DE112018000792T5 - Extruded flat perforated aluminum tube with excellent exterior surface corrosion resistance, and using aluminum heat exchanger obtained therefrom - Google Patents

Abstract

A flat extruded tube made of aluminum, wherein the corrosion resistance of the outer peripheral surface of the tube is effectively improved. A flat extruded aluminum perforated tube 10 formed by extruding an aluminum tube main body material and a more electrochemically based aluminum sacrificial anode material, wherein a sacrificial anode section 18 is exposed by exposing the aluminum sacrificial anode material along the entirety of the outer circumferential length L of the tube to the outer surface side of a tube peripheral wall section 14 or 14 is formed in at least a part of the flat portion thereof.

Description

TECHNICAL AREA

The present invention relates to a flat extruded aluminum tube having a plurality of openings whose outer surface is highly corrosion resistant and an aluminum heat exchanger using the tube. In particular, the invention relates to a flat extruded aluminum tube having a plurality of openings excellent in corrosion resistance from an outer surface of the tube to which outer fins and other components are joined, and the tube can be advantageously used as a heat transfer tube in a heat exchanger, in particular a heat exchanger for automobiles such. As an automotive air conditioner and a radiator used.

STATE OF THE ART

Conventionally, an extruded aluminum tube having a plurality of openings and having a substantially flat cross-sectional shape obtained by extruding an aluminum material is used as a refrigerant passageway for a heat exchanger used in automobiles, and a refrigerant is sent through the refrigerant passageway. Meanwhile, aluminum fins coated with an Al-Si based aluminum filler metal are soldered to the refrigerant passageway in the direction perpendicular to the tube and attached thereto to form a heat exchanger, and air as a heat exchanging fluid is sent along the aluminum fins. Thus, a heat exchange between the refrigerant and the air takes place.

The above-mentioned flat extruded multi-port tubes are generally produced by subjecting billets made of aluminum or an aluminum alloy to a chamber extrusion. The flat continuous-tube tubes having a plurality of openings having different cross-sectional shapes are shown in FIG JP 6-142755 A (Patent Document 1) JP 5-222480 A (Patent Document 2) and the WO 2013/125625 A1 (Patent Document 3) e.g. B. disclosed.

However, the flat extruded multi-port tube used as a heat transfer tube for a heat exchanger is generally not exposed to an anticorrosion treatment on its outer surface, so that there is an inherent problem that the outer surface of the tube is subject to corrosion. If a tube wall (peripheral wall) of the tube is pierced with corrosive holes due to the progress of corrosion, the function of the heat exchanger is completely lost.

Therefore, in order to prevent the corrosion in the outer surface of the flat tube having a plurality of openings in the above-mentioned heat exchanger, the following measure for improving the life of the tube with respect to its penetration resistance can be made: Zn is passed to the surface of the tube in advance thermal spraying or coating, and the adhered Zn is distributed by the subsequent heating for brazing. A Zn-distributed layer formed on the surface of the tube functions as a sacrificial anode for the underlying tube layer to suppress corrosion in the direction of the thickness of the tube, thereby improving the life of the tube with respect to its penetration resistance , In this case, the flat tube having a plurality of openings requires a step of adhering Zn to the surface of the tube after extrusion by thermal spraying or coating of Zn. Moreover, the tube also requires a step of coating the tube with a fluorinated flux required for brazing or a step of coating the entire part of a core with the flux after the tube is assembled with the heat exchanger, so that the number of production steps is inevitably increased, causing problems such. B. results in an increase in production costs.

For this reason, as an example, the method of obtaining a flat-tube, multi-orifice-type, flat-tube mentioned above suggests the above-mentioned document JP 5-222480 A (Patent Document 2), to extrude a billet of a single aluminum alloy having a certain composition, so that the flat, multi-orifice tube has an intended corrosion resistance. However, the multi-orifice tube thus obtained does not exhibit sufficient corrosion resistance of the outer surface of the tube, and therefore fails to meet the recent requirements for high-grade corrosion resistance and reduction in manufacturing cost. Moreover, when the entirety of the aluminum alloy tube of the particular composition is made, an inherent problem is that the Properties of the obtained tube are limited by the properties of the aluminum alloy having the specific composition.

Indes. discloses the document JP 63-97309 A (Patent Document 4) coextruding a composite billet composed of a core element material and a skin member material of an aluminum alloy AL-Si based filler metal to obtain a coated tube in which a filling metal layer is applied to a flat portion of the outer surface of a peripheral wall portion of the tube is coated. However, the above-mentioned coated tube has no sacrificial anode effect, and has no outer surface with a corrosion resistance.

