阅读说明：本技术 真空炉及石英玻璃制备方法 (Vacuum furnace and quartz glass preparation method ) 是由 薛钦 刘颖 王蒙非 汤明明 赵海伦 钱宜刚 沈一春 陈娅丽 于 2021-01-19 设计创作，主要内容包括：一种石英玻璃制备方法,包括步骤：提供多个石英锭以及真空炉。将所述石英锭容置于所述容置槽内,以及通过所述真空发生装置将所述腔体内的空气抽出,使所述腔体具有一真空度。启动所述底板加热件,所述底板加热件以第一升温速率将所述底板升温至第一温度,以及启动所述侧板加热件,所述侧板加热件以第二升温速率将所述侧板升温至所述第一温度,所述第一升温速率大于所述第二升温速率。保温熔化所述石英锭,退火以获得石英玻璃,所述石英玻璃的光学均匀性<1.5×10～(-6),所述石英玻璃的直径或对角距离高达1500mm。另外,本发明还提供一种真空炉。(A method for producing a silica glass, comprising the steps of: a plurality of quartz ingots and a vacuum furnace are provided. And accommodating the quartz ingot in the accommodating groove, and pumping out air in the cavity through the vacuum generating device to ensure that the cavity has a vacuum degree. The start the bottom plate heating member, the bottom plate heating member will with first intensification rate the bottom plate heaies up to first temperature, and starts the curb plate heating member, the curb plate heating member will with second intensification rate the curb plate heaies up to first temperature, first intensification rate is greater than second intensification rate. Melting the quartz ingot under heat, annealing to obtain quartz glass having optical uniformity<1.5×10 ‑6 The quartz glass has a diameter or diagonal distance of up to 1500 mm. In addition, the invention also provides a vacuum furnace.)

1. The vacuum furnace is characterized by comprising a shell, a mold, a heating body and a vacuum generating device, wherein the shell is provided with a hollow cavity, the mold and the heating body are accommodated in the cavity, and the vacuum generating device is communicated with the cavity;

the shell comprises a first shell layer, a second shell layer and a heat storage medium, the first shell layer is sleeved outside the second shell layer, a gap is formed between the first shell layer and the second shell layer, the heat storage medium is contained in the gap,

the mould includes bottom plate and curb plate, the curb plate encloses to be located around the bottom plate in order to form the storage tank, the heating member includes mutually independent bottom plate heating member and curb plate heating member, the bottom plate heating member set up in the bottom plate deviates from one side of storage tank, the curb plate heating member set up in the curb plate deviates from one side of storage tank.

2. The vacuum furnace of claim 1, further comprising a thermal insulation layer disposed on a side of the second envelope facing away from the gap.

3. The vacuum furnace of claim 1, wherein the mold further comprises graphite paper disposed on a side of the bottom plate and the side plate facing the receiving groove.

4. The vacuum furnace of claim 1, wherein the mold further comprises a plurality of temperature sensors for sensing the temperature of the bottom plate and the side plate, respectively.

5. The vacuum furnace of claim 1, wherein the first and second shells are made of stainless steel.

6. A method for producing a silica glass, characterized by comprising the steps of:

providing a plurality of quartz ingots and a vacuum furnace according to any one of claims 1 to 5;

placing the quartz ingot in the accommodating groove, and pumping out air in the cavity through the vacuum generating device to ensure that the cavity has a vacuum degree;

activating the base plate heating element to cause the base plate heating element to heat the base plate to a first temperature at a first heating rate;

starting the side plate heating element to heat the side plate to the first temperature at a second heating rate, wherein the first heating rate is greater than the second heating rate; and

keeping the temperature of the mold to melt the quartz ingot, and annealing to obtain quartz glass with optical uniformity<1.5×10^-6And the diameter or the diagonal distance of the quartz glass is not less than 1500 mm.

7. The method for producing a silica glass according to claim 6, wherein the degree of vacuum is 0 to 1X 10^-2Pa, the first heating rate is 8-10 ℃/min, the second heating rate is 6-8 ℃/min, and the first temperature is 1700-1750 ℃.

8. The method for producing the silica glass according to claim 6, wherein the heat-retaining time is 4 to 10 hours.

9. The method for producing the silica glass according to claim 6, wherein the annealing includes:

cooling from the first temperature to a second temperature at a first cooling rate for at least 5 hours; and

and cooling from the second temperature to the room temperature at a second cooling rate.

