Manufacturing method for eliminating edge cracks of aluminum alloy cast-rolled strip

Abstract

The invention relates to the technical field of continuous casting and rolling of metal materials, and discloses a manufacturing method for eliminating an edge gap of an aluminum alloy cast-rolled strip, which comprises the following steps of: providing an active gradient functional baffle plate, and mounting the active gradient functional baffle plate at a side plugging position where a cast-rolling machine is in contact with molten aluminum; nitrogen with preset flow is supplied to the contact interface of the baffle and the molten aluminum, and the high temperature of the molten aluminum is utilized to excite the active reaction source in the working surface of the baffle to generate in-situ chemical reaction with the nitrogen, so that a layer of hexagonal boron nitride solid lubricating film is continuously generated between the baffle and the edge part of the solidified aluminum alloy strip; by means of the hexagonal boron nitride solid lubricating film, original high-friction contact between the baffle and the edge of the aluminum alloy cast-rolled strip is converted into low-friction solid lubricating contact. By means of an in-situ lubricating mechanism, friction of a side plugging interface in the casting and rolling process is effectively reduced, and formation of edge cracks is restrained.

Description

Technical Field

[0001] This invention relates to the field of continuous casting and rolling technology of metal materials, specifically a manufacturing method for eliminating edge cracks in aluminum alloy cast and rolled strip. Background Technology

[0002] Twin-roll casting technology for aluminum alloys is a short-process manufacturing technology that closely integrates the continuous casting and hot rolling of molten aluminum alloys. By directly introducing molten aluminum between a pair of rotating casting rolls with internal cooling water, the molten aluminum solidifies rapidly and is simultaneously hot-rolled and deformed, thereby directly obtaining coiled aluminum alloy strips. Because twin-roll casting technology for aluminum alloys significantly shortens the production process and reduces equipment investment and energy consumption, it is widely used in the production of various aluminum alloy sheet and strip billets.

[0003] In twin-roll casting and rolling processes, in order to limit the width of the molten aluminum in the casting and rolling zone and prevent the molten metal from leaking from both ends of the casting rolls, side sealing baffles are usually installed on both sides of the rolls. The side sealing baffles are in direct contact with the high-temperature molten aluminum and the edge of the aluminum alloy strip that has initially solidified on the surface of the rolls. In existing casting and rolling process practices, as the molten aluminum solidifies in the casting and rolling zone and moves downward with the rolls to form strip, the edge of the strip that has initially solidified and is still in a high-temperature plastic state will slide relative to the stationary side sealing baffles, resulting in direct solid-phase contact and friction.

[0004] However, due to the lack of effective lubrication between the baffle and the solidified aluminum alloy edge, there is a huge frictional force between them. This frictional force generates a drag force opposite to the direction of movement at the strip edge, which is converted into a huge tensile stress and concentrated on the strip edge. Since the newly formed strip has a low fracture strength at high temperatures, when the tensile stress caused by the above friction exceeds the material's fracture strength at that temperature, it will directly lead to cracks in the strip edge, i.e., edge cracks. This edge crack defect is a common and difficult-to-eliminate quality problem in aluminum alloy casting and rolling production, which seriously affects the yield and surface integrity of the final product. Therefore, this invention proposes a manufacturing method to eliminate edge cracks in aluminum alloy casting and rolling strip to overcome the shortcomings of the prior art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip. This method solves the technical problem that the lack of effective lubrication between the side sealing baffle and the edge of the high-temperature solidified aluminum alloy strip results in huge frictional force, which in turn causes excessive tensile stress at the edge of the strip, ultimately leading to frequent edge cracks and affecting the yield.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip, the method comprising the following steps: S1. Provide an active gradient functional baffle, and install the active gradient functional baffle at the side sealing position of the casting and rolling mill in contact with the molten aluminum; S2. During the aluminum alloy casting and rolling process, nitrogen gas of a preset flow rate is supplied at the interface between the active gradient functional baffle and the molten aluminum. S3. Utilizing the high temperature of the molten aluminum, the active reaction source in the working surface of the active gradient functional baffle is activated to undergo an in-situ chemical reaction with the nitrogen gas, thereby continuously generating a layer of hexagonal boron nitride solid lubricating film between the active gradient functional baffle and the edge of the solidified aluminum alloy strip. S4. The original high-friction contact between the active gradient functional baffle and the edge of the aluminum alloy cast strip is transformed into a low-friction solid lubrication contact through the in-situ generated hexagonal boron nitride solid lubrication film.

