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
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/10—Alloys based on aluminium with zinc as the next major constituent

Definitions

• the invention relates to a high corrosion resistant aluminum alloy, especially an alloy intended to be used for manufacture of automotive air conditioning tubes for applications as heat exchanger tubing or refrigerant carrying tube lines, or generally fluid carrying tube tines.
• the alloy has extensively improved resistance to pitting corrosion and enhanced properties in bending and endforming.
• aluminium alloy materials for automotive heat exchange components are now widespread, applications including both engine cooling and air conditioning systems.
• the aluminium components include the condenser, the evaporator and the refrigerant routing lines or fluid carrying lines. In service these components may be subjected to conditions that include mechanical loading, vibration, stone impingement and road chemicals (e.g. salt water environments during winter driving conditions).
• Aluminium alloys of the AA3000 series type have found extensive use for these applications due to their combination of relatively high strength, light weight, corrosion resistance and extrudability. To meet rising consumer expectations for durability, car producers have targeted a ten-year service life for engine coolant and air conditioning heat exchanger systems.
• the AA3000 series alloys (like AA3102, AA3003 and AA3103), however, suffers from extensive pitting corrosion when subjected to corrosive environments, leading to failure of the automotive component. To be able to meet the rising targets/requirements for longer life on the automotive systems new alloys have been developed with significantly better corrosion resistance. Especially for condenser tubing, ‘long life’ alloy alternatives have recently been developed, such as those disclosed in U.S. Pat. Nos. 5,286,316 and WO97/46726. The alloys disclosed in these patents are generally alternatives to the standard AA3102 or AA1100 alloys for condenser tube uses, i.e. extruded tube material of relatively low mechanical strength.
• the corrosion focus have shifted towards the next area to fail, the manifold and the refrigerant carrying tube lines.
• the fluid carrying tube lines are usually fabricated by means of extrusion and final precision drawing in several steps to the final dimension, and the dominating alloys for this application are AA3003 or AA3103 with a higher strength and stiffness compared with the AA3102 alloy.
• the new requirements have therefore created a demand for an aluminium alloy with processing flexibility and mechanical strength similar or better than the AA3003/AA3103 alloys, but with significantly improved corrosion resistance.
• the object of this invention is to provide an extrudable, drawable and brazeable aluminium alloy that has improved corrosion resistance and is suitable for use in thin wall fluid carrying tube lines. It is a further object of the present invention to provide an aluminium alloy suitable for use in heat exchanger tubing or extrusions. It is another object of the present invention to provide an aluminium alloy suitable for use as finstock for heat exchangers or in foil packaging applications, subjected to corrosion, for instance salt water. A still further object of the present invention is to provide an aluminium alloy with improved formability (including grain size) during bending and end-forming operations.
• an aluminium-based alloy comprising 0.06-0.35% by weight of iron, 0.05-0.15% by weight of silicon, 0.01-1.0% by weight of manganese, 0.02-0.60% by weight of magnesium, 0.05-0.70% by weight of Zn, one or more of the elements zirconium, titanium, chromium or copper, up to a maximum of 1.30% by weight, up to 0.15% by weight of other impurities, each no greater than 0.03% by weight and the balance aluminium.
• the iron content of the alloy according to the invention is between 0.10-0.20% by weight.
• the corrosion resistance is increased due to smaller amounts of iron rich particles which generally creates sites for pitting corrosion attack.
• the relatively low iron content however, has a negative influence on the final grain size (due to less iron rich particles acting as nucleation sites for recrystallization).
• the manganese content is between 0.50-70% by weight, in order to counterbalance the increase in extrusion pressure obtained when adding magnesium, and reducing the negative effect of manganese with respect to precipitation of Mn bearing phases during final annealing.
• the level of this element should be kept low to make the alloy more recyclable and save cost in the cast house. Otherwise, zinc has a strong positive effect on the corrosion resistance up to at least 0.70% by weight, but for the reasons given above the amount of zinc is preferably between 0.10-0.30% by weight.
• the zirconium content is preferably between 0.10-0.18% in weight. In this range the extrudability of the alloy is practically not influenced by any change in the amount of zirconium.
• the copper content of the alloy should be kept as low as possible, preferably below 0.01% by weight, due to the strong negative effect on corrosion resistance and also due to the substantial influence on extrudability even for small additions.
• composition of the billets were determined by means of electron spectroscopy.
• a Baird Vacuum Instrument was used, and the test standards as supplied by Pechiney, were used.
• Extrusion billets were homogenised according to standard routines, using a heating rate of 100° C./hr to a holding temperature of approximately 600° C., followed by air cooling to room temperature.
• the extrudability is related to the die pressure and the maximum extrusion pressure (peak pressure). Those parameters are registered by pressure transducers mounted on the press, giving a direct read out of these values.
• Corrosion potential measurements were performed according to a modified version of the ASTM G69 standard test, using a Gamry PC4/300 equipment with a saturated calomel electrode (SCE) as a reference.
• the tube specimens were degreased in acetone prior to measurements. No filing or abrasion of the tube specimen surface was performed, and the measurements were done without any form of agitation.
• Corrosion potentials were recorded continuously over a 60 minute period and the values presented represents the average of those recorded during the final 30 minutes of the test.
• Extrusion data for the alloys are given in Table 2 below. TABLE 2 Extrusion data for long life alloy matrix (3 hole die) Peak Die Alloy Chemical composition (wt %) pressure pressure designation Fe Si Mn Mg Cr Zn Cu Ti (kN) (kN) AC1 0.24 0.08 0.67 0.29 — — — — 2573 1395 AC2 0.23 0.09 0.70 0.29 0.10 — — — 2584 1424 AC3 0.24 0.08 0.70 0.27 0.22 — — — 2597 1464 AC4 0.21 0.08 0.68 0.28 — 0.25 — — 2536 1373 AC5 0.20 0.08 0.67 0.27 0.07 0.24 — — 2559 1415 AC6 0.20 0.08 0.69 0.28 0.21 0.25 — — 2599 1470 AC7 0.20 0.09 0.68 0.29 0.22 0.11 — 0.05 2594 1495 AC8 0.21 0.10 0.69 0.27 0.18 0.23 — 0.16 2599 1508 AC9 0.25 0.13 0.67 0.05
• the electrochemical corrosion potentials of the test alloys AC1 to AC9 are generally decreased (more negative) as compared to the standard alloys AA3103/AA3003.
• the tube material In order for the tube material not to behave sacrificial towards the filler metal (for instance when connected to cladded header in a condenser) it is recommended to select clad materials that matches the electrochemical potential. This is the usual methodology applied when designing components/systems against corrosion, and this will curb any attack of the tube due to galvanic corrosion.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Extrusion Of Metal (AREA)
• Prevention Of Electric Corrosion (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Powder Metallurgy (AREA)
• Secondary Cells (AREA)
• Dowels (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Cookers (AREA)
• Laminated Bodies (AREA)
• Conductive Materials (AREA)
• Catalysts (AREA)