10. The method for producing a silica glass according to claim 9, wherein the first temperature reduction rate is 3 ℃/min to 5 ℃/min, the second temperature reduction rate is less than 3 ℃/min, and the second temperature is 1120 ℃ to 1200 ℃.

Technical Field

The invention relates to the technical field of material preparation, in particular to a vacuum furnace and a quartz glass preparation method.

Background

The preparation method of the quartz glass mainly comprises one-step synthesis methods such as electric melting, gas melting, chemical vapor deposition, plasma vapor deposition and the like, and the one-step synthesis method can only prepare the quartz glassIn the following silica column, it is generally necessary to melt a plurality of silica ingots again to obtain a large silica glass, but the silica glass obtained by melting again is liable to have bubbles, streaks, and the like, resulting in poor optical uniformity.

Disclosure of Invention

In view of the above, there is a need for a silica glass production method that can produce silica glass having a large size and high uniformity.

In addition, the invention also provides a vacuum furnace for preparing the large-size and high-uniformity quartz glass.

A vacuum furnace comprises a shell, a mold, a heating body and a vacuum generating device, wherein the shell is provided with a hollow cavity, the mold and the heating body are contained in the cavity, and the vacuum generating device is communicated with the cavity. The shell comprises a first shell layer, a second shell layer and a heat storage medium, the first shell layer is sleeved on the outer side of the second shell layer, a gap is formed between the first shell layer and the second shell layer, and the heat storage medium is contained in the gap. The mould includes bottom plate and curb plate, the curb plate encloses to be located around the bottom plate in order to form the storage tank, the heating member includes mutually independent bottom plate heating member and curb plate heating member, the bottom plate heating member set up in the bottom plate deviates from one side of storage tank, the curb plate heating member set up in the curb plate deviates from one side of storage tank.

Further, the vacuum furnace further comprises a heat insulation layer, and the heat insulation layer is arranged on one side, away from the gap, of the second shell.

Further, the mould still includes graphite paper, graphite paper set up in the bottom plate reaches the curb plate is towards one side of storage tank.

Further, the mold further comprises a plurality of temperature sensors, and the temperature sensors are respectively used for sensing the temperatures of the bottom plate and the side plates.

Furthermore, the first shell layer and the second shell layer are made of stainless steel.

A method for preparing large-size high-uniformity quartz glass comprises the following steps:

a plurality of quartz ingots and a vacuum furnace as described above are provided.

And placing the quartz ingot in the accommodating groove, and pumping out air in the cavity through the vacuum generating device to ensure that the cavity has a vacuum degree.

The base plate heating element is activated to cause the base plate heating element to heat the base plate to a first temperature at a first heating rate.

Starting the side plate heating element to heat the side plate to the first temperature at a second heating rate, wherein the first heating rate is higher than the second heating rate, and keeping the temperature of the mold to melt the quartz ingot, annealing to obtain quartz glass, and the optical uniformity of the quartz glass<1.5×10^-6And the diameter or the diagonal distance of the quartz glass is not less than 1500 mm.

Further, the vacuum degree is 0-1 x 10^-2Pa, the first heating rate is 8-10 ℃/min, the second heating rate is 6-8 ℃/min, and the first temperature isThe temperature is 1700 ℃ to 1750 ℃.

Further, the heat preservation time is 4-10 h.

Further, the annealing includes: and cooling from the first temperature to a second temperature at a first cooling rate for at least 5 hours, and cooling from the second temperature to room temperature at a second cooling rate.

Further, the first cooling rate is 3 ℃/min to 5 ℃/min, the second cooling rate is less than 3 ℃/min, and the second temperature is 1120 ℃ to 1200 ℃.

The preparation method of the large-size high-uniformity quartz glass provided by the invention has the following advantages: (I): the size of the prepared quartz glass is large, and the distance between two points which are farthest away on the contour line of the quartz glass is as high as 1500 mm; (II): the prepared quartz glass has good optical uniformity and optical uniformity<1.5×10^-6。

Drawings

Fig. 1 is a schematic view of a vacuum furnace according to an embodiment of the present invention.

FIG. 2 is a flow chart of a method for producing the silica glass according to the present invention.

Fig. 3 is a temperature/time diagram of the preparation method shown in fig. 2.

