CN111151834A - Brazing repair method for local leakage of vacuum brazing aluminum plate-fin heat exchanger core - Google Patents
Brazing repair method for local leakage of vacuum brazing aluminum plate-fin heat exchanger core Download PDFInfo
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- CN111151834A CN111151834A CN201911366743.XA CN201911366743A CN111151834A CN 111151834 A CN111151834 A CN 111151834A CN 201911366743 A CN201911366743 A CN 201911366743A CN 111151834 A CN111151834 A CN 111151834A
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- 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
- B23K1/0008—Soldering, e.g. brazing, or unsoldering specially adapted for particular articles or work
-
- 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
-
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0244—Powders, particles or spheres; Preforms made therefrom
- B23K35/025—Pastes, creams, slurries
-
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
- B23K35/286—Al as the principal constituent
-
- 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
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/04—Tubular or hollow articles
- B23K2101/14—Heat exchangers
-
- 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
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/08—Non-ferrous metals or alloys
- B23K2103/10—Aluminium or alloys thereof
Abstract
The invention discloses a rapid brazing repair method for local leakage of a vacuum brazing aluminum plate-fin heat exchanger core, and belongs to the technical field of aluminum alloy welding. The method adopts the traditional oxyacetylene brazing and is matched with the pasty aluminum alloy brazing filler metal to be applied to the repair of the local leakage of the core body of the plate-fin heat exchanger made of vacuum brazing aluminum. The method is simple, the paste solder is easy to coat, the oxyacetylene is convenient to heat, the operability and controllability are strong, and the repair qualification rate is high. Because the melting point of the paste aluminum alloy solder is lower than 490 ℃, the expansion of leakage defects during repair and the damage of parts such as fins and the like caused by large thermal stress can be effectively avoided during oxyacetylene heating.
Description
Technical Field
The invention belongs to the technical field of aluminum alloy welding, and particularly relates to a rapid brazing repair method for local leakage of a vacuum brazing aluminum plate-fin heat exchanger core.
Background
The aluminum plate-fin heat exchanger is a novel efficient heat exchanger taking aluminum alloy corrugated fins as heat transfer elements, is the most advanced heat exchanger at home and abroad at present, has the characteristics of small thermal resistance, high heat exchange efficiency, compact structure, small volume, light weight, strong adaptability, firmness, durability, good economy, capability of being designed into dozens of strands of fluids for simultaneous heat exchange and the like, is specially used in the military fields of aviation, submarines and the like at early stage, is widely applied to the fields of petrifaction, aerospace, electronics, atomic energy, ships, power machinery and the like at present, continuously replaces the traditional heat exchanger such as a shell and tube type heat exchanger and rapidly expands the application range of the heat exchanger.
The aluminum plate-fin heat exchanger is formed by assembling and welding a core body, an end enclosure, a connecting pipe, a flange and the like through argon arc welding, wherein the core part of the aluminum plate-fin heat exchanger is a core body of a unit body stacked structure consisting of five elements, namely a fin, a flow deflector, a partition plate, a side plate and a seal strip, and the aluminum plate-fin heat exchanger is usually formed by vacuum brazing. The fin, the guide vane, the side plate and the seal material are usually 3003 aluminum alloy, the partition plate is usually Q515 aluminum alloy composite plate, the middle core plate is 3003 aluminum alloy, and the upper surface layer and the lower surface layer are 4004 alloy coating layers which are 5-18% of the thickness of the composite plate and have silicon content of 9.0-10.5%, namely brazing filler metal layers.
The production process of the aluminum plate-fin heat exchanger is complex and has high technical requirements, and the common main production procedures are as follows: (1) part processing → (2) inspection → (3) cleaning before welding → (4) inspection → (5) core assembly → (6) inspection → (7) vacuum brazing → (8) outline and dimension inspection → (9) welding upper pressure testing end socket, performing airtightness test → (10) cutting pressure testing end socket → (11) cleaning → (12) and end socket assembling welding → (13) outline and dimension inspection, airtightness and strength test → (14) cleaning and drying → (15) nitrogen sealing and leaving the factory. Due to different design requirements of products, the working procedures from (9) to (11) can be omitted from some heat exchangers. All channels of the core body after brazing can bear pressure, and leakage is not allowed at all positions, but the core body after vacuum brazing cannot be completely avoided due to the fact that the aluminum plate-fin heat exchanger is complex in structure and production process and high in technical requirement, and the core body is manually assembled before brazing, which is a common practical problem for aluminum plate-fin heat exchanger production enterprises at home and abroad.
