JP2011245516A - Method for manufacturing braze-joined aluminum member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a braze-joined Al member which has excellent corrosion resistance at and around a braze-joined portion between Al members.SOLUTION: The method for manufacturing a braze-joined Al member includes a step of joining a plurality of Al members by use of an Al alloy brazing filler metal wire. The Al alloy brazing filler metal contains Si: 9.0-14.0 mass%, Zn; 0.5-6.0 mass%, Cu: 0.5 mass% or less, and Fe: 0.1-0.9 mass%, the remainder Al and inevitable impurities. The relation of pitting potential between a fillet after brazing using the wire and the circumferential Al member is (pitting potential of fillet)-(pitting potential of Al member)=-150 to 200 mV.

Description

  The present invention relates to a method for producing a brazed and joined Al member comprising a step of joining Al members together with a linear, rod-like or tubular Al alloy brazing wire.

  Conventionally, a heat exchanger of a room air conditioner has been manufactured by using an extruded tube made of Cu as a refrigerant tube and expanding and joining with an Al fin material. In recent years, there has been a move to replace Cu pipes with Al from the viewpoint of recycling and cost reduction of air conditioners. However, since Al is inferior in corrosion resistance to Cu, corrosion resistance life becomes a problem when an Al pipe is used.

  An Al—Si-based brazing material is used for joining the constituent members of the heat exchanger using an Al pipe. However, when the molten brazing material is solidified, the eutectic Si phase that promotes the cathode reaction and the eutectic α phase enriched with component elements such as Zn and Cu are precipitated as a eutectic structure. (Hereinafter referred to as a fillet) and the corrosion resistance of its peripheral part are particularly problematic.

  Patent Document 1 is characterized by comprising a hollow sheath constructed from an Al-Si-based alloy material, a fluoride-based non-corrosive flux powder containing cesium fluoride filled in the sheath, and a Cu wire. An aluminum alloy brazing wire is described.

  However, in Patent Document 1, Cu wire is used to lower the melting point of the brazing material, but Cu is concentrated in the fillet at a high concentration, and the potential of the fillet becomes higher than that of the peripheral portion, so that the corrosion rate is increased. There is a fear.

  In Patent Document 2, a powder made of Al or an Al—Si-based alloy and having two or more holes in the length direction is provided with flux powder and, if necessary, a metal for brazing filler metal components. The powder is filled, and the Si content in the brazing filler component excluding the flux is specified to be 3 to 15 wt%, and the weight ratio of the brazing filler component excluding the flux and the flux is 99.9: 0.1 to 70 : 30 describes a flux-containing Al alloy brazing material characterized in that it is defined by No. 30.

  However, Patent Document 2 does not particularly describe or suggest a method for reducing the pitting corrosion potential of the fillet, and the pitting corrosion potential of the fillet formed by brazing additional heat of the described brazing material with respect to the peripheral portion. This increases the corrosion rate around the fillet.

  Conventionally, since the pipe material was Cu, it was difficult for the problem of corrosion of the fillet part to occur, so there was no need to improve the corrosion resistance by adjusting the pitting corrosion potential of the pipe material and the fin material and the fillet part. It seems that there is no suggestion in the patent literature.

JP 2006-326621 A Japanese Patent Laid-Open No. 8-112691

  The subject of this invention is providing the manufacturing method of the brazing joining Al member excellent in the corrosion resistance of the brazing joining part of Al members, and its peripheral part.

  An Al-Si brazing wire is preferably used for brazing and bonding between Al members, but when the molten brazing material solidifies, the constituent elements are concentrated, so the corrosion resistance of the fillet and its surroundings is a problem. It becomes. The inventors of the present invention have made extensive studies on the wire components, particularly Si and Zn, which affect the corrosion resistance of the fillet and its peripheral part, and greatly improved the corrosion resistance of the fillet and its peripheral part by controlling the component range. I found out that I can do it. The present invention has been made based on this finding.

