A heat pipe with high thermal conductivity and its manufacturing process

Abstract

The present invention discloses a heat pipe with high thermal conductivity and a manufacturing process thereof, and relates to the technical field of spiral fin tube surface treatment. A base tube is used as a cathode and a nickel plate is used as an anode. The base tube is placed in a nickel-containing plating solution for electrolytic deposition to form a nickel layer. A zincizing agent is used to embed the base tube obtained after nickel plating, and powder zinc is infiltrated to form an alloy infiltration layer to obtain a heat pipe. The present invention forms a nickel layer on the surface of the base tube by electroplating. When the base tube and the steel strip are welded, a molten pool is generated at the interface between the two, and liquid phase infiltration occurs, which reduces the contact thermal resistance, improves the thermal conductivity efficiency of the heat pipe, and simultaneously improves the surface hardness and corrosion resistance of the base tube. The plating solution contains a thermally conductive carbon filler, which is deposited on the surface of the base tube to form a nickel / carbon composite layer, thereby improving the thermal conductivity of the heat pipe. Then, zinc infiltration is performed, and zinc diffuses in the nickel layer and diffuses inward to the surface of the base tube to form a nickel-zinc layer and a zinc-iron layer, thereby obtaining an alloy infiltration layer, which effectively improves the thermal conductivity, high-temperature performance, and corrosion resistance of the base tube.

Description

Technical Field

[0001] The invention relates to the technical field of spiral fin tube surface treatment, in particular to a heat pipe with high thermal conductivity and a manufacturing process thereof. Background Art

[0002] As a high-efficiency heat transfer element with spiral fins, spiral finned tubes are widely used in heat exchange equipment in various fields such as the chemical industry, boiler economizers, air preheaters, and heat recovery of waste heat boilers. Its heat transfer area is several times, or even dozens of times, that of a bare tube. It has the characteristics of enhanced heat transfer, reduced flow resistance, and reduced metal consumption, which has a good promoting effect on the economy and operational reliability of heat exchange equipment. There are many ways to manufacture spiral finned tubes, including high-frequency resistance welded spiral finned tubes, brazed spiral finned tubes, and integral spiral finned tubes. Generally, steel strips are spirally wound around the outer surface of the steel pipe at a predetermined angle and pitch, and welded to form fins. Conventional steel pipes and steel strips are made of 304 stainless steel, which requires further surface treatment to achieve performance optimization. Therefore, we propose a heat pipe with high thermal conductivity and a manufacturing process thereof. Summary of the Invention

[0003] The object of the present invention is to provide a heat pipe with high thermal conductivity and a manufacturing process thereof to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a process for manufacturing a heat pipe with high thermal conductivity, comprising the following processes:

[0005] The base tube is nickel plated to form a nickel layer; and zinc is infiltrated to form an alloy infiltration layer to obtain a heat pipe.

[0006] Furthermore, the nickel plating process is as follows: using the substrate tube as the cathode and the nickel plate as the anode, placing them in a plating solution for electrolytic deposition;

[0007] The plating solution includes the following components by mass: 250-280 g / L nickel sulfate, 16-45 g / L nickel chloride, 35-40 g / L boric acid, 0.05-0.15 g / L sodium dodecyl sulfate, 1-10 g / L thermal conductive carbon filler, and a pH of 4-5;

[0008] The process conditions of electrolytic deposition are: bath temperature 50-65°C, current density 2-4A / dm 2 , deposition time is 5 to 60 minutes;

[0009] The plating solution is continuously stirred while the electrolytic deposition is in progress.

[0010] In the above technical solution, the substrate tube is placed in a nickel-containing plating solution for electrochemical nickel plating, forming a metallic nickel layer on the surface of the substrate tube, namely the nickel layer. When the substrate tube and the steel strip are welded, the contact area between the two melts at high temperature, forming a molten pool, forming a liquid phase flow, and infiltrating the contact area between the steel strip and the substrate tube. This can effectively eliminate dimensional errors that occur when the steel strip is wound, or pores caused by wrinkles at its root, thereby reducing the contact thermal resistance between the fins and the steel strip, and improving the thermal conductivity of the heat pipe. At the same time, the provision of the nickel layer can increase the surface hardness of the substrate tube, thereby enhancing its wear resistance and anti-scratch ability. It can also significantly improve the corrosion resistance of the substrate tube, effectively preventing the heat pipe from resisting corrosion in harsh environments.

