Method for preparing 6111 aluminum alloy plate by casting and rolling electrolytic aluminum liquid

Abstract

The invention relates to the technical field of aluminum alloy strip billet preparation, in particular to a method for preparing a 6111 aluminum alloy plate through cast rolling of electrolytic aluminum liquid, and the method comprises the steps of electrolytic aluminum liquid screening, smelting, heat preservation furnace refining, online treatment, cast rolling and coiling. Qualified 6111 aluminum alloy cast-rolled strip blanks can be produced, the production cost is reduced, and competitive products can be produced; the 6111 alloy cast-rolled strip meeting the requirements is finally produced through electrolytic aluminum liquid screening and reasonable component proportioning, by adopting an advanced front box flow control technology and a series of process technical conditions matched with 6-series high alloy product cast-rolling; the cast-rolled strip is subjected to further cold rolling and annealing treatment, and the produced product completely meets the application requirements of automobile aluminum alloy panels, battery shells, anti-collision beams and the like.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy strip preparation technology, specifically a method for preparing 6111 aluminum alloy sheets by electrolytic aluminum liquid casting and rolling. Background Technology

[0002] 6111 aluminum alloy belongs to the Al-Mg-Si alloy system. It has good formability and medium strength. With its excellent strength-to-weight ratio and good formability, it is becoming increasingly popular in automobile manufacturing. It is commonly used in body panels, structural components, new energy battery housings and other components that are critical to weight reduction. It is produced by ingot hot rolling process.

[0003] However, the traditional hot rolling process is complex, requires a lot of energy, and has high production costs, which restricts the application of 6111 aluminum alloy sheets and strips in the automotive and other transportation sectors.

[0004] This invention overcomes the technical bottleneck of conventional casting and rolling processes being unable to produce high-alloy products, employing a unique casting and rolling process to produce 6111 alloy sheet and strip. This invention utilizes a twin-roll continuous casting and rolling method, directly transforming liquid metal into cast and rolled sheet and strip by passing it through a pair of water-cooled rolls. This eliminates the need for ingot casting and milling processes, combining multiple processes such as casting and hot rolling into a single continuous casting and rolling operation. This is a shortcut to directly producing cold-rolled thin slabs, greatly simplifying the production process of 6111 automotive sheet and providing an inherent advantage in cost control. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 6111 aluminum alloy sheets by electrolytic aluminum liquid casting and rolling. This method employs a unique aluminum alloy casting and rolling process that does not require large-scale equipment modifications. It can produce qualified 6111 aluminum alloy cast and rolled strips while reducing production costs.

[0006] To achieve the above-mentioned technical effects, the present invention provides a method for preparing 6111 aluminum alloy sheets by electrolytic aluminum liquid casting and rolling, comprising the following steps: S1. Screening of electrolytic aluminum liquid: The required composition for screening electrolytic aluminum liquid is: Fe≤0.15%, Si≤0.05%, Na≤60ppm, Ca≤50ppm, V≤0.03%, with the remainder being Al; the aluminum ingots used must have an Al ≥99.70%, with V ≤0.03%; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): 0.6%≤Si≤1.0%, 0.6%≤Cu≤0.9%, 0.05%≤Mn≤0.30%, 0.6%≤Mg≤0.9%, 0.02%≤Ti≤0.04%, Fe≤0.4%, Cr≤0.10%, Zn≤0.15%, impurities≤0.15%, balance Al; The melting temperature is controlled at 750℃-760℃, and the melting time is 8h-12h. The first refining in the melting furnace is Ar + remelting particles. The refining after adding alloys is carried out by remelting particle refining agent + powder refining agent. Argon is used as the carrier. After the refining operation is completed, the melt with the qualified composition and temperature is poured into the holding furnace. S3. Refining in a holding furnace: Within 30 minutes of the furnace being turned over, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 740℃-755℃, and the refining time is 30 minutes. This refining process is repeated every 4 hours until the next batch of aluminum melt is turned over, thus maintaining continuous production. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.3 MPa-0.4 MPa and a flow rate of 3 m³ / s. 3 / h -7m 3 / h, the refining medium uses high-purity argon gas with a purity of not less than 99.99%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is not higher than 0.25ml / 100g·Al; during the production process, nitrogen gas is introduced into the holding furnace to form a slight positive pressure inside the furnace, with a pressure of 10 Pa - 50 Pa. S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using Al-5Ti-1B alloy, with an addition amount of 1.5 kg / t to 3.0 kg / t. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 is cast and rolled using a twin-roll inclined casting mill. The upper and lower rolls of the mill are fitted with steel roll sleeves. A high-precision laser flow control system is used to control the liquid level in the front box. The roll surface lubrication employs a flame + graphite lubrication process. The casting and rolling zone length is 45mm-50mm, the front box temperature is controlled at 710℃-720℃, the casting and rolling speed is controlled at 450mm / min-900mm / min, the cooling water temperature is 30℃-35℃, and the cooling water flow rate is 120 m³ / min. 3 / h-160m3 / h, 6111 alloy cast-rolled billet with a thickness of 7.0±0.5mm is obtained through a two-stage split-flow casting nozzle structure; S7. Cold rolled: The S6 cast-rolled strip is cold-rolled to 5.0 mm in one pass at a rolling speed of 200 m / min - 400 m / min. Then, it undergoes homogenization annealing in a nitrogen-protected box annealing furnace. After annealing, the coil is cooled in the furnace. After the temperature drops below 300℃, it is air-cooled. Once the temperature drops below 40℃, the strip is thinned from 5.0 mm to 2.5 mm through two passes of rolling. Then, the strip is trimmed at the edges to remove any cracks. After two more passes of rolling, the strip is thinned from 2.5 mm to 1.0 mm - 1.8 mm. After trimming, coils of a specific width are obtained, packaged, and stored. The tensile strength is 180 MPa - 240 MPa, and the elongation is 5-8%. The 6111 aluminum alloy strip is now complete. S8, Winding: The produced cast-rolled strip is wound up, cut into coils and packaged according to the required weight.

