A method for processing a thin stainless steel plate-fin type heat dissipation core

Abstract

The present invention discloses a method for processing a thin stainless steel plate-fin heat dissipation core, including the steps of heat dissipation core brazing structure design, heat dissipation core parts preparation, heat dissipation core assembly, heat dissipation core trial welding, correction of heat dissipation core brazing parameters and implementation of formal brazing, connection of multiple heat dissipation cores, and heat dissipation core thermal correction. The present invention can divide a thin stainless steel plate-fin heat dissipation core into two, three, or even more heat dissipation cores with reduced heights according to the difference between the length or width and the height of the heat dissipation core, so as to ensure the stability of the heat dissipation core during the brazing process. The multiple heat dissipation cores can be connected by fusion welding, brazing, etc. according to the weldability characteristics. When brazing a single heat dissipation core, its brazing parameters are corrected and the deformation amount is controlled by using a brazing fixture, and finally, thermal correction is performed to remove stress and perform brazing repairs. The present invention solves the problems of brazing collapse, heat dissipation core deformation, and low sealing qualification rate in the processing of thin stainless steel plate-fin heat dissipation cores.

Description

Technical Field

[0001] The invention belongs to the technical field of welding processing, and in particular relates to a processing method for a thin stainless steel plate-fin type heat dissipation core. Background Art

[0002] There are three main types of radiators: plate type, shell and tube type, and plate-fin type. Under the same volume, the plate-fin radiator has the highest heat dissipation efficiency and the lightest weight.

[0003] The main materials of plate-fin radiators are aluminum alloy, stainless steel, titanium alloy, etc. At present, aluminum alloy plate-fin radiators have been widely used in machinery, chemical industry, automobile and other fields. Compared with aluminum alloy plate-fin radiators, stainless steel plate-fin radiators have the advantages of high operating temperature (melting point of stainless steel is 1750℃, melting point of aluminum alloy is 650℃) and good corrosion resistance. Therefore, they are widely used in military, aviation, aerospace and other fields. The processing plan of stainless steel plate-fin radiators with normal structure is relatively mature, but for thin plate-fin radiators (thin here means the width of the plate-fin radiator core is ≤30mm) with a large height to aspect ratio (for example, height-to-width (length) ratio ≥5), the traditional brazing method is still used. The main problems in processing are brazing collapse, deformation of the heat dissipation core, and low sealing qualification rate. Summary of the Invention

[0004] The present invention aims to provide a method for processing a thin stainless steel plate-fin heat sink core to solve the processing problem of thin stainless steel plate-fin heat sinks with a large ratio of height to length and width. The method optimizes the brazing structure, brazing material coating, brazing fixture and brazing parameters to solve problems such as brazing collapse, heat sink core deformation and low sealing qualification rate that exist during processing.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for processing a thin stainless steel plate-fin heat dissipation core, wherein the thin stainless steel plate-fin heat dissipation core is a cubic structure, wherein the height of the thin stainless steel plate-fin heat dissipation core is much greater than the length and width of the thin stainless steel plate-fin heat dissipation core. The processing method comprises the following steps:

[0007] Step 1: brazing structure design, splitting the thin stainless steel plate-fin heat dissipation core into at least two heat dissipation cores along the height direction, so that the ratio of the height to the width of each heat dissipation core becomes smaller than the ratio of the height to the width of the thin stainless steel plate-fin heat dissipation core before splitting, and the ratio of the height to the length of each heat dissipation core becomes smaller than the ratio of the height to the length of the thin stainless steel plate-fin heat dissipation core before splitting;

[0008] Step 2: Parts preparation: The heat sink core includes fins, seals, baffles, and side panels, which are processed by sheet metal stamping and / or machining, and then pickled to clean surface stains and oxide layers;

[0009] Step 3: Assemble the fins, seals, partitions and side panels prepared in step 2 on a brazing fixture and apply brazing filler metal;

[0010] Step 4: Test welding: Place the heat dissipation core and brazing fixture into the vacuum furnace together, and insert thermocouples at the side panels and seal positions respectively. Preset brazing parameters based on the heat dissipation core of the same material and the same brazing material. Observe the temperature of the thermocouple in real time during the brazing test process, control the vacuum furnace heating system, ensure that the maximum temperature difference of the thermocouple is not greater than the set maximum temperature difference, and that the maximum temperature difference of all holding sections before reaching the brazing temperature is not greater than the set maximum temperature difference, and record the corresponding time of each holding section and heating section.

