Composite material, process for pipe manufacturing, pipe and heat exchanger with pipe

Abstract

A composite material (1) comprising a core material (2), a first cover material (3) covering one side of the core material (2), and a second cover material (4) covering the other side of the core material (2), wherein the composite material (1) has two opposite side edge regions to be joined by high-frequency resistance welding in a state in which the opposite side edge regions are brought into contact with each other such that a region of the first cover material (3) arranged in one of the side edge regions and a region of the first cover material (3) arranged in the other side edge region face the same side, and a region of the second cover material (4) arranged in one side edge region and a region of the second cover material (4) arranged in the other side edge region face the same side, wherein the composite material (1) further comprises an intermediate material (5) arranged between the core material (2) and the first cover material (3), wherein the core material (2) is made of an Al alloy containing Cu in an amount of 0.3 to 0.5 mass%, Mn in an amount of 0.6 to 1.0 mass%, Ti in an amount of 0.05 to 0.15 mass%, Zn in an amount of 0.1 mass% or less, Fe in an amount of 0.3 mass% or less and Si in an amount of 0.2 mass% or less, wherein Al and unavoidable impurities complete the core material (2); the first cover material (3) is made of an Al alloy containing Si in an amount of 7.9 to 9.5 mass%, Fe in an amount of 0.1 to 0.3 mass% and Cu in an amount of 0.3 mass% or less, wherein Al and unavoidable impurities complete the first cover material (3); the second cover material (4) is made of an Al alloy containing Si in an amount of 4.5 to 5.5 mass%, Cu in an amount of 0.5 to 0.7 mass% and Fe in an amount of 0.8 mass% or less, wherein Al and unavoidable impurities complete the second cover material (4); and the intermediate material (5) is made of an Al alloy containing Mn in an amount of 0.2 to 0.4 mass%, Zn in an amount of 0.2 to 0.4 mass%, Fe in an amount of 0.4 mass% or less and Cu in an amount of 0.05 mass% or less, wherein Al and unavoidable impurities complete the intermediate material (5).

Description

[0001] The present invention relates to a composite material comprising a core material, a first cover material covering one side of the core material, and a second cover material covering the other side of the core material. This composite material is used, for example, for producing headers for a heat exchanger. Furthermore, the present invention relates to a method for producing a tube from the composite material, the tube, and a heat exchanger comprising the tube.

[0002] In this description and the claims, the term "aluminum" refers to both pure aluminum and aluminum alloys. Furthermore, substances designated by chemical symbols are pure substances, and the term "Al alloy" refers to an aluminum alloy.

[0003] In this specification, the term “spontaneous potential” of a material refers to the electrode potential of the material within an acidic aqueous solution (pH: 3) of 5% NaCl relative to a saturated calomel electrode (SCE) serving as a reference electrode.

[0004] Known composite materials for heat exchangers consist of a core material, a first cover material covering one side of the core material and forming the wall surface of a coolant pipe, and a second cover material covering the other side of the core material and forming an outer surface in contact with the atmosphere (see Japanese Patent Application Laid-Open (kokai) No. 2008-240084). Such a composite material is used to manufacture components for heat exchangers. In the known composite material, the core material is made of an Al alloy containing Si in an amount of 0.3 to 1.5 mass%, Mn in an amount of 0.5 to 1.8 mass%, Mg in an amount of 1.5 mass% or less, Cu in an amount of 1.0 mass% or less, and Ti in an amount of 0.1 to 0.35 mass%. Al and unavoidable impurities complete the composite material.The first covering material is made of an Al alloy containing Si in an amount of 1.5 mass% or less, Mn in an amount of 1.8 mass% or less, and Cu in an amount of 1.0 mass% or less, with Al and unavoidable impurities completing the first covering material. The second covering material is made of an Al alloy containing Si in an amount of 1.5 mass% or less, Mn in an amount of 1.8 mass% or less, and Zn in an amount of 2.5 to 7.0 mass%, with Al and unavoidable impurities completing the second covering material. The Cu content of the first covering material is equal to or greater than the Cu content of the core material.

[0005] In the composite material disclosed in the above-mentioned publication, the spontaneous potential of a layer (the second cover material) constituting an outer surface of a heat exchanger exposed to a corrosive environment is set to be less noble than the core material, so that the layer serves as a sacrificial anode layer for the core material; and the spontaneous material of a layer constituting an inner surface of the heat exchanger (the first cover material) that comes into contact with the coolant is set to be less noble relative to the core material, thereby achieving corrosion protection by sacrificial action at positions deeper than the center in the thickness direction of the core material.

[0006] Apart from that, a heat exchanger having the following structure is widely known and used as a condenser of an air conditioner for a vehicle.The heat exchanger comprises a plurality of heat exchange tubes arranged at predetermined intervals so as to have the same longitudinal direction; fins each arranged between adjacent heat exchange tubes; a plurality of headers arranged on opposite sides of the heat exchange tubes with respect to the longitudinal direction thereof such that the longitudinal direction of the headers coincides with the direction in which the heat exchange tubes are arranged next to each other; and a heat exchanger component formed of an uncovered material and attached to at least one of the headers, each header consisting of a tube having openings at its opposite ends and closing elements for closing the openings at the opposite ends of the tube.

[0007] For example, the tube of each header tank of the heat exchanger described above is manufactured by the following method.

