A method and application of in-situ growth of capillary structure on stainless steel surface

Abstract

The present application provides a method and application for in-situ growth of capillary structure on the surface of stainless steel, the method comprising: in an inert gas or a reducing gas, covering the surface of the stainless steel with a copper source, heating the surface of the stainless steel, and obtaining stainless steel with capillary structure grown on the surface. The present application promotes the diffusion of iron elements on the surface to the inside by performing local high temperature on the surface of the stainless steel, greatly reduces the free iron ions on the surface, and produces structural voids. The copper source on the surface enters the structural voids to form a porous capillary structure; at the same time, the activity of high-temperature resistant elements such as chromium and molybdenum is relatively low, and the inward diffusion is slow, thereby forming a high-copper, high-chromium, and high-molybdenum protective layer on the surface, further preventing water and water vapor from corroding the stainless steel; further, the present application is to grow a capillary structure in situ on the surface of the stainless steel, that is, part of the capillary structure is located in the original position of the stainless steel, without the need to subsequently provide capillaries through stainless steel wire mesh, copper wire mesh, etc., so that a thinner heat spreader can be obtained later.

Description

Technical Field

[0001] The present application relates to the technical field of stainless steel, and in particular to a method and application of in-situ growth of capillary structures on the surface of stainless steel. Background Art

[0002] Compared to copper vapor chambers, stainless steel vapor chambers offer a host of advantages, including high strength, low cost, and excellent corrosion resistance. However, stainless steel vapor chambers still have drawbacks that limit their widespread application. For example, under vacuum conditions, the free iron in the stainless steel reacts with water and steam to release hydrogen. This hydrogen release reduces the vacuum level within the vapor chamber, rapidly degrading heat uniformity and ultimately causing the vapor chamber to fail. Effectively addressing this hydrogen evolution reaction between stainless steel and water could significantly increase the widespread use of stainless steel vapor chambers.

[0003] At the same time, since the capillary structure of the heat spreader is mostly copper mesh or copper wire, it is difficult for the copper capillary structure to combine with the stainless steel plate during the assembly process. Usually, heat treatment or welding is required to assemble the stainless steel plate and the capillary structure. This exposes more free iron in the stainless steel, which further reacts with water and water vapor during use. Furthermore, if a heat spreader containing a passivation layer is used, the protective layer will become ineffective and lose its function of protecting the stainless steel.

[0004] In addition, the thickness of the vapor chamber is currently difficult to be less than 0.25mm. However, as electronic products such as mobile phones develop towards ultra-thinness, thinner vapor chambers are needed to meet the demand. Summary of the Invention

[0005] In response to the above-mentioned problems, the present application proposes a method for in-situ growth of a capillary structure on the surface of stainless steel; by subjecting the stainless steel surface to local high temperature, the iron elements on the surface are promoted to diffuse inward, which greatly reduces the free iron ions on the surface and produces structural voids. The copper source on the surface will enter the structural voids to form a porous capillary structure; at the same time, the activity of high-temperature resistant elements such as chromium and molybdenum is relatively low, and they diffuse inward more slowly, thereby forming a high-copper, high-chromium, and high-molybdenum protective layer on the surface, further preventing water and water vapor from corroding the stainless steel; further, the present application is to grow a capillary structure in situ on the surface of stainless steel, that is, part of the capillary structure is located in the original position of the stainless steel, which will further reduce the thickness of the stainless steel, so that a thinner heat spreader can be obtained later.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The invention of this application is to provide a method for in-situ growth of a capillary structure on a stainless steel surface, comprising: covering the stainless steel surface with a copper source in an inert gas, a reducing gas or a vacuum, and heating the stainless steel surface to obtain stainless steel with a capillary structure grown on the surface.

[0008] Optionally, the reducing gas includes at least one of hydrogen, methane, and carbon monoxide.

[0009] Sulfur-containing gases such as hydrogen sulfide and sulfur monoxide are not acceptable, as they will cause sulfur to diffuse in and affect the structure of the stainless steel.

[0010] Optionally, the inert gas includes at least one of helium, neon, argon, krypton, and xenon.

[0011] The vacuum refers to a vacuum degree less than 100Pa.

[0012] Optionally, the heating temperature is 800-1050° C., and the heating time is 5-30 minutes.

[0013] Optionally, the heating method is induction heating.

[0014] Optionally, the stainless steel is in the shape of a sheet.

[0015] Optionally, the angle between the sheet of stainless steel and the induced current is 30 to 150°, preferably 60 to 120°.

