Brazing sheet and production method

Abstract

Brazing sheet having a core layer made of a first aluminium alloy, attached to one side of said core layer a sacrificial cladding made of a second aluminium alloy, and attached to the other side of said core layer a braze cladding made of a third aluminium alloy. The first aluminium alloy consists of: Si 0.6 wt %; Fe 0.7 wt %; Cu 0.4-0.9 wt %; Mn 1.0-1.6 wt %; Mg 0.2 wt %; Cr 0.05-0.15 wt %; Zr 0.05-0.15 wt %; Ti 0.05-0.15 wt %; other elements 0.05 wt % each and 0.2 wt % total; Al balance up to 100 wt %; the second aluminium alloy consists of: Si 0.65-1.0 wt %; Fe 0.4 wt %; Cu 0.05 wt %; Mn 1.4-1.8 wt %; Zn 1.5-4.0 wt %; Zr 0.05-0.20 wt %; other elements 0.05 wt % each and 0.2 wt % total; Al balance up to 100 wt %. The third aluminium alloy has a melting point lower than said first and second aluminium alloys.

Claims

1. A brazing sheet comprising a core layer made of a first aluminium alloy, attached to one side of said core layer a sacrificial cladding made of a second aluminium alloy, attached to the other side of said core layer a braze cladding made of a third aluminium alloy, wherein said first aluminium alloy consists of: Si 0.2 wt % Fe 0.7 wt % Cu 0.4-0.9 wt % Mn 1.0-1.6 wt % Mg 0.2 wt % Cr 0.05-0.15 wt % Zr 0.05-0.15 wt % Ti 0.05-0.15 wt % Other elements 0.05 wt % each and 0.2 wt % in total Al balance up to 100 wt %; said second aluminium alloy consists of: Si 0.65-1.0 wt % Fe 0.4 wt % Cu 0.05 wt % Mn 1.4-1.8 wt % Zn 1.5-5.5 wt % Zr 0.05-0.20 wt % Other elements 0.05 wt % each and 0.2 wt % in total Al balance up to 100 wt %; and, said third aluminium alloy has a melting point lower than said first and second aluminium alloys.

2. Brazing sheet as claimed in claim 1, wherein the second alloy comprises 2-3 wt % of Zn.

3. Brazing sheet as claimed in claim 1, wherein the third alloy is an aluminium alloy comprising 4-15 wt % of Si.

4. Brazing sheet as claimed in claim 1, wherein the thickness of the brazing sheet is from 0.15 to 0.25 mm.

5. Brazing sheet as claimed in claim 1, wherein the thickness of the brazing sheet is from 0.18 to 0.22 mm.

6. Brazing sheet as claimed in claim 1, wherein contents of Si and Mn in the first alloy are set so a sacrificial brown band is formed during brazing, said brown band formed comprising intermetallic particles containing Cr.

7. Brazing sheet as claimed in claim 6, wherein said brown band comprises intermetallic particles containing Al, Mn, Si and Cr.

8. Brazing sheet as claimed in claim 1, wherein the intermetallic particles have an average mean equivalent diameter in the range from 50 to 500 nm.

9. Brazing sheet as claimed in claim 1, having a SWAAT resistance, after brazing, against corrosion from the side of the braze cladding is more than 25 days.

10. Brazing sheet as claimed in claim 1, wherein the brazing sheet is a three layer material with no further layers in addition to the core, the sacrificial cladding and the braze cladding.

11. Brazing sheet as claimed in claim 1, wherein the thickness of the sacrificial cladding constitutes from 3 to 20% of the total thickness of the brazing sheet.

12. A process for the production of a brazing sheet according to claim 1, comprising the steps of: providing a core ingot of a first alloy as defined in claim 1; cladding the core ingot on one side with a second alloy as defined in claim 1; cladding the core ingot on the other side with a third alloy as defined in claim 1; preheating the cladded ingot at a temperature from 400 to 575 C. during 1 to 25 hours; hot rolling the preheated cladded ingot to obtain a sheet; and, cold rolling the sheet obtained at the hot rolling to the final thickness.

13. A brazed heat exchanger made by forming tubes from a brazing sheet according to claim 1, assembling said tubes with fins and other parts of the heat exchanger followed by brazing.

14. Brazing sheet as claimed in claim 1, wherein the third aluminium alloy has a liquidus temperature lower than the solidus temperatures of the first and second aluminium alloys.

15. Brazing sheet as claimed in claim 1, wherein said third aluminium alloy consists of: Si 4-15wt % Bi 0.5 wt % Cu 0.25 wt % Mn 0.1 wt % Ti 0.2 wt % Fe 0.8 wt % Other elements 0.05 wt % each and 0.2 wt % in total Al balance up to 100 wt %.

