JPWO2018147348A1 - Aluminum extruded flat multi-hole tube excellent in outer surface anticorrosion property and aluminum heat exchanger using the same - Google Patents

Abstract

In aluminum extruded flat multi-hole pipes, to effectively enhance the corrosion resistance on the outer peripheral surface of the pipe. In an aluminum extruded flat multi-hole tube 10 formed by extrusion using an aluminum tube main body material and an aluminum sacrificial anode material that is electrochemically less basic than that, the tube outer peripheral length on the outer surface side of the tube peripheral wall portion 14 The sacrificial anode portion 18 was formed by exposing the aluminum sacrificial anode material over the entire circumference of L or at least at a part of the flat portion thereof.

Description

  The present invention relates to an aluminum extruded flat multi-hole tube having excellent outer surface anticorrosion properties and an aluminum heat exchanger using the same, and in particular, transmission of heat exchangers, particularly automobile heat exchangers such as car air conditioners and radiators. The present invention relates to an aluminum extruded flat multi-hole tube for a heat exchanger that can be suitably used as a heat tube and has excellent outer surface corrosion resistance.

  Conventionally, an aluminum extruded flat multi-hole tube having a flat cross-sectional shape as a whole obtained by extrusion processing of an aluminum material has been used as a refrigerant passage tube of an automotive heat exchanger, and a refrigerant is provided in the refrigerant passage. A heat exchanger is constructed by assembling and brazing and fixing aluminum fins clad with an Al-Si-based aluminum brazing material in a direction perpendicular to the refrigerant passage tube, and By flowing air as a heat exchange fluid along such fins, heat exchange is performed between the refrigerant and the air.

  In addition, as the extruded flat multi-hole tube used there, a tube obtained by extruding a billet of aluminum or aluminum alloy is usually employed. For example, JP-A-6-142755 (Patent Document 1). ), JP-A-5-222480 (Patent Document 2), WO2013 / 125625 (Patent Document 3) and the like disclose flat multi-hole tubes having various cross-sectional forms.

  However, in the flat multi-hole tube obtained by extrusion, which is used as a heat transfer tube of such a heat exchanger, the surface of the outer periphery of the tube is generally not subjected to any anticorrosion treatment, The problem of corrosion is inherent, and if such corrosion progresses to create corrosion holes that penetrate the tube wall, the function as a heat exchanger will be completely lost. .

  Therefore, in such a heat exchanger, in order to prevent corrosion of the outer surface of the extruded flat multi-hole tube, conventionally, Zn is adhered to the surface of the extruded flat multi-hole tube in advance by a method such as spraying or painting. Then, Zn is diffused by subsequent brazing heating, and at that time, the Zn diffusion layer formed on the tube surface layer acts as a sacrificial anode for the tube layer deeper than that, and corrodes in the tube thickness direction. Is used to extend the penetrating life of the tube. Thus, in this case, the extruded flat multi-hole tube requires a Zn adhesion step such as spraying or coating of Zn after being extruded, and further, after that, a fluoride flux required for brazing is applied. From the point where a flux coating process to the entire core is required after being assembled to the process or heat exchanger core, the increase in the manufacturing process is unavoidable, and there are problems such as increasing the manufacturing cost. Yes.

  Therefore, as one of the above-described extruded flat multi-hole pipes, an aluminum alloy having a specific component composition is used singly as disclosed in Japanese Patent Laid-Open No. 5-222480 (Patent Document 2). It has been proposed as a measure to produce a flat multi-hole tube having an appropriate anticorrosion property by extruding the billet, but the outer surface corrosion resistance is not sufficient and has recently been high. In addition to not being able to fully meet the demands for anticorrosion and cost reduction, the entire tube is made of a specific material aluminum alloy. The problem of restrictions is also inherent.

  JP-A-63-97309 (Patent Document 4) uses a composite billet composed of an aluminum core material forming material and a skin material forming material made of an Al—Si based aluminum brazing alloy material. A method of manufacturing a clad tube in which a brazing filler metal layer is clad on the outer surface flat portion of the tube peripheral wall by simultaneously extruding has been proposed, but such a clad tube has a sacrificial anode effect. There is no external anticorrosive property.

