is especially widely used as a core for mass production. An even more important factor behind this widespread use is that, as mentioned above, the dimensional accuracy is high and the strength is relatively high.
It is possible to assemble complex shapes with high precision by molding parts into individual or more parts and then inserting or pasting them together.

However, when inserting or pasting them together, the number of pieces is extremely large as these are mainly mass-produced cores, and although the strength is relatively high, the sand molds tend to peel off and break easily, so it must be done carefully. Because it cannot be handled, it requires a lot of man-hours, and the cost is not negligible.

Furthermore, in the case of bonding, not only does it take more man-hours to apply the adhesive, but there are also drawbacks that adversely affect the accuracy of the casting, such as deviations in size and shape due to extrusion of the coating agent or pinching of the coating agent. In addition, if only the sand is inserted, it may loosen or come off during transportation, and in that case, the sand may come off due to friction between the molds, which may cause irregularities in the dimensions and shape of the casting, or the sand can become loose. There is a flaw that causes this.

(Problems to be Solved by the Invention) The present invention is characterized by the fact that the conventional casting core, which is assembled by layering or bonding two or more parts molded by the shell molding method, requires a lot of man-hours. Becomes expensive. This invention is intended to solve problems such as irregularities in the shape and dimensions of casting cores, irregularities in dimensions and shapes, and defects such as sand traps in castings.

(Means for Solving the Problems) The present invention is an invention for solving the problems of the above-mentioned conventional shell mold manufacturing method for casting cores. This is a shell molding method for a casting core, in which a part or all of the remaining part of the casting core is molded so as to be integrated with this part after the child part is inserted into a mold.

Furthermore, by applying the shell mold making method of the present invention to a casting core for a valve component, which is a thin-walled casting that has a relatively complex shape and requires pressure resistance, the casting core and valve component can be produced into a casting. This is an attempt to solve the above-mentioned problems.

(Function) The present invention provides a casting core having a structure in which parts of a casting core molded by the shell molding method are assembled, and instead of inserting or bonding the parts for assembly, the present invention The part of the casting core that has been molded using the casting molding method is inserted into a mold that will mold part or all of the remaining core to which it is to be fixed. It is intended to mold part or all of the
For the part to be newly molded, granular coated sand for shell molding is fed into the molding mold, and is solidified by the heat of the heated molding mold, so the part of the core that has been inserted in advance is The coated sand of the newly molded core part bites into the surface, and the thermosetting resin covering the coated sand is welded and solidified by the heat inside the mold, so that there is no contact between the old and new parts. They stick firmly together as if they were molded at the same time. Moreover, since both the pre-molded part and the newly-molded part are positioned and fixed in the same mold, and no adhesive is used, there is no possibility of irregular shapes or dimensions or protrusion. .

Furthermore, it is economical as there is no need for the man-hours of inserting and pasting, and it does not come loose during transportation, etc.
Since the sand does not peel off due to rubbing between the parts, it is possible to supply a molding core that has the correct size and shape and is suitable for making castings without defects such as sand pits. This is especially true for gate valves,
This is suitable for casting thin-walled valve parts that have complex shapes and require pressure resistance, such as the bodies of globe valves, bonnets, and discs for gate valves.

(Example) As an example of the present invention, a body of a bronze threaded gate valve, which is manufactured in extremely large quantities among valve parts, will be described.

FIG. 1 is a longitudinal sectional view showing an example of the body of a bronze screw-in gate valve. FIG. 2 is a longitudinal sectional view of a casting core molded by a conventional molding method for casting the casting material of the body shown in FIG.

Inside the body 1, annular seat portions 2 and 2' protrude facing each other. The seat portions 2, 2' have through holes having a diameter smaller than that of the piping thread portions 3, 3'.

The casting core includes the annular seat portion 2,
An annular recess 4, 4' must be formed to form the groove 2'. A recessed portion 4 that is recessed not only with respect to the body portion 5 but also with respect to the flow path portions 6 and 6′,
It is impossible to mold a casting core having a diameter of 4' at once using a two-part mold. For this purpose, the casting core is divided into a part 7 of the core which does not have a recess in the flow passage parts 6 and 6', and a part 8 and 8' of the core which has a recess in the flow passage part. In order to insert or bond the parts 8 and 8' together, fitting parts 9 and 9' are provided in the part 7 and fitting parts 10 and 10' are provided in the parts 8 and 8'.

Part 7 and parts 8 and 8' of the casting core are separately molded by the shell molding method using respective molds, and then the fitting parts 9 and 8 of part 7 are molded separately.
9' and the fitting parts 10, 10' of the parts 8, 8'
Assemble by inserting or pasting together as shown in the figure.