  In other words, the first invention according to claim 1 is a method of manufacturing a brazed and joined Al member comprising a step of joining a plurality of Al members using an Al alloy brazing wire, wherein the Al alloy brazing wire is provided. Contains Si: 9.0 to 14.0 mass%, Zn: 0.5 to 6.0 mass%, Cu: 0.5 mass% or less, Fe: 0.1 to 0.9 mass%, the balance Al and inevitable The pitting corrosion potential between the fillet after brazing using the wire and the surrounding Al member is (fillet pitting potential) − (Al member pitting potential) = − 150 to 200 mV It is the manufacturing method of the brazing joined Al member characterized by being.

  According to a second aspect of the present invention, the content of Cu according to the first aspect of the present invention is 0.1 to 0.5 mass%.

  Furthermore, in the third invention according to claim 3, the Al alloy brazing wire according to claim 1 or 2 is a tubular structure having a hollow portion, and the hollow portion is filled with flux powder. Is a method for producing a brazed and joined Al member.

  Further, a fourth invention according to claim 4 is the Al alloy brazing material wire according to claim 3, wherein the ratio of the outer diameter to the inner diameter of the tube is 0.1 to 0.55. This is a method for producing a brazed and joined Al member.

  If brazing joining of Al members is performed according to the present invention, the corrosion resistance of the fillet and its peripheral portion can be greatly improved.

An arrangement example of brazing wire during brazing. Schematic diagram of fillet length measurement. The graph which shows the relationship between an electric current density and electrode potential for demonstrating the definition of a pitting corrosion potential.

Hereinafter, the manufacturing method of the brazed and joined Al member of one embodiment of the present invention will be described.
The method for producing a brazed and joined Al member according to this embodiment is a method for producing a brazed and joined Al member comprising a step of joining a plurality of Al members using an Al alloy brazing wire. The material wire contains Si: 9.0 to 14.0 mass%, Zn: 0.5 to 6.0 mass%, Cu: 0.5 mass% or less, Fe: 0.1 to 0.9 mass%, and the balance Al And the pitting corrosion potential between the fillet after brazing using the wire and the surrounding Al member is (pitting corrosion potential of the fillet) − (pitting corrosion potential of the Al member) = − 150 to It is 200 mV (this potential difference is hereinafter referred to as ΔE).

(1) Al alloy brazing material wire The brazing material component in the Al alloy brazing material wire according to the present embodiment will be described.
Si content shall be 9.0-14.0 mass%. Si is added to lower the melting point of the Al alloy. Since the liquidus temperature decreases most when the content is about 12%, if the content is less than 9.0 mass% or exceeds 14.0 mass%, the effect becomes insufficient and the liquidus temperature becomes high. End up. Therefore, Si content is made into the range of 9.0-14.0 mass%, and 9.5-12.5 mass% is especially preferable.

  The Zn content in the Al alloy brazing wire according to the present embodiment is 0.5 to 6.0 mass%. Zn has a function to make the pitting corrosion potential of the Al alloy base, and can reduce the pitting corrosion potential difference between the fillet containing Si at a high concentration and its peripheral portion. If it is less than 0.5 mass%, the effect is not sufficient, and if it exceeds 6.0 mass%, the pitting potential becomes too low and the dissolution of the fillet is promoted. Therefore, the Zn content is in the range of 0.5 to 6.0 mass%, and 1.0 to 3.0 mass% is particularly preferable.

  The Cu content in the Al alloy brazing wire according to this embodiment is 0.5 mass% or less. For example, when joining an Al material sprayed with Zn, Zn on the sprayed surface diffuses into the fillet, and the Zn is concentrated, so that the pitting corrosion potential of the fillet becomes too low, and the dissolution of the fillet may be promoted. . In such a case, when Cu is added, when the molten brazing material is solidified, the added Cu is concentrated, and the pitting corrosion potential of the fillet is made noble, so that the dissolution of the fillet is suppressed. Is preferred. The reason why the Cu content is 0.5 mass% or less is that if Cu exceeds 0.5 mass%, the pitting corrosion potential of the fillet becomes too noble and may increase the corrosion rate. Moreover, when adding Cu, it is preferable that the content shall be 0.1 mass% or more. This is because this effect is not sufficient when the content is less than 0.1 mass%.

