阅读说明：本技术 一种层状钎焊复合材料及其制造方法 (Layered brazing composite material and manufacturing method thereof ) 是由 马伟增 杜妮燕 于 2021-10-19 设计创作，主要内容包括：本发明涉及一种层状钎焊复合材料,其包含：芯材层(2),位于芯材层(2)一侧的无钎剂层(1),和位于芯材层(2)另一侧的免钎剂层(3)；其中,沿着远离所述芯材层(2)的方向,所述无钎剂层(1)依次包含：中间钎料层(1a)和覆盖层(1b)；所述无钎剂层(1)中的中间钎料层(1a)的厚度与覆盖层(1b)的厚度的比为20:1-1.5:1。本发明还涉及所述层状钎焊复合材料的制备方法及包含所述复合材料的热交换器。(The present invention relates to a layered brazing composite comprising: the brazing flux-free composite material comprises a core material layer (2), a brazing flux-free layer (1) positioned on one side of the core material layer (2), and a brazing flux-free layer (3) positioned on the other side of the core material layer (2); wherein, in a direction away from the core material layer (2), the flux-free layer (1) comprises in sequence: an intermediate solder layer (1a) and a covering layer (1 b); the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the non-solder layer (1) is 20:1-1.5: 1. The invention also relates to a preparation method of the layered brazing composite material and a heat exchanger comprising the composite material.)

1. A layered brazing composite comprising:

a core material layer (2),

a flux-free layer (1) on the side of the core layer (2), and

a soldering flux-free layer (3) positioned on the other side of the core material layer (2);

wherein the content of the first and second substances,

in the direction away from the core material layer (2), the flux-free layer (1) comprises in sequence: an intermediate solder layer (1a) and a covering layer (1 b);

the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the non-solder layer (1) is 20:1-1.5: 1.

2. The layered brazing composite of claim 1,

the thickness of the brazing flux-free layer (1) is 4-25% of the thickness of the layered brazing composite material.

3. The layered brazing composite of claim 1 or 2,

the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the non-solder layer (1) is 15:1 to 2:1, preferably 10:1 to 2:1, more preferably 7.5:1 to 2: 1.

4. The layered brazing composite as claimed in any one of claims 1 to 3,

the coating (1b) has a Mg content of 0.05 wt.% or less, preferably contains no Mg; and/or

The Mg content in the intermediate brazing filler metal layer (1a) is 0.1-0.5 wt%.

5. The layered brazing composite as claimed in any one of claims 1 to 4,

the alloy of the cover layer (1b) comprises:

bi of 0.2 wt.% or less, preferably 0.15 wt.% or less, more preferably 0.1 wt.% or less,

si1-14 wt.%, preferably 2-13 wt.%, more preferably 2.5-12.5 wt.%,

mg < 0.1 wt.%, preferably < 0.05 wt.%, more preferably < 0.02 wt.%,

cu is less than or equal to 1.0 weight percent,

fe is less than or equal to 0.7 weight percent,

zn < 6% by weight, and

each content of unavoidable impurities of less than 0.05 wt%, and

the total content of impurities is less than 0.2 wt%;

the balance being Al.

6. The layered brazing composite as claimed in any one of claims 1 to 5,

the alloy of the intermediate solder layer (1a) comprises:

si5-14 wt.%, preferably 6-13 wt.%, more preferably 7-12.5 wt.%,

from 0.01 to 2% by weight of Mg0.01 to 1% by weight, preferably from 0.05 to 1% by weight, more preferably from 0.1 to 0.5% by weight,

bi. ltoreq.1.0% by weight, preferably from 0.05 to 0.5% by weight, more preferably from 0.07 to 0.3% by weight,

fe is less than or equal to 0.7 weight percent,

cu is less than or equal to 1.0 weight percent,

zn is less than or equal to 6 percent by weight,

sr is less than or equal to 0.05 weight percent,

each content of unavoidable impurities of less than 0.05 wt%, and

the total content of impurities is less than 0.2 wt%;

the balance being Al.

7. The layered brazing composite as claimed in any one of claims 1 to 6,

the brazing flux-free layer (3) is a brazing flux layer (3a) containing brazing flux.

8. The layered brazing composite as recited in claim 7,

on the side of the solder layer (3a) containing solder far from the core layer (2), the solder-free layer (3) further comprises a general solder layer (3b), and/or

On the side of the solder layer (3a) containing solder flux, which is adjacent to the core layer (2), the solder-free layer (3) also contains a general solder layer (3 b').

9. The layered brazing composite as claimed in any one of claims 1 to 8,

the thickness of the brazing flux-free layer (3) is 5% -25% of that of the layered brazing composite material.

10. The layered brazing composite as claimed in any one of claims 1 to 9,

the content of Mg in the brazing flux layer (3a) containing the brazing flux is less than or equal to 0.05 wt%, and Mg is preferably not contained; and/or

The general brazing filler metal layer (3b) contains 0.05 wt% or less of Mg, and preferably contains no Mg.

11. The layered brazing composite as claimed in any one of claims 1 to 10,

the alloy of the brazing flux layer (3a) containing a brazing flux comprises:

1-20 wt%, preferably 2-15 wt%, more preferably 2.5-12.5 wt%,

si5-14 wt.%, preferably 6-13 wt.%, more preferably 7-12.5 wt.%,

mg < 0.2 wt.%, preferably < 0.1 wt.%, more preferably < 0.05 wt.%,

fe is less than or equal to 0.7 weight percent,

cu is less than or equal to 1.0 weight percent,

zn is less than or equal to 6 percent by weight,

sr is less than or equal to 0.05 weight percent,

each content of unavoidable impurities of less than 0.05 wt%, and

the total content of impurities is less than 0.2 wt%;

the balance being Al.

12. The layered brazing composite as claimed in any one of claims 1 to 11,

the alloy of the general solder layer (3b) comprises:

si5-14 wt.%, preferably 6-13 wt.%, more preferably 7-12.5 wt.%,

mg < 0.1 wt.%, preferably < 0.05 wt.%, more preferably < 0.02 wt.%,

fe is less than or equal to 0.7 weight percent,

cu is less than or equal to 1.0 weight percent,

zn is less than or equal to 6 percent by weight,

sr is less than or equal to 0.05 weight percent,

unavoidable impurities each in an amount of less than 0.05 wt%, and,

the total content of impurities is less than 0.2 wt%;

the balance being Al.

