JPH04220139A - Mold, core and core box - Google Patents

Abstract

PURPOSE:To present the mold, the core and the core box which can manufacture the casting with min. generation of flash at the core print part. CONSTITUTION:On the mold having the core, the projection is provided, at least, at one part of the core print of the core. The dimensional difference measured toward the inside of the core print between the outer surface of the projection and the inner front surface of the core print hole is made to -0.1-1.0mm, and the lateral dimension of the axial direction of the projection is made to 1-5mm. The outer front surface of the projection provided at the core print of the core is projected (delta-0.1) or (delta+1.0)mm (where, delta is the dimension of the one side clearance between the core print hole and the core print) from the front surface of the core print, and the lateral dimension of the axial direction of the projection is made to 1-5mm. Further, the bottom surface of the recessed part set at the core print part of the core box is made to (delta-0.1) or (delta+1.0)mm deep from the front surface of the core print part, and the lateral dimension of the axial direction of the recessed part is made to 1-4mm.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a mold used in manufacturing a casting, a core housed in the mold and forming a part of the casting, and a core used in molding the core. A mold, a core, and a core that can produce a casting that is extremely easy to finish and that has very little occurrence of casting tension, especially in the baseboard of the core and main mold. It is about taking.

0002

2. Description of the Related Art FIG. 6 is a vertical cross-sectional view of a main part of an example of a mold containing a core. In FIG. 6, numerals 1 and 2 are an upper mold and a lower mold, respectively, and each constitute a main mold forming the outer surface of the casting. 3 is a core, which forms the inner surface of the casting, such as a hollow hole. Baseboards 4 are integrally formed at the upper and lower ends of the core 3, and the core 3 is fixed in a predetermined position through baseboard holes 5 provided in the upper mold 1 and the lower mold 2, respectively. 6
1 is a cavity, and 7 is a sprue. The cavity 6 and the sprue 7 are communicated with each other so that molten metal can be introduced into the upper mold 1 and the lower mold 2.

FIG. 7 is a longitudinal sectional view of a main part showing the vicinity of the baseboard 4 of the core 3 shown in FIG. 6, and the same parts are designated by the same reference numerals as in FIG. 6. When the core 3 is formed into a cylindrical shape, for example, the baseboard 4 and the baseboard hole 5 are both formed into a truncated cone shape.

[0004] With the mold formed as described above, the sprue 7
By pouring molten metal into the cavity 6 via the molten metal, a hollow casting corresponding to the cavity 6 can be manufactured.

[0005]

[Problems to be Solved by the Invention] In the mold having the above structure, there is a space between the baseboard 4 and the baseboard hole 5 for adjusting the position and/or inclination of the core 3, and for storing the model and core due to continued use. The gap δ (usually 0.2 mm) is
It is normal to have a certain degree of i.e. baseboard 4
And the taper angle of the conical surface of the baseboard hole 5 is formed to be the same. Therefore, when the core 3 is assembled in the mold and molten metal is poured into the cavity 6, the molten metal enters into the gap δ between the baseboard 4 and the baseboard hole 5, causing so-called casting. It turns out.

[0006] When such casting occurs, there is a problem in that extra casting work is required to remove the casting after manufacturing the casting. In addition, if the model and the core are partially worn, the occurrence of the above-mentioned casting will be further promoted. On the other hand, if the gap δ between the baseboard 4 and the baseboard hole 5 is made extremely small in order to prevent the above-mentioned casting, the core 3 will not fit properly, and the straightness of the core 3 will be reduced. There is also the problem that the dimensional accuracy of the manufactured casting is reduced due to a decrease in the dimensional accuracy, and that the mold in the vicinity of the baseboard hole 5 is caused to break.

In order to solve the above problems, steps and hollows are provided in the baseboard 4 and the baseboard hole 5, and a seal packing made of a compressible material is interposed to form a cavity 6 for molten metal.
There have been proposals to prevent leakage (see, for example, Japanese Unexamined Patent Publication No. 58-20348).

However, the above proposal requires the additional work of interposing the seal packing between the baseboard 4 and the baseboard hole 5, which poses a problem in that the work is complicated. Furthermore, although it is possible to prevent molten metal from leaking out of the mold by interposing the seal packing, there is also the problem that it is not possible to completely prevent the occurrence of casting between the seal packing and the cavity.

[0009] Furthermore, a slurry mainly composed of a fire-resistant material and a plastic inorganic material is injected into a mold and left for a while, and then the excess slurry is drained and dried to form a coating layer on the inner wall surface of the mold and the gap between the molds. There have been proposals to do so (for example, see Japanese Patent Laid-Open No. 57-32846).