Description of the main elements

Housing 10

Cavity 11

The first shell 12

Second shell 13

Heat storage medium 14

Support rod 15

Gap 16

Mold 20

Bottom plate 21

Side plate 22

Accommodation groove 23

Heating body 30

Floor heating member 31

Side plate heating member 32

Vacuum generating device 40

A heat insulating layer 50

Temperature sensor 60

First temperature T2

Second temperature T1

First time period t1

Second time period t2

Detailed Description

So that the manner in which the above recited objects, features and advantages of embodiments of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. In addition, the features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth to provide a thorough understanding of embodiments of the invention, and the described embodiments are merely a subset of embodiments of the invention, rather than a complete embodiment. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the embodiments of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention.

Referring to fig. 1, the present invention provides a vacuum furnace 100, wherein the vacuum furnace 100 is used for melting a plurality of small-sized quartz ingots (not shown) to obtain larger-sized quartz glass 300. The vacuum furnace 100 includes a housing 10, a mold 20, a heating body 30, and a vacuum generating device 40. The housing 10 has a hollow cavity 11, the mold 20 and the heating body 30 are accommodated in the cavity 11, and the vacuum generating device 40 is disposed outside the cavity 11 and is communicated with the cavity 11.

The shell 10 comprises a first shell layer 12, a second shell layer 13, a heat storage medium 14 and a support rod 15, wherein the first shell layer 12 is sleeved outside the second shell layer 13, the support rod 15 is arranged between the first shell layer 12 and the second shell layer 13 to support the first shell layer 12 and the second shell layer 13, a gap 16 is formed between the first shell layer 12 and the second shell layer 13, the heat storage medium 14 is contained in the gap 16, the heat storage medium 14 is used for storing heat, the influence of the temperature difference of the environment on the temperature in the cavity 11 is reduced, and therefore the stability of the temperature field in the cavity 11 is improved.

The mold 20 comprises a bottom plate 21 and a side plate 22, the side plate 22 is arranged around the bottom plate 21 to form a containing groove 23, the containing groove 23 is used for containing a plurality of small-sized quartz ingots, the heating body 30 comprises a bottom plate heating element 31 and a side plate heating element 32, the bottom plate heating element 31 is arranged on one side of the bottom plate 21 deviating from the containing groove 23, and the side plate heating element 32 is arranged on one side of the side plate 22 deviating from the containing groove 23. The bottom plate heating members 31 and the side plate heating members 32 are independent of each other. The provision of the bottom plate heating member 31 and the side plate heating member 32 facilitates independent control of the temperatures of the bottom plate 21 and the side plate 22, respectively, and contributes to reduction of the streaks of the silica glass 300 and improvement of the optical uniformity. The optical uniformity is the degree of nonuniformity of the refractive index change of each part in the designated area and is expressed by the maximum difference of the refractive index change.

When the vacuum forming device is used specifically, a plurality of small-sized quartz ingots, for example, quartz columns with diameters smaller than 600mm, are firstly placed in the mold 20, and then the air in the cavity 11 is pumped out through the vacuum generating device 40, so that the vacuum degree in the cavity 11 reaches 1 × 10^-2Pa, the vacuum degree in the cavity 11 is set to reach 1 × 10^-2Pa to reduce the viscosity of the melted quartz ingot, and then rapidly raising the temperature of the bottom plate 21 to 1700-1750 ℃ by the bottom plate heating member 31 so that the quartz ingot 200 near the bottom plate 21 is first melted while slowly raising the temperature of the side plate 22 to 1700-1750 ℃ by the side plate heating member 32 so that the quartz ingot 200 near the side plate 22 is closer to the side plate 22 than to the side plateThe quartz ingot 200 of the bottom plate 21 is post-melted, thereby preventing the generation of striae in the quartz glass 300.

In this embodiment, the vacuum furnace 100 further includes a heat insulating layer 50, the heat insulating layer 50 is disposed on the inner side of the second shell 13, the heat insulating layer 50 is used to further enhance the heat insulating performance of the cavity 11, the material of the heat insulating layer 50 is high-purity graphite, and the thickness of the heat insulating layer 50 is 80mm to 150 mm.

In this embodiment, the mold 20 further includes graphite paper (not shown), and the graphite paper is disposed on one side of the bottom plate 21 and the side plate 22 facing the accommodating groove 23. The graphite paper is burnt off in the process of heating the cavity 11, so that the quartz glass 300 is prevented from being adhered to the mold 20.

In this embodiment, the graphite paper is provided with a plurality of ventilation holes (not shown), and the ventilation holes are used for facilitating the quartz ingot 200 to remove the air remained in the melting process, so as to reduce the air bubbles in the finally formed quartz glass 300 and improve the uniformity of the quartz glass 300.