13. A method of making the layered brazing composite of any one of claims 1 to 12, comprising the steps of:

(S1) preparing a core material layer (2) alloy, a brazing flux-free layer (1) alloy and a brazing flux-free layer (3) alloy;

(S2) rolling the flux-free layer (1) alloy and the flux-free layer (3) alloy into plate shapes, respectively, to obtain a plate-shaped flux-free layer (1) alloy and a plate-shaped flux-free layer (3) alloy;

(S3) roll-compounding a core material layer (2) alloy, a plate-shaped brazing flux-free layer (1) alloy, a plate-shaped brazing flux-free layer (3) alloy to obtain a composite body, wherein the plate-shaped core material layer (2) alloy is placed between the plate-shaped brazing flux-free layer (1) alloy and the plate-shaped brazing flux-free layer (3) alloy;

(S4) rolling the composite body to a target thickness;

(S5) softening annealing.

14. A heat exchanger comprising the layered brazing composite of any one of 1 to 12,

preferably, the flux-free layer (1) is located on the side of the heat exchanger that is intended for the flux residue, on a liquid medium, preferably coolant and/or pure water.

Technical Field

The invention relates to the technical field of aluminum brazing, in particular to a layered brazing composite material and a manufacturing method thereof.

Background

In the last 70-80 s, the invention based on F-Al-K non-corrosive flux and its application in the aluminium brazing industry opened a new era of aluminium heat exchanger production. After about 40 years of development, aluminum heat exchangers brazed in controlled atmosphere brazing furnaces by using brazing composite plates/strips/foils and F-Al-K brazing flux have replaced assembled aluminum heat exchangers, copper-soldered heat exchangers and vacuum-brazed aluminum heat exchangers, and become the leading technology in the commercial vehicle and passenger vehicle industries. The controllable atmosphere brazing technology is characterized in that F-Al-K brazing flux is applied to the surface of a material to be brazed and connected, and then the material is heated in a controllable atmosphere brazing furnace under the protection of nitrogen; melting the F-Al-K brazing flux, dissolving and removing an oxide film naturally formed on the surface of the aluminum; the molten solder wets the surface from which the oxide film is removed, and flows under capillary force to form a soldered joint. Meanwhile, residual flux may be present on the inner and outer surfaces of the heat exchanger.

Document 1(C.Alverson, M.Ranger, and H.J.DeBaun, "The Effects of Residual Controlled atomic Brazing fluorine on enzymes," in Global Testing of Extended Service enzymes and Related Fluids, ed.E.Eaton, West Conshohon, PA: ASTM International,2014,175- "194) discusses The interaction of Residual F-Al-K Flux with coolant under normal vehicle operation and standing conditions. Under normal vehicle operation, operation of engine coolant in a controlled atmosphere aluminum brazed aluminum heat exchanger with residual F-Al-K flux may result in K production⁺、F^-Or Al³⁺The color stability, PH, corrosion inhibitor level, corrosion protection performance, and deposit formation of the coolant can be affected.

The coolant for Fuel Cell vehicles or the Cooling medium for thermal management of electric power/electronics must satisfy strict Conductivity requirements, and as described in document 3 (short a. et. al, "learning of Ions from Fuel Cell Vehicle Cooling System and heat Removal to maintenance Low Conductivity," SAE Technical Paper 2003-01-0802,2003 "), since the coolant, medium and stack are not electrically insulated from the high voltage device, the target Conductivity of the Fuel Cell coolant needs to be less than 5 μ S/cm to avoid leakage current and short circuits. The traditional controlled atmosphere brazing aluminum heat exchanger with F-Al-K residual brazing flux is difficult to meet the strict requirement of electrical conductivity due to the precipitation of ions.

To reduce or eliminate the negative effects of residual flux, a number of techniques have been developed to reduce the amount of flux used or eliminate the use of flux. Broadly speaking, there are two main techniques:

one is the fluxless technique, by using Mg or Mg/Bi to break up the oxide film during brazing. Patent EP1306207 proposes the use of a multi-layer composite brazing aluminium sheet/strip for a controlled atmosphere brazing furnace, wherein a fluxless technique is used. The technology adopts an aluminum alloy brazing filler metal layer containing Mg and Bi and an aluminum alloy surface layer which is covered on the brazing filler metal layer and is higher than the melting point of the brazing filler metal layer. The solder layer contains 0.1-5% Mg and up to 0.5% Bi. Patent EP2323805 used a similar concept but specifically stated that the second braze layer was an Al-Si alloy containing 5-20% Si and 0.01-3% Mg; the first braze layer (skin) is also an Al-Si alloy containing 6-14% Si and less than 0.01% Mg. The innovation point is that the first brazing layer is Al-Si. Patent WO 2011/034496(Granges application) also uses a multilayer composite concept, but specifies that the thin covering layer (skin) has a Bi content of 0.01-1%, and that the brazing layer under the covering layer contains 0.01-5% Mg and up to 1.5% Bi. Bi of the capping layer can improve wettability. Based on laboratory testing and industrial practice, these techniques work well at very low oxygen content, dew point conditions, which are difficult to achieve at high oxygen content, dew point conditions; it is often difficult to form an acceptable braze joint for external joints while working well for braze joints located in the internal cavity.

Another technique is to incorporate flux into the solder with the goal of reducing flux usage by reducing flux evaporation and breaking the oxide film from the inside to the outside. Patent WO2008/110808a1 proposes a method of incorporating flux into an aluminium brazing filler metal, and brazing sheets/tapes comprising such a brazing filler metal show very good brazing properties. Patent WO2017/178181 uses a lower brazing flux amount while maintaining brazing performance, thereby reducing residual flux levels.

Because the coolant/cooling medium is not electrically isolated from the fuel cell stack or other high voltage devices, the coolant for fuel cells and the coolant for power/electronic thermal management must meet stringent thermal conductivity requirements to avoid leakage currents and short circuits, and therefore heat exchangers for fuel cells or power/electronic thermal management require zero or near zero flux residue on the coolant/cooling medium side. Some OEMs also require heat exchangers such as water cooled intercoolers, water cooled condensers for zero flux residue in view of corrosion performance.

