A manufacturing method of 3104 aluminum material shutter aluminum strip by continuous casting and rolling

Abstract

The application relates to the technical field of metal material processing, and discloses a manufacturing method for continuous casting and rolling of 3104 aluminum strip for blinds, which comprises the following steps: S1, after 3104 aluminum alloy is melted and refined, the molten aluminum is stably transported while maintaining the temperature at 680-720 DEG C; S2, the molten aluminum is introduced into a high-frequency electromagnetic induction suspension plasticizing area, the molten aluminum is suspended under the action of a main suspension coil, and a semi-solid strip blank with a solid outer layer and a liquid inner layer is formed; S3, the semi-solid strip blank is sequentially passed through a non-contact high-energy ultrasonic energy field and an atomization cooling area; and S4, the treated semi-solid strip blank is introduced into a flexible synchronous rolling roller for rolling to obtain a strip with a set thickness. According to the application, the molten aluminum is formed into a semi-solid strip blank in a non-contact state through electromagnetic induction suspension, direct contact between the molten aluminum and a low-temperature mold is avoided, and the formation of strip surface defects caused by the quenching effect is inhibited.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, specifically to a method for continuous casting and rolling of aluminum strip for 3104 aluminum louvers. Background Technology

[0002] Aluminum alloy strip, especially thin strip used in the manufacture of products such as Venetian blind slats, has strict requirements for its mechanical properties, repeated bending performance, and surface quality. Currently, the mainstream short-process technology for producing such aluminum strip is the twin-roll casting method. This method introduces refined molten aluminum directly between a pair of rotating casting rolls with internal cooling channels, where solidification and hot rolling are completed within the roll gap area to directly obtain the strip.

[0003] However, traditional twin-roll casting processes have inherent limitations in practical applications. During the casting process, the high-temperature molten aluminum comes into direct contact with the low-temperature casting roll surface, and the extreme temperature gradient leads to violent rapid solidification. This non-equilibrium solidification process easily forms defects such as uneven composition and coarse microstructure on the surface and subsurface of the strip, impairing the surface finish and coating performance of the final product. Simultaneously, because the strip undergoes most of its compression deformation in the solid-liquid two-phase region, the liquid metal at the solidification front is difficult to feed, resulting in internal metallurgical defects such as shrinkage porosity, shrinkage cavities, and center segregation in the central region of the strip. These internal and external defects work together to reduce the overall mechanical properties of the strip, especially its plasticity and fatigue resistance, making it prone to fracture during subsequent processing or use, such as the repeated opening and closing of blinds, thus failing to meet the requirements of high-performance applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a continuous casting and rolling method for aluminum strip used in 3104 aluminum louvers. This method solves the problem that the traditional twin-roll casting and rolling process, due to direct contact between the melt and the rolls and insufficient solidification and feeding, simultaneously causes internal metallurgical defects and surface quality problems in the strip, ultimately leading to a decline in its overall mechanical properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for continuous casting and rolling of aluminum strip for 3104 aluminum louvers, comprising the following steps: S1. After melting and refining 3104 aluminum alloy, the molten aluminum is steadily transported while maintaining the temperature at 680-720℃. S2. The aluminum liquid is introduced into the high-frequency electromagnetic induction suspension and shaping zone. Under the action of the main suspension coil, the aluminum liquid is suspended and a semi-solid strip blank with a solid outer layer and a liquid inner layer is formed. At the same time, the edge vortex coils located on both sides of the width direction of the aluminum liquid are activated to actively induce a pair of protective vortices on both sides of the aluminum liquid to stabilize the side profile of the semi-solid strip blank. S3. The semi-solid strip blank is passed sequentially through a non-contact high-energy ultrasonic energy field and an atomizing cooling zone. S4. The processed semi-solid strip blank is introduced into a flexible synchronous rolling roll for rolling to obtain a strip of a set thickness; wherein, the flexible synchronous rolling is dynamically controlled by a servo system to apply a feeding pressure to the region containing the liquid core and a rolling length reduction pressure to the all-solid region. S5. The rolled strip is subjected to online induction heating treatment, then cooled and wound up.

[0006] In this technical solution, step S2 uses high-frequency electromagnetic induction levitation to non-contactly constrain and solidify the molten aluminum. The main levitation coil generates an alternating magnetic field, inducing eddy currents within the molten aluminum. The interaction between these eddy currents and the magnetic field generates a Lorentz force, which balances the weight of the molten aluminum in the vertical direction and shapes it in the horizontal direction. This non-contact process allows the molten aluminum to solidify without physical contact, avoiding surface defects such as chilling layers, adhesion, and cracks caused by the contact between the high-temperature melt and the low-temperature roll surface in traditional casting and rolling, fundamentally improving the surface quality of the strip. Simultaneously, edge vortex coils positioned on both sides of the molten aluminum generate specific local magnetic fields. The vortices induced by these magnetic fields apply an inward electromagnetic pressure to the sides of the molten aluminum, thereby suppressing the instability of the side profile caused by surface tension fluctuations and uneven internal flow, ensuring that the semi-solid strip entering subsequent processes has a regular width and edge shape.

