Preparation method of aluminum-silicon alloy brazing filler metal plate containing brazing flux

Abstract

The invention provides a preparation method of a brazing flux-containing aluminum-silicon alloy brazing filler metal plate, which comprises the following steps of: mixing aluminum-silicon alloy powder with brazing flux powder, and rolling the mixed powder into a plate by adopting a powder rolling mill; and the plate is heated and subjected to heat preservation under the protective atmosphere, and the aluminum-silicon alloy brazing filler metal plate containing the brazing flux is obtained. The preparation method is simple in process, short in flow, capable of achieving continuous production, high in material utilization rate and yield, high in production efficiency and low in needed cost; the prepared aluminum-silicon alloy brazing filler metal plate containing the brazing flux is high in quality, good in flatness, uniform in thickness, free of edge warping, free of cracks, compact in structure and uniform in brazing flux distribution, and can be applied to large-scale production and preparation of composite aluminum alloy brazing strips containing the brazing flux.

Description

Technical Field

[0001] The invention belongs to the field of aluminum alloy brazing, and in particular, relates to the preparation of a self-containing flux aluminum-silicon alloy brazing material plate, which is a key technology in the preparation of a self-containing flux composite aluminum alloy brazing plate strip. Background Art

[0002] The brazing method is currently a common method for producing aluminum alloy heat exchangers. However, aluminum and aluminum alloy materials are usually produced in an atmospheric environment, and a dense oxide film will form on their surface. This dense oxide film does not wet the aluminum brazing material during brazing, which hinders the flow of the brazing material melt and the fusion welding with the aluminum material. Therefore, during brazing, it is necessary to break the dense oxide film and allow the molten brazing material to contact and wet the fresh aluminum alloy surface.

[0003] At present, the two methods of pre-spraying Nocolock flux and vacuum brazing are commonly used in industrial production to eliminate the influence of oxide film. The pre-coating flux method is generally to spray or dip a layer of Nocolock flux on the surface of the assembled aluminum heat exchanger, and braze in an inert gas protection brazing furnace. When the brazing material melts, the flux destroys the dense oxide film layer to expose the fresh aluminum surface, improve the wetting of the brazing material melt and the fresh aluminum surface, and ensure the welding quality of the product, but it will cause a large amount of residual flux residue. Once these residues enter the coolant, they will accelerate the corrosion of the aluminum heat exchanger and affect its service life. The vacuum brazing method uses the evaporation of the Mg element in the brazing material layer at the brazing temperature to destroy the strong and dense oxide film layer, improve the wettability of the brazing material and the aluminum material, and thus obtain a high-quality aluminum heat exchanger. However, the entire brazing process is in a sub-vacuum state (3.5*10 -3 The production process is completed in a vacuum furnace under 200 Pa. The price of vacuum furnace equipment is high, resulting in high production costs. In addition, the production is intermittent and the production efficiency is low.

[0004] With the advancement of science and technology, aluminum heat exchangers are developing in the direction of small size, light weight and long life. High-performance aluminum heat exchangers have higher and higher requirements for the uniformity of the flux spray layer in the inert gas shielded brazing process. Therefore, it is necessary to provide high-performance aluminum alloy brazing materials to meet the needs of industrial production. In this context, the use of self-containing flux brazing aluminum alloy composite materials can solve this problem well. The most critical material in the self-containing flux brazing aluminum alloy composite material is the self-containing flux brazing filler metal plate.

[0005] At present, a process of pre-embedding brazing flux in aluminum alloy brazing material to replace the original spraying brazing flux and brazing under a protective atmosphere has been disclosed, and the brazing quality is good. However, the currently known brazing flux-containing brazing flux layer preparation process is relatively complicated. For example, CN113210608A discloses that the brazing flux powder and aluminum silicon alloy powder are mixed evenly, loaded into a pure aluminum sheath, evacuated to 0.5-2Pa, hot isostatic pressing is performed at 450-500°C and a pressure of 100-150MPa, and the holding time is 4-6h. The hot isostatic pressing billet is then milled (to remove the outer pure aluminum layer) and rolled to obtain the brazing flux layer. This preparation method not only requires expensive equipment, but also has a complex process flow and a long preparation time. In addition, the mass of the brazing flux layer produced at a single time is small, and only about 100kg of the brazing flux layer can be prepared, resulting in low production efficiency. In addition, the pressed billet needs to have the surrounding pure aluminum layer milled, resulting in a lot of waste and high production cost. This preparation method is difficult to achieve large-scale industrial production.