Disclosure of Invention

In one aspect, the present invention relates to a layered brazing composite comprising: the brazing flux-free composite material comprises a core material layer (2), a brazing flux-free layer (1) positioned on one side of the core material layer (2), and a brazing flux-free layer (3) positioned on the other side of the core material layer (2); wherein, in the direction away from the core material layer (2), the flux-free layer (1) comprises in sequence: an intermediate solder layer (1a) and a covering layer (1 b); the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the non-solder layer (1) is 20:1-1.5: 1.

In one embodiment, the thickness of the fluxless layer (1) in the layered brazing composite is 4% to 25% of the thickness of the layered brazing composite.

In one embodiment, the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the clad layer (1b) in the flux-free layer (1) in the layered brazing composite is 15:1 to 2: 1.

In a preferred embodiment, the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the fluxless layer (1) in the layered brazing composite is 10:1 to 2: 1.

In a more preferred embodiment, the ratio of the thickness of the intermediate solder layer (1a) to the thickness of the covering layer (1b) in the fluxless layer (1) in the layered brazing composite is 7.5:1 to 2: 1.

In one embodiment, the Mg content of the clad layer (1b) is 0.05 wt% or less in the layered brazing composite. In a preferred embodiment, the clad layer (1b) does not contain Mg in the layered brazing composite.

In one embodiment, the Mg content in the intermediate brazing filler metal layer (1a) is 0.1 to 0.5 wt% in the layered brazing composite material.

In one embodiment, the flux-free layer (3) in the layered brazing composite is a brazing flux layer (3a) containing a brazing flux.

In one embodiment, the brazing-free layer (3) further comprises a general brazing material layer (3b) on the side of the brazing material layer (3a) containing the brazing material remote from the core material layer (2).

In one embodiment, the brazing-free layer (3) further comprises a general brazing material layer (3 b') on the side of the brazing material layer (3a) containing the brazing material adjacent to the core material layer (2).

In one embodiment, the Mg content in the brazing flux layer (3a) containing the brazing flux is 0.05 wt% or less in the layered brazing composite. In a preferred embodiment, the brazing flux layer (3a) containing the brazing flux does not contain Mg in the layered brazing composite.

In one embodiment, the layered brazing composite material typically has a Mg content of 0.05 wt.% or less in the brazing filler metal layer. In a preferred embodiment, the layered brazing composite material typically does not contain Mg in the brazing filler metal layer.

In another aspect, the present invention also relates to a method of making a layered brazing composite comprising the steps of: (S1) preparing a core material layer (2) alloy, a brazing flux-free layer (1) alloy and a brazing flux-free layer (3) alloy; (S2) rolling the flux-free layer (1) alloy and the flux-free layer (3) alloy into plate shapes, respectively, to obtain a plate-shaped flux-free layer (1) alloy and a plate-shaped flux-free layer (3) alloy; (S3) roll-compounding a core material layer (2) alloy, a plate-shaped brazing flux-free layer (1) alloy, a plate-shaped brazing flux-free layer (3) alloy to obtain a composite body, wherein the plate-shaped core material layer (2) alloy is placed between the plate-shaped brazing flux-free layer (1) alloy and the plate-shaped brazing flux-free layer (3) alloy; (S4) rolling the composite body to a target thickness; (S5) softening annealing.

In yet another aspect, the present invention is also directed to a heat exchanger comprising the layered brazing composite of the present invention.

In one embodiment, the non-flux layer (1) is located on the side of the heat exchanger that has the required liquid medium for flux residue.

Drawings

FIG. 1: the structure of the layered brazing composite material is shown schematically.

FIG. 2: the structure of the embodiment 1 and 2 of the invention is schematically shown.

FIG. 3: (a) the results of testing the Mg content by glow spectroscopy (GD-OES) on the side of the brazing flux-free layer (1) in comparative example 1; (b) in comparative example 1, the result of measuring the Mg content by glow spectroscopy (GD-OES) was obtained on the side of the brazing flux-free layer (3).

FIG. 4: (a) the results of measuring the Mg content by glow spectroscopy (GD-OES) on the side of the brazing flux-free layer (1) in example 1; (b) in example 1, the result of measuring the Mg content by glow spectroscopy (GD-OES) was obtained on the side of the flux-free layer (3).

FIG. 5: EXAMPLE 2 brazing of the non-flux layer (1) side to non-composite fins

FIG. 6: comparative example 2 the side without the flux layer (1) was brazed to a non-composite fin.

FIG. 7: in example 1 of the present invention, the brazing flux layer (3) -free side was brazed to a non-composite fin.

FIG. 8: in example 1 of the present invention, the side without the flux layer (1) was brazed to a non-composite fin.

FIG. 9: (a) example 1 of the invention plate/plate brazing between sides of flux-free layer (3); (b) example 1 of the invention plate/plate brazing between sides of the flux-free layer (1); (c) plate/plate brazing between the flux-free layer (3) side and the non-composite AA3003 plate of example 1 of the present invention; (d) example 1 of the invention plate/plate brazing between the no flux layer (1) side and the non-composite AA3003 plate.

Detailed Description

General definitions and terms

All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety if not otherwise indicated.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the definitions provided herein will control. All percentages, parts, ratios, etc., are by weight unless otherwise indicated.

When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a pair of upper and lower preferable values or specific values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. When numerical ranges are recited herein, unless otherwise stated, the stated ranges are meant to include the endpoints thereof, and all integers and fractions within the ranges. The scope of the invention is not limited to the specific values recited when defining a range. For example, "1-8" encompasses 1, 2, 3, 4, 5, 6, 7, 8, as well as any subrange consisting of any two values therein, e.g., 2-6, 3-5.

The terms "about" and "approximately," when used in conjunction with a numerical variable, generally mean that the value of the variable and all values of the variable are within experimental error (e.g., within 95% confidence interval for the mean) or within ± 10% of the specified value, or more.

The terms "comprising," "including," "having," "containing," or "involving," and other variations thereof herein, are inclusive or open-ended and do not exclude additional unrecited elements or method steps. It will be understood by those skilled in the art that terms such as "including" and "comprising" encompass the meaning of "consisting of …. The expression "consisting of …" excludes any element, step or ingredient not specified. The expression "consisting essentially of …" means that the scope is limited to the specified elements, steps or components, plus optional elements, steps or components that do not materially affect the basic and novel characteristics of the claimed subject matter. It is to be understood that the expression "comprising" covers the expressions "consisting essentially of …" and "consisting of …".

The term "selected from …" means that one or more elements in the later listed groups are independently selected and may include a combination of two or more elements.

When values or range ends are described herein, it is to be understood that the disclosure includes the particular values or ends recited.

