Aluminum alloy clad material having excellent brazing performance

Abstract

To provide an aluminum alloy clad material for brazing use.SOLUTION: An aluminum alloy clad material in which a first brazing material layer is arranged on one face of a core material, a second brazing material layer is arranged on the other face of the core material, the first brazing material layer is made of Al-Si alloy, and the second brazing material layer is made of Al-Si-Mg-Bi alloy. It is preferable that the first brazing material layer contain Si:2.0 to 14.0% in mass%, and have a composition of the balance Al and inevitable impurities, and the second brazing material layer contain Si:2.0 to 14.0% in mass, Mg:0.01 to 4.0%, Bi:0.005 to 1.0%, and have a composition of the balance Al and inevitable impurities.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy clad material having excellent brazability. [Background technology]

[0002] Aluminum alloy automotive heat exchangers, such as radiators, condensers, and oil coolers, are manufactured by brazing. Currently, the brazing method using fluoride-based flux is the mainstream, but if the material contains Mg, the flux reacts with the Mg and becomes inactive, significantly impeding the brazing process. For this reason, the Mg content of aluminum alloys used in automotive heat exchangers is restricted.

[0003] However, if the restrictions on Mg content could be lifted, there would be significant benefits, such as even higher strength and thinner materials and improved recycling rates. Therefore, a brazing technology that can join Mg-added aluminum alloys without using flux is desired. While flux achieves brazing by breaking down the tough natural oxide film that forms on the aluminum surface, Mg can also play a similar role by destroying the aluminum oxide film. However, after destroying the aluminum oxide film, Mg generates MgO on the material surface, which inhibits brazing.

[0004] Patent Document 1 discloses a technique in which Li and Ca are added to a brazing filler metal along with Mg to destroy the oxide film formed on the surface of the brazing filler metal, effectively exposing the newly formed surface of the molten brazing filler metal. Patent Document 2 describes an aluminum alloy brazing sheet in which Si, Mg, and Bi are contained in the brazing filler metal, and the content of alkaline earth metals Ca, Sr, and Ba is kept low, in order to suppress the effects of reaction products between the alkaline earth metals contained in the master alloy and the Bi contained in the brazing filler metal. Furthermore, Patent Document 3 below discloses a technology in which specific amounts of Mn, Mg, Fe, and Si are contained in the core material of an aluminum alloy brazing sheet, and specific amounts of Si, Mn, Ti, Zr, Cr, and Bi are contained in the brazing filler metal, thereby suppressing Mg diffusion to the brazing filler metal surface during brazing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 204167 [Patent Document 2] Patent Publication No. 2021-21107 [Patent Document 3] Patent Publication No. 2021-13936 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, various techniques have been investigated to embrittle MgO by adding Bi to the brazing filler metal, but this has not yet achieved sufficient bondability in flux-free brazing. Based on the background described above, the inventors of the present application have studied flux-free brazing technology and have found that excellent brazing properties can be obtained by using an Al-Si-Mg-Bi composition for one of the brazing filler metals applied to both sides of the core material and an Al-Si composition for the other brazing filler metal.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide an aluminum alloy clad material that can be applied to fluxless brazing and can ensure excellent brazing properties using a technology in which Mg and Bi are added to the brazing filler metal. [Means for solving the problem]

[0008] (1) The aluminum alloy clad material having excellent brazing properties according to this embodiment is an aluminum alloy clad material used for brazing joints without using flux, characterized in that a first brazing filler metal layer is disposed on one side of a core material and a second brazing filler metal layer is disposed on the other side of the core material, the first brazing filler metal being made of an Al-Si alloy, and the second brazing filler metal 2 being made of an Al-Si-Mg-Bi alloy. (2) In the aluminum alloy clad material having excellent brazing properties according to this embodiment, it is preferable that the first brazing filler metal layer is made of an aluminum alloy containing, by mass%, 2.0 to 14.0% Si, with the balance being Al and unavoidable impurities, and the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, 2.0 to 14.0% Si, 0.01 to 4.0% Mg, and 0.005 to 1.0% Bi, with the balance being Al and unavoidable impurities. (3) In the aluminum alloy clad material having excellent brazability according to this embodiment, in the second brazing material layer, when observed in the surface (RD-TD) direction, Mg-Bi based intermetallic compounds having a circle equivalent diameter of 0.01 μm or more and less than 5.0 μm are present in an area of ​​10,000 μm or more. 2 Preferably there are more than 10 per field of view. (4) In the aluminum alloy clad material having excellent brazeability according to (1) or (2) of this embodiment, the second brazing filler metal layer preferably has an atomic concentration ratio of Mg to Bi of Mg / Bi=1.5 or more. (5) In the aluminum alloy clad material having excellent brazeability as described in (3) of this embodiment, the second brazing filler metal layer preferably has an atomic concentration ratio of Mg to Bi of Mg / Bi=1.5 or more.