[0008] First, a composite material is provided, which consists of a core material, a first covering material made of an Al alloy brazing material and covering one side of the core material, and a second covering material made of an Al alloy brazing material and covering the other side of the core material. On the upper surface of a side edge portion of the composite material, a first inclined surface is formed such that the first inclined surface slopes downward toward the end, and the first inclined surface is covered with the first covering material. Between the lower end of the first inclined surface and the lower surface, a first flat surface is formed such that the first flat surface forms an obtuse angle with the first inclined surface and a right angle with the lower surface.A second inclined surface is formed on the lower surface of the other side edge portion of the composite material such that the second inclined surface slopes upward toward the end, and the second covering material is provided on the second inclined surface. A second flat surface is formed between the lower end of the second inclined surface and the lower surface such that the second flat surface forms an obtuse angle with the second inclined surface and a right angle with the lower surface. Subsequently, the composite material is formed into a tubular shape such that the first surface covered with the first covering material is on the outer side and the second surface covered with the second covering material is on the inner side.The inclined surfaces on the opposite side edge portions are then brought into surface contact with each other such that the first covering material and the second covering material overlap each other, and the flat surfaces are arranged in abutment against each other, thereby obtaining a tubular body for the pipe. The tubular body is then heated to a predetermined temperature. As a result, the inclined surfaces of the tubular body are brazed together, and the flat surfaces of the tubular body are brazed together, thus completing the pipe.

[0009] However, when the header tubes are made of the composite material according to the method described in the above-mentioned publication, the spontaneous potential of a eutectic brazing material formed after brazing between the first inclined surface and the second inclined surface becomes lower than the spontaneous potential of the core material. Therefore, the eutectic brazing material corrodes preferentially, resulting in the problem that the corrosion resistance of the brazed portion is low. Especially in an acidic environment, the preferential corrosion of the brazed portions of the header tubes becomes significant because the dissolution rate of the eutectic brazing material becomes high. To prevent the preferential corrosion of the brazed portions of the tubes, painting or chemical conversion treatment such as chromating must be performed.The work of performing a painting or chemical conversion treatment is prone to errors and increases costs.

[0010] To solve such a problem, the present applicant has proposed an improved composite material (see Japanese Patent Application Laid-Open (kokai) No. 2015-9244). The improved composite material consists of a core material, a first cover material covering one side of the core material, and a second cover material covering the other side of the core material. The composite material is brazed in a state where the first cover material and the second cover material overlap each other. The core material is made of an Al alloy containing Mn in an amount of 0.6 to 1.5 mass%, Ti in an amount of 0.05 to 0.25 mass%, Cu in an amount less than 0.05 mass%, Zn in an amount less than 0.05 mass%, Fe in an amount of 0.2 mass% or less and Si in an amount of 0.45 mass% or less, with Al and unavoidable impurities completing the core material.The first cover material is made of an Al alloy containing Si in an amount of 6.8 to 11.0 mass% and Zn in an amount of 0.05 mass% or less, with Al and unavoidable impurities completing the first cover material. The second cover material is made of an Al alloy containing Si in an amount of 4.0 to 6.0 mass% and Cu in an amount of 0.5 to 1.0 mass%, with Al and unavoidable impurities completing the second cover material.The above-mentioned publication further discloses a method for producing a brazed pipe by forming the above-described composite material into a tubular shape such that the first surface covered with the first covering material is on the outside and the second surface covered with the second covering material is on the inside, wherein opposite side edge portions of the composite material are joined to each other such that the first covering material and the second covering material overlap each other, and opposite side edge portions of the composite material are brazed together using the first covering material of the composite material.The above-mentioned publication further discloses a brazed tube manufactured by the method described above, wherein the eutectic brazing material present between the brazed opposite side edge portions of the composite material is higher in spontaneous potential than the core material.

[0011] In the case of a pipe manufactured by the above-described method using the composite material disclosed in Japanese Patent Application Laid-Open No. 2015-9244, the spontaneous potential of the eutectic brazing material formed between the first inclined surface after brazing becomes higher than and superior to the spontaneous potential of the core material. Therefore, the eutectic brazing material is prevented from being preferentially corroded over the core material, thereby improving the corrosion resistance of the joined portion.

[0012] However, in the case where the pipe of each collecting tank has a cylindrical shape and a relatively large diameter, it becomes difficult to manufacture the pipe by the method described above.

[0013] A conceivable pipe manufacturing method that overcomes the above-mentioned difficulty is as follows. The composite material disclosed in Japanese Patent Application Laid-Open No. 2015-9244 is formed into a tubular shape such that the first surface covered with the first covering material is on the outside and the second surface covered with the second covering material is on the inside, and opposite side edge portions of the composite material are welded together by high-frequency resistance welding in a state where the opposite side edge portions of the composite material abut against each other as a result of the application of pressure between the opposite side edge portions.However, pipes manufactured by such a method have a problem in that corrosion of the welded joint portion progresses remarkably when a joint portion formed as a result of welding (hereinafter referred to as "welded joint portion") has a weak point.

[0014] Another composite material comprising a core material and cover materials covering both sides of the core material and welded at the side edge regions is known from EP 2 065 180 A1.

[0015] Against this background, it is an object of the present invention to solve the above-described problem and to provide a composite material suitable for manufacturing a pipe, in which the composite material is formed into a tubular shape and opposite side edge portions of the composite material are welded together by high-frequency resistance welding in a state where the opposite side edge portions abut against each other as a result of application of pressure between the opposite side edge portions. Another object of the present invention is to provide a method for manufacturing a pipe from the composite material. Also another object of the present invention is to provide the pipe and a heat exchanger comprising the pipe.

