An anti-sagging aluminum alloy composite foil for a heat exchanger and a method of manufacturing the same

Abstract

The application discloses an anti-sagging aluminum alloy composite foil for heat exchangers and a preparation method thereof, and comprises the following steps: (1) preparing a core material layer, wherein the core material comprises the following components in mass percentage: Fe 0.25-0.45%, Si 0.2-0.35%, Mn 1.2-1.3%, Mg 0.5-1.0%, Ti 0.1-0.2%, Cr 0.2-0.3%, other inevitable impurity elements, and the balance of Al; (2) preparing a cladding layer, wherein an Al-Si aluminum alloy with a brand of AA4343 is used as raw material and added into a smelting furnace, V accounting for 0.2-0.5% of the mass fraction of the raw material is added after complete melting; (3) milling surface treatment; and (4) composite rolling and heat treatment. The application combines the formula design of the core material layer and the cladding layer with the design of composite surface polishing, low-temperature hot rolling and heat treatment and other process conditions, and effectively improves the mechanical strength and anti-sagging performance of the aluminum alloy composite foil.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat exchanger materials, in particular to an anti-sagging aluminum alloy composite foil for heat exchanger and a preparation method thereof. BACKGROUND

[0002] Aluminum alloy composite foil is the main material of radiator fins for automobiles due to its good heat transfer performance. With the development of technology, aluminum heat exchangers have developed from mechanical assembly to widely used brazing process. In recent years, in order to save energy and protect the environment and save costs, the structure design of aluminum heat exchangers has been continuously improved, and the composite brazing aluminum foil has shown a trend of thinning, and its thickness will gradually change to 0.07mm and below. The composite brazing aluminum foil is manufactured into a heat exchanger by brazing at a high temperature of about 600℃, and the impact of fin material thinning is that it is prone to softening and deformation at high temperature, and collapse phenomenon occurs, affecting the performance of the radiator.

[0003] Chinese patent CN 102676884 A discloses a high anti-sagging aluminum alloy composite foil for heat exchanger brazing, which strictly controls the formula design of the core material, that is, by strictly controlling the Cu and Mg content, adjusting the content of Mn, Si, Fe and Zn, and adding V, Zr and Ti, and combining the optimization of rolling and annealing process, the foil material obtains stable fine fiber structure and uniform and dispersed distribution of composite high temperature strengthening phase in the grain and grain boundary, thereby preventing grain coarsening during high temperature brazing, and the alloy material has higher anti-sagging performance.

[0004] However, the present inventors found in the process of implementing the technical scheme in the embodiments of the present application that the above-mentioned technology still cannot effectively solve the softening phenomenon of the aluminum alloy composite foil during brazing, which affects the performance after brazing. SUMMARY

[0005] The present application provides an anti-sagging aluminum alloy composite foil for heat exchanger and a preparation method thereof, which solves the above-mentioned problems in the prior art.

[0006] To solve the above-mentioned technical problems, the present application provides a preparation method of an anti-sagging aluminum alloy composite foil for heat exchanger, comprising the following steps:

[0007] (1) preparing a core material layer: adding raw materials of each element into a smelting furnace according to the composition of the core material, melting, refining, and casting to obtain a core alloy ingot; wherein the core material comprises the following components by mass percentage: Fe 0.25-0.45%, Si 0.2-0.35%, Mn 1.2-1.3%, Mg 0.5-1.0%, Ti 0.1-0.2%, Cr 0.2-0.3%, other unavoidable impurity elements, and the balance of Al;

[0008] (2) Preparation of cladding layer: Al-Si aluminum alloy with AA4343 brand is used as raw material and added into a smelting furnace, after complete melting, 0.2-0.5% of V in mass fraction of the raw material is added, after stirring and mixing, slagging is performed, and the cladding layer alloy ingot is obtained by casting;

[0009] (3) Milling surface treatment: the core material alloy ingot prepared in step (1) and the cladding layer alloy ingot prepared in step (2) are respectively subjected to defect sawing and milling surface treatment, and then the upper and lower surfaces of the core material alloy ingot and the surface of the cladding layer alloy ingot combined with the core material alloy ingot are respectively subjected to polishing treatment;

[0010] (4) Composite rolling and heat treatment: the cladding layer alloy ingot is combined on both sides of the core material alloy ingot with the polished surface facing the core material alloy ingot, and then hot rolling, multi-pass cold rolling, first heat treatment, final rolling and second heat treatment are performed to obtain the aluminum alloy composite foil for anti-sag heat exchanger.

