JPH01201033A - Melting device and melting vessel using same - Google Patents

Abstract

PURPOSE:To provide the title melting vessel so designed that a vessel made of noble metal (alloy) with its outer surface coated with a ceramic reinforcing film is supported by a supporting member having radiation heat-transmissible part, thereby enhancing heat-receiving efficiency and reducing the vaporization of the vessel material and foreign substance contamination into glass. CONSTITUTION:The outer surface of roughly cylindrical vessel base 22 open upward, made of such a noble metal (alloy) as Pt, Pt-Rh or Pt-Au is subjected to plasma spray coating with a powder mixture comprising forsterite with a mean particle size of 5-7mum and Al2O3 with a man particle size of 1-2mum to form the first layer 24a. Thence, the second layer 24b is formed on the first layer 24a by plasma spray coating with a second powder mixture comprising Al2O3 with a mean particle size of 1-2mum and TiO2 with a mean particle size of 1-2mum, thus obtaining a melting vessel 12 with its outer surface coated with the resultant ceramic reinforcing film 24, 0.1-5.0mm thick. This vessel 12 is then supported by a supporting member 14 with many penetrating holes 28 as the radiation heat-transmissible part so as to externally cover the lower half part of said vessel 12.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a melting device, a melting container used in the device, and a method for manufacturing the same. It is suitably used for glass melting.

[Prior Art and Problems to be Solved by the Invention] Optical glass used as a material for optical elements is manufactured by melting various powdered oxides as raw materials at high temperatures. This optical glass requires precise optical properties, so when manufacturing it, not only must the raw materials be strictly mixed, but great care must be taken to avoid contamination with impurities.

Glass melting for producing optical glass is carried out by placing a glass melting container called a crucible in a furnace, putting glass raw materials into the container, and heating the glass in the furnace.

Recently, noble metals such as platinum and platinum-rosium are used as glass melting containers due to their high temperature resistance, low reactivity with molten glass raw materials, and resistance to impurity contamination and compositional changes. 1. Those made of noble metal alloys such as alloys are used.

However, since containers made of these precious metals or precious metal alloys are expensive, their thickness is at most 0.8 to 1.5 m.
It is about m. For this reason, the container alone does not have sufficient mechanical strength and cannot provide sufficient durability under the high temperature of 11'F for glass melting. The conventional method is to support it from the ground and place it inside the furnace.

FIG. 3 is a schematic cross-sectional view showing an example of a conventional glass melting apparatus as described above.

In the figure, l is a platinum container having a substantially cylindrical shape, and a reinforcing rib 2 is formed at the edge of the container. Reference numeral 3 denotes a support member made of refractory material and having partial strength, which is called a supporter, and is arranged so as to cover the entire outer surface of 1: description; ζ: 2. The material of the supporter is one that is compatible with the glass melting conditions, for example, a ceramic such as alumina, mullite, zirconia, zircon, silica, etc., made of a multilayered material using a Chinese or German lining method. Can be done. ]; A buffer material 4 made of alumina powder or bubble-shaped alumina or zirconia is filled between the container l and the supporter 3. 5 is a cover material for the cushioning material portion. The supporter 3 is installed on the furnace floor 6 via a stand 7. G is molten glass.

However, such conventional glass melting apparatuses or glass melting containers have the following problems.

That is, when assembling the melting device, it is necessary to house the container l in the supporter 3, and to distribute the layer of the melting material 1 and material 4 to a uniform thickness between them, and such an operation is complicated. This problem is particularly noticeable when using a container with a complicated shape, which requires considerable skill.

Next, the device is heated in the furnace, and the supporter 3 must be heated by heat radiation from the furnace heat source, and heat must be transferred from the supporter to the container l via the buffer material 4. Therefore, the heat receiving efficiency of container 1 is quite low, and yX
It takes a considerable amount of time from adding the materials to melting the glass.

