Method for preparing cast-rolled strip to reduce occurrence of five-level grains of 1060 aluminum alloy

Abstract

The present application relates to the technical field of aluminum alloy strip preparation, in particular to a cast-rolled strip blank preparation method for reducing the occurrence rate of five-grade grains of 1060 aluminum alloy; the present application reduces the influence of overburning of molten aluminum in the heating and holding stages, increases the number of active nucleation points of the molten aluminum itself, improves the cooling uniformity of the crystallization process, reduces the temperature gradient conducive to the development of lamellar crystallization, systematically inhibits the development of the crystallization process in the direction of lamellar crystallization, effectively controls the occurrence of five-grade grains in the cast-rolling process of 1060 alloy, realizes the stable batch production of cast-rolled 1060 alloy strip blanks from electrolytic aluminum liquid, and has a significant effect on controlling the occurrence of five-grade grains in the cast-rolling process of 1060 alloy; the present application controls the temperature control range of each link of smelting and online processing by smooth control, avoids large fluctuations in temperature, controls the occurrence of five-grade grains in the cast-rolling process of 1060 alloy, greatly reduces the loss of waste caused thereby, and plays an important role in reducing energy consumption and controlling production cost.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy strip preparation technology, specifically to a method for preparing cast-rolled strip billets that reduces the occurrence rate of grade 5 grains in 1060 aluminum alloy. Background Technology

[0002] 1060 alloy aluminum sheet and strip, due to its high purity (belonging to industrial pure aluminum), has good elongation and tensile strength, as well as high plasticity, corrosion resistance, electrical conductivity, and thermal conductivity. After further processing, it is often used in billboards, building exterior decoration, lighting fixtures, electronic devices, as well as chemical instruments, deep-drawn or spun concave vessels, reflective devices, etc., and has a wide range of applications in various fields. In recent years, with the rise of new energy vehicles, the application of 1060 alloy aluminum foil in power batteries has also become an important application area.

[0003] Twin-roll continuous casting and rolling technology is a shortcut to directly produce cold-rolled thin slabs from liquid metal. It combines multiple processes such as casting and hot rolling into a single casting and rolling process, greatly simplifying the production process of plates, strips, and foils, and significantly reducing the production cost of aluminum alloy strip billets. Pure aluminum alloys, due to their low alloy content, have weak nucleation capabilities during crystallization, making them prone to grade 5 grains under conventional casting and rolling conditions. This is especially true when using electrolytic aluminum liquid to directly cast and roll high-purity pure aluminum alloys such as 1060, where grade 5 grains occur frequently. This can lead to scrapped coils or even batch quality incidents, significantly disrupting normal production. Therefore, the industry urgently needs to develop a casting and rolling technology to improve the quality of high-purity pure aluminum alloys such as 1060. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing cast-rolled strip billets that reduces the occurrence rate of grade 5 grains in 1060 aluminum alloy, effectively controlling the occurrence of grade 5 grains in the casting and rolling process of 1060 alloy, and realizing stable mass production of 1060 alloy strip billets cast from electrolytic aluminum liquid.

