Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • 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
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • 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
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions

Definitions

• the present invention relates to an aluminum piping material excellent in corrosion resistance suitable for piping of heat exchangers, such as automobile air-conditioners, oil coolers, radiators, and heaters.
• JIS 1000-series alloys JIS 3000-series alloys, JIS 6000-series alloys, or the like
• JIS 1000-series alloys JIS 3000-series alloys
• JIS 6000-series alloys or the like
• known as a JIS 6000-series alloy is an aluminum alloy excellent in intergranular corrosion resistance and pitting corrosion resistance, which comprises 0.35 to 1.5 mass% (hereafter simply referred to as %) of Mg, 0.2 to 0.8% of Si, and 0.1 to 0.3% of Zn, further comprises 0.02 to 0.1% of Sn, and 0.15 to 0.4% of Cu (e.g. see JP-B-61-36577 ("JP-B" means examined Japanese patent publication)).
• a method for producing a tube material for a heat exchanger excellent in tube formability which comprises 0.5 to 2.0% of Mn, 0.25 to 0.75% of Cu, and further comprises one or more elements of 0.05 to 0.2% of Mg, 0.05 to 1.0% of Si, 0.5 to 1.2% of Fe, 0.05 to 0.2% of Ti, 0.05 to 0.2% of Zr, 0.05 to 0.15% of Cr, and 0.05 to 0.15% of V (e.g. JP-A-2001-26850 ("JP-A" means unexamined published Japanese patent application)).
• this material has a sheet shape, and is a type that is to be subjected to electric resistance welding (ERW or seam welding) or the like for formation of a pipe.
• the document US-A-3 938 991 discloses an aluminium base alloy possessing a fine recrystallized grain size in the annealed condition which consists of in weight %: 0.03 - 0.6% silicon, 0.03 - 0.7% iron, 0.03 - 1.5% manganese, 0.03 - 0.20% vanadium, up to 0.3% copper, up to 0.2% titanium, balance aluminium.
• an aluminum brazing sheet to be used as a tube material there is a proposal of a material, in which an Al-Si-based alloy filler alloy is clad on one side of a core alloy, and in which a sacrificial anode alloy, such as an Al-Zn-based alloy or an AI-Zn-Mg-based alloy, is clad on the other side (e.g. JP-A-06-073480 ).
• a sacrificial anode alloy such as an Al-Zn-based alloy or an AI-Zn-Mg-based alloy
• JIS 3003-series alloys excellent in mechanical strength, workability, weldability, and corrosion resistance are heretofore used for automobile piping materials, but the corrosion resistance is insufficient under severe conditions.
• perforation corrosion may occur when the alloy is used in an automobile engine room of harsh environment, or when used at high-temperature and high-humidity environments, such as in Southeast Asia.
• the refrigerant (cooling water) in the piping will leak, resulting in that the cooling function is lost in the case of the piping in an air conditioner or that an engine is burned in the case of the piping in a radiator.
• the present invention resides in an aluminum piping material for an automobile heat exchanger as defined in claim 1, which comprises 0.05 to 0.2 mass% of Si, 0.05 to 0.2 mass% of Fe, 0.05 mass% or lower of Cu, 0.15 to 1.5 mass% of Mn, 0.05 to 0.3 mass% of Ti, and 0.05 to 0.3 mass% of V, with the balance being Al and inevitable impurities, wherein the aluminum piping material is excellent in corrosion resistance.
• the present invention resides in an aluminum piping material for an automobile heat exchanger, which is produced by: subjecting an aluminum alloy ingot having any one of the above-mentioned compositions to hot extrusion, to form a raw pipe for extrusion; and subjecting the resultant raw pipe to drawbench drawing or continuous drawing, to form said aluminum piping material, wherein the aluminum piping material is excellent in corrosion resistance.
• the inventors of the present invention having conducted intensive study to solve the above-mentioned problems in the conventional technique, found that corrosion resistance is remarkably improved by adding both of Ti and V to an Al-Mn-based alloy.
• the present invention has been attained based on this finding.
• Si is an essential alloying element
• the Si content is 0.05 to 0.2 mass% (hereinafter simply referred to as %).
• Si has an effect of enhancing the mechanical strength after brazing, by forming a solid solution in a matrix of the aluminum alloy structure and/or by forming an Al-Mn-Si-series compound, and thus Si is an essential alloying element.
• the Si content needs to be 0.05% or more. When the content exceeds the upper limit, corrosion resistance and extrusion property (the life of a dice to be used) will be lowered. Thus, the Si content is set to 0.05 to 0.2%.
• Fe is an essential alloying element, and the Fe content is 0.05 to 0.2%.
• Fe has an effect of enhancing the mechanical strength, by being crystallized or precipitated as an Al-Fe-series intermetallic compound. To achieve this effect, the Fe content needs to be 0.05% or more. However, when Fe is excessively contained, the excessive Fe or compound therefrom is crystallized on the surface, to increase a corrosion speed. Thus, the Fe content is set to 0.05 to 0.2%.
• the Cu content is 0.05 or lower, and Cu is an optional element that may not be added (i.e. the Cu content may be 0%) or may be added, if required.
• Cu has an effect of enhancing the mechanical strength, by forming a solid solution.
• the Cu content is set to 0.05% or lower.
• the Mn content is 0.15 to 1.5%, and Mn is an essential alloying element in the present invention. Mn is added in an amount of 0.15 to 1.5% so as to enhance the mechanical strength. When the Mn content is 0.15% or lower, the effect is not sufficiently exhibited, and when the Mn content exceeds 1.5%, extrusion property and drawing workability are lowered.
• the Mn content is more preferably 0.8 to 1.2%.
• Ti and V contents is 0.05 to 0.3%, and Ti and V are essential alloying elements in the present invention.
• Ti and V have an effect of further improving the corrosion resistance. More specifically, Ti and V each are separated into a high concentration region and a low concentration region, to alternately disperse those regions in the direction of the sheet thickness to form layers. Then, the region having low Ti and V concentrations preferentially corrodes as compared with the region having high Ti and V concentrations, to form a layered corrosion state. This prevents corrosion from progressing in the thickness direction, to thereby improve the resistance to pitting corrosion. By adding both of Ti and V, this effect is exhibited more notably.