Furthermore, damage to the container J due to volatilization of platinum constituting the container L
There is a problem with L. Platinum evaporates when the temperature of the melon reaches the melting temperature of the glass. In the air or in an oxygen atmosphere, it oxidizes even at lower temperatures and becomes volatile PtO2. Therefore, after a long period of operation of the melting device, a large amount of ffl decreases in the container l. For example, at 1400-1500℃
It is known that after three years of operation, the reduction in Type S can reach 30 to 40%. Most of this is due to volatilization. The volatilized platinum is deposited outside the furnace at a relatively low temperature. In order to suppress such volatilization, it may be operated in a nitrogen gas atmosphere, but this is not economical as it has a negative effect on the clarification effect, requires extensive sealing, and increases gas running costs. .

In addition, there is also one 1st Steam title from Platinum Inclusion. That is,
A part of the platinum volatilized as described in 1U is mixed into the molten glass as a foreign substance. The foreign matter is an amorphous foreign matter with a size of several microns to several hundred microns, and is difficult to remove from high-viscosity glass, deteriorating the quality of the glass.

Furthermore, there is the problem of the strength of the container l. When the temperature rise and fall are repeated frequently, the container 1 repeatedly undergoes slight deformation, and due to the compressive and tensile internal stresses at this time, the platinum Mt weave ++
T-crystallization (crystal grain growth) is likely to occur, and as this progresses, cracks may occur and the container may be damaged. In particular, when the container shape is complicated, the above recrystallization is 1liI
It is a sheet music.

Therefore, in view of the above-mentioned conventional technology, the present invention does not require skill for installation in the furnace, has high heat receiving efficiency, has low volatilization of the container material, and has low foreign matter contamination into the glass. It is an object of the present invention to provide a glass melting device or a glass melting container that is highly productive and has a strong Iff of 1 minute.

[Means for Solving the Problems] According to the present invention, the above objects are achieved.

A reinforcing film made of ceramic is attached to the outer surface of a container base material made of a noble metal or a noble metal alloy to form a melting container, and the container is supported by a support member having a radiant heat transmitting portion 41. , melting equipment.

A reinforcing film made of ceramic is attached to the outer surface of a container base material made of a noble metal or a noble metal alloy, and the reinforcing film is made up of multiple layers, and the layer on the container base material side has a coefficient of thermal expansion that corresponds to the coefficient of thermal expansion of the base material. A melting vessel is provided, the layers having similar coefficients of thermal expansion [and the outer layer being a layer with good heat receiving efficiency].

In Book 5111, platinum can be used as the container material.

In addition, in manufacturing the above-mentioned melting device or melting container, a reinforcing film made of ceramic can be formed using plasma spraying, and in this case, the surface of the ceramic layer formed by plasma spraying is ground to form the reinforcing film made of ceramic. can be formed.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cross-sectional schematic side view showing a first embodiment of a melting device using unexploited I shellfish.

In the figure, 12 is a melting container, 14 is a support member (supporter) for supporting the melting container, and 16 is a floor of the electric furnace.

The container 12 has a substantially cylindrical container base 22 that is open at the top.
A ceramic reinforcement pattern 24 is formed on the outer surface.

The container base material 22 is made of platinum, has a thickness of 0.8 mm, and a diameter of 1
It is 40mm long, 150mm deep, and contains 2 sentences. still,
A collar 26 for scooping out molten glass is integrally attached to a part of the edge of the blade of the container material 22. The brim has a length of 50 mm and a radius of 80 mm.

As the container base material 22, platinum-rhodium, platinum-gold,
Platinum-containing alloys such as platinum-rhodium-gold, rhodium, gold,
Other noble metals such as iridium and palladium can also be used.

The ceramic reinforcing film 24 consists of two layers, and the first layer 24a on the side of the container base material is made of 7 orsterite (7 orsterite) with an average grain size of 5 to 7 pm.
A powder mixture consisting of 70 tons of 2MgO・5i02) and 30 tons of alumina (A 1203) with an average particle size of 1 to 2 μm is sprayed to a thickness of 0.4 to 0.5 m by plasma spraying.
It is formed in the shape of m. In addition, the outer second layer 24
b is the uniform grain pf of the above, 1 to 24 m of alumina (A1
203) It is made by plasma spraying a powder mixture consisting of 50% titania (Ti02) and 50% titania (Ti02) with an average particle size of l to 2 m, and the first layer 24
The total thickness of layer a and second layer 24b is 4.5 mm.