[0016] A composite material according to the present invention comprises a core material, a first cover material covering one side of the core material, and a second cover material covering the other side of the core material, the composite material having opposite side edge portions joined by high-frequency resistance welding in a state where the opposite side edge portions are abutted against each other such that a portion of the first cover material disposed at one of the two side edge portions and a portion of the first cover material disposed at the other side edge portion face the same side, and a portion of the second cover material disposed at the one side edge portion and a portion of the second cover material disposed at the other side edge portion face the same side.The composite material further comprises an intermediate material disposed between the core material and the first cover material. The core material is made of an Al alloy containing Cu in an amount of 0.3 to 0.5 mass%, Mn in an amount of 0.6 to 1.0 mass%, Ti in an amount of 0.05 to 0.15 mass%, Zn in an amount of 0.1 mass% or less, Fe in an amount of 0.3 mass% or less, and Si in an amount of 0.2 mass% or less, with Al and unavoidable impurities completing the core material. The first cover material is made of an Al alloy containing Si in an amount of 7.9 to 9.5 mass%, Fe in an amount of 0.1 to 0.3 mass%, and Cu in an amount of 0.3 mass% or less, with Al and unavoidable impurities completing the first cover material.The second cover material is made of an Al alloy containing Si in an amount of 4.5 to 5.5 mass%, Cu in an amount of 0.5 to 0.7 mass%, and Fe in an amount of 0.8 mass% or less, with Al and unavoidable impurities completing the second cover material. The intermediate material is made of an Al alloy containing Mn in an amount of 0.2 to 0.4 mass%, Zn in an amount of 0.2 to 0.4 mass%, Fe in an amount of 0.4 mass% or less, and Cu in an amount of 0.05 mass% or less, with Al and unavoidable impurities completing the intermediate material.

[0017] A pipe manufacturing method according to the present invention comprises: forming the composite material according to the present invention into a tubular shape such that a first surface of the composite material covered with the first covering material is on an outer side, and a second surface of the composite material covered with the second covering material is on an inner side; and welding the opposite side edge portions of the composite material by high-frequency resistance welding in a state where the opposite side edge portions of the composite material abut against each other as a result of application of pressure between the opposite side edge portions.

[0018] A pipe according to the present invention is a pipe manufactured by a method according to the present invention. The pipe consists of the core material, the first cover material covering an outer peripheral surface of the core material, the second cover material covering an inner peripheral surface of the core material, and the intermediate material disposed between the core material and the first cover material. The core material is exposed on outer and inner peripheral surfaces of the pipe, in a welded joint portion formed as a result of welding between the opposite side edge portions of the composite material, and in the vicinity of the welded joint portion.

[0019] A heat exchanger according to the present invention comprises a plurality of heat exchange tubes formed of an uncovered material and provided such that they have the same longitudinal direction and are arranged at a distance from each other; fins each formed of a brazing sheet and arranged between adjacent heat exchange tubes; and a plurality of headers arranged on opposite sides of the heat exchange tubes with respect to the longitudinal direction of the heat exchange tubes such that the longitudinal direction of the headers coincides with a direction in which the heat exchange tubes are arranged side by side, wherein at least one of the headers is composed of the tube according to claim 3, and closing elements close the openings of the tube at its opposite end;the tube has a plurality of tube insertion holes formed in a portion remote from the welded joint portion of the tube; the heat exchange tubes are inserted into the tube insertion holes and brazed to the tube by means of the first and second covering materials; and a heat exchange component is provided on the tube at a position remote from the welded joint portion and welded to the tube by using the first covering material.

[0020] In the drawing Fig. 1 is an enlarged cross-sectional view of a portion of a composite material according to an embodiment of the present invention; Fig. 2 is an enlarged front view of the overall structure of a capacitor in which the Fig. 1, pipes formed from the composite material shown can be used for collecting containers; Fig.3 a schematic front view of the Fig. 2 shown capacitor; Fig. 4 is an enlarged cross-sectional view of the capacitor along the Fig. 2 line marked A - A; and Fig. 5 an enlarged view of a section of the Fig. 4.

[0021] An embodiment of the composite material according to the present invention will be described below.

[0022] The top side, bottom side, left side and right side of the Fig. 1 are referred to here as “top”, “bottom”, “left” and “right” respectively.

[0023] Fig. Figure 1 shows the composite material according to the present invention and the Fig. 2 to 5 show a condenser in which tubes made of the composite material of the Fig. 1 are used for collection containers.

[0024] As in Fig.1, the composite material 1 consists of a core material 2, a first cover material 3 covering one side of the core material 2, a second cover material 4 covering the other side of the core material 2, and an intermediate material 5 arranged between the core material 2 and the first cover material 3.

[0025] The core material 2 is made of an Al alloy containing Cu in an amount of 0.3 to 0.5 mass%, Mn in an amount of 0.6 to 1.0 mass%, Ti in an amount of 0.05 to 0.15 mass%, Zn in an amount of 0.1 mass% or less, Fe in an amount of 0.3 mass% or less, and Si in an amount of 0.2 mass% or less, with Al and unavoidable impurities completing the core material. It is noted that the core material 2 may contain Cr as an unavoidable impurity in an amount of 0.05 mass% or less.

[0026] The first covering material 3 is made of an Al alloy containing Si in an amount of 7.9 to 9.5 mass%, Fe in an amount of 0.1 to 0.3 mass%, and Cu in an amount of 0.3 mass% or less, with Al and unavoidable impurities completing the first covering material 3. Note that the first covering material 3 may contain Mn in an amount of 0.05 mass% or less, Zn in an amount of 0.05 mass% or less, Cr in an amount of 0.05 mass% or less, and Ti in an amount of 0.05 mass% or less as unavoidable impurities.

[0027] The second covering material 4 is made of an Al alloy containing Si in an amount of 4.5 to 5.5 mass%, Cu in an amount of 0.5 to 0.7 mass%, and Fe in an amount of 0.8 mass% or less, with Al and unavoidable impurities completing the second covering material 4. It should be noted that the second covering material 4 may contain Mn in an amount of 0.05 mass% or less, Zn in an amount of 0.05 mass% or less, Cr in an amount of 0.05 mass% or less, and Ti in an amount of 0.05 mass% or less as unavoidable impurities.

