JP3692511B2 - Stretch molding method for crystalline glass - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a phenomenon in which undesired crystals precipitate when a glass preform is heated, so-called devitrification glass (hereinafter referred to as crystalline glass), and particularly to a method of stretch-molding. The present invention relates to a method of stretching and molding a highly accurate product such as a rod-shaped spacer, rod-shaped lens, thin plate or capillary tube having a circular or rectangular cross-sectional shape.
[0002]
[Prior art]
Conventionally, a stretch molding method called a redraw molding method is known as a method for remolding a glass material. In this method, first, molten glass is molded by an appropriate molding method to prepare a preform, and then one end of the preform is gripped by the chuck portion of the feed mechanism unit, and is placed in a molding furnace at a constant speed. The preform is heated to a temperature at which the preform can be softened and deformed, and stretched by applying a tensile force from the other end of the preform that has been softened and deformed using a pair of driven rollers or the like. This is a stretch molding method for forming into a reshaped body having accuracy.
[0003]
According to the conventional stretch molding method described above, when glass has a property that hardly causes devitrification, as described above, if the preform is simply heated and stretched to a temperature at which it can be softened and deformed, stretch molding is performed. A remolded body having high dimensional accuracy can be obtained without devitrification.
[0004]
[Problems to be solved by the invention]
However, in the case of crystalline glass having the property of easily causing devitrification, if the preform is heated and molded by a conventional stretch molding method, undesired crystals may be precipitated in the glass of the preform body. The devitrified material is generated and cannot be extended at all, or the glass in the middle of stretching is devitrified and does not extend, so that there is a problem that the stretch molding itself becomes difficult. Even if the film can be stretched, the formed devitrified material has poor molding accuracy and deviates from the desired dimensional tolerance, or the desired characteristics in terms of thermal expansion coefficient and hardness due to undesired crystal precipitation. The problem that cannot be obtained occurred.
[0005]
Therefore, conventionally, it has been difficult to adopt a stretch molding method for a crystalline glass material, and when manufacturing a product made of crystalline glass having high dimensional accuracy and having desired characteristics, it is necessary to melt There is a method in which glass is directly molded into a shape close to the final dimensional shape, and the molded body is subjected to several degrees of grinding, polishing, etc. to obtain the final dimensional shape. There were a lot of problems.
[0006]
An object of the present invention is to provide a method for stretch-forming crystalline glass that solves the above-described problems.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the crystalline glass stretch molding method of the present invention is capable of softening and deforming the preform while holding one end of the preform made of crystalline glass and feeding it at a constant speed. In a crystalline glass stretch molding method comprising heating to a temperature and stretching by applying a tensile force from the other end of the preform, the preform composed of the crystalline glass is less than the devitrification region of the crystalline glass. Heating to the temperature of, and then devitrification does not occur, or even when partial devitrification occurs, the devitrification does not adversely affect the moldability during stretching and the properties of the obtained remolded product Even if devitrification does not occur or partially devitrification occurs, the moldability during stretching and the properties of the resulting remolded product are reduced by devitrification. to cooling cooled in a degree that does not adversely affect the time And butterflies.
[0008]
In the method of the present invention, the temperature and time conditions (hereinafter referred to as a molding temperature schedule) required for a preformed body made of crystalline glass to be stretch-molded to become a reshaped body are important. It is important to perform the stretch molding so as not to enter the devitrification region. Therefore, in the present invention, the crystalline glass preform is first preliminarily heated to a temperature below the devitrification region of the crystalline glass, and then softened and deformable within a time period during which no devitrification occurs substantially. The film is heated and heated to stretch, and then cooled down within a time period during which devitrification does not substantially occur. Here, substantially devitrification does not occur, even if devitrification partially occurs, when the devitrification does not adversely affect the formability at the time of stretching and the properties of the obtained remolded body It is meant to include.
