JPH06305827A - Production of glass ceramic having machinability - Google Patents

Abstract

PURPOSE:To obtain the subject ceramic resistant to cracking, chipping, etc., and having excellent heat-resistance, electrical insulation, mechanical strength, etc., by forming a plate composed of two kinds of crystalline glass powders having respective specific compositions at a specific ratio and burning the formed plate by a specific method at a specific temperature. CONSTITUTION:A plate 1 is formed by the compression forming of a mixture of (A) 25-95wt.% of crystalline glass powder composed of 11.0-11.5wt.% of K2O, 23.5-24.8wt.% of MgO, 55.0-56.8wt.% of SiO2, 8.4-12.6wt.% of F2 and 0.86-0.99wt.% of ZrO2 and (B) 5-75wt.% of crystalline glass powder composed of 5.0-6.0wt.% of K2O, 9.5-11.0wt.% of MgO, 46.0-48.0wt.% of SiO2, 21.0-23.0wt.% of CaO, 0.2-0.5wt.% of CaF2, 5.0-6.5wt.% of MgF2 and 8.0-8.5wt.% of P305. The formed plate 1 is surrounded by granular or flaky fluorine-containing mineral 3, placed on a supporting refractory 5 placed in a refractory container 2 in a state inclined to the furnace floor surface by 15-65 deg. and heated at 1050-1100 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electric insulation, heat resistance,
The present invention relates to a process for producing glass ceramics, which has excellent mechanical strength and has machinability that allows machined parts that require precise dimensional accuracy to be easily obtained by machining. More specifically, heat-resistant insulating parts (substrates, heat treatment jig materials), structural support members (heat-resistant bobbins, etc.) for electrical and electronic equipment, precision equipment, etc.
The present invention relates to a method for producing glass ceramics having machinability that can be usefully used as a sensor support part).

[0002]

2. Description of the Related Art Examples of machinable ceramics include those composed of mica powder and ZnO-SiO ₂ -B ₂ O ₃ -based ceramics disclosed in JP-A-63-50365, and the Glass Handbook. (Mitsuo Sakuhana, Teruo Sakaino, Katsuaki Takahashi, Asakura Shoten Co., Ltd., published in 1982) It is known that mica crystals are precipitated in glass as shown on pages 215 to 216.

The method for producing ceramics disclosed in Japanese Patent Laid-Open No. 63-50365 is based on mica powder and ZnO-SiO ₂ -B ₂ O.
_This is a method of hot pressing a mixture with ₃ series ceramics at a temperature around 1000 ° C.

Further, the manufacturing method shown in the above glass handbook only describes a method of precipitating mica crystals (fluorine phlogopite) in the glass, and the details thereof are not mentioned, but from the glass Although it is similar to the method of the present invention in which a mica crystal (tetrasilicon mica), a diopside crystal, an apatite crystal and the like is crystallized, in that it produces a fine crystallized glass by firing, the firing method is Although it is unknown, it is presumed that it was carried out by the usual method of horizontally setting the molded body.

[0005]

Since Japanese Patent Laid-Open No. 63-50365 is manufactured by hot pressing, the manufacturing method described in the above glass handbook is not known in detail, unlike the manufacturing method of the present invention. However, using the composition described in the conventional method,
It is presumed that it is difficult to deposit desired crystals from glass and obtain glass ceramics having few defects (cracks, chips) by conventional firing at room temperature and atmospheric pressure.

Further, as the size (thickness, size) of the molded product increases, defects such as cracks and chips are more likely to occur, especially during the firing process, resulting in more product loss.

[0007]

Means for Solving the Problems The present inventor first found that 1000 ° C.
A high-strength and easily-processable glass-ceramic manufacturing method with a new material composition that has the above heat resistance, excellent mechanical strength and electrical insulation properties, can be easily manufactured into precision-machined parts, and is easy to manufacture large-sized products. (Japanese Patent Application No. 2-30253), the present invention is a further development of the present invention, a crystallized glass in which desired crystals are deposited, with few defects such as cracks and chips, and excellent workability. The present inventors have found a method for producing the glass ceramics.