[0028] The intermediate material 5 is made of an Al alloy containing Mn in an amount of 0.2 to 0.4 mass%, Zn in an amount of 0.2 to 0.4 mass%, Fe in an amount of 0.4 mass% or less, and Cu in an amount of 0.05 mass% or less, with Al and unavoidable impurities completing the intermediate material 5. Note that the intermediate material 5 may contain Si in an amount of 0.25 mass% or less, Cr in an amount of 0.05 mass% or less, and Ti in an amount of 0.05 mass% or less as unavoidable impurities.

[0029] The aluminum compounds of the core material 2, the first cover material 3, the second cover material 4 and the intermediate material 5 of the composite material 1 will now be described. [Core Material 2]

[0030] Cu makes the spontaneous potential of the core material 2 noble, thereby improving the corrosion resistance of the core material 2. If the Cu content is excessively low, the core material 2 may not have sufficiently high corrosion resistance, and pitting corrosion may occur. If the Cu content is excessively high, the hardness of the core material 2 becomes excessively high, and a deformation defect may occur when the composite material 1 is formed into a tubular shape. Accordingly, the Cu content must be 0.3 to 0.5 mass%.

[0031] Mn increases the hardness of the core material 2, thereby increasing the compressive strength of header tanks made using the composite material 1. If the Mn content is excessively low, a sufficient degree of hardness cannot be achieved. If the Mn content is excessively high, the hardness of the core material 2 becomes excessively high, and a deformation defect may occur when the composite material 1 is formed into a tubular shape. Accordingly, the Mn content must be 0.6 to 1.0 mass%.

[0032] Ti forms a Ti-Al complex in the Al alloy and disperses in layers. Since the spontaneous potential of the Ti-Al complex is noble, corrosion can occur in layers, and the occurrence of corrosion in the thickness direction (pitting corrosion) becomes unlikely. Therefore, Ti improves corrosion resistance. If the Ti content is excessively low, its effect on layered corrosion is reduced, and corrosion resistance is reduced. If the Ti content is excessively high, its effect on improving corrosion resistance is saturated, and costs increase. Accordingly, the Ti content must be 0.05 to 0.15 mass%.

[0033] Zn, Fe, and Si are unavoidable impurities in core material 2. If their contents are excessively high, the corrosion resistance of core material 2 itself decreases. Therefore, their contents must be as described above.

[0034] It should be noted that the amounts of Zn, Fe and Si contained as unavoidable impurities may be 0 in some cases. [First Cover Material 3]

[0035] The first cover material 3 is a typical Al alloy brazing filler material, and the Si content of the first cover material 3 is 7.9 to 9.5 mass%.

[0036] Fe improves the flowability of the first cover material 3 in a molten state. If the Fe content is excessively low, sufficient brazing fluidity will not be achieved. If the Fe content is excessively high, corrosion resistance will decrease. Accordingly, the Fe content must be 0.1 to 0.3 mass%.

[0037] Cu is contained in the first cover material 3 as an unavoidable impurity. If the Cu content is excessively high, corrosion of the intermediate material 5 accelerates. Therefore, the Cu content must be as described above.

[0038] It should be noted that the amount of Cu contained as an unavoidable impurity may be 0 in some cases. [Second Cover Material 4]

[0039] The second cover material 4 serves as a brazing material. As with ordinary Al alloy brazing filler materials, Si affects the fluidity of the second cover material 4 in a molten state. If the Si content is excessively low, the second cover material 4 lacks sufficient fluidity in a molten state. Therefore, a brazing failure may occur when brazing the header tanks and heat exchange tubes together if the composite material 1 is used for the header tanks. If the Si content is excessively high, the second cover material 4 has excessive fluidity in a molten state. Then, the second cover material 4 may flow into the channels of the heat exchange tubes brazed to the header tanks if the composite material 1 is used for the header tanks. Therefore, the Si content must be 4.5 to 5.5 mass%.

[0040] In the case where the composite material 1 is used for the header tanks, Cu suppresses the progression of corrosion in the areas of the header tanks that are brazed to the heat exchange tubes. If the Cu content is excessively low, the progression of corrosion in the brazed areas cannot be sufficiently suppressed. If the Cu content is excessively high, the second cover material 4 will crack when it hardens during casting. Accordingly, the Cu content must be 0.5 to 0.7 mass%.

[0041] Fe is contained in the second cover material 4 as an unavoidable impurity. If the Fe content is excessively high, a problem arises in that the corrosion resistance of the areas of the header tanks that are brazed to the heat exchange tubes decreases when the composite material 1 is used for the header tanks. Therefore, the Fe content must be as mentioned above.

[0042] It should be noted that the amount of Fe contained as an unavoidable impurity may be 0 in some cases. [Intermediate material 5]

[0043] Mn increases the hardness of the intermediate material 5, thereby making it possible to create a proper pressure bond between the intermediate material 5 and the core material 2, and between the intermediate material 5 and the first cover material 3, at the time of rolling. If the Mn content is excessively low, it is impossible to create a proper pressure bond between the intermediate material 5 and the core material 2, and between the intermediate material 5 and the first cover material 3, at the time of rolling. If the Mn content is excessively high, the hardness of the intermediate material 5 becomes excessively high, and a pressure bond failure occurs at the time of rolling between the intermediate material 5 and the core material 2, or between the intermediate material 5 and the first cover material 3. Accordingly, the Mn content must be 0.2 to 0.4 mass%.

[0044] Zn regulates the corrosion rate of the intermediate material 5. If the Zn content is excessively low, the potential difference between the intermediate material 5 and the core material 2 becomes insufficient, and corrosion occurs in the core material 2. If the Zn content is excessively high, the corrosion rate of the intermediate material 5 becomes excessively high, and the intermediate material 5 is consumed within a relatively short period of time. Accordingly, the Zn content must be 0.2 to 0.4 mass%.

