Interface directional regulation method for substrate-selective pre-micro-oxidized steel-aluminum composite thin strip

Abstract

This invention discloses a method for directional control of the interface of steel / aluminum composite strips using selective pre-micro-oxidation of the matrix. The method includes: determining the target interfacial bonding strength based on service requirements; pre-treating the bonding surfaces of the steel and aluminum strips; selecting either the steel or aluminum strip as the pre-micro-oxidation matrix based on the target interfacial bonding strength and preheating it to form a pre-micro-oxidation layer on the bonding surface; then stacking the preheated matrix with the other matrix to form a composite billet; and rolling the resulting composite billet to cause localized cracking of the pre-micro-oxidation layer and induce the aluminum matrix to embed into cracks and pores, forming a mechanically interlocking structure. This invention achieves directional control of the interfacial bonding strength of steel / aluminum composite strips, improving interfacial bonding stability and control precision.

Description

Technical Field

[0001] This invention belongs to the field of preparation and precision rolling technology of dissimilar metal composite materials, and particularly relates to a method for directional control of the interface of steel-aluminum composite strips by selective pre-micro-oxidation of the matrix. Background Technology

[0002] Steel / aluminum composite strips combine the high strength, wear resistance, and corrosion resistance of stainless steel with the lightweight, corrosion resistance, and good conductivity of aluminum alloys, making them promising for applications in flexible electronic devices, precision sensors, microrobots, and functional structural materials.

[0003] Existing steel / aluminum composite strips are mainly produced using cold rolling composite methods. However, due to significant differences between steel and aluminum in terms of yield strength, elastic modulus, coefficient of thermal expansion, and deformation resistance, problems such as incoordination of interlayer deformation, insufficient interfacial bonding strength, and sheet warping easily occur during traditional cold rolling composite processes. Although appropriately increasing the reduction rate can improve the bonding to some extent, it also significantly increases work hardening and residual stress, which is detrimental to the overall performance and forming stability of the composite strip.

[0004] To improve deformation compatibility and bonding performance during dissimilar metal composite processes, previous studies have proposed using differential temperature rolling. By adjusting the difference in deformation resistance between the two substrates, this method effectively improves the plastic deformation compatibility of dissimilar metals during the composite process and further enhances the interfacial bonding strength. For steel / aluminum composite strips, differential temperature rolling not only affects the plastic deformation behavior of the steel and aluminum substrates but also directly relates to the formation state of the micro-oxide layer at the bonding interface and the evolution of the interfacial structure during rolling, thus significantly impacting the interfacial bonding performance of the composite strip.

[0005] Different service scenarios for steel / aluminum composite strips impose varying requirements on interfacial bonding strength. If the interfacial oxide layer is too thin, the interfacial structure reconstruction and mechanical interlocking are insufficient; if the interfacial oxide layer is too thick or too continuous and dense, it will hinder the contact of fresh metal and weaken effective bonding. Therefore, there is an urgent need for an interfacial control method that can select the type of preheated substrate and preheating parameters based on the target bonding strength, and utilize the rolling process to induce localized cracking of the pre-micro-oxide layer and embedding of the aluminum substrate. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for directional control of the interface of steel-aluminum composite thin strips with selective pre-micro-oxidation of the matrix, thereby resolving the issues existing in the prior art.

[0007] To achieve the above objectives, the present invention provides a method for directional control of the interface of steel-aluminum composite thin strips with selective pre-micro-oxidation of the matrix, comprising: Determine the target interfacial bonding strength based on the service requirements of the steel / aluminum composite strip; Obtain steel strips and aluminum strips, and perform interface pretreatment on the surfaces of the steel strips and aluminum strips to be bonded; Based on the target interface bonding strength, one of the steel strip and the aluminum strip is selected as the pre-micro-oxidation substrate. The pre-micro-oxidation substrate is preheated to form a pre-micro-oxidation layer on the bonding surface of the pre-micro-oxidation substrate. The preheated pre-micro-oxidation substrate is then stacked with the other substrate to form a billet, so that the bonding surface of the steel strip and the bonding surface of the aluminum strip are in close contact with each other to form a steel / aluminum heterothermal composite billet. The steel / aluminum heterothermal composite billet is rolled and composited, causing local cracking of the pre-micro-oxidation layer and prompting the aluminum matrix to embed into the cracks and pores of the pre-micro-oxidation layer to form a mechanical interlocking structure, thereby achieving directional control of the interfacial bonding strength of the steel / aluminum composite strip.

