A low-temperature diffusion-welded honeycomb core and a method for preparing the same

Abstract

The present invention belongs to the technical field of aluminum honeycomb panels, and specifically relates to a low-temperature diffusion welding honeycomb core and a preparation method thereof. The preparation method of the low-temperature diffusion welding honeycomb core of the present invention comprises the following steps: (1) applying active alloy powder to the surface of an aluminum alloy foil at equal intervals, setting a solder resist in the uncoated area, and then superimposing different aluminum alloy foils; (2) vacuum diffusion welding the aluminum alloy foils, and then cutting and stretching them. The present invention replaces the adhesive used in the preparation process of the stretching method with a low-melting-point alloy powder, and uses diffusion welding to achieve the metallurgical bonding of the honeycomb core interlayer. Since no adhesive is used in the welding process, the problem of black residue of the adhesive at the brazing temperature of the honeycomb panel can be solved; Al‑Zn‑Mg‑Ge‑In mixed powder is used as the intermediate connection layer material, and the synergistic effect of each element can effectively improve the mechanical strength of the joint while reducing the diffusion welding temperature, which is suitable for the preparation and application of the honeycomb core.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum honeycomb panels, and in particular relates to a low-temperature diffusion-welded honeycomb core and a preparation method thereof. Background Art

[0002] Aluminum honeycomb panel is a composite panel with a "sandwich" structure, consisting of upper and lower panels and a honeycomb core layer in the middle. It has the characteristics of high flatness, high specific strength, good specific stiffness, low density, sound insulation, heat insulation, and high energy absorption. It has been widely used in aerospace, shipbuilding, high-speed trains, rail transit and other fields.

[0003] As the core component of aluminum honeycomb panels, the manufacturing methods of honeycomb core can be mainly divided into two methods: stretching method and forming method. The stretching method is to first print the adhesive strips on the raw materials in a staggered manner, stack them together and solidify them, and cut them into honeycomb core strips of the required height. The honeycomb core strips occupy a small area, are convenient for transportation and storage, and are stretched before use to obtain the unfolded honeycomb core. The forming method is to roll or stamp the material into corrugated strips, and then assemble the corrugated strips into a honeycomb core. The corrugated strips are bonded with organic glue or connected by spot welding according to the needs and thickness to obtain the honeycomb core.

[0004] Since there is adhesive in the honeycomb core interlayer prepared by the existing stretching method, when the honeycomb core and the upper and lower panels are brazed by conventional brazing to prepare the honeycomb panel, the adhesive will be cracked and ineffective at the brazing temperature, resulting in a large amount of black residue, which seriously affects the brazing quality. Therefore, when the honeycomb panel is prepared by brazing in the prior art, the honeycomb core is generally prepared by molding, but the molding method has low production efficiency and cannot meet the needs of mass production.

[0005] In view of the above problems, it is necessary to develop a new method for preparing honeycomb core, which can not only solve the problem of black residue produced by adhesive during brazing, but also has high production efficiency and welding quality. Summary of the invention

[0006] To solve the above problems, the first purpose of the present invention is to provide a method for preparing a low-temperature diffusion welding honeycomb core, which can solve the problem of black residue of adhesive at brazing temperature, and the honeycomb core interlayer can achieve metallurgical bonding with high welding strength and welding efficiency.

[0007] The second object of the present invention is to provide a low-temperature diffusion-welded honeycomb core, in which the honeycomb core interlayer can achieve metallurgical bonding, has good welding quality, and is suitable for use in high-performance honeycomb panels.

[0008] In order to achieve the above-mentioned purpose, the method for preparing the low-temperature diffusion-welded honeycomb core of the present invention adopts the following technical scheme:

[0009] A method for preparing a low-temperature diffusion-welded honeycomb core comprises the following steps:

[0010] (1) coating the active alloy powder on the surface of the aluminum alloy foil strip at equal intervals, coating or placing a solder resist on the area not coated with the active alloy powder, and then stacking different aluminum alloy foil strips, while keeping the active alloy powder on the surface of each layer of aluminum alloy foil strips in an alternating manner, to obtain a laminated structure with active alloy powder and solder resist distributed at intervals on the surface of the aluminum alloy foil strip;

[0011] (2) vacuum diffusion welding the laminated aluminum alloy foil strips, and then cutting and stretching them into honeycomb cores to obtain;

[0012] Wherein, the active alloy powder is Al-Zn-Mg-Ge-In active alloy powder.

