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US20070017605A1 - Aluminum alloy extruded product exhibiting excellent surface properties, method of manufacturing the same, heat exchanger multi-port tube, and method of manufacturing heat exchanger including the multi-port tube - Google Patents

Aluminum alloy extruded product exhibiting excellent surface properties, method of manufacturing the same, heat exchanger multi-port tube, and method of manufacturing heat exchanger including the multi-port tube Download PDF

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Publication number
US20070017605A1
US20070017605A1 US11/489,941 US48994106A US2007017605A1 US 20070017605 A1 US20070017605 A1 US 20070017605A1 US 48994106 A US48994106 A US 48994106A US 2007017605 A1 US2007017605 A1 US 2007017605A1
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United States
Prior art keywords
aluminum alloy
ingot
extruded product
port tube
heat exchanger
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Abandoned
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US11/489,941
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English (en)
Inventor
Tomohiko Nakamura
Masaaki Kawakubo
Yoshiharu Hasegawa
Naoki Yamashita
Tatsuya Hikida
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Denso Corp
Sumitomo Light Metal Industries Ltd
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Individual
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Assigned to DENSO CORPORATION, SUMITOMO LIGHT METAL INDUSTRIES, LTD. reassignment DENSO CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HASEGAWA, YOSHIHARU, HIKIDA, TATSUYA, KAWAKUBO, MASAAKI, NAKAMURA, TOMOHIKO, YAMASHITA, NAOKI
Publication of US20070017605A1 publication Critical patent/US20070017605A1/en
Priority to US12/930,793 priority Critical patent/US20110114228A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/02—Tubular elements of cross-section which is non-circular
    • F28F1/022—Tubular elements of cross-section which is non-circular with multiple channels
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
    • F28F21/081—Heat exchange elements made from metals or metal alloys
    • F28F21/084—Heat exchange elements made from metals or metal alloys from aluminium or aluminium alloys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2255/00—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes
    • F28F2255/16—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes extruded

Definitions

  • the present invention relates to an aluminum alloy extruded product exhibiting excellent surface properties, a method of manufacturing the same, a heat exchanger multi-port tube, and a method of manufacturing a heat exchanger including the multi-port tube.
  • an aluminum alloy which has a reduced weight and exhibits excellent thermal conductivity has been generally used.
  • an aluminum alloy tube such as an aluminum alloy extruded flat multi-port tube (hereinafter called “multi-port tube”) having a plurality of hollow portions divided by a plurality of partitions, is used as the material for a working fluid passage.
  • the multi-port tube and other members such as a fin material are assembled into a specific structure and joined by brazing in a heating furnace containing inert gas.
  • Mn and Si dissolved in the matrix increase the deformation resistance of the alloy.
  • the extrusion ratio reaches several hundred to several thousand such as when manufacturing the multi-port tube
  • the alloy exhibits significantly inferior extrudability in comparison with a pure Al material.
  • extrudability is evaluated using the ram pressure necessary for extrusion and the maximum extrusion rate at which the partition wall of the hollow portion of the multi-port tube is completely formed (i.e. limiting extrusion rate) as indices.
  • a material which requires a high ram pressure or exhibits a low limiting extrusion rate is determined to have poor extrudability.
  • An alloy containing Mn and Si at high concentrations requires a ram press higher than that of a pure Al material, whereby the die tends to break or wear. Moreover, productivity decreases due to a decrease in the limiting extrusion rate.
  • the film-shaped deposit on the bearing of the die is increased in thickness and amount during continuous extrusion.
  • the deposit is finally removed from the bearing and adheres to the surface of the extruded tube.
  • the deposition, removal, and adhesion process then repeatedly occurs. As a result, the deposit adheres to the surface of the extruded tube at specific intervals.
  • an object of the present invention is to provide an aluminum alloy extruded product exhibiting excellent surface properties which exhibits improved strength and excellent extrudability, allows extrusion of a thin multi-port tube at a high limiting extrusion rate, prevents the deposit from adhering to the surface of the extruded tube, and may be suitably used as a constituent member for an aluminum alloy automotive heat exchanger, and a method of manufacturing the same.
