JPH0747444A - Manufacture of casting mold for precise casting - Google Patents

Abstract

PURPOSE:To scarcely generate deformation of a casting mold caused at a high temperature, and to attain both the improvement of dimension accuracy of a precise casting and the prevention of damage of the casting mold, etc. CONSTITUTION:At the time manufacturing a casting mold for precise cadting, the casting mold is manufactured by using slurry obtained by mixing 150 parts to 300 parts zircon powder or mullite powder whose particle diameter of <=44mum as filler, and ceramics obtained by zircon particles or mullite particles singly or combining them, as a stack material, with respect to 100 parts mixed binder of alumina sol and silica mixed within a range of 30 parts to 60 parts alumina in alumina sol, and 70 parts to 40 parts silica sol whose hydrogen ion cencentration index is <=7 as a stucco material. This casting mold is fired at >=1200 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a precision casting mold.

[0002]

2. Description of the Related Art In a precision casting ceramic mold, a wax model is generally immersed in a slurry made of a binder and a ceramic powder (filler) to adhere the slurry (dipping), and then the ceramic particles are adhered to the slurry. (Sanding or stuccoing), and the above steps are repeated about 7 to 10 times to form a ceramic layer having a predetermined thickness. Then, the wax is eluted, heated and fired at a predetermined temperature (generally around 1000 ° C.), and molten steel is poured into a high temperature mold.

Generally, silica sol (colloidal silica or ethyl silicate) is used as the binder, zircon powder is used as the ceramic (filler) in the slurry, and zircon particles or mullite particles are used as the sanding ceramic.

[0004]

The thickness of the ceramic mold for precision casting manufactured by the above method is about 7 to 1.
0 mm or more, and the mold temperature during casting is 1000 ° C
Before and after the casting, the mold is further heated, and is heated to 1400 ° C. or higher in the vicinity of the contact surface with the casting and 1200 ° C. or higher even in the center of the thickness of the mold.

In a mold using silica sol as a binder, since silica as a binder is easily softened and deformed, the mold is deformed by the static pressure of molten steel, which causes a problem in dimensional accuracy.
In particular, the larger the precision-cast product, the greater the amount of deformation of the mold, and the mold is damaged rather than merely due to the problem of dimensional accuracy. The present invention is proposed in view of the above problems,
The purpose is to reduce the deformation of the mold at high temperature, to improve the dimensional accuracy of precision castings and prevent damage to the mold, etc. is there.

[0006]

In order to achieve the above object, a method for producing a precision casting mold according to the present invention is a silica sol having 30 to 60 parts of alumina in an alumina sol and a hydrogen ion concentration index of less than 7. 70 to 40 parts of silica
To 100 parts of a mixed binder of alumina sol and silica blended in the range of 100 parts by weight, a slurry obtained by blending 150 parts to 300 parts of zircon powder having a particle size of 44 μm or less as a filler, and zircon particles or mullite particles alone or It is characterized in that a mold was produced by using the ceramics obtained by the combination as a stucco material, and the mold was fired at 1200 ° C. or higher.

Further, according to the method for producing a precision casting mold of the present invention, 30 to 60 parts of alumina in the alumina sol and 7 parts of silica in the silica sol having a hydrogen ion concentration index of less than 7.
A slurry obtained by mixing 150 to 300 parts of mullite powder having a particle size of 44 μm or less as a filler with 100 parts of a mixed binder of alumina sol and silica mixed in the range of 0 to 40 parts, zircon particles or mullite. It is characterized in that a ceramic is obtained by using a ceramic obtained by combining particles alone or in combination as a stucco material, and the template is fired at 1200 ° C. or higher.

[0008]

The method for producing a precision casting mold of the present invention is configured as described above. During the production of the precision casting mold, 30 to 60 parts of alumina in the alumina sol and a hydrogen ion concentration index of less than 7 are used. The particle size as a filler is 44μ with respect to 100 parts of a mixed binder of alumina sol and silica mixed with silica in the silica sol in the range of 70 to 40 parts.
A slurry obtained by blending 150 to 300 parts of zircon powder or mullite powder having a particle size of m or less and a ceramic obtained by combining zircon particles or mullite particles alone or in combination was used as a stucco material to manufacture a mold.
Bake above ℃.

