Optical fiber cable, preparation method and extrusion coating machine for preparing optical fiber cable

Abstract

The invention discloses an optical fiber cable, a preparation method and an extrusion cladding machine for preparing the optical fiber cable, the optical fiber cable comprises an optical unit, a sheath layer and an outer coating aluminum layer which are sequentially arranged from inside to outside, and the outer coating aluminum layer is formed by cladding aluminum on the surface of the sheath layer through an extrusion cladding process. During preparation, firstly, the optical unit is provided, then the aluminum-clad steel wire stranded layer can be additionally arranged between the optical unit and the sheath layer as required, then the sheath layer is prepared, and finally, the surface of the sheath layer is coated with aluminum by using an extrusion coating process to form the outer coating aluminum layer, so that the optical fiber cable is obtained. And the extrusion cladding machine is used for preparing an aluminum-clad steel wire or preparing an outer coating aluminum layer on the surface of the sheath layer. The invention also discloses an optical fiber cable preparation method and an extrusion coating machine for optical fiber cable preparation. The mechanical performance and the corrosion resistance of the optical cable are improved, the service life of the optical cable is prolonged, the production cost is reduced, and the product competitiveness is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical cables, and in particular relates to an optical fiber cable, a preparation method and an extrusion coating machine for preparing the optical fiber cable. Background Art

[0002] Special optical cables usually need to withstand extreme environments, such as high temperature, high pressure, and high hydrogen sulfide or other corrosive gases in oil and gas wells. High temperature environment will accelerate the aging of ordinary optical fiber and fiber paste, resulting in fiber breakage. Hydrogen molecules can diffuse into the fiber glass core, react chemically with the core defects to produce hydroxide ions, or remain in the core in a molecular state. The above phenomena are ultimately reflected in the increase of optical fiber attenuation due to the presence of hydrogen in the environment, which is called "hydrogen loss" in the field of optical fiber.

[0003] Existing oil well optical cables use stainless steel pipes as anti-corrosion layers. Stainless steel pipes are generally made of 304 or 316L materials. This material selection has low cost, but its corrosion resistance is weak in long-term high temperature and high pressure environments. 825 high nickel alloy material is selected, which has better corrosion resistance in long-term high temperature and high pressure environments, but its cost is 8 to 10 times that of 304 and 316L materials. At the same time, the processing difficulty and cost of 825 high nickel alloy steel pipes are much higher than those of 316L and 304. Summary of the invention

[0004] The object of the present invention is to provide an optical fiber cable with high corrosion resistance in view of the above technical problems.

[0005] Another object of the present invention is to provide a method for preparing an optical fiber cable, which has low difficulty in preparing the optical fiber cable and has strong corrosion resistance.

[0006] Another object of the present invention is to provide an extrusion coating machine for preparing optical fiber cables, which can prepare an outer aluminum coating layer for optical cables with strong corrosion resistance.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an optical fiber cable, comprising an optical unit, a sheath layer and an outer aluminum coating layer arranged in sequence from inside to outside, wherein the outer aluminum coating layer is formed by coating aluminum on the surface of the sheath layer through an extrusion coating process.

[0008] Preferably, an aluminum-clad steel wire twisted layer is provided between the optical unit and the sheath layer, and the aluminum-clad steel wire twisted layer is formed by coating aluminum on the surface of steel wires through an extrusion coating process and then twisting the aluminum-clad steel wires.

[0009] Preferably, the sheath layer is made of stainless steel tube with an outer diameter of 4~10 mm and a wall thickness of 0.4~2 mm; the thickness of the outer aluminum coating layer is 0.1~2 mm, and / or, in the aluminum-clad steel wire twisted layer, the aluminum-clad steel wire includes a steel wire and an aluminum coating layer coated on the surface of the steel wire, wherein the outer diameter of the steel wire is 0.5~2.0 mm, and the thickness of the aluminum coating layer is 0.1~1.5 mm.

[0010] Preferably, the sheath layer is a stainless steel tube made of 304, 316L, 625 or 825 material.

[0011] Preferably, in the aluminum-clad steel wire twisted layer, the coverage rate of the aluminum-clad steel wire reaches 95-100%.

[0012] Preferably, the number of twisted wires in the aluminum-clad steel wire twisted layer is 8 to 15.

[0013] Preferably, in the aluminum-clad steel wire twisted layer, the outer diameter after twisting needs to be controlled to ≤4.9 mm.

[0014] In another aspect, the present invention provides a method for preparing an optical fiber cable, comprising the following steps: providing a light unit; forming a sheath layer outside the light unit; The aluminum layer is coated on the surface of the sheath layer through the extrusion coating process to form an aluminum layer on the outside of the steel pipe.

[0015] Preferably, a method for preparing an optical fiber cable further comprises the steps of: The extrusion coating process is used to coat the surface of the steel wire with aluminum to form aluminum-clad steel wire; The aluminum-clad steel wires are twisted on the surface of the optical unit by adopting a twisting process to form an aluminum-clad steel wire twisted layer on the surface of the optical unit.

[0016] Preferably, the optical unit includes a stainless steel pipe and a plurality of optical fibers located in the stainless steel pipe. Specifically, the optical unit is obtained by using a roll forming process to wrap the optical fibers and related fillers with a corrosion-resistant stainless steel tape.

[0017] Preferably, in the extrusion coating process, the inner cavity pressure of the diverter die of the extrusion coating machine is not greater than 700 MPa, and the temperature of the diverter cavity is 470-530°C.

[0018] Preferably, in the extrusion coating process, the pulling speed of the wire and the rotation speed of the extrusion wheel are controlled to meet the following conditions: , where v is the wire pulling speed (m / min), r is the speed of the extrusion wheel (rpm), K is the coefficient, K is 0.2~0.4, S1 is the cross-sectional area of ​​the aluminum layer formed after the wire is coated with aluminum (mm 2 ), S2 is the cross-sectional area of ​​the aluminum rod (mm 2 ); and / or, before the outer aluminum layer is coated by the extrusion coating process, the splitter die and the jacket layer are preheated respectively, the preheating temperature of the splitter die is controlled to be 420-450° C., and the preheating temperature of the jacket layer is controlled to be 280-320° C.; And / or, before the aluminum-clad steel wire is produced through the extrusion coating process, the splitter die and the steel wire are preheated respectively, the preheating temperature of the splitter die is controlled to be 410°C to 430°C, and the preheating temperature of the steel wire is controlled to be 260°C to 300°C.