[0011] Step 5: After correcting the brazing parameters, the heat dissipation core is formally brazed. According to the actual time of each heat preservation section and heating section recorded in step 4, the preset brazing parameters in step 4 are corrected to obtain the brazing parameters suitable for the heat dissipation core, and then the heat dissipation core is formally brazed.

[0012] Step 6: Connect the heat dissipation cores. Stack multiple heat dissipation cores in the height direction and connect them by welding to form an integral core. Weld transition sections in the height direction on two parallel sides in the length direction of the connected cores. The transition sections are rectangular strips.

[0013] Step seven, heat correction, apply solder to the welding point between the core body and the transition section welded in step six, then put it into a vacuum furnace and make the height direction of the core body horizontal, and then add counterweights at both ends of the core body in the height direction.

[0014] Furthermore, the aspect ratio and height-to-length ratio of the thin stainless steel plate-fin type heat dissipation core are ≥5, and the width of the thin stainless steel plate-fin type heat dissipation core is ≤30 mm.

[0015] As an option, in step 2, the fins are made of industrial pure nickel alloy N4, and the seals, partitions and side plates are made of stainless steel 06Cr19Ni10, and the tolerance between the fins and the seals is controlled to ensure the capillary gap requirements during brazing.

[0016] As an option, in the step three, amorphous brazing material BNi82CrSiBFe is pre-placed between the fin and the partition during assembly, the brazing gap is controlled between 0.02 and 0.08 mm, the brazing fixture is made of heat-resistant stainless steel 06Cr25Ni20, and channel steel is brazed together with the heat dissipation core. Two pieces of channel steel are respectively installed at both ends of the length direction of the heat dissipation core, and the notches of the two channel steels face each other, clamping the heat dissipation core.

[0017] As an option, in step 4, a temperature 20 to 50° C. higher than the liquidus of the solder is selected as the brazing temperature.

[0018] As an option, in step 4, the brazing parameters include vacuum degree, heating rate, brazing temperature and holding time, cooling rate and method, and furnace exit temperature.

[0019] As an option, in step 5, the following factors may be considered when modifying the brazing parameters:

[0020] Avoid the intergranular corrosion zone of the stainless steel heat dissipation core;

[0021] Before brazing, ensure the temperature of the thin stainless steel plate-fin heat sink is uniform;

[0022] The thin stainless steel plate-fin heat dissipation core has the characteristics of short heat conduction distance and small temperature difference between inside and outside.

[0023] As an option, in step five, when the heat dissipation core is formally brazed, the heat dissipation core is kept below the solidus line of the solder before brazing, the brazing temperature is 20 to 50° C. above the liquidus line of the solder, and the brazing holding time is 5 to 15 minutes.

[0024] As an option, in step six, argon arc welding is used to connect multiple heat dissipation cores, and argon arc welding is used to weld transition sections on two parallel sides of the cores.

[0025] As an option, in step seven, the parameters of the heat correction are consistent with the brazing parameters corrected in step five.

