JPH0280153A - Expendable pattern casting method - Google Patents

Abstract

PURPOSE:To surely obtain a casting product having the desired shape so as not to deform an expendable pattern dy fixing the expendable pattern to a base plate and pouring molten metal after embedding the pattern into molding sand together with the base plate. CONSTITUTION:Suitable quantity of the molding sand 3 is charged into lower part in a casting vessel 2 and the expendable pattern 1 fixed with the desired position is laid on the base plate 9. The molding sand 3 is packed in the vessel 2 to completely embed the expendable pattern 1. Successively, the molten metal 5 is poured into inner part of the expendable pattern 1 through a sprue to replace the expendable pattern 1 with the molten metal 5. When the molten metal 5 cools, the desired casting product is obtd. By this method, the deformation of the expendable pattern 1 with the molding sand 3 can be prevented. This method is suitable to casting of a cylinder block, etc., in engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is particularly suitable for casting engine cylinder blocks and the like. Regarding the vanishing model casting method.

[Prior art] Compared to the conventional sand casting method, the loss-making model casting method (EPC method) has the following advantages: (1) it does not require a core when manufacturing hollow parts; (2) it does not mix adhesive into the sand; It has various advantages such as easy recovery and reuse of sand, and can be applied to objects with complex shapes.For example, its development is progressing. This method is attracting attention as a casting method for cylinder blocks, etc.

In this investment model casting method, an investment model (Eps model) of a Styrofoam ring having the same shape as the cast product to be obtained is usually housed in a casting container, and the casting container is filled with casting sand to form the investment model. This is done by burying the mold in casting sand, and then injecting molten metal through the sprue of a Styrofoam ring connected to the fugitive mold.

As a result, within the casting sand, the sprue and the extinguishing mold are sequentially thermally decomposed, and these parts are replaced with the corresponding molten metal.

The desired metal casting is produced.

Incidentally, a case can be considered in which, for example, a cylinder block of an engine is cast by such an investment casting method.

When manufacturing this cylinder block by the effacement model casting method, as shown in FIGS. 3(a) and 3(b), a styrofoam ring effusion mold 1 having the same shape as the cylinder block to be obtained is formed. In this Figure 3 (a) and (b),
Reference numeral 1a denotes a portion corresponding to a water jacket formed in the upper part of the cylinder block 1 around the cylinder liner.

1b is a portion corresponding to a skirt portion formed at the lower part of the cylinder block, 1c is a portion corresponding to a bearing forming portion that supports the crankshaft housed in the skirt portion corresponding portion 1b, and 1d is a rib supporting the bearing forming portion. This is the part corresponding to .

Then, as shown in FIG. 3(a), such an extinguishable mold 1 is housed in a casting container 2, and casting sand 3 is placed in this container 2.
Filled with
As shown in b), molten metal 5 is injected through the sprue 4 of the expanded polystyrene ring connected to the fugitive mold 1, and the fugitive mold 1 is replaced with the molten metal 5 while burning the fugitive mold 6.

In addition, when filling the vI sand 3, by performing the filling while shaking the container 2 with the vibration device 6 installed in the casting container 2, it is also possible to fill the hollow part of the water jacket equivalent part 1a of the vanishable mold 1. , casting sand 5 is filled. At the same time, the bonding force between each particle of the casting sand 5 is also strengthened.

[Problems to be Solved by the Invention] By the way, in the above-mentioned vanishing model casting method, in the process of filling the T4 molding container 2 with casting sand 3 and burying the vanishing mold 1 in the casting sand 3, the vanishing mold 1 is deformed into the vanishing mold 1. may occur. In other words, casting sand 3
The filling is performed while the container 2 is vibrated by the vibration device 6. At this time, the casting sand 3 in the casting container 2 is
), as shown by the arrow a, to deform the portion 1b corresponding to the skirt portion of the vanishing mold 1, as shown in FIG. 3(b).

In FIG. 3(b), the original shape of the skirt portion 1b of the vanishing mold 1 is indicated by a two-dot chain line, and the actual shape (deformed shape) of the skirt portion 1b is indicated by a solid line. It is shown as

Such deformation of the vanishing mold by the casting sand 3 is not limited to the vanishing mold 1 of the cylinder block.