The core body leakage is divided into an outer leakage and an inner leakage, wherein the outer leakage accounts for the most part. The leakage refers to the outward leakage of the medium in the channel through the gap between the seal and the side plate; the inner leakage refers to the mutual leakage caused by the serial communication between two adjacent different channels. The core part is not allowed to have any leakage, and can only be discarded if large-area leakage occurs; for the core body which only has local leakage, the core body should be repaired as far as possible on the premise of ensuring the service performance of the product in consideration of cost and energy conservation.
For the local leakage of the core body, the current repair methods adopted at home and abroad are three types: 1. blocking a heat exchange channel; 2. plugging with a high polymer material; 3. and (5) repairing by argon arc welding. Because the heat exchange efficiency of the whole heat exchanger can be influenced by blocking the heat exchange channel, the design has very strict limitation on the heat exchange efficiency, the compact and precise heat exchanger core body, such as a military heat exchanger, is not allowed to block the heat exchange channel, and the heat exchange channel blocking method is only suitable for a very small number of heat exchanger core bodies and can be adopted only under the design permission condition. High polymer materials such as widely used DW polyurethane adhesives have high mechanical properties and good low-temperature properties, and can be used for repairing local leakage of a core body, but because the requirements on surface pretreatment of a repaired part are very high, the actual product repair is difficult to achieve a relatively ideal effect, and the DW polyurethane adhesives are not suitable for heat exchangers with high working temperature and high working pressure, and are very limited in application. The method is a feasible method for repairing the local leakage of the heat exchanger core by adopting manual argon tungsten-arc welding with strictly controlled welding standard parameters and small linear energy, but the method is only suitable for the heat exchanger core with thicker partition plates and sealing strips. The manual argon tungsten-arc welding has the disadvantages of large electric arc, large arc spot size, small electric arc energy density, large heating area, high requirements on the core structure and size precision of the heat exchanger, small thickness of the partition plate and the seal strip, and particularly small thickness (usually less than 2.0mm) of the partition plate, so the manual argon tungsten-arc welding also puts high requirements on the welding operation technology of welding personnel. How to effectively repair the local leakage of the core body of the heat exchanger is a hot spot concerned by aluminum plate-fin heat exchanger production enterprises at home and abroad at present, and is a common technical problem to be solved urgently. The heat exchanger core body is scrapped due to the fact that local leakage cannot be effectively repaired, not only can great direct economic loss be brought, but also the production process can be seriously affected.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an effective, rapid and convenient brazing repair method aiming at the technical problem of repair of local leakage of a core body of a vacuum brazing aluminum plate-fin heat exchanger.
The purpose of the invention is realized as follows: a rapid brazing repair method for local leakage of a core body of a vacuum brazing aluminum plate-fin heat exchanger comprises the following steps:
(1) and cleaning the local leakage part and the adjacent area of the heat exchanger core body to ensure that the local leakage part and the adjacent area are free of water, oil and other dirt.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is parallel to the horizontal plane.
(3) And (3) coating the pasty aluminum alloy solder on the local outer leakage part of the core within 20 minutes after the local outer leakage part and the adjacent area of the core are cleaned, filling the outer leakage gap and increasing by about 2mm, wherein the increased pasty aluminum alloy solder and the metal part of the core are in round transition, the melting point of the pasty aluminum alloy solder is lower than 490 ℃, and the brazing temperature is 500-520 ℃.
(4) Heating the outer leakage part and the area adjacent to 20mm by using an oxyacetylene welding torch within 10 minutes after the pasty brazing filler metal is coated, and removing the oxyacetylene welding torch after the pasty brazing filler metal is completely melted.
(5) And polishing and scrubbing the repaired part with acetone, and finishing the repair. And after repairing, inspecting the local leakage part of the core body of the heat exchanger.