However, this proposal requires complicated operations such as pouring, discharging and drying the slurry, and therefore has the problem that it takes a large amount of man-hours and time to complete the mold. Furthermore, since it requires a step of drying the slurry, it has the disadvantage that it cannot be applied to so-called green sand molds formed from foundry sand containing moisture.

[0011] In addition to the above method, there is also a method of bonding the mating surfaces of the core and the mold with adhesive, but this requires an adhesive application process, which is complicated, and does not completely prevent the occurrence of cast sticking. The drawback is that there is no certainty that it will.

On the other hand, a proposal has been made to solve the problem of the casting problem by modifying the parting surface of the mold itself. That is, a band-like protrusion of a predetermined height and a predetermined width is formed along the outer periphery of the cavity on one or both mating surfaces of a pair of molds constituting a mating mold, and after the two molds are matched, the band-like protrusion is removed. In order to form such a mold, an engraving of a predetermined depth is made on the upper surface, and this engraving is There is a method (see Japanese Utility Model Publication No. 64-3560) in which a model such as a product model or sprue model is provided at a predetermined distance from the outer periphery of the engraving.

[0013] It is stated that the above proposals have the effect of preventing the occurrence of casting, but all of the above proposals prevent casting from occurring between a pair of molds whose parting surfaces or mating surfaces are flat. The purpose of this method is only to prevent the occurrence of casting, and it cannot be applied as is when preventing the occurrence of casting on the core baseboard of a mold that accommodates a core, which is intended for castings with complex shapes.

[0014] Next, as a means for preventing the occurrence of casting on the baseboard of the core in a mold containing a core, a protrusion for preventing casting is formed near the base of the baseboard of the mold to prevent this casting. A method is disclosed in which the base of the fixing part of the core is brought into close contact with the prevention protrusion (Japanese Patent Laid-Open No. 105511/1983).
(see publication). In order to form such casting prevention protrusions on the mold, a groove with an appropriate depth is provided in the vicinity of the boundary between the skirting board forming part and the model body. It is necessary to use

[0015] With the above structure, when the core is housed in the mold and the upper and lower molds are aligned, the overcast prevention protrusion comes into close contact with the fixing part of the core, and the gap between the two is sealed. It is said that this prevents the occurrence of overcasting due to the intrusion of molten metal.

However, the object of the above proposal is a mold made by a vacuum molding method called the so-called V process, which is possible because an airtight film is interposed on the parting surface or mating surface, and the mold itself has high plasticity. It becomes. Therefore, even if the above-mentioned method is applied to a mold made of so-called green sand, not only will it be impossible to form the protrusions for preventing casting to the prescribed shape and dimensions, but it will also be difficult to mold the part concerned, and the mold will actually be damaged. This may cause undesirable problems such as breakage and defects due to sand infiltration.

The present invention solves the problems existing in the above-mentioned prior art, and provides a casting in which the occurrence of casting in the core baseboard is extremely small, the dimensional accuracy is high, and the casting work is extremely easy. An object of the present invention is to provide a mold, a core, and a core holder that can be manufactured.

[0018]

[Means for Solving the Problem] In order to achieve the above object, in the first invention, a main mold and a core are connected to a baseboard provided in the core and a baseboard hole provided in the main mold. In a mold that is assembled via a main mold and a core, a technical measure is adopted in which a protrusion is provided on at least a part of the baseboard at the boundary between the baseboard and the cavity formed by the main mold and the core.

In the above invention, the dimensional difference t between the outer surface of the protrusion and the inner surface of the baseboard hole measured toward the inside of the baseboard is -0.1 to 1.0 mm, and the dimensional difference t in the axial direction of the protrusion is It is preferable to form the width dimension w of 1 to 5 mm.

[0020] Next, in the second invention, in a core having a baseboard, a technical means is adopted in which a protrusion is provided on at least a part of the baseboard at the boundary between the cavity forming part and the baseboard.

In the above invention, the outer surface of the protrusion is (δ-0.1) to (δ+1.0) mm from the surface of the baseboard (where δ is the one-sided gap dimension between the baseboard hole and the baseboard). ) protrude;
In addition, it is preferable that the axial width w of the protrusion is 1 to 5 mm.

Furthermore, in the third aspect of the present invention, in the core making for molding the core having a baseboard, a recess is provided in at least a part of the baseboard at the boundary between the cavity forming part and the baseboard. Technological measures were adopted.

[0023] In the above invention, the bottom surface of the recess is (δ-0.1) to (δ+1.0) mm from the surface of the baseboard (where δ is the one-sided gap dimension between the baseboard hole and the baseboard). ), and the axial width w of the recess is preferably 1 to 5 mm.

