Vacuum brazing apparatus and method for plate-fin heat exchangers

Abstract

The application relates to a vacuum brazing device and method for plate-fin heat exchangers, and relates to the field of welding. The application aims at solving the problems of low heating efficiency and difficult deformation control caused by the structural features of plate-fin heat exchangers and the characteristics of vacuum radiation heating. The application adds a hydraulic control system, an upper water-cooled sealing conductive pressure head, a lower conductive base and a tooling and the like to the traditional vacuum brazing equipment, and the structure is combined with a furnace body. The upper electrode of the upper water-cooled sealing conductive pressure head adopts a distributed structure, can be moved up and down through the hydraulic control system, and can guarantee that the workpiece is always subjected to uniform stress and can guarantee that self-resistance is rapidly heated, power is continuously and stably supplied and the like through cooperation with the tooling. Double heat source heating is realized through double feedback series control, the heating process time is shortened, the stress is uniformly ensured through a pressure-temperature coupling control method, the deformation is reduced, and the heating efficiency and welding quality consistency are improved. Rapid and uniform heating and small deformation control of the workpiece can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of brazing technology in the high-end equipment manufacturing technology of industrial mother machine, and particularly relates to a high-efficiency vacuum brazing equipment and method for plate-fin heat exchangers. BACKGROUND

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

[0003] Due to the multi-layer combination and self-shielding structure between layers of large-size titanium alloy plate-fin heat exchangers, the following problems usually exist when the traditional vacuum brazing equipment is used:

[0004] (1) Brazing quality control is difficult, and the yield is low. In order to ensure the high toughness of the brazed joint, the brazing process usually requires that the overall temperature uniformity of the product be controlled within ±5℃ at the brazing temperature, and the total holding time be short enough. The thermal conductivity of titanium is about 1 / 20 of that of copper and 1 / 15 of that of aluminum. Using single vacuum radiation heating method, at least 30min (for large-size heat exchangers, the time is longer) is needed to reach the overall temperature uniformity after the surface of the heat exchanger reaches the brazing temperature, which will lead to serious surface embrittlement, easy crack defects, serious thin wall corrosion and other quality problems of large titanium alloy plate-fin heat exchangers, and the yield is difficult to guarantee.

[0005] (2) The thin wall structure of the product is easy to deform, and the size performance is difficult to guarantee. In order to ensure that tens of thousands of brazing seams are firmly welded, the plate-fin heat exchanger requires that the contact stress of the brazing seam position be uniform when initially assembled, and be maintained within a suitable stress range during the entire brazing process. Using traditional special tooling for brazing, for large-size heat exchangers, only the appropriate pre-tightening force is provided during initial assembly, which is easy to cause uneven contact stress of the edge and core of the workpiece, and the thermal expansion state under strong constraint condition is more likely to cause uncontrollable deformation during the heating process, resulting in size out-of-tolerance or low local welding joint strength of the product.

[0006] (3) The brazing process cycle is long, and the production efficiency is extremely low. 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 be relatively uniform during heating and cooling, and the temperature difference between the surface and the core be ≤50℃. As is known to all, vacuum heating and cooling are extremely slow, especially at low temperatures below 500℃. Due to the structural characteristics of the heat exchanger, only in the process of radiation heating can the product be uniformly heated by frequent insulation to ensure the overall temperature uniformity. Therefore, the brazing heating time of large-size titanium alloy plate-fin heat exchangers is as long as 20 hours or more, and the cooling process is as long as 7 hours or more, which is extremely low in efficiency.

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

[0008] In view of the above problems, the present application provides a vacuum brazing equipment and method for plate-fin heat exchangers, which is reliable in structure, easy to install, can improve the load distribution of the brazing workpiece, ensure the 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 function of radiation heating, the hydraulic control system, the upper water-cooled sealing and conductive pressure head assembly, and the lower conductive base and other components are configured to provide self-resistance heating function under the premise of meeting the special needs of vacuum brazing equipment cooling and sealing, etc., to solve the problems of low heating efficiency and difficult deformation control caused by the structural characteristics of plate-fin heat exchangers and the characteristics of vacuum radiation heating.

[0009] According to an aspect of the present application, a vacuum brazing apparatus for plate-fin heat exchanger is provided, the vacuum brazing apparatus for plate-fin heat exchanger comprises: a hydraulic control system, the hydraulic control system is used for providing constant pressure control for the vacuum brazing apparatus; a furnace body, the furnace body is fixed on a main frame of the hydraulic control system, the furnace body is used for providing a vacuum environment and interfaces of subsystems, and containing a brazing piece, wherein the interfaces comprise a temperature control couple and an infrared temperature detector interface; the temperature control couple output signal is a first feedback signal, which is used as a main temperature control feedback signal to regulate the power of each heating band; the infrared temperature detector output signal is a second feedback signal, which is used for monitoring the temperature of the plate-fin heat exchanger, and assisting in controlling the power of the self-resistance electrode rapid heating electrode of the plate-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; a furnace liner, the furnace liner is arranged in the furnace body, the furnace liner comprises a furnace liner frame, a heat shield and a plurality of heating bands, each zone heating band is uniformly distributed on the inner wall of the furnace liner, and independent control can be realized; the furnace liner is 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 for providing a translational sealing interface, and maintaining the system working vacuum degree; a vacuum system, the vacuum system is connected with the furnace body, the vacuum system is used for discharging gas in the furnace body to obtain a vacuum environment; an upper water-cooled sealing and conducting voltage head, the upper water-cooled sealing and conducting voltage head is connected with the hydraulic control system, and the lower end penetrates through the top of the furnace body and maintains the vacuum degree in the furnace by the dynamic sealing structure; the upper water-cooled sealing and conducting voltage head comprises a water-cooled sealing pressure head seat, a pressure head backing plate, an upper insulation heat shield, an upper electrode and a first electrode leading device, wherein the water-cooled sealing pressure head seat, the pressure head backing plate, the upper insulation heat shield and the upper electrode are connected in sequence, the water-cooled sealing pressure head seat comprises a flange, a pressure head column, an inlet pipe, an outlet pipe, a sealing sleeve and a sealing ring, the pressure head column is welded with the flange through the flange, the upper end surface of the sealing sleeve is welded with the flange, the sealing sleeve is a hollow circular pipe, the inlet pipe and the outlet pipe are welded on the outer circle upper end of the sealing sleeve respectively, the inlet pipe extends to the bottom of the sealing sleeve, the inner circle lower end of the sealing ring is welded with the pressure head column, and the outer circle upper end of the sealing ring is welded with the sealing sleeve, the first electrode leading device is connected with the upper electrode, and is used for leading the current of the upper water-cooled sealing and conducting voltage head; the upper water-cooled sealing and conducting voltage head and a lower conducting base are used for self-resistance electrode rapid heating and uniform loading of the brazing piece; a lower conducting base, the lower conducting base comprises a base backing plate, a lower insulation heat shield, a lower electrode and a second electrode leading device connected in sequence, the second electrode leading device is connected with the lower electrode, and is used for leading the current of the lower conducting base; the lower conducting base and the upper water-cooled sealing and conducting voltage head are used for self-resistance electrode rapid heating and uniform loading of the brazing piece; a tool, the tool is used for providing constraint for the plate-fin heat exchanger.

