A lightweight and high-strength Fe-Al composite plate for finned tube radiators, its preparation method and application

Abstract

The present invention discloses a lightweight and high-strength Fe-Al composite plate for a finned tube radiator, its preparation method and application, belonging to the technical field of layered products composed of metals. The preparation method of the present invention includes the following steps: (1) Metal material treatment: Prepare iron sheets and aluminum sheets, and polish the two metal sheets until polished stripes with the same direction appear; Stack the polished iron sheets and aluminum sheets alternately and keep the polished stripes in the same direction to obtain a laminated blank; (2) Room temperature pre-bonding: The laminated blank is rolled to obtain an intermediate material preliminarily bonded at room temperature; (3) High-temperature diffusion bonding: The intermediate material is heat-insulated at a certain temperature, immediately taken out after the treatment and hot-rolled to obtain a lightweight and high-strength Fe-Al composite plate. Through rolling, the surface of the sheet metal is broken and mechanically meshed, and diffusion reaction occurs during heat preservation to generate an intermetallic compound layer, and pores are eliminated to make the interface better bonded, so that the finished product has good tensile properties.

Description

Technical Field

[0001] The invention relates to the technical field of layered products composed of metals, and in particular to a lightweight and high-strength Fe-Al composite plate for a fin tube radiator, and a preparation method and application thereof. Background Art

[0002] Metal composite panels refer to a layer of metal plate covered with another metal plate to save resources and reduce costs without reducing the use effect (anti-corrosion performance, mechanical strength, etc.). In metal composite panels, based on cost and lightweight structure considerations, two or more materials with different properties are usually combined to achieve the purpose of material weight reduction and cost reduction, and to achieve the optimal configuration of each component material resource to achieve performance requirements that cannot be met by a single metal. Commonly used composite panels on the market include titanium / aluminum, titanium / steel, titanium / zinc, copper / aluminum, nickel / titanium, etc.

[0003] Fe-Al composite plate can effectively reduce the weight of the plate by adding lightweight material Al, and can reduce the cost compared with stainless steel, which makes it have broad application prospects in many industries related to people's livelihood, such as construction, automobile, electricity, etc. In addition, Fe-Al composite plate is the key material used in the production of bimetallic elliptical fin tubes for high-efficiency heat exchangers of air-cooling equipment, but my country currently relies heavily on imports of this material, and breakthroughs in its preparation technology are particularly important. The essence of Fe-Al composite plate preparation is the welding and connection process of iron and aluminum, involving the reaction of Fe and Al. It can be welded by a variety of welding methods, mainly including: fusion welding, brazing, and solid phase welding. These welding methods have achieved the connection between Fe and Al to a certain extent, but are prone to generate a large number of aggregated intermetallic compounds, and there are many types of Fe-Al intermetallic compounds, and most of them are hard and brittle. The generation of a large number of intermetallic compounds is not conducive to the bonding of the composite plate interface.

[0004] Chinese patent CN106319167A discloses a corrosion-resistant rolled aluminum-steel composite material and a preparation method thereof, and the preparation method includes four steps: material preparation, rolling, annealing and heat treatment. Material preparation: prepare aluminum plate and steel plate, and grind the surfaces of the aluminum plate and the steel plate; rolling: cold rolling the prepared aluminum plate and steel plate to form an aluminum-steel composite material; annealing: annealing the aluminum-steel composite material rolled and composited in the rolling step to make the steel completely recrystallized; heat treatment: keep the rolled aluminum-steel composite material treated in the annealing step at 610-620°C for 10-30 minutes, so that there is a layer of iron-aluminum intermetallic compound with a thickness of 4-12μm at the interface of the aluminum layer and the steel layer. This patent mainly relies on the generation of Fe-Al intermetallic compounds to improve corrosion resistance, so long annealing is required, and the generated compound layer is thicker, which cannot meet the formation of a thin compound layer to improve the bonding strength, and it is difficult to achieve the purpose of light weight and high strength. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, in the first aspect of the present invention, a method for preparing a lightweight and high-strength Fe-Al composite plate with a simple process and suitable for industrial scale production is provided, including the following steps:

