JPH02217131A - Lost foam pattern casting method - Google Patents

Abstract

PURPOSE:To smoothly discharge gas to outside from upper opening hole and to reduce the development of gas blowing deffect by packing a hollow space for a lost foam pattern with molding sand for hollow space having larger grain diameter than that of the molding sand for casting bed. CONSTITUTION:In the packing stage of the molding sand for hollow space, the molding sand S1 for hollow space is packed into a water jacket corresponding part 11 as the hollow space for a part of the lost foam pattern 10. The molding sand S1 for hollow space used in there uses one having larger grain diameter, better permeability and coarser grain than these of the molding sand for casting bed 12. By this method, the gas discharged into the hollow space can be smoothly shifted toward the upper opening hole, and rising of the gas pressure in the hollow space is eliminated and the development of gas blowing defect of casting blow hole, etc., in the cast product can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vanishing model casting method for casting a cast object having a shape corresponding to the vanishing model using a vanishing model made of foamed resin.

(Prior art) A vanishing model with the same shape as the object to be cast is prepared in advance, the vanishing model is embedded in the casting sand of each casting bed, and hot water made of casting material is poured into the area occupied by the vanishing model. A vanishing model casting method is known, in which a cast product is obtained by pouring metal, and in particular,
This method is widely used as it is suitable for mass production.

By the way, in this vanishing model casting method, a mold-embedding process is performed in which the vanishing model is embedded in the casting sand of the casting bed, but the shape of the vanishing model 1 to be implanted is, for example, like a cylinder block as shown in Fig. 4. If so.

A part 2 corresponding to a water jacket is formed as a hollow space.

The water jacket equivalent portion 2 is filled with casting sand S in the same manner as the other portions.

Then, in the casting process after the mold filling process, the disappearing model generates water vapor and gas. The gas at this time passes through the casting sand and is diffused and released.

(Problems to be Solved by the Invention) However, during this gas diffusion, gas is blown into the water jacket equivalent portion 2 from the surrounding cylinder equivalent portion 3 and outer wall equivalent portion 4, respectively. For this reason,
A large amount of gas discharged here moves toward the narrow upper opening 5, but the flow resistance passing through the casting sand becomes relatively large, and the gas pressure in that part tends to increase.

For this reason, the part of the casting that faces the water jacket equivalent part 2 is likely to have gas blow defects, for example, the casting surface is likely to have blowholes, which is a problem.

An object of the present invention is to provide an effacement model casting method that can reduce the occurrence of gas blow defects.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention uses a vanishing model made of foamed resin and having a hollow area with an opening facing upward during casting, and This method involves performing a mold filling step of embedding mold sand in the same casting bed, and then performing a casting step to cast a cast object having a shape corresponding to the above-mentioned vanishing model. Prior to that,
The above-mentioned casting process, filling process of casting sand for hollow area, mold filling process of embedding the vanishing model in the casting bed with casting sand S, casting process, cooling process, and mold splitting sand recovery process. The cylinder block is cast.

In the model forming process, we prepare raw material beads made of foamed polystyrene, blow them into a mold for molding a vanishing model, heat them with steam, and then cool them to create a vanishing model with the same shape as the cylinder block to be cast. Manufacture 10.

In the preparatory step for mold filling of the vanishing model, the sprue 19 and the runner 21 are adhered to the vanishing model 10, and a coating material for ensuring the surface roughness of the workpiece is applied to the vanishing model 10 and dried. Note that the coating material used here is produced by mixing mica and a binder.

After this, the process of filling molding sand for the hollow area begins. Here, a portion 11 corresponding to the water jacket as a part of the hollow area of the vanishing model 10 is filled with casting sand S1 for hollow area.

The casting sand Sl for hollow areas used here has a larger particle size than that used in the casting bed 12, and has a larger particle size than the casting sand used for the well-ventilated bed. Prepare,
The present invention is characterized by carrying out a step of filling the hollow area casting sand into the hollow area of the vanishing model.

(Function) The hollow area of the vanishing model is filled with casting sand for hollow areas, which has a larger grain size than the casting sand used for the casting bed.

The gas released into the same part during casting is not subject to much flow resistance and is smoothly released to the outside from the upper opening.

(Embodiment) FIG. 1 shows a cross-sectional view of a cast bed used when casting a cylinder block as a cast object by a disappearing model casting method as an embodiment of the present invention.

In the vanishing model casting method here, the cylinder block is cast by performing each process as shown in FIG. 3(a).

