CN116638167A - Method for improving brazing qualification rate of heat exchanger - Google Patents
Method for improving brazing qualification rate of heat exchanger Download PDFInfo
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- CN116638167A CN116638167A CN202310271132.7A CN202310271132A CN116638167A CN 116638167 A CN116638167 A CN 116638167A CN 202310271132 A CN202310271132 A CN 202310271132A CN 116638167 A CN116638167 A CN 116638167A
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- 238000005219 brazing Methods 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000012797 qualification Methods 0.000 title claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 52
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 22
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000004140 cleaning Methods 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 13
- 239000002184 metal Substances 0.000 claims abstract description 13
- 238000007598 dipping method Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 12
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 8
- 229910000679 solder Inorganic materials 0.000 claims abstract description 8
- 239000012190 activator Substances 0.000 claims abstract description 7
- 239000012808 vapor phase Substances 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000001816 cooling Methods 0.000 claims description 21
- 239000000428 dust Substances 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- 238000004321 preservation Methods 0.000 claims description 6
- 238000009825 accumulation Methods 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 5
- 239000003973 paint Substances 0.000 claims description 5
- 238000010079 rubber tapping Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 230000001939 inductive effect Effects 0.000 claims description 4
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 4
- 230000000087 stabilizing effect Effects 0.000 claims description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 abstract description 3
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 230000003213 activating effect Effects 0.000 abstract description 2
- 239000003795 chemical substances by application Substances 0.000 abstract description 2
- 239000011777 magnesium Substances 0.000 description 18
- 229910000838 Al alloy Inorganic materials 0.000 description 7
- 239000000945 filler Substances 0.000 description 5
- 239000000956 alloy Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/008—Soldering within a furnace
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
- B23K1/203—Fluxing, i.e. applying flux onto surfaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
- B23K1/206—Cleaning
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
The application discloses a method for improving the brazing qualification rate of a heat exchanger, which comprises the following steps of hot dipping and cleaning heat exchanger parts needing vacuum brazing, then cold dipping and ultrasonic rinsing, finally vapor phase drying and cleaning, and putting the cleaned heat exchanger aluminum material into a vacuum brazing furnace, wherein the vacuum degree is 5 multiplied by 10 ‑ 3 And after Pa, heating and brazing are started, and a certain amount of Mg is added to be used as a metal activator. According to the method for improving the brazing qualification rate of the heat exchanger, heat exchanger parts needing vacuum brazing are subjected to hot dipping cleaning, then subjected to cold dipping ultrasonic rinsing, finally subjected to vapor phase drying cleaning, and added with a certain amount of Mg as a metal activating agent, and when brazing is carried out, aluminum expands rapidly to crack an oxide film; the volatilization of Mg damages the oxide film on the surface of the solder during heating; volatilized Mg and CO remaining in vacuum 2 、O 2 Reacts with water vapor to prevent the formation of alumina film, thereby obtaining good performanceWelding quality products.
Description
Technical Field
The application relates to the technical field of heat exchanger processing, in particular to a method for improving the brazing qualification rate of a heat exchanger.
Background
Aiming at the requirements of energy conservation and high efficiency of modern industry, high-efficiency and miniaturized heat exchange and reaction equipment is developed, and meanwhile, aiming at some special processes, a miniature chemical mechanical system with good controllability is developed. And miniaturization of the heat exchange device is a key for realizing a miniature chemical mechanical system. With the development of the enhanced heat transfer theory and the improvement of the machining technology, a plurality of novel efficient enhanced heat transfer surface structures are developed, and further, small heat exchange devices represented by plate-fin type, plate type and heat pipe heat exchangers are developed. The most common material in heat exchangers is aluminum alloy.
