Preparation method of round cast ingot for 7003 aluminum alloy extruded profile

Abstract

The invention relates to the technical field of preparation processes of round ingots for extruded profiles, in particular to a preparation method of a round ingot for a 7003 aluminum alloy extruded profile. The alloy comprises the following components: Zn, Mg, Cu, Fe, Si, Zr, Ti and Al. The method mainly comprises the steps of smelting of electrolytic aluminum liquid and aluminum ingots, alloying, refining, standing, heat preservation, online degassing, filtering and casting. Compared with a traditional casting process, the whole production process is short, the machining cost is low, the casting production speed is increased, the performance of the round ingot alloy product for the extruded profile is expanded, the high-performance characteristic of the 7003 aluminum alloy is ensured through strict component control and refining processes, and the requirements of the modern industry for light-weight and high-strength materials are met.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation process of round ingots for extruded profiles, and particularly to a preparation method for round ingots for 7003 aluminum alloy extruded profiles. Background Art

[0002] Due to the advantages of high strength, light weight, stability, strong corrosion resistance, good plasticity with small deformation, non-toxic and pollution-free, long service life (up to 50 - 100 years), good recyclability and re-melting in the furnace, etc., the 7003 aluminum alloy material is widely used in modern industrial production. As one of the main varieties of high-end aluminum, zinc, and magnesium alloy products for industrial processing materials, with the advantages of one-time extrusion forming, high mechanical and physical properties, good thermal conductivity, and high specific strength, etc., it is increasingly widely used in transportation (automobile, rail transit lightweight), electronics, electrical, machinery, light industry, petroleum, chemical industry, electromechanics, aerospace and other fields.

[0003] In recent years, with the lightweight of modern transportation tools typified by high-speed trains, urban subways, and light rail trains, as well as the rapid development of the aerospace, shipbuilding, and machinery manufacturing industries, the demand for high-performance aluminum and magnesium alloy extruded materials has increased rapidly. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method for round ingots for 7003 aluminum alloy extruded profiles, so as to achieve the improvement of the solidification speed of aluminum melt, the improvement of production speed, the broadening of alloy products, the reduction of production energy consumption, and the significant improvement of the economic benefits of product production.

[0005] To achieve the above technical effects, a preparation method for round ingots for 7003 aluminum alloy extruded profiles of the present invention includes the following steps: S1. Batching: S1.1. Select pure aluminum ingots and electrolytic aluminum liquid as raw materials, without adding other waste materials, and the mass ratio of pure aluminum ingots in the raw materials is 30% - 45%; S1.2. The feeding method is: add aluminum scrap cakes to the bottom of the furnace, add the sawed head and tail materials of 7003 grade to the combustion chamber, press the aluminum cakes with the head and tail of the rod, and pour the aluminum liquid into the furnace from the pouring port; S1.3. The feeding sequence is: first add aluminum scrap cakes and press them with the water pot head or the head and tail of the rod, add aluminum ingots stack by stack, then close the furnace door and start firing and pouring aluminum. The cold materials must be completely soaked with aluminum liquid; S1.4. Control the temperature of the melting furnace at 730°C - 760°C; 730 - 760°C is the best melting temperature, and overheating will occur if it is too high; S1.5. The pure aluminum ingots can be added to the electrolytic aluminum liquid before the melting furnace is heated. During the melting process of the raw materials, stirring is carried out 2 - 3 times to evenly stir the materials at the bottom of the furnace. The stirring time for each time is 4 min - 6 min; S2. When the furnace charge is completely melted and the temperature of the melting furnace reaches 740°C - 750°C, slag skimming is carried out, stirring is carried out for 8 min - 10 min, and then the first sampling is carried out; the alloy composition analysis is carried out on the first sampling; The alloy composition requirements are as follows: Zn is 5.5% - 5.7%; Mg is 0.7% - 0.9%; Cu is 0.13% - 0.18%; Fe is 0.3% - 0.35%; Si is 0.2% - 0.25%; Zr is 0.1% - 0.2%; Ti is 0.1% - 0.2%; the rest is Al; S3. In - furnace refining: S3.1. When the temperature of the aluminum liquid reaches 745°C - 750°C, the first refining starts. Argon and a refining agent are used for powder injection refining; the refining agent is a remelting - type refining agent, and the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 15 min - 30 min; after the refining is completed, it is left to stand for slag skimming; S3.2. When the temperature of the aluminum liquid reaches 720°C - 750°C, the second refining starts. Argon and a refining agent are used for powder injection refining; the refining agent is a sodium - free granular refining agent, a fluoride - free and sodium - free refining agent or a composite refining agent, the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 10 min - 20 min; after the refining is completed, it is left to stand for slag skimming; S3.3. When the temperature of the aluminum liquid reaches 720°C - 750°C, the third refining starts. Argon and a refining agent are used for powder injection refining; the refining agent is a rare - earth - element - containing refining agent, a composite inorganic salt refining agent or a new - type environmental - protection refining agent, the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 15 min - 30 min; after the refining is completed, it is left to stand for slag skimming; S3.4. After the three - time refining is completed, sampling is carried out again to detect the alloy composition; after the alloy composition meets the alloy composition requirements in step S1.6, it is left to stand, and the standing time is 10 min - 20 min; if the alloy composition detected by sampling after the three - time refining does not meet the alloy composition requirements in step S1.6, then repeat step S2 and step S3 until the alloy composition detected by sampling after the three - time refining meets the alloy composition requirements in step S2; S4. On - line treatment: The melt that has completed step S3 is processed online. After being preheated to no less than 400 °C, the Al-Ti5-B1 grain refiner is continuously added into the aluminum melt at the inlet of the degassing box through a metering feeding device. The addition amount is strictly controlled at 1.8 kg / t•Al, and the melt temperature at the addition point is maintained at 720 °C - 740 °C to ensure the full dissolution and diffusion of Ti element. Finally, the Ti content in the melt is accurately controlled within the range of 0.010% - 0.020%. The aluminum liquid after degassing treatment then enters a filtration box equipped with a 40-mesh + 50-mesh double-stage foam ceramic filter plate for deep purification. The operating temperature of the filtration system is maintained within the range of 710 - 725 °C. The 40-mesh filter plate mainly intercepts large-sized inclusions, and the 50-mesh filter plate further removes fine impurities. The combined action of the two-stage filtration can effectively control the inclusion size in the aluminum liquid below 20 μm. At the same time, the operating temperature of the filtration system is maintained within the range of 710 - 725 °C to ensure the best filtration effect and the fluidity of the aluminum liquid. S5. Cast rolling: A twin-roll inclined cast rolling mill is used for cast rolling. The temperature of the front box is controlled at 695 °C ± 2 °C to ensure good fluidity of the aluminum liquid. The cast rolling speed is adjusted within the range of 700 mm / min - 900 mm / min to achieve stable solidification and forming. The cooling system uses circulating cooling water at 25 °C - 35 °C, and the cooling water flow rate of the single-side cast rolling roll is controlled within the range of 110 m³ / t•Al - 130 m³ / t•Al to ensure uniform and efficient cooling effect. Finally, an aluminum alloy cast rolling strip with a thickness of 7.0 mm - 8.0 mm, excellent surface quality, and uniform internal structure is obtained. During casting, according to the length of the chute and the heat loss situation, a temperature measuring device such as a thermocouple is used to control the water discharge temperature at: 735 °C ± 5 °C, and the measurement frequency is once every 10 minutes; the temperature of the die head is controlled at: 700 °C - 710 °C using a temperature measuring device such as a thermocouple, and the measurement frequency is once every 15 minutes; the temperature of the die tail is controlled at: 680 °C - 695 °C using a temperature measuring device such as a thermocouple, and the measurement frequency is once every 15 minutes. During casting, according to different specifications of the round ingot, the control of the casting speed and water flow rate is within the following range: When the specification of the cast round ingot is 90, the starting casting speed is 108 ± 2 mm / min, the steady-state casting speed is 155 mm / min - 160 mm / min, the casting water flow rate is 320 m³ / h, and the die tail temperature is 685 °C - 695 °C. When the specification of the cast round ingot is 120, the starting casting speed is 90 ± 2 mm / min, the steady-state casting speed is 130 mm / min - 135 mm / min, the casting water flow rate is 360 m³ / h, and the die tail temperature is 685 °C - 695 °C. When the specification of the cast round ingot is 127, the starting casting speed is 99 ± 2 mm / min, the steady-state casting speed is 125 mm / min - 130 mm / min, the casting water flow rate is 350 m³ / h, and the temperature at the end of the coil is 685°C - 695°C; When the specification of the cast round ingot is 152, the starting casting speed is 90 ± 2 mm / min, the steady-state casting speed is 115 mm / min - 120 mm / min, the casting water flow rate is 340 m³ / h, and the temperature at the end of the coil is 685°C - 695°C; When the specification of the cast round ingot is 178, the starting casting speed is 81 ± 2 mm / min, the steady-state casting speed is 105 mm / min - 110 mm / min, the casting water flow rate is 280 m³ / h, and the temperature at the end of the coil is 685°C - 695°C; When the specification of the cast round ingot is 203, the starting casting speed is 67 ± 2 mm / min, the steady-state casting speed is 95 mm / min - 100 mm / min, the casting water flow rate is 240 m³ / h, and the temperature at the end of the coil is 685°C - 695°C; When the specification of the cast round ingot is 228, the starting casting speed is 58 ± 1 mm / min, the steady-state casting speed is 90 mm / min - 92 mm / min, the casting water flow rate is 210 m³ / h, and the temperature at the end of the coil is 685°C - 695°C.

