JP2009068083A - Heat exchanger member made of aluminum having excellent corrosion resistance, and method for manufacturing heat exchanger made of aluminum having excellent corrosion resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger member used for the manufacture of a heat exchanger and having superior brazeability and excellent long-term corrosion resistance. <P>SOLUTION: The member comprises a tube to which an Si powder of ≤30 μm maximum particle size is applied together with a Zn-containing fluoride-based flux and a fin. The tube is composed of a material which has a composition consisting of 0.001 to 0.10 mass% Cu and the balance aluminum with inevitable impurities and is ≥30 mV nobler in electric potential after brazing than the fin. By carrying out brazing using the fine Si powder, the occurrence of local melting of the tube at brazing can be prevented and excellent brazing can be done. Because the tube is ≥30 mV nobler than the fin and further a moderately base layer is formed in the surface layer of the tube, the corrosion of the tube can be satisfactorily prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a member for an aluminum heat exchanger excellent in corrosion resistance and a method for manufacturing an aluminum heat exchanger excellent in corrosion resistance, which are used in the manufacture of an aluminum heat exchanger suitable for an air conditioner capacitor of an automobile. is there.

  In aluminum heat exchangers manufactured by brazing, brazing sheets in which an Al-Si alloy brazing material is clad on an Al core material have been widely used so far. A product can be manufactured at a low cost by using a tube (extruded tube or the like) coated in the form of a mixture of a binder and a binder.

  However, in brazing using Si powder, Si diffuses from the tube surface to the inside due to heating during brazing, so the Si concentration is high on the surface and low inside, and the tube has a high potential on the surface and low inside. A potential gradient is formed. For this reason, when corrosion occurs in the tube, it becomes pitting corrosion, causing refrigerant leakage and strength reduction.

Therefore, by using zinc-containing flux, a method was proposed in which a sacrificial layer formed by zinc diffusion during brazing was formed on the tube surface, and even when the tube was corroded, the entire surface was corroded and the generation of through holes was suppressed. (See, for example, Patent Document 1)
JP 2004-330233 A

  However, in the method of brazing using the above-mentioned Si powder and zinc-containing flux, when the Si powder is alloyed with the surrounding aluminum during brazing to form an Al-Si alloy brazing, a dent due to local melting of the tube occurs. Since the zinc component of the flux is also concentrated in this recess, there is a problem that corrosion tends to occur starting from this recess when the product is used. Moreover, since there is no application | coating of Zn containing flux except a tube flat part, if this part is not more noble than a fin, the problem that a pitting corrosion will generate | occur | produce will arise.

  The present invention has been made against the background of the above circumstances, and is excellent in corrosion resistance, which can effectively improve the corrosion resistance of the tube by enabling the brazing of the tube using a Zn-containing flux. Another object is to provide a member for aluminum heat exchanger and a method for producing the aluminum heat exchanger.

  That is, among the aluminum heat exchanger members of the present invention, the first present invention includes a tube and a fin coated with Si powder having a maximum particle size of 30 μm or less together with a fluoride-based flux containing Zn, and the tube Is composed of a material containing Cu: 0.001% to 0.10% by mass%, the balance being aluminum and unavoidable impurities, and being noble more than 30 mV than the fin at the potential after brazing. Features.

  The member for an aluminum heat exchanger according to the second aspect of the present invention is the composition of the tube according to the first aspect of the present invention, further in mass%, Mn: 0.05 to 0.50%, Si: 0.10%. It contains more than 0.5% and less than 0.50%.

  The member for aluminum heat exchanger according to the third aspect of the present invention is the composition of the tube according to the first or second aspect of the present invention, further in mass%, Fe: 0.10 to 0.50%, Ti: 0. It contains 1 type or 2 types or more among 0.01 to 0.20%.

  The aluminum heat exchanger member according to the fourth aspect of the present invention is characterized in that, in any of the first to third aspects of the present invention, the average particle size of the Si powder is less than 1 to 5 μm.

