JPH0539737U - Graphite mold for vacuum casting - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a cast body having excellent transferability and smoothness of casting surface. [Composition] In a reduced pressure casting facility that is equipped with a gas suction means and sucks molten metal in a cavity and a gas between the graphite mold walls through a porous graphite mold wall to cast molten metal, the gas in the cavity is prioritized on the mold wall. A graphite mold for vacuum casting, which is provided with a defective ventilation portion for mechanically sucking.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a graphite mold for vacuum casting, and an object of the present invention is to provide a graphite mold suitable for obtaining a cast body having excellent transferability and smoothness of casting surface.

A vacuum forming method is used in which a container such as a plastic container is formed from a plastic sheet. The mold used in this vacuum forming method has a smooth surface with no surface defects on the vacuum forming surface. Is essential.

However, what has been conventionally generally used as a mold for obtaining this vacuum-formed product is typically manufactured by the following steps. (1) A rough mold material is made by the gravity sand casting method. (2) Machine the outer shape so that it can be set on the vacuum forming machine. (3) Polish the vacuum forming surface to make it smooth.

In the sand mold casting method as described above, the sand mold itself is cheap in terms of material and suitable for a small amount of a wide variety of products, but the surface condition of the rough material obtained in the step (1) is Therefore, since there is a disadvantage that the number of steps in the step (3) increases, for example, in JP-A-60-191631, by using a graphite mold having air permeability, a casting having few surface defects (casting defects) can be obtained. It is also stated that the reduced pressure casting improves the casting surface and sharpens the appearance of the casting.

[0005]

[Problems to be solved by the device]

 However, when pressure-reduced casting is performed using the conventional graphite mold as described above, atmospheric air flows not only from the entire mold wall, not only the inner surface of the cavity, but also the outer peripheral wall, and the gas between the molten metal in the cavity and the mold surface is discharged. There is a disadvantage in that the appearance of the obtained cast product is not molded well because suction is not sufficiently obtained.

In order to avoid the above disadvantages, it is possible to increase the suction force, but the equipment is inevitably large in size, sophisticated, and expensive, which is an effective disadvantage and is a preferable solution. I can't do it.

[0007]

[Means for Solving the Problems]

 The present invention has made extensive studies to solve the above-mentioned problems in the prior art, eliminates the above-mentioned disadvantages by the simple processing in the graphite mold as described above, and achieves a good surface property by efficient casting. It is designed so that a cast body can be obtained appropriately, and is as follows.

(1) In a reduced pressure casting facility for casting molten metal by sucking a molten metal in a cavity and a gas between the graphite mold walls through a porous graphite mold wall, the cavity is formed in the casting mold wall. A graphite mold for vacuum casting, which is provided with a poor ventilation portion for preferentially sucking internal gas.

(2) The graphite mold for vacuum casting according to item (1), characterized in that a fine graphite powder suspended in a liquid is applied to the mold wall.

[0010]

[Action]

 In a vacuum casting facility that is equipped with gas suction means and sucks molten metal in the cavity and gas between the mold walls through a porous graphite mold wall to cast molten metal, preferentially apply the gas in the cavity to the mold wall. By providing the poorly ventilated portion for sucking, the air permeability of the portion at the time of reduced pressure casting is prevented or lowered, and the gas suction on the inner surface of the cavity can be appropriately obtained.

It is not necessary to apply the poor ventilation to the entire surface of the mold wall, and it is sufficient to select a site that allows gas suction on the cavity mold surface during reduced pressure casting, and it is possible to form the defective ventilation part. A method in which fine graphite powder or the like is suspended in a liquid such as water, alcohol, or an inorganic binder and applied by a brush or spray, or a heat-resistant member having no air permeability is attached and formed is sufficient.

[0012]

【Example】

 A concrete embodiment of the present invention as described above will be described with reference to the accompanying drawings. An outline of the casting equipment using the mold according to the present invention is as shown in FIG. The graphite lower mold 2 and the upper mold 1 are polymerized and set, and a cavity 8 is formed between the two molds 1 and 2, and the upper mold 1 is provided with a sprue 9 and a frying part 10. ..

Further, a pressure reducing port 12 is formed in the center of the lower mold 2, and a pipe line 4 is connected to the pressure reducing port 12 through a through hole 15 in the base plate 3, and the pipe line 4 is an opening / closing valve 5. Further, a decompression tank 6, a decompression pump 7 and a decompression gauge 17 are provided so as to exert a decompression action on the upper mold 1 and the lower mold 2 as described above.

According to the present invention, the shape of the mold can be arbitrarily determined based on the shape and size of the target cast body, the arrangement relationship of the decompression tank, the on-off valve, and the like. That is, not only the rectangular shape shown in FIG. 1 but also the square shape shown in FIG. 2 or the planar circular shape shown in FIG. 3 can be implemented. In either case, the internal structure is the same as that shown in FIG.

In the case of the one shown in FIG. 1 described above, the lower die 2 is provided with the design surface 14 having irregularities, and the space between the base plate 3 and the lower die 2 and between the lower die 2 and the upper die 1 is also reduced. A sealing material 13 such as an O-ring is interposed between them, and the air-poor layer 11 is bonded and formed on the side surfaces of the upper mold 1 and the lower mold 2.