[0007] Step S3 modulates the internal microstructure of the semi-solid strip by applying a non-contact high-energy ultrasonic field. The high-frequency vibrations transmit acoustic energy into the liquid core region of the strip, generating acoustic flow and cavitation effects. The acoustic flow agitates the liquid metal, homogenizing the temperature and composition fields; the instantaneous collapse of cavitation bubbles generates localized high temperature and pressure, as well as microjets, effectively breaking up growing dendrites and promoting their transformation into fine equiaxed crystals. It also facilitates the aggregation and escape of tiny bubbles in the liquid phase. This step refines the solidification structure and reduces porosity defects without contacting the strip, laying the microstructural foundation for obtaining materials with high mechanical and fatigue properties.

[0008] Step S4 employs flexible synchronous rolling to precisely control the pressure on the semi-solid strip. The servo system applies zoned, dynamic pressure to the rolls based on the solid-liquid phase distribution of the strip. For the region in the center of the strip that still contains a liquid core, a lower feeding pressure is applied. The main function of this pressure is to force the liquid metal into the solidifying dendrite network, effectively filling the micropores formed by solidification shrinkage, thereby significantly improving the final strip density and eliminating central porosity defects. For the completely solidified regions on both sides of the strip, a higher rolling reduction pressure is applied to achieve precise control of the final strip thickness. This zoned pressure rolling method synergistically solves the two technical problems of solidification feeding and dimensional control.

[0009] As a further technical solution, the composition of the 3104 aluminum alloy raw material in step S1, by mass parts, may include: silicon 0-0.6 parts; iron 0-0.8 parts; copper 0.05-0.25 parts; manganese 0.8-1.4 parts; magnesium 0.8-1.3 parts; zinc 0-0.25 parts; titanium 0-0.10 parts; and aluminum balance.

[0010] As a further technical solution, the main suspension coil in step S2 operates at a frequency of 8-15kHz and a current of 1800-2500A; the edge vortex coil operates at a frequency of 2-5kHz and a current of 1000-1600A.

[0011] As a further technical solution, the high-energy ultrasonic energy field in step S3 operates at a frequency of 19-24 kHz and has an output power of 2.5-3.5 kW. The high-energy ultrasonic energy field is generated by a non-contact ultrasonic transducer, with the transducer end face being 25-35 mm away from the surface of the semi-solid strip. The atomization cooling uses deionized water as the cooling medium, and the atomization pressure is 0.4-0.6 MPa.

[0012] As a further technical solution, the feeding pressure in step S4 is 8-15 MPa, and the rolling reduction pressure is 25-38 MPa. Before rolling begins, the solidified shell thickness of the semi-solid strip is controlled at 1.5-2.5 mm.

[0013] As a further technical solution, the surface of the flexible synchronous rolling roll is provided with a composite ceramic coating, which consists of a NiCr binder layer with a thickness of 100-150 μm and a YSZ working layer with a thickness of 300-400 μm. The NiCr binder layer provides the bonding strength between the coating and the roll substrate, while the YSZ working layer has low thermal conductivity and good wear resistance, which can reduce heat loss during the rolling process and improve the service life of the roll.

[0014] As a further technical solution, the heating temperature of the online induction heating process in step S5 is 460-510℃, the residence time in this temperature range is 6-12 seconds, and the cooling rate of the subsequent cooling step is 50-80℃ / s.

[0015] As a further technical solution, the manufacturing method also includes a feedforward control mechanism. This mechanism receives and processes the real-time operating parameters from the edge vortex coil in step S2, and transmits the processed data to the servo system for flexible synchronous rolling in step S4. This system predicts the state changes of the semi-solid strip based on the input data and adjusts the rolling pressure distribution strategy in advance to improve the stability of the process.

[0016] As a further technical solution, the manufacturing method also includes a feedback control loop. This loop monitors the heating temperature of the strip in step S5 in real time, and automatically adjusts the rolling speed in step S4 and the induction heating power in step S5 based on the deviation between the monitored value and the target temperature, so as to ensure the uniformity of the final product's microstructure and properties.