[0006] (1) Metal material treatment: Prepare iron sheets and aluminum sheets, and polish the two metal sheets until polished stripes with the same direction appear; Stack the polished iron sheets and aluminum sheets alternately and keep the polished stripes in the same direction to obtain a laminated blank;

[0007] (2) Room temperature pre-bonding: The laminated blank is rolled to obtain an intermediate material preliminarily bonded at room temperature;

[0008] (3) High-temperature diffusion bonding: The intermediate material is heat-insulated at a certain temperature, and immediately taken out for hot rolling after the treatment to obtain a lightweight and high-strength Fe-Al composite plate.

[0009] Preferably, in the step (1), sandpaper with a mesh size of 180-400 is used to polish the two metal sheets.

[0010] Preferably, in the step (1), aluminum sheets are arranged on the outermost layers on both sides of the laminated blank.

[0011] Placing the aluminum sheet on the outer layer is beneficial to protecting the internal metal from oxidation during subsequent processing, and a protective atmosphere is not required.

[0012] Preferably, in the step (2), after the laminated blank is rolled, the reduction ratio in the vertical direction is 40-50%.

[0013] Preferably, in the step (3), the temperature of the heat-insulating treatment is 500-650°C, and the treatment time is 0.5-2 h.

[0014] Preferably, in the step (3), after the intermediate material subjected to the heat-insulating treatment is hot rolled, the reduction ratio in the vertical direction is 17-30%.

[0015] Based on the above process, the design concept of the present invention is that after the iron sheet and the aluminum sheet are polished and stacked, they are subjected to rolling deformation under the condition of no lubrication at room temperature. By polishing, the contact area between dissimilar metals is increased to promote bonding (if not polished, the mechanical meshing degree between metal sheets will be unsatisfactory and the design effect cannot be achieved). During the room-temperature rolling process, under the huge pressure of the rolling mill, the material undergoes severe plastic deformation, the surface of the sheet metal is broken, and a fresh and non-smooth surface is exposed for mechanical meshing, causing the iron sheet and the aluminum sheet to be initially bonded. During the subsequent high-temperature heat preservation process, a diffusion reaction occurs at the Fe-Al interface, generating a thin Fe-Al intermetallic compound layer that does not affect the interface bonding effect. And during the subsequent high-temperature rolling, continuous plastic deformation occurs while eliminating the pores left by the formation of the intermetallic compound layer, enabling better bonding at the Fe-Al interface. The present invention does not need to prepare materials by means of liquid solidification, thus avoiding various metallographic defects during the solidification process. In addition, the equipment involved in the process is an industrial rolling mill and a muffle furnace, which can achieve industrial-scale production.

[0016] Due to the hard and brittle nature of the intermetallic compound, during the subsequent service process, the intermetallic compound at the interface will become a weak phase, affecting the overall mechanical properties of the composite plate. Therefore, in the preparation of the composite plate, the formation of the intermetallic compound is usually avoided. However, the thickness of the intermetallic compound generated under the process of the present invention is moderate, and it does not reduce the interface bonding strength and thus the mechanical properties of the material as conventionally understood. This composite plate exhibits good strength and toughness. First, its contribution to the bonding between iron and aluminum dissimilar metals is greater than its adverse effect on the composite plate itself. Second, this intermetallic compound instead acts as a strengthening phase to enhance the strength of the composite plate, making it have a tensile strength superior to that calculated by the mixing law of pure iron and pure aluminum.

[0017] In the second aspect of the present invention, there is provided a lightweight and high-strength Fe-Al composite plate with good interface bonding effect and few metallographic defects, which is prepared by the method of the first aspect of the present invention.

[0018] In the third aspect of the present invention, there is provided an application of a lightweight and high-strength Fe-Al composite plate, specifically as a metal material in the preparation of finned tube radiators.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] The present invention provides a method for preparing a lightweight and high-strength Fe-Al composite plate, the process of which is simple, does not need to prepare materials by means of liquid solidification, and is suitable for industrial-scale production.