PRINCIPLES OF THE PRIOR ART

PATENT DOCUMENTS

• Patent Document 1: JP 6-142755 A
• Patent Document 2: JP 5-222480 A
• Patent Document 3: WO 2013/125625 A1
• Patent Document 4: JP 63-97309 A

SUMMARY OF THE INVENTION

TECHNICAL PROBLEMS

Under these circumstances, the inventors made a thorough investigation to improve corrosion resistance in an outer peripheral portion of a flat, multi-orifice, continuously cast aluminum tube obtained by continuously casting an aluminum material. As a result, it was found that an Al-Zn-based aluminum sacrificial anode material is advantageously exposed in the outer circumference of the flat extruded aluminum multi-port tube to provide a sacrificial anode section by providing a known aluminum tube core material and the Al-Zn based aluminum sacrificial anode material as the aluminum materials, which are extrusions and at the same time hot extrusion of these aluminum materials, whereby the outer surface of the peripheral portion of the multi-orifice tube can be given excellent corrosion resistance owing to a sacrificial anode effect due to the presence of the sacrificial anode portion.

The present invention has been completed in consideration of the findings described above. It is therefore a problem to be solved by the invention to provide an extruded tube having a plurality of openings with a substantially flat cross-sectional shape obtained by extruding an aluminum material configured to allow an effective increase in corrosion resistance of an outer surface of the tube. It is another problem to be solved by the invention to provide a flat extruded aluminum multi-port tube in which corrosion resistance of the outer surface of the tube is significantly increased due to a sacrificial anode effect, and to provide a useful aluminum heat exchanger using the flat tube having a plurality of openings, and having excellent corrosion resistance.

SOLUTION OF PROBLEMS

The above-mentioned problem can be solved according to a quintessence of the invention to provide an aluminum tube having a plurality of openings with a substantially flat cross-sectional shape obtained by extruding an aluminum material and the aluminum tube having a plurality of openings is an extruded tube having a plurality of flow passages independently extending parallel to an axial direction of the tube, the flow passages being arranged in a longitudinal direction of the flat cross-sectional shape over inner partition wall portions extending in the axial direction of the tube, characterized in that: the aluminum tube having a plurality of openings an extrusion process is formed in which an aluminum tube core material and an aluminum sacrificial anode material having a lower electrochemical potential than the aluminum tube core material than the aluminum mat are used erial; and exposing the aluminum sacrificial anode material to form a sacrificial anode portion in an entirety of an outer periphery of the tube or in at least a part of a flat portion of the outer circumference of the tube, wherein the multi-aperture aluminum tube has excellent corrosion resistance of the inner and outer surfaces.

In the invention, the sacrificial anode portion is advantageously provided on a peripheral wall portion which is not the inner partition portions in the cross section of the tube, and a thickness of the sacrificial anode portion is not greater than 90% of a thickness of the peripheral wall portion.

Moreover, in the invention, the sacrificial anode portion preferably has a length of 50% to 100% of an outer circumferential length in the cross section of the tube.

In a preferred embodiment of the invention, the aluminum sacrificial anode material has an electrochemical potential lower than that of the aluminum tubular core material, and a difference in potential between the aluminum sacrificial anode material and the aluminum tubular core material is in a range of 5mV to 300mV.

In one of the other preferred embodiments of the multi-port aluminum tube according to the invention, the aluminum extrudable material is a composite billet consisting of the aluminum tubing core material and the aluminum sacrificial anode material.

In another one of the other preferred embodiments of the invention, the composite billet has a one-piece sheath-core structure consisting of a core billet formed of the aluminum tubular core material and a layer billet formed of the aluminum sacrificial anode material and the billet billet is arranged to surround the core billet.

The multi-port aluminum tube according to the invention is generally formed by extruding the aluminum material using a chamber press die.

In one of the other preferred embodiments of the multi-port aluminum tube according to the invention, the aluminum tube core material is a pure aluminum according to a Japanese Industrial Standard (JIS) A1000 series or an aluminum alloy according to the JIS A3000 series.

Moreover, in yet another of the other preferred embodiments, the aluminum sacrificial anode material is a Zn-containing aluminum alloy.

It is another aspect of the invention to provide an aluminum heat exchanger comprising the above-mentioned aluminum tube having a plurality of openings and aluminum outer fins brazed to an outer surface of the multi-port aluminum tube.

ADVANTAGEOUS EFFECTS OF THE INVENTION

The flat extruded aluminum multi-port tube according to the present invention has the sacrificial anode portion formed of the aluminum sacrificial anode material, and the portion is exposed in the entirety of the outer surface of the tube or at least part of a flat portion of the outer tube. The sacrificial anode effect obtained by the sacrificial anode material advantageously improves the corrosion resistance of the outer surface of the tube. Thus, the multi-port tube can be used as a heat transfer tube for a heat exchanger having excellent outer surface corrosion resistance. Examples of the heat exchanger include a radiator and a heater.

In addition, since the flat extruded multi-aperture aluminum tube according to the invention comprises the aluminum tube core material and the aluminum sacrificial anode material, and is produced by simultaneously extruding or coextruding the two materials, characteristics required for the tube are obtained by the aluminum tube core material, while the Corrosion resistance outer surface of the tube can be effectively improved by the aluminum sacrificial anode material. Thus, the freedom of designing the flat extruded multi-port extruded tube to be obtained is advantageously improved.