[0026] Compared with the prior art, the present invention has the following characteristics:

[0027] (1) The processing method of the present invention is not only applicable to stainless steel materials, but can also be extended to high-temperature alloys. In the heat dissipation core involved in brazing, the side panels, seals, fins, partitions, etc. do not need to be made of the same brand of material, as long as they have the characteristics of being brazed with each other;

[0028] (2) The present invention is directed to a thin stainless steel plate-fin heat dissipation core. Based on the difference between the length or width and the height, the heat dissipation core can be divided into two, three or even more heat dissipation cores with reduced heights to ensure the stability of the heat dissipation core during the brazing process. The multiple heat dissipation cores can be connected by fusion welding, brazing, etc. based on their weldability characteristics.

[0029] (3) The present invention uses a special brazing fixture in the processing to ensure that the heat dissipation core body does not tilt, dislocate or even collapse during the assembly and brazing process. The brazing fixture refers to Chinese utility model patent CN220679627U, 2024.03.09, a brazing assembly and fixing fixture for plate-fin radiator core components;

[0030] (4) The present invention uses a thermal calibration method during the processing to ensure the verticality and parallelism of the heat dissipation core before connecting the end cover;

[0031] (5) The present invention welds transition sections on both sides of the heat dissipation core, thereby improving the heat dissipation core's anti-deformation ability and achieving secondary brazing through thermal correction, thereby avoiding leakage problems caused by the previous process and improving the sealing qualification rate;

[0032] (6) In the present invention, thermocouples are installed at the positions that best reflect the temperature difference between the inside and outside of the radiator core (maximum temperature difference), namely, at the side plate and seal positions, to obtain brazing parameters closest to the actual situation and ensure that brazing can be implemented correctly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the heat dissipation core;

[0034] Figure 2 This is a schematic diagram of the heat dissipation core assembly;

[0035] Figure 3 This is a schematic diagram of the heat dissipation core brazing;

[0036] Figure 4 This is a schematic diagram of argon arc welding of the heat dissipation core;

[0037] Figure 5 This is a schematic diagram of the core thermal correction;

[0038] In the figure: 1-cold side fin, 2-hot side fin, 3-partition, 4-cold side seal, 5-hot side seal, 6-side plate, 7-brazing fixture, 8-counterweight, 9-core, 10-transition section. DETAILED DESCRIPTION

[0039] The present invention is further described below with reference to the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0040] The present invention addresses the problem of machining thin stainless steel plate-fin radiators with a high ratio of heat sink height to length and width. The machining method of the present invention is designed from aspects such as the brazing structure, brazing material coating, brazing fixture, and brazing parameters. Generally speaking, the machining method of the present invention includes the following steps:

[0041] Step 1: brazing structure design. Since the height of the heat dissipation core is too large and the length and width are too small, it is cut in the middle into two or more heat dissipation cores, and the height-to-length-to-width ratio is reduced to ensure the stability of the heat dissipation core during the brazing process. Subsequently, multiple heat dissipation cores are connected by argon arc welding.

[0042] Step 2: Parts preparation. The main parts of the heat dissipation core are fins, seals, partitions 3, side panels 6, etc., which are processed by sheet metal stamping, machining, etc., and then pickled to clean surface stains and oxide layers;

[0043] Step 3: Assemble, place the fins, seals, partitions 3, side plates 6, brazing materials, etc. prepared in step 2 on the brazing fixture in sequence;

[0044] Step 4: test welding. Put the heat dissipation core and the brazing fixture into the vacuum furnace as a whole, and insert thermocouples at the side plate 6 and the seal position respectively (after actual verification, the temperature difference at these two positions can best reflect the internal and external temperatures of the plate-fin radiator. Of course, thermocouples can also be installed at other positions). Preset brazing parameters according to the same type of products (that is, products using the same brazing material and the same material, but different sizes). Observe the temperature of the two thermocouples in real time during the brazing process, and manually control the heating system of the vacuum furnace to ensure that the overall temperature difference between the two thermocouples is no more than 150°C, and the maximum temperature difference of all insulation sections before reaching the brazing temperature is no more than 50°C. Record the time of each stage (insulation section and heating section). The insulation section refers to the length of time the temperature in the vacuum furnace is kept at a set temperature.