[0016] Optionally, the copper source is located on the surface of a single layer of sheet stainless steel and abuts against the surface of the single layer of sheet stainless steel; or is located between two layers of sheet stainless steel and abuts against the surfaces of both layers of sheet stainless steel.

[0017] Optionally, the particle size of the copper source is 50-150 mesh.

[0018] Optionally, the copper source includes at least one of copper, copper oxide, cuprous oxide, copper nitrate, and copper carbonate.

[0019] Another invention of the present application is to provide a stainless steel with capillary structure grown on the surface, which is prepared by any of the methods described above.

[0020] Optionally, the capillary structure has a thickness of 1 to 10 μm.

[0021] Another invention point of the present application is to provide a heat spreader, comprising any of the stainless steels described above with capillary structures grown on the surface.

[0022] Compared with the prior art, the present application has the following advantages (the advantages of the material and method are described separately):

[0023] (1) The present application can avoid the interface problem between the capillary structure and the stainless steel by in-situ generating a capillary structure on the surface of the stainless steel. At the same time, the high-copper, high-chromium, and high-molybdenum protective layer on the surface can further avoid the hydrogen evolution reaction between the working fluid water and the stainless steel; and can reduce the thickness of the stainless steel, thereby reducing the thickness of the heat spreader, and can obtain a thinner heat spreader with better application scenarios.

[0024] (2) The present application locally heats the surface of stainless steel so that the iron on the surface diffuses inward, forming structural voids that facilitate the infiltration of copper elements and the generation of capillary structures; the diffusion of iron ions inward can increase the content of elements such as chromium and molybdenum, and the infiltration of copper significantly improves the corrosion resistance of the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the surface of stainless steel with capillary structures grown on the surface provided in Experimental Example 1 of this application;

[0026] Figure 2 for Figure 1 Element content map of region 1;

[0027] Figure 3 for Figure 1 Element content map of region 2. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below. However, it should be understood that the description herein is only used to explain this application and is not intended to limit the scope of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended solely for the purpose of describing specific embodiments and are not intended to limit this application. The reagents and instruments used herein are commercially available, and the characterization methods involved can be found in the relevant descriptions in the prior art and will not be further elaborated herein.

[0030] In order to further understand the present application, the present application is further described in detail below in conjunction with the best embodiment.

[0031] Example 1

[0032] This embodiment provides a method for in-situ growth of a capillary structure on a stainless steel surface, comprising: covering the stainless steel surface with a copper source in an inert gas, a reducing gas, or a vacuum, and heating the stainless steel surface to obtain stainless steel with a capillary structure grown on the surface.

[0033] By heating the surface of the stainless steel, local high temperatures are quickly formed on the surface of the stainless steel sheet, causing iron to diffuse inward faster, reducing the surface iron content and the content of free iron ions. The chromium and molybdenum in stainless steel are high-temperature resistant elements with relatively low activity. At the same time, copper diffuses to the surface of the stainless steel. The combined effect of the two forms an uneven structure on the surface of the stainless steel. A high-copper and high-chromium component is formed on the surface, which not only solves the compatibility problem with water (the surface iron content is very low and there are no free iron ions), but also forms a porous capillary structure on the stainless steel surface.

[0034] The stainless steel includes at least one of 304, 304L, 316, and 316L.

[0035] The reducing gas includes at least one of hydrogen, methane, and carbon monoxide. The inert gas includes at least one of helium, neon, argon, krypton, and xenon. Vacuum refers to a vacuum degree of less than 100 Pa.

[0036] Inert gas, reducing gas or vacuum can prevent the formation of oxide film on the surface of stainless steel, block the penetration of copper, and avoid iron oxidation, which causes corrosion of stainless steel.

[0037] The reducing gas can also further remove the oxide film on the surface of the stainless steel, promoting faster and greater penetration of copper.

[0038] The copper source includes at least one of copper, copper oxide, cuprous oxide, copper nitrate, and copper carbonate.

[0039] The reducing gas can further reduce the copper source, remove the oxide film on the surface of the copper source, or reduce copper oxide to generate copper, thereby infiltrating copper.

[0040] The heating temperature is 800-1050°C for 5-30 minutes. Under these temperature conditions, copper easily diffuses into the surface of the stainless steel. Furthermore, because only the surface of the stainless steel is heated for a short time, the copper powder not in contact with the stainless steel surface will not melt or agglomerate.