Vacuum brazing is the most common method of manufacturing stainless steel plate-fin heat exchangers. The brazing technology of the aluminum plate-fin heat exchanger is researched by students at home and abroad, and some achievements are achieved. However, the brazing process of the stainless steel plate-fin heat exchanger is not researched much, and factors influencing the brazing qualification rate are many, such as brazing temperature, brazing gap, heat preservation time, cooling mode and the like. When the aluminum alloy is vacuum brazed, the wetting and flowing of the liquid brazing filler metal are influenced by an oxide film on the surface of the product. In the vacuum brazing process, it is difficult to form a good quality brazed joint if the oxide film on the surface of the component is not removed effectively. In order to remove the oxide film and prevent the aluminum from forming the oxide film again in the vacuum brazing process, a small amount of magnesium is added into the brazing filler metal to serve as an activating agent, so that the breakage and dispersion of the oxide film on the surface of the part can be effectively promoted, and the wetting and spreading of the liquid brazing filler metal can be effectively promoted. Vacuum brazing of aluminum alloys is a complex process involving both physical and chemical changes. Since the linear expansion coefficient of the alumina film is only about one third of that of aluminum. According to calculations, after temperatures above 400 ℃, thermal stress is sufficient to locally crack the aluminum oxide film, exposing a clean aluminum surface. And magnesium in the solder begins to volatilize in large quantity above 550 ℃. Forming a magnesium-containing atmosphere in the vacuum brazing furnace heating chamber to protect the exposed aluminum surface from oxidation. On the other hand, the aluminum alloy surface is permeated through gaps on the aluminum oxide film to form alloy, the alloy is locally melted, and the oxide film is further tunneled.
Therefore, a method for improving the brazing qualification rate of the heat exchanger is needed, and the formation of intermetallic compounds in the brazing seam can be well controlled, so that a product with good welding quality is obtained.
Disclosure of Invention
(one) solving the technical problems
Aiming at the defects of the prior art, the application provides a method for improving the brazing qualification rate of the heat exchanger, which has the advantages of good welding quality and the like, and solves the problem of forming intermetallic compounds in a brazing seam.
(II) technical scheme
In order to achieve the above purpose, the present application provides the following technical solutions: a method for improving the brazing qualification rate of a heat exchanger, comprising the following steps:
s1: and (3) performing hot dip cleaning on the heat exchanger parts needing vacuum brazing, performing cold dip ultrasonic rinsing, performing vapor phase drying cleaning, and cooling and drying for later use.
S2: and placing the cleaned heat exchanger aluminum material into a vacuum brazing furnace, and clamping by using a clamp.
S3: heating from room temperature for 20 min to 360 ℃ or heating rate of 8-10 ℃/S, and preserving heat for 40-60 min. The temperature difference is not more than + -25 ℃ and the vacuum degree is less than 7.5-10 -3 The temperature is raised to 470 ℃ or a temperature raising rate of 6-8 ℃/S in 25 minutes. The temperature of the core body of the workpiece is kept for 60-100 minutes when the temperature is higher than 330 ℃, and the temperature difference is not more than +/-15 ℃. Vacuum degree less than 6.5 x 10 -3 Heating to 520 ℃ for 20 minutes, and preserving heat for 60 minutes when the core temperature of the workpiece is higher than 510 ℃ and the temperature difference is not more than +/-10 ℃ and the vacuum degree is less than 5.0 x 10 -3 。
S4: heating to 570 ℃ in 15 minutes, or preserving heat for 50 minutes at a heating rate of 15-20 ℃/S when the core temperature of the workpiece is higher than 560 ℃, wherein the temperature difference is not more than +/-5 ℃, heating to 620 ℃ in 10 minutes, or preserving heat for 20-50 minutes at a heating rate of 10-15 ℃/S when the core temperature of the workpiece is 598 ℃ -605 ℃, cooling to 603 ℃ in 10 minutes, and preserving heat for 10-30 minutes, wherein the temperature difference is not more than +/-2 ℃. Cooling to below 520 ℃ and discharging.
S5: vacuum degree reaches 5 multiplied by 10 -3 And after Pa, heating and brazing are started, and a certain amount of Mg is added to be used as a metal activator.
Preferably, the method comprises the steps of: and in the step S1, the workpiece basket is manually placed into the feeding and discharging device, the whole cleaning process is automatically completed by two workpiece moving carts, and finally the workpiece basket is lifted out.