That is, this vanishing model casting method employs a model molding process for producing a vanishing model and a rough preparation for inserting the vanishing model into the mold (see FIG. 2).

The vanishing model 10 in which the water jacket equivalent part 11 is filled with the hollow area casting sand S1 is placed in the casting bed in the next mold filling process, and the prepared casting sand S
(Fig. 1, Fig. 3 (b-
4)). The casting sand S here has a smaller particle size than the casting sand S1 for hollow areas, and is binder-free sand. Note that this casting bed 12 is operated by a vibrator 13 and is completely filled with casting sand S.
Filled with.

In the casting process, molten aluminum alloy 1 for casting, for example AC4B, is supplied from an expanded polystyrene sprue 19 in the upper part of the cast bed 12 by an automatic pouring machine (not shown).

Thereafter, the cast bed 12 is cooled for a required period of time in a cooling process.

In the mold sand recovery step, the flask 15 of the cast bed 12 is removed at a predetermined sand recovery position, and the cast cylinder block 14 is taken out from the sand S. The casting sand S recovered at this time is reused in the mold filling process by using a sand cooler, recycling treatment, sieving, and supplying new sand.

The cylinder block 14 that has been taken out is further moved to a predetermined recovery position for hollow area casting sand S1, is turned over there, and hollow area casting sand S1 is recovered.

This casting sand S1 for hollow areas is also reused in the filling process of casting sand for hollow areas by using a sand cooler, regenerating treatment, sieving, and supplying new sand.

The cylinder block 14 from which the casting sand S has been completely removed is the completed cylinder block 14 through post-processing such as deburring.
becomes.

Here, FIG. 1 shows a sectional view of a cast bed 12 used when casting a cylinder block according to this embodiment. It is composed of a casting flask 15, a vibrator 17 for placing the casting flask on a base 16, and casting sand S filled in the casting bed 12.

As shown in FIG. 1, the casting flask 15 is formed into a box-shaped body having a capacity that allows the cylinder block 14, which is the object to be cast, to be sufficiently embedded in the casting sand S. This flask 15
is supported on the base 16 by a spring 18. When the vibrator 17 is driven, it fills the casting flask 15 with casting sand for the hollow area and performs the filling process of the casting sand for the hollow area, so that the gas released into the hollow area is smoothly moved upward. It can be moved towards the opening, eliminating the increase in gas pressure in the hollow area.
It is possible to prevent the occurrence of gas blow defects such as cavities in the cast product.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the cast bed used in one embodiment of the present invention, Figure 2
The figure is a partial enlarged sectional view of the part corresponding to the water jacket in Figure 1, Figure 3 (,) is a block diagram explaining the process of the vanishing model casting method performed using the same casting bed, and Figure 3 (b- 1
) to (b-6) are schematic explanatory diagrams of each process, and FIG. 4 is a sectional view of a cast bed when a cylinder block is cast by a conventional method. 10...Disappearance model, 11...Water jacket equivalent part, 12...Cast bed, Sl...Casting sand for hollow space, S.
・Casting sand. Casting sand S is filled into the casting bed 12 by vibrating vertically and horizontally.
It operates so as to fill the surroundings of the disappearing model 10 without any gaps. The vanishing model 10 consists of a portion having the same external shape as the cylinder block to be cast, and attached portions forming a sprue 19 and a runner 21, and is entirely a molded product of expanded polystyrene. Furthermore, this cast object, the cylinder block E0
is equipped with a closed deck water jacket, and the hollow area corresponds to the water jacket part 11.
has openings 20 and connecting portions (not shown) alternately formed at appropriate positions on its upper portion. For this reason, the opening 20 is used to fill and remove the casting sand S1 for the hollow area. In the above description, the cylinder block has been described as an object to be cast having a hollow area, but the present invention can also be applied to the casting of intake manifolds, exhaust manifolds, and the like. (Effect of the invention)

Claims (1)

[Claims] A vanishing model made of foamed resin and equipped with a hollow area with an opening facing upward during casting is used, and a mold filling process is carried out in which this vanishing model is embedded in the casting bed with casting sand, followed by a casting process. In the vanishing model casting method of casting a cast object having a shape corresponding to the vanishing model, prior to the mold filling step, hollow space casting sand having a particle size larger than that of the casting sand used in the casting bed is prepared. A method for casting a vanishing model, comprising: carrying out a filling step of casting sand for hollow cavities in which the hollow cavities of the vanishing model are filled with the casting sand for hollow cavities.