[0041] The heating method is induction heating.

[0042] Induction heating can quickly generate local high temperatures at a depth of about 10 microns on the surface of the stainless steel sheet; other conventional heating methods heat the entire stainless steel, preventing iron ions from diffusing into the interior.

[0043] The stainless steel is in the form of a sheet. If the stainless steel is too thick, the efficiency of induction heating will be affected. The thickness of the stainless steel is preferably 0.06 mm to 0.25 mm.

[0044] The angle between the sheet of stainless steel and the induced current is 30 to 150 degrees, preferably 60 to 120 degrees.

[0045] The current can be generated by placing the stainless steel in a non-parallel manner to the induced current, and a certain angle can be generated. The angle range is 30 to 150 degrees, preferably 60 to 120 degrees, and more preferably 90 degrees.

[0046] When the stainless steel sheet is perpendicular to the direction of the induced current, the heat generation efficiency is maximized.

[0047] The copper source is located on the surface of the single-layer sheet stainless steel and abuts against the surface of the single-layer sheet stainless steel. After induction heating, stainless steel with a capillary structure on one side, namely capillary structure-stainless steel, can be produced.

[0048] The copper source is located between the two layers of stainless steel sheets and abuts against the surfaces of the two layers of stainless steel sheets. After induction heating, a workpiece can be produced in which the two stainless steel sheets are connected by a capillary structure, that is, stainless steel-capillary structure-stainless steel.

[0049] The particle size of the copper source is 50 to 150 mesh, preferably 70 to 100 mesh, and more preferably 80 mesh.

[0050] The above preparation method comprises:

[0051] (1) Separate the stainless steel sheets so that they are perpendicular to the direction of the induced current and sprinkle copper oxide powder (no larger than 80 mesh) between them. Place the workpiece and the copper oxide powder in a bell jar made of quartz glass or ceramic. A metal container is not used to prevent the metal container from induction heating itself, which would prevent the stainless steel sheets from being heated.

[0052] (2) Continue to introduce hydrogen or methane gas and start induction heating. When the temperature of the stainless steel surface reaches 800℃~1050℃ as measured by the thermocouple, keep it warm for 5~30 minutes. Turn off induction heating and cool down.

[0053] Reduction reaction using H2 as reducing agent:

[0054] 2CuO+H2=Cu2O+H2O (1)

[0055] Cu2O+H2=2Cu+H2O (2)

[0056] When using methane as reducing agent:

[0057] 8CuO+CH4=4Cu2O+CO2++2H2O (3)

[0058] 4Cu2O+CH4=8Cu+CO2++2H2O (4)

[0059] (3) Cool down to below 100°C and remove the workpiece.

[0060] Since the stainless steel grows a capillary structure in situ, no additional capillary wick is required when preparing the heat sink, and a capillary wick with a porous structure is formed on its own surface.

[0061] Example 2

[0062] This embodiment provides a stainless steel having a capillary structure grown on the surface. The preparation method of the stainless steel having a capillary structure grown on the surface of this embodiment is the same as the preparation method described in Example 1 and will not be described in detail here.

[0063] The stainless steel with capillary structure grown on the surface is prepared by any of the above methods.

[0064] The thickness of the capillary structure is 1 to 10 μm.

[0065] The composition and content of the stainless steel surface are:

[0066] When the raw materials of stainless steel are 304 and 304L: Cr 25-40%; Fe 15-30%; Cu 30-40%; Ni 2-12%, and the rest are trace metal elements.

[0067] When the raw materials of stainless steel are 316 and 316L: Cr 25-35%; Fe 15-25%; Cu 30-40%; Mo 7-10%, Ni 2-3.5%, and the rest are trace metal elements.

[0068] The trace metal elements include any one or more of carbon, manganese, vanadium, titanium, aluminum, cobalt, and barium.

[0069] The porosity of the capillary structure is 35% to 70%.

[0070] Example 3

[0071] This embodiment provides a vapor chamber comprising any of the above-described stainless steels with capillary structures grown on the surface.

[0072] The heat spreader also includes a stainless steel upper cover; the material of the stainless steel upper cover can be selected from the stainless steel with a capillary structure grown on the surface of Example 1, or the stainless steel with a protective layer on the surface.

[0073] When the material of the stainless steel upper cover is selected from the stainless steel with capillary structure grown on the surface in Example 1, two pieces of stainless steel with capillary structure grown on the surface are joined together, and the capillary structure of one is abutted against the capillary structure of the other to merge into one capillary structure, and its structure is: stainless steel-capillary structure-capillary structure-stainless steel.