[0011] In a preferred embodiment of the present application, the amount of V added is 0.25-0.35% in mass fraction of the raw material.

[0012] In a preferred embodiment of the present application, in step (3), the surface roughness Ra of the upper and lower surfaces of the core material alloy ingot and the surface of the cladding layer alloy ingot combined with the core material alloy ingot after polishing treatment is 10-20 um.

[0013] In a preferred embodiment of the present application, in step (3), after milling surface treatment, the thickness of the cladding layer alloy ingot is 1 / 3-1 / 5 of the thickness of the core material alloy ingot.

[0014] In a preferred embodiment of the present application, in step (4), the process conditions of hot rolling are: hot rolling temperature 300-330℃, final rolling temperature 220-230℃, and total deformation of hot rolling 93%.

[0015] In a preferred embodiment of the present application, in step (4), the process conditions of multi-pass cold rolling are: 4-pass cold rolling, the deformation of each pass is gradually increased, and the total reduction rate of 4-pass cold rolling is controlled to be 95-98%.

[0016] In a preferred embodiment of the present application, in step (4), the process conditions of final rolling are: multi-stand cold precision rolling to a composite foil with a thickness of 0.05-0.07 mm.

[0017] In a preferred embodiment of the present application, in step (4), the process conditions of the first heat treatment are: temperature 320-350℃, and time 2-3 h.

[0018] In a preferred embodiment of the present application, in step (4), the process conditions of the second heat treatment are: temperature 350-380℃, time 4-6h.

[0019] To solve the above technical problems, the present application provides an anti-sagging aluminum alloy composite foil for heat exchangers prepared by the above method.

[0020] The present application has the advantages that: the anti-sagging aluminum alloy composite foil for heat exchangers and the preparation method thereof effectively improve the mechanical strength and anti-sagging performance of the aluminum alloy composite foil based on the concept of improving the mechanical strength of the core layer and reducing the migration of Si elements in the cladding layer, by combining the formula design of the core layer and the cladding layer with the design of composite surface polishing, low-temperature hot rolling and heat treatment process conditions, the prepared composite foil with a thickness of less than 0.07mm has excellent tensile strength, yield strength and anti-sagging performance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a preparation process flow chart of an anti-sagging aluminum alloy composite foil for heat exchangers. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application can be more clearly defined.

[0023] Please refer to Figure 1 The embodiments of the present application include:

[0024] Embodiment 1

[0025] An anti-sagging aluminum alloy composite foil for heat exchangers is a composite foil material with a thickness of less than 0.07mm, which includes a core layer and cladding layers cladded on both sides of the core layer.

[0026] The preparation method of the anti-sagging aluminum alloy composite foil for heat exchangers includes the following steps:

[0027] (1) Preparation of the core layer: the core material includes the following components by mass percentage: Fe 0.35%, Si 0.3%, Mn 1.2%, Mg 0.8%, Ti 0.2%, Cr 0.3%, and other unavoidable impurity elements, and the balance is Al; the formula design of the core material raw material effectively improves the structural strength of the core material by optimizing the ratio of each element, especially the use of Mn, Mg and Cr, which helps to improve the anti-sagging performance;

[0028] According to the components of the core material, raw materials containing each element are added into a smelting furnace, melted at 750 DEG C, then refined, deslagged, and cast to obtain the core material alloy ingot;