That is, in the present invention, (a) the composition is K ₂ O 11.0 to 11.5% (wt%, the same applies hereinafter), MgO 2
_{3.5~24.8%, SiO 2 55.0~56.8%,} F 2 8.4~12.6%
And ZrO ₂ 0.86 to 0.99% crystallized glass powder A25 to
95% and (b) composition is K ₂ O 5.0 to 6.0%, M
gO 9.5 to 11.0%, SiO ₂ 46.0 to 48.0%, CaO 2
_{1.0~23.0%, CaF 2 0.2~0.5%,} MgF 2 5.0~6.5
% And P ₂ O ₅ 8.0 to 8.5% of the crystallized glass powder B5~7
A method for producing a plate-shaped molded body by pressure-molding a mixture of 5% and a glass ceramics by heating at 105-1100 ° C., wherein the plate-shaped molded body has a granular or scaly periphery. Machining, characterized in that heat treatment is carried out on a supporting heat-resistant material having an angle of 15 to 65 ° with respect to the hearth surface of the firing furnace in a refractory container so as to be surrounded by the fluorine-containing mineral The present invention relates to a method for producing glass ceramics having properties.

[0009]

According to the manufacturing method of the present invention, since the plate-shaped molded body of the raw powder is fired on the supporting heat resistant material having an angle of 15 to 65 ° with respect to the hearth surface of the firing furnace, the molded body shrinks. Even if it starts to occur, the frictional resistance is small, the self-weight works effectively, and defects such as cracks and chips are unlikely to occur. In particular, the larger the molded body, the more remarkable the effect.

According to the manufacturing method of the present invention, it has a heat resistance of 950 ° or more and an excellent mechanical strength (bending strength) of 800 to 2000 kg / cm ² , has few defects, and can be used for precision machining such as cutting. You can easily select inexpensive glass ceramics.

[0011]

EXAMPLE In the present invention, glass powders having two kinds of compositions, crystallized glass powder A and crystallized glass powder B, are used as raw materials.

Crystallized glass powder A used in the present invention
Is calculated as K ₂ O: 11.0 to 11.5%, MgO: 23.5%
_{~24.8%, SiO 2: 55.0~56.8%} , F 2: 8.4~12.6%
And ZrO _2: consisting of from 0.86 to 0.99% of the composition.

The crystallized glass powder A is not particularly limited as long as it is produced by a method capable of obtaining a crystallized glass having the above-mentioned composition. For example, a raw material prepared to have the above-mentioned composition is put into a molten crucible. It is possible to use one that is heated and melted at a temperature of 1400 to 1500 ° C., rapidly cooled to obtain a glass lump, and then finely pulverized with a ball mill, a jet mill or the like to have an average particle size of about 5 μm or less.

Next, the crystallized glass powder B used in the present invention contains K ₂ O: 5.0 to 6.0% and MgO: 9.5 in terms of compound.
_{~11.0%, SiO 2: 46.0~48.0%} , CaO: 21.0~23.
_{0%, CaF 2: 0.2~0.5%} , MgF 2: consisting of 8.0 to 8.5% of the composition: 5.0 to 6.5% and P ₂ O _5.

The crystallized glass powder B is not particularly limited as long as it is produced by a method capable of obtaining crystallized glass having the above-mentioned composition. For example, a raw material prepared to have the above-mentioned composition is used as the crystallized glass. A powder obtained by heating and melting under the same conditions as in the production method of powder A and then finely pulverized to an average particle size of about 5 μm or less can be used.

If both the crystallized glass powder A and the crystallized glass powder B deviate from the above compositional range, it is not preferable because vitrification is difficult during heating and melting, and a part of crystallization occurs when taking out from the melting furnace.

The grain size of the crystallized glass powders A and B is 5 μm.
It is preferably not more than about a certain degree, and if it exceeds it, a molded body using it cannot be uniformly fired in the heating process, and it becomes difficult to obtain a dense glass ceramics.

The two kinds of glass powders thus obtained are mixed so as to have a ratio of glass powder A 25 to 95%, glass powder B 5 to 75%, preferably glass powder A 30 to 90% and glass powder B 10 to 70%. To prepare a mixed powder.

The reason why the two kinds of glass are mixed and used in the above ratio is as follows.

That is, the crystallized glass powder A is of a type in which tetrasilicon mica crystals are mainly precipitated from around 600 ° C. when heated, and this crystallized glass alone is excellent in machinability but does not give a dense fired body. It is difficult to obtain and mechanical strength is unfavorable.

On the other hand, the crystallized glass powder B is heated to 85
It is a type in which crystals mainly composed of diopside crystals, apatite crystals, mica crystals, etc. precipitate from around 0 ° C. The fired body can be densified and has excellent mechanical strength, but it is hard. The glass ceramics, which are the object of the present invention, cannot be obtained by themselves, such as poor machinability.