JP-A-6-142755 Japanese Patent Laid-Open No. 5-222480 WO2013 / 125625 JP-A-63-97309

  Under such circumstances, as a result of intensive studies to improve the outer surface corrosion resistance of the outer peripheral portion of the aluminum extruded flat multi-hole tube obtained by extruding the aluminum material, the present inventors, as an aluminum material to be extruded, By using a normal aluminum tube body material and an Al—Zn-based aluminum sacrificial anode material and simultaneously performing hot extrusion, the Al—Zn-based material is applied to the outer peripheral portion of the obtained aluminum extruded flat multi-hole tube. The sacrificial anode part can be advantageously exposed to form a sacrificial anode part, and the sacrificial anode effect exhibited by the presence of the sacrificial anode part can be Thus, it has been found that excellent outer surface corrosion resistance can be imparted.

  Therefore, the present invention has been completed based on such knowledge, and the problem to be solved is an aluminum extrusion flattened shape which is obtained by extrusion processing of an aluminum material and exhibits a flat cross-sectional shape as a whole. In the multi-hole tube, there is to effectively enhance the anticorrosion property at the outer peripheral portion of the tube, and another problem is that the aluminum extruded flat multi-hole tube in which the anticorrosion property at the outer peripheral portion of the tube is remarkably enhanced by the sacrificial anode effect Another object of the present invention is to provide an aluminum heat exchanger having excellent corrosion resistance obtained by using the heat exchanger.

  In the present invention, in order to solve the problems as described above, an extruded tube having an overall flat cross-sectional shape obtained by extrusion processing of an aluminum material, the tube shafts independently of each other. An aluminum extruded flat multi-hole tube having a plurality of flow paths extending in parallel to the direction and arranged in the longitudinal direction of the flat shape through internal partition walls extending in the tube axis direction. The aluminum material is formed by extrusion using an aluminum tube main body material and an aluminum sacrificial anode material that is electrochemically lower than the aluminum tube main body material, and is formed over the entire outer peripheral surface of the tube or at least the tube. The outer surface anticorrosive, characterized in that the sacrificial anode part is formed by exposing the aluminum sacrificial anode material to a part of the flat part on the outer peripheral surface. Excellent aluminum extruded flat multi-hole tube, it is an gist thereof.

  In the present invention, advantageously, the sacrificial anode portion is present at a ratio of 90% or less of the thickness of the tube peripheral wall portion in the tube peripheral wall portion other than the internal partition wall portion in the tube cross section. Yes.

  In the present invention, the sacrificial anode portion described above is present in a ratio of 50% or more and 100% or less of the peripheral length of the outer peripheral surface of the tube in the cross section of the tube, and is exposed to the outer peripheral surface of the tube. It is desirable that

  Furthermore, in one of the desirable embodiments of the aluminum extruded flat multi-hole tube according to the present invention, the aluminum sacrificial anode material is electrochemically lower than the aluminum tube body material, and the potential difference is 5 mV. As mentioned above, it is preferable that it is 300 mV or less.

  Furthermore, in another desirable aspect of the aluminum extruded flat multi-hole tube according to the present invention, the extruded aluminum material is composed of the aluminum tube main body material and the aluminum sacrificial anode material. A composite billet will be used.

  In addition, in another desirable aspect of the present invention, the composite billet includes a core billet made of the aluminum tube main body material, and a sheath billet made of the aluminum sacrificial anode material, which is located around the core billet. Has an integral core-sheath structure.

  Moreover, in the aluminum extrusion flat multi-hole tube according to the present invention, the extrusion tube is generally formed by extrusion processing of the aluminum material using a porthole die.

  In one preferred embodiment of the aluminum extruded flat multi-hole tube according to the present invention, JIS-named A1000 series pure aluminum material or A3000 series aluminum alloy material is used as the aluminum pipe body material.

  Furthermore, in another preferred embodiment of the present invention, an aluminum alloy material containing Zn is used as the aluminum sacrificial anode material.

  And in this invention, it is comprised including the aluminum extrusion flat multi-hole pipe | tube according to this invention as mentioned above, and the aluminum outer fin brazed and joined to the outer surface of this aluminum extrusion flat multi-hole pipe | tube. The gist of the present invention is also an aluminum heat exchanger.

  Thus, in the aluminum extruded flat multi-hole tube configured according to the present invention, a sacrificial anode portion made of an aluminum sacrificial anode material is formed over the entire outer peripheral surface of the tube or at least a part of the flat portion of the outer peripheral surface of the tube. Is exposed, and the sacrificial anode effect based on the sacrificial anode material can effectively enhance the outer surface anticorrosive property, and thereby, tubes such as radiators, heaters, etc. It can be advantageously used as a heat transfer tube of a heat exchanger excellent in corrosion resistance on the outer surface side.

