Aluminum alloy vacuum brazing method and vacuum brazing equipment

Abstract

The invention relates to the technical field of welding, and provides an aluminum alloy vacuum brazing method and vacuum brazing device.The aluminum alloy vacuum brazing method comprises the steps that a welded workpiece and brazing filler metal are controlled to be preheated to the preheating temperature in a vacuum brazing scene in a graded mode; the workpiece to be welded and the brazing filler metal are controlled to be heated to the brazing temperature from the preheating temperature so that brazing can be conducted at the brazing temperature, and the temperature difference between the brazing temperature and the solidus temperature of the workpiece to be welded is larger than 30 DEG C; and the welded workpiece is controlled to be cooled to the cooling temperature from the brazing temperature in a graded mode, and then the welded workpiece is controlled to be moved out of the vacuum brazing scene. According to the aluminum alloy vacuum brazing method, the temperature difference between the solidus temperature and the brazing temperature of the welded workpiece is controlled, the brazing difficulty is lowered, and the brazing quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, and particularly to a method for vacuum brazing aluminum alloy and a vacuum brazing device. Background Art

[0002] Reference Figures 2 to 5 As shown, the structure of a cold plate heat exchanger or a cold plate assembly generally includes a flow channel plate and a cover plate. Flow channels are arranged on the flow channel plate, and the flow channels are used to accommodate a cooling medium, and the cooling medium can be a liquid medium. The materials of the flow channel plate and the cover plate usually use 6-series aluminum alloy (such as 6061 or 6063). The joint between the flow channel plate and the cover plate is connected by welding. For example, when connected as a whole by a brazing method, a nitrogen protection continuous furnace brazing process is usually adopted to hermetically connect the flow channel plate and the cover plate and ensure that the flow channels form a closed space. Among them, the cold plate heat exchanger or the cold plate assembly can be applied to heat exchange occasions such as the thermal management system of new energy vehicles and the thermal management system of energy storage systems. The cold plate can be used to exchange heat with the battery or the energy storage system to achieve the established functions of the vehicle integrated management module.

[0003] The nitrogen protection continuous furnace brazing process has problems such as residual aluminum brazing flux after welding, resulting in increased product resistance, large hidden dangers, high brazing difficulty, low brazing qualification rate, and large investment in brazing equipment; based on the solid-liquid phase line temperature of aluminum alloy material being 640°C to 668°C, the nitrogen protection brazing temperature of common aluminum alloys is usually about 620°C. The brazing temperature is relatively close to the melting point of the base material, and the base material is prone to over-temperature and brazing defects, and the brazing difficulty is high.

[0004] The nitrogen protection continuous furnace brazing process also needs to add an aluminum brazing flux (usually such as potassium hexafluoroaluminate aluminum brazing flux KAlF4) to remove the oxide film on the surface of the aluminum alloy. The residual brazing flux inside the flow channel after welding will cause the flow resistance and resistivity of the flow channel to increase, resulting in potential hazards such as performance degradation and failure of the system; when the magnesium (Mg) content in the base material to be welded is about 0.5 wt.% or more (usually the Mg element content in 6061 / 6063 aluminum alloy is higher than 0.5 wt.%), using the aluminum brazing flux KAlF4, the aluminum brazing flux reacts chemically with Mg at high temperature to form high melting point products such as MgF2 and KMgF3, reducing the effective components of the aluminum brazing flux and making the aluminum brazing flux partially or completely ineffective. The high melting point products form a film on the surface of the workpiece to be welded, hindering the wetting, flow, and filling of the molten brazing filler metal, etc., resulting in defects such as porosity and false soldering at the weld. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the related art. For this purpose, the present invention provides a method for vacuum brazing aluminum alloy, which controls the temperature difference between the solidus temperature of the workpiece to be welded and the brazing filler metal during the vacuum brazing process, so that the performance of the brazed product is more stable, the brazing difficulty is reduced, and there is no need to add an aluminum brazing flux.

[0006] The present invention also provides a vacuum brazing apparatus.

[0007] A method for vacuum brazing aluminum alloy according to an embodiment of the first aspect of the present invention includes:

[0008] Controlling the workpieces to be brazed and the filler metal to be preheated step by step to a preheating temperature in a vacuum brazing scenario;

[0009] Controlling the workpieces to be brazed and the filler metal to be heated from the preheating temperature to a brazing temperature for brazing at the brazing temperature, wherein the temperature difference between the brazing temperature and the solidus temperature of the workpieces to be brazed is greater than 30°C;

[0010] Controlling the workpieces to be brazed to be cooled step by step from the brazing temperature to a cooling temperature, and then controlling the workpieces to be brazed to be removed from the vacuum brazing scenario.

[0011] In the vacuum brazing method according to an embodiment of the present invention, controlling the temperature difference between the brazing temperature and the solidus temperature of the workpieces to be brazed to be greater than 30°C, and determining the filler metal according to this condition can ensure the brazing performance and quality; before the brazing process, preheating the welding container and the workpieces to be brazed by step-by-step preheating also helps to ensure the brazing quality. After the brazing process, controlling the workpieces to be brazed to be cooled step by step can ensure that the filler metal solidifies stably and smoothly at the weld.

[0012] According to an embodiment of the present invention, after the step of controlling the workpieces to be brazed to be removed from the vacuum brazing scenario, the method further includes:

[0013] Controlling the workpieces to be brazed to be heated to a fifth temperature for solution treatment, and then controlling the workpieces to be brazed to be cooled to the ambient temperature.

[0014] According to an embodiment of the present invention, after the step of controlling the workpieces to be brazed to be cooled to the ambient temperature, the method further includes:

[0015] Controlling the workpieces to be brazed to be heated to a seventh temperature for aging treatment, and then controlling the workpieces to be brazed to be cooled to the ambient temperature;

[0016] wherein, the seventh temperature is less than the fifth temperature.

[0017] According to an embodiment of the present invention, before the step of controlling the workpieces to be brazed and the filler metal to be preheated step by step in the vacuum brazing scenario, the workpieces to be brazed are clamped by a welding fixture;

[0018] And / or, in at least one of the solution treatment and the aging treatment, the workpieces to be brazed are clamped by the welding fixture.

[0019] According to an embodiment of the present invention, the fifth temperature is greater than or equal to 510°C and less than or equal to 560°C, and is maintained for 5 ± 2 hours;

[0020] And / or, the seventh temperature is greater than or equal to 140°C and less than or equal to 200°C, and is maintained for 8 ± 2 hours.

[0021] According to an embodiment of the present invention, in the step of controlling the workpiece to be welded to be heated to the fifth temperature for solution treatment and then controlling the workpiece to be welded to be cooled down to the ambient temperature,

[0022] Controlling the workpiece to be welded to be cooled to the ambient temperature in a water environment with an initial temperature of the sixth temperature, where the sixth temperature is greater than or equal to 35°C and less than or equal to 40°C.

[0023] According to an embodiment of the present invention, the temperature difference between the brazing temperature and the solidus temperature of the workpiece to be welded is greater than or equal to 50°C and less than or equal to 65°C.

[0024] According to an embodiment of the present invention, in the step of controlling the workpiece to be welded and the filler metal to be preheated step by step to the preheating temperature in a vacuum brazing scenario, it includes:

[0025] Controlling the ambient temperature of the vacuum brazing scenario to be preheated to the initial preheating temperature, and then controlling the workpiece to be welded and the filler metal to be preheated to the preheating temperature.

[0026] According to an embodiment of the present invention, the brazing temperature is greater than or equal to 580°C and less than or equal to 595°C, and is maintained for a duration greater than or equal to 5 minutes and less than or equal to 30 minutes;

[0027] And / or, the initial preheating temperature is greater than or equal to 420°C and less than or equal to 500°C, and is maintained for a duration greater than or equal to 20 minutes and less than or equal to 30 minutes;

[0028] And / or, the preheating temperature is greater than or equal to 530°C and less than or equal to 570°C, and is maintained for a duration greater than or equal to 20 minutes and less than or equal to 30 minutes.

