Vacuum brazing equipment and method for plate-fin heat exchanger

Abstract

The invention discloses vacuum brazing equipment and method for a plate-fin heat exchanger, relates to the field of welding, and aims to solve the problems of low heating efficiency and difficulty in deformation control caused by structural characteristics of the plate-fin heat exchanger and characteristics of vacuum radiation heating at present. Structures such as a hydraulic control system, an upper water-cooling sealing conductive pressure head, a lower conductive base and a tool are added on the basis of traditional vacuum brazing equipment, the structures are compounded with a furnace pipe, an upper electrode of the upper water-cooling sealing conductive pressure head is of a distributed structure and can move up and down through the hydraulic control system, and the upper electrode of the lower water-cooling sealing conductive pressure head can move up and down through the tool. And by matching with a tool, a workpiece can be always stressed uniformly, and continuous and stable self-resistance extremely-fast heat generation electrifying can be ensured. Double-feedback series control is adopted to achieve double-heat-source heating, the heating process time is shortened, a pressure-temperature coupling control method is adopted, it is ensured that stress is uniform, deformation is reduced, and the heating efficiency and the welding quality consistency are improved. And rapid and uniform heating and small deformation control of the workpiece can be realized.

Description

Technical Field

[0001] The invention belongs to the brazing technology in the technical field of high-end equipment manufacturing of industrial mother machines, and specifically relates to a high-efficiency vacuum brazing device and method for a plate-fin heat exchanger. Background Art

[0002] Titanium alloy plate-fin heat exchangers have excellent properties of light weight, high strength and corrosion resistance, and are widely used in industrial fields such as petroleum, chemical industry, light industry, electricity, metal smelting, machinery, energy, etc. As the core components of the power and environmental control systems of high-end equipment such as aircraft and submarines in the frontier fields of aerospace technology and deep sea, the design and manufacturing level of large titanium alloy plate-fin heat exchangers restricts the improvement of the power system of major national equipment. my country has shortcomings in the manufacturing of high-efficiency titanium alloy heat exchangers with large size, high pressure resistance, large load, strong vibration, high temperature corrosion and other extreme services.

[0003] Since large-size titanium alloy plate-fin heat exchangers have the characteristics of multi-layer combination and interlayer self-shielding structure, the use of traditional vacuum brazing equipment usually has the following prominent problems:

[0004] (1) Brazing quality control is difficult and the yield rate is low. In order to ensure the high strength and toughness of the brazed joint, the brazing process usually requires that the overall temperature uniformity of the product be controlled within ±5°C at the brazing temperature, and the total insulation time must be short enough. The thermal conductivity of titanium is about 1 / 20 of copper and 1 / 15 of aluminum. Using a single vacuum radiation heating method, after the surface of the heat exchanger reaches the brazing temperature, it must be kept warm for at least 30 minutes (for large-sized heat exchangers, the time is longer) to achieve overall temperature uniformity. This will cause large titanium alloy plate-fin heat exchangers to have severe surface embrittlement, prone to crack defects, severe thin-wall dissolution and other quality problems, and the yield rate is difficult to guarantee.

[0005] (2) The thin-walled structure of the product is prone to deformation, and the dimensional performance is difficult to guarantee. In order to ensure that tens of thousands of brazing seams are welded firmly and reliably, the plate-fin heat exchanger requires that the contact stress at the brazing seam position is uniform when the furnace is initially loaded, and that it is maintained within the appropriate stress range during the entire brazing process. For large-sized heat exchangers, traditional special tooling is used for brazing. For only appropriate preload force is provided during initial assembly, which can easily cause uneven contact stress at the edge and center of the workpiece. In addition, during the heating process, the thermal expansion state under strong constraints is more likely to cause uncontrollable deformation, resulting in product size deviations or low strength of local welded joints.

[0006] (3) The brazing process has a long cycle and extremely low production efficiency. In order to ensure the overall dimensional accuracy of the heat exchanger and reduce thermal stress deformation, the brazing process usually requires that the product is relatively uniform during the heating and cooling process, and the temperature difference between the surface and the core is ≤50°C. As we all know, vacuum heating and cooling are extremely slow, especially in the low temperature range below 500°C. Due to the structural characteristics of the heat exchanger, it can only be frequently kept warm during the radiation heating process to ensure the overall temperature uniformity of the product. Therefore, the brazing heating time of large-size titanium alloy plate-fin heat exchangers is as long as more than 20 hours, and the cooling process is as long as more than 7 hours, which is extremely inefficient.

[0007] For large-sized plate-fin heat exchangers, the above problems are more significant. Therefore, in order to achieve high-quality vacuum brazing of large titanium alloy plate-fin heat exchangers, it is necessary to break through the technology of rapid and uniform heating and small deformation control. Summary of the invention

[0008] In view of the above problems, the present invention provides a vacuum brazing device and method for a plate-fin heat exchanger, which has a reliable structure and is easy to install. The vacuum brazing device can improve the load distribution of the brazing workpiece, ensure uniform stress and controllable deformation during the entire brazing process, and improve the dimensional accuracy of the product; at the same time, on the basis of the radiation heating function, a hydraulic control system, an upper water-cooled sealed conductive voltage head assembly and a lower conductive base and other components are configured to provide a self-resistance heat generation function while ensuring special requirements such as cooling and sealing of the vacuum brazing equipment, thereby solving the problems of low heating efficiency and difficult deformation control caused by the structural characteristics of the plate-fin heat exchanger and the characteristics of vacuum radiation heating.

[0009] According to one aspect of the present invention, a vacuum brazing device for a plate-fin heat exchanger is provided, and the vacuum brazing device for a plate-fin heat exchanger comprises: a hydraulic control system, the hydraulic control system is used to provide a fixed-range and fixed-pressure control for the vacuum brazing device; a furnace body, the furnace body is fixed to the main frame of the hydraulic control system, the furnace body is used to provide a vacuum environment and interfaces of various subsystems, and to accommodate parts to be welded, wherein the interface comprises a temperature control couple and an infrared thermometer interface; the output signal of the temperature control couple is a first feedback signal, which is used as a main temperature control feedback signal to adjust the power of each heating belt; the output signal of the infrared thermometer is a second feedback signal, which is used to monitor the temperature of the plate-fin heat exchanger, and the auxiliary control board The self-resistance extremely fast heating electrode power of the fin heat exchanger, the temperature in the furnace body is controlled by a double feedback series control method according to the first feedback signal and the second feedback signal; the furnace core, the furnace core is arranged in the furnace body, the furnace core includes a furnace core frame, a heat insulation screen and a plurality of heat-generating belts, and the heat-generating belts in each zone are evenly distributed on the inner wall of the furnace core, and can be independently controlled; used for vacuum radiation heating and heat preservation; a dynamic sealing structure, the dynamic sealing structure is fixed on the furnace body, the dynamic sealing structure is used to provide a translational sealing interface to maintain the working vacuum degree of the system; a vacuum system, the vacuum system is connected to the furnace body, and the vacuum system is used to discharge the gas in the furnace body to obtain a vacuum environment; an upper water-cooled seal Conductive voltage head, the upper water-cooled sealed conductive voltage head is connected to the hydraulic control system, the lower end passes through the top of the furnace body and maintains the vacuum in the furnace through a dynamic sealing structure; the upper water-cooled sealed conductive voltage head includes a water-cooled sealed pressure head seat, a pressure head pad, an upper insulating heat-insulating plate, an upper electrode and a first electrode lead-out device, wherein the water-cooled sealed pressure head seat, the pressure head pad, the upper insulating heat-insulating plate and the upper electrode are connected in sequence, the water-cooled sealed pressure head seat includes a flange, a pressure head column, a water inlet pipe, a water outlet pipe, a sealing sleeve and a sealing ring, the pressure head column is welded to the pressure head through the flange, the upper end face of the sealing sleeve is welded to the flange, the sealing sleeve is a hollow circular tube, and the upper end of the outer circle of the sealing sleeve is respectively welded with a water inlet pipe and a sealing ring. Pipe and water outlet pipe, the water inlet pipe extends to the bottom of the sealing sleeve, the lower end of the inner circle of the sealing ring is welded to the pressure head column, and the upper end of the outer circle is welded to the sealing sleeve, the first electrode lead-out device is connected to the upper electrode, used to lead out the upper water-cooled sealed conductive voltage head current; together with the lower conductive base, it is used for self-resistance rapid heating and uniform loading of the workpiece to be welded; lower conductive base, the lower conductive base includes a base pad, a lower insulating and heat-insulating plate, a lower electrode and a second electrode lead-out device connected in sequence, the second electrode lead-out device is connected to the lower electrode, used to lead out the lower conductive base current; together with the upper water-cooled sealed conductive voltage head, it is used for self-resistance rapid heating and uniform loading of the workpiece to be welded; tooling, the tooling is used to provide constraints for the plate-fin heat exchanger.

