Classifications

• • 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
• • 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
  • C22C21/003—Alloys based on aluminium containing at least 2.6% of one or more of the elements: tin, lead, antimony, bismuth, cadmium, and titanium
• • 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 an aluminium alloy for making fin stock material.
• Fin stock material is used in heat exchanger devices.
• the fin stock material is used for making for instance corrugated fins, by which the heat from the heat exchanger must be removed.
• the invention relates to fin stock material made from the aluminium alloy according to the invention, and to a brazed heat exchanger having fins made of this alloy.
• aluminium alloys are used for fins in heat exchanger applications because of their desirable combination of strength, low weight, good thermal conductivity, brazeability, corrosion resistance and formability.
• Heat exchangers from aluminium can be fabricated by stacking aluminium alloy sheets, which have been formed to a desired configuration, so as to form fluid passageways or tubes, and by securing aluminium alloy fins between the fluid passageways by brazing.
• the aluminium alloy sheets used to make the fluid passageways and/or the aluminium alloy used for the fins are provided with a low melting clad layer.
• the bonding between the alloy clad sheets and the fins is achieved by melting the cladding or filler material of the sheets and/or fin material.
• a brazing method typically vacuum brazing or controlled atmosphere brazing is used.
• fin materials are used which are electrochemically anodic (less noble) relative to the fluid passageways material, so that this fin material has a sacrificial anode effect.
• an aluminium alloy for making fin material is given in International patent application no. WO 01/36697.
• This alloy has the following composition, in weight percent: Si 0.7 - 1.2 Mn 0.7 - 1.2 Mg up to 0.35 Fe up to 0.8 Zn up to 3.0 Ni up to 1.5 Cu up to 0.5 Ti up to 0.20 In up to 0.20 Zr up to 0.25 V up to 0.25 Cr up to 0.25 others up to 0.05 each, and up to 0.15 in total. Al balance.
• This disclosed alloy is said to have an improved post-braze 0.2% yield strength over conventional alloys for the same application.
• an aluminium alloy for making fin stock material having the composition in weight percent: Si ⁇ 1.2 Mn ⁇ .010 Mg ⁇ 0.15 Fe ⁇ 2.0 0.05 ⁇ Ni ⁇ 2.0 0.05 ⁇ Cu ⁇ 1.0 0.5 ⁇ Zn ⁇ 4.0 and/or 0.1 ⁇ Sn ⁇ 2.0 and/or 0.01 ⁇ In ⁇ 0.5 ⁇ Ti and/or V and/or Cr and/or Zr ⁇ ⁇ 0.40 other elements up to 0.05 each, up to 0.15 in total Al balance.
• This aluminium alloy has a very good thermal conductivity, thereby improving the heat exchange properties of the fins made from this aluminium alloy . Moreover, this aluminium alloy has a satisfactory mechanical properties in the post-brazed condition, such as tensile strength and corrosion potential.
• this aluminium alloy is primarily intended as fin stock material for heat exchangers, it may be used for other parts of heat exchange units, such as tube plate, or other uses.
• the heat exchanger market requires a balance of properties for fin stock alloys, which includes strength, conductivity, formability, brazeability and corrosion potential. If one of these properties should be improved where the other properties must remain as good as they are, often many of the alloying elements in the composition must be changed in relation to each other.
• Si is an important alloying element in the alloy according to the invention; it is expected that Si improves the strength of the alloy by solid solution hardening and precipitation hardening. Because the solid solution in the alloy should be as low as possible for the required conductivity, the amount of Si should not be higher than 1.2 %. When the amount of Si is higher, too much Si will remain in solid solution, resulting in a lower conductivity. A more preferred range for Si is 0.4 to 0.8 %. Within this range the required combination of strength and conductivity is reached best.
• Mn is an important alloying element in conventional alloys for making fin stock material. Mn is normally added for strength. In the alloy according to this invention, the Mn content is kept very low so as to reduce the amount of solid solution in the alloy. Preferably Mn ⁇ 0.05 %, and more preferably Mn ⁇ 0.01 %, thereby improving the conductivity as much as possible.
• Mg increases the strength of the alloy significantly, but has a detrimental effect on controlled atmosphere brazeability because it tends to interact with the flux material. For this reason the Mg content has a maximum of 0.15 %, and preferably Mg ⁇ 0.05 %, and more preferably Mg ⁇ 0.01%, to keep the Mg content as low as possible.
• Fe is an alloying element that is present in all known aluminium alloys. Fe is added for post-braze strength and sag resistance. It is supposed to form precipitates with Al, Ni and Si. The solid solubility of Fe in Al is extremely low, therefore Fe can be used to improve the strength without compromising the conductivity.
• Fe is in the range of 0.3 % to 1.6 %, and more preferably in the range of 0.7 % to 1.3 %, so as to reach a preferred strength without compromising the formability.