Therefore, in the present invention, a combination of the crystallized glass powder A and the crystallized glass powder B in a weight ratio of 25 to 95: 5 to 75 is used.

When used in this range, the obtained fired body is
It is possible to obtain a glass ceramic that is densified, has excellent electrical insulation, heat resistance and mechanical strength, and has good machinability.

Next, the powder compounded as described above is pressure-molded to prepare a plate-shaped molded body, which is heated at 1050 to 1100 ° C. to obtain a ceramic. At that time, in the present invention, the plate-shaped molding is carried out. The body is surrounded by granular or scaly fluorine-containing minerals and placed in a refractory container against the hearth of the firing furnace.
Heat treatment is performed on a supporting heat-resistant material having an angle of ~ 65 °, which is different from the conventional method.

First, the method for producing the plate-shaped molded article can be carried out by a method generally used and is not particularly limited, but one example thereof will be shown below.

To the mixed powder mixed in the above proportion, an organic binder aqueous solution such as polyvinyl alcohol having a concentration of about 5 to 10% is usually added to 100 parts by weight of the mixed powder.
Add 10 parts, and granulate into particles of about 50 to 100 μm with a granulator such as a Spartan Luzer. This granulated product is filled in a mold and molded at a pressing force of 500 to 1000 kg / cm ² to prepare a molded body.

Glass ceramics are manufactured by heating the obtained molded body at 1050-1100 ° C. for 3-5 hours to obtain a fired body. If the heating temperature is less than 1050 ° C., it is difficult to obtain a sufficiently dense fired product, and mechanical strength and electrical insulation are particularly poor, which is not preferable. On the other hand, if the temperature exceeds 1100 ° C., large pores are present inside, and the precipitated crystal grows, which is not preferable because it becomes porous.
If the heating time is shorter than 3 hours, the amount of precipitated crystals (for example, mica, diopside, etc.) will be small and the strength will be poor.

On the other hand, if it is longer than 5 hours, it tends to become porous.

Next, an embodiment of a method of installing a plate-shaped molded article in a refractory container and a method of firing, which is a feature of the present invention when firing the above-mentioned molded article, will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional general method for firing a plate-shaped molded product. Here, 1 is a plate-shaped molded body, 2 is a refractory container, 3 is a fluorine-containing mineral, and 4 is a hearth surface of a firing furnace.
Reference numeral 5 is a supporting heat-resistant material that supports the plate-shaped compact and has an angle of 15 to 65 ° C. with respect to the hearth surface. Further, α indicates an angle between the plate-shaped compact 1 and the hearth surface 4 of the firing furnace at that time.

The plate-shaped molded body 1 is obtained by the above-described molding method, and its dimensions are preferably about 30 mm in thickness, 200 mm in width and 200 mm in length.

As an example of the refractory container 2 used in the present invention, for example, a mullite or alumina refractory material having a height of 600 mm, a width of 300 mm and a length of 300 mm can be used. As shown in FIG. 1, the method for installing the green compact has an angle α of 15 to 65 with respect to the hearth surface 4 of the firing furnace.
It is placed on a supporting refractory material having an angle of ° and embedded in a fluorine-containing mineral. If the installation angle is less than 15 ° C, the effect is small, and if the installation angle exceeds 65 °, the weight of the plate-shaped molded body is concentrated on the lower end portion, so that the deformation easily occurs. As an example of the firing furnace, for example, an electric furnace or a gas furnace can be used.

When the plate-shaped compact is fired, the periphery of the plate-shaped compact is surrounded by the granular or scale-like fluorine-containing mineral 3 and fired to prevent the scattering of the fluorine component in the crystallized glass. In order to facilitate the formation of the desired crystals,
This is the method usually adopted.

As examples of the fluorine-containing mineral 3, synthetic fluorophlogopite, magnesium fluoride, potassium silicofluoride and the like are used, but the particle size is preferably about 30 to 100 μm. When it is less than 30 μm, it is difficult to embed a plate-shaped molded body,
Further, if it exceeds 100 μm, contact with the plate-shaped molded body is poor,
Fluorine in crystallized glass easily diffuses.

Defects often occur when the compact begins to contract due to heating, that is, near the temperature of 600 to 850 ° C. at which crystals start to precipitate from the glass. The shrinkage rate of the glass-ceramics of the present invention has a linear shrinkage rate of 16 to 20% based on the dimensions of the molded body, so that when the molded body begins to shrink, frictional resistance occurs at the portion in contact with the supporting heat resistant material, If the molded body does not overcome this, defects such as cracks and chips are likely to occur. In particular, these defects occur on the lower surface of the compact, which is subject to its own weight, and grow with shrinkage.