[0010] Furthermore, the temperature inside the furnace body is controlled according to the first feedback signal and the second feedback signal by a dual feedback series control method, specifically including: if the temperatures of the first feedback signal and the second feedback signal do not reach the set temperature, the heating stage is entered, and the heating belt and the self-resistance extremely fast heating electrode are heated simultaneously by adopting PID control; when the temperature of the second feedback signal minus the temperature of the first feedback signal is greater than the set first temperature difference threshold, the heating of the self-resistance extremely fast heating electrode is stopped; when the temperature of the second feedback signal minus the temperature of the first feedback signal is less than the set second temperature difference threshold, the self-resistance extremely fast heating electrode is controlled to heat, wherein the first temperature difference threshold is greater than the second temperature difference threshold; when the temperature of the second feedback signal reaches the set temperature, the workpiece insulation stage is entered; when the temperature of the second feedback signal is equal to the set temperature, the heating of the self-resistance extremely fast heating electrode is stopped; when the set temperature minus the temperature of the second feedback signal is greater than the set third temperature difference threshold, the heating of the self-resistance extremely fast heating electrode is resumed; when the temperature of the first feedback signal reaches the set temperature, the furnace is entered into the insulation stage, and the heating of the self-resistance extremely fast heating electrode is completely stopped at this time.

[0011] Furthermore, the vacuum brazing equipment of the plate-fin heat exchanger also includes a temperature control system, which includes: an infrared thermometer output module, which is used to transmit the second feedback signal output by the infrared thermometer; a thermocouple output module, which is used to transmit the first feedback signal output by the thermocouple; a temperature control meter, which is used to receive the first feedback signal and the second feedback signal, and output a digital signal according to the dual feedback series control method; an analog output module, which converts the digital signal into an electrical signal, and a thyristor voltage regulation module, which realizes precise control of the voltage according to the electrical signal, thereby realizing control of the self-resistance extreme-speed heating electrode and radiation heating.

[0012] Furthermore, the hydraulic control system adopts a pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature ranges.

[0013] Furthermore, the dynamic sealing structure includes a sealing seat, a sealing ring, a spacer ring and a pressure cover. One end of the sealing seat has an outer flange edge, which is fixed to the furnace body by bolts. The other end of the sealing seat has an inner circular table surface, on which multiple sealing rings and spacer rings are stacked in sequence and tightened by the pressure cover, which is fixedly connected to the sealing seat.

[0014] Furthermore, the upper electrode is composed of an upper electrode plate, an upper electrode column and an insulating porcelain tube. The upper electrode plate is connected to the upper insulating and heat-insulating plate. The lower end of the upper electrode passes through the electrode porcelain tube on the top of the furnace. The upper surface of the upper electrode is evenly distributed with upper electrode column countersunk holes, and the lower surface is evenly distributed with bolt countersunk holes and threaded holes of the first electrode lead-out device. The insulating porcelain tube is provided with an inner hole. The upper electrode column is placed in the upper electrode column countersunk hole on the upper electrode plate and fits with the upper insulating and heat-insulating plate. The insulating porcelain tube is placed in the bolt countersunk hole on the upper electrode plate.

[0015] The lower electrode is composed of a lower electrode plate, a lower electrode column and an insulating porcelain tube; the lower electrode plate is connected to the lower insulating heat-insulating plate, the upper end of the lower electrode passes through the electrode porcelain tube at the bottom of the furnace, the lower electrode plate is evenly provided with lower electrode column blind holes and bolt countersunk holes, the lower end of the lower electrode column is arranged in the lower electrode column blind hole of the lower electrode plate, and the insulating porcelain tube is arranged in the bolt countersunk hole.

[0016] Furthermore, the first electrode lead-out device includes a first copper bar, a first copper pigtail assembly, a first water-cooled sealed electrode and a first connecting plate. The first copper bar adopts a double lead-out structure and is in the shape of a rectangular frame, connected to the upper electrode plate. The first copper pigtail assembly is located on both sides of the first copper bar rectangular frame. The first copper pigtail assembly has two groups, which are respectively located on the left and right sides of the first copper bar rectangular frame. Each group has two copper pigtails. One end of the copper pigtail is connected to the first copper bar, and the other end is connected to the first water-cooled sealed electrode through the first connecting plate. The length of the first copper pigtail assembly is greater than the working stroke of the upper water-cooled sealed conductive voltage head, and the first water-cooled sealed electrode is connected to the furnace body.

[0017] The second electrode lead-out device consists of a second copper bar, a second copper pigtail assembly, a second water-cooled sealed electrode and a second connecting plate. The second copper bar adopts a double lead-out structure and is in the shape of a rectangular frame, which is connected to the lower electrode plate. The second copper pigtail assembly is located on the left and right sides of the second copper bar rectangular frame. The second copper pigtail assembly has two groups, which are respectively located on the left and right sides of the second copper bar rectangular frame. Each group has two copper pigtails. One end of the copper pigtail is connected to the second copper bar, and the other end is connected to the second water-cooled sealed electrode through the second connecting plate. The second water-cooled sealed electrode is firmly connected to the furnace body.

[0018] According to another aspect of the present invention, a plate-fin heat exchanger brazing method is provided, the method adopts the vacuum brazing equipment provided by the present invention, and the plate-fin heat exchanger brazing method specifically comprises: processing the partition, fin, and seal parts of the plate-fin heat exchanger according to size requirements, and cleaning them; coating the brazing material layer on the upper and lower sides of the partition; assembling the parts of the plate-fin heat exchanger on the tooling, placing the upper thick plate, the pad, the plate-fin heat exchanger, the pad, and the lower thick plate in sequence from bottom to top, using a screw to pass through the edge through holes of the upper thick plate, the pad, and the lower thick plate and tightening them with nuts at the upper and lower ends; placing the above-mentioned tooling as a whole on the material cart Place it on the lower conductive base and press it with the upper water-cooled sealed conductive voltage head, loosen the tooling to tighten the lower nut and keep the pressure constant; turn on the vacuum system and evacuate to the working vacuum degree; use double feedback series control to heat and keep the plate-fin heat exchanger warm; use the pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature sections; heat the plate-fin heat exchanger to the brazing process temperature ±5℃, keep it warm for 10 to 60 minutes, and complete the brazing; cool the welded plate-fin heat exchanger evenly to below 150℃, turn off the vacuum system 80, and then continue to cool to room temperature.

[0019] Furthermore, the pressure-temperature coupling relationship set by the pressure-temperature coupling control method is as follows: temperature <150°C, pressure 0.1Mpa; 200°C≤temperature <400°C, pressure 0.08MPa; 400°C≤temperature <600°C, pressure 0.06MPa; 600°C≤temperature <800°C, pressure 0.04MPa.

[0020] The present invention has the following beneficial effects:

[0021] 1) By adopting the scheme of the present invention, the existing multi-stage insulation heating process can be changed to a short composite heating heating process, and the temperature of the large-sized titanium alloy plate-fin heat exchanger can be ensured to remain uniform during the heating process, thereby improving the heating efficiency.

[0022] 2) By adopting the solution of the present invention, the overall load distribution of the large-sized titanium alloy plate-fin heat exchanger during the brazing process is uniform and adjustable and controllable, thereby ensuring the dimensional precision requirements of the flatness of the product.

[0023] 3) By adopting the scheme of the present invention, the insulation time of the large-sized titanium alloy plate-fin heat exchanger at the brazing process temperature is short enough, and the stress at the weld is uniform enough, which can ensure the consistency of the quality of tens of thousands of brazing welds.

[0024] 4) The solution of the present invention reduces heat loss by shortening the heating process time, thereby reducing energy consumption.

[0025] Combined with the structure and method of the present invention, it is explained how the present invention solves the following technical problems:

[0026] Compared with traditional vacuum brazing equipment, the present invention adds the functions of self-resistance rapid heating and uniform pressure loading of the workpiece. Through the design of the conductive voltage loading device and tooling, dual-feedback series control is adopted to realize dual-heat source heating, shorten the heating process time, and adopt the pressure-temperature coupling control method to ensure that the stress is uniform and the deformation is reduced, thereby improving the heating efficiency and welding quality consistency. Specifically, a hydraulic control system, an upper water-cooled sealed conductive voltage head, a lower conductive base and tooling are added. The structure is compounded with the furnace, wherein the upper electrode of the upper water-cooled sealed conductive voltage head adopts a distributed structure, which can be moved up and down through the hydraulic control system. The combination with the tooling can ensure that the workpiece is always uniformly stressed, and the self-resistance rapid heating is continuously and stably energized. During brazing, the above-mentioned structural scheme, dual-feedback series control and pressure-temperature coupling control method can be adopted to realize rapid and uniform heating and small deformation control of the workpiece, and can be extended to the vacuum brazing of large-size plate-fin heat exchangers used in the aviation and navigation fields, fundamentally solving the problems of low heating efficiency and difficult deformation control caused by the structural characteristics of the plate-fin heat exchanger and the characteristics of vacuum radiation heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A front view of a vacuum brazing device for a plate-fin heat exchanger provided according to a specific embodiment of the present invention;