  • a first aspect of the present invention provides an aluminum alloy extruded product exhibiting excellent surface properties, comprising 0.8 to 1.6% (mass %; hereinafter the same) of Mn and 0.4 to 0.8% of Si at a ratio of Mn content to Si content (Mn %/Si %) of 0.7 to 2.4, with the balance being Al and inevitable impurities, the number of intermetallic compounds with a diameter (circle equivalent diameter; hereinafter the same) of 0.1 to 0.9 ⁇ m dispersed in a matrix being 2 ⁇ 10 5 or more per square millimeter.
  • This aluminum alloy extruded product may further comprise 0.05% or less of Cu.
  • This aluminum alloy extruded product may further comprise 0.2% or less of Mg.
  • This aluminum alloy extruded product may further comprise 0.3% or less of Ti.
  • a second aspect of the present invention provides a heat exchanger multi-port tube comprising the above aluminum alloy extruded product.
  • a third aspect of the present invention provides a method of manufacturing an aluminum alloy extruded product exhibiting excellent surface properties, the method comprising: melting and casting an aluminum alloy having the above composition to obtain an ingot; subjecting the ingot to homogenization which includes a first-stage heat treatment in which the ingot is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the ingot is cooled to 400 to 500° C. at an average temperature decrease rate of 20 to 60° C./h and maintained at that temperature for three hours or more; heating the ingot at 480 to 560° C.; and extruding the ingot.
  • a fourth aspect of the present invention provides a method of manufacturing a aluminum alloy extruded product exhibiting excellent surface properties, the method comprising: melting and casting an aluminum alloy having the above composition to obtain an ingot; subjecting the ingot to homogenization which includes a first-stage heat treatment in which the ingot is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the ingot is cooled to room temperature, heated to 400 to 500° C. at an average temperature increase rate of 20 to 60° C./h, and maintained at that temperature for three hours or more; heating the ingot at 480 to 560° C.; and extruding the ingot.
  • a fifth aspect of the present invention provides a method of manufacturing a heat exchanger comprising extruding a heat exchanger multi-port tube using the above method, and joining the multi-port tube to a heat exchanger by brazing.
  • an aluminum alloy extruded product exhibiting excellent surface properties which exhibits improved strength and excellent extrudability, allows extrusion of a thin multi-port tube at a high limiting extrusion rate, prevents the deposit from adhering to the surface of the extruded tube, and may be suitably used as a constituent member for an aluminum alloy automotive heat exchanger, a method of manufacturing the same, a heat exchanger multi-port tube made of the aluminum alloy extruded product, and a method of manufacturing a heat exchanger including the multi-port tube can be provided.
  • FIG. 1 is a cross-sectional view of an aluminum alloy flat multi-port tube extruded in the examples of the present invention.
  • Mn and Si are dissolved in the matrix during heating for brazing to improve the strength of the alloy.
  • the Mn content is preferably 0.8 to 1.6%
  • the Si content is preferably 0.4 to 0.8%. If the content of Mn and Si is greater than the upper limit, extrudability deteriorates to a large extent to impair the strength improvement effect. If the content of Mn and Si is less than the lower limit, a sufficient strength cannot be obtained.
  • the ratio of the Mn content to the Si content is preferably 0.7 to 2.4. If the ratio of the Mn content to the Si content is within this range, Mn and Si dissolved in the matrix during casting of the alloy can be mainly precipitated as an Al—Mn—Si intermetallic compound during homogenization of the by ingot, whereby the solid solubility in the matrix can be minimized.
  • the dispersion state in which a number of minute Al—Mn—Si intermetallic compounds are precipitated reduces the deformation resistance of the alloy during hot extrusion performed after homogenization heat treatment, whereby the extrudability of the alloy can be improved.
  • the ratio “Mn %/Si %” is less than 0.7, since Si is contained in the alloy in an amount exceeding the range of the ratio “Mn %/Si %” which can minimize the solid solubility of Mn and Si in the matrix, Si remains dissolved in the matrix after the homogenization heat treatment, whereby the deformation resistance of the alloy during the subsequent hot extrusion is not reduced. As a result, the extrudability of the alloy cannot be improved.
