Preparation method of large-proportion pipe and stretching equipment of large-proportion pipe

Abstract

The invention relates to a preparation method and stretching equipment of a large-proportion pipe. The large-proportion pipe is characterized in that the outer diameter / inner diameter of the pipe is larger than 5. The preparation method comprises the following steps: preparing a pure quartz hollow pipe blank by using OVD, carrying out inner and outer diameter grinding processing on the pure quartz hollow pipe blank to obtain a pure quartz hollow sleeve with small wall thickness deviation, drawing the pure quartz hollow sleeve into a pure quartz pipe by using a vertical melting and drawing device, vacuumizing in the drawing process, and giving a certain relative vacuum degree to obtain the pure quartz pipe. And controlling the ratio of the pipe to the outer diameter / inner diameter to be more than 5. The pure quartz hollow tube blank is prepared through the OVD technology, the requirement for high purity of the quartz tube material is met, the hydroxyl content is low, the machining efficiency is high, and the manufacturing cost is low; the vertical melting and stretching equipment is simple and reasonable in structural arrangement, the annular thermal field is uniformly distributed, and the drawing processing quality of the pure quartz pipe is ensured; and meanwhile, the ratio of the outer diameter to the inner diameter is changed and controlled through the vacuumizing function of the vertical melting and stretching equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber preform rod and quartz tube preparation, and in particular relates to a preparation method of a large-proportion tube and a stretching device thereof. Background Art

[0002] Pure quartz tubes have been widely used in the field of optical fiber preform production. Pure quartz tubes with large proportions are usually made by stretching quartz tube embryos under high temperature melting. Compared with normal pressure and positive pressure stretching, large proportion tubes must be stretched and prepared under vacuum pump negative pressure conditions. The outer diameter of a normal quartz tube embryo is 210mm, the inner diameter is 49mm, and the outer diameter / inner diameter ratio is equal to 4.2. Under normal pressure-free stretching conditions, the outer diameter / inner diameter ratio of the stretched tube is also close to 4.2. Under the condition of blowing in the tube, the outer diameter / inner diameter of the drawn tube is less than or equal to the outer diameter / inner diameter of the parent material before drawing, that is, under normal pressure or positive pressure conditions, the outer diameter / inner diameter ratio of the tube cannot be increased. When it is necessary to increase the outer diameter / inner diameter ratio of the tube, it is necessary to achieve negative pressure inside the tube during the stretching process. Negative pressure is generally used in the optical fiber drawing process. During the optical fiber drawing process, the core rod and the sleeve are melted together under negative pressure conditions to draw into optical fiber. The negative pressure of the wire drawing process is generally -990mbar relative pressure and constant pressure. Under the negative pressure of -990mbar, the stretched pipe is easy to melt. In order to achieve a certain proportion of pipes, it is necessary to change the outer diameter / inner diameter ratio of the stretched pipe under specific negative pressure conditions. The specific negative pressure requires stable and reliable pressure conditions. The pipe drawing process also requires a stable and controllable outer diameter control program. The corresponding control logic program needs to be matched to stabilize the outer diameter and inner diameter of the pipe. Summary of the invention

[0003] The technical problem to be solved by the present invention is to propose a preparation method and stretching equipment for large-ratio tubes in view of the deficiencies in the above-mentioned prior art. The method can improve and increase the ratio of the outer diameter / inner diameter of the drawn quartz tube by vacuuming, and the structure of the processing equipment is simple and reasonable, which is convenient for industrialization.

[0004] The technical solution of the preparation method adopted by the present invention to solve the above-mentioned problem is:

[0005] A method for preparing a large-scale pipe, characterized in that it comprises the following steps:

[0006] S1. First, prepare a pure quartz hollow tube blank by OVD;

[0007] S2. Grinding the inner and outer diameters of the pure quartz hollow tube blank to produce a pure quartz hollow sleeve with a small wall thickness deviation;

[0008] S3. Through vertical melt stretching equipment, under the condition of negative pressure inside the pure quartz hollow sleeve, the pure quartz hollow sleeve is stretched and contracted into a pure quartz large-proportion tube.