[0007] By spontaneously generating a layer of hexagonal boron nitride solid lubricant with a layered crystal structure in situ at the friction interface, the physical properties of the interface contact are changed, and the interaction force between the interfaces is transformed into low-intensity shear force between the hexagonal boron nitride crystal layers. This reduces the original high frictional contact between the edges of the aluminum alloy cast and rolled strip and eliminates the key stress source that causes cracks at the edges of the aluminum alloy cast and rolled strip.

[0008] Preferably, in step S3, the active reaction source is amorphous boron that is gradient-distributed inside the active gradient functional baffle. Compared with crystalline boron, amorphous boron has higher chemical reactivity and can react with nitrogen more quickly and fully at the limited temperature provided by the aluminum liquid, ensuring the formation rate and coverage of the hexagonal boron nitride solid lubricating film.

[0009] Preferably, the active gradient functional baffle includes a base layer, a transition layer, and a working layer sequentially along the thickness direction of the active gradient functional baffle. The mass fraction of amorphous boron in the three layers is distributed in a gradient: the mass fraction of amorphous boron in the working layer is 25.0%-30.0%, the mass fraction of amorphous boron in the transition layer is 10.0%-15.0%, and the mass fraction of amorphous boron in the base layer is 1.0%-5.0%. This gradient distribution structure ensures that the working layer, which is in direct contact with the molten aluminum, contains the highest concentration of active reaction source to guarantee the rapid formation of the lubricating film. The concentration of amorphous boron decreases inward, ensuring the overall mechanical strength and thermal stability of the baffle.

[0010] Preferably, the substrate layer, the transition layer and the working layer of the active gradient functional baffle are all made of α-phase silicon nitride as the matrix material and contain yttrium oxide and aluminum oxide as sintering aids. The α-phase silicon nitride matrix provides excellent high temperature resistance, thermal shock resistance and chemical inertness to molten aluminum.

[0011] Preferably, the working layer powder comprises: 58.0%-67.0% by mass of α-phase silicon nitride powder, 25.0%-30.0% by mass of amorphous boron powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder; The transition layer powder comprises: 73.0%-82.0% by mass of α-phase silicon nitride powder, 10.0%-15.0% by mass of amorphous boron powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder; The base layer powder comprises: 83.0%-91.0% by mass of α-phase silicon nitride powder, 1.0%-5.0% by mass of amorphous boron powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder.

[0012] Preferably, in step S1, when the active gradient functional baffle is installed at the side sealing position of the casting and rolling mill, the top of the working surface of the active gradient functional baffle is ensured to be 5.0mm ± 0.5mm higher than the roll surface. This installation height ensures that the working surface of the baffle can effectively contact the molten aluminum in the casting and rolling pool, thereby utilizing the high temperature of the molten aluminum to stimulate the in-situ reaction, and at the same time forming an effective physical seal for the molten pool.

[0013] Preferably, in step S2, the total flow rate of nitrogen supplied to the interface region where the active gradient functional baffle contacts the molten aluminum is 0.1 L / min to 0.5 L / min. This flow rate range ensures that sufficient nitrogen is provided for the in-situ reaction, while avoiding excessive gas flow causing disturbance to the molten pool surface or excessive cooling effect on the interface region.

[0014] Preferably, the process parameters for the aluminum alloy casting and rolling process are: aluminum alloy melt temperature of 688℃-692℃, and casting and rolling speed of 0.65m / min-0.68m / min. This range of process parameters provides stable temperature conditions for the occurrence of in-situ chemical reactions and matches the formation and consumption rate of the lubricating film.

[0015] Preferably, during the aluminum alloy casting and rolling process, the thickness of the aluminum alloy strip is 6.5mm-6.6mm.

[0016] Preferably, during the aluminum alloy casting and rolling process, the exit temperature of the aluminum alloy strip is 280℃-288℃.

[0017] This invention provides a manufacturing method for eliminating edge cracks in cast aluminum alloy strip. It has the following beneficial effects: 1. This invention generates a hexagonal boron nitride solid lubricating film in situ between the side sealing baffle and the edge of the aluminum alloy strip, thereby changing the physical properties at the interface between the active gradient functional baffle and the molten aluminum. Utilizing the unique layered crystal structure of hexagonal boron nitride and its easy slippage between layers, the original high-friction solid-phase contact that leads to cracking is transformed into a low-friction solid lubricating contact. This change in the properties at the interface between the active gradient functional baffle and the molten aluminum reduces the frictional force acting on the edge of the strip and the destructive tensile stress generated by the frictional force, thereby effectively inhibiting the initiation and propagation of edge cracks and improving the edge quality and yield of the aluminum alloy cast and rolled strip.