  • Mn %/Si % exceeds 2.4, since Mn is contained in the alloy in an amount exceeding the range of the ratio “Mn %/Si %” which can minimize the solid solubility of Mn and Si in the matrix, Mn remains dissolved in the matrix after the homogenization heat treatment, whereby the deformation resistance of the alloy during the subsequent hot extrusion is not reduced. As a result, the extrudability of the alloy cannot be improved.
  • the Cu content is preferably limited to 0.05% or less. This reduces intergranular corrosion during use of an automotive heat exchanger manufactured by brazing the aluminum alloy extruded product according to the present invention. If the Cu content exceeds 0.05%, since the operating temperature of a heat exchanger using carbon dioxide as a refrigerant becomes as high as about 150° C., Al—Mn compounds and the like are significantly precipitated at the boundaries, whereby intergranular corrosion susceptibility increases.
  • Mg improves the strength of the alloy when contained in an amount of 0.2% or less. Moreover, when manufacturing an automotive heat exchanger by brazing using a fluoride-type flux contain potassium fluoroaluminate, excellent brazeability can be stably obtained. If the Mg content exceeds 0.2%, when manufacturing an automotive heat exchanger by brazing, a fluoride-type flux containing potassium fluoroaluminate which is melted during heating for brazing reacts with Mg in the material to produce compounds such as MgF 2 and KMgF 3 . This reduces the activity of the flux, whereby brazeability deteriorates. Moreover, the extrudability of the alloy decreases when the Mg content exceeds 0.2%.
  • Ti form a high-Ti-concentration area and a low-Ti-concentration area in the alloy. These areas are alternately distributed in layers in the direction of the thickness of the material. Since the low-Ti-concentration area is preferentially corroded in comparison with the high-Ti-concentration area, corrosion occurs in layers. This prevents corrosion from proceeding in the direction of the thickness of the material. As a result, pitting corrosion resistance and intergranular corrosion resistance are improved. Moreover, the strength of the material at room temperature and a high temperature is improved by adding Ti.
  • the Ti content is preferably 0.06 to 0.3%. If the Ti content is less than 0.06%, the effect is insufficient. If the Ti content exceeds 0.3%, coarse compounds are produced during casting, whereby workability is impaired.
  • Fe is contained as an inevitable impurity.
  • the Fe content is preferably limited to about 0.7% or less, and still more preferably 0.3% or less.
  • the B content is preferably about 0.01% or less.
  • Impurities such as Cr, Zr, Ni, and Zn may be contained in the alloy in an amount of 0.25% or less in total.
  • intermetallic compounds with a diameter (circle equivalent diameter) of 0.1 to 0.9 ⁇ m be dispersed in the matrix in a number of 2 ⁇ 10 5 or more per square millimeter (mm 2 ).
  • These intermetallic compounds are mainly Al—Mn—Si intermetallic compounds.
  • the above dispersion structure is obtained by homogenizing an unextruded ingot (billet), which reduces adhesion of the deposit to the surface of the aluminum alloy extruded product and improves the strength of the aluminum alloy extruded product after heating for brazing.
  • the extruded aluminum alloy is deposited on the bearing of the die in the shape of a film.
  • the deposit When extruding a billet in which the above intermetallic compounds are dispersed, since the surface of the film-shaped deposit formed on the bearing of the die is continuously scraped off by the dispersed minute intermetallic compounds during extrusion, the deposit is formed in the shape of a thin uniform film. Since the deposit is maintained in the shape of a thin uniform film during continuous extrusion, removal of the deposit is prevented. As a result, adhesion of the deposit to the surface of the aluminum alloy extruded product is significantly reduced. Since the deposit is maintained in the shape of a thin uniform film, the extruded product is provided with excellent surface properties to exhibit a gloss.
  • the extruded tube is attached to a heat exchanger (e.g. automotive heat exchanger) and joined by brazing.
