JP5680857B2 - Aluminum alloy flat tube for heat exchanger and aluminum alloy heat exchanger - Google Patents

Description

  The present invention relates to aluminum alloy flat tubes for heat exchangers, in particular, aluminum alloy automobile heat exchange such as evaporators, condensers, radiators, and heater cores joined by inert gas atmosphere brazing using a fluoride flux or vacuum brazing. The present invention relates to an aluminum alloy flat tube for a heat exchanger that is suitable as a tube of a heat exchanger, and an aluminum alloy heat exchanger that is manufactured using the aluminum alloy flat tube.

  2. Description of the Related Art An automobile heat exchanger, for example, a radiator, includes a tube and a header that have fins on the outer surface and the inner surface serves as a passage for a working fluid (refrigerant). As a tube material and header plate material such as an automobile radiator or heater core, an Al-Mn alloy such as JIS A3003 is used as a core material, and an Al-Si alloy brazing material is clad on one side of the core material. A three-layered aluminum alloy clad material clad with a sacrificial anode material of an Al-Zn alloy or Al-Zn-Mg alloy is used on the surface of this, and a bare fin not having a brazing material is combined with this clad material Heat exchanger cores are manufactured.

  When manufacturing an aluminum alloy heat exchanger, the clad Al-Si brazing material is used when a tube is manufactured by joining a tube and a fin, joining a tube and a header plate, or brazing a clad plate. It is clad for brazing. In recent years, inert gas atmosphere brazing using a fluoride flux is generally applied to these brazings. Further, the sacrificial anode material is used, for example, on the inner surface side of the tube, and exerts a sacrificial anode action in contact with the working fluid, thereby preventing the occurrence of pitting corrosion and crevice corrosion of the core material.

  In addition to the aluminum alloy clad material having the above three-layer structure, a two-layer structure in which an Al—Mn alloy is used as a core, and a sacrificial anode material of an Al—Zn alloy or an Al—Zn—Mg alloy is clad on one surface of the core. The aluminum alloy clad material is also used. In an aluminum alloy clad material having a two-layer structure, a brazing material clad with an Al—Si brazing material is applied to a fin material brazed to the clad material.

  In recent years, with the demand for lighter automobiles, automobile heat exchangers are also required to be made thinner from the viewpoint of energy saving and resource saving, and the tube materials are also becoming thinner. In the manufacture of various heat exchangers, the clad plate is formed into a tubular shape with a forming roll or the like, the end is subjected to high-frequency welding, and further formed into a flat tube with a forming roll or the like. It is assembled and brazed together.

  In the radiator thus assembled, in particular, in the tube, the refrigerant from high temperature to low temperature and from high pressure to normal pressure is repeatedly circulated and circulated. That is, since a stress is repeatedly applied to the tube, fatigue characteristics that can withstand these are required. Fatigue properties are generally known to be related to static tensile strength, and in order to improve the tensile strength of materials in heat exchangers, for example, materials with added Cu have been proposed. .

JP-A-10-53827

Generally in the case of aluminum alloy, the elastic region, i.e. fatigue strength at high cycle range (about repeated several 10 ⁷ times) has a positive correlation with the static tensile strength, in order to enhance the fatigue strength, the core material and the inner covering Si, Cu, and Mg have been added to improve the tensile strength of the entire tube. However, since the refrigerant from high temperature to low temperature and from high pressure to normal pressure repeatedly circulates and circulates inside the actual radiator, especially the tube, the tube is subjected to repeated stress, and this repeated stress exceeds the elastic range and is plastic. It has been found that it extends to the area. The fatigue life in the plastic region, that is, the low cycle region (approximately 10 ³ cycles) is different from high cycle fatigue and fatigue properties, and no correlation with static tensile strength is seen. At present, the effects of various factors have not been clarified. When the clad material is formed into a flat tube shape and incorporated in a heat exchanger, fatigue cracks are likely to occur from the outer surface side of the tube. To obtain the durability of the heat exchanger, the fatigue strength on the outer surface of the flat tube It is necessary to improve.

Fatigue strength in the high cycle region within the elastic region can be measured with an axial force tester or a rotary bending tester, etc., but the fatigue test of thin plate materials in the low cycle region with plastic deformation is tested with the above tester. The inventors have conducted tests and examinations using the thin plate bending fatigue tester shown in FIG. 1 in order to examine the influence of the material constituting the clad material on the low cycle fatigue life. This bending fatigue tester performs a double-bending bending fatigue test on a test piece, determines the strain range and frequency, measures the number of cycles until breakage, and determines the fatigue life to be 10 ³ to 10 ^The evaluation is performed in a low cycle range of about ⁴ .