[0009] (6) In the aluminum alloy clad material having excellent brazability according to (1) or (2) of this embodiment, it is preferable that the Mg content of the first brazing filler metal layer is restricted to less than 0.05% by mass. (7) In the aluminum alloy clad material having excellent brazeability as described in (3) according to this embodiment, it is preferable that the Mg content of the first brazing filler metal layer is restricted to less than 0.05% by mass. (8) In the aluminum alloy clad material having excellent brazability as described in (4) according to this embodiment, it is preferable that the Mg content of the first brazing filler metal layer is restricted to less than 0.05% by mass.

[0010] (9) In the aluminum alloy clad material having excellent brazability described in (1) or (2) according to this embodiment, it is preferable that the core material is made of an aluminum alloy containing, by mass%, one or more of Mn: 0.1 to 2.0%, Si: 0.1 to 1.5%, Fe: 0.05 to 1.0%, Cu: 0.01 to 2.0%, Mg: 0.01 to 2.0%, Zn: 0.01 to 5.0%, Zr: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Ti: 0.01 to 0.3%, and Bi: 0.005 to 1.5%, with the remainder being Al and unavoidable impurities. (10) In the aluminum alloy clad material having excellent brazability described in (3) of this embodiment, the core material is preferably made of an aluminum alloy containing, by mass%, one or more of Mn: 0.1-2.0%, Si: 0.1-1.5%, Fe: 0.05-1.0%, Cu: 0.01-2.0%, Mg: 0.01-2.0%, Zn: 0.01-5.0%, Zr: 0.01-0.3%, Cr: 0.01-0.5%, Ti: 0.01-0.3%, and Bi: 0.005-1.5%, with the remainder being Al and unavoidable impurities. (11) In the aluminum alloy clad material having excellent brazability described in (4) according to this embodiment, the core material is preferably made of an aluminum alloy containing, by mass%, one or more of Mn: 0.1-2.0%, Si: 0.1-1.5%, Fe: 0.05-1.0%, Cu: 0.01-2.0%, Mg: 0.01-2.0%, Zn: 0.01-5.0%, Zr: 0.01-0.3%, Cr: 0.01-0.5%, Ti: 0.01-0.3%, and Bi: 0.005-1.5%, with the remainder being Al and unavoidable impurities. (12) In the aluminum alloy clad material having excellent brazability described in (6) according to this embodiment, the core material is preferably made of an aluminum alloy containing, by mass%, one or more of Mn: 0.1-2.0%, Si: 0.1-1.5%, Fe: 0.05-1.0%, Cu: 0.01-2.0%, Mg: 0.01-2.0%, Zn: 0.01-5.0%, Zr: 0.01-0.3%, Cr: 0.01-0.5%, Ti: 0.01-0.3%, and Bi: 0.005-1.5%, with the remainder being Al and unavoidable impurities.

[0011] (13) In the aluminum alloy clad material having excellent brazing properties described in (1) or (2) according to this embodiment, it is preferable that the first brazing filler metal layer or the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, one or more of Fe, Sr, Na, Cr, B, Ni, and Sb, each in an amount of 0.6% or less, with the remainder being Al and unavoidable impurities. (14) In the aluminum alloy clad material having excellent brazing properties described in (3) according to this embodiment, it is preferable that the first brazing filler metal layer or the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, one or more of Fe, Sr, Na, Cr, B, Ni, and Sb, each in an amount of 0.6% or less, with the remainder being Al and unavoidable impurities. (15) In the aluminum alloy clad material having excellent brazing properties described in (4) according to this embodiment, it is preferable that the first brazing filler metal layer or the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, one or more of Fe, Sr, Na, Cr, B, Ni, and Sb, each in an amount of 0.6% or less, with the remainder being Al and unavoidable impurities. (16) In the aluminum alloy clad material having excellent brazing properties described in (6) according to this embodiment, it is preferable that the first brazing filler metal layer or the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, one or more of Fe, Sr, Na, Cr, B, Ni, and Sb, each in an amount of 0.6% or less, with the remainder being Al and unavoidable impurities. (17) In the aluminum alloy clad material having excellent brazing properties described in (9) according to this embodiment, it is preferable that the first brazing filler metal layer or the second brazing filler metal layer is made of an aluminum alloy containing, by mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, one or more of Fe, Sr, Na, Cr, B, Ni, and Sb, each in an amount of 0.6% or less, with the remainder being Al and unavoidable impurities.

[0012] (18) In the aluminum alloy clad material having excellent brazability according to (1) or (2) of this embodiment, the outermost surface of the brazing material layer is preferably an etched outermost surface having a thickness of 5 nm or more. (19) In the aluminum alloy clad material having excellent brazability as described in (3) according to this embodiment, it is preferable that the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more. (20) In the aluminum alloy clad material having excellent brazability as described in (4) according to this embodiment, it is preferable that the outermost surface of the brazing material layer is an outermost surface that has been etched to a thickness of 5 nm or more. (21) In the aluminum alloy clad material having excellent brazability as described in (6) according to this embodiment, it is preferable that the outermost surface of the brazing material layer is an outermost surface that has been etched to a thickness of 5 nm or more. (22) In the aluminum alloy clad material having excellent brazability as described in (9) according to this embodiment, it is preferable that the outermost surface of the brazing material layer is an outermost surface that has been etched to a thickness of 5 nm or more. (23) In the aluminum alloy clad material having excellent brazability as described in (13) according to this embodiment, it is preferable that the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more. [Effects of the Invention]