[0029] Figure 2 A top view of a vacuum brazing device for a plate-fin heat exchanger provided according to a specific embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the structure of an upper water-cooled sealed conductive voltage head provided according to a specific embodiment of the present invention;

[0031] Figure 4 It is an enlarged schematic diagram of a dynamic sealing structure between an upper water-cooled sealed conductive voltage head and a furnace body provided according to a specific embodiment of the present invention;

[0032] Figure 5 A schematic diagram of a first electrode lead-out device of an upper water-cooled sealed conductive voltage head provided in a specific embodiment of the present invention;

[0033] Figure 6 A schematic diagram of the structure of a lower conductive base provided in a specific embodiment of the present invention;

[0034] Figure 7 A schematic diagram of a second electrode lead-out device of a lower conductive base provided in a specific embodiment of the present invention;

[0035] Figure 8 A schematic diagram of a tooling provided for a specific embodiment of the present invention;

[0036] Fig. 9 It is a schematic diagram of the structure of a titanium alloy plate-fin heat exchanger;

[0037] Fig.10 A schematic diagram of a temperature control system of a vacuum brazing equipment for a plate-fin heat exchanger provided in a specific embodiment of the present invention;

[0038] Fig.11 This is the process curve of brazing titanium alloy plate-fin heat exchanger using traditional vacuum brazing equipment;

[0039] Fig.12 A process curve diagram of brazing a titanium alloy plate-fin heat exchanger using a vacuum brazing device provided by a specific embodiment of the present invention;

[0040] Fig.13 Titanium alloy plate-fin heat exchanger that has been brazed;

[0041] The above drawings include the following reference numerals:

[0042] 10. Hydraulic control system; 11. Mainframe; 12. Pressure head; 13. Control system;

[0043] 20. Upper water-cooled sealed conductive voltage head; 21. Water-cooled sealed pressure head seat; 211. Flange; 212. Pressure head column; 213. Water inlet pipe; 214. Water outlet pipe; 215. Sealing sleeve; 216. Sealing ring; 22. Pressure head pad; 23. Upper insulating heat-insulating plate; 24. Upper electrode; 241. Upper electrode plate; 242. Upper electrode column; 243. First insulating porcelain tube; 25. First electrode lead-out device; 251. First copper busbar; 252. First copper pigtail assembly; 253. First water-cooled sealed electrode; 254. First connecting plate;

[0044] 30. Lower conductive base; 31. Base pad; 32. Lower insulating heat-insulating plate; 33. Lower electrode; 331. Lower electrode plate; 332. Lower electrode column; 333. Second insulating porcelain tube; 34. Second electrode lead-out device; 341. Second copper busbar; 342. Second copper pigtail assembly; 343. Second water-cooled sealed electrode; 344. Second connecting plate;

[0045] 40. Tooling; 41. Upper thick plate; 42. Pad; 43. Lower thick plate;

[0046] 50. Furnace body; 51. Flange cover with holes; 52. Blind flange cover; 53. Temperature control couple; 54. Observation window; 55. Infrared thermometer;

[0047] 60. Furnace; 61. Furnace frame; 62. Heat shield; 63. Heat-generating belt; 64. Electrode porcelain tube; 65. Observation hole

[0048] 70. Dynamic sealing structure; 71. Sealing seat; 72. Sealing ring; 73. Spacer ring; 74. Gland;

[0049] 80. Vacuum system; 81. Vacuum pump; 82. Vacuum valve; 83. Pipeline. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0052] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0053] like Figures 1 to 13As shown, according to a specific embodiment of the present invention, a vacuum brazing device for a plate-fin heat exchanger is provided, and the vacuum brazing device for a plate-fin heat exchanger includes: a hydraulic control system 10, a furnace body 50, a furnace 60, a dynamic sealing structure 70, a vacuum system 80, an upper water-cooled sealing conductive voltage head 20, a lower conductive base 30, and a tooling 40. The hydraulic control system 10 is used to provide a fixed-range and constant-pressure control for the vacuum brazing device; the furnace body 50 is fixed on the main frame 11 of the hydraulic control system 10, and the furnace body 50 is used to provide a vacuum environment and interfaces of various subsystems, and to accommodate parts to be welded, wherein the interface includes a temperature control couple 53 and an infrared thermometer 55 interface; the output signal of the temperature control couple 53 is a first feedback signal, which is used as the main temperature control feedback signal to adjust the power of each heat-generating belt 63; the output signal of the infrared thermometer 55 is a second feedback signal, which is used to monitor the temperature of the plate-fin heat exchanger and assist in controlling the self-resistance and extreme acceleration of the plate-fin heat exchanger. Thermoelectrode power, the working temperature of the infrared thermometer 55 is controlled by a double feedback series control method according to the first feedback signal and the second feedback signal; a furnace 60, the furnace 60 is arranged in the furnace body 50, the furnace 60 includes a furnace frame 61, a heat insulation screen 62 and a plurality of heat-generating belts 63, and the heat-generating belts in each zone are evenly distributed on the inner wall of the furnace, and can be independently controlled; used for vacuum radiation heating and heat preservation; a dynamic sealing structure 70, the dynamic sealing structure 70 is fixed on the furnace body 50, and the dynamic sealing structure 70 is used to provide a translational sealing interface to maintain the working vacuum degree of the system; a vacuum system 80, the vacuum system 80 is connected to the furnace body 50 The vacuum system is used to discharge the gas in the furnace body 50 to obtain a vacuum environment; an upper water-cooled sealed conductive voltage head 20, the upper water-cooled sealed conductive voltage head 20 is connected to the hydraulic control system 10, the lower end passes through the top of the furnace body 50 and maintains the vacuum degree in the furnace through the dynamic sealing structure 70; the upper water-cooled sealed conductive voltage head 20 includes a water-cooled sealed pressure head seat 21, a pressure head pad 22, an upper insulating heat insulation plate 23, an upper electrode 24 and a first electrode lead-out device 25, wherein the water-cooled sealed pressure head seat 21, the pressure head pad 22, the upper insulating heat insulation plate 23, and the upper electrode 24 are connected in sequence, and the water-cooled sealed pressure head seat 21 includes a flange 211, a pressure head column 2 12, water inlet pipe 213, water outlet pipe 214, sealing sleeve 215 and sealing ring 216, the pressure head column 212 is welded to the pressure head 12 through the flange 211, the upper end face of the sealing sleeve 215 is welded to the flange 211, the sealing sleeve 215 is a hollow circular tube, the water inlet pipe 213 and the water outlet pipe 214 are welded to the upper end of the outer circle of the sealing sleeve 215, the water inlet pipe 213 extends to the bottom of the sealing sleeve 215, the inner circle lower end of the sealing ring 216 is welded to the pressure head column 212, and the outer circle upper end is welded to the sealing sleeve 215, the first electrode lead-out device 25 is connected to the upper electrode 24, and is used to lead out the current of the upper water-cooled sealed conductive voltage head 20;Together with the lower conductive base 30, it is used for self-resistance extremely fast heating and uniform loading of the welded parts; the lower conductive base 30, the lower conductive base 30 includes a base pad 31, a lower insulating heat insulation board 32, a lower electrode 33 and a second electrode lead-out device 34 connected in sequence, the second electrode lead-out device 34 is connected to the lower electrode 33, and is used to lead the current of the lower conductive base 30; together with the upper water-cooled sealed conductive voltage head 20, it is used for self-resistance extremely fast heating and uniform loading of the welded parts; the tooling 40, the tooling 40 is used to provide constraints for the plate-fin heat exchanger. ;

[0054] The hydraulic control system 10, the furnace body 50, the infrared thermometer 55, the upper water-cooled sealed conductive voltage head assembly, and the lower conductive base 30, the hydraulic control system 10 is used to provide welding pressure for the vacuum brazing equipment; the furnace body 50 is fixed to the hydraulic control system 10, and the furnace body 50 includes a temperature control couple 53 and a plurality of heat-generating belts 63, and the output signal of the temperature control couple 53 is a first feedback signal.

[0055] This configuration is applied to realize the self-resistance rapid heating of the workpiece by configuring the conductive voltage load device, and dual heat source heating is realized by adopting double feedback series control, which shortens the heating process time and improves the heating efficiency and welding quality consistency. Specifically, a hydraulic control system, an upper water-cooled sealed conductive voltage head and a lower conductive base are added. The structure is compounded with the furnace, wherein the upper water-cooled sealed conductive voltage head assembly has multiple electrodes and adopts a distributed structure, which can be moved up and down by the hydraulic control system, which can ensure that the workpiece is always uniformly stressed and that the self-resistance rapid heating is continuously and stably energized. The temperature of the electrode and surrounding components is effectively reduced by the water cooling system design, extending the service life of the equipment. During brazing, the above structural scheme and double feedback series control can realize rapid and uniform heating of the workpiece and small deformation control, and can be extended to vacuum brazing of large-size plate-fin heat exchangers used in aviation and navigation fields, fundamentally solving the problems of low heating efficiency and difficult deformation control caused by the structural characteristics of the plate-fin heat exchanger and the characteristics of vacuum radiation heating.