When an effacement mold is deformed, a cast product obtained from the effacement mold is naturally also deformed, and the problem in the effacement model casting method is how to prevent this deformation of the effacement mold.

The present invention was devised in view of these problems.
By preventing the fugitive mold from being deformed by the casting sand, it is possible to reliably obtain a cast product having a desired shape. The purpose is to provide a vanishing model casting method.

[Means for Solving the Problems] In order to achieve this object, the fugitive model casting method of the present invention involves embedding the fugitive mold in casting sand, and then injecting molten metal into the inside of the fugitive mold. In the vanishing model casting method in which the mold is replaced with the molten metal, the vanishing mold is fixed to a surface plate before being buried in the casting sand, and the vanishing mold is buried together with the surface plate in the casting sand. It is characterized by

[Function] In the above-described vanishing model casting method of the present invention, the vanishing mold is fixed to a surface plate and then buried in casting sand, so when burying the vanishing mold in the casting sand, While a deforming external force acts on the evanescent mold from the casting sand, the elusive mold maintains a predetermined shape with the help of the rigidity of the surface plate.

[Example] Hereinafter, a disappearance model v as an example of the present invention will be explained with reference to the drawings.
To explain the fia method, FIG. 1 is a front view of an evanescent mold according to this embodiment, and FIGS. 2(a) to 2(d) are schematic cross-sectional views sequentially showing the casting process of this embodiment.

An effacement mold (EPS model) 1 according to this embodiment is used to manufacture a cylinder block for an engine, and is made of expanded polystyrene (polystyrene). Therefore, as shown in Fig. 1, this vanishing mold 1 is formed in the same shape as the cylinder block to be obtained, and corresponds to the water jacket formed in the upper part of the cylinder block around the cylinder liner. A portion 1a, a portion 1b corresponding to a skirt portion formed at the lower part of the cylinder block, a portion 1c corresponding to a bearing forming portion that supports the crankshaft housed in the skirt portion corresponding portion 1b, and this bearing forming portion. A portion 1d corresponding to a rib supported by the skirt portion is provided.

This vanishing type 1 includes a gate 8 and a runner 7a.
, 7b, and 7c are connected to hot water D4. In other words, gates 8 are provided at a plurality of locations on the evanescent mold 1 (here, a plurality of locations in the skirt portion equivalent portion 1b and the bearing forming portion equivalent portion 1c), and each gate 8 is provided with a runner 7c. A runner 7b and a runner 7a are provided. Note that these gates 8. Runners 7a-7
C and the sprue 4 are also made of expanded polystyrene like the fugitive mold 1.

Casting is carried out using the thus formed fugitive mold 1. In the present fugitive model casting method, the fugitive mold 1 is fixed to a surface plate 9 before being buried in casting sand. In other words, the lower surface of the runner 7b is fixed to the surface plate 9 by adhesive or the like, and thereby the lower part of the evanescent mold 1 (that is, multiple locations in the portion corresponding to the skirt portion ib and the portion corresponding to the g receiving forming portion 1c) is attached to the runner 7b. .

It is fixed to the surface plate 9 through 7c. In addition, the surface plate 9 is.

For example, it is made of iron-based metal such as cast iron, and is formed in a honeycomb shape with a large number of vertically communicating holes 9a, and has a predetermined rigidity.

Then, when the vanishing mold l is fixed to the surface plate 9 in this way,
First, a coating agent (a solution containing a binder as a main component mixed with fine refractory particles) is applied to the entire surface of the fugitive mold 1, and then this is dried.

The solution containing the binder as the main component used at this time is an organic solvent that does not attack the evanescent type 1.
Examples include aqueous or alcoholic solutions. In the case of an aqueous solution, it is an aqueous solution containing a binder, a surfactant and an antifoaming agent,
Among these, starch, vinyl acetate, carboxymethylcellulose (CMC), etc. can be used as the binder, cationic, anionic or amphoteric surfactants can be used as the surfactant, and alcohol-based antifoaming agent can be used. Commonly used antifoaming agents or silicones can be used. Further, in the case of an alcohol solution, for example, one containing about 1 to 30% of vinyl acetate resin as a binder in alcohol can be mentioned, and in this case, a surfactant and an antifoaming agent are not necessary.