[0005] The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to the present invention includes the following steps: S1. Selection of electrolytic aluminum solution: Electrolytic aluminum liquid produced by electrolytic cells was selected as the main raw material for producing 1060 aluminum alloy cast and rolled strip. S2. Alloy smelting: The melt is composed of the following components by weight percentage: Fe: 0.28%-0.32%, Si≤0.06%, Mg≤0.02%, Ti: 0.02%-0.03%, Mn≤0.02%, Cu≤0.02%, Zn≤0.02%, impurities≤0.015%, balance Al; Solid materials such as aluminum ingots and scrap of the same grade account for 30% to 35% of the total weight of the furnace charge, and the rest is the electrolytic aluminum liquid selected in step S1. S2 includes the following steps: S2.1. First, load in the cold material, then pour in the molten aluminum. Heat the furnace until the molten aluminum reaches 720°C, then stir the molten aluminum. S2.2. Refining begins when the temperature reaches 730℃, using an Ar+ remelting granular refining agent process for the first refining step. S2.3. After settling and slag removal, the chemical composition of the molten aluminum is adjusted to ensure that all alloy components except Ti are in place. S2.4. A second refining process using Ar+ remelting granular refining agent is performed, followed by settling and slag removal. S2.5. When the temperature of the molten aluminum reaches 750℃-755℃, it is ready for a converter, and the smelting cycle is ≤16h; S3. Static furnace treatment: S3.1. Transfer the molten aluminum obtained in step S2 from the smelting furnace to the holding furnace. Add AlTi10 master alloy to the molten aluminum with the Ti content controlled at 0.012%-0.015%. During the converter process, the molten aluminum is evenly poured into the furnace twice through the chute. S3.2. Within 20 minutes after the converter is completed, the first remelting granular refining agent is started. Argon gas is used for refining every 4 hours thereafter. Before refining, 0.5% of the mass of the melt in the furnace is added to the furnace. The temperature of the aluminum liquid in the furnace is controlled at 745℃-750℃ before refining. The refining time is 24 minutes. The temperature of the aluminum liquid at the furnace opening is controlled at 725℃-730℃. S4. Online processing: The melt obtained in step S3 is subjected to online processing. After flowing out of the holding furnace, the melt first passes through a degassing box. The temperature of the molten aluminum at the inlet of the degassing box is controlled at 715-720℃. An Al-Ti5-B1 ​​grain refiner rod is added at the inlet of the degassing box. After being preheated by a flame, the Al-Ti5-B1 ​​grain refiner rod is added in a bipolar manner with a transverse reciprocating oscillation in the chute. The temperature of the preheated Al-Ti5-B1 ​​grain refiner rod is 500℃-600℃. The amount of Al-Ti5-B1 ​​grain refiner added is 0.20%-0.25% of the molten aluminum flow rate. The online Ti increment is controlled. The concentration is controlled at 0.008-0.012%; the degassing box uses a silicon nitride rotor for online degassing, and the online refining gas is argon, with an argon pressure of 0.35MPa-0.45MPa and an argon flow rate of 15L / Min-20L / Min. During the degassing process, there should be no obvious turbulence on the surface of the aluminum liquid, and the bubbles should be small and dispersed. The outlet temperature of the aluminum liquid in the degassing box is controlled at 715℃-720℃; the filter box uses a bipolar 30+40 mesh ceramic filter plate to filter the aluminum liquid, and the outlet temperature of the aluminum liquid in the filter box is controlled at 705℃-710℃, while the temperature of the aluminum liquid in the front box is controlled at 695℃-700℃. S5. Casting and rolling: A twin-roll inclined casting and rolling mill is used. The roll sleeves are made of conventional alloy steel. The roll surface lubrication adopts flame spraying process. The temperature of the front box is controlled at 695℃-700℃, the casting and rolling speed is controlled at 1000 mm / min-1100 mm / min, and the cooling water inlet temperature of the lower roll is 37℃-40℃. A 1060 alloy cast and rolled billet with a thickness of 6.5mm±0.2mm is obtained.

[0006] Furthermore, in step S1, the source of the electrolytic aluminum liquid is controlled. The selected electrolytic aluminum liquid has an electrolytic cell temperature of 925℃-940℃, an electrolytic cell working voltage of ≤4.0V, and an Fe content of ≤0.15% in the aluminum liquid.

[0007] Furthermore, in step S2.1, the cold material is added to the smelting furnace without being heated. The molten aluminum is poured into the smelting furnace and left to stand for 5-10 minutes before being heated.

[0008] Furthermore, in step S2.1, the heating process of the smelting furnace should be uniform and smooth, and the furnace gas temperature inside the smelting furnace should be ≤850℃ during the heating and holding process.

[0009] Furthermore, in step S3, based on the target temperature control range of 725℃-730℃ for the molten aluminum at the furnace opening, the temperature of the molten aluminum during the holding process is controlled within a suitable range of 740℃-750℃ to ensure the stability of the output temperature at the furnace opening. During the heating and holding process, the temperature of the furnace gas inside the smelting furnace is ≤800℃.