[0019] Preferably, in the process of realizing the outer aluminum coating by the extrusion coating process, the rotation speed of the extrusion wheel is 4-12 rpm, the pulling speed of the sheath is 20-70 m / min, and the diameter of the aluminum rod is 7-9 mm; And / or, in the process of realizing aluminum-clad steel wire through extrusion coating process, the rotation speed of the extrusion wheel is 4~12 rpm, the pulling speed of the steel wire is 40~120 m / min, and the diameter of the aluminum rod is 7~9 mm.

[0020] Preferably, the sheath layer is made of stainless steel tube, and during the aluminum coating process on the surface of the sheath layer, the thickness of the aluminum layer is controlled to be 0.1-2 mm by the outer diameter of the die.

[0021] Preferably, the outer diameter of the steel wire is 0.5-2.0 mm, and during the aluminum coating process on the surface of the steel wire, the thickness of the aluminum layer is controlled to be 0.1-1.5 mm by the outer diameter of the die.

[0022] Preferably, in the twisting process, the number of twisted aluminum-clad steel wires is 8 to 15; and the coverage of the aluminum-clad steel wires is 95% to 100%.

[0023] On the other hand, the present invention provides an extrusion coating machine for coating an aluminum layer on the surface of a wire in the process of preparing an optical cable, comprising: Splitting die: The splitting die includes a splitting cavity and a feed port at the bottom of the splitting cavity; Extrusion wheel: The extrusion wheel is located below the diverter die. A groove is provided on the outer circumferential surface of the extrusion wheel along the rotation direction of the extrusion wheel. The groove is connected with the inner cavity of the diverter die through the feed port of the diverter die. Stopper: fixed on the lower side of the feed port of the diverter die, corresponding to the groove of the extrusion wheel, to prevent the billet from continuing to move along the circumferential direction of the groove, and to guide the extruded billet upward into the feed port of the diverter die.

[0024] Preferably, the width of the groove of the extrusion wheel is 6-7.5 mm, and the diameter of the feed port of the diverter die is 10-12 mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, an aluminum layer is coated on the outer surface of the sheath layer, which is specifically achieved by adopting an improved continuous coating extrusion process. The outer aluminum layer is used as the outermost layer. The aluminum oxide on the surface of the outer aluminum layer has good chemical stability, which can improve the corrosion resistance of the oil well optical cable. Compared with the outermost layer of the 825 material sheath layer, the present invention can coat an aluminum layer on the 316L material sheath layer with lower processing and material costs, and achieve the same good long-term corrosion resistance as the 825 material sheath layer. The comprehensive cost is about 1 / 8 of that of the 825 material.

[0026] (2) Since the present invention coats an outer aluminum coating layer on the outside of the sheath, it has a dense structure, thereby improving the air tightness of the optical cable and strengthening the isolation effect against hydrogen penetration.

[0027] (3) The present invention sets an aluminum-clad steel wire twisted layer between the optical unit and the sheath layer. The twisted layer is composed of aluminum-clad steel wires twisted together. The strength of the aluminum-clad steel wires reaches the gigapascal level, which significantly improves the overall mechanical strength of the optical cable. Even if the sheath layer encounters related mechanical damage and causes it to break and fail, this design will continue to protect the mechanical stability and communication stability of the optical unit. In the case of sheath damage and failure, the outer aluminum coating will also fail. At this time, the aluminum-clad steel wire twisted layer is coated with an aluminum layer on the outside of the steel wire, which ensures that after the outer anti-corrosion layer steel pipe fails, the twisted layer still has good corrosion resistance. Therefore, the structural safety of the inner layer is greatly improved, which corresponds to more stable and long-lasting use in actual use.

[0028] (4) In the optical fiber cable preparation process of the present invention, the inner cavity pressure of the diverter die of the extrusion coating machine that controls the extrusion coating process is no more than 700 Mpa, which can achieve successful aluminum coating on the outer surface of a 0.5-2.0 mm thin steel wire and the outer surface of a 4-10 mm outer diameter and 0.4-2 mm thick steel pipe. During the extrusion coating process, the steel wire and the thick-walled steel pipe can withstand the pressure during the extrusion process and be successfully coated.

[0029] (5) In the present invention, the traction speed and the rotation speed of the extrusion wheel meet , where v is the wire pulling speed (m / min), r is the speed of the extrusion wheel (rpm), K is the coefficient, K is 0.2~0.4, S1 is the cross-sectional area of ​​the aluminum layer formed after the wire is coated with aluminum (mm 2 ), S2 is the cross-sectional area of ​​the aluminum rod (mm 2); the coverage rate of the aluminum coating layer on the steel wire and the bonding strength of the aluminum layer to the steel wire sheath can be achieved during the coating process, wherein the extrusion wheel rotation speed and the aluminum rod cross-sectional area S2 determine the total mass of the aluminum material entering per unit time, the corresponding aluminum layer cross-sectional area S1 after coating, and the traction speed determine the extrusion mass of the aluminum material per unit time. Under the action of the above formula and the corresponding coefficient K, it can be ensured that the aluminum layer has a high coverage rate on the steel wire or steel pipe sheath without any related abnormal conditions such as exposed steel, and at the same time, the aluminum material will be more tightly bonded to the cavity per unit time.

[0030] (6) In the present invention, in the process of realizing the outer aluminum coating by extrusion coating process, the rotation speed of the extrusion wheel is 4-12 rpm, the pulling speed of the sheath is 20-70 m / min, and the diameter of the aluminum rod is 7-9 mm; and / or, in the process of realizing aluminum-clad steel wire by extrusion coating process, the rotation speed of the extrusion wheel is 4-12 rpm, the pulling speed of the steel wire is 40-120 m / min, and the diameter of the aluminum rod is 7-9 mm. The above parameters can achieve high stability of aluminum extrusion in the process of coating steel wire or steel pipe, avoiding problems such as pipe breakage and extrusion fluctuation.