Priority Applications (14)

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Cited By (15)

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• 1999
  • 1999-04-13 US US09/291,255 patent/US20020007881A1/en not_active Abandoned
• 2000
  • 2000-02-21 WO PCT/EP2000/001518 patent/WO2000050656A1/en active IP Right Grant
  • 2000-02-21 CA CA002356486A patent/CA2356486C/en not_active Expired - Fee Related
  • 2000-02-21 ES ES00907618T patent/ES2198289T3/es not_active Expired - Lifetime
  • 2000-02-21 JP JP2000601218A patent/JP2002538296A/ja not_active Withdrawn
  • 2000-02-21 CN CNB008040311A patent/CN1159468C/zh not_active Expired - Lifetime
  • 2000-02-21 EA EA200100904A patent/EA003950B1/ru not_active IP Right Cessation
  • 2000-02-21 AU AU29144/00A patent/AU2914400A/en not_active Abandoned
  • 2000-02-21 KR KR1020017009079A patent/KR100650004B1/ko not_active IP Right Cessation
  • 2000-02-21 BR BRPI0008407-7A patent/BR0008407B1/pt not_active IP Right Cessation
  • 2000-02-21 AT AT00907618T patent/ATE241709T1/de not_active IP Right Cessation
  • 2000-02-21 DE DE60002990T patent/DE60002990T2/de not_active Expired - Lifetime
  • 2000-02-21 EP EP00907618A patent/EP1155157B1/en not_active Expired - Lifetime

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