[0010] Furthermore, in step S4, in order to ensure that the aluminum liquid is kept warm but not heated when passing through the degassing box and the filter box, the chute through which the aluminum liquid passes is tightly covered with refractory material to reduce heat loss. The aluminum liquid temperature at the furnace opening, the outlet of the degassing box, the outlet of the filter box, and the front box is set to decrease in a gradient, and the temperature difference gradient between adjacent measurement points is 10℃±3℃.

[0011] Furthermore, in step S5, a higher casting and rolling speed is used to appropriately reduce the undercooling during the casting and rolling crystallization process. When the wall thickness of the casting roll sleeve is <35mm, the casting and rolling speed is controlled at 1050mm / min-1100mm / min; when the wall thickness of the casting roll sleeve is ≥35mm, the casting and rolling speed is controlled at 1000mm / min-1050mm / min.

[0012] Furthermore, in step S5, the cooling water for the upper and lower casting rolls adopts an independent circulation transportation technical route. After determining the water inlet temperature of the lower roll, the water inlet temperature of the upper roll is set to be 3°C lower than that of the lower roll.

[0013] Furthermore, in step S5, the rotational speed of the lower casting roll is appropriately fine-tuned so that the rotational speed of the lower casting roll is 10 mm / min-30 mm / min faster than that of the upper casting roll.

[0014] Furthermore, in step S5, the length of the casting and rolling zone is set to 43mm-48mm.

[0015] The beneficial effects of this invention are as follows: This invention reduces the impact of heating and holding stages on overheating of molten aluminum, increases the number of active nucleation sites in the molten aluminum, improves the cooling uniformity of the crystallization process, reduces the temperature gradient conducive to the development of layered crystallization, systematically inhibits the development of the crystallization process towards layered crystallization, effectively controls the occurrence of grade 5 grains in the casting and rolling process of 1060 alloy, and realizes stable batch production of 1060 alloy strip billets cast from electrolytic aluminum liquid. This invention has a significant effect on controlling the occurrence of grade 5 grains in the casting and rolling process of 1060 alloy. By smoothly controlling the temperature control range of each stage of melting and online processing, this invention avoids large temperature fluctuations, controls the occurrence of grade 5 grains in the casting and rolling process of 1060 alloy, and greatly reduces the scrap loss caused by this. It plays an important role in reducing energy consumption and controlling production costs. Detailed Implementation