[0009]
As called crystalline glass used in the present invention, for example, a glass having a composition of _{SiO 2 -Al 2 O 3 -Li 2} O system. When this crystalline glass is crystallized after being subjected to a predetermined heat treatment, β-quartz solid solution or β-spodumene solid solution is precipitated as a main crystal, and becomes a crystallized glass having low expansion and high mechanical strength characteristics. As the crystalline glass used in the method of the present invention, when the preform is subjected to stretch molding, the preform is a glass body that is both in a glass state and a glass body that has been previously crystallized by a predetermined heat treatment. It is. Here, the crystalline glass exemplified above is referred to as glass A. In the case of this glass A, as shown in FIG. 1, the temperature and time condition regions in which crystals are precipitated in the glass A and devitrification occurs are as follows. Can be expressed as a devitrification region Z indicated by hatching.
[0010]
The inventors of the present invention pay attention to the characteristics of the above-mentioned crystalline glass, and stretch-mold a preform made of crystalline glass that easily causes devitrification without causing devitrification to the extent that the characteristics are adversely affected. I found a way. That is, when performing the above-mentioned stretch molding, in the region other than the devitrification region Z of the crystalline glass A, by substantially defining the molding temperature schedule by combining the temperature and time conditions in the case of stretch molding, It became possible to mold without devitrification.
[0011]
FIG. 2 shows that a preform 1 made of crystalline glass is supplied to a molding furnace 4 by a feed mechanism 3 by a molding method of the present invention, heated to a temperature at which it can be softened and deformed, and stretched and molded by a tension mechanism 5. An outline of an apparatus for obtaining the remolded body 2 is shown.
[0012]
Hereinafter, the case where the preforming body 1 made of the crystalline glass A having the devitrification region Z shown in FIG. 1 is molded by using the stretch molding method will be described.
[0013]
First, the molten glass A is cast and formed, for example, to produce a preform 1 of a round bar. As shown in FIG. 2, the upper end of the preform 1 is gripped by the chuck portion 3a of the feed mechanism portion 3 and supplied to the molding furnace 4 at a constant speed.
[0014]
As shown in FIG. 3, the molding temperature schedule in which the preform 1 is stretched and molded into the remolded body 2 in the molding furnace 4 is from the highest temperature T1 to the lowest temperature T2 in the devitrification region Z of the crystalline glass A. It is set so as not to stay within the temperature range and for more than the devitrification time tm at which devitrification occurs. That is, at the position of the first heating unit 4a of the molding furnace 4 in FIG. 2, the preform 1 is heated to a temperature lower than the devitrification region Z of the glass A and to its highest temperature, and the position of the second heating unit 4c. Then, the preform 1 is softened and deformed and rapidly heated to a temperature exceeding T1 in the vicinity of 1 × 10 ⁴ to 1 × 10 ⁶ poise, which is suitable for stretch molding. At that time, the second heating unit 4c raises the temperature range from T2 to T1 so that the temperature raising time t1 is within tm. In order to make such a temperature gradient capable of rapid temperature increase, a heat insulating part 4b is provided between the two heating parts so that the heat of the second heating part 4c is not transmitted to the first heating part 4a. The heat insulating part 4b may have a jacket-like structure having a hollow part for flowing a fluid such as water or air as a refrigerant, or may be made of a plate-like metal having a large heat radiation area. Next, using a pair of driving rollers 5a and 5b of the pulling mechanism 5, a tensile force is applied from the lower end of the preform 1 that has been heated and softened in the molding furnace 4 at a predetermined tensile speed. Stretch. In the cooling unit 4d, the temperature range from T1 to T2 is cooled so that the temperature drop time t2 is within tm so that devitrification does not occur in the stretched and molded remolded body. In order to form a temperature gradient capable of such a rapid temperature decrease, the cooling unit 4d blocks the heat of the second heating unit 4c. The structure of the cooling part 4d may be a jacket-like structure having a hollow part for flowing a fluid such as water or air as a coolant, or may be made of a plate-like metal having a large heat radiation area, similarly to the heat insulating part 4b.
