High thermal conductive thin composite pipe and manufacturing method and use thereof

Abstract

To provide a high thermal conductive thin composite pipe improved in billet formability and quality of an extrusion pipe surface, reduced in mold cracks, and extended in mold use life, and a manufacturing method and use thereof.SOLUTION: An AlNp / ZA27 billet after reciprocal extrusion through a plurality of paths at 250-350°C is used as a raw material, and put into a pipe extrusion mold. A temperature gradient is constructed so as to gradually increase from the billet to an extrusion pipe outlet in an extruding direction. The temperature of a gradient distribution is 250-350°C. Extrusion is executed at the extrusion speed of 0.1-0.5 mm / s after warming to provide a high thermal conductive AlNp / ZA27 composite material thin pipe.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention belongs to the technical field of power transmission conductor materials, and specifically relates to a high thermal conductivity thin-walled composite pipe, a manufacturing method thereof, and its use.

Background Art

[0002] Copper conductors are widely used in fields such as power transmission and electronic devices due to their advantages such as good electrical conductivity, strong corrosion resistance, good thermal conductivity, and high strength. Compared with conductors made of other materials, both the resistance and loss of copper conductors are relatively small, and they have better performance in power transmission. However, the production cost of copper conductors is too high, and the strength during use in a tension state is insufficient. Instead of copper conductors, it is important to search for materials with low cost, excellent electrical conductivity and thermal conductivity, form copper composite pipelines, and reduce the consumption of copper resources.

[0003] In order to reduce the consumption of metallic copper, the development of copper-clad aluminum composite materials began in the 1970s of the last century. Copper-clad aluminum composite wires have advantages such as small diameter and good electrical conductivity. At present, mass production has been realized, solving the problems of "alternative copper wires" and "alternative imports". In recent years, zinc-aluminum (ZA) alloys have been widely applied due to their excellent castability, wear resistance, good thermal conductivity and electrical conductivity. Among them, the performance of ZA 27 alloy is the most excellent and it is gradually replacing conventional casting alloys such as Al and Cu in various process applications. The ZA 27 alloy is an alloy containing 71 wt.% zinc, 27 wt.% aluminum and 2 wt.% copper, and its conductivity can reach 29.7% IACS, which is an ideal substitute for Cu wires. In the process of power transmission, when current passes through the wire, it generates vibrations in the crystal lattice inside the wire, causing the wire to heat up. If the heat cannot be dissipated in a timely manner, the overheating of the wire will reduce the conductivity. Manufacturing metal matrix composites by adding high thermal conductivity ceramic particle reinforcements to metal materials is an effective way to improve the metal thermal conductivity performance. At present, the mainstream high thermal conductivity ceramic particle reinforcements mainly include AlN, SiC, etc. Among many ceramic particle reinforcement phases, AlN is widely used due to its high strength, high thermal conductivity and high stability. Therefore, adding high thermal conductivity AlN ceramic particles to ZA 27 alloy to improve the thermal conductivity performance, as well as the strength and wear resistance, and manufacturing zinc-coated copper composite materials can effectively improve the comprehensive performance and service life of copper wires and reduce the consumption of copper resources.