[0016] The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to the present invention includes the following steps: S1. Selection of electrolytic aluminum solution: Electrolytic aluminum liquid produced by an electrolytic cell was selected as the raw material for producing 1060 aluminum alloy cast-rolled strip billets; the selected electrolytic aluminum liquid was produced in an electrolytic cell with a cell temperature of 925℃-940℃, an electrolytic cell working voltage of ≤4.0V, and an Fe content of ≤0.15% in the aluminum liquid; S2. Alloy smelting: The melt is composed of the following components by weight percentage: Fe: 0.28%-0.32%, Si≤0.06%, Mg≤0.02%, Ti: 0.02%-0.03%, Mn≤0.02%, Cu≤0.02%, Zn≤0.02%, impurities≤0.015%, balance Al; Solid materials such as aluminum ingots and scrap of the same grade account for 30% to 35% of the total weight of the furnace charge, and the rest is the electrolytic aluminum liquid selected in step S1. S2 includes the following steps: S2.1. First, load the cold material and then pour in the electrolytic aluminum liquid. Do not heat up the furnace after the cold material is added. Wait for the electrolytic aluminum liquid to be poured into the furnace and stand for 5-10 minutes before heating. Stir the aluminum liquid when the furnace temperature reaches 720℃. The furnace temperature should be uniform and smooth during the heating process. The furnace gas temperature should be ≤850℃ during the heating and holding process. S2.2. Refining begins when the temperature reaches 730℃, using an Ar+ remelting granular refining agent process for the first refining step. S2.3. After settling and slag removal, the chemical composition of the molten aluminum is adjusted to ensure that all alloy components except Ti are in place. S2.4. A second refining process using Ar+ remelting granular refining agent is performed, followed by settling and slag removal. S2.5. When the temperature of the molten aluminum reaches 750℃-755℃, it is ready for a converter, and the smelting cycle is ≤16h; S3. Static furnace treatment: S3.1. Transfer the molten aluminum obtained in step S2 from the smelting furnace to the holding furnace. Add AlTi10 master alloy to the molten aluminum with the Ti content controlled at 0.012%-0.015%. During the converter process, the molten aluminum is evenly poured into the furnace twice through the chute. S3.2. Within 20 minutes after the converter is completed, the first remelting granular refining agent should be used for refining. Argon gas should be used for refining every 4 hours thereafter. Before refining, 0.5% of the mass of aluminum ingot or aluminum plate of the same alloy should be added to the furnace melt. The temperature of the aluminum liquid in the holding furnace should be controlled at 745℃-750℃ before refining. The refining time is 24 minutes. The temperature of the aluminum liquid at the furnace opening should be controlled at 725℃-730℃. During the holding furnace heat preservation process, the temperature of the aluminum liquid should be controlled within a suitable range of 740℃-750℃ to ensure the stability of the output temperature at the furnace opening. During the heating and heat preservation process of the holding furnace, the furnace gas temperature in the melting furnace should be ≤800℃. S4. Online processing: The melt obtained in step S3 is subjected to online processing. After flowing out of the holding furnace, the melt first passes through a degassing box. The temperature of the molten aluminum at the inlet of the degassing box is controlled at 715-720℃. An Al-Ti5-B1 ​​grain refiner rod is added at the inlet of the degassing box. After being preheated by a flame, the Al-Ti5-B1 ​​grain refiner rod is added in a bipolar manner with a transverse reciprocating oscillation in the chute. The temperature of the preheated Al-Ti5-B1 ​​grain refiner rod is 500℃-600℃. The amount of Al-Ti5-B1 ​​grain refiner added is 0.20%-0.25% of the molten aluminum flow rate, and the online Ti increment is controlled at 0.008-0.012%. The degassing box uses a silicon nitride rotor for online degassing, and the online refining gas is argon at a pressure of 0.35MPa. -0.45MPa, argon flow rate of 15L / min-20L / min, no obvious turbulence on the surface of the aluminum liquid during degassing, small and diffuse bubbles, and aluminum liquid temperature at the outlet of the degassing box controlled at 715℃-720℃; the filter box uses a bipolar 30+40 mesh ceramic filter plate to filter the aluminum liquid, and the aluminum liquid temperature at the outlet of the filter box controlled at 705℃-710℃, and the aluminum liquid temperature in the front box controlled at 695℃-700℃; in order to ensure that the aluminum liquid only maintains its temperature and does not rise when passing through the degassing box and the filter box, the chute through which the aluminum liquid passes is tightly covered with refractory material to reduce heat loss, and the aluminum liquid temperature at the furnace opening, the outlet of the degassing box, the outlet of the filter box and the front box is set to decrease in a gradient trend, with a temperature difference gradient of 10℃±3℃ between adjacent measurement points. S5. Casting and rolling: A twin-roll inclined casting and rolling mill is used. The roll sleeves are made of conventional alloy steel, and the roll surface lubrication is achieved through flame spraying. The front chamber temperature is controlled at 695℃-700℃, the casting and rolling speed is controlled at 1000mm / min-1100mm / min, and the cooling water inlet temperature of the lower roll is 37℃-40℃. This produces 1060 alloy cast-rolled billets with a thickness of 6.5mm±0.2mm. When the roll sleeve wall thickness is <35mm, the casting and rolling speed is controlled at 1050mm / min-1100mm / min. When the wall thickness of the casting roll sleeve is ≥35mm, the casting speed is controlled at 1000mm / min-1050mm / min; the cooling water for the upper and lower casting rolls adopts an independent circulation transportation technical route. After determining the water inlet temperature of the lower roll, the water inlet temperature of the upper roll is set to be 3℃ lower than that of the lower roll; in step S5, the speed of the lower casting roll is adjusted appropriately to make the speed of the lower casting roll 10mm / min-30mm / min faster than that of the upper casting roll; in step S5, the length of the casting zone is set at 43mm-48mm.