[0017] As a further technical solution, to ensure the matching and continuity of each process, the flow rate of the aluminum liquid in step S1 is 0.8-1.5 kg / s, the residence time of the aluminum liquid in the high-frequency electromagnetic induction suspension shaping zone in step S2 is 2-4 seconds, and the rolling linear speed in step S4 is 30-50 m / min.

[0018] This invention provides a method for the continuous casting and rolling of aluminum strip for 3104 aluminum louvers. It has the following advantages: 1. This invention utilizes electromagnetic induction levitation to form a semi-solid strip from molten aluminum in a non-contact state, avoiding direct contact between the molten aluminum and the low-temperature mold, thereby suppressing the formation of surface defects in the strip caused by the chilling effect. Simultaneously, by inducing protective vortices on both sides of the molten aluminum, the edges of the suspended liquid metal strip are constrained, resulting in a stable strip width and regular side profile, which helps reduce edge cracking during subsequent processing.

[0019] 2. This invention achieves synergistic control of the internal microstructure and density of strip by combining ultrasonic energy field action with flexible rolling. The ultrasonic energy field acts within the liquid core of the semi-solid strip, refining the solidification structure and inducing preferred grain orientation. Subsequent flexible rolling applies specific feeding pressure to the region containing the liquid core, utilizing the residual liquid metal to fill the pores formed by solidification shrinkage, thereby simultaneously improving the final strip's internal microstructure and density.

[0020] 3. This invention tightly integrates rolling and online heat treatment, realizing continuous manufacturing from semi-solid strip blanks to strips with final properties. It eliminates the offline intermediate or finished product annealing processes found in traditional methods, shortening the overall manufacturing process. Furthermore, by introducing a control loop combining feedforward and feedback, a linkage adjustment mechanism between upstream and downstream steps in the process chain is established, improving the stability of the entire manufacturing process and its adaptive adjustment capability to process fluctuations. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0022] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0023] 3104 aluminum alloy raw material: 3104 aluminum alloy ingot: Formulated from industrial pure aluminum ingots conforming to GB / T3190-2020 standard and master alloys, its chemical composition includes: Silicon CAS: 7440-21-3; Iron CAS: 7439-89-6; Copper CAS: 7440-50-8; Manganese CAS: 7439-96-5; Magnesium CAS: 7439-95-4; Zinc CAS: 7440-66-6; Titanium CAS: 7440-32-6; Aluminum CAS: 7429-90-5.

[0024] Raw materials related to flexible rolling rolls and surface coatings: Roll matrix material: H13 tool steel has the following main chemical components: iron (CAS: 7439-89-6), chromium (CAS: 7440-47-3), molybdenum (CAS: 7439-98-7), vanadium (CAS: 7440-62-2), and silicon (CAS: 7440-21-3).

[0025] Matrix pretreatment materials: White corundum sand, whose main component is aluminum oxide, CAS: 1344-28-1, has a particle size of 24 mesh.

[0026] Composite ceramic coating raw materials: Adhesive layer powder: Nickel-chromium alloy powder, containing: Nickel CAS: 7440-02-0; Chromium (CAS: 7440-47-3) has a powder particle size range of 30-60 μm and a mass ratio of Ni:Cr = 80:20.

[0027] Working layer powder: Yttrium-stabilized zirconia (YSZ) powder, which contains: Zirconia CAS: 1314-23-4; Yttrium oxide (CAS: 1314-36-9) has a powder particle size range of 20-50 μm.

[0028] Process auxiliary materials: Refined gases: High-purity argon gas CAS: 7440-37-1, purity ≥ 99.999%.

[0029] Atomized cooling medium: Deionized water CAS: 7732-18-5, resistivity ≥15MΩ·cm.

[0030] Preparation Example 1: Preparation of Flexible Synchronous Rolling Rolls This preparation example uses a flexible synchronous rolling roll with a composite ceramic coating on its surface, which is used in the preparation examples.

[0031] Matrix pretreatment: H13 tool steel was selected as the roll base. First, the working surface of the roll was degreased and cleaned to remove oil and dirt. Then, it was sandblasted with 24-mesh white corundum abrasive at a pressure of 0.6 MPa and a distance of 150 mm until the roll surface had a uniform grayish-white rough finish. After treatment, the surface was blown clean with high-pressure clean air at 0.7 MPa to remove all residual sand particles and dust.

[0032] Spraying NiCr bonding layer: The pretreated roll substrate was clamped onto the rotating table of the plasma spraying equipment, and the rotation speed was set to 60 rpm. An atmospheric plasma spraying system was used to spray the bonding layer using nickel-chromium alloy powder as the raw material. The spraying process parameters were set as follows: plasma arc current 600A, main gas (Ar) flow rate 45L / min, carrier gas (Ar) flow rate 5L / min, powder feed rate 40g / min, and spraying distance 100mm. Spraying was continued until the bonding layer thickness reached 120μm.