Further, in the step (1), the method for cleaning the local leakage part and the adjacent area of the heat exchanger core comprises the following steps: and cleaning the local leakage part of the heat exchanger core and the area adjacent to 10mm by using a copper wire brush or a stainless steel wire brush with the wire diameter less than or equal to 0.15mm, a scraper and acetone in sequence until the natural color of the metal is exposed.
Further, in the step (3), the paste aluminum alloy brazing filler metal comprises the following components in parts by weight: 400g of low-melting-point high-strength aluminum alloy powder brazing filler metal, 100-110 mL of powdery brazing flux QJ 20160-65 g of liquid paraffin oil and 2-2.2 g of polyvinylpyrrolidone. The low-melting-point high-strength aluminum alloy powder brazing filler metal consists of 8.6-9.5% by mass of Si, 16.5-17.5% by mass of Cu, 8.5-9.5% by mass of Ge, 4.5-5.0% by mass of Ni, 4.0-5.0% by mass of Zn, 0.70-0.75% by mass of Sr, 0.35-0.40% by mass of Bi, 0.40-0.45% by mass of La, 0.40-0.55% by mass of Ce, 0.10-0.20% by mass of Yb and the balance of Al.
Further, in the step (4), a small welding torch and a neutral flame are used for heating, and the welding torch continuously swings in the heating process so as to uniformly heat the heating area.
Compared with other methods for repairing the local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger, the method has the beneficial effects that:
1. the repair method is convenient and fast, the paste solder is easy to coat, and the oxyacetylene is convenient and fast to heat.
2. The melting point of the paste solder is lower than 490 ℃, the brazing temperature can be as low as 500-520 ℃, and the expansion of leakage defects during repair and the damage of parts such as fins and the like caused by large thermal stress can be effectively avoided during oxyacetylene heating.
3. The repairing method is simple, the process is controllable, the operation is convenient, the process consumption is low, and the repairing qualified rate is high.
Detailed Description
The invention relates to a repair method for local leakage of a core body of an aluminum plate-fin heat exchanger for vacuum brazing by heating and melting pasty aluminum alloy brazing filler metal through oxyacetylene flame, which is a manual flame brazing method. Flame brazing is to use the gasification product of combustible gas or liquid fuel and oxygen or air to mix and burn the flame formed to carry on the braze welding and heat, wherein use oxyacetylene flame brazing to employ the most extensively, mainly used for braze welding carbon steel, copper and thin-walled and small-scale weldment of the copper alloy, can also be used for braze welding low alloy steel and aluminium and aluminum alloy. Oxyacetylene brazing processes are relatively simple and do not require a shielding gas, but require the use of a flux. Prior to the present invention, oxyacetylene brazing was not used for the repair of local leaks in vacuum brazed aluminum plate fin heat exchanger cores. Due to the particularity of local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger, a series of key technical problems must be solved by adopting oxyacetylene brazing for repair. The method comprises the following steps of determining the type of brazing material (components, forms and specifications of brazing filler metal and brazing flux, and the proportion of the brazing filler metal and the brazing flux), effectively applying the brazing material, determining the nature of oxyacetylene flame, cleaning a leakage gap before brazing, avoiding the phenomenon that local leakage is continuously expanded and a new local leakage defect occurs due to excessive thermal stress generated during brazing heating, and avoiding the damage of fins, partition plates and seals adjacent to the repaired part.