[0029] According to an embodiment of the present invention, in the step of controlling the workpiece to be welded to be cooled step by step from the brazing temperature to the cooling temperature, it further includes:

[0030] Controlling the workpiece to be welded to be cooled to the third temperature in the vacuum brazing scenario and then cooled to the cooling temperature;

[0031] Wherein, the temperature difference between the third temperature and the brazing temperature is less than or equal to 50°C, and it is cooled from the third temperature to the cooling temperature.

[0032] According to an embodiment of the present invention, the third temperature is greater than or equal to 571°C and less than or equal to 585°C, and is maintained for a duration greater than or equal to 15 minutes and less than or equal to 30 minutes;

[0033] And / or, the cooling temperature is greater than or equal to 250°C and less than or equal to 300°C.

[0034] According to an embodiment of the present invention, in the step of controlling the preheating of the workpiece to be welded and the filler metal to the preheating temperature in a vacuum brazing scenario, it further includes:

[0035] Controlling the vacuum degree in the vacuum brazing scenario to a first set vacuum degree;

[0036] In the step of controlling the heating of the workpiece to be welded and the filler metal from the preheating temperature to the brazing temperature for brazing at the brazing temperature, it further includes:

[0037] Controlling the vacuum degree in the vacuum brazing scenario to a second set vacuum degree,

[0038] wherein, the second set vacuum degree is less than the first set vacuum degree.

[0039] According to an embodiment of the present invention, the first set vacuum degree is greater than 10 -2 Pa, and the second set vacuum degree is greater than 10 -3 Pa.

[0040] According to an embodiment of the present invention, the filler metal is a bimetallic composite plate, the workpiece to be welded includes a flow channel plate and a cover plate, a flow channel is formed between the flow channel plate and the cover plate, and the flow channel plate and the cover plate are aluminum alloy plates.

[0041] According to the vacuum brazing equipment of the second aspect embodiment of the present invention, it includes:

[0042] A welding container, forming the vacuum brazing scenario;

[0043] A heating device, used to heat the welding container and the workpiece to be welded;

[0044] A temperature detection component, used to detect the temperature inside the welding container and the workpiece to be welded;

[0045] A controller, used to execute the aluminum alloy vacuum brazing method described in any one of the above.

[0046] According to an embodiment of the present invention, the temperature detection component includes:

[0047] A first temperature sensor, arranged inside the welding container, used to detect the ambient temperature of the vacuum brazing scenario;

[0048] A second temperature sensor and a third temperature sensor, arranged inside the welding container, the second temperature sensor is used to detect the outer wall temperature of the workpiece to be welded, and the third temperature sensor is used to detect the inner wall temperature of the workpiece to be welded.

[0049] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the related art, the following will briefly introduce the drawings required for use in the description of the embodiments or the related art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0051] Figure 1 is a schematic flowchart of the aluminum alloy vacuum brazing method provided by the embodiment of the present invention;

[0052] Figure 2 is a front view structural schematic diagram of a cold plate assembly in the related art;

[0053] Figure 3 is a side view structural schematic diagram of a cold plate assembly in the related art;

[0054] Figure 4 is a structural schematic diagram of a flow channel plate of a cold plate assembly in the related art;

[0055] Figure 5 is a structural schematic diagram of a cover plate of a cold plate assembly in the related art;

[0056] Figure 6 is a curve graph of the melting point test of the aluminum plate raw material 6063 applicable to the aluminum alloy vacuum brazing method provided by the embodiment of the present invention;

[0057] Figure 7 is a curve graph of the melting point test of the aluminum plate raw material 6061 applicable to the aluminum alloy vacuum brazing method provided by the embodiment of the present invention;

[0058] Figure 8 is a curve graph of the melting point test of the brazing filler metal applicable to the aluminum alloy vacuum brazing method provided by the embodiment of the present invention;

[0059] Figure 9 is an organizational diagram of the original state of the aluminum plate raw material 6063 in the related art;

[0060] Figure 10 is after being processed by the aluminum alloy vacuum brazing method provided by the embodiment of the present invention Figure 9 the organizational diagram of the aluminum plate raw material shown before solution treatment and aging treatment after being taken out of the welding container;

[0061] Figure 11treated by the aluminum alloy vacuum brazing method provided by the embodiments of the present invention Figure 9 The microstructure diagram of the aluminum plate raw material shown after solution treatment and aging treatment;

[0062] Figure 12 The side view structural schematic diagram of the welding fixture applied to the aluminum alloy vacuum brazing method provided by the embodiments of the present invention;

[0063] Figure 13 The front view structural schematic diagram of the welding fixture applied to the aluminum alloy vacuum brazing method provided by the embodiments of the present invention;

[0064] Figure 14 The structural schematic diagram of the disassembled state of the parts of the welding fixture applied to the aluminum alloy vacuum brazing method provided by the embodiments of the present invention.

[0065] Reference numerals:

[0066] 10, cold plate assembly; 1, flow channel plate; 2, cover plate; 20, tooling bottom plate; 30, tooling cover plate; 40, support rod; 50, tooling pressing block; 60, limit plate; 70, elastic pressing assembly. Detailed implementation manners

[0067] The following further describes the embodiments of the present invention in detail with reference to the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0068] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meanings of "multiple", "multiple roots", "multiple groups" are two or more.

[0069] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0070] In the embodiments of the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature in terms of horizontal height. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature in terms of horizontal height.

[0071] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0072] The aluminum alloy vacuum brazing method is performed by a vacuum brazing device. The vacuum brazing device includes a welding container, a heating device, and a temperature detection component. The welding container can provide a vacuum brazing scenario. The heating device is used to heat the workpiece to be welded in the welding container. The temperature detection component is used to detect the temperature of at least one of the welding container and the workpiece to be welded, so as to adjust the heating power and start / stop and other working states of the heating device in a timely manner. The types of vacuum brazing devices for performing the aluminum alloy vacuum brazing method are not limited, as long as they can provide a vacuum welding condition for the workpiece to be welded.

[0073] The following aluminum alloy vacuum brazing method is applicable to the welding and processing of various workpieces to be welded. In the embodiments of the present invention, taking the workpiece to be welded as a cold plate heat exchanger or a cold plate assembly as an example, refer to Figures 2 to 5As shown, the cold plate heat exchanger or cold plate assembly includes an aluminum alloy plate. The cold plate heat exchanger or cold plate assembly is welded and processed by the following aluminum alloy vacuum brazing method to improve the welding quality of the cold plate heat exchanger or cold plate assembly.

[0074] In an embodiment of the first aspect of the present invention, refer to Figure 1 As shown, a method for aluminum alloy vacuum brazing is provided, including:

[0075] Step 110, controlling the workpieces to be welded and the filler metal to be preheated in stages to the preheating temperature in a vacuum brazing scenario;

[0076] Step 110 can be understood as a preheating step. The workpieces to be welded and the filler metal are preheated step by step in sections, and a slow preheating method is adopted to ensure the uniform temperature of the workpieces to be welded and the filler metal, as well as the stable performance of the workpieces to be welded and the filler metal.

[0077] During the staged preheating process, it is at least divided into two stages of preheating, and it can be divided into three stages, four stages, etc. The specific form of staging is not limited. Regardless of the form of several stages of preheating, at the end of the staged preheating, it is necessary to ensure that the workpieces to be welded and the filler metal are heated to the preheating temperature.

[0078] The vacuum brazing scenario can be provided by a welding container, and the welding container can be of various types such as a vacuum furnace, a vacuum tank, etc.