  In the aluminum heat exchanger member according to the fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the fluoride-based flux containing Zn contains zinc potassium fluoride (KZnF3). It is characterized by.

  The aluminum heat exchanger member according to a sixth aspect of the present invention is the member according to any one of the first to fifth aspects, wherein the fin is in mass% and contains Zn: 0.3 to 5.0%. The remainder has a composition comprising Al and inevitable impurities.

  The member for aluminum heat exchanger according to the seventh aspect of the present invention is the composition of the fin according to any one of the first to sixth aspects of the present invention, further in mass%, Mn: 0.8 to 1.50%, Zr: 0.01 to 0.20%, Ti: 0.01 to 0.20%, Cr: 0.01 to 0.20%, Fe: 0.20 to 0.50%, Si: 0.10 It contains 1 type or 2 types or more among 1.0%.

  The manufacturing method of the aluminum heat exchanger excellent in corrosion resistance according to the eighth aspect of the present invention has a maximum particle size of 30 μm or less on the surface of the tube having the composition and material according to any one of the first to third aspects of the present invention. Applying a coating containing Si powder and a fluoride-based flux containing Zn, and brazing the tube and the fin by brazing and heating to produce the reaction between the coating and the Al component of the tube. It is characterized by attaching.

  In the present invention, a finer Si powder is used, and when this is uniformly applied, a thin Al-Si alloy melting braze is formed on the entire tube surface by heating during brazing, and almost local melting of the tube occurs. Therefore, no dent is generated on the tube surface, the strength of the tube is sufficiently maintained, and deterioration of the corrosion resistance of the product due to the generation of the dent can be suppressed. When the particle diameter exceeds 30 μm, a through-hole due to the local melting is generated. Suitably, the average particle diameter of Si powder shall be less than 1-5 micrometers. This is because when the average particle size is less than 1 μm, the formation of the Al—Si alloy melt brazing is not sufficient, and the brazing property is remarkably lowered, and when it is 5 μm or more, a dent due to local melting occurs. is there.

In addition, since zinc is contained in the flux, zinc diffuses into the tube during brazing, the surface zinc concentration is high and the inside is low, the potential on the surface of the tube is base, and the sacrificial layer with a potential gradient where the inside is noble Is formed. For this reason, even if corrosion occurs in the tube, it does not become a pitting corrosion form, and refrigerant leakage and strength reduction can be suppressed. As the flux, zinc potassium fluoride (KZnF ₃ ) alone or a mixture containing the same can be suitably used. The flux containing zinc, furthermore, can be exemplified such as ZnF _2. Examples of the flux that can be used by mixing with a flux containing zinc such as zinc potassium fluoride (KZnF ₃ ) include KAlF ₄ and K ₃ AlF ₆ .

  Furthermore, in this invention, since the tube alloy which adjusted Cu content moderately is used, while being able to adjust so that the effect of a sacrificial layer may fully be demonstrated and the potential of a tube may not become too low, long-term Good pitting corrosion resistance can be obtained even in a corrosive environment. Moreover, containing an appropriate amount of Cu also has the effect of improving the strength of the tube. These effects are sufficiently exhibited by an alloy having a Cu content of 0.001% by mass or more and 0.10% by mass or less. When Cu content is less than 0.001% by mass, sufficient strength improvement and potential adjustment effects cannot be obtained. On the other hand, when Cu content exceeds 0.10% by mass, a large amount of Cu is absorbed in the molten brazing during brazing, so that a high potential distribution is formed inside the tube with a high surface and low inside. Corrosion resistance deteriorates.

  In addition, the sacrificial anode effect of the fin also acts by ensuring a potential difference of 30 mV or more between the tube and the fin. As a result, the double anticorrosive effect is exhibited, and the corrosion in the tube is more strongly suppressed.