  As a result, the conventional three-layer clad material clad with the brazing material on the outer surface side of the clad material (the brazing material is the outer surface side of the tube and the inner skin material (sacrificial anode material) is the inner surface side of the tube) It is clear that the low-cycle fatigue strength of the one clad on the opposite surface is inferior, whereas in the two-layer clad material that does not have the brazing material on the outer surface side, the low-cycle fatigue strength is remarkable. I found it to improve.

  In addition, the fatigue strength in the low-cycle region is determined by the fact that the surface shape is concave and the position of the triple point of the crystal grain boundary, that is, the branch point of the crystal grain boundary observed when observing the crystal grain structure of the cladding material In this process, an initial crack occurs, and then a crack between triple points progresses along the grain boundary in a direction perpendicular to the direction in which the repeated stress is applied, and the progressed crack is connected. As a result, it was found that the grain boundary fracture occurs and the cracks develop into large cracks that affect the fatigue life. This is because the stress applied to the clad material is concentrated at the crystal grain boundary rather than within the crystal grain, and further, the stress concentration is caused by the concave part having a thin surface shape. This is because the stress is most easily concentrated at the triple point. In particular, it has been clarified that the initial crack is more likely to occur at the triple point at the end of the grain boundary facing the direction perpendicular to the direction in which the repeated stress is applied among the triple points. The number of triple points after brazing heating has a correlation inversely proportional to the crystal grain size. The larger the crystal grain size, the smaller the number of triple points, and the smaller the crystal grain size, the greater the number of triple points. is there. In consideration of the occurrence of cracks in low cycle fatigue at the branch point of the grain boundary, it is effective to control the number of triple points rather than the crystal grain size.

  The present invention has been made as a result of repeated testing and examination based on the above knowledge, and its purpose is heat exchange with high cycle fatigue strength as well as excellent low cycle fatigue strength and good corrosion resistance. An object of the present invention is to provide an aluminum alloy flat tube formed by bending and welding an aluminum alloy double-layer clad material, and an aluminum alloy heat exchanger manufactured using the aluminum alloy flat tube.

In order to achieve the above object, the aluminum alloy flat tube for heat exchanger according to claim 1 is mass%, Si: 0.3-1.2%, Fe: 0.05-0.7%, Cu: 0. 0.3 to 1.0%, Mn: 0.6 to 1.8%, Ti: 0.06 to 0.35%, Mg as impurities is limited to less than 0.5%, the balance Al and A two-layer clad containing Zn: 0.5-5.0%, Mg: 0.5-3.0% on one side of a core material made of inevitable impurities, and clad with the remainder Al and an endothelial material made of inevitable impurities Aluminum for heat exchangers in which the brazing material is bent so that the core is on the surface side, the end is high-frequency welded, and the aluminum brazing fins clad with the Al-Si alloy brazing material are assembled and brazed on the surface side Alloy flat tube, brazed heating (600 ° C (material When the center line average roughness was heated to degrees) 3 min hold) the core material surface after Ra, per 1 mm ² of the triple point number of the grain boundaries was ^{N, N · e 2Ra <300} ( provided that, e is characterized by satisfying the relationship of the base of natural logarithm). In the following description, all alloy composition percentages are indicated by mass%.

  An aluminum alloy flat tube for a heat exchanger according to claim 2 is the aluminum alloy flat tube according to claim 1, wherein the endothelial material is further selected from Si: 0.3 to 1.2% and Mn: 0.6 to 1.8%. Or it contains 2 types, It is characterized by the above-mentioned.

  The aluminum alloy flat tube for a heat exchanger according to claim 3 is the aluminum alloy flat tube according to claim 1 or 2, wherein the core material is Cr: 0.01 to 0.3%, Zr: 0.01 to 0.3%. It is characterized by including 1 type or 2 types.

  An aluminum alloy flat tube for a heat exchanger according to claim 4 is any one of claims 1 to 3, wherein the endothelial material is further Cr: 0.01 to 0.3%, Zr: 0.01 to 0.3%. Ti: 0.01-0.3% of 1 type or 2 types or more are included.