  • a heat exchanger e.g. automotive heat exchanger
  • brazing since the Al—Mn—Si intermetallic compounds dispersed in the matrix are redissolved in the matrix, the strength of the tube after joining by brazing is improved due to solid solution hardening. Since the operating temperature is as high as about 150° C. when using carbon dioxide as a refrigerant, the aluminum alloy extruded product is required to exhibit creep strength. Since Mn and Si (solute elements) are redissolved in the matrix after joining by brazing, these elements hinder the motion of dislocation in the matrix to improve the creep strength of the aluminum alloy extruded product.
  • the aluminum alloy extruded product according to the present invention is manufactured by melting an aluminum alloy having the above composition, casting the aluminum alloy by semicontinuous casting or the like to obtain an ingot (billet), and homogenizing and hot-extruding the ingot.
  • a structure in which the above intermetallic compounds are dispersed is obtained by specifying the homogenization conditions, whereby adhesion of a deposit to the surface of the aluminum alloy extruded product is reduced, and the strength of the aluminum alloy extruded product is improved after heating for brazing.
  • an improved hot extrudability is obtained by combining specific homogenization conditions and hot extrusion conditions.
  • homogenization which includes a first-stage heat treatment in which the billet is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the billet is cooled to 400 to 500° C. at an average temperature decrease rate of 20 to 60° C./h and maintained at that temperature for three hours or more.
  • homogenization may be performed which includes a first-stage heat treatment in which the billet is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the billet is cooled to room temperature, heated to 400 to 500° C. at an average temperature increase rate of 20 to 60° C./h, and maintained at that temperature for three hours or more.
  • Coarse crystals formed during casting/solidification are decomposed, granulated, or redissolved during the first-stage heat treatment in which the billet is maintained at 550 to 650° C. for two hours or more. If the temperature is less than 550° C., the above reaction proceeds to only a small extent. The rate of reaction increases as the homogenization temperature becomes higher. On the other hand, local melting occurs when the homogenization temperature is too high. Therefore, the upper limit is preferably set at 650° C.
  • the temperature range of the first-stage heat treatment is still more preferably 580 to 620° C. The reaction proceeds to a larger extent as the treatment time increases. Therefore, it is preferable to set the treatment time at 10 hours or more. On the other hand, a further effect cannot obtained even if the treatment is performed for more than 24 hours. This is disadvantageous from the viewpoint of cost. Therefore, the treatment time is preferably 10 to 24 hours.
  • the first-stage heat treatment performed at a high temperature is effective for decomposing, granulating, or redissolving coarse crystals formed during casting/solidification.
  • the first-stage heat treatment promotes dissolution of Mn and Si (solute elements) in the matrix. If the solid solubility of these solute elements in the matrix is high, the moving speed of dislocation in the matrix decreases, whereby the deformation resistance of the aluminum alloy increases. Therefore, the extrudability of the aluminum alloy decreases when the aluminum alloy is hot-extruded after homogenization including only the first-stage heat treatment.
  • the second-stage heat treatment is performed after the first-stage heat treatment at a temperature lower than that of the first-stage heat treatment to precipitate Mn and Si dissolved in the matrix, whereby the solid solubility of Mn and Si is decreased. This reduces the deformation resistance of the aluminum alloy, whereby the extrudability of the aluminum alloy is improved.
  • the second-stage heat treatment is preferably performed at 400 to 500° C. for three hours or more. If the temperature is less than 400° C., only a small amount of Al—Mn—Si intermetallic compounds precipitate, whereby the effect of decreasing the deformation resistance becomes insufficient. If the temperature exceeds 500° C., the intermetallic compounds precipitate to only a small extent, whereby the effect of decreasing the deformation resistance becomes insufficient. If the treatment time is less than three hours, since precipitation does not sufficiently proceed, the effect of deceasing the deformation resistance becomes insufficient. The reaction proceeds to a larger extent as the treatment time increases. On the other hand, a further effect cannot be obtained even if the treatment is performed for more than 24 hours. This is disadvantageous from the viewpoint of cost. The treatment time is still more preferably 5 to 15 hours.