[0004] To manufacture a zinc-coated copper composite material, first, it is necessary to manufacture an AlNp / ZA 27 composite pipe with good thermal conductivity and electrical conductivity. The as-cast AlNp / ZA 27 composite material cannot achieve the direct forming of a thin-walled pipe due to defects such as shrinkage cavities and porosity generated during casting. By processing the as-cast composite material using a reciprocating extrusion large plastic deformation process, casting defects can be effectively removed, the crystal grains can be refined, the material strength and plastic toughness can be improved, which is an effective pretreatment process before extruding the thin-walled pipe. At the same time, during the process of pressing the pipe, the frictional heat and deformation heat of the material increase the temperature of the material, which significantly affects the uniformity of the material's deformation flow. To achieve uniform deformation of the material, improve the service life of the mold, and realize labor-saving forming, temperature-variable extrusion is the optimal solution. By changing the temperature distribution when the billet is extruded along the length direction, it compensates for the temperature increase caused by deformation heat or the temperature decrease caused by the heat dissipation effect of different parts of the mold, preventing the occurrence of cracks during the extrusion process of the billet or the mold. Meanwhile, by controlling the temperature, the hardness, deformation resistance, fluidity, and extrusion forming performance along the length direction of the billet are controlled, and the billet is extruded by utilizing the principle of "the hard part extrudes the soft part", that is, the temperature of the billet near the press head of the extrusion rod is slightly lower, the hardness of the material is relatively high, the temperature of the billet near the mold extrusion is slightly higher, the hardness of the material is low, the fluidity is good, the extrusion resistance is low, and the upper part is hard and the lower part is soft in the extrusion direction of the billet, which can greatly improve the extrusion formability of the thin-walled pipe material, improve the pipe forming rate, and reduce the cracks of the mold and the billet.

[0005] As described above, considering the process of manufacturing the AlNp / ZA 27 pipe by combining reciprocating extrusion and temperature-variable extrusion, it can effectively promote the application of zinc alloys to zinc-coated copper composite materials, and has broad application prospects in terms of improving the comprehensive performance of copper conductors and reducing the consumption of copper resources.

Summary of the Invention

[0006] The problem to be solved by the present invention is to improve the forming performance of the billet and the quality of the surface of the extruded pipe by controlling and heating the gradient temperature along the length direction of the billet in response to the deficiencies in the above prior art, reduce the cracking of the mold, extend the service life of the mold, and solve the technical problems such as low fluidity, non-uniform deformation, large forming force, cracking of the extrusion mold and the extruded pipe, generation of cracks on the surface, and difficulty in forming in the thin-wall pipe extrusion forming. The present invention provides a high thermal conductivity thin-wall composite pipe, its manufacturing method, and its use.

[0007] The technical means of the present invention are as follows.

[0008] AlN after reciprocating extrusion in multiple passes p / ZA27 billet is heated, and the heating temperature is an increasing distribution in a temperature gradient in the extrusion direction from the AlN p / ZA27 billet to the pipe outlet. After heat preservation treatment, it is extruded to obtain a high thermal conductivity thin-wall composite pipe AlN p / ZA27. A manufacturing method of a high thermal conductivity thin-wall composite pipe including this step.

[0009] Preferably, the temperature of the multiple-pass reciprocating extrusion is 250 - 350 °C. Preferably, the gradient distribution temperature along the extrusion direction is 250 - 350 °C. Preferably, the time of the heat preservation treatment is 0.5 - 1.5 h. Preferably, after the heat preservation treatment, the extrusion speed is controlled to v = 0.1 - 0.5 mm / s to obtain a high thermal conductivity thin-wall composite pipe AlN p / ZA27. Preferably, in the manufacturing process of the high thermal conductivity thin-wall composite pipe AlN p / ZA27, the temperature along the length direction of the reciprocating extrusion billet is 250 - 350 °C, and the temperature interval is 10 - 30 °C.

[0010] Another technical solution of the present invention is a high thermal conductivity thin-wall composite pipe whose chemical composition is AlN p / ZA27. The volume percentage of AlN particles is φ = 4%.

[0011] Preferably, in terms of mass percentage, in ZA27, Zn accounts for 70.05% - 71.00%, Al accounts for 27.00% - 27.20%, Cu accounts for 2.00% - 2.05%, and the balance is Mg. Preferably, the particle size of the AlN particles is 0.8 - 1 μm.

[0012] Another technical solution of the present invention is the application in the power transmission wire material of the high - thermal - conductivity thin - wall composite pipe.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects.

[0014] The high - thermal - conductivity thin - wall composite pipe and its manufacturing method of the present invention heat the billet along the vertical direction at a gradient temperature, thereby compensating for the temperature rise caused by the deformation of the billet during the extrusion process and the temperature drop caused by heat dissipation at different positions of the mold, improving the forming performance of the billet and the quality of the pipe surface, reducing the cracking of the mold, and extending the service life of the mold. In the high - thermal - conductivity thin - wall composite pipe manufactured by variable - temperature - controlled extrusion, significant dynamic recrystallization occurs, the average grain size is less than 1 μm, and the toughness improvement of fine grains is realized.