[0011] The plating solution contains carbon fillers with high thermal conductivity (thermal conductive carbon fillers), which are deposited on the surface of the base tube under the action of electrolysis to form a nickel / carbon composite layer (nickel layer). This makes the nickel layer have good thermal conductivity, helps to establish heat conduction channels on the surface of the heat pipe, promotes the improvement of its heat transfer performance, and thus improves its thermal conductivity.

[0012] Furthermore, the thermally conductive carbon filler is a mixture of one or more of graphite, expanded graphite, carbon fiber, and carbon black.

[0013] Furthermore, the thermally conductive carbon filler is graphite and is modified. The modification process is as follows:

[0014] Titanium, silicon and graphite are mixed, ball-milled, an igniter is added, and the mixture is placed in a self-propagating high-temperature furnace. The igniter is ignited in an argon atmosphere to obtain a modified filler.

[0015] Furthermore, the ignition agent is a Ti-C ignition agent, and the mass ratio of titanium to carbon black is 1:4;

[0016] The mass ratio of graphite, titanium, silicon and igniter is 10: (13-20): (2.6-3.9): (0.05-0.10).

[0017] Furthermore, before ball milling, the reaction material also contains rare earth gel, which is prepared by the following process:

[0018] Lanthanum nitrate and glycine are mixed in deionized water to obtain a precursor; the mixture is heated to 98-102° C. and stirred until it becomes a gel; and the mixture is dried at 118-122° C. for 24 hours to obtain a rare earth gel.

[0019] Furthermore, the ratio of lanthanum nitrate, glycine, and deionized water is (50-55) g: (30-45) g: 100 mL.

[0020] Furthermore, the added amount of rare earth gel is 0.01% to 0.10% of the mass of graphite.

[0021] In the above technical solution, graphite is selected as the thermal conductive carbon filler, and a self-propagating high temperature reaction is carried out with titanium and silicon to synthesize TiC and SiC on the surface of graphite, and the graphite is loaded and coated to obtain a modified filler. The titanium on its surface exists in the form of Ti + , can undergo dissociative adsorption with water, form coordination, and produce hydrophilic groups (hydroxyl groups), making the modified graphite hydrophilic and having good wettability to water, improving the dispersion of the filler in the plating solution, thereby promoting the uniform distribution of the filler in the nickel layer and improving the quality of the nickel layer.

[0022] The TiC and SiC on the graphite surface have excellent thermal conductivity and hardness. As the interface layer between graphite and nickel metal, they build interfacial interaction between the two, promote heat transfer, reduce interfacial thermal resistance, and increase the thermal conductivity efficiency of the nickel layer, thereby improving the overall thermal conductivity of the heat pipe. They can also act as a reinforcing phase to increase the hardness, corrosion resistance, and high-temperature performance of the nickel layer, optimizing its performance.

[0023] Through the complexation of glycine and rare earth lanthanum ionic bonds, a gel is prepared and dried to obtain a dry gel (rare earth gel). The dry gel is then co-ball-milled with the raw material system of the modified filler to participate in self-propagation to form a modified filler doped with nano-lanthanum. This can improve the stability of the self-propagating high-temperature reaction, reduce the formation temperature of carbides, and improve the particle size of carbides, thereby improving the performance of the modified filler; it can also act as a reducing agent to prevent the oxidation of titanium, which is conducive to the formation of the target product of the subsequent sherardizing process.

[0024] The prepared nickel layer is a graphite / nickel composite layer doped with lanthanum, which can promote the nickel crystals to be arranged more closely and in smaller sizes, and help further improve the comprehensive capabilities of the nickel layer, such as high-temperature performance, corrosion resistance and thermal conductivity.

[0025] Furthermore, the sherardizing process is as follows: using a sherardizing agent, embedding the substrate tube obtained after nickel plating, and performing powder sherardizing;

[0026] The zirconizing agent includes the following components by mass: 65-70 parts of zinc powder, 30-32 parts of aluminum oxide, 3-4 parts of ammonium chloride, and 0.2-1.2 parts of lanthanum hydroxide;

[0027] The process conditions of powder sherardizing are: heating to 390-410°C at a heating rate of 3°C / min, keeping warm for 5-6 hours, and vacuum degree of -0.0100 to -0.0090 MPa.