[0045] Fe is contained in the intermediate material 5 as an unavoidable impurity. If the Fe content is excessively high, the corrosion resistance of the intermediate material 5 decreases. Therefore, the Fe content must be as mentioned above.

[0046] Cu is contained in the intermediate material 5 as an unavoidable impurity. If the Cu content is excessively high, the potential difference between the intermediate material 5 and the core material 2 becomes insufficient, and corrosion occurs in the core material 2. Therefore, the Cu content must be the above-mentioned content.

[0047] It should be noted that the amounts of Fe and Cu contained as unavoidable impurities may be 0 in some cases.

[0048] The Fig. 2 and Fig. 3 show the overall structure of a condenser in which tubes formed from the composite material 1 are used for collecting tanks, and the Fig. 4 and Fig. 5 shows the structure of a main section of the capacitor.

[0049] In the Fig.2 to 4, a condenser 10 has a condensing section 10A and a supercooling section 10B provided below the condensing section 10A. The condenser 10 comprises a plurality of flat heat exchange tubes 11 formed of aluminum extrusion, three headers 12, 13, 14 formed of aluminum, corrugated fins 15 formed of aluminum, and side plates 16 formed of aluminum. The heat exchange tubes 11 are arranged at predetermined intervals in the vertical direction such that their width direction coincides with the air flow direction (a direction perpendicular to the sheets on which the Fig. 2 and Fig.3) and their longitudinal direction coincides with the left-right direction. The headers 12, 13, 14 are provided such that their longitudinal direction coincides with the vertical direction, and left and right end portions of the heat exchange tubes 11 are brazed to the headers 12, 13, 14. Each of the corrugated fins 15 is arranged between adjacent heat exchange tubes and brazed to them, or is arranged on the outer side of the uppermost or lowermost heat exchange tube 11 and brazed to the corresponding heat exchange tube 11. The side plates 16 are arranged on the respective outer sides of the uppermost and lowermost corrugated fins 15 and brazed to these corrugated fins 15.

[0050] Both the condensing section 10A and the supercooling section 10B of the condenser 10 each have at least one (in the present embodiment, exactly one) heat exchange path P1, P2 formed by the plurality of heat exchange tubes 11 arranged sequentially in the vertical direction. The heat exchange path P1 provided in the condensing section 10A serves as a refrigerant condensation path. The heat exchange path P2 provided in the supercooling section 10B serves as a refrigerant supercooling path. The flow direction of the refrigerant is the same in all the heat exchange tubes 11 each forming a heat exchange path P1, P2.The flow direction of the coolant in the heat exchange tubes 11 forming a specific heat exchange path is opposite to the flow direction of the coolant in the heat exchange tubes 11 forming another heat exchange path adjacent to the specific heat exchange path. The heat exchange path P1 of the condensing section 10A is referred to as the first heat exchange path, and the heat exchange path P2 of the supercooling section 10B is referred to as the second heat exchange path.

[0051] The first header tank 12 and the second header tank 13 are individually provided at the left end of the condenser 10 in such a manner that the second header tank 13 is arranged outside the first header tank 12 in the left-right direction. Left end portions of all the heat exchange tubes 11 constituting the first heat exchange path P1 provided in the condensing section 10A are connected to the first header tank 12 by brazing. Left end portions of all the heat exchange tubes 11 constituting the second heat exchange path P2 provided in the super-cooling section 10B are connected to the second header tank 13 by brazing. The lower end of the header tank 13 is arranged below the lower end of the first header tank 12, and the upper end of the second header tank 13 is arranged above the lower end of the first header tank 12.All the heat exchange tubes 11 of the second heat exchange path P2 are connected to a portion of the second header tank 13 located below the lower end of the first header tank 12. Specifically, the second header tank 13 is divided into an upper portion 13a and a lower portion 13b by a plate-shaped partition member 17 made of aluminum and provided at a height between the first heat exchange path P1 and the second heat exchange path P2. Left end portions of all the heat exchange tubes 11 constituting the second heat exchange path P2 provided in the supercooling portion 10B are connected to the lower portion 13b by brazing. The upper portion 13a and the lower portion 13b are connected to each other through a communication hole 17a formed in the partition member 17.The second header tank 13 has a function of storing the refrigerant flowing from the condensation section 10A, separating it into a gaseous and a liquid phase, and supplying the predominantly liquid refrigerant phase to the supercooling section 10B. A desiccant not shown in the drawing is provided in the upper portion 13a of the second header tank 13.

[0052] A connecting element 18, which is made of aluminum and is brazed to the first and second header tanks 12 and 13, establishes a connection between a region of the interior of the first header tank 12 near its lower end and a region of the interior of the upper portion 13a of the second header tank near its lower end.

[0053] The first collecting container 12 consists of an aluminum tube 19 having openings at its upper and lower ends and having a non-circular cross-section in the transverse direction, and closure elements 21 made of aluminum which are soldered to the upper and lower ends of the tube 19 in such a way that they close the openings at the upper and lower ends.

[0054] The second header tank 13 consists of an aluminum tube 22 having openings at its upper and lower ends and a circular cross-section in the transverse direction, a member 23 brazed to the lower end of the tube 22 to close the opening at the lower end, and an upper closure member 24 removably attached to the upper end of the tube 22 to close the opening at the upper end. Two aluminum clamps 25, which are components of the heat exchanger, are brazed to the tube 22 of the second header tank 13 so as to be spaced apart from each other in the vertical direction.