[0079] Step 120, controlling the workpieces to be welded and the filler metal to be heated from the preheating temperature to the brazing temperature for brazing at the brazing temperature, and the temperature difference between the brazing temperature and the solidus temperature of the workpieces to be welded is greater than 30°C;

[0080] Step 120 can be understood as a brazing step. The brazing temperature is determined according to the solidus temperature of the workpieces to be welded. The brazing temperature is lower than the solidus temperature of the workpieces to be welded, and the temperature difference is greater than 30°C. At the brazing temperature, the workpieces to be welded remain in the solid phase. Brazing is carried out at a temperature close to the liquidus temperature of the filler metal, and the filler metal can be automatically added to the brazing seam. The filler metal can be heated and welded at the brazing temperature at the gap of the workpieces to be welded, such as the gap between the flow channel plate and the cover plate of the cold plate heat exchanger. Therefore, after determining that the brazing temperature is 30°C lower than the solidus temperature of the workpieces to be welded, the type of filler metal can be selected according to this condition. At the brazing temperature, the filler metal can be heated and welded to the workpieces to be welded.

[0081] The brazing temperature is set to be lower than the solidus temperature of the workpiece to be brazed and the temperature difference is greater than 30°C. In the case of low heating accuracy during vacuum brazing, such as a heating deviation of ±10°C, it is possible to avoid the situation where the welding performance is affected due to a large heating deviation. It can be understood that if the brazing temperature is set at 620°C, the solid-liquid phase transition temperature of the workpiece to be brazed is between 640°C and 668°C, and the heating deviation is ±10°C, the workpiece to be brazed can be heated to 630°C. The actual temperature of the workpiece to be brazed is very close to the solid-liquid phase transition temperature, which will affect the performance of the workpiece to be brazed. Therefore, the temperature difference between the brazing temperature and the solidus temperature of the workpiece to be brazed in the embodiments of the present invention is greater than 30°C. Even if there is a heating deviation, the influence on the workpiece to be brazed can be significantly reduced, ensuring the welding performance.

[0082] It should be noted that the brazing temperature is lower than the solidus temperature of the workpiece to be brazed and the temperature difference is greater than 30°C, which limits the upper limit value of the brazing temperature. The lower limit value of the brazing temperature can be determined according to the performance of the selected filler metal.

[0083] According to the upper limit value of the brazing temperature, select a filler metal to ensure that the solid-liquid phase transition temperature of the selected filler metal is lower than the solid-liquid phase transition temperature of the workpiece to be brazed, that is, the liquidus temperature of the filler metal needs to be lower than the solidus temperature of the workpiece to be brazed. When the filler metal melts, the workpiece to be brazed remains in the solid phase, which can solve the problem of overheating of the base material of the workpiece to be brazed due to the proximity of the base material of the workpiece to be brazed and the filler metal temperature, avoid affecting the brazing heating uniformity, workpiece oxidation and film removal effect, etc., and ensure the brazing effect.

[0084] Determining the filler metal can include determining the type, grade, etc. of the filler metal, selecting a suitable filler metal, and improving the welding performance of the workpiece to be brazed by selecting a suitable filler metal. The filler metal can be a bimetallic composite plate, such as the filler metal includes a core plate and double-sided filler metal plates.

[0085] The solidus temperature refers to the temperature at which the alloy of some components begins to melt or liquefy. The liquidus temperature generally refers to the temperature at the intersection of the solid state and the liquid state of the liquid material. Above the liquidus line, it is all liquid phase, and below the solidus line, it is all solid phase. Between the solidus line and the liquidus line, there are solid and liquid phases. The solid-liquid phase transition temperature is the temperature between the solidus line and the liquidus line.

[0086] When the workpiece to be brazed is a cold plate heat exchanger or cold plate assembly 10 made of aluminum alloy, the cold plate heat exchanger or cold plate assembly 10 (workpiece to be brazed) includes a flow channel plate 1 and a cover plate 2. A flow channel is formed between the flow channel plate 1 and the cover plate 2. The flow channel plate 1 and the cover plate 2 can be aluminum alloy plates, and the model of the aluminum alloy plate can be 6063 or 6061. Refer to Figures 6 to 9As shown, the solid-liquid phase transition temperature of the 6063 aluminum alloy plate is greater than or equal to 650 °C and less than or equal to 668 °C, the solid-liquid phase transition temperature of the 6061 aluminum alloy plate is greater than or equal to 645 °C and less than or equal to 660 °C. The type of the filler metal can be 4004 or 4104. The solid-liquid phase transition temperature of 4004 or 4104 is greater than or equal to 560 °C and less than or equal to 596 °C. The difference between the solid-liquid phase transition temperature of the filler metal and the starting melting temperature of the aluminum alloy plate (taking the solidus line of the 6061 base material) is widened to between 50 °C and 65 °C (the temperature difference between the brazing temperature and the solidus line temperature of the workpiece to be brazed is between 50 °C and 65 °C). While ensuring that the filler metal is completely melted and filled, it can also ensure that the aluminum base material does not overheat or burn, preventing brazing defects such as corrosion and pitting.

[0087] It should be noted that according to the different properties of the filler metal, the temperature difference between the brazing temperature and the solidus line temperature of the workpiece to be brazed can also be between 40 °C and 60 °C, between 35 °C and 50 °C, etc. The setting of the temperature difference is not limited.

[0088] After determining the filler metal, the steps of preheating and brazing can be carried out, and the workpiece to be brazed is sent into the vacuum brazing scenario.

[0089] Among them, the solid-liquid phase transition temperature of the workpiece to be brazed is the first temperature, and the solid-liquid phase transition temperature of the filler metal is the second temperature. The maximum value of the second temperature is less than the minimum value of the first temperature.

[0090] Combined with the above content, when the solid-liquid phase transition temperature (the first temperature) of the aluminum alloy plate is greater than or equal to 645 °C and less than or equal to 668 °C, and the solid-liquid phase transition temperature (the second temperature) of the filler metal is greater than or equal to 560 °C and less than or equal to 596 °C, the brazing temperature can be set between 560 °C and 596 °C. For example, the brazing temperature can be between 580 °C and 596 °C or 596 °C, etc. The brazing temperature is set within the range between the solidus line temperature and the liquidus line temperature of the filler metal, and the brazing temperature is as close as possible to the liquidus line temperature of the filler metal. The specific value of the brazing temperature is not limited. If the brazing temperature is set to 596 °C, the temperature difference between the brazing temperature and the solidus line temperature of the aluminum alloy plate of 645 °C is close to 50 °C. Even if the temperature control accuracy of the brazing temperature is ±10 °C, the brazing temperature will not reach the solidus line temperature of the aluminum alloy plate, ensuring the performance of the aluminum alloy plate.

[0091] Step 130, control the workpiece to be brazed to cool down from the brazing temperature to the cooling temperature in stages, and then control the workpiece to be brazed to move out of the vacuum brazing scenario.

[0092] Step 130 can be understood as a cooling step. The workpieces to be welded are cooled in stages and gradually, and a slow cooling method is adopted to ensure uniform temperature change of the workpieces to be welded, provide sufficient fusion time for the workpieces to be welded and the filler metal, and ensure the performance of the workpieces to be welded and the filler metal. It should be noted that after the brazing step, the filler metal is filled at the weld of the workpieces to be welded and is integrated with the workpieces to be welded. In step 130 and subsequent steps, they are collectively referred to as the workpieces to be welded.

[0093] During the process of stepwise cooling, it is at least divided into two levels of cooling, and can be divided into three levels, four levels, etc. The specific form of stepwise division is not limited. Regardless of the form of stepwise cooling adopted, after the stepwise cooling is completed, it is necessary to ensure that the workpieces to be welded and the filler metal are cooled to the cooling temperature.

[0094] The cooling temperature is: the temperature at which the workpieces to be welded and the filler metal can be removed from the vacuum brazing scenario without affecting their performance. The cooling temperature can be between 250°C and 300°C. The cooling temperature is not higher than the preheating temperature.

