JPH01237045A - Method for casting lost foam pattern - Google Patents

Abstract

PURPOSE:To pack molding sand into inner part of a lost foam pattern at high density and to simply cast a cylindrical casting having bend without any casting defect by fitting sand packing jigs having the specific construction at both end parts of the lost foam pattern at the time of casting the cylindrical casting having bend with full mold casting method. CONSTITUTION:At the time of casting the hollow cylindrical casting having bend with the full mold method, on the opening parts at both ends in the lost foam pattern 2 formed with polystyrene foaming material, etc., the sand packing jigs 1 arranging plural tapered holes 1a having 20-30 deg. tapered angle so as to become smaller hole diameter toward hollow part 2a in the pattern 2 are fitted. A runner 4 having a sprue 3 is set in the pattern 2 and embedded into the molding sand 6 in a flask 5 and the molding sand 6 is made to ram around the pattern 2 with a vibrator 7 and also packed into the hollow part 2a in the pattern 2 from one side of the tapered hole 1a. Under this condition, by pouring molten metal into the pattern 2 through the runner 4, the pattern is burnt and vaporized and the molten metal is cast and solidified.

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 to a casting method using a cylindrical lost form with a curved interior.

(Prior art) Generally, when obtaining a cylindrical casting with a curved interior, it is difficult to fill the inside (hole) of the cylindrical lost form with molding sand without any gaps. There was a problem in that casting defects occurred in the portion corresponding to the curved portion of the lost form hole.

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 doing so, when the lost foam is buried in foundry sand in a casting flask, even if the hole in the lost foam is not filled with molding sand, the strength of the curved hole in the lost foam can be maintained as above. A method is known in which a cylindrical original is reinforced with an up layer and finished with high accuracy without casting defects.

(Problem to be Solved by the Invention) However, in the method according to the above-mentioned publication example, before placing the cylindrical lost form with a curved inside into the casting flask, back-up is applied to the curved part of the hole where the molding sand filling is defective. It has to go through a coating process that forms a layer, so
This has the disadvantage of reducing 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 an object of the present invention is to introduce the lost foam into the casting flask by providing an appropriate means to the opening of the cylindrical lost foam having a curved hole. A coating that ensures that the foundry sand fills the curved part of the hole without any gaps when buried in foundry sand, thereby forming a back-up layer in the curved part of the hole before the lost form is placed in the casting flask. The purpose is to improve casting workability by eliminating the need for a process. Furthermore, as mentioned above, the back-up layer is not required, eliminating the problem of air permeability due to the back-up layer during pouring, and casting defects in the portion corresponding to the curved part of the lost form hole in the resulting cylindrical casting. The aim is to reliably prevent the occurrence of

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention embeds a cylindrical lost form having a curved inside in molding sand in a casting flask, and then embeds the lost form in the molten metal. In the lost form casting method, in which a cylindrical casting is obtained while the sand disappears, a sand-filling jig is installed in advance in the opening of the lost form to move the foundry sand only into the inside of the lost form. Then, the lost foam fitted with the sand filling jig is placed in the casting flask, and the inside of the lost foam is filled with molding sand via the sand filling jig.

(Function) With the above configuration, in the method of the present invention, the foundry sand is filled into the inside of the cylindrical lost form buried in foundry sand in the flask through the sand filling jig attached to the lost form opening. The filled molding sand is moved only to the inside of the lost foam by the sand filling jig and is prevented from being discharged to the outside of the lost foam. From this, the foundry sand is reliably filled inside the lost form without any gaps.
As a result, before putting the lost foam into the flask,
There is no need for a coating process to form a back-up layer on the curved portion of the hole, thereby improving casting workability. Furthermore, since it is not necessary to form a back-up layer as described above, the air permeability caused by the back-up layer during pouring is eliminated, and the part corresponding to the curved part of the lost form hole of the obtained cylindrical casting is The occurrence of casting defects will be reliably prevented.

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

First, two disc-shaped refractory sand filling jigs 1 as shown in FIG. 1(a) and FIG. 1(b) are prepared. Each sand filling jig 1 has a large number of tapered holes 1a.

la, . . . are formed to penetrate in the thickness direction, and the inclination angle of each tapered hole 1a is set to, for example, 20 to 30@. Further, the narrowest hole diameter of each of the tapered holes 1a is, for example, 6.6 mm of the molding sand used. ...(Figure 3 (a) to (C)
If the grain size of the foundry sand is 35 to 70 mesh, it is set to 3 to 4 mm. It is determined appropriately according to the particle size of... Each sand filling jig 1 in which a large number of tapered holes la, la, . It has a so-called one-way function in which it can pass from the widest hole diameter side to the narrowest hole diameter side of 1a, but cannot pass in the opposite direction.

Next, as shown in FIG. 2, polystyrene foam or the like was formed into the desired casting shape (the bent shape shows a bent shape as a deformed tube). Both sand filling jigs 1,
1 are fitted to each other with the narrowest hole diameter side of each tapered hole 1a facing toward each opening.