  From the above viewpoint, it is desirable that the tube of the present heat exchanger is excellent in corrosion resistance and is an electrochemically noble alloy as much as possible. Mn can improve strength without lowering the potential of the tube, and may preferably contain 0.05 to 0.50% of Mn. When the content is less than 0.05%, the effect is small. On the other hand, when the content exceeds 0.50%, the extrudability of the material is lowered.

  In addition, when Si is contained together with Mn, a fine Al—Mn—Si-based compound is formed and the strength is effectively improved, so that it can be contained together with Mn in a tube as desired. However, if the content is 0.10% or less, the above effect is not sufficient. On the other hand, if the content is 0.50% or more, the melting point of the alloy is lowered, and surface defects are caused by partial melting of the material during the extrusion process. Therefore, the Si content is more than 0.10% and less than 0.5%.

  In addition, one or two of Ti and Fe may be added. These elements also have the effect of improving the material strength. When Ti and Fe are contained, the content is Fe: 0.10 to 0.50% and Ti: 0.01 to 0.20%. When these components are contained in an amount exceeding the upper limit, not only excellent properties can be imparted but also the workability of the material is deteriorated. On the other hand, if it is less than the lower limit, the desired characteristics cannot be imparted.

  Similarly, the material of the fin included in the heat exchanger member is excellent in corrosion resistance, is an electrochemically base alloy as much as possible, has excellent high temperature strength that does not easily deform by heating during brazing, and is a product. It is desirable that the alloy has excellent room temperature strength.

  Zn can be contained because the decrease in corrosion resistance is minimized and the potential can be effectively reduced. On the other hand, any of the alloy elements of Mn, Zr, Ti, Cr, Fe, and Si can be contained for improving the high temperature and room temperature strength. Suitable contents are: Mn: 0.8 to 1.50%, Zn: 0.3 to 5.0%, Zr: 0.01 to 0.20%, Ti: 0.01 to 0.20%, Cr: 0.01-0.20%, Fe: 0.20-0.50%, Si: 0.10-1.0%. When the content exceeds the upper limit, not only excellent properties can be imparted but also the workability of the material is deteriorated. On the other hand, if it is less than the lower limit, the desired characteristics cannot be imparted.

  That is, according to the aluminum heat exchanger member excellent in corrosion resistance of the present invention, the tube comprises a tube and a fin coated with a Si-based powder having a maximum particle size of 30 μm or less together with a fluoride-based flux containing Zn, Since it contains Cu: 0.001% to 0.10% by mass and has a composition composed of the balance aluminum and inevitable impurities, and is made of a material that is 30 mV or more noble than the fin at the potential after brazing. In this case, good brazing properties can be obtained, excellent corrosion resistance can be exhibited for a long time after brazing, and deterioration of heat exchange performance with time due to corrosion can be avoided.

  Moreover, according to the manufacturing method of the aluminum heat exchanger excellent in corrosion resistance of the present invention, the maximum particle size of 30 μm or less is formed on the surface of the tube having the composition and material according to any one of the first to third aspects of the present invention. A coating material containing Si powder and a fluoride-based flux containing Zn is applied, and the tube and the fin are formed by a brazing heating and generated by a reaction between the coating material and the Al component of the tube. Since it brazes, there is no local melt | dissolution at the time of brazing and favorable brazing property is obtained. Further, the manufactured heat exchanger has excellent corrosion resistance, and the deterioration of the heat exchange performance with time due to fillet corrosion is also prevented.

Below, one Embodiment of this invention is described based on FIG.
The tube for heat exchanger contains Cu: 0.001-0.10%, and if necessary, Mn: 0.05-0.50% and Si: more than 0.10 to less than 0.50%, Further, if necessary, an Al alloy containing one or two of Fe: 0.10 to 0.50% and Ti: 0.01 to 0.20%, with the balance being composed of Al and inevitable impurities. Use. The Al alloy is melted by a conventional method, and is usually formed into a tube 2 through an extrusion process. In this embodiment, the tube 2 has a multi-hole tube structure, and a plurality of passages 2a are formed therein.