[0028] Before the sherardizing process begins, the sherardizing agent and the substrate tube are kept at 250°C for 60 minutes.

[0029] In the above technical solution, the zirconizing agent includes zinc powder as a zirconizing agent, aluminum oxide as a dispersant, ammonium chloride as a reducing agent, and lanthanum hydroxide as a rare earth source. In the zirconizing process, the metallic element zinc diffuses in the nickel layer, and the nickel layer is gradually converted into a nickel-zinc layer. As the zirconizing reaction proceeds, the metallic element zinc continues to diffuse inward to the surface of the substrate tube, forming a zinc-iron layer, obtaining an alloy zirconized layer, thereby improving the bonding force between the nickel layer and the substrate tube, and effectively further improving the thermal conductivity, welding performance, high-temperature performance, and corrosion resistance of the substrate tube. Rare earth lanthanum can refine the zirconized layer structure and has a positive effect on improving its mechanical properties. The titanium present on the surface of the modified filler replaces zinc, attracting the iron in the zinc-iron layer to diffuse into the zinc and titanium regions, forming a composite layer of zinc, iron, and titanium, which can improve the corrosion resistance and high-temperature stability of the zirconized layer, while also improving its welding performance and processing performance.

[0030] Furthermore, after the sherardizing process, the heat pipe is subjected to hydrothermal treatment and thermal spraying-diffusion aluminizing.

[0031] Furthermore, the process of hydrothermal treatment is as follows:

[0032] The heat pipe obtained after zinc infiltration is placed in a mixed solution of potassium hydroxide and ammonium persulfate at a temperature of 150-160° C. and kept warm for 8-12 hours to form a zinc oxide layer.

[0033] Furthermore, in the potassium hydroxide and ammonium persulfate mixed solution, the concentration of potassium hydroxide is 3.0-3.5M, and the concentration of ammonium persulfate is 0.21-0.27M.

[0034] In the above technical solution, sodium hydroxide and ammonium persulfate are used as reaction liquids to hydrothermally treat the alloy diffusion layer. First, ammonium persulfate will oxidize zinc to form a zinc oxide film, which can subsequently serve as the nucleation core for zinc oxide generation. At the same time, the newly formed zinc oxide dissolves in the sodium hydroxide solution and reacts to form a hydroxyl complex, which acts as a zinc source and grows outside the zinc oxide nucleation core. As the oxidation and solution reaction proceed, zinc oxide nanorods are eventually formed, which are recorded as zinc oxide layers. This further improves the hardness, high temperature stability and corrosion resistance of the heat pipe, while still being able to exhibit good thermal conductivity. At the same time, the surface roughness of the heat pipe is improved, which helps to optimize the subsequent process performance.

[0035] Furthermore, the process of thermal spraying-diffusion aluminizing is as follows:

[0036] Thermal spraying: Arc spraying is used to melt the aluminum wire and spray it onto the surface of the heat pipe obtained by hydrothermal treatment; voltage is 30-32V, current is 180-200A;

[0037] Diffusion aluminizing: Place at 1000-1100℃, keep warm for 3-4 hours, perform diffusion aluminizing, vacuum degree 0.01-0.001Pa, and form an aluminizing layer.

[0038] In the above technical solution, molten aluminum is atomized and sprayed onto the surface of the zinc oxide layer through arc spraying. The aluminum atoms are then exposed to high temperatures, causing them to diffuse and form iron-aluminum phases, titanium-aluminum phases, zinc-aluminum oxide, and other phases. This effectively improves the heat pipe's stability in high-temperature and corrosive media, enhancing its high-temperature performance and corrosion resistance. Its moderate thermal conductivity allows for effective management of heat distribution, promoting heat transfer between the base tube and the outside world, and improving thermal conductivity. During the molten aluminum atomization and spraying process, a certain degree of oxidation occurs. The resulting aluminum oxide, along with the jet flow, forms a relatively dense aluminum oxide film on the heat pipe surface, effectively blocking oxygen and corrosive media, improving the heat pipe's corrosion resistance and apparent hardness.