The term "one or more" or "at least one" as used herein refers to one, two, three, four, five, six, seven, eight, nine or more.

Unless otherwise indicated, the terms "combination thereof" and "mixture thereof" refer to a multi-component mixture of the elements described, such as two, three, four, and up to the maximum possible multi-component mixture.

Furthermore, no number of elements or components of the invention has been previously indicated and no limitation on the number of occurrences (or presence) of an element or component is intended. Thus, it should be read to include one or at least one and singular forms of a component or ingredient also include the plural unless the numerical value explicitly indicates the singular.

The terms "optionally" or "optionally" as used herein mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

The term "surface" as used herein refers to the interface of an object and the environment, which is generally free of thickness, such as the interface of a composite material in contact with the environment. The shape of which generally depends on the shape of the object, and may be, for example, a planar or curved structure, etc.

The term "skin" as used herein refers to a portion of an object that is within a certain distance of the surface of the object, and which typically has a certain thickness. For example, in the composite material, the portion has a certain thickness within a certain distance (e.g., within several micrometers, within tens of micrometers, within hundreds of micrometers, etc.) from the surface thereof. The shape of which is generally related to the shape of the object and may be, for example, a flat plate, a curved strip, or the like.

The term "3-series aluminum alloy" as used herein is a generic alloy designation in the art that is well known to those skilled in the art, such as GB-T3190-2016 wrought aluminum and aluminum alloy chemistries. For example, the 3-series alloy is a series of alloys containing aluminum manganese as a main element. The 3-series alloys herein include, but are not limited to, 3003 aluminum alloy (AA3003), 3004 aluminum alloy (AA3004), 3005 aluminum alloy (AA 3005).

Layered brazing composite material

The present invention relates to a layered brazing composite comprising: the brazing flux-free composite material comprises a core material layer (2), a brazing flux-free layer (1) positioned on one side of the core material layer (2) and a brazing flux-free layer (3) positioned on the other side of the core material layer (2). The layered brazing composite material has the structure shown in figure 1.

The thickness of the layered brazing composite material is related to the number of layers thereof and needs to be adjusted in consideration of the thickness of each layer thereof. When the thickness is too small, the requirements on the strength and the corrosion resistance of the composite material are not satisfied. In one embodiment, the laminar brazing composite has a thickness of 0.15 to 3mm, for example 0.4mm, 0.48 mm.

The form of the layered brazing composite material can be processed according to actual needs, including but not limited to plates and strips. In one embodiment, the layered brazing composite material is a layered brazing composite panel.

Core material layer (2)

The core material layer (2) is positioned between the brazing flux-free layer (1) and the brazing flux-free layer (3). The core material layer (2) is one of the main structures of the layered brazing composite material, and the characteristics (such as hardness, strength, toughness and the like) of the core material layer affect the layered brazing composite material. The material of the core material is not particularly limited, and a suitable metal or alloy may be selected according to the actual application, for example, an aluminum alloy, such as a 3-series aluminum alloy, including but not limited to 3003 aluminum alloy (AA3003), 3004 aluminum alloy (AA3004), and 3005 aluminum alloy (AA 3005). In one embodiment, the core alloy is a3003 MOD aluminum alloy. In a particular embodiment, the alloy of the core material comprises: 0.06 wt% Si, 0.22 wt% Fe, 0.37 wt% Cu, 1.47 wt% Mn, 0.16 wt% Ti.

The thickness of the core material layer (2) can be selected according to actual needs, and generally, the thickness should not be too thin. The thickness of the core material layer (2) may be 50-92% of the layered brazing composite material to obtain suitable properties (e.g. strength, hardness, deformation resistance, etc.) of the final composite material.

Without brazing flux layer (1)

The brazing flux-free layer (1) comprises, in order along a direction away from the core material layer (2): an intermediate solder layer (1a) and a covering layer (1 b). The structure of the brazing flux-free layer (1) can be as shown in fig. 1.

The thickness of the brazing flux-free layer (1) can be selected according to actual conditions, and the thickness of the brazing flux-free layer (1) can be 5% -25% of that of the layered brazing composite material, so that the brazing effect is achieved.

The melting temperature of the coated intermediate solder layer (1a) is lower than that of the coating layer (1b) and the core material layer (2). During the brazing process, the brazing filler metal in the intermediate brazing filler metal layer (1a) is melted, the volume of the brazing filler metal is expanded, so that the covering layer (1b) is broken, an oxide film is broken, and the melted brazing filler metal penetrates through the covering layer (1b) and can be contacted with the adjacent material on the surface of the covering layer (1b) to finish the brazing.

Bi is added to the coating layer (1b) to improve the wettability and enhance the brazing effect, thereby forming a brazed joint more rapidly. The Mg content in the cover layer (1b) is kept low to avoid the growth of oxide films on the surface during the brazing heating. In one embodiment, the Mg content in the cover layer (1b) is below 0.1 wt.%, preferably below 0.05 wt.%, more preferably below 0.02 wt.%, most preferably the cover layer (1b) does not contain Mg.

In one embodiment, the alloy of the covering layer (1b) in the flux-free layer (1) comprises:

bi of 0.2 wt.% or less, preferably 0.15 wt.% or less, more preferably 0.1 wt.% or less,

si1-14 wt%, preferably 2-13 wt%, more preferably 2.5-12.5 wt%,

mg < 0.1 wt.%, preferably < 0.05 wt.%, more preferably < 0.02 wt.%, most preferably 0 wt.%,

cu of not more than 1.0 wt%, Fe of not more than 0.7 wt%, Zn of not more than 6 wt%, and

unavoidable impurities each in an amount of less than 0.05 wt%, and a total content of impurities of less than 0.2 wt%; the balance being Al.

In a particular embodiment, the alloy of the covering layer (1b) in the flux-free layer (1) comprises: 3.6 wt% Si, 0.13 wt% Fe, 0.09 wt% Bi.

The intermediate brazing material layer (1a) is added with proper content of Mg, so that proper hardness is favorably obtained, and a better brazing effect is obtained. The intermediate brazing filler metal layer (1a) contains 0.01 to 2 wt% of Mg, preferably 0.05 to 1 wt% of Mg, more preferably 0.1 to 0.5 wt% of Mg.