Therefore, in the conventional method as shown in FIG. 2 in which the supporting heat-resistant material on which the plate-shaped compact is placed is installed in parallel with the firing surface of the firing furnace, defects are likely to occur on the lower surface of the plate-shaped compact 2. .

The effect of the present invention is that the plate-shaped molded body is fired on the supporting heat-resistant material having an angle of 15 to 65 ° with respect to the hearth surface,
It is considered that the shrinkage causes the friction coefficient to decrease due to the self-weight of the molded body, which prevents the occurrence of defects.

Comparing the method of the present invention with the conventional method, the effect becomes clearer as the plate-shaped molded article becomes larger in size, and cracks, as compared with the conventional method of firing parallel to the hearth surface,
Occurrence of defects such as chips is significantly reduced.

The glass-ceramic of the present invention contains a mica crystal and a diopside crystal and does not contain cracks, chips, etc. for the reasons described above. Therefore, the glass ceramics of the present invention have heat resistance of 950 ° C. or higher, and have mechanical strength (bending strength) of 800 to 2000 kg / cm ² depending on the compounding ratio of crystallized glass. In addition, it has excellent machinability such as machinability and can easily process precision products.

Next, the production method of the present invention will be further described based on examples.

Example 1 1000 g of crystallized glass powder A having an average particle size of 4 μm and 1000 g of crystallized glass powder B having an average particle size of 4 μm were weighed and mixed in a ball mill for 5 hours.

Next, to 1000 g of this mixture, 100 g of polyvinyl alcohol (3% aqueous solution) was added and granulated with a Spartan Luzer to produce a granulated product having an average particle size of 60 μm. And dried for 12 hours.

This operation was repeated to prepare 2000 g of a granulated product. Next, the granules are 300 mm thick, 200 mm wide, and long
Fill a mold of 200mm, gradually pressurize and bleed air, and finally pressurize at a pressure of 1ton / cm ² for 3 minutes to obtain a plate-shaped molded body with a thickness of about 28mm, a width of 200mm, and a length of 200mm. Was produced.

Next, a refractory container made of mullite having a height of 220 mm, a width of 250 mm and a length of 250 mm was prepared, and the average particle diameter was 45 μm inside.
About a certain amount of synthetic fluorophlogopite powder was filled, and the molded body was inserted therein. The compact was placed on a supporting heat-resistant material having an angle of 15 ° with respect to the hearth surface and further filled with fluorophlogopite powder to set. Next, put it in a firing furnace at room temperature, raise the temperature up to 1080 ° C at a rate of 1.5 ° C / min, and hold for 3 hours.
The switch was turned off, and the mixture was allowed to cool slowly, and the temperature of the furnace became 50 ° C or lower, and it was taken out of the firing furnace.

Shrinkage rate is 18% on average for thickness, width and length
When the appearance was observed with a microscope (10 times magnification), there were no defects such as cracks and chips. From this sample, mechanical strength (bending strength), electric insulation resistance, Shore hardness and machinability, thermal expansion coefficient, and thermal deformation temperature were measured.

The bending strength is 3 mm in thickness, 4 mm in width and 50 mm in length.
Using the autograph manufactured by Shimadzu Corporation as a test piece, the three-dimensional bending method was evaluated by a three-point bending method with a fulcrum distance of 30 mm and a crosshead speed of 0.5 mm / min.

As the electrical insulation resistance, the volume resistivity is JIS C
It was measured in the normal state according to 2141 (Ceramic material test method for electrical insulation). The Shore hardness was measured using a Shore hardness meter.

Machinability is as follows: thickness 5 mm, width 50 mm, length 50
A test piece having a size of mm was used for the judgment by the following method. That is, drilling machine and drill diameter 0.2, 0.5, 1.0, 3.
Judgment was made by using a 0, 5.0 mmφ carbide drill (K-10) to form a through hole on the test side and observing the processed state of the hole. If no through hole is possible, machining is not possible,
Through holes can be provided, but if there is a defect such as a chip around the hole, it is possible to machine.If the through hole can be processed smoothly without defects such as a chip, it is judged to be good. , As shown in Table 1.

The coefficient of thermal expansion is 3 mm in thickness, 3 mm in width, and 20 mm in length.
The specimen with the dimension of was used as a test piece, and the temperature was measured from room temperature to about 900 ° C to obtain the average coefficient of thermal expansion. The heating rate was 10 ° C./min.

