JP3339675B2 - Mold making method and casting method - Google Patents

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 precision casting mold and a casting method suitable for producing a precision cast product having high shape accuracy at a low cost in a short time.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional casting method suitable for producing a precision casting having high shape accuracy.

[0003] The casting method shown in FIG. 3 is a so-called investment casting method, and is shown in FIG.
31 of a cast product 40 to be manufactured as shown in FIG.
As shown in FIG. 3B, a molding space 32a having a shape corresponding to the shape of the casting 40 to be manufactured is obtained.
The injection molding die 32 for model molding having the following is manufactured. Using the injection molding die 32 for model molding, a vanishing model 33 made of a vanishing material such as wax or resin as shown in FIG. To manufacture.

[0004] Next, as shown in FIG. 3 (D), an auxiliary member 34 for forming a gate and an auxiliary member 35 for forming a runner are also attached to the vanishing model 33 as shown in FIG. 3 (D). Thereafter, as shown in FIG. 3 (E), the fugitive model 33 is immersed in a slurry 36 for molding a mold containing colloidal silica as a binder and zircon sand as refractory sand. As shown in FIG. 3 (F), fire-resistant sand (stucco material, casting sand) 37 such as chamotte is applied by sprinkling, and then natural drying is performed for 4 to 8 hours per layer as shown in FIG. 3 (G). 5 to 8 layers of refractory by repeating the steps of attaching the slurry, attaching the refractory sand (ceramic powder), and air drying shown in FIGS. 3 (E), (F), and (G) about 5 to 8 times. Coated laminate ( Mold thickness was assumed that for example, 5 to 8 mm) was formed. In order to manufacture such a refractory-coated laminate having 5 to 8 layers, a molding period of about 3 to 4 days was required.

[0005] Next, as shown in FIG.
Demodeling is performed by removing heat-dissipating materials such as wax and resin inside by applying a heat shock heating at a temperature exceeding 0 ° C. (for example, 1000 ° C. for 30 minutes), and has a casting cavity inside. A template 38 as shown in FIG.

When a casting is manufactured using such a mold 38, a molten metal 39 is poured into the gate of the mold 38 and cast as shown in FIG. After solidification, finishing is performed as shown in FIG. 3 (J), and unnecessary parts such as gates and runners are removed to obtain a casting 40 as shown in FIG. 3 (K). Was.

[0007]

However, in the above-described conventional method of manufacturing and casting a mold, drying is performed in a short time in the drying step shown in FIG. When hot air or the like is used for the purpose, the refractory-coated laminate may be damaged due to thermal expansion or the like of the vanishing model 33. Therefore, there is a problem that the production of the mold requires a considerably long time.

At the time of de-modeling, at a relatively low temperature of about 500 ° C., the portion of the refractory coated laminate may be damaged due to expansion of the vanishing model 33. There was a problem that it was necessary to apply a heat shock.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to make it possible to manufacture a precision casting mold having high dimensional accuracy in a considerably shorter time than before. The purpose is.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing a mold having a shape corresponding to a shape of a casting to be manufactured, and comprising a binder-coated refractory sand. After producing a porous model laminated and formed by repeating layered uniform spraying and local heating, the porous model is immersed in a slurry of a mold material, and the slurry is adhered to a surface layer of the model to form a mold material layer portion. Is formed, and the inside of the model is collapsed and removed by heating, and the mold material layer is fired to form a mold having a casting cavity formed therein.

In the method of manufacturing a mold according to the present invention, as described in claim 2, the inorganic fibers are added to the slurry, and the inorganic fibers are added to the model surface layer after being immersed in the slurry. It can be made to adhere.

Similarly, in the method of manufacturing a mold according to the present invention, as described in claim 3, the porous model is a sand model in which refractory sand is bound by a binder,
The binder can be destroyed by heating to collapse and remove the inside of the model.

[0013]

Similarly, in the method of manufacturing a mold according to the present invention, the local heating can be performed by laser heating.

According to a fifth aspect of the present invention, there is provided a casting method using a mold according to any one of the first to fourth aspects, wherein molten metal is poured into a casting cavity and then solidified. The feature is that the mold is separated afterwards.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows one embodiment of a method for manufacturing a mold according to the present invention. First, in step (IA), the shape of a casting to be manufactured is determined. In the other hand, a slurry is prepared in step (IB) and a porous model is immersed (dipped) in the slurry of the mold material in step (II). Then, the slurry is adhered to the model surface layer to form a mold material layer. Then, in step (III), after drying, in step (IV), heating is performed to collapse and remove the inside of the model (demodeling). ) And baking the mold material layer to obtain a mold having a casting cavity formed therein in step (V).