[0006] Furthermore, if the alloy composition analysis result of the first sampling in step S2 does not meet the alloy composition requirements, then intermediate alloy is added to adjust the composition at a temperature of 745°C - 750°C in the melting furnace, stirred for 8 min - 10 min, and a second sampling analysis is carried out to analyze the alloy composition of the second sampling; until the alloy composition in the melting furnace meets the alloy composition requirements.

[0007] Furthermore, after the first refining in step S3.1, a sample is taken and the alloy composition of the sample is analyzed; if the alloy composition analysis meets the alloy composition requirements in step S2, then the next step is carried out; if the alloy composition analysis does not meet the alloy composition requirements in step S2, intermediate alloy is added to adjust the composition, and after stirring for 8 min - 10 min, a sample is taken and analyzed again until the alloy composition analysis meets the alloy composition requirements in step S2 and then the next step is carried out.

[0008] Further, after the second refining in step S3.2, sampling is carried out, and the alloy composition of the sample is analyzed. If the alloy composition analysis meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis does not meet the alloy composition requirements in step S2, the second refining in step S3.2 is repeated, and then sampling is carried out again and the alloy composition of the sample is analyzed. If the alloy composition analysis of the sample after repeating the second refining in step S3.2 meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis of the sample after repeating the second refining in step S3.2 does not meet the alloy composition requirements in step S2, master alloy is added to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2, and then the next step is carried out.

[0009] Further, after the third refining in step S3.3, sampling is carried out, and the alloy composition of the sample is analyzed. If the alloy composition analysis meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis does not meet the alloy composition requirements in step S2, the third refining in step S3.3 is repeated, and then sampling is carried out again and the alloy composition of the sample is analyzed. If the alloy composition analysis of the sample after repeating the third refining in step S3.3 meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis of the sample after repeating the third refining in step S3.3 does not meet the alloy composition requirements in step S2, master alloy is added to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2, and then the next step is carried out.

[0010] Further, if casting is not carried out after refining is completed, and the residence time of the melt in the furnace exceeds 1 h but does not exceed 2 h, including the static time of 10 min - 20 min, sampling needs to be carried out again to detect the alloy composition, and casting can be carried out only after the alloy composition meets the alloy composition requirements in step S2. If casting is not carried out after refining is completed, and the residence time of the molten aluminum in the furnace exceeds 2 h, and the residence time of the molten aluminum in the furnace includes the static time of 10 min - 20 min in step S3.4, the three - step refining in step S3 must be carried out on the melt again.

[0011] Further, when using the refining pipe in step S3, first check the curvature of the refining pipe. It is required that the vertical height of the refining pipe is close to the height of the furnace bottom and the furnace edge, so that the refining agent in the refining pipe can be sprayed onto the furnace bottom to the maximum extent. If the refining pipe is severely deformed or cannot be used continuously, the refining pipe needs to be replaced; during the refining process, if there is air leakage or powder leakage around the refining pipe extending into the molten aluminum, it is necessary to cut this part with a cutting machine before continuing the refining to achieve the purpose of uniform refining; during refining, carry out "#-type" refining, with the end of the refining pipe close to the furnace bottom being appropriate. The single control of horizontal refining and vertical refining is within min-8min. Try to reduce the moving steps during horizontal refining and vertical refining, and require horizontal refining and vertical refining on both sides; thus realizing "#-type" refining; blow in argon gas through the refining pipe for degassing and stirring for 10 minutes, stir on both sides of the furnace door to completely melt the molten aluminum and solid materials. The operation should be stable and the stirring should be sufficient to ensure the uniformity of chemical composition; pour the refining agent into the refining powder sprayer, ventilate first and then spray the refining agent. The refining pipe should move horizontally and vertically in the melting furnace without leaving dead zones. There must be refining agent spraying during the refining process. The refining agent and argon gas are required to be sprayed from the furnace bottom, and the four dead corners and the furnace mouth in the furnace must be refined in place. Skim off a large amount of oxidized slag floating on the surface of the melt. The slag skimming should be stable to prevent the slag from being involved in the melt; when the spraying of the refining agent is completed and the slag skimming is completed, continue to ventilate for 1 minute to completely remove the residual refining agent in the pipeline, and then withdraw the refining pipe from the melt and close the refining gas.

[0012] Further, in step S5, use a boron nitride spray bucket to evenly spray the diluted boron nitride on the surface of the diverter plate. The specification of the diluted boron nitride is 1:3-1:4 to increase the durability of the diverter plate and extend the service life of the diverter plate, and enable the disk surface to be separated from the aluminum slag quickly after casting to protect the disk surface.

[0013] The beneficial effects of the present invention are as follows: The alloy composition requirements of the present invention include Zn, Mg, Cu, Fe, Si, Zr, Ti, and Al; mainly including steps of smelting electrolytic aluminum liquid, aluminum ingots, alloying, refining, standing, heat preservation, online degassing, filtration, and casting; compared with the traditional casting process, the whole production process of the present invention is short, the processing cost is low, the casting production speed is increased, and the performance of round ingot alloys for extruded profiles is expanded. Through strict composition control and refining process, the present invention ensures the high-performance characteristics of 7003 aluminum alloy and meets the requirements of modern industry for lightweight and high-strength materials. Specific Embodiments