An aluminum heat exchanger is made by assembling the flat extruded aluminum tube with multiple openings according to the invention and the components such. Aluminum fins and joining the tube and fins together by heating to braze. In this Heat exchangers also advantageously improve the excellent exterior surface corrosion resistance of the flat extruded aluminum multi-port tube, as well as the corrosion resistance of the heat exchanger itself.

list of figures

• The 1 10 are schematic cross-sectional views showing a flat extruded aluminum multi-port tube according to an embodiment of the present invention, in which FIGS 1 (a) is a cross-sectional view showing an entirety of the tube, the 1 (b) is an enlarged view, which shows a part of the central portion in the direction of the width of the tube, and the 1 (c) Fig. 10 is an enlarged view of a part of the end portion of the tube in the direction of the width, showing an example in which a sacrificial anode portion of different thickness is exposed;
• the 2 Fig. 12 is a schematic view which is a cross section of a composite billet used in Examples; and
• the 3 Fig. 3 is a schematic view showing a cross section of a single component billet used in the examples.

MODES FOR CARRYING OUT THE INVENTION

In order to further clarify the present invention, representative embodiments of the invention will be described in detail with reference to the drawings.

With reference to the first schematic cross-sectional views of 1 For example, an example of a flat extruded aluminum multi-port tube according to this invention is shown in a transverse plane perpendicular to a longitudinal direction (axial direction) of the tube. The tube 10 multi-orifice according to the invention is an extruded tube having a substantially flat cross-sectional shape made of an aluminum material and a plurality of flow passages 12 in the form of rectangular holes extending independently of each other in parallel with the axial direction of the tube, and the plurality of flow passages 12 is arranged at a predetermined distance in the direction of the width of the tube, namely in the longitudinal direction of the flat shape (left and right direction in the figures). The upper and lower outer surfaces of the tube 10 with multiple openings are flat surfaces to the known outer fins (not shown in the figures), made of aluminum or an aluminum alloy, such. As disc fins and welded fins are joined by brazing or any other joining method to be used as a heat exchanger. While the cross-sectional shape of the flow passage 12 In this example, the rectangular shape, various other known forms such. As a circle, an oval, a triangle, a trapezoid or combinations thereof be used.

Like from the 1 (a) is clear, in the invention, the flat tube 10 having a plurality of openings having the above-mentioned structure, configured such that a sacrificial anode section 18 made of an aluminum sacrificial anode material into the outer surface of a peripheral wall portion 14 along the entirety of an outer circumferential length L of the tube 10 or is exposed along at least a part of a flat portion in the peripheral wall portion (along the entirety of the circumference in this example). On the other hand, portions in which the sacrificial anode portion is not exposed, namely, portions along a cross-sectional circumference of each flow passage are 12 including an inner partition wall section 16 that is between the adjacent flow passages 12 . 12 is formed from a known aluminum tube core material to ensure the properties of the tube. As can be seen from the figure, the peripheral wall portion determines 14 an outer peripheral wall of the flat tube 10 with multiple openings and serves as an external partition for each of the flow passages 12 ,

When in the peripheral wall section 14 in the flat tube 10 formed with multiple openings sacrificial anode section 18 in the peripheral wall portion 14 is provided, a thickness Ta of the sacrificial anode portion is generally not greater than 90% and preferably not greater than 80% of a thickness Ts of the peripheral wall portion 14 , like from the 1 (b) is apparent. A desirable lower limit of the thickness Ta is 1% and more preferably 5% of the thickness Ts. Namely, Ta ≦ 0.9 × Ts and preferably Ta ≥ 0.01 × Ts. Where the thickness of the sacrificial anode portion 18 90% of the thickness Ts of the peripheral wall portion 14 exceeds, spreads in the sacrificial anode section 18 Zn contained simply over the entire thickness of the peripheral wall portion 14 at the time of heating for soldering. As a result, it is likely that after the consumption of the sacrificial anode section 18 due to corrosion of the peripheral wall portion 14 suffers from the generation of corrosion holes, and also too thin, causing problems such. B. a deterioration of the pressure resistance of the flat tube 10 with multiple openings. By providing the sacrificial anode section 18 in the outer surface of the peripheral wall portion 14 with a predetermined thickness, the peripheral wall portion 14 preferably exposed to the progress of corrosion due to a sacrificial anode effect, such that the outer circumference of the tube advantageously enjoys a remarkable corrosion resistance of the outer surface.

The above-mentioned sacrificial anode section 18 is in the peripheral wall portion 14 along the entirety of the outer peripheral surface L the flat tube 10 with a plurality of openings or in at least a part of a flat portion in the outer circumferential length L the peripheral wall section 14 exposed. The sacrificial anode section 18 is preferably configured to be in the peripheral wall portion 14 with a length of 50% to 100% of the total outer circumferential length L is exposed. The desired exposure ratio is not less than 60%, and more preferably not less than 70% of the outer circumferential length L , The exposure of the sacrificial anode section 18 along the outer circumferential length L the tube with a length not less than 50% of the length L allows corrosion resistance to be advantageously achieved by sacrificial anode effects. In particular, the most desirable embodiment is in the 1 (a) shown in the sacrificial anode section 18 along the entirety of the outer circumferential length L the tube is present. It is noted that the sacrificial anode section 18 along the outer circumferential length L of the tube need not have a constant thickness over the entirety of the exposed area. For example, the sacrificial anode section 18 in the peripheral wall portion 14 be exposed with a thickness that varies in a circumferential direction of the tube, as shown in 1 (c) is apparent. The sacrificial anode section is preferred 18 continuously along the outer circumferential length L exposed in the axial direction of the tube. However, the sacrificial anode portion may be partially discontinuously exposed or exposed to a desired length so as to extend in the axial direction of the tube at a plurality of positions in a circumferential direction of the tube.