[0056] Furthermore, in order to realize dual-heat source heating, the working temperature is controlled according to the first feedback signal and the second feedback signal by a dual feedback series control method, specifically including: if the temperatures of the first feedback signal and the second feedback signal do not reach the set temperature, the heating stage is entered, and the PID (proportional integral differential control) is used to control the heating belt and the self-resistance extremely fast heating electrode to heat simultaneously; when the temperature of the second feedback signal minus the temperature of the first feedback signal is greater than the set first temperature difference threshold, the self-resistance extremely fast heating electrode is stopped from heating; when the temperature of the second feedback signal minus the temperature of the first feedback signal is less than the set second temperature difference threshold, the self-resistance extremely fast heating electrode is controlled to heat, wherein the first temperature difference threshold is greater than the second temperature difference threshold; when the temperature of the second feedback signal reaches the set temperature, the workpiece insulation stage is entered; when the temperature of the second feedback signal is equal to the set temperature, the self-resistance extremely fast heating electrode is stopped from heating; when the set temperature minus the temperature of the second feedback signal is greater than the set third temperature difference threshold, the self-resistance extremely fast heating electrode is resumed from heating; when the temperature of the first feedback signal reaches the set temperature, the furnace insulation stage is entered, and the self-resistance extremely fast heating electrode is completely stopped from heating.

[0057] According to a specific embodiment of the present invention, when the temperature of the second feedback signal reaches the set temperature of 680°C, the workpiece enters the heat preservation stage. When the temperature of the second feedback signal is equal to the set temperature of 680°C, the self-resistance extremely fast heating electrode heating is stopped; when the set temperature of 680°C minus the temperature of the second feedback signal is greater than the set temperature difference of 30°C, the self-resistance extremely fast heating electrode heating is resumed. When the temperature of the first feedback signal reaches the set temperature of 680°C, the furnace enters the heat preservation stage, and the self-resistance extremely fast heating electrode heating is completely stopped at this time.

[0058] By applying this configuration, the temperature regulation mode in the furnace is divided into a heating stage, a workpiece insulation stage and a furnace insulation stage according to the temperature range of the first feedback signal and the second feedback signal, and the dual heat source heating mode of self-resistance rapid heat generation and radiation heating is controlled. The dual heat source heating stage can be carried out in sections, and the section temperature, insulation time and number of sections can be set according to the size of the titanium alloy plate-fin heat exchanger and the type of brazing material, thereby improving the heating efficiency and flexibility.

[0059] Furthermore, in order to achieve precise control of temperature, Fig.10As shown, the vacuum brazing equipment for plate-fin heat exchangers also includes a temperature control system, which includes an infrared thermometer output module, a thermocouple output module, a temperature control meter, an analog output module, and a thyristor voltage regulator module. The infrared thermometer output module is used to transmit the second feedback signal output by the infrared thermometer 55, the thermocouple output module is used to transmit the first feedback signal output by the thermocouple, the temperature control meter is used to receive the first feedback signal and the second feedback signal, and output a digital signal according to the dual feedback series control method, the analog output module converts the digital signal into an electrical signal, and the thyristor voltage regulator module realizes precise control of the voltage according to the electrical signal, thereby realizing the control of the self-resistance extreme speed heating electrode and radiation heating.

[0060] With this configuration, the temperature control system can accurately monitor the temperature inside the furnace and automatically adjust it according to the preset dual-feedback series control method, thereby maintaining a stable temperature environment and achieving automatic and precise temperature control.

[0061] Furthermore, in order to ensure uniform stress and improve welding quality consistency, the hydraulic control system 10 adopts a pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature sections. This configuration ensures uniform stress and reduces deformation, thereby improving heating efficiency and welding quality consistency.

[0062] Furthermore, if Figure 4 As shown, in order to achieve effective sealing, the dynamic sealing structure 70 includes a sealing seat 71, a sealing ring 72, a spacer ring 73 and a gland 74. One end of the sealing seat 71 has an outer flange edge, which is fixed to the furnace body 50 by bolts. The other end of the sealing seat 71 has an inner circular table surface, and multiple sealing rings 72 and spacer rings 73 are stacked in sequence and pressed by a gland 74. The gland 74 is fixedly connected to the sealing seat 71. Applying this configuration mode can meet the special requirements of the vacuum environment in the vacuum brazing equipment for sealing, and improve the overall reliability and stability of the equipment.

[0063] Furthermore, if Figure 3As shown, in order to effectively realize electrical insulation and heat insulation between the electrode and the surrounding environment and enhance the safety and stability of the equipment, the upper electrode 24 is composed of an upper electrode plate 241, an upper electrode column 242 and a first insulating porcelain tube 243. The upper electrode plate 241 is connected to the upper insulating heat-insulating plate 23. The lower end of the upper electrode 24 passes through the electrode porcelain tube 64 on the top of the furnace 60. The upper surface thereof is evenly distributed with upper electrode column countersunk holes, and the lower surface is evenly distributed with bolt countersunk holes and threaded holes of the first electrode lead-out device 25. The first insulating porcelain tube 243 is provided with an inner hole; the upper electrode column 242 is placed in the upper electrode column countersunk hole on the upper electrode plate 241, and fits with the upper insulating heat-insulating plate 23; the first insulating porcelain tube 243 is placed in the bolt countersunk hole on the upper electrode plate; the mounting bolts pass through the inner hole of the first insulating porcelain tube 243, the through hole of the upper insulating heat-insulating plate, and the through hole of the pressure head pad in sequence and are fastened to the water-cooled sealed pressure head seat 21. The lower electrode 33 is composed of a lower electrode plate 331, a lower electrode column 332 and an insulating second porcelain tube 333; the lower electrode plate 331 is connected to the lower insulating heat-insulating plate 32, the upper end of the lower electrode 33 passes through the electrode porcelain tube 64 at the bottom of the furnace 60, the lower electrode plate 331 is evenly distributed with lower electrode column blind holes and bolt countersunk holes, the lower end of the lower electrode column 332 is arranged in the lower electrode column blind hole of the lower electrode plate 331, and the first insulating porcelain tube 333 is arranged in the bolt countersunk hole; the mounting bolts pass through the first insulating porcelain tube 333 and the through holes of the lower insulating heat-insulating plate 32 in sequence and are fastened to the base pad 31.

[0064] Furthermore, if Figures 5 to 7As shown, in order to meet the demand of vacuum brazing equipment for connecting large current active electrodes, the first electrode lead-out device 25 includes a first copper bar 251, a first copper pigtail assembly 252, a first water-cooled sealed electrode 253 and a first connecting plate 254. The first copper bar 251 adopts a double lead-out structure, which is in the shape of a rectangular frame and is connected to the upper electrode plate 241. The first copper bar 251 adopts a double lead-out structure, which is in the shape of a rectangular frame and is connected to the upper electrode plate 241. The first copper pigtail assembly 252 is located on both sides of the rectangular frame of the first copper bar 251. The first copper pigtail assembly 252 has two groups, which are respectively located on the left and right sides of the rectangular frame of the first copper bar 251. Each group has two copper pigtails. One end of the copper pigtail is connected to the first copper bar 251, and the other end is connected to the first water-cooled sealed electrode 253 through the first connecting plate 254. The first copper pigtail assembly The length of 252 is greater than the working stroke of the upper water-cooled sealed conductive voltage head 20, and the first water-cooled sealed electrode 253 is connected to the furnace body 50; the second electrode lead-out device 34 is composed of a second copper bar 341, a second copper pigtail assembly 342, a second water-cooled sealed electrode 343 and a second connecting plate 344. The second copper bar 341 adopts a double lead-out structure, which is in a rectangular frame shape and is connected to the lower electrode plate 331. The second copper pigtail assembly 342 is located on the left and right sides of the rectangular frame of the second copper bar 341. The second copper pigtail assembly 342 has two groups, which are respectively located on the left and right sides of the rectangular frame of the second copper bar 341. Each group has two copper pigtails. One end of the copper pigtail is connected to the second copper bar 341, and the other end is connected to the second water-cooled sealed electrode 343 through the second connecting plate 344. The second water-cooled sealed electrode 343 is fastened to the furnace body 50. The second water-cooled sealed electrode 343 is fastened to the right-angle electrode seat on the furnace body 50 by bolts.

[0065] This configuration adopts a double lead structure, which enhances the stability and reliability of the electrode lead device, and provides a more flexible installation and connection method, which can better adapt to complex electrical connection requirements and reduce resistance and heat accumulation. The water-cooled sealed electrode not only provides a good electrical connection, but also effectively reduces the temperature of the electrode and surrounding components through the water cooling system, meeting the cooling requirements of vacuum brazing equipment.