[0007] Furthermore, in step S2, the proportion of solid materials such as aluminum ingots and other waste materials in the total weight of the melt is 25%-50%, and the remainder is the electrolytic aluminum liquid screened in step S1.

[0008] Furthermore, the adjustments to each component in step S2 are all made in the form of intermediate alloys to prevent foreign inclusions from entering the melt.

[0009] Furthermore, in step S2, the weight ratio of remelted granular refining agent to powdered refining agent is 1:1, and both the remelted granular refining agent and the powdered refining agent use sodium-free formulation refining agents.

[0010] Furthermore, in step S6, differential speed control is required between the upper and lower rolls during the casting and rolling process, specifically, the casting and rolling speed of the upper roll is 10 mm / min to 30 mm / min faster than that of the lower roll.

[0011] Furthermore, in step S6, it is required that the high-precision laser flow control system control the fluctuation range of the liquid level in the front tank to be ≤ ±0.5mm.

[0012] Furthermore, the homogenization annealing process in step S7 is as follows: annealing temperature 510℃-560℃, holding time 6h.

[0013] The beneficial effects of this invention are as follows: This invention fully utilizes the potential of casting and rolling processes to produce high-alloy products. By using high-alloy product casting and rolling processes to prepare 6111 aluminum alloy strip blanks, production costs are significantly reduced, and the market competitiveness of the products is improved. This invention uses conventional casting and rolling steel roller sleeves, eliminating the need for large-scale equipment modifications, and can produce qualified 6111 aluminum alloy cast and rolled strip blanks, reducing production costs and enabling the production of competitive products. This invention, through electrolytic aluminum liquid screening, reasonable component ratios, the adoption of advanced front box flow control technology, and a series of process technology conditions matching the casting and rolling of 6-series high-alloy products, ultimately produces 6111 alloy cast and rolled strip that meets the requirements. After further cold rolling and annealing treatment, the cast and rolled strip produces products that fully meet the needs of automotive aluminum alloy panels, battery housings, anti-collision beams, and other applications.

