Novel foamed aluminum interlayer composite structure and plasma spraying-hot rolling-brazing composite preparation process thereof

Abstract

The invention relates to a novel foamed aluminum interlayer composite structure and a plasma spraying-hot rolling-brazing composite preparation process thereof, and belongs to the technical field of composite structures. The problem that in the prior art, due to a machining mode of a foamed aluminum interlayer composite structure, the interface performance of the foamed aluminum interlayer composite structure is poor is solved. According to the method, oxidation films and oil stains on the surfaces of foamed aluminum, an aluminum alloy panel and a brazing filler metal piece are removed firstly, then the surface of the foamed aluminum is sprayed with the brazing filler metal through the plasma spraying technology, the sprayed foamed aluminum is obtained, the brazing filler metal piece serves as a skin, the aluminum alloy panel is subjected to coating treatment and heating rolling, and the aluminum-brazing filler metal composite panel is obtained. And finally, in a vacuum brazing furnace, the two aluminum-brazing filler metal composite panels are welded to the two surfaces of the sprayed foamed aluminum in a vacuum brazing mode, and the foamed aluminum interlayer composite structure is obtained. According to the preparation method, the interface strength is improved through the spraying process and the hot rolling process, and the prepared foamed aluminum interlayer composite structure is high in interface strength and good in stability.

Description

Technical Field

[0001] The invention belongs to the technical field of composite structures, and in particular relates to a novel foam aluminum sandwich composite structure and a plasma spraying-hot rolling-brazing composite preparation process thereof. Background Art

[0002] Cellular structure materials have the advantages of light weight, versatility and designability, providing more possibilities for achieving lightweight and multifunctional structural integration.

[0003] Aluminum foam is a cellular structure material that combines lightness, structure and functionality. In the 1990s, the German automotive industry first proposed the concept of aluminum foam sandwich structure and conducted in-depth research. Aluminum foam sandwich structure is a sandwich structure composed of metal panels and aluminum foam core. It not only has many excellent properties of aluminum foam materials, but also solves the disadvantage of low strength of single aluminum foam. It has the characteristics of isotropy, flame retardancy, and maintaining structural integrity. It is a cellular structure material with excellent comprehensive performance.

[0004] In the prior art, the main processing method for foam aluminum sandwich structures is brazing process. The brazing process has good corrosion resistance and processability for the welded joints of foam aluminum sandwich structures. However, due to the small weldable area on the surface of foam aluminum, the presence of pores will also affect the wettability of liquid brazing material and the ability to spread and fill the weld in the weld. Thin-walled foam aluminum is prone to burning or collapse during welding, which reduces its own weldability and has a significant impact on the interface performance of the sandwich structure. Summary of the invention

[0005] The present invention aims to solve the problem that the processing method of the foam aluminum sandwich structure in the prior art leads to poor interface performance of the foam aluminum sandwich structure, and provides a novel foam aluminum sandwich composite structure and a plasma spraying-hot rolling-brazing composite preparation process thereof.

[0006] The technical problems adopted by the present invention to solve the above-mentioned technical problems are as follows.

[0007] The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure of the present invention comprises the following steps:

[0008] Step 1: Plasma spraying of foamed aluminum

[0009] First, the oxide film and oil stain on the surface of the aluminum foam are removed, and then the aluminum foam is ultrasonically cleaned, and then the surface of the aluminum foam is sandblasted for roughening, and finally the dry brazing powder is sprayed on the surface of the aluminum foam by plasma spraying technology to obtain the sprayed aluminum foam;

[0010] Step 2: Rolling and laminating of aluminum alloy panels

[0011] First, the oxide film and oil stain on the surface of the aluminum alloy panel and the solder sheet are removed, and then the gloss treatment and ultrasonic cleaning are performed. Finally, the solder sheet is used as a skin to cover the aluminum alloy panel, and after heating, rolling is performed to obtain an aluminum-solder composite panel.

[0012] Step 3: Brazing of foam aluminum and composite panel

[0013] First, the oxide film and oil stains on the surface of the sprayed foam aluminum and aluminum-brazing alloy composite panels are removed, ultrasonically cleaned, and vacuum dried. Then, in a vacuum brazing furnace, two aluminum-brazing alloy composite panels are vacuum welded on the two surfaces of the sprayed foam aluminum to obtain a foam aluminum sandwich composite structure.

