FLUX CORED BRAZING PREFORMS
The invention relates to a shaped, small diameter brazing preform for brazing components to one another, the preform comprising a length of aluminium-based filler alloy wire having a continuous, uniform cavity in a centre of the preform along its length, and a brazing flux material retained within the cavity, and wherein the aluminium-based filler alloy has a composition comprising, in wt. %, Si 7-14%, Zn 0.5 -%, Cu 1.0-2.0%, balance aluminium, and having a liquidus temperature in a range of 560° C. to 585° C.
1 . A shaped, small diameter brazing preform for brazing components to one another, comprising a length of aluminium-based filler alloy wire having a continuous, uniform cavity in a centre of the preform along its length, and a brazing flux material retained within the cavity, and wherein the aluminium-based filler alloy has a composition comprising, in wt. %,
Si 7% to 14%,
Zn 0.5% to 5%,
Cu 1.0% to 2.0%,
balance aluminium and inevitable impurities, and having a liquidus temperature in the range of 560° C. to 585° C.
2 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy has a composition comprising, in wt. %,
Si 7% to 14%,
Zn 0.5% to 5%,
Cu 1.0% to 2.0%,
Fe up to 0.8%,
Mn up to 0.3%,
Mg up to 0.5%,
Cr up to 0.1%,
V up to 0.1%,
Zr up to 0.1%,
Ti up to 0.2%,
balance aluminium and inevitable impurities.
3 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy has a Si-content of at least 9.0%.
4 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy has a Si-content of up to 13.0%.
5 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy has a Zn content of maximum 3%.
6 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy has a Cu content of maximum 1.75%.
7 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy further contains up to 0.8% of one or more wetting elements selected from the group consisting of Be, Bi, Ce, La, Li, Na, Pb, Se, Sb, Sr, Th, and Y.
8 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy further contains Bi in a range of 0.01% to 0.8%.
9 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy is Ag-free.
10 . The shaped brazing preform according to claim 1 , wherein the aluminium-based alloy has having a liquidus temperature in a range of 570° C. to 585° C.
11 . The shaped brazing preform according to claim 1 , wherein the aluminium-based filler alloy wire is devoid of any metallic layer(s) covering substantial parts of said wire.
12 . The shaped brazing preform according to claim 1 , wherein the amount of brazing flux material is in a range of 10 wt. % to 40 wt. % of the shaped brazing preform.
13 . The shaped brazing preform according to claim 1 , wherein the shaped brazing preform has a cross-sectional diameter of up to 4 mm.
14 . Use of a shaped brazing preform according to claim 1 to braze a pipe or tube of a heat exchanger.
15 . A method of joining by means of brazing using an aluminium alloy brazing filler metal to form a joint between at least two base metals, preferably at least one being a pipe or tube of a heat exchanger, comprising the steps of: (a) preparing at least two base metals to be joined by brazing; (b) providing an aluminium filler alloy according to claim 1 having a liquidus temperature in a range of 560° C. to 585° C.; (c) providing a brazing flux material, (d) heating at least the joint portion of the base metals with a heating cycle; (e) joining the at least two base metals by means of brazing using the aluminium filler alloy and the brazing flux material to form the joint; and (f) cooling of the joined assembly.
16 . The method according to claim 15 , wherein the aluminium filler alloy brazing filler metal is provided as a continuous length of wire is a shaped brazing preform having the brazing flux material in the core of the wire according to claim 1 .