[0024]

[Operation] With the above configuration, the protrusion provided on the baseboard of the core can enter the inner surface of the baseboard hole of the main mold, sealing the gap between the two, and preventing the intrusion of molten metal. It can be done. Even if there is a slight gap between the inner surface of the baseboard hole and the protrusion, the surface tension of the molten metal can prevent the molten metal from entering the gap.

[0025] In the first invention, the dimensional difference t is -0
．． Less than 1mm, that is, the distance between the inner surface of the baseboard hole and the protrusion is 0
．． If the thickness exceeds 1 mm, it is inconvenient because molten metal will penetrate and cause casting. On the other hand, if the dimensional difference t exceeds 1.0 mm, the amount that the protrusion enters into the inner surface of the baseboard hole increases, causing mold breakage, which is not preferable. Further, if the width w in the axial direction of the protrusion is less than 1 mm, it cannot be expected to prevent the intrusion of molten metal, whereas if it exceeds 5 mm, mold breakage will occur, which is disadvantageous since casting will occur. .

Next, in the second and third inventions, the protrusion dimension of the protrusion from the baseboard surface and the depth dimension of the recess from the baseboard surface are less than (δ-0.1) mm. This is disadvantageous because the gap between the inner surface of the baseboard hole of the mold and the protrusion on the baseboard of the core becomes too large, allowing molten metal to enter. On the other hand, if the above-mentioned dimension exceeds (δ+1.0) mm, the amount of penetration of the protrusions formed on the baseboard of the core into the inner surface of the baseboard hole becomes large, which is undesirable because it causes mold breakage. The reason why the axial width w of the protrusion and the recess is set to 1 to 5 mm is the same as that in the first invention.

[0027]

[Embodiment] Fig. 1 is a vertical cross-sectional view of main parts showing an embodiment of the present invention.
FIG. 2 is an enlarged view of part A in FIG. 1, and the same parts are designated by the same reference numerals as in FIGS. 6 and 7. Note that the dimensional unit in FIG. 1 is mm. In FIGS. 1 and 2, the core 3 has a circular cross section, and the baseboard 4 and baseboard hole 5 have a truncated conical shape, and the radial difference δ is generally 0. .2mm. Next, reference numeral 4a denotes a protrusion, which is formed in a band shape around the outer periphery of the baseboard at the boundary between the cavity 6 and the baseboard 4, and is integrally provided.

That is, the protrusion 4a has an outer dimension larger than the inner dimension of the baseboard hole 5 by 2t, and an axial width dimension w.
to form. Therefore, when the core 3 is placed in the upper mold 1 and the lower mold 2, the protrusion 4a provided on the baseboard 4 slightly enters the inner surface of the baseboard hole 5, which means that the sand contacts each other, so it is not possible to It adapts appropriately to differences in size and width, and completely seals the gap between the two.

In order to form the protrusion 4a as described above integrally with the baseboard 4, at the relevant part of the baseboard of the core holder (not shown),
A concave portion having an axial width dimension w and a predetermined depth dimension from the surface of the baseboard 4 may be bored. This depth dimension t' is, for example, (δ
-0.1) to (δ+1.0) mm (where δ is baseboard hole 5
and baseboard 4).

Table 1 shows the width w of the projection 4a shown in FIG. 1 and the width of the baseboard 4 between the outer surface of the projection 4a and the inner surface of the baseboard hole 5.
The number of occurrences of casting and mold breakage at the boundary between the cavity 6 and the baseboard 4 is shown when the dimensional difference t measured in the direction is changed. In this case, the number of molded pieces is 10 each.
It is individual. The upper mold 1 and the lower mold 2 were both green molds containing 3.2% moisture, the core 3 was a shell core, and molten metal made of spheroidal graphite cast iron was injected into the cavity 6.

[0031]

[Table 1]

In Table 1, No. The columns with parentheses indicate comparative examples. In addition, "casting" refers to molten metal entering between the baseboard hole 5 and the baseboard 4 or protrusion 4a to form a thin-walled protrusion, as shown in FIGS. In the same figure, a part of the upper die 1 or the projection 4a is damaged and a lump-like projection is formed by molten metal. That is, in FIG. 3, the casting 6
Among the foreign substances generated at the end of a, 8a is cast-fitting, and 8b is a broken mold.