[0014] This invention, based on a deep expansion of aluminum alloy casting and rolling technology, overcomes the technical bottleneck of conventional casting and rolling processes being unable to produce high-alloy products. It employs a unique casting and rolling process to produce 6111 alloy strip and sheet. This invention utilizes advanced furnace bottom permeable brick technology to maintain the uniformity and consistency of the melt composition in the holding furnace through continuous gas refining. Then, the melt undergoes online degassing, plate filtration, and tubular filtration to further improve its purity. By developing a dedicated casting and rolling technology, 6111 liquid metal is directly transformed into cast and rolled strip and sheet. Finally, through appropriate cold rolling and heat treatment, the elongation (A) is obtained. 50 The 6111 alloy sheet and strip contain more than 5%. After being used in batches by downstream automotive parts manufacturers, automotive parts such as door inner panels, water channels, and battery casings produced using thermoforming processes have tensile strengths exceeding 300 MPa and elongation exceeding (A...). 50 With a yield of over 10%, it fully meets the relevant performance requirements of automotive OEMs. Compared with the traditional ingot hot rolling method, it eliminates the ingot casting, milling, heating, and hot rolling processes, combining multiple processes such as casting and hot rolling into a single continuous casting and rolling process. This greatly simplifies the production process of 6111 automotive steel sheets, and the processing cost is only 40% of that of the traditional ingot hot rolling process, giving it significant advantages in cost control and production cycle. Detailed Implementation

[0015] The present invention discloses a method for preparing 6111 aluminum alloy sheets by electrolytic aluminum liquid casting and rolling, comprising the following steps: S1. Screening of electrolytic aluminum liquid: The required composition for screening electrolytic aluminum liquid is: Fe≤0.15%, Si≤0.05%, Na≤60ppm, Ca≤50ppm, V≤0.03%, with the remainder being Al; the aluminum ingots used must have an Al ≥99.70%, with V ≤0.03%; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): 0.6%≤Si≤1.0%, 0.6%≤Cu≤0.9%, 0.05%≤Mn≤0.30%, 0.6%≤Mg≤0.9%, 0.02%≤Ti≤0.04%, Fe≤0.4%, Cr≤0.10%, Zn≤0.15%, impurities≤0.15%, balance Al; The proportion of solid materials such as aluminum ingots and other waste materials in the total weight of the melt is 25%-50%, and the remainder is the electrolytic aluminum liquid screened in step S1; the adjustment of each component is added in the form of intermediate alloy to avoid foreign inclusions from entering the melt. The smelting temperature is controlled at 750℃-760℃, and the smelting time is 8h-12h. The first refining in the smelting furnace is Ar + remelting particles. The refining after adding alloys is carried out by remelting particle refining agent + powder refining agent. The weight ratio of remelting particle refining agent to powder refining agent is 1:1. Both remelting particle refining agent and powder refining agent use sodium-free formula refining agent. Argon is used as the carrier. After the refining operation is completed, the melt with the qualified composition and temperature is poured into the holding furnace. S3. Refining in a holding furnace: Within 30 minutes of the furnace being turned over, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 740℃-755℃, and the refining time is 30 minutes. This refining process is repeated every 4 hours until the next batch of aluminum melt is turned over, thus maintaining continuous production. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.3 MPa-0.4 MPa and a flow rate of 3 m³ / s. 3 / h -7m 3 / h, the refining medium uses high-purity argon gas with a purity of not less than 99.99%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is not higher than 0.25ml / 100g·Al; during the production process, nitrogen gas is introduced into the holding furnace to form a slight positive pressure inside the furnace, with a pressure of 10 Pa - 50 Pa. S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using Al-5Ti-1B alloy, with an addition amount of 1.5 kg / t to 3.0 kg / t. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 is cast and rolled using a twin-roll inclined casting mill. The upper and lower rolls of the mill are fitted with steel roll sleeves. Differential speed control is required for the upper and lower rolls during the casting and rolling process, specifically, the upper roll's casting speed is 10-30 mm / min faster than the lower roll. A high-precision laser flow control system is used to control the liquid level in the front box, ensuring the liquid level fluctuation is ≤±0.5 mm. The roll surface lubrication uses a flame + graphite lubrication process. The casting and rolling zone length is 45-50 mm, the front box temperature is controlled at 710℃-720℃, the casting and rolling speed is controlled at 450-900 mm / min, the cooling water temperature is 30-35℃, and the cooling water flow rate is 120 m³ / min. 3 / h-160m 3 / h, 6111 alloy cast-rolled billet with a thickness of 7.0±0.5mm is obtained through a two-stage split-flow casting nozzle structure; S7. Cold rolled: The S6 cast-rolled strip is cold-rolled to 5.0 mm in one pass at a rolling speed of 200 m / min - 400 m / min. Then, it undergoes homogenization annealing in a nitrogen-protected box annealing furnace. After annealing, the coil is cooled in the furnace. After the temperature drops below 300℃, it is air-cooled. Once the temperature drops below 40℃, the strip is thinned from 5.0 mm to 2.5 mm through two passes of rolling. Then, the strip is trimmed at the edges to remove any cracks. After two more passes of rolling, the strip is thinned from 2.5 mm to 1.0 mm - 1.8 mm. After trimming, coils of a specific width are obtained, packaged, and stored. The tensile strength is 180 MPa - 240 MPa, and the elongation is 5-8%. The 6111 aluminum alloy strip is now complete. S8, Winding: The produced cast-rolled strip is wound up, cut into coils and packaged according to the required weight.