[0095] The above steps 110 to 130 are executed in sequence. In step 120, the filler metal can be determined before welding according to the types, compositions, etc. of the workpieces to be welded.

[0096] During the process from step 110 to step 130, the workpieces to be welded and the filler metal are both kept in the vacuum brazing scenario. During the process from step 110 to step 130, the workpieces to be welded are clamped and fixed by welding fixtures to prevent deformation of the workpieces to be welded and ensure the structural stability of the workpieces to be welded.

[0097] In the aluminum alloy vacuum brazing method of the embodiment of the present invention, the temperature difference between the brazing temperature and the solidus temperature of the workpieces to be welded is set to be greater than 30°C. Then, according to this condition, the filler metal is selected. After determining the filler metal, according to the solid-liquid phase line temperature of the filler metal, the lower limit value of the brazing temperature is determined. The brazing temperature is related to the brazing performance of the workpieces to be welded, ensuring the brazing quality. Combined with stepwise heating and preheating before brazing and stepwise cooling and cooling after brazing, the welding performance of the workpieces to be welded is ensured.

[0098] In step 110, in the step of controlling the workpieces to be welded and the filler metal to be preheated in stages to the preheating temperature in the vacuum brazing scenario, it includes:

[0099] Step 111, controlling the ambient temperature of the vacuum brazing scenario to be preheated to the initial preheating temperature;

[0100] Step 112, then controlling the workpieces to be welded to be heated to the preheating temperature;

[0101] Among them, the initial preheating temperature is less than the preheating temperature;

[0102] In step 111, the vacuum brazing scenario is controlled to be preheated to the initial preheating temperature and maintained at the initial preheating temperature for the first preset duration. While preheating the vacuum brazing scenario, the workpiece to be brazed inside the vacuum brazing scenario is heated. By monitoring the temperature inside the vacuum brazing scenario, the heating power of the heating device is controlled. The preheating duration of the vacuum brazing scenario is controlled within the first preset duration to ensure that the temperature inside the vacuum brazing scenario is heated to the initial preheating temperature and maintained for the first preset duration. The first preset duration can be determined according to the temperature of the workpiece to be brazed, the duration obtained through experiments, the ambient temperature inside the welding container, etc. The determination conditions of the first preset duration are diverse and can be selected according to needs. The initial preheating temperature can be determined based on at least one factor such as the ambient temperature, the performance of the workpiece to be brazed at different temperatures, the heating power of the heating device, and the energy consumption of the vacuum brazing equipment.

[0103] In step 111, ensure that the temperature of the vacuum brazing scenario can reach the initial preheating temperature and be maintained for the first preset duration. When it is determined that the first preset duration is reached, step 111 ends and step 112 can be carried out.

[0104] In step 112, the workpiece to be brazed is controlled to be preheated to the preheating temperature and maintained for the second preset duration. The workpiece to be brazed is preheated to the initial preheating temperature (or slightly lower than the initial preheating temperature) in step 111. Therefore, within the second preset duration, the workpiece to be brazed is heated from the initial preheating temperature (or slightly lower than the initial preheating temperature) to the preheating temperature, and the workpiece to be brazed is heated in a stepwise manner. Both the initial preheating temperature and the preheating temperature are not limited to temperature point values and can be temperature ranges. For example, the initial preheating temperature is greater than or equal to 420°C and less than or equal to 500°C, and the preheating temperature is greater than or equal to 530°C and less than or equal to 570°C. The preheating temperature is greater than the initial preheating temperature, which can be understood as the minimum value of the preheating temperature is greater than the maximum value of the initial preheating temperature, ensuring that step 112 represents a temperature increase compared to step 111. The first preset duration is greater than or equal to 20 minutes and less than or equal to 30 minutes, and the second preset duration is greater than or equal to 20 minutes and less than or equal to 30 minutes. The first preset duration and the second preset duration are similar.

[0105] It should be noted that the preheating process is at least divided into two levels of step 111 and step 112, and can also be preheated in more levels such as three levels or four levels. For example, adding one or more levels of preheating between step 111 and step 112 can be adjusted flexibly.

[0106] Two - stage preheating is carried out using the above - mentioned step 111 and step 112. In step 111, that is, during the initial preheating process, monitor the ambient temperature of the vacuum brazing scenario. The heating accuracy can be reduced, and it is only necessary to ensure that the ambient temperature basically reaches the set temperature range. The requirements for the temperature - detecting sensor and the temperature - control program are both reduced. At this time, a first temperature sensor is configured in the vacuum brazing scenario, and the first temperature sensor is used to detect the ambient temperature. In step 112, that is, during the secondary preheating process, monitor the temperature of the workpiece to be welded to ensure that the workpiece to be welded is accurately heated to the preheating temperature, avoid too high a preheating temperature from affecting the brazing performance, and also avoid too low a preheating temperature from affecting the duration of the brazing step and ensure the welding efficiency. Among them, in step 112, the workpiece to be welded is provided with a second temperature sensor and a third temperature sensor. The second temperature sensor is used to detect the outer - wall temperature of the workpiece to be welded, and the third temperature sensor is used to detect the inner - wall temperature of the workpiece to be welded to fully detect the temperature of the workpiece to be welded.

[0107] It should also be noted that in step 110, that is, during the preheating process, the method of monitoring the temperature is not limited to the above - mentioned way. The temperature of the workpiece to be welded can be monitored in each stage of preheating to accurately control the temperature of the workpiece to be welded. Or, the ambient temperature of the vacuum brazing scenario can be monitored in each stage of preheating, or the temperature of the workpiece to be welded and the ambient temperature of the vacuum brazing scenario can be monitored alternately. If a preheating method with three or more stages is adopted during the preheating process, the temperature of the workpiece to be welded should be collected at least in the last stage of preheating to ensure the accuracy of the preheating temperature.

[0108] In step 110, the vacuum degree in the vacuum brazing scenario can be set as needed.

[0109] After determining that the second preset duration is reached, it is determined that step 112 is completed, and step 120 can be carried out for the brazing process.

[0110] When the workpiece to be welded is a cold - plate heat exchanger made of aluminum alloy, and the workpiece to be welded includes a flow - channel plate and a cover plate, the temperature parameters and duration parameters in the above - mentioned step 110 and step 120 can refer to the following content:

[0111] It can be understood that the brazing temperature is greater than or equal to 580 °C and less than or equal to 595 °C, and the third preheating duration is maintained at the brazing temperature. The third preset duration is greater than or equal to 5 minutes and less than or equal to 30 minutes. The third preset duration is the duration that can ensure the completion of welding by the filler metal. The third preset duration can also be between 5 minutes and 20 minutes, and the third preset duration is related to the welding duration.

[0112] It can also be understood that the initial preheating temperature is greater than or equal to 420 °C and less than or equal to 500 °C, and the first preheating duration is maintained at the initial preheating temperature. The first preset duration is greater than or equal to 20 minutes and less than or equal to 30 minutes.

[0113] It can also be understood that the preheating temperature is greater than or equal to 530 °C and less than or equal to 570 °C, and the second preset duration is maintained at the preheating temperature, and the second preset duration is greater than or equal to 20 minutes and less than or equal to 30 minutes.

[0114] The above content describes the soldering steps. After the soldering step lasts for the third preset duration, the workpiece to be soldered is cooled in stages and then taken out of the welding container after the staged cooling.