[0009] According to the above technical solution, in step S3, the vacuum degree in the pure quartz hollow sleeve is controlled by the vacuum pump negative pressure control device, and the pressure in the pure quartz hollow sleeve is pumped into negative pressure by controlling the vacuum pump to run at a fixed frequency and fully open, and the vacuum degree in the pure quartz hollow sleeve is controlled by the control valve, wherein the ratio of the outer diameter to the inner diameter of the pure quartz large-proportion tube to the pressure in the tube is:

[0010] OD1 / ID1=OD2 / ID2-95.33*P-101.4;

[0011] Among them, OD1 is the outer diameter of the pure quartz hollow sleeve, ID1 is the inner diameter of the pure quartz hollow sleeve, OD2 is the outer diameter of the pure quartz large-proportion tube, ID2 is the inner diameter of the pure quartz large-proportion tube, and P is the pressure inside the pure quartz hollow sleeve.

[0012] According to the above technical solution, in step S2, the outer diameter of the pure quartz hollow sleeve is processed to ≥210 mm, the inner hole diameter is processed to 43-52 mm, and the single-side tube wall thickness deviation is ≤0.45 mm.

[0013] According to the above technical solution, the outer diameter of the pure quartz tube is 10-50 mm, the outer diameter / inner diameter>5, the ovality is ≤0.15 mm, and the single-side tube wall thickness deviation is ≤0.15 mm.

[0014] A vertical melt stretching device for processing large-proportion pipes includes a vertical furnace body, a cylindrical heating element is arranged inside the furnace body, a traction wheel for pulling pure quartz large-proportion pipes is arranged below the furnace body corresponding to the lower end of the furnace outlet, and a clamping rod device for clamping pure quartz hollow sleeves is arranged above the furnace body at the upper end of the furnace outlet. The upper end of the pure quartz hollow sleeve is sealed and connected to a vacuum pump negative pressure control device through a pipeline. The vacuum pump negative pressure control device includes a vacuum pump and a differential pressure gauge arranged on the pipeline for monitoring the pressure inside the pure quartz hollow sleeve, and a control valve arranged between the differential pressure gauge and the vacuum pump and used to control the opening size of the vacuum pump.

[0015] According to the above technical scheme, in the vacuum pump negative pressure control device, the vacuum pump is operated at full speed at a fixed frequency to evacuate the pressure in the pipeline to negative pressure, and the vacuum degree in the pipeline is controlled by a butterfly valve. The butterfly valve is associated with a differential pressure gauge to control the vacuum degree required for a large proportion of pipes.

[0016] According to the above technical solution, the cylindrical heater includes a graphite heating tube installed above the furnace body, the outer periphery of the graphite heating tube is covered with a thermal insulation layer, and an induction coil is installed outside the thermal insulation layer.

[0017] According to the above technical solution, the inner diameter of the graphite heating tube is 240-300 mm, and the axial height is 500-800 mm; the inner diameter of the induction coil is 300-400 mm, and the axial height is 300-400 mm.

[0018] According to the above technical solution, the traction wheel comprises a pair of traction wheels with parallel axles that rotate at the same speed and in opposite directions, and a radial constant pressure device is installed between the pair of traction wheels.

[0019] According to the above technical solution, the heating temperature of the cylindrical heating element is 1900-2100°C, the traction line speed of the traction wheel is 500-800mm / min; the sealing air ring is connected to the inert pressure air source; and the clamping rod device is connected to the lifting mechanism.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention first prepares a pure quartz hollow tube blank through the OVD process, which not only ensures the high purity requirement of the quartz tube material and low hydroxyl content, but also has high processing efficiency and low production cost; then, the pure quartz hollow tube blank is ground with inner and outer diameters to make it a pure quartz hollow sleeve with good geometric dimensions and small wall thickness deviation, which lays a good foundation for the next step of contactless melt stretching; the drawn pure quartz large-scale tube has high geometric accuracy, ellipticity and wall deviation parameters, which effectively improves the processing accuracy of contactless preparation and stretching of pure quartz tubes; under the cooperation of a vacuum pump and a control valve, a specified negative pressure is provided, and a PID control program of the joint pressure and outer diameter / inner diameter is used, which can effectively stabilize the pressure and the outer diameter / inner diameter of the tube, and stretch out a tube with an outer diameter / inner diameter greater than 3 that meets the requirements.