14. Ceramics constituting the ceramic reinforcing film 24 include alumina (A1203) and titania (T i 0
2), stable zirconia (ZrO2), forsterite ・'2MgolISi02), steatite (M
gO-Si02), Mullite (3Al2O3・2S
An oxide ceramic obtained by thermal spraying quartz (Si02), quartz (Si02), etc. alone or in combination can be used. This oxide ceramic can also be used when melting is carried out in the atmospheric atmosphere F. Furthermore, the ceramics constituting the ceramic reinforcement group 24 include nitrides such as silicon nitride (Si3N+), titanium oxide (T i N), silicon carbide (SiC), and titanium oxide (TiC).
A carbide such as IR-treated tungsten (WE) may be used alone or by thermal spraying the mixture as appropriate. These nitride-based and carbide-based ceramics will alloy with platinum at high temperatures if they are exposed to direct waves of 1'N on the S material of a platinum container, so they should be used under relatively low melting conditions of 1000°C or less. Or, should it be used as the second layer or an outer layer? ing.

As mentioned above, when the ceramic reinforcing membrane is composed of two or more layers, the material for the layer closest to the container base material is selected based on its coefficient of thermal expansion being close to that of the base material, and the material for the layer closest to the outside Materials can be selected based on the higher the heat receiving efficiency.

The thickness of the ceramic reinforcing film is, for example, 0.1 to 5.0 mm.
It is. If it is less than 0.1 mm, the effect obtained will be small, and if it exceeds 5.0 mm, the effect will not increase much but the wall will become too thick ii (increase in IJ and cost (2): increase).

When forming a relatively thick ceramic reinforcing film by thermal spraying, unevenness may occur on the outer surface, and these unevenness may cause uneven temperature rise and temperature drop. Therefore, if the unevenness is large, It is preferable to flatten the surface by grinding it after thermal spraying.

Now, as shown in the figure, the porter 14 indicated by L supports the container base material 12 so as to cover it from the outside.

The supporter has a large number of through holes 28 formed on its side surfaces as radiant heat sections. The supporter also has legs 30. The supporter 14 is made of refractory material similar to the supporter of the conventional melting apparatus shown in FIG.

Note that G is molten glass.

An example of glass melting using the melting equipment of this embodiment is shown below.

The molten glass is tungsten sealing glass, and its composition is 4 parts of 5i02Nia 4 tons, B2Q3: 16.2 parts by weight, Al2O3: 2 parts by weight, Na2O: 4.5 parts by weight, K2O: 2 parts by weight, CaO: 1lri part, A S20
3:0, consists of 3 ton f part. The molten raw material is 60
One batch of 6 kg is mixed on a scale with kg as the loft.
Average of 10 times/il! Melting was performed at a frequency of In each melting process, the raw material was charged at 1350° C. into the container from the inlet at the top of the furnace using a water-cooled hopper, and after the batch was completely melted, the temperature inside the furnace was raised to 1500° C. and maintained for 4 hours. After the glass was melted, a crank-shaped platinum stirring rod was inserted into the container from the top of the furnace and rotated at 15 rpm to homogenize the glass.
The temperature was lowered to 250° C. and held for 20 minutes. By partially opening the side wall of the furnace, grasping the lower part of the supporter using a stainless steel gripping tool, and tilting the supporter inside the furnace, it is possible to remove the inside of the water tank with an internal volume of 68 cm placed outside the furnace. Molten glass was poured into the container to obtain approximately 1.8 grams of crushed cullet.

Such glass melting was carried out for 6 months. Furthermore, at the same time,
For comparison, glass melting using a conventional melting apparatus as shown in FIG. The results are shown below.

(1) The apparatus of this embodiment requires only that the melting container be placed inside the supporter, and can be easily installed in the furnace as it is. Therefore, unlike conventional devices, the assembly work is not complicated and requires skill.