Thereafter, as shown in FIG. 3(a), the runner 4 provided with the sprue 3 is attached to the lost form 2 to which the sand filling jigs 1 and 1 are attached, and then the runner 4 is installed. The attached lost form 2 is placed in a casting flask 5, and molding sand 6, 6 . . . , the casting flask 5 is vibrated in three axial directions under predetermined vibration conditions by a vibrator 7, and the lost foam 2 is mixed with molding sand 6, 6, . Buried in...

At this time, pressurized air is supplied from an air supply source (not shown) into the flask 5 through the piping 8 to cause the molding sand 6, 6°, . . . to flow.

Thereafter, as shown in FIG. 3(b) and FIG. 3(C), the flask 5 is heated, for example, by 30° while continuing to supply molding sand 6,6°... to the flask 5 and vibrating it. Tilt left and right two or three times at an angle of 2 to 3 seconds, and fill the lost form hole 2a with the foundry sand 6, 6,... through each sand filling jig 1.The foundry sand 6, 6... During filling, the foundry sand 6, 6, etc. filled in the lost foam hole 2a is moved only inward of the lost foam by the one-way function of each sand filling jig 1, and in the opposite direction. Since a certain lost foam is prevented from moving outward, the molding sand 6, 6, etc. in the lost foam cavity 2a gradually increases and does not decrease, so that the lost foam hole 2a is filled without any gaps. The Rukoto.

Thereafter, molten metal (not shown) is poured from the sprue 3.

As a result, the lost foam 2 receives the high heat of the molten metal and completely thermally decomposes and disappears, and a part of it becomes soot-like carbon and becomes carbon dioxide gas and water vapor, and the foundry sand 6
,6. ...The space occupied by Lost Form 2 inside is replaced by a cylindrical casting. After the obtained cylindrical casting has cooled, it is taken out from the flask 5, and the sand filling jig 1.1 that blocks the openings at both ends is removed to form the cylindrical casting (vent) as a product. It's done.

As described above, in this embodiment, the sand filling jigs 1 and 1 are attached to both openings of the cylindrical lost form 2, and the lost form 2 with each of the sand filling jigs 1 attached is placed in the casting flask 5. Foundry sand 6
,6. ... by burying the foundry sand 6,6.
. . . in the numerous taber holes 1a, la, of each sand filling jig 1.
... can be filled into the lost foam cavity 2a while preventing the lost foam from being discharged to the outside. From this, the foundry sand 6°6,... is reliably filled into the lost form hole 2a without any gaps, and as a result, before the lost form 2 is put into the casting flask 5, a back-up layer is applied to the curved part of the hole. It is no longer necessary to go through a coating process to form a coating process, thereby improving casting workability.

Furthermore, since it is not necessary to form a back-up layer as described above, the air permeability caused by the back-up layer during pouring is eliminated, and the portion corresponding to the curved part of the lost form hole of the obtained cylindrical casting is eliminated. It is possible to reliably prevent the occurrence of casting defects.

In addition, in the above embodiment, the case where the cylindrical casting is a vent as an irregularly shaped pipe is illustrated, but the present invention is not limited to this, and can also be applied to the case of obtaining irregularly shaped pipes such as an elbow, a T-shaped joint, a Y-shaped joint, etc. Of course. Furthermore, it is not limited to a deformed pipe, but may be a cylindrical casting having a curved part in the hole 2a, for example, a bottomed cylindrical one having one opening.

In addition, in the above embodiment, the method for attaching both sand filling jigs 1 and 1 to the lost foam 2 was done by fitting them together.
Needless to say, it is also possible to use adhesives, adhesive tapes, etc.

(Effects of the Invention) As explained above, according to the method of the present invention, a sand filling jig is attached to the opening of the cylindrical lost form having a curved inside to move the foundry sand only inward of the lost form. The lost form with the sand filling jig attached is placed in the casting flask and the inside of the lost form is filled with molding sand via the sand filling jig, so that the foundry sand can be reliably filled inside the lost form without any gaps. Casting workability can be improved by omitting the trouble of forming a back-up layer on the curved portion of the hole of the lost form by coating. 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 invention, and FIG. 1(a) and FIG.
Figure (b) is a vertical side view and front view of the sand filling jig, and the second
The figure is a vertical front view of the lost foam with the sand filling jig attached, Figure 3(a) is a diagram showing the lost foam placed in the flask, Figures 3(b) and 3(C) FIG. 2 is an explanatory diagram for explaining the procedure for filling the inside of the lost foam with foundry sand. 1... Sand filling jig, 2... Lost form, 2a.
... Hole, 5... Casting flask, 6... Foundry sand. (hole (#stuffed silk) 1' Δ (C1) Fig. 2, Iku) 2 Fig. 1 (b)

Claims (1)

[Claims] (1) A lost form casting method for obtaining a cylindrical casting by embedding a cylindrical lost form with a curved inside in molding sand in a casting flask and then disappearing the lost form with molten metal, the method comprising: A sand filling jig that moves the foundry sand only inward to the lost form is installed in the opening of the lost form, and the lost form with the sand filling jig attached is placed in the flask and the casting is placed inside the lost form. A lost foam casting method characterized in that sand is filled through the sand filling jig.