[0014] A method for preparing a round ingot for 7003 aluminum alloy extruded profiles of the present invention includes the following steps: S1. Batching: S1.1. Select pure aluminum ingots and electrolytic aluminum liquid as raw materials, without adding other waste materials to the raw materials, and the mass ratio of pure aluminum ingots in the raw materials is 30%-45%; S1.2. The feeding method is as follows: Add aluminum chip cakes to the bottom of the furnace, add sawing head and tail materials of 7003 grade to the combustion chamber, press the aluminum cakes with the head and tail of the rod, and pour the aluminum liquid into the furnace from the pouring port; S1.3. The feeding sequence is: First, add aluminum chip cakes and press them with the water pot head or the head and tail of the rod. Add aluminum ingots stack by stack, then close the furnace door, start the fire, and pour aluminum. The cold materials must be completely soaked with molten aluminum; S1.4. Control the temperature of the melting furnace at 730°C - 760°C; S1.5. The pure aluminum ingots can be heated in the melting furnace only after all the electrolytic aluminum liquid is added. During the melting process of the raw materials, stir 2 - 3 times to stir the materials at the bottom of the furnace evenly. Each stirring time is 4 min - 6 min; S2. When the furnace charge is completely melted and the temperature of the melting furnace is 740°C - 750°C, skim the slag, stir for 8 min - 10 min, and then take the first sample; conduct alloy composition analysis on the first sample; The alloy composition requirements are: Zn is 5.5% - 5.7%; Mg is 0.7% - 0.9%; Cu is 0.13% - 0.18%; Fe is 0.3% - 0.35%; Si is 0.2% - 0.25%; Zr is 0.1% - 0.2%; Ti is 0.1% - 0.2%; the rest is Al; If the alloy composition analysis result of the first sample does not meet the alloy composition requirements, add intermediate alloy to adjust the composition at the temperature of 745°C - 750°C in the melting furnace, stir for 8 min - 10 min, take the second sample for analysis, and conduct alloy composition analysis on the second sample; until the alloy composition in the melting furnace meets the alloy composition requirements; Zinc and magnesium in 7003 aluminum alloy are two main alloying elements. Add zinc and magnesium simultaneously in aluminum to form MgZn2 phase and AL2MgZn3. They have a phase transformation effect. When the two phases coexist, the strengthening effect will be better. However, if the contents of zinc and magnesium are too large, the plasticity and stress corrosion resistance of the material will be reduced, especially when zinc is excessive. Zinc is controlled at 5.5% - 5.7%, and magnesium is controlled at 0.7% - 0.9%. Copper can improve the strength and corrosion resistance of the alloy, but it will affect the welding performance of the alloy. Therefore, copper is controlled at 0.13% - 0.18%. Iron not only reduces the corrosion resistance of the alloy but also reduces the mechanical properties of the alloy. Silicon reduces the mechanical properties of the alloy because silicon forms MgSi phase with magnesium, thus reducing the amount of magnesium forming MgZn phase. So, iron and silicon should be controlled as low as possible. Zirconium and titanium can refine the grains. Zirconium can also improve the mechanical properties and corrosion resistance. Zirconium is controlled at 0.1% - 0.2%. The balance is A1; S3. In - furnace refining: S3.1. When the temperature of the molten aluminum reaches 745°C - 750°C, start the first refining, and use argon gas and a refining agent for powder injection refining; the refining agent is a remelting type refining agent, and the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, and the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 15 min - 30 min; after the refining is completed, let it stand and skim the slag; After completing the first refining in step S3.1, take a sample and conduct an alloy composition analysis on the sample; if the alloy composition analysis meets the alloy composition requirements in step S2, proceed to the next step; if the alloy composition analysis does not meet the alloy composition requirements in step S2, add master alloy to adjust the composition, stir for 8 min - 10 min and then take a sample for analysis again until the alloy composition analysis meets the alloy composition requirements in step S2 and then proceed to the next step; S3.2. When the temperature of the molten aluminum reaches 720°C - 750°C, start the second refining, and use argon gas and a refining agent for powder injection refining; the refining agent is a sodium-free granular refining agent, a fluoride-free and sodium-free refining agent or a composite refining agent, and the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, and the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 10 min - 20 min; after the refining is completed, let it stand and skim the slag; After completing the second refining in step S3.2, take a sample and conduct an alloy composition analysis on the sample; if the alloy composition analysis meets the alloy composition requirements in step S2, proceed to the next step; if the alloy composition analysis does not meet the alloy composition requirements in step S2, repeat the second refining in step S3.2 and then take a sample again and conduct an alloy composition analysis on the sample; if the alloy composition analysis of the sample after repeating the second refining in step S3.2 meets the alloy composition requirements in step S2, proceed to the next step; if the alloy composition analysis of the sample after repeating the second refining in step S3.2 does not meet the alloy composition requirements in step S2, add master alloy to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2 and then proceed to the next step; S3.3. When the temperature of the molten aluminum reaches 720°C - 750°C, start the third refining, and use argon gas and a refining agent for powder injection refining; the refining agent is a rare earth element-containing refining agent, a composite inorganic salt refining agent or a new type of environmental protection refining agent, and the dosage of the refining agent is (1.5 kg - 2.5 kg) / t•Al, and the working pressure of the refining gas is 0.15 Mpa - 0.20 Mpa; the refining time is 15 min - 30 min; after the refining is completed, let it stand and skim the slag; After completing the third refining in step S3.3, sampling is carried out, and the alloy composition of the sample is analyzed; if the alloy composition analysis meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis does not meet the alloy composition requirements in step S2, the third refining in step S3.3 is repeated, then sampling is carried out again and the alloy composition of the sample is analyzed; if the alloy composition analysis of the sample after repeating the third refining in step S3.3 meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis of the sample after repeating the third refining in step S3.3 does not meet the alloy composition requirements in step S2, master alloy is added to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2 and then the next step is carried out; S3.4. After the three - time refining is completed, sampling is carried out again to detect the alloy composition; after the alloy composition meets the alloy composition requirements in step S1.6, standing is carried out, and the standing time is 10 min - 20 min; if the alloy composition detected by sampling after the three - time refining is completed does not meet the alloy composition requirements in step S1.6, steps S2 and S3 are repeated until the alloy composition detected by sampling after the three - time refining is completed meets the alloy composition requirements in step S2; If casting is not carried out after refining is completed, and the residence time of the melt in the furnace exceeds 1 h and does not exceed 2 h, including the standing time of 10 min - 20 min, sampling for detecting the alloy composition needs to be carried out again, and casting can be carried out only after the alloy composition meets the alloy composition requirements in step S2; if casting is not carried out after refining is completed, and the residence time of the molten aluminum in the furnace exceeds 2 h, and the residence time of the molten aluminum in the furnace includes the standing time of 10 min - 20 min in step S3.4, the three - time refining in step S3 must be carried out on the melt again; When using the refining tube in step S3, the curvature of the refining tube must be checked first. The vertical height of the refining tube is required to be close to the height of the furnace bottom and the furnace edge so that the refining agent in the refining tube can be sprayed to the furnace bottom to the maximum extent. If the refining tube is severely deformed or cannot be put into use, the refining tube needs to be replaced; during the refining process, if there is air leakage and powder leakage around the refining tube extending into the aluminum liquid, it is necessary to use a cutting machine to cut this part before continuing to refine, so as to achieve the purpose of uniform refining; during refining, it is necessary to follow the "# type" refining, with the end of the refining tube close to the furnace bottom, and the horizontal refining and vertical refining are controlled at min-8min per time. The moving steps during horizontal refining and vertical refining are minimized as much as possible, and horizontal refining and vertical refining are required on both sides; thereby achieving "# type" refining ; Use the refining tube to blow in argon gas for degassing and stirring for 10 minutes, and stir on both sides of the furnace door to make the aluminum liquid and solid materials completely melted. The operation should be smooth and the stirring should be sufficient to ensure the uniformity of chemical composition; Pour the refining agent into the refining powder sprayer, ventilate first and then spray the refining agent. The refining tube should move horizontally and vertically in the smelting furnace without leaving dead areas. The refining agent must be sprayed during the refining process. The refining agent and argon gas are required to be sprayed from the bottom of the furnace. The four dead corners and the furnace mouth in the furnace must be refined in place, and a large amount of oxide slag floating on the surface of the melt should be removed. The slag removal should be smooth to prevent the slag from being drawn into the melt; After the refining agent is sprayed and the slag is removed, ventilation should continue for 1 minute to completely remove the residual refining agent in the pipeline, and then the refining tube is removed from the melt and the refining gas is turned off.