[0031] (7) In the extrusion coating machine of the present invention, the diverter die includes a diverter cavity and a feed port at the bottom of the diverter cavity. The extrusion wheel is located below the diverter die. A groove is provided on the outer circumferential surface of the extrusion wheel along the rotation direction of the extrusion wheel. The groove is connected to the inner cavity of the diverter die through the diverter die feed port. The stopper is fixed on the lower side of the diverter die feed port, corresponding to the groove of the extrusion wheel, to prevent the blank from continuing to move along the circumferential direction of the groove, and is used to extrude the blank upward into the diverter die feed port. The above structure ensures the stability of the aluminum material pressure during the extrusion of the aluminum rod by the extrusion wheel, thereby ensuring the mechanical stability of the wire to be coated, wherein the groove notch width of the extrusion wheel is 6-7.5 mm, and the feed port diameter of the diverter die is 10-12 mm. The purpose is to control the amount of aluminum material entering per unit time, and then combine relevant parameters to make the inner cavity pressure of the diverter cavity not greater than 700 Mpa.

[0032] (8) The structure of the present invention has high compatibility. After the aluminum layer is coated, the subsequent outer sheath packaging can continue to play a relevant protective role. The relevant high-temperature resistant sheath can protect the state of the optical cable during the construction process. When used at a temperature of 200~300℃, it can play a good effect in the short term. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram (cross section) of optical fiber cable according to embodiment 1 of the present invention.

[0034] Figure 2 Schematic diagram (cross section) of optical fiber cable according to embodiment 2 of the present invention.

[0035] Figure 3 This is a schematic diagram of the single-layer aluminum-clad steel wire twisted layer structure in Example 2 of the present invention.

[0036] Figure 4 This is a schematic diagram of the double-layer aluminum-clad steel wire twisted layer structure in Example 2 of the present invention.

[0037] Figure 5 This is a schematic diagram of the cross-section of the aluminum-clad steel wire in Example 2 of the present invention.

[0038] Figure 6 This is a process flow chart for preparing optical fiber cables in Example 3 of the present invention.

[0039] Figure 7 This is a process flow chart for preparing optical fiber cables in Example 4 of the present invention.

[0040] Figure 8 This is a working principle diagram of the extrusion coating machine in Example 5 of the present invention.

[0041] Fig. 9 Schematic diagram of the flow splitter in Example 5 of the present invention, Figure 8 The schematic diagram is cut at the center line a.

[0042] Fig.10 This is a schematic diagram of the extrusion wheel in Example 5 of the present invention.

[0043] 100-optical unit, 110-optical fiber, 120-fiber paste, 130-stainless steel pipe; 200-aluminum clad steel wire stranded layer, 210-aluminum clad steel wire, 211-steel wire, 212-aluminum coating layer; 300-sheath layer, 400-outer aluminum coating layer; 600-extrusion coating machine, 610-coating cavity, 620-punch, 630-die, 640-stopper, 650-aluminum rod, 660-diverter die, 661-diverter cavity, 662-feed port, 670-extrusion wheel, 671-groove. DETAILED DESCRIPTION

[0044] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" 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 an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Example 1: Figure 1 As shown, the present invention provides an optical fiber cable, comprising: an optical unit 100 , a sheath layer 300 and an outer aluminum coating layer 400 .

[0048] The optical unit 100 is used to transmit an optical signal; it can be any optical unit in the prior art, for example, Figure 1 As shown, the present invention provides a preferred solution, the optical unit 100 includes a stainless steel tube 130 and a plurality of optical fibers 110 located in the stainless steel tube 130, and the material of the stainless steel tube 130 is 316L, 304, 825, 625 or other materials, taking into account the requirements of cost and protection capability. The outer diameter of the stainless steel tube 130 is preferably 1.5~3.0 mm, and the wall thickness of the steel tube is 0.1~0.5 mm; it not only meets the protection requirements, but also has a certain flexibility under the length scale of the optical fiber 110, and has good protection capability. For the optical unit 100, the fiber paste 120 can be filled between the optical fiber 110 and the stainless steel tube 130 as needed. Exemplarily, the fiber paste 120 is a high temperature resistant fiber paste or aramid, which plays the role of protecting the optical fiber connection, reducing reflection loss, compensating for optical fiber dislocation, protecting the core surface, providing a stable environment, waterproofing and moisture-proofing, etc., and can increase the service life of the optical fiber.

[0049] The sheath layer 300 is coated on the optical unit 100, provides the optical unit 100 with the main mechanical properties and corrosion resistance protection, and is also the main pressure-resistant layer; the sheath layer 300 is a stainless steel tube that is resistant to high temperature, corrosion and high pressure, and the material of the stainless steel tube can be selected from 316L, Inconel 625 or Incoloy 825, etc. Among them, the Incoloy 825 material corresponds to the application scenario of 300°C and above in a high temperature environment, and its comprehensive performance such as corrosion resistance is better, but the cost is high; 316L has a lower cost and better performance. Compared with the Incoloy 825 material, its corrosion resistance under high temperature and high pressure conditions is slightly weaker. Considering the cost and performance issues, 316L stainless steel material can be used; Generally speaking, when the outer diameter of the sheath layer 300 is 4~10 mm and the wall thickness is 0.4~2.0 mm, the strength of the above materials is sufficient to meet the use requirements, for example, in a high temperature and high pressure environment exceeding 200°C and 50 Mpa, it still has a good service life.

[0050] The outer aluminum coating layer 400 is coated on the sheath layer 300, which further improves the mechanical strength, corrosion resistance and other properties. In the present invention, the outer aluminum coating layer 400 is formed by coating the outer aluminum coating layer of the sheath layer 300, and the outer aluminum coating layer 400 is used as the outermost layer. The sheath layer 300 significantly improves the corrosion resistance of the outer layer while continuing to use the 316L material, so that the high temperature and high pressure corrosion resistance of the comprehensive solution of the sheath layer 300 using the 316L material and the outer aluminum coating layer 400 exceeds the sheath layer 300 solution using the Incoloy 825 material alone, thanks to the 0.1~2 The surface layer of the outer aluminum coating 400 of mm can be oxidized to form an aluminum oxide layer when it contacts the external environment. As a surface layer with high hardness, good density and excellent wear resistance, the aluminum oxide layer has excellent wear resistance, corrosion resistance and chemical stability. This surface layer can improve the overall corrosion resistance of optical fiber cables within a certain temperature range (200℃~300℃). Because the aluminum oxide layer itself has a very high melting point of about 2053℃; therefore, in an environment where the temperature does not exceed 400℃, it can ensure good high temperature stability. Compared with Incoloy 825 material, this comprehensive solution of the sheath layer 300 of 316L material and the outer aluminum coating 400 means that the outer aluminum coating 400 can help 316L physically isolate the external corrosion environment, and play a long-term anti-corrosion function through the chemical stability of the aluminum oxide surface layer. At the same time, the sheath layer 300 of 316L material can provide long-term and stable mechanical stability under the protection of the outer aluminum coating 400, while the use of Incoloy alone The 825 material solution means that the sheath layer 300 needs to cope with the external corrosive environment and provide mechanical stability at the same time. As time accumulates and corrosive substances gradually invade, the mechanical stability of the Incoloy 825 sheath layer will show a downward trend and may eventually fail. Therefore, compared with the Incoloy 825 sheath layer 300 solution, the comprehensive solution of using 316L sheath layer 300 and outer aluminum coating layer 400 has lower costs and brings better corrosion resistance and longer service life.