[0006] CN111843280A discloses a method for manufacturing a self-brazing aluminum alloy layer composite material, wherein Al-Si brazing alloy powder and brazing agent powder are mechanically mixed uniformly, and then formed into a self-brazing aluminum alloy layer block blank of 8mm*600mm*800mm rectangular parallelepiped shape by a press. This method requires a large hydraulic press to achieve good forming, the equipment cost is high, and only about 10Kg of rectangular brazing material blank can be prepared each time. The amount of brazing material blank prepared at a single time is small, and it is difficult to achieve large-scale production.

[0007] For example, CN114473385A discloses that a frame structure is set on the surface of the core aluminum alloy slab to form a concave frame, and aluminum alloy powder and mixed powder mixed with flux are filled into the concave frame in three layers to form a powder layer, and then a cover plate and the frame are welded, and the powder layer is sealed in the concave frame to obtain a pre-embedded flux billet, and then heated and hot rolled to obtain a flux-containing composite plate. Although this method is simple in process, the powder layer enclosed in the concave frame is in a natural accumulation state, there are gaps between powder particles and a large amount of gas exists therein, which brings difficulty to the subsequent composite rolling, and the enclosed gas is also difficult to remove, and bubbles will occur during annealing, affecting the quality of the material. This problem needs to be solved in industrial production. Summary of the invention

[0008] In order to solve the above technical problems, the present application provides a method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate.

[0009] To achieve the above objectives, this application proposes the following solutions: The present application provides a method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) The aluminum-silicon alloy powder and the brazing flux powder are mixed evenly, and the mixed powder is rolled into a plate using a powder rolling mill; (2) The plate is heated and kept warm under a protective atmosphere to obtain a brazing flux-containing aluminum-silicon alloy brazing plate.

[0010] Preferably, in step (1), the rolling speed is 0.5-6 m / min, more preferably 1.5-4.5 m / min. The preferred powder rolling speed is conducive to obtaining a self-containing flux aluminum-silicon alloy brazing plate with a dense structure, a flat surface, a uniform thickness, no cracks, and no warping.

[0011] Preferably, in step (1), the powder rolling used may be hot rolling or cold rolling; when the powder rolling is hot rolling, the hot rolling temperature is 400-450° C. Cold rolling is further preferred, as cold rolling can prevent oxidation of the powder during heating and hot rolling, shorten the process flow, and reduce energy consumption.

[0012] Preferably, in step (2), the thickness of the self-containing flux aluminum-silicon alloy brazing plate is 8-10 mm.

[0013] Preferably, in step (2), the protective atmosphere may be a nitrogen atmosphere or an argon atmosphere. Based on cost considerations, a nitrogen atmosphere is further preferred.

[0014] Preferably, in step (2), the temperature of the insulation is 300-550°C, and the insulation time is 2-5 hours. More preferably, the temperature of the heating insulation is 450-520°C, and the insulation time is 3.5-5 hours.

[0015] Preferably, the mass ratio of the aluminum-silicon alloy powder to the flux powder is (92-98):(8-2).

[0016] Preferably, the Si content in the aluminum-silicon alloy powder is 5.5~12.5wt.%, and more preferably 6.8~11.8wt.%; the oxygen content in the aluminum-silicon alloy powder is less than or equal to 1000ppm; the particle size of the aluminum-silicon alloy powder is 80~250 mesh, and more preferably 100~180 mesh.

[0017] Preferably, the flux is at least one of potassium fluoroaluminate powder and cesium fluoroaluminate powder. Based on cost considerations, potassium fluoroaluminate powder is preferred. The particle size of the flux is 180-400 mesh.

[0018] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: The preparation method of the self-containing flux aluminum-silicon alloy brazing plate provided by the present application has a simple process, a short flow, can realize continuous production, and has high material utilization rate, yield rate, and production efficiency, can reduce costs, has good benefits, and can be applied to large-scale production; the prepared self-containing flux aluminum-silicon alloy brazing plate has high quality, good flatness, uniform thickness, no warping, dense structure, and uniform flux distribution. The prepared self-containing flux aluminum-silicon alloy brazing plate can be single-sided or double-sided composited with the core aluminum alloy, and can realize large-scale production of self-containing flux aluminum alloy composite brazing plates and strips, which can reduce costs and achieve good economic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a picture of the self-fluxing aluminum-silicon alloy brazing sheet obtained by powder rolling in Example 1.