[0039] The roughened zinc oxide layer can form a mechanical fit with the aluminized layer, enhancing the bonding strength between it and the heat pipe. At the same time, the specific surface area of ​​the zinc oxide layer increases, making it easier for active chlorine atoms to adsorb on the surface of the heat pipe, increasing the relative concentration, and enhancing the ability of aluminum atoms to diffuse into the heat pipe. The number of atomic channels for diffusion increases, which can effectively reduce the diffusion energy barrier and help form a fine-grained and dense aluminized layer, thereby improving its hardness and corrosion resistance.

[0040] Furthermore, the base tube includes the following mass components: carbon 0.07% to 0.13%, silicon ≤0.30%, manganese ≤1.00%, chromium 17.00% to 19.00%, nickel 7.50% to 10.50%, niobium 0.30% to 0.60%, nitrogen 0.05% to 0.12%, copper 2.50% to 3.50%, boron 0.001% to 0.010%, aluminum 0.003% to 0.015%, phosphorus ≤0.03%, sulfur ≤0.01%, and the balance is iron.

[0041] In the above technical solution, the predecessor steel strip of the fin is treated in the same way as the base tube, and nickel plating and zinc infiltration processes are performed on its surface in sequence to provide an alloy infiltration layer. Among the metal elements with better thermal conductivity than iron, nickel and zinc have good corrosion resistance and welding performance, thereby improving its thermal conductivity, corrosion resistance and welding performance; then it is welded to the heat pipe to improve the contact thermal resistance and further improve the performance of the spiral fin tube. DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The substrate tube comprises the following mass components: carbon 0.11%, silicon 0.21%, manganese 0.76%, chromium 18.10%, nickel 8.95%, niobium 0.47%, nitrogen 0.09%, copper 2.85%, boron 0.004%, aluminum 0.011%, phosphorus 0.003%, sulfur 0.002%, and the balance is iron; the dimensions are Φ38 mm × 4.5 mm;

[0044] Pure nickel plate: purity ≥99.99%, sourced from Jinchuan Group Co., Ltd.

[0045] The igniter is Ti-C igniter, and the mass ratio of titanium to carbon black is 1:4;

[0046] Titanium: particle size 48μm, purity ≥99%; silicon: particle size 45μm, purity ≥99%; zinc powder: particle size 800 mesh, purity ≥99%; alumina: particle size 25μm, purity ≥99%, all sourced from Beijing October New Materials Technology Co., Ltd.

[0047] Graphite: Flake graphite, particle size 150μm, purity ≥99%, sourced from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0048] Example 1: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following steps:

[0049] Step 1: Take lanthanum nitrate and glycine, mix them in deionized water to obtain a precursor; heat to 98°C and stir until it becomes a gel; place it at 118°C and dry it for 24 hours to obtain a rare earth gel; the ratio of lanthanum nitrate, glycine and deionized water is 50g:30g:100mL;

[0050] Titanium, silicon, graphite, and rare earth gel are mixed and ball-milled, an igniter is added, and the mixture is placed in a self-propagating high-temperature furnace. The igniter is ignited in an argon atmosphere to react and obtain a modified filler. The mass ratio of graphite, titanium, silicon, and igniter is 10:13:2.6:0.05. The amount of rare earth gel added is 0.01% of the mass of graphite.

[0051] The substrate tube is used as the cathode and the pure nickel plate is used as the anode. The substrate tube is placed in a plating solution for electrolytic deposition to form a nickel layer. The plating solution contains the following mass components: 250g / L nickel sulfate, 16g / L nickel chloride, 35g / L boric acid, 0.05g / L sodium dodecyl sulfate, 1g / L thermal conductive carbon filler, and a pH of 4. The process conditions for electrolytic deposition are: plating temperature 50°C, current density 2A / dm 2 , the deposition time is 30min; during the electrolytic deposition, the plating solution is continuously stirred;

[0052] Step 2: Using a sherardizing agent, the substrate tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 65 parts of zinc powder, 32 parts of aluminum oxide, 4 parts of ammonium chloride, and 0.2 parts of lanthanum hydroxide. The process conditions of the powder sherardizing are: heating to 390°C at a heating rate of 3°C / min, holding for 5 hours, and a vacuum degree of -0.0100 MPa. Before the sherardizing process begins, the sherardizing agent and the substrate tube are kept at 250°C for 60 minutes.

