Aluminum fin alloy and method of making the same

Abstract

The present invention relates to an aluminum alloy product for use as a finstock material within brazed heat exchangers and, more particularly, to a finstock material having high strength and conductivity after brazing. The invention is an aluminum alloy finstock comprising the following composition in weight %: TABLE-US-00001 Fe  0.8-1.25; Si  0.8-1.25; Mn 0.70-1.50; Cu 0.05-0.50; Zn up to 2.5; other elements less than or equal to 0.05 each and less than or equal to 0.15 in total; and balance aluminum.
The invention also relates to a method of making the finstock material.

Claims

1. An aluminum alloy finstock consisting of the following composition in weight %: TABLE-US-00009 Fe  0.8-1.25; Si  0.8-1.25; Mn 0.70-1.50; Cu 0.05-0.50; Zn up to 2.5; and balance aluminum, wherein the aluminum alloy finstock possesses a longitudinal UTS≧140 MPa and a conductivity≧46% IACS after brazing at 600° C., wherein a gauge of the aluminum alloy finstock is <0.07 mm.

2. The aluminum alloy finstock of claim 1, wherein the Si content is 0.9-1.1 weight %.

3. The aluminum alloy finstock of claim 1, wherein the Mn content is 0.9-1.1 weight %.

4. The aluminum alloy finstock of claim 1, wherein the Zn content is 0.25-2.5 weight %.

5. The aluminum alloy finstock of claim 4, wherein the aluminum alloy finstock possesses a conductivity>48% IACS after brazing.

6. The aluminum alloy finstock of claim 1, wherein the Fe content is 0.9-1.1 weight %.

7. The aluminum alloy finstock of claim 1, wherein the Mn content is 0.7-1 weight %.

8. The aluminum alloy finstock of claim 1, wherein the gauge of the aluminum alloy finstock is <0.06 mm.

9. The aluminum alloy finstock of claim 1, wherein the gauge of the aluminum alloy finstock is <0.055 mm.

10. The aluminum alloy finstock of claim 1, wherein an average grain size of the aluminum alloy finstock after brazing is >110 μm.

11. The aluminum alloy finstock of claim 1, wherein an average grain size of the aluminum alloy finstock after brazing is >240 μm.

12. A method of making aluminum alloy finstock comprising the following steps: a) continuously casting an aluminum alloy melt consisting of the following composition in weight %: TABLE-US-00010 Fe  0.9-1.25; Si  0.8-1.25; Mn  0.7-1.5; Cu 0.05-0.5; Zn up to 2.5; and balance aluminum; b) hot rolling the continuously cast sheet; c) interannealing the hot rolled sheet; and d) cold rolling the sheet to a foil gauge, wherein the aluminum alloy finstock possesses a longitudinal UTS≧140 MPa and a conductivity≧46% IACS after brazing at 600° C., wherein the foil gauge is <0.07 mm.

13. The method of claim 12, wherein the continuous casting step a) is a twin roll casting process.

14. The method of claim 12, wherein the foil gauge is <0.06 mm.

15. The method of claim 12, wherein the foil gauge is <0.055 mm.

16. An aluminum alloy finstock consisting of the following composition in weight %: TABLE-US-00011 Fe  0.9-1.25; Si  0.8-1.25; Mn  0.7-1.5; Cu 0.05-0.5; Zn up to 2.5; and balance aluminum, wherein the aluminum alloy finstock is produced by a method comprising casting an aluminum alloy melt comprising the composition of the aluminum alloy finstock by a continuous strip casting process, wherein a gauge of the aluminum alloy finstock is <0.07 mm, and wherein the continuous strip casting process is twin roll casting with an average cooling rate not exceeding 1500° C./sec or belt and block casting with a maximum average cooling rate of less than 250° C./sec.

17. The aluminum alloy finstock of claim 16, wherein the continuous strip casting process is the twin roll casting with the average cooling rate greater than 200° C./sec.

18. An aluminum alloy finstock comprising the following composition in weight %: TABLE-US-00012 Fe  0.8-1.25; Si  0.8-1.25; Mn  0.7-1.5; Cu 0.05-0.5; Zn up to 2.5; other elements less than or equal to 0.05 each and less than or equal to 0.15 in total; and balance aluminum, wherein the content of Fe and Si are approximately equal; and wherein the aluminum alloy finstock possesses a longitudinal UTS≧140 MPa and a conductivity≧46% IACS after brazing at 600° CU, and wherein a gauge of the aluminum alloy finstock is <0.07 mm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The following Examples are provided as further illustration of the exemplary embodiments. In the following, reference is made to the accompanying drawing, in which the FIGURE is a graph showing the effect of Fe, Si and Cu on the ultimate tensile strength (UTS) of the alloys of Example 3 after brazing.

