JPH06106327A - Casting method of thin casting - Google Patents

Abstract

PURPOSE:To produce a sound thin casting which has been decreased in mis-run defects by reducing the pressure in casting molds and by the consequent increase in the injection rate of a molten metal, is easily controlled in cooling by the thin layer of sand and is decreased in shrinkage cavities by effecting directional solidification. CONSTITUTION:This casting method consists in injecting the molten metal into a casting mold cavity by a vacuum effect within a reduced pressure box. The molten metal injected into the casting mold by changing the coefft. of heat conduction of the casting molds by changing the thickness of the sand mold between metallic foil 8 transferred with a mold and a mold and a plastic film 9 within a 0 to 100mm range is directionally solidified in a feeding direction. The metallic foil 8 prevents the melting of the plastic film in contact with the molds even if the molds rise to a high temp. Continuous casting is thus possible. The casting having favorable casting surfaces is produced by using fine sand without contg. a binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a casting having a good quality, such as a stainless casting or a heat-resistant casting, and a sound thin casting having no casting defects such as non-rotation and shrinkage cavities.

[0002]

2. Description of the Related Art Since cast stainless steel and heat-resistant cast steel have high melting points, they are poured into the mold and come into contact with the mold to solidify immediately. Therefore, the fluidity is poor and non-rotating defects are likely to occur. Further, in the case of a thin-walled casting having a complicated shape, it is particularly easy for air or gas generated from the mold to be involved, and gas defects such as blowholes are likely to occur. Furthermore, since the molten metal is high in temperature and easily reacts with the sand mold, insertion defects are likely to occur, the surface roughness of the casting surface is deteriorated, and it is extremely difficult to manufacture a sound casting.

As a general method for solving this problem,
Using the lost wax casting method. This uses a ceramics mold, and the mold is 700 ° C to 900 ° C during casting.
By heating to ℃, the cooling rate of the molten metal at the time of filling is slowed and the fluidity is improved. However,
Since the expensive ceramic mold is used, the manufacturing cost of the casting is considerably increased. On the other hand, as a method of improving fluidity, there is a method of reducing the pressure in the mold to perform casting (a reduced pressure molding mold, a CLAS method, etc.), which has recently been used as a method of manufacturing a thin cast product.

[0004]

However, in these conventional vacuum casting methods, since the mold is depressurized by a vacuum pump, the molten metal is disturbed during pouring, and air, slag, or a ladle is caught. Occurs, a casting defect occurs, and repairing this causes an increase in manufacturing cost and deterioration in quality. Further, in the reduced pressure molding mold (V process mold),
Only sand is used as an aggregate without a binder, and the shape of the mold is maintained by the pressure difference from the atmospheric pressure through the plastic film, but the plastic film burns and disappears during pouring, so the mold The holding power is lost, and insertion defects and shape defects are likely to occur.

The purpose of this utility model is to reduce casting defects,
It is an object of the present invention to provide a method for producing a high quality thin wall casting at low cost.

[0006]

In order to achieve the above object, the casting method of the thin casting of the present invention is a casting method in which molten metal is injected into the mold cavity (2) in the depressurization box (1) by a vacuum action. Yes, (A) a cast product part (3) and a cast design part having a vent (6) communicating with the outside in a model (5) having a transfer part of the cast product part (3) and the cast design part (4) 0 to 1 from the outer shape of the transfer part of (4)
A process of covering the whole or a part of the mold (7), which is larger by 00 mm, with the metal foil (8) and adhering it, (B) Model (5)
At least a part of the metal foil (8) adhered to and the part of the model (5) not covered with the metal foil (8) with the plastic film (9), (C) the model (5)
A step of setting the mold (7) while closely adhering the metal foil (8) and the plastic film (9) to each other, (D) the metal foil (8) and the plastic film (9) and the mold (7)
A step of filling sand (10) containing no binder between
(E) A step of releasing the adhesion of the metal foil (8) and the plastic film (9) to the model (5), (F) a step of applying a vacuum from the vent hole (6) of the mold (7), (G )
Step of releasing the model (5) from the metal foil (8) and the plastic film (9), (H) If necessary, on the filled sand (10), the metal foil (8) and the plastic film (9) Step of arranging the core, (I) Step of assembling another mold in the above steps (A) to (H), (J) Vacuum from the vacuum suction pipe (11) of the vacuum box (1) A step of injecting a molten metal by a vacuum action into the mold cavity (2) having the sprue part (12) exposed to the outside while depressurizing with a pump and hardening the sand (10) by a pressure difference from the atmospheric pressure, the above (A ) To (J).

Then, the thickness of the sand (10) layer is changed so that the poured molten metal is directionally solidified in the direction of the feeder.