[0014] Preferably, in step 1, 16-mesh brown corundum is used to perform sandblasting roughening on the foamed aluminum, and the working pressure is 0.6-0.8 MPa.

[0015] Preferably, in step 1, the drying conditions of the solder powder are: temperature 80-100° C., and heat preservation for 4-6 hours.

[0016] Preferably, in step 1, the working current of the plasma spraying technology is 400-420A, and the spraying distance is 10-12cm.

[0017] Preferably, in step 2, the heating temperature is 400-450° C. and the heating time is 3-5 min.

[0018] Preferably, in step 2, the rolling speed is 9.33-10.5 rpm, and multiple rolling passes are performed until the deformation reaches 10%-15%.

[0019] Preferably, in step 1 to step 3, the oxide film and oil stains on the surface are removed by soaking in a 10% Na2CO3 solution at 60-70°C and a 10% NaOH solution at 20-40°C for 5-10 minutes respectively.

[0020] Preferably, in step 2, the gloss treatment is performed by soaking in 10% HNO3 for 5-10 minutes.

[0021] Preferably, in step 1 to step 3, the ultrasonic cleaning conditions are: ultrasonic cleaning with deionized water, the ultrasonic frequency is 20-40 kHz, and the ultrasonic time is 20-30 min.

[0022] Preferably, before step one, the method further includes cutting the foamed aluminum, the solder sheet, and the aluminum alloy panel into required sizes respectively using wire cutting.

[0023] Preferably, the relative density of the foamed aluminum is 0.5-0.7, the thickness is 10 mm, the thickness of the aluminum alloy panel is 1-2 mm, and the thickness of the solder sheet is 0.1-0.2 mm.

[0024] The present invention also provides a foam aluminum sandwich composite structure prepared by the plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure.

[0025] The principle of the present invention is:

[0026] While the porous structure of foam aluminum gives it excellent properties, it greatly reduces the surface weldable area, greatly affecting the welding quality of brazing, and the interface strength is low. Plasma spraying is a thermal spraying technology that uses a high-temperature plasma arc to heat the powder material to a molten or semi-molten state, and sprays it onto the surface of the substrate through a high-speed airflow to form a high-performance coating. The present invention uses a plasma spraying process to fill the solder powder into the pores, so that the surface of the foam aluminum approaches a plane. While ensuring its excellent performance, the weldable area is greatly increased, and the problem of uneven distribution of solder and poor fluidity due to the capillary action of the pores is avoided to a great extent. During the brazing process, the solder in the pores has a supporting effect on the inner wall of the foam aluminum, preventing the thin wall of the foam aluminum from burning and collapsing.

[0027] The hot rolling process refers to a process in which the metal is heated to above the recrystallization temperature for rolling. The two plates produce adhesive friction under the action of shear force, so that the metals are fixed between the contact surfaces. Thereby, the bonding between the metals is achieved. The residual heat after rolling makes the atoms between the two metals diffuse more fully and form a good composite. The present invention diffuses the brazing sheet and the aluminum alloy panel with each other through the hot rolling process and combines them with each other. During the brazing process, it can diffuse more fully, form a diffusion zone, form a strong metallurgical bond, and enhance the bonding strength of the joint. In addition, the amount of brazing material can be accurately controlled to ensure the uniform thickness of the brazing material layer, avoid welding defects caused by too much or too little brazing material, and ensure the stability of welding quality.

[0028] Both processes play a significant role in the interface strength of foam aluminum brazing. The two processes work together to significantly improve the interface strength of foam aluminum.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The plasma spraying-hot rolling-brazing composite preparation process of the present invention solves the influence of the pores of foamed aluminum on the welding interface performance during the brazing process through the spraying process, and gives full play to the fluidity and spreadability of the brazing material.

[0031] 2. The plasma spraying-hot rolling-brazing composite preparation process of the present invention improves the diffusion degree between the brazing material and the base material through the hot rolling process, increases the brazing diffusion area, and thus improves the interface strength.

[0032] 3. The foam aluminum sandwich structure of the present invention has high interface strength and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments and comparative examples of the present invention, the drawings required for use in the embodiments and comparative examples will be briefly introduced below. Obviously, the drawings described below are only some embodiments and comparative examples of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 The peel strength curves of the samples of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments and comparative examples.