[0008] Optionally, the interface pretreatment includes mechanically grinding and cleaning the surfaces of the steel strip and the aluminum strip to be bonded, removing the passivation film and adhering impurities from the surfaces to be bonded.

[0009] Optionally, based on the target interface bonding strength, the corresponding steel substrate preheating temperature, aluminum substrate preheating temperature, and holding time are determined so that the thickness of the pre-micro-oxide layer corresponds to the target interface bonding strength.

[0010] Optionally, preheating can be performed using one of the following methods: annealing furnace heating, resistance heating, or induction heating, and the holding time is 1 to 10 minutes.

[0011] Optionally, when the steel strip is selected as the pre-micro-oxidized substrate, the preheating temperature of the steel substrate is 300–600°C.

[0012] Optionally, when the aluminum strip is selected as the pre-micro-oxidation substrate, the preheating temperature of the aluminum substrate is 200–600°C.

[0013] Optionally, the steel strip is SS304 stainless steel strip, the aluminum strip is 5052 aluminum alloy strip, and the single-layer thickness of both the steel strip and the aluminum strip is 0.05-0.2mm.

[0014] Optionally, during the rolling composite process, the pre-micro-oxidation layer cracks in the local stress concentration area, exposing a new metal contact surface and providing an embedding channel for the aluminum substrate. The aluminum substrate flows and fills the cracks, pores, and uneven areas of the interface in the pre-micro-oxidation layer, so that the interface evolves from a flat direct contact to a tenon structure with mechanical interlocking characteristics.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention selectively preheats either the steel or aluminum substrate to pre-construct an adjustable-thickness pre-micro-oxide layer at the steel / aluminum bonding interface. It also synergistically controls the target bonding strength, the selection of the preheated substrate, the thickness of the pre-micro-oxide layer, and the evolution of the rolling-induced interface structure. Instead of solely relying on temperature differences to improve the deformation compatibility between dissimilar metals, this invention achieves proactive design of the steel / aluminum composite strip interface structure and bonding performance. During subsequent high-temperature rolling, the interface region is under the coupled effect of rolling compressive stress and interfacial shear stress. The pre-micro-oxide layer cracks in localized stress concentration areas, exposing new metal contact surfaces and promoting effective steel / aluminum interface contact. Furthermore, it provides an embedding channel for the highly ductile aluminum substrate, allowing it to flow and fill oxide layer cracks, pores, and uneven areas of the interface under rolling pressure. This causes the interface to evolve from a locally flat, direct contact to a tenon-and-mortise structure with mechanical interlocking characteristics, improving the stability of the interface bonding.

[0016] This invention achieves controllable preparation of the interfacial bonding strength of steel / aluminum composite strips by adjusting the type of preheating substrate, the preheating temperature of the steel substrate, the preheating temperature of the aluminum substrate, and the holding time. This is done by adjusting the preheating substrate thickness, the preheating temperature of the steel substrate, the preheating temperature of the aluminum substrate, and the holding time. When the preheating substrate is within a suitable thickness range, it is more likely to undergo effective cracking and interfacial reconstruction during rolling, which is beneficial for fresh metal contact, the formation of mechanical interlocking structures, and improved bonding strength. When the preheating substrate is too thin, its promoting effect on interfacial structure reconstruction is limited; when the preheating substrate is too thick, it may weaken effective metal contact at the interface, hindering further improvement in interfacial bonding strength. Therefore, this invention allows for the selection of either steel substrate preheating or aluminum substrate preheating processes to obtain different levels of interfacial bonding strength based on the differentiated requirements for the interfacial bonding performance of steel / aluminum composite strips under different service scenarios.