[0013] The aluminum alloy clad material for fluxless brazing according to the present invention has excellent gap-filling properties during brazing, allowing brazing in which the brazing filler metal is well filled even in small gaps, and also provides an aluminum alloy clad material that can be brazed by increasing the fluidity of the brazing filler metal, allowing brazing in which the brazing filler metal is well filled even in gaps that are located far apart. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an aluminum alloy clad material according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a side view showing a test material including an aluminum alloy clad material used in a molten brazing filler flow test in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an example of an embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings used in the following description may show characteristic portions in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand.

[0016] As shown in Figure 1, the aluminum alloy clad material A for fluxless brazing of the first embodiment of the present invention has a three-layer structure in which a first brazing material layer 1 is laminated on one side (upper side) of a sheet-like core material C made of an aluminum alloy, and a second brazing material layer 2 is laminated on the other side (lower side).

[0017] The aluminum alloy clad material A according to the present invention may have a different structure. For example, a multilayer structure may be adopted in which the core material C has a multi-layer structure, or another layer, such as an intermediate layer, may be interposed between the core material C and the first brazing filler metal layer 1, or between the core material C and the second brazing filler metal layer 2. For example, a combination of the first brazing filler metal layer or the second brazing filler metal layer / intermediate layer / core material / second brazing filler metal layer or the first brazing filler metal layer, or a combination of the first brazing filler metal layer or the second brazing filler metal layer / intermediate layer / core material / intermediate layer / second brazing filler metal layer or the first brazing filler metal layer, may be realized. Furthermore, the aluminum alloy clad material A may have a multilayer structure with three or more layers, such as a three- to seven-layer structure. In this embodiment, the first brazing filler metal layer 1 and the second brazing filler metal layer 2 are formed on both sides of the core material C, and they only need to constitute the outermost surface, so there is no limit to the number of layers in the aluminum alloy clad material A.

[0018] When the aluminum alloy clad material A is heated to a temperature equal to or higher than the melting temperature of the brazing filler metal layers 1 and 2, the brazing filler metal layers 1 and 2 melt and the brazing filler metal wets and spreads on one or both sides of the aluminum alloy clad material A, and the aluminum alloy clad material A is used to braze other components to be brazed to the aluminum alloy clad material A. The aluminum alloy clad material A can also be used for fluxless brazing applications. When the aluminum alloy clad material A is applied to a heat exchanger, it is processed into a required shape, such as a tube or other heat exchanger component, and is heated for brazing while being brought close to or in contact with the object to be brazed. In this embodiment, an effect is obtained when the brazing filler metal 1 and the brazing filler metal 2 are joined together. For example, this is effective when the clad material A is processed into a cup shape and laminated, or when it is processed into a tube shape and the brazing material 1 and the brazing material 2 are joined so that they come into contact with each other at the joining portion.

[0019] In the aluminum alloy clad material A of this embodiment, it is important to use an Al-Si-Mg-Bi based brazing filler metal containing Mg and Bi as one brazing filler metal, and to use a brazing filler metal that does not substantially contain Mg or contains a small amount of Mg as the other brazing filler metal. For example, when joining the first brazing filler metal layer 1 and the second brazing filler metal layer 2 of a double-sided clad material in the crimped portion of a B-type tube or in a laminated heat exchanger, if both layers contain Mg, the brazing property will be reduced due to the formation of MgO in the surface layer of each brazing filler metal. By containing Mg in only one brazing material and leaving the other Mg-free, it is possible to suppress the generation of excessive MgO at the joint interface while ensuring a sufficient amount of brazing fillet to form a fillet at the joint, resulting in good brazing properties.

[0020] Each layer constituting the aluminum alloy clad material A will be described in detail below. "First brazing layer" The first brazing filler metal layer 1 is made of an Al-Si alloy containing, for example, 2.0 to 14.0% by mass of Si, with the remainder being Al and unavoidable impurities. The first brazing filler metal layer 1 may also contain other elements, which will be described later. In this specification, when a specific range is expressed using "to," the range includes the lower and upper limits unless otherwise noted. Therefore, 2.0 to 14.0% means a range of 2.0% or more and 14.0% or less. Si: 2.0 to 14.0% In the first brazing filler metal layer 1, Si is an element necessary for forming the brazing filler metal and for forming a fillet after brazing. If the Si content is less than 2.0%, the molten brazing filler metal will be insufficient, resulting in insufficient flet formation during brazing. If the Si content exceeds 14.0%, the material will become brittle, making it difficult to manufacture the material. It is preferable to limit the Mg content to less than 0.05% in the first brazing filler metal layer 1. It is preferable that the first brazing filler metal layer 1 does not contain Mg, and by limiting it to less than 0.05%, better brazing properties can be obtained.