The Fe content in the Al alloy brazing wire according to this embodiment is 0.1 to 0.9 mass%.
Fe may crystallize out as an Fe-based intermetallic compound during casting and may reduce the corrosion resistance. Therefore, it is preferable that the amount be less, more preferably 0.4 mass% or less, and further 0.2 mass% or less. desirable. The reason why the lower limit is set to 0.1 mass% is that if the wire is manufactured by a normal manufacturing method, the Fe content becomes 0.1 mass% or more.

  The inevitable impurities of the Al alloy brazing wire according to the present embodiment are desirably limited to 0.05 mass% or less for each component and 0.15 mass% or less as a whole.

  Next, the relationship between the fillet pitting potential of the fillet and the surrounding pitting corrosion potential in the present embodiment is in a range of ΔE = −150 to 200 mV. Here, the periphery of the fillet is a range in which electrical contact can be made with the fillet when corrosion progresses, specifically, an area of about 50 mm from the fillet. Furthermore, when a plurality of members having different pitting corrosion potentials are joined around the fillet, it is desirable that the potential difference with the most base part is within the above range. The base phase of pitting potential dissolves preferentially over the noble phase. The pitting potential difference is an index representing the preferential dissolution rate. The larger the pitting potential difference, the higher the dissolution rate of the base phase of the pitting potential. In the case of ΔE <0 mV, the fillet becomes the most basic phase, so that the fillet can be preferentially dissolved. In the range of −150 mV ≦ ΔE <0 mV, preferential dissolution of the fillet occurs, but since the dissolution rate is slow, it does not cause significant corrosion of the fillet. At ΔE <−150 mV, the fillet pitting potential is too low compared to the Al member pitting corrosion potential, so that the fillet dissolution rate increases and the fillet disappears early. On the other hand, when ΔE ≧ 0 mV, the Al member around the fillet becomes the most basic phase, and therefore the Al member around the fillet can be preferentially dissolved. In the range of 0 mV ≦ ΔE ≦ 200 mV, preferential dissolution of the Al member around the fillet occurs, but since the dissolution rate is slow, the Al member around the fillet is not significantly corroded. At ΔE> 200 mV, since the pitting potential of the Al member is too low compared to the pitting corrosion potential of the fillet, the dissolution rate of the Al member increases and the Al member disappears early. For the above reasons, the fillet pitting potential has a relationship with the surrounding pitting corrosion potential in a range of ΔE = −150 to 200 mV. More desirably, the relationship between the pitting corrosion potential of the fillet and the surrounding pitting corrosion potential is more preferably ΔE = −50 to 100 mV.

  In the present embodiment, the flux powder filled in the hollow portion is preferably an Al fluoride flux or a fluoride Cs flux. At this time, the volume ratio of the flux to Al is preferably 1 to 30%, and the ratio between the outer diameter and the inner diameter of the tube is 0.1 to 0.55.

  A method for producing the Al alloy brazing wire according to the present embodiment will be described. First, an Al alloy cylindrical billet having the above alloy composition is prepared. When the flux powder is filled, a hollow hole is made in the billet, and the flux is filled inside the hole. Next, the billet is extruded into a rod shape or a line shape by a normal method, and is subjected to a drawing process as necessary to obtain a predetermined shape.

(2) Al member The Al member joined by the Al alloy brazing wire is a member made of an Al alloy (an alloy containing Al as a main component). As the Al alloy, 1000 series alloys represented by JIS 1100, 1200, etc., 3000 series alloys represented by JIS 3003, 3004, etc. and 6000 series alloys represented by JIS 6061, 6063, etc. are preferably used. A sacrificial anticorrosive layer is generally provided on the surface of the Al member. When it is applied by Zn spraying, the spraying amount is preferably 5 to ²⁰ g / m ² , and when it is applied by an Al—Zn cladding layer, the Zn content is preferably 0.5 to 3%. For example, when a 2000 series alloy typified by JIS2024 is used as the Al member, the potential of the Al member becomes too noble and the relationship ΔE <−150 mV is likely to occur. Further, when the Zn concentration of the Al—Zn cladding layer exceeds 5%, the potential of the Al member becomes too low, and the relationship ΔE> 200 mV is likely to occur.
The Al member is, for example, a pipe material. Any ordinary extruded tube, conform extruded tube, and portfall tube are preferably used as the tube material.