[0036] Comparative Example 1

[0037] First, use wire cutting to cut the foamed aluminum (relative density of 0.5-0.7, thickness of 10mm), solder sheet (0.1mm), and aluminum alloy panel (thickness of 1mm) into the required size. Then soak them in 10% Na2CO3 solution at 60-70℃ and 10% NaOH solution at 20-40℃ for 5-10min to remove the oxide film and oil stains on the surface of the foamed aluminum, solder sheet, and aluminum alloy panel. Then use an ultrasonic cleaner to use deionized water at a frequency of 20-40kHz for 20-30min. Finally, place the dried aluminum alloy panel, solder sheet, and foamed aluminum in a vacuum brazing furnace for vacuum brazing to finally obtain a foamed aluminum sandwich structure.

[0038] Comparative Example 2

[0039] First, use wire cutting to cut the foam aluminum (relative density of 0.5-0.7, thickness of 10mm), solder sheet (thickness of 0.1mm), and aluminum alloy panel (thickness of 1mm) into the required size. Then use 10% Na2CO3 solution at 60-70℃ and 10% NaOH solution at 20-40℃ to soak for 5-10min to remove the oxide film and oil stains on the surface of the foam aluminum, solder sheet, and aluminum alloy panel. Then use an ultrasonic cleaner to use deionized water at a frequency of 20-40kHz for 20-30min. Then use 16-mesh brown corundum to sandblast the surface of the foam aluminum at a working pressure of 0.6-0.8MPa to obtain roughened foam aluminum. Then dry the solder powder in a drying oven, keep it warm at a temperature of 80-100℃ for 4-6h, and then plasma spray the roughened foam aluminum to obtain sprayed foam aluminum. Finally, the dried aluminum alloy panel, brazing sheet, and sprayed foamed aluminum are placed in a vacuum brazing furnace for vacuum brazing to finally obtain a foamed aluminum sandwich structure.

[0040] Example 1

[0041] Step 1: Plasma spraying of foamed aluminum

[0042] First, the oxide film and oil stain on the surface of the foamed aluminum (relative density of 0.5-0.7, thickness of 10 mm) are removed, and then the foamed aluminum is ultrasonically cleaned with deionized water, and then the surface of the foamed aluminum is sandblasted and roughened using 16-mesh brown corundum at a working pressure of 0.6 MPa, and finally the solder powder is dried in a drying oven, kept warm for 4-6 hours at a temperature of 80-100° C., and then plasma sprayed, the working current of the plasma spraying is 400-420A, and the spraying distance is 10 cm, to obtain the sprayed foamed aluminum;

[0043] Step 2: Rolling and laminating of aluminum alloy panels

[0044] First, the oxide film and oil stain on the surface of the aluminum alloy panel (thickness of 1 mm) and the solder sheet (thickness of 0.1 mm) are removed, and then the gloss treatment is performed, and ultrasonic cleaning is performed with deionized water. Finally, the aluminum alloy panel is coated with the solder sheet as a skin, and after heating at 400-450° C. for 3-5 minutes, multiple rolling is performed until the deformation reaches 10%-15%, and the rolling speed is 9.33-10.5 rpm, to obtain an aluminum-solder composite panel;

[0045] Step 3: Brazing of foam aluminum and composite panel

[0046] First, the oxide film and oil stain on the surface of the sprayed foam aluminum and aluminum-brazing alloy composite panel are removed, and then the panels are ultrasonically cleaned with deionized water and vacuum dried. Then, two aluminum-brazing alloy composite panels are vacuum welded on the two surfaces of the sprayed foam aluminum in a vacuum brazing furnace to obtain a foam aluminum sandwich composite structure.

[0047] Among them, 10% Na2CO3 solution at 60-70℃ and 10% NaOH solution at 20-40℃ are used for soaking for 5-10 minutes to remove the oxide film and oil stains on the surface of foam aluminum, solder sheet and aluminum alloy panel; gloss treatment is: soaking in 10% HNO3 for 5-10 minutes for gloss treatment; ultrasonic cleaning is: using an ultrasonic cleaner at a frequency of 20-40kHz for 20-30 minutes.

[0048] The samples prepared in Comparative Example 1, Comparative Example 2 and Example 1 were subjected to peel strength tests to test the interface performance. The experimental conditions were: loading speed 1 mm / min. The equipment was a WDW-200 universal testing machine. After the experiment, a peel strength-peel length curve was obtained, as shown in FIG. Figure 1 shown.