[0017] Example 1: S1. Screening of electrolytic aluminum liquid: The working conditions of the electrolytic cells were classified, and those with good cell conditions, stable cell temperature, and good control of aluminum melt overheating were selected. The electrolytic cells with an aluminum melt temperature of 925℃, an electrolytic cell working voltage of 3.983V, and an aluminum melt Fe content of 0.15% were selected. The electrolytic aluminum melt produced by these cells was used as the raw material for producing 1060 aluminum alloy cast and rolled strip. S2. Alloy smelting: During the batching process, solid materials such as aluminum ingots and scrap of the same grade account for 30% of the total weight of the furnace charge, with the remainder being molten aluminum. The total charge is 19.3 tons. Cold materials are added first, followed by molten aluminum. After the molten aluminum is poured into the melting furnace and left to stand for 5 minutes, the furnace is heated. During the heating and holding process, the furnace gas temperature reaches a maximum of 850°C. When the molten aluminum reaches 720°C, it is stirred. Refining begins at 730°C using an Ar + remelting granular refining agent. Except for Ti, all other alloy components are adjusted before the second refining. The melt consists of the following components by weight percentage: Fe 0.32%, Si 0.04%, Mg 0.01%, Mn 0.01%, Cu 0.01%, Zn 0.01%, with the balance being Al. After the second refining process using Ar+ remelting granular refining agent, the aluminum liquid is allowed to stand and slag is removed. When the temperature of the aluminum liquid reaches 755℃, the converter is prepared and the smelting cycle is 14 hours. S3. Static furnace treatment: The aluminum melt with the required temperature and composition obtained in step S1 is transferred from the smelting furnace to the holding furnace. The amount of Ti alloy to be added is calculated based on the melt mass and the target Ti addition range in the smelting furnace, i.e., 0.012%-0.015% AlTi10 by melt mass composition. During the converter process, 30 kg of AlTi10 alloy is evenly poured into the aluminum melt through a chute in two batches. Within 20 minutes after the converter is completed, the first remelting with granular refining agent is started. After refining, a sample of 0.015% Ti is taken. Subsequently, argon gas is used for refining every 4 hours. Before refining, 97 kg of the same alloy aluminum plate is added. During the heating and holding process in the holding furnace, the highest temperature of the furnace gas in the smelting furnace is 785℃. Before refining, the temperature of the aluminum melt in the holding furnace is controlled at 745℃-750℃. The refining time is 24 minutes. During the holding process, the temperature of the aluminum melt is controlled at 742℃±2℃, and the temperature of the aluminum melt at the furnace opening is controlled at 726℃±1℃. S4. Online processing: The melt obtained in step S2 is processed online. After flowing out of the holding furnace, the melt first passes through a degassing box. The temperature of the aluminum liquid at the inlet of the degassing box is controlled at 715℃-720℃. An Al-Ti5-B1 ​​grain refiner rod is added to the inlet of the degassing box. The Al-Ti5-B1 ​​grain refiner rod is added in a chute in a transverse oscillating bipolar manner after being preheated by a flame. The addition amount is 2kg / t·Al, and the online Ti increment is 0.008%. The temperature of the rod after preheating is 510℃±10℃. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon, with an argon pressure of 0.45MPa and a flow rate of 20L / Min. During the degassing process, the bubbles on the surface of the aluminum liquid are small and dispersed. The temperature of the aluminum liquid at the outlet of the degassing box is controlled at 717℃-720℃. The filter box uses a bipolar 30+40 mesh ceramic filter plate to filter aluminum liquid. The temperature of aluminum liquid at the outlet of the filter box is controlled at 705℃-718℃, and the temperature of aluminum liquid in the front box is controlled at 698-700℃. S5. Casting and rolling: A twin-roll inclined casting and rolling mill was adopted. The roll sleeves were made of conventional alloy steel, and the roll surface lubrication was achieved using a flame spraying process. Due to the roll sleeve wall thickness of 32mm, the casting and rolling speed was controlled at 1100mm / min. By appropriately fine-tuning the speed of the lower casting roll, the speed of the lower casting roll was made 30mm / min faster than that of the upper casting roll. The temperature of the front box was controlled at 695-700℃, the cooling water inlet temperature of the lower roll was set to 37℃, the cooling water inlet temperature of the upper roll was set to 34℃, and the length of the casting and rolling zone was set to 43mm. A 1060 alloy cast and rolled strip with a thickness of 6.45mm was obtained, and the grain size of the cast and rolled strip was normal.