[0066] Furthermore, if Figure 8 As shown, in order to realize the assembly of the workpiece and ensure uniform contact stress, the tooling 40 includes an upper thick plate 41, a pad 42 and a lower thick plate 43. The upper thick plate 41 and the lower thick plate 43 are tightly fitted with the upper electrode column 242 and the lower electrode 33 respectively. The edges of the upper thick plate 41, the pad 42 and the lower thick plate 43 are fixedly connected, and the lower thick plate 43 is placed on the lower conductive base 30.

[0067] When brazing with traditional special tooling, for large-sized heat exchangers, only appropriate preload is provided during initial assembly, which can easily cause uneven contact stress between the edge and the core of the workpiece. In addition, during the heating process, the thermal expansion state under strong constraints is more likely to cause uncontrollable deformation, resulting in product size deviation or low strength of local welded joints. This configuration can keep the stress within the appropriate range throughout the brazing process.

[0068] Furthermore, according to another aspect of the present invention, a plate-fin heat exchanger brazing method is provided, wherein the baffle, fin, and seal parts of the plate-fin heat exchanger are processed according to the size requirements and cleaned; a brazing material layer is applied to the upper and lower sides of the baffle; the parts of the plate-fin heat exchanger are assembled on the tooling 40, and the upper thick plate 41, the pad 42, the plate-fin heat exchanger, the pad 42, and the lower thick plate 43 are placed in sequence from bottom to top, and a screw is passed through the edge through holes of the upper thick plate 41, the pad 42, and the lower thick plate 43 and fastened with nuts at the upper and lower ends; the above-mentioned tooling 40 is placed as a whole on the lower conductive base 30 by a material cart , and press it with the upper water-cooled sealing conductive voltage head 20, loosen the tooling 40 to tighten the lower nut to keep the pressure constant; open the vacuum system 80, and evacuate to the working vacuum degree; use the double feedback series control method to heat and keep the plate-fin heat exchanger warm; use the pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature sections; heat the plate-fin heat exchanger to the brazing process temperature ±5℃, keep it warm for 10 to 60 minutes, and complete the brazing; cool the welded plate-fin heat exchanger evenly to below 150℃, close the vacuum system 80, and then continue to cool it to room temperature.

[0069] By applying this configuration, the vacuum brazing method for plate-fin heat exchangers of the present invention can enable the vacuum brazing equipment to improve the load distribution of the brazing workpiece, ensure uniform stress and controllable deformation during the entire brazing process, and improve the dimensional accuracy of the product; at the same time, the self-resistance heat generation function of the workpiece is added on the basis of the radiation heating function, thereby solving the current problems of low heating efficiency and difficult deformation control caused by the structural characteristics of the plate-fin heat exchanger and the characteristics of vacuum radiation heating.

[0070] Furthermore, in order to meet the requirements of vacuum brazing equipment for plate-fin heat exchanger welding stress uniformity and deformation control, a pressure-temperature coupling control method is adopted, and the set pressure-temperature coupling relationship is as follows: temperature <150°C, pressure 0.1Mpa; 200°C≤temperature <400°C, pressure 0.08MPa; 400°C≤temperature <600°C, pressure 0.06MPa; 600°C≤temperature <800°C, pressure 0.04MPa.

[0071] In order to further understand the present invention, the following Figures 1 to 13 The vacuum brazing equipment and method for plate-fin heat exchangers of the present invention are described in detail. Figures 1 to 10As shown, a vacuum brazing device for a plate-fin heat exchanger comprises:

[0072] The hydraulic control system 10 can realize the fixed range and fixed pressure control of the upper water-cooled sealed conductive pressure head. The hydraulic control system 10 includes a main frame 11, a pressure head 12, and a control system 13. The pressure head 12 is located in the main frame 11, and the control system 13 is electrically connected to the pressure head 12.

[0073] The furnace body 50 is a closed chamber that can withstand both negative and positive pressure. The furnace body 50 is fixed on the main frame 11 of the hydraulic control system 10 and is provided with interfaces of various subsystems, including a flange cover 51 with holes for connecting the top pressure head, a flange blind cover 52 for fixing the bottom, a temperature control couple 53, an observation window 54 at the front and an infrared thermometer 55.

[0074] The furnace 60 is located inside the furnace body 50, and the furnace 60 includes a furnace frame 61, a heat shield 62, a plurality of heat-generating belts 63, an electrode porcelain tube 64 and an observation hole 65. The heat shield 62 is arranged inside the furnace frame 61, and the heat-generating belt 63 is arranged inside the heat shield 62 of the furnace frame 61. The heat-generating belt 63 is in a snake shape and is placed inside the furnace frame 61 with a square structure, and is fixed on four sides, namely, up, down, left, right, or six sides, namely, up, down, left, right, front, and back. The output power of each heat-generating belt can be independently controlled, so as to solve the problem of uneven temperature distribution caused by the introduction of upper and lower electrodes.

[0075] The dynamic sealing structure 70 includes a sealing seat 71, a sealing ring 72, a spacer ring 73 and a pressure cover 74. The upper end of the sealing seat 71 has an outer flange edge, which is fixed to the furnace body 50 by bolts, and the lower end has an inner circular table surface, on which multiple sealing rings 72 and spacer rings 73 are stacked in sequence and pressed by the lower end surface of the pressure cover 74. The pressure cover 74 is connected to the sealing seat 71 by bolts.

[0076] The vacuum system 80 includes a vacuum pump 81 , a vacuum valve 82 and a pipeline 83 . The vacuum pump 81 is connected to the furnace body 50 through the pipeline 83 , and the vacuum valve 82 is provided on the pipeline 83 .

[0077] The upper water-cooled sealed conductive voltage head 20 is mechanically connected to the pressure head 12 of the hydraulic control system 10, and the vacuum degree in the furnace is maintained through the dynamic sealing structure 70; the upper water-cooled sealed conductive voltage head 20 includes a water-cooled sealed pressure head seat 21, a pressure head pad 22, an upper insulating and heat-insulating plate 23, an upper electrode 24 and a first electrode lead-out device 25.

[0078] The water-cooled sealing pressure head seat 21 is welded by a flange 211, a pressure head column 212, a water inlet pipe 213, a water outlet pipe 214, a sealing sleeve 215 and a sealing ring 216. The pressure head column 212 is a solid cylinder with a flange 211 welded on it and is fastened to the pressure head 12 by bolts. The sealing sleeve 215 is a hollow circular tube. The pressure head column 212 is arranged inside the sealing sleeve 215, and the upper end surface is welded to the flange 211. The water inlet and outlet are respectively welded at the water inlet and outlet at the upper end of the outer circle. Water pipe 214, wherein the water inlet of the water inlet pipe 213 extends to the bottom of the sealing sleeve 215, the inner circle lower end of the sealing ring 216 is welded to the pressure head column 212, and the outer circle upper end is welded to the sealing sleeve 215, thereby forming a ring-shaped closed cavity that can be cooled by water; the bottom of the water-cooled sealing pressure head seat 21 passes through the perforated flange cover 51 located on the top of the furnace body of the vacuum brazing equipment, and a dynamic sealing structure 70 is adopted between the furnace body 50, which can realize the reliable movement of the upper water-cooled sealing conductive pressure head within the working stroke range.

[0079] The pressure head pad 22 and the upper insulating heat-insulating plate 23 are both provided with through holes, and are fastened to the lower end of the water-cooled sealed pressure head seat 21 by bolts. The upper insulating heat-insulating plate 23 is arranged on the lower end surface of the pressure head pad 22, and the upper electrode 24 is arranged on the upper insulating heat-insulating plate 23.

[0080] The upper electrode 24 includes an upper electrode plate 241, an upper electrode column 242 and an insulating porcelain tube 243. The upper electrode plate 241 is arranged below the upper insulating heat-insulating plate 23. The upper surface of the upper electrode column is uniformly distributed with upper electrode column countersunk holes, and the lower surface is uniformly distributed with bolt countersunk holes and threaded holes of the first electrode lead-out device 25. The upper electrode column 242 is placed in the upper electrode column countersunk hole on the upper electrode plate 241, and fits with the upper insulating heat-insulating plate 23. The upper electrode column 242 is in the shape of a cylindrical head long rod, with the big end facing upward, and the upper end surface is higher than the upper plane of the upper electrode plate 241. The insulating porcelain tube 243 is provided with an inner hole, and the insulating porcelain tube 243 is placed in the bolt countersunk hole on the upper electrode plate. The mounting bolts pass through the inner hole of the insulating porcelain tube, the through hole of the upper insulating heat-insulating plate, and the through hole of the pressure head pad in sequence to be fastened to the water-cooled sealed pressure head seat 21. The lower end of the upper electrode 24 passes through the electrode porcelain tube 64 at the top of the furnace 60.