[0018] 2. This invention utilizes the gradient distribution of amorphous boron, an active reaction source, inside the baffle, and the continuous supply of nitrogen during the casting and rolling process. By using the high temperature of the molten aluminum itself as the reaction activation condition, when the cast and rolled strip moves downward and consumes the lubricating film, the newly replenished high-temperature molten aluminum at the interface will continuously stimulate the baffle working surface to generate a new lubricating film. This ensures that the low-friction solid lubrication state is stably maintained throughout the entire continuous casting and rolling production cycle, thereby guaranteeing the continuity of the effect of suppressing edge cracks in the strip and the stability of the process.

[0019] 3. The active gradient functional baffle used in this invention has both excellent surface functionality and overall structural stability. The active gradient functional baffle uses α-phase silicon nitride as the matrix material, which ensures that the active gradient functional baffle itself has excellent high temperature resistance, thermal shock resistance and chemical inertness to aluminum melt. At the same time, the active reaction source amorphous boron is distributed in a gradient form, so that the most active component is concentrated on the working surface where the reaction needs to occur, while the performance of the matrix material of the active gradient functional baffle body is preserved to the greatest extent. This not only ensures the structural stability and service life of the baffle under harsh working conditions, but also avoids secondary pollution to the aluminum alloy melt due to the controllable reaction products and stable matrix material, thus ensuring the purity of the final product. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to comparative examples and test cases. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Examples 1-3: Example 1: This embodiment provides a manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip, comprising the following steps: Fabrication of active gradient functional baffles: Powder preparation: Weigh and mix the powders according to the following mass percentages to obtain the mixed powders for the base layer, transition layer, and working layer: Working layer mixed powder: 67.0% α-phase silicon nitride powder, 25.0% amorphous boron powder, 6.0% yttrium oxide powder, and 2.0% aluminum oxide powder; Transition layer mixed powder: 82.0% α-phase silicon nitride powder, 10.0% amorphous boron powder, 6.0% yttrium oxide powder, and 2.0% aluminum oxide powder; The substrate layer mixed powder consists of 91.0% α-phase silicon nitride powder, 1.0% amorphous boron powder, 6.0% yttrium oxide powder, and 2.0% aluminum oxide powder.

[0022] Molding: The above three mixed powders are sequentially filled into the mold and cold isostatically pressed under a pressure of 200MPa to obtain a mixed powder green body consisting of a base layer, a transition layer and a working layer.

[0023] Sintering: The mixed powder green body is placed in a sintering furnace and heated to 1650°C at a heating rate of 5°C / min under a nitrogen atmosphere. After holding at this temperature for 2 hours, it is cooled with the furnace to obtain the final active gradient functional baffle.

[0024] Manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip: Pre-treatment: The levelness of the rolls of the casting and rolling mill was measured to confirm that the levelness of the aluminum alloy rolls was 0.02 mm / m.

[0025] Installation: Install the prepared active gradient functional baffle at the side sealing position of the casting and rolling mill, and ensure that the top of the working surface of the active gradient functional baffle is 4.5mm higher than the roll surface.

[0026] Casting and rolling: A3003 aluminum alloy is used for casting and rolling. The casting and rolling process parameters are set as follows: The total flow rate of nitrogen supplied to the interface region where the active gradient functional baffle contacts the molten aluminum is 0.1 L / min; The melting temperature of the aluminum alloy is 688℃; The casting and rolling speed is 0.65 m / min; The thickness of the finished aluminum alloy strip is 6.5mm; The exit temperature of finished aluminum alloy strip is 280℃.

[0027] Example 2: This embodiment provides a manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip, comprising the following steps: Fabrication of active gradient functional baffles: Powder preparation: Weigh and mix the powders according to the following mass percentages to obtain the mixed powders for the base layer, transition layer, and working layer: Working layer mixed powder: 58.0% α-phase silicon nitride powder, 30.0% amorphous boron powder, 8.0% yttrium oxide powder, and 4.0% aluminum oxide powder; Transition layer mixed powder: 73.0% α-phase silicon nitride powder, 15.0% amorphous boron powder, 8.0% yttrium oxide powder, and 4.0% aluminum oxide powder; The substrate layer mixed powder consists of 83.0% α-phase silicon nitride powder, 5.0% amorphous boron powder, 8.0% yttrium oxide powder, and 4.0% aluminum oxide powder.