[0045] Step 5: After correcting the brazing parameters, formally braze the heat sink core. Using the actual time recorded in step 4, correct the preset brazing parameters to obtain brazing parameters suitable for thin stainless steel plate-fin heat sink cores, and then formally braze the heat sink core. The heat sink core that has been trial-welded does not need to be brazed again according to the corrected brazing parameters and can be directly argon arc welded with other heat sink cores. When correcting the brazing parameters, the results (quality indicators, performance indicators, etc.) of the heat sink core after brazing are used for evaluation.

[0046] Step 6: Argon arc welding: connect multiple heat dissipation cores by argon arc welding to form an integral core 9, and use argon arc welding to weld a rectangular strip-shaped transition section 10 on each side of the connected core 9 to form a square frame-like structure in the height direction of the core 9;

[0047] Step 7: Heat calibration: Apply solder to the four sides of the core 9 welded in step 6 and place it in a vacuum furnace. Add counterweights 8 at both ends of the core 9 in the height direction for calibration during the heat calibration process.

[0048] As an option, in step 2, the fins are made of industrial pure nickel alloy N4, and the seals, partitions 3 and side plates 6 are made of stainless steel 06Cr19Ni10. The tolerance between the fins and the seals is controlled to ensure the capillary gap requirements in the brazing process. Pickling treatment is carried out in accordance with relevant navigation standards, and kraft paper is used for protection after pickling and before brazing.

[0049] As an option, in the step three, amorphous brazing material BNi82CrSiBFe is pre-placed between the fin and the partition 3 during assembly, the brazing gap is controlled between 0.02 and 0.08 mm, the brazing fixture is made of heat-resistant stainless steel 06Cr25Ni20, and channel steel is brazed together with the heat dissipation core. The channel steel is designed as an integral part and is easy to disassemble to ensure the stability of the heat dissipation core during the brazing process. The notches of the two channel steels are opposite to each other, and the heat dissipation core is clamped between the two.

[0050] As an option, in step 4, a temperature 20 to 50° C. higher than the liquidus of the solder is selected as the brazing temperature.

[0051] As an option, in step 5, the brazing parameters are modified based on the following three aspects:

[0052] 1) The raw material is austenitic stainless steel, and the intergranular corrosion zone must be avoided;

[0053] 2) The brazing temperature is 20-50℃ above the liquidus line of the solder. Before brazing, in order to ensure the overall temperature is uniform, it is necessary to keep it below the solidus line of the solder;

[0054] 3) The heat dissipation core is a thin plate fin type radiator, with a short heat conduction distance and a small temperature difference between the inside and outside;

[0055] The holding time and brazing temperature are designed based on the above reasons. Since there is no diffusion treatment requirement, the brazing holding time is designed to be 5 to 15 minutes.

[0056] As an option, in step six, argon arc welding is used to connect the two heat dissipation cores, and the transition section 10 connected to the end cover is welded to reduce welding deformation of the core 9 generated during subsequent end cover welding.

[0057] As an option, in step seven, heat treatment is set for stress removal, thermal correction and brazing repair, the brazing material is crystalline BNi82CrSiBFe, and the heat treatment parameters are the brazing parameters in step five.

[0058] The processing method of the present invention is described in detail below using a thin stainless steel plate-fin heat dissipation core with a length of 100 mm, a width of 22 mm, and a height of 540 mm as an example. After processing according to the method of the present invention, a thin stainless steel plate-fin heat dissipation core with an overall deformation of no more than 5 mm can be obtained.

[0059] like Figures 1 to 5 As shown, the processing method of the thin stainless steel heat dissipation core is performed according to the following steps:

[0060] Step 1: Assemble the cold side fin 1, hot side fin 2, partition 3, cold side seal 4, hot side seal 5 and side plate 6 (such as Figure 1 (As shown) Use pickling solution to clean the surface of the parts. A clean surface without oxides is a necessary condition to ensure a high-quality brazing joint.