The heat distortion temperature is as follows: thickness 1 mm, width 5 mm, length 5
A load of 2.5 kg / cm ² was applied to a test piece with a size of mm as a test piece, and thermomechanical analysis (TMA) was performed. The temperature at which heat shrinkage started was taken as the heat distortion temperature. The temperature rising rate was 10 ° C./min.

Table 1 shows the mixed composition of the glass-ceramics produced in Example 1, firing conditions and their respective properties.

Example 2 500 g of crystallized glass powder A having an average particle size of 4 μm and 1500 g of crystallized glass powder B having an average particle size of 4 μm were weighed and mixed in a ball mill for 5 hours.

Next, to 1000 g of this mixture, 100 g of polyvinyl alcohol (3% aqueous solution) was added, and the mixture was granulated with a Spartan Luzer to produce a granulated product having an average particle size of 60 μm. It was dried for 12 hours. This operation was repeated to prepare 2000 g of a granulated product.

Next, the production of the plate-shaped molded body was carried out in the same manner as in Example 1 to obtain a size product having a thickness of about 26 mm, a width of 200 mm and a length of 200 mm (though the thickness is thinner than that in Example 1). This is because the compounding ratio of the crystallized glass powder B having a large specific gravity is large).

In Example 2, the plate-shaped molded product placed in the refractory container was set on a supporting heat-resistant material having an angle of 45 ° with respect to the hearth surface, as in Example 1. Then, put it in a normal temperature firing furnace, raise it to 1050 ° C at a heating rate of 1.5 ° C / min, hold for 3 hours, turn off the switch, and allow it to cool slowly to 200 ° C.
When the temperature fell below ℃, it was taken out of the firing furnace. The shrinkage ratio was almost the same as that in Example 1, and similarly, no defects such as cracks and chips were observed even when the appearance was observed with a microscope.

Then, in the same manner as in Example 1, the mechanical strength (bending strength) of the glass ceramics produced in Example 2
The electrical insulation properties (volume resistivity), Shore hardness, machinability, coefficient of thermal expansion, thermal deformation temperature, etc. were evaluated. The results are shown in Table 1 as in Example 1.

Example 3 1900 g of crystallized glass powder A having an average particle size of 4 μm and 100 g of crystallized glass powder B having an average particle size of 4 μm were weighed and mixed in a ball mill for 5 hours.

Next, to 1000 g of this mixture, 100 g of polyvinyl alcohol (3% aqueous solution) was added, and the mixture was granulated by a Spartan Luzer to produce a granulated product having an average particle size of 60 μm. It was dried for 12 hours.

This operation was repeated to prepare 2000 g of a granulated product.

The plate-shaped molded product was obtained by the same method as in Example 1 to obtain a product having a thickness of about 30 mm, a width of 200 mm and a length of 200 mm (thicker than Example 1 is a crystal with a small specific gravity). This is because the compounding ratio of the fog glass A is large).

Then, the plate-shaped molded article placed in the refractory container was placed on a supporting heat-resistant material having an angle of 65 ° with respect to the hearth surface in the same manner as in Example 1, and the refractory container was placed in a firing furnace, and 1100 Up to ℃
The temperature was raised at a rate of 1.5 ° C./min and held for 3 hours, then switched off, and allowed to cool slowly, and the temperature of the furnace was reduced to 200 ° C. or lower, and the furnace was taken out of the firing furnace. The shrinkage rate was 16% on average. In the glass ceramics obtained, the lower part (the part close to the refractory container) had a slightly thicker thickness, and although changes were recognized compared to before firing, defects such as cracks and chips were recognized. There wasn't. The deformation of the lower part is probably due to the concentration of the weight of the glass ceramic itself. If defects such as cracks and cracks do not occur, the surface accuracy is obtained by cutting, so there is no problem as a product.

Hereinafter, the mechanical strength (bending strength) of the glass ceramics produced in Example 3 in the same manner as in Example 1,
The electrical insulation properties (volume resistivity), Shore hardness, machinability, coefficient of thermal expansion, thermal deformation temperature, etc. were evaluated. The results are shown in Table 1 as in Example 1.

