THIN-WALLED COMPOSITE PIPE WITH HIGH THERMAL CONDUCTIVITY, AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

A method for preparing a thin-walled composite pipe is provided, in which an AlN particle/zinc-aluminum 27 (AlN.sub.p/ZA27) composite billet is subjected to multi-pass reciprocating extrusion at 250-350 C., and then loaded into a pipe extrusion die. The composite billet is heated with the temperature being in an ascending gradient distribution (within a range of 250-350 C.) along an extrusion direction from the billet to an outlet of the die, then kept a preset temperature for a period of time, and finally extruded at a rate of 0.1-0.5 mm/s to obtain the thin-walled composite pipe. A thin-walled composite pipe prepared by this method is also provided, including an AlN particle and a ZA27 alloy.

Claims

1. A method for preparing a thin-walled composite pipe, comprising: (1) subjecting an AlN particle/zinc-aluminum alloy 27 (AlN.sub.p/ZA27) composite billet to multi-pass reciprocating extrusion to obtain an extruded AlN.sub.p/ZA27 composite; (2) heating the extruded AlN.sub.p/ZA27 composite to a preset temperature, wherein a temperature of the heating is in an ascending gradient distribution along an extrusion direction from the extruded AlN.sub.p/ZA27 composite to an outlet of an extrusion die; and (3) keeping the extruded AlN.sub.p/ZA27 composite at the preset temperature followed by extrusion to obtain the thin-walled composite pipe.

2. The method of claim 1, wherein the multi-pass reciprocating extrusion is performed at 250-350 C.

3. The method of claim 1, wherein the temperature of the heating is in the ascending gradient distribution within a range of 250-350 C.

4. The method of claim 1, wherein the extruded AlN.sub.p/ZA27 composite is kept at the preset temperature for 0.5-1.5 h.

5. The method of claim 1, wherein in step (3), the extrusion is performed at a speed of 0.1-0.5 mm/s.

6. The method of claim 1, wherein a temperature of the multi-pass reciprocating extrusion is altered within a range of 250-350 C. at an interval of 10-30 C. along a length direction to meet an increasing gradient temperature distribution from top to bottom of the extrusion die.

7. A thin-walled composite pipe prepared by the method of claim 1, wherein a chemical composition of the thin-walled composite pipe comprises an AlN particle and (AlN.sub.p) and a ZA27 alloy; and a volume percentage of the AlN particle in the thin-walled composite pipe is 4%.

8. The thin-walled composite pipe of claim 7, wherein the ZA27 alloy comprises 70.05%-71.00% by weight of zinc (Zn), 27.00%-27.20% by weight of aluminum (Al), 2.00%-2.05% by weight of copper (Cu), and magnesium (Mg) being remainder.

9. The thin-walled composite pipe of claim 7, wherein a particle size of the AlN particle is 0.8-1 m.

10. A power transmission wire, comprising: the thin-walled composite pipe of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 schematically illustrates assembly of a variable-temperature extrusion die for pipes according to an embodiment of the present disclosure.

[0037] FIG. 2 shows a temperature gradient distribution of heating a billet along an extrusion direction according to an embodiment of the present disclosure.

[0038] In the figures: 1, ram; 2, die core; 3, screw; 4, clamp plate; 5, thermocouple; 6, screw rod; 7, heating coil; 8, die; and 9, billet.

DETAILED DESCRIPTION OF EMBODIMENTS

[0039] The technical solutions of the present disclosure will be clearly and completely described below. It is obvious that described herein are only some embodiments of the present disclosure, rather than all embodiments. Based on the embodiments provided herein, other embodiments obtained by those of ordinary skill in the art without making creative effort shall fall within the scope of the present disclosure.

[0040] In the present disclosure, unless otherwise defined, individual embodiments described herein and technical features therein can be combined to form new technical solutions in the absence of contradiction.

[0041] In the present disclosure, unless otherwise defined, the symbol % indicates a weight percent of individual components relative to a composition, and the term part indicates part by weight.

[0042] In the present disclosure, unless otherwise defined, components described herein or their preferred components can be combined with each other to form new technical solutions.

[0043] In the present disclosure, unless otherwise defined, a numerical range a-b covers any real number combination between a and b, where both a and b are real numbers. For example, a numerical range 6-22 represents that all real numbers between 6 and 22 are listed in the present disclosure, and 6-22 is only an abbreviated representation of a combination of these values.