[0081] The first electrode lead-out device 25 can realize high current power supply of more than 8000A and safe and reliable movement of the upper water-cooled sealed conductive voltage head. The first electrode lead-out device 25 includes a first copper busbar 251, a first copper pigtail assembly 252, a first water-cooled sealed electrode 253 and a first connecting plate 254. The first copper busbar 251 adopts a double lead-out structure and is in a rectangular frame shape. It is placed under the upper electrode plate 241 and is connected to the upper electrode plate 241 by bolts. The first copper pigtail assembly 252 has two groups, which are respectively located on the left and right sides of the rectangular frame of the first copper busbar 251. Each group of the first copper pigtail assembly 252 has two copper pigtails, one end of which is connected to the first copper busbar 251, and the other end is connected to the first water-cooled sealed electrode 253 through the first connecting plate 254. 3 is connected, the length of the first copper pigtail assembly 252 covers the working stroke of the upper water-cooled sealed conductive voltage head 20, the first water-cooled sealed electrode 253 is fastened to the electrode seat on the furnace body 50 by bolts, and the motor seat can adopt a right-angle structure. One end face of the first connecting plate 254 is connected to the first copper pigtail 252. After the upper water-cooled sealed conductive voltage head 20 is installed, it and the first copper pigtail 252 are passed through the right-angle electrode seat on the furnace body 50 together, and the other end face of the first connecting plate 254 is fastened to the installed water-cooled sealed electrode 253 by bolts, and the first connecting plate 254 is a 90° bent part.

[0082] The lower conductive base 30 is welded to the bottom fixed mounting flange blind cover 52 of the furnace body 50 ; the lower conductive base 30 includes a base pad 31 , a lower insulating heat-insulating plate 32 , a lower electrode 33 and a second electrode lead-out device 34 .

[0083] The base pad 31 is provided with threaded holes and welded to the flange blind cover 52. The lower insulating and heat-insulating plate 32 has a through hole and is arranged above the base pad 31. The upper insulating and heat-insulating plate 23 and the lower insulating and heat-insulating plate 32 are both temperature-resistant above 300°C.

[0084] The lower electrode 33 is fastened to the base plate 31 by bolts passing through the insulating porcelain tube and the through hole of the lower insulating heat insulation plate 32 in sequence. The lower electrode 33 includes a lower electrode plate 331, a lower electrode column 332 and an insulating porcelain tube 333. The lower electrode plate 331 is evenly provided with lower electrode column blind holes and bolt countersunk holes. The lower end of the lower electrode column 332 is arranged in the lower electrode column blind hole of the lower electrode plate 331, and the upper end passes through the electrode porcelain tube 64 at the bottom of the furnace 60. The lower electrode column 332 is in the shape of an equal-diameter long rod, and the lower end is arranged in the lower electrode column blind hole of the lower electrode plate 331, and the upper end passes through the electrode porcelain tube 64 at the bottom of the furnace 60. The insulating porcelain tube 333 is arranged in the bolt countersunk hole, and the insulating porcelain tube 333 is in the shape of a shouldered sleeve with the large end facing upward.

[0085] The second electrode lead-out device 34 can realize high current power supply of more than 8000A. The second electrode lead-out device 34 includes a second copper bar 341, a second copper pigtail assembly 342, a second water-cooled sealed electrode 343 and a second connecting plate 344. The second copper bar 341 adopts a double lead-out structure and is in a rectangular frame shape. It is placed above the lower electrode plate 331 and is connected to the lower electrode plate 331 by bolts. The second copper pigtail 342 has two groups, which are respectively located on the left and right sides of the rectangular frame of the second copper bar 341. Each group of the second copper pigtail assembly 342 has two copper pigtails, one end of which is connected to the second copper bar 341, and the other end is connected to the second water-cooled sealed electrode 343 by the second connecting plate 344. It is connected to the second water-cooled sealed electrode 343, and the second water-cooled sealed electrode 343 is fastened to the right-angle electrode seat on the furnace body 50 by bolts. The second connecting plate 344 is a 90° bent part. One end face of the second connecting plate 344 is connected to the second copper pigtail 342. After the upper water-cooled sealed conductive voltage head 20 is installed, it and the second copper pigtail 342 are passed through the right-angle electrode seat on the furnace body 50. The other side of the second connecting plate 344 is fastened to the installed second water-cooled sealed electrode 343 by bolts. The second connecting plate 344 is a 90° bent part.

[0086] The tooling 40, including an upper thick plate 41, a pad 42 and a lower thick plate 43, is located in the effective heating working area of ​​the furnace 60 between the upper water-cooled sealed conductive voltage head 20 and the lower conductive base 30. The upper thick plate 41 and the lower thick plate 43 have smooth surfaces, and the upper and lower surfaces are parallel. Through holes are provided on the edges, and they are tightly fitted with the upper electrode column 242 and the lower electrode column 332 respectively. The pad 42 has a smooth surface, and the upper and lower surfaces are parallel. Through holes are provided on the edge, and a conductive material that does not chemically react with the plate-fin heat exchanger is used. Through holes are provided on the edges of the upper thick plate 41, the pad 42 and the lower thick plate 43. Screws are used to pass through the through holes on the edges of the upper thick plate 41, the pad 42 and the lower thick plate 43, and are fixed by nuts. The upper water-cooled sealed conductive voltage head 20 is placed on the upper thick plate 41, and the lower thick plate 43 is placed on the lower conductive base 30. When loading, place the lower thick plate 43, pad 42, plate-fin heat exchanger, pad 42, upper thick plate 41 in order from bottom to top, use screws to pass through the edge through holes and tighten with nuts at the upper and lower ends, then place the whole on the lower conductive base, and make the upper water-cooled sealed conductive head press the upper thick plate, loosen the lower nut, and realize constant pressure control by the control system during operation. During brazing, the hydraulic control system presses the plate-fin heat exchanger through the upper water-cooled sealed conductive head, the lower conductive base and the tooling, and heats and keeps warm by radiation heating and self-resistance heat generation.

[0087] The temperature control system includes a temperature control couple 53, a radiation heating device, an infrared thermometer 55, an extremely fast heating resistor, a thermocouple output module, an infrared thermometer output module, a temperature control meter, an analog output module and a thyristor voltage regulating module. The output signal of the temperature control couple 53 is the first feedback signal, which is used as the main temperature control feedback signal to adjust the power of each heat-generating belt 63 of the radiation heating device; the output signal of the infrared thermometer 55 is the second feedback signal, which is used to monitor the temperature of the extremely fast heating resistor plate-fin heat exchanger and assist in controlling the power of the self-resistance extremely fast heating electrodes 24 and 33 of the plate-fin heat exchanger. The working temperature is controlled according to the first feedback signal and the second feedback signal using a double feedback series control method; the thermocouple output module is used to transmit the first feedback signal output by the temperature control couple 53, the infrared thermometer output module is used to transmit the second feedback signal output by the infrared thermometer 55, the temperature control meter is used to receive the first feedback signal and the second feedback signal, and output a digital signal according to the double feedback series control method, the analog output module converts the digital signal into an electrical signal, and the thyristor voltage regulator module realizes precise control of the voltage according to the electrical signal, thereby realizing control of the radiation heating and self-resistance extremely fast heating electrodes.

[0088] With this configuration, the titanium alloy plate-fin heat exchanger can be heated mainly by self-resistance extreme-speed heating in the low-temperature section, and radiation heating can be used to follow the heating furnace. In the high-temperature section, radiation heating can be used alone to heat the titanium alloy plate-fin heat exchanger to the brazing temperature. This method greatly improves the brazing efficiency of the vacuum brazing equipment, and at the same time solves the brazing quality problems such as severe surface embrittlement, easy crack defects, severe thin-wall dissolution, etc. caused by the large temperature difference between the core and the surface and the long insulation time at the brazing temperature.

[0089] Figures 11 to 13 A specific embodiment of a brazing method for a titanium alloy plate-fin heat exchanger is given.

[0090] The workpiece dimensions are 300mm (width) × 500mm (length) × 300mm (height).

[0091] The brazing method of the vacuum brazing device and method of the plate-fin heat exchanger of the present embodiment is as follows:

[0092] 1) Process the parts of titanium alloy plate-fin heat exchanger such as partitions, fins, seals, guide vanes, etc. according to the size requirements and clean them. The material is TC4 titanium alloy;

[0093] 2) Assembling fins, baffles, seals, guide vanes and other parts to form a heat exchanger core, wherein the upper and lower sides of the baffles contain a certain thickness of amorphous titanium brazing material layer;

[0094] 3) Assemble the parts of the plate-fin heat exchanger on the tooling 40, and place the upper thick plate 41, the pad 42, the plate-fin heat exchanger, the pad 42, and the lower thick plate 43 in order from bottom to top, and use screws to pass through the edge through holes of the upper thick plate 41, the pad 42, and the lower thick plate 43 and fasten them with nuts at the upper and lower ends;

[0095] 4) Place the tooling 40 as a whole on the lower conductive base 30 by means of a material cart, and press it with the upper water-cooled sealed conductive voltage head 20, loosen the tooling 40 and tighten the lower nut, keeping the pressure constant at 0.1 MPa;

[0096] 5) Close the furnace door, turn on the vacuum system, and evacuate to 5×10 -3 Pa;

[0097] 6) The vacuum brazing furnace heats the furnace and the titanium alloy plate-fin heat exchanger by radiation heating. At the same time, the titanium alloy plate-fin heat exchanger itself is heated by extremely fast resistance heating. The voltage of the self-resistance extremely fast heating power supply is 5V and the current is 8000A. The total heating rate of the titanium alloy plate-fin heat exchanger in the dual heat source heating stage is as high as 45.3℃ / min. During this stage, the pressure is kept constant at 0.08MPa.