[0053] Step 3: placing the substrate tube obtained by zincification in a mixed solution of potassium hydroxide and ammonium persulfate, placing it at a temperature of 150° C., and keeping the temperature for reaction for 8 hours to form a zinc oxide layer; in the mixed solution of potassium hydroxide and ammonium persulfate, the concentration of potassium hydroxide is 3.5M, and the concentration of ammonium persulfate is 0.27M;

[0054] Arc spraying was used to melt the aluminum wire and spray it onto the surface of the hydrothermal treated base tube at a voltage of 30V and a current of 180A. The tube was then placed at 1000°C for 4 hours for diffusion aluminum infiltration with a vacuum degree of 0.01Pa to obtain a heat pipe.

[0055] Example 2: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following steps:

[0056] Step 1: Take lanthanum nitrate and glycine, mix them in deionized water to obtain a precursor; heat to 100°C, stir until it becomes a gel; dry at 120°C for 24 hours to obtain a rare earth gel; the ratio of lanthanum nitrate, glycine, and deionized water is 52g:38g:100mL;

[0057] Titanium, silicon, graphite, and rare earth gel are mixed, ball-milled, and an igniter is added. The mixture is placed in a self-propagating high-temperature furnace and the igniter is ignited in an argon atmosphere to obtain a modified filler. The mass ratio of graphite, titanium, silicon, and igniter is 10:16:3.2:0.08. The amount of rare earth gel added is 0.5% of the mass of graphite.

[0058] The substrate tube was used as the cathode and the nickel plate was used as the anode. The nickel layer was formed by electrolytic deposition in a plating solution containing the following components by mass: 265 g / L nickel sulfate, 30 g / L nickel chloride, 38 g / L boric acid, 0.10 g / L sodium dodecyl sulfate, 5 g / L thermal conductive carbon filler, and a pH of 4.5. The process conditions for electrolytic deposition were: plating temperature of 58°C, current density of 3 A / dm 2 , the deposition time is 30min; during the electrolytic deposition, the plating solution is continuously stirred;

[0059] Step 2: Using a sherardizing agent, the substrate tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 68 parts of zinc powder, 31 parts of aluminum oxide, 3.5 parts of ammonium chloride, and 0.7 parts of lanthanum hydroxide. The process conditions of the powder sherardizing are: heating to 400°C at a heating rate of 3°C / min, holding for 5.5 hours, and a vacuum degree of -0.0095 MPa. Before the sherardizing process begins, the sherardizing agent and the substrate tube are kept at 250°C for 60 minutes.

[0060] Step 3: placing the substrate tube obtained by zincification in a mixed solution of potassium hydroxide and ammonium persulfate, placing it at a temperature of 155° C., and keeping the temperature for reaction for 10 hours to form a zinc oxide layer; in the mixed solution of potassium hydroxide and ammonium persulfate, the concentration of potassium hydroxide is 3.2M, and the concentration of ammonium persulfate is 0.24M;

[0061] Arc spraying was used to melt the aluminum wire and spray it onto the surface of the hydrothermal treated base tube at a voltage of 31V and a current of 190A. The heat pipe was then placed at 1050°C for 3.5 hours for diffusion aluminum infiltration with a vacuum degree of 0.005Pa.

[0062] Example 3: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following steps:

[0063] Step 1: Take lanthanum nitrate and glycine, mix them in deionized water to obtain a precursor; heat to 102°C, stir until it becomes a gel; place it at 122°C and dry it for 24 hours to obtain a rare earth gel; the ratio of lanthanum nitrate, glycine, and deionized water is 55g:45g:100mL;

[0064] Titanium, silicon, graphite, and rare earth gel are mixed, ball-milled, and an igniter is added. The mixture is placed in a self-propagating high-temperature furnace and the igniter is ignited in an argon atmosphere to obtain a modified filler. The mass ratio of graphite, titanium, silicon, and igniter is 10:20:3.9:0.10. The amount of rare earth gel added is 0.10% of the mass of graphite.