[0017] This invention solves the problems of difficulty in effectively controlling the state of the interface oxide layer, large fluctuations in bonding strength, and difficulty in consistently obtaining target performance in the existing steel / aluminum composite strip preparation process. It avoids the shortcomings of traditional processes, such as increased residual stress, process complexity, and decreased performance stability caused by simply relying on large reduction or subsequent heat treatment to improve bonding strength. It improves the interfacial bonding strength and its control precision of steel / aluminum composite strips, realizing the transformation from traditional passive composite to active control of interface structure, and provides a new technical approach for the optimization of interface structure and performance-oriented design of steel / aluminum composite strips. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 2 These are diagrams illustrating the interfacial bonding strength of steel / aluminum composite strips under different substrate preheating conditions according to embodiments of the present invention. Figure 3 This is a topographic image of the steel / aluminum composite strip interface tenon joint structure obtained by preheating the steel substrate to 400℃ according to an embodiment of the present invention. Figure 4 This is a topographic image of the steel / aluminum composite strip interface tenon joint structure obtained by preheating the aluminum substrate to 300°C according to an embodiment of the present invention. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0021] Example 1 like Figure 1 As shown, this embodiment provides a method for directional control of the interface of steel / aluminum composite strips with selective pre-micro-oxidation of the matrix. By selecting one side of the steel strip or aluminum strip as the pre-micro-oxidation matrix, a pre-micro-oxidation layer with controllable thickness is pre-constructed on the bonding surface. During subsequent rolling, the pre-micro-oxidation layer is locally fractured, the aluminum matrix is ​​embedded, and a mechanical interlocking structure is formed at the interface, thereby achieving directional control of the bonding strength of the steel / aluminum composite strip interface. The method includes: Step S1: Determine the target interfacial bonding strength. Based on the service requirements of the steel / aluminum composite strip, determine the range of target interfacial bonding strength.

[0022] Step S2, Raw Material Preparation. Steel strip and aluminum strip are provided as composite raw materials.

[0023] The steel strip is SS304 stainless steel strip, and the aluminum strip is 5052 aluminum alloy strip; the single-layer thickness of the steel strip and the aluminum strip is 0.05~0.2mm respectively.

[0024] Step S3, Interface Pretreatment. The surfaces of the steel strip and the aluminum strip to be bonded are mechanically ground and cleaned in sequence to remove the passivation film and adhering impurities from the surfaces to be bonded.

[0025] The interface pretreatment includes mechanical polishing and cleaning. The mechanical polishing is done with a wire brush, and the cleaning is done with alcohol, acetone or other organic solvents.

[0026] Step S4: Selective pre-micro-oxidation of the substrate. Based on the target interfacial bonding strength range, select one side of the steel strip or aluminum strip as the pre-micro-oxidation substrate, selectively preheat the pre-micro-oxidation substrate, and keep the other side of the substrate at room temperature or below the temperature of the preheated side, so that a pre-micro-oxidation layer with a thickness of 1.0 to 2 μm is formed on the bonding surface of the pre-micro-oxidation substrate.

[0027] The selective preheating involves selecting the type of preheating substrate based on the target interface bonding strength, and determining the corresponding steel substrate temperature, aluminum substrate temperature, and holding time, so that the interface to be bonded forms a pre-micro-oxidation layer of a thickness corresponding to the target bonding strength.

[0028] Preheating is performed using one of the following methods: annealing furnace heating, resistance heating, or induction heating. The preheating holding time is 1 to 10 minutes.

[0029] When preheating the steel substrate, the preheating temperature is 300–600 ℃.

[0030] When preheating the aluminum substrate, the preheating temperature is 200–600 °C.

[0031] Step S5, Differential Temperature Assembly. The preheated hot substrate and the room temperature substrate are stacked together to form a steel / aluminum differential temperature composite billet.