As is known, the welding materials adopted by the traditional aluminum alloy brazing are powdered brazing flux and aluminum alloy brazing filler metals such as powder, wires, foils, sheets, rods and the like, and for repairing local leakage of a vacuum brazing aluminum plate-fin heat exchanger core, the traditional aluminum alloy brazing material is difficult to effectively apply due to small gaps at the leakage position, the cleaning of the leakage gap before brazing is very difficult, and the cleaning directly determines the success or failure of brazing repair. Therefore, for the repair of the local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger, the paste-shaped brazing filler metal is adopted most effectively, and the method has the unique advantages that: (1) the brazing filler metal is convenient to accurately add, and the method is particularly suitable for brazing seams with irregular shapes; (2) the proportion of the brazing flux and the brazing filler metal is accurate, the film removing capability is strong, and the residues after brazing are very little. So far, the research and development of paste solder at home and abroad mainly focuses on tin-based, copper-based and silver-based solder, the paste aluminum alloy solder is very few and has marketable yield index, and the soldering temperature is high during soldering because the solder powder in the paste solder is Al-Si-based solder powder. The Al-Si based solder is the most widely used solder for brazing aluminum alloys, and is based on an A1-Si eutectic composition (Al-12.6Si), and the eutectic alloy has good wettability, fluidity, corrosion resistance and workability of a brazed joint, and high strength of the brazed joint. However, the Al-Si brazing filler metal has a high melting point (the Al-12.6Si eutectic crystal temperature is 577 ℃), the brazing temperature is more than 600 ℃ during brazing, and the phenomena of overburning, corrosion and the like of an aluminum alloy base metal are easily caused by the excessively high brazing temperature, so that the performance of a brazed joint is reduced. In some special applications, such as brazing of thin-walled aluminum plate-fin heat exchangers, the use of Al-Si based brazing filler metals is greatly restricted.
On the basis of analyzing the structure and the local leakage characteristics of the core body of the vacuum brazing aluminum plate-fin heat exchanger systematically, the invention solves the key technical problem through a series of experiments based on the medium-temperature pasty aluminum alloy brazing filler metal (ZL201810582571.9) invented by the inventor, and invents a rapid brazing repair method for the local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger. The method has the advantages that the traditional oxyacetylene brazing is applied to repair of local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger, remarkable progress is achieved, and the oxyacetylene brazing is not only a brazing method for aluminum and aluminum alloy, but also can be used as a repair method for local leakage of the core body of the vacuum brazing aluminum plate-fin heat exchanger. The method is simple, the paste solder is easy to coat, the oxyacetylene is convenient to heat, the operability and controllability are strong, and the repair qualification rate is high. Because the melting point of the paste solder is low, the expansion of leakage defects during repair and the damage of parts such as fins and the like caused by large thermal stress can be effectively avoided during oxyacetylene heating.
The present invention will be described in detail with reference to specific examples, and the objects and effects of the present invention will become more apparent. The medium-temperature paste aluminum alloy brazing filler metal comprises the following components in parts by weight: 400g of low-melting-point high-strength aluminum alloy powder brazing filler metal, 100-110 mL of powdery brazing flux QJ 20160-65 g of liquid paraffin oil and 2-2.2 g of polyvinylpyrrolidone. The low-melting-point high-strength aluminum alloy powder brazing filler metal consists of 8.6-9.5% by mass of Si, 16.5-17.5% by mass of Cu, 8.5-9.5% by mass of Ge, 4.5-5.0% by mass of Ni, 4.0-5.0% by mass of Zn, 0.70-0.75% by mass of Sr, 0.35-0.40% by mass of Bi, 0.40-0.45% by mass of La, 0.40-0.55% by mass of Ce, 0.10-0.20% by mass of Yb and the balance of Al.
Example 1
The core body of the aluminum plate-fin heat exchanger with the two cooling liquid-air flow heat exchange channels has the following dimensions (length, width and height): 1440X 150X 488 mm. The side plate is made of 3003 aluminum alloy plate, and has the dimensions of (length multiplied by width multiplied by thickness): 1440X 150X 4 mm; the fins are made of 3003 aluminum alloy plates, the thickness of the fins is 0.2mm, and the fins are saw-tooth-shaped; the partition plate is a Q515 aluminum alloy cladding plate, and the size is (length multiplied by width multiplied by thickness): 1440X 150X 0.8 mm; the seal material is 3003 aluminum alloy, wherein the dimensions of the airflow side cold seal are (length × width × height): 1440X 8X 3mm, coolant-side heat-seal bar dimensions (length X width X height): 150X 12X 9.5 mm; the brazing flux for brazing the side plates, the fins and the seals is a 4004 brazing sheet with the thickness of 0.1mm, and the size is (length multiplied by width): 1440X 150 mm. After the heat exchanger core body is subjected to vacuum brazing, a sealing test shows that 3 leakage parts exist, the leakage parts are located between the airflow side cold seal strip and the partition plate, and the lengths of the leakage defects are respectively 1mm, 3mm and 5 mm.