[0016] Example 1: The following are the production steps for preparing 6111 aluminum alloy strip using the method of the present invention; S1. Screening of electrolytic aluminum liquid: The required composition for screening electrolytic aluminum liquid is: Fe=0.14%, Si=0.03%, Na=40ppm, Ca=30ppm, V=0.03%, with the remainder being Al; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): Si=1.0%, Cu=0.9%, Mn=0.30%, Mg=0.9%, Ti=0.02%, Fe=0.4%, Cr=0.10%, Zn=0.15%, with the balance being Al; The converter capacity for aluminum ingots and other solid materials such as waste is 7t, and the converter capacity for electrolytic aluminum liquid screened in step S1 is 21t, with a total charge of 28t. The composition is adjusted by adding intermediate alloys. The melting temperature is controlled at 750℃, and the melting time is 8 hours. The first refining in the melting furnace uses Ar + remelted particles. After adding the alloy, the refining process uses remelted particle refining agent + powdered refining agent, with a weight ratio of remelted particle refining agent to powdered refining agent of 1:1. Argon is used as the carrier gas in both cases. After refining, the melt with the required composition and temperature is poured into a holding furnace. S3. Holding Furnace Refining: S3. Refining in a holding furnace: Within 30 minutes of the furnace being poured, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 740℃, and the refining time is 30 minutes. This refining is repeated every 4 hours thereafter until the next batch of aluminum melt is poured. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.4 MPa and a flow rate of 7 m³ / s. 3 / h, the refining medium uses high-purity argon gas with a purity of 99.999%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is 0.25ml / 100g·Al; nitrogen gas is introduced into the holding furnace during the production process, and the pressure inside the furnace is 50Pa; S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using an Al-5Ti-1B alloy at an addition rate of 1.5 kg / t, resulting in a final Ti content of 0.026%. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 was cast and rolled using a twin-roll inclined casting mill with steel roll sleeves on the upper and lower rolls. Differential speed control was implemented for the upper and lower rolls during the casting and rolling process, with the upper roll's rolling speed being 10 mm / min faster than the lower roll. A high-precision laser flow control system was used to control the liquid level in the front box, with a fluctuation range of ±0.5 mm. The roll surface lubrication employed a flame + graphite spraying lubrication process. The casting and rolling zone length was 45 mm, the front box temperature was controlled at 720℃, the casting and rolling speed was controlled at 450 mm / min, the cooling water temperature was 35℃, and the cooling water flow rate was 120 m³ / min. 3 / h, 6111 alloy cast-rolled billet with a thickness of 6.5mm is obtained through a two-stage split-flow casting nozzle structure; S7. Cold rolled: The S6 cast-rolled strip was cold-rolled to 5.0 mm in one pass at a rolling speed of 400 m / min, followed by homogenization annealing at 560℃ for 6 hours. A nitrogen-protected box-type annealing furnace was used. After annealing, the coil cooled in the furnace until it reached 295℃, at which point it was air-cooled. Once the coil temperature dropped to 39℃, it was thinned from 5.0 mm to 2.5 mm in two passes, followed by edge trimming to remove any cracks. This process was repeated to further thin the strip from 2.5 mm to 1.0 mm in two more passes. After trimming, coils of a specific width were packaged and stored. The tensile strength was 240 MPa, and the elongation was 5%. The 6111 aluminum alloy strip was then completed.

[0017] In this embodiment, step S8, winding, is not included.