[0055] The third header tank 14 is provided at the right end of the condenser 10, and right end portions of all the heat exchange tubes 11 constituting the first and second heat exchange paths P1 and P2 are connected to the third header tank 14. The third header tank 14 is divided into an upper portion 14a and a lower portion 14b by a plate-shaped partition member 26 provided at a height between the first heat exchange path P1 and the second heat exchange path P2. Right end portions of all the heat exchange tubes 11 constituting the first heat exchange path P1 provided in the condensing section 10A are connected to the upper portion 14a by brazing, and right end portions of all the heat exchange tubes 11 constituting the second heat exchange path P2 provided in the supercooling section 10B are connected to the lower portion 14b by brazing.Furthermore, the upper portion 14a of the third header tank 14 has a coolant inlet 27 provided at the center in the height direction of the upper portion 14a, and the lower portion 14b of the third header tank 14 has a coolant outlet 28. Furthermore, a coolant inlet member 29 made of aluminum, which communicates with the coolant inlet 27, and a coolant outlet member 31 made of aluminum, which communicates with the coolant outlet 28, are brazed to the third header tank 14. Two aluminum brackets 25 are also brazed to the third header tank 14 such that they are spaced apart from each other in the vertical direction.

[0056] The third collecting container 14 consists of an aluminum tube 32 having openings at its upper and lower ends and having the same cross-sectional shape in the transverse direction as that of the first collecting container 12, and closure elements 33 made of aluminum which are soldered to the upper and lower ends of the tube 32 in such a way that they close the openings at the upper and lower ends.

[0057] In the condenser 10, coolant flows through the coolant inlet member 29 and the coolant inlet 27 into the upper portion 14a of the third header tank 14. The coolant flows through the first heat exchange path P1, the first header tank 12, the connecting member 18, the upper portion 13a of the second header tank 13, the connecting opening 17a, the lower portion 13b of the header tank 13, the second heat exchange path P2, and the lower portion 14b of the third header tank 14, and then flows out through the coolant outlet 28 and the coolant outlet member 31.

[0058] The tube 22 of the second header tank 13 of the condenser 10 is formed using the composite material 1. As shown in the Fig. 4 and Fig.As shown in Fig. 5, the tube 22 is formed by bending the composite material 1 into a cylindrical tubular shape such that the first cover material 3 is disposed on the outer surface side, and opposite side edge portions of the composite material 1 are welded to each other by high-frequency resistance welding in a state where the opposite side edge portions abut against each other as a result of the application of pressure between the opposite side edge portions. The tube 22 is composed of the core material 2, the first cover material 3 covering the outer peripheral surface of the core material 2, the second cover material 4 covering the inner peripheral surface of the core material 2, and the intermediate material 5 disposed between the core material 2 and the first cover material 3.In the welded joint portion 34 formed as a result of welding between the opposite side edge portions of the composite material 1 of the pipe 22, and in the vicinity thereof, the core material is exposed on the outer and inner peripheral surfaces of the pipe 22. The outer peripheral surface of the pipe 22, except for a portion where the core material 2 is exposed, is covered with the first covering material 3, and the inner peripheral surface of the pipe 22, except for a portion where the core material 2 is exposed, is covered with the second covering material 4. The welded joint portion 34 of the pipe 22 is arranged upstream of the air flow direction (on the upper side of the . Fig. 4) arranged on the downstream side.

[0059] A plurality of elongated tube insertion holes 35 extending in the air flow direction are formed in a right side portion of the tube 22 at predetermined intervals in the vertical direction such that the tube insertion holes 35 are spaced from the welded joint portion 34. The heat exchange tubes 11 are inserted into the tube insertion holes 35 and brazed to the tube 22 using the first covering material 3 and the second covering material 4 of the composite material 1. The brackets 25 are brazed to a left side portion of the tube 22 spaced from the welded joint portion 34 using the first covering material 3.

[0060] Note that the tubes 19 and 32 of the first header tank 12 and the third header tank 14 are manufactured, for example, by the method described in Japanese Patent Application Laid-Open No. 2015-9244. Specifically, a composite material consisting of a core material, a cover material covering one side of the core material, and a second cover material covering the other side of the core material is prepared. The core material is made of an Al alloy containing Mn in an amount of 0.6 to 1.5 mass%, Ti in an amount of 0.05 to 0.25 mass%, Cu in an amount of less than 0.05 mass%, Zn in an amount of less than 0.05 mass%, Fe in an amount of 0.2 mass% or less, and Si in an amount of 0.45 mass% or less, with Al and unavoidable impurities completing the core material.The first covering material is made of an Al alloy containing Si in an amount of 6.8 to 11.0 mass% and Zn in an amount of 0.05 mass% or less, with Al and unavoidable impurities completing the first covering material. The second covering material is made of an Al alloy containing Si in an amount of 4.0 to 6.0 mass% and Cu in an amount of 0.5 to 1.0 mass%, with Al and unavoidable impurities completing the second covering material. The composite material is bent into a tubular shape such that the first surface covered with the first covering material is on the outside and the second surface covered with the second covering material is on the inside.Subsequently, opposite side edge portions of the composite material are joined together such that the first cover material and the second cover material overlap each other, and the opposite end edge portions of the composite material are brazed together by bonding the first cover material to the composite material. It should be noted that the fabrication of the tubes 19 and 32 takes place simultaneously with the brazing of other components of the capacitor 10.

[0061] The condenser 10 using the above-described tube 22 is constructed by combining the heat exchange tubes 11 of the composite material formed into a tubular shape for the tube 19 of the first header tank 12, the upper and lower sealing members 21, the tube 22 constituting the second header tank 13, the lower sealing member 23, the partition member 17, the composite material formed into a tubular shape for the tube 32 of the third header tank 14, the upper and lower sealing members 33, the partition wall 26, the connecting member 18, the corrugated fins 15, and the side plates 16; and by brazing these components together.

[0062] A particular embodiment of the present invention is described below.