[0051] The outer aluminum coating can also improve the overall airtightness of the optical cable. This is because the aluminum oxide on the surface of the outer aluminum coating provides strong chemical stability and long-term corrosion resistance through direct contact with the outside world. In addition to the surface oxide layer, the inner aluminum layer of the outer aluminum coating can obtain a dense aluminum layer due to the extrusion coating technology. This aluminum layer will enhance the airtightness of the optical cable and isolate hydrogen and other related corrosive gases from entering the interior.

[0052] The thickness of the outer aluminum coating is preferably 0.1~2.0 mm, which can ensure the thickness and chemical stability of the oxide layer on the surface of the aluminum layer, so it can play a good anti-corrosion role in a high temperature and high pressure environment. At the same time, the outer aluminum coating will not fall off the surface of the sheath layer 300 due to related mechanical damage or vibration in a high temperature and high pressure environment due to the aluminum layer being too thick.

[0053] Example 2: Figure 2 As shown, other structures are the same as those of Embodiment 1, except that an aluminum-clad steel wire twisted layer 200 is provided between the optical unit 100 and the sheath layer 300 .

[0054] This embodiment uses an aluminum-clad steel wire twisted layer 200, and uses a twisting process to provide good mechanical strength protection while also having a certain toughness. The present invention improves the anti-corrosion performance of the steel wire through the excellent anti-corrosion performance of the aluminum layer on the surface of the aluminum-clad steel wire. After twisting multiple aluminum-clad steel wires, an aluminum-clad steel wire twisted layer 200 covering a large area of ​​the optical unit and having a physical isolation function is formed, which physically isolates the optical unit 100 from the outside. In the case of damage and failure of the sheath layer 300, it can also provide relatively durable mechanical properties and certain anti-corrosion performance; thereby increasing the service life of the entire optical fiber cable.

[0055] like Figure 3 As shown, the aluminum-clad steel wire twisted layer 200 of the present invention is obtained by twisting aluminum-clad steel wires 210. The aluminum-clad steel wire twisted layer 200 is a single-layer structure formed by twisting aluminum-clad steel wires 210, and can also be a two-layer structure (such as Figure 4 As shown) or a multi-layer structure, the coverage of the aluminum-clad steel wire 210 on the aluminum-clad steel wire stranding layer 200 is 95% to 100%; the coverage is controlled by the pitch-diameter ratio, which is generally controlled at 10 to 14; the pitch-diameter ratio is the ratio of the pitch to the diameter of the aluminum-clad steel wire 210 during the stranding process; the pitch is defined as the distance that a single wire travels around the stranded wire in the axial direction of the stranding direction, which is called a pitch. When the diameter of the stranded wire is fixed, the size of the pitch directly affects the stranding quality. If it is too large, it is easy to loosen the strands, the optical cable seam is large, the stranding is not tight, and the electrical properties are affected. If it is too small, the stranding is too tight, the mechanical properties are affected, and sometimes the outer layer may bulge. Therefore, the pitch is generally 10 to 14 times the diameter to obtain a high-quality stranded layer.

[0056] As a preferred example, the outer diameter of the aluminum-clad steel wire 210 is 0.6~3.5 mm. If the diameter of the aluminum-clad steel wire 210 is too large, it will lead to the inability to twist. If the diameter is too small, the performance improvement of the twisted layer is limited and the production cost is greatly increased. It is further preferred that 0.7~1.5 mm can obtain the best balance between the quality of the twisted layer and the production cost. In the aluminum-clad steel wire 210, the outer diameter of the steel wire 211 is 0.5~2.0 mm, and the thickness of the aluminum coating layer 212 is 0.1~1.5 mm. This thickness range not only meets the anti-corrosion requirements, but also has a certain plastic deformation ability, which has a positive effect on the twisting stability.

[0057] like Figure 5 As shown, the aluminum-clad steel wire 210 of the present invention is obtained by coating an aluminum coating layer 212 on a steel wire 211. The surface of the aluminum coating layer 212 is oxidized to form aluminum oxide, which has good corrosion resistance. Compared with the steel wire, the aluminum coating layer 212 has good ductility and is easy to plastically deform. Therefore, during the twisting process of the aluminum-clad steel wire 210, the aluminum coating layer 212 will be tightly attached together under the twisting force and produce a certain plastic deformation so that the formed aluminum-clad steel wire twisted layer 200 has the function of a physical isolation layer with good airtightness; in addition, the flexibility and high strength characteristics of the steel wire 211 make the aluminum-clad steel wire twisted layer 200 have good toughness and strength.

[0058] The present invention adopts an aluminum coating process to coat a layer of aluminum on the steel wire 211 to form an aluminum coating layer 212. The outer diameter range of the steel wire 211 is 0.5~2.0 mm. This outer diameter range of the steel wire ensures that the aluminum-clad steel wire 210 of the required size can be obtained after the aluminum material is coated. The thickness of the aluminum coating layer outside the steel wire is set to 0.1~1.5 mm, which can not only meet the anti-corrosion requirements, but also has a certain plastic deformation ability, which has a positive effect on the twisting stability, and at the same time ensures that the aluminum coating layer can be well combined with the steel wire and will not fall off under high temperature and high pressure environment.

[0059] In the present invention, the tensile strength of the raw material steel wire 211 of the aluminum-clad steel wire 210 is 1200-1650 MPa. After the steel wire 211 is coated with the aluminum coating layer 212 to form the aluminum-clad steel wire 210, the mechanical strength is mainly provided by the steel wire 211. Therefore, the tensile strength of the formed aluminum-clad steel wire 210 is basically above 1200 MPa, which can provide good protection capability when the external steel pipe is damaged.