[0015] S4. Online processing: The melt that has completed step S3 is processed online. The Al-Ti5-B1 grain refiner is preheated to not less than 400°C and then continuously added to the aluminum melt at the inlet of the degassing box through a quantitative feeding device. The amount added is strictly controlled at 1.8kg / t•Al. The melt temperature at the adding point is maintained at 720°C to 740°C. The aluminum liquid after degassing treatment then enters a filter box equipped with a 40-mesh + 50-mesh double-stage foam ceramic filter plate for deep purification. The operating temperature of the filtration system is maintained in the range of 710-725°C. S5. Casting and rolling: The casting and rolling adopts a double-roll inclined casting and rolling mill, and the front box temperature is controlled at 695℃±2℃; the casting and rolling speed is adjusted at 700mm / min-900mm / min, and the cooling system adopts circulating cooling water at 25℃-35℃. The cooling water flow of the single-side casting and rolling roll is controlled at 110m³ / t•Al-130m³ / t•Al, and finally the aluminum alloy cast-rolled strip with a thickness of 7.0 mm-8.0 mm, excellent surface quality and uniform internal structure is obtained; During casting, according to the length of the chute and the heat loss situation, use temperature measuring devices such as thermocouples to control the water discharge temperature at: 735°C ± 5°C, and the measurement frequency is once every 10 minutes; use temperature measuring devices such as thermocouples to control the temperature of the mold head at: 700°C - 710°C, and the measurement frequency is once every 15 minutes; use temperature measuring devices such as thermocouples to control the temperature of the mold tail at: 680°C - 695°C, and the measurement frequency is once every 15 minutes. During casting, according to different specifications of the round ingot, the control of the casting speed and water flow rate is within the following range: When the specification of the cast round ingot is 90, the starting casting speed is 108 ± 2 mm / min, the steady-state casting speed is 155 mm / min - 160 mm / min, the casting water flow rate is 320 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 120, the starting casting speed is 90 ± 2 mm / min, the steady-state casting speed is 130 mm / min - 135 mm / min, the casting water flow rate is 360 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 127, the starting casting speed is 99 ± 2 mm / min, the steady-state casting speed is 125 mm / min - 130 mm / min, the casting water flow rate is 350 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 152, the starting casting speed is 90 ± 2 mm / min, the steady-state casting speed is 115 mm / min - 120 mm / min, the casting water flow rate is 340 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 178, the starting casting speed is 81 ± 2 mm / min, the steady-state casting speed is 105 mm / min - 110 mm / min, the casting water flow rate is 280 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 203, the starting casting speed is 67 ± 2 mm / min, the steady-state casting speed is 95 mm / min - 100 mm / min, the casting water flow rate is 240 m³ / h, and the temperature of the mold tail is 685°C - 695°C; When the specification of the cast round ingot is 228, the starting casting speed is 58 ± 1 mm / min, the steady-state casting speed is 90 mm / min - 92 mm / min, the casting water flow rate is 210 m³ / h, and the temperature of the mold tail is 685°C - 695°C.

[0016] The round ingot specifications 90, 120, 127, 152, 178, 203, and 228 represent the diameters of the round ingots, with the unit of millimeters.

[0017] In the actual casting process, if there are abnormal conditions such as poor surface quality of the ingot and internal defects, the casting speed, water flow and other parameters can be fine-tuned according to the specific situation. For example, if a cold shut occurs on the surface of the ingot, the casting speed can be appropriately reduced and the water flow can be increased; if shrinkage occurs inside the ingot, the casting speed can be appropriately increased and the water flow can be reduced.

[0018] In step S5, a boron nitride spray barrel is used to evenly spray the diluted boron nitride on the surface of the diverter plate. The specification of the diluted boron nitride is 1:3-1:4, so as to increase the durability of the diverter plate and extend the service life of the diverter plate. After casting, the plate surface can be quickly separated from the aluminum slag to protect the plate surface.

[0019] The present invention ensures the high performance characteristics of 7003 aluminum alloy through strict composition control and refining process, meeting the demand of modern industry for lightweight and high-strength materials.

[0020] Before implementing the present invention, the online degassing device, online filtering device, wire feeder, casting machine and casting system parameters must be checked and confirmed, it must be ensured that there are no clamped rods and slag accumulation around the casting plate, and the casting system, tooling inspection and working environment inspection must be carried out.

[0021] In the present invention, the filter box and the degassing box use a boron nitride spray barrel to evenly spray the diluted boron nitride of 1:3-1:4 on the surface of the filter box and the degassing box to increase the durability of the filter box and the degassing box and extend the service life of the filter box and the degassing box. Before placing the filter plate, the filter plate should be carefully checked to see if there are damaged lines and potholes on both sides of the filter plate. If the above problems occur, a new filter plate should be replaced in time to ensure the normal filtering effect of the filter plate. When placing the filter plate, align the front side of the filter plate with the side of the filter box close to the furnace eye, and then slowly put down the filter plate. Be sure to pay attention to it and handle it with care to avoid the filter plate being put down too quickly and causing the filter plate to shatter. After placing the filter plate, gently press the four corners of the filter plate. The purpose is to make the filter plate more firmly attached to the wall of the filter box to prevent casting failure due to loosening and floating of the filter plate during the casting process.

[0022] After turning over the mold, be sure to check the hydraulic system first. If any abnormality occurs, contact the maintenance personnel immediately for on-site maintenance. Before turning over the diverter plate, raise the ingot plate to the horizontal limit position with the anti-tilt frame. After turning over the diverter plate, pull up the support rod and put it into the angle steel on the diverter plate to prevent the diverter plate from turning down and ensure the safety of the operator. Turn over the side of the diverter plate and check whether the support rod, anti-tilt frame, and turntable are damaged or cracked.

[0023] When using the present invention for casting, attention should be paid to preparing the tools for disassembling the mold in advance: air guns, tool knives, small hammers, small wrenches, and hexagon wrenches to ensure the smooth and orderly progress of the disassembly work. Hold the socket and align the inner four corners with the air gun head and insert it. Before starting the air gun, pay attention to the rotation mark on the back seat of the air gun. "R" indicates counterclockwise rotation, and "F" indicates clockwise rotation. Hold the female end of the quick connector, press down the outer ring of the male end of the air valve and insert it into the female end to connect the air pipe. Hold the male end of the quick connector and press down the outer ring of the male end, then insert the male end into the air gun interface to connect the air gun. After the two ends of the interface are connected, slowly press down the air valve handle to prevent the connecting pipe from bursting due to excessive air pressure and affecting the replacement process. Adjust the rotation direction of the air gun head to counterclockwise rotation, put it on the marked fixing screw of the mold, press the trigger of the air gun to remove the fixing screw of the mold, and gently turn and pull out the mold with both hands holding the two corners of the mold; When using the present invention for casting, the casting equipment is generally a split sleeve. Therefore, after the mold is taken out, the sleeve is still on the diverter plate, and the sleeve is slowly pulled out by hand. The disassembly process of the integral sleeve mold is the same as that of the split sleeve mold. After pulling out the mold, gently sweep the slag at the sleeve port of the diverter plate with a brush. Insert the retaining ring wrench into the retaining ring hole and turn it counterclockwise. If the retaining ring is very tight, you can first brush a layer of clear oil on the retaining ring and then turn the wrench to disassemble it. If the retaining ring is still very tight, you can consider inserting the tip of a thick steel bar into the retaining ring hole in the counterclockwise direction and then hitting the tail of the thick steel bar with a hammer. However, this method should not be used under normal circumstances to avoid damaging the retaining ring hole due to excessive hitting force and affecting the next disassembly work. Remove the retaining ring, take out the adapter plate, and clean the rust and slag inside the mold and on the retaining ring. Check whether the sealing rubber ring of the mold is damaged. Pry up the damaged rubber ring with a thin iron bar, and then scrape off the stains in the rubber ring groove with a thin iron bar. Prepare a new rubber ring of the corresponding specification. To prevent the new rubber ring from warping and deforming, you can first apply glass glue in the rubber ring groove, then press one end of the new rubber ring into the rubber ring groove, and slowly press the rubber ring into the groove with your thumb along the rubber ring groove. The sealing rubber ring is a disposable item. It is best to replace all the sealing rubber rings with new ones when replacing the mold.