[0009]

【Example】

(First Embodiment) Next, a method for manufacturing a precision casting mold of the present invention will be described with reference to a first embodiment. About 10 wt% alumina
Containing about 20 wt% of alumina sol and silica having a hydrogen ion concentration index (PH) of 3.5, and having a hydrogen ion concentration index of 3, silica sol having alumina ion in the alumina sol and silica in the silica sol is shown in Table 1. A wax of 130 × 130 × 10 mm is immersed (dipping) in a slurry in which 200 parts of zircon (ZrO ₂ .SiO ₂ ) powder having a particle size of 44 μm or less as a filler is mixed with 100 parts of the binder thus mixed.

Next, zircon powder having a particle size of 150 μm or less is adhered (stuccoing), dried, and then dipping, stuccoing and drying are performed again, and then mullite particles having a particle size of 1 mm or less are used as a ceramic for stuccoing. Then, dipping and stuccoing are performed eight more times. Then, the mixture is heated to about 170 ° C., the wax is flown out, and the mold is placed in an electric furnace in an atmospheric atmosphere for 120
Hold for 1 hour at 0 ° C., then cool.

20 mm wide and 120 mm long from this mold
A test piece for measuring the amount of flexure (thickness is about 10 mm) was prepared, and this test piece was placed in an electric furnace in the air atmosphere at a fulcrum distance of 100 mm as shown in FIG.
After holding for a period of time, it was cooled and the deformation amount (deflection amount) at the position shown in FIG. 2 was measured. The amount of deflection of the test piece for each condition is shown in FIG. 1 in FIG. 1 is a test piece for measuring the amount of flexure of the mold, 2 is a surface for constructing the first layer of the mold, 3 is a surface for constructing the tenth layer of the mold, 4 is a fulcrum made of an alumina ceramic, and 5 in FIG. Is.

As a result, the amount of deflection becomes small when the amount of alumina and the amount of silica are within a certain range, and the amount of deflection increases even if there is too much alumina or too much silica. That is, when the amount of alumina is large, mullite and acmina are magnified by firing at 1200 ° C., but since the sintering temperature of alumina is high, the bonding force between particles is small and the deformation at high temperature becomes large. Further, when the amount of alumina is large, the viscosity of the slurry becomes high, the amount of zircon powder blended as a filler becomes small, and the density of the template after firing becomes small, so that the strength becomes small and the deformation becomes large.

On the other hand, when the amount of alumina is small, a large amount of excess silica is present after the mullite reaction, and the silica is likely to be deformed at high temperatures, resulting in large deformation. Although it is difficult to determine the proper mixing ratio of the alumina sol and the silica sol in a strict sense, from the viewpoint of the amount of deformation, 30 to 60 parts of alumina in the alumina sol and 70 to 40 parts of silica in the silica sol are used in the present invention. The mixing ratio of the alumina sol and the silica sol forming a part is in the preferable range.

There are various types of hydrogen ion concentration index in the silica sol, and the hydrogen ion concentration index of the used alhana sol is about 3 which is acidic. When this is mixed with an alkaline silica sol, the sol suddenly forms. Gel.
Therefore, in this example, an acidic silica sol having a hydrogen ion concentration index of 5 was used. In this embodiment, 200 parts of zircon (ZrO ₂ .SiO ₂ ) powder as a filler is mixed with 100 parts of a mixed binder of alumina sol and silica sol. The amount of filler mixed with the amount of binder is important in terms of the viscosity of the thriller, but the amount of zircon powder blended is not more than 150 parts or 30 parts with respect to 100 parts of binder.
If it is 0 parts or more, the viscosity of the slurry becomes too low or too high, and the dipping and stuccoing make it difficult to construct the mold well, and the mold tends to crack during drying. From such a viewpoint, in the present invention, the compounding amount of zircon as a filler is in the range of 150 to 300 parts with respect to 100 parts of the binder.

The mullite (3Al ₂ O ₃ .2SiO ₂ ) conversion rate due to the reaction between alumina and silica is determined by the heating temperature and the holding time at that temperature. Since the size of alumina in the alumina sol is several 10 to 100 μm and the size of silica in the silica sol is several 10 μm, mullite is formed at a relatively low temperature in a short time. The starting temperature of mullite formation was 170 ° C., and by heating (baking) at 1200 ° C. for 1 hour, most of them reacted and changed to mullite. Therefore, the firing temperature of the mold in the present invention is 1
It is necessary to be 200 ° C or higher.