[0060] In an oil well environment, if the sheath layer 300 is damaged or fails, the aluminum-clad steel wire twisted layer 200 first has a physical isolation effect, preventing the environmental medium from directly contacting the stainless steel pipe 130 of the optical unit 100; the aluminum-clad steel wire 210 forming the aluminum-clad steel wire twisted layer 200 is further coated with an aluminum coating layer 212 on the outer layer of the steel wire 211, and the aluminum oxide formed by oxidation of the aluminum coating layer 212 has good corrosion resistance, further improving the anti-corrosion performance. Therefore, the aluminum-clad steel wire twisted layer 200 of the present invention plays a better role in protecting the inner layer optical unit 100.

[0061] Example 3: Figure 6 As shown, the present invention provides a method for preparing an optical fiber cable in Example 1, comprising the following steps: S100, providing an optical unit 100; S200, forming a sheath layer 300 outside the optical unit 100 by using a roll forming process; S300 , coating aluminum on the surface of the jacket layer 300 through an extrusion coating process to form an outer coating aluminum layer 400 .

[0062] The extrusion coating process realizes continuous aluminum coating of the sheath 300 by extruding the aluminum rod at high temperature. The extrusion coating process uses aluminum rod as raw material, which can be easily supplied, without extrusion pressure surplus, high material utilization rate, generally up to 95%, good uniformity and density of organizational performance, high dimensional accuracy of products, and good finish. In addition, the extrusion coating process has fewer overall corresponding processes, high production efficiency, and high product yield. Taking pipe processing as an example, this processing technology omits more than 15 processes compared with general pipe processing methods, and the yield rate can reach more than 90%, so the process flow and production cycle can be shortened, thereby reducing costs. The extrusion coating process can produce ultra-long products, the length of which can generally range from several thousand meters to tens of thousands of meters. The extrusion coating process can obtain an outer aluminum coating layer with stable thickness and strong bonding with the surface of the sheath layer 300, which can ensure that the bonding with the sheath layer 300 will not fall off under high temperature and high pressure environment.

[0063] In the extrusion coating process of this example, the inner cavity temperature of the manifold of the extrusion coating machine is preferably 470-530° C., and the inner cavity pressure of the manifold is preferably no greater than 700 MPa.

[0064] The inner cavity temperature of the diversion die is preferably 470~530℃, which can ensure the fluidity and plasticity of the aluminum material. Within this temperature range, the physical properties of the aluminum material can achieve a better extrusion coating effect and avoid excessive inner cavity pressure or uneven pressure caused by the hard aluminum material, which may lead to local mechanical damage to the sheath layer.

[0065] The temperature of the coating mold cavity is controlled by offline heating in an electric furnace, and the production starts after the temperature is kept warm for at least 2 to 3 hours. The preheating temperature of the diverter mold is controlled to be around 420 to 450°C. The control at 420 to 450°C is based on the consideration that the extrusion friction of the aluminum rod during the extrusion process will generate heat, which will further increase on the basis of 420°C. In order to achieve a temperature of 470 to 530°C in the diverter mold cavity, it is necessary to control the temperature at 420°C in advance to finally reach the preferred cavity temperature of the diverter mold. At the same time, the preheating temperature of the diverter mold should be controlled below 450°C. If the temperature reaches 450°C or above, the extrusion heat will cause the final cavity temperature of the diverter mold to rise to above 530°C, resulting in an excessively high cavity temperature, which will affect the quality of the coating, increase the difficulty of aluminum molding, and increase the wear of the tooling.

[0066] Preheat the jacket layer, and control the preheating temperature between 280 and 320°C. Before the jacket layer enters the mold cavity of the coating cavity, it is preheated by an induction heater. The appropriate preheating temperature of the jacket layer can ensure the normal coating process. If the preheating temperature of the jacket layer is too low, the jacket layer will absorb a large amount of heat when passing through the mold cavity, causing the interface temperature of aluminum and steel to be too low, and exposed steel will appear on the surface of the coated product; in severe cases, aluminum will be blocked at the die mouth, and the coating process will be interrupted. If the preheating temperature of the jacket layer is too high, on the one hand, the tensile strength of the jacket layer will be reduced, and the jacket layer will be broken under the action of extrusion and traction. On the other hand, the high heating temperature will make the surface of the jacket layer easy to oxidize, affecting the steel-aluminum bonding of the coated product.

[0067] During the coating process, the pressure in the diversion cavity of the diversion die of the extrusion coating machine is preferably maintained at no more than 700 Mpa, which can achieve the smooth coating of aluminum material on the outer periphery of the sheath layer 300, and the sheath layer does not break or break during the coating process. It can also reduce the risk of sheath layer shaking due to high pressure during the coating process. The shaking of the sheath layer will cause concentric deviation during the aluminum coating process, resulting in uneven thickness and local exposure of steel or loose bonding between the aluminum material and the sheath surface. In addition, the stability of the long-distance production coating of the sheath layer can be achieved to obtain an optical cable with a stable thickness of the outer aluminum coating layer and strong bonding between the sheath layer and the outer aluminum coating layer.

[0068] In the extrusion coating process of the present invention, the pulling speed of the sheath and the rotation speed of the extrusion wheel are preferably controlled to meet the following conditions: , where v is the wire pulling speed (m / min), r is the speed of the extrusion wheel (rpm), K is the coefficient, K is 0.2~0.4, S1 is the cross-sectional area of ​​the aluminum layer formed after the sheath is coated with aluminum (mm 2 ), S2 is the cross-sectional area of ​​the aluminum rod (mm 2 ).

[0069] The coverage rate of the aluminum coating layer on the sheath and the bonding strength of the aluminum layer to the sheath can be achieved during the coating process, wherein the extrusion wheel rotation speed and the aluminum rod cross-sectional area S2 determine the total mass of the aluminum material entering per unit time, and the corresponding aluminum layer cross-sectional area S1 after coating and the traction speed determine the extrusion mass of the aluminum material per unit time. Under the action of the above formula and the corresponding coefficient K, it can be ensured that the aluminum layer has a high coverage rate on the sheath layer, and more accurately avoids related abnormal situations such as exposed steel, and at the same time more accurately controls the bonding strength between the outer coating aluminum layer and the sheath layer by controlling the time of the aluminum material combining with the sheath layer in the cavity per unit time.