(2) In the conventional apparatus, it took 1.5 to 20 hours to input the raw materials, but in the apparatus of this embodiment, the raw materials were input four times at intervals of 15 to 20 minutes, and it took only 70 minutes. This is because 7 (in the example device, the supporter is formed with the through hole fL28, and only the lower half of the container is covered with the supporter, so the heat receiving efficiency of the container is as high as 1%. Also, compared to the conventional device) However, due to the large heat capacity of the supporter, there was a time lag between the warm air inside the furnace and the container temperature when the temperature was just heating up and when the temperature was falling. The time delay was relatively small, and therefore hot air control was easy.

(3) In the conventional device, the container was deformed even though a part of the container l was provided with a collar over the entire circumference, but in the device of this embodiment, a ceramic reinforcing film is formed on the container. It was found that no deformation occurred in this example, even though the mechanical strength of the wind was high in some parts. In addition, the thickness of the wood (container wood in the example) was changed from that of a conventional container (thickness 1.2 mm).
It was possible to reduce the thickness by 1 mm.

(4) In conventional equipment, platinum crystal grains grow violently near the surface of the molten glass, causing cracks to occur within three months of molten glass and causing the glass to leak. Each time, the furnace was shut down, the platinum 6th base was repaired, and the supports were replaced with new ones. In contrast, in the apparatus of this example, even after 6 months of operation, there was only slight growth of crystal grains on the inner surface of the joint, and no cracks were observed at all. In addition, there were no chips or cracks in the ceramic reinforcing film, and L(
) It was my life.

(5) After 6 months of operation, we re-refined the platinum in the container base material of this example and the container of the conventional device, and found that the amount of platinum wasted was about 3% in the case of the conventional device; In this case, about 173 liters.

It was 1%. Therefore, it was found that in the container of this example, platinum loss 41 due to volatilization and other causes was extremely small, and the container had a long life.

FIG. 2 is a sectional view showing a second embodiment of the melting apparatus according to the present invention. In this figure, the same members as in FIG. 51 are given the same reference numerals.

In this embodiment, the shape of the container 12 is different from that of the first embodiment. That is, the container has a portion 12a which is gradually constricted at the top and has a smaller diameter, and a portion 12b which is smaller in diameter and continues from the portion 12a. Further, a receiving portion 12c for introducing raw materials is formed in the small diameter portion. The bottom of the container 12 is inclined in one direction, and a molten glass outflow pipe 32 is installed on the side wall of the container at the lowest point t.
It is continued. The container 12 is made of a container base material 22 with a ceramic reinforcing film 24 formed on the outer surface, and the ceramic reinforcing film consists of two layers 24a and 24b, and this structure is similar to that of the first embodiment.・The container 12 is
The internal volume of is 15 sentences.

In this embodiment, the container 12 is housed in the supporter 14, and since the bottom of the container 12 has a slope,
A wedge-shaped member 34 is arranged within the supporter 14. The legs of the supporter 14 are not sunk, and the supporter 14 is placed on a stand 36 and placed on the floor of the furnace.

Reference numeral 38 is a stirrer, and is attached to the end of a drive rotating shaft 40 extending into the furnace from above. The stirring χ 38 is located within the container 12 . Further, 42 is a heater serving as an in-furnace heat source, and 44 is a thermocouple for measuring the in-furnace temperature.

Note that G is molten glass.

! , the molten glass outflow pipe 32 is connected to the side 1 (t) of the furnace 16.
The pipe extends to the outside of the furnace through the container 12, and its tip is used as a glass outflow nozzle (this pipe is also made of platinum, similar to the container 12). A ceramic reinforcing film is formed on the outer surface of the material. However, the reinforcement j! ! 2 is a first layer in which alumina (A 1203 ) with an average particle size of 1 to 2 μm is formed to a thickness of 0.2 mm by plasma spraying, and a second layer is made of alumina (A 1203 ) with an average particle size of 5 μm. A powder mixture consisting of 50 silicon carbide (SiC) heavy walls is formed into a thickness of 0.3 mm by plasma spraying. The reason why the structure of the outflow pipe was changed from the structure of the container in this way was to uniformly heat the pipe.
This is to improve the emissivity at low temperatures by including SiC in the outer layer.