In one embodiment, the alloy of the intermediate solder layer (1a) comprises:

si5-14 wt%, preferably 6-13 wt%, more preferably 7-12.5 wt%,

mg0.01-2 wt%, preferably 0.05-1 wt%, more preferably 0.1-0.5 wt%,

bi. ltoreq.1.0% by weight, preferably from 0.05 to 0.5% by weight, more preferably from 0.07 to 0.3% by weight,

fe is less than or equal to 0.7 wt%, Cu is less than or equal to 1.0 wt%, Zn is less than or equal to 6 wt%, Sr is less than or equal to 0.05 wt%, and

unavoidable impurities each in an amount of less than 0.05 wt%, and a total content of impurities of less than 0.2 wt%; the balance being Al.

The thickness ratio of the intermediate brazing filler metal layer (1a) to the clad layer (1b) should be within a suitable range, which enables the Mg content of the surface layer on the brazing filler metal-free layer (1) side (i.e., the outer surface layer of the clad layer (1 b)) to be controlled within a low range while maintaining a good brazing effect. In the present invention, the thickness ratio of the intermediate solder layer (1a) to the cover layer (1b) is 20:1 to 1.5:1, preferably 15:1 to 2:1, more preferably 10:1 to 2:1, most preferably 7.5:1 to 2:1, such as 20:1, 19:1, 18:1, 17:1, 16:1, 14:1, 13:1, 12:1, 11:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2.5:1, 2:1, 1.5:1 and any subrange consisting of any two values therein. When the thickness ratio of the intermediate brazing filler metal layer (1a) to the covering layer (1b) is too high, the covering layer (1b) is relatively too thin, and during the preparation process, the Mg content of the surface layer on the side of the brazing filler-free layer (1) (i.e. the outer surface layer of the covering layer (1 b)) is too high, for example, more than 0.05 wt% along with the diffusion of Mg contained in the intermediate brazing filler metal layer (1a) to the covering layer (1b), so that the brazing filler-free layer (3) side is polluted in the preparation process, the Mg content is increased on the brazing filler-free layer (3) side, and the brazing effect on the brazing filler-free layer (3) side is deteriorated due to the increase of the Mg content. When the thickness ratio of the intermediate solder layer (1a) to the clad layer (1b) is too low, the clad layer (1b) is relatively too thick, and Mg in the intermediate solder layer (1a) is difficult to diffuse during brazing, so that an oxide film on the surface cannot be removed, which is not favorable for brazing. The thickness of the covering layer (1b) is kept in a certain range, and may be 4 to 30 μm. An excessively thin coating layer (1b) may result in Mg contamination on the side of the non-flux layer (3), while an excessively thick coating layer (1b) may be disadvantageous in breaking the oxide film on the side of the non-flux layer (1) and in brazing.

Brazing flux-free layer (3)

The brazing flux-free layer (3) may be a brazing flux layer (3a) containing brazing flux. When the brazing flux-free layer (3) is entirely composed of the brazing flux layer (3a) containing the brazing flux, the amount of the brazing flux can be increased, thereby achieving a better brazing effect.

The flux-free layer (3) can also comprise a general brazing flux layer (3b) and/or (3 b'), so that the requirement on brazing atmosphere during brazing can be reduced while the brazing quality is maintained. The solder layer (3b) can be situated on the side of the solder layer (3a) containing the solder remote from the core layer (2), as shown in fig. 1. In general, the solder layer (3 b') can also be located on the side of the solder layer (3a) containing the solder close to the core layer (2), the structure of which can be seen in fig. 1. The general solder layers (3b) and (3b ') can also be located on both sides of the solder layer (3a) (i.e. on the side remote from the core layer (2) there is the general solder layer (3b) and on the side remote from the core layer (2) there is the general solder layer (3 b'), respectively) simultaneously, as shown in fig. 1.

The structure of the brazing flux-free layer (3) can be flexibly adjusted to meet the actual requirement. In order to reduce rolling defects that may occur on the surface after rolling, and to obtain better surface quality, the surface layer on the flux-free layer (3) side of the layered brazing composite may be provided as a general brazing filler metal layer (3b), such as the structures shown in fig. 1 through 3 and 1 through 4.

The thickness of the brazing flux-free layer (3) can be selected according to actual conditions. The thickness of the brazing flux-free layer (3) can be 4% -25% of that of the layered brazing composite material, so that a good brazing effect is achieved.

The solder layer (3a) containing the flux is composed of a solder (as a matrix) and the flux. Preferably, the flux is uniformly dispersed in the matrix filler metal in the form of particles.

The brazing filler metal in the brazing filler metal layer (3a) containing the brazing flux, which may be a matrix, may be substantially an Al — Si alloy, and may be, for example, AA4045, AA 4343.

The brazing flux layer (3a) containing the brazing flux may contain a brazing flux made of a substance that destroys oxides on the surface to be brazed during brazing. The flux may be an inorganic salt, preferably comprising F, and may further comprise at least one of the following elements: al, K, Li, Na and Cs. Examples of inorganic salts include, but are not limited to: potassium fluoroaluminate (e.g. KAlF)₄、K₂AlF₅·H₂O、K₃AlF₆Etc.), hydroxyfluoroaluminium, fluoroaluminium aluminate, cesium aluminum fluoride, potassium fluorosilicate, etc. Other possible inorganic salts include: AlF₃、NaF、KF、LiF、K_{1- 3}AlF_4-6、Cs_1-3AlF_4-6、Li₃AlF₆And Cs_xAl_yF₂. The above salts may be used alone or in a mixture. Hydrates of the above salts may also be used. In one embodiment, the flux of the flux layer (3a) containing flux is F-Al-K flux. The flux content of the flux layer (3a) containing flux may be 1 to 20 wt%, preferably 2 to 15 wt%, more preferably 2.5 to 12.5 wt%.

The Mg content in the brazing flux layer (3a) containing the brazing flux is controlled within a certain range to ensure brazing quality, for example: the Mg content is 0.2 wt.% or less, preferably 0.1 wt.% or less, more preferably 0.05 wt.% or less, and most preferably 0 wt.%.

In one embodiment, the alloy of the brazing flux layer (3a) containing the brazing flux comprises:

1-20 wt%, preferably 2-15 wt%, more preferably 2.5-12.5 wt%,

si5-14 wt%, preferably 6-13 wt%, more preferably 7-12.5 wt%,

mg < 0.2 wt.%, preferably < 0.1 wt.%, more preferably < 0.05 wt.%,

fe is less than or equal to 0.7 weight percent, Cu is less than or equal to 1.0 weight percent, Zn is less than or equal to 6 weight percent, Sr is less than or equal to 0.05 weight percent,

unavoidable impurities each in an amount of less than 0.05 wt%, and a total content of impurities of less than 0.2 wt%; the balance being Al.