[0021] Figure 2 This is the SEM image of the self-containing flux aluminum-silicon alloy brazing plate prepared in Example 1.

[0022] Figure 3 This is the SEM image of the self-containing flux aluminum-silicon alloy brazing plate prepared in Example 2.

[0023] Figure 4 This is the SEM image of the self-containing flux aluminum-silicon alloy brazing plate prepared in Example 3.

[0024] Figure 5 This is the SEM image of the self-containing flux aluminum-silicon alloy brazing plate prepared in Example 4.

[0025] Figure 6 This is a sample image obtained by powder rolling in Comparative Example 1.

[0026] Figure 7 This is a sample image obtained by powder rolling in Comparative Example 2. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0028] Example 1 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 270 mesh and aluminum silicon alloy powder with a particle size of 120 mesh are mixed in a weight ratio of 3:97, the silicon content in the aluminum silicon alloy is 9%, and the oxygen content is less than 800 ppm, and the materials are mixed in a mixer at a mixing speed of 10 revolutions / min for a mixing time of 4 hours to obtain a mixture; (2) The mixed material is continuously conveyed into a powder rolling mill for cold rolling into a plate. The powder rolling mill is a 2-roll rolling mill with a rolling speed of 3 m / min to obtain a plate with a thickness of 9 mm. Figure 1 As shown, it can be seen that the surface of the rolled self-containing brazing flux aluminum-silicon alloy brazing sheet is smooth and has no cracks; (3) The plate is sent to an annealing furnace and heated and kept warm in a nitrogen atmosphere at a temperature of 500°C for 4 hours to obtain a finished self-contained brazing flux aluminum-silicon alloy brazing plate. The plate has good flatness, uniform thickness, no warping, dense structure, and no cracks. The metallographic examination of the finished plate is performed. Figure 2 As shown in the figure, it can be seen that the obtained self-containing flux aluminum-silicon alloy brazing plate has a uniform and dense structure and the flux is evenly distributed.

[0029] Example 2 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 250 mesh and aluminum silicon alloy powder with a particle size of 125 mesh are mixed in a weight ratio of 6:94, the silicon content in the aluminum silicon alloy is 11%, and the oxygen content is less than 800 ppm, and the materials are mixed in a mixer at a mixing speed of 12 revolutions per minute for a mixing time of 2 hours to obtain a mixture; (2) The mixed material is cold rolled into a plate by a powder rolling mill, the powder rolling mill is a 2-roll rolling mill, the rolling speed is 4.5 m / min, and a plate with a thickness of 10 mm is obtained; (3) The plate is heated and kept warm in a nitrogen atmosphere at a temperature of 450°C for 5 hours to obtain a finished self-contained brazing flux aluminum-silicon alloy brazing plate. The finished plate is dense, smooth, flat, uniform in thickness, without warping or cracks. Metallographic examination is performed on the finished plate. Figure 3 As shown in the figure, it can be seen that the obtained self-containing flux aluminum-silicon alloy brazing plate has a uniform and dense structure and the flux is evenly distributed.

[0030] Example 3 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 300 mesh and aluminum silicon alloy powder with a particle size of 80 mesh are mixed in a weight ratio of 8:92, the silicon content in the aluminum silicon alloy is 7%, and the oxygen content is less than 600 ppm, and the materials are mixed in a mixer at a mixing speed of 15 revolutions per minute for a mixing time of 4 hours to obtain a mixture; (2) The mixed material is cold rolled into a plate by a powder rolling mill, the powder rolling mill is a 2-roll rolling mill, the rolling speed is 1.5 m / min, and a plate with a thickness of 8 mm is obtained; (3) The plate is heated and kept warm in a nitrogen atmosphere at a temperature of 520°C for 3.5 hours to obtain a finished self-contained brazing flux aluminum-silicon alloy brazing plate. The finished plate is dense, smooth, flat, uniform in thickness, without warping or cracks. Metallographic examination is performed on the finished plate. Figure 4 As shown in the figure, it can be seen that the obtained self-containing flux aluminum-silicon alloy brazing plate has a uniform and dense structure and the flux is evenly distributed.