An aluminum alloy flat tube for a heat exchanger according to a fifth aspect is characterized in that in any one of the first to fourth aspects, the endothelial material further contains Ni: 0.1 to 1.5% .

  An aluminum alloy heat exchanger according to a sixth aspect of the present invention is an aluminum alloy flat tube according to any one of the first to fifth aspects, wherein an aluminum brazing fin clad with an Al-Si alloy brazing material is assembled, and a fluoride flux is obtained. It was produced by brazing in an inert gas atmosphere or vacuum brazing used.

  According to the present invention, an aluminum alloy flat tube for a heat exchanger that is excellent in low cycle fatigue strength as well as high cycle fatigue strength and excellent in corrosion resistance, and an aluminum alloy heat exchanger manufactured using the aluminum alloy flat tube Is provided.

  The aluminum alloy flat tube according to the present invention is a tube of an aluminum alloy automobile heat exchanger such as an evaporator, a condenser, a radiator, and a heater core, which are joined by inert gas atmosphere brazing using a fluoride-based flux or vacuum brazing. Is preferably used.

It is a figure which shows the outline of a bending fatigue testing machine.

  Low cycle fatigue strength is affected by the surface roughness of the material (core material side), and if the surface roughness is large, the concave portion becomes the starting point of cracking, so brazing heating (600 ° C (material The center line average roughness of the surface of the core material after heating to (temperature) and holding for 3 minutes is preferably set to Ra of 0.6 μm or less. In order to reduce the center line average roughness Ra of the core surface after brazing heating to 0.6 μm or less, the core material itself is not clad on the outer surface of the tube without cladding the brazing material that has been disposed on the outer surface side of the tube. It is to do.

If there are many triple points of crystal grain boundaries on the surface of the core material on the tube surface side, the number of crack initiation points will increase, and the distance between the triple points will be shortened. Propagation is likely to occur. Accordingly, the number of triple points per 1 mm ^{2 on the} surface of the core material after the brazing heating is preferably 250 or less.

Thus, if the center line average roughness of the core material surface is lower and the number of triple points per 1 mm ² is reduced, the fatigue strength in the low cycle region of the clad material can be made excellent. However, from the results of more detailed experiments, the fatigue life in the low cycle region is proportional to the number of triple points per 1 mm ² , and the natural logarithm of the fatigue life in the low cycle region is the centerline average roughness of the core surface. In order to obtain the durability required as a heat exchanger, it is clear that the center line average roughness of the core surface is Ra, and the number of triple points per mm ² is N. , N · e ^2Ra <300 (where e is the base of the natural logarithm). When N · e ^2Ra ≧ 300, the notch effect and the propagation path of cracks increase, and the fatigue life in the low cycle range decreases.

  On the other hand, the high cycle fatigue strength correlates with the static strength of the material as conventionally known, and the higher the strength (hardness) of the material, the better. By satisfying the conditions for improving the fatigue strength in the high cycle region (elastic region) and the conditions for improving the fatigue strength in the low cycle region (plastic region), the low cycle fatigue strength is secured while ensuring the high cycle fatigue strength. The prepared cladding material can be obtained.

  The first means for improving the fatigue life in the present invention is to eliminate the brazing material conventionally provided on the surface side (core material side) of the tube and to form a two-layer structure of the core material and the endothelial material. As a result, in the conventional clad material in which the brazing material is arranged, the brazing is once melted by brazing, and the brazing remaining on the tube surface is solidified. Since the average roughness Ra is large, cracks were likely to occur at the concave portions of the surface shape and triple points, but the cracks were prominent because the center line average roughness of the tube surface was significantly reduced by eliminating the brazing material. To be suppressed. A flat tube made of a clad material having a two-layer structure can be joined to a fin or header material by using a fin clad with a brazing material and a header material clad with a brazing material. Secondly, the outer surface (core material surface) of the tube has good surface properties and the number of triple points on the outer surface (core material surface) is reduced. By reducing the number of triple points, the starting point of the initial crack can be reduced, the distance between the triple points can be secured as large as possible, and the material structure can suppress the propagation path of the crack. In addition, in order to ensure high cycle fatigue strength, static strength above a certain level was ensured.

  The surface roughness of the core material in the two-layer clad material constituting the aluminum alloy flat tube of the present invention is adjusted by the surface quality of the roll surface during material rolling, and the surface quality of the rolling roll surface during clad material rolling is smoother. The low cycle fatigue strength can be improved by adjusting to a smooth surface. The roughness of the preferable rolling roll surface for obtaining the effect of the present invention is 0.1 to 0.6 μm in terms of centerline average roughness.