[0033] Spraying YSZ working layer: Immediately after the NiCr binder layer is coated and still warm, begin coating the YSZ working layer. The coating process parameters are set as follows: plasma arc current 650A, main gas (Ar) flow rate 50L / min, auxiliary gas (H2) flow rate 10L / min, carrier gas (Ar) flow rate 4L / min, powder feed rate 35g / min, and coating distance 90mm. Continue coating until the working layer thickness reaches 350μm.

[0034] After the entire coating process is completed, heating is stopped, and the rolls are allowed to cool naturally to room temperature in the equipment to obtain the final flexible synchronous rolling rolls, which are then ready for use.

[0035] Example 1: A method for continuously casting and rolling aluminum strip for 3104 aluminum louvers specifically includes the following steps: S1. Melt preparation and conveying: Add 3104 aluminum alloy raw material to the melting furnace for melting. After refining, maintain the temperature of the aluminum liquid at 680℃ and convey it steadily through the heat-insulating flow channel at a flow rate of 0.8kg / s.

[0036] S2, Electromagnetic Levitation Shaping: The molten aluminum is introduced into the high-frequency electromagnetic induction levitation shaping zone. The main levitation coil is set to a working frequency of 8kHz and a working current of 1800A; the edge vortex coil is set to a working frequency of 2kHz and a working current of 1000A. The molten aluminum stays in this zone for 4 seconds.

[0037] S3. Texture Induction and Cooling: The formed semi-solid strip blank is sequentially passed through the processing unit. The solidified shell thickness of the strip blank is controlled at 1.5 mm. The operating frequency of the non-contact high-energy ultrasonic energy field is set to 19 kHz, the output power is 2.5 kW, and the distance between the transducer end face and the strip blank surface is 35 mm. The deionized water atomization pressure in the atomization cooling zone is set to 0.4 MPa.

[0038] S4. Flexible Synchronous Rolling: The treated semi-solid strip is introduced into the flexible synchronous rolling rolls, and the rolling speed is set to 30 m / min. The servo system controls the application of a feeding pressure of 8 MPa to the region containing the liquid core and a rolling reduction pressure of 25 MPa to the all-solid region.

[0039] S5. Online Heat Treatment and Coiling: The rolled strip is subjected to online induction heating at a temperature of 460℃, and held at this temperature for 12 seconds. It is then subjected to forced air cooling at a cooling rate of 50℃ / s, and finally cooled to room temperature before being coiled.

[0040] Example 2: A method for continuously casting and rolling aluminum strip for 3104 aluminum louvers specifically includes the following steps: S1. Melt preparation and conveying: Add 3104 aluminum alloy raw material to the melting furnace for melting. After refining, maintain the temperature of the aluminum liquid at 700℃ and convey it steadily through the heat-insulating flow channel at a flow rate of 1.2kg / s.

[0041] S2, Electromagnetic Levitation Shaping: The molten aluminum is introduced into the high-frequency electromagnetic induction levitation shaping zone. The main levitation coil is set to a working frequency of 12kHz and a working current of 2200A; the edge vortex coil is set to a working frequency of 3.5kHz and a working current of 1300A. The molten aluminum stays in this zone for 3 seconds.

[0042] S3. Texture Induction and Cooling: The formed semi-solid strip blank is sequentially passed through the processing unit. The solidified shell thickness of the strip blank is controlled at 2.0 mm. The operating frequency of the non-contact high-energy ultrasonic energy field is set to 22 kHz, the output power is 3.0 kW, and the distance between the transducer end face and the strip blank surface is 30 mm. The deionized water atomization pressure in the atomization cooling zone is set to 0.5 MPa.

[0043] S4. Flexible Synchronous Rolling: The treated semi-solid strip is introduced into the flexible synchronous rolling rolls, and the rolling speed is set to 40 m / min. The servo system controls the application of a 12 MPa feeding pressure to the region containing the liquid core and a 32 MPa rolling reduction pressure to the all-solid region. In this step, the feedforward control module of the servo system is activated, receiving the real-time operating current parameters of the edge vortex coils from step S2, and is used to adjust the rolling strategy in advance.

[0044] S5. Online Heat Treatment and Coiling: The rolled strip undergoes online induction heating to 480℃, held at this temperature for 9 seconds. Forced air cooling is then applied at a rate of 65℃ / s. In this step, a feedback control loop is activated to monitor the strip heating temperature in real time and automatically adjusts the rolling speed from step S4 and the induction heating power in this step based on the deviation from the set value of 480℃. Finally, the strip is coiled after cooling to room temperature.

