Method of Manufacturing a Brazing Sheet Product
The invention relates to a method of manufacturing a brazing sheet product having a core layer of a 3xxx-series aluminium alloy clad on one or both sides with a 4xxx-series aluminium alloy brazing layer, the method comprising the steps of: (i) casting a rolling ingot of the core layer of a 3xxx-series aluminium alloy having the following composition, in wt. %: Mn 0.5-1.8, Si≤1.5, Fe≤0.7, Cu≤1.5, Mg≤1.0, Cr≤0.25, Zr≤0.25, Ti≤0.25, Zn≤0.5, balance impurities and aluminium; (ii) hot rolling of the rolling ingot to a hot rolled sheet having thickness of 2.5-10 mm; (iii) cold rolling of the hot rolled sheet to a gauge of 0.1-4 mm, optionally with an intermediate annealing step during the cold rolling operation; (iv) soft annealing to recrystallize the microstructure of the aluminium sheet, preferably at a temperature in the range of 250° C.-450° C.; (v) further cold rolling of the soft annealed sheet with a cold rolling reduction in the range of 5% to <10% to a final cold rolling thickness; and (vi) recovery annealing at 200° C.-420° C. of the cold rolled aluminium sheet at final cold rolling thickness.
1 . A method of manufacturing a brazing sheet product having a core layer of a 3xxx-series aluminium alloy clad on one or both sides with a 4xxx-series aluminium alloy brazing layer, the method comprising the steps of:
(a) casting a rolling ingot of the core layer of a 3xxx-series aluminium alloy having the following composition, in wt. %:
Mn
0.5 to 1.8,
Si
up to 1.5,
Fe
up to 0.7,
Cu
up to 1.5,
Mg
up to 1.0,
Cr
up to 0.25,
Zr
up to 0.25,
Ti
up to 0.25,
Zn
up to 0.5,
other elements and impurities each <0.05, total <0.15; balance aluminium.
(b) hot rolling of the rolling ingot to a hot rolled sheet having thickness of 2.5 to 10 mm;
(c) cold rolling of the hot rolled sheet to a gauge of 0.1 to 4 mm;
(d) soft annealing to recrystallize the microstructure of the aluminium sheet;
(e) further cold rolling of the soft annealed sheet with a cold rolling reduction in the range of 5% to <10% to a final cold rolling thickness; and
(f) recovery annealing of the cold rolled aluminium sheet at final cold rolling thickness, wherein the recovery annealing is performed at a temperature in the range of 200° C. to 420° C.
2 . The method according to claim 1 , wherein the recovery annealing during step (f) is performed at a temperature in the range of 200° C. to 400° C.
3 . The method according to claim 1 , wherein the recovery annealing during step (f) is to an elongation of more than 10% in the brazing sheet product.
4 . The method according to claim 1 , wherein an intermediate annealing step is performed during the cold rolling operation and wherein the intermediate annealing during the cold rolling operation of step (c) is at a temperature in the range of 200° C. to 450° C.
5 . The method according to claim 1 , the 3xxx-series aluminium alloy has a Mg-content in the range of up to 0.7%.
6 . The method according to claim 1 , wherein the final cold rolling thickness during step (e) is to a thickness in the range of 0.1 mm to 3 mm.
7 . The method according to claim 1 , wherein the 3xxx-series aluminium alloy has a Mn-content in the range of 0.6% to 1.5%.
8 . The method according to claim 1 , wherein the 3xxx-series aluminium alloy has a Si-content in the range of up to 0.9%.
9 . The method according to claim 1 , wherein the 3xxx-series aluminium alloy has a Cu-content in the range of up to 1.2%.
10 . The method according to claim 1 , wherein the 3xxx-series aluminium alloy has a Cu-content in the range of up to 0.25.
11 . The method according to claim 1 , wherein the 3xxx-series aluminium sheet is clad on one or both sides with a 4xxx-series aluminium alloy brazing layer with each brazing layer having a thickness of 4% to 20% of the total brazing sheet thickness.
12 . The method according to claim 1 , wherein the brazing sheet product having a core layer of a 3xxx-series aluminium alloy clad on one or both sides with a 4xxx-series aluminium alloy brazing layer is devoid of any intermediate aluminium alloy layer positioned between the core layer and the brazing layer.
13 . Heat exchanger incorporating a tube or plate made from the aluminium sheet manufactured according to claim 1 .
14 . The heat exchanger according to claim 13 , wherein the heat exchanger is a stacked plate heat exchanger.
15 . Use of an aluminium alloy brazing sheet product having a 3xxx-series aluminium alloy core layer manufactured according to claim 1 in a heat exchanger.
16 . The method of claim 1 , wherein the soft annealing is performed at a temperature in the range of 250° C. to 450° C.
17 . The method of claim 2 , wherein the recovery annealing during step (f) is performed at a temperature in the range of 250° C. to 380° C.
18 . The method of claim 3 , wherein the recovery annealing during step (f) is to an elongation of more than 14%.
19 . The method of claim 5 , wherein the Mg-content is in the range of 0.1% to 0.7%.
20 . The method of claim 7 , wherein the Mn-content is in the range of 0.6% to 1.25%.