  In one example, the Al member is Si: 0.2 to 1.0 mass%, Cu: 0.05 to 0.7 mass%, Mn: 0.3 to 1.5 mass%, Fe: 0.1 to 0.7 mass%. And the balance is Al and inevitable impurities.

  The Si content is preferably in the range of 0.2 to 1.0 mass%. Si is an element that improves the strength by dissolving in Al or generating an intermetallic compound. Furthermore, the addition of Si makes the potential of Al noble. When the Si content is 0.2 mass% or more, such a Si addition effect can be sufficiently obtained. Moreover, when there is too much Si content, there exists a possibility that the crystallized single-piece | unit Si may become a cathode and may reduce corrosion resistance, but if it is 1.0 mass% or less, there is no such fear. Therefore, the Si content is set to 0.2 to 1.0 mass%. A more desirable Si content is 0.3 to 0.6 mass%.

  The Cu content is preferably in the range of 0.05 to 0.7 mass%. Cu has a function of making the pitting corrosion potential noble. In order to obtain this effect, it is desirable that the amount of Cu be 0.05 mass% or more. Also, if the Cu content is too high, Cu-based intermetallic compounds may precipitate in the Al alloy due to the thermal history during material production, and this Cu-based intermetallic compound promotes the cathode reaction, so the corrosion rate. May be increased. This phenomenon hardly occurs when the amount of Cu is 0.7 mass% or less. Therefore, the content of Cu is desirably 0.05 to 0.7 mass%. A more desirable Cu content is 0.1 to 0.5 mass%.

  The Mn content is desirably in the range of 0.3 to 1.5 mass%. Mn is an element that crystallizes or precipitates as an Al—Mn intermetallic compound to improve the strength. Moreover, the Al—Mn intermetallic compound takes in Fe when it is generated. The Al—Fe—Mn intermetallic compound is more inactive in the cathode reaction than the Al—Fe intermetallic compound, and has a function of suppressing the influence of corrosion resistance inhibition by Fe. When the Mn content is 0.3 mass% or more, such a Mn addition effect can be sufficiently obtained. If the Mn content is too large, a huge intermetallic compound may be crystallized and the extrusion processability may be impaired. However, if the Mn content is 1.5 mass% or less, there is no such fear. Therefore, it is desirable that the amount of Mn added is 0.3 to 1.5 mass%. A more desirable Mn content is 0.8 to 1.3 mass%.

  If the content of Fe contained in the Al alloy is too large, it may crystallize out as an Fe-based intermetallic compound during casting and reduce the corrosion resistance, but the Fe content is 0.1 to 0.7 mass%. In such cases there is no such risk. The Fe content is more preferably 0.4 mass% or less, and further preferably 0.2 mass% or less. The reason why the lower limit is 0.1 mass% is that the content of Fe becomes 0.1 mass% or more when an Al member is manufactured by a normal manufacturing method.

  The Al alloy may contain Mg, Cr, Ti, V, In, Sn, etc. for the purpose of improving strength and corrosion resistance. As for these elements, it is desirable that it is 0.3 mass% or less on the whole.

  In addition to the above components, the remainder of the Al alloy is composed of Al and inevitable impurities. Ingredients that are inevitable impurities are each preferably 0.05 mass% or less, and the total amount is preferably 0.15 mass% or less.

  Examples of the present invention and comparative examples will be described below. In the following Examples and Comparative Examples, Al pipes were joined using a cylindrical Al alloy brazing wire and an Al alloy brazing wire in which a hollow portion was filled with a flux.