[0022] 2. The vertical melt stretching equipment of the present invention has a simple and reasonable structure, uniform annular heat field distribution, improved tube geometric parameters, and guaranteed the drawing processing quality of pure quartz tubes.

[0023] 3. The vacuum pumping system of the present invention has a vacuum pump negative pressure control device. The vacuum pump runs at a fixed frequency and fully open to evacuate the pressure in the pipeline to a negative pressure. The vacuum degree in the pipeline is controlled by a butterfly valve. The butterfly valve is associated with a differential pressure gauge to control the vacuum degree required for large-proportion pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1It is a front sectional structural diagram of the vertical melt stretching equipment provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0028] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0030] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0031] This embodiment provides a method for preparing a large-scale pipe, comprising the following steps:

[0032] S1. First, a pure quartz hollow tube blank is prepared by OVD, wherein the hydroxyl content of the pure quartz hollow tube blank is ≤1ppm by weight;

[0033] S2, grinding the inner and outer diameters of the pure quartz hollow tube blank to produce a pure quartz hollow sleeve with a small wall thickness deviation, wherein the inner and outer diameter grinding includes rough grinding of the outer diameter and the inner hole, and then fine grinding of the outer diameter and the inner hole; specifically, the outer diameter of the pure quartz hollow sleeve is processed to ≥210mm, the inner hole diameter is processed to 43-52mm, and the single-side tube wall thickness deviation is ≤0.45mm;

[0034] S3. Through the vertical melt stretching equipment, under the condition of negative pressure in the pure quartz hollow sleeve, the pure quartz hollow sleeve is stretched and contracted into a pure quartz large-proportion tube. Specifically, the vacuum degree in the pure quartz hollow sleeve needs to be controlled by the vacuum pump negative pressure control device. By controlling the vacuum pump to run at full speed at a fixed frequency, the pressure in the pure quartz hollow sleeve is pumped into negative pressure. The vacuum degree in the pure quartz hollow sleeve is controlled by the control valve. The relationship between the ratio of the outer diameter to the inner diameter of the pure quartz large-proportion tube and the pressure in the tube is:

[0035] OD1 / ID1=OD2 / ID2-95.33*P-101.4;

[0036] In the above formula, OD1 is the outer diameter of the pure quartz hollow sleeve, ID1 is the inner diameter of the pure quartz hollow sleeve, OD2 is the outer diameter of the pure quartz large-scale tube, ID2 is the inner diameter of the pure quartz large-scale tube, and P is the pressure inside the pure quartz hollow sleeve. Among them, the speed of the large-scale tube stretching process is constant, and the linear speed range is between 2.0mm / s and 5mm / s, but the linear speed still needs to be fine-tuned, and the speed adjustment range is ±5% of the normal speed to stabilize the outer diameter.

[0037] The outer diameter of the pure quartz large-proportion tube is 10-50 mm, the outer diameter / inner diameter>5, the ovality is ≤0.15 mm, and the single-side tube wall thickness deviation is ≤0.15 mm.

[0038] Specific examples:

[0039] First, a pure quartz hollow tube blank is prepared by OVD (external vapor deposition method), the material purity is high, and the hydroxyl content is 0.6ppm (wt), and then the pure quartz hollow tube blank is subjected to inner and outer diameter grinding, the inner and outer diameter grinding includes rough grinding of the outer diameter and the inner hole, and then fine grinding of the outer diameter and the inner hole is performed to process the outer diameter size to 210mm and the inner hole diameter to 43mm of the pure quartz hollow sleeve; finally, the pure quartz hollow sleeve is drawn into a pure quartz tube by a vertical melt stretching device, and the drawn pure quartz tube has an outer diameter range of 30mm, a wall thickness of 10mm, an ellipticity of 0.15mm, and a wall offset of 0.15mm. The detailed parameters of the tube are shown in Table 1 (Table 1 is the data after the test), and Table 2 is the process condition data of the stretching.