• Ti and V can also contribute to enhancement of the mechanical strength, and further higher effects can be obtained by adding a combination of Ti and V.
• Ti and V each need to be contained in an amount of 0.05% or more. When each content exceeds 0.3% (upper limit), a giant or coarse intermetallic compound is generated at the time of casting, which may adversely affect the extrusion property and/or drawing workability.
• the Ti and V contents each are more preferably 0.1 to 0.2%.
• the aluminum alloy piping materials of the present invention for automobile heat exchangers can be produced, by processing the aluminum alloy having the aforementioned composition, according to the following procedure.
• the aluminum alloy for use in the present invention can be produced by melting (to give an ingot) in a usual manner in which the target is set to have the above-mentioned alloying elements, and there is no particular limitation on the production method for the aluminum alloy.
• a raw pipe for extrusion is produced using the thus-obtained alloy, it is preferable to subject the aluminum alloy (ingot) to homogenization.
• the homogenization is conducted, by maintaining the aluminum alloy under the conditions in a usual manner of, for example, at 550 to 620°C, preferably 590 to 620°C, for 1 to 10 hours, preferably 2 to 4 hours, in a process of precipitating dispersed particles composed of Si, Mn, or the like, into a matrix uniformly with a high density. Then, the resultant alloy is heated to 450 to 550°C at least before extrusion, and subjected to soaking, followed by hot extrusion. There is no particular limitation on heating methods, heating furnaces, etc., for use in the above-mentioned homogenization and soaking processes.
• the thus-obtained raw pipe for extrusion is then drawn by drawbench drawing or continuous drawing, followed by working to a product size. Then, the resultant is annealed, for example, by maintaining it at 300 to 520°C for 1 to 10 hours, to give a final product.
• the above-mentioned extruded materials are to be used as heat exchanger materials, and may be usually used for piping materials for circulating a heating medium and/or piping materials for circulating water in a radiator, a heater core, or the like. Further, the heat exchangers may be used at any places or sites, without particular limitation.
• an aluminum alloy material whose corrosion resistance is higher than that of JIS 3003 alloy in a single layered form, without cladding, and can be provided an excellent aluminum piping material for an automobile heat exchanger.
• heat exchanger piping materials having excellent corrosion resistance can be obtained, even if the aluminum alloy piping materials for automobile heat exchangers are not clad materials but single-layer bear materials. Furthermore, according to the present invention, it is possible to eliminate the necessity of forming pipes from a sheet material with electric resistance welding or the like; to provide aluminum alloy piping materials capable of being worked by simple extrusion and drawing; and to reduce the production cost of the resultant heat exchangers. Thus, the present invention exhibits industrially remarkable effects.
• the conventional example No. 1 is JIS 3003 alloy.
• the Ti, V, and Mn alloying elements of the samples of Comparative examples 1 and 2 each were outside the range defined in the present invention, and it was impossible to subject those samples for comparison to extrusion and/or drawing, and no product was obtained.
• the Ti and V contents of the sample of Comparative example 3 were less than the range defined in the present invention, and the corrosion resistance of the sample for comparison was not improved and was inferior to that of the conventional example.
• the Cu and Fe contents of the samples of Comparative examples 4 and 5 each exceeded the range defined in the present invention, and the corrosion resistance of the samples for comparison was inferior to that of the conventional example.
• the Si content of the sample of Comparative example 6 exceeded the range defined in the present invention, and the corrosion resistance of the sample for comparison was inferior to that of the conventional example and the extrusion property was poor.
• each sample was subjected to a CASS test, according to JIS H8601, for 1,500 hours. After the test, surface corrosion products of each sample were removed, and the corrosion state of each sample was evaluated. Evaluation was made, by measuring the maximum pitting corrosion depth by a method using depth of focus with an optical microscope. The results are shown in Table 2.
• the Ti, V, and Mn alloying elements of the samples of Comparative examples 1 and 2 each were outside the range defined in the present invention, and it was impossible to subject those samples for comparison to extrusion and/or drawing, and no product was obtained.
• the Ti and V contents of the sample of Comparative example 3 were less than the range defined in the present invention, and the corrosion resistance of the sample for comparison was not improved and was inferior to that of the conventional example.
• the Cu and Fe contents of the samples of Comparative examples 4 and 5 each exceeded the range defined in the present invention, and the corrosion resistance of the samples for comparison was inferior to that of the conventional example.
• the Si content of the sample of Comparative example 6 exceeded the range defined in the present invention, and the corrosion resistance of the sample for comparison was inferior to that of the conventional example and the extrusion property was poor.
• the examples according to the present invention were extremely excellent in the corrosion resistance outside the piping, as compared with that of the comparative examples and conventional example. Further, it is also found that the tensile strength of each example according to the present invention was at least substantially equivalent to or much higher than that of the conventional example.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Extrusion Of Metal (AREA)

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• 2006
  • 2006-08-24 JP JP2006228383A patent/JP5049536B2/ja not_active Expired - Fee Related
• 2007
  • 2007-08-22 US US11/843,280 patent/US20080050269A1/en not_active Abandoned
  • 2007-08-23 DE DE602007010872T patent/DE602007010872D1/de active Active
  • 2007-08-23 EP EP07016585A patent/EP1892308B1/en not_active Expired - Fee Related

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