[0010] Further, the furnace body temperature is controlled by a double feedback series control method according to the first feedback signal and the second feedback signal, specifically including: if the first feedback signal and the second feedback signal temperature do not reach the set temperature, entering the heating stage, using PID control to heat the heating band and the self-resistance electrode heating electrode to heat at the same time, when the second feedback signal temperature minus the first feedback signal temperature is greater than the set first temperature difference threshold, the self-resistance electrode heating electrode heating is stopped, when the second feedback signal temperature minus the first feedback signal temperature is less than the set second temperature difference threshold, the self-resistance electrode 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, entering the workpiece heat preservation stage, when the second feedback signal temperature is equal to the set temperature, the self-resistance electrode 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 electrode heating electrode heating is resumed; when the first feedback signal temperature reaches the set temperature, the furnace liner heat preservation stage is entered, at this time the self-resistance electrode heating electrode heating is completely stopped.

[0011] Further, the vacuum brazing equipment of the plate-fin heat exchanger further comprises a temperature control system, the temperature control system comprising: an infrared thermometer output module for transmitting the second feedback signal output by the infrared thermometer; a thermocouple output module for transmitting the first feedback signal output by the temperature control device; a temperature control table for receiving the first feedback signal and the second feedback signal and outputting a digital signal according to a double feedback series control method; an analog output module for converting the digital signal into an electrical signal; and a silicon-controlled voltage regulating module for accurately controlling the voltage according to the electrical signal, thereby controlling the self-resistance electrode heating electrode and the radiant heating.

[0012] Further, the hydraulic control system adopts a pressure-temperature coupling control method to keep the pressure constant at different set values at different temperature stages.

[0013] Further, the dynamic sealing structure comprises a sealing seat, a sealing ring, a spacer ring and a gland, 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, a plurality of sealing rings and spacer rings are stacked in turn and are compressed by the gland, and the gland is fixedly connected with the sealing seat.

[0014] Further, 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 with the upper insulating heat insulation plate, the lower end of the upper electrode plate passes through the electrode porcelain tube at the top of the furnace liner, the upper surface of the upper electrode plate is uniformly distributed with upper electrode column countersunk holes, the lower surface is uniformly 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 arranged in the upper electrode column countersunk hole on the upper electrode plate and is attached to the upper insulating heat insulation plate, and the insulating porcelain tube is arranged 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 with a lower insulating heatproof 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 uniformly 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] Further, the first electrode lead-out device comprises a first copper bar, a first copper soft braid assembly, a first water-cooled sealing 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 and is connected with the upper electrode plate, the first copper soft braid assembly is located on both sides of the rectangular frame of the first copper bar, the first copper soft braid assembly has two groups and is respectively located on the left and right sides of the rectangular frame of the first copper bar, each group has two copper soft braids, one end of the copper soft braid is connected with the first copper bar, the other end is connected with the first water-cooled sealing electrode through the first connecting plate, the length of the first copper soft braid assembly is greater than the working stroke of the upper water-cooled sealing conductive pressure head, and the first water-cooled sealing electrode is connected with the furnace body.

[0017] The second electrode lead-out device is composed of a second copper bar, a second copper soft braid assembly, a second water-cooled sealing 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 and is connected with the lower electrode plate, the second copper soft braid assembly is located on both sides of the rectangular frame of the second copper bar, the second copper soft braid assembly has two groups and is respectively located on the left and right sides of the rectangular frame of the second copper bar, each group has two copper soft braids, one end of the copper soft braid is connected with the second copper bar, the other end is connected with the second water-cooled sealing electrode through the second connecting plate, and the second water-cooled sealing electrode is tightly connected with the furnace body.

[0018] According to another aspect of the present application, a brazing method for plate-fin heat exchangers is provided, which uses the vacuum brazing equipment provided by the present application, and specifically comprises: processing the partition plates, fins, and seal parts of the plate-fin heat exchangers according to the size requirements and cleaning; coating a brazing filler metal layer on the upper and lower sides of the partition plates; assembling the parts of the plate-fin heat exchanger on a tooling, and placing the upper thick plate, the spacer plate, the plate-fin heat exchanger, the spacer plate, and the lower thick plate in sequence from bottom to top, and using a screw to pass through the edge through holes of the upper thick plate, the spacer plate, and the lower thick plate and fasten the screw with nuts at the upper and lower ends; placing the above tooling as a whole on the lower conductive base by using a material cart, and pressing tightly by using the upper water-cooled sealing conductive pressure head, loosening the lower nut fastening the tooling, and keeping the pressure constant; opening the vacuum system, and vacuumizing to the working vacuum degree; heating and heat-insulating the plate-fin heat exchanger by using a double feedback series control mode; keeping the pressure constant at different set values in different temperature sections by using a pressure-temperature coupling control method; heating the plate-fin heat exchanger to the brazing process temperature ± 5℃, heat-insulating for 10-60 min, and completing the brazing; uniformly cooling the brazed plate-fin heat exchanger to below 150℃, and closing the vacuum system 80, and then continuously cooling to room temperature.

[0019] Further, the pressure-temperature coupling relationship set by the pressure-temperature coupling control method is as follows: when the temperature is below 150℃, the pressure is 0.1 MPa; when the temperature is 200℃-400℃, the pressure is 0.08 MPa; when the temperature is 400℃-600℃, the pressure is 0.06 MPa; and when the temperature is 600℃-800℃, the pressure is 0.04 MPa.

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

[0021] 1) By using the present application, the existing multi-section heat-insulating heating process can be changed into a short composite heating process, and the temperature of the large-size titanium alloy plate-fin heat exchanger can be kept uniform during the heating process, and the heating efficiency is improved.

[0022] 2) By using the present application, the overall load of the large-size titanium alloy plate-fin heat exchanger is uniformly distributed during the brazing process, and is adjustable and controllable, so that the planeness and size precision requirements of the product can be guaranteed.

[0023] 3) By using the present application, the heat-insulating time of the large-size titanium alloy plate-fin heat exchanger at the brazing process temperature is short enough, and the stress at the weld is uniform enough, so that the consistency of the brazing quality of tens of thousands of products can be guaranteed.

[0024] 4) By using the present application, the heating process time is shortened, the heat loss is reduced, and thus the energy consumption is reduced.

[0025] The present application solves the following technical problems:

[0026] Compared with the traditional vacuum brazing equipment, the workpiece self-resistance rapid heating and uniform ballast function are added, through the design of the conductive ballast device and the tooling, the double heat source heating is realized by adopting the double feedback series control, the heating process time is shortened, the stress uniformity and deformation are ensured by adopting the pressure-temperature coupling control method, and the heating efficiency and the welding quality consistency are improved. Specifically, the hydraulic control system, the upper water-cooled sealing conductive pressure head, the lower conductive base and the tooling and the like structures are added, the structure is combined with the furnace body, the upper electrode of the upper water-cooled sealing conductive pressure head adopts a distributed structure, the upper and lower movements can be realized through the hydraulic control system, and the combination of the tooling can ensure that the workpiece is always stressed uniformly and the self-resistance rapid heating power supply is continuously stable. When brazing, the above structure scheme and the double feedback series control and the pressure-temperature coupling control method can realize the rapid and uniform heating of the workpiece and the small deformation control, and can be expanded to the vacuum brazing of large-size plate-fin heat exchangers in the aviation and navigation fields, and fundamentally solve 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 the vacuum radiation heating. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings included to provide a further understanding of the embodiments of the present application, constitute a part of the specification and serve to explain the principles of the present application together with the text. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0028] Figure 1 A vacuum brazing equipment for plate-fin heat exchangers according to a specific embodiment of the present application is provided in a front view;