The pipe has an inner diameter of 1110 mm, an outer diameter of 12 mm, and a length of 1.6 m. 46 is a tube furnace for controlling the temperature of the pipe 32, and 48 is a heater. Note that 50 is a thermocouple for measuring the temperature inside the furnace 46.

When SF optical glass was melted and flowed out using the device of this example, the amount of foreign matter mixed into the molten glass, the main cause of which was volatilization of platinum, was sufficiently small. That is, the coefficient of the number of foreign particles in a unit volume of glass was about 1710 compared to the case using the conventional apparatus, and the yield was sufficiently high.

In the device of this embodiment, the reinforcing film is formed on the outflow pipe 32, so that it does not deform even when exposed to high temperatures during outflow, and can be sufficiently shaped into M+, ? did. In addition, since the device of this embodiment is reinforced with ceramic, the ceramic reinforcing film evenly transfers heat to the molten glass by adding the heat t-1 from the furnace, and has high heat receiving efficiency, so that the glass outflow is prevented. Reduction could be carried out easily and reliably.

Although the above embodiments relate to glass melting, the present invention is equally applicable to melting of various other crystals. Furthermore, in the above embodiment, the ceramic reinforcing membrane is made up of two layers, but in the present invention it may be made up of three or more layers. In that case, which layer is closer to the container base material? It is preferable to select materials based on the fact that they have similar thermal expansion coefficients, and to select materials based on the fact that the closer they are to the outside, the higher the heat receiving efficiency.

[Effects of the Invention] 1: As explained in detail in IJ1, according to this Qljl, the melting vessel has a ceramic reinforcing film formed on the outer surface of the noble metal or noble metal alloy, so the strength is improved. 1
-No skill required for placing the glass in the furnace, high aging efficiency, less volatilization of the container material, long life, less contamination of foreign matter into the glass, and good production. You can get sex.

Furthermore, according to the unheated melting device 1j1, since the melting device is configured by supporting the melting container by a support member having a radiant heat transmitting portion, a high heat receiving efficiency can be obtained in 1 minute.

Further, according to the present invention, by forming the ceramic reinforcing film by plasma spraying, it is possible to easily form a reinforcing film with good performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view, partially in section, showing a melting device according to the present invention. FIG. 2 is a cross-sectional view of a melting device according to the invention. FIG. 3 is a schematic cross-sectional view showing an example of a conventional glass melting apparatus. 12: Melting container, 14; Supporter, 16: Furnace,
22: Container base material, 24: Ceramic reinforcement membrane, 28 Two through holes, 32: Outflow pipe, 46: Tubular furnace. Agent Patent Attorney Seki Yamashita Figure 1 Figure 3

Claims (8)

[Claims] (1) A reinforcing film made of ceramic is attached to the outer surface of a container base material made of a noble metal or a noble metal alloy to form a melting container, and the container is supported by a support member having a radiant heat transmitting section. Features: Melting equipment. (2) The melting device according to claim 1, wherein the container base material is made of platinum. (3) A method for manufacturing a melting device according to claim 1 or 2, characterized in that the reinforcing film made of ceramic is formed using plasma spraying. (4) The method for manufacturing a melting device according to claim 3, wherein the reinforcing film made of ceramic is formed by grinding the surface of the ceramic layer formed by plasma spraying. (5) A reinforcing film made of ceramic is attached to the outer surface of the container base material made of a noble metal or a noble metal alloy, and the reinforcing film is made up of multiple layers, and the layer on the container base material side expands due to the thermal expansion of the base material. 1. A melting container characterized by having a layer having a coefficient of thermal expansion close to the coefficient and an outer layer having a good heat receiving efficiency. (6) The melting container according to claim 5, wherein the container base material is made of platinum. (7) A method for manufacturing a melting container according to claim 5 or 6, characterized in that the reinforcing film made of ceramic is formed using plasma spraying. (8) The method for manufacturing a melting container according to claim 7, wherein a reinforcing film made of ceramic is formed by grinding the surface of the ceramic layer formed by plasma spraying.