[0031] Example 4 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 200 mesh and aluminum silicon alloy powder with a particle size of 180 mesh are mixed in a weight ratio of 8:92, the silicon content in the aluminum silicon alloy is 7%, and the oxygen content is less than 700 ppm, and the materials are mixed in a mixer at a mixing speed of 15 revolutions per minute for a mixing time of 4 hours to obtain a mixture; (2) hot rolling the mixed material into a plate by a powder rolling mill, the powder rolling mill is a 2-roll rolling mill, the hot rolling temperature is 450-480°C, the rolling speed is 4.5 m / min, and a plate with a thickness of 8 mm is obtained; (3) The plate is heated and kept warm in a nitrogen atmosphere at 400°C for 4 hours to obtain a finished self-contained brazing flux aluminum-silicon alloy brazing plate. The finished plate is dense, smooth, flat, uniform in thickness, without warping or cracks. Metallographic examination is performed on the finished plate. Figure 5 As shown in the figure, it can be seen that the obtained self-containing flux aluminum-silicon alloy brazing plate has a uniform and dense structure and the flux is evenly distributed.

[0032] Comparative Example 1 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 270 mesh and aluminum silicon alloy powder with a particle size of 120 mesh are mixed in a weight ratio of 3:97, the silicon content in the aluminum silicon alloy is 9%, and the oxygen content is less than 800 ppm, and the materials are mixed in a mixer at a mixing speed of 10 revolutions / min for a mixing time of 4 hours to obtain a mixture; (2) The mixed material is continuously conveyed into a powder rolling mill for cold rolling into a plate. The powder rolling mill is a 2-roll rolling mill with a rolling speed of 6.5 m / min. The sample obtained by rolling is as follows: Figure 6 As shown in the figure, it can be seen that the rolling is not formed. After analysis, it may be because the rolling speed is too fast, which makes it difficult to roll successfully.

[0033] Comparative Example 2 A method for preparing a self-containing brazing flux aluminum-silicon alloy brazing plate, comprising: (1) Potassium fluoroaluminate powder with a particle size of 270 mesh and aluminum silicon alloy powder with a particle size of 500 mesh are mixed in a weight ratio of 3:97, the silicon content in the aluminum silicon alloy is 9%, and the oxygen content is less than 800 ppm, and the materials are mixed in a mixer at a mixing speed of 10 revolutions / min for a mixing time of 4 hours to obtain a mixture; (2) The mixed material is continuously conveyed into a powder rolling mill and cold rolled into a plate. The powder rolling mill is a 2-roll rolling mill with a rolling speed of 3m / min. The sample obtained by rolling is as follows Figure 7 As shown in the figure, it can be seen that the rolled product is broken. After analysis, it may be because the aluminum silicon powder particles are too fine to be rolled into shape.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a self-containing flux aluminum-silicon alloy brazing plate, characterized in that: include: (1) Mixing aluminum silicon alloy powder and brazing flux powder, and rolling the mixed powder into a plate using a powder rolling mill; (2) The plate is heated and kept warm under a protective atmosphere to obtain a brazing flux-containing aluminum-silicon alloy brazing plate.

2. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: In step (1), the rolling speed is 0.5-6 m / min.

3. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 2, characterized in that: In step (1), the rolling speed is 1.5-4.5 m / min.

4. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: In step (2), the thickness of the self-containing flux aluminum-silicon alloy brazing plate is 8-10 mm.

5. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: In step (2), the protective atmosphere is a nitrogen atmosphere; the heating and insulation temperature is 300-550° C.; and the insulation time is 2-5 h.

6. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 5, characterized in that: In step (2), the heating and insulation temperature is 450-520° C. and the insulation time is 3.5-5 h.

7. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: The mass ratio of the aluminum silicon alloy powder to the flux powder is (92-98): (8-2).

8. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: The Si content in the aluminum-silicon alloy powder is 5.5-12.5wt.%; the oxygen content in the aluminum-silicon alloy powder is less than or equal to 1000ppm; and the particle size of the aluminum-silicon alloy powder is 80-250 mesh.

9. The method for preparing the self-containing flux aluminum-silicon alloy brazing plate according to claim 1, characterized in that: The flux is at least one of potassium fluoroaluminate powder and cesium fluoroaluminate powder; the particle size of the flux is 180-400 meshes.

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