Repairing the leakage with the length of 1 mm:
(1) and carefully cleaning the local leakage part and the area adjacent to the local leakage part by using a scraper, a stainless steel wire brush with the wire diameter of 0.15mm and acetone until the natural color of metal is exposed, and removing water, oil and other dirt at the local leakage part and the adjacent area.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is basically parallel to the horizontal plane.
(3) And (3) coating the medium-temperature paste aluminum alloy brazing filler metal on the local outer leakage position of the core body within 3 minutes after the local outer leakage position of the core body and the area adjacent to 10mm are cleaned by using a clean stainless steel scraper, filling the outer leakage gap and enabling the outer leakage gap to be higher by-2 mm, and enabling the higher paste brazing filler metal to be in round transition with the metal position of the core body.
(4) And heating the outer leakage part and the area adjacent to 20mm by adopting an oxyacetylene welding torch within 5 minutes after the pasty brazing filler metal is coated, and using a small welding torch and a neutral flame, wherein the welding torch continuously swings in the heating process so as to uniformly heat the heating area. After the paste solder was completely melted, the oxyacetylene torch was removed.
(5) And (5) carefully polishing and scrubbing the repaired part with acetone, and finishing the repair.
Repairing the leakage with the length of 3 mm:
the steps are the same as the steps (1) - (5)
Repairing the leakage with the length of 5 mm:
the steps are the same as the steps (1) - (5)
(6) And (4) checking: and (4) sending the repaired core body to an inspection process, and carrying out a vibration strength test and a gas tightness test, wherein the core body is all qualified. The vibration strength test is as follows: horizontally placing at normal temperature, water pressure of 0.20Mpa, vibration frequency of 60-80 times/min, amplitude of 50mm, and duration of 5min, wherein leakage and abnormal deformation are not allowed; the air tightness test is as follows: keeping the pressure at 0.20MPa for 5min at normal temperature, and not allowing leakage and abnormal deformation.
Example 2
The core body size of the aluminum plate-fin heat exchanger with the two heat exchange channels of the engine oil and the airflow is (length multiplied by width multiplied by height): 367X 150X 472 mm. The side plate is made of 3003 aluminum alloy plate, and has the dimensions of (length multiplied by width multiplied by thickness): 367X 150X 6 mm; the fins are made of 3003 aluminum alloy plates, the thickness of the fins is 0.2mm, and the fins are saw-tooth-shaped; the partition plate is a Q515 aluminum alloy cladding plate, and the size is (length multiplied by width multiplied by thickness): 367X 150X 0.8 mm; the seal material is 3003 aluminum alloy, wherein the dimensions of the airflow side cold seal are (length × width × height): 367 × 8 × 3mm, and the dimensions of the oil side heat seal are (length × width × height): 150X 12X 9.5 mm; the brazing flux for brazing the side plates, the fins and the seals is a 4004 brazing sheet with the thickness of 0.1mm, and the size is (length multiplied by width): 367X 150 mm. The heat exchanger core body is subjected to vacuum brazing and then is subjected to sealing test, and the existence of 1 part of leakage: and the length of the leakage defect is-2 mm and is positioned between the heat seal strip at the engine oil side and the partition plate.
Repairing the local outer leakage of the core body by argon arc welding:
(1) and carefully cleaning the local leakage part and the area adjacent to the local leakage part by using a scraper, a copper wire brush with the wire diameter of 0.15mm and acetone until the natural color of metal is exposed, wherein the local leakage part and the adjacent area have no water, oil or other dirt.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is basically parallel to the horizontal plane.
(3) And (3) coating the medium-temperature paste aluminum alloy brazing filler metal on the local outer leakage position of the core body by using a clean stainless steel scraper within 5 minutes after the local outer leakage position of the core body and the area adjacent to 10mm are cleaned, filling the outer leakage gap and enabling the outer leakage gap to be higher by-2 mm, and enabling the higher paste brazing filler metal to be in round transition with the metal position of the core body.