Preferably, the specific step of ultrasonic cleaning in S1 is as follows: firstly, an operator sequentially puts workpieces to be cleaned into a tool basket, then puts the workpieces into a feeding trolley to push the workpieces to a feeding position, the workpieces are conveyed to a first station by a full-automatic manipulator to clean through the linkage of an inductive switch, the workpieces are put on a discharging trolley after being rinsed, bath washed and dried, and then the workpieces are taken out by the operator and transferred to a next procedure.
Preferably, in S5, al 2 O 3 The thermal expansion coefficient of the aluminum is only 1/3 of that of the aluminum, and the aluminum expands sharply, so that the oxide film is cracked; the volatilization of Mg damages the oxide film on the surface of the solder during heating; volatilized Mg and CO remaining in vacuum 2 、O 2 And water vapor.
Preferably, in the step S5, the workshop air does not contain weighing particles (dust and dust), and is not polluted by acid or other substances, steam, waterproof paint is painted on the four walls and the ceiling, and the cleaning is performed regularly, so that mechanical particles are prevented from falling into the device. The floor must be smooth and clean without cracks so as to avoid dust accumulation and maintain a certain degree of dryness and humidity.
Preferably, in the step S5, the vacuum degree, the heating rate, the stabilizing temperature and time, the brazing temperature, the brazing heat preservation time, the cooling rate and the tapping temperature of the brazing are required to be recorded.
(III) beneficial effects
Compared with the prior art, the application provides a method for improving the brazing qualification rate of the heat exchanger, which has the following beneficial effects:
1. according to the method for improving the brazing qualification rate of the heat exchanger, heat exchanger parts needing vacuum brazing are subjected to hot dipping cleaning, then subjected to cold dipping ultrasonic rinsing, finally subjected to vapor phase drying cleaning, and cooled and dried for later use, ultrasonic waves have high energy, when the ultrasonic waves are transmitted in a media liquid, the energy is transmitted to the media particles, and the media particles transmit the energy to the surfaces of the heat exchanger parts again to cause dirt dissociation and dispersion.
2. The method for improving the brazing qualification rate of the heat exchanger is realized by reaching 5 multiplied by 10 in vacuum degree -3 Heating and brazing after Pa, adding a certain amount of Mg as a metal activator, and rapidly expanding aluminum when brazing is performed, so that an oxide film is cracked; the volatilization of Mg damages the oxide film on the surface of the solder during heating; volatilized Mg and CO remaining in vacuum 2 、O 2 And water vapor, and prevent the formation of an alumina film, so that a product of good welding quality can be obtained.
Detailed Description
The technical solutions of the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Embodiment one:
a method for improving the brazing qualification rate of a heat exchanger, which is characterized by comprising the following steps:
s1: hot dipping and cleaning the heat exchanger parts needing vacuum brazing, then cold dipping and ultrasonic rinsing, and finally vapor phase drying and cleaning, and cooling and drying for later use;
the specific steps of ultrasonic cleaning are as follows: firstly, an operator sequentially puts workpieces to be cleaned into a tool basket, then puts the workpieces into a feeding trolley to push the workpieces to a feeding position, the workpieces are conveyed to a first station by a full-automatic manipulator to clean through the linkage of an inductive switch, the workpieces are put on a discharging trolley after being rinsed, bath washed and dried, and then the workpieces are taken out by the operator and transferred to a next procedure.