[0013] The method for preparing a low-temperature diffusion-welded honeycomb core of the present invention replaces the adhesive used in the existing stretching preparation process with active alloy powder with a low melting point, and adopts diffusion welding to achieve metallurgical bonding of the honeycomb core interlayer.

[0014] The welding process of the present invention can solve the problem of black residue of adhesive at the brazing temperature of honeycomb panels because no adhesive is used. In addition, the present invention adopts diffusion welding, which refers to a method of applying pressure under certain temperature conditions to make the connected surfaces close to each other and in contact with each other, ensuring that atoms are fully diffused and metallurgical bonding is formed at the interface to achieve effective connection of materials. Since the honeycomb core foil is relatively thin, if the honeycomb core is prepared by the existing brazing method, the aluminum alloy foil will be deformed. The present invention adopts diffusion welding, which has a low connection temperature and can achieve metallurgical bonding of the honeycomb core interlayer on the basis of avoiding deformation, which is convenient for the subsequent preparation of the honeycomb core by stretching.

[0015] In addition, the present invention adopts Al-Zn-Mg-Ge-In active alloy powder as the intermediate connection layer material. Adding Al powder during diffusion welding is beneficial to the deoxidation of the diffusion welding intermediate layer. Zn and Mg react eutectically at 342°C, and the magnesium vapor generated by Mg evaporation can promote the breaking of the oxide film. The addition of Ge element can further reduce the temperature of diffusion welding. At the same time, the reaction of Ge and Mg can generate Mg2Ge strengthening phase, thereby improving the mechanical properties of the joint. In element is solid-dissolved with aluminum, and has a close thermal expansion coefficient to aluminum element, and In element has a low melting point. In as an intermediate layer can further reduce the diffusion welding temperature. Therefore, the synergistic effect of Al, Zn, Mg, Ge, and In elements can significantly reduce the diffusion welding temperature while improving the mechanical strength of the joint.

[0016] Compared with the traditional foil-shaped intermediate layer, the thickness of the honeycomb core foil is small and the thickness of the intermediate layer foil is large, which leads to an increase in reaction temperature and an increase in reaction time, which makes the honeycomb core prone to corrosion and reduces strength. The present invention adopts a powdered intermediate layer, which can strictly control the amount of powder, and due to the change in temperature during the welding process, the powdered intermediate layer will undergo physical and chemical changes such as bonding between the powder particles, thereby increasing the strength, hardness and density of the diffusion layer, reducing pores and densifying the grain structure. Preferably, the particle size of the Al-Zn-Mg-Ge-In active alloy powder is 20-40μm; the weight percentage composition of the Al-Zn-Mg-Ge-In active alloy powder is: Zn 15-20%, Ge 10-20%, Mg 5-10%, In 3-5%, and Al balance.

[0017] Furthermore, the aluminum alloy foil strip is one of 3003 aluminum alloy, 6061 aluminum alloy and 6063 aluminum alloy. The thickness of the aluminum alloy foil strip is 0.1-0.3 mm.

[0018] Furthermore, the aluminum alloy foil strip is cleaned before coating.

[0019] The present invention uses solder resist to define the non-welding area. Preferably, the solder resist is aluminum oxide powder or organic mica sheet. When aluminum oxide powder is used as the solder resist, the solder resist can be brushed on the surface of the aluminum alloy foil strip by coating; when organic mica sheet is used as the solder resist, the organic mica sheet can be directly placed on the surface of the aluminum alloy foil strip. When the aluminum oxide solder resist is applied, trichloroethylene can be used as a solvent.

[0020] In step (1), when coating the active alloy powder, the active alloy powder is mixed with trichloroethylene and then subjected to coating operation; the mixing mass ratio of the active alloy powder to trichloroethylene is 10:(0.5-1.0), more preferably 10:0.8. The present invention uses trichloroethylene to effectively coat the active alloy powder on the aluminum alloy foil strip, which is volatile and does not produce black residue, and can improve the coating quality. Furthermore, in order to improve the coating stability, a small amount of PS glue can be further added, and the ratio of PS glue to trichloroethylene is 0.5:5.

[0021] Furthermore, the thickness of the active alloy powder and the solder resist are the same; the thickness of the active alloy powder is 0.02-0.05 mm; and in each aluminum alloy foil strip, the length ratio of the solder resist to the active alloy powder is 3:1.