[0018] Example 2: S1. Screening of electrolytic aluminum liquid: The electrolytic cells were classified according to their working conditions, and those with good cell conditions, stable cell temperature, and good control of aluminum melt overheating were selected. The electrolytic cells with an aluminum melt temperature of 939℃, an electrolytic cell working voltage of 3.996V, and an aluminum melt Fe content of 0.12% were selected. The electrolytic aluminum melt produced by these cells was used as the raw material for producing 1060 aluminum alloy cast and rolled strip. S2. Alloy smelting: During the batching process, aluminum ingots and other solid materials of the same grade account for 35% of the total weight of the furnace charge, while the rest is molten aluminum. The total charge is 18.5t. First, cold material is loaded, then electrolytic aluminum liquid is poured in. After the electrolytic aluminum liquid is poured into the melting furnace and left to stand for 10 minutes, the temperature is raised. During the heating and holding process, the furnace gas temperature in the melting furnace reaches a maximum of 830℃. When the temperature of the aluminum liquid reaches 720℃, the aluminum liquid is stirred. When the temperature reaches 730℃, refining begins. The refining process is carried out using Ar + remelting granular refining agent. Except for Ti, the other alloy components are adjusted before the second refining. The melt consists of the following components by weight percentage: Fe 0.28%, Si 0.06%, Mg 0.01%, Mn 0.01%, Cu 0.01%, Zn 0.01%, with the balance being Al. After the second refining process using Ar + remelting granular refining agent, the molten aluminum is allowed to stand and slag is removed. When the temperature of the aluminum liquid reaches 750℃, the converter is prepared. The melting cycle is 16 hours. S3. Static furnace treatment: The aluminum melt with the required temperature and composition obtained in step S1 is transferred from the smelting furnace to the holding furnace. The amount of Ti alloy to be added is calculated based on the melt mass and the target Ti addition range in the smelting furnace, i.e., 0.012%-0.015% AlTi10 by melt mass composition. During the converter process, 28 kg of AlTi10 alloy is evenly poured into the aluminum melt through a chute in two batches. Within 20 minutes after the converter is completed, the first remelting with granular refining agent is started. After refining, a sample of 0.014% Ti is taken. Subsequently, argon refining is performed every 4 hours. Before refining, 93 kg of aluminum ingot is added. During the heating and holding process in the holding furnace, the highest temperature of the furnace gas in the smelting furnace is 800℃. Before refining, the temperature of the aluminum melt in the holding furnace is controlled at 745℃-750℃. The refining time is 24 minutes. During the holding process, the temperature of the aluminum melt is controlled at 748℃±2℃, and the temperature of the aluminum melt at the furnace opening is controlled at 729℃±1℃. S4. Online processing: The melt obtained in step S2 is processed online. After flowing out of the holding furnace, the melt first passes through a degassing box. The temperature of the aluminum liquid at the inlet of the degassing box is controlled at 715℃-720℃. An Al-Ti5-B1 ​​grain refiner rod is added to the inlet of the degassing box. The Al-Ti5-B1 ​​grain refiner rod is added in a chute in a transverse oscillating bipolar manner after being preheated by a flame. The addition amount is 2.5 kg / t Al, and the online Ti increment is 0.011%. The temperature of the rod after preheating is 570℃±10℃. The degassing box uses a silicon nitride rotor for online degassing. The online refining gas is argon, with an argon pressure of 0.35 MPa and a flow rate of 15 L / min. During the degassing process, the bubbles on the surface of the aluminum liquid are small and dispersed. The temperature of the aluminum liquid at the outlet of the degassing box is controlled at 715℃-718℃. The filter box uses a bipolar 30+40 mesh ceramic filter plate to filter the aluminum liquid. The temperature of the aluminum liquid at the outlet of the filter box is controlled at 708℃-710℃, and the temperature of the aluminum liquid in the front box is controlled at 695-698℃. S5. Casting and rolling: A twin-roll inclined casting and rolling mill was adopted. The roll sleeves were made of conventional alloy steel, and the roll surface lubrication was achieved using a flame spraying process. Due to the roll sleeve wall thickness of 59mm, the casting and rolling speed was controlled at 1000mm / min. By appropriately fine-tuning the speed of the lower casting roll, the speed of the lower casting roll was made 10mm / min faster than that of the upper casting roll. The temperature of the front box was controlled at 695℃-700℃. The cooling water inlet temperature of the lower roll was set to 40℃, and the cooling water inlet temperature of the upper roll was set to 37℃. The length of the casting and rolling zone was set to 48mm, resulting in a 6.68mm thick 1060 alloy cast and rolled strip with normal grain structure.