• Ni is also present to improve the post-braze strength of the alloy. Like Fe, the solid solubility of Ni in Al is extremely low, therefore Ni can be used to improve the strength without compromising the conductivity. However, when the Ni content is > 2 %, the formability becomes too low. Ni is preferably present in the range of 0.5 to 1.5 %, and more preferably in the range of 0.8 to 1.2 % because in these ranges the best combination of strength and formability is found.
• Cu is present in the alloy according to the invention to improve the post-braze strength of the alloy.
• the amount of Cu is preferably restricted to the range of 0.1 % to 0.8 %, and more preferably to the range of 0.1 % to 0.6 %, so as to reach the required strength.
• Cu is believed to increase the corrosion potential of the alloy, whereas the corrosion potential should be low to allow the fin material to act as a sacrificial anode. For this reason, at least one of the elements Zn, Sn or In should be present.
• Zn, Sn or In, or a combination of these three elements are present to counteract the effect of Cu on the corrosion potential of the alloy.
• the amount of these elements must therefore be higher than zero, taking into account the stronger effect of Sn and especially In as compared to Zn.
• the amounts of Zn, Sn and In should not be higher than necessary and therefor preferably Zn is in the range of 1.0 % to 3.0 % and/or Sn is in the range of 0.1 % to 1.0 % and/or In is in the range of 0.01 % to 0.05 %.
• Zn can be (partly) replaced by Sn and/or In.
• Ti, V, Cr and Zr are to be avoided as much as possible, because they have a negative effect on the conductivity of the alloy.
• these elements are below 0.01 % each.
• fin stock material made from the aluminium alloy as specified above, wherein the fin stock material has a post-braze conductivity of at least 26 MS/m (45 % IACS), and preferably at least 29 MS/m (50 % IACS). A conductivity of more than 45 % IACS is good and a conductivity of more than 50 % IACS is very good in comparison to conventional fin stock material for heat exchangers.
• the fin stock material has a corrosion potential between -750 mV and -950 mV versus SCE (ASTM G69), more preferably between -750 mV and -850 mV according to SCE (ASTM G69).
• SCE means that the voltage in mV has been measured in relation to a saturated calomel electrode.
• the fin stock material has a post braze UTS (Ultimate Tensile Strength) between 135 and 155 MPa, and/or a 0.2%PS > 50 MPa. This strength is sufficiently high for normal use of fin stock material.
• a brazed heat exchanger having fins made of an aluminium alloy according the first aspect of the invention, or having fins made of fin stock material according to the second aspect of the invention.
• alloy conductivity [%IACS] corrosion potential [mV SCE] UTS [MPa] proof stress 0.2% [MPa] 1 49.3 -783 137 53 2 51.4 -779 143 59 3 46.0 -786 149 57 4 43.2 -778 134 54 5 42.8 -732 142 56 6 42.3 -770 156 70 7 40.5 -748 166 76 8 36.6 -805 154 67 9 43.3 -747 161 69
• the nine different chemistries as specified in table 1 were cast and sawed to pieces with a thickness of 80 mm, and thereafter preheated to a temperature below 540°C, the alloys were not homogenised. Subsequently hot rolled at a temperature below 540°C and cold rolled to a thickness of 0.15 mm. After inter annealing, the pieces were cold rolled to a thickness of 0.1 mm.
• the alloys 1 to 4 of table 1 no Ti, V, Cr or Zr are present.
• the Zn present in the alloys can be (partly) replaced by Sn and/or In, as is known in the art.
• the alloys 4 to 9 are comparative examples that do not fit in the alloy ranges according to the invention.
• the amount of Mn is too high.
• alloys 6.7 and 8 additions of Zr, Ti and V, respectively, are also present.
• the Mn level of alloys 4 and 5 is increased as compared to alloys 1, 2 and 3, the strength is not significantly increased. This is attributed to the decrease in Ni.
• Alloys 6, 7 and 8 show that with the Ni level of alloys 4 and 5 high strength can be reached when Zr, Ti or V additions are present.
• the conductivity of these alloys is comparatively low.
• the three alloys 1, 2 and 3 having a composition according to the invention clearly have a high conductivity, a sufficiently high strength and a corrosion potential within the required range to get the sacrificial anode effect.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Prevention Of Electric Corrosion (AREA)
• Laminated Bodies (AREA)
• Conductive Materials (AREA)

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• 2001
  • 2001-10-05 EP EP01203759A patent/EP1300480A1/de not_active Withdrawn
• 2002
  • 2002-10-02 JP JP2003534636A patent/JP2005504890A/ja not_active Withdrawn
  • 2002-10-02 CA CA002462074A patent/CA2462074A1/en not_active Abandoned
  • 2002-10-02 WO PCT/EP2002/011191 patent/WO2003031667A1/en not_active Ceased
  • 2002-10-02 EP EP02782840A patent/EP1436438A1/de not_active Withdrawn
  • 2002-10-02 CN CNA028215192A patent/CN1578844A/zh active Pending
  • 2002-10-02 US US10/491,494 patent/US20050019204A1/en not_active Abandoned
  • 2002-10-02 MX MXPA04003133A patent/MXPA04003133A/es not_active Application Discontinuation
  • 2002-10-02 KR KR10-2004-7004941A patent/KR20040045477A/ko not_active Ceased

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