[0044] A range disclosed in the present disclosure is in the form with a lower limit and an upper limit, where the lower limit includes one or more lower limits, and the upper limit includes one or more upper limits.

[0045] In the present disclosure, the term and/of used herein includes a combination of one or more associated items or all possible combinations thereof.

[0046] In the present disclosure, unless otherwise defined, each individual reaction or operating step can be performed sequentially or be performed according to a sequence. In some embodiments, reaction method in the present disclosure is performed in sequence.

[0047] Unless otherwise defined, technical terms and scientific terms used herein have the same meaning as those familiar to those of ordinary skill in the art. In addition, any method or material which is similar or equal to disclosure herein may be applied to the present disclosure.

[0048] A thin-walled composite pipe with high thermal conductivity, and a preparation method and application thereof are provided herein. An outer side of an extrusion container of a pipe extrusion die is provided with four heating coils, and each of the four heating coils is connected to a thermocouple. An AlN.sub.p/ZA27 composite billet is subjected to multi-pass reciprocating extrusion at 250-350 C. to obtain a tubular extrusion raw material. The tubular extrusion raw material, after being applied with a boron nitride lubricant, is loaded into the extrusion container together with a die core. Then, a die is put into the extrusion container. A clamp plate is assembled at two ends of the extrusion container, and is configured to clamp the die. After a complete assembly of the pipe extrusion die, the pipe extrusion die is put into the intelligent-control pressure processing system to be pre-compacted. Each of the four heating coils is controlled to heat to 250-350 C. The tubular extrusion raw material is kept at 250-350 C. for 0.5-1.5 h, and is extruded at an extrusion rate (movement rate of a ram) of 0.1-0.5 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity. The method for preparing the thin-walled composite pipe with high thermal conductivity by variable temperature extrusion provided herein has reasonable control of extrusion temperature distribution, uniform extrusion of pipe controlled by gradient temperature along an extrusion direction, high output rate of pipe and appropriate extrusion rate, and can effectively compensate for temperature changes of the billet and the die through gradient temperature extrusion, which ensures a high extrusion ratio section of the billet has a higher temperature during flowing, forms a temperature control of the billet, improves gradient fluidity of the billet and an extrusion material of an outlet of the pipe, improves the formability of the billet, reduces the cracking of the die, prolongs the service life of die and has good application prospect in the power transmission line materials.

[0049] A method for preparing a thin-walled composite pipe with high thermal conductivity is provided, including the following steps.

[0050] (S1) An AlN.sub.p/ZA27 composite billet is subjected to reciprocating extrusion and turning processing to obtain a raw tubular extrusion billet for extrusion-waiting billet. Around hole is formed in the extrusion billet centre to place the die core or mold core to form thin-walled pipes of different thicknesses when the billet and the mold core simultaneously are applied to move through the die under the extrusion force. A boron nitride lubricant is applied onto a surface of the tubular extrusion billet.

[0051] The extrusion billet with a centre through hole (i.e. tubular extrusion billet as raw material for extrusion) has an external diameter of (=29.5-30.5 mm, a length of L=55.0-60.0 mm and an inner diameter of =6.0-10.0 mm.

[0052] (S2) Four heating coils 7 are respectively provided on an outer side of an extrusion container, and are respectively connected to a thermocouple 5 and a temperature control system.

[0053] (S3) The tubular extrusion billet obtained from the step (S1) is loaded into the extrusion container together with the mold core or die core. A die 8 is mounted on a bottom of the extrusion container. Two ends of the extrusion container are each provided with a clamp plate to fix the middle die.

[0054] (S4) The pipe extrusion die assembled in the step (S3) is pre-compacted by an intelligent-control pressure processing system.

[0055] (S5) A power supply is turned on to control the four heating coils to heat the billet to 250-350 C. in a gradient temperature pattern along a length direction of the billet with a temperature interval of 10-30 C., and the billet is kept at 250-350 C. for 0.5-1 h. An outside of each heating coil is wrapped with a flame-resistant cotton for thermal insulation.

[0056] (S6) The pressure processing system is started to extrude the billet at a rate of 0.1-0.5 mm/s (i.e., movement rate of a ram).