[0029] Figure 2 A vacuum brazing equipment for plate-fin heat exchangers according to a specific embodiment of the present application is provided in a top view;

[0030] Figure 3 A structure of the upper water-cooled sealing conductive pressure head according to a specific embodiment of the present application is provided in a schematic view;

[0031] Figure 4 An enlarged schematic view of the dynamic sealing structure between the upper water-cooled sealing conductive pressure head and the furnace body according to a specific embodiment of the present application is provided;

[0032] Figure 5 A first electrode lead-out device of the upper water-cooled sealing conductive pressure head according to a specific embodiment of the present application is provided in a schematic view;

[0033] Figure 6 A structure of the lower conductive base according to a specific embodiment of the present application is provided in a schematic view;

[0034] Figure 7 The second electrode lead-out device schematic view of the lower conductive base provided for the specific embodiment of the present application;

[0035] Figure 8 The tooling schematic view provided for the specific embodiment of the present application;

[0036] Figure 9 The structure schematic view of the titanium alloy plate fin heat exchanger;

[0037] Figure 10 The vacuum brazing equipment temperature control system schematic view provided for the specific embodiment of the present application for the plate fin heat exchanger;

[0038] Figure 11 The process curve graph of brazing the titanium alloy plate fin heat exchanger by using the traditional vacuum brazing equipment;

[0039] Figure 12 The process curve graph of brazing the titanium alloy plate fin heat exchanger by using the specific embodiment of the present application;

[0040] Figure 13 The titanium alloy plate fin heat exchanger brazed;

[0041] Among the above-mentioned drawings, the following reference signs are included:

[0042] 10, hydraulic control system; 11, main frame; 12, pressure head; 13, control system;

[0043] 20, upper water-cooled sealing conductive pressure head; 21, water-cooled sealing pressure head seat; 211, flange plate; 212, pressure head column; 213, water inlet pipe; 214, water outlet pipe; 215, sealing sleeve; 216, sealing ring; 22, pressure head pad plate; 23, upper insulating heat insulation 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 bar; 252, first copper soft braid assembly; 253, first water-cooled sealing electrode; 254, first connecting plate;

[0044] 30, lower conductive base; 31, base pad plate; 32, lower insulating heat insulation 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 bar; 342, second copper soft braid assembly; 343, second water-cooled sealing electrode; 344, second connecting plate;

[0045] 40, tooling; 41, upper thick plate; 42, pad plate; 43, lower thick plate;

[0046] 50, furnace body; 51, flange cover with hole; 52, flange blind cover; 53, temperature control couple; 54, observation window; 55, infrared temperature measuring instrument;

[0047] 60, furnace tube; 61, furnace tube frame; 62, heat insulation screen; 63, heating band; 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 the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[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, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations, devices, components and / or their combinations.

[0052] Unless otherwise specifically stated, the relative arrangements of parts and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in accordance with the actual proportion relationship for the convenience of description. The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but should be considered as part of the authorized specification under appropriate circumstances. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0053] As Figures 1 to 13As shown, according to the specific embodiments of the present application, a vacuum brazing equipment for plate-fin heat exchanger is provided, which comprises 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 and conductive pressure head 20, a lower conductive base 30 and a tooling 40. The hydraulic control system 10 is used to provide constant pressure and constant volume control for the vacuum brazing equipment; the furnace body 50 is fixed on the main frame 11 of the hydraulic control system 10, and is used to provide a vacuum environment and interfaces of various subsystems, and accommodate the workpiece to be welded, wherein the interfaces include the temperature control couple 53 and the infrared temperature detector 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 regulate the power of each heating band 63; the output signal of the infrared temperature detector 55 is a second feedback signal, which is used to monitor the temperature of the plate-fin heat exchanger, and assist in controlling the power of the self-resistance electrode rapid heating electrode of the plate-fin heat exchanger; the working temperature of the infrared temperature detector 55 is controlled by a double feedback series control method according to the first feedback signal and the second feedback signal; the furnace 60 is arranged in the furnace body 50, and comprises a furnace frame 61, a heat shield 62 and a plurality of heating bands 63; each zone heating band is uniformly distributed on the inner wall of the furnace, and can be independently controlled; it is used for vacuum radiation heating and heat preservation; the dynamic sealing structure 70 is fixed on the furnace body 50, and is used to provide a translational sealing interface to maintain the system working vacuum degree; the vacuum system 80 is connected with the furnace body 50, and is used to exhaust the gas in the furnace body 50 to obtain a vacuum environment; the upper water-cooled sealing and conductive pressure head 20 is connected with the hydraulic control system 10, and the lower end penetrates 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 sealing and conductive pressure head 20 comprises a water-cooled sealing pressure head seat 21, a pressure head backing plate 22, an upper insulating heat shield 23, an upper electrode 24 and a first electrode lead-out device 25, wherein the water-cooled sealing pressure head seat 21, the pressure head backing plate 22, the upper insulating heat shield 23 and the upper electrode 24 are connected in sequence; the water-cooled sealing pressure head seat 21 comprises a flange plate 211, a pressure head column 212, an inlet water pipe 213, an outlet water pipe 214, a sealing sleeve 215 and a sealing ring 216; the pressure head column 212 is welded with the pressure head 12 through the flange plate 211; the upper end surface of the sealing sleeve 215 is welded with the flange plate 211; the sealing sleeve 215 is a hollow circular tube; the inlet water pipe 213 and the outlet water pipe 214 are welded on the outer circle of the upper end of the sealing sleeve 215; the inlet water pipe 213 extends to the bottom of the sealing sleeve 215; the inner circle of the lower end of the sealing ring 216 is welded with the pressure head column 212, and the outer circle of the upper end is welded with the sealing sleeve 215; the first electrode lead-out device 25 is connected with the upper electrode 24, and is used to lead out the current of the upper water-cooled sealing and conductive pressure head 20.The lower conductive base 30 is used for self-resistance electrode rapid heating and uniform loading of the workpiece to be welded, and comprises a base pad plate 31, a lower insulating heat insulation 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 with the lower electrode 33 and used for leading out current of the lower conductive base 30; the upper water-cooled sealing conductive pressure head 20 is used for self-resistance electrode rapid heating and uniform loading of the workpiece to be welded; and the tooling 40 is used for providing restraint for the plate-fin heat exchanger.

[0054] The hydraulic control system 10, the furnace body 50, the infrared temperature measuring instrument 55, the upper water-cooled sealing conductive pressure head assembly, the lower conductive base 30, and the hydraulic control system 10 are used for providing welding pressure for the vacuum brazing equipment; the furnace body 50 is fixed to the hydraulic control system 10, and the furnace body 50 comprises a temperature control couple 53 and a plurality of heating bands 63, and the output signal of the temperature control couple 53 is a first feedback signal.