[0049] from Figure 1 It can be seen that the peel strength curves of different samples have the same trend. In the rising stage, due to the relatively high strength and stiffness of the aluminum alloy panel, the aluminum alloy panel needs to be corrected after the test starts, resulting in a higher test value; in the descending stage, due to the fluidity of the solder, the sample is a little firmer around the inside relative to the inside. As the test proceeds to the peeling interlayer interface layer, the curve tends to be stable, and the average value of the stable section curve is the peel strength of the sample. Compared with the ordinary brazing sample (Comparative Example 1) and the spray-brazing foam aluminum sandwich structure (Comparative Example 2), the peel strength of the foam aluminum sandwich structure (Example 1) after spraying and rolling processes has been significantly improved. Explanation: The pores on the surface of the foam aluminum after spraying are greatly reduced, the weldable area is improved, the spreadability and fluidity of the solder are fully utilized, and the diffusion degree of the solder of the aluminum-brazing composite material after rolling is also improved during the brazing process. Both spraying and rolling play a major role in the interface strength of foam aluminum brazing. The two cooperate with each other to significantly improve the interface strength of foam aluminum.

[0050] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A plasma spraying-hot rolling-brazing composite preparation process for a foamed aluminum sandwich composite structure, characterized in that: The following steps are involved: Step 1: Plasma spraying of foamed aluminum First, the oxide film and oil stain on the surface of the aluminum foam are removed, and then the aluminum foam is ultrasonically cleaned, and then the surface of the aluminum foam is sandblasted for roughening, and finally the dry brazing powder is sprayed on the surface of the aluminum foam by plasma spraying technology to obtain the sprayed aluminum foam; Step 2: Rolling and laminating of aluminum alloy panels First, the oxide film and oil stain on the surface of the aluminum alloy panel and the solder sheet are removed, and then the gloss treatment and ultrasonic cleaning are performed. Finally, the solder sheet is used as a skin to cover the aluminum alloy panel, and after heating, rolling is performed to obtain an aluminum-solder composite panel. Step 3: Brazing of foam aluminum and composite panel First, the oxide film and oil stains on the surface of the sprayed foam aluminum and aluminum-brazing alloy composite panels are removed, ultrasonically cleaned, and vacuum dried. Then, in a vacuum brazing furnace, two aluminum-brazing alloy composite panels are vacuum welded on the two surfaces of the sprayed foam aluminum to obtain a foam aluminum sandwich composite structure.

2. The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 1, 16-mesh brown corundum is used to perform sandblasting roughening on the foamed aluminum, and the working pressure is 0.6 MPa.

3. The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 1, the drying conditions of the solder powder are: temperature 80-100° C., and heat preservation for 4-6 hours.

4. The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 1, the working current of the plasma spraying technology is 400-420A, and the spraying distance is 10cm.

5. The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 2, the heating temperature is 400-450° C. and the heating time is 3-5 min.

6. The plasma spraying-hot rolling-brazing composite preparation process of the foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 2, the rolling speed is 9.33-10.5 rpm, and multiple rolling passes are performed until the deformation reaches 10%-15%.

7. The plasma spraying-hot rolling-brazing composite preparation process of foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 1 to step 3, the oxide film and oil stains on the surface are removed by soaking in 10% Na2CO3 solution at 60-70°C and 10% NaOH solution at 20-40°C for 5-10 minutes respectively; The ultrasonic cleaning conditions are: ultrasonic cleaning with deionized water, an ultrasonic frequency of 20-40 kHz, and an ultrasonic time of 20-30 min.

8. The plasma spraying-hot rolling-brazing composite preparation process of foam aluminum sandwich composite structure according to claim 1, characterized in that: In step 2, the gloss treatment method is: soaking in 10% HNO3 for 5-10 minutes.

9. The plasma spraying-hot rolling-brazing composite preparation process of foam aluminum sandwich composite structure according to claim 1, characterized in that: The relative density of the foamed aluminum is 0.5-0.7 and the thickness is 10 mm; The thickness of the aluminum alloy panel is 1-2 mm; The thickness of the solder sheet is 0.1-0.2 mm.

10. A foamed aluminum sandwich composite structure prepared by the plasma spraying-hot rolling-brazing composite preparation process of the foamed aluminum sandwich composite structure according to any one of claims 1 to 9.

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