Comparative Example 1 In the same manner as in Example 1, a plate-shaped molded product was produced. Next, glass-ceramics were produced by firing in exactly the same manner as in Example 1 except that a plate-shaped molded article was set in a refractory container on a supporting heat-resistant material that was parallel to the hearth surface and approximated to the conventional method. . In the obtained glass ceramics, a crack penetrated from the lower part to the upper surface at one place at the center of the edge part, and small cracks were recognized at four places on the lower surface corner part. Next, excluding the defective part, mechanical strength (bending strength), electrical insulation (volume resistivity),
The Shore hardness, machinability, coefficient of thermal expansion, heat distortion temperature, etc. were evaluated. The results are shown in Table 1 as in Example 1.

[Comparative Example 2] In the same manner as in Example 2, a plate-shaped molded product was produced. Next, as in Comparative Example 1, a plate-shaped molded product was set in a refractory container parallel to the hearth surface and fired in the same manner as in Example 2 to produce glass ceramics. As with Comparative Example 1, the obtained glass ceramic had a crack penetrating from the lower part to the upper surface at one place at the center of the end part, and a slight warp was observed on the entire plate. Next, the mechanical strength (bending strength), electrical insulation (volume resistivity), Shore hardness, machinability, coefficient of thermal expansion, thermal deformation temperature, etc. were evaluated excluding the defective portion. The results are shown in Table 1 as in Example 1.

[Comparative Example 3] In the same manner as in Example 3, a plate-shaped molded product was produced. Next, as in Comparative Example 1, a plate-shaped molded article was set in a refractory container parallel to the hearth surface and fired in the same manner as in Example 3 to produce glass ceramics. In the obtained glass ceramics, cracks penetrating from the lower portion to the upper surface were observed at four locations in the center of the end portion.

Next, the mechanical strength (bending strength), electrical insulation (volume resistivity), Shore hardness, machinability, coefficient of thermal expansion, thermal deformation temperature, etc. were evaluated excluding the defective portion. The results are shown in Table 1 as in Example 1.

[0067]

[Table 1]

[0068]

According to the manufacturing method of the present invention, it is possible to obtain glass ceramics in which defects such as cracks and chips are unlikely to occur, which reduces manufacturing loss and reduces cost.

The glass ceramics thus obtained are electrically insulating, have a heat resistance temperature (heat deformation temperature) of 950 to 1000 ° C., and have a mechanical strength (bending strength) of 800 to 200.
It exhibits excellent characteristics of 0 kg / cm ² and can meet various required characteristics by properly mixing the kinds of raw material crystallized glass powder.

Since the glass ceramics obtained according to the present invention has machinability such as cutting work,
Heat-resistant insulating parts (boards, heat treatment jig materials), structural support members (heat-resistant bobbins,
It can be usefully used for sensor support parts).

Further, since the production method of the present invention is simple, the glass ceramic can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method for firing a plate-shaped molded article according to an embodiment of the method for producing a glass ceramic having machinability according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional method for firing a general plate-shaped molded article of glass ceramics.

[Explanation of symbols]

 1 Plate-shaped compact 2 Refractory container 3 Fluorine-containing mineral 4 Hearth of firing furnace

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C03C 3/112 10/04 (72) Inventor Yasuhiko Ikeda 2-6-1, Miwa, Mita City, Hyogo Prefecture Ryoden Kasei Co., Ltd. (72) Inventor Tadashi Murakami ▲ 1-1 2-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation

Claims (1)

[Claims] 1. The composition (a) has a compound conversion of K ₂ O 11.0 to 11.
5% by weight, MgO 23.5 to 24.8% by weight, SiO ₂ 55.0 to 5
6.8 wt%, F ₂ 8.4 to 12.6 wt% and ZrO ₂ 0.86 to
0.99% by weight of crystallized glass powder A 25-95% by weight, and (b) the composition is K ₂ O 5.0-6.0% by weight, MgO 9.5-
11.0% by weight, SiO ₂ 46.0-48.0% by weight, CaO 21.
0 to 23.0% by weight, CaF ₂ 0.2 to 0.5% by weight, MgF ₂ 5.0
To 6.5 wt% and P ₂ O ₅ 8.0 to 8.5 wt% crystallized glass powder B _{5 to} 75 wt% were blended to form a plate-shaped compact, which was heated at 1050-1100 ° C. A method for producing glass ceramics, wherein the plate-shaped molded body is surrounded by a granular or scale-like fluorine-containing mineral, and is contained in a refractory container with respect to the hearth surface of the firing furnace.
A process for producing a glass-ceramic having machinability, which comprises performing heat treatment on a supporting heat-resistant material having an angle of ~ 65 °.