  • the temperature decrease rate from the first-stage heat treatment temperature to the second-stage heat treatment temperature (the temperature increase rate from room temperature to the second-stage heat treatment temperature when the billet is cooled to room temperature after the stage heat treatment) in order to precipitate Mn and Si dissolved in the matrix to decrease the solid solubility of Mn and Si and to achieve the above dispersion state of the intermetallic compounds.
  • the average temperature decrease rate from the first-stage heat treatment temperature to the second-stage heat treatment temperature is preferably 20 to 60° C./h.
  • the average temperature decrease rate is less than 20° C./h, intermetallic compounds are grown to a large extent due to the progress of precipitation, whereby it is difficult to obtain a structure in which intermetallic compounds with a diameter of 0.1 to 0.9 ⁇ m are dispersed in a number of 2 ⁇ 10 5 or more per square millimeter. Moreover, it is not economical because the treatment requires time. If the average temperature decrease rate exceeds 60° C./h, the temperature distribution of the billet becomes nonuniform, whereby precipitation tends to become nonuniform. It is also preferable that the average temperature increase rate to the first-stage heat treatment temperature and the average temperature decrease rate from the second-stage heat treatment temperature to 300° C. be 20 to 60° C./h.
  • the average temperature increase rate is preferably 20 to 60° C./h. If the average temperature increase rate is less than 20° C./h, since precipitated intermetallic compounds are grown to a large extent, the number of intermetallic compounds is decreased, whereby the above intermetallic compound dispersion structure may not be obtained. Moreover, it is not economical because heating requires time. If the average temperature increase rate exceeds 60° C./h, it is difficult to obtain the above intermetallic compound dispersion structure since precipitation does not proceed. It is also preferable that the average temperature decrease rate from the second-stage heat treatment temperature to 300° C. be 20 to 60° C./h.
  • the solid solubility of the solute elements in the matrix is decreased by homogenizing the billet by combining the above specific high-temperature heat treatment and low-temperature heat treatment. This reduces the deformation resistance of the aluminum alloy during the subsequent hot extrusion, whereby the extrudability of the aluminum alloy can be improved.
  • the heating temperature of the billet before hot extrusion is preferably 480 to 560° C. If the heating temperature exceeds 560° C., the precipitate mainly containing Al—Mn—Si intermetallic compounds formed during homogenization is redissolved to increase the solid solubility in the matrix. This results in an increase in deformation resistance during hot extrusion, whereby the extrudability of the aluminum alloy is decreased.
  • the heating temperature is less than 480° C., deformation resistance is increased due to too low a temperate, whereby the extrudability of the aluminum alloy is decreased.
  • the heating temperature is still more preferably 480 to 530° C.
  • the holding time at the above heating temperature is preferably 30 minutes or less. If the holding time exceeds 30 minutes, the intermetallic compounds precipitated during homogenization are redissolved to increase the solid solubility in the matrix. This results in an increase in deformation resistance during hot extrusion, whereby the extrudability of the aluminum alloy is decreased.
  • the holding time is still more preferably 10 minutes or less.
  • the aluminum alloy extruded product according to the present invention has been described above taking a tube as an example.
  • the extrusion shape is not particularly limited.
  • the extrusion shape is appropriately selected depending on the application such as the form of the heat exchanger.
  • Multi-port tubes of various shapes may be extruded using a porthole die.
  • the aluminum alloy extruded product and other constituent members e.g. fin material and header material
  • An automotive heat exchanger in which the working fluid passage is formed using the above multi-port tube exhibits excellent corrosion resistance and exhibits excellent durability even under a severe corrosive environment.
  • An aluminum alloy having the composition shown in Table 1 was melted and cast by semicontinuous casting to obtain a billet.
  • the resulting billet was homogenized.
  • the billet was homogenized by increasing the temperature of the billet to a first-stage heat treatment temperature of 600° C. at an average temperature increase rate of 50° C./h, maintaining the billet at the first-stage heat treatment temperature for 15 hours, decreasing the temperature of the billet to a second-stage heat treatment temperature of 450° C. at an average temperature decrease rate of 50° C./h, maintaining the billet at the second-stage heat treatment temperature for 10 hours, and decreasing the temperature of the billet from the second-stage heat treatment temperature to 300° C. at an average temperature decrease rate of 50° C./h.