[0061] Step 2: Assemble and clamp the cold side fin 1, hot side fin 2, partition 3, cold side seal 4, hot side seal 5, side plate 6 and amorphous brazing material (BNi82CrSiBFe) on the brazing fixture 7, and retain the brazing fixture channel steel (see Chinese utility model patent CN220679627U, 2024.03.09, a channel steel in a brazing assembly and fixing fixture for a plate-fin radiator core assembly) for the stability of the heat dissipation core. The upper and lower covers of the brazing fixture should be pre-coated with solder resist, such as Figure 2 shown.

[0062] Step 3: Brazing of the heat dissipation core. Add a weight block 8 to the brazing fixture 7, and place the heat dissipation core and the brazing fixture into a vacuum heat treatment furnace (in the traditional method, the channel steel is removed after assembly and does not enter the vacuum furnace; in the present invention, the channel steel is placed in the furnace together with the heat dissipation core to ensure the stability of the heat dissipation core during the vacuum brazing process). Control the brazing parameters, including vacuum degree, heating rate, brazing temperature and holding time, cooling rate and method, and furnace exit temperature. Specifically, the vacuum degree must be paid attention to at all times during the brazing process to ensure that the vacuum degree of the entire process is less than 4×10 -2 Pa, a total of 3 insulation points are designed at 550℃, 930℃ and 1040℃. Since there is no diffusion treatment requirement, the brazing insulation time is designed to be 10min, and the brazing temperature is selected to be 20-50℃ above the liquidus. The specific brazing temperature is 1040℃, and the insulation time is 10min. The selected heating rate is 4-5℃ / min. After the brazing is completed, the heat dissipation core is first cooled to 800℃ with the furnace, and then filled with high-purity argon gas and the fan in the vacuum chamber is started to stir to quickly reduce the furnace temperature to avoid intergranular corrosion in the material. For stainless steel components, it is advisable to take out the furnace temperature less than 60℃. Figure 3 shown.

[0063] Step 4: Adjust the argon arc welding parameters, connect the two heat dissipation cores using argon arc welding to form a core 9 with a larger height. After the sheet metal is corrected (after the argon arc welding connection, the width of the core 9 changes greatly and needs to be corrected), connect the core 9 and the transition section 10 using argon arc welding, as shown in the following figure: Figure 4 shown.

[0064] Step 5: Use crystalline solder (BNi82CrSiBFe) and solvent (trichloroethylene) to make it viscous, and apply the solder on the argon arc weld of the core 9 and the transition section 10, then put it into a vacuum heat treatment furnace and place the counterweight 8 (such as Figure 5 , the left and right ends of the cold edge channel in the height direction of the core 9), and then perform brazing heat correction according to the brazing parameters in step three. It should be noted that using the same brazing parameters as in step three to implement heat correction has no effect on the original brazing seam (the brazing seam in step three). After the first brazing, the melting-reducing elements in the original brazing seam will diffuse, causing the melting temperature of the original brazing seam to increase significantly, and it will not melt when brazed again.

[0065] Step 6: Perform a 1.33 MPa sealing test on the processed core 9.