[0021] "Second brazing layer" The second brazing filler metal layer 2 is made of an Al-Si-Mg-Bi alloy containing, by mass %, 2.0 to 14.0% Si, 0.01 to 4.0% Mg, 0.005 to 1.0% Bi, with the remainder being Al and unavoidable impurities. Si: 2.0 to 14.0% In the second brazing material layer 2, Si is an element necessary for forming the brazing material. If the Si content is less than 2.0%, the fret formation during brazing will be insufficient, and if the Si content exceeds 14.0%, the material will become brittle and difficult to manufacture. Mg: 0.01 to 4.0% Mg is added to reduce and decompose the aluminum oxide film (Al2O3). If the Mg content is below the lower limit, the effect is insufficient, but if it is above the upper limit, the material strength is too high, making it difficult to manufacture, and the dense MgO film formed on the material surface reduces brazing joinability. Bi: 0.005 to 1.0% Bi penetrates and concentrates in the MgO film during the brazing temperature rise process, weakening the MgO and improving brazability. If the content is below the lower limit, the effect is insufficient, but if it is above the upper limit, the effect saturates and corrosion resistance decreases. In addition, elements that are generally inevitably contained in aluminum alloys may also be contained, and this does not impair the effects of the present invention and is therefore permissible.

[0022] In the second brazing material layer 2, by observing the surface (RD-TD) direction, it was found that Mg-Bi based intermetallic compounds having a circle equivalent diameter of 0.01 μm or more and less than 5.0 μm were present in an area of ​​10,000 μm. 2 There are more than 10 per field of view. The dispersion of such fine Mg-Bi intermetallic compounds makes it easier to melt the compounds during the brazing temperature rise process, and uniformly distributing Bi in the brazing material makes it possible to uniformly embrittle MgO. If there are 10 or fewer Mg-Bi intermetallic compounds per field, sufficient effect cannot be obtained and brazability deteriorates. For the same reason, it is desirable that there are 20 or more Mg-Bi intermetallic compounds dispersed per field. The dense and fine dispersion of the Mg-Bi intermetallic compounds as described above can be achieved by controlling the cooling rate during casting, the homogenization treatment conditions, the rolling time at a specified temperature during hot rolling, and the reduction rate per pass during cold rolling.

[0023] In the second brazing material layer 2, the atomic concentration ratio of Mg to Bi (Mg / Bi) is preferably 1.5 or more. By satisfying the above atomic concentrations, it is possible to suppress the generation of elemental Bi in the second brazing filler metal layer 2 and improve brazability. If the atomic concentration ratio (Mg / Bi) is less than 1.5, the generation of elemental Bi may cause a significant growth of an oxide film on aluminum, which may result in a decrease in brazability.

[0024] "Other common elements between the first and second brazing filler metal layers" The first brazing filler metal layer 1 and the second brazing filler metal layer 2 may contain specific amounts of one or more of the elements described below. Cu: 0.01 to 1.0% Cu is concentrated in the eutectic α phase, which is the final solidification portion after brazing, reducing the potential difference with the primary α phase and improving corrosion morphology. If the Cu content is below the lower limit, the effect is insufficient, and if it exceeds the upper limit, corrosion resistance decreases. Mn: 0.01 to 1.0% Mn increases the viscosity of the brazing filler metal, preventing the filler metal from concentrating locally due to gravity or capillary force. If the Mn content is below the lower limit, the effect is insufficient, while if it exceeds the upper limit, large intermetallic compounds are formed during casting, reducing rollability. Ti: 0.01 to 0.3% Ti increases the viscosity of the brazing filler metal, preventing the filler metal from concentrating locally due to gravity or capillary force. If the Ti content is below the lower limit, the effect is insufficient, but if it exceeds the upper limit, large intermetallic compounds are formed during casting, reducing rollability.

[0025] Zr: 0.01 to 0.3% Zr increases the viscosity of the brazing filler metal, preventing the filler metal from concentrating locally due to gravity or capillary force. If the Zr content is below the lower limit, the effect is insufficient, while if it exceeds the upper limit, large intermetallic compounds are formed during casting, reducing rollability. Zn: 0.01 to 5.0% Zn can be added as desired because it dissolves in the matrix and reduces the natural potential of the material, thereby providing a sacrificial corrosion protection effect. However, if the Zn content exceeds the upper limit, the self-corrosion resistance will be significantly reduced. Fe, Sr, Na, Cr, B, Ni, Sb, one or more of which is 0.6% or less each These elements form intermetallic compounds and are distributed on the surface of the brazing filler metal, suppressing the formation of a dense oxide film at that location and serving as the starting point for joining, thereby improving brazing performance. If the content of each of these elements exceeds 0.6%, large intermetallic compounds are formed during casting, reducing rollability. Therefore, it is preferable that the content of one or more of Fe, Sr, Na, Cr, B, Ni, and Sb is individually 0.6% or less. After manufacturing a clad material by combining the first brazing filler metal layer 1 and the second brazing filler metal layer 2 having the aforementioned composition with a core material C having the composition described below, it is preferable to carry out an etching treatment in order to remove an oxide film or coarse oxides that may have formed on the outermost layer. It is preferable to remove the outermost layer of the first brazing filler metal layer 1 and the second brazing filler metal layer 2 by etching, the layer having a thickness of about 5 nm.