[0115] In step 130, in the step of controlling the workpiece to be soldered and the filler metal to cool down from the soldering temperature to the cooling temperature and then controlling the workpiece to be soldered to be removed from the vacuum soldering scenario, it includes:

[0116] Step 131, controlling the workpiece to be soldered to cool down to the third temperature, where the third temperature is less than the soldering temperature and greater than the solidus temperature of the filler metal;

[0117] After the soldering step is completed, the workpiece to be soldered is cooled down so that the workpiece to be soldered cools down to the third temperature. The temperature difference between the third temperature and the soldering temperature is within a set range. The set range is less than 100 °C, and the set range can also be less than 50 °C. That is, the cooling range of the workpiece to be soldered is less than 100 °C (or 50 °C). For example, it cools down to between 571 °C and 585 °C (the third temperature may overlap with the soldering temperature), and the temperature drops by 10 °C relative to the soldering process, ensuring the workpiece to be soldered cools down smoothly. The third temperature is higher than the solidus temperature of the filler metal. At this time, the filler metal is in a solid-liquid mixed state, and the filler metal is maintained at the third temperature for the fourth preset duration, which helps to stabilize the welding performance of the filler metal.

[0118] The smaller the temperature difference between the third temperature and the soldering temperature, the more conducive it is to stabilizing the performance of the workpiece to be soldered. However, the third temperature also needs to meet the cooling requirements. Therefore, the third temperature is combined and matched with the fourth preset duration.

[0119] The workpiece to be soldered is cooled for the fourth preset duration, and the fourth preset duration can be between 15 minutes and 30 minutes.

[0120] Step 132, controlling the workpiece to be soldered to cool down to the cooling temperature and controlling the workpiece to be soldered to be removed from the welding container. The cooling temperature is lower than the third temperature.

[0121] After step 131 is executed, step 132 is executed. In step 132, the workpiece to be soldered can be cooled down. In step 130, the workpiece to be soldered is cooled down in a vacuum environment.

[0122] During the process of the workpiece to be welded cooling down from the third temperature to the cooling temperature, it can be reduced from the third temperature to the fourth temperature and then to the cooling temperature. The value of the fourth temperature is between the third temperature and the cooling temperature. The cooling process is divided into multiple stages to facilitate the control of the cooling efficiency and duration to ensure the quality of the workpiece to be welded. Currently, in the cooling step, it is not limited to three-stage cooling, but can also be four-stage cooling, five-stage cooling, etc.

[0123] In step 132, in the step of controlling the workpiece to be welded to cool down to the cooling temperature, it further includes:

[0124] Control the workpiece to be welded to cool to the cooling temperature.

[0125] Cooling down the workpiece to be welded under vacuum conditions can achieve slow cooling and avoid the influence of ambient air on the weld effect. Of course, in step 132, natural cooling can be used, or external cold sources can be used to assist cooling, such as cooling through cooling pipelines.

[0126] In the case of a cold plate heat exchanger with the workpiece to be welded made of aluminum alloy, the workpiece to be welded includes a flow channel plate and a cover plate. The temperature parameters and duration parameters in step 130 above can refer to the following content:

[0127] It can also be understood that the third temperature is greater than or equal to 571 °C and less than or equal to 585 °C, and is maintained at the third temperature for a fourth preset duration, and the fourth preset duration is greater than or equal to 15 minutes and less than or equal to 30 minutes.

[0128] It can also be understood that the fourth temperature is greater than or equal to 400 °C and less than or equal to 430 °C.

[0129] It can also be understood that the cooling temperature is greater than or equal to 250 °C and less than or equal to 300 °C.

[0130] At least one of the steps adopts the above temperature and preset duration, or all steps can correspond to the above temperature and preset duration one by one. During the process from step 110 to step 130, the workpiece to be welded is clamped and fixed by a welding fixture to prevent the workpiece to be welded from deforming and ensure the structural stability of the workpiece to be welded.

[0131] It can be understood that in step 110, in the step of controlling the workpiece to be welded and the filler metal to be preheated to the preheating temperature in a vacuum brazing scenario, it further includes:

[0132] Control the vacuum degree in the vacuum brazing scenario to the first set vacuum degree;

[0133] The vacuum degree in the preheating stage can be kept consistent to prepare for the brazing stage.

[0134] In step 120, in the step of controlling the workpiece to be welded to be heated to the brazing temperature and performing brazing at the brazing temperature, it further includes:

[0135] Controlling the vacuum degree in the vacuum brazing scenario to be the second set vacuum degree,

[0136] wherein, the second set vacuum degree is less than the first set vacuum degree.

[0137] Among them, the first set vacuum degree can be greater than 10 -2 Pa, and the second set vacuum degree is greater than 10 -3 Pa. Step 110 is the preheating stage, and step 120 is the brazing stage. The vacuum degree in the brazing stage is higher than that in the preheating stage to ensure the brazing effect.

[0138] In the aluminum alloy vacuum brazing method according to the embodiment of the present invention, the vacuum brazing scenario can be surrounded by a vacuum furnace, and the workpiece to be welded can be an aluminum alloy cold plate. During the process from step 110 to step 130, the vacuum degree in the vacuum brazing scenario can be set as needed. For example, in step 110, the first set vacuum degree of the vacuum brazing scenario is higher than 10 -2 Pa, and in step 120, the second set vacuum degree of the welding container is higher than 10 -3 Pa. Under the condition of high vacuum degree, heating is carried out to heat the base material and the filler metal of the workpiece to be welded to the melting temperature of the filler metal; in step 130, the welding container can be maintained at the second set vacuum degree or the first set vacuum degree.

[0139] When the workpiece to be welded is a cold plate heat exchanger or a cold plate assembly, including an aluminum alloy plate structure, a dense aluminum oxide film Al2O3 on the aluminum alloy surface, under high temperature and high vacuum conditions, it reacts with an active agent (such as magnesium, etc.) and penetrates into the oxide film, removing and destroying the surface oxide film, enabling the molten filler metal to wet the base material, filling the welding gap, and undergoing a metallurgical reaction with the base material. After the workpiece to be welded cools, a firm brazed joint is formed. During the vacuum brazing process, there is no need to add an aluminum brazing flux (such as KAlF4), which can solve problems such as flux residue inside the workpiece to be welded and low brazing qualification rate, and realize the brazing connection between the cover plate and the flow channel plate of the cold plate heat exchanger.

[0140] When the cover plate and the flow channel plate of the cold plate heat exchanger or the cold plate assembly are made of 6063 or 6061 aluminum alloy, the temperature difference between the solid-liquid phase transition temperature of 6063 or 6061 and the melting point of the 4004 or 4104 filler metal is relatively large, which can solve problems such as difficult brazing of 6061 or 6063 aluminum alloy and the risk of overheating and overburning. Combined with the high-precision heating of the vacuum furnace, the heating temperature and time can be accurately controlled to ensure that the brazing heating of the 6-series aluminum alloy plate and the filler metal meet the quality requirements. The 4004 or 4104 filler metal adopts a double-metal composite plate of a core plate + double-sided filler metal plates, which can be automatically added to the brazing weld.

[0141] Compared with the method of brazing using a nitrogen continuous protection brazing furnace, there is a problem of relatively large fluctuations in the heating temperature. In the vacuum brazing method of the present invention, the temperature control accuracy inside the welding container can be within ±2°C, the heating temperature uniformity is high, and the heating temperature of the workpiece to be welded can be accurately controlled, avoiding defects such as overheating and corrosion of the base material of the workpiece to be welded.

[0142] When aluminum alloy is brazed using the vacuum brazing method of the embodiment of the present invention, the surface oxidation of the aluminum alloy is removed by the action of a metal activator (such as Mg, etc.). The specific mechanism is shown in the following reaction formulas:

[0143] Mg + 1 / 2O2 → MgO (1)

[0144] Mg + H2O → MgO + H2O (2)

[0145] Mg + 1 / 3Al2O3 → MgO + 2 / 3Al (3)

[0146] Based on the foregoing, the vacuum brazing method of the embodiment of the present invention can achieve brazing connection without adding aluminum brazing flux. The surface magnesium element in the 6061 or 6063 aluminum cold plate will increase the brazing activity, which is beneficial to the removal of the oxide film. After vacuum brazing, there is no brazing flux residue inside the aluminum cold plate, achieving a high cleanliness of the internal flow channel, and problems such as an increase in the resistivity and internal flow resistance of the cold plate caused by brazing flux residue can be eliminated. The vacuum brazing method of the embodiment of the present invention also has the advantages of high brazing qualification rate, good process consistency, high weld strength, and bright and dense base material and weld after welding, and can solve problems such as brazing flux residue, low heating uniformity, and low brazing qualification rate existing in nitrogen-protected aluminum brazing.