[0070] In the process of coating the outer surface of the sheath layer with an aluminum layer by an extrusion coating process, the rotation speed of the extrusion wheel is preferably 4-12 rpm, the pulling speed of the sheath layer is preferably 20-70 m / min, and the diameter of the aluminum rod is preferably 7-9 mm.

[0071] It can achieve high stability of aluminum extrusion, extrusion fluctuation and smooth aluminum layer surface during the sheath layer coating process. The extrusion wheel speed is controlled in the range of 4~12 rpm to ensure that the aluminum rod is fully extruded during the extrusion process while avoiding the increase of cavity pressure caused by excessive speed extrusion or the steel exposure caused by insufficient aluminum material delivery due to slow speed.

[0072] Example 4: Figure 7 As shown, the present invention provides a method for preparing an optical fiber cable in Example 2, comprising the following steps: S100, providing an optical unit 100; S200, coating a layer of aluminum on the surface of the steel wire by an extrusion coating process to form an aluminum-clad steel wire 210; S300, twisting a plurality of aluminum-clad steel wires 210 on the surface of the optical unit 100 using a twisting process to form an aluminum-clad steel wire twisted layer 200 that wraps the optical unit 100; S400, using a roll forming process to cover the corrosion-resistant stainless steel belt on the aluminum-clad steel wire twisted layer 200 to form a sheath layer 300; S500 , coating aluminum on the surface of the jacket layer 300 through an extrusion coating process to form an outer coating aluminum layer 400 .

[0073] In S200, a layer of aluminum is coated on the surface of the steel wire by an extrusion coating process to form the aluminum-clad steel wire 210. The specific method of forming the aluminum coating layer 400 is as follows: The extrusion coating process uses aluminum rods as raw materials, which can achieve convenient supply, no extrusion pressure surplus, high material utilization rate, generally up to 95%, good uniformity and density of organizational performance, high dimensional accuracy and good finish of the product. In addition, the extrusion coating process has fewer corresponding processes as a whole, high production efficiency and high product yield. Taking steel wire processing as an example, this processing technology omits more than 10 processes compared with general steel wire processing methods, and the yield rate can reach more than 95%, so it can shorten the process flow and production cycle, thereby reducing costs. The extrusion coating process can produce ultra-long products, the length of which can generally range from several thousand meters to tens of thousands of meters. The extrusion coating process can obtain an outer aluminum coating layer with stable thickness and strong bonding with the surface of the steel wire, which can ensure that the bonding with the steel wire will not fall off under high temperature and high pressure environments.

[0074] In the extrusion coating process of this example, the inner cavity temperature of the manifold of the extrusion coating machine is preferably 470-530° C., and the inner cavity pressure of the manifold is preferably no greater than 700 MPa.

[0075] The inner cavity temperature of the diversion die is preferably 470~530℃, which can ensure the fluidity and plasticity of the aluminum material. Within this temperature range, the physical properties of the aluminum material can achieve a better extrusion coating effect, avoiding excessive inner cavity pressure caused by the harder aluminum material or uneven pressure that causes local mechanical damage to the steel wire. For steel wire, its own tensile strength is relatively large, about 1200 Mpa, and uniform pressure means the stability of the overall coating during the production process.

[0076] The temperature of the coating mold cavity is controlled by offline heating in an electric furnace, and the production starts after the temperature is kept warm for at least 2 to 3 hours. The preheating temperature of the mold should reach about 410℃~430℃. The control at about 410℃~430℃ is to take into account the heat generated by the extrusion friction of the aluminum rod during the extrusion process, which will further increase on the basis of 410℃~430℃. In order to achieve the temperature of the inner cavity of the diverter mold of 470~530℃, it is necessary to control the temperature at 410℃~430℃ in advance, and finally reach the preferred inner cavity temperature of the diverter mold. At the same time, its coating temperature should be controlled below 430℃. If the temperature reaches 430℃ and above, the extrusion heat will cause the inner cavity temperature of the final diverter mold to rise to above 530℃, resulting in excessive temperature in the cavity, which will affect the quality of the coating, increase the difficulty of aluminum molding, and increase the wear of the tooling.

[0077] The steel wire is preheated, and the preheating temperature is controlled between 260 and 300°C. Before the steel wire enters the mold cavity of the coating cavity 610, the steel wire is preheated by an induction heater. The coating process can proceed normally only when the preheating temperature of the steel wire is appropriate. If the preheating temperature of the steel wire is too low, the steel wire will absorb a large amount of heat when passing through the mold cavity, causing the interface temperature of aluminum and steel to be too low, and exposed steel will appear on the surface of the coated product; in severe cases, aluminum will be blocked at the die mouth, and the coating process will be interrupted. If the preheating temperature of the steel wire is too high, on the one hand, the tensile strength of the steel wire will be reduced, causing the steel wire to be broken under the action of extrusion and traction. On the other hand, the high heating temperature will make the surface of the steel wire layer easily oxidized, affecting the steel-aluminum bonding of the coated product.

[0078] During the coating process, the pressure in the diversion cavity of the diversion die of the extrusion coating machine is preferably maintained at no more than 700 Mpa, so that the aluminum material can be smoothly coated on the outer periphery of the steel wire. On the premise that the steel wire does not break or break during the coating process, the risk of steel wire shaking due to high pressure during the coating process can be reduced. The shaking of the steel wire will cause concentric deviation during the aluminum coating process, resulting in uneven thickness and local exposure of steel or loose bonding between the aluminum material and the steel wire surface. In this way, the stability of the long-distance production coating of the steel wire can be achieved, and the thickness of the outer aluminum coating layer is stable and the bonding between the steel wire and the outer aluminum coating layer is strong.

[0079] In the extrusion coating process of the present invention, the pulling speed of the steel wire and the rotation speed of the extrusion wheel are preferably controlled to meet the following conditions: , where v is the wire pulling speed (m / min), r is the speed of the extrusion wheel (rpm), K is the coefficient, K is 0.2~0.4, S1 is the cross-sectional area of ​​the aluminum layer formed after the wire is coated with aluminum (mm 2 ), S2 is the cross-sectional area of ​​the aluminum rod (mm 2 ).