  In addition, the aluminum extruded flat multi-hole tube according to the present invention is composed of an aluminum tube main body material and an aluminum sacrificial anode material, and is formed by co-extrusion of these two materials. The outer surface anticorrosion property can be effectively exhibited by the aluminum sacrificial anode material while ensuring the aluminum tube body material, which allows the design of the desired extruded flat multi-hole tube. It also has the advantage that the degree can be increased advantageously.

  Furthermore, in an aluminum heat exchanger constructed by assembling an aluminum extruded flat multi-hole tube according to the present invention and an aluminum outer fin and joining them by brazing heating, the aluminum extruded flat The excellent outer surface anticorrosive properties of the hole tube can advantageously increase the anticorrosion properties as a heat exchanger.

It is sectional explanatory drawing which shows typically an example of the aluminum extrusion flat multi-hole pipe | tube according to this invention, Comprising: (a) shows the whole figure, (b) expands a part of the width direction center part. (C) is a cross-sectional explanatory view showing an enlarged part of the width direction end portion of the example in which the sacrificial anode portion is formed in different thicknesses. It is explanatory drawing which shows the cross section of the composite billet used in the Example. It is explanatory drawing which shows the cross section of the single billet used in the Example.

  Hereinafter, in order to clarify the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings.

  First, FIG. 1 schematically shows an example of an aluminum extruded flat multi-hole tube according to the present invention in the form of a cross section in a direction perpendicular to the longitudinal direction (tube axis direction). Yes. The flat multi-hole tube 10 according to the present invention is an extruded tube made of an aluminum material having a flat cross-sectional shape as a whole, and is composed of rectangular holes extending in parallel to the tube axis direction independently of each other. A structure in which a plurality of the channels 12 are provided and the plurality of channels 12 are arranged at predetermined intervals in the tube width direction, in other words, in the longitudinal direction of the flat shape (left and right in the drawing). It is said that. Further, the corresponding upper surface and lower surface of the flat multi-hole tube 10 are respectively flat surfaces, and there are outer fins such as well-known plate fins or corrugated fins made of aluminum or an alloy thereof (see FIG. (Not shown) can be attached by a joining method such as brazing and used as a heat exchanger. In addition, although the cross-sectional shape of the flow path 12 is a rectangular shape here, it is possible to adopt a known circular shape, an elliptical shape, a triangular shape, a trapezoidal shape, or various shapes that are combinations thereof. Is possible.

  In the present invention, in the flat multi-hole tube 10 having such a structure, as is clear from FIG. 1A, the entire circumference of the outer peripheral surface of the tube peripheral wall portion 14 or at least one flat portion is provided. The sacrificial anode portion 18 made of the aluminum sacrificial anode material is exposed in the portion (here, the entire circumference), while the portion where the sacrificial anode portion 18 is not exposed, that is, the adjacent flow paths 12 and 12. An ordinary aluminum tube main body material is present around the flow path 12 including the internal partition wall portion 16 positioned between them so that the characteristics as a tube can be maintained. Here, as shown in the drawing, the tube peripheral wall portion 14 constitutes the outer peripheral wall of the flat multi-hole tube 10 and functions as an external partition wall for each flow path 12.

  Further, when the sacrificial anode portion 18 formed on the tube peripheral wall portion 14 is located on the tube peripheral wall portion 14 as shown in FIG. The thickness Ts is 90% or less, desirably 80% or less, and the lower limit thereof is preferably 1% or more, more preferably 5% or more. . That is, Ta ≦ 0.9 × Ts and Ta ≧ 0.01 × Ts are preferable. When the thickness Ta of the sacrificial anode portion 18 exceeds 90% of the wall thickness Ts of the tube peripheral wall portion 14, Zn contained in the sacrificial anode portion 18 becomes thicker in the tube peripheral wall portion 14 during brazing heating. It becomes easy to diffuse to the whole, and after the sacrificial anode part 18 is corroded, the pipe peripheral wall part 14 is likely to be penetrated and the pipe peripheral wall part 14 becomes too thin. As a result, problems such as a decrease in pressure resistance are caused. As described above, the sacrificial anode portion 18 is configured to be present on the outer peripheral surface side of the tube peripheral wall portion 14 at a predetermined thickness, whereby the pipe peripheral wall portion 14 is preferentially corroded by the sacrificial anode effect. As a result, excellent outer surface anticorrosive properties can be advantageously imparted to the outer peripheral portion of the pipe.