[0147] Combining the above content, the vacuum brazing method of the embodiment of the present invention is described for welding a cold plate assembly.

[0148] The brazing temperature range is set according to the temperature close to the liquidus temperature of the filler metal, that is, the brazing temperature is determined to be close to the liquidus temperature of the filler metal. For example, the brazing temperature range is selected as 580°C to 595°C;

[0149] In steps 110 to 130, a brazing heating curve is set using the idea of multi-gradient and slow heating to ensure uniform temperature of the cold plate assembly;

[0150] The brazing temperature is divided into four sections: the first section (initial preheating temperature) of 420°C to 500°C, the second section (preheating temperature) of 530°C to 570°C, the third section (brazing temperature) of 580°C to 595°C, and the fourth section (third temperature) of 571°C to 585°C;

[0151] After the cold plate assembly enters the welding container, the vacuum degree inside the welding container is pumped to 10 -2After reaching Pa, raise the furnace temperature to the first stage (initial preheating temperature) of 420°C to 500°C, with a heating temperature accuracy of ±2°C, keep warm for the first preset duration of 20 min to 30 min, and maintain the vacuum degree in the welding container at 10 -2 Pa;

[0152] Raise the temperature of the cold plate assembly to the second stage (preheating temperature) of 530°C to 570°C, with a heating temperature accuracy of ±2°C, keep warm for the second preset duration of 20 min to 30 min, and maintain the vacuum degree in the welding container at 10 -2 Pa;

[0153] Raise the temperature of the workpiece to be welded to the third stage (brazing temperature) of 580°C to 595°C, with a heating temperature accuracy of ±2°C, keep warm for the third preset duration of 5 min to 20 min, and evacuate the vacuum degree in the welding container to 10 -3 Pa;

[0154] Lower the temperature of the workpiece to be welded to the fourth stage (third temperature) of 571°C to 585°C, keep warm for the fourth preset duration of 15 min to 30 min, with a heating temperature accuracy of ±2°C, make the cold plate assembly heated evenly, and melt the brazing material in each part. The vacuum degree in the welding container can be maintained at 10 -3 Pa;

[0155] The cold plate assembly cools naturally in the furnace, and the furnace remains vacuum; after the cold plate assembly with the welding fixture cools naturally to the (cooling temperature) of 250°C to 300°C under vacuum conditions in the welding container, the cold plate assembly is removed from the welding container.

[0156] Among them, the vacuum degree in the preheating stage (in step 110) is higher than 10 -2 Pa; the vacuum degree in the brazing stage (in step 120) is higher than 10 -3 Pa. The vacuum degree in step 130 can be selected as needed to ensure the quality of vacuum brazing; a high vacuum degree can prevent oxidation of the aluminum base material and the brazing material during the heating process, and can ensure the full removal of the oxide film on the surface of the aluminum base material and the brazing material, facilitating the rapid flow of the molten brazing material to fill the weld seam and ensuring the quality of brazing.

[0157] According to the aforementioned vacuum brazing method of the present invention, problems such as the base material overheating caused by the close temperatures of the aluminum plate base material and the brazing material, the heating uniformity of brazing, the oxidation of the workpiece, and the film removal effect can be solved, thereby ensuring the quality of vacuum brazing.

[0158] Set the soldering temperature range according to a temperature close to the liquidus temperature of the filler metal, that is, select the soldering temperature range from 580 °C to 595 °C, so that the difference between the soldering temperature and the starting melting temperature of the aluminum base material (taking the solidus of the 6061 base material) is widened to 50 °C to 65 °C. While ensuring complete melting and filling of the filler metal, it can also ensure that the aluminum base material does not overheat or burn, preventing soldering defects such as corrosion and pitting (see the solid-liquid phase lines and measured temperatures of the cold plate base material and the filler metal in Figures 6 to 8 ).

[0159] In the related technologies of the soldering process, the soldering temperatures of 6061 and 6063 are usually around 600 °C. Considering factors such as large fluctuations in the soldering heating temperature of the welding container (temperature fluctuations within ±10 °C), the actual soldering temperature is closer to the melting point of the base material, and problems such as overheating and corrosion of the workpiece are likely to occur. However, in the vacuum soldering method of the embodiment of the present invention, the heating temperature of the welding container has high precision (the temperature uniformity in the furnace can reach ±2 °C), high uniformity, and the soldering heating curve is set using a multi-gradient (at least 4 segments) and slow heating concept for the temperature, which can ensure uniform internal and external temperatures of the cold plate assembly, make the melted filler metal flow and fill evenly in the gap, and ensure the soldering quality.

[0160] After step 130, perform heat treatment on the workpiece to be welded to improve the performance of the workpiece to be welded, which can make up for the performance degradation of the workpiece to be welded after high-temperature heating.

[0161] It can be understood that after step 130, after the step of controlling the workpiece to be welded to move out of the vacuum soldering scenario, it further includes:

[0162] Step 140, control the workpiece to be welded to be heated to a fifth temperature for solution treatment, and then control the workpiece to be welded to cool down to the ambient temperature.

[0163] Step 140 can be understood as performing heat treatment on the workpiece to be welded through solution treatment to ensure the performance of the workpiece to be welded. After the workpiece to be welded reaches the fifth temperature, maintain the fifth preset duration to ensure the duration of the solution treatment.

[0164] It can be understood that the fifth temperature is greater than or equal to 510 °C and less than or equal to 560 °C. The fifth temperature is close to and less than the solidus temperature of the filler metal to avoid affecting the quality of the weld seam.

[0165] It can also be understood that the fifth preset duration is 5 ± 2 hours to ensure the solution effect. The fifth preset duration can be adjusted according to conditions such as the size, material, and performance requirements of the workpiece to be welded. It can also be understood that in step 140, that is, in the step of controlling the workpiece to be welded to be heated to a fifth temperature for solution treatment and then controlling the workpiece to be welded to cool down to the ambient temperature, it includes:

[0166] Control the water-cooled temperature reduction of the workpiece to be welded to the ambient temperature. The initial water temperature for water cooling is the sixth temperature, where the sixth temperature is greater than or equal to 35°C and less than or equal to 40°C. The workpiece to be welded is cooled to the ambient temperature through water cooling, and the cooling efficiency of water cooling is high, which helps to ensure the welding quality of the workpiece to be welded. Of course, it can also be cooled to the ambient temperature through air cooling, and the sixth temperature is the temperature of the cold air. For example, the workpiece to be welded is placed in the air with an initial temperature of 35°C to 40°C and cooled to room temperature (the ambient temperature can be understood as room temperature). In the solution treatment step, try to shorten the cooling time, which helps to improve the welding quality.

[0167] For cold plate heat exchangers made of 6063 or 6061 materials, during the brazing heating process, there will be a decrease in performance (such as tensile strength and hardness), and it is difficult to ensure the system sealing strength. After welding, the solution treatment process is used to improve the component performance, which can make up for the performance degradation of the flow channel plate and cover plate of the cold plate heat exchanger after high-temperature heating. Among them, after welding, the cold plate heat exchanger is heat-treated according to the T5 or T6 heat treatment system.

[0168] Among them, during the solution treatment process, the workpiece to be welded is heat-treated with a welding fixture to maximize the prevention of deformation of the workpiece to be welded.

[0169] Solution treatment is a way of heat treatment, and heat treatment can also be carried out for aging treatment. Solution treatment and aging treatment can be selected alternatively, or, after solution treatment, aging treatment is carried out.