It should be noted that the aluminum sacrificial anode material used in accordance with the invention has a lower electrochemical potential than the aluminum tubular core material. The difference in potential between these two materials is thus more than 0 mV, and preferably falls within a range of 5 mV to 300 mV. The difference of the potential of not less than 5 mV allows a stable display of the sacrificial anode effect even under harsher corrosive environments. On the other hand, the potential difference of more than 300 mV causes a marked sacrificial anode effect, resulting in problems such as excessive consumption of the sacrificial anode material due to the corrosion. In summary, the sacrificial anode section allows 18 that has the lower potential than sections on the side of the flow passages 12 and other portions in the peripheral wall portion 14 have made of the aluminum tubular core material, an effective improved sacrificial anode effect, and a more advantageous realization of the corrosion resistance of the inner surfaces of the flow passages.

In the flat tube described above 10 with multiple openings than the aluminum tube core material that surrounds the peripheral portion of the flow passage 12 with the between the adjacent flow passages 12 . 12 formed inner bulkhead section, known aluminum materials are used, which are used in the manufacture of flat extruded multi-port tubes. For example, according to the Japanese Industrial Standard (JIS), materials such as pure aluminum of the 1000 series and aluminum alloy of the 3000 series can be used. Further, a predetermined amount of Cu (for example, 0.1 to 0.7 mass%) may be contained as an alloying ingredient in the aluminum material to increase the potential of the aluminum material. Moreover, as the aluminum sacrificial anode material, around the sacrificial anode section 18 To provide a known aluminum alloy material are used, which has a lower electrochemical potential than the aluminum tube core material described above, ie a lower natural potential. For example, an aluminum alloy containing a predetermined amount of Zn, namely about 0.1-10 mass%, may be used.

In the production of the above-mentioned flat tube 10 with multiple openings according to the invention, the above-mentioned aluminum tube core material and the aluminum sacrificial anode material are used as the aluminum materials, and these aluminum materials are exposed to coextrusion from a porthole die. Generally, the aluminum tube core material and the aluminum sacrificial anode material are provided in the form of a composite billet having a sheath-core structure. In particular, the composite billet has a structure in which the sacrificial anode material is provided within a hollow portion formed in the interior (a central portion) of a Elements of the tube core material is provided. The sacrificial anode material has a cross-sectional shape corresponding to that of the hollow portion, namely shapes such. For example, a rectangle (including one with rounded corners), a circle, an oval, an ellipse, a combination of the oval and the ellipse, and a polygon having its cross-sectional dimensions optimized. The tube core material and the sacrificial anode material are united and integrated by welding or other joining method such that a shell portion consisting of the tube core material is formed around a core portion consisting of the sacrificial anode material.

To manufacture the composite billet, the following various known methods can be employed: a method in which a shell billet is obtained by providing a through hole of a predetermined size in a central part of a billet formed of the sacrificial anode material, and inserting a through hole into the through hole Tube core material trained core billet is introduced and assembled with the Mantelknüppel; and a method in which the sheath billet described above is divided into two pieces, the core billet is placed in a hollow portion defined by the two pieces, and all the above-mentioned members are fixed by a joining method such as welding or another joining method and be connected with each other.

Moreover, as in the case of conventionally fabricating a flat multi-port tube using a so-called chamber shape (chamber pad, chamber tool) having a plurality of extrusion openings, the composite billet described above is subjected to hot extrusion so as to obtain a desired flat tube having a plurality of openings. When the hot extrusion is performed, the composite billet is arranged such that the longitudinal direction in the predetermined cross-sectional shape of the tube core material placed inside the composite billet relative to the die having the longitudinal extrusion openings corresponding to the plurality of flow passages of the flat tube Correspond openings with the longitudinal direction of the extrusion openings of the mold. In this way, the composite billet is subjected to hot extrusion. The above-described extrusion method of the composite billet with the chamber shape allows effective distribution of the sacrificial anode material within the composite billet as far as the flow channel defining partitions existing at the opposite end portions of the flat cross sectional shape of the thus obtained multi-orifice tube such that the sacrificial anode portion is advantageously exposed on the inner surfaces of the flow channels.

The flat extruded multi-hole aluminum extruded tube of the present invention described above is advantageously used in a heat exchanger as a flow channel element for a refrigerant. For example, when the flat tube of the present invention having a plurality of openings is used as a passage tube for the refrigerant, the heat exchanger includes: a pair of spaced apart aluminum balance tanks; a plurality of flat tubes having a plurality of openings arranged between the two surge tanks at a pitch interval parallel to each other in a longitudinal direction of the surge tanks, with their width direction parallel to the ventilation direction, that the opposite ends of each flat tube having a plurality of openings with the respective surge tanks are connected; Outer ribs in the form of aluminum corrugated fins disposed in the spaces between the adjacent flat tubes having a plurality of openings and at the opposite ends of the array outside the flat tubes having a plurality of openings and fixedly connected to the flat tubes having a plurality of openings by brazing ; and aluminum side plates disposed outside of the shaft ribs and connected to the ribs by brazing. The multi-port flat tube according to the present invention may, of course, be used as the passage tube for the refrigerant in various other known heat exchangers than the heat exchanger having the above-described configuration.