Claims

1. A method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy, characterized in that: The steps include the following: S1. Selection of electrolytic aluminum solution: Electrolytic aluminum liquid produced by electrolytic cells was selected as the main raw material for producing 1060 aluminum alloy cast and rolled strip. The source of electrolytic aluminum liquid was controlled. The selected electrolytic cell temperature was 925℃-940℃, the electrolytic cell working voltage was ≤4.0V, and the Fe content in the aluminum liquid was ≤0.15%. S2. Alloy smelting: The melt consists of the following components by weight percentage composition: Fe: 0.28%-0.32%, Si≤0.06%, Mg≤0.02%, Ti: 0.02%-0.03%, Mn≤0.02%, Cu≤0.02%, Zn≤0.02%, impurities≤0.015%, balance Al; Solid materials such as aluminum ingots and scrap of the same grade account for 30% to 35% of the total weight of the furnace charge, and the rest is the electrolytic aluminum liquid selected in step S1. S2 includes the following steps: S2.

1. First, load in the cold material, then pour in the molten aluminum. Heat the furnace until the molten aluminum reaches 720°C, then stir the molten aluminum. S2.

2. Refining begins when the temperature reaches 730℃, using an Ar+ remelting granular refining agent process for the first refining step. S2.

3. After settling and slag removal, the chemical composition of the molten aluminum is adjusted to ensure that all alloy components except Ti are in place. S2.

4. A second refining process using Ar+ remelting granular refining agent is performed, followed by settling and slag removal. S2.

5. When the temperature of the molten aluminum reaches 750℃-755℃, it is ready for a converter, and the smelting cycle is ≤16h; S3. Static furnace treatment: S3.

1. Transfer the molten aluminum obtained in step S2 from the smelting furnace to the holding furnace. Add AlTi10 master alloy to the molten aluminum with the Ti content controlled at 0.012%-0.015%. During the converter process, the molten aluminum is evenly poured into the furnace twice through the chute. S3.