In this embodiment, the mold 20 further includes a plurality of temperature sensors 60, the first shell 12 and the second shell 13 are provided with through holes (not shown) for inserting the temperature sensors 60, and the temperature sensors 60 are used for sensing the temperatures of the bottom plate 21 and the side plates 22. The temperature sensor 60 is a tungsten-rhenium thermocouple.

In this embodiment, the first shell layer 12 and the second shell layer 13 are made of stainless steel of SUS304 or SUS316L, and the heat storage medium 14 is water. In other embodiments of the present invention, the first shell 12 and the second shell 13 may be made of other materials besides stainless steel, such as iron, copper, nickel, etc. In other embodiments of the present invention, the heat storage medium 14 may also be other organic solvents besides water, such as silicon oil.

In this embodiment, the mold 20 is made of isostatic graphite, the thickness of the bottom plate 21 or the side plate 22 is 10 to 15mm, and the diameter or the diagonal distance of the accommodating groove 23 is 1500 mm.

Hereinafter, a method for manufacturing a large-sized, highly uniform silica glass provided in an embodiment of the present invention will be described in detail with reference to the vacuum furnace 100. The order of the steps of the preparation method can be changed according to different requirements, and certain steps can be omitted or combined. The preparation method comprises the following steps:

s1, please refer to FIG. 2 and FIG. 3, providing a plurality of quartz ingots and the vacuum furnace 100, wherein the quartz ingots are quartz columns with a diameter less than 600 mm;

s2, accommodating the quartz ingots in the accommodating grooves, and extracting air in the cavity 11 through the vacuum generating device 40 to ensure that the cavity 11 has a vacuum degree;

s3, starting the bottom plate heating element 31, the bottom plate heating element 31 heating the bottom plate 21 to a first temperature T2 at a first heating rate, and starting the side plate heating element 32, the side plate heating element 32 heating the side plate 22 to the first temperature T2 at a second heating rate, the first heating rate is larger than the second heating rate, and the bottom plate 21 is firstly heated to the first temperature T2 compared with the side plate 22 by setting the first heating rate to be larger than the second heating rate, so that the quartz ingot close to the bottom plate 21 is firstly melted, and then the quartz ingot close to the side plate 22 is melted, and therefore the risk of stripes generated on the quartz glass 300 is reduced;

in this embodiment, in step S3, the vacuum degree is 0-1 × 10^-2Pa, the first heating rate is 8-10 ℃/min, the second heating rate is 6-8 ℃/min, and the first temperature T2 is 1700-1750 ℃. Wherein, under the vacuum degree of 1 x 10 < -2 > Pa and at the temperature of 1700 ℃ to 1750 ℃, the viscosity of the quartz glass is 1 x 102 to 1.5 x 103Pa · s, thereby being beneficial to the flowing and paving in the subsequent quartz glass process.

S4 holding to melt the quartz ingot, annealing to obtain quartz glass with optical uniformity<1.5×10^-6The quartz glass has a diameter or diagonal distance of up to 1500 mm.

In the present embodiment, step S4, step "keep warm to meltThe quartz ingot' comprises: at 0 to 1 × 10^-2And keeping the mold 20 at a first temperature T2 for a first time period T1 under the vacuum degree of Pa, wherein the first time period T1 is 4-10 hours, so as to melt the quartz ingot.

In the present embodiment, in step S4, the step "annealing" includes: at 0 to 1 × 10^-2Pa, the mold 20 is cooled from the first temperature T2 to the second temperature T1 at a first cooling rate, for at least a second time period T2, the second time period T2 is more than 5h, and the temperature is cooled from the second temperature T1 to the room temperature at a second cooling rate.

In this embodiment, the first temperature reduction rate is 3 ℃/min to 5 ℃/min, the second temperature reduction rate is less than 3 ℃/min, and the second temperature T1 is 1120 ℃ to 1200 ℃.

Compared with the prior art, the preparation method of the quartz glass with large size and high uniformity provided by the invention has the following advantages:

(I): the size of the prepared quartz glass is large, and the distance between two points which are farthest away on the contour line of the quartz glass is as high as 1500 mm;

(II): the prepared quartz glass has good optical uniformity and optical uniformity<1.5×10^-6。

An example of the production method of large-size high-uniformity silica glass of the present invention and properties of the silica glass produced by the production method are illustrated below.