The significance and reasons for limitation of the alloy components of the core material and the endothelial material in the two-layer clad material constituting the aluminum alloy flat tube of the present invention will be described.
(Core material)
Si has a function of improving the strength of the core material. In particular, by coexisting with Mg diffused from the sacrificial anode material during brazing, age hardening is caused after brazing to further increase the strength. The preferable content range is 0.3 to 1.2%, and if the content is less than 0.3%, the effect is small. If the content exceeds 1.2%, the corrosion resistance is lowered, the melting point of the core material is lowered, and brazing is performed. Sometimes local melting tends to occur. A more preferable content range of Si is 0.3 to 1.0%.

  Fe is contained as an impurity. Fe acts as a cathode with respect to the aluminum base material and reduces corrosion resistance. Therefore, it is preferable to limit it to 0.7% or less. Further, Fe in the core material has an effect of making the recrystallized grains fine, and in order to increase the number of triple points, it is more preferable to make it 0.3% or less. In order to reduce the Fe content extremely, it is necessary to use high-purity aluminum ingots with high cost. Therefore, the content range is practically 0.05% or more.

  Cu functions to improve the anticorrosion effect by improving the strength of the core material, making the potential of the core material noble, and increasing the potential difference from the sacrificial anode material. Further, Cu in the core material diffuses in the sacrificial anode material and the brazing material during brazing, and forms a gentle concentration gradient. As a result, the potential on the core material side becomes noble, and the potential on the surface side of the sacrificial anode material. Becomes a base, and a gentle potential distribution is formed in the sacrificial anode material, so that the corrosion form becomes a full corrosion type. The preferable content of Cu is in the range of 0.3 to 1.0%. If the content is less than 0.3%, the effect is small. If the content exceeds 1.0%, the corrosion resistance of the core material is lowered, and the melting point is lowered. Thus, local melting is likely to occur during brazing. A more preferable content range of Cu is 0.5 to 0.9%.

  Mn functions to improve the corrosion resistance by improving the strength of the core material and making the potential of the core material noble and increasing the potential difference from the sacrificial anode material. The preferable content range of Mn is 0.6 to 1.8%. If the content is less than 0.6%, the effect is small, and if the content exceeds 1.8%, a coarse compound is produced at the time of casting, and the rolling processability is reduced. As a result, it is difficult to obtain a healthy plate material. A more preferable content range of Mn is 1.1 to 1.6%.

  Ti is divided into a high-concentration region and a low region in the thickness direction of the core material, and they are in a layered form in which they are alternately distributed. Has the effect of layering, thereby preventing the progress of corrosion in the thickness direction and improving the pitting corrosion resistance of the material. The preferable content is in the range of 0.06 to 0.35%. If the content is less than 0.06%, this effect is small, and if it exceeds 0.35%, casting becomes difficult, and workability deteriorates and the material is healthy. Is difficult to manufacture.

  Mg has the effect of improving the strength of the core material, but it is preferable to limit the content to less than 0.5% from the viewpoint of reducing brazing properties. In the case of brazing with an inert gas atmosphere using a fluoride-based flux, if the Mg content is 0.5% or more, Mg reacts with the fluoride-based flux and the brazing property with the fin material is hindered. In addition, Mg fluoride is generated, and the appearance of the brazed portion becomes unclear.

  Cr and Zr coarsen the crystal grain size after brazing, reduce the number of triple points, and improve brazing properties. Preferable contents are each in the range of 0.01 to 0.3%, and if it is less than 0.01%, there is no effect, and if it exceeds 0.3%, a coarse compound is produced and it becomes difficult to produce a normal plate material .

(Endothelial material)
Zn lowers the potential of the sacrificial anode material and maintains the sacrificial anode effect on the core material. As a result, pitting corrosion and crevice corrosion of the core material are prevented. The preferable content is in the range of 0.5 to 5.0%. If the content is less than 0.5%, the effect is small, and if it exceeds 5.0%, the self-corrosion resistance is lowered. A more preferable content range of Zn is 3.0 to 5.0%.

  Mg diffuses into the core material during heat brazing and increases the strength together with Si and Cu in the core material. Further, Mg remaining in the sacrificial anode material increases the strength together with Si. These effects contribute to improving the strength of the clad material. The preferable content for obtaining the above effect is in the range of 0.5 to 3.0%. If the content is less than 0.5%, the effect is small, and if it exceeds 3.0%, the rolling processability decreases. A more preferable content range of Mg is 1.5 to 2.5%.