[0018] Example 2: The following are the production steps for preparing 6111 aluminum alloy strip using the method of the present invention; S1. Screening of electrolytic aluminum liquid: The required composition for electrolytic aluminum liquid is: Fe=0.15%, Si=0.05%, Na=60ppm, Ca=50ppm, V=0.03%, with the remainder being Al; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): Si=0.6%, Cu=0.6%, Mn=0.05%, Mg=0.6%, Ti=0.03%, Fe=0.2%, Cr=0.05%, Zn=0.08%, with the balance being Al; The proportion of solid materials such as aluminum ingots and other waste materials in the total weight of the melt is 25-50%. The converter volume of aluminum ingots and other solid materials is 5.5t, the converter volume of electrolytic aluminum liquid is 16.5t, and the total charge volume is 22t. The composition is adjusted by adding intermediate alloys. The melting temperature is controlled at 760℃, and the melting time is 12h. The first refining in the melting furnace is Ar + remelting particles. The refining after adding alloys is remelting particles + powdered refining agent. The weight ratio of remelting particles to powdered refining agent is 1:1. Argon is used as the carrier gas. After the refining operation is completed, the melt with the required composition and temperature is poured into the holding furnace. S3. Refining in a holding furnace: Within 30 minutes of the furnace being turned over, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 755℃, and the refining time is 30 minutes. This refining is repeated every 4 hours thereafter until the next batch of aluminum melt is turned over. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.3 MPa and a flow rate of 3 m³ / h. 3 / h, the refining medium uses high-purity argon gas with a purity of 99.99%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is 0.20ml / 100g·Al; during the production process, nitrogen gas is introduced into the holding furnace to form a slight positive pressure of 10Pa inside the furnace. S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using an Al-5Ti-1B alloy at an addition rate of 3.0 kg / t, resulting in a final Ti content of 0.040%. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 was cast and rolled using a twin-roll inclined casting mill with steel roll sleeves on the upper and lower rolls. Differential speed control was implemented for the upper and lower rolls during the casting and rolling process, with the upper roll's rolling speed 30 mm / min faster than the lower roll. A high-precision laser flow control system was used to control the liquid level in the front box, with a fluctuation range of ±0.5 mm. The roll surface lubrication employed a flame + graphite spraying lubrication process. The casting and rolling zone length was 50 mm, the front box temperature was controlled at 710℃, the casting and rolling speed was controlled at 900 mm / min, the cooling water temperature was 30℃, and the cooling water flow rate was 160 m³ / min. 3 / h, 6111 alloy cast-rolled billet with a thickness of 7.5mm is obtained through a two-stage split-flow casting nozzle structure; S7, Winding: The S6 cast-rolled strip was cold-rolled to 5.0 mm in one pass at a speed of 200 m / min, followed by homogenization annealing at 510℃ for 6 hours. A nitrogen-protected box-type annealing furnace was used. After annealing, the coil cooled in the furnace until it reached 220℃, then air-cooled. Once the coil temperature dropped to 35℃, it was thinned from 5.0 mm to 2.5 mm in two passes, followed by edge trimming to remove cracks. This process was repeated to further thin the strip from 2.5 mm to 1.8 mm in two more passes. The finished product was then trimmed to obtain coils of a specific width, packaged, and stored. The tensile strength was 180 MPa, and the elongation was 8%. The 6111 aluminum alloy strip was then completed.

[0019] In this embodiment, step S8, winding, is not included.