In such a method of manufacturing a mold, a sand model in which fire sand is bonded with a binder can be used as a porous model, and a binder-coated fire sand (for example, Particle size 0.1-0.2
Use a porous model laminated and formed on a table by repeating layered uniform spraying of resin-coated sand (resin-coated sand with a resin binder coated on the surface of refractory sand of about mm) and repeated local heating and sintering by laser heating or the like. Can be.

When the porous model is immersed in the slurry, a slurry obtained by adding inorganic fibers to the slurry can be used. For example, a slurry of a mold material having the composition shown in Table 1 is used. be able to.

[0019]

[Table 1]

Then, after the slurry-like inorganic particles, inorganic fibers, etc., which are the template material, are attached to the surface layer of the porous model, the interior of the model is collapsed and removed (demodeling) by heating, and the template material layer is removed. It is fired to obtain a mold having a casting cavity formed therein.

[0021]

According to the method for manufacturing a mold according to the present invention, as described in claim 1, a layered uniform spray of binder-coated fire-resistant sand having a shape corresponding to the shape of a casting to be manufactured. After producing a porous model laminated and formed by repeating local heating, the porous model is immersed in a slurry of a mold material to adhere the slurry to the model surface layer to form a mold material layer, The model was heated to disintegrate and remove the interior of the model (demodeling), and the mold material layer was fired to form a mold with a casting cavity formed inside. Molding becomes possible, the time required for mold production can be greatly reduced, and the thickness of the mold per layer can be increased, so the number of layers can be reduced, and the porous model has a low coefficient of thermal expansion. After being immersed in the slurry, drying with hot air is also possible, making it difficult for the mold to be damaged. Can be prevented,
By using a mold made of a completely inorganic material, it is possible to prevent the occurrence of gas defects in the cast product as if there is no gas generated during casting, and to mold a mold with excellent shape accuracy in a short time A remarkable effect that it can be manufactured at low cost is brought about.

And, as described in claim 2,
By adding inorganic fibers to the slurry and attaching the inorganic fibers to the surface layer of the model after immersion in the slurry, reinforcement by entanglement of the inorganic fibers becomes possible, and at the time of molding and demodeling In some cases, reinforcement is effective and damage is unlikely to occur, and it is possible to produce a high-precision casting mold with high strength at a low cost in a short time. Is brought.

Further, as described in claim 3,
The porous model is a sand model in which refractory sand is bound by a binder.The binder is burned off by heating to collapse and remove the inside of the model. Since the components easily adhere to the surface layer of the porous model, a remarkable effect that instantaneous molding using the capillary phenomenon of the porous model is possible is brought about.

Further, as described in the first aspect, the porous model is formed by laminating a layered uniform spray of the binder-coated refractory sand on an appropriate base and repeating local heating. By burning down the binder by heating to collapse and remove the inside of the model,
It is possible to produce a porous model in a very short time based on dimensional data, and a master model such as a wooden mold is not required for producing a porous model, so that the time for producing a mold is greatly reduced. A remarkable effect that it is possible to reduce the cost and to realize a reduction in cost is provided.

Furthermore, by making the local heating by laser heating, the porous model can be manufactured in a short time and with high shape accuracy. Is a great effect.

According to a fifth aspect of the present invention, there is provided a casting method comprising: pouring a molten metal into a casting cavity using the mold according to any one of the first to fourth aspects; Since the mold is separated afterwards, a remarkable effect that it is possible to produce a cast product with high shape accuracy at a low cost in a short time is brought about.

[0027]

FIG. 2 shows an embodiment of a method for producing and casting a mold according to the present invention. First, three-dimensional CAD data 1 as shown in FIG. 2A is prepared in a personal computer. Keep it.

Next, as shown in FIG. 2B, based on the three-dimensional CAD data 1, as shown in FIG. 2B, resin binder-coated fire-resistant sand (resin-coated sand:
Selective laser sintering method (SLS method) by repeating layered uniform spraying on a platform (table) of silica sand that is refractory sand and phenolic resin that is a binder) 2 and local heating by laser light 3 By performing lamination molding using the same, a porous model (sand model) 4 as shown in FIG. 2C was obtained.