  Further, the sacrificial anode portion 18 as described above is exposed over the entire tube circumferential length L of the flat multi-hole tube 10 or at least on the outer surface side of the tube peripheral wall portion 14 of a part of the flat portion. The exposure range is desirably configured to be exposed in a range corresponding to 50% or more and 100% or less of the total circumference L of the outer peripheral surface of the pipe, preferably 60% or more, more preferably 70% or more is advantageously employed. As described above, since the sacrificial anode portion 18 is exposed over a region of 50% or more of the total circumference L of the tube, the corrosion resistance due to the sacrificial anode effect can be expressed more advantageously. In particular, the most preferable state is a case where the sacrificial anode portion 18 exists over the entire circumference L of the tube as shown in FIG. Note that the thickness of the sacrificial anode portion 18 in the entire circumference L of the tube does not have to be the same over the entire exposed region. For example, as shown in FIG. It is also possible to expose the sacrificial anode portion 18 having a large proportion. Further, it is desirable that the sacrificial anode portion 18 is continuously exposed with respect to the entire circumference L of the tube, but is partially discontinuous or at a predetermined length. Even if it is exposed in a form extending in the pipe axis direction at a plurality of positions in the pipe circumferential direction, there is no problem.

  Note that the aluminum sacrificial anode material used in the present invention is electrochemically lower than the aluminum tube body material. Therefore, the potential difference between these materials exceeds 0 mV, but is preferably in the range of 5 mV to 300 mV. When this potential difference is 5 mV or more, the sacrificial anode effect is surely easily exhibited even in a more severe corrosive environment. On the other hand, when the potential difference exceeds 300 mV, the sacrificial anode effect becomes prominent, and problems such as severe corrosion consumption of the sacrificial anode material are caused. In this way, the sacrificial anode portion 18 is effective in the sacrificial anode effect due to being lower in potential than the flow passage 12 side portion made of the aluminum tube main body material in the tube peripheral wall portion 14, and the like. This is because the corrosion resistance of the inner surface of the flow path can be expressed more advantageously.

  By the way, in such a flat multi-hole tube 10, the aluminum tube main body material which comprises the circumference | surroundings of the flow path 12 containing the internal partition part 16 located between the adjacent flow paths 12 and 12 is conventionally used by extrusion process. Aluminum materials used in the production of flat multi-hole tubes can be used as they are, and for example, JIS-named A1000 series pure aluminum materials, A3000 series aluminum alloy materials, etc. can be used. In order to make the electric potential noble in such an aluminum material, a predetermined amount (for example, about 0.1 to 0.7 mass%) of Cu may be contained as an alloy component. Further, as the sacrificial anode material for providing the sacrificial anode portion 18, a known aluminum alloy material that is electrochemically lower than the above-described tube body material, in other words, has a lower natural potential, is used. An aluminum alloy containing a predetermined amount of Zn as an alloy component, generally about 0.1 to 10% by mass, or the like will be used.

  The flat multi-hole tube 10 according to the present invention as described above uses the above-described tube body material and sacrificial anode material as the aluminum material to be extruded, and simultaneously extrudes these materials from the port hole die. However, the tube body material and the sacrificial anode material are generally used as a composite billet having a core-sheath structure. Specifically, in the hollow portion provided in the sacrificial anode material (center portion), for example, a rectangular shape (including a curved corner portion), a circle, an oval, an ellipse, an oval and an oval A pipe body material having a cross-sectional shape corresponding to the hollow portion, such as a combination of polygons and the like, and having a cross-sectional dimension optimized, and joining and integrating them by welding or the like, thereby A composite billet having a structure in which a sheath portion made of a sacrificial anode material is integrally formed around a core portion made of a main body material is used.

  In addition, various known means can be adopted for the production of such a composite billet, for example, a sheath billet is formed by providing a through-hole of a predetermined size at the center of a billet made of a sacrificial anode material, and In addition to the method of inserting and integrating the core billet made of the tube body material into the through hole, such a sheath billet is produced in the form of being divided into two, and the core is formed in the space of the two divided billets. In the form in which the billet is arranged, it is possible to form the target composite billet by a method of fixing the whole by welding or the like and integrating them.

  In addition, a method of hot extrusion using a die having a plurality of extrusion ports, a so-called porthole die, is applied to such a composite billet as in the case of manufacturing a conventional extruded flat multi-hole tube. Thus, the target extruded flat multi-hole tube can be obtained. At this time, a die having a long extrusion port arranged to correspond to a plurality of flow paths of the flat multi-hole tube On the other hand, the composite billet is arranged so that the longitudinal direction in the predetermined cross-sectional shape of the tube body material arranged inside the composite billet coincides with the longitudinal direction of the extrusion port of the die, Extrusion is performed. By adopting the extrusion form for the port hole die of such a composite billet, the sacrificial anode material arranged on the outer surface of the composite billet is effective over the circumference of the flat shape of the resulting flat multi-hole tube. Therefore, the sacrificial anode part can be advantageously exposed to the pipe outer peripheral surface of the pipe peripheral wall part.