[0066] The above is only one specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for processing a thin stainless steel plate-fin heat dissipation core, wherein the thin stainless steel plate-fin heat dissipation core is a cubic structure, wherein the height is much greater than the length and width, and wherein: The processing method comprises the following steps: Step 1: brazing structure design, splitting the thin stainless steel plate-fin heat dissipation core into at least two heat dissipation cores along the height direction, so that the ratio of the height to the width of each heat dissipation core becomes smaller than the ratio of the height to the width of the thin stainless steel plate-fin heat dissipation core before splitting, and the ratio of the height to the length of each heat dissipation core becomes smaller than the ratio of the height to the length of the thin stainless steel plate-fin heat dissipation core before splitting; Step 2: Parts preparation: the heat dissipation core includes fins, seals, partitions (3) and side panels (6), which are respectively processed by sheet metal stamping and / or machining, and then pickled to clean surface stains and oxide layers; Step 3: assembling, assembling the fins, seals, partitions (3) and side plates (6) prepared in step 2 on a brazing fixture (7) and coating them with brazing material; Step 4, trial welding, placing the heat dissipation core and the brazing fixture (7) together into a vacuum furnace, and inserting thermocouples at the side plate (6) and the seal position respectively, referring to the preset brazing parameters of the heat dissipation core of the same material and the same brazing material, observing the temperature of the thermocouple in real time during the brazing trial welding process, controlling the vacuum furnace heating system, ensuring that the maximum temperature difference of the thermocouple is not greater than the set maximum temperature difference, and the maximum temperature difference of all insulation sections before reaching the brazing temperature is not greater than the set maximum temperature difference, and recording the corresponding time of each insulation section and heating section; Step 5: After correcting the brazing parameters, the heat dissipation core is formally brazed. According to the actual time of each heat preservation section and heating section recorded in step 4, the preset brazing parameters in step 4 are corrected to obtain the brazing parameters suitable for the heat dissipation core, and then the heat dissipation core is formally brazed. Step 6: Connecting the heat dissipation cores: stacking the plurality of heat dissipation cores in the height direction and connecting them by welding to form an integral core (9); and welding transition sections (10) along the height direction on two parallel side surfaces in the length direction of the connected core (9); the transition sections (10) are in the shape of rectangular strips; Step seven, heat correction, apply solder to the welding point of the core (9) and the transition section (10) welded in step six, then place it in a vacuum furnace and make the height direction of the core (9) horizontal, and then add counterweights (8) at both ends of the height direction of the core (9).

2. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: The height-to-width ratio and height-to-length ratio of the thin stainless steel plate-fin type heat dissipation core are ≥5, and the width of the thin stainless steel plate-fin type heat dissipation core is ≤30 mm.

3. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In the second step, the fins are made of industrial pure nickel alloy N4, and the seals, partitions (3) and side plates (6) are made of stainless steel 06Cr19Ni10, and the tolerance between the fins and the seals is controlled to ensure the capillary gap requirements during brazing.

4. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In the step 3, amorphous brazing material BNi82CrSiBFe is pre-placed between the fin and the partition (3) during assembly, and the brazing gap is controlled between 0.02 and 0.08 mm. The brazing fixture (7) is made of heat-resistant stainless steel 06Cr25Ni20, and channel steel is brazed together with the heat dissipation core. Two pieces of channel steel are respectively installed at both ends of the heat dissipation core in the length direction, and the notches of the two pieces of channel steel face each other, thus clamping the heat dissipation core.

5. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In the step 4, a temperature 20 to 50° C. higher than the liquidus of the solder is selected as the soldering temperature.

6. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In the step 4, the brazing parameters include vacuum degree, heating rate, brazing temperature and holding time, cooling rate and method, and furnace temperature.

7. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In step 5, the following factors are considered when correcting the brazing parameters: Avoid the intergranular corrosion zone of the stainless steel heat dissipation core; Before brazing, ensure the temperature of the thin stainless steel plate-fin heat sink is uniform; The thin stainless steel plate-fin heat dissipation core has the characteristics of short heat conduction distance and small temperature difference between inside and outside.

8. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In step five, when the heat dissipation core is formally brazed, the heat dissipation core is kept below the solidus line of the solder before brazing, the brazing temperature is 20-50° C. above the liquidus line of the solder, and the brazing holding time is 5-15 minutes.

9. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In the step six, argon arc welding is used to connect the plurality of heat dissipation cores, and argon arc welding is used to weld the transition section (10) on two parallel sides of the core (9).

10. The method for processing a thin stainless steel plate-fin heat dissipation core according to claim 1, characterized in that: In step seven, the parameters of the heat correction are consistent with the brazing parameters corrected in step five.

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