Next, as shown in FIG. 2D, the porous model 4 is provided with a sprue forming auxiliary member 5 and a runner forming auxiliary member 6 which are also made of a sand model. Alternatively, the sprue forming part and the runner forming part may be simultaneously formed integrally with the main body by CAD data), and the assembled body of the porous model 4 is put into the slurry 7 as shown in FIG. Dipped.

The slurry 7 used here was water: 1000
Alumina silica short fiber: 100 parts by weight, alumina particles: 100 parts by weight, alumina sol: 10 parts by weight
Parts by weight, frit: 100 parts by weight, polyvinyl alcohol: 1 part by weight.

Then, three layers of the slurry 7 are adhered to the surface layer of the assembled body of the porous model 4 to form a mold material layer so that the mold thickness becomes 5 to 7 mm, and then FIG. As shown in the figure, about 3 hours (about 30
Min) dried. The required molding time so far was approximately 1.5 hours. Further, sprinkling of refractory sand (ceramic powder) as in the prior art was not performed.

Subsequently, after drying, the model is placed in an electric furnace and heated at about 500 ° C. for 15 minutes as shown in FIG. 2 (G) to burn off the binder and to collapse and remove the inside of the model (sand removal). The mold 8 made of a completely inorganic material as shown in FIG. 2 (H) was obtained by removing the model and firing the mold material layer to form a casting cavity therein.

When producing a cast product, the mold 8
2H, an aluminum alloy for casting (equivalent to JIS AC2A) was used as the molten metal 9 shown in FIG. 2H, and the molten metal 9 was poured into the gate of the mold 8 at a casting temperature of 720 ° C. Hot water.

Next, after the molten metal is solidified, the mold is separated, and the cast body shown in FIG. 2I is subjected to finish processing, whereby a cast product having a predetermined shape as shown in FIG. 10 was obtained.

In the mold 8 thus obtained, the shape precision was high and the shape holding strength was good.

Also, the casting shape of the casting 10 was faithfully transferred, and was excellent in shape accuracy.

Tables 2 and 3 show a comparison between the case where the castings 10 and 40 were manufactured by the casting method according to the embodiment of the present invention and the conventional investment casting method shown in FIG. It was.

[0038]

[Table 2]

[0039]

[Table 3]

As shown in Table 3, according to the method of the present invention, it was possible to considerably reduce the number of days for producing and casting the mold as compared with the conventional investment casting method.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing a mold according to the present invention.

FIG. 2 is an explanatory view showing an embodiment of a method for producing and casting a mold according to the present invention.

FIG. 3 is an explanatory view illustrating a method of manufacturing and casting a mold according to a conventional example.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koji Iwata 1-8-1 Shintoda, Hamamatsu-shi, Shizuoka Nichiasu Corporation Hamamatsu Research Laboratory (72) Inventor Takayuki Ohashi Kanagawa-ku, Kanagawa-ku, Kanagawa No. 2 Takaracho Nissan Motor Co., Ltd. (56) References JP-A-48-10026 (JP, A) JP-A-3-221238 (JP, A) JP-A-3-210934 (JP, A) JP-A Sho 59-39447 (JP, A) JP-A-57-175049 (JP, A) JP-A-53-125227 (JP, A) JP-A-3-60846 (JP, A) JP-A 2000-343180 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B22C 1/00-9/30

Claims (5)

(57) [Claims] 1. A porous model having a shape corresponding to the shape of a casting to be manufactured and having a laminated model formed by repeating layered uniform spraying of binder-coated refractory sand and local heating is produced. The quality model is immersed in the slurry of the mold material and the slurry is adhered to the surface layer of the model to form the mold material layer. A method for producing a mold, wherein the mold has a cavity. 2. The method according to claim 1, wherein inorganic fibers are added to the slurry, and the inorganic fibers are adhered to a surface portion of the model after being immersed in the slurry. 3. The method according to claim 1, wherein the porous model is a sand model in which refractory sand is bound by a binder, and the inside of the model is collapsed and removed by heating to burn off the binder. 4. The method according to claim 1, wherein the local heating is performed by laser heating. 5. A casting method comprising: pouring a molten metal into a casting cavity using the mold according to claim 1; and solidifying the molten metal.