[0015] Furthermore, before pipe extrusion, by performing a reciprocating extrusion treatment on the cast AlN p / ZA27 billet at 250 - 350 °C, casting defects such as porosity and microporosity generated during the casting process can be effectively eliminated, the crystal grains can be refined, and the strength, plasticity, and toughness of the material can be improved.

[0016] Furthermore, the eutectoid transformation temperature of the ZA27 alloy is 275 °C. By setting the extrusion temperature at 250 - 350 °C, the hot extrusion forming performance of the β - phase and (α + η) - phase of the ZA27 alloy can be investigated, and by changing the temperature, an AlN p / ZA27 pipe with optimal microstructure, mechanical, and thermal - conductivity performance can be obtained.

[0017] Furthermore, after heating the billet to a predetermined temperature, by performing a heat preservation treatment for 0.5 to 1.5 h, the billet is sufficiently heated, and a gradient temperature distribution in which the temperature changes uniformly along the length direction of the billet can be obtained.

[0018] Furthermore, by controlling the extrusion speed (the moving speed of the extrusion head) to v = 0.1 to 0.5 mm / s, while maintaining the fluidity and forming performance of the billet, the production efficiency can be maximized, the shape and size of the extruded pipe are accurate, and the uniformity of the microstructure and mechanical and heat conduction performance along the cross-section and length direction can be improved.

[0019] Furthermore, when performing variable temperature control extrusion, the temperature of the billet on the side close to the extrusion rod is set to 250 to 300 °C, the temperature of the billet on the side close to the pipe discharge die orifice is set to 300 to 350 °C, and the temperature interval is set to 10 to 30 °C. As a result, the billet on the side close to the extrusion rod has a high hardness due to its low temperature, while the billet on the side close to the pipe discharge die has a low hardness and high fluidity due to its high temperature. By "extruding the hard part by the soft part", the forming performance of the billet, the pipe forming rate and the good product rate are effectively improved.

[0020] Furthermore, for the high thermal conductivity AlN p / ZA27 thin-walled composite pipe manufactured by variable temperature control extrusion, as a result of performing microscopic structure observation, significant dynamic recrystallization occurred in the AlN p / ZA27 composite pipe after variable temperature extrusion, the forms of α-Al and η-Zn were converted into equiaxed crystals without distortion, the average grain size reached less than 1 μm, and the α-Al fine grains were distributed in a network in the η-Zn matrix. A precipitation phase rich in obvious Cu was observed between the crystals. Some AlN particles were also crushed and distributed along the extrusion direction, and under the combined action of fine grain strengthening and second phase strengthening, the mechanical and heat conduction performance of the material was effectively improved.

[0021] Furthermore, by ensuring a constant temperature of the pipe discharge die hole, the deformation resistance of the metal and the uniformity of the metal deformation flow in the deformation region near the die hole can be effectively maintained. The pressure on the die surface at the pipe discharge die opening hardly changes, the service life of the concave die and the die core is extended, and the surface quality of the AlN p / ZA27 heat transfer tube is significantly improved, and the cracking of the pipe during the extrusion process is reduced.

[0022] Furthermore, by wrapping the outside of the heating coil with refractory wool before heating, the heating efficiency of the coil can be significantly improved, the heat loss of the billet during the pipe extrusion process can be reduced, and the quality and stability of the formed pipe can be guaranteed.

[0023] Furthermore, after the pipe extrusion billet is placed in the die, by pre-pressing the die with an intelligent control pressure processing system, the gap between the die and the pipe extrusion billet can be reduced, and the extrusion efficiency of the pipe can be improved.

