JPH0647149B2 - Mold and vacuum casting method using the mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold using a fluid mold and a vacuum casting method using the mold.

[Conventional technology]

The mold is roughly classified into a mold and a sand mold according to its constituent materials. Each of these molds and sand molds has advantages and disadvantages, and they are used in their respective characteristics.

In the sand casting method, casting is easy to perform and degassing is performed well, so that casting defects are less likely to occur, but the cooling ability is low, so that the casting structure becomes rough.

Further, in the die casting, since the die is used as a casting mold, it has advantages that the casting is cooled at a high speed, a casting having excellent mechanical properties can be obtained, and high rigidity provides high dimensional accuracy.

However, on the other hand, it costs more time and money to make a mold than sand mold, and once the mold is made,
However, there are drawbacks such as inability to change the cooling location for controlling mold cooling and directional solidification.

On the other hand, there is known a backside mold that reduces the cost and time required for manufacturing a mold, and also has good degassing, which is an advantage of a sand mold (Japanese Patent Laid-Open No. 60-1661).
55). Since this back mold is equipped with a sand mold that communicates with the atmosphere on the inner surface of the mold, it is not necessary to finish the inner surface of the mold with high precision, and the high rigidity of the mold improves dimensional accuracy and The casting defects are reduced by utilizing the breathability of the.

[Problems to be solved by the invention]

Although the above mold has the above-mentioned advantages in the mold using the back mold, the mold production still requires a considerable amount of time and cost, and the directional solidification has not been taken into consideration.

Therefore, an object of the present invention is to combine the advantages of a sand mold and a mold, reduce the time and cost required for manufacturing a mold, and to prevent the occurrence of shrinkage cavities by enabling directional solidification, and such. It is to make the mold applicable to the vacuum casting method.

[Means for solving problems]

Therefore, the present invention is characterized in that a fluid mold made of metal powder having fluidity is used as a back die, and a cooling pipe for directional solidification is provided in advance in the fluid mold.

Specifically, the mold as the first invention is held by an outer frame, has a cavity inside, and is molded from a metal powder having fluidity, and a mold having a predetermined thickness along the cavity surface. A mold comprising a sand mold that is held and molded to form a product cavity therein, wherein the fluid mold is provided with a cooling pipe.

Further, the vacuum casting method as the second invention is such that a fluid metal mold which is held by an outer frame, has a cavity inside, and is molded from a fluid metal and has a predetermined thickness along the cavity surface. It is a reduced pressure casting method using a mold that is molded and has a sand mold that forms a product cavity therein, and a cooling pipe is provided in the fluid mold, and the mold is placed on a bottom plate. , A step of reducing the pressure so as to have a predetermined negative pressure in the product cavity of the mold by covering the periphery of the mold, a step of pouring molten metal into the mold, a cooling medium to the cooling pipe of the mold after pouring is completed. It is characterized in that the steps of cooling the feed mold and the like are sequentially performed.

In the present invention, in addition to cooling the fluid mold, the cooling pipe is preliminarily arranged near the portion where cooling of the mold and the molten metal is desired due to directional solidification, and is integrated with the fluid mold. Molded. At that time, if a chill is provided in place of the sand mold in the cooled portion of the molten metal, cooling by the cooling pipe is promoted and directional solidification is more reliably performed.

[Action]

According to the mold of the present invention, since the cooling pipe is arranged in the fluid mold, the low cooling ability of the conventional sand mold can be improved. In addition, the cooling pipes can be arranged in the fluid mold at desired locations as desired, and the advantages of the sand mold, such as air permeability, are not lost.

Further, according to the second invention, it is possible to apply to the mold vacuum casting of the present invention, and a product with less casting defects can be obtained.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

Here, FIG. 1 is a sectional view of a mold according to the present invention.

In FIG. 1, 1 is a mold, which comprises an upper mold 2 and a lower mold 3. The upper mold 2 comprises a box-shaped metal outer frame 4 and a fluid metal 5 filled and molded in the outer frame. Similarly, the lower mold 3 comprises a box-shaped metallic outer frame 6 and a fluid mold 7 filled and molded in the outer frame.