[0065] The substrate tube is used as the cathode and the nickel plate is used as the anode. The substrate tube is placed in a plating solution for electrolytic deposition to form a nickel layer. The plating solution contains the following components by mass: 280g / L nickel sulfate, 45g / L nickel chloride, 40g / L boric acid, 0.15g / L sodium dodecyl sulfate, 10g / L thermal conductive carbon filler, and a pH of 5. The process conditions for electrolytic deposition are: plating temperature 65°C, current density 4A / dm 2 , the deposition time is 30min; during the electrolytic deposition, the plating solution is continuously stirred;

[0066] Step 2: Using a sherardizing agent, the substrate tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 70 parts of zinc powder, 30 parts of aluminum oxide, 3 parts of ammonium chloride, and 1.2 parts of lanthanum hydroxide. The process conditions of the powder sherardizing are: heating to 410°C at a heating rate of 3°C / min, holding for 6 hours, and a vacuum degree of -0.0090 MPa. Before the sherardizing process begins, the sherardizing agent and the substrate tube are kept at 250°C for 60 minutes.

[0067] Step 3: placing the substrate tube obtained by zincification in a mixed solution of potassium hydroxide and ammonium persulfate, placing it at a temperature of 160° C., and keeping the temperature for reaction for 12 hours to form a zinc oxide layer; in the mixed solution of potassium hydroxide and ammonium persulfate, the concentration of potassium hydroxide is 3.0M, and the concentration of ammonium persulfate is 0.21M;

[0068] Arc spraying was used to melt the aluminum wire and spray it onto the surface of the hydrothermal treated base tube at a voltage of 32V and a current of 200A. The heat pipe was then placed at 1100°C for 3 hours for diffusion aluminum infiltration with a vacuum degree of 0.001Pa.

[0069] Comparative Example 1: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following processes:

[0070] Step 1: Take lanthanum nitrate and glycine, mix them in deionized water to obtain a precursor; heat to 98°C and stir until it becomes a gel; place it at 118°C and dry it for 24 hours to obtain a rare earth gel; the ratio of lanthanum nitrate, glycine and deionized water is 50g:30g:100mL;

[0071] Titanium, silicon, graphite, and rare earth gel are mixed and ball-milled, an igniter is added, and the mixture is placed in a self-propagating high-temperature furnace. The igniter is ignited in an argon atmosphere to react and obtain a modified filler. The mass ratio of graphite, titanium, silicon, and igniter is 10:13:2.6:0.05. The amount of rare earth gel added is 0.01% of the mass of graphite.

[0072] The substrate tube is used as the cathode and the pure nickel plate is used as the anode. The substrate tube is placed in a plating solution for electrolytic deposition to form a nickel layer. The plating solution contains the following mass components: 250g / L nickel sulfate, 16g / L nickel chloride, 35g / L boric acid, 0.05g / L sodium dodecyl sulfate, 1g / L thermal conductive carbon filler, and a pH of 4. The process conditions for electrolytic deposition are: plating temperature 50°C, current density 2A / dm 2 , the deposition time is 30min; during the electrolytic deposition, the plating solution is continuously stirred;

[0073] Step 2: Using a sherardizing agent, the substrate tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 65 parts of zinc powder, 32 parts of aluminum oxide, 4 parts of ammonium chloride, and 0.2 parts of lanthanum hydroxide. The process conditions of the powder sherardizing are: heating to 390°C at a heating rate of 3°C / min, holding for 5 hours, and a vacuum degree of -0.0100 MPa. Before the sherardizing process begins, the sherardizing agent and the substrate tube are kept at 250°C for 60 minutes.

[0074] Step 3: Use arc spraying to melt the metal aluminum wire and spray it on the surface of the base tube obtained by hydrothermal treatment at a voltage of 30V and a current of 180A to obtain a heat pipe.