[0024] From the above, the method for extruding and manufacturing a high thermal conductivity thin-walled composite pipe by variable temperature control of the present invention has a reasonable extrusion temperature, an appropriate extrusion speed, can effectively compensate for the temperature changes of the billet and the die by gradient temperature extrusion, improves the forming performance of the billet, reduces the cracking of the die, extends the service life of the die, and has good application prospects in the field of power transmission conductor materials.

[0025] Hereinafter, the technical solution of the present invention will be further described in detail with reference to the drawings and embodiments.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0027] The following clearly and completely describes the technical solution of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present invention.

[0028] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods described in the text can be combined with each other to form a new technical solution.

[0029] In the present invention, unless otherwise explained, all the technical features and preferred features described in this specification can be combined with each other to form a new technical solution.

[0030] In the present invention, unless otherwise specified, the percentage (%) or part refers to the weight percentage or weight part with respect to the composition.

[0031] In the present invention, unless otherwise explained, each of these components or their preferred components can be combined with each other to form a new technical solution.

[0032] In the present invention, unless otherwise explained, the numerical range "a - b" represents an abbreviation of any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "6 - 22" indicates that all real numbers between "6 - 22" in the text are all enumerated, and "6 - 22" is only an abbreviated representation of these numerical combinations.

[0033] The "range" disclosed in the present invention may be in the form of a lower limit and an upper limit, each of which may be one or more lower limits and one or more upper limits respectively.

[0034] In the present invention, the term "and / or" used in this specification refers to any combination and all possible combinations of one or more of the related items listed, including these combinations.

[0035] In the present invention, unless otherwise specified, each reaction or operation step may be carried out in order or may not be carried out in order. Preferably, the reaction method in this specification is carried out sequentially.

[0036] Unless otherwise specified, the technical and scientific terms used in this specification have the same meaning as those well known to those skilled in the art. Also, any method or material similar or equivalent to the described content can be applied to the present invention.

[0037] The present invention provides a high thermal conductivity thin-walled composite pipe, a method for manufacturing the same, and uses thereof. Four heating coils are provided on the outside of the extrusion cylinder of the pipe extrusion die in the vertical direction, each connected to a thermocouple, and after reciprocally extruding in multiple passes at 250 - 350 °C, an AlN p / ZA27 billet is used as the pipe extrusion raw material. After applying a boron nitride lubricating paint to the surface of the billet, it is placed into the extrusion cylinder together with the pipe core, a pipe discharge die is placed into the extrusion cylinder, and clamping plates are attached and fastened to both ends of the extrusion cylinder. After the assembly of the entire pipe extrusion die is completed, it is placed in an intelligent control pressure processing system, temporarily tightened, and controlled to heat the four heating coils to 250 - 350 °C at a gradient temperature, keep warm for 0.5 - 1.5 h, and then extrude at an extrusion speed (the moving speed of the extrusion head) v = 0.1 - 0.5 mm / s to obtain an AlN p / ZA27 high thermal conductivity pipe. In the present invention, in the method for manufacturing a high thermal conductivity pipe by extruding with a gradient temperature change, the control of the extrusion temperature distribution is reasonable, the uniform extrusion of the pipe is controlled at a gradient temperature along the extrusion direction, the pipe forming rate is high, the extrusion speed is appropriate, the temperature changes of the billet and the die extrusion outlet can be effectively compensated by gradient temperature extrusion, the temperature during the flow of the billet in the high extrusion ratio part is relatively high is compensated, a temperature control is formed in such a form that the billet "the hard part extrudes the soft part", the gradient fluidity of the billet and the pipe outlet extrusion material and the formability of the extruded pipe are improved, the cracks in the die are reduced, the service life of the die is extended, and it has broad application prospects in the field of power transmission conductor materials.