In addition, the heat exchanger fins preferably have Mn: 0.8 to 1.50%, Zn: 0.3 to 5.0%, Cu: 0.01 to 0.50%, Fe: 0.00. An Al alloy having a composition containing 20% to 0.50%, Si: 0.10% to 1.0% or more, and the balance of Al and inevitable impurities is used. The Al alloy is melted by a conventional method, and the corrugated fins 3 are formed through a rolling process or the like. In addition, the manufacturing method of the tube 2 and the fin 3 is not specifically limited as this invention, A well-known manufacturing method can be employ | adopted suitably.
The tube 2 and the fin 3 are made of a material having a potential at which the tube 2 is no less than 30 mV nobler than the fin 3 in the potential after brazing.

The tube 2 is coated with an Si powder brazing material, a fluoride-based flux containing Zn, and a coating material to which a binder and a solvent are added as necessary. The Si powder has a maximum particle size of 30 μm or less, and preferably has an average particle size of less than 1 to 5 μm. As the fluoride flux, a fluoride-based flux containing zinc such as KZnF ₃ is used. If desired, one or more of KAlF ₄ and K ₃ AlF ₆ may be used in combination. it can. The size of the fluoride-based flux is not particularly limited as the present invention, but an average particle size of 10 μm or less is desirable. This is because if the thickness exceeds 10 μm, the thickness of the coating film increases, so that the center of the product shrinks during brazing, and the fins peel off after brazing. Moreover, a known thing can be used for a binder and an acrylic resin is used suitably. These materials are mixed with an appropriate solvent such as water or alcohol to obtain a coated product. The mixing ratio of these materials is not particularly limited in the present invention, but preferably the mixing ratio of Si powder: flux: binder: alcohol = 2-4: 7-15: 1-3: 13: 25 And

The coated material is applied to the tube surface by an appropriate method. The method for applying the coated material is not particularly limited, and a spray method, a shower method, a flow coater method, a roll coater method, a brush coating method, a dipping method, and the like can be appropriately employed.
In addition, as for the application quantity of a coated material, the range of 1-5 g / m < ² > is desirable for Si powder. If the amount is less than the lower limit, the amount of the molten solder formed is insufficient and the bonding strength is not sufficient, and if the upper limit is exceeded, the amount of melting of the tube increases and the wall thickness of the tube decreases, which is not preferable. .

The tube 2 and the fins 3 are assembled together with the header plate 4 and the like as necessary to constitute the heat exchanger member 1 and used for brazing. At the time of brazing, the brazing material is dissolved by heating to an appropriate temperature in an appropriate atmosphere such as an inert atmosphere. Examples of the heating temperature at this time include 580 to 620 ° C. Moreover, 1 to 10 minutes are mentioned as a heating holding time. However, these temperatures and heating times are exemplary, and the present invention is not limited to specific conditions.
At the time of brazing, a part of the matrix of the tube reacts with the coated material, and the members are brazed well. On the tube surface, Zn in the flux is diffused by brazing and becomes lower than the inside of the tube.

In the brazing, the flux removes the surface oxide film of the brazing material, prevents oxidation during brazing heating, and further promotes the spreading and wetting of the brazing to improve the brazing property.
At the time of brazing, there is no local dissolution of the tube with Si powder, and good brazing is performed, and an appropriate fillet is formed between the tube and the fin. Further, in the brazed heat exchanger, the tube potential is no less than 30 mV higher than the fin, and the tube corrosion is effectively prevented. Furthermore, the tube surface layer is more base than the inside, and when the tube is corroded, it becomes a surface corrosion state to prevent pitting corrosion and improve corrosion resistance over a long period of time.