[0015]
As described above, the round bar reshaped body 2 having a desired cross-sectional dimension is stretch-molded. Thereafter, the remolded body 2 is cut to a predetermined length by a cutting mechanism (not shown) located below the pulling mechanism 5.
[0016]
When crystalline glass that is still in the glass state is used as the preform 1, a crystal having characteristics such as desired mechanical strength and expansion coefficient by crystallization treatment of the remolded body 2 after the above stretch molding. Make a vitrified glass. This is heat-treated at a predetermined temperature schedule, and a predetermined amount of crystals made of β-quartz solid solution or β-spodumene solid solution is precipitated in the glass of the reshaped body 2 so as to obtain desired characteristics.
[0017]
In the above description, the method of stretch-molding a round bar has been described as an example. However, the shape of an object to be stretch-molded may be plate-shaped, tubular, or other various shapes.
[0018]
In the case illustrated in FIG. 3, the temperature is raised to a temperature exceeding T1, but even if the temperature does not exceed T1, if the residence time in the devitrification region is within the devitrification time tm , Stretch molding can be sufficiently performed without causing devitrification to such an extent that adverse effects are caused.
[0019]
[Action]
In the crystalline glass stretch molding method of the present invention, the preformed body made of the crystalline glass is first heated to a temperature lower than the devitrification region of the crystalline glass, so that the time required for the crystal to precipitate and devitrify in the glass. The preform can be preliminarily heated uniformly and uniformly without being restricted by the above, and even when devitrification does not occur or partial devitrification occurs, molding at the time of stretching is caused by the devitrification. The preform is heated to a temperature that can be softened and deformed within a time that does not adversely affect the properties and the properties of the resulting remolded body, so the preform that has already been heated to a temperature below the devitrification region is softened. It is possible to rapidly raise the temperature in a short time without causing devitrification at the deformable temperature, and after that, even if devitrification does not occur or partial devitrification occurs, the devitrification causes moldability during stretching and time so as not adversely affect the properties of the resulting reshaped body In since the cooling cooling, it is possible to prevent the short time into the rapid temperature drop is achieved by devitrification area, thus high has a dimensional accuracy and characteristics of the re-formed body without devitrification adversely affect Obtainable.
[0020]
【Example】
(Example 1)
One embodiment of the method for stretch-forming crystalline glass according to the present invention will be described below.
[0021]
As a specific example of the crystalline glass to be stretch-molded, a glass having a SiO ₂ —Al ₂ O ₃ —Li ₂ O composition and precipitating β-spodumene solid solution as a main crystal when subjected to a predetermined crystallization heat treatment One composition example is shown. The composition of this crystalline glass is expressed as% by weight of SiO ₂ 65%, Al ₂ O ₃ 18%, Li ₂ O 2%, MgO 1%, ZnO 3%, BaO 1%, TiO ₂ 3%, ZrO ₂ 2 %, K ₂ O 5%. This crystalline glass has almost the same devitrification region as previously shown in FIG. 1. The maximum temperature T1 of the devitrification region is 1200 ° C., the minimum temperature T2 is 780 ° C., and the devitrification time tm is 5 minutes.
[0022]
First, as the material of the preform 1, a molten glass having the above composition is molded to prepare a glass-like material that does not contain devitrified substances or crystals. The glass material has a square cross-sectional shape and dimensions. Is processed into a square bar having a length of 40 ± 0.1 mm × 40 ± 0.1 mm and a length of 1000 mm, and the preform 1 is prepared. As shown in FIG. Gripped by the chuck part 4a of the part 3 and supplied to the molding furnace 4 at a constant speed of 5 mm / min, the preform 1 is gradually heated up to 750 ° C. below the devitrification region at the position of the first heating part 4a. Then, the preform 1 is heated at a temperature of the second heating unit 4c within a period of 5 minutes up to 1230 ° C. where the preform 1 is softened beyond the devitrification region. Next, a tensile force is applied to the lower end of the preform 1 that has been softened by being heated by the second heating unit 4c using the pair of drive rollers 5a and 5b of the pulling mechanism unit 5 at a tension of 2 m / min. Stretched at a speed, cooled within 5 minutes to 750 ° C. below the devitrification region in the cooling part 4d, and the cross-sectional dimension is 2.0 mm × 2.0 mm which is 1/20 of the preform 1 and the cross-sectional shape is square Remolded body 2 was obtained.