[0038] The method for manufacturing the high thermal conductivity thin-walled composite pipe of the present invention includes the following steps. S1: AlN p Turn a / ZA27 reciprocating extrusion billet by turning to obtain a pipe extrusion billet. Machine a circular hole for inserting pipe cores of different diameters in the core part of the billet, and apply a boron nitride lubricant to the surface of the pipe extrusion billet. The pipe extrusion billet has a diameter φ = 29.5 - 30.5 mm, a length L = 55.0 - 60.0 mm, and a circular hole diameter φ = 6.0 - 10.0 mm. S2: Attach four heating coils 7 to the outside of the extrusion cylinder respectively and connect them to the thermocouple 5 and temperature control. S3: Put the pipe extrusion billet obtained in step S1 into the extrusion cylinder together with the pipe core. Attach a pipe discharge die 8 to the bottom of the extrusion cylinder, and attach clamping plates 4 to both ends of the extrusion cylinder to fix the pipe discharge die. S4: Place the pipe extrusion die assembled in step S3 in an intelligent control pressure processing system and clamp it temporarily. S5: Turn on the power supply, heat the heating coil along the length direction of the billet in a gradient manner to 250 - 350 °C (temperature interval 10 - 30 °C, heat preservation for 0.5 - 1 h), and wrap the outside of the heating coil with refractory wool for heat preservation. S6: Start the pressure processing system and complete the pipe extrusion at an extrusion speed (the moving speed of the extrusion head) v = 0.1 - 0.5 mm / s. S7: Turn off the power supply, clean the pipe discharge die and the extrusion cylinder to obtain a high - thermal - conductivity thin - wall composite pipe.

[0039] The composition of the chemical components of the high - thermal - conductivity thin - wall composite pipe manufactured by the method of the present invention is AlN p / ZA27. The volume percentage of AlN particles is φ = 4%, the particle size is 0.8 - 1 μm. By mass%, in the matrix ZA27 alloy, Zn accounts for 70.05% - 71.00%, Al accounts for 27.00% - 27.20%, Cu accounts for 2.00% - 2.05%, and the balance is Mg.

[0040] As can be seen from the microstructure diagram of the extruded pipe, for the high thermal conductivity thin-walled composite pipe manufactured by the method of the present invention, significant dynamic recrystallization occurs in the high thermal conductivity thin-walled pipe manufactured by variable temperature extrusion, and the average crystal grain size of the equiaxed crystals without generated strain reaches 1 μm or less, and the cooperative toughness strengthening of the material is achieved under the action of fine grain strengthening.

[0041] The high thermal conductivity thin-walled composite pipe manufactured by the method of the present invention can be applied to power transmission wire materials.

[0042] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, hereinafter, with reference to the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. The components of the embodiments of the present invention generally described and illustrated in this specification can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings does not limit the scope of the present invention described in the claims, but only shows alternative embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present invention.

[0043] Example 1 AlN reciprocally extruded at 250 °C in multiple passes p The / ZA27 billet was put into a pipe extrusion die as a raw material, and four heating coils were attached to the outside of the extrusion cylinder. The billet was heated so that the temperatures along the length direction were 250 °C, 260 °C, 270 °C, and 280 °C respectively, and after heat preservation for 0.5 h, extrusion was carried out at an extrusion speed (the moving speed of the extrusion head) v = 0.1 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN p / ZA27. The composite pipe obtained in Example 1 has a smooth surface without cracks, uniform size, significant dynamic recrystallization occurring in its structure, the crystal grain size reaching 0.9 μm, indicating that the formability of the billet, the comprehensive mechanical and thermal conductivity properties of the pipe have been effectively improved by variable temperature extrusion.

[0044] Example 2 AlN reciprocally extruded in multiple passes at 250 °C p The / ZA27 billet was put into a pipe extrusion die as raw material, four heating coils were attached to the outside of the extrusion barrel, the billet was heated so that the temperatures were 250 °C, 275 °C, 300 °C, and 325 °C respectively along the length direction, and after heat preservation for 1.0 h, extrusion was carried out at an extrusion speed (the moving speed of the extrusion head) v = 0.2 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN p / ZA27 was obtained. The pipe obtained in Example 2 had a smooth surface, stable size, significant dynamic recrystallization occurred in its structure, the crystal grain size reached 0.85 μm, and the formability of the billet and the comprehensive mechanical and thermal conductivity properties of the pipe were effectively improved by variable temperature extrusion.