[0040] Table 1: Detailed parameters of pipes (unit: mm)

[0041] Tube No. outer diameter inner diameter Wall thickness Roundness Partial wall A 30.22 6.14 12.04 0.11 0.08 B 29.88 5.62 12.13 0.08 0.07 C 30.18 4.98 12.60 0.08 0.08 D 30.22 4.21 13.01 0.07 0.09 E 30.08 3.31 13.39 0.06 0.07

[0042] Table 2: Tensile conditions and geometric relationships

[0043]

[0044] In addition, if Figure 1 As shown, this embodiment also provides a vertical melt stretching device for processing large-scale pipes, including a vertical furnace body 4, a cylindrical heating element 6 is installed inside the furnace body, a sealing gas ring 7 is installed at the upper end of the cylindrical heating element 6, a through hole corresponding to the inner hole of the graphite heating sleeve is opened in the middle of the sealing gas ring 7, and an annular stop is provided on the lower end face of the sealing gas ring 7, the inner hole and inner end face of the annular stop are configured with the cylindrical heating element 6, the outer periphery of the sealing gas ring 7 is configured with the furnace hole of the top cover plate of the furnace body 4, and the sealing gas ring 7 is connected to the inert pressure gas source. A traction wheel 2 for pulling a large-scale pure quartz pipe 3 is installed at the bottom of the furnace body corresponding to the lower end outlet, and a clamping rod device for clamping a pure quartz hollow sleeve 1 is installed at the upper end of the furnace mouth above the furnace body, and the clamping rod device is connected to the lifting and rotating mechanism. The upper end of the pure quartz hollow sleeve is sealed and connected to the vacuum pump negative pressure control device through a pipeline. The vacuum pump negative pressure control device includes a vacuum pump and a differential pressure gauge arranged on the pipeline for monitoring the pressure inside the pure quartz hollow sleeve, and a control valve arranged between the differential pressure gauge and the vacuum pump and used to control the opening size of the vacuum pump.

[0045] In this embodiment, the cylindrical heater comprises a graphite heating tube installed above the furnace body, the outer periphery of the graphite heating tube is covered with a thermal insulation layer 5, and an induction coil is installed outside the thermal insulation layer 5. The inner diameter of the graphite heating tube is 240-300 mm, preferably 280 mm, and the axial height is 500-800 mm, preferably 600 mm. The inner diameter of the induction coil is 300-400 mm, preferably 350 mm, and the axial height is 300-400 mm, preferably 380 mm.

[0046] In this embodiment, the traction wheel 2 includes a pair of traction wheels with parallel axles that rotate at equal speeds in opposite directions. A radial constant pressure device is installed between the pair of traction wheels. The constant pressure traction wheel can stably output pressure, provide power for stretching the pipe, and stretch the pipe out of the hot zone.

[0047] In this embodiment, the heating temperature of the cylindrical heater is 1900-2100°C, the traction line speed of the traction wheel is 500-800 mm / min; the sealing air ring is connected to the inert pressure air source; and the clamping rod device is connected to the lifting mechanism.

[0048] In this embodiment, the vacuum pressure of the vacuum pump negative pressure control device is controlled by a PID control program. The lower the vacuum pressure, the smaller the outer diameter of the pipe. During the stable stretching process, the control of the outer diameter is achieved by adjusting the pressure slightly. Among them, the control valve of this embodiment uses a butterfly valve, which can automatically control the opening. Different openings correspond to different pressures, and the pressure is controlled by the butterfly valve.

[0049] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A method for preparing a large-scale pipe, characterized in that: The steps include: S1. First, prepare a pure quartz hollow tube blank by OVD; S2. Grinding the inner and outer diameters of the pure quartz hollow tube blank to produce a pure quartz hollow sleeve with a small wall thickness deviation; S3. Through vertical melt stretching equipment, under the condition of negative pressure inside the pure quartz hollow sleeve, the pure quartz hollow sleeve is stretched and contracted into a pure quartz large-proportion tube.