(4) And heating the outer leakage part and the area adjacent to 20mm by adopting an oxyacetylene welding torch within 5 minutes after the pasty brazing filler metal is coated, and using a small welding torch and a neutral flame, wherein the welding torch continuously swings in the heating process so as to uniformly heat the heating area. After the paste solder was completely melted, the oxyacetylene torch was removed.
(5) And (5) carefully polishing and scrubbing the repaired part with acetone, and finishing the repair.
(6) And (4) checking: and (4) sending the repaired core body to an inspection process, and carrying out a vibration strength test and a gas tightness test, wherein the core body is all qualified. The vibration strength test is as follows: horizontally placing at normal temperature, water pressure of 0.39Mpa, vibration frequency of 60-80 times/min, amplitude of 50mm, and duration of 5min, wherein leakage and abnormal deformation are not allowed; the air tightness test is as follows: keeping the pressure at 0.39MPa for 5min at normal temperature, and not allowing leakage and abnormal deformation.
Example 3
The core body of the aluminum plate-fin heat exchanger of the two heat exchange channels of a certain engine oil-air flow has the following dimensions (length multiplied by width multiplied by height): 427X 102X 190 mm. The side plate is made of 3003 aluminum alloy plate, and has the dimensions of (length multiplied by width multiplied by thickness): 427X 102X 8 mm; the fins are made of 3003 aluminum alloy plates, the thickness of the fins is 0.2mm, and the fins are straight; the partition plate is a Q515 aluminum alloy cladding plate, and the size is (length multiplied by width multiplied by thickness): 427X 102X 0.8 mm; the seal material is 3003 aluminum alloy, wherein the dimensions of the airflow side cold seal are (length × width × height): 102 × 6 × 3mm, and the oil side heat seal dimensions (length × width × height): 427X 3X 8 mm; the brazing flux for brazing the side plates, the fins and the seals is a 4004 brazing sheet with the thickness of 0.1mm, and the size is (length multiplied by width): 427X 102 mm. The heat exchanger core body is subjected to vacuum brazing and then is subjected to sealing test, and 3 external leakage positions are found: 2 is positioned between the airflow side cold seal and the partition plate, and the length of the leakage defect is respectively 10mm to 3 mm; the 1 position is positioned between the heat seal strip at the engine oil side and the clapboard, and the length of the leakage defect is 8 mm.
And (3) repairing local leakage between the airflow side cold seal strip and the partition plate by argon arc welding:
(1) and carefully cleaning the local leakage part and the area adjacent to the local leakage part by using a scraper, a stainless steel wire brush with the wire diameter of 0.15mm and acetone until the natural color of metal is exposed, and removing water, oil and other dirt at the local leakage part and the adjacent area.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is basically parallel to the horizontal plane.
(3) And (3) coating the medium-temperature paste aluminum alloy brazing filler metal on the local outer leakage position of the core body by using a clean stainless steel scraper within 8 minutes after the local outer leakage position of the core body and the area adjacent to 10mm are cleaned, filling the outer leakage gap and enabling the outer leakage gap to be higher by-2 mm, and enabling the higher paste brazing filler metal to be in round transition with the metal position of the core body.
(4) And heating the outer leakage part and the area adjacent to 20mm by adopting an oxyacetylene welding torch within 7 minutes after the pasty brazing filler metal is coated, and using a small welding torch and a neutral flame, wherein the welding torch continuously swings in the heating process so as to uniformly heat the heating area. After the paste solder was completely melted, the oxyacetylene torch was removed.
(5) And (5) carefully polishing and scrubbing the repaired part with acetone, and finishing the repair.
And (3) argon arc welding repair of local leakage of 10mm between the airflow side cold seal strip and the partition plate:
the steps are the same as the steps (1) - (5)
Repairing local leakage of 8mm between the engine oil side heat seal strip and the partition plate by argon arc welding:
(1) and carefully cleaning the local leakage part and the area adjacent to the local leakage part by using a scraper, a stainless steel wire brush with the wire diameter of 0.15mm and acetone until the natural color of metal is exposed, and removing water, oil and other dirt at the local leakage part and the adjacent area.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is basically parallel to the horizontal plane.