[0045] Example 3 AlN reciprocally extruded in multiple passes at 300 °C p The / ZA27 billet was put into a pipe extrusion die as raw material, four heating coils were attached to the outside of the extrusion barrel, the billet was heated so that the temperatures were 250 °C, 265 °C, 280 °C, and 295 °C respectively along the length direction, and after heat preservation for 0.5 h, extrusion was carried out at an extrusion speed (the moving speed of the extrusion head) v = 0.5 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN p / ZA27 was obtained. The pipe obtained in Example 3 had a smooth surface, uniform size, significant dynamic recrystallization occurred in its structure, the crystal grain size reached 0.8 μm, and the formability of the billet and the comprehensive mechanical and thermal conductivity properties of the pipe were effectively improved by variable temperature extrusion.

[0046] Example 4 AlN reciprocally extruded in multiple passes at 300 °C pUsing the / ZA27 billet as the raw material, place it into the pipe extrusion die, attach four heating coils outside the extrusion cylinder, heat the billet along the length direction so that the temperatures are 250°C, 260°C, 270°C, and 280°C respectively, keep it warm for 1.0 h, and then extrude it at an extrusion speed (the moving speed of the extrusion head) v = 0.1 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN p / ZA27 was obtained. The pipe obtained in Example 4 has a smooth surface without cracks, uniform size, no sticky substances on the die surface, a clean cavity, significant dynamic recrystallization occurred in the structure of the extruded pipe, the crystal grain size reached 0.82 μm, and the formability of the billet, the comprehensive mechanical and thermal conductivity properties of the pipe were effectively improved by variable temperature extrusion.

[0047] Example 5 AlN reciprocally extruded at 250°C in multiple passes p Using the / ZA27 billet as the raw material, place it into the pipe extrusion die, attach four heating coils outside the extrusion cylinder, heat the billet along the length direction so that the temperatures are 250°C, 270°C, 290°C, and 310°C respectively, keep it warm for 0.5 h, and then extrude it at an extrusion speed (the moving speed of the extrusion head) v = 0.3 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN p / ZA27 was obtained. The pipe obtained in Example 5 has a smooth surface without cracks, uniform size, no sticky substances on the die surface, a clean cavity, significant dynamic recrystallization occurred in the structure of the extruded pipe, the crystal grain size reached 0.75 μm, and the formability of the billet, the comprehensive mechanical and thermal conductivity properties of the pipe were effectively improved by variable temperature extrusion.

[0048] Figure 1 is a schematic die diagram of a variable-temperature extrusion high thermal conductivity pipe. A pipe core die 2 of the pipe extrusion die is provided below an extrusion head 1 of an intelligent control pressure processing system. A pipe discharge die 8 is provided below the pipe core die 2. The extrusion head 1, the pipe core die 2 and the pipe discharge die 8 are provided between two upper and lower clamping plates 4. The two clamping plates 4 are connected by a screw 6. Both ends of the screw 6 and the corresponding clamping plate 4 are fastened by nuts 3. A billet 9 is provided between the pipe core die 2 and the pipe discharge die 8. A heating coil 7 is provided outside the pipe core die 2. The four heating coils 7 are respectively connected to a thermocouple 5 to control the heating of the billet at a gradient temperature along the length direction. During the extrusion process of the extrusion head 1, the pipe core 2 and the billet 9 move synchronously to prevent the pipe core from tilting due to uneven material flow during extrusion. In the pipe discharge die 8, the cylindrical billet is extruded into a thin-walled pipe. Thus, the manufacture of the high thermal conductivity composite thin-walled pipe is completed.

[0049] Figure 2 is a schematic diagram of the gradient temperature distribution in the extrusion direction when heating a stable billet. Taking the upper end face of the billet as the origin, the temperatures of each part along the extrusion direction are 250°C, 275°C, 300°C, and 325°C respectively, and the temperature gradually increases along the extrusion direction. By changing the temperature of each part of the billet along the extrusion direction, the forming performance of the billet, the surface quality of the thin-walled pipe and the pipe forming rate can be effectively improved.