The solder layer (3b) typically consists of a solder, wherein the solder may be substantially an Al — Si alloy, which may be, for example, an AA4045 aluminum alloy. The Mg content in the brazing filler metal layer (3b) is generally controlled within a certain range to ensure brazing quality, for example: the Mg content is 0.2 wt% or less, preferably 0.1 wt% or less, more preferably 0.05 wt% or less, and it is most preferable that Mg is not contained in the general brazing filler metal layer (3 b).

In one embodiment, the alloy of the general solder layer (3b) comprises:

si5-14 wt%, preferably 6-13 wt%, more preferably 7-12.5 wt%,

mg < 0.1 wt.%, preferably < 0.05 wt.%, more preferably < 0.02 wt.%, most preferably 0 wt.%,

fe is less than or equal to 0.7 weight percent, Cu is less than or equal to 1.0 weight percent, Zn is less than or equal to 6 weight percent, Sr is less than or equal to 0.05 weight percent,

unavoidable impurities each in an amount of less than 0.05 wt%, and a total content of impurities of less than 0.2 wt%; the balance being Al.

The general solder layer (3 b') is composed of a solder, and the same alloy composition as the general solder layer (3b) can be used.

Manufacture of layered brazing composites

The present invention relates to a method of making the layered brazing composite of the invention, comprising the steps of:

(S1) preparing a core material layer (2) alloy, a brazing flux-free layer (1) alloy and a brazing flux-free layer (3) alloy;

(S2) rolling the alloy of the flux-free layer (1) and the alloy of the flux-free layer (3) into a plate shape;

(S3) rolling and compounding the slab core material layer (2) alloy, the slab brazing flux-free layer (1) alloy and the slab brazing flux-free layer (3) alloy to obtain a composite body, wherein the slab core material layer (2) alloy is placed between the slab brazing flux-free layer (1) alloy and the slab brazing flux-free layer (3) alloy;

(S4) rolling the composite body to a target thickness;

(S5) softening annealing.

Wherein the step (S1) includes the steps of:

(S1.1) casting the alloy ingot of the core material layer (2);

(S1.2) casting the intermediate brazing filler metal layer (1a) alloy ingot and the covering layer (1b) alloy ingot;

(S1.3) producing the brazing filler metal layer (3a) alloy containing the brazing flux;

optionally including (S1.4) casting said general solder layer (3b) alloy ingot.

The alloy ingot may be cast by any suitable method. In one embodiment, the core layer (2) alloy ingot, the intermediate solder layer (1a) alloy ingot and the cap layer (1b) alloy ingot are cast by semi-continuous Direct water-cooled chill casting (Direct chill casting). In one embodiment, the general brazing filler metal layer (3b) alloy ingot is cast by semi-continuous direct water-cooling chill.

The brazing filler metal layer (3a) alloy containing the brazing filler metal can be produced by a suitable method. In an exemplary embodiment, the alloy of the brazing filler metal layer (3a) containing the brazing flux is produced by spray deposition.

Wherein the step (S2) includes the steps of:

(S2.1) respectively rolling the alloy ingot of the intermediate brazing filler metal layer (1a) and the alloy ingot of the covering layer (1b) into plates;

(S2.2) extruding and rolling the brazing filler metal layer (3a) alloy containing the brazing flux into a plate shape;

optionally (S2.3) rolling the general brazing filler metal layer (3b) and/or (3b ') alloy ingot into a plate shape, and rolling and compounding the plate-shaped brazing filler metal layer (3a) containing the brazing filler metal and the plate-shaped general brazing filler metal layer (3b) and/or (3 b') alloy on one side or two sides thereof.

The alloy ingot may be rolled into a sheet shape by a suitable method. In one embodiment, the intermediate brazing filler metal layer (1a) alloy ingot and the covering layer (1b) alloy ingot are respectively hot-rolled into a plate shape to obtain a corresponding plate-shaped intermediate brazing filler metal layer (1a) alloy and a plate-shaped covering layer (1b) alloy. Wherein the plate-shaped intermediate brazing filler metal layer (1a) alloy and the plate-shaped covering layer (1b) alloy form a plate-shaped brazing filler metal-free layer (1) alloy.

The alloy of the brazing material layer (3a) containing the brazing agent can be formed into a plate shape by an appropriate method. In one embodiment, the brazing filler metal layer (3a) alloy containing the brazing filler metal is extruded and rolled into a plate-like brazing filler metal layer (3a) alloy containing the brazing filler metal.

The plate-shaped brazing flux-free layer (3) alloy may be composed of only a plate-shaped brazing flux layer (3a) alloy containing brazing flux.

The plate-shaped brazing flux-free layer (3) alloy can also be obtained by rolling and compounding a plate-shaped brazing flux layer (3a) alloy containing brazing flux and a plate-shaped general brazing flux layer (3b) and/or (3 b') alloy. The rolling and compounding can be performed by any suitable method, for example: and (6) hot rolling and compounding.

The general brazing filler metal layer (3b) and/or (3b ') alloy ingot may be rolled into a plate shape by a suitable method to obtain a plate-shaped general brazing filler metal layer (3b) and/or (3 b') alloy. In one embodiment, the general brazing filler metal layer (3b) alloy ingot is hot rolled to obtain a plate-like general brazing filler metal layer (3b) and/or (3 b') alloy.

The specific structure (for example, the number of layers contained, the relative position of each layer and the like) of the plate-shaped brazing flux-free layer (3) alloy can be adjusted according to actual needs.

In one embodiment, a single layer plate-like flux-containing solder layer (3a) alloy is roll-compounded with a single layer plate-like general solder layer (3b) or (3 b') alloy to obtain a 2-layer plate-like flux-free layer (3) alloy. In another embodiment, a single-layer plate-like flux-containing solder layer (3a) alloy is roll-compounded with plate-like general solder layers (3b) and (3 b') alloys to obtain a 3-layer plate-like flux-free layer (3) alloy.

In a preferred embodiment, of the 3 plate-like flux-free layer (3) alloys, the plate-like flux-containing (3a) alloy is located between the plate-like general flux layers (3b) and (3 b') alloys.