  By the way, the aluminum extruded flat multi-hole tube according to the present invention as described above can be suitably used as a refrigerant flow path member in a heat exchanger. And when using the aluminum extrusion flat multi-hole pipe according to the present invention as a refrigerant passage pipe, for example, a pair of aluminum header tanks arranged at a distance from each other, and a width direction ventilation direction between both header tanks And a plurality of extruded aluminum flat multi-hole tubes arranged in parallel with each other at intervals in the longitudinal direction of the header tank and connected to both header tanks, and adjacent flat multi-holes Aluminum corrugated fins, outer fins, placed between the tubes and outside the flat multi-hole tubes at both ends and brazed to the flat multi-hole tubes, and arranged outside the corrugated fins at both ends The heat exchanger is constructed in a structure comprising an aluminum side plate brazed to such fins. Of course, in addition to the heat exchanger having such a structure, it is needless to say that the aluminum extruded flat multi-hole pipe according to the present invention can be used as a refrigerant passage pipe in various known heat exchangers. That's where it is.

  As is well known, a pair of header tanks in a heat exchanger distributes and flows refrigerant or coolant from one header tank to a flat multi-hole tube, and the other header tank is flat flat. The coolant or coolant that has flowed out of the hole tube is gathered. For example, as is known, the header plate and the header plate are brazed oppositely, or the plate is bent into a tubular shape. In addition to the one formed by welding or brazing the joining portion of the tubular shape, an extruded tube extruded into a tubular shape or the like is used.

  The exemplary embodiments of the present invention have been described in detail above, but these are merely examples, and the present invention is interpreted in a limited manner by specific descriptions according to such embodiments. It should be understood that it is not done.

  And this invention can be implemented in the aspect which added various change, correction, improvement, etc. based on the knowledge of those skilled in the art, and such an aspect does not deviate from the meaning of this invention. Needless to say, all of them belong to the category of the present invention.

  Hereinafter, representative examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is not limited by the description of such examples. That should also be understood.

  Composite billets a to h and j made of a tube body material and a sacrificial anode material having the component composition (%: based on mass) shown in Table 1 below are manufactured, and each of them is a flat multi-hole tube by hot extrusion. A to H and J were obtained. Moreover, the single billet i of the component composition shown in following Table 1 was manufactured, and the flat multi-hole pipe I was obtained by the hot extrusion process. Then, using the obtained flat multi-hole tubes A to J, the following (1) measurement of the formation range of the sacrificial anode part, (2) potential measurement, and (3) outer surface anticorrosion evaluation were performed.

  Specifically, first, various pipe body billets of 90 mmφ were produced by DC casting according to a conventional method using the components for the tube body material in the composite billets a to h and j shown in Table 1. . On the other hand, sacrificial anode billets prepared in the same manner using the components for sacrificial anode materials in the composite billets a to h and j shown in Table 1 above are variously combined within a circular dimension range of 5 mm to 85 mm to obtain predetermined Molded and processed to the dimensions of Then, a through hole into which the processed tube body material billet can be inserted is formed in the central portion of the cross section of the sacrificial anode billet, and the tube body billet is inserted into the through hole, and the tubes are further inserted. The billet for main body and the billet for sacrificial anode are fixed and joined to each other in the longitudinal direction by MIG welding, and each composite billet ah and j has a cross-sectional form as shown in FIG. It was produced as an integral composite billet 20. Moreover, the simple billet i which consists of a pipe | tube main body component shown by the said Table 1 was produced. The single billet i made of the tube body material component is a single billet shown as 30 in FIG. 3, which is the same as the conventional material not using the sacrificial anode billet. In FIGS. 2 and 3, reference numerals 22 and 32 denote tube body billets, and reference numeral 24 denotes a sacrificial anode billet.

  Subsequently, the composite billet 20 or the single billet 30 thus obtained is heated to 500 ° C. with a billet heater, and then provided with an extrusion port for forming eight rectangular holes (eight flow paths). By using a port hole die similar to that shown in FIG. 1 to perform hot extrusion processing, 8-hole flat multi-hole tubes A to H and I to J (total thickness: 2.0 mm, flat direction) as shown in FIG. Width: 16 mm, pipe peripheral wall portion and inner partition wall thickness: 0.25 mm), respectively.