[0026] "Heartwood" Although a wide range of common aluminum alloys can be used for the core material C of this embodiment, the following composition can be used as an example. The core material C is preferably made of an aluminum alloy containing, for example, by mass, one or more of the following elements: Mn: 0.1-2.0%, Si: 0.1-1.5%, Fe: 0.05-1.0%, Cu: 0.01-2.0%, Mg: 0.01-2.0%, Zn: 0.01-5.0%, Zr: 0.01-0.3%, Cr: 0.01-0.5%, Ti: 0.01-0.3%, and Bi: 0.005-1.5%, with the remainder being Al and unavoidable impurities.

[0027] The elements contained in the aluminum alloy that constitutes the core material C will be described below. Mn: 0.1 to 2.0% Mn is added to improve material strength by precipitating as intermetallic compounds such as Al-Mn, Al-Mn-Si, Al-Mn-Fe, and Al-Mn-Si-Fe. If the content is below the lower limit, the effect is insufficient, but if it is above the upper limit, large intermetallic compounds (crystallized particles) are formed during casting, reducing rollability. Si: 0.1 to 1.5% Silicon is added to improve material strength by forming a solid solution, and also by precipitating as intermetallic compounds such as Al-Mn-Si and Al-Mn-Si-Fe. If the content is below the lower limit, the effect is insufficient, and if it is above the upper limit, the melting point of the material decreases.

[0028] Fe: 0.05 to 1.0% Fe is added to improve material strength by precipitating as intermetallic compounds such as Al-Mn-Fe and Al-Mn-Si-Fe. If the content is below the lower limit, costs will increase, and if it is above the upper limit, large intermetallic compounds (crystallized particles) will form during casting, reducing rollability. Cu: 0.01 to 2.0% Cu is added to dissolve in the matrix to improve the strength of the material. If the content is below the lower limit, the effect is insufficient, but if the content is above the upper limit, the material strength becomes too high, making it difficult to manufacture the material. Mg: 0.01 to 2.0% Mg is added to improve material strength by forming a solid solution and by precipitating as intermetallic compounds such as Mg2Si. If the content is below the lower limit, the effect is insufficient, but if it is above the upper limit, the material strength becomes too high, making it difficult to manufacture the material.

[0029] Zn: 0.01 to 5.0% Zn is added to the base material to make the natural potential of the material more base than other components, and to improve the pitting corrosion resistance of the clad material through its sacrificial corrosion protection effect. If the content is below the lower limit, the effect is insufficient, but if it is above the upper limit, the potential becomes too base, increasing the rate of self-corrosion. Zr: 0.01 to 0.3% Zr forms fine intermetallic compounds to improve material strength. If the content is below the lower limit, the effect is insufficient, but if the content is above the upper limit, large intermetallic compounds are formed during casting, reducing rollability. Cr: 0.01 to 0.5% Cr forms fine intermetallic compounds to improve material strength. If the content is below the lower limit, the effect is insufficient, but if the content is above the upper limit, large intermetallic compounds are formed during casting, reducing rollability.

[0030] Ti: 0.01 to 0.3% Ti forms fine intermetallic compounds to improve material strength. If the content is below the lower limit, the effect is insufficient, but if the content is above the upper limit, large intermetallic compounds are formed during casting, reducing rollability. Bi: 0.005 to 1.5% Bi partially diffuses into the brazing filler metal layer, contributing to the embrittlement of MgO formed on the surface of the brazing filler metal layer. If the content is below the lower limit, the effect is insufficient, but if it exceeds the upper limit, large intermetallic compounds are formed during casting, reducing rollability.

[0031] "About the manufacturing method of clad materials" The raw material for the first brazing filler metal layer 1 and the raw material for the second brazing filler metal layer 2 can be manufactured through processes such as casting, homogenization treatment, soaking treatment, facing, and hot rolling. The core material C can be manufactured through steps such as casting, homogenization, and facing. Once the base material for the first brazing filler metal layer 1, the base material for the second brazing filler metal layer 2, and the base material for the core material C are prepared, they can be made into a clad material by clad rolling. In clad rolling, two brazing material materials and a core material are assembled, and then the clad material is obtained through soaking, hot rolling, and cold rolling. Intermediate annealing and final annealing can be performed between these processes as needed. Etching can also be performed during the cold rolling process, or between the processes after the cold rolling process and the brazing heat treatment.

[0032] In the above-described process, when preparing the second brazing filler metal layer 2, it is preferable that the cooling rate during casting of the cast material from which the second brazing filler metal layer is made be in the following condition. Cooling rate of 0.1°C / s or more. If the cooling rate during casting is less than the specified rate, the Mg-Bi intermetallic compounds will grow coarsely, making it impossible to densely distribute compounds of the specified size. For the same reason, a cooling rate of 1°C / s or more during casting is desirable. Homogenization conditions when manufacturing the base material for the second brazing layer Homogenization at a temperature between 400°C and 550°C for 1 to 10 hours. By performing homogenization at the specified temperature, the Mg-Bi intermetallic compounds can be distributed sufficiently densely. Homogenization temperatures below 400°C do not produce sufficient results. Homogenization temperatures above 550°C cause the material to melt. For the same reason, it is desirable to use a homogenization temperature between 430°C and 530°C. A homogenization time of approximately 3 to 8 hours can be used.