[0028] Molding: The above three mixed powders are sequentially filled into the mold and cold isostatically pressed under a pressure of 200MPa to obtain a mixed powder green body consisting of a base layer, a transition layer and a working layer.

[0029] Sintering: The mixed powder green body is placed in a sintering furnace and heated to 1850°C at a heating rate of 5°C / min under a nitrogen atmosphere. After holding at this temperature for 2 hours, it is cooled with the furnace to obtain the final active gradient functional baffle.

[0030] Manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip: Pre-treatment: The levelness of the rolls of the casting and rolling mill was measured to confirm that the levelness of the aluminum alloy rolls was 0.02 mm / m.

[0031] Installation: Install the prepared active gradient functional baffle at the side sealing position of the casting and rolling mill, and ensure that the top of the working surface of the active gradient functional baffle is 5.5mm higher than the roll surface.

[0032] Casting and rolling: A3003 aluminum alloy is used for casting and rolling. The casting and rolling process parameters are set as follows: The total flow rate of nitrogen supplied to the interface region where the active gradient functional baffle contacts the molten aluminum is 0.5 L / min; The melting temperature of the aluminum alloy is 692℃; The casting and rolling speed is 0.68 m / min; The thickness of the finished aluminum alloy strip is 6.6mm; The exit temperature of the finished aluminum alloy strip is 288℃.

[0033] Example 3: This embodiment provides a manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip, comprising the following steps: Fabrication of active gradient functional baffles: Powder preparation: Weigh and mix the following powders according to the following mass percentages to obtain the mixed powders of the base layer, transition layer and working layer.

[0034] Working layer mixed powder: 62.5% α-phase silicon nitride powder, 27.5% amorphous boron powder, 7.0% yttrium oxide powder, and 3.0% aluminum oxide powder; Transition layer mixed powder: 77.5% α-phase silicon nitride powder, 12.5% ​​amorphous boron powder, 7.0% yttrium oxide powder, and 3.0% aluminum oxide powder; The substrate layer mixed powder consists of 87.0% α-phase silicon nitride powder, 3.0% amorphous boron powder, 7.0% yttrium oxide powder, and 3.0% aluminum oxide powder.

[0035] Molding: The above three mixed powders are sequentially filled into the mold and cold isostatically pressed under a pressure of 200MPa to obtain a mixed powder green body consisting of a base layer, a transition layer and a working layer.

[0036] Sintering: The mixed powder green body is placed in a sintering furnace and heated to 1750°C at a heating rate of 5°C / min under a nitrogen atmosphere. After holding at this temperature for 2 hours, it is cooled with the furnace to obtain the final active gradient functional baffle.

[0037] Manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip: Pre-treatment: The rolls of the casting and rolling mill are measured for levelness, and the roll levelness is confirmed to be 0.02 mm / m.

[0038] Installation: Install the prepared active gradient functional baffle at the side sealing position of the casting and rolling mill, and ensure that the top of the working surface of the active gradient functional baffle is 5.0 mm higher than the roll surface.

[0039] Casting and rolling: A3003 aluminum alloy is used for casting and rolling. The casting and rolling process parameters are set as follows: The total flow rate of nitrogen supplied to the interface region where the active gradient functional baffle contacts the molten aluminum is 0.3 L / min; The melting temperature of the aluminum alloy is 690℃; The casting and rolling speed is 0.67 m / min; The thickness of the finished aluminum alloy strip is 6.55mm; The exit temperature of the finished aluminum alloy strip is 284℃.

[0040] Comparative Examples 1-2: Comparative Example 1: Compared with Example 1, the difference is that a common silicon nitride baffle without amorphous boron is used for side sealing, otherwise the same.

[0041] Comparative Example 2: Compared with Example 1, the difference is that nitrogen gas is not supplied to the interface area where the active gradient functional baffle contacts the molten aluminum during the aluminum alloy casting and rolling process; otherwise, they are the same.

[0042] Test Example 1-2: Test Example 1: Edge Crack Performance Test.

[0043] Test method: A continuous 300-meter length of aluminum alloy cast-rolled strip obtained in Examples 1-3 and Comparative Examples 1-2 was taken as the test sample. Visual inspection and eddy current flaw detection were combined to inspect the edge of the aluminum alloy cast-rolled strip meter by meter along the length direction. The location of macroscopically visible cracks was recorded, and the total length of the edge containing cracks in the aluminum alloy cast-rolled strip was counted.