(1) Measurement of the formation range of the sacrificial anode part About the various flat multi-hole pipes (10) of 8 holes thus obtained, they were cut at a half position in the longitudinal direction of the extrusion, and the cross section was observed. did. That is, the formation range of the sacrificial anode part (18) was measured by measuring the area of the sacrificial anode part (18) with a ruler using a photograph taken of the microstructure of the cross section at a magnification of 25 times. In the measurement of the formation range of the sacrificial anode part (18), the thickness (maximum thickness) of the sacrificial anode part (18) is 90% or less of the thickness of the pipe peripheral wall part (14). Was evaluated as (◯), and when exceeding 90%, it was evaluated as (×). Furthermore, the ratio of the length of the exposed portion of the sacrificial anode portion (18) to the tube outer peripheral length (L) of the tube peripheral wall portion (14) (the sacrificial anode material portion (18) was formed on the outer peripheral surface of the flat multi-hole tube) When the total length of the range was 50% or more, it was evaluated as (◯), and when the pipe outer peripheral length (L) was 0% or more and less than 50%, it was evaluated as (x). Table 2 below shows the results of measuring the formation range of the sacrificial anode part (18) for the flat multi-hole pipes A to H and the flat multi-hole pipes I and J, and the thickness of the pipe peripheral wall part (14). The ratio of the portion of the sacrificial anode part (18) with respect to the maximum thickness and the ratio of the total length of the sacrificial anode part (18) to the tube outer peripheral length (L) are shown.

  As a result of the cross-sectional observation, in the flat multi-hole tubes A to H obtained by the above extrusion processing, the thickness of the sacrificial anode portion (18) formed on the tube peripheral wall portion (14) is the thickest. In the region, it is 80% or less of the thickness of the pipe peripheral wall (14), and more than 50% of the pipe outer peripheral length (L) of such a flat multi-hole pipe (10). It was observed that the sacrificial anode part (18) was exposed.

  Further, in the flat multi-hole tube (10) obtained by hot extrusion in this way, the sacrificial anode portion (18) formed by the sacrificial anode billet in the longitudinal direction of the extrusion has a tube peripheral wall portion. It was also confirmed that (14) was stably exposed on the outer periphery of the tube.

  On the other hand, a flat multi-hole tube I obtained by carrying out hot extrusion using a porthole die using a single billet 30 composed of a billet composition i (Al-0.4% Cu) is a sacrificial anode billet. Since it was not used, no exposed portion of the sacrificial anode portion 18 was present on the outer peripheral surface of the tube. Moreover, in the flat multi-hole pipe J obtained from the composite billet j produced using the billet processed into a square shape of 60 mm × 60 mm as the pipe body billet, the sacrifice formed on the pipe peripheral wall portion (14) The thickness of the anode part (18) was 93% of the thickness of the pipe peripheral wall part (14) at the thickest part. Further, the ratio of the total length of the sacrificial anode portion (18) to the tube outer peripheral length (L) was 90%.

(2) Potential measurement Using the flat multi-hole tubes A to H and flat multi-hole tubes I and J obtained above, the potentials of the tube body material and the sacrificial anode material were measured, respectively. The flat multi-hole tube I is manufactured from a single billet made of only the tube body material, and the sacrificial anode portion (18) is not formed.

  Specifically, brazing heating for fin joining is assumed for flat multi-hole tubes A to H and flat multi-hole tubes I and J, respectively, when they are used as heat transfer tubes in a heat exchanger. And after heat-processing 600 degreeC * 3 minutes, they were cut | disconnected by the length of 40 mm in the extrusion longitudinal direction, respectively. Then, the test material for measuring the potential of the tube body material is cut at a thickness of 1/2 on the cut surface extending in the longitudinal direction of the flat shape (direction perpendicular to the tube axis). Mask the entire surface with the silicone resin except for the part where the lead wire for potential measurement is connected to one side of the cut end face, leaving the exposed surface of the 10mm x 10mm sacrificial anode part (18) at the center in the width direction on the inner surface side. By electrically insulating. Further, the test material for measuring the potential of the sacrificial anode part (18) (sacrificial anode material) leaves an exposed surface of the sacrificial anode material of 10 mm × 10 mm at the center in the width direction of the outer surface on one side of the peripheral wall part, All the portions except for the portion where the potential measurement lead wire was connected to one side of the cut end face were masked with silicone resin to be electrically insulated.