[0024] The steps for replacing the split casing of the casting equipment are as follows: a) Prepare a new split casing and an adapter plate. Place the new adapter plate into the mold and tighten the retaining ring to firmly press the adapter plate. Put the prepared new integral sleeve into the mold and put on the retaining ring. The retaining ring should be horizontal with the mold opening so that the retaining ring can be smoothly screwed into the inner thread of the mold; b) Turn the mold over so that its front side is facing up. Use an Allen wrench to remove the fixing screws of the outer cover and take off the cover; c) Insert a thin iron rod into each cooling water hole in sequence to clean it, and then use a steel wool ball to clean the stains inside. After cleaning, reinstall the outer cover; d) Insert the split sleeve into the sleeve opening of the flow divider plate, and align the processed mold with the split sleeve and insert it to fit; e) Manually screw the mold fixing screws into the screw holes; f) Then use an air gun to tighten the screws. Note that when tightening the screws, the order is to tighten the screws along the diagonal; g) After fixing the mold, insert a water slot knife into the water slot of the mold, press the water slot knife and slowly turn it in a circle. This can be repeated to ensure the smoothness of the water slot. After the treatment is completed, turn down the mold and conduct a water test again until there is no water shortage in all molds.

[0025] The steps for the mold closing of the casting equipment are as follows: a) Stir the talcum powder into a paste and evenly apply it along the inner wall of the conduit in a circle with a brush; b) Use an air duct to gently blow off the floating slag in the sleeve at a distance of about 30 cm from the mold; c) Repair the graphite ring. Evenly apply talcum powder putty by hand at the connection between the graphite ring and the adapter plate. Use the middle finger to pick up a little putty and evenly smear the putty along the inner edge of the graphite ring on the peripheral wall. After applying the putty, use the middle finger to clean up and press down the burrs around the putty. After finishing applying the putty, check the width of the remaining graphite ring, leaving at least half of the graphite ring; d) Use a brush to evenly apply a layer of boiled linseed oil on the surface of the putty in a circle. After brushing the oil, wipe off the residual oil by hand to prevent too much oil from soaking the putty and affecting the surface quality of the aluminum rod. Use an air duct to blow dry the moisture in the dummy bar head; e) Start the casting machine, turn on the rising switch of the casting machine, and adjust the speed to 300 - 500 mm / min by turning the speed button, and raise the dummy bar head completely above the anti-tilting frame; f) Use a tool knife to cut a piece of high-temperature cotton and place it at the interface between the tundish and the launder. Cut off the excess high-temperature cotton along the edge of the launder opening, evenly sprinkle talcum powder into the launder and compact it (seal the aluminosilicate fiber felt to prevent aluminum leakage); g) Lower the support rod, start the hydraulic switch, and click the "lower mold" button to slowly close the mold. Make the dummy bar tray slowly approach the upper mold at the original speed. When approaching the tundish of the mold, adjust the speed to about 100 mm / min and click the "mount on machine" button to prevent the dummy bar head from damaging the mold due to too high a speed. Gently click the "mount on machine" button according to the instructions of the operator on the tray. When the gap between the four-corner studs and the tundish reaches a certain distance (1 - 3 mm for small bars, 3 - 5 mm for large bars), check and adjust each spacing to make the spacing consistent. After the adjustment is completed, zero the length display; h) Prepare the tools required for casting (4 - 6 aluminum liquid leakage blocking pins, with 2 cone caps on each pin, intercepting shunt knife gate, slag shovel, slag ladle, etc.). Place the slag shovel according to the layout of the tundish channels. Press a large cotton bale at the port of the launder.

[0026] The casting operation steps of the casting equipment are as follows: a) After the furnace front melting is qualified, pull out the stopper rod, open the tapping hole and dredge it. This operation must wear a large face mask and stand in a reasonable position to prevent burns caused by splashing of molten aluminum; b) Open the aluminum-titanium-boron wire machine and adjust the feeding speed according to the process requirements; c) After the tapping hole is dredged and the molten aluminum flows out, remove the liquefied gas gun and close the liquefied gas valve. When the molten aluminum in the first section of the launder reaches eight-tenths full, remove the shovel baffle and let it flow into the filter box. After the molten aluminum in the second section of the launder of the filter box reaches eight-tenths full, pull up the large cotton bale and let it flow into the casting pan. The flowing-in order of the molten aluminum into the pan is: first in the middle and then on both sides, first in the front of the pan and then in the back of the pan. Use the shunt knife and slag spoon to control the flow direction, so that the molten aluminum flows into each crystallizer evenly at the same time, with the same flow rate and the same velocity. When all the molten aluminum has filled each conduit, standby according to the size of the aluminum rod specification. If the temperature is not enough and the water drainage effect of the filter plate is obviously poor, do not pull up the cotton bale, directly block the tapping hole, pierce the drainage port of the filter box to open the water hole and drain the molten aluminum in the launder; d) The standby time is calculated from the time when the molten aluminum enters the shunt pan; e) Close the water valve of the casting pan before the molten aluminum enters the casting pan, then turn on the water pump and wait for the water pump indicator light to come on. When the flow rate of the molten aluminum entering the casting pan reaches six or seven tenths of the total pan, open the cooling water inlet valve and close the return water valve. Let the molten aluminum stand for about 20 - 40 s. After the molten aluminum has finished standing, start the casting machine to lower (slowly accelerate to 150 - 210 mm / min). When the casting machine reaches the lower machine speed smoothly, test again whether each conduit is unobstructed. After all the conduits are tested and dredged, closely monitor the liquid level of the shunt pan and control the flow; f) Observe the speed display in real time. According to the different specifications of the aluminum rods, the adjusted speeds are also different; g) When the dummy bar descends, observe whether the surface condition of the aluminum rod is normal and whether the cooling water indicator light flashes normally; h) The tapping hole worker observes the height of the molten aluminum in the shunt pan and adjusts the flow rate of the molten aluminum at the tapping hole in time before the shunt pan is fast or slow. Use a liquid level controller to adjust the flow rate of the molten aluminum; i) Prepare a sampling spoon, take a sample in the front section of the launder with a cone cap. Note that there must be no water in the sampling spoon. Wear a face mask and gloves when sampling, and measure the temperature of the tapping hole at the same time; j) Mark the sample clearly with the specification and furnace number and send it to the laboratory for inspection; k) Measure the temperature at the end of the pan according to the requirements on the process card and record it truthfully on the process tracking card; l) Note that when using the thermometer for measurement, it must be placed in the middle of the molten aluminum so that the measured value will be accurate. Check the surface quality of the aluminum rod during casting at any time. The casting speed can be adjusted appropriately according to the condition of the aluminum rod surface and the temperature of the molten aluminum at the launder; m) Observe the wire feeding situation of the titanium-boron wire. In case of wire jamming, wire breakage, etc., deal with it immediately to avoid affecting the grain refinement of the molten aluminum; n) Before the casting is almost finished and preparing to block the tapping hole, keep the liquid level of the molten aluminum on the pan surface, in the filter box and at the launder at the highest state to ensure that the remaining molten aluminum flow rate meets the length of the cast rod.