[0170] It can be understood that after step 140, after the step of controlling the cooling temperature reduction of the workpiece to be welded to the ambient temperature, it also includes:

[0171] Step 150, control the workpiece to be welded to be heated to the seventh temperature for aging treatment, and control the workpiece to be welded to be cooled to the ambient temperature;

[0172] Among them, the seventh temperature is less than the fifth temperature.

[0173] The workpiece to be welded can be subjected to artificial aging treatment. After the workpiece to be welded is heated to the seventh temperature, aging treatment is maintained for the sixth preset duration.

[0174] It can be understood that the seventh temperature is greater than or equal to 140°C and less than or equal to 200°C, the sixth preset duration is 8 ± 2 hours, and the workpiece to be welded can be naturally cooled to the ambient temperature in the air, or it can also be cooled to the ambient temperature through water cooling.

[0175] During the aging treatment process, the workpiece to be welded is heat-treated in a clamped state by a welding fixture to maximize the prevention of deformation of the workpiece to be welded.

[0176] When the vacuum welding method of the embodiments of the present invention is combined with solution treatment and aging treatment, the properties such as the strength and hardness of the base material and the weld seam of the workpiece to be welded can be improved. For example, the hardness, tensile strength and pressure resistance strength of the base material and the weld seam can be greatly improved, thereby meeting the system pressure resistance requirements, and the problem that the properties of the base material and the weld seam decrease due to long-term heating in the welding container can be solved.

[0177] When the cold plate assembly is made of 6063 or 6061 material, due to the performance degradation (such as tensile strength and hardness) of 6063 or 6061 material during the brazing heating process, it is difficult to ensure the system sealing strength. The main reason is that after the cold plate is gradually heated at high temperature for a long time during the brazing process, the sizes of the strengthening phases Mg and Cu in the aluminum base material significantly grow, and precipitate and deposit on the existing CuAl2 or Mg2Si, resulting in local segregation and a decrease in the strength and hardness of the 6063 base material. From Figure 9 and Figure 10 It can be seen from the comparison that the strengthening phases (the black parts in the figure) of the 6063 base material after brazing are significantly aggregated and grown, and the distribution is uneven. After the solution + aging treatment process is adopted after brazing, the sizes of the aggregated and grown strengthening phases in the welded state can be made to become small again and the distribution can be homogenized (see Figure 11 ), thereby improving the strength (such as tensile strength, hardness and sealing strength) of the cold plate base material and the weld seam.

[0178] Taking the 6063 cold plate assembly as an example, comparative verification tests were carried out on the tensile strength, hardness and burst pressure of the cold plate assembly in different states (before brazing, without solution + aging after brazing, and with solution + aging after welding), and the following results were obtained:

[0179] The influence of solution treatment and aging treatment on the tensile strength: The measured average tensile strength before brazing was 235 MPa; the measured average tensile strength after welding without solution treatment + aging treatment was 156 MPa, which was 33.6% lower than that before brazing; the measured average tensile strength after welding with solution treatment + aging treatment was 216 MPa, the tensile strength was 8% lower than that before welding, and the tensile strength after solution + aging after welding increased by 25.6%; After solution and aging treatment are carried out on the cold plate assembly after vacuum brazing, the tensile strength of the aluminum base material can be greatly improved.

[0180] The influence of solution treatment and aging treatment on the hardness: The average hardness value before brazing was 192.4 HV; the average hardness value after welding without solution treatment and aging treatment was 77 HV, which was 60% lower than that before welding; the average hardness value after welding with solution treatment and aging treatment was 150.6 HV, which was 16% lower than that before welding, and the hardness after solution treatment + aging treatment after welding increased by about 34%; The solution treatment + aging treatment can greatly improve the hardness of the 6063 aluminum base material after welding.

[0181] The influence of solution treatment and aging treatment on the burst pressure. The average burst pressure of the workpiece without solution treatment and aging treatment after welding is 8.7 Mpa, and the average burst pressure of the workpiece with solution treatment and aging treatment after welding is 12.2 Mpa. By using solution + aging treatment, the burst pressure can be increased by 40%. After solution treatment and aging treatment of 6063 workpieces after welding, the pressure resistance strength of the aluminum base material and the weld can be greatly improved.

[0182] Based on the above, after solution treatment and aging treatment of 6063 cold plates after welding, the hardness, tensile strength and pressure resistance strength of the aluminum base material and the weld can be greatly improved, so as to meet the system pressure resistance requirements. The normal working pressure of the welded workpiece is usually > 2.8 MPa, the pressure resistance is > 5 MPa, and the burst pressure is > 10 Mpa.

[0183] The above content describes the vacuum brazing method of the embodiment of the present invention. Next, the fixing method of the workpiece to be welded during the vacuum brazing process will be described.

[0184] It can be understood that before step 110, before the step of controlling the workpiece to be welded and feeding it into the vacuum brazing scenario, the workpiece to be welded is clamped by a welding fixture;

[0185] And / or, in at least one of the solution treatment and the aging treatment, the workpiece to be welded is clamped by a welding fixture.

[0186] In the above steps 110 to 150, the welding fixture can be maintained in the state of clamping the workpiece to be welded to ensure the accurate positioning of the workpiece to be welded and also ensure the performance maintenance of the workpiece to be welded after welding.

[0187] Reference Figures 12 to 14As shown in the figure, the welding fixture includes a tooling base plate 20, a tooling cover plate 30, a limiting plate 60 for limiting the cold plate assembly 10, a tooling pressing block 50, a support rod 40, and an elastic pressing assembly 70. The workpiece to be welded (the cold plate assembly 10 is schematically shown in the figure) is arranged between the tooling base plate 20 and the tooling cover plate 30. The tooling cover plate 30 and the tooling base plate 20 are fixedly connected through the support rod 40 and the tooling pressing block 50. The tooling pressing block 50 is fixed at the end of the support rod 40 so that the end of the support rod 40 is pressed and fixed to the tooling cover plate 30. The workpiece to be welded is limited between the limiting plate 60 and the elastic pressing assembly 70. The limiting plate 60 abuts against the tooling base plate 20, and the elastic pressing assembly 70 abuts against the tooling cover plate 30. The elastic pressing assembly 70 presses the workpiece to be welded through an elastic acting force. Both the tooling base plate 20 and the tooling cover plate 30 are provided with through holes, and the limiting plate 60 is also provided with through holes to ensure the heat exchange performance of the workpiece to be welded. Through holes are opened on the tooling base plate 20, the tooling cover plate 30, and the limiting plate 60 at a certain interval (the positions of the through holes are determined according to the structural characteristics of the cold plate assembly 10), so that the heating heat of the welding container can directly radiate to the surface of the cold plate assembly, ensuring the direct heat radiation of the brazing area and the surface of the workpiece to be welded, which can ensure the rapid temperature rise and temperature uniformity of each part of the cold plate assembly 10, improve the heating speed and temperature uniformity, and ensure the brazing quality. The welding fixture can be made of stainless steel, with guaranteed material stiffness, which can overcome the deformation during processing and brazing heating, and can ensure the strength.

[0188] The elastic pressing assembly 70 is provided with a high-temperature spring, which forms a pre-tightening force on the parts of the cold plate assembly 10, ensuring that the parts of the workpiece to be welded can be closely attached together during the whole brazing process (including heating up and cooling, etc.), preventing the deformation of the base material or the cracking of the weld seam, etc.

[0189] Adopting the vacuum brazing method of the embodiment of the present invention, through the high-precision flexible positioning by the welding fixture, the problems of the complex structure of the cold plate assembly, difficult accurate positioning and pressing, and the large brazing positioning difficulty and poor positioning consistency of the cold plate assembly can be solved. The defects of inconsistent brazing gaps and local virtual soldering of the workpiece to be welded can be avoided. The welding fixture has a compact structure, a simple shape, and is convenient for loading and unloading. The precision of the welding fixture meets the product positioning requirements, which can ensure the positioning consistency of the workpiece to be welded and the brazing heating uniformity, and ensure the brazing quality.