[0045] Example 3: A method for continuously casting and rolling aluminum strip for 3104 aluminum louvers specifically includes the following steps: S1. Melt preparation and conveying: Add 3104 aluminum alloy raw material to the melting furnace for melting. After refining, maintain the temperature of the aluminum liquid at 720℃ and convey it steadily through the heat-insulating flow channel at a flow rate of 1.5kg / s.

[0046] S2, Electromagnetic Levitation Shaping: The molten aluminum is introduced into the high-frequency electromagnetic induction levitation shaping zone. The main levitation coil is set to a working frequency of 15kHz and a working current of 2500A; the edge vortex coil is set to a working frequency of 5kHz and a working current of 1600A. The molten aluminum stays in this zone for 2 seconds.

[0047] S3. Texture Induction and Cooling: The formed semi-solid strip blank is passed sequentially through the processing unit. The solidified shell thickness of the strip blank is controlled at 2.5 mm. The operating frequency of the non-contact high-energy ultrasonic energy field is set to 24 kHz, the output power is 3.5 kW, and the distance between the transducer end face and the strip blank surface is 25 mm. The deionized water atomization pressure in the atomization cooling zone is set to 0.6 MPa.

[0048] S4. Flexible Synchronous Rolling: The treated semi-solid strip is introduced into the flexible synchronous rolling rolls, and the rolling speed is set to 50 m / min. The servo system controls the application of a feeding pressure of 15 MPa to the region containing the liquid core and a rolling reduction pressure of 38 MPa to the all-solid region.

[0049] S5. Online Heat Treatment and Coiling: The rolled strip is subjected to online induction heating at a temperature of 510℃, held at this temperature for 6 seconds. It is then subjected to forced air cooling at a cooling rate of 80℃ / s, and finally cooled to room temperature before being coiled.

[0050] Comparative Example 1: 3104 aluminum strip was prepared using a traditional twin-roll casting process. Molten aluminum with the same composition as in Example 2, at a temperature of 700°C, was directly introduced between casting rolls with internal water-cooling channels for solidification and rolling, followed by offline homogenization annealing.

[0051] Comparative Example 2: Compared with Example 2, the difference is that in step S2, the edge vortex coil is not activated, and the aluminum liquid is suspended only by the main suspension coil. The remaining steps and parameters are exactly the same as in Example 2.

[0052] Comparative Example 3: Compared with Example 2, the difference is that in step S3, no high-energy ultrasonic energy field is applied, and the semi-solid strip directly enters the rolling mill through the atomization cooling zone. The remaining steps and parameters are exactly the same as in Example 2.

[0053] Comparative Example 4: Compared with Example 2, the difference is that in step S4, a constant rolling reduction pressure (32MPa) is used to roll the entire strip blank without distinguishing between the liquid core region and the all-solid region, that is, no feeding pressure is applied. The remaining steps and parameters are exactly the same as in Example 2.

[0054] Test Example 1: Mechanical Property Test Experimental steps: To determine the mechanical properties of the aluminum strips prepared in each example and comparative example, the tests were conducted in accordance with the national standard GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0055] First, samples were cut from the strip coils prepared in Examples 1-3 and Comparative Examples 1-4 along the rolling direction. The samples were processed into plate-shaped tensile specimens using a wire EDM machine, with a gauge length of 60 mm and a width of 12.5 mm. The original cross-sectional area was calculated based on the actual measured thickness.

[0056] The prepared specimens were then subjected to tensile testing on a universal testing machine. The machine clamps applied a tensile load to the specimen at a constant rate of 2 mm / min until the specimen fractured. The testing machine system automatically recorded the load-displacement data.

[0057] For each embodiment and comparative example strip, five parallel specimens were prepared and tested. Based on the recorded load-displacement curves, the tensile strength (Rm), specified plastic extension strength (Rp0.2, i.e., yield strength), and elongation at break (A) of each specimen were calculated. The final result was the arithmetic mean of the five parallel specimens.

[0058] Experimental data: Table 1. Mechanical property test results of aluminum strips in each embodiment and comparative example. Results analysis: As shown in Table 1, the aluminum strips prepared by the methods of Examples 1, 2, and 3 all exhibit higher tensile strength, yield strength, and elongation after fracture than the samples prepared by the method of Comparative Example 1. This difference stems from the manufacturing method of the present invention, which avoids the chilling structure and surface defects caused by direct contact between the melt and the rolls in traditional casting and rolling through non-contact suspension solidification in step S2; and further treats the internal grain structure and density of the material through the ultrasonic energy field in step S3 and the flexible rolling in step S4, respectively.