[0074] When the material of the stainless steel upper cover is selected from stainless steel with a protective layer on the surface, the stainless steel with the protective layer is processed into the shape of the upper cover and combined with the stainless steel with a capillary structure grown on the surface. The structure is: stainless steel-capillary structure-protective layer-stainless steel.

[0075] The protective layer can be a chromium-copper alloy layer, a chromium-molybdenum alloy layer, a chromium-tantalum alloy layer, a chromium-aluminum alloy layer, or a fluoride layer. The method for preparing stainless steel with a protective layer comprises: mixing a material containing a chromium source and a copper source, a material containing a chromium source and a molybdenum source, a material containing a chromium source and a tantalum source, a material containing a chromium source and an aluminum source, or a fluoride-containing material with stainless steel under a vacuum degree of less than 13 Pa or under hydrogen conditions, and heating the mixture to a temperature of 917 to 1050° C. for more than 2 hours to obtain stainless steel with a surface protective layer.

[0076] After the stainless steel with capillary structure grown on the surface is assembled with the stainless steel upper cover, the edge is sealed by laser welding. The laser welding process parameters are: power 60-120W, speed 50-200m / s.

[0077] After laser welding, the stainless steel soaking pan undergoes high-temperature shaping at temperatures between 880°C and 1000°C for more than 10 minutes. The flatness of the reshaped soaking pan is less than 0.2. This shaping improves the bonding of chromium and copper to the stainless steel, while also promoting weldability and strengthening the weld. While welding can damage the alloy layer at the weld, shaping can evenly distribute the elements in the damaged alloy layer, re-forming the alloy layer.

[0078] Afterwards, the rat tail was connected, water was injected, and the vacuum was drawn to seal the mouth.

[0079] The injection pipe is used for water injection, vacuuming, sealing and other processes; subsequent shaping and other processes are used to obtain the final stainless steel heat sink product.

[0080] The above-mentioned heat spreader can also be prepared by a workpiece with a structure of stainless steel-capillary structure-stainless steel. Since this structure (stainless steel-capillary structure-stainless steel) already has the upper cover, capillary structure and lower cover required for the heat spreader, it is only necessary to seal the upper cover and the lower cover together. For example, the above-mentioned laser welding can be adopted, and then shaping, water injection, vacuum sealing and other treatments can be carried out.

[0081] Example 4

[0082] According to the content of this application, the method of in-situ growth of capillary structure on the surface of stainless steel in Example 1 and the stainless steel with capillary structure grown on the surface in Example 2 are specifically described as follows:

[0083] Test Example 1

[0084] (1) Separate 0.06mm thick 316L stainless steel sheets, perpendicular to the direction of the induced current, and sprinkle copper oxide powder with a particle size of no more than 80 mesh between them, evenly covering the surface of the stainless steel sheets. The stainless steel sheet workpiece and copper oxide powder are placed in a bell jar made of quartz glass.

[0085] (2) Continue to introduce hydrogen gas and start induction heating. When the temperature of the stainless steel surface reaches 900°C as measured by the thermocouple, keep the temperature for 20 minutes. Turn off the induction heating and cool down.

[0086] like Figure 1 As shown, the stainless steel surface contains a porous structure, and the porous structure is relatively evenly distributed, with a porosity of 58% and a thickness of 5 μm.

[0087] right Figure 1 The element content in the two areas was tested, and the test results are shown in Figure 2 、 Figure 3 and Table 1.

[0088] Table 1

[0089]

[0090]

[0091] like Figure 2 、 Figure 3 As shown in Table 1, the surface composition of the treated stainless steel has changed significantly. Compared to the original 316L stainless steel composition of 18.5% chromium, 8.2% nickel, 2.1% molybdenum, 0% copper, and 70.4% iron, the treated surface has a chromium content of approximately 30%, a molybdenum content of nearly 10%, and a copper content of approximately 35%. The proportion of high-melting-point metals on the surface has increased significantly, while the higher copper content ensures compatibility with water and reliable welding.

[0092] Test Example 2

[0093] (1) Separate 0.08mm thick 316 stainless steel sheets, with the sheets perpendicular to the direction of the induced current. Sprinkle cuprous oxide powder with a particle size of no more than 80 mesh between the sheets, evenly covering the surface of the sheets. Place the stainless steel sheet and cuprous oxide powder in a bell jar made of quartz glass.