[0020] Example 3: The following are the production steps for preparing 6111 aluminum alloy strip using the method of the present invention; S1. Screening of electrolytic aluminum liquid: The required composition for electrolytic aluminum liquid is: Fe=0.12%, Si=0.04%, Na=50ppm, Ca=40ppm, V=0.02%, with the remainder being Al; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): Si=0.8%, Cu=0.7%, Mn≤0.20%, Mg=0.8%, Ti=0.02%, Fe=0.25%, Cr=0.06%, Zn=0.10%, with the balance being Al; The converter capacity for aluminum ingots and other solid materials such as waste is 6.4t, and the converter capacity for electrolytic aluminum liquid is 19.2t, with a total charge of 25.6t. The composition is adjusted by adding intermediate alloys. The melting temperature is controlled at 757℃, and the melting time is 11h. The first refining in the melting furnace uses Ar + remelting particles. The refining after adding alloys uses remelting particle refining agent + powder refining agent, with a weight ratio of remelting particle refining agent to powder refining agent of 1:1. Argon is used as the carrier gas for both. After the refining operation is completed, the melt with the required composition and temperature is poured into the holding furnace. S3. Refining in a holding furnace: Within 30 minutes of the furnace being poured, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 751℃, and the refining time is 30 minutes. Refining is then repeated every 4 hours until the next batch of aluminum melt is poured, thus maintaining continuous production in this cycle. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.35 MPa and a flow rate of 5.3 m³ / h. 3 / h, the refining medium uses high-purity argon gas with a purity of 99.996%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is 0.23ml / 100g·Al; during the production process, nitrogen gas is introduced into the holding furnace to form a slight positive pressure inside the furnace, with a pressure of 31Pa; S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using an Al-5Ti-1B alloy at an addition rate of 2.2 kg / t, resulting in a final Ti content of 0.029%. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 was cast and rolled using a twin-roll inclined casting mill with steel roll sleeves on the upper and lower rolls. Differential speed control was implemented for the upper and lower rolls during the casting and rolling process, with the upper roll's rolling speed being 22 mm / min faster than the lower roll. A high-precision laser flow control system was used to control the liquid level in the front box, with a fluctuation range of 0.4 mm. The roll surface lubrication employed a flame + graphite spraying lubrication process. The casting and rolling zone length was 48 mm, the front box temperature was controlled at 717℃, the casting and rolling speed was controlled at 780 mm / min, the cooling water temperature was 33℃, and the cooling water flow rate was 145 m³ / min. 3 / h, a 7.1mm thick 6111 alloy cast-rolled billet is obtained through a two-stage split-flow casting nozzle structure; S7, Winding: The S6 cast-rolled strip was cold-rolled to 5.0 mm in one pass at a rolling speed of 310 m / min, followed by homogenization annealing at 530℃ for 6 hours. A nitrogen-protected box-type annealing furnace was used. After annealing, the coil cooled in the furnace until the temperature reached 270℃, at which point it was air-cooled. Once the coil temperature dropped to 35℃, it was thinned from 5.0 mm to 2.5 mm in two passes, followed by edge trimming to remove any cracks. This process was repeated to further thin the strip from 2.5 mm to 1.2 mm in two more passes. After trimming, coils of a specific width were packaged and stored. The tensile strength was 213 MPa, and the elongation was 6.7%. The 6111 aluminum alloy strip was then successfully processed.

[0021] In this embodiment, step S8, winding, is not included.

[0022] This invention, based on a deep expansion of aluminum alloy casting and rolling technology, overcomes the technical bottleneck of conventional casting and rolling processes being unable to produce high-alloy products. It employs a unique casting and rolling process to produce 6111 alloy strip and sheet. This invention utilizes advanced furnace bottom permeable brick technology to maintain the uniformity and consistency of the melt composition in the holding furnace through continuous gas refining. Then, the melt undergoes online degassing, plate filtration, and tubular filtration to further improve its purity. By developing a dedicated casting and rolling technology, 6111 liquid metal is directly transformed into cast and rolled strip and sheet. Finally, through appropriate cold rolling and heat treatment, the elongation (A) is obtained. 50 The 6111 alloy sheet and strip contain more than 5%. After being used in batches by downstream automotive parts manufacturers, automotive parts such as door inner panels, water channels, and battery casings produced using thermoforming processes have tensile strengths exceeding 300 MPa and elongation exceeding (A...). 50With a yield of over 10%, it fully meets the relevant performance requirements of automotive OEMs. Compared with the traditional ingot hot rolling method, it eliminates the ingot casting, milling, heating, and hot rolling processes, combining multiple processes such as casting and hot rolling into a single continuous casting and rolling process. This greatly simplifies the production process of 6111 automotive steel sheets, and the processing cost is only 40% of that of the traditional ingot hot rolling process, giving it significant advantages in cost control and production cycle.