[0059] A comparison of the performance data of Sample 2 with Comparative Examples 2, 3, and 4 demonstrates the effect of specific process steps. Compared to Comparative Example 3, Sample 2, due to the high-energy ultrasonic field treatment in step S3, exhibits a refined internal solidification structure, resulting in higher strength and plasticity. Compared to Comparative Example 4, Sample 2, by applying feeding pressure to the region containing the liquid core in step S4, effectively reduces central porosity defects during solidification, which is reflected in its superior mechanical properties compared to Comparative Example 4. Similarly, compared to Comparative Example 2, the activation of the edge vortex coil in Sample 2 ensures the stability of the strip side profile, providing a prerequisite for subsequent uniform rolling, thus yielding a final product with superior performance.

[0060] The data trends among Examples 1, 2, and 3 indicate that, within the parameter range described in this invention, the mechanical properties of the final strip can be controlled by adjusting the process parameters of each step. The combination of process parameters used in Example 3 (such as higher heating temperature, current, power, and pressure) resulted in more thorough grain refinement in step S3 and densification through shrinkage compensation in step S4, ultimately yielding the highest tensile strength, yield strength, and elongation after fracture values ​​among the three examples.

[0061] Test Example 2: Repeated Bending Performance Test Experimental steps: To determine the fatigue resistance of each sample under cyclic loading, repeated bending tests were conducted.

[0062] First, rectangular samples with a length of 150 mm and a width of 20 mm were cut from the strips prepared in Examples 1-3 and Comparative Examples 1-4 along the rolling direction.

[0063] The sample is then clamped onto a dedicated repeated bending tester. The bending chuck of the tester has a 5mm radius (R=5mm). During the test, the tester drives the chuck at a frequency of 60 times / minute, fixing one end of the sample while the other end, using the bending chuck as a fulcrum, bends upward from the initial horizontal position (0°) to 90°, then downward back to the horizontal position, continuing downward to -90°, and finally returning to the horizontal position. This process is recorded as one bending cycle.

[0064] The test was conducted continuously until the specimen completely broke at the bend. The total number of cycles at which the specimen broke was recorded. For each example and comparative example strip, five parallel specimens were prepared and tested, and the final result was the arithmetic mean of the number of cycles for the five parallel specimens.

[0065] Experimental data: Table 2. Results of repeated bending performance tests on aluminum strips of each embodiment and comparative example. Results analysis: Table 2 shows that the aluminum strips prepared by the methods in Examples 1, 2, and 3 all have higher values ​​for the number of bending failure cycles than the sample in Comparative Example 1. This difference indicates that the manufacturing method described in this invention, through the combination of non-contact suspension forming, ultrasonic energy field treatment, and flexible synchronous rolling, produces materials with higher fatigue resistance compared to products manufactured using traditional twin-roll casting and rolling processes.

[0066] The comparison of cycle counts between Example 2 and Comparative Examples 2, 3, and 4 reveals the impact of specific process steps on material properties. Compared to Comparative Example 3, the sample in Example 2 underwent high-energy ultrasonic field treatment in step S3, which promoted the refinement of the internal structure. The fine, uniform grains can hinder the initiation and propagation of fatigue cracks, thereby increasing the fatigue life of the material. Compared to Comparative Example 4, Example 2 applied feeding pressure to the region containing the liquid core in step S4, which helped fill the micropores that might be generated during solidification, improving the internal density of the material and reducing internal defects that could act as stress concentration points and fatigue sources. Therefore, its cycle count was higher than that of Comparative Example 4. Compared to Comparative Example 2, the use of edge vortex coils in Example 2 ensured the regularity of the strip sidewalls, reducing the possibility of cracks caused by edge defects, thus improving its fatigue performance.

[0067] The data trends in Examples 1, 2, and 3 indicate that, within the range of process parameters described in this invention, the fatigue performance of the final product can be affected by adjusting the parameter combinations of each step. From Example 1 to Example 3, as the values ​​of parameters such as the main suspension coil current, ultrasonic output power, and rolling pressure increase, the number of bending failure cycles of the final product also increases accordingly. This demonstrates that more thorough electromagnetic confinement, energy field treatment, and pressure densification of the material can further optimize the internal structure and integrity of the material, thereby obtaining higher fatigue resistance.

[0068] Test Example 3: Surface Quality Test Experimental steps: To quantitatively evaluate the surface smoothness of each sample, the surface roughness of the strip was tested using a stylus-type surface roughness tester in accordance with the national standard GB / T1031-2009 "Product Geometric Specification (GPS) Surface Structure Profile Method Surface Roughness Parameters and Their Values".

