Metal treatment – Process of modifying or maintaining internal physical... – With casting or solidifying from melt
Reexamination Certificate
2000-01-21
2001-05-29
Wyszomierski, George (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
With casting or solidifying from melt
C148S693000, C148S437000
Reexamination Certificate
active
06238497
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates to an improved aluminum alloy product for use in making heat exchanger fins and, more particularly, to a fin stock material having high thermal conductivity.
II. Background Art
Aluminum alloys have long been used in the production of heat exchanger fins, e.g. for automotive radiators, condensers, evaporators etc. Traditional heat exchanger fin alloys are designed to give a high strength (UTS) after brazing, a good brazeability (high brazing temperature) and a good sag resistance during brazing. Alloys used for this purpose usually contain a high level of manganese. An example is the aluminum alloy AA3003. The thermal conductivity of such alloys is relatively low. Low thermal conductivity has not been a serious problem in the past because of the significant thickness of the finstock material. If the material is of suitable thickness it can conduct a significant quantity of heat, even if the coefficient of thermal conductivity of the alloy is low. However, in order to make vehicles lighter in weight, there is a demand for thinner finstock material, and this has emphasised the need for improved thermal conductivity. Obviously, thinner gauges tend to impede heat flux as they become thinner.
In addition, fin material properties demanded by the automotive heat exchanger industry require a low (more negative) corrosion potential than the alloys used in the tubes and other parts of the heat exchanger.
The inventors of the present invention have previously found that specific aluminum alloys are particularly suitable for use in finstock material (as disclosed in Applicants' prior unpublished U.S. patent application Ser. No. 09/121,638 filed Jul. 23, 1998, which is assigned to the same assignee as the present application, and which is incorporated herein by reference). These alloys contain Fe, Si, Mn, usually Zn and optionally Ti in particular content ranges. However, an improvement in the thermal conductivity of alloys of this kind would make these alloys even more useful in meeting the stringent demands of the automotive industry, particularly for finstock of thinner gauge.
SUMMARY OF THE INVENTION
It is an object of the invention to improve the property is of aluminum finstock material.
Another object of the present invention to produce a new aluminum alloy fin stock that has a high thermal conductivity.
Another object of the invention is to make it possible to reduce the gauge of aluminum finstock material without compromising the performance of those materials.
Another object of the invention is to improve the thermal conductivity of aluminum finstock alloys containing Fe, Si, Mn, Zn and optionally Ti whilst achieving good strength, brazeability and low (more negative) corrosion potentials.
According to one aspect of the invention, there is provided a method of producing an aluminum alloy fin stock alloy material, comprising the steps of continuously strip casting the alloy to form a cast strip, rolling the strip to form a sheet article of intermediate gauge, annealing the sheet article of intermediate gauge, and cold rolling the sheet article of intermediate gauge to form an aluminum finstock alloy material of final gauge, wherein said steps are carried out on an alloy which comprises the following elements in weight percent:
Fe
1.6 to 2.4
Si
0.7 to 1.1
Mn
0.3 to 0.6
Zn
0.3 to 2.0
Ti (optional)
0.005 to 0.040
Incidental elements
less than 0.05 each, total no more than 0.15
Al
balance.
The invention also relates to an aluminum alloy finstock material produced by the above method, particularly finstock material having a thickness of 100 &mgr;m or less, preferably 80 &mgr;m or less, and ideally 60 ±10 &mgr;m.
The present invention produces a novel fin stock material that is suitable for manufacturing brazed heat exchangers using thinner fins that previously possible. This is achieved while retaining adequate thermal conductivity and strength in the fins to permit their use in heat exchangers.
The alloys incorporate higher amounts of Zn, Si and/or Mn than would normally be employed for alloys of this kind and yet thermal conductivity levels can be maintained by employing compensating elevated amounts of iron.
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Anami Toshiya
Gallerneault Willard Mark Truman
Gatenby Kevin
Jin Iljoon
Okamoto Ichiro
Alcan International Limited
Combs-Morillo Janelle
Cooper & Dunham LLP
Wyszomierski George
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