  As a method for measuring the potential, a saturated KCl calomel electrode (SCE) is used as a reference electrode, while a 5% NaCl aqueous solution adjusted to pH 3 with acetic acid is used as a test solution. A method of measuring each potential after immersing the test material in the solution for 24 hours while stirring at room temperature was employed.

  The results of the potential difference between the tube body material and the sacrificial anode material obtained by the above measurement are shown in Table 3 below. In addition, when the potential difference between the tube body material and the sacrificial anode material is 5 mV or more and 300 mV or less, (◎), and when the potential difference exceeds 0 mV and less than 5 mV or exceeds 300 mV, (◯) In the case of 0 mV, it evaluated as (x).

  As apparent from the potential measurement results shown in Table 3, the potential difference between the sacrificial anode portion (18) (sacrificial anode material) and the tube body material of the flat multi-hole tubes A to H after the assumed brazing heating is as follows. 3 to 350 mV, all showing results with an effective sacrificial anode effect.

  On the other hand, in the case where the flat multi-hole tube I is used as a test material, the flat multi-hole tube I is composed of only the tube main body material similar to the conventional material without using the sacrificial anode material. The potential difference was 0 mV because it was a flat multi-hole tube.

  Further, when the same potential measurement as described above was performed using the flat multi-hole tube J as a test material, the sacrificial anode portion (18) (sacrificial anode material) of the flat multi-hole tube J after the assumed brazing heating was performed. ) And the tube body material was 150 mV, which resulted in a sacrificial anode effect.

(3) Evaluation of outer surface anticorrosion property Using the obtained flat multi-hole tubes A to H and flat multi-hole tubes I and J as test materials, SWAAT tests defined in ASTM-G85-Annex A3 are performed. We carried out and verified effect of each outer surface corrosion prevention. This SWAAT test evaluates the outer surface anticorrosion property by repeatedly applying an artificial seawater spray and a wet environment under constant temperature (49 ° C.) conditions. In addition, the corrosion test period was a three-level period of 10 days, 20 days, and 30 days. A case where there was no penetration was evaluated as (◯), and a case where there was penetration was evaluated as (×).

  Specifically, assuming flat multi-hole pipes A to H and flat multi-hole pipes I to J, brazing heating for fin bonding when they are used as heat transfer pipes in a heat exchanger is assumed. After heat treatment at 600 ° C. for 3 minutes, they were cut to a length of 100 mm in the longitudinal direction of extrusion, and both ends of the cut end face where the flow channel was exposed were masked with silicone resin. Moreover, the test liquid used for the SWAAT test produced the artificial seawater by ASTM D1141, and added acetic acid to this artificial seawater, and adjusted it to pH3. In addition, the test condition was 0.5 hour spray-wet 1.5 hour as one cycle, and this cycle was repeated, and the outer surface anticorrosion evaluation test was conducted in three levels of 10 days, 20 days, and 30 days. .

  Then, for the test material for which the outer surface anticorrosion evaluation test was completed, after peeling the silicone sealant resin at both ends, the test material surface was put into a phosphoric acid chromic acid solution heated by a heater. The corrosion product was removed, and the presence or absence of through-holes on the surface of the test material was examined. Specifically, a highly penetrable colored flaw detection liquid is dropped into each flow path of the flat multi-hole tube, and the penetration hole is confirmed by a method of confirming the exudation of the flaw detection liquid from the inner surface of the flat multi-hole pipe. The presence or absence was examined. Furthermore, after embedding the test material whose through-holes were embedded with embedding resin, the cross-section was made with water-resistant paper for the maximum corroded part, and further mirror-finished by buffing. The corrosion situation of the pipe outer peripheral surface of the material was observed. In the SWAAT test of the test material used in the above test, penetration did not occur after 20 days, and if penetration was observed after 30 days or not penetrated (◎), penetration after 10 days. When it did not occur and penetration was observed after 20 days, it was evaluated as (◯), and when penetration was observed after 10 days, it was evaluated as (x).

  Table 4 below shows the results of evaluating the SWAAT test for 10, 20, and 30 days for flat multi-hole tubes A to H and flat multi-hole tubes I to J, respectively.

  As is clear from the results in Table 4, it was confirmed that the flat multi-hole tubes A to H did not have through holes penetrating the peripheral wall portion in the evaluation after 10 days of the SWAAT test. Further, in the evaluation after 20 days, in the flat multi-hole tubes B, C, F, and H, a through-hole penetrating the tube peripheral wall portion was confirmed. Furthermore, in the evaluation after 30 days, no through hole was observed in any flat multi-hole tube other than B, C, F, and H. Therefore, it was recognized that the flat multi-hole tubes A to H are all effectively subjected to external corrosion protection due to the sacrificial anode effect due to the presence of the sacrificial anode portion (18).