In this upper mold 2, a sand mold 9 and a sprue 10 are formed along the cavity surface 8 of the fluid mold 5 by the cold box method, and the inner surface of the sand mold 9 defines the upper side of the product cavity 11. A cooling pipe 12 is disposed inside the fluid mold 5, and a cooling water circulation port 13 is provided from the outer frame 4.
Is protruding.

When arranging the cooling pipe 12, the cooling pipe 12
While the circulation port 13 side of the is attached to the outer frame 4 and the opposite side is suspended by a wire, the sprue 10 and the cavity 11
A model in which the thickness of the sand mold 9 is observed is placed in the above, and a commercially available slurry containing metal powder, ceramic fibers and a binder as a main component is poured from above, dried and fired to obtain a fluid mold.

The sand mold 9 is formed for each casting of each product. Specifically, a model is placed in the product cavity 11, and silica sand coated with a phenol resin and polyisocyanate is used for the cavity surface 8 of the model and the fluid mold in a depressurized state utilizing the air permeability of the fluid mold 5. After being blown into the gap, an amine gas is circulated and cured to form a sand mold 9.

In the lower mold 3, along the cavity surface 30 of the fluid mold 7,
A sand mold 15 having a chill 14 is formed in the same manner as the upper mold 2, and the inner surfaces thereof define the lower side of the product cavity 11. A cooling pipe 16 is arranged inside the fluid mold 7 in the same manner as the upper mold 2, a circulation port 17 is attached, and the lower mold 3 and the cooling mold 14 are cooled by cooling water. It is supposed to do.

Next, a gravity casting method using the mold of this embodiment will be described.

With respect to the lower mold 3 and the upper mold 2 formed as described above, a cylinder (not shown) is operated to lower the upper mold 2, and the lower mold 3 is brought into contact with the upper mold 2 for clamping. As a result, the state shown in FIG. 1 is reached, and the product cavity 11 is defined by the sand molds 9 and 15.

In this state, after pouring molten metal (SCS-13, austenitic stainless cast steel) from a ladle (not shown) into the sprue 10 from above, the cooling water was immediately circulated through the circulation ports 13 and 17 to make the fluid mold 5 , 7 and chill 14
Was cooled.

As a result, the cast steel obtained was sound without cast defects such as shrinkage cavities and blow holes. This is because, in addition to the good gas-releasing and hot-water-flowing properties of a fluid mold with a sand mold formed on the cavity surface, cooling hardening by a cooling pipe and a chill was sufficient and directional solidification was achieved. Be understood.

By the way, the center of the product cavity 11 (A in FIG. 1)
Time the temperature of the point) is 500 ° C. or less, the conventional CO ₂
It is about one-third shorter than the sand mold, and it has been confirmed that the cooling effect is great.

Next, an embodiment according to the second invention will be described.

Here, FIG. 2 is a cross-sectional view showing a vacuum casting method using the mold of the present invention.

Since the mold 1 is the same as that of the previous embodiment, the same number is assigned. In Fig. 2, the upper mold 2 and the lower mold 3 are clamped,
The state where the pressure inside the cavity 11 is reduced and pouring is performed is shown.

In this state, the mold 1 is placed on the metal bottom plate 19 via the spacer 18. On the upper surface of the mold 1, a weight 20 also serving as a spill receiver is placed, and the upper mold 2 and the lower mold 3 are placed.
The mold is clamped, and an opening 21 having a diameter substantially the same as that of the sprue 10 is provided at a position facing the sprue 10. Further, the box-shaped chamber 22 made of a metal plate covering the mold 1 is attached to the bottom plate 19.
It is placed on the top and sealed with a gum tape 23 between the bottom plate 19 and the bottom plate 19 to keep a reduced pressure.

A spout pool 24 is provided in the chamber 22 above the spout 10. In the sprue pool 24, a funnel-shaped spout pool outer skin 25 made of an iron plate is attached to the chamber 22, and an inner lining 26 made of a refractory having almost no air permeability is formed inside the outer skin. Lining 2
A molten metal stopper lid 27 made of an iron plate having a plate thickness of about 0.8 mm is placed on the lower step portion of 6 to keep the gate 24 for a predetermined time.
It holds the molten metal 25 that has been poured into.