[0080] The coverage rate of the aluminum coating layer on the steel wire and the bonding strength of the aluminum layer on the steel wire can be achieved during the coating process, wherein the extrusion wheel rotation speed and the aluminum rod cross-sectional area S2 determine the total mass of the aluminum material entering per unit time, and the corresponding cross-sectional area S1 of the aluminum layer after coating, and the traction speed determine the extrusion mass of the aluminum material per unit time. Under the action of the above formula and the corresponding coefficient K, it can be ensured that the aluminum layer has a high coverage rate on the steel wire, and more accurately avoids related abnormal situations such as exposed steel, and at the same time more accurately controls the bonding strength between the outer coating aluminum layer and the steel wire by controlling the time for the aluminum material to combine with the steel wire in the cavity per unit time.

[0081] In the process of achieving the outer coating of the aluminum layer through the extrusion coating process, the rotation speed of the extrusion wheel is preferably 4-12 rpm, the pulling speed of the steel wire is preferably 20-70 m / min, and the diameter of the aluminum rod is preferably 7-9 mm.

[0082] It can achieve high stability of aluminum extrusion, extrusion fluctuation and smooth aluminum layer surface during the steel wire coating process. The speed of the extrusion wheel is controlled in the range of 4~12 rpm to ensure that the aluminum rod is fully extruded during the extrusion process while avoiding the increase of cavity pressure caused by extrusion at too fast a speed or the exposure of steel caused by insufficient aluminum material delivery due to slow speed.

[0083] In S300, the aluminum clad steel wire is twisted as follows: S310, preforming the aluminum clad steel wire 210; S320, simultaneously twisting a certain number of aluminum-clad steel wires 210 by a twisting cage device of a cage twisting process or a tube twisting process to form a twisted layer; S330, fixing the outer diameter of the aluminum-clad steel wire twisted layer by a sizing die to obtain the aluminum-clad steel wire twisted layer 200.

[0084] It should be noted that in step S320, after twisting, a detwisting operation is required to obtain a high-quality twisted layer.

[0085] In the event of damage or failure of the sheath layer, the inner aluminum-clad steel wire twisted layer 200 can adapt to the underground environment for a period of time regardless of whether it is tensile or compressive, and will continue to protect the innermost optical unit 100 to ensure the stability of communication sensing, thereby greatly improving the structural safety of the inner layer, which corresponds to more stable and long-lasting use in actual use. In particular, the outer layer of the steel wire is further coated with an aluminum coating layer to form an aluminum-clad steel wire 210. After oxidation, the outer layer of the aluminum coating layer will form aluminum oxide, which has good corrosion resistance. At the same time, the aluminum coating layer 212 will be tightly attached together during the twisting process to form a physical isolation layer with good airtightness, thereby achieving longer-term protection of the optical unit.

[0086] The aluminum clad steel wire stranded layer 200 may be provided as one layer (e.g. Figure 3 ), can also be set to multiple layers (such as Figure 4 As shown in the figure), considering the actual application, it is generally 1 to 3 layers.

[0087] The process used for twisting is the cage twisting process or the tube twisting process in the prior art, which is a mature process in the prior art and will not be described in detail in the present invention.

[0088] Specific control method: according to the outer diameter of the optical unit 100 and the outer diameter of the stranded aluminum-clad steel wire 210, the number and coverage of the theoretical stranded steel wires are determined, and then the stranding parameters of the stranding cage are adjusted. Exemplary related parameters are as follows: If the optical unit 100 with an outer diameter of 2.6 mm is selected, the aluminum-clad steel wire 210 with a diameter of 0.7 mm is twisted, and 14 wires correspond to a coverage rate of 95.25%; If the optical unit 100 with an outer diameter of 2.6 mm is selected, the aluminum-clad steel wire 210 with a diameter of 0.8 mm is twisted, and 13 wires correspond to a coverage rate of 98.29%; If a light unit 100 with an outer diameter of 2.6 mm is selected, and an aluminum-clad steel wire 210 with a diameter of 1 mm is twisted, 11 wires correspond to a coverage rate of 98.56%; If the optical unit 100 with an outer diameter of 2.7 mm is selected, the aluminum-clad steel wire 210 with a diameter of 0.9 mm is twisted, and 11 wires correspond to a coverage rate of 96.52%; During the twisting process, the pay-off tension of the aluminum clad steel wire 210 is 10-20 N. The smaller the diameter, the smaller the pay-off tension. There is no special requirement. Just keep the aluminum clad steel wire 210 taut.

[0089] As a preferred case, the preferred aluminum-clad steel wire twisting needs to have a back-twisting function, and the back-twisting operation allows the aluminum-clad steel wire twisting layer 200 to maintain good stability.

[0090] As a preferred example, the aluminum clad steel wire 210 is selected for single-layer twisting process, and the coverage rate of the aluminum clad steel wire 210 reaches 95-100%.

[0091] The number of twisted aluminum-clad steel wires is selected according to the coverage and size. For commonly used products, the number of twisted wires is preferably 8 to 15; for products with practical use, the preferred outer diameter after twisting needs to be controlled at ≤4.9 mm.

[0092] The process of forming the outer coating aluminum layer 400 in step S500 is the same as that in embodiment 3, and will not be further described in this embodiment.

[0093] Example 5: Figures 8 to 10 As shown, this embodiment provides an extrusion coating machine 600 for coating an aluminum layer on the surface of a wire during the preparation of an optical cable. The wire may include a steel wire or a sheath.

[0094] The extrusion coating machine 600 comprises: The splitter mold 660: The splitter mold 660 includes a splitter cavity 661 and a feed port 662 at the bottom of the splitter cavity 661; Extrusion wheel 670: The extrusion wheel 670 is located below the diverter die 660. A groove 671 is provided on the outer circumferential surface of the extrusion wheel 670 along the rotation direction of the extrusion wheel 670. The groove 671 is connected to the inner cavity of the diverter die 660 through the feed port 662 of the diverter die 660. Stopper 640 is fixed on one side below the feed port 662 of the diverter die 660 , corresponding to the groove 671 of the extrusion wheel 670 , to block the blank from continuing to move along the circumferential direction of the groove 671 , and is used to extrude the blank and guide it upward into the feed port 662 of the diverter die 660 .

[0095] The working principle of the extrusion coating machine 600 of the present invention is as follows Figure 8 As shown, it includes a coating cavity 610 and an extrusion wheel 670. The coating cavity 610 is provided with a punch 620, a diverter die 660 and a die 630 in sequence along the wire feeding direction. The punch 620, the diverter die 660 and the die 630 constitute a mold for coating aluminum material. The punch 620 and the die 630 are provided with coating holes for the wire to pass through in sequence. The diverter cavity 661 of the diverter die 660 is a cavity for the aluminum coated wire.