For this insertion or bonding, although portions 7 and 8, 8' are sand molds that have relatively high strength, the sand tends to peel off and break easily, so they cannot be handled roughly, and they are mass-produced products. In the case of a nominal diameter of 3/4B, only about 3,000 pieces can be assembled in a day, and the cost cannot be ignored.

Furthermore, when bonding is performed using an adhesive, it takes more time to apply the adhesive, and the adhesive may protrude from the fitting portion, or the fitting portion 9 of the portion 7 may become stuck due to the adhesive being caught. , 9' and the fitting part 1 of the parts 8, 8'
0 and 10' cannot be brought into close contact with each other, and deviations in size and shape are likely to occur. Furthermore, if it is only inserted, there is a risk that the fitting portion may loosen or come off during transportation or the like. In this case, friction occurs between the fitting parts, and the sand on the surface is likely to peel off or peel off. Castings made using such cores have dimensions,
Defects such as misshapen shapes and sand deposits occur.

FIG. 3 is a longitudinal sectional view of the casting core of the body shown in FIG. 1, which was molded by the shell mold manufacturing method of the present invention. After the remaining portions 18, 18' of the core to be fixed to the portion 17 are inserted into the predetermined positions of the molding die to be molded, the portions 18, 18' are molded and integrated for casting. Showing the core.

In this case, the portions 18 and 18' may be molded separately, but it is preferable to mold them simultaneously using one set of molding molds, since deviations in shape and dimensions are less likely to occur and the number of man-hours is reduced.

The molding die for molding the portions 18, 18' is provided with an appropriate guide portion so as to insert the previously molded portion 17 into the correct position. The position relative to 18' can be corrected. Coated sand for a shell mold is introduced into the cavity of the mold in which the parts 18, 18' are to be formed. This coated sand may be the same as that used for section 17, or it may be of another suitable material depending on its shape and volume. The fed coated sand is solidified by the heat of the heated mold. part 1
The coated sand is also fed into the surfaces of the fitting parts 19 and 19' of No. 7, and the coated sand bites into the surface, and then the heat of the molding die causes the coated sand to heat-cure. The resin is welded and solidified to the fitting parts 19 and 19' of part 17, and part 1
8, 18' are the fitting parts 20, 20'. Therefore, the portion 17 and the portions 18, 18' are connected to the fitting portion 19.
, 20 and 19', and 20' are welded and solidified, and are firmly fixed as if they were molded at the same time.

Note that the two-part dividing surface of the molding die is A-, which is indicated by a dashed line in FIG.
If it is provided on the same plane as the cross section shown in FIG. It is possible to divide the mold and extract the mold.

Therefore, with the casting core molded by the molding method of the present invention, there is no need to insert or bond parts together, the dimensions and shape of the core are accurate, and the dimensions and dimensions of the castings cast using this core are accurate. The shape is correct and there are few defects.

An example of the body of a bronze screw-in gate valve has been described above, but the present invention can be made of bronze, gray cast iron,
Regardless of the type of valve, such as gate valves or globe valves, the body,
Regardless of the type of parts such as bonnets and disks, and not only valve parts, the present invention can be applied to the shell mold manufacturing method for casting cores with complex shapes that cannot be molded in one go.

In addition, in the above example, after inserting the core into the mold, the rest of the core was molded.
This can also be applied to the case of molding the remaining part.

(Effects of the Invention) As explained above, the present invention provides the following effects by applying the method of making a shell mold for a casting core, which is assembled by inserting or pasting together, as in the present invention. It will be done.

(1) There is no need for insertion or pasting, so it is economical and requires no man-hours.

(2) Since the core parts are assembled in a mold, a casting core with consistent dimensions and shape can be obtained.

(3) The assembly will not loosen or come off when transporting the casting core.

(4) As a result, castings with no irregularities in size or shape and fewer defects can be obtained.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view showing an example of the body of a bronze screw-in gate valve, and Fig. 2 is a longitudinal cross-section of a casting core molded by a conventional molding method for casting the casting material for the body of Fig. 1. The plan view and FIG. 3 are longitudinal cross-sectional views of the casting core of the body shown in FIG. 1, which was molded by the shell mold manufacturing method of the present application. 1...Body, 2, 2'...Seat portion, 3,
3'... Threaded part, 4, 4', 14, 14'... Recessed part, 7, 8, 8', 17, 18, 18'... Core part, 9, 9', 10, 10',19,19',2
0,20'...Fitting part.

Claims (1)

[Scope of Claims] 1. After the part of the casting core molded by the shell molding method is inserted into the mold, a part or all of the remaining part of the casting core is inserted so as to be integrated with this part. A shell molding method for casting cores. 2. The shell mold making method according to claim 1, wherein the casting piece to be molded is a casting core for a valve component.