The alloys 1-8 for tubes and comparative alloys 1 and 2, the alloys 1-3 for fins, and the comparative alloy 1 which show a chemical composition (balance Al and an unavoidable impurity) in Table 1 were respectively melted. The tube alloy was formed into a flat multi-hole tube having a thickness of 0.25 mm as shown in FIG. 1 by hot extrusion after homogenization heat treatment. On the other hand, the fin alloy was formed into a 0.07 mm thick plate by hot rolling and cold rolling after homogenization. Next, the tube material was roll-coated with Si powder having an average particle size of 2.3 μm and a maximum particle size of 30 μm and a fluoride flux as a mixture of an acrylic resin and isopropyl alcohol and dried. The amount of Si powder applied was 3 g / m ² . As shown in FIG. 2, a mini-core was assembled by combining a tube material and a corrugated fin material, and brazed at 600 ° C. for 3 minutes in a furnace with various oxygen concentrations of nitrogen gas. All cores were well bonded.

  Cores composed of these various material combinations were subjected to a SWAAT 32 day corrosion test. The depth of corrosion that occurred in the tube material after the test was measured. The results are summarized in Table 3. From Table 3, the core made of the combination of the materials of the present invention has a slight degree of corrosion of the tube due to the sacrificial layer effect on the tube surface and the sacrificial anticorrosive effect of the fin, whereas the comparative core has a sacrificial tube sacrifice. It is clear that the corrosion is severe due to the insufficient sacrificial protection effect of the layers and fins.

  As described above, in the heat exchanger satisfying the present invention, the corrosion resistance of the tube is very good, not only causing problems such as gas leakage even after long-term use, but also the pressure resistance strength and heat exchange performance of the product. It is useful for practical use.

It is a figure which shows the tube contained in the member of one Embodiment of this invention. Similarly, it is a figure which shows the member for heat exchangers.

Explanation of symbols

1 Heat exchanger component 2 Tube 3 Fin

Claims (8)

  It is provided with a tube and a fin coated with Si powder having a maximum particle size of 30 μm or less together with a fluoride-based flux containing Zn, and the tube contains, by mass, Cu: 0.001 to 0.10%, and the balance A heat exchanger member made of aluminum having excellent corrosion resistance, characterized in that it has a composition comprising aluminum and inevitable impurities, and is made of a material in which the non-flux coated portion of the tube is no less than 30 mV of the fin at the potential after brazing . The composition of the tube further comprises, in mass%, Mn: 0.05 to 0.50%, Si: more than 0.10% to less than 0.50%. Excellent aluminum heat exchanger component. The composition of the tube further includes one or more of Fe: 0.10 to 0.50% and Ti: 0.01 to 0.20% in terms of mass%. An aluminum heat exchanger member having excellent corrosion resistance according to 1 or 2.   The average particle diameter of the said Si powder is less than 1-5 micrometers, The member for aluminum heat exchangers excellent in corrosion resistance in any one of Claims 1-3 characterized by the above-mentioned. The member for aluminum heat exchangers with excellent corrosion resistance according to any one of claims 1 to 4, wherein the fluoride-based flux containing Zn contains zinc potassium fluoride (KZnF ₃ ).   The corrosion resistance according to any one of claims 1 to 5, wherein the fin contains, in mass%, Zn: 0.3 to 5.0%, and the balance is composed of Al and inevitable impurities. Aluminum heat exchanger member with excellent resistance.   In addition to the composition of the fin, by mass, Mn: 0.8 to 1.50%, Zr: 0.01 to 0.20%, Ti: 0.01 to 0.20%, Cr: 0.01 to One or more of 0.20%, Fe: 0.20 to 0.50%, and Si: 0.10 to 1.0% are contained. An aluminum heat exchanger member having excellent corrosion resistance as described in 1.   Applying a coating containing a Si powder having a maximum particle size of 30 μm or less and a fluoride-based flux containing Zn to the surface of the tube having the composition and material according to claim 1, A method for producing an aluminum heat exchanger having excellent corrosion resistance, wherein the fin is brazed by brazing that is generated by a reaction between the coated material and the Al component of the tube by brazing heating.

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