[0098] Dual heat source heating stage, such as Fig.10 As shown, the same temperature controller is used to implement a dual-feedback series control strategy, in which the temperature-controlled thermocouple is used as the main temperature-controlled feedback signal to control the radiation heating component, and the infrared thermometer is connected to a specific port of the temperature controller as an auxiliary temperature-controlled feedback signal to assist in controlling the self-resistance extreme-speed heating component;

[0099] Specifically, the first feedback signal is a temperature control couple arranged near the effective working area of ​​the furnace, which is installed and fixed on the furnace body and is used to adjust the power of the heating belt on each surface and accurately control the uniformity of the furnace temperature; the second feedback signal is an infrared thermometer arranged at the front of the furnace body, which monitors the temperature of the plate-fin heat exchanger through the observation window and the through-hole of the furnace, and is used to assist in controlling the power of the self-resistance extreme-speed heating electrode of the plate-fin heat exchanger; the two temperature feedback signals are simultaneously connected to the specific port of the temperature controller and compared. In the heating stage, if the temperature of the first feedback signal and the second feedback signal does not reach the set temperature of 680°C, PID control is used to heat the heating belt and the self-resistance extremely fast heating electrode at the same time; when the temperature of the second feedback signal minus the temperature of the first feedback signal is greater than the set temperature difference of 100°C, the self-resistance extremely fast heating electrode is stopped for heating; when the temperature of the second feedback signal minus the temperature of the first feedback signal is less than the set temperature difference of 30°C, the self-resistance extremely fast heating electrode is controlled for heating; when the temperature of the second feedback signal reaches the set temperature of 680°C, the workpiece enters the heat preservation stage, and the self-resistance extremely fast heating electrode is stopped for heating. If the set temperature minus the temperature of the second feedback signal is greater than the set temperature difference of 30°C, the self-resistance extremely fast heating electrode is resumed for heating; when the temperature of the first feedback signal reaches the set temperature of 680°C, the furnace enters the heat preservation stage, and the self-resistance extremely fast heating electrode is completely stopped for heating;

[0100] The dual heat source heating stage can be carried out in sections, and the section temperature, insulation time and number of sections can be set according to the size of the titanium alloy plate-fin heat exchanger and the type of brazing material;

[0101] 7) When the temperature of the titanium alloy plate-fin heat exchanger reaches 680°C, stop applying current. When the temperature of the workpiece is lower than the furnace temperature, apply current again. Repeat this cycle until the temperature of the furnace and the titanium alloy plate-fin heat exchanger both rise to 680°C. Keep warm for 25 minutes to make the temperature of each part of the brazing part uniform. This dual heat source heating stage can be carried out in stages.

[0102] 8) The titanium alloy plate-fin heat exchanger is heated by single radiation heating at a rate of 10°C / min to 780°C, kept at this temperature for 80 minutes, then heated to 840°C at a rate of 10°C / min, kept at this temperature for 60 minutes, and finally heated to the optimal brazing temperature of 920°C at a rate of 10°C / min, with an optimal brazing time of 30 minutes;

[0103] 9) Rapidly cool the welded titanium alloy plate-fin heat exchanger to below 150°C and close the vacuum system to prevent oxidation and discoloration;

[0104] 10) After the temperature of the titanium alloy plate-fin heat exchanger drops to room temperature, take out the titanium alloy plate-fin heat exchanger.

[0105] like Fig.11 and Fig.12As shown, the traditional vacuum brazing process curve of the titanium alloy plate-fin heat exchanger (size W×L×H, 300mm×500mm×300mm) in the embodiment takes 1740 minutes for the entire production cycle and the product flatness is 8mm / m; the dual-heat source vacuum brazing process curve of the titanium alloy plate-fin heat exchanger (size W×L×H, 300mm×500mm×300mm) brazed by the equipment of the present invention takes 870 minutes for the entire production cycle and the product flatness is 3mm / m, the manufacturing efficiency is improved by 50%, and the deformation control accuracy is improved by 62.5%.

[0106] The vacuum brazing method of the plate-fin heat exchanger of the present invention first loads the plate-fin heat exchanger between the upper water-cooled sealed conductive voltage head and the lower conductive base of the equipment through a tooling, and then adopts a dual feedback series control and pressure-temperature coupling control method to automatically realize the self-resistance rapid heat generation and uniform pressure loading of the workpiece. The vacuum brazing method proposed based on the present invention improves the brazing process manufacturing efficiency of the titanium alloy plate-fin heat exchanger by 50%, and the deformation control accuracy by 62.5%, fundamentally solving the problems of low heating efficiency and difficult deformation control caused by the structural characteristics of the plate-fin heat exchanger and the characteristics of vacuum radiation heating. The technology of the present invention has important engineering application value in the vacuum brazing of large-sized plate-fin heat exchangers used in the aviation and navigation fields.

[0107] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0108] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0109] In addition, it should be noted that the use of words such as "one" and "two" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A vacuum brazing device for plate-fin heat exchangers, characterized in that: The vacuum brazing equipment of the plate-fin heat exchanger comprises: A hydraulic control system (10), the hydraulic control system (10) being used to provide constant range and constant pressure control for the vacuum brazing equipment; A furnace body (50), the furnace body (50) being fixed on a main frame (11) of the hydraulic control system (10), the furnace body (50) being used to provide a vacuum environment and interfaces for each subsystem and to accommodate parts to be welded, wherein the interfaces include a temperature control couple (53) and an infrared thermometer (55) interface; the output signal of the temperature control couple (53) is a first feedback signal, which is used as a main temperature control feedback signal to adjust the power of each heat-generating belt (63); the output signal of the infrared thermometer (55) is a second feedback signal, which is used to monitor the temperature of the plate-fin heat exchanger and to assist in controlling the power of the self-resistance extreme-speed heating electrode of the plate-fin heat exchanger; the temperature inside the furnace body is controlled according to the first feedback signal and the second feedback signal by adopting a double feedback series control method; A furnace (60), the furnace (60) being arranged in the furnace body (50), the furnace (60) comprising a furnace frame (61), a heat shield (62) and a plurality of heat-generating belts (63), each heat-generating belt (63) being evenly distributed on the inner wall of the furnace and capable of being independently controlled; and being used for vacuum radiation heating and heat preservation; A dynamic sealing structure (70), the dynamic sealing structure (70) being fixed on the furnace body (50), the dynamic sealing structure (70) being used to provide a translational sealing interface to maintain the working vacuum degree of the system; A vacuum system (80), the vacuum system (80) being connected to the furnace body (50), and the vacuum system being used to discharge gas in the furnace body (50) to obtain a vacuum environment; An upper water-cooled sealed conductive voltage head (20), the upper water-cooled sealed conductive voltage head (20) is connected to the hydraulic control system (10), the lower end of which passes through the top of the furnace body (50) and maintains the vacuum degree in the furnace through a dynamic sealing structure (70); the upper water-cooled sealed conductive voltage head (20) comprises a water-cooled sealed pressure head seat (21), a pressure head pad (22), an upper insulating heat-insulating plate (23), an upper electrode (24) and a first electrode lead-out device (25), wherein the water-cooled sealed pressure head seat (21), the pressure head pad (22), the upper insulating heat-insulating plate (23) and the upper electrode (24) are connected in sequence, and the water-cooled sealed pressure head seat (21) comprises a flange (211), a pressure head column (212), a water inlet pipe (213), a water outlet pipe (214), a sealing sleeve (215) and a sealing ring (216), the pressure head column (212) is welded to the pressure head (12) through the flange (211), the upper end surface of the sealing sleeve (215) is welded to the flange (211), the sealing sleeve (215) is a hollow circular tube, the upper end of the outer circle of the sealing sleeve (215) is respectively welded to the water inlet pipe (213) and the water outlet pipe (214), the water inlet pipe (213) extends to the bottom of the sealing sleeve (215), the lower end of the inner circle of the sealing ring (216) is welded to the pressure head column (212), and the upper end of the outer circle is welded to the sealing sleeve (215), the first electrode lead-out device (25) is connected to the upper electrode (24) and is used to lead the current of the upper water-cooled sealed conductive voltage head (20); together with the lower conductive base (30), it is used for self-resistance extreme-speed heating and uniform loading of the welded part; A lower conductive base (30), the lower conductive base (30) comprising a base pad (31), a lower insulating heat-insulating plate (32), a lower electrode (33) and a second electrode lead-out device (34) connected in sequence, the second electrode lead-out device (34) being connected to the lower electrode (33) and used for leading out current from the lower conductive base (30); and being used together with the upper water-cooled sealed conductive voltage head (20) for self-resistance extremely fast heating and uniform loading of the welded part; A tooling (40) is used to provide constraints for a plate-fin heat exchanger.