16. A brazing sheet comprising a core layer made of a first aluminium alloy, attached to one side of said core layer a sacrificial cladding made of a second aluminium alloy, attached to the other side of said core layer a braze cladding made of a third aluminium alloy, wherein the first aluminium alloy consists of: Si 0.04-0.2 wt % Fe 0.1-0.6 wt % Cu 0.4-0.9 wt % Mn 1.0-1.6 wt % Mg 0.05-0.15 wt % Cr 0.06-0.13 wt % Zr 0.06-0.13 wt % Ti 0.06-0.12 wt % Other elements 0.05 wt % each and wt % in total Al balance up to 100 wt %, wherein the second aluminium alloy consists of: Si 0.65-1.0 wt % Fe 0.4 wt % Cu 0.05 wt % Mn 1.4-1.8 wt % Zn 1.5-5.5 wt % Zr 0.05-0.20 wt % Other elements 0.05 wt % each and 0.2 wt % in total Al balance up to 100 wt %, wherein the third aluminium alloy comprises 4-15 wt % of Si, wherein the third aluminium alloy has a melting point lower than said first and second aluminium alloys, and wherein a total thickness of the brazing sheet is from 0.15 to 0.6 mm.

17. Brazing sheet as claimed in claim 16, wherein a thickness of the sacrificial cladding constitutes from 3 to 20% of the total thickness of the brazing sheet and wherein a thickness of the braze cladding constitutes from 3 to 20% of the total thickness of the brazing sheet.

18. Brazing sheet as claimed in claim 16, wherein a thickness of the sacrificial cladding constitutes from 5 to 12% of the total thickness of the brazing sheet and wherein a thickness of the braze cladding constitutes from 5 to 15% of the total thickness of the brazing sheet.

19. Brazing sheet as claimed in claim 16, wherein the total thickness of the brazing sheet is from 0.15 to 0.25 mm, and wherein a content of Zn in the second aluminium alloy is 2-3 wt %.

Description

EXAMPLE

(1) A 0.20 mm gauge tube stock material according to the invention (referred to as Material A) was produced in the following process route: (a) DC casting a core alloy ingot of the composition in wt.%: 0.04% Si, 0.23% Fe, 0.68% Cu; 1.27% Mn, 0.07% Mg, 0.09% Cr, 0.09% Zr, 0.1% Ti, balance Al and unavoidable impurities; (b) cladding the core on one side with a braze alloy of the composition 7.8% Si, 0.21% Fe, 0.02% Mn balance Al and unavoidable impurities; (c) cladding the core one the other side with a sacrificial alloy of the composition, in wt %, 0.73% Si, 0.26% Fe, 0.04% Cu, 1.58% Mn, 2.47% Zn, 0.13 Zr, 0.03% Ti, balance Al and unavoidable impurities; (d) preheating the resulting sandwich assembly to a temperature of 500 C. for 15 hours prior to hot rolling; (e) hot rolling to a thickness of 3.8 mm; (f) cold rolling to the final thickness of 0.20 mm; and, (f) final partial annealing at 250 C. for 3 hours to H24 temper. Of the total thickness the braze cladding constituted 10% and the sacrificial cladding 5%.

(2) As a comparison, a 0.20 mm gauge tube stock material (referred to as Material B) was made with the same process route, but with different alloy compositions. The core alloy had the composition, in wt %, 0.03% Si, 0.22% Fe, 0.61% Cu; 1.68% Mn, 0.05% Mg, 0.13% Zr, 0.03% Ti, balance Al and unavoidable impurities; the braze alloy had the composition, in wt %, 7.9% Si, 0.18% Fe, balance Al and unavoidable impurities; the sacrificial alloy had the composition, in wt %, 0.81% Si, 0.26% Fe, 0.03% Cu, 1.59% Mn, 2.46% Zn, 0.12% Zr, 0.03% Ti, balance Al and unavoidable impurities. Further, the braze cladding constituted 7% of the total thickness. The main difference from Material A is the core alloy composition. The slight differences in the compositions of the other alloys are due to inevitable variations in the production of the alloys and do not change the properties of the final material. Further, the difference in the thickness of the braze cladding, do not change the corrosion properties of the materials after brazing.

(3) 6 coupon samples from each material produced were brazed at 600 C. /3 minutes in a Nocolok furnace and tested in SWAAT chamber (ASTM G85-A3). Results of the tests as measured by the time to first perforation are shown below:

(4) TABLE-US-00001 Coup. 1 Coup. 2 Coup. 3 Coup. 4 Coup. 5 Coup. 6 (days) (days) (days) (days) (days) (days) Material A 56-60 63-67 63-67 56-60 63-67 56-60 (invention Material B 8 8 9 9 11 11 (comparison)