[0033] "Temperature and time in hot rolling of clad materials" Regarding the temperature and time in hot rolling of the clad material, it is preferable to set the rolling time between 400 and 500°C to 5 minutes or more. By meeting the specified rolling time in which dynamic strain is introduced in the specified high temperature range, it is possible to promote the precipitation of Mg-Bi-based intermetallic compounds of the specified size defined in the present invention in the core material C. If the specified time is not met, sufficient effects cannot be obtained. For the same reason, a rolling time of 10 minutes or more is desirable.

[0034] "Reduction rate per pass in cold rolling of clad materials" Regarding the reduction rate per pass in cold rolling of clad material, it is preferable to set the reduction rate per pass to 25% or more for plate thicknesses of 0.5 mm or more. By achieving a predetermined reduction rate, the Mg-Bi-based intermetallic compounds can be crushed and densely distributed. If the predetermined reduction rate is not achieved, sufficient effects cannot be obtained. "Etching processing conditions" When cleaning the surface by etching, the NaOH concentration is set to 0.5 to 30%, the solution temperature is set to 3.0 to 80°C, and dissolution is carried out for 2 to 100 seconds. After alkaline etching, it is desirable to perform desmutting using an acidic solution such as HNO3.

[0035] When the aluminum alloy clad material A manufactured as described above is heated to a temperature equal to or higher than the melting temperature of the brazing filler metal layers 1 and 2, the brazing filler metal layers 1 and 2 melt, and the brazing filler metal wets and spreads on one or both sides of the aluminum alloy clad material A, allowing other members to be brazed to the aluminum alloy clad material A. Furthermore, the aluminum alloy clad material A can be used for fluxless brazing applications.

[0036] When this aluminum alloy clad material A is applied to a heat exchanger, it is processed into a required shape, such as a tube or other heat exchanger component, and can be effectively used in a configuration in which the brazing filler metal from brazing filler metal layer 1 and the brazing filler metal from brazing filler metal layer 2 are joined in the brazing object. By including Mg in the mating material with respect to brazing filler metal layer 1, it can be used for fluxless brazing. In this case, flux-free brazing is possible, and when joining the first brazing filler metal layer 1 and the second brazing filler metal layer 2 of a double-sided clad material in the crimped part of a B-type tube or in a stacked heat exchanger, good brazing properties can be obtained, which can suppress the generation of excessive MgO at the joining interface while ensuring a sufficient amount of brazing fillet to form a fillet at the joining part. [Example]

[0037] By semi-continuous casting, a core material (the balance being unavoidable impurities and Al) with the composition shown in Table 1 below and materials for multiple brazing filler metal layers (the balance being unavoidable impurities and Al) shown in Table 2 below were produced, and these were combined as shown in Table 3 below to produce an aluminum alloy clad material with a three-layer structure. Brazing filler metal layer 1 was placed on one side of the core material, and brazing filler metal layer 2 was placed on the other side of the core material. When manufacturing the aluminum alloy clad material, a double-sided brazed clad material with an overall thickness of 1 mm and a clad ratio of 10% was manufactured according to the process A shown in Table 4 below. The aluminum alloy clad material was subjected to final annealing at 360°C for 3 hours to produce a tempered O material test material. These test materials were used for the evaluations described later.

[0038] [Table 1]

[0039] [Table 2]

[0040] [Table 3]

[0041] [Table 4]

[0042] <Evaluation items> "Distribution of compounds (test material before brazing)" The surface of each test material was polished with abrasive grains of about 0.1 μm, washed, and then fully automated particle analysis was performed from the surface direction using an EPMA (electron probe microanalyzer). Furthermore, in order to measure fine intermetallic compounds of 1 μm or less, mechanical polishing and electrolytic polishing were performed on the surface of the brazing layer 2 cut out from each test material to prepare a thin film, which was then observed with a TEM (transmission electron microscope) and analyzed by a TEM (transmission electron microscope) at a size of 10,000 μm in the surface direction. 2 The number of intermetallic compound particles was counted in an observation field (100 μm square: RD-TD direction) and recorded in the column of the number of Mg—Bi-based intermetallic compounds in Table 3. The measured intermetallic compound particles are Mg-Bi based intermetallic compound particles having a circle equivalent diameter of 0.01 μm or more and 5.0 μm or less.