(1) Joining Using Cylindrical Al Alloy Brazing Wire In Invention Examples 1 to 28 and Comparative Examples 1 to 13, two Al pipes are formed using a cylindrical Al alloy brazing wire by the following method. Bonding was performed.
First, a billet of an Al alloy having the alloy composition shown in Table 1 was prepared, and then the billet was heated to 520 ° C. and then extruded to form a wire having a diameter of 2 mm. 1 to 28 Al alloy brazing wire was prepared.
Next, two Al pipes were joined using the produced Al alloy brazing wire. The joining Al tube used for the evaluation was obtained by extruding a cylindrical billet of JIS3003 and through a drawing process to produce a tube having an outer diameter of φ10 mm and an inner diameter of φ8 mm (A tube) and a tube having an outer diameter of φ8 mm and an inner diameter of φ6 mm (B tube). . Next, the same amount of Zn was sprayed on both the A tube and the B tube, and diffusion treatment was performed at 480 ° C. for 5 hours. The amount of sprayed Zn is as shown in Table 2.

Next, as shown in FIG. 1, 5 mm of the B tube was inserted into the A tube, and the wire processed into a ring shape was arranged at the joint. A 10 g / m ² Al fluoride flux was applied to the joint in advance. Thereafter, two Al tubes were joined by torch brazing at 610 ° C. for 5 seconds.

  The following evaluation was performed on the bonded Al pipe produced as described above.

(1) Brazing As shown in FIG. 2, it was confirmed by cross-sectional structure observation whether a fillet was formed in a 5 mm region where the B tube was inserted into the A tube. The case where the length of the fillet was 4.5 mm or more and 5 mm or less was rated as ◯, the fillet length was 4.0 mm or more and less than 4.5 mm, and the fillet length was less than 4.0 mm as x.

(2) Corrosion test Using a bonded Al pipe, a CASS test according to JIS H8601 was conducted for 500 hours. After the test, cross-sectional observation was performed, and the case where the fillet disappeared due to corrosion or the through hole was generated in the Al tube was evaluated as x, and the others were evaluated as ◯.

(3) Pitting potential The pitting corrosion potential of the fillet and the surrounding tube was measured by an anodic polarization curve. Specifically, the pitting potential was measured by the following method. Using a three-electrode cell, the polarization curve in the dynamic potential method was measured at room temperature at a potential sweep rate of 20 mV / min. For the measurement of the anodic polarization curve, a 5% NaCl aqueous solution, which was previously deaerated by blowing nitrogen gas, was used as a test solution. The test electrode was used by cutting the test material into a predetermined size, leaving an exposed portion of 1 × 1 cm ² and covering with a seal and an epoxy resin. A platinum electrode was used as the counter electrode, and a silver / silver chloride electrode (Ag / AgCl) in a saturated KCl solution was used as the reference electrode. An example of the anodic polarization curve is shown in FIG. In the anodic polarization curve of FIG. 3, the potential when the anode current density rapidly increased was defined as the pitting corrosion potential.
In this example, the most base part around the fillet was the Zn sprayed surface of the tube surface, and the potential difference between this and the fillet was evaluated.

  The results of (1) to (3) are summarized and shown in Table 2.

  As is apparent from Table 2, in Examples 1 to 28 of the present invention, the brazing property was good, and the corrosion resistance of the fillet and its peripheral portion was excellent.

  In Comparative Examples 1, 2, 7, and 8, since the Si content of the wire deviated from the scope of the present invention, the fillet length was short and through-hole corrosion occurred in the fillet. In Comparative Examples 3 and 9, through-holes were generated in the Al tube due to the small amount of Zn in the wire. In Comparative Examples 4 and 10, through wire pitting was generated in the fillet because of the large amount of Zn in the wire. In Comparative Examples 5 and 12, since the pitting corrosion potential of the fillet was too low compared to the tube surface, through pitting corrosion occurred on the fillet. In Comparative Examples 6 and 13, since the pitting corrosion potential of the fillet was too noble compared to the tube surface, a through hole was generated in the Al tube. In Comparative Example 11, a through-hole was generated in the Al tube because of a large amount of Cu in the wire.