  • the billet was heated at 510° C. for eight minutes and hot-extruded to obtain a multi-port tube having a shape shown in FIG. 1 .
  • the resulting multi-port tube was used as a test specimen.
  • the extrudability of the aluminum alloy during hot extrusion was evaluated according to the following method. Likewise, the number of deposit portions adhering to the surface of the extruded multi-port tube was calculated, and the gloss of the multi-port tube was observed. The distribution of intermetallic compounds precipitated and dispersed in the matrix was also determined.
  • the multi-port tube was subjected to joining by brazing, and brazeability, tensile strength after heating for brazing, and intergranular corrosion susceptibility were evaluated. The results are shown in Table 2. In Tables 1 and 2, values outside the conditions according to the present invention are underlined.
  • the limiting extrusion rate (i.e. the maximum extrusion rate at which the partition wall of the hollow portion of the extruded multi-port tube (see FIG. 1 ) is completely formed) was taken as the extrudability index.
  • the limiting extrusion rate indicates the ratio of the limiting extrusion rate of the aluminum alloy to the limiting extrusion rate of a known alloy (see Table 1) (ratio when the limiting extrusion rate of the known alloy is 1.0).
  • An aluminum alloy with a limiting extrusion rate ratio of 0.9 or more was indicated as “Excellent”, an aluminum alloy with a limiting extrusion rate ratio of 0.8 or more and less than 0.9 was indicated as “Good”, an aluminum alloy with a limiting extrusion rate ratio of 0.7 or more and less than 0.8 was indicated as “Fair”, and an aluminum alloy with a limiting extrusion rate ratio of less than 0.7 was indicated as “Bad”.
  • Measurement of number of deposit portions adhering to surface and observation of gloss of surface of extruded product A portion to which foreign matter adhered was detected using an eddy current test, and the number of portions of the surface of the extruded product to which an aluminum alloy deposit adhered was determined to calculate of the number of deposit portions per unit length of the extruded product.
  • the gloss of the surface of the extruded product was evaluated by naked eye observation, and was also taken as the index of adhesion of deposit to the surface of the extruded product.
  • Measurement of tensile strength after heating for brazing The multi-port tube obtained by extrusion was heat-treated at 600° C. for three minutes in a nitrogen atmosphere as simulated heating for brazing, cooled at an average temperature decrease rate of 50 to 250° C./min, and subjected to a tensile test to determine the strength of the multi-port tube. A multi-port tube with a tensile strength of 110 MPa or more was determined to have a sufficient tensile strength.
  • a fluoride-type flux containing potassium fluoroaluminate was applied to the surface of the extruded multi-port tube in an amount of 10 g/m 2 .
  • the multi-port tube and a fin were assembled and joined by brazing by heat-treating the product at 600° C. for three minutes in a nitrogen atmosphere and cooling the product at an average temperature decrease rate of 50 to 250° C./min.
  • the joining state of the multi-port tube with the fin was then observed. A case where the multi-port tube and the fin were sufficiently joined was indicated as “Good”, and a case where the multi-port tube and the fin were not sufficiently joined was indicated as “Bad”.
  • the multi-port tube subjected to the above simulated heating for brazing was heat-treated at 150° C. for 120 hours and immersed for 24 hours in a solution prepared by adding 10 ml/l HCl to a 30 g/l NaCl aqueous solution. The cross section of the multi-port tube was then observed. A multi-port tube in which intergranular corrosion did not occur was indicated as “Good”, and a multi-port tube in which intergranular corrosion occurred was indicated as “Bad”.
  • test specimens 1 to 5 according to the present invention exhibited excellent extrudability, did not show adhesion of deposit to the surface, and exhibited excellent brazeability, intergranular corrosion resistance, and strength.
  • test specimens 6 to 9 and the test specimen 10 (known alloy) were inferior in at least one of extrudability, adhesion of deposit, strength, brazeability, and intergranular corrosion resistance.
  • An aluminum alloy having the composition A shown in Table 1 was melted and cast by semicontinuous casting to obtain a billet.
  • the resulting billet was homogenized under the conditions shown in Table 3.