As is well known, the refrigerant or refrigerant in the heat exchanger is distributed from one of the two surge tanks into the flat tubes having a plurality of openings and discharged out of the flat tubes having a plurality of openings so that it flows into the other surge tank. The conventional surge tanks, for example, take the form of a pair of opposed balancing plates brazed to the flat tubes having a plurality of openings; a tube formed by bending a plate, and welding and brazing end portions of the obtained tube; and an extruded tube.

Although a typical embodiment of the invention has been described in detail for purposes of illustration, it will be understood that the invention is not limited to the details of the foregoing embodiment.

It is understood that the invention can be practiced with various changes, modifications and improvements that will be apparent to those skilled in the art without departing from the spirit and scope of this invention, and that such changes, modifications, and improvements are also within the scope of this invention.

EXAMPLES

To illustrate the invention in more detail, some typical examples of the invention will be described. It is understood, however, that the invention is not limited to the details of the examples.

Composite billets (a) - (h) and (j) comprising tubular core materials and sacrificial anode materials each having compositions (mass%) shown in the following Table 1 were produced. Each of the composite billets produced was subjected to hot extrusion so that flat tubes AH and J was obtained with multiple openings. In addition, a one-component stick (i) having the composition shown in Table 1 was also produced, so that a flat tube I was obtained with several openings by exposing the billet to hot extrusion. The obtained flat tubes AJ with multiple openings were then evaluated by the following measurements and evaluations: (1) Measurement of a range of formation of a sacrificial anode portion; (2) measurement of an electric potential; and (3) Evaluation of corrosion resistance of the outer surface. Table 1 Type of composite billet Composition of the billet Tube core material Sacrificial anode material (A) Al-0.4% Cu Al-2% Zn (B) Al-0.4% Cu Al-0.2% Zn (C) Al-0.4% Cu Al-0.5% Zn (D) Al-0.4% Cu Al-1% Zn (E) Al-0.4% Cu Al-3% Zn (F) Al-0.4% Cu Al-8% Zn (G) JIS A3003 alloy Al-2% Zn (H) Al-0.4% Cu Al-2% Zn (I) Al-0.4% Cu - (J) Al-0.4% Cu Al-2% Zn

More specifically, various sacrificial anode billets having a diameter of 90 mm were produced by a known continuous casting extrusion process according to the compositions of the sacrificial anode materials for the composite billets (a) - (h) and (j) shown in Table 1. On the other hand, various tube core billets similar to those of the tube core materials for the composite billets (a) - (h) and (j) shown in Table 1 were produced. These tube core material billets were subjected to a molding operation to have a circular shape with a predetermined diameter within a range of 5 mm to 85 mm. Then, a through-hole was formed through a center part in the cross section of each of the above sacrificial anode sticks, and the tube core billet was inserted into the through-hole. In addition, the tube core billet and the sacrificial anode billet were MIG-welded to the opposite longitudinal end faces of the billets and joined so that each of the composite billets (a) - (h) and (j) was a one-piece composite billet 20 which was produced from the 2 having apparent cross-sectional shape. In addition, a one-component billet (i) having the composition of the tube core material shown in Table 1 was produced. This one-component billet having the composition of the tube core material is one of 3 apparent one-component billet 30 which is equivalent to a known billet containing no sacrificial anode stick. In the 2 and 3 represent the reference numerals 22 and 32 the tube core billets, and 24 represents the sacrificial anode stick.

Next was the composite billet thus obtained 20 or one-component billet 30 heated in a billet heating to 500 ° C and subjected to hot extrusion by a conventional Chamber form with extrusion holes was used to form eight rectangular holes (eight flow passages), so that the flat tubes with multiple openings A to H and I to J (Total thickness: 2.0 mm, width in the flat direction: 16 mm and thicknesses of the peripheral wall portion and inner partition portion: 0.25 mm), as shown in FIG 1 can be seen, were produced.