[0055] By using the configuration mode, the workpiece is rapidly heated by self-resistance electrode through the configuration of the conductive pressure head device, and the heating process time is shortened and the heating efficiency and the welding quality consistency are improved through the double feedback series control to realize double heat source heating. Specifically, the hydraulic control system, the upper water-cooled sealing conductive pressure head and the lower conductive base are added, and the structure is combined with the furnace body, wherein the upper water-cooled sealing conductive pressure head assembly has a plurality of electrodes and adopts a distributed structure, and the upper and lower movements can be realized through the hydraulic control system, so that the workpiece can be uniformly stressed at all times and the self-resistance electrode rapid heating can be continuously and stably powered. The temperature of the electrode and the surrounding components is effectively reduced through the water cooling system design, and the service life of the equipment is prolonged. During brazing, the above structure scheme and the double feedback series control can realize rapid and uniform heating of the workpiece and small deformation control, and can be expanded to vacuum brazing of large-size plate-fin heat exchangers in the aviation and marine fields, and fundamentally solve 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] Further, to realize the double heat source heating, the working temperature is controlled according to the first feedback signal and the second feedback signal by using a double feedback series control method, specifically including: if the first feedback signal and the second feedback signal temperature both do not reach the set temperature, entering the heating stage, using PID (proportional integral derivative control) to control the heating band and the self-resistance fast heating electrode to heat simultaneously, when the second feedback signal temperature minus the first feedback signal temperature is greater than the set first temperature difference threshold, stopping the self-resistance fast heating electrode heating, when the second feedback signal temperature minus the first feedback signal temperature is less than the set second temperature difference threshold, controlling the self-resistance fast heating electrode 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, entering the workpiece heat preservation stage, when the second feedback signal temperature is equal to the set temperature, stopping the self-resistance fast heating electrode heating, when the set temperature minus the second feedback signal temperature is greater than the set third temperature difference threshold, resuming the self-resistance fast heating electrode heating; when the first feedback signal temperature reaches the set temperature, entering the furnace body heat preservation stage, at this time, the self-resistance fast heating electrode heating is completely stopped.

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

[0058] By using this configuration mode, according to the temperature range of the first feedback signal and the second feedback signal, the furnace temperature adjustment mode is distinguished and set as the heating stage, the workpiece heat preservation stage and the furnace body heat preservation stage, the self-resistance fast heating and the radiation heating double heat source heating mode is controlled, the double heat source heating stage can be segmented, the segmented temperature, the heat preservation time and the number of segments can be set according to the size of the titanium alloy plate fin heat exchanger and the type of the brazing filler metal, the heating efficiency and the flexibility are improved.

[0059] Further, to realize the precise control of the temperature, for example, Figure 10As shown, the vacuum brazing equipment of the plate-fin heat exchanger further comprises a temperature control system, which comprises an infrared thermometer output module, a thermocouple output module, a temperature control meter, an analog output module and a silicon controlled voltage regulating 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 temperature control 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 double feedback series control method, the analog output module converts the digital signal into an electric signal, and the silicon controlled voltage regulating module accurately controls the voltage according to the electric signal, thereby realizing the control of the self-resistance rapid heating electrode and the radiation heating.

[0060] By using this configuration, the temperature control system can accurately monitor the temperature in the furnace and automatically adjust according to the preset double feedback series control method, thereby maintaining a stable temperature environment and realizing automatic and accurate control of the temperature.

[0061] Further, 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 at different temperature stages. By using this configuration, the stress is uniformly reduced and the deformation is reduced, thereby improving the heating efficiency and the welding quality consistency.

[0062] Further, as shown in Figure 4 In order to realize effective sealing, the dynamic sealing structure 70 comprises 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 on the furnace body 50 by bolts. The other end of the sealing seat 71 has an inner circular table surface. A plurality of sealing rings 72 and spacer rings 73 are stacked in sequence and are pressed tightly by the gland 74. The gland 74 is fixedly connected with the sealing seat 71. By using this configuration, the special needs of the sealing in the vacuum environment in the vacuum brazing equipment can be met, and the overall reliability and stability of the equipment can be improved.

[0063] Further, as shown in Figure 3As shown, in order to effectively realize the electrical insulation and thermal insulation of the electrode and the surrounding environment, enhance the safety and stability of the device, 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 with the upper insulating and heat insulating plate 23. The lower end of the upper electrode 24 penetrates the electrode porcelain tube 64 at the top of the furnace barrel 60. The upper surface of the upper electrode 24 is uniformly distributed with upper electrode column countersunk holes. The lower surface of the upper electrode 24 is uniformly 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 arranged in the upper electrode column countersunk hole on the upper electrode plate 241 and is attached to the upper insulating and heat insulating plate 23. The first insulating porcelain tube 243 is arranged in the bolt countersunk hole on the upper electrode plate. The mounting bolt is sequentially threaded through the inner hole of the first insulating porcelain tube 243, the through hole of the upper insulating and heat insulating plate, the through hole of the pressure head backing plate and the water-cooled sealing pressure head seat 21 to be fastened and connected. 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 with the lower insulating and heat insulating plate 32. The upper end of the lower electrode 33 penetrates the electrode porcelain tube 64 at the bottom of the furnace barrel 60. The lower electrode plate 331 is uniformly 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. The first insulating porcelain tube 333 is arranged in the bolt countersunk hole. The mounting bolt is sequentially threaded through the first insulating porcelain tube 333, the through hole of the lower insulating and heat insulating plate 32 and the backing plate 31 to be fastened and connected.

[0064] Further, as Figures 5 to 7As shown, in order to meet the needs of the vacuum brazing equipment for large current active electrode connection, the first electrode lead-out device 25 includes a first copper bar 251, a first copper soft braid assembly 252, a first water-cooled sealing electrode 253 and a first connecting plate 254. The first copper bar 251 adopts a double lead-out structure and is in the shape of a rectangular frame, connected with the upper electrode plate 241. The first copper soft braid assembly 252 is located on both sides of the rectangular frame of the first copper bar 251. The first copper soft braid assembly 252 has two groups, respectively located on the left and right sides of the rectangular frame of the first copper bar 251. Each group has two copper soft braids. One end of the copper soft braids is connected with the first copper bar 251, and the other end is connected with the first water-cooled sealing electrode 253 through the first connecting plate 254. The length of the first copper soft braid assembly 252 is greater than the working stroke of the upper water-cooled sealing conductive pressure head 20. The first water-cooled sealing electrode 253 is connected with the furnace body 50. The second electrode lead-out device 34 is composed of a second copper bar 341, a second copper soft braid assembly 342, a second water-cooled sealing electrode 343 and a second connecting plate 344. The second copper bar 341 adopts a double lead-out structure and is in the shape of a rectangular frame, connected with the lower electrode plate 331. The second copper soft braid assembly 342 is located on both sides of the rectangular frame of the second copper bar 341. The second copper soft braid assembly 342 has two groups, respectively located on the left and right sides of the rectangular frame of the second copper bar 341. Each group has two copper soft braids. One end of the copper soft braids is connected with the second copper bar 341, and the other end is connected with the second water-cooled sealing electrode 343 through the second connecting plate 344. The second water-cooled sealing electrode 343 is tightly connected with the furnace body 50. The second water-cooled sealing electrode 343 is tightly connected with the right-angle electrode seat on the furnace body 50 through a bolt.

[0065] By using this configuration, the double lead-out structure enhances the stability and reliability of the electrode lead-out device, provides more flexible installation and connection methods, and better adapts to complex electrical connection requirements, reducing resistance and heat accumulation. The water-cooled sealing electrode not only provides good electrical connection, but also effectively reduces the temperature of the electrode and surrounding components through the water cooling system, meeting the cooling needs of the vacuum brazing equipment.

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

[0067] The traditional special tool is used for brazing, and for the large-sized heat exchanger, only the appropriate pre-tightening force is provided in the initial assembly, and the contact stress of the edge and the core of the workpiece is extremely easy to be uneven, and in the heating process, the thermal expansion state under the strong constraint condition is more likely to cause uncontrollable deformation, resulting in the product size out of tolerance or the low strength of the local welded joint. The configuration mode can keep the whole brazing process in the appropriate stress range.