[0029] (2) Preparation of the cladding layer: Al-Si aluminum alloy with AA4343 brand is used as raw material and added into a smelting furnace to be smelted at 740 DEG C. After complete melting, 0.25% of V in mass fraction of the raw material is added, stirred and mixed, deslagged, and cast to obtain the cladding layer alloy ingot;

[0030] By adding V (vanadium) into the Al-Si aluminum alloy as the cladding layer, Al(Fe,V)Si phase is formed in the cladding layer, which is a high-temperature stable phase. On the one hand, it can reduce the content of free Si in the cladding layer, and on the other hand, it can effectively prevent the diffusion of Si element to the core material during brazing, thereby protecting the core material layer and preventing problems such as sagging and burning;

[0031] (3) Milling surface treatment: the core material alloy ingot prepared in step (1) is first sawn to remove the defect part, and then the surface is milled to obtain a core material layer with a thickness of d1;

[0032] The cladding layer alloy ingot prepared in step (2) is first sawn to remove the defect part, and then the surface is milled to obtain a cladding layer with a thickness of d2; wherein d1 = 3d2;

[0033] Then the upper and lower surfaces of the milled core material alloy ingot are polished to make the surface roughness Ra reach 15um; and the side of the milled cladding layer alloy ingot facing the core material alloy ingot is polished to make the surface roughness Ra reach 15um;

[0034] Through polishing, the bonding strength between the core material alloy ingot and the cladding layer alloy ingot can be improved, which helps to improve the rolling composite effect;

[0035] (4) Composite rolling and heat treatment: the cladding layer alloy ingot is composite on both sides of the core material alloy ingot with the polished side facing the core material alloy ingot, then hot rolling composite is carried out at 320 DEG C, and the total deformation amount of hot rolling is controlled to be 93%, and the final rolling temperature is 220 DEG C. On the basis of polishing, low-temperature hot rolling treatment is carried out, which helps to prolong the grain size of the composite foil core material, especially for the originally coarse grain structure, the prolonging effect is more obvious, forming strip structure existing on the grain boundary, which can effectively prevent the migration of Si and other elements to the core material layer during brazing, thereby reducing the collapse of the composite foil during brazing;

[0036] After hot rolling, multi-pass cold rolling is carried out at room temperature; the process conditions of the multi-pass cold rolling are: 4-pass cold rolling, the deformation amount of each pass is gradually increased, and the total cold rolling reduction is controlled to be 97%;

[0037] After multi-pass cold rolling, the first heat treatment is performed at 340℃ for 2.5h;

[0038] Then, cooling to room temperature, the multi-stand cold finishing is performed to obtain the composite foil with a thickness of 0.05-0.07mm; finally, the second heat treatment is performed at 360℃ for 5h to obtain the aluminum alloy composite foil for anti-sag heat exchanger with a thickness less than 0.07mm.

[0039] Example 2

[0040] The difference from Example 1 is that the amount of V added in the cladding layer is 0.035% by mass percentage; the time of the first heat treatment is 3h; and the process conditions of the second heat treatment are 380℃ and 4h.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that no V is added in the cladding layer.

[0043] Comparative Example 2

[0044] The difference from Example 1 is that no polishing treatment is performed.

[0045] Comparative Example 3

[0046] The difference from Example 1 is that the temperature of hot rolling is 450℃.

[0047] The aluminum alloy composite foils prepared in the above Examples 1 and 2 and Comparative Examples 1-3 are subjected to performance test, and the results are shown in the following table. The anti-sag value is tested according to the anti-sag test method of the Japanese Low Temperature Welding Committee, and the tensile strength and yield strength are tested according to the current standard.

[0048]

[0049] From the above data, it can be seen that the core material formula design effectively improves the mechanical strength of the aluminum alloy composite foil; from the data comparison of Comparative Example 1 and Example 1, it can be seen that the addition of V in the cladding layer effectively prevents the diffusion of Si, which has a significant effect on improving the anti-sag performance; from the data comparison of Comparative Example 2 and Example 1, it can be seen that the polishing treatment before low-temperature hot rolling can affect the compounding effect, and thus affect the mechanical strength of the composite foil.