S2: placing the cleaned heat exchanger aluminum material into a vacuum brazing furnace, and clamping by using a clamp;
s3: heating from room temperature for 20 min to 360 ℃ or heating rate of 8-10 ℃/S, and preserving heat for 40-60 min. The temperature difference is not more than + -25 ℃ and the vacuum degree is less than 7.5-10 -3 The temperature is raised to 470 ℃ or a temperature raising rate of 6-8 ℃/S in 25 minutes. The temperature of the core body of the workpiece is kept for 60-100 minutes when the temperature is higher than 330 ℃, and the temperature difference is not more than +/-15 ℃. Vacuum degree less than 6.5 x 10 -3 Heating to 520 ℃ for 20 minutes, and preserving heat for 60 minutes when the core temperature of the workpiece is higher than 510 ℃ and the temperature difference is not more than +/-10 ℃ and the vacuum degree is less than 5.0 x 10 -3 ；
S4: heating to 570 ℃ in 15 minutes, or preserving heat for 50 minutes at a heating rate of 15-20 ℃/S when the core temperature of the workpiece is higher than 560 ℃, wherein the temperature difference is not more than +/-5 ℃, heating to 620 ℃ in 10 minutes, or preserving heat for 20-50 minutes at a heating rate of 10-15 ℃/S when the core temperature of the workpiece is 598 ℃ -605 ℃, cooling to 603 ℃ in 10 minutes, and preserving heat for 10-30 minutes, wherein the temperature difference is not more than +/-2 ℃. Cooling to below 520 ℃ and discharging;
s5: vacuum degree reaches 5 multiplied by 10 -3 After Pa, heating and brazing are started, a certain amount of Mg is added to serve as a metal activator, weighing particles (dust and dust) are not contained in workshop air, the workshop air cannot be polluted by acid or other substances, waterproof paint needs to be brushed on four walls and ceilings, and mechanical particles are prevented from falling into the device. The ground must be smooth and clean without cracks so as to avoid dust accumulation, maintain a certain degree of dryness and humidity, and record the vacuum degree, heating rate, stable temperature and time, brazing temperature, brazing heat preservation time, cooling rate and tapping temperature of brazing.
When the brazing temperature reaches 598-605 ℃, the base metal expands sharply, so that the surface oxide film is cracked, the liquid brazing filler metal flows into the lower part of the oxide film layer from the cracking part, and the oxide film on the surface of the aluminum alloy material is lifted and crushed further. The surface of Al is easy to form a layer of compact and stable Al with high melting point (about 2050℃) 2 O 3 And a film which prevents the brazing filler metal and the base material from wetting and bonding during vacuum brazing. Vacuum brazing of Al and aluminum alloys does not use flux, but rather, under vacuum conditions (3-5.0X10-3 Pa), with a relatively high vapor pressure to O 2 Mg with higher affinity than Al is used as a metal activator to remove the film, and Mg is used as an alloy element to be added into the aluminum-silicon solder, and the content of Mg in the aluminum-silicon solder for vacuum brazing is generally controlled to be 1% -1.5%.
The mechanism of aluminum vacuum brazing stripping is as follows:
1.Al 2 O 3 the thermal expansion coefficient of (2) is only 1/3 of that of aluminum, and the aluminum expands sharply, so that the oxide film is cracked.
2. The volatilization of Mg damages the oxide film on the solder surface when heated.
3. Volatilized Mg and CO remaining in vacuum 2 、O 2 And steam reaction:
2Mg+O 2 ＝2MgO
Mg+H 2 O＝MgO+H 2
Mg+CO 2 ＝MgO+C
3Mg+Al 2 O 3 ＝3MgO+2Al
embodiment two:
a method for improving the brazing qualification rate of a heat exchanger, which is characterized by comprising the following steps:
s1: cleaning the heat exchanger parts needing vacuum brazing, and cooling and drying for later use;
s2: placing the cleaned heat exchanger aluminum material into a vacuum brazing furnace, and clamping by using a clamp;
s3: heating from room temperature for 20 min to 360 ℃ or heating rate of 8-10 ℃/S, and preserving heat for 40-60 min. The temperature difference is not more than + -25 ℃ and the vacuum degree is less than 7.5-10 -3 The temperature is raised to 470 ℃ or a temperature raising rate of 6-8 ℃/S in 25 minutes. The temperature of the core body of the workpiece is kept for 60-100 minutes when the temperature is higher than 330 ℃, and the temperature difference is not more than +/-15 ℃. Vacuum degree less than 6.5 x 10 -3 Heating to 520 ℃ for 20 minutes, and preserving heat for 60 minutes when the core temperature of the workpiece is higher than 510 ℃ and the temperature difference is not more than +/-10 ℃ and the vacuum degree is less than 5.0 x 10 -3 ；
S4: heating to 570 ℃ in 15 minutes, or preserving heat for 50 minutes at a heating rate of 15-20 ℃/S when the core temperature of the workpiece is higher than 560 ℃, wherein the temperature difference is not more than +/-5 ℃, heating to 620 ℃ in 10 minutes, or preserving heat for 20-50 minutes at a heating rate of 10-15 ℃/S when the core temperature of the workpiece is 598 ℃ -605 ℃, cooling to 603 ℃ in 10 minutes, and preserving heat for 10-30 minutes, wherein the temperature difference is not more than +/-2 ℃. Cooling to below 520 ℃ and discharging;
s5: vacuum degree reaches 5 multiplied by 10 -3 After Pa, heating and brazing are started, a certain amount of Mg is added to serve as a metal activator, weighing particles (dust and dust) are not contained in workshop air, the workshop air cannot be polluted by acid or other substances, waterproof paint needs to be brushed on four walls and ceilings, and mechanical particles are prevented from falling into the device. The ground must be smooth and clean without cracks so as to avoid dust accumulation, maintain a certain degree of dryness and humidity, and record the vacuum degree, heating rate, stable temperature and time, brazing temperature, brazing heat preservation time, cooling rate and tapping temperature of brazing.