As is clear from Table 1, No. 1 uses a core with a conventional shape, lacks the protrusion shown in Fig. 1, has a gap of 0.2 mm between the inner surface of the baseboard hole 5 and the baseboard 4, and is completely cast. was recognized. On the other hand, No. 10
In this case, since the dimensional difference t is large, the degree of intrusion of the protrusion 4a into the baseboard hole 5 is too large, that is, the crimping action between the two becomes excessive, which is effective in preventing casting. It is observed that mold breakage occurs which damages the baseboard holes 5 in some parts.

Next, No. In No. 11, since the width dimension of the protrusion 4a is small, the close contact with the baseboard hole 5 is insufficient,
Occurrence of casting is observed. On the other hand, No. In No. 15, the pressing action of the baseboard hole 5 by the protrusion 4a was excessive, and mold breakage was observed.

On the other hand, No. 2~No. 9 and N
o. 12~No. 14, the baseboard hole 5 of the protrusion 4a
The degree of penetration into the mold is appropriate, suppressing the occurrence of overcasting, and almost no mold breakage is observed.

FIGS. 4 and 5 are end views of essential parts showing core baseboards in other embodiments of the present invention. First, Figure 4
The one shown in FIG. 5 has a plurality of protrusions 4a disposed intermittently on the outer periphery of the baseboard 4, and the one shown in FIG. For example, t1 < t2.

Even when formed as described above, by appropriately selecting the protruding dimensions t', t1, and t2 of the protrusion 4a from the baseboard 4, it is possible to prevent casting and mold breakage.

In the above embodiment, a cylindrical core is used, and the baseboard and baseboard holes are each formed in the shape of a truncated cone. However, shapes other than the above may be used. For example, the baseboard and the baseboard hole may each be formed into a truncated polygonal pyramid, or even if they are formed into a spherical crown or other curved surface, the effect will be the same. Furthermore, in the above embodiments, an example of a single mold with one core inserted was described, but even if multiple cores are used, or in the case of a multi-core mold, The effect is the same. Of course, the present invention can also be applied to a core that forms part of the outer surface of a casting.

[0039]

[Effects of the Invention] Since the present invention has the structure and operation described above, the following effects can be expected.

(1) The skirting board and the baseboard hole can be brought into close contact with each other completely at the boundary with the cavity, and the occurrence of casting can be prevented or the casting can be made extremely small.

(2) As a result of the above, the dimensional accuracy of the casting can be improved, and the casting work can be extremely facilitated.

(3) When inserting the core and matching the molds, the baseboard and the baseboard hole fit very well, so
This prevents mold breakage and greatly improves the dimensional accuracy of castings.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is an enlarged view of part A in FIG. 1;

FIG. 3 is an explanatory cross-sectional view of a main part showing an example of casting and mold breakage occurring in a casting.

FIG. 4 is an end view of a main part showing a baseboard of a core in another embodiment of the present invention.

FIG. 5 is an end view of essential parts showing a baseboard of a core in still another embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a main part showing an example of a mold containing a core.

7 is a vertical sectional view of a main part showing the vicinity of the baseboard of the core shown in FIG. 6; FIG.

[Explanation of symbols]

1 Upper mold 2 Lower mold 3 Core 4 Baseboard 4a Protrusion 5 Baseboard hole 6 Cavity

Claims (6)

[Claims] Claim 1: A mold in which a main mold and a core are combined through a baseboard provided in the core and a baseboard hole provided in the main mold, in which the main mold and the core are formed. A mold characterized in that a protrusion is provided on at least a part of the baseboard at the boundary between the cavity and the baseboard. [Claim 2] The dimensional difference t between the outer surface of the protrusion and the inner surface of the baseboard hole, measured toward the inside of the baseboard, is -0.1 to 1.
．． 0 mm, and the axial width w of the protrusion is 1 to 5 mm.
2. The mold according to claim 1, wherein the mold is formed as follows. 3. A core having a baseboard, characterized in that a protrusion is provided on at least a part of the baseboard at the boundary between the cavity forming part and the baseboard. Claim 4: The outer surface of the protrusion is separated from the surface of the baseboard by (δ−
0.1) to (δ+1.0) mm (where δ is the one-sided gap dimension between the baseboard hole and the baseboard), and the axial width w of the protrusion is formed to be 1 to 5 mm. The core according to claim 3, characterized by: 5. A core for molding a core having a baseboard, characterized in that a recess is provided in at least a part of the baseboard at the boundary between the cavity forming part and the baseboard. Tori. [Claim 6] The bottom surface of the recess is separated from the surface of the baseboard by (δ−
The recess is formed to a depth of 0.1) to (δ+1.0) mm (where δ is the one-sided gap dimension between the baseboard hole and the baseboard), and the axial width w of the recess is 1 to 5 mm. The core holder according to claim 5, characterized in that it is formed as follows.