[0023]
When the remolded body obtained in Example 1 was examined, it was molded with high accuracy and no devitrification was observed.
[0024]
After cutting the reshaped body 2 obtained in Example 1 to 500 mm, the temperature was raised from room temperature to 780 ° C. at 2 ° C./min, maintained at 780 ° C. for 30 minutes, and then to 780 to 1000 ° C. Was heated at 0.5 ° C./min, and crystallization heat treatment was performed at 1000 ° C. for 30 minutes. By this heat treatment, 80% by volume of crystals made of a β-spodumene solid solution having an average diameter of 0.3 μm was precipitated on the reshaped body 2, and a crystallized glass having a vitreous portion of about 20% by volume was obtained. The crystallized glass had a thermal expansion coefficient of 35 × 10 ⁻⁷ / ° C., a Vickers hardness of 600, and had desired characteristics.
[0025]
(Example 2)
A glass material of crystalline glass having the same composition as in Example 1 is processed into a square bar having dimensions of 40 ± 0.1 mm × 40 ± 0.1 mm × length 1000 mm, and this is processed at room temperature to 780 ° C. at 3 ° C. / The temperature was raised at 780 ° C., held at 780 ° C. for 60 minutes, then heated from 780 to 1000 ° C. at 0.5 ° C./minute, and crystallization heat treatment was held at 1000 ° C. for 60 minutes. By this heat treatment, 50% by volume of a crystal composed of a β-spodumene solid solution having an average diameter of 0.2 μm is deposited on the preform 1, the vitreous part is about 50% by volume, and the thermal expansion coefficient is 30 × 10. Crystallized glass having a Vickers hardness of 650 at ^-7 / ° C. As a preform for subjecting this crystallized glass to stretch molding, stretch molding was performed at the same molding temperature schedule as in Example 1 to obtain a remolded body having a cross-sectional dimension of 2.0 mm × 2.0 mm. .
[0026]
As a result of examining the remolded body thus obtained, it was stretch-molded with high accuracy while maintaining the crystallization state, and a re-molded body having desired characteristics was obtained without causing devitrification in stretch molding. It was.
[0027]
【The invention's effect】
According to the stretch molding method for crystalline glass according to the present invention, it is possible to produce a large number of remolded bodies having desired characteristics and high dimensional accuracy without causing devitrification to an extent that adversely affects the characteristics. There is an excellent practical effect.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a devitrification region Z of a crystalline glass A. FIG.
FIG. 2 is a conceptual diagram showing an example of an apparatus used for stretch molding of the crystalline glass of the present invention.
FIG. 3 is an explanatory diagram showing an example of a molding temperature schedule in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Preliminarily molded object 2 Reformed object 3 Feed mechanism part 4 Molding furnace 4a 1st heating part 4b Heat insulation part 4c 2nd heating part 4d Cooling part 5 Pulling mechanism parts 5a and 5b Drive roller

Claims (1)

Because one end of a preform made of crystalline glass is gripped and heated to a temperature at which the preform can be softened and deformed while being fed at a constant speed, and stretched by applying a tensile force from the other end of the preform. In the crystalline glass stretch molding method,
A preform formed of crystalline glass is heated to a temperature lower than the devitrification region of the crystalline glass, and then, when devitrification does not occur or partial devitrification occurs, molding during stretching is caused by the devitrification. Even if the devitrification does not occur or the devitrification partially occurs, it is heated up to a temperature at which it can be softened and deformed within a time period that does not adversely affect the properties and the properties of the obtained reshaped product. A method for stretching and forming a crystalline glass, characterized by cooling and cooling within a time that does not adversely affect the formability at the time of stretching and the properties of the obtained remolded body due to devitrification .

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