(2) Joining using Al alloy brazing filler metal wire filled with flux in hollow portion In inventive examples 29 to 60, comparative examples 14 to 26, and reference examples 1 to 4, the hollow portion was fluxed by the following method. Two Al pipes were joined using an Al alloy brazing filler metal wire filled with.
The Al alloy brazing material wire in which the hollow portion was filled with the flux was produced by the following method. First, an Al alloy billet having the alloy composition shown in Table 3 was prepared, and then the billet was heated to 520 ° C. and then extruded to form a wire having a diameter of 2 mm. Next, a hollow hole was made in the billet, and the inside of the hole was filled with an Al fluoride flux. Al alloy brazing wire having a tubular structure of 30 to 66 was produced. The size of the hollow hole formed in the billet was determined so that the ratio of the outer diameter to the inner diameter of the Al alloy brazing material wire having a tubular structure was a value shown in Table 3.
Two Al pipes were joined using the produced Al alloy brazing wire, and the above evaluations (1) to (3) were performed. The joining method of the Al pipe is as described in the section “(1) Joining using a cylindrical Al alloy brazing wire”. However, since the flux was contained in the wire, the flux was not applied to the joint.

  The evaluation results of the above (1) to (3) are summarized and shown in Table 4.

  As is apparent from Table 4, in inventive examples 29 to 60, the brazing property was good, and the corrosion resistance of the fillet and its peripheral portion was excellent.

  In Comparative Examples 14, 15, 20, and 21, since the Si content of the wire deviated from the scope of the present invention, the fillet length was short and through-hole corrosion occurred in the fillet. In Comparative Examples 16 and 22, through-holes were generated in the Al tube due to the small amount of Zn in the wire. In Comparative Examples 17 and 23, through-hole corrosion occurred in the fillet because of the large amount of Zn in the wire. In Comparative Examples 18 and 25, the pitting corrosion potential of the fillet was too low as compared with the tube surface, and thus, through pitting corrosion occurred in the fillet. In Comparative Examples 19 and 26, since the pitting corrosion potential of the fillet was too noble compared with the tube surface, a through hole was generated in the Al tube. In Comparative Example 24, since there was much Cu of the wire, a through hole was generated in the Al tube.

  In Reference Examples 1 and 3, since the amount of flux was small with respect to Al of the wire, the fillet length was somewhat shortened, but the corrosion resistance of the fillet and its peripheral part was excellent. In Reference Examples 2 and 4, since the amount of flux was large with respect to Al of the wire, the fillet length was somewhat shortened, but the corrosion resistance of the fillet and its peripheral part was excellent.

  Thus, according to the present invention, a method for producing a brazed and joined Al member having excellent corrosion resistance at the brazed joint and its peripheral part can be provided. This method has a remarkable industrial effect.

Claims (4)

A method for producing a brazed joined Al member comprising a step of joining a plurality of Al members using an Al alloy brazing wire,
The Al alloy brazing wire contains Si: 9.0 to 14.0 mass%, Zn: 0.5 to 6.0 mass%, Cu: 0.5 mass% or less, Fe: 0.1 to 0.9 mass% The balance Al and inevitable impurities,
The relationship between the pitting corrosion potential of the fillet after brazing using the wire and the surrounding Al member is (fillet pitting potential) − (pitting corrosion potential of the Al member) = − 150 to 200 mV A method for producing a brazed bonded Al member. The method for producing a brazed and joined Al member, wherein the Cu content according to claim 1 is 0.1 to 0.5 mass%. The method for producing a brazed and joined Al member, wherein the Al alloy brazing wire according to claim 1 or 2 has a tubular structure having a hollow portion, and the hollow portion is filled with a flux powder. .   The method for producing a brazed and joined Al member according to claim 3, wherein the ratio of the outer diameter to the inner diameter of the pipe is 0.1 to 0.55.