[0044] The edge pass rate is defined as an evaluation index, and its calculation formula is as follows: Edge pass rate (%) = ; Test results: Table 1. Edge pass rate test results for each embodiment and comparative example Results analysis: Test results show that the aluminum alloy cast-rolled strip prepared using the technical solutions of Examples 1-3 achieved an edge qualification rate of over 99.5%. This is because, during the casting and rolling process, the amorphous boron active source within the working surface of the active gradient functional baffle undergoes an in-situ chemical reaction with the supplied nitrogen gas at high temperatures in the molten aluminum. This forms a continuous and stable hexagonal boron nitride solid lubricating film between the active gradient functional baffle and the edge of the aluminum alloy strip. The hexagonal boron nitride solid lubricating film transforms the interface of the aluminum alloy cast-rolled strip from a solid-phase high-friction contact to a low-friction solid lubricating contact, reducing the tensile stress acting on the edge of the aluminum alloy cast-rolled strip and thus suppressing the generation of edge cracks in the aluminum alloy cast-rolled strip.

[0045] Comparative Example 1 uses an active gradient functional baffle without amorphous boron. This baffle lacks in-situ reaction capability and cannot generate a lubricating film at the interface. Consequently, a high-friction state is maintained between the baffle and the edge of the aluminum alloy cast-rolled strip, resulting in severe edge cracking and a pass rate below 50.0%. Comparative Example 2, although using a baffle containing an active reaction source, also lacks another key reactant for the chemical reaction due to the absence of nitrogen supply. This also prevents the formation of a hexagonal boron nitride lubricating film, leaving the aluminum alloy cast-rolled strip interface in a high-friction state and resulting in a low edge pass rate.

[0046] Data comparison confirms that providing a baffle containing a gradient distribution of active reaction sources and supplying specific gaseous reactants at the interface during the casting and rolling process, thereby activating an in-situ chemical reaction using the process's own temperature, is the key to achieving the transformation of interfacial frictional properties and ultimately eliminating edge cracks. The complete implementation of this technical solution ensures the dynamic stability of the low-friction interface during continuous casting and rolling, thus obtaining high-quality aluminum alloy cast and rolled strip edges.

[0047] Test Example 2: Interfacial Friction Coefficient Test Test method: To quantitatively evaluate the frictional characteristics of the interface between baffle materials with different activity gradients and aluminum alloy strip edges, this test uses a high-temperature friction and wear testing machine for simulation testing.

[0048] Sample preparation: The active gradient functional baffles prepared in Examples 1-3 and the ordinary silicon nitride baffle in Comparative Example 1 were cut into block samples with a size of 10mm×10mm×5mm. The samples from Examples 1-3 were placed in a tube furnace and kept at 690℃ in a nitrogen atmosphere for 30 minutes to simulate the in-situ reaction to generate a hexagonal boron nitride lubricating film.

[0049] The ordinary silicon nitride baffle of Comparative Example 1 was placed in a tube furnace and held at 690°C in an argon atmosphere for the same duration to simulate the surface state of the ordinary silicon nitride baffle in an inert environment.

[0050] Another active gradient functional baffle sample prepared by the process of Example 1 was placed in a tube furnace and kept at 690°C in an argon atmosphere for the same duration. This active gradient functional baffle sample was used for the test of Comparative Example 2 to simulate the interface state where there is an active reaction source but no lubricating film can be generated due to the lack of nitrogen.

[0051] Friction test: The block sample treated above is fixed on the high temperature friction and wear tester as the lower sample. The upper sample is an A3003 aluminum alloy pin with a diameter of 5 mm. The test temperature is set to 285℃, the normal load is 5N, the sliding speed is 0.1m / s, and the total test time is 600 seconds. The high temperature friction and wear tester automatically records the friction torque and calculates the average friction coefficient in the stable friction stage.

[0052] Test results: Table 2. Average coefficient of friction at the interface between each sample and A3003 aluminum alloy Results analysis: The test results quantitatively show that the average friction coefficient between the active gradient functional baffle material used in Examples 1-3 and the A3003 aluminum alloy after high-temperature nitrogen atmosphere treatment is less than 0.25. This reduction in the average friction coefficient is due to the chemical reaction between the amorphous boron in the working surface of the active gradient functional baffle and nitrogen at high temperature, which generates a hexagonal boron nitride solid lubricating film on the surface between the active gradient functional baffle and the edge of the A3003 aluminum alloy strip. The layered crystal structure of the hexagonal boron nitride solid lubricating film is prone to slippage when subjected to shear force, thus exhibiting an extremely low friction coefficient on a macroscopic scale.