[0043] "Brazability evaluation" Each test material was cut into pieces of 30 mm x 65 mm and 25 mm x 50 mm (with the long sides parallel to the rolling direction), and the former was stacked as the lower plate 5 and the latter as the upper plate 6, as shown in Figure 2. The lower plate 5 and the upper plate 6 were fixed together by spot welding at two locations 10 mm inside one of the short sides of the upper plate 6 (the left edge in Figure 2). In Figure 2, the spot weld S was formed at the position shown by the thick chain line, penetrating the lower plate 5 and the upper plate 6 in the thickness direction. A 0.3 mm diameter SUS rod (stainless steel rod) 7 was placed between the upper plate 6 and the lower plate 5, 2 mm inward from the short side opposite the spot welded side, and a test specimen was prepared in which the gap gradually widened from the spot weld to the position of the SUS rod 7. The upper plate 6 had the first brazing filler metal layer 1 on the lower side, and the lower plate 5 had the second brazing filler metal layer 2 on the upper side, and these were arranged so as to contribute to the brazing joint.

[0044] The brazing heat treatment was carried out in an atmosphere with an oxygen concentration of 10 to 15 ppm and a dew point controlled to below -60°C. The test pieces were heated to 600°C, held there for 3 minutes, and then air-cooled. The average heating rate from room temperature to 600°C was 100°C / min. After the brazing test, the joint interface on the upper plate side was measured using an ultrasonic imaging diagnostic (Insight IS-350). The brazeability was evaluated as A, B, or C below, where the braze filling area ratio is 100% for an area of ​​25 mm x 50 mm, and the results are shown in the brazeability column in Table 3. A: 80% or more is good B: Between 60% and 80% - Fairly good C: Less than 60% is considered poor

[0045] As shown in the test results shown in Table 3, the test pieces of Samples 1 and 2 have more than 10 Mg-Bi based intermetallic compound particles and are excellent in brazability. In contrast, sample 3 is a combination of brazing filler metal layer B1 and brazing filler metal layer B4. Although the number of Mg-Bi-based intermetallic compound particles in brazing filler metal layer B4 is greater than 10, the brazing performance is reduced due to the low Si content of brazing filler metal layer B4. Sample 4 is a combination of brazing filler metal layer B1 and brazing filler metal layer B5. Since brazing filler metal layer B5 does not contain Bi, the number of intermetallic compound particles is zero, and therefore brazeability is reduced.

[0046] Samples 5 and 6 were combinations of brazing filler metal layer B1 and brazing filler metal layer B1, neither of which contained Mg or Bi, and the number of intermetallic compound particles was zero, resulting in reduced brazeability. Sample 7 is a combination of brazing filler metal layer B5 and brazing filler metal layer B2, and although the number of intermetallic compound particles is 20, brazing performance is reduced because the brazing filler metal layer B5 does not contain Bi. Sample 8 is a combination of brazing filler metal layers B2 and B3, and although the number of intermetallic compound particles is 35, both brazing filler metal layers contain Bi and Mg, which deteriorates the brazeability. This is thought to be because both brazing filler metal layers contain Mg, which generates excessive MgO at the brazed joint interface, causing the brazeability to deteriorate. [Explanation of symbols]

[0047] A...aluminum alloy clad material, C...core material, 1...first brazing filler layer, 2...second brazing filler layer.

Claims

1. An aluminum alloy clad material with excellent brazing properties, characterized in that a first brazing filler metal layer is disposed on one side of a core material and a second brazing filler metal layer is disposed on the other side of the core material, the first brazing filler metal layer being made of an Al-Si alloy, and the second brazing filler metal layer 2 being made of an Al-Si-Mg-Bi alloy.

2. the first brazing filler metal layer is made of an aluminum alloy containing, by mass%, 2.0 to 14.0% Si, the remainder being Al and unavoidable impurities; The aluminum alloy clad material having excellent brazing properties according to claim 1, characterized in that the second brazing filler metal layer is made of an aluminum alloy containing, in mass%, Si: 2.0 to 14.0%, Mg: 0.01 to 4.0%, Bi: 0.005 to 1.0%, with the remainder being Al and unavoidable impurities.

3. In the second brazing material layer, when observed in the surface (RD-TD) direction, Mg—Bi-based intermetallic compounds having a circle equivalent diameter of 0.01 μm or more and less than 5.0 μm are present in an amount of 10,000 μm or more. ２ 3. The aluminum alloy clad material having excellent brazability according to claim 1, wherein more than 10 particles are present per field of view.

4. 3. The aluminum alloy clad material having excellent brazeability according to claim 1, wherein the atomic concentration ratio of Mg to Bi in the second brazing filler metal layer is Mg / Bi=1.5 or more.

5. 4. The aluminum alloy clad material having excellent brazeability according to claim 3, wherein the atomic concentration ratio of Mg to Bi in the second brazing filler metal layer is Mg / Bi=1.5 or more.

6. 3. The aluminum alloy clad material having excellent brazeability according to claim 1, wherein the content of Mg in the first brazing filler metal layer is restricted to less than 0.05% by mass.

7. 4. The aluminum alloy clad material having excellent brazeability according to claim 3, wherein the Mg content in the first brazing filler metal layer is restricted to less than 0.05% by mass.

8. 5. The aluminum alloy clad material having excellent brazeability according to claim 4, wherein the Mg content in the first brazing filler metal layer is restricted to less than 0.05% by mass.