[0050] The preparation method of the aluminum alloy composite foil has the following advantages:

[0051] 1. The formula design is based on the combination of improving the mechanical strength of the core material layer and improving the migration performance of Si element in the cladding layer, which is novel in concept and good in effect, and the prepared composite foil has high mechanical strength and beneficial anti-sag performance.

[0052] 2. Improving the performance of the existing AA4343 alloy by adding V is highly feasible;

[0053] 3. By designing process conditions such as composite surface grinding, low-temperature hot rolling and heat treatment, the structure of grains in the alloy microstructure, especially large-sized grains at grain boundaries, is effectively protected and deformed (elongated), thereby preventing the diffusion of elements between layers. This effectively prevents Si elements from diffusing into the core material layer, thereby further improving the anti-sagging performance.

[0054] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing an anti-sagging aluminum alloy composite foil for a heat exchanger, characterized by, It comprises the following steps: (1) preparing core material layer: according to the components of the core material, raw materials of each element are added into a smelting furnace, and after melting, refining and slag removal, the core material alloy ingot is obtained; wherein the core material comprises the following components by mass percentage: Fe 0.25-0.45%, Si 0.2-0.35%, Mn 1.2-1.3%, Mg 0.5-1.0%, Ti 0.1-0.2%, Cr 0.2-0.3%, and other unavoidable impurity elements, and the balance is Al; (2) preparing cladding layer: AA4343 Al-Si aluminum alloy is used as raw material and added into a smelting furnace, and after complete melting, 0.2-0.5% of V by mass fraction of raw material is added, and after stirring and mixing, slag removal and casting, the cladding layer alloy ingot is obtained; (3) face milling treatment: the core material alloy ingot prepared in step (1) and the cladding layer alloy ingot prepared in step (2) are respectively subjected to defect sawing and face milling treatment, and then the upper and lower surfaces of the core material alloy ingot and the surface of the cladding layer alloy ingot combined with the core material alloy ingot are polished, and the surface roughness Ra after polishing is 10-20um; (4) composite rolling and heat treatment: the cladding layer alloy ingot is combined on both sides of the core material alloy ingot with the polished surface facing the core material alloy ingot, and then hot rolling, multi-pass cold rolling, first heat treatment, final rolling and second heat treatment are carried out to obtain the aluminum alloy composite foil for anti-sag heat exchanger; The process conditions of the hot rolling are: hot rolling temperature 300-330℃, final rolling temperature 220-230℃, and total deformation of hot rolling 93%; The process conditions of the first heat treatment are: temperature 320-350℃, and time 2-3h; The process conditions of the second heat treatment are: temperature 350-380℃, and time 4-6h.

2. The method for preparing an aluminum alloy composite foil for an anti-sagging heat exchanger according to claim 1, characterized in that, The addition amount of V is 0.25-0.35% by mass fraction of raw material.

3. The method of claim 1, wherein the method is characterized by: In step (3), after face milling treatment, the thickness of the cladding layer alloy ingot is 1 / 3-1 / 5 of the thickness of the core material alloy ingot.

4. The method of claim 1, wherein the aluminum alloy composite foil for a sag-resistant heat exchanger is prepared by the steps of: In step (4), the process conditions of the multi-pass cold rolling are: 4-pass cold rolling, and the deformation of each pass is gradually increased, and the total cold rolling reduction rate is controlled to be 95-98%.

5. The method of claim 1, wherein the method further comprises the step of:

5. annealing the aluminum alloy composite foil at a temperature of 300°C to 400°C for 1 to 10 hours. In step (4), the process conditions of the final rolling are: multi-stand cold precision rolling to a composite foil material with a thickness of 0.05-0.07mm.

6. An aluminum alloy composite foil for an anti-sagging heat exchanger, characterized in that, Prepared by the method of any one of claims 1-5.

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