[0053] The ordinary silicon nitride baffle in Comparative Example 1, lacking an active reaction source, has a surface of pure silicon nitride ceramic, forming a typical ceramic-metal dry friction pair with the aluminum alloy. The strong interfacial bonding results in an average friction coefficient as high as 0.78. Although the sample in Comparative Example 2 was taken from Example 1 and has the material basis for generating a lubricating film, the simulation of casting and rolling was conducted in an argon atmosphere without nitrogen supply, which prevented the in-situ chemical reaction from proceeding. The active gradient functional baffle and the edge of the A3003 aluminum alloy strip remained in a high-friction contact state, and the measured average friction coefficient was 0.73, which is on the same order of magnitude as the result of Comparative Example 1.

[0054] The test data on the coefficient of friction confirmed the working mechanism of this technical solution from the perspective of interface physical properties. The solid lubricating film generated on the surface of the sample in the embodiment is the reason for the change of interface friction properties from high friction to low friction. This change in interface properties effectively reduces the frictional resistance applied to the edge of the strip during the casting and rolling process, providing a basis for the improvement in the edge qualification rate of aluminum alloy strip observed in Test Example 1.

Claims

1. A manufacturing method for eliminating edge cracks in cast-rolled aluminum alloy strip, characterized in that, Includes the following steps: S1. Provide an active gradient functional baffle, and install the active gradient functional baffle at the side sealing position of the casting and rolling mill in contact with the molten aluminum; S2. During the aluminum alloy casting and rolling process, nitrogen gas of a preset flow rate is supplied at the interface between the active gradient functional baffle and the molten aluminum. S3. Utilizing the high temperature of the molten aluminum, the active reaction source in the working surface of the active gradient functional baffle is activated to undergo an in-situ chemical reaction with the nitrogen gas, thereby continuously generating a layer of hexagonal boron nitride solid lubricating film between the active gradient functional baffle and the edge of the solidified aluminum alloy strip. S4. The original high-friction contact between the active gradient functional baffle and the edge of the aluminum alloy cast strip is transformed into a low-friction solid lubrication contact through the in-situ generated hexagonal boron nitride solid lubrication film, thereby eliminating the edge cracks of the aluminum alloy cast strip.

2. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, In step S3, the active reaction source is amorphous boron that is gradient-distributed inside the active gradient functional baffle.

3. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 2, characterized in that, The active gradient functional baffle includes, along the thickness direction of the active gradient functional baffle, a base layer, a transition layer and a working layer in sequence. The mass fraction of amorphous boron in the three layers is distributed in a gradient: the mass fraction of amorphous boron in the working layer is 25.0%-30.0%, the mass fraction of amorphous boron in the transition layer is 10.0%-15.0%, and the mass fraction of amorphous boron in the base layer is 1.0%-5.0%.

4. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 3, characterized in that, The substrate layer, transition layer and working layer of the active gradient functional baffle are all made of α-phase silicon nitride as the matrix material and contain yttrium oxide and alumina as sintering aids.

5. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 4, characterized in that, The working layer powder comprises: 58.0%-67.0% by mass of α-phase silicon nitride powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder; The transition layer powder comprises: 73.0%-82.0% by mass of α-phase silicon nitride powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder; The base layer powder comprises: 83.0%-91.0% by mass of α-phase silicon nitride powder, 6.0%-8.0% by mass of yttrium oxide powder, and 2.0%-4.0% by mass of alumina powder.

6. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, In step S1, when the active gradient functional baffle is installed at the side sealing position of the casting and rolling mill, ensure that the top of the working surface of the active gradient functional baffle is 5.0mm ± 0.5mm higher than the roll surface.

7. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, In step S2, the total flow rate of nitrogen supplied to the interface region where the active gradient functional baffle contacts the molten aluminum is 0.1 L / min to 0.5 L / min.

8. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, The process parameters for the aluminum alloy casting and rolling process are as follows: the aluminum alloy melt temperature is 688℃-692℃, and the casting and rolling speed is 0.65m / min-0.68m / min.

9. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, During the aluminum alloy casting and rolling process, the thickness of the aluminum alloy strip is 6.5mm-6.6mm.

10. The manufacturing method for eliminating edge cracks in aluminum alloy cast-rolled strip according to claim 1, characterized in that, During the aluminum alloy casting and rolling process, the exit temperature of the aluminum alloy strip is 280℃-288℃.

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