[0021] The present invention provides a lightweight and high-strength Fe-Al composite plate, which has few metallographic defects and good tensile properties.

[0022] The present invention also provides an application of a lightweight and high-strength Fe-Al composite plate in the preparation of finned tube radiators. Description of the Drawings

[0023] Figure 1 It is a light microscope photograph of the lightweight and high-strength Fe-Al composite plate of Example 1;

[0024] Figure 2 It is a light microscope photograph of the hardness indentation of the lightweight and high-strength Fe-Al composite plate of Example 1;

[0025] Figure 3 It is the tensile curve of the lightweight and high-strength Fe-Al composite plate of Example 1. Detailed Embodiments

[0026] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0027] In the following examples:

[0028] Iron sheet specifications: 5 mm × 5 mm × 0.5 mm; aluminum sheet specifications: 5 mm × 5 mm × 0.2 mm.

[0029] Example 1

[0030] Preparation method of lightweight and high-strength Fe-Al composite plate:

[0031] (1) Metal material treatment: Take 3 iron sheets and 4 aluminum sheets, remove the surface impurities, and polish the surfaces of the two metal sheets in one direction with 180-mesh sandpaper until the polished stripes with the same direction appear, and then wash them clean and set aside; Stack the polished iron sheets and aluminum sheets alternately in the stacking order of "Al-Fe-Al-Fe-Al-Fe-Al", and keep the polished stripes of the metal sheet surfaces in the same direction, stack the iron sheets and aluminum sheets neatly to obtain a stacked blank;

[0032] (2) Room temperature pre-bonding: Wrap the obtained stacked blank in a steel sheet and perform rolling deformation at room temperature, control the reduction rate in the vertical direction of the rolled stacked blank to be 40%, and obtain a preliminarily bonded intermediate material;

[0033] (3) High-temperature diffusion bonding: Place the obtained intermediate material in a muffle furnace at 600 °C and keep it warm for 1 h, then immediately take it out and perform hot rolling and thinning, control the reduction rate in the vertical direction to be 17%, and obtain a lightweight and high-strength Fe-Al composite plate with good interfacial bonding.

[0034] The interlayer morphology of the lightweight and high-strength Fe-Al composite plate obtained in this example was observed through an optical microscope (model: Carl Zeiss Axio Lab.A1; magnification: 200 times). From Figure 1 It can be seen that there are two types of bonding methods for the composite plate, namely mechanical meshing and diffusion bonding. The Fe layer and the Al layer are tightly bonded, and there is a thin intermetallic compound layer (IMCs) between the layers, which improves the bonding strength between the plates. In contrast to the laminated blank polished in this example, if the iron sheet and the aluminum sheet are directly rolled without polishing, the metal sheets do not rely on mechanical meshing, and it is very difficult to achieve pre-bonding at room temperature, that is, there are voids between different metal sheet layers without bonding. During the subsequent heat preservation process, oxides will be generated on the surfaces of both Fe and Al, and the effect of tight bonding between the Fe layer and the Al layer cannot be achieved.

[0035] The lightweight and high-strength Fe-Al composite plate obtained in this example was tested using a microhardness tester (model: Magui-H200; load: 500 g; holding time: 10 s). Figure 2 It shows that the Fe-Al interface is well bonded. Even under a pressure of 500 g, there is no cracking at the interface position, indicating good interface bonding; and the indentation morphology is clear, and the indentations in the Fe area and the Al area are not much different, reflecting the result of coordinated deformation

[0036] Four standard tensile specimens of the lightweight and high-strength Fe-Al composite plate of this example were prepared, and their tensile properties were tested using an electronic universal testing machine (model: MTS E45.105; displacement speed: 0.5 mm / s). As Figure 3 shown, the tensile strength of the composite plate is 520 - 570 MPa, and the elongation is 8.0% - 9.2%, showing good tensile properties.