[0063] A composite material 1 shown in Table 1 is provided. The thickness of the composite material 1 is 1.6 mm, the layer thickness ratios of the first cover material 3 and the second cover material 4 are 6%, and the layer thickness ratio of the intermediate material 5 is 10%. Table 1 Aluminum compounds (mass%) Si Fe Cu Mn Zn Ti Al First cover material 8,7 0,2 0,2 - - - rest Intermediate material - 0,2 - 0,2 0,3 - rest Nuclear material - 0,2 0,4 0,8 - 0,1 rest Second cover material 5,0 0,4 0,6 - - - rest

[0064] Subsequently, the pipe 22 is manufactured by bending the composite material 1 of Table 1 into a tubular shape such that the first cover material 3 is arranged on the outer surface side, and welding opposite side edge portions of the composite material together by high-frequency resistance welding in a state where the opposite side edge portions abut against each other as a result of the application of pressure between the opposite side edge portions.

[0065] Next, the tube 22 is combined with other components, a non-corrosive fluoride-based flux is applied to the resulting assembly, and the assembly is heated in a furnace filled with nitrogen gas so that the actual temperature is between 598.0 and 603.66°C, producing the capacitor 10 with the structure described above. The heating rate is between 35 and 50°C per minute in a temperature range of 100 to 500°C, between 14.7 and 18.7°C per minute in a temperature range of 500 to 580°C, and between 3.7 and 5.5°C per minute in a temperature range of 580 to 600°C. The time during which the assembly is maintained at 58°C or higher is between 4.0 and 6.8 minutes.

[0066] An ASTM-SWAAT test was conducted on the capacitor 10 manufactured as above for 40 days. Even after the test period, no leakage occurred. Furthermore, it was observed that the cross-section of the peripheral wall of the second header tank 3 determines the progression of corrosion. No corrosion occurred on the core material 2 with the welded joint area 34 and its vicinity.

[0067] The present invention includes the following embodiments. 1. A composite material (1) comprising a core material (2), a first cover material (3) covering one side of the core material (2), and a second cover material (4) covering the other side of the core material (2), wherein the composite material (1) has two opposite side edge regions to be joined by high-frequency resistance welding in a state in which the opposite side edge regions are brought into contact with each other such that a region of the first cover material (3) arranged in one of the side edge regions and a region of the first cover material (3) arranged in the other side edge region face the same side, and a region of the second cover material (4) arranged in one side edge region and a region of the second cover material (4) arranged in the other side edge region face the same side, wherein the composite material (1) further comprises an intermediate material (5) arranged between the core material (2) and the first cover material (3), wherein the core material (2) is made of an Al alloy containing Cu in an amount of 0.3 to 0.5 mass%, Mn in an amount of 0.6 to 1.0 mass%, Ti in an amount of 0.05 to 0.15 mass%, Zn in an amount of 0.1 mass% or less, Fe in an amount of 0.3 mass% or less and Si in an amount of 0.2 mass% or less, wherein Al and unavoidable impurities complete the core material (2); the first cover material (3) is made of an Al alloy containing Si in an amount of 7.9 to 9.5 mass%, Fe in an amount of 0.1 to 0.3 mass% and Cu in an amount of 0.3 mass% or less, wherein Al and unavoidable impurities complete the first cover material (3); the second cover material (4) is made of an Al alloy containing Si in an amount of 4.5 to 5.5 mass%, Cu in an amount of 0.5 to 0.7 mass% and Fe in an amount of 0.8 mass% or less, wherein Al and unavoidable impurities complete the second cover material (4); and the intermediate material (5) is made of an Al alloy containing Mn in an amount of 0.2 to 0.4 mass%, Zn in an amount of 0.2 to 0.4 mass%, Fe in an amount of 0.4 mass% or less and Cu in an amount of 0.05 mass% or less, wherein Al and unavoidable impurities complete the intermediate material (5). 2. A method for producing a pipe, comprising: Forming the composite material (1) according to claim 1 into a tubular shape such that a first surface of the composite material (1) covered with the first cover material (3) is on an outer side and a second surface of the composite material (1) covered with the second cover material (4) is on an inner side; and welding the opposite side edge portions of the composite material (1) by means of high-frequency resistance welding in a state in which the opposite side edge portions of the composite material (1) abut against each other as a result of the application of pressure between the opposite side edge portions. 3. A pipe manufactured by a method according to claim 2, which consists of the core material (2), the first cover material (3) covering an outer peripheral surface of the core material (2), the second cover material (4) covering an inner peripheral surface of the core material (2), and the intermediate material (5) arranged between the core material (2) and the first cover material (3), wherein the core material (2) is exposed on outer and inner peripheral surfaces of the pipe in a welded joint portion (34) formed as a result of welding between the opposite side edge portions of the composite material (1) and in the vicinity of the welded joint portion (34). 4. Heat exchanger, comprising: a plurality of heat exchange tubes (11) formed of an uncovered material and arranged to have the same longitudinal direction and to be spaced apart from each other; fins (15) each formed from a brazing sheet and provided between adjacent heat exchange tubes (11); and a plurality of collecting tanks (12, 13, 14) which are provided on opposite sides of the heat exchange tubes (11) with respect to the longitudinal direction of the heat exchange tubes (11) in such a way that the longitudinal direction of the collecting tanks (12, 13, 14) coincides with a direction in which the heat exchange tubes (11) are arranged next to one another, wherein opposite end regions of the heat exchange tubes (11) are connected to the collecting tanks (12, 13, 14), wherein at least one of the collecting containers (12, 13, 14) consists of the tube according to claim 3, and closure elements (33) close the openings of the tube at its opposite ends; the pipe has a plurality of pipe insertion openings (35) arranged in a region remote from the welded joint region (34) of the pipe; the heat exchange tubes (11) are inserted into the tube insertion openings (35) and soldered to the tube by means of the first (3) and second cover material (4); and a heat exchanger component is provided on the tube in a position remote from the welded joint portion (34) and brazed to the tube by means of the first covering material (3).