[0075] Comparative Example 2: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following processes:

[0076] Step 1: titanium, silicon, and graphite are mixed, ball-milled, an igniter is added, and the mixture is placed in a self-propagating high-temperature furnace. The igniter is ignited in an argon atmosphere to react and obtain a modified filler; the mass ratio of graphite, titanium, silicon, and igniter is 10:13:2.6:0.05;

[0077] The substrate tube is used as the cathode and the pure nickel plate is used as the anode. The substrate tube is placed in a plating solution for electrolytic deposition to form a nickel layer. The plating solution contains the following mass components: 250g / L nickel sulfate, 16g / L nickel chloride, 35g / L boric acid, 0.05g / L sodium dodecyl sulfate, 1g / L thermal conductive carbon filler, and a pH of 4. The process conditions for electrolytic deposition are: plating temperature 50°C, current density 2A / dm 2 , the deposition time is 30min; during the electrolytic deposition, the plating solution is continuously stirred;

[0078] Step 2: Using a sherardizing agent, the base tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 65 parts of zinc powder, 32 parts of aluminum oxide, and 4 parts of ammonium chloride. The process conditions of the powder sherardizing are: heating to 390° C. at a heating rate of 3° C. / min, holding for 5 hours, and a vacuum degree of -0.0100 MPa. Before the sherardizing process begins, the sherardizing agent and the base tube are held at 250° C. for 60 minutes. The heat pipe is obtained.

[0079] Comparative Example 3: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following processes:

[0080] Step 1: Using a substrate tube as a cathode and a pure nickel plate as an anode, the substrate tube is placed in a plating solution for electrolytic deposition to form a nickel layer; the plating solution comprises the following components by mass: 250 g / L nickel sulfate, 16 g / L nickel chloride, 35 g / L boric acid, 0.05 g / L sodium dodecyl sulfate, and 1 g / L graphite, with a pH of 4; the process conditions for the electrolytic deposition are: a plating temperature of 50° C., a current density of 2 A / dm2, and a deposition time of 30 minutes; and the plating solution is continuously stirred during the electrolytic deposition process;

[0081] Step 2: Using a sherardizing agent, the base tube obtained after nickel plating is embedded and powder sherardized to form an alloy layer. The sherardizing agent includes the following components by weight: 65 parts of zinc powder, 32 parts of aluminum oxide, and 4 parts of ammonium chloride. The process conditions of the powder sherardizing are: heating to 390° C. at a heating rate of 3° C. / min, holding for 5 hours, and a vacuum degree of -0.0100 MPa. Before the sherardizing process begins, the sherardizing agent and the base tube are held at 250° C. for 60 minutes. The heat pipe is obtained.

[0082] Comparative Example 4: A process for manufacturing a heat pipe with high thermal conductivity, comprising the following processes:

[0083] Step 1. Using the base tube as the cathode and the pure nickel plate as the anode, the base tube is placed in a plating solution for electrolytic deposition to form a nickel layer. The plating solution includes the following components by mass: 250 g / L nickel sulfate, 16 g / L nickel chloride, 35 g / L boric acid, 0.05 g / L sodium dodecyl sulfate, and 1 g / L graphite, with a pH of 4. The process conditions for the electrolytic deposition are: a plating solution temperature of 50° C., a current density of 2 A / dm2, and a deposition time of 30 minutes. During the electrolytic deposition, the plating solution is continuously stirred to obtain a heat pipe.

[0084] Comparative Example 5: A heat pipe with high thermal conductivity, using a base tube as the heat pipe.

[0085] Experiment: Take the heat pipes obtained in Examples 1-3 and Comparative Examples 1-5, make samples, test their performance and record the test results:

[0086] Hardness: Use Vickers hardness tester to test the surface hardness of the sample;

[0087] Thermal conductivity test: Use laser thermal conductivity meter to detect the thermal conductivity of the sample;

[0088] Corrosion resistance test: A three-electrode system was used as the test system, with the sample as the working electrode, platinum sheet as the auxiliary electrode, saturated calomel as the reference electrode, and 3.5wt% sodium chloride solution as the electrolyte. The electrochemical corrosion parameters of the sample were tested at a test temperature of 25°C, a scanning voltage range of -0.2 to 0.5V, and a scanning rate of 1mv / s.

[0089] High temperature performance test: solid sodium chloride is placed on the surface of the sample with a deposition rate of 2.5mh / cm2 , placed in a tube furnace, heated to 600℃ at a heating rate of 8℃ / min, introduced 65℃ water vapor, and tested the time when 30% of the sample surface area was corroded or peeled off.