[0037] Example 2

[0038] Preparation method of lightweight and high-strength Fe-Al composite plate:

[0039] (1) Metal material treatment: Take 2 iron sheets and 3 aluminum sheets, remove the surface impurities, and polish the surfaces of the two metal sheets in one direction using 320-mesh sandpaper until the polished stripes with the same direction appear, and then wash them clean and set aside; stack the polished iron sheets and aluminum sheets alternately in the stacking order of "Al-Fe-Al-Fe-Al", and keep the polished stripes of the metal sheet surfaces in the same direction, stack the iron sheets and aluminum sheets neatly to obtain a laminated blank;

[0040] (2) Room temperature pre-bonding: Wrap the obtained laminated blank in a steel sheet and perform rolling deformation at room temperature, control the reduction rate of the laminated blank in the vertical direction after rolling to be 50%, and obtain a preliminarily bonded intermediate material;

[0041] (3) High-temperature diffusion bonding: Place the obtained intermediate material in a muffle furnace at 500 °C and keep it for 2 h. Then immediately take it out and perform hot rolling to thin it, controlling the reduction rate in the vertical direction to be 20%, to obtain a lightweight and high-strength Fe-Al composite plate with good interfacial bonding.

[0042] Example 3

[0043] Preparation method of lightweight and high-strength Fe-Al composite plate:

[0044] (1) Metal material treatment: Take 4 iron sheets and 5 aluminum sheets, remove the surface impurities, and use 400-mesh sandpaper to polish the surfaces of the two metal sheets in one direction until the polished stripes with the same direction appear. Then wash them clean and set aside; Stack the polished iron sheets and aluminum sheets alternately in the stacking order of "Al-Fe-Al-Fe-Al-Fe-Al-Fe-Al", and keep the polished stripes of the metal sheet surfaces in the same direction. Stack the iron sheets and aluminum sheets neatly to obtain a laminated blank.

[0045] (2) Room-temperature pre-bonding: Wrap the obtained laminated blank in a steel sheet and perform rolling deformation at room temperature, controlling the reduction rate of the laminated blank in the vertical direction after rolling to be 40%, to obtain a preliminarily bonded intermediate material.

[0046] (3) High-temperature diffusion bonding: Place the obtained intermediate material in a muffle furnace at 650 °C and keep it for 0.5 h. Then immediately take it out and perform hot rolling to thin it, controlling the reduction rate in the vertical direction to be 30%, to obtain a lightweight and high-strength Fe-Al composite plate with good interfacial bonding.

[0047] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A preparation method of a lightweight and high-strength Fe-Al composite plate, characterized in that It includes the following steps: (1) Metal material treatment: Prepare iron sheets and aluminum sheets, and polish the two metal sheets until polishing streaks with the same direction appear; alternately stack the polished iron sheets and aluminum sheets and keep the polishing streaks in the same direction to obtain a laminated blank; The outermost layers on both sides of the laminated blank are aluminum sheets; (2) Room temperature pre-bonding: The laminated blank is rolled to obtain an intermediate material preliminarily bonded at room temperature; After the laminated blank is rolled, the reduction ratio in the vertical direction is 40-50%; (3) High-temperature diffusion bonding: The intermediate material is heat-insulated at a certain temperature, immediately taken out and hot-rolled after the treatment to obtain a lightweight and high-strength Fe-Al composite plate; The temperature of the heat-insulation treatment is 500-650 °C, and the treatment time is 0.5-2 h; after the heat-insulated intermediate material is hot-rolled, the reduction ratio in the vertical direction is 17-30%.

2. The method according to claim 1, characterized in that: In the step (1), 180-400 mesh sandpaper is used to polish the two metal sheets.

3. A lightweight and high-strength Fe-Al composite plate, characterized in that: It is prepared by the method described in claim 1 or 2.

4. Use of a lightweight and high-strength Fe-Al composite plate as described in claim 3, characterized in that: Use it as a metal material in the application of preparing finned tube radiators.

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