Claims

1. A method for preparing 6111 aluminum alloy sheets by electrolytic aluminum liquid casting and rolling, characterized in that: The steps include the following: S1. Screening of electrolytic aluminum liquid: The required composition for screening electrolytic aluminum liquid is: Fe≤0.15%, Si≤0.05%, Na≤60ppm, Ca≤50ppm, V≤0.03%, with the remainder being Al; the aluminum ingots used must have an Al ≥99.70%, with V ≤0.03%; S2. Smelting: The melt is composed of the following components in weight percentage (Wt%): 0.6%≤Si≤1.0%, 0.6%≤Cu≤0.9%, 0.05%≤Mn≤0.30%, 0.6%≤Mg≤0.9%, 0.02%≤Ti≤0.04%, Fe≤0.4%, Cr≤0.10%, Zn≤0.15%, impurities≤0.15%, balance Al; The melting temperature is controlled at 750℃-760℃, and the melting time is 8h-12h. The first refining in the melting furnace is Ar + remelting particles. The refining after adding alloys is carried out by remelting particle refining agent + powder refining agent. Argon is used as the carrier. After the refining operation is completed, the melt with the qualified composition and temperature is poured into the holding furnace. S3. Refining in a holding furnace: Within 30 minutes of the furnace being turned over, the melt in the holding furnace is refined using argon gas and remelting granular refining agent. The refining temperature is controlled at 740℃-755℃, and the refining time is 30 minutes. This refining process is repeated every 4 hours until the next batch of aluminum melt is turned over, thus maintaining continuous production. The holding furnace bottom is equipped with 12 permeable bricks, which operate continuously during production at a pressure of 0.3 MPa-0.4 MPa and a flow rate of 3 m³ / s. 3 / h -7m 3 / h, the refining medium uses high-purity argon gas with a purity of not less than 99.99%, and the hydrogen content of the aluminum liquid at the outlet of the holding furnace is not higher than 0.25ml / 100g·Al; during the production process, nitrogen gas is introduced into the holding furnace to form a slight positive pressure inside the furnace, with a pressure of 10 Pa - 50 Pa. S4. Grain refinement treatment: The melt obtained from S3 was subjected to grain refinement treatment using Al-5Ti-1B alloy, with an addition amount of 1.5 kg / t to 3.0 kg / t. S5. Online processing: The melt obtained from S4 is subjected to online purification treatment. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon. The filter box first uses a 30PPI+50PPI dual-stage ceramic filter plate to filter the melt, and then filters the melt through a tubular filter device using a 60PPI filter tube. S6. Casting and rolling: The melt obtained from S5 is cast and rolled using a twin-roll inclined casting mill. The upper and lower rolls of the mill are fitted with steel roll sleeves. A high-precision laser flow control system is used to control the liquid level in the front box. The roll surface lubrication employs a flame + graphite lubrication process. The casting and rolling zone length is 45mm-50mm, the front box temperature is controlled at 710℃-720℃, the casting and rolling speed is controlled at 450mm / min-900mm / min, the cooling water temperature is 30℃-35℃, and the cooling water flow rate is 120 m³ / min. 3 / h-160m 3 / h, 6111 alloy cast-rolled billet with a thickness of 7.0±0.5mm is obtained through a two-stage split-flow casting nozzle structure; S7. Cold rolled: The S6 cast-rolled strip is cold-rolled to 5.0 mm in one pass at a rolling speed of 200 m / min - 400 m / min. Then, it undergoes homogenization annealing in a nitrogen-protected box annealing furnace. After annealing, the coil is cooled in the furnace. After the temperature drops below 300℃, it is air-cooled. Once the temperature drops below 40℃, the strip is thinned from 5.0 mm to 2.5 mm through two passes of rolling. Then, the strip is trimmed at the edges to remove any cracks. After two more passes of rolling, the strip is thinned from 2.5 mm to 1.0 mm - 1.8 mm. After trimming, coils of a specific width are obtained, packaged, and stored. The tensile strength is 180 MPa - 240 MPa, and the elongation is 5-8%. The 6111 aluminum alloy strip is now complete. S8, Winding: The produced cast-rolled strip is wound up, cut into coils and packaged according to the required weight.

2. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: In step S2, the proportion of solid materials such as aluminum ingots and other waste materials in the total weight of the melt is 25%-50%, and the remainder is the electrolytic aluminum liquid screened in step S1.

3. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: In step S2, the adjustments to each component are made by adding them in the form of an intermediate alloy to prevent foreign inclusions from entering the melt.

4. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: In step S2, the weight ratio of remelting granular refining agent to powder refining agent is 1:1, and both remelting granular refining agent and powder refining agent use sodium-free formula refining agents.

5. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: In step S6, differential speed control is required for the upper and lower rolls during the casting and rolling process. Specifically, the casting and rolling speed of the upper roll is 10 mm / min to 30 mm / min faster than that of the lower roll.

6. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: In step S6, it is required that the high-precision laser flow control system control the fluctuation range of the liquid level in the front tank to be ≤ ±0.5mm.

7. The method for preparing 6111 aluminum alloy sheet by electrolytic aluminum liquid casting and rolling according to claim 1, characterized in that: The homogenization annealing process in step S7 is as follows: annealing temperature 510℃-560℃, holding time 6h.