[0069] First, square samples of 50 mm × 50 mm were cut from the strips prepared in Examples 1-3 and Comparative Examples 1-4. The surface of the samples was wiped with anhydrous ethanol to remove surface oil and contaminants.

[0070] The cleaned sample was then placed on the measuring platform of the surface roughness tester, ensuring it was level. The instrument's measurement parameters were set as follows: sampling length 0.8 mm, evaluation length 4.0 mm, and stylus scanning rate 0.5 mm / s. Measurements were taken in the central region of each sample, perpendicular to the rolling direction.

[0071] For each embodiment and comparative example strip, five parallel specimens were prepared and tested, with each specimen measured three times. The final result was the arithmetic mean of all measurements, which was taken as the surface arithmetic mean roughness (Ra) of the sample.

[0072] Experimental data: Results analysis: The test data in Table 3 show that the aluminum strips prepared by the methods of Examples 1, 2, and 3 have significantly lower surface arithmetic mean roughness Ra values ​​than the sample of Comparative Example 1. This difference is because in step S2 of the manufacturing method of the present invention, electromagnetic induction suspension is used to allow the molten aluminum to solidify and form an initial shell in a non-contact state. This process avoids the direct contact between the high-temperature melt and the low-temperature casting roll surface in the traditional twin-roll casting process (Comparative Example 1), thereby suppressing the formation of macroscopic and microscopic surface unevenness defects caused by chilling effect and adhesion behavior.

[0073] The Ra values ​​of Example 2 are compared with those of Comparative Examples 2 and 4, demonstrating the effect of specific process steps on surface quality. Compared to Comparative Example 4, Example 2 employs flexible synchronous rolling in step S4, where a servo system applies dynamically varying pressure to different areas, and the roll surface is coated with a ceramic coating. This results in more uniform material flow during the deformation of the semi-solid strip, reducing surface scratches or wrinkles caused by improper pressure or uneven friction, thus achieving a lower Ra value. Compared to Comparative Example 2, the activation of the edge vortex coils in Example 2 stabilizes the flow at the melt edge, thereby improving the stability of the entire suspended strip. This helps to form an initial solidified shell with more uniform thickness and a smoother surface, ultimately resulting in a lower surface roughness of the finished product.

[0074] The data changes between Examples 1, 2, and 3 demonstrate that, within the process parameter range described in this invention, the surface quality of the strip can be further improved by adjusting the parameter combinations. From Example 1 to Example 3, as the values ​​of parameters such as the main suspension coil current, the edge vortex coil current, and the rolling pressure increase, the ability to constrain the morphology of the suspended melt and the ability to shape the subsequent strip are both enhanced. The stronger electromagnetic field and more precise pressure control work together to continuously improve the surface smoothness of the final product, as evidenced by a sequential decrease in the Ra value.

[0075] To determine the internal density of each sample, the density was measured using the static weighing method based on Archimedes' principle in GB / T6157-2018 "Determination of Density of Metallic Materials".

[0076] First, block samples weighing approximately 10g were cut from the strips prepared in Examples 1-3 and Comparative Examples 1-4. The samples were ultrasonically cleaned with anhydrous ethanol for 5 minutes to remove surface contaminants, then dried in an oven at 100°C for 1 hour and cooled to room temperature for later use.

[0077] Next, using an analytical balance with an accuracy of 0.1 mg, the mass of the dried sample in air (denoted as ) was weighed. ).

[0078] Subsequently, the sample was immersed in a beaker containing deionized water at a constant temperature of 25°C (the density of deionized water is denoted as...). Weigh the sample in water (denoted as ), and measure the mass of the sample in water. .

[0079] Finally, according to the formula Calculate the density of the specimens. For each example and comparative example strip, five parallel specimens were prepared and tested, and the final result was the arithmetic mean of the densities of the five parallel specimens.

[0080] Experimental data: Results analysis: The data in Table 4 show that the measured densities of the samples obtained in Examples 1, 2, and 3 are all numerically higher than those of the sample in Comparative Example 1. This difference stems from the fact that in step S4 of the manufacturing method of the present invention, a specific feeding pressure is applied to the semi-solid strip containing the liquid core through flexible synchronous rolling. This pressure acts on the incompletely solidified area in the center of the strip, driving the residual liquid metal to fill the pores formed by solidification shrinkage, thereby reducing the internal porosity of the final product and obtaining a higher material density than that of the conventional casting and rolling process (Comparative Example 1).