2. Within 20 minutes after the converter is completed, the first remelting granular refining agent is started. Argon gas is used for refining every 4 hours thereafter. Before refining, 0.5% of the mass of the melt in the furnace is added to the furnace. The temperature of the molten aluminum in the furnace is controlled at 745℃-750℃ before refining. The refining time is 24 minutes. The temperature of the molten aluminum at the furnace opening is controlled at 725℃-730℃. S4. Online processing: The melt obtained in step S3 is subjected to online processing. After flowing out of the holding furnace, the melt first passes through a degassing box. The temperature of the molten aluminum at the inlet of the degassing box is controlled at 715-720℃. An Al-Ti5-B1 ​​grain refiner rod is added at the inlet of the degassing box. After being preheated by a flame, the Al-Ti5-B1 ​​grain refiner rod is added in a bipolar manner with a transverse reciprocating oscillation in the chute. The temperature of the preheated Al-Ti5-B1 ​​grain refiner rod is 500℃-600℃. The amount of Al-Ti5-B1 ​​grain refiner added is 0.20%-0.25% of the molten aluminum flow rate. The online Ti increment is controlled. The concentration is controlled at 0.008-0.012%; the degassing box uses a silicon nitride rotor for online degassing, and the online refining gas is argon, with an argon pressure of 0.35MPa-0.45MPa and an argon flow rate of 15L / Min-20L / Min. During the degassing process, there should be no obvious turbulence on the surface of the aluminum liquid, and the bubbles should be small and dispersed. The outlet temperature of the aluminum liquid in the degassing box is controlled at 715℃-720℃; the filter box uses a bipolar 30+40 mesh ceramic filter plate to filter the aluminum liquid, and the outlet temperature of the aluminum liquid in the filter box is controlled at 705℃-710℃, while the temperature of the aluminum liquid in the front box is controlled at 695℃-700℃. S5. Casting and rolling: A twin-roll inclined casting and rolling mill is used. The roll sleeves are made of conventional alloy steel. The roll surface lubrication is achieved by flame spraying. The temperature of the front box is controlled at 695℃-700℃, the casting and rolling speed is controlled at 1000mm / min-1100mm / min, and the cooling water inlet temperature of the lower roll is 37℃-40℃. This produces 1060 alloy cast and rolled billets with a thickness of 6.5mm±0.2mm. In step S5, the casting and rolling speed is appropriately reduced to reduce the undercooling during the casting and rolling crystallization process. When the wall thickness of the casting roll sleeve is <35mm, the casting and rolling speed is controlled at 1050mm / min-1100mm / min; when the wall thickness of the casting roll sleeve is ≥35mm, the casting and rolling speed is controlled at 1000mm / min-1050mm / min. In step S5, the cooling water for the upper and lower casting rolls adopts an independent circulation transportation technical route. After determining the water inlet temperature of the lower roll, the water inlet temperature of the upper roll is set to be 3°C lower than that of the lower roll. In step S5, the speed of the lower casting roll is finely adjusted so that the speed of the lower casting roll is 10 mm / min-30 mm / min faster than that of the upper casting roll.

2. The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to claim 1, characterized in that: In step S2.1, the cold material is added to the smelting furnace without heating. The molten aluminum is poured into the smelting furnace and left to stand for 5-10 minutes before being heated.

3. The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to claim 1, characterized in that: In step S2.1, the heating process of the smelting furnace should be uniform and smooth, and the furnace gas temperature inside the smelting furnace should be ≤850℃ during the heating and holding process.

4. The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to claim 1, characterized in that: In step S3, the aluminum liquid temperature during the holding process is controlled within a suitable range of 740℃-750℃, based on the target temperature control range of 725℃-730℃ for the aluminum liquid at the furnace opening, in order to ensure the stability of the output temperature at the furnace opening. During the heating and holding process, the furnace gas temperature inside the smelting furnace is ≯800℃.

5. The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to claim 1, characterized in that: In step S4, to ensure that the molten aluminum is kept warm but not heated when passing through the degassing box and the filter box, the chute through which the molten aluminum passes is tightly covered with refractory material to reduce heat loss. The temperature of the molten aluminum at the furnace opening, the outlet of the degassing box, the outlet of the filter box, and the front box is set to decrease in a gradient, and the temperature difference gradient between adjacent measurement points is 10℃±3℃.

6. The method for preparing cast-rolled strip billets to reduce the occurrence rate of grade 5 grains in 1060 aluminum alloy according to claim 1, characterized in that: In step S5, the length of the casting and rolling zone is set to 43mm-48mm.