[0016]

[Table 1] (Second Embodiment) As in the first embodiment, about 10 alumina is added.
A first embodiment in which alumina sol having a hydrogen ion concentration index of 35 and silica having a hydrogen ion concentration index of 3 is contained in the alumina sol and silica in the alumina sol and silica in the silica sol are shown in Table 1. The particle size is 44 with respect to 100 parts of the binder mixed in exactly the same proportion as the example.
μm following mullite _{(3Al 2 O 3 · 2SiO 2} ) 130 × 130 × 10mm powder slurry was blended 200 parts of
Dip the wax in (dipping).

Next, zircon powder having a particle size of 150 μm or less is adhered (stuccoing), dried, and then dipping, stuccoing and drying are performed again, and then mullite particles having a particle size of 1 mm or less are used as a ceramic for stuccoing. Then, dipping and stuccoing are performed eight more times. Then, as in the first embodiment, about 1
The wax is flown out by heating to 70 ° C., and the mold is kept at 1200 ° C. for 1 hour in an electric furnace in the air atmosphere, and then cooled.

A test piece exactly the same as that of the first embodiment was prepared and a flexure test was conducted under the same conditions. The result is shown in FIG. Similar to the case where zircon is used as the filler in the slurry, there is a region where the amount of deflection becomes small when the amount of alumina and the amount of silica are within a certain range. The absolute value of the amount of deflection is slightly different from that of zircon filler, but the tendency is almost the same.

Accordingly, in the present invention, even when mullite is used as the filler, the mixing ratio of the alkanasol and the silica sol is 30 to 60 parts of alumina in the alumina sol and 70 to 40 parts of silica in the silica sol. It is in the preferred range. As with the zircon filler, the amount of mullite filler mixed with the binder is appropriate from the viewpoint of the viscosity of the slurry in the range of 150 parts to 300 parts per 100 parts of the mixed binder of alumina sol and silica sol. is there.

[0020]

As described above, according to the method for producing a precision casting mold of the present invention, when the precision casting mold is produced, 30 to 60 parts of alumina in the alumina sol and silica sol having a hydrogen ion concentration index of less than 7 are contained. A slurry obtained by mixing 150 to 300 parts of zircon powder or mullite powder having a particle diameter of 44 μm or less as a filler with respect to 100 parts of a mixed binder of alumina sol and silica mixed in the range of 70 to 40 parts with silica. , A ceramic obtained by using single or a combination of zircon particles or mullite particles as a stucco material is used to manufacture a mold, and this mold is fired at 1200 ° C. or higher. It is possible to improve the dimensional accuracy of the product and prevent damage to the mold.

[Brief description of drawings]

FIG. 1 is a side view showing a procedure for a deflection amount test of a test piece for measuring deflection of a mold obtained by a first embodiment of a method for manufacturing a precision casting mold according to the present invention.

FIG. 2 is a side view showing a deflection amount measurement position of the test piece.

FIG. 3 is an explanatory diagram showing a result of a deflection amount test for each condition of the test piece.

FIG. 4 is an explanatory diagram showing a result of a flexure amount test for each condition of the test piece of the mold obtained in the second example.

Claims (2)

[Claims] 1. A mixed binder of 100 parts by weight of alumina sol and silica compounded with 30 to 60 parts of alumina in the alumina sol and 70 to 40 parts of silica in the silica sol having a hydrogen ion concentration index of less than 7. As a filler, a slurry obtained by mixing 150 to 300 parts of zircon powder having a particle size of 44 μm or less, and a ceramic obtained by combining zircon particles or mullite particles alone or in combination are manufactured as a stucco material, and a mold is manufactured. 1200 ° C
A method for producing a precision casting mold, characterized by being fired as described above. 2. A mixed binder of 100 parts of alumina sol and silica in which alumina in the alumina sol is 30 to 60 parts and silica in the silica sol having a hydrogen ion concentration index of less than 7 is mixed in the range of 70 to 40 parts. As a filler, a slurry obtained by mixing 150 to 300 parts of mullite powder having a particle size of 44 μm or less and a ceramic obtained by combining zircon particles or mullite particles alone or in combination is used as a stucco material to manufacture a mold, and this mold is used. 1200 ° C
A method for producing a precision casting mold, characterized by being fired as described above.