In addition, as the refractory fine particles used at this time, for example,
Fine particles such as silica (sio2) + zirconia (ZrO2) or mica can be cited, but in the case of forging iron materials,
Usually, silica or zirconia is used, but in the case of forging aluminum-based materials, mica fine particles with a heat-insulating space are suitable.

After the surface treatment is applied to the fugitive mold 1 in this manner, in the subsequent step, the fugitive mold 1 is buried in the casting sand 3 together with the sprue 4 and the like.

That is, first, as shown in FIG. 2(a), the casting container 2
An appropriate amount of casting sand (casting sand to which no binder has been added or mixed) 3 is stored in the lower part of the container, and the fugitive mold 1 is placed in the desired posture in this container. At this time, for example, by placing the fugitive mold 1 on the runner 7a while clamping a portion near the sprue 4, the fugitive mold 1 can be prevented from being damaged.

Then, the container is further filled with casting sand (casting sand to which no binder has been added or mixed) 3, and the fugitive mold 1 is completely buried.

Note that this filling of the casting sand 3 is done in order to ensure that the hollow part of the part 1a corresponding to the water jacket of the fugitive mold 1 is also filled with the casting sand 3, and also to strengthen the bonding force between each particle of the casting sand 3. In order to do this, the casting volume r;2 is vibrated using a vibrator.

At this time, the casting sand 3 in the casting container 2 is excited and the disappearing mold 1
The evanescent mold 1 moves so as to deform the skirt portion 1b and the bearing forming portion 1c, but the vanishing mold 1 has its skirt portion 1b and bearing forming portion 1c fixed to the surface plate 9. Therefore, with the help of the rigidity of the surface plate 9,
A predetermined shape is maintained against the moving casting sand 3.

In addition, since the surface plate 9 is formed in a honeycomb shape with holes 9a that communicate with each other vertically, it does not hinder the filling of the casting sand 3 into each part, but the surface plate 9 has a certain limit. It can also be expected that harmful movement of the casting sand 3 can be suppressed within the casting sand 3.

In this way, as shown in FIG. 2(b), the vanishing type 1
is buried in the casting sand 3, in the subsequent process, the sprue 4 is buried.
A molten metal (for example, molten aluminum alloy) 5 is injected into the fugitive mold 1 through the molten metal 5, and the molten metal 5 replaces the fugitive mold 1.

In other words, when the molten metal 5 is injected into the fugitive mold 1 through the sprue 4, the high-temperature molten metal 5 invades the fugitive mold 1, which is still thermally decomposing the sprue 4 and the runners 7a to 7c. This vanishing type 1 is gradually thermally decomposed [Figure 2 (c)
reference].

Then, this thermally decomposed part, that is, the sprue 4 and the extinguishing mold 1
The space where there was was replaced by molten metal 5, and when this molten metal 5 is cooled to a predetermined temperature, a desired metal casting (
In other words, the engine cylinder block 10 is manufactured [see FIG. 2(d)]. In addition, thermally decomposed vanishing type 1 etc.

It becomes gaseous and is discharged to the outside through the gaps in the casting sand 3.

Thereafter, the casting 11 formed by the runners 78 to 7c and the sprue 4 is removed from the lower part of the casting 10 where the gate 8 was located, and the necessary parts such as the liner surface are polished. It will be completed.

Further, after casting, the fixed g 19 is also removed from the casting 11.

In this way, in the investment model casting method of this embodiment, deformation of the investment mold 1 of the cylinder block due to casting sand can be prevented, so that the cylinder block 1o can be reliably cast into a desired shape.

Although this embodiment describes an engine cylinder block, the present invention is applicable not only to cylinder blocks but also to a wide range of applications in which an extinguishable mold is easily deformed during filling with casting sand. For example, the present invention can be applied to an engine cylinder head. It can also be applied to

Further, in this embodiment, the surface plate 9 is made of iron-based metal, but the material of the surface plate 9 is not limited to this, and for example, ceramics or the like may be used.