  Si has a function of improving the strength of the endothelium. The preferred content range is 0.3 to 1.2%, and if it is less than 0.3%, there is a problem of insufficient strength, and if it exceeds 1.2%, the corrosion resistance is lowered, the melting point is lowered, and the brazing property is inferior. . A more preferable content range of Si is 0.3 to 0.8%.

  Mn improves the strength and the deformation resistance of the sacrificial anode material. The preferable content range is 0.6 to 1.8%, and if the content is less than 0.6%, the effect is small. If the content exceeds 1.8%, a coarse compound is produced during casting, and the self-corrosion resistance is lowered. A more preferable content range of Mn is 1.0 to 1.8%.

  Cr and Zr coarsen the crystal grain size after brazing and improve brazing properties. The preferred contents are each in the range of 0.01 to 0.3%, and if the content is less than 0.01%, the effect is small, and if it exceeds 0.3%, a coarse compound is produced, making it difficult to produce a sound plate material. Become.

  Ti is distributed in a layered manner in the endothelial material and causes corrosion to spread laterally, thereby improving the corrosion resistance. The preferred content is in the range of 0.01 to 0.3%, and if it is less than 0.01%, the effect is small, and if it exceeds 0.3%, a coarse compound is produced, and it becomes difficult to produce a normal plate material.

  Ni has an effect of improving the corrosion resistance. The preferable content is in the range of 0.1 to 1.5%, and if it is less than 0.1%, the effect is small, and if it exceeds 1.5%, the corrosion resistance is lowered. A more preferable content range of Ni is 0.6 to 1.2%.

  In the aluminum alloy flat tube of the present invention, the number of triple points of the core material after brazing heating is the production condition of the clad material, that is, the homogenization temperature and time of the core material, hot rolling temperature, intermediate annealing temperature, It can be controlled by adjusting the cold rolling degree after intermediate annealing.

In the present invention, Si: 0.3-1.2%, Cu: 0.3-1.0%, Mn: 0.6-1.8%, Ti: 0.06-0. In order to obtain a sacrificial anode effect in a high-strength core material containing 35%, limiting Mg as an impurity to less than 0.5%, and the balance Al and inevitable impurities, Zn: 0.5-5. 2% clad material containing 0% and further Mg: 0.5-3.0%, clad with the remainder material of Al and unavoidable impurities and bent at the end and high-frequency welded , a heat exchanger to braze by assembling aluminum brazing fins clad Al-Si alloy filler metal of an aluminum alloy flat tube, the center line average roughness of brazing the core material after heating Ra, per 1 mm ² when the triple point number was ^{N, N · e 2Ra <300} ( E is a natural logarithm base). By using the aluminum alloy flat tube as a heat exchanger tube, the tensile strength of the tube is ensured and the fatigue life in a high cycle range is achieved. In addition, the fatigue life of the low cycle region is improved, and a heat exchanger having excellent durability can be obtained.

  The aluminum alloy heat exchanger according to the present invention is an inert gas atmosphere in which an aluminum brazing fin clad with a commonly used Al-Si alloy brazing material is assembled to the aluminum alloy flat tube, and a fluoride flux is used. It is produced by brazing or vacuum brazing.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects of the present invention. Note that. These examples show one embodiment of the present invention, and the present invention is not limited thereto.

Example 1
The core material alloy having the composition shown in Table 1 and the endothelial material alloy having the composition shown in Table 2 were dissolved and ingoted by continuous casting. Both the ingot for the core material alloy and the ingot for the endothelial material alloy were homogenized at 600 ° C. for 10 hours.

  Next, after hot rolling the ingot of the alloy for endothelial material to obtain a hot rolled material having a thickness of 6 mm, the hot rolled material and the ingot of the core material alloy are combined as shown in Table 3. Hot-rolled to obtain a clad material. Thereafter, the clad material was subjected to cold rolling, intermediate annealing, and cold rolling to obtain a clad material (H14) having a thickness of 0.20 mm. In the cladding configuration, the thickness of the endothelial material was 0.020 mm. The roll for final cold rolling was prepared so that the surface quality of the rolling roll surface was smoother than usual (centerline average roughness: 0.2 μm).