A specific example carried out by the present inventors will be described. The upper mold 1 and the lower mold 2 are made of a graphite material as shown in Table 1 below, that is, the upper mold 1 is a GMC manufactured by Nippon Electrode Co., Ltd. -30, the lower mold 2 was also made of GMC-100 manufactured by Nippon Electrode Co., Ltd., and the lower mold 2 was made of a material having lower air permeability than the upper mold 1.

[0017]

[Table 1]

Further, the air-impermeable layer 11 is formed by applying fine powder of phosphorous graphite and an inorganic binder of 50% aqueous solution of aluminum phosphate suspended in an inorganic binder by brush coating and repeating drying 3 times to form a layered layer. did.

The alloy prepared for obtaining the rough shape material of the aluminum mold for vacuum forming by the graphite molds 1 and 2 constituted by the upper and lower molds as described above is AC4C, and the casting temperature is 720 ° C. A mold temperature of 420 ° C. was applied to 3.5 kg under a suction pressure of 550 mmHg.

In the concrete operation of casting, the negative pressure condition was controlled in advance so as to be 550 mmHg as described above, and the pouring was performed from the sprue 9 to see when the molten metal reached the frying part 10. The on-off valve 5 for decompression is opened and the negative pressure condition is applied to the cavity of the lower mold 2 from the decompression tank 6. That is, due to the presence of the air-impermeable layer 11, the negative pressure acting area is prevented from being released to the entire side surface of the lower mold 2 and the upper mold 1, and the negative pressure working area is caused to act between the molten metal and the cavity surface of the lower mold 2, so that the space between The gas generated in the can be removed by suction.

Therefore, the adhesion due to the negative pressure on the cavity surface between the molten metal and the lower mold 2 is effectively secured, and the reduction of the negative pressure can be appropriately suppressed by the relatively small pressure reducing means, and the molding can be performed. Suction depressurization is performed until just before the product is solidified (about 50 seconds after pouring in the above-mentioned conditions), the on-off valve 5 is closed to stop the depressurizing action, and the state is maintained for about 100 seconds after pouring. The product casting was taken out through.

The obtained product was machined and hand-finished to be used as a mold for a vacuum forming machine. The obtained cast product itself was excellent in sharp transferability of a garment especially in the design section. From the above, it was confirmed that the man-hours and time required for finishing the cavity were reduced to about one-third as compared with the conventional rough shape material, and therefore the processing cost could be reduced by about 25%. The results of measuring the casting surface roughness are shown in Table 2 below. The conventional example is a case where the graphite mold in the example is not provided with a poor air-permeable layer.

[0023]

[Table 2]

It is clear that defects such as minute molten metal boundaries, blowholes, scratches, and sweating on the surface of the casting will be improved, and a sound casting can be obtained efficiently. The formation of the layer 11 can be easily adopted, and if a ventilation cutoff is required during casting, a quick response can be made on site, and the degree of freedom of operation of the casting operator can be sufficiently enhanced.

Although the above has described the case where depressurization and suction are performed only from the lower mold, suction means can also be provided in the upper mold. In such a case, on the upper mold surface of the product cast body. It is clear that a product having good transferability can be obtained.

[0026]

[Effect of the device]

 According to the present invention as described above, it is possible to efficiently obtain a cast body having good surface properties, excellent transferability and smoothness of the casting surface by using the reduced pressure casting mold, and it is also possible to easily deal with it in the field. It is a device that has a great effect industrially.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one embodiment according to the present invention.

FIG. 2 is a perspective view of another embodiment of the present invention.

FIG. 3 is a perspective view of still another embodiment of the present invention.

[Explanation of symbols] 1 Upper mold 2 Lower mold 3 Base plate 4 Pipe line 5 Open / close valve 6 Pressure reducing tank 7 Pressure reducing pump 8 Cavity 9 Gate 10 Lifting part 11 Poor ventilation layer 12 Pressure reducing port 13 Sealing material such as O-ring 14 Design surface 15 through hole 17 decompressor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Kawai 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nichiritsu Giken Co., Ltd. (72) Shoichi Kobayashi 1-chome, Kambara-cho, Anbara-gun, Shizuoka 34-1 No. 1 Nipparu Giken Co., Ltd. (72) Inventor Tsutomu Wakasa 5600 Kambara, Kambara-cho, Anbara-gun, Shizuoka Nihon Denki Co., Ltd. Kambara factory (72) Inventor Shinzo Aoki 1805 Ushibuchi, Kikugawa-cho, Ogasa-gun, Shizuoka Address No. 1 in EEIKOSAN Co., Ltd. (72) Inventor Masatoshi Nanba 3-13-12 Mita, Minato-ku, Tokyo Inside Nippon Light Metal Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. A pressure reducing casting facility for suctioning a molten metal in a cavity and a gas between the graphite mold walls through a porous graphite mold wall to cast a molten metal, the gas in the cavity being provided in the mold wall. A graphite mold for reduced pressure casting, which is provided with a poor ventilation portion for preferentially sucking. 2. The graphite mold for vacuum casting according to claim 1, wherein fine graphite powder suspended in a liquid is applied to the mold wall.