[0090]

[0091] According to the data in the above table, we can clearly draw the following conclusions:

[0092] The heat pipes obtained in Examples 1-3 were compared with the heat pipes obtained in Comparative Examples 1-5. The test results show that:

[0093] Compared to the comparative example, the heat pipes obtained in Examples 1-3 have higher hardness, thermal conductivity, corrosion time, and lower self-corrosion current density, which fully demonstrates that the present invention achieves improvements in the hardness, thermal conductivity, corrosion resistance, and high-temperature performance of the heat pipes.

[0094] Compared to Example 1, Comparative Example 1 did not undergo hydrothermal treatment or thermal diffusion. Based on Comparative Example 1, Comparative Example 2 did not include thermal spraying, and the alloying layer did not contain the metallic element lanthanum. Based on Comparative Example 2, the graphite in the plating solution in Comparative Example 3 was not modified. Comparative Example 4 used a nickel-plated substrate as a heat pipe, and Comparative Example 5 used a substrate as a heat pipe. The heat pipes obtained in Comparative Examples 1-5 showed decreased hardness, thermal conductivity, and corrosion time, while their self-corrosion current density data deteriorated. This indicates that the present invention's design of the heat pipe process and its components can promote comprehensive improvements in hardness, thermal conductivity, corrosion resistance, and high-temperature performance.

[0095] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A process for manufacturing a heat pipe with high thermal conductivity, characterized by: The substrate tube is used as cathode and the nickel plate is used as anode, and is placed in a nickel plating solution for electrolytic deposition to form a nickel layer; The base tube obtained after nickel plating is embedded with a zincizing agent, and powder zinc is infiltrated to form an alloy infiltration layer to obtain a heat pipe; The nickel-containing plating solution comprises the following components by mass: 250-280 g / L nickel sulfate, 16-45 g / L nickel chloride, 35-40 g / L boric acid, 0.05-0.15 g / L sodium dodecyl sulfate, 1-10 g / L thermal conductive carbon filler, and a pH of 4-5; The thermal conductive carbon filler is graphite and is modified. The modification process is as follows: Titanium, silicon, graphite and rare earth gel are mixed, ball-milled, and an igniter is added. The mixture is placed in a self-propagating high-temperature furnace, and the igniter is ignited in an argon atmosphere to obtain a modified filler.

2. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: The mass ratio of the graphite, titanium, silicon and igniter is 10:(13-20):(2.6-3.9):(0.05-0.10); the added amount of the rare earth gel is 0.01%-0.10% of the mass of the graphite.

3. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: After the sherardizing process, the heat pipe is subjected to hydrothermal treatment and thermal spraying-diffusion aluminizing; The hydrothermal treatment process is as follows: the heat pipe obtained after the sherardization is placed in a mixed solution of potassium hydroxide and ammonium persulfate at a temperature of 150-160°C and kept warm for 8-12 hours to form a zinc oxide layer; The thermal spraying-diffusion aluminizing process is as follows: using arc spraying, the metal aluminum wire is melted and sprayed on the surface of the heat pipe obtained by hydrothermal treatment; then placed at a temperature of 1000-1100°C, kept warm for 3-4 hours, and diffused aluminized, with a vacuum degree of 0.01-0.001Pa.

4. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: The rare earth gel is prepared by the following process: Lanthanum nitrate and glycine are mixed in deionized water to obtain a precursor; the mixture is heated to 98-102° C. and stirred until it becomes a gel; and the mixture is dried at 118-122° C. for 24 hours to obtain a rare earth gel.

5. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: The process conditions of the electrolytic deposition are: bath temperature 50-65°C, current density 2-4A / dm 2 , the deposition time is 5 to 60 minutes.

6. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: The sherardizing agent comprises the following components by weight: 65-70 parts of zinc powder, 30-32 parts of aluminum oxide, 3-4 parts of ammonium chloride, and 0.2-1.2 parts of lanthanum hydroxide.

7. The process for manufacturing a heat pipe with high thermal conductivity according to claim 1, characterized in that: The process conditions of the powder sherardizing are: heating to 390-410° C. at a heating rate of 3° C. / min, keeping the temperature for 5-6 hours, and a vacuum degree of -0.0100 to -0.0090 MPa.

8. A heat pipe with high thermal conductivity manufactured according to the manufacturing process according to any one of claims 1 to 7.

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