(3) The medium-temperature paste aluminum alloy brazing filler metal (application No. 201810582571.9) invented by the inventor is coated on the local outer leakage position of the core body by a clean stainless steel scraper within 20 minutes after the local outer leakage position of the core body and the area adjacent to 10mm are cleaned, the outer leakage gap is filled up and is higher by 2mm, and the higher paste brazing filler metal and the metal position of the core body are in round transition.
(4) And heating the outer leakage part and the area adjacent to 20mm by adopting an oxyacetylene welding torch within 10 minutes after the pasty brazing filler metal is coated, and using a small welding torch and a neutral flame, wherein the welding torch continuously swings in the heating process so as to uniformly heat the heating area. After the paste solder was completely melted, the oxyacetylene torch was removed.
(5) And (5) carefully polishing and scrubbing the repaired part with acetone, and finishing the repair.
(6) And (4) checking: and (4) sending the repaired core body to an inspection process, and carrying out a vibration strength test and a gas tightness test, wherein the core body is all qualified. The vibration strength test is as follows: horizontally placing at normal temperature, water pressure of 0.50Mpa, vibration frequency of 60-80 times/min, amplitude of 50mm, and duration of 5min, wherein leakage and abnormal deformation are not allowed; the air tightness test is as follows: keeping the pressure at 0.50MPa for 5min at normal temperature, and not allowing leakage and abnormal deformation.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.
Claims (4)
1. A rapid brazing repair method for local leakage of a core body of a vacuum brazing aluminum plate-fin heat exchanger is characterized by comprising the following steps:
(1) and cleaning the local leakage part and the adjacent area of the heat exchanger core body to ensure that the local leakage part and the adjacent area are free of water, oil and other dirt.
(2) And the position of the core body is adjusted to ensure that the repairing surface faces upwards and is parallel to the horizontal plane.
(3) And (3) coating the pasty aluminum alloy solder on the local outer leakage part of the core within 20 minutes after the local outer leakage part and the adjacent area of the core are cleaned, filling the outer leakage gap and increasing by about 2mm, wherein the increased pasty aluminum alloy solder and the metal part of the core are in round transition, the melting point of the pasty aluminum alloy solder is lower than 490 ℃, and the brazing temperature is 500-520 ℃.
(4) Heating the outer leakage part and the area adjacent to 20mm by using an oxyacetylene welding torch within 10 minutes after the pasty brazing filler metal is coated, and removing the oxyacetylene welding torch after the pasty brazing filler metal is completely melted.
(5) And polishing and scrubbing the repaired part with acetone, and finishing the repair.
2. The rapid brazing repair method according to claim 1, wherein in the step (1), the method for cleaning the local leakage part and the adjacent area of the heat exchanger core is as follows: and cleaning the local leakage part of the heat exchanger core and the area adjacent to 10mm by using a copper wire brush or a stainless steel wire brush with the wire diameter less than or equal to 0.15mm, a scraper and acetone in sequence until the natural color of the metal is exposed.
3. The rapid brazing repair method according to claim 1, wherein in the step (3), the paste aluminum alloy brazing filler metal comprises the following components in percentage by weight: 400g of low-melting-point high-strength aluminum alloy powder brazing filler metal, 100-110 mL of powdery brazing flux QJ 20160-65 g of liquid paraffin oil and 2-2.2 g of polyvinylpyrrolidone. The low-melting-point high-strength aluminum alloy powder brazing filler metal consists of 8.6-9.5% by mass of Si, 16.5-17.5% by mass of Cu, 8.5-9.5% by mass of Ge, 4.5-5.0% by mass of Ni, 4.0-5.0% by mass of Zn, 0.70-0.75% by mass of Sr, 0.35-0.40% by mass of Bi, 0.40-0.45% by mass of La, 0.40-0.55% by mass of Ce, 0.10-0.20% by mass of Yb and the balance of Al.
4. The rapid brazing repair method according to claim 1, wherein in the step (4), a small welding torch and a neutral flame are used for heating, and the welding torch is continuously oscillated during heating so as to uniformly heat the heating area.
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