  On the other hand, the flat multi-hole tube I is a flat multi-hole tube using only the tube main body material similar to the conventional material without using the sacrificial anode material, and therefore the SWAAT test is performed for 10, 20, and 30 days. As a result, it was confirmed that corrosion holes penetrating the pipe peripheral wall portion were generated in all the evaluations after the test. This is because, like the flat multi-hole tube according to the present invention, the sacrificial anode portion (18) does not exist on the outer peripheral portion of the tube, so the sacrificial anode effect cannot be obtained and the outer surface anticorrosive effect cannot be exhibited. It was recognized that penetration had occurred early.

  In addition, when the flat multi-hole tube J was subjected to the SWAAT test similar to the above for 10, 20, and 30 days, it was found that in all the evaluations after the test, corrosion holes penetrating the peripheral wall portion were formed. It was. Each of the penetrating portions is a portion where the sacrificial anode portion (18) is formed to exceed 90%, and the Zn contained in the sacrificial anode portion (18) is heat treatment corresponding to brazing heating. Occasionally, it diffused throughout the pipe wall (14), and as a result, the sacrificial anode part (18) was consumed at an early stage, and it was recognized that penetration occurred early.

10 flat multi-hole tube 12 flow path (hole)
14 Pipe peripheral wall part 16 Internal partition part 18 Sacrificial anode part 20 Composite billet 22 Pipe body billet 24 Sacrificial anode billet 30 Single billet 32 Pipe body billet

Claims (10)

An extruded tube having a flat cross-sectional shape as a whole obtained by extrusion of an aluminum material, and having a plurality of channels extending in parallel to the tube axis direction independently of each other, and these channels are An aluminum extruded flat multi-hole tube arranged in the longitudinal direction of a flat shape through an internal partition extending in the tube axis direction,
The aluminum material is formed by extrusion using an aluminum tube main body material and an aluminum sacrificial anode material that is electrochemically less basic than the aluminum tube main body material, and at least the outer periphery of the tube An aluminum extruded flat multi-hole tube excellent in corrosion resistance on the outer surface, wherein the sacrificial anode part is formed by exposing the aluminum sacrificial anode material to a part of a flat part on the surface.   2. The outer surface anticorrosive property according to claim 1, wherein the sacrificial anode part is present at a ratio of 90% or less of the thickness of the pipe peripheral wall part in the pipe peripheral wall part other than the inner partition wall part in the pipe cross section. Excellent aluminum extruded flat multi-hole tube.   The said sacrificial anode part was excellent in the outer surface anticorrosive property of Claim 1 or Claim 2 made to exist in the ratio of 50% or more of the circumference of the said pipe | tube outer peripheral surface in a pipe cross section, and 100% or less. Aluminum extruded flat multi-hole tube.   4. The aluminum having excellent outer surface anticorrosion properties according to claim 1, wherein a potential difference between the aluminum sacrificial anode material and the aluminum tube main body material is 5 mV or more and 300 mV or less. 5. Extruded flat multi-hole tube.   The outer surface anticorrosive property according to any one of claims 1 to 4, wherein the extruded aluminum material is a composite billet composed of the aluminum tube main body material and the aluminum sacrificial anode material. Aluminum extruded flat multi-hole tube.   The composite billet has an integral core-sheath structure comprising a core billet made of the aluminum tube main body material and a sheath billet made of the aluminum sacrificial anode material, which is located around the core billet. 5. An aluminum extruded flat multi-hole tube having excellent outer surface anticorrosion properties according to 5.   The aluminum extruded flat multi-hole tube excellent in outer surface anticorrosion property according to any one of claims 1 to 6, wherein the extruded tube is formed by extruding the aluminum material using a porthole die.   The aluminum extruded flat multi-hole tube excellent in outer surface anticorrosion property according to any one of claims 1 to 7, wherein the aluminum tube main body material is an A1000 series pure aluminum material or an A3000 series aluminum alloy material of JIS name. .   The aluminum extruded flat multi-hole tube excellent in outer surface anticorrosion properties according to any one of claims 1 to 8, wherein the aluminum sacrificial anode material is an aluminum alloy material containing Zn.   An aluminum extruded flat multi-hole tube according to any one of claims 1 to 9, and an aluminum outer fin brazed to the outer surface of the aluminum extruded flat multi-hole tube. An aluminum heat exchanger characterized by that.

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