[0068] Further, according to another aspect of the present application, a plate-fin heat exchanger brazing method is provided, the plate-fin heat exchanger's partition plate, fin, and seal parts are processed according to the size requirements and cleaned; the brazing material layer is coated on the upper and lower sides of the partition plate; the plate-fin heat exchanger parts are assembled on the tool 40, the upper thick plate 41, the backing plate 42, the plate-fin heat exchanger, the backing plate 42, and the lower thick plate 43 are sequentially placed from bottom to top, the screw rod is passed through the edge through holes of the upper thick plate 41, the backing plate 42, and the lower thick plate 43 and is fastened at the upper and lower ends by the nuts; the above-mentioned tool 40 is placed on the lower conductive base 30 as a whole by the material car, and is pressed tightly by the upper water-cooled sealing conductive pressure head 20, the lower nut of the tool 40 is loosened, and the pressure is kept constant; the vacuum system 80 is started, and the vacuum is extracted to the working vacuum degree; the plate-fin heat exchanger is heated and kept warm by the double feedback series control mode; the pressure-temperature coupling control method is used to keep the pressure constant at different set values in different temperature sections; the plate-fin heat exchanger is heated to the brazing process temperature ± 5℃, kept warm for 10-60 min, and the brazing is completed; the brazed plate-fin heat exchanger is uniformly cooled to below 150℃, the vacuum system 80 is closed, and then the cooling continues to room temperature.

[0069] By using the configuration mode, the plate-fin heat exchanger vacuum brazing method of the present application can improve the load distribution of the vacuum brazing equipment for the brazing workpiece, ensure the uniform stress and controllable deformation in the whole brazing process, and improve the product size precision; at the same time, the workpiece self-resistance heat generation function is added on the basis of the radiation heating function, and 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 the vacuum radiation heating are solved.

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

[0071] In order to have a further understanding of the present application, the following will be combined with the specific embodiments of the present application. Figures 1 to 13 The plate-fin heat exchanger vacuum brazing equipment and method of the present application will be described in detail. As shown in Figures 1 to 10As shown, a vacuum brazing equipment for plate-fin heat exchanger comprises:

[0072] The hydraulic control system 10 can realize the constant pressure control of the water-cooled sealing conductive pressure head. The hydraulic control system 10 comprises 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 with the pressure head 12.

[0073] The furnace body 50 is a closed chamber that can withstand negative pressure 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 top pressure head connecting flange cover 51, a bottom fixed mounting flange blind cover 52, a temperature control couple 53, an observation window 54 at the front and an infrared temperature measuring instrument 55.

[0074] The furnace body 50 is a closed chamber that can withstand negative pressure 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 top pressure head connecting flange cover 51, a bottom fixed mounting flange blind cover 52, a temperature control couple 53, an observation window 54 at the front and an infrared temperature measuring instrument 55.

[0075] The dynamic sealing structure 70 comprises a sealing seat 71, a sealing ring 72, a spacer ring 73 and a gland 74. The upper end of the sealing seat 71 has an outer flange edge and is fixed on the furnace body 50 by bolts. The lower end has an inner circular table surface. A plurality of sealing rings 72 and spacer rings 73 are sequentially stacked and are pressed by the lower end surface of the gland 74. The gland 74 is connected with the sealing seat 71 by bolts.

[0076] The vacuum system 80 comprises a vacuum pump 81, a vacuum valve 82 and a pipeline 83. The vacuum pump 81 is communicated with the furnace body 50 through the pipeline 83. The vacuum valve 82 is arranged on the pipeline 83.

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

[0078] The water-cooled sealing ram base 21 is welded by a flange plate 211, a ram column 212, a water inlet pipe 213, a water outlet pipe 214, a sealing sleeve 215 and a sealing ring 216. The ram column 212 is a solid cylinder, and the flange plate 211 is welded on the upper surface of the ram column 212 and is fastened and connected with the ram 12 by bolts. The sealing sleeve 215 is a hollow pipe, and the ram column 212 is arranged inside the sealing sleeve 215. The upper end surface of the ram column 212 is welded with the flange plate 211, and the water inlet pipe 213 and the water outlet pipe 214 are welded at the water inlet and the water outlet of the outer circle of the upper end of the sealing sleeve 215, respectively. The water inlet of the water inlet pipe 213 extends to the bottom of the sealing sleeve 215, and the sealing ring 216 is welded with the ram column 212 at the inner circle of the lower end and is welded with the sealing sleeve 215 at the outer circle of the upper end, so as to form a closed cavity in the shape of a ring column, which can be cooled by water. The bottom of the water-cooled sealing ram base 21 penetrates the flange cover 51 with holes located at the top of the furnace body of the vacuum brazing equipment, and the dynamic sealing structure 70 is adopted between the water-cooled sealing ram base 21 and the furnace body 50, so as to realize reliable movement of the water-cooled sealing ram within the working stroke range.

[0079] The ram pad plate 22 and the upper insulating and heat insulating plate 23 are both provided with through holes and are fastened and connected with the lower end of the water-cooled sealing ram base 21 by bolts. The upper end surface of the ram pad plate 22 is provided with the upper insulating and heat insulating plate 23, and the upper electrode 24 is arranged on the upper insulating and 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 and heat insulating plate 23, and the upper surface of the upper electrode plate 241 is uniformly provided with upper electrode column countersunk holes, and the lower surface of the upper electrode plate 241 is uniformly provided with bolt countersunk holes and threaded holes of the first electrode lead-out device 25. The upper electrode column 242 is arranged in the upper electrode column countersunk holes of the upper electrode plate 241 and is attached to the upper insulating and heat insulating plate 23. The upper electrode column 242 is in the shape of a long rod with a cylindrical head, and the large head faces upward, and the upper end surface is higher than the upper surface of the upper electrode plate 241. The insulating porcelain tube 243 is provided with an inner hole, and the insulating porcelain tube 243 is arranged in the bolt countersunk holes of the upper electrode plate 241. The mounting bolts pass through the inner hole of the insulating porcelain tube, the through hole of the upper insulating and heat insulating plate, the through hole of the ram pad plate and the water-cooled sealing ram base 21 in sequence and are fastened and connected with the water-cooled sealing ram base 21. The lower end of the upper electrode 24 penetrates the electrode porcelain tube 64 at the top of the furnace body 60.

[0081] The first electrode lead-out device 25 can realize power supply of large current of 8000A or more and safe and reliable movement of the upper water-cooled sealing conductive voltage head. The first electrode lead-out device 25 comprises a first copper bar 251, a first copper soft braid assembly 252, a first water-cooled sealing electrode 253 and a first connecting plate 254. The first copper bar 251 adopts a double lead-out structure and is in the shape of a rectangular frame, is arranged below the upper electrode plate 241, is connected with the upper electrode plate 241 through bolts, the first copper soft braid assembly 252 has two groups and is arranged on the left and right sides of the rectangular frame of the first copper bar 251, each group of the first copper soft braid assembly 252 has two copper soft braids, one end of each copper soft braid is connected with the first copper bar 251, and the other end of each copper soft braid is connected with the first water-cooled sealing electrode 253 through the first connecting plate 254, the length of the first copper soft braid assembly 252 covers the working stroke of the upper water-cooled sealing conductive voltage head 20, the first water-cooled sealing electrode 253 is fastened and connected with the electrode seat on the furnace body 50 through bolts, the motor seat can be selected to be in a right-angle structure, one end surface of the first connecting plate 254 is connected with the first copper soft braid 252, after the upper water-cooled sealing conductive voltage head 20 is installed, the first connecting plate 254 and the first copper soft braid 252 are arranged to pass out of the right-angle electrode seat on the furnace body 50, the other end surface of the first connecting plate 254 is fastened and connected with the installed water-cooled sealing electrode 253 through bolts, and the first connecting plate 254 is a 90° bending piece.