[0022] Preferably, the vacuum degree of the vacuum diffusion welding is not less than 9×10 -3 Furthermore, the vacuum degree of the vacuum diffusion welding is (4-6)×10 -3 Pa.

[0023] As a further preferred solution, the vacuum diffusion welding conditions are: heating to 320-360° C. at a rate of (8-12)° C. / min, applying a pressure of (0.8-1.5) MPa, and heat preservation for 2-4 hours.

[0024] In the above method, slitting refers to slitting the height of the welded laminated aluminum alloy foil strip according to usage requirements, and stretching refers to stretching the laminated aluminum alloy foil strip into a honeycomb core shape, which are both conventional operations in the art.

[0025] The low-temperature diffusion-welded honeycomb core of the present invention is prepared by adopting the above-mentioned preparation method.

[0026] The low-temperature diffusion welding honeycomb core of the present invention replaces the adhesive in the stretching method with low-temperature diffusion welding to form a metallurgical bond during preparation, which not only improves the black residue problem caused by the adhesive, but also makes the honeycomb core high in strength and has a good forming effect. Compared with the forming method, the production efficiency is greatly improved. In addition, the added active alloy powder reduces the diffusion welding temperature, makes the honeycomb core bonding strength higher, reduces the deformation of the aluminum alloy foil, makes the honeycomb core obtained by stretching more standardized, has better formability, and is suitable for the preparation and application of the honeycomb core. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of aluminum alloy foil lamination in the method for preparing a low-temperature diffusion welding honeycomb core of the present invention;

[0028] Figure 2 It is a schematic diagram of the stretching process in the method for preparing the low-temperature diffusion welding honeycomb core of the present invention;

[0029] Figure 3 This is a real picture of the honeycomb core obtained by the method for preparing the low-temperature diffusion welding honeycomb core of the present invention;

[0030] Figure 4 This is a microstructure diagram of the low-temperature diffusion welded honeycomb core of Example 1 of the present invention;

[0031] Figure 5 This is a microstructure diagram of the low-temperature diffusion welded honeycomb core of Comparative Example 1;

[0032] Figure 6 The microstructure diagram of the honeycomb panel obtained by welding the honeycomb core prepared in Example 1 of the present invention is shown in FIG. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0034] Example 1

[0035] The method for preparing the low-temperature diffusion welded honeycomb core of this embodiment comprises the following steps:

[0036] (1) A 0.2 mm thick 6063 aluminum alloy foil is cleaned by ultrasonic wave; then, an Al-Zn-Mg-Ge-In active alloy powder (mass percentage composition of Zn 20%, Ge 20%, Mg 10%, In 5%, Al balance) with a mesh size of 40 μm is mixed with trichloroethylene in a mass ratio of 10:0.8 as an intermediate layer solder, and coated on the surface of the 6063 foil according to the honeycomb core side length of 10 mm. The coating thickness of the active alloy powder is 0.03 mm. In the area where the active alloy powder is not coated, a 0.03 mm thick alumina solder resist (the composition of the alumina solder resist is a mixture of alumina: trichloroethylene = 10:1.2) is sprayed; then, different aluminum alloy foils are stacked so that the active alloy powder is located between the two layers of aluminum alloy foils; at the same time, the active alloy powders on the surface of each layer of aluminum alloy foil are kept staggered during stacking, and a total of 100 layers are stacked to obtain a laminated structure in which the active alloy powder and the solder resist are distributed at intervals on the surface of the aluminum alloy foil. In each aluminum alloy foil strip, the length ratio of the solder resist to the active alloy powder is 3:1.

[0037] (2) The stacked aluminum alloy foil strips are placed in a fixture and sent into a vacuum diffusion welding furnace for diffusion welding. The diffusion welding steps are as follows: first, vacuum is drawn to 5.0×10 -3 Pa, raise the temperature to 340℃ at a rate of 10℃ / min, apply a pressure of 1.0MPa, and keep warm for 3h. After the end of the heat preservation, the furnace temperature drops below 150℃, stop vacuuming, and turn off the furnace. When the furnace cools to 60℃, take it out of the furnace. After the diffusion welding is completed, the laminated aluminum foil is cut into 20mm heights and stretched into a honeycomb core shape, thus obtaining a low-temperature diffusion welded honeycomb core.

[0038] In the above-mentioned method for preparing the low-temperature diffusion welding honeycomb core, the schematic diagram of the aluminum alloy foil lamination is shown in Figure 1 The schematic diagram of the stretching process is shown in Figure 2 The actual picture of the honeycomb core finished product is as shown in Figure 3 shown.