The thickness of the plate-like alloy rolled in step (S2) needs to be selected according to the thickness ratio of the final product.

In step (S3), the complex may be obtained in any suitable manner. In one embodiment, the composite is obtained using hot roll compounding.

In step (S4), the composite may be rolled to a target thickness in any suitable manner. In one embodiment, the composite is cold rolled to a target thickness. The target thickness is determined based on the desired thickness of the layered brazing composite. In one embodiment, the target thickness is 0.15 to 3mm, e.g. 0.4mm, 0.48 mm.

In the step (S5), the softening annealing can improve and reduce the rolling oil residue, eliminate the internal stress and reduce the strength, and prevent the cracking caused in the subsequent processing. The temperature of the softening annealing can be reasonably selected according to the specific composition of the layered brazing composite material. But should be below the melting temperature of the braze contained in the layered brazing composite to avoid melting of the braze during the softening annealing. In one embodiment, the temperature of the softening anneal is from 200 ℃ to 450 ℃, e.g., 340 ℃, 420 ℃.

The softening annealing temperature is increased, and the thickness ratio of the intermediate brazing filler metal layer (1a) to the covering layer (1b) in the brazing filler metal-free layer (1) needs to be correspondingly increased, so that the qualified layered brazing composite material is obtained. In one embodiment, the softening annealing temperature is 420 ℃, and the thickness ratio of the intermediate solder layer (1a) to the capping layer (1b) is 2.5: 1. In a specific embodiment, the softening annealing temperature is 340 ℃, and the thickness ratio of the intermediate solder layer (1a) to the capping layer (1b) is 7: 1.

The invention also relates to a heat exchanger comprising the layered brazing composite of the invention. In a preferred embodiment, the flux-free layer (1) is located on the liquid medium side, wherein it is generally required that the flux residue in the liquid medium is below a certain level. The liquid medium includes, but is not limited to, the heat exchanger coolant, pure water, and the like.

Advantageous effects

The layered brazing composite material has a brazing flux-free layer and a brazing flux-free layer, can form a satisfactory brazing joint and reduce the level of brazing flux in a furnace under the general controllable atmosphere brazing condition, thereby obviously reducing the pollution of the brazing flux to the surface of an inner cavity and simultaneously meeting the requirement of the residual brazing flux on the side of a cooling liquid/medium or the side of the inner cavity. Suitable for fuel cells and heat exchangers for electrical/electronic thermal management.

Meanwhile, in the processes of production, storage and transportation of the layered brazing composite material, Mg pollution possibly caused by a brazing flux-free layer due to a brazing flux-free layer can be avoided, so that a satisfactory brazing effect is obtained in the brazing using process.

Examples

The present invention will be described in further detail with reference to specific examples.

It should be noted that the following examples are only for clearly illustrating the technical solutions of the present invention, and are not intended to limit the present invention. It will be apparent to those skilled in the art that other variations and modifications may be made in the foregoing disclosure without departing from the spirit or essential characteristics of the invention, and it is not desired to exhaustively enumerate all embodiments, but rather those obvious variations and modifications are within the scope of the invention. Unless otherwise indicated, both the instrumentation and reagent materials used herein are commercially available.

The compositions of the layered brazing composites prepared are shown in table 1.

TABLE 1

Example 1

Step 1: the alloy of the core material layer (2) is subjected to semi-continuous direct water cooling and chilling, and the alloy of the brazing filler metal layer (3a) containing the brazing flux is produced by spray deposition, and the compositions of the alloy are shown in the table 1.

Step 2: the alloy cast ingots of the intermediate brazing filler metal layer (1a), the alloy cast ingots of the covering layer (1b) and the alloy cast ingots of the common brazing filler metal layer (3b) are respectively hot-rolled into thick plates with the thicknesses of 50mm, 20mm and 50mm, and the alloy of the brazing filler metal layer (3a) containing the brazing flux is extruded and rolled into a thick plate with the thickness of 50 mm.

Placing the brazing filler metal layer (3a) alloy thick plate containing the brazing filler metal between a common brazing filler metal layer (3b) alloy thick plate and a common brazing filler metal layer (3 b') alloy (AA4045) cast ingot, performing hot rolling compounding, and further rolling to 50mm to obtain a 3-layer brazing filler metal layer-free (3) alloy thick plate.

And step 3: the alloy thick plate of the core material layer (2) is placed between the alloy thick plate of the brazing flux-free layer (1) and the alloy thick plate of the brazing flux-free layer (3), and then the alloy of the core material layer (2), the alloy thick plate of the brazing flux-free layer (1) and the alloy thick plate of the brazing flux-free layer (3) are rolled and compounded to obtain a composite body, wherein the specific structure is shown in figure 2.

And 4, step 4: the composite was cold rolled to 0.48 mm.

And 5: softening and annealing at 420 ℃ to obtain a layered brazing composite plate;

the cross-sectional structure of the finally obtained layered brazing composite plate is schematically shown in FIG. 2.

The thickness of the core material layer (2) is 365 mu m. The thickness of the brazing filler metal-free layer (1) was 67 μm, the thickness of the intermediate brazing filler metal layer (1a) was 48 μm, and the thickness of the covering layer (1b) was 19 μm. The thickness of the solder-free layer (3) is 48 μm, wherein the total thickness of the solder layers (3b) and (3 b') is generally 44 μm, and the thickness of the solder layer (3a) containing solder is 4 μm.

Wherein the thickness ratio of the intermediate solder layer (1a) to the covering layer (1b) is 2.5: 1.

Example 2

The preparation method is the same as example 1, and is different from the following steps: the thickness ratio of the intermediate solder layer (1a) to the covering layer (1b) was 7: 1. In step 4, the composite was cold rolled to 0.40 mm. And 5: softening and annealing at 340 ℃ to obtain the layered brazing composite plate.

The cross-sectional structure of the finally obtained layered brazing composite plate is schematically shown in FIG. 2. The thickness of the core material layer (2) is 300 mu m. The thickness of the brazing filler metal-free layer (1) is 62 μm, wherein the thickness of the intermediate brazing filler metal layer (1a) is 55 μm and the thickness of the covering layer (1b) is 7 μm. The thickness of the flux-free layer (3) is 38 μm, wherein the total thickness of the solder layers (3b) and (3 b') is generally 34 μm, and the thickness of the solder layer (3a) containing the flux is 4 μm.