Measurement of the area of formation of the sacrificial anode section

The thus obtained flat tubes ( 10 ) having a plurality of openings having eight openings were cut at a 1/2 position in the extrusion longitudinal direction, and their cross-sectional areas were examined. More specifically, the training areas of the sacrificial anode section ( 18 by measuring with a ruler of a region of the sacrificial anode section (FIG. 18 ) were evaluated in a photomicrograph with 25x magnification of the cross-sectional area. With reference to the above-mentioned measurement of the region of formation of the sacrificial anode section (FIG. 18 ), the results were evaluated as "good" where the ratio of the thickness (largest thickness) of the sacrificial anode portion does not exceed 90% of the thickness of the peripheral wall portion (FIG. 14 ), and as "bad" where the ratio of the thickness is more than 90% of the thickness of the peripheral wall portion (FIG. 14 ) amounted to. Moreover, with respect to a ratio of a length of the exposed portion of the sacrificial anode portion (FIG. 18 ) to the outer peripheral length (L) of the peripheral wall portion (FIG. 14 ), namely a total length of the area in which the sacrificial anode section ( 18 ) was exposed in the outer circumference of the flat tube having a plurality of openings, the results were evaluated as "good" where the ratio is not smaller than 50% of the outer peripheral length (FIG. L ) of the tube, and as "bad" where the ratio was in a range of not less than 0% to less than 50% of the length. In the following Table 2, the results of the above measurement of the formation area of the sacrificial anode section (FIG. 18 ) with respect to each of the flat tubes AH with several openings, the flat tube I and the flat tube J shown with several openings. The following items are shown in the table: the ratio of the largest thicknesses of the sacrificial anode section (FIG. 18 ) in the peripheral wall section (FIG. 14 ); and the ratio of the total length of the exposed sacrificial anode section (FIG. 18 ) to the outer circumferential length ( L ) of the tube. Table 2 Type of flat tube with multiple openings n Condition of formation of the sacrificial anode section (18) Ratio (%) of the largest thickness in the peripheral wall section evaluation Ratio (%) of the total length to the outer circumferential length of the tube evaluation A 80 Well 95 Well B 70 Well 90 Well C 75 Well 80 Well D 50 Well 60 Well e 40 Well 50 Well F 50 Well 60 Well G 80 Well 70 Well H 80 Well 90 Well I 0 Bad 0 Bad J 93 Bad 90 Well

As a result of examination of the cross-sectional surface, it was confirmed that with respect to each of the flat tubes AH having a plurality of openings obtained by the above-mentioned extrusion molding in the peripheral wall portion (FIG. 14 ) formed thickest portion of the sacrificial anode section ( 18 ) a thickness not greater than 80% of the thickness of the peripheral wall portion ( 14 ) would have. Additionally, in each of the flat tubes ( 10 ) with a plurality of openings, the ratio of the total length of the exposed sacrificial anode section ( 18 ) to the outer circumferential length ( L ) of the tube is greater than 50% of the outer circumferential length.

With respect to each of the flat tubes ( 10 ) having a plurality of openings obtained by the hot extrusion described above was also confirmed to be Sacrificial anode section ( 18 ) formed from the sacrificial anode stick, stably along the outer circumference of the peripheral wall portion (FIG. 14 ) were exposed in the longitudinal direction of the extrusion.

On the other hand, the flat tube pointed I with several openings, which was obtained by the one-component billet 30 having the billet composition (i) (aluminum - 0.4% Cu) subjected to hot extrusion with the chamber die, an exposed part of the sacrificial anode section ( 18 ) in the outer circumference of the tube, since no sacrificial anode stick was used. With reference to the flat tube J with multiple openings obtained from the composite billet (j) prepared by forming the tubular billet billet to have 60 mm x 60 mm square cross-sectional shape, it was confirmed that the highest thickness ratio did not exceed 100% of the thickness of the inner billet Partition section ( 16 ) in the middle part of the direction of the width of the tube J was trained after. The highest ratio of the thickness of the sacrificial anode section ( 18 ), which in the peripheral wall section ( 14 ) was 93% of the thickness of the peripheral wall portion ( 14 ) amounted to. The ratio of the total length of the sacrificial anode section ( 18 ) was 90% of the outer circumferential length ( L ) of the tube.

Measurement of the electrical potential

Regarding each of the flat tubes with multiple openings A to H and the flat tubes with multiple openings I and J obtained as described above, the electric potential of each of the tube core material and the sacrificial anode material was measured. It should be noted that the flat tube with multiple openings I was formed from the one-component billet, which consisted solely of the tube core material and no sacrificial anode section ( 18 ) would have.

More specifically, each of the flat tubes has multiple openings A to H and the flat tubes with multiple openings I and J in consideration of heating the tube in brazing for joining the ribs when the tube is used as a heat transfer tube for a heat exchanger, subjected to heat treatment at 600 ° C for 3 minutes, and cut into pieces each having a length of 40 mm in the longitudinal direction of extrusion. The test piece for measuring the electric potential of the tube core material was cut into two half-pieces in a plane extending in the longitudinal direction of the cross-sectional flat shape (in the direction perpendicular to the axis of the tube) so that the thickness of each half-piece becomes half as large What was the thickness of the original specimen, and the entirety of each of the two half-pieces was masked with the silicone resin except for the end surface to which the electric measurement line was connected so that a 10 mm × 10 mm area of the core core material would be in one central part of the half-piece remained exposed in the width direction of the half-piece so as to be electrically insulated. With respect to the specimen for measuring the electric potential of the sacrificial anode portion (FIG. 18 ) (Sacrificial anode material), the entirety of the piece except for one of the opposite end faces to which the lead for the electrical measurement was connected was marked with the silicone resin so as to be electrically insulated so as to have a 10 mm pitch × 10 mm face maintained in the widthwise direction by middle portion exposed from one of the opposite outer surface of the peripheral wall portion of the tube.