The obtained cladding material was heated for 3 minutes at 600 ° C. (material temperature) corresponding to the brazing temperature in a nitrogen gas atmosphere, and then evaluated as follows.
Measurement of tensile strength after brazing heating: A clad material was molded into a JIS No. 5 test piece, held at room temperature for 4 weeks after brazing heating, and then subjected to a tensile test at room temperature.

Surface roughness measurement after brazing heating: Using a surfcom manufactured by Tokyo Seimitsu Co., Ltd., the center line average roughness (Ra) of the core material surface was measured in the direction perpendicular to the rolling direction.
Measurement of the triple point number after brazing heating (triple points): The core material surface a polarizing microstructure observation, by image analysis from 50 times the polarization microstructure photograph to extract the crystal grain boundary, the core material surface 1mm per ² The number of triple points was obtained.

Low cycle bending fatigue test: Using the bending fatigue tester shown in FIG. 1, the bending fatigue test was performed on the clad plate after brazing and heating in the strain range, that is, the strain amplitude of 1.0%. (Times) was measured. Those that broke when the number of repetitions was 3000 times or more were evaluated as acceptable (◯), and those that were broken when the number of repetitions was less than 3000 were evaluated as unacceptable (x).
High cycle fatigue test: A fatigue strength of 10 ⁷ times was measured by a tensile-tensile axial fatigue test. 50 MPa or more was regarded as acceptable (◯), and less than 50 MPa as unacceptable (x).

Internal corrosion test: A test was conducted by the following method using the following corrosive liquid.
Etchant: poor water simulant, weakly acidic solution _{^{pH3~7 (Cl -: 195ppm, SO}} 4 2-: 60ppm, Cu 2+: 1ppm, Fe 3+: 30ppm)
Method: A cycle of heating at 88 ° C for 8 hours, cooling and holding at 25 ° C for 16 hours was repeated for 4 months, and the maximum corrosion depth of the clad material inner surface (endothelium material side) after the test was measured. A thickness exceeding 0.06 mm was evaluated as acceptable (◯), and a value exceeding 0.06 mm was evaluated as unacceptable (x).

The evaluation results are shown in Table 3. As shown in Table 3, all of the clad materials 1 to 13 , 15 to 25 , 27 and 28 according to the present invention have excellent tensile strength after brazing heating, and excellent low cycle fatigue strength and high cycle fatigue strength. In addition, it had good corrosion resistance.

Comparative Example 1
The core material alloy having the composition shown in Table 4 and the endothelial material alloy having the composition shown in Table 5 were melted and ingoted by continuous casting. Both the ingot for the core material alloy and the ingot for the endothelial material alloy were homogenized at 600 ° C. for 10 hours. In Tables 4 and 5, those outside the conditions of the present invention are underlined.

  Next, after hot rolling the ingot of the alloy for endothelial material to obtain a hot rolled material having a thickness of 6 mm, the hot rolled material and the ingot of the core material alloy are combined as shown in Table 6. Hot-rolled to obtain a clad material. Thereafter, the clad material was subjected to cold rolling, intermediate annealing, and cold rolling to obtain a clad material (H14) having a thickness of 0.25 mm (clad materials 30 to 48). In the cladding configuration, the thickness of the endothelial material was 0.050 mm. The final cold rolling roll was prepared by adjusting the surface quality of the rolling roll surface to a smooth surface (center line average roughness: 0.2 μm). The evaluation results are shown in Table 6.

  In Table 6, the clad material 29 contains Si: 10% together with the core material alloy and the endothelium alloy, and ingots the brazing material alloy composed of the balance Al and inevitable impurities. The ingot of the alloy and the alloy for the endothelial material is subjected to a homogenization treatment at 600 ° C. for 10 hours, and the ingot of the alloy for the endothelial material and the ingot of the alloy for the brazing material are hot-rolled to a predetermined thickness. As shown in Table 6, the ingots for core material are combined and hot-rolled to make a clad material, and then the clad material is cold-rolled, intermediate-annealed and cold-rolled, and a clad having a thickness of 0.20 mm The material (H14) is used. The configuration of the clad was 0.020 mm for the thickness of the endothelial material and 0.030 mm for the brazing material. The fluoride-based flux was applied to the brazing material surface of the obtained clad material, heated in a nitrogen gas atmosphere to 600 ° C. (material temperature) corresponding to the brazing temperature, and then evaluated as described above.

