JPH01237046A - Method for casting lost foam pattern - Google Patents

Abstract

PURPOSE:To cast a cylindrical body having bend without any casting defect by setting bend of a lost foam pattern into a sand packing vessel so as to come to face downward at the time of casting the cylindrical body having bend with full mold casting method, turning over at 180 deg. angle after packing molding sand into the inner and outer parts of the lost foam pattern, inserting it into a flask, further packing the molding sand and pouring molten metal from a runner. CONSTITUTION:At the time of producing a pipe-like member having bend with the full mold casting method, the lost foam pattern 4 for the pipe-like member is manufactured, and after fitting the runner 5, the pattern is set in the sand packing vessel 2 so that the bend comes to face downward, to make the position, where the molding sand easily comes in the hollow part of the lost foam pattern 4, and the molding sand 6 is packed and under condition of sufficiently packing the molding sand 6 into the hollow part, too, the molding sand 6 is packed into the outer circumferential part. This is turned over 180 deg. angle and set in the flask and further the molding sand is rammed and the molten metal is poured from a sprue 8 arranged on the runner 5 and the lost foam pattern 4 is lost with heat to cast the cylindrical body having bend.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention involves embedding a lost form (disappearing model) made of polystyrene foam or the like into a desired casting shape in casting sand in a casting flask. A casting is obtained by pouring molten metal to eliminate the lost foam.

The present invention relates to a lost form casting method called a so-called full mold casting method, and particularly relates to a lost form casting method suitable for cases where the lost form has a portion, such as a curved portion, that is difficult to fill with molding sand.

(Prior art) Conventionally, when obtaining an irregularly shaped pipe or the like by casting, the cylindrical lost form used therein has a hole formed in a curve corresponding to the shape of the casting. When buried in molding sand in the frame, it is difficult to fill the holes of the lost form with molding sand without any gaps, and as a result, casting defects occur in the parts corresponding to the curved parts of the lost form holes in the obtained casting. There was a problem.

Therefore, as a countermeasure against such casting defects, for example, as disclosed in Japanese Patent Laid-Open No. 59-39447, a back-up layer made of a refractory material is formed in advance by coating on the curved part of the hole of the cylindrical lost form. By placing the lost form in the molding sand in the casting flask,
A method is known in which, even if a defective filling of molding sand occurs in the curved part of the hole of the lost foam, the strength of the curved part of the hole is reinforced by the backup layer to finish the cylindrical casting with high precision without any casting defects.

(Problem to be Solved by the Invention) However, in the method according to the above-mentioned publication example, before the cylindrical lost form is placed in the casting flask, a back-up layer is formed at the curved part of the hole where the molding sand filling is defective. This requires a coating process, which tends to reduce casting workability.

Furthermore, the above-mentioned coating part (backup layer) reduces the permeability of the gas generated by the disappearance of the lost form during pouring, and therefore, the part corresponding to the curved part of the lost form hole of the obtained cylindrical casting is There was also a risk that casting defects would occur.

The present invention has been made in view of the above, and its purpose is to reduce the amount of molding sand in the casting flask when producing a casting using a lost form that has curved parts and other parts that are difficult to fill with molding sand. By taking appropriate measures for burying the lost foam, when the lost foam is buried in the molding sand in the casting flask, the molding sand can be reliably filled into curved parts of the lost foam and other areas where it is difficult to fill with molding sand without any gaps. Filling, so that before placing the lost foam into the flask,
It is an object of the present invention to improve casting workability by eliminating the need for a coating process to form a back-up layer in areas where it is difficult to fill with foundry sand. Furthermore, as mentioned above, the back-up layer is not required, and the air permeability caused by the back-up layer during pouring is eliminated, and the lost form curved parts of the obtained castings, which correspond to the parts that are difficult to fill with molding sand, are eliminated. The purpose is to reliably prevent the occurrence of casting defects in parts.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention embeds lost foam in foundry sand in a casting flask, and then casts the lost foam while disappearing with molten metal. The method for casting the lost foam is as follows: First, the lost foam is held in a position that makes it easy to fill with molding sand in a sand-filling container, and then the lost foam is buried in the molding sand by filling the sand-filling container with molding sand. do. Next, the sand-filled container is placed in a casting flask so that the lost foam is changed to a normal casting position. After that, the flask is filled with molding sand.

(Function) With the above configuration, in the method of the present invention, the lost foam is held in a position that makes it easy to fill the sand filling container with molding sand, and then is buried in the foundry sand filled in the sand filling container, Thereafter, the sand-filled container is put into a casting flask with its attitude changed to the normal casting attitude. In this way, before putting the lost foam into the flask, the molding sand is reliably filled in the curved parts of the lost foam and other areas that are difficult to fill with molding sand, without any gaps. This eliminates the need for a coating process to form a back-up layer in areas where it is difficult to fill the molding sand before the molding sand is poured into the mold, thereby improving casting workability. Furthermore, since there is no need to form a backup layer as mentioned above,
Elimination of air permeability due to the back-up layer during pouring, and reliably preventing the occurrence of casting defects in parts that are difficult to fill with molding sand, such as lost form curved parts of the obtained casting. becomes.

(Example) Hereinafter, a lost foam casting method according to an example of the present invention will be described.

First, as shown in FIG. 1, a full-mesh sand container 2 has openings at the top and bottom, and a lid 1 that can be opened and closed at one of the openings (top in FIG. 1). Prepare the sand container 2! ! Place 1 on vinyl sheet 3 with side 1 facing up.