[0057] (S7) The power supply is turned off, and the die and the extrusion container are cleaned. A thin-walled composite pipe with high thermal conductivity is obtained.

[0058] A chemical composition of the thin-walled composite pipe prepared by the above method is represented by AlN.sub.p/ZA27, where a volume percentage Y of the AlN particle is 4%, and a particle size of the AlN particle is 0.8-1 m; and the ZA27 alloy includes 70.05%-71.00% by weight of zinc (Zn), 27.00%-27.20% by weight of aluminum (Al), 2.00%-2.05% by weight of copper (Cu), and magnesium (Mg) being remainder.

[0059] According to a microstructure diagram, the thin-walled composite pipe prepared by the method (variable-temperature extrusion) of the present disclosure undergoes obvious dynamic recrystallization, and an average grain size of the generated undistorted equiaxed crystal is less than 1 m, thereby realizing the strengthening and toughening of the material under the action of fine grain strengthening.

[0060] The thin-walled composite pipe prepared by the method of the present disclosure can be applied in the power transmission wire materials.

[0061] In order to illustrate the objects, technical solutions and advantages of embodiments of this application more clearly, the technical solutions of the embodiments of this application will be clearly and fully described below with reference to the accompanying drawings. It is obvious that described herein are only some embodiments of the present disclosure, rather than all embodiments. In general, the components in the embodiments described and shown herein can be arranged and designed in different configurations. Therefore, the detailed description of the embodiments of this application with reference to the accompanying drawings is only illustrative, rather than limiting the scope of this application. Based on the embodiments provided herein, other embodiments obtained by those of ordinary skill in the art without making creative effort shall fall within the scope of this application.

Embodiment 1

[0062] An AlN.sub.p/ZA27 composite billet was subjected to multi-pass reciprocating extrusion at 250 C., and transferred to the pipe extrusion die. Four heating coils are mounted on the outer side of the extrusion container, and are respectively turned on to heat the billet at 250 C., 260 C., 270 C. and 280 C. along the length direction. Then the billet is kept at the heating temperature for 0.5 h and extruded at an extrusion rate (movement rate of the ram) of 0.1 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity.

[0063] The AlN.sub.p/ZA27 composite pipe obtained from Embodiment 1 had a smooth surface without cracking and a uniform size, and the obvious dynamic recrystallization occurred in its microstructure, and a grain size reached 0.9 m, indicating that the variable-temperature extrusion can effectively improve the formability of the billet and the comprehensive mechanical property and thermal conductivity of the pipe.

Embodiment 2

[0064] An AlN.sub.p/ZA27 composite billet was subjected to multi-pass reciprocating extrusion at 250 C., and transferred to the pipe extrusion die. Four heating coils are mounted on the outer side of the extrusion container, and are respectively turned on to heat the billet at 250 C., 275 C., 300 C. and 325 C. along the length direction. Then the billet is kept at the heating temperature for 1.0 h and extruded at an extrusion rate (movement rate of the ram) of 0.2 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity.

[0065] The AlN.sub.p/ZA27 composite pipe obtained from Embodiment 2 had a smooth surface without cracking and a uniform size, and the obvious dynamic recrystallization occurred in its microstructure, and a grain size reached 0.85 m, indicating that the variable-temperature extrusion can effectively improve the formability of the billet and the comprehensive mechanical property and the thermal conductivity of the pipe.

Embodiment 3

[0066] An AlN.sub.p/ZA27 composite billet was subjected to multi-pass reciprocating extrusion at 300 C., and transferred to the pipe extrusion die. Four heating coils are mounted on the outer side of the extrusion container, and are respectively turned on to heat the billet at 250 C., 265 C., 280 C. and 295 C. along the length direction. Then the billet is kept at the heating temperature for 0.5 h and extruded at an extrusion rate (movement rate of the ram) of 0.5 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity.

[0067] The AlN.sub.p/ZA27 composite pipe obtained from Embodiment 3 had a smooth surface without cracking and a uniform size, and the obvious dynamic recrystallization occurred in its microstructure, and a grain size reached 0.8 m, indicating that the variable-temperature extrusion can effectively improve the formability of the billet and the comprehensive mechanical property and the thermal conductivity of the pipe.