[0027] The steps for plugging the furnace eye and collecting water in the casting equipment are as follows: Observe the water level on the disk and in the filter box at all times. If the water level continues to drop, you can choose to pull out all the plug rods to ensure that the furnace eye flow can keep up with the disk water level flow in a timely manner. Calculate the required length of the aluminum rod, and combine the disk water level and flow rate to plug the furnace eye in advance. After the water level in the tundish at the furnace eye end has completely dropped, the aluminum-titanium-boron wire feeder can be turned off. After reaching the required casting length, use an iron rod to pierce the drain hole of the filter box to let out the water eye and drain the aluminum liquid remaining in the tundish and filter box. After the aluminum water on the surface of the splitter plate has drained dry and the aluminum liquid has completely passed through the conduit, quickly use an iron rod to cut open the aluminum skin on the wall of each sleeve and the aluminum skin at the aluminum inlet of the splitter plate to ensure the smooth progress of subsequent slag removal. Select the appropriate time to turn off the water pump switch according to the size of the aluminum rod (do not immediately turn off the water pump switch for large rods). Turn off the inlet valve and turn the speed adjustment button to let the aluminum rod separate from the disk as soon as possible. After the aluminum rod has separated from the disk by a certain distance, the switch can be turned off. When the tail of the rod is about 20 cm away from the anti-tilting frame, the lowering switch can be turned off to prevent the aluminum rod from dropping too much and directly falling into the well. Turn on the hydraulic switch and flip up the mold plate. Turn on the upper machine button and adjust the speed to 200 - 300 mm / min. When the upper machine has risen to about 50 cm, stop rising, and then immediately raise the support rod to ensure the safety of the subsequent rod lifting operation personnel. Fill in the process tracking card completely and truthfully.

[0028] The operations of hooking aluminum dross and cleaning the chute for the casting equipment are as follows: Use an iron hook to lift the slag skin on the inner lining wall of the diverter plate, and then hook down the entire piece of slag skin. The purpose is to protect the inner lining of the diverter plate to the greatest extent and reduce the loss of the inner lining caused by hooking slag. Use an iron poker to pry up the aluminum skin of the sleeve and poke it out. After hooking the slag, first use a dry brush or bamboo stick to brush the diverter plate, and then slowly and evenly place the casting plate horizontally through the hydraulic pump. Open the cooling water valve to cool down the hot plate for 3 - 5 minutes (this step is not required for the cold plate). Prevent burns when repairing the plate. After the water cooling is completed, raise the casting plate, and then use a sponge to clean the inner ring of the mold again. After cleaning with the sponge, open the air duct to blow the residue clean. After poking open the water outlet of the filter box to clear the water hole, the water level of the aluminum liquid in the chute drops. The furnace eye worker should use an iron shovel to scrape the remaining aluminum in the chute into the filter box. Repeat scraping the remaining aluminum several times to make the thickness of the remaining aluminum in the chute as thin as possible for easy hooking. After scraping the remaining aluminum, cut off the bottom aluminum skin at a certain distance. Use a shovel to shovel the remaining aluminum dross on the filter plate to one corner and then remove it. Then use an iron poker to cut open all around the gaps of the filter plate. Use a steel pipe to make an opening on the filter plate, and then insert an iron hook into the opening to lift the filter plate. Since the filter plate has been heated for a long time, it is easy to break when lifting the filter plate. For the broken filter plate, it should also be immediately set upright to drain the aluminum liquid in it as much as possible, reduce the loss of aluminum liquid in the filter plate, and lower the production cost. After the aluminum liquid in the filter plate stops flowing out, crush it and use a shovel to shovel it into the aluminum dross box below. After shoveling off the broken filter plate, use an iron shovel to cut open the aluminum liquid at the water outlet of the filter box for easy hooking of the aluminum skin of the filter box. Use an iron hook to remove the aluminum skin on the wall and bottom of the filter box, pry off the thick aluminum skin at the front entrance of the chute, and brush the entire chute clean with high-temperature cotton to ensure that the chute and the filter box are as clean as possible. Clean the remaining aluminum at the water hole and the remaining aluminum in the bottom groove of the filter box. When cleaning the chute, also pay attention to the condition around the furnace eye to see if there is any aluminum leakage. If any aluminum leakage is found, it should be blocked immediately. If the aluminum dross box is full of aluminum, it should be lifted out in time. Use wire rope sleeves to connect the overhead crane hook and the lifting ear of the aluminum dross box at both ends. Command the overhead crane to lift the aluminum dross box first. Note that when lifting, be careful not to touch the chute at the water hole, and continuously jog the overhead crane to slowly pull out the aluminum dross box. After pulling out the aluminum dross box, be sure to move the overhead crane back to a straight line with the aluminum dross box, and then lift the aluminum dross box and place it on the ground to avoid the aluminum dross box swaying due to misalignment and causing a safety accident. After lifting out the aluminum dross box, use a broom to sweep the residue on the peripheral wall of the aluminum dross box into the aluminum dross box and put in the cooling rod. After cleaning the chute, clean and sweep the site in time; Operating position for lifting rods of casting equipment: Select slings and lifting tools of corresponding specifications according to the size of the rod, hook the overhead crane hook into the ear hole of the lifting ring. Insert the safety bolt, and slowly move the lifting ring closer to the aluminum rod. For each aluminum rod, put the ring sleeve onto the rod body. After putting the ring sleeve on the aluminum rod, slowly lower the lifting ring. After the crossbeam of the lifting ring passes over the rod tail, the aluminum rod can be lifted. Lift the aluminum rod until the rod head completely exceeds the anti-tilting frame, and then move the aluminum rod to the sawing track. When the aluminum rod is close to the track, control the distance between the rod head and the ground according to the length of the aluminum rod itself, and then jog the overhead crane to slowly lower the aluminum rod. During this period, always tighten the steel wire rope of the overhead crane. After the rod, observe the surface of each aluminum rod to check for aluminum rods with surface defects such as black spots, variegated rods, pitted rods, holes, and bent rods, and pick them out for marking.

[0029] The main reason for the generation of center cracks in the 7003 aluminum alloy casting center is that during the solidification process of the ingot, due to the hindrance of the outer completely solidified metal to the crystallization shrinkage of the center melt, anti-stress is generated in the center of the ingot. When the anti-stress exceeds the allowable deformation value of the metal at that time, center cracks are generated. The corresponding measures are as follows: a) Improve the plasticity of the alloy at high and low temperatures to form the ability to resist thermal cracks and cold cracks. It is necessary to control the chemical composition and impurity content of the alloy according to the process requirements; prevent the melt from overheating and staying in the furnace for too long. b) Raise the bottom of the liquid cavity so that it is above the secondary water cooling zone to reduce the temperature difference between the inner and outer layers of the ingot. For this purpose, the casting speed can be reduced or the height of the mold and the height of the metal in the mold can be increased. c) Reduce the starting speed of the machine and standardize the standby time. Finally, the center crack phenomenon of five specifications and four alloy grades has been eliminated.