[0050] As described above, the high thermal conductivity thin-walled composite pipe, its manufacturing method and use of the present invention can improve the formability of the billet and the pipe forming rate, reduce the cracks of the die, and extend the service life of the die by heating the billet at a gradient temperature in the vertical direction. As can be seen from the microstructure diagram of the thin-walled pipe, significant dynamic recrystallization occurs in the high thermal conductivity pipe manufactured by combining reciprocating extrusion and variable-temperature extrusion, and the average grain size of the equiaxed crystals without generated strain reaches below 1 μm, realizing the coordinated strengthening of the material under the action of fine grain strengthening, and providing research ideas for the further development of wire materials for power transmission.

[0051] Finally, it should be noted that each of the above embodiments is only for explaining the technical solution of the present invention and does not limit it. Although the present invention has been described in detail with reference to each of the above embodiments, those skilled in the art can modify the technical solutions described in each of the above embodiments or equivalently replace some or all of the technical features therein. It should be understood that these modifications or replacements do not depart from the essence of the corresponding technical solutions from the scope of the technical solutions of each embodiment of the present invention.

Description of Reference Numerals

[0052] 1. Extrusion head; 2. Pipe core mold; 3. Nut; 4. Clamping plate; 5. Thermocouple; 6. Screw; 7. Heating coil; 8. Pipe discharge mold; 9. Billet.

Claims

1. AlN after reciprocating extrusion in multiple passes ｐ Heat the / ZA27 billet, and the heating temperature increases in a gradient distribution in the extrusion direction from the / ZA27 billet to the pipe outlet. After heat preservation treatment, extrude to obtain the high thermal conductivity thin-walled composite pipe AlN ｐ / ZA27. The manufacturing method of the high thermal conductivity thin-walled composite pipe is characterized by including the step of obtaining ｐ / ZA27

2. The method for manufacturing a high thermal conductivity thin-walled composite pipe according to claim 1, wherein the temperature for reciprocating extrusion in a plurality of passes is 250 to 350 °C.

3. The method for manufacturing a high thermal conductivity thin-walled composite pipe according to claim 1, wherein the gradient distribution temperature along the extrusion direction is 250 to 350 °C.

4. The method for manufacturing a high thermal conductivity thin-walled composite pipe according to claim 1, wherein the time for heat preservation treatment is 0.5 to 1.5 h.

5. After the heat insulation treatment, control the extrusion speed at v = 0.1 to 0.5 mm / s to obtain the high thermal conductivity thin-walled composite pipe AlN ｐ / ZA27, and the method for manufacturing a high thermal conductivity thin-walled composite pipe according to claim 1, characterized in that.

6. High thermal conductivity thin-wall composite pipe AlN ｐ In the manufacturing process of / ZA27, the temperature along the length direction of the reciprocating extruded billet is changed to 250 to 350 °C, and the temperature interval is 10 to 30 °C. The manufacturing method of the high thermal conductivity thin-wall composite pipe according to claim 1, characterized in that.

7. The chemical composition of the high thermal conductivity thin-walled composite pipe is AlN ｐ / ZA27, where the volume percentage of AlN particles is φ = 4%, and the high thermal conductivity thin-walled composite pipe manufactured by the method according to claim 1.

8. In ZA27, by mass%, Zn accounts for 70.05% to 71.00%, Al accounts for 27.00% to 27.20%, Cu accounts for 2.00% to 2.05%, and the balance is Mg. The high thermal conductivity thin-walled composite pipe according to claim 7.

9. The high thermal conductivity thin-walled composite pipe according to claim 7, wherein the particle size of the AlN particles is 0.8 to 1 μm.

10. Use of the high thermal conductivity thin-walled composite pipe manufactured by the method according to any one of claims 1 to 6 or the high thermal conductivity thin-walled composite pipe according to any one of claims 7 to 9 as an electric power transmission wire material.

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