[0008]

The thickness of the sand (10) layer filled between the mold (7) and the plastic film (9) is as thin as 0 to 100 mm, so that the reduced pressure reaches the end of the sand layer and the mold becomes strong, which makes Precise casting with little deformation is possible. In addition, sand (1
0) By changing the thickness of the layer in the range of 0 to 100 mm and changing the thermal conductivity coefficient of the mold, the injected metal melt is directionally solidified in the direction of the riser, and a casting having a thin portion with a thickness of 5 mm or less. Can be manufactured soundly. Sand (10)
In the part where the layer thickness is 0 mm, the molten metal is in direct contact with the mold, so the solidification progresses quickly and the sand (10) layer thickness is 100 m.
m to slow the progress of coagulation relatively. If the thickness of the sand (10) layer exceeds 100 mm, the vacuum suction force decreases and the mold strength decreases, so the thickness is set to 100 mm or less. When the metal foil (8) is continuously cast, the mold (7) becomes hot,
It prevents the plastic film (9) coming into contact with the high temperature part of the mold (7) from melting during molding.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view of a parting portion of a mold for casting a thin-walled cast steel cast part having a wall thickness of 2.5 mm in a cast product part 3 using the method for casting a thin cast product of the present invention. Figure 2
FIG. 6 is a diagram showing suction of the metal foil 8 to the model 5. Figure 3
FIG. 6 is a diagram showing suction of the plastic film 9 to the model 5. FIG. 4 is a plan view showing a state in which the mold 5 with the decompression box 1 is installed, the sand 10 is vibration-filled, and then the model 5 is separated. As shown in FIGS. 1 to 4, a thin-walled cylindrical casting part is cast. The mold 7 was FC25 flake graphite cast iron. First, the vent hole 13 is driven into a wooden model for a thin-walled cylindrical casting part as shown in FIG. 1, and is installed on a suction box (not shown) in which the vacuum suction pipe 11 is installed. Metal foil 8 on all or part of the model 5 that contacts the mold 7
To adhere. By covering the heated plastic film 9, the plastic film 9 is deformed into a shape along the model 5. And mold 7 with decompression box 1
Is placed in a predetermined place, and sand 10 is filled between the plastic film 9 and the mold 7 while vibrating. Sand 10
Use sand sand 7. The lower opening of the decompression box 1 is connected to a decompression device, and decompression suction is performed by a vacuum pump (not shown). By injecting the molten metal, the plastic film 9, the casting product part 3 and the casting plan part 4 replace metal. Table 1 shows the chemical composition of the cast steel.

[0010]

[Table 1] Chemical composition (% by weight) C Si Mn P S Cr Fe 0.10 1.8 0.6 0.01 0.01 17.5 Balance

When the thin-walled cylindrical cast parts made of cast steel having the chemical composition shown in Table 1 are cast by the above method, non-rotating defects, leak defects,
It is possible to manufacture sound castings that have no air entrapment and blow holes, and have no shrinkage cavity defects due to the cooling effect of the mold. By using the metal foil in the portion that contacts the high temperature portion of the mold, casting can be performed 10 times in succession. By using No. 7 silica sand that does not contain a binder, a product having a surface roughness (Rmax display) of 70 μm or less and a good casting surface can be obtained.

[0012]

As described above, according to the casting method of the thin cast product of the present invention, since the molten metal is injected at a high speed due to the reduced pressure of the mold, there are few non-rotating defects, and the sand layer is thin so that the cooling rate is high. It is easy to control and there are few shrinkage cavity defects by directional solidification. Further, by using the metal foil and the plastic film together, even if the temperature of the mold is high, it is possible to prevent the plastic film in contact with the mold from being melted and continuously perform casting. Further, by using fine sand containing no binder, it is possible to manufacture a casting having a good casting surface.

[Brief description of drawings]

FIG. 1 is a plan view of a parting part of a mold for casting a thin-walled cylindrical casting part by using the method for casting a thin-walled casting according to an embodiment of the present invention.

FIG. 2 is a diagram showing suction of a metal foil to a model according to an embodiment of the present invention.

FIG. 3 is a view showing suction of a plastic film according to an embodiment of the present invention to a model.

FIG. 4 is a plan view showing a state in which the model according to the embodiment of the present invention is also separated.

[Explanation of symbols]

1: vacuum box, 2: mold cavity,
3: casting product department, 4: casting plan department, 5: model,
6: Vent hole, 7: Mold,
8: Metal foil, 9: Plastic film, 1
0: Sand, 11: Vacuum suction tube, 1
2: Gate, 13: Vent hole.

Claims (2)

[Claims] 1. A casting method for injecting molten metal into a mold cavity (2) by a vacuum action in a depressurization box (1), comprising: (A) a casting product part (3) and a casting plan part (4) transfer part. A mold (7) having a vent hole (6) communicating with the outside and having a diameter of 0 to 100 mm larger than the outer shape of the transfer portion of the casting product part (3) and the casting plan part (4) comes into contact with the model (5) having the (B) at least a part of the metal foil (8) adhered to the model (5) and the metal foil (8) on the model (5)
A step of adhering the plastic film (9) to the portion not covered with the resin, (C) a step of setting the mold (7) while adhering the metal foil (8) and the plastic film (9) to the model (5), (D) A step of filling sand (10) containing no binder between the metal foil (8) and the plastic film (9) and the mold (7), (E) Metal foil for the model (5) (8) A step of releasing the close contact between the plastic film (9) and (F) a step of applying a vacuum from the vent hole (6) of the mold (7), (G) a model (5) of the metal foil (8)
And the step of releasing from the plastic film (9),
(H) A step of arranging the core on the filled sand (10), the metal foil (8) and the plastic film (9), if necessary, (I). (J) A step of assembling another mold in the step (J) While depressurizing with a vacuum pump from the depressurizing suction pipe (11) of the depressurizing box (1) and hardening the sand (10) by the pressure difference from the atmospheric pressure, A method for casting a thin casting, comprising the step of injecting a molten metal into a mold cavity (2) having (12) exposed to the outside by a vacuum action, and the combination of (A) to (J) above. 2. A method for casting a thin cast product, characterized in that the thickness of the sand (10) layer is changed so that the poured molten metal is directionally solidified in the direction of the feeder.