To measure the electric potential, the following method was used: As a reference electrode, a saturated KCl calomel electrode (SCE) was used, while as a test solution, a 5% NaCl solution adjusted to pH 3 with acetic acid was used; the solution was stirred at room temperature; the sample remained immersed in the solution for 24 hours; and then the electrical potential of each of the samples was measured.

The results obtained by the above measurement of the electric potential differences between the tube core materials and the sacrificial anode materials are given below in Table 3 below. The differences in electric potential between the tube core materials and the sacrificial anode materials were judged "excellent" when the difference in a range was 5mV to 300mV, with "good" when the difference was in a range of more than 0mV to 5mV or more than 300 mV, and "bad" if the difference was 0 mV. Table 3 Type of flat tube with multiple openings Difference of the potential (mV) evaluation A 150 Outstanding B 3 Well C 10 Outstanding D 100 Outstanding e 250 Outstanding F 350 Well G 100 Outstanding H 150 Outstanding I 0 Bad J 150 Outstanding

As is apparent from the electric potential measurement results shown in Table 3, each of the multi-ported flat tubes A to H after the expected brazing heating has the electric potential difference of 3 to 350 mV between the sacrificial anode portion (FIG. 18 ) (Sacrificial anode material) and the tube core material, indicating that a sufficient sacrificial anode effect has been achieved.

On the other hand, the difference in electric potential with respect to the sample was that on the flat tube having a plurality of openings I 0 mV, since the flat tube with multiple openings like the conventional tube was formed only of the tube core material without containing the sacrificial anode material.

In addition, the difference in electrical potential in the sample, which was on the flat tube with multiple openings J was measured by the same method as described above. The difference in electrical potential between the sacrificial anode section ( 18 ) (the sacrificial anode material) and the tube core material after the expected brazing for brazing was 150 mV, indicating that the sufficient sacrificial anode effect was achieved.

Evaluation of the corrosion resistance of the outer surface

The SWAAT test (seawater acetic acid experiment) defined in ASTM G85 Appendix A3 was made with respect to each of the flat tubes AH having multiple openings and the flat tubes I and J with multiple openings obtained as described above to examine the corrosion resistance of the outer surface of each of the tubes. In the SWAAT experiment, each of the tubes was sampled and subjected to load by repeating the spraying of synthetic seawater and holding in a steam environment at a constant temperature (49 ° C) while evaluating the corrosion resistance of the outer surface of the sample. The corrosion test was conducted in three different periods of 10 days, 20 days and 30 days, and the results were evaluated as "good" if the sample did not suffer from penetration, and "bad" if the sample suffered from penetration ,

More specifically, each of the flat tubes AH has multiple openings and the flat tubes I and J with several openings subjected to a heat treatment at 600 ° C for 3 minutes considering the heating of the tube due to brazing for joining the fins when the tube is used as a heat transfer tube for a heat exchanger, and was cut into pieces, each of which has a length of 100 mm in the longitudinal direction of extrusion, and each of the opposite end surfaces of the cut surfaces to which the flow passages were exposed was masked with a silicone resin. One test fluid used for the SWAAT trial was synthetic salt water prepared according to ASTM D1141. The synthetic salt water was adjusted to pH3 by adding an acetic acid. As an experimental condition, 0.5 hours of spraying the synthetic salt water followed by 1.5 hours holding in a humidity was considered to be one Cycle determined and the cycle was repeated to carry out the evaluation test on the corrosion resistance of the outer surface for three different periods of times of 10 days, 20 days and 30 days.

With respect to the samples subjected to the above-mentioned external surface corrosion resistance evaluation test, the silicone sealant resin on the surfaces of the samples was peeled off, and then a corrosion product on the surface thereof was removed by immersing the sample in a phosphoric acid / chromic acid solution whose Temperature has been raised by a heater. The sample was examined to see if it had penetration holes in its surface or not. More specifically, an error detection liquid, which is highly penetrated and colored red, was dropped into each of the flow passages of the multi-port flat tube, and seepage of the error detection liquid from the outer surface of the multi-port flat tube was examined to detect the presence or absence of the Penetration holes to confirm. Subsequently, the sample examined for the presence or absence of the penetration holes was covered with an encapsulating resin, and the portion of maximum corrosion of the sample was subjected to a cross-sectional surface treatment by a waterproof paper, and further, by buffing, high-gloss polishing. Then, the state of corrosion of the outer surface of each sample was examined. It is noted that with respect to the samples used in the SWAAT trial, the results were evaluated as "Excellent" if penetration did not occur after 20 days but occurred after 30 days, or no penetration at all occurred; "Good" if the penetration did not occur after 10 days, but occurred after 20 days; and "bad" if the penetration has occurred after 10 days.

