Thin stainless steel plate fin type heat dissipation core machining method

Abstract

The invention discloses a thin stainless steel plate fin type heat dissipation core body machining method. The method comprises the steps of heat dissipation core body brazing structure design, heat dissipation core body part preparation, heat dissipation core body assembly, heat dissipation core body test welding, heat dissipation core body brazing parameter correction and formal brazing implementation, multiple heat dissipation core body connection and heat dissipation core body hot shape correction. According to the difference between the length or the width and the height of the heat dissipation core body, the thin stainless steel plate fin type heat dissipation core body can be divided into two, three and even more heat dissipation core bodies with the reduced height, so that the stability of the heat dissipation core bodies in the brazing process is guaranteed, and the heat dissipation core bodies are connected in series according to the weldability characteristic. Connection can be conducted in a fusion welding mode, a brazing mode and the like, the brazing parameters of the single heat dissipation core body are corrected when brazing is conducted, deformation is controlled in cooperation with a brazing clamp, and finally hot shape correction stress removal and brazing repair are conducted. The problems of brazing collapse, heat dissipation core deformation, low sealing qualification rate and the like in the machining process of the thin stainless steel plate fin type heat dissipation core are solved.

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 type radiator has the highest heat dissipation efficiency and the lightest weight.

[0003] The materials of plate-fin radiators are mainly 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 scheme of stainless steel plate-fin radiators with normal structure is relatively mature, but for thin plate-fin radiators with large height to length-width ratio (for example, height-width (length) ratio ≥5) (thin here means the width of the plate-fin radiator core is ≤30mm), the traditional brazing method is still used. There are mainly problems in the processing such as 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 a thin stainless steel plate-fin heat sink with a large ratio of height to length and width, optimize the brazing structure, brazing material coating, brazing fixture and brazing parameters, and solve the problems of brazing collapse, heat sink core deformation, low sealing qualification rate, etc. in the 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 type heat dissipation core, wherein the thin stainless steel plate-fin type heat dissipation core is a cubic structure, and its height is much greater than its length and width. The processing method comprises the following steps:

[0007] Step 1: brazing structure design, splitting the thin stainless steel plate-fin type 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 type heat dissipation core before splitting, and the ratio of the height to the length becomes smaller than the ratio of the height to the length of the thin stainless steel plate-fin type heat dissipation core before splitting;

[0008] Step 2: Parts preparation: the heat sink 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: assembling, assembling the fins, seals, partitions and side plates prepared in step 2 on a brazing fixture and coating them with brazing material;

[0010] Step 4: test welding. Put the heat dissipation core and the brazing fixture into the vacuum furnace together, and insert thermocouples at the side plate and the seal respectively. Preset brazing parameters with reference to 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 welding 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 the maximum temperature difference of all insulation sections before reaching the brazing temperature is not greater than the set maximum temperature difference, and record the corresponding time of each insulation 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, and weld transition sections along the height direction on two parallel sides in the length direction of the connected cores, wherein 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-set 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 pieces of channel steel 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 line of the solder is selected as the soldering 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 are considered when modifying the brazing parameters:

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

[0021] Before brazing, ensure that 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 sink core is formally brazed, the heat sink 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. are not required to be made of the same grade of materials, 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 type heat dissipation core, which can be divided into two, three or even more heat dissipation cores with reduced heights according to the difference between the length or width and the height, 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;

[0029] (3) The present invention uses a special brazing fixture in the processing to ensure that the heat sink core is not tilted, misaligned or even collapsed during the assembly and brazing process. The brazing fixture refers to Chinese utility model patent CN220679627U, 2024.03.09, a plate-fin radiator core assembly brazing assembly and fixing fixture;

[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 realizes 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 the seal position, to obtain the brazing parameters closest to the actual situation and ensure that the brazing can be implemented correctly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a 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 in conjunction with the accompanying drawings and specific embodiments, but 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-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0040] The present invention is used to solve the problem of processing a thin stainless steel plate-fin radiator with a large ratio of the height to the length and width of the radiator core. The processing method of the present invention is designed from the aspects of brazing structure, brazing material coating, brazing fixture, brazing parameters, etc. In general, the processing method of the thin stainless steel plate-fin radiator core of the present invention includes the following steps:

[0041] Step 1: brazing structure design. Since the height of the heat sink is too large and the length and width are too small, it is cut in the middle into two or more heat sinks to reduce the ratio of height to length and width to ensure the stability of the heat sink during brazing. Subsequently, multiple heat sinks 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 sink core and the brazing fixture into the vacuum furnace, 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 with different sizes). During the brazing process, observe the temperature of the two thermocouples in real time, manually control the heating system of the vacuum furnace, ensure that the overall temperature difference of 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, and 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. Use the actual time recorded in step 4 to 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 tested 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 of the two sides of the connected core 9 to form a frame-like structure in the height direction of the core 9;

[0047] Step 7: Heat calibration: coat the four sides of the core 9 welded in step 6 with brazing material and put it into 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. The 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, an amorphous brazing material BNi82CrSiBFe is pre-set 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 for easy disassembly to ensure the stability of the heat dissipation core during brazing. 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 line of the solder is selected as the soldering 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 brazing material. To ensure uniform overall temperature before brazing, it is necessary to keep the temperature below the solidus line of the brazing material.

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

[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 welding of the end cover.

[0057] As an option, in step seven, heat treatment is provided for stress removal, heat 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 by taking a thin stainless steel plate-fin heat sink 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 sink with an overall deformation of no more than 5 mm can be obtained.

[0059] like Figure 1 to Figure 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 liquid 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 plate-fin radiator core assembly brazing assembly and fixing fixture) for the stability of the heat dissipation core. The upper and lower cover plates 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 put the heat dissipation core and the brazing fixture into a vacuum heat treatment furnace as a whole (in the traditional method, the channel steel is disassembled after assembly and does not enter the vacuum furnace; in the present invention, the channel steel is put into the furnace together with the heat dissipation core to ensure the stability of the heat dissipation core during vacuum brazing). Control the brazing parameters, which include vacuum degree, heating speed, brazing temperature and holding time, cooling speed and method, and furnace exit temperature. Specifically, the vacuum degree should 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 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 stirring in the vacuum chamber is started to quickly drop 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 by argon arc welding to form a core 9 with a larger height dimension, and after the sheet metal is corrected (after the argon arc welding connection, the width dimension of the core 9 changes greatly and needs to be corrected), then connect the core 9 and the transition section 10 by argon arc welding, such as 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 a 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 inspection on the processed core 9.

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

Claims

1. A method for processing a thin stainless steel plate-fin type heat dissipation core, wherein the thin stainless steel plate-fin type heat dissipation core is a cubic structure, and its height is much greater than its length and width, and is characterized in that: The processing method comprises the following steps: Step 1: brazing structure design, splitting the thin stainless steel plate-fin type 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 type heat dissipation core before splitting, and the ratio of the height to the length becomes smaller than the ratio of the height to the length of the thin stainless steel plate-fin type 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 sealing strip 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 a plurality of heat dissipation cores in the height direction, and connecting them by welding to form an integral core (9), and welding a transition section (10) along the height direction on two parallel side surfaces in the length direction of the connected core (9), wherein the transition section (10) is in the shape of a rectangular strip; Step seven, heat correction, apply solder to the welding point of the core body (9) and the transition section (10) welded in step six, then put it into a vacuum furnace and make the height direction of the core body (9) horizontal, and then add counterweights (8) at both ends of the height direction of the core body (9).

2. A method for processing a thin stainless steel plate-fin type heat dissipation core according to claim 1, characterized in that: 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.

3. A method for processing a thin stainless steel plate-fin type heat dissipation core according to claim 1, characterized in that: In the 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, and the tolerance between the fins and the seals is controlled to ensure the capillary gap requirements during brazing.

4. A method for processing a thin stainless steel plate-fin type heat dissipation core according to claim 1, characterized in that: In the step three, 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, thereby clamping the heat dissipation core.

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

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

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

9. A method for processing a thin stainless steel plate-fin type heat dissipation core according to claim 1, characterized in that: In the step six, argon arc welding is used to connect a 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. A method for processing a thin stainless steel plate-fin type 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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