[0082] The lower conductive base 30 is fixedly welded with the flange blind cover 52 on the bottom of the furnace body 50. The lower conductive base 30 comprises a base pad 31, a lower insulating heat insulation plate 32, a lower electrode 33 and a second electrode lead-out device 34.

[0083] The base pad 31 is provided with threaded holes on the upper surface and is welded with the flange blind cover 52, the lower insulating heat insulation plate 32 is provided with a through hole and is arranged above the base pad 31, and the upper insulating heat insulation plate 23 and the lower insulating heat insulation plate 32 are both resistant to temperature of 300℃ or more.

[0084] The lower electrode 33 is fastened and connected with the base pad 31 through bolts in sequence and passes through the insulating porcelain tube and the through hole of the lower insulating heat insulation plate 32. The lower electrode 33 comprises a lower electrode plate 331, a lower electrode column 332 and an insulating porcelain tube 333. The lower electrode plate 331 is uniformly provided with lower electrode column blind holes and bolt countersunk holes, the lower electrode column 332 is arranged in the lower electrode column blind hole of the lower electrode plate 331, passes through the electrode porcelain tube 64 at the bottom of the furnace body 60 and is in the shape of an equal-diameter long rod, and the insulating porcelain tube 333 is arranged in the bolt countersunk hole and is in the shape of a sleeve with a shoulder, with the large head facing upward.

[0085] The second electrode lead-out device 34 can realize power supply of large current of 8000A or more. The second electrode lead-out device 34 comprises a second copper bar 341, a second copper soft braid assembly 342, a second water-cooled sealing electrode 343 and a second connecting plate 344. The second copper bar 341 adopts a double lead-out structure and is in the shape of a rectangular frame, which is arranged above the lower electrode plate 331 and connected with the lower electrode plate 331 through bolts. The second copper soft braid 342 has two groups, which are respectively arranged on the left and right sides of the rectangular frame of the second copper bar 341. Each group of the second copper soft braid assembly 342 has two copper soft braids, one end of which is connected with the second copper bar 341 respectively, and the other end is connected with the second water-cooled sealing electrode 343 through the second connecting plate 344 respectively. The second water-cooled sealing electrode 343 is connected with the right-angle electrode seat on the furnace body 50 through bolt fastening. The second connecting plate 344 is a 90° bending piece. One end surface of the second connecting plate 344 is connected with the second copper soft braid 342. After the upper water-cooled sealing conductive pressure head 20 is installed, it is jointly penetrated out of the right-angle electrode seat on the furnace body 50 together with the second copper soft braid 342. The other surface of the second connecting plate 344 is connected with the installed second water-cooled sealing electrode 343 through bolt fastening. The second connecting plate 344 is a 90° bending piece.

[0086] The tooling 40 comprises an upper thick plate 41, a gasket plate 42 and a lower thick plate 43, which are arranged in the heating effective working area of the furnace tube 60 between the upper water-cooled sealing conductive pressure head 20 and the lower conductive base 30. The upper thick plate 41 and the lower thick plate 43 have smooth surfaces and parallel upper and lower surfaces, and the edges thereof are provided with through holes which are tightly combined with the upper electrode column 242 and the lower electrode column 332 respectively. The gasket plate 42 has a smooth surface and parallel upper and lower surfaces, and the edges thereof are provided with through holes. The gasket plate 42 is made of conductive material which does not react with the plate-fin heat exchanger. The edges of the upper thick plate 41, the gasket plate 42 and the lower thick plate 43 are provided with through holes. A screw rod is penetrated through the through holes of the edges of the upper thick plate 41, the gasket plate 42 and the lower thick plate 43 and is fixed through nuts. The upper water-cooled sealing conductive pressure head 20 is arranged on the upper thick plate 41, and the lower thick plate 43 is arranged on the lower conductive base 30. During loading, the lower thick plate 43, the gasket plate 42, the plate-fin heat exchanger, the gasket plate 42 and the upper thick plate 41 are sequentially arranged from bottom to top. A screw rod is penetrated through the edge through holes and is fastened through nuts at the upper and lower ends. Then, the whole is arranged on the lower conductive base, and the upper water-cooled sealing conductive pressure head is pressed against the upper surface of the upper thick plate. The lower nut is loosened, and the pressure is controlled by the control system during working.

[0087] The temperature control system comprises a temperature control couple 53, a radiant heating device, an infrared temperature detector 55, a high-speed heating resistor, a thermocouple output module, an infrared temperature detector 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 a first feedback signal, which is used as a main temperature control feedback signal to regulate the power of each heating band 63 of the radiant heating device. The output signal of the infrared temperature detector 55 is a second feedback signal, which is used to monitor the temperature of the high-speed heating resistor plate-fin heat exchanger and to assist in controlling the power of the self-resistance high-speed heating electrode 24, 33 of the plate-fin heat exchanger. The working temperature is controlled according to the first feedback signal and the second feedback signal by 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 temperature detector output module is used to transmit the second feedback signal output by the infrared temperature detector 55. The temperature control meter is used to receive the first feedback signal and the second feedback signal and to output a digital signal according to the double feedback series control method. The analog output module converts the digital signal into an electric signal. The thyristor voltage regulating module accurately controls the voltage according to the electric signal, thereby realizing the control of the radiant heating and the self-resistance high-speed heating electrode.

[0088] By using the configuration mode, the titanium alloy plate-fin heat exchanger can be mainly heated by the self-resistance high-speed heating mode in the low-temperature section, and the radiant heating mode is used to follow the heating of the furnace. In the high-temperature section, the titanium alloy plate-fin heat exchanger is heated to the brazing temperature by the radiant heating mode. The brazing efficiency of the vacuum brazing equipment is greatly improved, and the brazing quality problems such as serious surface embrittlement, easy crack defects and serious thin-wall corrosion caused by large core-surface temperature difference and long holding time at the brazing temperature are solved.

[0089] Figures 11 to 13 The brazing method of the titanium alloy plate-fin heat exchanger is given.

[0090] The size of the workpiece is 300 mm (width) x 500 mm (length) x 300 mm (height).

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

[0092] 1) The parts of the titanium alloy plate-fin heat exchanger such as the partition plate, the fin, the sealing strip and the flow guide plate are processed according to the size requirements, and are cleaned. The material is TC4 titanium alloy.

[0093] 2) The parts such as the fin, the partition plate, the sealing strip and the flow guide plate are assembled to form the heat exchanger core. The partition plate has a certain thickness of amorphous titanium filler layer on the upper and lower sides.