2. A vacuum brazing device for a plate-fin heat exchanger according to claim 1, characterized in that: The operating temperature is controlled according to the first feedback signal and the second feedback signal by using a dual feedback series control method, specifically including: If the temperatures of the first feedback signal and the second feedback signal do not reach the set temperature, the heating stage is entered, and the heat-generating belt and the self-resistance extremely fast heating electrode are heated simultaneously by adopting PID control. When the temperature of the second feedback signal minus the temperature of the first feedback signal is greater than the set first temperature difference threshold, the heating of the self-resistance extremely fast heating electrode is stopped. When the temperature of the second feedback signal minus the temperature of the first feedback signal is less than the set second temperature difference threshold, the self-resistance extremely fast heating electrode is controlled to heat, wherein the first temperature difference threshold is greater than the second temperature difference threshold; When the second feedback signal temperature reaches the set temperature, the workpiece enters the heat preservation stage. When the second feedback signal temperature is equal to the set temperature, the self-resistance extreme-speed heating electrode heating is stopped. When the set temperature minus the second feedback signal temperature is greater than the set third temperature difference threshold, the self-resistance extreme-speed heating electrode heating is resumed. When the temperature of the first feedback signal reaches the set temperature, the furnace enters the insulation stage, and the self-resistance extreme-speed heating electrode heating is completely stopped.

3. The vacuum brazing equipment for plate-fin heat exchanger according to claim 2, characterized in that: The vacuum brazing equipment for the plate-fin heat exchanger further includes a temperature control system, which includes: An infrared thermometer output module, the infrared thermometer output module being used to transmit a second feedback signal output by the infrared thermometer (55); A thermocouple output module, the thermocouple output module is used to transmit a first feedback signal output by the temperature control couple; A temperature control meter, the temperature control meter is used to receive the first feedback signal and the second feedback signal, and output a digital signal according to the dual feedback series control method; An analog output module converts the digital signal into an electrical signal; The thyristor voltage regulating module realizes precise control of the voltage according to the electrical signal, thereby realizing control of the self-resistance extremely fast heating electrode and radiation heating.

4. The vacuum brazing equipment for plate-fin heat exchanger according to claim 1, characterized in that: The hydraulic control system (10) adopts a pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature sections.

5. The vacuum brazing equipment for plate-fin heat exchanger according to claim 1, characterized in that: The dynamic sealing structure (70) comprises a sealing seat (71), a sealing ring (72), a spacer ring (73) and a pressure cover (74); one end of the sealing seat (71) has an outer flange edge, which is fixed to the furnace body (50) by bolts; the other end of the sealing seat (71) has an inner circular table surface, and a plurality of sealing rings (72) and spacer rings (73) are stacked in sequence and compressed by the pressure cover (74); the pressure cover (74) is fixedly connected to the sealing seat (71).

6. The vacuum brazing equipment for plate-fin heat exchanger according to claim 1, characterized in that: The upper electrode (24) is composed of an upper electrode plate (241), an upper electrode column (242) and a first insulating porcelain tube (243); the upper electrode plate (241) is connected to the upper insulating heat-insulating plate (23); the lower end of the upper electrode (24) passes through the electrode porcelain tube (64) at the top of the furnace (60); the upper surface of the upper electrode (24) is evenly distributed with upper electrode column countersunk holes; the lower surface is evenly distributed with bolt countersunk holes and threaded holes of the first electrode lead-out device (25); the first insulating porcelain tube (243) is provided with an inner hole; the upper electrode column (242) is placed in the upper electrode column countersunk hole on the upper electrode plate (241) and fits with the upper insulating heat-insulating plate (23); the first insulating porcelain tube (243) is placed in the bolt countersunk hole on the upper electrode plate; The lower electrode (33) is composed of a lower electrode plate (331), a lower electrode column (332) and a second insulating porcelain tube (333); the lower electrode plate (331) is connected to the lower insulating heat-insulating plate (32); the upper end of the lower electrode (33) passes through the electrode porcelain tube (64) at the bottom of the furnace (60); the lower electrode plate (331) is evenly distributed with lower electrode column blind holes and bolt countersunk holes; the lower end of the lower electrode column (332) is arranged in the lower electrode column blind hole of the lower electrode plate (331); and the second insulating porcelain tube (333) is arranged in the bolt countersunk hole.

7. The vacuum brazing equipment for plate-fin heat exchanger according to claim 6, characterized in that: The first electrode lead-out device (25) comprises a first copper bar (251), a first copper pigtail assembly (252), a first water-cooled sealed electrode (253) and a first connecting plate (254); the first copper bar (251) adopts a double lead-out structure, is in a rectangular frame shape, and is connected to the upper electrode plate (241); the first copper pigtail assembly (252) is located on both sides of the rectangular frame of the first copper bar (251); the first copper pigtail assembly (252) has two groups, which are respectively located on the left and right sides of the rectangular frame of the first copper bar (251); each group has two copper pigtails; one end of the copper pigtail is connected to the first copper bar (251), and the other end is connected to the first water-cooled sealed electrode (253) through the first connecting plate (254); the length of the first copper pigtail assembly (252) is greater than the working stroke of the upper water-cooled sealed conductive voltage head (20); and the first water-cooled sealed electrode (253) is connected to the furnace body (50); The second electrode lead-out device (34) is composed of a second copper bar (341), a second copper pigtail assembly (342), a second water-cooled sealed electrode (343) and a second connecting plate (344). The second copper bar (341) adopts a double lead-out structure and is in a rectangular frame shape, connected to the lower electrode plate (331). The second copper pigtail assembly (342) is located on the left and right sides of the rectangular frame of the second copper bar (341). The second copper pigtail assembly (342) has two groups, which are respectively located on the left and right sides of the rectangular frame of the second copper bar (341). Each group has two copper pigtails. One end of the copper pigtail is connected to the second copper bar (341), and the other end is connected to the second water-cooled sealed electrode (343) through the second connecting plate (344). The second water-cooled sealed electrode (343) is firmly connected to the furnace body (50).

8. The vacuum brazing equipment for plate-fin heat exchanger according to claim 1, characterized in that: The tooling (40) comprises an upper thick plate (41), a pad (42) and a lower thick plate (43); the upper thick plate (41) and the lower thick plate (43) are respectively tightly fitted with the upper electrode column (242) and the lower electrode (33); the edges of the upper thick plate (41), the pad (42) and the lower thick plate (43) are fixedly connected; and the lower thick plate (43) is placed on the lower conductive base (30).

9. A plate-fin heat exchanger brazing method, characterized in that: The plate-fin heat exchanger brazing method adopts the vacuum brazing equipment for plate-fin heat exchangers described in any one of claims 7 to 8, and the plate-fin heat exchanger brazing method specifically comprises: 1) Process the baffles, fins and seal parts of the plate-fin heat exchanger according to the size requirements and clean them; 2) Coating a solder layer on the upper and lower sides of the partition; 3) Assembling the parts of the plate-fin heat exchanger on the tooling (40), placing the upper thick plate (41), the pad (42), the plate-fin heat exchanger, and the lower thick plate (43) in order from bottom to top, passing screws through the edge through holes of the upper thick plate (41), the pad (42), and the lower thick plate (43), and fastening them with nuts at the upper and lower ends; 4) placing the tooling (40) as a whole on the lower conductive base (30) by means of a material cart, and pressing it with the upper water-cooled sealed conductive voltage head (20), loosening the tooling (40) and tightening the lower nut to keep the pressure constant; 5) Turn on the vacuum system (80) and evacuate to the working vacuum degree; 6) Use double feedback series control to heat and keep the plate-fin heat exchanger warm; 7) Use pressure-temperature coupling control method to keep the pressure constant at different set values ​​in different temperature ranges; 8) Raise the temperature of the plate-fin heat exchanger to the brazing process temperature ±5°C, keep it warm for 10 to 60 minutes, and complete the brazing; 9) The welded plate-fin heat exchanger is uniformly cooled to below 150° C., the vacuum system ( 80 ) is closed, and then the heat exchanger is further cooled to room temperature.

10. The method according to claim 9, characterized in that The pressure-temperature coupling relationship set by the pressure-temperature coupling control method is as follows: temperature <150°C, pressure 0.1Mpa; 200°C≤temperature <400°C, pressure 0.08MPa; 400°C≤temperature <600°C, pressure 0.06MPa; 600°C≤temperature <800°C, pressure 0.04Mpa.

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