Embodiment III:
a method for improving the brazing qualification rate of a heat exchanger, which is characterized by comprising the following steps:
s1: hot dipping and cleaning the heat exchanger parts needing vacuum brazing, then cold dipping and ultrasonic rinsing, and finally vapor phase drying and cleaning, and cooling and drying for later use;
the specific steps of ultrasonic cleaning are as follows: firstly, an operator sequentially puts workpieces to be cleaned into a tool basket, then puts the workpieces into a feeding trolley to push the workpieces to a feeding position, the workpieces are conveyed to a first station by a full-automatic manipulator to clean through the linkage of an inductive switch, the workpieces are put on a discharging trolley after being rinsed, bath washed and dried, and then the workpieces are taken out by the operator and transferred to a next procedure.
S2: placing the cleaned heat exchanger aluminum material into a vacuum brazing furnace, and clamping by using a clamp;
s3: heating from room temperature for 20 min to 360 ℃ or heating rate of 8-10 ℃/S, and preserving heat for 40-60 min. The temperature difference is not more than + -25 ℃ and the vacuum degree is less than 7.5-10 -3 The temperature is raised to 470 ℃ or a temperature raising rate of 6-8 ℃/S in 25 minutes. The temperature of the core body of the workpiece is kept for 60-100 minutes when the temperature is higher than 330 ℃, and the temperature difference is not more than +/-15 ℃. Vacuum degree less than 6.5 x 10 -3 Heating to 520 ℃ for 20 minutes, and preserving heat for 60 minutes when the core temperature of the workpiece is higher than 510 ℃ and the temperature difference is not more than +/-10 ℃ and the vacuum degree is less than 5.0 x 10 -3 ；
S4: heating to 570 ℃ in 15 minutes, or preserving heat for 50 minutes at a heating rate of 15-20 ℃/S when the core temperature of the workpiece is higher than 560 ℃, wherein the temperature difference is not more than +/-5 ℃, heating to 620 ℃ in 10 minutes, or preserving heat for 20-50 minutes at a heating rate of 10-15 ℃/S when the core temperature of the workpiece is 598 ℃ -605 ℃, cooling to 603 ℃ in 10 minutes, and preserving heat for 10-30 minutes, wherein the temperature difference is not more than +/-2 ℃. Cooling to below 520 ℃ and discharging;
s5: vacuum degree reaches 5 multiplied by 10 -3 After Pa, heating and brazing are started, the air in a brazing workshop does not contain weighing particles (dust and dust), the air cannot be polluted by acid or other substances and steam, waterproof paint needs to be brushed on the four walls and the ceiling, and mechanical particles are prevented from falling into the device. The ground must be smooth and clean without cracks so as to prevent dust accumulation, maintain a certain degree of dryness and humidity, and record the vacuum degree, heating rate, stable temperature and time, brazing temperature and brazing rate of brazingWelding heat preservation time, cooling rate and tapping temperature.
The quality of the brazing products obtained in the first embodiment, the second embodiment and the third embodiment is detected, the brazing product of the first embodiment is good in quality, the assembly gap of the brazing product parts in the second embodiment is too large, the brazing product composite layer in the third embodiment is uneven, and the local skin is too thick. Thus, embodiment one is the best mode of carrying out the application.
Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. A method for improving the brazing qualification rate of a heat exchanger, which is characterized by comprising the following steps:
s1: hot dipping and cleaning the heat exchanger parts needing vacuum brazing, then cold dipping and ultrasonic rinsing, and finally vapor phase drying and cleaning, and cooling and drying for later use;
s2: placing the cleaned heat exchanger aluminum material into a vacuum brazing furnace, and clamping by using a clamp;
s3: heating from room temperature for 20 min to 360 ℃ or heating rate of 8-10 ℃/S, and preserving heat for 40-60 min. The temperature difference is not more than + -25 ℃ and the vacuum degree is less than 7.5-10 -3 The temperature is raised to 470 ℃ or a temperature raising rate of 6-8 ℃/S in 25 minutes. The temperature of the core body of the workpiece is kept for 60-100 minutes when the temperature is higher than 330 ℃, and the temperature difference is not more than +/-15 ℃. Vacuum degree less than 6.5 x 10 -3 Heating to 520 ℃ for 20 minutes, and preserving heat for 60 minutes when the core temperature of the workpiece is higher than 510 ℃ and the temperature difference is not more than +/-10 ℃ and the vacuum degree is less than 5.0 x 10 -3 ；
S4: heating to 570 ℃ in 15 minutes, or preserving heat for 50 minutes at a heating rate of 15-20 ℃/S when the core temperature of the workpiece is higher than 560 ℃, wherein the temperature difference is not more than +/-5 ℃, heating to 620 ℃ in 10 minutes, or preserving heat for 20-50 minutes at a heating rate of 10-15 ℃/S when the core temperature of the workpiece is 598 ℃ -605 ℃, cooling to 603 ℃ in 10 minutes, and preserving heat for 10-30 minutes, wherein the temperature difference is not more than +/-2 ℃. Cooling to below 520 ℃ and discharging;
s5: vacuum degree reaches 5 multiplied by 10 -3 And after Pa, heating and brazing are started, and a certain amount of Mg is added to be used as a metal activator.
2. A method for improving brazing qualification rate of a heat exchanger as recited in claim 1, wherein: and in the step S1, the workpiece basket is manually placed into the feeding and discharging device, the whole cleaning process is automatically completed by two workpiece moving carts, and finally the workpiece basket is lifted out.
3. A method for improving brazing qualification rate of a heat exchanger as recited in claim 1, wherein: the specific steps of ultrasonic cleaning in the step S1 are as follows: firstly, an operator sequentially puts workpieces to be cleaned into a tool basket, then puts the workpieces into a feeding trolley to push the workpieces to a feeding position, the workpieces are conveyed to a first station by a full-automatic manipulator to clean through the linkage of an inductive switch, the workpieces are put on a discharging trolley after being rinsed, bath washed and dried, and then the workpieces are taken out by the operator and transferred to a next procedure.
4. A method for improving brazing qualification rate of a heat exchanger as recited in claim 1, wherein: in the S5, al 2 O 3 The thermal expansion coefficient of the aluminum is only 1/3 of that of the aluminum, and the aluminum expands sharply, so that the oxide film is cracked; the volatilization of Mg damages the oxide film on the surface of the solder during heating; volatilized Mg and CO remaining in vacuum 2 、O 2 And water vapor.
5. A method for improving brazing qualification rate of a heat exchanger as recited in claim 1, wherein: in the step S5, the workshop air does not contain weighing particles (dust and dust), can not be polluted by acid or other substances steam, and the four walls and the ceiling are painted with waterproof paint and cleaned regularly so as to prevent mechanical particles from falling into the device. The floor must be smooth and clean without cracks so as to avoid dust accumulation and maintain a certain degree of dryness and humidity.
6. A method for improving brazing qualification rate of a heat exchanger as recited in claim 1, wherein: when the brazing is performed in the step S5, the vacuum degree, the heating rate, the stabilizing temperature and time, the brazing temperature, the brazing heat preservation time, the cooling rate and the tapping temperature of the brazing are required to be recorded.
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