[0096] A reasonable working gap is maintained between the extrusion wheel 670 and the coating cavity 610. During operation, the extrusion wheel 670 moves Figure 8 The die 660 rotates in the direction indicated by the middle arrow, thereby biting the blank, and the coated wire also passes through the shunt cavity 661 through the cladding hole of the die; when the blank reaches the stopper 640 of the cladding cavity 610, the convex part on the cladding cavity 610 that matches the groove 671 on the extrusion wheel 670, namely the stopper 640, blocks the movement of the blank in the circumferential direction. At this time, the friction between the groove 671 of the extrusion wheel 670 and the blank causes the blank to shear and deform, and the temperature and pressure are increased. When the temperature and pressure required for the plastic deformation of aluminum are reached, the blank is forced to flow along the upward flow channel and enter the shunt cavity 661 through the feed port 662 of the shunt die 660. At this time, the aluminum material is combined with the wire at 470℃~530℃ and a pressure not exceeding 700 MPa, and is extruded from the cladding hole together with the wire in the middle to form an aluminum clad wire product. As long as the blanks are continuously fed in, the wires are continuously pulled out, and the extrusion wheel 670 is continuously rotated, aluminum clad wire products of any length can be obtained.

[0097] As a specific embodiment, the present invention sets a feed port 662 at the bottom of the diverter cavity 661 of the diverter die 660 of the extrusion coating machine 600, and the size of the feed port 662 is 10~12 mm, and at the same time, a groove 671 is opened on the outer circular surface of the extrusion wheel 670 along the rotation direction of the extrusion wheel 670, and the size of the groove 671 is 6~7.5 mm. Therefore, when the diameter of the aluminum rod 650 is controlled to be 7~9 mm, the inner cavity pressure of the diverter die in this example can be achieved to be no more than 700 Mpa.

[0098] The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the scope of the claims of the present invention.

Claims

1. An optical fiber cable, characterized in that: The invention comprises an optical unit, a sheath layer and an outer aluminum coating layer which are arranged in sequence from the inside to the outside. The outer aluminum coating layer is formed by coating aluminum on the surface of the sheath layer through an extrusion coating process.

2. The optical fiber cable according to claim 1, characterized in that: An aluminum-clad steel wire twisted layer is arranged between the optical unit and the sheath layer. The aluminum-clad steel wire twisted layer is formed by coating aluminum on the surface of steel wires through an extrusion coating process and then twisting the aluminum-clad steel wires.

3. The optical fiber cable according to claim 2, characterized in that: The sheath layer is made of stainless steel tube with an outer diameter of 4~10 mm and a wall thickness of 0.4~2 mm; the thickness of the outer aluminum coating layer is 0.1~2 mm, and / or, in the aluminum-clad steel wire twisted layer, the aluminum-clad steel wire includes a steel wire and an aluminum coating layer coated on the surface of the steel wire, wherein the outer diameter of the steel wire is 0.5~2.0 mm, and the thickness of the aluminum coating layer is 0.1~1.5 mm.

4. A method for preparing an optical fiber cable, characterized in that: The following steps are involved: providing a light unit; forming a sheath layer outside the light unit; Aluminum is coated on the surface of the sheath layer through an extrusion coating process to form an outer coating aluminum layer.

5. The method for preparing an optical fiber cable according to claim 4, characterized in that: Also includes the steps: The aluminum is coated on the surface of the steel wire by extrusion coating process to form aluminum-clad steel wire; The aluminum-clad steel wires are twisted on the surface of the optical unit by adopting a twisting process to form an aluminum-clad steel wire twisted layer on the surface of the optical unit.

6. The method for preparing an optical fiber cable according to claim 4 or 5, characterized in that: In the extrusion coating process, the inner cavity temperature of the diverter die of the extrusion coating machine is 470~530℃, and the inner cavity pressure of the diverter die is not more than 700 MPa.

7. The method for preparing an optical fiber cable according to claim 6, characterized in that: In the extrusion coating process, the wire pulling speed and the speed of the extrusion wheel are controlled to meet the following conditions: , where v is the wire pulling speed (m / min), r is the speed of the extrusion wheel (rpm), K is the coefficient, K is 0.2~0.4, S1 is the cross-sectional area of ​​the aluminum layer formed after the wire is coated with aluminum (mm 2 ), S2 is the cross-sectional area of ​​the aluminum rod (mm 2 ); and / or, before the outer aluminum layer is coated by the extrusion coating process, the splitter die and the jacket layer are preheated respectively, the preheating temperature of the splitter die is controlled to be 420-450° C., and the preheating temperature of the jacket layer is controlled to be 280-320° C.; And / or, before the aluminum-clad steel wire is produced through the extrusion coating process, the splitter die and the steel wire are preheated respectively, the preheating temperature of the splitter die is controlled to be 410°C to 430°C, and the preheating temperature of the steel wire is controlled to be 260°C to 300°C.

8. The method for preparing an optical fiber cable according to claim 7, characterized in that: In the process of achieving the outer aluminum coating by the extrusion coating process, the rotation speed of the extrusion wheel is 4~12 rpm, the pulling speed of the sheath is 20~70 m / min, and the diameter of the aluminum rod is 7~9 mm; And / or, in the process of realizing aluminum-clad steel wire through extrusion coating process, the rotation speed of the extrusion wheel is 4~12 rpm, the pulling speed of the steel wire is 40~120 m / min, and the diameter of the aluminum rod is 7~9 mm.

9. An extrusion coating machine, used to coat an aluminum layer on the surface of a wire in the process of preparing an optical cable, characterized in that: include: Splitting die: The splitting die includes a splitting cavity and a feed port at the bottom of the splitting cavity; Extrusion wheel: The extrusion wheel is located below the diverter die. A groove is provided on the outer circumferential surface of the extrusion wheel along the rotation direction of the extrusion wheel. The groove is connected with the inner cavity of the diverter die through the feed port of the diverter die. Stopper: fixed on the lower side of the feed port of the diverter die, corresponding to the groove of the extrusion wheel, to prevent the billet from continuing to move along the circumferential direction of the groove, and to guide the extruded billet upward into the feed port of the diverter die.

10. The extrusion coating machine according to claim 9, characterized in that The groove width of the extrusion wheel is 6~7.5mm, and the feed port diameter of the diverter die is 10~12mm.

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