[0068] The composite material of paragraph 1) has the following advantageous effects. The spontaneous potential of the intermediate material becomes less noble than that of the core material, so that the intermediate material is corroded preferentially to the core material if the pipe is manufactured by a method in which the composite material is formed into a tubular shape such that a first surface of the composite material covered with the first covering material is on the outside and a second surface of the composite material covered with the second covering material is on the inside, and opposite side edge portions of the composite material are welded together by high-frequency resistance welding in a state where the opposite side edge portions abut against each other as a result of the application of pressure between the opposite side edge portions.Therefore, even if a welding defect occurs in the welded joint area, the progression of corrosion in the welded joint area is inhibited. Accordingly, the corrosion resistance of the welded joint area of ​​the pipe is improved. Furthermore, chemical treatments such as chromating and painting are eliminated, thus reducing costs.

[0069] In the case of the pipe manufactured using the method from section 2) and for the pipe from section 3), similar effects to those already described in section 1) are achieved.

[0070] The heat exchanger of section 4) has the following advantageous effects. In the header tank with the pipe of section 3), the spontaneous potential of the intermediate material of the pipe becomes less noble than the core material, so that the intermediate material is corroded preferentially than the core material. Therefore, even if a welding defect exists in the welded joint, the progress of corrosion of the welded joint is inhibited. Accordingly, the corrosion resistance of the welded joint of the pipe is improved. Furthermore, chemical conversion treatments such as chromating and painting are eliminated, thereby reducing costs.

Claims

[1] A composite material (1) comprising a core material (2), a first cover material (3) covering one side of the core material (2), and a second cover material (4) covering the other side of the core material (2), wherein the composite material (1) has two opposite side edge regions to be joined by high-frequency resistance welding in a state in which the opposite side edge regions are brought into abutment against each other such that a region of the first cover material (3) arranged in one of the side edge regions and a region of the first cover material (3) arranged in the other side edge region face the same side, and a region of the second cover material (4) arranged in one side edge region and a region of the second cover material (4) arranged in the other side edge region face the same side, wherein the composite material (1) further comprises an intermediate material (5) arranged between the core material (2) and the first cover material (3), wherein the core material (2) is made of an Al alloy containing Cu in an amount of 0.3 to 0.5 mass%, Mn in an amount of 0.6 to 1.0 mass%, Ti in an amount of 0.05 to 0.15 mass%, Zn in an amount of 0.1 mass% or less, Fe in an amount of 0.3 mass% or less and Si in an amount of 0.2 mass% or less, wherein Al and unavoidable impurities complete the core material (2); the first cover material (3) is made of an Al alloy containing Si in an amount of 7.9 to 9.5 mass%, Fe in an amount of 0.1 to 0.3 mass% and Cu in an amount of 0.3 mass% or less, wherein Al and unavoidable impurities complete the first cover material (3); the second cover material (4) is made of an Al alloy containing Si in an amount of 4.5 to 5.5 mass%, Cu in an amount of 0.5 to 0.7 mass% and Fe in an amount of 0.8 mass% or less, wherein Al and unavoidable impurities complete the second cover material (4); and the intermediate material (5) is made of an Al alloy containing Mn in an amount of 0.2 to 0.4 mass%, Zn in an amount of 0.2 to 0.4 mass%, Fe in an amount of 0.4 mass% or less and Cu in an amount of 0.05 mass% or less, wherein Al and unavoidable impurities complete the intermediate material (5). [2] A method of manufacturing a pipe, comprising: Forming the composite material (1) according to claim 1 into a tubular shape such that a first surface of the composite material (1) covered with the first cover material (3) lies on an outer side and a second surface of the composite material (1) covered with the second cover material (4) lies on an inner side; and Welding the opposite side edge portions of the composite material (1) by means of high-frequency resistance welding into a state in which the opposite side edge portions of the composite material (1) abut against each other as a result of the application of pressure between the opposite side edge portions. [3] A pipe manufactured by a method according to claim 2, which consists of the core material (2), the first cover material (3) covering an outer peripheral surface of the core material (2), the second cover material (4) covering an inner peripheral surface of the core material (2), and the intermediate material (5) arranged between the core material (2) and the first cover material (3), wherein the core material (2) is exposed on outer and inner peripheral surfaces of the pipe in a welded joint portion (34) formed as a result of welding between the opposite side edge portions of the composite material (1) and in the vicinity of the welded joint portion (34). [4] Heat exchanger, comprising: a plurality of heat exchange tubes (11) formed of an uncovered material and arranged to have the same longitudinal direction and to be spaced apart from each other; fins (15) each formed from a brazing sheet and provided between adjacent heat exchange tubes (11); and a plurality of collecting tanks (12, 13, 14) which are provided on opposite sides of the heat exchange tubes (11) with respect to the longitudinal direction of the heat exchange tubes (11) in such a way that the longitudinal direction of the collecting tanks (12, 13, 14) coincides with a direction in which the heat exchange tubes (11) are arranged next to one another, wherein opposite end regions of the heat exchange tubes (11) are connected to the collecting tanks (12, 13, 14), wherein at least one of the collecting containers (12, 13, 14) consists of the pipe according to claim 3, and Closure elements (33) close the openings of the tube at its opposite ends; the pipe has a plurality of pipe insertion openings (35) arranged in a region remote from the welded joint region (34) of the pipe; the heat exchange tubes (11) are inserted into the tube insertion openings (35) and soldered to the tube by means of the first (3) and second cover material (4); and a heat exchanger component is provided on the tube in a position remote from the welded joint portion (34) and brazed to the tube by means of the first covering material (3).

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