[0081] The density comparison between Example 2 and Comparative Examples 3 and 4 reveals the effect of specific process steps on material compactness. Compared to Comparative Example 4, Example 2 has a higher density because Comparative Example 4 uses constant pressure rolling, lacking a feeding mechanism for the liquid core region, resulting in ineffective filling of solidification shrinkage pores. Compared to Comparative Example 3, Example 2 has a higher density because a high-energy ultrasonic field is introduced in step S3. The resulting acoustic flow and cavitation effects help bubbles escape from the melt, reducing porosity defects in the finished product, thus improving material compactness.

[0082] The data trends in Examples 1, 2, and 3 indicate that, within the range of process parameters described in this invention, the density of the material can be further improved by adjusting the combination of parameters. From Example 1 to Example 3, with the increase of parameters such as ultrasonic output power in step S3 and feeding pressure in step S4, the venting effect on the melt and the feeding effect on the solidified structure are both enhanced. The synergistic effect of stronger energy field treatment and greater feeding pressure more fully suppresses microscopic porosity defects inside the material, ultimately resulting in a sequential increase in the measured density value.

Claims

1. A method for continuously casting and rolling aluminum strip for 3104 aluminum louvers, characterized in that, Includes the following steps: S1. After melting and refining 3104 aluminum alloy, the molten aluminum is steadily transported at a temperature maintained at 680-720℃, and the flow rate of the molten aluminum is 0.8-1.5 kg / s. S2. The molten aluminum is introduced into the high-frequency electromagnetic induction suspension shaping zone. Under the action of the main suspension coil, the molten aluminum is suspended and forms a semi-solid strip blank with a solid outer layer and a liquid inner layer. At the same time, the edge vortex coils located on both sides of the width direction of the molten aluminum are activated to actively induce a pair of protective vortices on both sides of the molten aluminum to stabilize the side profile of the semi-solid strip blank. The operating frequency of the main suspension coil is 8-15kHz, the operating frequency of the edge vortex coil is 2-5kHz, and the residence time of the molten aluminum in the high-frequency electromagnetic induction suspension shaping zone is 2-4 seconds. S3. The semi-solid strip blank is sequentially passed through a non-contact high-energy ultrasonic energy field and an atomizing cooling zone; the high-energy ultrasonic energy field has a working frequency of 19-24kHz and an output power of 2.5-3.5kW, and is used to induce preferential grain orientation in the internal liquid core of the semi-solid strip blank. S4. The processed semi-solid strip blank is introduced into a flexible synchronous rolling roll for rolling to obtain a strip of a set thickness; wherein, the flexible synchronous rolling is dynamically controlled by a servo system to apply a feeding pressure of 8-15MPa to the region containing the liquid core and a rolling length reduction pressure of 25-38MPa to the all-solid region, and the rolling linear speed is 30-50m / min. S5. The rolled strip is subjected to online induction heating treatment at a temperature of 460-510℃, followed by cooling and winding. The dwell time of the online induction heating treatment in the target temperature zone is 6-12 seconds, and the cooling rate of the subsequent cooling step is 50-80℃ / s.

2. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, In step S1, the 3104 aluminum alloy raw material comprises the following components in parts by mass: silicon 0-0.6 parts; iron 0-0.8 parts; copper 0.05-0.25 parts; manganese 0.8-1.4 parts; magnesium 0.8-1.3 parts; zinc 0-0.25 parts; titanium 0-0.10 parts; and aluminum as the balance.

3. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, In step S2, the operating current of the main suspension coil is 1800-2500A; the operating current of the edge vortex coil is 1000-1600A.

4. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, In step S3, the high-energy ultrasonic energy field is generated by a non-contact ultrasonic transducer, and the distance between the transducer end face and the surface of the semi-solid strip blank is 25-35mm; the atomization cooling uses deionized water as the cooling medium, and the atomization pressure is 0.4-0.6MPa.

5. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, In step S4, the servo system for flexible synchronous rolling adopts feedforward control. The feedforward control receives and processes the real-time operating parameters from the edge vortex coil in step S2 to predict the state of the semi-solid strip and adjust the rolling strategy in advance.

6. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, In step S4, the surface of the flexible synchronous rolling roll is provided with a composite ceramic coating, which consists of a NiCr bonding layer with a thickness of 100-150μm and a YSZ working layer with a thickness of 300-400μm.

7. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, Before step S4 begins, the thickness of the solidified shell of the semi-solid strip is controlled to be 1.5-2.5 mm.

8. The manufacturing method of continuous casting and rolling of aluminum strip for 3104 aluminum louvers according to claim 1, characterized in that, The manufacturing method also includes a feedback control loop that monitors the heating temperature of the strip in step S5 in real time, and automatically adjusts the rolling line speed in step S4 and the induction heating power in step S5 according to the deviation between the monitored value and the target temperature.

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