Comparative example 1

The preparation method is the same as example 1, and is different from the following steps: the thickness ratio of the intermediate solder layer (1a) to the covering layer (1b) was 22: 1. In step 4, the composite was cold rolled to 0.40 mm. And 5: softening and annealing at 340 ℃ to obtain the layered brazing composite plate.

The cross-sectional structure of the finally obtained layered brazing composite plate is schematically shown in FIG. 2. The thickness of the core material layer (2) is 290 μm. The thickness of the brazing filler metal-free layer (1) is 69 μm, wherein the thickness of the intermediate brazing filler metal layer (1a) is 66 μm and the thickness of the covering layer (1b) is 3 μm. The thickness of the solder-free layer (3) is 41 μm, wherein the total thickness of the solder layers (3b) and (3 b') is generally 36 μm, and the thickness of the solder layer (3a) containing solder is 5 μm.

Comparative example 2

The preparation method is the same as example 1, and is different from the following steps: the thickness ratio of the intermediate solder layer (1a) to the covering layer (1b) is 1: 1. In step 4, the composite is cold rolled to 0.48 mm. And 5: softening and annealing at 420 ℃ to obtain the layered brazing composite plate.

The cross-sectional structure of the finally obtained layered brazing composite plate is schematically shown in FIG. 2. The thickness of the core material layer (2) is 360 mu m. The thickness of the brazing filler metal-free layer (1) is 70 μm, wherein the thickness of the intermediate brazing filler metal layer (1a) is 35 μm, and the thickness of the covering layer (1b) is 35 μm. The thickness of the flux-free layer (3) is 50 μm, wherein the total thickness of the solder layers (3b) and (3 b') is generally 45 μm, and the thickness of the solder layer (3a) containing the flux is 5 μm.

Examples of the experiments

GD-OES (glow Spectroscopy) testing

The instrument comprises the following steps: GDA750 (supplier: SPECTR M MA).

Detection standard: ISO/TS 25138 ISO 14707.

The layered brazing composite plate of comparative example 1 and example 1 was subjected to GD-OES test on the brazing flux-free layer (1) side and the brazing flux-free layer (3) side, respectively. The test results of the side without flux layer (1) and the side without flux layer (3) in comparative example 1 are shown in fig. 3(a) and 3(b), respectively, and the test results of the side without flux layer (1) and the side without flux layer (3) in example 1 are shown in fig. 4(a) and 4(b), respectively. Fig. 3(a) shows that the Mg content at a distance of 0 μm from the surface on the side of the flux-free layer (1) of comparative example 1 (i.e., the side surface of the flux-free layer (1)) is about 0.08% by weight, while fig. 3(b) shows that the surface layer on the side of the flux-free layer (3) of comparative example 1 is contaminated with Mg and the Mg content in the side of the flux-free layer (3) within a distance of about 0.5 μm from the surface is higher than 0.05% by weight. In contrast, FIG. 4(a) shows that the Mg content of the surface layer on the side of the non-flux layer (1) of example 1 was kept in a low range, and the Mg content within a distance of 10 μm from the surface was 0.05 wt% or less. Fig. 4(b) shows that the flux-free layer (3) side of example 1 is not contaminated with Mg, and its Mg content remains in a very low range, about 0.02 wt%. The above results show that when the ratio of the thickness of the intermediate brazing filler metal layer (1a) to the thickness of the covering layer (1b) is too high, the magnesium content of the surface layer on the brazing filler-free layer (1) side is too high, and the brazing filler-free layer (3) side is contaminated during the production process, which affects the final brazing quality on the brazing filler-free layer (3) side.

Brazing of layered brazing clad sheets

Brazing conditions are as follows: heating to 600 ℃ in 21 minutes, and keeping the temperature for 3 minutes, wherein the oxygen content is less than 50ppm, and the dew point is less than-40 ℃. Brazing was carried out in a SECO/WARWICK 2 chamber batch furnace.

Metallographical microscope picture

The instrument comprises the following steps: ziess upright metallographic microscope.

Detection conditions are as follows: the sample is inlaid, polished, eroded by 0.5% HF water solution for 10-20 seconds, then flattened and placed under a microscope for observation and photographing.

The sides of the flux-free layer (1) of example 2 and comparative example 2 were each subjected to non-composite fin brazing under the brazing conditions as described above. Fig. 5 is a microscopic picture of the metallographic phase of the brazing material obtained in example 2, and during the brazing process, Mg contained in the intermediate brazing material layer (1a) on the side of the brazing material-free layer (1) can smoothly diffuse to the surface layer, so that the oxide film on the surface is broken, the brazing is smoothly completed, and a brazed joint with good quality is obtained. Comparative example 2 a metallographic microscope picture after brazing is shown in figure 6. The results show that in comparative example 2, Mg in the side of the non-flux layer (1) could not diffuse out under the same brazing conditions as described above, so that the oxide film on the surface could not be removed and a brazed joint could not be formed. Therefore, when the thickness ratio of the intermediate solder layer (1a) to the coating layer (1b) is too low, brazing cannot be completed.

Example 1 the flux-free layer (3) side was brazed to a non-composite fin, and a metallographic microscope photograph thereof is shown in fig. 7. Example 1 the side without the flux layer (1) was brazed to a non-composite fin, and a metallographic microscope photograph thereof is shown in fig. 8. Fig. 7-8 show that either the flux-free layer (3) side or the flux-free layer (1) side of the layered brazing composite sheet of the present invention can be brazed to a non-composite fin and form a good quality brazed joint.

Example 1 plate/plate brazing was performed between the sides of the flux-free layer (3), and a metallographic microscope photograph thereof is shown in fig. 9 (a). Example 1 plate/plate brazing was performed between the sides of the flux-free layer (1), and a metallographic microscope photograph thereof is shown in fig. 9 (b). Example 1 plate/plate brazing was performed between the flux-free layer (3) side and the non-composite AA3003 plate, and the metallographic microscope photograph thereof is shown in fig. 9 (c). Example 1 plate/plate brazing was performed between the side without the flux layer (1) and the non-composite AA3003 plate, and the metallographic microscope picture thereof is shown in fig. 9 (d). Fig. 7 shows that the brazing laminate according to the invention, either on the flux-free (3) side or on the flux-free (1) side, can be brazed to a clad laminate (e.g. the brazing laminate according to the invention) or to a non-clad laminate (e.g. an AA3003 laminate) with good brazing quality.