[0039] Example 2

[0040] (1) A 0.2 mm thick 6063 aluminum alloy foil was cleaned by ultrasonic wave. Then, Al-Zn-Mg-Ge-In active alloy powder (mass percentage composition of Zn 15%, Ge 10%, Mg 5%, In 3%, Al balance) with a mesh size of 40 μm was mixed with trichloroethylene in a mass ratio of 10:0.8 as an intermediate layer brazing material and coated on the surface of the 6063 foil according to the honeycomb core side length of 8 mm. The coating thickness of the active alloy powder was 0.05 mm. In the area where the active alloy powder was not coated, a 0.05 mm thick mica sheet of corresponding size was placed. Then, different aluminum alloy foils were stacked so that the active alloy powder was located between the two layers of aluminum alloy foils. When stacking, the active alloy powders on the surface of each layer of aluminum alloy foil were staggered. A total of 100 layers were stacked to obtain a laminated structure in which the active alloy powder and the solder resist were distributed at intervals on the surface of the aluminum alloy foil. In each aluminum alloy foil, the length ratio of the solder resist to the active alloy powder was 3:1.

[0041] (2) The stacked aluminum alloy foil strips are placed in a fixture and sent into a vacuum diffusion welding furnace for diffusion welding. The diffusion welding steps are as follows: first, vacuum is drawn to 5.0×10 -3 Pa, raise the temperature to 360℃ at a rate of 10℃ / min, apply a pressure of 1.5MPa, and keep warm for 3h. After the end of the heat preservation, the furnace temperature drops below 150℃, stop vacuuming, and turn off the furnace. When the furnace cools to 60℃, take it out of the furnace. After the diffusion welding is completed, the laminated aluminum foil is cut into 15mm heights and stretched into a honeycomb core shape, thus obtaining a low-temperature diffusion welded honeycomb core.

[0042] Comparative Example 1

[0043] In the preparation method of the honeycomb core provided in Comparative Example 1, the intermediate layer material used is a conventional foil intermediate layer material, specifically: 0.03 mm thick Al foil, 0.02 mm thick Zn foil, 0.02 mm thick Ge foil, 0.01 mm thick Mg foil. The welding temperature is 380° C., the holding time is 6 hours, and the other steps and parameters are the same as those in Example 1.

[0044] Comparative Example 2

[0045] The preparation method of the honeycomb core provided in Comparative Example 2 is basically the same as that in Example 1, except that the intermediate layer solder used is different, and the solder composition used in Comparative Example 2 is: Zn 20%, Mg 10%, In 5%, and Al balance. The welding temperature is 400°C, the holding time is 6h, and the other steps and parameters are the same as in Example 1.

[0046] Comparative Example 3

[0047] The preparation method of the honeycomb core provided in Comparative Example 3 is basically the same as that in Example 1, except that the intermediate layer solder used is different, and the solder composition used in Comparative Example 3 is: Zn 20%, Ge 20%, Mg 10%, and Al balance. The welding temperature is 420°C, the holding time is 6h, and the other steps and parameters are the same as in Example 1.

[0048] Test Example 1

[0049] The microstructure of the honeycomb core prepared in Example 1 and Comparative Example 1 was examined by scanning electron microscopy. Figure 4 , 5 shown.

[0050] Depend on Figure 4 It can be seen that in the honeycomb core obtained in Example 1 of the present invention, good metallurgical bonding occurs between the two layers of aluminum alloy foil strips.

[0051] Figure 5 FIG. 1 is a microstructure diagram of a honeycomb core prepared using the conventional foil tape intermediate layer of Comparative Example 1. Figure 5 It can be seen that a clearer foil interface appears in the center of the picture, indicating that a good metallurgical bond is not formed between the two layers of foil.

[0052] The honeycomb core prepared in Example 1 was further brazed with a 1 mm thick 6063 aluminum alloy honeycomb panel to prepare a honeycomb panel. The microstructure of the honeycomb panel obtained by welding is as follows: Figure 6 shown.

[0053] Depend on Figure 6 It can be seen that the honeycomb panel obtained by brazing the honeycomb core prepared in Example 1 has good metallurgical bonding, and does not produce defects such as unwelded, inclusions, and pores. It can be seen that the honeycomb core of the present invention is suitable for brazing preparation of honeycomb panels.