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

[0095] 4) Place the tooling 40 on the lower conductive base 30 by the trolley, and press it with the upper water-cooled sealing conductive pressure head 20, loosen the lower nut of the tooling 40, and keep the pressure constant at 0.1 MPa;

[0096] 5) Close the furnace door, open the vacuum system, and pump to 5x10 -3 Pa;

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

[0098] In the double heat source heating stage, as shown in Figure 10 , the same temperature controller is used to implement a double feedback series control strategy, in which the temperature control thermocouple is used as the main temperature control feedback signal to control the radiation heating part, and the infrared temperature instrument is connected to the specific port of the temperature controller as the auxiliary temperature control feedback signal to control the self-resistance extremely fast heating part;

[0099] Specifically, the first feedback signal is a temperature control couple arranged near the effective working area of the furnace tube, fixed on the furnace body, for regulating the power of the heating band of each surface and precisely controlling the uniformity of the furnace temperature; the second feedback signal is an infrared temperature measuring instrument arranged at the front of the furnace body, monitoring the temperature of the plate-fin heat exchanger through the observation window and the through hole of the furnace tube, for assisting in controlling the power of the self-resistance rapid heating electrode of the plate-fin heat exchanger; the two temperature feedback signals are simultaneously connected to specific ports of the temperature controller and compared. In the heating stage, if the temperatures of the first feedback signal and the second feedback signal do not reach the set temperature of 680℃, the PID control is adopted to simultaneously heat the heating band and the self-resistance rapid heating electrode; 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℃, the self-resistance rapid heating electrode stops 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℃, the self-resistance rapid heating electrode is controlled to heat; when the temperature of the second feedback signal reaches the set temperature of 680℃, the workpiece enters the temperature maintaining stage, the self-resistance rapid heating electrode stops heating, and if the set temperature minus the temperature of the second feedback signal is greater than the set temperature difference of 30℃, the self-resistance rapid heating electrode resumes heating; when the temperature of the first feedback signal reaches the set temperature of 680℃, the furnace tube enters the temperature maintaining stage, and the self-resistance rapid heating electrode stops heating completely;

[0100] The double heat source heating stage can be carried out in stages, and the stage temperature, holding time and number of stages can be set according to the size of the titanium alloy plate-fin heat exchanger and the type of brazing filler metal;

[0101] 7) When the temperature of the titanium alloy plate-fin heat exchanger reaches 680℃, the current is stopped, and when the temperature of the workpiece is lower than that of the furnace tube, the current is applied again, and the cycle is repeated until the temperature of the furnace chamber and the titanium alloy plate-fin heat exchanger both rise to 680℃, and the temperature is maintained for 25 min, so that the temperature of each part of the brazed part is uniform. This double heat source heating stage can be carried out in stages;

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

[0103] 9) The welded titanium alloy plate-fin heat exchanger is quickly cooled to below 150℃, and the vacuum system is turned off to prevent oxidation and discoloration;

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

[0105] For example, Figure 11 and Figure 12As shown, the traditional vacuum brazing process curve of the titanium alloy plate-fin heat exchanger (size WxLxH, 300mmx500mmx300mm) in the embodiment, the whole production cycle takes 1740min, and the product flatness is 8mm / m; the double heat source vacuum brazing process curve of the titanium alloy plate-fin heat exchanger (size WxLxH, 300mmx500mmx300mm) brazed by the equipment of the application, the whole production cycle takes 870min, the product flatness is 3mm / m, the manufacturing efficiency is improved by 50%, and the deformation control precision is improved by 62.5%.

[0106] The vacuum brazing method of the plate-fin heat exchanger of the application first loads the plate-fin heat exchanger through a tool into the upper water-cooled sealing conductive pressure head and the lower conductive base of the equipment, and then automatically realizes self-resistance rapid heating and uniform pressure loading of the workpiece by using a double feedback series control and pressure-temperature coupling control method. The vacuum brazing method proposed in the application improves the brazing process manufacturing efficiency of the titanium alloy plate-fin heat exchanger by 50%, improves the deformation control precision by 62.5%, and fundamentally solves 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 application has important engineering application value in the vacuum brazing of large-size plate-fin heat exchangers in the fields of aviation and navigation.

[0107] In the description of the application, it should be understood that the orientation words such as "front, rear, upper, lower, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and in the absence of contrary description, these orientation words do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the application; the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0108] For purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "rear", "front", "vertical" and "horizontal" as can be perceived herein relative to the accompanying drawings refer to the orientation of the components being described. However, it is to be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device described herein relative to the other device or structure is inverted, then a spatially relative term such as "above" can be interpreted as meaning "below" or "below" can be interpreted as meaning "above". The device can also be oriented in other ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terms "first", "second", "third", etc. do not necessarily denote any ordinal, chronological or other sequence unless specified.

[0109] In addition, it should be pointed out that the use of the words "one", "two", etc. to qualify parts is only intended to facilitate the distinction between the corresponding parts, and unless otherwise stated, the above words do not have a special meaning and therefore cannot be understood as limiting the scope of protection of the present application.

[0110] The above description is merely the preferred embodiments of the present application, and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A vacuum brazing apparatus for plate-fin heat exchangers, characterized by, The vacuum brazing equipment for the plate-fin heat exchanger comprises: a hydraulic control system (10) for providing constant pressure control for the vacuum brazing equipment; a furnace body (50) fixed on a main frame (11) of the hydraulic control system (10), the furnace body (50) being used for providing a vacuum environment and interfaces of subsystems and containing a brazing piece, wherein the interfaces comprise a temperature control couple (53) and an infrared temperature detector (55) interface; the temperature control couple (53) outputs a first feedback signal as a main temperature control feedback signal to regulate power of each heating band (63); the infrared temperature detector (55) outputs a second feedback signal for monitoring temperature of the plate-fin heat exchanger and assisting in controlling power of a self-resistance electrode rapid heating electrode of the plate-fin heat exchanger; the furnace body is controlled according to the first feedback signal and the second feedback signal by using a double feedback series control method; a furnace tube (60) arranged in the furnace body (50), the furnace tube (60) comprising a furnace tube frame (61), a heat insulation screen (62) and a plurality of heating bands (63), each zone heating band (63) being uniformly distributed on an inner wall of the furnace tube and being independently controllable for vacuum radiation heating and heat preservation; a dynamic sealing structure (70) fixed on the furnace body (50), the dynamic sealing structure (70) being used for providing a translational sealing interface and maintaining a system working vacuum degree; a vacuum system (80) connected with the furnace body (50), the vacuum system being used for discharging gas in the furnace body (50) to obtain a vacuum environment; and a vacuum system (80) connected with the furnace body (50), the vacuum system being used for discharging gas in the furnace body (50) to obtain a vacuum environment. The upper water-cooled sealing and conducting pressure head (20) is connected with the hydraulic control system (10), and the lower end penetrates 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 sealing and conducting pressure head (20) comprises a water-cooled sealing pressure head base (21), a pressure head backing plate (22), an upper insulating and heat insulating plate (23), an upper electrode (24) and a first electrode leading-out device (25), wherein the water-cooled sealing pressure head base (21), the pressure head backing plate (22), the upper insulating and heat insulating plate (23) and the upper electrode (24) are sequentially connected; the water-cooled sealing pressure head base (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 with the pressure head (12) through the flange (211); the upper end surface of the sealing sleeve (215) is welded with the flange (211); the sealing sleeve (215) is a hollow circular pipe; the upper end of the outer circle of the sealing sleeve (215) is welded with the water inlet pipe (213) and the water outlet pipe (214) respectively; 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 with the pressure head column (212), and the upper end of the outer circle is welded with the sealing sleeve (215); the first electrode leading-out device (25) is connected with the upper electrode (24) and is used for leading out the current of the upper water-cooled sealing and conducting pressure head (20); and the lower conducting base (30) is used for self-resistance electrode rapid heating and uniform loading of the workpiece together with the upper water-cooled sealing and conducting pressure head (20). The lower conducting base (30) comprises a base backing plate (31), a lower insulating and heat insulating plate (32), a lower electrode (33) and a second electrode leading-out device (34) which are sequentially connected; the second electrode leading-out device (34) is connected with the lower electrode (33) and is used for leading out the current of the lower conducting base (30); and the lower conducting base (30) is used for self-resistance electrode rapid heating and uniform loading of the workpiece together with the upper water-cooled sealing and conducting pressure head (20). The tooling (40) is used for providing constraint for the plate-fin heat exchanger.

2. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 1, characterized in that The working temperature is controlled according to the first feedback signal and the second feedback signal by using a double feedback series control method, and specifically includes the following steps: If the temperatures of the first feedback signal and the second feedback signal do not reach the set temperature, the heating stage is entered, the PID control is used to control the heating band and the self-resistance electrode rapid heating electrode to heat 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 first temperature difference threshold, the self-resistance electrode rapid heating electrode stops 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 electrode rapid 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 heat preservation stage is entered, when the temperature of the second feedback signal is equal to the set temperature, the self-resistance electrode rapid heating electrode stops 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 electrode rapid heating electrode resumes heating. When the first feedback signal temperature reaches the set temperature, the furnace reaches the heat preservation stage, and the self-resistance electrode rapid heating electrode heating is completely stopped.

3. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 2, characterized in that The vacuum brazing equipment for the plate-fin heat exchanger further comprises a temperature control system, which comprises: The infrared thermometer output module is used for transmitting the second feedback signal output by the infrared thermometer (55). The thermocouple output module is used for transmitting the first feedback signal output by the thermocouple. The temperature control meter is used for receiving the first feedback signal and the second feedback signal and outputting a digital signal according to the double feedback series control method. The analog output module converts the digital signal into an electric signal. The silicon-controlled voltage regulating module accurately controls the voltage according to the electric signal, thereby controlling the self-resistance electrode rapid heating electrode and the radiation heating.

4. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 1, wherein The hydraulic control system (10) adopts a pressure-temperature coupling control method to keep the pressure constant at different set values at different temperature stages.

5. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 1, wherein The dynamic sealing structure (70) comprises 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, and the sealing seat (71) is fixed on the furnace body (50) through bolts, the other end of the sealing seat (71) has an inner circular platform, a plurality of sealing rings (72) and spacer rings (73) are sequentially stacked, and the sealing rings (72) and the spacer rings (73) are compressed by the gland (74), and the gland (74) is fixedly connected with the sealing seat (71).

6. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 1, wherein 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 with the upper insulating heat insulation plate (23), the lower end of the upper electrode (24) penetrates through the electrode porcelain tube (64) at the top of the furnace body (60), the upper surface of the upper electrode (24) is uniformly distributed with upper electrode column countersunk holes, the lower surface of the upper electrode (24) is uniformly 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 arranged in the upper electrode column countersunk hole in the upper electrode plate (241) and is attached to the upper insulating heat insulation plate (23), and the first insulating porcelain tube (243) is arranged in the bolt countersunk hole in 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 with the lower insulating heat insulation plate (32), the upper end of the lower electrode (33) penetrates through the electrode porcelain tube (64) at the bottom of the furnace body (60), the lower electrode plate (331) is uniformly 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 in the lower electrode plate (331), and the second insulating porcelain tube (333) is arranged in the bolt countersunk hole.

7. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 6, characterized in that The first electrode lead-out device (25) comprises a first copper bar (251), a first copper soft braid assembly (252), a first water-cooled sealing electrode (253) and a first connecting plate (254), the first copper bar (251) adopts a double lead-out structure and is in the shape of a rectangular frame and is connected with the upper electrode plate (241), the first copper soft braid assembly (252) is located on both sides of the rectangular frame of the first copper bar (251), the first copper soft braid assembly (252) has two groups and is respectively located on the left and right sides of the rectangular frame of the first copper bar (251), each group has two copper soft braids, one end of the copper soft braids is connected with the first copper bar (251), the other end is connected with the first water-cooled sealing electrode (253) through the first connecting plate (254), the length of the first copper soft braid assembly (252) is greater than the working stroke of the upper water-cooled sealing conductive pressure head (20), and the first water-cooled sealing electrode (253) is connected with the furnace body (50); The second electrode lead-out device (34) comprises a second copper bar (341), a second copper soft braid assembly (342), a second water-cooled sealing electrode (343) and a second connecting plate (344), the second copper bar (341) adopts a double lead-out structure and is in the shape of a rectangular frame and is connected with the lower electrode plate (331), the second copper soft braid assembly (342) is located on both sides of the rectangular frame of the second copper bar (341), the second copper soft braid assembly (342) has two groups and is respectively located on the left and right sides of the rectangular frame of the second copper bar (341), each group has two copper soft braids, one end of the copper soft braids is connected with the second copper bar (341), the other end is connected with the second water-cooled sealing electrode (343) through the second connecting plate (344), and the second water-cooled sealing electrode (343) is tightly connected with the furnace body (50).

8. A vacuum brazing apparatus for plate-fin heat exchangers according to claim 1, wherein The tooling (40) comprises an upper thick plate (41), a gasket (42) and a lower thick plate (43), the upper thick plate (41) and the lower thick plate (43) are respectively tightly attached to the upper electrode column (242) and the lower electrode (33), the edges of the upper thick plate (41), the gasket (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 brazing method for a plate-fin heat exchanger, characterized by, The plate-fin heat exchanger brazing method adopts the vacuum brazing equipment for a plate-fin heat exchanger according to any one of claims 7 to 8, and specifically comprises the following steps: 1) machining the partition plate, the fin, the sealing strip parts of the plate-fin heat exchanger according to the size requirements and cleaning; 2) coating a brazing filler metal layer on the upper and lower sides of the partition plate; 3) assembling the parts of the plate-fin heat exchanger on the tooling (40), sequentially placing the upper thick plate (41), the gasket (42), the plate-fin heat exchanger and the lower thick plate (43) from bottom to top, and screwing through the edge through holes of the upper thick plate (41), the gasket (42) and the lower thick plate (43) and fastening with nuts at the upper and lower ends; 4) placing the above tooling (40) on the lower conductive base (30) as a whole by a material cart, and pressing tightly with the upper water-cooled sealing conductive pressure head (20), loosening the lower nut of the tooling (40) and keeping the pressure constant; 5) Start the vacuum system (80) and vacuumize to working vacuum degree; 6) Heat and keep the plate-fin heat exchanger by double feedback series control mode; 7) Keep the pressure constant at different set values in different temperature sections by pressure-temperature coupling control method; 8) Raise the plate-fin heat exchanger to brazing process temperature ±5℃, keep for 10-60 min, and complete brazing; 9) Cool the brazed plate-fin heat exchanger evenly to below 150℃, shut down the vacuum system (80), and then continue to cool to room temperature.

10. The method of claim 9, wherein The pressure-temperature coupling control method sets the pressure-temperature coupling relationship as follows: temperature < 150℃, pressure 0.1 Mpa; 200℃ ≤ temperature < 400℃, pressure 0.08 MPa; 400℃ ≤ temperature < 600℃, pressure 0.06 MPa; 600℃ ≤ temperature < 800℃, pressure 0.04 Mpa.

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