[0094] (2) Continue to introduce methane gas and start induction heating. When the temperature of the stainless steel surface reaches 920°C as measured by the thermocouple, keep the temperature for 18 minutes. Turn off induction heating and cool down.

[0095] The stainless steel surface contains a porous structure, and the porous structure is evenly distributed, with a porosity of 52% and a thickness of 6 μm.

[0096] Energy spectrum analysis of the surface elemental composition revealed 30% chromium, 3.0% nickel, 8.1% molybdenum, 34% copper, and 23% iron. Compared to the original 316 stainless steel composition (16.2% chromium, 10.0% nickel, 2.1% molybdenum, and the balance iron), the proportions of chromium and molybdenum, high-melting-point, low-reactivity metals, have increased significantly, and the copper content has reached over 30%. This ensures water compatibility and weld reliability.

[0097] Test Example 3

[0098] (1) Separate 0.1mm thick 304L stainless steel sheets, perpendicular to the direction of the induced current, and sprinkle copper powder with a particle size of no more than 80 mesh between them, evenly covering the surface of the stainless steel sheets. The stainless steel sheet workpiece and copper powder are placed in a ceramic bell jar.

[0099] (2) Continue to evacuate the chamber. When the pressure inside the bell jar is less than 100 Pa, start induction heating to increase the temperature. At the same time, maintain the vacuum pressure less than 100 Pa. The temperature of the stainless steel surface measured by the thermocouple reaches 950°C. Keep the temperature for 22 minutes. Turn off the induction heating and cool down.

[0100] The stainless steel surface contains a porous structure, and the porous structure is evenly distributed, with a porosity of 47% and a thickness of 9 μm.

[0101] Energy spectrum analysis of the surface elemental composition revealed 33% chromium, 2.8% nickel, 37% copper, and 18% iron. Compared to the original 304L stainless steel composition (18.8% chromium, 8.2% nickel, and the balance iron), the proportions of high-melting-point, low-reactivity metals like chromium and copper have increased significantly, with the copper content approaching 40%. This ensures water compatibility and weld reliability.

[0102] Test Example 4

[0103] (1) Separate 0.1mm thick 304 stainless steel sheets, perpendicular to the direction of the induced current, and sprinkle copper powder with a particle size of no more than 80 mesh between them, evenly covering the surface of the stainless steel sheets. The stainless steel sheet workpiece and copper powder are placed in a ceramic bell jar.

[0104] (2) Continue to introduce argon inert gas and start induction heating after 10 minutes. The temperature of the stainless steel surface measured by the thermocouple reaches 960°C. Keep warm for 25 minutes. Turn off induction heating and cool down.

[0105] The stainless steel surface contains a porous structure, and the porous structure is evenly distributed, with a porosity of 44% and a thickness of 10 μm.

[0106] Energy spectrum analysis of the surface elemental composition revealed 30% chromium, 3.2% nickel, 39% copper, and 19% iron. Compared to the original 304 stainless steel composition (18.8% chromium, 8.2% nickel, and the balance iron), the proportions of high-melting-point, low-reactivity metals like chromium and copper have increased significantly, with the copper content approaching 40%. This ensures water compatibility and weld reliability.

[0107] Comparative Example 1

[0108] The 316L stainless steel vapor chamber (VC) is constructed using a combination of 500-mesh stainless steel mesh and stainless steel sheet. The upper and lower covers are stamped out of 0.06mm thick 316L stainless steel. The 316L stainless steel mesh is welded to the 316L lower cover. The upper and lower covers are then joined using laser welding (608W power, 70m / s rate) and shaped. Finally, a rat tail is inserted, water is injected, vacuum is applied, and the cover is sealed, resulting in a 0.35mm thick stainless steel VC.

[0109] Comparative Example 2

[0110] Copper VC, a heat spreader VC made of a combination of 500 mesh copper mesh and copper sheet.

[0111] Using 0.1mm and 0.256mm thick oxygen-free copper, the lower and upper covers were etched out, respectively. The copper mesh was welded to the lower cover, and then the upper and lower covers were sealed by brazing. Finally, a rat tail was inserted, water was injected, vacuum was applied, and the cover was sealed to obtain a 0.35mm thick copper VC.

[0112] Performance Testing

[0113] (1) Stainless steel sheets with capillary structures grown on their surfaces, as in Examples 1-4, were assembled into vapor chambers according to conventional methods. Capillary performance was tested simultaneously with the vapor chambers from Comparative Examples 1 and 2. The vertical water absorption method was used to measure the time it took for water to rise from the bottom of the VC cover to the top, at a height of 10 cm. The results are shown in Table 1.