EXAMPLE 1

(2) Alloys with compositions shown in Table 1, (all values in weight %), were twin roll cast to a gauge of 6.0 mm and then cold rolled in a number of rolling steps to a gauge of 0.78 mm. The intermediate sheet of 0.78 mm gauge was annealed is with a peak furnace temperature of 420° C. for a total cycle time of 35 hrs. After this interanneal, the sheet gauge was further reduced to finstock by cold rolling in steps down to a final gauge of 0.052 mm to provide material in an H18 temper. Four alloys were prepared.

(3) TABLE-US-00003 TABLE 1 Sample # Fe Si Mn Cu A 0.99 0.96 0.73 0.17 B 1.01 0.97 1.30 0.15 C 0.71 0.65 0.71 0.16 D 0.70 0.65 1.33 0.17

(4) In each case other elements present as impurities and trace elements were <0.05 and the balance was Al.

(5) Samples A and B are alloys according to the invention, samples C and D are alloys outside the scope of the invention.

(6) The final gauge finstock was then subject to a brazing cycle intended to simulate typical industrial controlled-atmosphere brazing conditions. The brazing cycle involved placing samples in a controlled atmosphere furnace preheated to 570° C., the temperature was then raised to 600° C. in approximately 12 minutes and held at 600° C. for 3 minutes, after which the furnace was allowed to cool to 400° C. at 50° C./min, after which point the samples were removed and allowed to cool to room temperature.

(7) Tensile properties were measured in the normal manner for material of this gauge and the conductivity after brazing was measured in accordance with JIS-N0505. The results are shown in Table 2.

(8) TABLE-US-00004 TABLE 2 UTS after brazing Electrical Conductivity Sample MPa % IACS A 143.1 48.5 B 149 46.0 C 126 47.7 D 134 43.2

(9) The alloys according to the invention, A and B, combined high post-braze strength (above 140 MPa), and high electrical conductivity (above 46% IACS).

EXAMPLE 2

(10) 2 further alloy compositions were tested that incorporated additions of Zn. The alloy compositions are shown in Table 3, (all values in weight %).

(11) TABLE-US-00005 TABLE 3 Sample # Fe Si Mn Cu Zn E 0.90 0.89 0.78 0.20 0.34 F 0.96 0.93 0.95 0.18 0.47

(12) In each case other elements present as impurities and trace elements were <0.05 and the balance was Al.

(13) Alloys according to each sample were twin roll cast to a gauge of 6.0 mm. Sample E was interannealed after hot rolling at an intermediate gauge of 0.78 mm with a peak furnace temperature of 420° C. for a total cycle time of 35 hrs and then cold rolled to a final gauge of 0.052 mm to provide material in an H18 temper.

(14) Sample F was also provided in an H18 temper but with the interanneal occurring after hot rolling at a gauge of 0.38 mm, with the same interanneal temperature and duration as sample E.

(15) The final gauge finstock was then subjected to the same brazing cycle as described in Example 1.

(16) Tensile properties were measured in the normal manner for material of this gauge and the conductivity after brazing was measured in accordance with JIS-N0505. The results are shown in Table 4.

(17) TABLE-US-00006 TABLE 4 UTS after brazing Electrical Conductivity Sample MPa % IACS E 143 49.4 F 148 49.0

(18) The addition of Zn improved the electrical conductivity but did not cause any deterioration in strength.

EXAMPLE 3

(19) The alloys described in Table 5 were cast in “book-mould” sizes, 25 mm×150 mm×200 mm. The cast ingots were pre-heated from room temperature to 525° C. over 9 hrs and allowed to soak for 5.5 hrs. They were then hot rolled to a gauge of 5.8 mm followed by cold rolling to 0.1 mm gauge.

(20) TABLE-US-00007 TABLE 5 Sample # Fe Si Mn Cu Fe + Si G 1.01 1.00 1.01 0.11 2.01 H 1.01 1.01 1.00 0.28 2.02 J 0.81 0.79 1.00 0.11 1.60 K 0.82 0.80 1.01 0.29 1.62 L 1.21 1.19 1.01 0.11 2.40 M 1.20 1.18 1.00 0.29 2.38

(21) In each case other elements present as impurities and trace elements were <0.05 and the balance was Al.

(22) They were then subjected to the same controlled-atmosphere brazing cycle as described in examples 1 and 2 and tensile tested for post-braze UTS. The properties are shown in Table 6.

(23) TABLE-US-00008 TABLE 6 Sample # UTS (MPa) G 155.0 H 164.0 J 145.8 K 153.5 L 163.5 M 170.6

(24) The FIGURE illustrates that, as the Fe+Si content increases, so too does the UTS after brazing and that increasing the Cu content for the same Fe+Si content also increases the UTS after brazing.