Example one

The purity is more than 99.9999 percent, and the hydroxyl content is high<1ppm, diameterHigh-purity quartz ingot with the height of 1000mm is accommodated in the mold 20, and the mold is vacuumized to ensure that the vacuum degree in the cavity 11 is less than or equal to 1 multiplied by 10^-2And Pa, starting the bottom plate heating element 31, heating the bottom plate 21 to 1600 ℃ at 8-10 ℃/min, simultaneously starting the side heating element 32, heating the side plate 22 to 1600 ℃ at 6-8 ℃/min, and keeping the temperature constant for 6h to obtain the square quartz glass with the diagonal distance of 1500 mm. The mold 20 is then placed at 5 deg.C/minThe temperature of the mold 20 is lowered from 1600 ℃ to 1150 ℃ at a constant temperature for 5 hours, so as to eliminate the stress in the quartz glass 300. And finally, cooling the mold 20 from 1150 ℃ to normal temperature at a cooling speed of less than or equal to 3 ℃/min.

Any four points (1#, 2#, 3#, 4#) of the produced large-size quartz glass 300 are detected to obtain five indexes of metal impurity content, hydroxyl content, optical uniformity, stress birefringence, bubbles and gas line grade, which are shown in table 1.

Table 1.

Example two

The purity is more than 99.9999 percent, and the hydroxyl content is high<1ppm, diameterHigh-purity quartz ingot with the height of 1000mm is accommodated in the mold 20, and the mold is vacuumized to ensure that the vacuum degree in the cavity 11 is less than or equal to 1 multiplied by 10^-2Pa, starting the bottom plate heating element 31, heating the bottom plate 21 to 1730 ℃ at 8-10 ℃/min, simultaneously starting the side plate heating element 32, heating the side plate 22 to 1730 ℃ at 6-8 ℃/min, and keeping the temperature constant for 6h to obtain the square quartz glass 300 with the diagonal distance of 1500 mm. Then, the temperature of the mold 20 is reduced from 1600 ℃ to 1150 ℃ at a cooling rate of 5 ℃/min, and the temperature is kept constant for 5h, so that the stress in the quartz glass 300 is eliminated. And finally, cooling the mold 20 from 1150 ℃ to normal temperature at a cooling speed of less than or equal to 3 ℃/min.

Any four points (5#, 6#, 7#, 8#) of the produced large-size quartz glass 300 are detected to obtain five indexes of metal impurity content, hydroxyl content, optical uniformity, stress birefringence, bubbles and gas line grade, which are shown in table 2.

TABLE 2

EXAMPLE III

The purity is more than 99.9999 percent, and the hydroxyl content is high<1ppm, diameterHigh-purity quartz ingot with the height of 1000mm is accommodated in the mold 20, and the mold is vacuumized to ensure that the vacuum degree in the cavity 11 is less than or equal to 1 multiplied by 10^-2And Pa, starting the bottom plate heating element 31, heating the bottom plate 21 to 1750 ℃ at a speed of 8-10 ℃/min, simultaneously starting the side plate heating element 32, heating the side plate 22 to 1750 ℃ at a speed of 6-8 ℃/min, and keeping the temperature constant for 6h to obtain the square quartz glass with the diagonal distance of 1500 mm. Then, the temperature of the mold 20 is reduced from 1600 ℃ to 1150 ℃ at a cooling rate of 5 ℃/min, and the temperature is kept constant for 5h, so that the stress in the quartz glass is eliminated. And finally, cooling the mold 20 from 1150 ℃ to normal temperature at a cooling speed of less than or equal to 3 ℃/min.

Any four points (9#, 10#, 11#, 12#) of the produced large-size quartz glass 300 are detected to obtain five indexes of metal impurity content, hydroxyl content, optical uniformity, stress birefringence, bubbles and gas line grade, which are shown in table 3.

Table 3.

Through the analysis of the processes and the detection results of the first embodiment, the second embodiment and the third embodiment, it can be found that the preparation method of the large-size high-uniformity quartz glass mainly comprises the following steps: heating quartz ingot, high-temperature melting to form large quartz glass, cooling, annealing and destressing quartz glass, wherein the vacuum degree is less than or equal to 1 × 10^-2Pa, and the melting process needs to melt the quartz ingot close to the bottom plate of the mold first and then melt the quartz ingot close to the side plate of the mold. The diagonal distance of the quartz glass prepared by the method is up to 1500mm, and the optical uniformity of the quartz glass<1.5×10^-6。

Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the embodiments of the present invention.