9. 3. The aluminum alloy clad material with excellent brazeability according to claim 1, wherein the core material is made of an aluminum alloy containing, by mass%, one or more of Mn: 0.1 to 2.0%, Si: 0.1 to 1.5%, Fe: 0.05 to 1.0%, Cu: 0.01 to 2.0%, Mg: 0.01 to 2.0%, Zn: 0.01 to 5.0%, Zr: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Ti: 0.01 to 0.3%, and Bi: 0.005 to 1.5%, with the remainder being Al and unavoidable impurities.

10. 4. The aluminum alloy clad material with excellent brazability according to claim 3, wherein the core material is made of an aluminum alloy containing, in mass%, one or more of Mn: 0.1 to 2.0%, Si: 0.1 to 1.5%, Fe: 0.05 to 1.0%, Cu: 0.01 to 2.0%, Mg: 0.01 to 2.0%, Zn: 0.01 to 5.0%, Zr: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Ti: 0.01 to 0.3%, and Bi: 0.005 to 1.5%, with the remainder being Al and unavoidable impurities.

11. 5. The aluminum alloy clad material with excellent brazeability according to claim 4, characterized in that the core material is made of an aluminum alloy containing, in mass%, one or more of Mn: 0.1 to 2.0%, Si: 0.1 to 1.5%, Fe: 0.05 to 1.0%, Cu: 0.01 to 2.0%, Mg: 0.01 to 2.0%, Zn: 0.01 to 5.0%, Zr: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Ti: 0.01 to 0.3%, and Bi: 0.005 to 1.5%, with the remainder being Al and unavoidable impurities.

12. 7. The aluminum alloy clad material with excellent brazeability according to claim 6, wherein the core material is made of an aluminum alloy containing, in mass%, one or more of Mn: 0.1 to 2.0%, Si: 0.1 to 1.5%, Fe: 0.05 to 1.0%, Cu: 0.01 to 2.0%, Mg: 0.01 to 2.0%, Zn: 0.01 to 5.0%, Zr: 0.01 to 0.3%, Cr: 0.01 to 0.5%, Ti: 0.01 to 0.3%, and Bi: 0.005 to 1.5%, with the remainder being Al and unavoidable impurities.

13. The first brazing filler metal layer or the second brazing filler metal layer, In mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, and one or more of Fe, Sr, Na, Cr, B, Ni, and Sb each being 0.6% or less.

3. The aluminum alloy clad material having excellent brazability according to claim 1 or claim 2, characterized in that it is an aluminum alloy containing one or more of the above, with the remainder being Al and unavoidable impurities.

14. The first brazing filler metal layer or the second brazing filler metal layer, In mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, and one or more of Fe, Sr, Na, Cr, B, Ni, and Sb each being 0.6% or less.

4. The aluminum alloy clad material having excellent brazability according to claim 3, characterized in that it is made of an aluminum alloy having a composition containing one or more of the above, with the remainder being Al and unavoidable impurities.

15. The first brazing filler metal layer or the second brazing filler metal layer, In mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, and one or more of Fe, Sr, Na, Cr, B, Ni, and Sb each being 0.6% or less.

5. The aluminum alloy clad material having excellent brazability according to claim 4, characterized in that it is made of an aluminum alloy having a composition containing one or more of the above, with the remainder being Al and unavoidable impurities.

16. The first brazing filler metal layer or the second brazing filler metal layer, In mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, and one or more of Fe, Sr, Na, Cr, B, Ni, and Sb each being 0.6% or less.

7. The aluminum alloy clad material having excellent brazability according to claim 6, characterized in that it is made of an aluminum alloy having a composition containing one or more of the above, with the remainder being Al and unavoidable impurities.

17. The first brazing filler metal layer or the second brazing filler metal layer, In mass%, Cu: 0.01 to 1.0%, Mn: 0.01 to 1.0%, Ti: 0.01 to 0.3%, Zr: 0.01 to 0.3%, Zn: 0.01 to 5.0%, and one or more of Fe, Sr, Na, Cr, B, Ni, and Sb each being 0.6% or less.

10. The aluminum alloy clad material having excellent brazability according to claim 9, characterized in that it is made of an aluminum alloy having a composition containing one or more of the above, with the remainder being Al and unavoidable impurities.

18. 3. The aluminum alloy clad material having excellent brazability according to claim 1, wherein the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more.

19. 4. The aluminum alloy clad material having excellent brazability according to claim 3, wherein the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more.

20. 5. The aluminum alloy clad material having excellent brazability according to claim 4, wherein the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more.

21. 7. The aluminum alloy clad material having excellent brazability according to claim 6, wherein the outermost surface of the brazing material layer is an etched outermost surface having a thickness of 5 nm or more.

22. 10. The aluminum alloy clad material having excellent brazability according to claim 9, wherein the outermost surface of the brazing filler metal layer is an etched outermost surface having a thickness of 5 nm or more.

23. 14. The aluminum alloy clad material having excellent brazability according to claim 13, wherein the outermost surface of the brazing filler metal layer is an etched outermost surface having a thickness of 5 nm or more.

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