Next, the desired casting shape (
If it is troublesome, it is molded into a bent shape as an irregularly shaped pipe. A runner 5 is attached to a cylindrical lost form 4 having a curved interior, and the lost form 4 with the runner 5 attached is placed in molding sand 6, 6, . ... (shown in Fig. 2) for easy filling, that is, with the concave curved side of the hole 4a facing upward,
It is placed in the sand filling container 2 in a posture bent back into a letter shape and with the runner 5 facing down. Thereafter, the lower end of the runner 5 is fixed to the vinyl sheet 3 with adhesive or adhesive tape, and the lost form 4 is attached to the molding sand 6, 6. ...
Hold it in a position that makes it easy to fill.

Thereafter, as shown in FIG. 2, the sand filling container 2 is filled with foundry sand 6, 6. By filling the foundry sand 6,6°... until it swells outward due to the filling pressure of the foundry sand 6,6.・
Buried in... As a result, the holes 4a of the lost form 4 are formed in the molding sand 6, 6. ... is filled without any gaps.

Thereafter, after closing the Ml of the sand filling container 2, as shown in FIG.
A predetermined amount of foundry sand 6 is added as bed sand in advance.
,6. Place it on top of... As a result, the lost foam 4 buried in the molding sand 6, 6°, etc. of the sand filling container 2 is placed in the normal casting position, that is, in an inverted V-shape with the concave curved part side of the hole 4a facing downward. The casting flask 7 is placed in the flask 7 with its posture changed to a curved posture.

Next, after removing the vinyl sheet 3 covering one (upper side in FIG. 3) opening of the sand filling container 2, a sprue 8 is attached to the end of the runner 5 of the lost form 4.

Thereafter, while the flask 7 is vibrated in three axial directions under predetermined vibration conditions by the vibrator 8, the molding sand 6, 6, . .
Buried in... At this time, pressurized air is supplied from an air supply source (not shown) into the flask 7 through the plumber 0, and the molding sand 6, 6. Make ... flow.

Thereafter, molten metal (not shown) is poured from the sprue 8. As a result, the lost foam 4 receives the high heat of the molten metal and completely thermally decomposes and disappears, and a part of it becomes soot-like carbon, but also becomes carbon dioxide gas and water vapor, and the foundry sand 6, 6. ...The space occupied by Lost Form 4 inside is replaced by a cylindrical casting. Then, by waiting for the obtained cylindrical casting to cool down and taking it out from the flask 7, a cylindrical casting (bent) as a product is completed.

In this way, in this embodiment, the lost form 4 is placed in the casting flask 7.
Foundry sand inside 6,6. When burying the lost foam 4 in the sand filling container 2, first, the lost foam 4 is buried in the foundry sand 6, 6.・
... foundry sand 6,6. The sand filling container 2 is then placed in the casting flask 7 with the sand-filled container 2 inverted 180@ to change the posture of the lost form 4 to the regular casting posture. Then, the molding flask 7 is filled with molding sand 6, 6°, . . . . In this way, the lost form 4 is divided into two stages and the molding sand 6, 6 in the flask 7 is formed.
．． Since it is buried in ..., foundry sand 6, 6. . Since there is no need to go through a coating process for forming, it is possible to improve casting workability. Furthermore, since it is not necessary to form a back-up layer as described above, the problem of air permeability caused by the back-up layer during pouring can be eliminated, and the resulting cylindrical casting can be cast in the part corresponding to the lost form. The occurrence of defects can be reliably prevented.

In addition, in the above embodiment, the case where the casting is a vent as a deformed pipe is illustrated, but the invention is not limited to this, and for example, an elbow,
Of course, the present invention can also be applied to the case of obtaining irregularly shaped pipes such as T-type joints and Y-type joints, and furthermore, it is not limited to cylindrical objects such as irregularly shaped pipes, but may be solid ones.

(Effects of the Invention) As explained above, according to the method of the present invention, after burying the lost foam in the foundry sand filled in the sand filling container while holding it in an easy-to-fill position, the sand filling container is Since the lost form is placed in the casting flask so that its posture is changed to the normal casting position, the work of forming a back-up layer on the parts of the lost form that are difficult to fill with molding sand is eliminated, improving casting workability. can be achieved. Furthermore, it is possible to reliably prevent the occurrence of casting defects due to the lack of air permeability due to the back-up layer.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is a layout diagram showing a state in which lost foam is placed in a sand-packing container, FIG. 2 is a layout diagram showing a state in which foundry sand is filled in a sand-packing container, and FIG. The figure is a layout diagram showing a state in which lost foam is placed in a casting flask. 2... Sand-filled container, 4... Lost foam, 6...
- Foundry sand, 7... Casting flask. Figure 1 Figure 2 (' Figure 3 De

Claims (1)

[Claims] (1) A lost foam casting method in which the lost foam is buried in molding sand in a casting flask, and then a casting is obtained while the lost foam is disappeared by molten metal, and the lost foam is buried in molding sand in a sand-filling container. After holding it in a position that is easy to fill, the lost foam is buried in the foundry sand by filling the sand filling container with molding sand, and then the sand filling container is changed to a normal casting posture for the lost foam. 1. A method for casting lost foam, which comprises placing the foam in a flask, and then filling the flask with molding sand.