[0054] Test Example 2

[0055] The tensile strength, compressive strength, flexural strength, roller peeling strength and shear strength of honeycomb panels of the same size obtained by brazing the aluminum alloy honeycomb cores of Examples 1 to 2 of the present invention and Comparative Examples 1 to 3 under the same process were investigated. The mechanical properties of honeycomb panels prepared by commercially available gluing method and molding method were compared. Among them, the test methods for tensile strength, compressive strength, flexural strength, roller peeling strength and shear strength are: GBT 1452 sandwich structure flat tensile strength test method, GBT 1453 sandwich or core structure flat compression performance test method, GB-T 1456-2005 sandwich structure bending performance test method, GBT-1457-2005 sandwich structure roller peeling strength test method, GB-T 1455-2005 sandwich or core structure shear test method. The test results are shown in Table 1.

[0056] Table 1 Comparison of mechanical properties of aluminum alloy honeycomb panels obtained by welding honeycomb cores of the embodiment and the comparative example

[0057]

[0058]

[0059] It can be seen from Table 1 that the mechanical strengths of the honeycomb panels prepared from the aluminum alloy honeycomb cores of Examples 1 to 2 of the present invention are better than those of the comparative examples, indicating that the preparation method of the low-temperature diffusion welding honeycomb core of the present invention has high strength and good forming effect, and is suitable for the preparation and application of high-performance honeycomb cores.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature diffusion-welded honeycomb core, characterized in that: The following steps are involved: (1) coating the active alloy powder on the surface of the aluminum alloy foil strip at equal intervals, coating or placing a solder resist on the area not coated with the active alloy powder, and then stacking different aluminum alloy foil strips, while keeping the active alloy powder on the surface of each layer of aluminum alloy foil strips in an alternating manner, to obtain a laminated structure with active alloy powder and solder resist distributed at intervals on the surface of the aluminum alloy foil strip; (2) vacuum diffusion welding the laminated aluminum alloy foil strips, and then cutting and stretching them into honeycomb cores to obtain; Wherein, the active alloy powder is Al-Zn-Mg-Ge-In active alloy powder; The particle size of the Al-Zn-Mg-Ge-In active alloy powder is 20-40 μm; the weight percentage composition of the Al-Zn-Mg-Ge-In active alloy powder is: Zn 15-20%, Ge 10-20%, Mg 5-10%, In 3-5%, and Al balance.

2. The method for preparing a low-temperature diffusion welded honeycomb core according to claim 1, characterized in that: The aluminum alloy foil strip is one of 3003 aluminum alloy, 6061 aluminum alloy and 6063 aluminum alloy; the thickness of the aluminum alloy foil strip is 0.1-0.3 mm.

3. The method for preparing a low-temperature diffusion-welded honeycomb core according to claim 1, characterized in that: The aluminum alloy foil strip is cleaned in advance before being coated with the active alloy powder.

4. The method for preparing a low-temperature diffusion-welded honeycomb core according to claim 1, characterized in that: The solder resist is aluminum oxide powder or organic mica sheet.

5. The method for preparing a low-temperature diffusion welded honeycomb core according to any one of claims 1 to 4, characterized in that: In step (1), when coating the active alloy powder, the active alloy powder is mixed with trichloroethylene and then subjected to coating operation; the mixing mass ratio of the active alloy powder to trichloroethylene is 10:(0.5-1.0).

6. The method for preparing a low-temperature diffusion-welded honeycomb core according to any one of claims 1 to 4, characterized in that: The thickness of the active alloy powder and the solder resist are the same; the coating thickness of the active alloy powder is 0.02-0.05 mm; in each aluminum alloy foil strip, the length ratio of the solder resist to the active alloy powder is 3:

1.

7. The method for preparing a low-temperature diffusion-welded honeycomb core according to any one of claims 1 to 4, characterized in that: The vacuum degree of the vacuum diffusion welding is not less than 9×10 -3 Pa.

8. The method for preparing a low-temperature diffusion-welded honeycomb core according to any one of claims 1 to 4, characterized in that: The vacuum diffusion welding conditions are: heating to 320-360° C. at a rate of (8-12)° C. / min, applying a pressure of (0.8-1.5) MPa, and heat preservation for 2-4 hours.

9. A low-temperature diffusion welding honeycomb core prepared by the method for preparing a low-temperature diffusion welding honeycomb core according to any one of claims 1 to 8.

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