[0030] The main reason for the bending problem in the 7003 aluminum alloy casting is that the dummy bar head is loose, swinging, misaligned, and uneven, lacking stability, resulting in the bending of the casting rod. The corresponding measure is to require the inspection of the dummy bar head before casting every shift to ensure stability and firmness, regular lubrication and maintenance, and two mold closings for large specifications; The main reason for the problem of coarse grains in the 7003 aluminum alloy casting is the coarse grains caused by overheating during melting, inappropriate high-temperature casting, and unreasonable intermediate grain refinement alloys. The corresponding measure is to add elements such as Mn, Zn, and Cr for the purpose of refining grains, increasing strength, and preventing stress corrosion. If the composition selection and casting conditions are improper, coarse intermetallic compound primary crystals will be generated during the solidification process. It is a kind of hard and brittle phase, which significantly reduces the alloy performance. The main measure to eliminate the primary crystal compound is to control the content of the elements that form the compound, appropriately increase the casting temperature, and at the same time enhance the refinement effect.

[0031] The main reason for the bamboo joint problem in 7003 aluminum alloy casting is that the crystallizer is not cast, and the cooling water directly hits the ingot head, which causes impact on the surrounding casting rods. The countermeasure is to set a tool on the anti-dumping rack under the corresponding crystallizer to prevent the cooling water from directly hitting the ingot head, and drain the turbulent cooling water to the well wall to naturally descend to solve the bamboo joint problem.

[0032] The main reason for the scratch problem in 7003 aluminum alloy casting is that the oil sludge at the R corner of the crystallizer is partially detached after long-term friction with the high-temperature melt, and the restraining pressure of the graphite ring causes groove-shaped scratches on the surface of the cast rod. Secondly, due to the high casting speed, the absolute shrinkage of the ingot is small during solidification, and the contact surface between the ingot and the inner wall of the crystallizer is expanded, so the friction stress increases, making it more likely to crack or even break. If the casting cooling conditions are not sufficient, for example, the cooling water pressure is low, the cooling water temperature is too high, or the scale in the crystallizer is too thick, this defect is easy to occur. The countermeasures are as follows: 1. Keep the working surface of the crystallizer flat and smooth; 2. Cool the four sides of the crystallizer evenly and increase the water pressure appropriately; 3. Reduce the casting speed and casting temperature appropriately according to the actual casting situation; 4. Correctly install the crystallizer and distributor to prevent uneven liquid flow distribution; 5. Clean the crystallizer scale and calibrate the crystallizer regularly; 6. Select 1250~3000 mesh regular brand (K brand) talcum powder to increase the density and viscosity of the sludge, and use first-grade soybean oil to blend it into sludge with moderate hardness, and make thick and solid repairs on the transition corners of the crystallizer, and at the same time, carefully clean and polish the graphite ring.

[0033] The main reason for the pit problem in 7003 aluminum alloy casting is that the temperature of the aluminum liquid drops during the casting process, and the three major casting process parameters do not match it, resulting in cracks and pits of varying sizes on the surface of the cast rod during the casting process. The countermeasure is that technicians and team leaders increase the frequency of plate mouth temperature detection during the casting process. When the temperature is lower than the working temperature, ignite the furnace in front of the furnace to heat up the aluminum liquid in the furnace, so that the plate mouth temperature is controlled within the temperature range of the process parameters until the casting is completed.

Claims

1. A method for preparing round ingots for 7003 aluminum alloy extrusion profiles, characterized in that: It includes the following steps: S1. Batching: S1.

1. Select pure aluminum ingots and electrolytic aluminum liquid as raw materials, without adding other waste materials. The mass ratio of pure aluminum ingots in the raw materials is 30%-45%; S1.

2. The feeding method is as follows: Add aluminum chip cakes to the furnace bottom, add sawing head and tail materials of 7003 grade to the combustion chamber, press the aluminum cakes with the head and tail of the rod, and pour the aluminum liquid into the furnace from the pouring port; S1.

3. The feeding sequence is: First, add aluminum chip cakes and press them with the water pot head or the head and tail of the rod. Add aluminum ingots stack by stack, then close the furnace door, start the fire, and pour aluminum. The cold materials must be completely soaked with aluminum liquid; S1.

4. Control the temperature of the melting furnace at 730℃-760℃; S1.

5. The melting furnace can be heated only after all the pure aluminum ingots are added to the electrolytic aluminum liquid. During the melting process of the raw materials, stir 2-3 times to stir the materials at the bottom of the furnace evenly. Each stirring time is 4min-6min; S2. When the furnace charge is completely melted and the temperature of the melting furnace is 740℃-750℃, skim the slag, stir for 8min-10min, and then take the first sample; Analyze the alloy composition of the first sample; The alloy composition requirements are: Zn is 5.5%-5.7%; Mg is 0.7%-0.9%; Cu is 0.13%-0.18%; Fe is 0.3%-0.35%; Si is 0.2%-0.25%; Zr is 0.1%-0.2%; Ti is 0.1%-0.2%; The rest is Al; S3. In-furnace refining: S3.

1. Start the first refining when the temperature of the aluminum liquid reaches 745℃-750℃. Use argon and a refining agent for powder spraying refining; The refining agent is a remelting type refining agent. The dosage of the refining agent is (1.5kg-2.5kg) / t•Al. The working pressure of the refining gas is 0.15Mpa-0.20Mpa; The refining time is 15min-30min; After the refining is completed, let it stand and skim the slag; S3.

2. Start the second refining when the temperature of the aluminum liquid reaches 720℃-750℃. Use argon and a refining agent for powder spraying refining; The refining agent is a sodium-free granular refining agent, a fluoride-free and sodium-free refining agent or a composite refining agent. The dosage of the refining agent is (1.5kg-2.5kg) / t•Al. The working pressure of the refining gas is 0.15Mpa-0.20Mpa; The refining time is 10min-20min; After the refining is completed, let it stand and skim the slag; S3.

3. Start the third refining when the temperature of the aluminum liquid reaches 720℃-750℃. Use argon and a refining agent for powder spraying refining; The refining agent is a rare earth element-containing refining agent, a composite inorganic salt refining agent or a new type of environmental protection refining agent. The dosage of the refining agent is (1.5kg-2.5kg) / t•Al. The working pressure of the refining gas is 0.15Mpa-0.20Mpa; The refining time is 15min-30min; After the refining is completed, let it stand and skim the slag; S3.