  As shown in Table 6, since the clad material 29 was provided with a brazing material, the surface roughness of the core material surface was increased, and the low cycle fatigue strength was inferior. Since the clad material 30 had a large amount of Zn in the endothelial material, the self-corrosion resistance was lowered and the corrosion resistance was poor. The clad material 31 was inferior in corrosion resistance because the amount of Zn in the endothelial material was small. Since the clad material 32 has a large amount of Mg in the endothelium material, the rolling processability is lowered and the clad material cannot be manufactured. The clad material 33 had a low tensile strength because the amount of Mg in the endothelial material was small.

The clad materials 34 and 35 were inferior in corrosion resistance because of the large amount of Mn and Si in the endothelial material, respectively. Since the clad material 37 has a large amount of Ni in the endothelial material, the corrosion resistance is reduced. Since the clad material 38 has a high Si content in the core material, the melting point is lowered, and local melting occurs during brazing heating, resulting in an increase in the number of triple points on the surface of the core material. The clad material 39 has a low tensile strength due to a small amount of Si in the core material.

  Since the clad material 40 has a large amount of Mn in the core material, a coarse compound is produced during casting, the rollability is impaired, and the number of triple points on the surface of the core material is increased, resulting in a low cycle fatigue strength. The clad material 41 had a low tensile strength because the core material had a small amount of Mn. Since the clad material 42 has a large amount of Cu, the melting point is lowered, local melting occurs during brazing heating, and the number of triple points on the surface of the core material is increased, so that the low cycle fatigue strength is lowered. The clad material 43 had a low tensile strength because the amount of Cu in the core material was small.

  Since the clad material 44 has a large amount of Ti in the core material, a coarse product is generated and a normal clad material cannot be manufactured. Since the clad material 45 has a small amount of Ti in the core material, the corrosion resistance is lowered. Since the clad material 46 has a large amount of Fe in the core material, the corrosion resistance is lowered. Since the clad material 47 has a large amount of Mg in the core material, the surface of the core material is oxidized during brazing heating and the number of triple points on the surface of the core material is increased, so that the low cycle fatigue strength is reduced. In addition, when brazing with an inert gas atmosphere using a fluoride-based flux, Mg reacts with the flux, so that brazing is inferior and brazing with a fin material or the like becomes difficult. Since the clad material 48 had a large surface roughness after brazing of the core material, the low cycle fatigue strength was inferior.

Claims (6)

In mass% (hereinafter the same) , Si: 0.3-1.2%, Fe: 0.05-0.7%, Cu: 0.3-1.0%, Mn: 0.6-1. 8%, Ti: 0.06 to 0.35%, Mg as an impurity is limited to less than 0.5%, and Zn: 0.5 to End portion by bending a two-layer clad material containing 5.0%, Mg: 0.5-3.0%, and clad with an endothelial material composed of the remaining Al and inevitable impurities so that the core is on the surface side Is an aluminum alloy flat tube for a heat exchanger that is brazed with an aluminum brazing fin clad with an Al—Si alloy brazing material on the surface side and brazed and heated (600 ° C. (material temperature ) And hold for 3 minutes) Raise the centerline average roughness of the core material surface after Ra An aluminum alloy flattening for heat exchangers that satisfies the relationship N · e ^2Ra <300 (where e is the base of natural logarithm), where N is the number of triple points of grain boundaries per mm ² tube. The heat exchange according to claim 1, wherein the endothelial material further contains one or two of Si: 0.3 to 1.2% and Mn: 0.6 to 1.8%. Aluminum alloy flat tube for dexterity. 3. The core material according to claim 1, wherein the core material further contains one or two of Cr: 0.01 to 0.3% and Zr: 0.01 to 0.3%. Aluminum alloy flat tube for heat exchanger. The endothelium material further contains one or more of Cr: 0.01 to 0.3%, Zr: 0.01 to 0.3%, and Ti: 0.01 to 0.3%. The aluminum alloy flat tube for heat exchangers according to any one of claims 1 to 3. 5. The aluminum alloy flat tube for a heat exchanger according to claim 1, wherein the endothelial material further contains Ni: 0.1 to 1.5% . An aluminum brazing fin clad with an Al-Si alloy brazing material is assembled to the aluminum alloy flat tube according to any one of claims 1 to 5, and brazing or vacuum brazing in an inert gas atmosphere using a fluoride flux. An aluminum alloy heat exchanger produced by the above method.

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