  • the billet was homogenized by increasing the temperature of the billet to a first-stage heat treatment temperature at an average temperature increase rate of 50° C./h, maintaining the billet at the first-stage heat treatment temperature, decreasing the temperature of the billet to a second-stage heat treatment temperature, maintaining the billet at the second-stage heat treatment temperature, and decreasing the temperature of the billet to 300° C. at an average temperature decrease rate of 50° C./h.
  • Table 3 shows the first-stage heat treatment temperature, the average temperature decrease rate from the first-stage heat treatment temperature to the second-stage heat treatment temperature, and the second-stage heat treatment temperature.
  • the billet was hot-extruded under the conditions shown in Table 3 to obtain a multi-port tube shown in FIG. 1 .
  • the resulting multi-port tube was used as a test specimen.
  • the extrudability of the aluminum alloy during hot extrusion was evaluated in the same manner as in Example 1. Likewise, the number of deposit portions adhering to the surface of the extruded multi-port tube was calculated, and the gloss of the multi-port tube was observed. The distribution of intermetallic compounds precipitated and dispersed in the matrix was also determined.
  • the multi-port tube was subjected to joining by brazing, and brazeability, tensile strength after heating for brazing, and intergranular corrosion susceptibility were evaluated. The results are shown in Table 4. In Tables 3 and 4, values outside the conditions according to the present invention are underlined.
  • test specimens 11 to 15 homogenized under the conditions outside the conditions according to the present invention were inferior in at least one of extrudability, number of deposit portions, strength, brazeability, and intergranular corrosion resistance.
  • An aluminum alloy containing 0.6% of Si, 0.2% of Fe, and 1.0% of Mn (Mn %/Si %: 1.7) was melted and cast by semicontinuous casting to obtain a billet.
  • the resulting billet was homogenized under the conditions shown in Table 5.
  • the billet was homogenized by increasing the temperature of the billet to a first-stage heat treatment temperature at an average temperature increase rate of 50° C./h, maintaining the billet at the first-stage heat treatment temperature, decreasing the temperature of the billet to room temperature, increasing the temperature of the billet to a second-stage heat treatment temperature, maintaining the billet at the second-stage heat treatment temperature, and decreasing the temperature of the billet to 300° C. at an average temperature decrease rate of 50° C./h.
  • Table 5 shows the first-stage heat treatment temperature, the second-stage heat treatment temperature, and the average temperature increase rate from room temperature to the second-stage heat treatment temperature.
  • the extrudability of the aluminum alloy during hot extrusion was evaluated in the same manner as in Example 1. Likewise, the number of deposit portions adhering to the surface of the extruded multi-port tube was calculated, and the gloss of the multi-port tube was observed. The distribution of intermetallic compounds precipitated and dispersed in the matrix was also determined.
  • the multi-port tube was subjected to joining by brazing, and brazeability, tensile strength after heating for brazing, and intergranular corrosion susceptibility were evaluated. The results are shown in Table 6. In Tables 5 and 6, values outside the conditions according to the present invention are underlined.
  • test specimen 16 according to the present invention exhibited excellent extrudability, did not show adhesion of deposit to the surface, and exhibited excellent brazeability, intergranular corrosion resistance, and strength.
  • test specimens 17 to 21 were inferior in at least one of extrudability, adhesion of deposit, strength, brazeability, and intergranular corrosion resistance.

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US11/489,941 2005-07-22 2006-07-20 Aluminum alloy extruded product exhibiting excellent surface properties, method of manufacturing the same, heat exchanger multi-port tube, and method of manufacturing heat exchanger including the multi-port tube Abandoned US20070017605A1 (en)

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EP2330226A1 (en) 2009-12-03 2011-06-08 Rio Tinto Alcan International Limited High strenght aluminium alloy extrusion
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EP2514555A1 (en) 2011-04-21 2012-10-24 Aleris Aluminum Koblenz GmbH Extruded aluminium alloy tube product
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US20150060035A1 (en) * 2012-03-27 2015-03-05 Mitsubishi Aluminum Co., Ltd. Heat transfer tube and method for producing same
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