Aluminium multi-layered brazing sheet product and fluxless brazing method

Abstract

A multi-layered brazing sheet product having an aluminium core alloy layer provided on one or both sides with a brazing clad layer material, and an inter-layer material positioned between the aluminium core alloy layer and at least one of the brazing clad layer materials, wherein the brazing layer material(s) is made from an 4xxx-series aluminium alloy having 5% to 15% Si and up to 3% Mg, and wherein the inter-layer material is made from a 1xxx-series aluminium alloy having a purposive addition of Mg of 0.10% to 2.0%. The invention relates also to the use of the brazing sheet product in a fluxless controlled atmosphere brazing process.

Claims

1. A method of manufacturing an assembly of joined components, joined by brazing in a controlled atmosphere brazing process, the method comprising the steps of: (a) providing of components to be brazed together of which at least one is made from a multi-layered brazing sheet product having an aluminium core alloy layer provided on one side with a brazing clad layer material and an inter-layer positioned between the aluminium core alloy layer and said brazing clad layer material, and is provided with a corrosion protective layer on the other side, wherein the brazing clad layer material is made from a 4xxx-series aluminium alloy having, in weight percent, 5% to 15% Si and greater than 0.05% to 0.5% Mg, and wherein the inter-layer is made from a 1xxx-series aluminium alloy having, in weight percent, a purposive addition of Mg of 0.10 to 1.5%, wherein Mg is purposively present in the brazing clad layer material and wherein the Mg-content in the inter-layer is higher than the Mg-content in the brazing clad layer material; wherein the corrosion protective layer is made from a 3xxx-series aluminium alloy consisting of, in weight percent: Mn 1.0% to 1.8%, Zn 1% to 3.5%, Ti 0.01% to <0.25%, remainder aluminium and unavoidable impurities each <0.05%, total <0.2%, (b) assembling of the components into an assembly; (c) brazing the assembly without applying brazing flux onto the assembly components, and brazing the whole assembly in a dry inert gas atmosphere at a brazing temperature, and wherein an oxygen content of the dry inert gas atmosphere is less than 35 ppm, wherein the Mg in the inter-layer diffuses into the brazing clad layer material; and (d) cooling of the brazed assembly.

2. The method according to claim 1, wherein the brazing clad layer material has been pre-treated by means of etching with an alkaline or acidic etchant.

3. The method according to claim 1, wherein a dwell time at brazing temperature is in a range of 1 to 10 minutes.

4. The method according to claim 1, wherein the oxygen content of the dry inert gas atmosphere is less than 25 ppm.

5. The method according to claim 1, wherein the oxygen content of the dry inert gas atmosphere is controlled to be at least 5 ppm.

6. The method according to claim 1, wherein the assembly of joined components form a charge-air-cooler or oil cooler.

7. The method according to claim 3, wherein the dwell time at brazing temperature is in a range of 1 to 6 minutes.

8. The method according to claim 4, wherein the oxygen content of the dry inert gas atmosphere is less than 20 ppm.

9. The method according to claim 1, wherein the brazing clad layer material has a composition, consisting of, in weight percent: TABLE-US-00004 Si 5% to 15%, Mg 0.1% to 0.5%, Fe up to 0.8%, Cu up to 0.3%, Mn up to 0.8%, Zn up to 0.25%, Ti up to 0.3%, balance aluminium and unavoidable impurities each <0.05%, total <0.2%, wherein Mg is purposively present in the brazing clad layer material.

10. The method according to claim 1, wherein the brazing clad layer material has a composition, consisting of, in weight percent: Si 5% to 15%, Mg 0.1% to 0.5%, Fe up to 0.8%, Cu up to 0.3%, Mn up to 0.8%, Zn up to 0.25%, Ti up to 0.3%, balance aluminium and unavoidable impurities each <0.05%, total <0.2%, wherein Mg is purposively present in the brazing clad layer material.

11. The method according to claim 1, wherein the aluminium core alloy layer is made from an 3-series alloy having a composition consisting of, in weight percent: TABLE-US-00005 Mn 0.8% to 1.5%, Si 0.25% to 0.75%, Cu 0.5% to 1.1%, Fe up to 0.45%, Mg up to 0.35%, Cr up to 0.25%, Zr up to 0.25%, Ti up to 0.20%, Zn up to 0.15%, unavoidable impurities each <0.05%, total <0.2%, and balance aluminium.

12. The method according to claim 1, wherein the inter-layer is made from 1xxx-series aluminium alloy having purposive addition of Mg of 0.10 wt. % to 1.0 wt. %.

13. The method according to claim 1, wherein the inter-layer is made from 1xxx-series aluminium alloy having purposive addition of Mg of 0.10 wt. % to 0.7 wt. %.

Description

(1) The invention shall also be described with reference to the appended FIG. 1 to FIG. 3 showing a schematic representation of the multi-layered brazing sheet product according to this invention.

(2) FIG. 1 shows a schematic representation of an embodiment of the multi-layered brazing sheet product formed by an aluminium alloy core layer (1) on one surface clad with an Al—Si brazing clad layer material (2) and interposed between the core layer (1) and brazing clad layer material (2) there is an inter-layer material (3) made from an 1xxx-series alloy having a purposive addition of Mg.