Embodiment 4

[0068] An AlN.sub.p/ZA27 composite billet was subjected to multi-pass reciprocating extrusion at 300 C., and transferred to the pipe extrusion die. Four heating coils are mounted on the outer side of the extrusion container, and are turned on to respectively heat the billet at 250 C., 260 C., 270 C. and 280 C. along the length direction. Then the billet is kept at the heating temperature for 1.0 h and extruded at an extrusion rate (movement rate of the ram) of 0.1 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity.

[0069] The AlN.sub.p/ZA27 composite pipe obtained from Embodiment 4 had a smooth surface without cracking, a uniform size, no adhesive on a die surface and a clean inner cavity, and the obvious dynamic recrystallization occurred in its microstructure, and a grain size reached 0.82 m, indicating that the variable-temperature extrusion can effectively improve the formability of the billet and the comprehensive mechanical property and the thermal conductivity of the pipe.

Embodiment 5

[0070] An AlN.sub.p/ZA27 composite billet was subjected to multi-pass reciprocating extrusion at 250 C., and transferred to the pipe extrusion die. Four heating coils are mounted on the outer side of the extrusion container, and are respectively turned on to heat the billet at 250 C., 270 C., 290 C. and 310 C. along the length direction. Then the billet is kept at the heating temperature for 0.5 h and extruded at an extrusion rate (movement rate of the ram) of 0.3 mm/s to obtain an AlN.sub.p/ZA27 composite pipe with high thermal conductivity.

[0071] The AlN.sub.p/ZA27 composite pipe obtained from Embodiment 5 had a smooth surface without cracking, a uniform size, no adhesive on a die surface and a clean inner cavity, and the obvious dynamic recrystallization occurred in its microstructure, and a grain size reached 0.75 m, indicating that the variable-temperature extrusion can effectively improve the formability of the billet and the comprehensive mechanical property and the thermal conductivity of the pipe.

[0072] Referring to FIG. 1, which schematically illustrates assembly of a variable-temperature extrusion die for pipes, a die core 2 of the pipe extrusion die is arranged below a ram 1 of the intelligent-control pressure processing system. The die 8 is arranged below the die core 2. The ram 1, the die core 2 and the die 8 are arranged between two clamp plates 4 arranged up and down. The two clamp plates 4 are connected to each other through a screw rod 6, and two ends of the screw rod 6 are respectively in fastening connection with a corresponding clamp through a screw 3. The billet 9 is arranged between the die core 2 and the die 8. Each of the four heating coils 7 is arranged on the outer side of the die core 2, and is connected to the thermocouple 5 to control the gradient temperature heating along the length direction on the billet. During the extrusion process conducted by the ram 1, the die core 2 and the billet 9 move synchronously to prevent the die core 2 from tilting caused by uneven flow of the material, and the billet is extruded into a thin-walled pipe at a cylinder of the die 8 to complete the preparation of the thin-walled composite pipe with high thermal conductivity.

[0073] FIG. 2 shows the temperature gradient distribution of heating the billet along the extrusion direction. An upper end face of the billet is regarded as an origin point. Temperatures of each section are in an ascending gradient distribution along the extrusion direction from the extruded AlN.sub.p/ZA27 composite to an outlet of an extrusion die, and are respectively 250 C., 275 C., 300 C. and 325 C. The formability of the billet, the surface quality of the thin-walled pipe and the pipe production can be effectively improved by changing the temperatures of each section.

[0074] In summary, this application provides a thin-walled composite pipe with high thermal conductivity, and a preparation method and application thereof to improve the formability of the billet and the pipe production, reduce cracking of the die and prolong the service life of the die by controlling the gradient temperature heating along the vertical direction on the billet. According to the microstructure diagram of the thin-walled composite pipe, the thin-walled composite pipe with high thermal conductivity prepared by the method of the present disclosure undergoes obvious dynamic recrystallization, and an average grain size of the generated undistorted equiaxed crystal is less than 1 m, thereby realizing the strengthening and toughening of the material under the action of fine grain strengthening, and providing research ideas for further development of reliable power transmission line materials.

[0075] It should be noted that embodiments described above are only illustrative, and are not intended to limit this application. Although this application is described in detail with reference to the above embodiments, those of ordinary skill in the art can still make various modifications and replacements to the technical solutions described by the above embodiments. However, any modifications and replacements made without departing from the spirit of the present disclosure shall fall within the scope of the disclosure defined by the appended claims.