2. The method for preparing a large-proportion pipe according to claim 1, characterized in that: In step S3, the vacuum degree in the pure quartz hollow sleeve is controlled by the vacuum pump negative pressure control device, and the pressure in the pure quartz hollow sleeve is pumped into negative pressure by controlling the vacuum pump to run at a fixed frequency and fully open, and the vacuum degree in the pure quartz hollow sleeve is controlled by the control valve, wherein the relationship between the ratio of the outer diameter to the inner diameter of the pure quartz large-proportion tube and the pressure in the tube is: OD1 / ID1=OD2 / ID2-95.33*P-101.4; Among them, OD1 is the outer diameter of the pure quartz hollow sleeve, ID1 is the inner diameter of the pure quartz hollow sleeve, OD2 is the outer diameter of the pure quartz large-proportion tube, ID2 is the inner diameter of the pure quartz large-proportion tube, and P is the pressure inside the pure quartz hollow sleeve.

3. The method for preparing a large-ratio pipe according to claim 1 or 2, characterized in that: In step S2, the outer diameter of the pure quartz hollow sleeve is processed to be ≥210 mm, the inner hole diameter is processed to be 43-52 mm, and the single-side tube wall thickness deviation is ≤0.45 mm.

4. The method for preparing a large-ratio pipe according to claim 1 or 2, characterized in that: The outer diameter of pure quartz tube is 10-50mm, the outer diameter / inner diameter>5, the ovality ≤0.15mm, and the single-side tube wall thickness deviation ≤0.15mm.

5. A vertical melt-stretching device for processing large-scale pipes, characterized in that: The utility model comprises a vertical furnace body, wherein a cylindrical heating element is arranged inside the furnace body, a traction wheel for pulling a large-proportion pure quartz pipe is arranged below the furnace body corresponding to the lower end furnace outlet, and a clamping rod device for clamping a pure quartz hollow sleeve is arranged above the furnace body at the upper end of the furnace outlet, and the upper end of the pure quartz hollow sleeve is sealedly connected to a vacuum pump negative pressure control device through a pipeline, and the vacuum pump negative pressure control device comprises a vacuum pump and a differential pressure gauge arranged on the pipeline for monitoring the pressure inside the pure quartz hollow sleeve, and a control valve arranged between the differential pressure gauge and the vacuum pump and used for controlling the opening size of the vacuum pump.

6. The vertical melt-stretching equipment for large-scale pipes according to claim 5, characterized in that: The vacuum pump negative pressure control device operates the vacuum pump at a fixed frequency and fully open to pump the pressure in the pipeline into negative pressure. The vacuum degree in the pipeline is controlled by a butterfly valve. The butterfly valve is associated with a differential pressure gauge to control the vacuum degree required for a large proportion of pipes.

7. The vertical melt-stretching equipment for large-scale pipes according to claim 5, characterized in that: The cylindrical heater comprises a graphite heating tube arranged above the furnace body, the outer periphery of the graphite heating tube is covered with a heat preservation layer, and an induction coil is arranged outside the heat preservation layer.

8. The vertical melt-stretching equipment for large-scale pipes according to claim 6, characterized in that: The inner diameter of the graphite heating tube is 240-300 mm, and the axial height is 500-800 mm; the inner diameter of the induction coil is 300-400 mm, and the axial height is 300-400 mm.

9. The vertical melt-stretching equipment for large-ratio pipes according to claim 6 or 7, characterized in that: The traction wheel comprises a pair of traction wheels with parallel axles and constant speed counter-rotating traction wheels, and a radial constant pressure device is arranged between the pair of traction wheels.

10. The vertical melt-stretching equipment for large-ratio pipes according to claim 6 or 7, characterized in that: The heating temperature of the cylindrical heating element is 1900-2100°C, the traction line speed of the traction wheel is 500-800mm / min; the sealing air ring is connected to the inert pressure air source; the clamping rod device is connected to the lifting mechanism.

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