[0032] Step S6: Heterothermal Rolling Composite. The heterothermal composite billet is fed into a rolling mill for rolling composite. Under the combined action of rolling compressive stress and interfacial shear stress, the pre-micro-oxidation layer at the interface undergoes localized cracking, prompting the aluminum matrix to embed into interfacial cracks, pores, and uneven areas, thereby forming an interfacial mechanical interlocking structure. This improves the interfacial bonding stability of the composite strip. The interfacial bonding strength of the steel / aluminum composite strip under different matrix preheating conditions is as follows: Figure 2 As shown.

[0033] Example 1; This example illustrates a method for controlling the interfacial bonding strength of steel / aluminum composite strips under selective preheating of the steel matrix.

[0034] Based on the usage requirements of the steel / aluminum composite strip, the required interfacial bonding strength range is set, and the corresponding steel substrate preheating process parameters are selected.

[0035] SS304 stainless steel strip and 5052 aluminum alloy strip are selected as composite materials. The dimensions of the steel strip and aluminum strip are 100 mm in length, 30 mm in width and 0.10 mm in thickness.

[0036] The surfaces to be bonded by the steel strip and aluminum strip are pretreated by mechanically grinding the surfaces with a wire brush to remove the oxide film, passivation layer and attached impurities. Then, they are cleaned with alcohol and dried.

[0037] Steel strip was used as the pre-micro-oxidation matrix, while aluminum strip was kept at room temperature. The steel strip was placed in a heating furnace for preheating treatment, and the holding time was 3 minutes. After preheating, the hot steel strip and the room temperature aluminum strip were stacked together to form a steel / aluminum heterothermal composite billet, which was then sent to a rolling mill for heterothermal rolling to obtain a steel / aluminum composite thin strip.

[0038] Table 1 shows the thickness of the pre-micro-oxidation layer formed at the interface to be bonded under different preheating temperatures of the steel substrate, as well as the rolling process and bonding strength of the resulting steel / aluminum composite strip.

[0039] Table 1 As can be seen from Table 1, under selective preheating of the steel substrate, the thickness of the pre-micro-oxide layer and the interfacial bonding strength of the interface to be bonded change significantly with the change of the preheating temperature of the steel substrate. The interfacial bonding strength first increases and then decreases with the increase of the preheating temperature. Under the conditions of this embodiment, a preheating temperature of 400 ℃ is more conducive to obtaining a higher interfacial bonding strength.

[0040] Figure 3 The image shows the interface morphology of the steel / aluminum composite strip obtained by preheating the steel substrate to 400 °C. Figure 3 As shown, the interface between the 304 stainless steel layer and the 5052 aluminum alloy layer exhibits obvious local undulations and interlocking characteristics. The interface is no longer a completely flat contact state, but rather forms a protruding, embedded, and interlocking structure in local areas. This interface morphology indicates that after selective preheating of the steel substrate, the pre-micro-oxidation layer formed at the interface to be bonded undergoes local cracking under the combined action of rolling compressive stress and interface shear stress. This provides a channel for the aluminum substrate to flow and fill into the interface cracks, pores, and undulating areas, thereby forming a tenon joint structure with mechanical interlocking effect.

[0041] Example 2; This example illustrates a method for controlling the interfacial bonding performance of steel / aluminum composite strips under selective preheating of the aluminum matrix.

[0042] SS304 stainless steel strip and 5052 aluminum alloy strip are selected as composite materials. The dimensions of the steel strip and aluminum strip are 100 mm in length, 30 mm in width and 0.10 mm in thickness.

[0043] The surfaces to be bonded by the steel strip and aluminum strip are pretreated by mechanically grinding the surfaces with a wire brush to remove the oxide film, passivation layer and attached impurities, followed by cleaning with alcohol.

[0044] An aluminum strip was used as the preheating substrate, while the steel strip was kept at room temperature. The aluminum strip was placed in a heating furnace for preheating treatment, and the holding time was 3 minutes.