[0114] Table 1

[0115] sample Test Example 1 Test Example 2 Test Example 3 Test Example 4 Comparative Example 1 Comparative Example 2 time 8 seconds 9 seconds 11 seconds 13 seconds 21 seconds 18 seconds

[0116] As can be seen from Table 1, the capillary prepared by the method of the present application has extremely strong capillary performance, and its capillary siphon speed is much higher than the traditional combination of stainless steel mesh + stainless steel sheet and copper mesh + copper sheet.

[0117] (2) The stainless steel sheets with capillary structures on the surfaces of Experimental Examples 1 to 4 were assembled into vapor chambers according to conventional methods. The vapor chambers of Comparative Examples 1 and 2 were tested for their temperature uniformity. The temperature difference between the two farthest ends (test distance 8 cm) after VC was formed was measured. The results are shown in Table 2.

[0118] Table 2

[0119] sample Test Example 1 Test Example 2 Test Example 3 Test Example 4 Comparative Example 1 Comparative Example 2 temperature difference 1.5℃ 1.8℃ 2.0℃ 2.5℃ 3.6℃ 2.8℃

[0120] As can be seen from Table 2, the capillary prepared by the method of the present application has extremely strong capillary performance, and the temperature difference of the VC is within 3°C, which is significantly better than the traditional method.

[0121] (3) The stainless steel samples with capillary structures on the surfaces of Examples 1 to 4 were assembled into vapor chambers according to conventional methods. Accelerated aging life tests were performed simultaneously with the vapor chambers of Comparative Examples 1 and 2. High-temperature accelerated aging tests were performed at 150°C for 48 hours. The results are shown in Table 3.

[0122] Table 3

[0123] sample Test Example 1 Test Example 2 Test Example 3 Test Example 4 Comparative Example 1 Comparative Example 2 temperature difference 1.6℃ 1.8℃ 2.1℃ 2.7℃ 34.6℃ 22.2℃

[0124] As can be seen in Table 3, the VC produced by the present method exhibited excellent stability after a rigorous 150°C high-temperature aging test, with no degradation after 48 hours, meeting the VC aging requirement of less than 5°C. The VC produced using untreated stainless steel failed after the test, primarily due to a hydrogen evolution reaction between the stainless steel and water. Similarly, the copper VC also failed, primarily due to the brazing of the upper and lower covers, which resulted in a hydrogen evolution reaction between the brazing material and water.

[0125] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for in-situ growth of capillary structures on a stainless steel surface, characterized in that: include: In an inert gas, reducing gas or vacuum, a copper source is covered on a stainless steel surface, and the stainless steel surface is heated to obtain stainless steel with a capillary structure grown on the surface; The heating method is induction heating, which quickly forms local high temperature on the surface of the stainless steel; the heating temperature is 800-1050° C., and the heating time is 5-30 minutes.

2. The method according to claim 1, characterized in that The reducing gas includes at least one of hydrogen, methane, and carbon monoxide; The inert gas includes at least one of helium, neon, argon, krypton, and xenon; The vacuum refers to a vacuum degree less than 100Pa.

3. The method according to claim 1, characterized in that The stainless steel is in the shape of a sheet; the angle between the sheet of stainless steel and the induced current is 30-150 degrees.

4. The method according to claim 3, characterized in that The angle between the sheet of stainless steel and the induced current is 60-120 degrees.

5. The method according to claim 4, characterized in that The copper source is located on the surface of the single-layer stainless steel sheet and abuts against the surface of the single-layer stainless steel sheet; Or it is located between the two layers of sheet stainless steel surfaces and abuts against the surfaces of the two layers of sheet stainless steel.

6. The method according to claim 1, wherein The particle size of the copper source is 50-150 mesh; The copper source includes at least one of copper, copper oxide, cuprous oxide, copper nitrate, and copper carbonate.

7. A stainless steel having a capillary structure grown on its surface, characterized in that: The method is prepared by any one of claims 1 to 6.

8. The stainless steel having capillary structures grown on the surface according to claim 7, characterized in that: The capillary structure has a thickness of 1-10 μm.

9. A heat sink, characterized in that: The stainless steel having a capillary structure grown on the surface thereof comprises the stainless steel as claimed in any one of claims 7 or 8.

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