A duct 28 is connected below the side surface of the chamber 22, and the other end of the duct 28 is connected to a vacuum pump (not shown).

Next, a vacuum casting method using the mold of this example will be described.

The upper mold 2 and the lower mold 3 are formed as in the previous embodiment, and the mold 1 matched on the bottom plate 19 is clamped by placing the weight 20 on the upper surface of the upper mold 2. Mold closed mold 1
Is covered with a chamber 22 hung by a crane, and gum tape is attached between the bottom plate 19 and the chamber 22,
Sealing is done.

In this state, the vacuum pump is started to reduce the pressure in the chamber 22 via the duct 28. When the degree of pressure reduction of about 300 mmHg was secured, the same molten metal as in the first embodiment was poured from the ladle 29 into the sprue pool 24. When the melt stop lid 27 is melted 10 seconds after pouring, the melt 25 in the spout sump 24 is poured into the spout 10 in the chamber 22 in a depressurized state, and flows into the product cavity 11. At this time, since the sprue pool 24 was filled with the molten metal 25 and had a sealing action, the air leaked into the chamber 22 did not occur.

Immediately after pouring into the sprue 10 is completed, the chamber 2
2, the cooling water supply pipe was connected to the circulation ports 13 and 17, and the cooling water was sent to the cooling pipes 12 and 16 to cool the fluid molds 5 and 7 and the cooling metal 14.

The cast steel product made in this way was cut and inspected, and as a result, there were no hollows, a sound casting was obtained, and there was no gas defect, and air was trapped in the chamber. It was confirmed that not.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and includes various embodiments within the scope of the claims.

For example, in the vacuum casting method of the present embodiment, the chamber was removed from the mold after pouring, and then water was supplied to the cooling pipe, but the chamber itself had a connection for connecting with an internal circulation port and an external supply port. A joint may be provided so that cooling can be performed without removing the chamber.

〔The invention's effect〕

As described above, according to the mold of the present invention and the vacuum casting method using the mold, the following effects can be obtained.

(A) Since solidification of molten metal is easily controlled, directional solidification can be achieved, and a sound casting free of casting defects such as shrinkage cavities can be obtained.

(B) Directional solidification can be easily achieved, so that the amount of molten metal can be reduced and the yield is improved.

(C) Since a fluid mold is used, the cost and time required to manufacture the mold can be reduced as compared with the mold.

(D) By using a fluid mold and further arranging a cooling pipe, the solidification time of the molten metal can be shortened compared to the case where a conventional sand mold is used, and productivity is improved by shortening the cycle time. To do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold according to the first embodiment of the present invention, and FIG. 2 is related to a second embodiment of the present invention, in which a vacuum casting method using the mold of the first embodiment is sealed. FIG. 1 ... Mold 2 ... Upper mold 3 ... Lower mold 4, 6 ... Outer frame 5, 7 ... Fluid mold 8, 30 ... Cavity surface 9, 15 ... Sand mold 11 ... Product cavity 12, 16 ...... Cooling pipe

Claims (3)

[Claims] 1. A fluid mold which is held by an outer frame, has a cavity inside, and is molded from metal powder having fluidity, and is molded with a predetermined thickness along the cavity surface, and has a product cavity inside. A mold comprising a sand mold for forming a mold, wherein the fluid mold is provided with a cooling pipe. 2. The mold according to claim 1, wherein a chill is provided in a part of the sand mold so as to face the product cavity. 3. A fluid mold which is held by an outer frame, has a cavity inside, and is molded from metal powder having fluidity, and a mold having a predetermined thickness along the cavity surface, and a product cavity inside. Comprising a sand mold for forming a mold, which is a reduced pressure casting method using a mold in which a cooling pipe is provided in the fluid mold, a step of placing the mold on a bottom plate,
A step of covering the periphery of the mold to reduce the pressure so that the inside of the product cavity of the mold has a predetermined negative pressure, a step of pouring the molten metal into the mold, and a cooling medium is sent to the cooling pipe of the mold after the pouring is completed. A reduced pressure casting method, which comprises sequentially performing a step of cooling a mold or the like.