In the following Table 4, the results of the SWAAT experiment are for 10, 20 and 30 days with respect to the flat tubes AH with several openings and the flat tubes I and J shown with several openings. Table 4 Type of flat tube with multiple openings Result of examination of the corrosion resistance of the outer surface evaluation A No penetration Outstanding B Penetration after 20 days Well C Penetration after 20 days Well D Penetration after 30 days Outstanding e No penetration Outstanding F Penetration after 20 days Well G Penetration after 30 days Outstanding H Penetration after 20 days Well I Penetration after 10 days Bad J Penetration after 10 days Bad

As is clear from the results shown in Table 4, the flat tubes suffered AH with multiple openings no penetration hole formed by the peripheral wall portion in the evaluation after 10 days from the beginning of the SWAAT experiment. In the evaluation after 20 days pointed the flat tubes B . C . F and H with a plurality of openings penetrating holes formed through the peripheral wall portion. Moreover, in the evaluation after 30 days, none suffered from the flat tubes except the flat tubes B . C F and H with multiple openings creating penetration holes. The flat tubes AH with multiple openings, an effective improvement in the corrosion resistance of the outer surface owed to the sacrificial anode effect due to the presence of the sacrificial anodic segment ( 18 ) was obtained.

On the other hand, the flat tube suffered I with multiple apertures formed from the known tube core material alone without using the sacrificial anode material in all evaluations corresponding 10 . 20 and 30 Days since the beginning of the SWAAT experiment with generation of corrosion holes penetrated through the peripheral wall portion. It was realized that the tube I penetrated at an early stage, since the tube did not penetrate the sacrificial anode section (FIG. 18 ) in the outer circumference of the tube, in contrast to the flat tubes with multiple openings according to the invention, which tube did not enjoy the sacrificial anode effect and did not show the effect of corrosion resistance of the outer surface.

In addition, the flat tube suffered J with multiple openings at the production of corrosion holes, which penetrated through the peripheral wall portion, in all evaluations after each 10 . 20 respectively. 30 Days since the SWAAT trial mentioned above. Each corrosion hole was formed in the sections where the sacrificial anode section (FIG. 18 ) had a thickness of more than 90% of the thickness of the peripheral wall portion. For this reason, in the upper anode section ( 18 ) contained Zn in the entirety of the peripheral wall portion ( 14 ) at the time of heat treatment equivalent to heating for brazing. As a result, the sacrificial anode section ( 18 ) consumed at an early stage, causing early penetration of the tube.

LIST OF REFERENCE NUMBERS

10

flat tube with several openings

12

Flow passages (hollow holes)

14

Peripheral wall sections

16

inner partition sections

18

Sacrificial anode section

20

composite billet

22

Tube core billets

24

Sacrificial anode stick

30

Einkomponentknüppel

32

Tube core billets

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 6142755 A [0003, 0007]
• JP 5222480 A [0003, 0006, 0007]
• WO 2013/125625 A1 [0003, 0007]
• JP 63097309 A [0007]

Claims (10)

A multi-aperture aluminum tube having a generally flat cross-sectional shape obtained by extruding an aluminum material, the multi-port aluminum tube being an extruded tube having a plurality of flow passages extending independently in an axial direction of the tube, the flow passages is arranged in a longitudinal direction of the flat cross-sectional shape by means of inner partition portions extending in a peripheral wall portion of the tube in the axial direction of the tube, characterized in that the aluminum tube having a plurality of openings is formed by extrusion molding using as the aluminum material an aluminum tube core material and a Aluminum sacrificial anode material having a lower electrochemical potential than the aluminum tube core material is used, and the sacrificial aluminum anode material is exposed so that it can be used in a total with an outer periphery of the tube or at least part of a flat portion of the outer circumference of the tube forms a sacrificial anode portion, whereby the multi-hole aluminum tube has excellent outer surface corrosion resistance. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface after Claim 1 wherein the sacrificial anode portion is provided on a peripheral wall portion other than the inner partition wall portions in the cross section of the tube, and a thickness of the sacrificial anode portion is not greater than 90% of a thickness of the peripheral wall portion. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface after Claim 1 or 2 wherein the sacrificial anode section has a length of 50% to 100% of an outer circumferential length of the tube in the cross-section of the tube. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface, according to one of Claims 1 to 3 wherein a difference in potential between the sacrificial anode material and the aluminum tube core material is in a range of 5 mV to 300 mV. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface, according to one of Claims 1 to 4 wherein the aluminum extrudable material is a composite billet consisting of the aluminum tubing core material and the aluminum sacrificial anode material. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface after Claim 5 wherein the composite billet comprises a one-piece sheath-core structure consisting of a core billet formed of the aluminum tubular core material and a sheath billet formed of the aluminum sacrificial anode material, the sheath billet being arranged to surround the core billet. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface, according to one of Claims 1 to 6 wherein the extruded tube is formed by extruding the aluminum material using a chamber tool. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface, according to one of Claims 1 to 7 wherein the aluminum tube core material is a pure aluminum according to a Japanese Industrial Standard (JIS) A1000 series or an aluminum alloy according to an A3000 series of the JIS. Aluminum tube with multiple openings, which has excellent corrosion resistance of an outer surface, according to one of Claims 1 to 8th wherein the aluminum sacrificial anode material is a Zn-containing aluminum alloy. Aluminum heat exchanger with aluminum tube with several openings after one of Claims 1 to 9 and aluminum outer fins brazed to an outer surface of the multi-port aluminum tube.

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