(3) FIG. 2 shows another embodiment of the multi-layered brazing sheet product in which starting from the embodiment of FIG. 1 the other surface of the core layer is also provided with an Al—Si brazing clad layer material (2) and interposed between the core layer (1) and brazing clad layer material (2) there is also an inter-layer material (3) made from a 1xxx-series alloy having a purposive addition of Mg.

(4) FIG. 3 shows another embodiment of the multi-layered brazing sheet product in which starting from the embodiment of FIG. 1 the other surface of the core layer (1) is provided with a waterside liner material (4).

(5) In an embodiment the waterside liner material is made from an 3xxx-series aluminium alloy, and more preferably it is made of an aluminium alloy consisting of:

(6) TABLE-US-00003 Mn 0.5% to 1.8%, preferably 0.6% to 1.3%, more preferably 0.75% to 1.0%, Zn 1% to 3.5%, preferably 1.5% to 3%, Mg <0.3%, preferably <0.10%, Si <1.2%, preferably <0.5%, Fe <0.8%, preferably <0.5%, Cu <0.8%, preferably <0.1%, Ti <0.25%, preferably 0.01% to 0.12%,

(7) unavoidable impurities each <0.05%, total <0.2%, remainder aluminium.

(8) At too high Zn-levels, in particular with thin gauge materials, too much Zn may diffuse into the core alloy during the heat-up and the brazing cycle. Furthermore, a too high Zn content may lead to evaporation of Zn from the liner during the heat-up and the brazing cycle.

(9) The waterside liner has typically a thickness of 3% to 20% of the total thickness of the 4-layered brazing sheet structure, for example of about 15%. In an embodiment the waterside liner has a gauge in the range of 25 μm to 70 μm, for example of about 30 μm or about 40 μm, to provide the required corrosion resistance.

(10) In another aspect of the invention it relates to a brazing method using the multi-layered brazing sheet product and its preferred embodiments, the method relates to manufacturing an assembly of joined components, in particular a heat exchanger, joined by brazing in a controlled atmosphere brazing process, comprising the steps of:

(11) (a) providing of the components to be brazed together of which at least one is made from a multi-layered brazing sheet product having an aluminium core alloy layer provided one or both sides with a brazing clad layer material, and an inter-layer positioned between the aluminium core alloy layer and at least one of said brazing clad layer materials, wherein the brazing layer material(s) is made from an 4xxx-series aluminium alloy having 5% to 15% Si and up to 3% Mg, preferably up to 0.90% Mg, and more preferably up to 0.5%, and wherein the inter-layer is made from an 1xxx-series aluminium alloy having a purposive addition of Mg of about 0.10% to 2.0%, and wherein preferably the outer-surface of the brazing clad layer material(s) has been pre-treated by means of etching with an alkaline or acidic etchant,

(12) (b) assembling the components into an assembly;

(13) (c) brazing the assembly without applying brazing flux onto the assembly components, and brazing the whole assembly in a dry inert gas atmosphere at a brazing temperature, preferably at a temperature in a range of about 540° C. to 615° C., for example at about 590° C. or at about 600° C., for a period long enough for melting and spreading of the brazing clad layer materials, for example a dwell time of about 1 to 10 minutes, preferably of about 1 to 6 minutes, typically at around 2 or 4 minutes, to form a fillet between the multi-layered brazing sheet product and at least one other component; and wherein the oxygen content of the dry inert gas atmosphere is controlled to be less than 35 ppm, preferably less than 25 ppm;

(14) (d) cooling of the brazed assembly, typically to below about 100° C., e.g. to ambient temperature.

(15) The brazing inert gas atmosphere should be dry, meaning that the dew point is less than −40° C., and more preferably of −45° C. or even lower.

(16) In another aspect of the invention it relates to the use or method of use of a multi-layered brazing sheet product having an aluminium core alloy layer provided one or both sides with a brazing clad layer material, and an inter-layer positioned between the aluminium core alloy layer and at least one of said brazing clad layer materials, wherein the brazing layer material(s) is made from an 4xxx-series aluminium alloy having 5% to 15% Si and up to 3% Mg, preferably up to 0.9% Mg, and more preferably up to 0.5%, and wherein the inter-layer is made from a 1xxx-series aluminium alloy having a purposive addition of Mg of 0.10% to 2.0%, and preferably the outer-surface of the brazing clad layer material(s) having been pre-treated by means of etching with an alkaline or acidic etchant, and applied or used in a fluxless controlled atmosphere brazing process performed in a dry inert gas atmosphere at a brazing temperature for a period long enough for melting and spreading of the brazing clad layer material to form a fillet between the multi-layered brazing sheet product and another component, and wherein the oxygen content of the dry inert gas atmosphere is controlled to be less than 35 ppm, preferably less than 25 ppm, more preferably less than 20 ppm. Preferably, the oxygen content of the dry inert gas atmosphere is controlled to be at least 5 ppm.

(17) Preferred embodiments of the multi-layered brazing sheet product and of the brazing process conditions have been set out herein when describing the product and method according to this invention.

(18) The multi-layered brazing sheet product and the brazing method according to this invention have proven to be of particular use in the production of heat exchanger devices having very high requirements on inner cleanliness, in particular oil coolers and charge-air-coolers. These heat exchangers are not suitable for production by vacuum brazing either due to their large size or for economic reasons.

(19) The invention is not limited to the embodiments described before, which may be varied widely within the scope of the invention as defined by the appending claims.