[0190] An embodiment of the second aspect of the present invention provides a vacuum brazing device, including:

[0191] A welding container, forming a vacuum brazing scenario;

[0192] A heating device, used for heating the welding container and the workpiece to be welded;

[0193] A temperature detection component, used for detecting the temperature inside the welding container and the workpiece to be welded;

[0194] A controller is communicatively connected to a heating device and a temperature sensor, and is configured to execute the vacuum brazing method of any one of the above.

[0195] The welding container is used to accommodate the workpiece to be welded and the filler metal as described above. The heating device is used to provide the heat required in the above steps 110 to 130. The temperature detection component is used to detect the temperature in the above steps to adjust the working state of the heating device. The controller is communicatively connected to the heating device and the temperature detection component. The controller sends a signal to the heating device to start or stop heating, and can also control the heating power of the heating device. The temperature detected by the temperature detection component is transmitted to the controller so that the controller controls the heating device according to the temperature detected by the temperature detection component.

[0196] The vacuum brazing equipment is a device that can be used to execute the above aluminum alloy vacuum brazing method. The type and model of the vacuum brazing equipment are not limited and can be selected according to needs. In the case that the above aluminum alloy vacuum brazing method has the above beneficial effects, the vacuum brazing equipment for executing the above aluminum alloy vacuum brazing method also has the above beneficial effects. For details, reference can be made to the above content and will not be elaborated here.

[0197] The temperature detection component includes a first temperature sensor, a second temperature sensor, and a third temperature sensor. The first temperature sensor is disposed inside the welding container and is used to detect the ambient temperature of the vacuum brazing scenario. The first temperature sensor can be connected to the welding container. The second temperature sensor and the third temperature sensor are also disposed inside the welding container. The second temperature sensor is used to detect the outer wall temperature of the workpiece to be welded, and the third temperature sensor is used to detect the inner wall temperature of the workpiece to be welded. The second temperature sensor and the third temperature sensor can both be connected to the workpiece to be welded. The second temperature sensor can also be connected inside the welding container and face the outer wall surface of the workpiece to be welded. The third temperature sensor needs to be disposed inside the workpiece to be welded for accurate temperature measurement.

[0198] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0199] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the vacuum brazing method described in each embodiment or some parts of the embodiments.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for vacuum brazing aluminum alloy, characterized in that, Including: Controlling the workpieces to be welded and the filler metal to be preheated step by step to a preheating temperature in a vacuum brazing scenario; Controlling the workpieces to be welded and the filler metal to be heated from the preheating temperature to a brazing temperature for brazing at the brazing temperature, where the temperature difference between the brazing temperature and the solidus temperature of the workpieces to be welded is greater than 30°C; Controlling the workpieces to be welded to be cooled step by step from the brazing temperature to a cooling temperature, and then controlling the workpieces to be welded to be removed from the vacuum brazing scenario.

2. The method for vacuum brazing aluminum alloy according to claim 1, characterized in that, After the step of controlling the workpieces to be welded to be removed from the vacuum brazing scenario, it further includes: Controlling the workpieces to be welded to be heated to a fifth temperature for solution treatment, and then controlling the workpieces to be welded to be cooled down to the ambient temperature.

3. The method for vacuum brazing aluminum alloy according to claim 2, characterized in that, After the step of controlling the workpieces to be welded to be cooled down to the ambient temperature, it further includes: Controlling the workpieces to be welded to be heated to a seventh temperature for aging treatment, and then controlling the workpieces to be welded to be cooled down to the ambient temperature; wherein, the seventh temperature is less than the fifth temperature.

4. The method for vacuum brazing aluminum alloy according to claim 3, characterized in that, Before the step of controlling the workpieces to be welded and the filler metal to be preheated step by step in the vacuum brazing scenario, the workpieces to be welded are clamped by a welding fixture; and / or, in at least one of the solution treatment and the aging treatment, the workpieces to be welded are clamped by the welding fixture.

5. The method for vacuum brazing aluminum alloy according to claim 3, characterized in that, The fifth temperature is greater than or equal to 510°C and less than or equal to 560°C, and is maintained for 5 ± 2 hours; and / or, the seventh temperature is greater than or equal to 140°C and less than or equal to 200°C, and is maintained for 8 ± 2 hours.

6. The method for vacuum brazing aluminum alloy according to claim 1, characterized in that, The temperature difference between the brazing temperature and the solidus temperature of the workpieces to be welded is greater than or equal to 50°C and less than or equal to 65°C.

7. The method for vacuum brazing aluminum alloy according to claim 1, characterized in that, In the step of controlling the workpieces to be welded and the filler metal to be preheated step by step to the preheating temperature in the vacuum brazing scenario, it includes: Controlling the ambient temperature of the vacuum brazing scenario to be preheated to an initial preheating temperature, and then controlling the workpieces to be welded and the filler metal to be preheated to the preheating temperature.

8. The method for vacuum brazing aluminum alloy according to claim 7, characterized in that, The brazing temperature is greater than or equal to 580°C and less than or equal to 595°C, and is maintained for a duration greater than or equal to 5 minutes and less than or equal to 30 minutes; and / or, the initial preheating temperature is greater than or equal to 420°C and less than or equal to 500°C, and is maintained for a duration greater than or equal to 20 minutes and less than or equal to 30 minutes; and / or, the preheating temperature is greater than or equal to 530°C and less than or equal to 570°C, and is maintained for a duration greater than or equal to 20 minutes and less than or equal to 30 minutes.

9. The method for vacuum brazing aluminum alloy according to any one of claims 1 to 8, characterized in that, In the step of controlling the workpieces to be welded to be cooled step by step from the brazing temperature to the cooling temperature, it further includes: Controlling the workpieces to be welded to be cooled down to a third temperature in the vacuum brazing scenario, and then cooled down to the cooling temperature; wherein, the temperature difference between the third temperature and the brazing temperature is less than or equal to 50°C, and it is cooled from the third temperature to the cooling temperature.

10. The method for vacuum brazing aluminum alloy according to claim 9, characterized in that, The third temperature is greater than or equal to 571°C and less than or equal to 585°C, and is maintained for a duration greater than or equal to 15 minutes and less than or equal to 30 minutes; and / or, the cooling temperature is greater than or equal to 250°C and less than or equal to 300°C.

11. The method for vacuum brazing aluminum alloy according to any one of claims 1 to 8, characterized in that, In the step of controlling the workpieces to be welded and the filler metal to be preheated step by step to the preheating temperature in the vacuum brazing scenario, it further includes: Controlling the vacuum degree in the vacuum brazing scenario to be a first set vacuum degree; In the step of controlling the workpiece to be welded and the filler metal to be heated from the preheating temperature to the brazing temperature for brazing at the brazing temperature, it further includes: Controlling the vacuum degree in the vacuum brazing scenario to be a second set vacuum degree, wherein the second set vacuum degree is less than the first set vacuum degree.

12. The aluminum alloy vacuum brazing method according to claim 11, wherein, The first set vacuum degree is greater than 10 -2 Pa, and the second set vacuum degree is greater than 10 -3 Pa.

13. A vacuum brazing device, wherein, It includes: A welding container, forming the vacuum brazing scenario; A heating device for heating the welding container and the workpiece to be welded; A temperature detection component for detecting the temperature inside the welding container and the workpiece to be welded; A controller for executing the aluminum alloy vacuum brazing method according to any one of claims 1 to 12.

14. The vacuum brazing device according to claim 13, wherein, The temperature detection component includes: A first temperature sensor, arranged inside the welding container, for detecting the ambient temperature of the vacuum brazing scenario; A second temperature sensor and a third temperature sensor, arranged inside the welding container, the second temperature sensor for detecting the outer wall temperature of the workpiece to be welded, and the third temperature sensor for detecting the inner wall temperature of the workpiece to be welded.

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