[0045] After preheating, the hot aluminum strip and the room-temperature steel strip are stacked together to form a steel / aluminum heterothermal composite billet, which is then fed into a rolling mill for heterothermal rolling to obtain a steel / aluminum composite thin strip.

[0046] Table 2 shows the thickness of the pre-micro-oxide layer formed at the interface to be bonded and the interfacial bonding strength of the resulting steel / aluminum composite strip under different aluminum substrate preheating temperatures.

[0047] Table 2 As shown in Table 2, under selective preheating of the aluminum substrate, the thickness of the pre-micro-oxide layer formed at the bonding interface and the interfacial bonding strength of the resulting steel / aluminum composite strip both change significantly with the change of the aluminum substrate preheating temperature. Among them, the interfacial bonding strength of the resulting composite strip is higher when the aluminum substrate preheating temperature is 300 ℃ and the holding time is 3 min.

[0048] Figure 4 Interface morphology of steel / aluminum composite strips obtained by preheating the aluminum substrate to 300 °C. (See diagram below.) Figure 4 As shown, the interface between the 304 stainless steel layer and the 5052 aluminum alloy layer is generally smooth, but intermittent protrusions and embedding features can be observed in local areas, indicating that a certain degree of local plastic flow and interlocking occurred at the interface during rolling. Compared with a completely flat interface, this local embedding structure is beneficial to improving the mechanical bonding effect of the steel / aluminum interface, indicating that selective preheating of the aluminum matrix can improve the plastic flow capacity of the aluminum matrix, promote its filling into the undulating areas of the interface, and thus form a local mechanical interlocking structure.

[0049] The above results show that by adjusting the preheating temperature of the aluminum substrate, the state of the pre-micro-oxide layer at the interface to be bonded and the flow and filling behavior of the aluminum substrate can be changed, and the bonding performance of the steel / aluminum composite strip interface can be further controlled.

[0050] Example 3; This example illustrates the corresponding controllable relationship between substrate selective preheating process parameters, interfacial pre-micro-oxide layer thickness, and the interfacial bonding strength of steel / aluminum composite strips. According to the experimental data in Tables 1 and 2, under different substrate selective preheating conditions, variations in steel substrate temperature, aluminum substrate temperature, and holding time lead to the formation of pre-micro-oxide layers of varying thicknesses at the bonding interface, resulting in different corresponding interfacial bonding strengths.

[0051] SS304 stainless steel strip and 5052 aluminum alloy strip are selected as composite materials. The dimensions of the steel strip and aluminum strip are both a mm in length, b mm in width, and h mm in thickness.

[0052] The surfaces to be bonded by the steel strip and aluminum strip are pretreated by mechanically grinding the surfaces with a wire brush to remove the oxide film, passivation layer and attached impurities, followed by cleaning with alcohol.

[0053] Based on the service requirements of steel / aluminum composite strips, the target interfacial bonding strength range is pre-set. The mechanical properties correspond to the thickness of the interface oxide layer. And select the appropriate preheating process parameters. Use stainless steel strip as the preheating substrate, and the temperature is... The aluminum strip is kept at room temperature; or the aluminum strip is used as a preheating substrate at a temperature of The stainless steel strip is kept at room temperature.

[0054] The stainless steel or aluminum strip is placed in a heating furnace for preheating treatment, and the holding time is [duration missing]. t / min.

[0055] The preheated hot substrate and the unpreheated substrate are stacked together to form a steel / aluminum heterothermal composite billet, which is then sent to a rolling mill for heterothermal rolling composite.

[0056] In some embodiments, the thickness of the interface pre-micro oxide layer With the temperature of the steel substrate Aluminum substrate temperature and heat preservation time t The following relationship exists between them: Preferably, the relation can be expressed as: in, The thickness of the pre-micro-oxidation layer at the interface is expressed in μm. The preheating temperature of the steel substrate is expressed in °C. The preheating temperature of the aluminum substrate is expressed in °C. t The heat preservation time is expressed in minutes. a, b, d, g ，C These are the fitting coefficients. K This is the temperature factor coefficient. Its value can be obtained by fitting experimental data based on the specific material system, surface condition, and rolling process parameters.