When the surface plate 9 is made of ceramics, ceramics generally have low heat absorption, so when pouring the molten metal 5, the molten metal 5
There is also the advantage that the molten metal 5 is less likely to lose heat to the surface plate, and the injection of the molten metal 5 is performed smoothly, which can contribute to improving the quality of the cast product.

Further, in this embodiment, an aluminum alloy is used as the molten metal, but a metal other than an aluminum alloy, such as an iron-based metal, may be used as the molten metal.

In this embodiment, after fixing the fugitive mold 1 to the surface plate 9, a coating agent is applied to the entire surface of the fugitive mold 1 and dried. The fixing process may be performed before embedding the fugitive mold 1 in the casting sand 3. For example, after applying a coating agent to the surface of the fugitive mold 10 and drying it, the fugitive mold 1 is placed on a surface plate. It may be fixed to 9.

In addition, in the case of the process sequence of fixing the fugitive mold 1 to a constant 1119 and then applying the coating agent to the entire surface of the fugitive mold 1 as in this example, the fugitive mold 1 (runner 7c in this case)
Since the coating mold M is not formed between the surface plate 9 and the surface plate 9, the bond between the surface plate 9 and the casting 11 is strengthened, and the casting 11 is formed after casting.
This makes it difficult to remove the surface plate 9. Therefore, in this case, it is preferable that the surface plate 9 and the molten metal 5 are made of different materials. In other words, if the molten metal 5 is an aluminum-based alloy as in this embodiment, the surface plate 9 is made of, for example, iron-based metal or ceramics, and if the molten metal 5 is an iron-based metal, the surface plate 9 is made of, for example, ceramics. Are suitable.

However, in the case of step 11i, which involves applying a mold coating agent to the entire surface of the fugitive mold 1 and drying it, the fugitive mold 1 is fixed to the surface plate 9, the fugitive mold 1 (here, runner 7 c) and Since a coating layer is formed between the surface plate 9 and the surface plate 9, the surface plate 9 and tJ
The connection with the f structure 11 is weakened, and it becomes easy to remove the surface plate 9 from the f4 structure 11 after the vI structure. For this reason,
In such a case, the surface plate 9 and the molten metal 5 do not necessarily have to be made of different materials.

[Effects of the Invention] As detailed above, according to the investment model casting method of the present invention, after the investment model is buried in casting sand, molten metal is poured into the interior of the investment model to remove the investment model. In a fugitive model casting method in which molten metal is substituted, the fugitive die is fixed to a surface plate before being buried in the casting sand, and the fugitive mold is buried together with the surface plate in the casting sand. This prevents deformation caused by vanishable casting sand and creates the desired shape of the V! There is an advantage that it is possible to reliably obtain a built-up object.

[Brief explanation of the drawing]

Figures 1 and 2 show the vanishing model U-adic system as an embodiment of the present invention. Figure 1 is a front view of the vanishing model according to this embodiment, and Figures 2 (a) to (d) are FIG.
b) is a longitudinal cross-sectional view of an effacement mold in an effacement container, each showing a conventional effusion mold casting method; 1-disappearing type (EPS model), 1a-part corresponding to water jacket, 1b-part corresponding to skirt part, 1
c-portion corresponding to the bearing forming part, 1d...portion corresponding to the rib, 2-v! Container making, 3. - Foundry sand (casting sand with no binder added and mixed), 4 - Sprue, 5 - Molten metal, 6
- Vibration device, 7a, 7b, 7cm runner, 8-gate, 9 fixed plate, 9a/fixed plate hole, Io-metal casting (
In other words, engine cylinder block), 11...castings made by runners and sprues.

Claims (1)

[Claims] In the fugitive model casting method, which involves embedding the fugitive mold in casting sand and then injecting molten metal into the fugitive mold to replace the fugitive mold with the molten metal, before burying the fugitive mold in the sand. A method for casting an effaceable model, characterized in that the effaceable mold is fixed to a surface plate, and the effluent mold is buried together with the surface plate in the casting sand.