[0057] In some embodiments, the interfacial bonding strength of the steel / aluminum composite strip... With the thickness of the pre-micro oxide layer at the interface The following relationship exists between them: When using a steel substrate preheating condition, the thickness of the interfacial pre-micro oxide layer is... Temperature factor coefficient K and interfacial bonding strength They respectively satisfy the following relations: When using aluminum substrate preheating conditions, the thickness of the interface pre-micro oxide layer is... Temperature factor coefficient K and interfacial bonding strength They respectively satisfy the following relations: As shown in the examples above, by adjusting the type of preheated substrate, the temperature of the steel substrate, the temperature of the aluminum substrate, and the holding time, pre-micro-oxidation layers of different thicknesses can be formed at the interface to be bonded, and the bonding strength of the steel / aluminum composite strip interface can be further controlled. The correspondence between the target interface bonding strength and the selective pre-micro-oxidation process parameters is shown in Table 3.

[0058] Table 3 The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for directional control of the interface of steel-aluminum composite thin strips with selective pre-micro-oxidation of the matrix, characterized in that, Includes the following steps: Determine the target interfacial bonding strength based on the service requirements of the steel / aluminum composite strip; Obtain steel strips and aluminum strips, and perform interface pretreatment on the surfaces of the steel strips and aluminum strips to be bonded; Based on the target interface bonding strength, one of the steel strip and the aluminum strip is selected as the pre-micro-oxidation substrate. The pre-micro-oxidation substrate is preheated to form a pre-micro-oxidation layer on the bonding surface of the pre-micro-oxidation substrate. The preheated pre-micro-oxidation substrate is then stacked with the other substrate to form a billet, so that the bonding surface of the steel strip and the bonding surface of the aluminum strip are in close contact with each other to form a steel / aluminum heterothermal composite billet. The steel / aluminum heterothermal composite billet is rolled and composited, causing local cracking of the pre-micro-oxidation layer and prompting the aluminum matrix to embed into the cracks and pores of the pre-micro-oxidation layer to form a mechanical interlocking structure, thereby achieving directional control of the interfacial bonding strength of the steel / aluminum composite strip.

2. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strip interface orientation control according to claim 1, characterized in that, Interface pretreatment includes mechanically grinding and cleaning the surfaces of the steel strip and the aluminum strip to be bonded, removing the passivation film and adhering impurities from the surfaces to be bonded.

3. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 1, characterized in that, Based on the target interface bonding strength, the corresponding steel substrate preheating temperature, aluminum substrate preheating temperature, and holding time are determined so that the thickness of the pre-micro-oxide layer corresponds to the target interface bonding strength.

4. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 3, characterized in that, The preheating is performed using one of the following methods: annealing furnace heating, resistance heating, or induction heating, and the holding time is 1 to 10 minutes.

5. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 3, characterized in that, When the steel strip is selected as the pre-micro-oxidation substrate, the preheating temperature of the steel substrate is 300-600°C.

6. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 3, characterized in that, When the aluminum strip is selected as the pre-micro-oxidation substrate, the preheating temperature of the aluminum substrate is 200–600°C.

7. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 1, characterized in that, The steel strip is SS304 stainless steel strip, and the aluminum strip is 5052 aluminum alloy strip. The single-layer thickness of both the steel strip and the aluminum strip is 0.05-0.2 mm.

8. The method for selective pre-micro-oxidation of the matrix in steel-aluminum composite thin strips with directional interface control according to claim 1, characterized in that, During the rolling process, the pre-micro-oxidation layer cracks in the local stress concentration area, exposing a new metal contact surface and providing an embedding channel for the aluminum substrate. The aluminum substrate flows and fills the cracks, pores, and uneven areas of the interface in the pre-micro-oxidation layer, causing the interface to evolve from a flat direct contact to a tenon structure with mechanical interlocking characteristics.

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