4. After the third refining is completed, sample and detect the alloy composition again; after the alloy composition meets the alloy composition requirements in step S1.6, let it stand still for 10 min - 20 min; if the alloy composition detected by sampling after the third refining does not meet the alloy composition requirements in step S1.6, repeat step S2 and step S3 until the alloy composition detected by sampling after the third refining meets the alloy composition requirements in step S2; S4. Online treatment: Perform online treatment on the melt that has completed step S3. The Al-Ti5-B1 grain refiner is preheated to not less than 400 °C and then continuously added into the aluminum melt at the inlet of the degassing box through a metering feeding device. The addition amount is strictly controlled at 1.8 kg / t•Al, and the melt temperature at the addition point is maintained at 720 °C - 740 °C. The aluminum liquid after degassing treatment then enters a filtration box equipped with a 40-mesh + 50-mesh double-stage foam ceramic filter plate for deep purification, and the working temperature of the filtration system is maintained within the range of 710 - 725 °C; S5. Cast-rolling: The cast-rolling is carried out using a twin-roll inclined cast-rolling mill, and the temperature of the front box is controlled at 695 °C ± 2 °C; the cast-rolling speed is adjusted within 700 mm / min - 900 mm / min, the cooling system uses circulating cooling water at 25 °C - 35 °C, and the cooling water flow rate of the single-sided cast-rolling roll is controlled within 110 m³ / t•Al - 130 m³ / t•Al, finally obtaining an aluminum alloy cast-rolled strip with a thickness of 7.0 mm - 8.0 mm, excellent surface quality, and uniform internal structure; During casting, according to the length of the chute and the heat loss situation, use temperature measuring devices such as thermocouples to control the water discharge temperature at: 735 °C ± 5 °C, and the measurement frequency is once every 10 minutes; use temperature measuring devices such as thermocouples to control the temperature of the die head at: 700 °C - 710 °C, and the measurement frequency is once every 15 minutes; use temperature measuring devices such as thermocouples to control the temperature of the die tail at: 680 °C - 695 °C, and the measurement frequency is once every 15 minutes; During casting, according to different round ingot specifications, the casting speed and water flow rate are controlled within the following ranges: When the round ingot specification for casting is 90, the starting casting speed is 108 ± 2 mm / min, the steady-state casting speed is 155 mm / min - 160 mm / min, the casting water flow rate is 320 m³ / h, and the die tail temperature is 685 °C - 695 °C; When the round ingot specification for casting is 120, the starting casting speed is 90 ± 2 mm / min, the steady-state casting speed is 130 mm / min - 135 mm / min, the casting water flow rate is 360 m³ / h, and the die tail temperature is 685 °C - 695 °C; When the round ingot specification for casting is 127, the starting casting speed is 99 ± 2 mm / min, the steady-state casting speed is 125 mm / min - 130 mm / min, the casting water flow rate is 350 m³ / h, and the die tail temperature is 685 °C - 695 °C; When the specification of the cast round ingot is 152, the starting casting speed is 90±2 mm / min, the steady-state casting speed is 115 mm / min - 120 mm / min, the casting water flow rate is 340 m³ / h, and the tail-end temperature of the coil is 685℃ - 695℃; When the specification of the cast round ingot is 178, the starting casting speed is 81±2 mm / min, the steady-state casting speed is 105 mm / min - 110 mm / min, the casting water flow rate is 280 m³ / h, and the tail-end temperature of the coil is 685℃ - 695℃; When the specification of the cast round ingot is 203, the starting casting speed is 67±2 mm / min, the steady-state casting speed is 95 mm / min - 100 mm / min, the casting water flow rate is 240 m³ / h, and the tail-end temperature of the coil is 685℃ - 695℃; When the specification of the cast round ingot is 228, the starting casting speed is 58±1 mm / min, the steady-state casting speed is 90 mm / min - 92 mm / min, the casting water flow rate is 210 m³ / h, and the tail-end temperature of the coil is 685℃ - 695℃.

2. A method for preparing a round ingot for a 7003 aluminum alloy extrusion profile according to claim 1, characterized in that: If the alloy composition analysis result of the first sampling in step S2 does not meet the alloy composition requirements, then add master alloy to adjust the composition at the temperature of 745℃ - 750℃ in the melting furnace, stir for 8 min - 10 min, conduct the second sampling analysis, and perform the alloy composition analysis on the second sampling; until the alloy composition in the melting furnace meets the alloy composition requirements.

3. The preparation method of a round ingot for a 7003 aluminum alloy extrusion profile according to claim 1, characterized in that: After the first refining in step S3.1, take a sample and perform the alloy composition analysis on the sample; if the alloy composition analysis meets the alloy composition requirements in step S2, then proceed to the next step; if the alloy composition analysis does not meet the alloy composition requirements in step S2, add master alloy to adjust the composition, stir for 8 min - 10 min and then take the sample for analysis again until the alloy composition analysis meets the alloy composition requirements in step S2 and then proceed to the next step.

4. A method for preparing a round ingot for a 7003 aluminum alloy extrusion profile according to claim 3, characterized in that: After the second refining in step S3.2, take a sample and perform the alloy composition analysis on the sample; if the alloy composition analysis meets the alloy composition requirements in step S2, then proceed to the next step; if the alloy composition analysis does not meet the alloy composition requirements in step S2, then repeat the second refining in step S3.2 and take a sample again and perform the alloy composition analysis on the sample; if the alloy composition analysis of the sample after repeating the second refining in step S3.2 meets the alloy composition requirements in step S2, then proceed to the next step; if the alloy composition analysis of the sample after repeating the second refining in step S3.2 does not meet the alloy composition requirements in step S2, then add master alloy to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2 and then proceed to the next step.

5. A method for preparing a round ingot for use in extruded profiles of 7003 aluminum alloy according to claim 4, characterized in that: After the third refining in step S3.3, sampling is carried out, and the alloy composition of the sample is analyzed; if the alloy composition analysis meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis does not meet the alloy composition requirements in step S2, the third refining in step S3.3 is repeated, and then sampling is carried out again and the alloy composition of the sample is analyzed; if the alloy composition analysis of the sample after repeating the third refining in step S3.3 meets the alloy composition requirements in step S2, the next step is carried out; if the alloy composition analysis of the sample after repeating the third refining in step S3.3 does not meet the alloy composition requirements in step S2, intermediate alloy is added to adjust the composition until the alloy composition analysis meets the alloy composition requirements in step S2, and then the next step is carried out.

6. The preparation method of a round ingot for a 7003 aluminum alloy extrusion profile according to claim 5, characterized in that: If casting is not carried out after refining is completed, and the residence time of the melt in the furnace exceeds 1 h but does not exceed 2 h, including the static time of 10 min - 20 min, re-sampling is required to detect the alloy composition, and casting can be carried out only after the alloy composition meets the alloy composition requirements in step S2; if casting is not carried out after refining is completed, and the residence time of the molten aluminum in the furnace exceeds 2 h, and the residence time of the molten aluminum in the furnace includes the static time of 10 min - 20 min in step S3.4, the three - step refining in step S3 must be carried out on the melt again.

7. A method for preparing a round ingot for a 7003 aluminum alloy extrusion profile according to claim 1, characterized in that: In step S3, when using the refining tube, first check the bend of the refining tube. It is required that the vertical height of the refining tube is close to the height of the furnace bottom and the furnace edge, so that the refining agent in the refining tube can be sprayed onto the furnace bottom to the maximum extent. If the refining tube is severely deformed or cannot be used continuously, the refining tube needs to be replaced; during the refining process, if there is air leakage and powder leakage around the refining tube extending into the molten aluminum, this part needs to be cut with a cutting machine before continuing the refining to achieve the purpose of uniform refining; when refining, " # - type” refining is carried out, and it is appropriate that the end of the refining tube is close to the furnace bottom. The single - time control of horizontal refining and vertical refining is within min - 8 min. When moving during horizontal refining and vertical refining, the moving steps should be minimized as much as possible, and it is required to carry out horizontal refining and vertical refining twice each; thus, " # - type” refining is realized; argon is blown into the molten aluminum through the refining tube for degassing and stirring for 10 min, and stirring is carried out on both sides of the furnace door to completely melt the molten aluminum and solid materials. The operation should be stable and the stirring should be sufficient to ensure the uniformity of the chemical composition; pour the refining agent into the refining powder sprayer, first ventilate and then spray the refining agent. The refining tube should move horizontally and vertically in the melting furnace without leaving dead zones. During the refining process, the refining agent must be sprayed out. The refining agent and argon are required to be sprayed from the furnace bottom, and the four dead corners and the furnace mouth in the furnace must be refined in place. Skim off a large amount of floating oxidation slag on the surface of the melt. The slag skimming should be stable to prevent the slag from being involved in the melt; after the refining agent is sprayed out and the slag skimming is completed, ventilation should be continued for 1 min to completely remove the residual refining agent in the pipeline, and then the refining tube is withdrawn from the melt and the refining gas is turned off.

8. A method for preparing a round ingot for 7003 aluminum alloy extrusion profiles according to claim 1, characterized in that: In step S5, the diluted boron nitride is evenly sprayed on the surface of the diverter plate by using a boron nitride spray bucket. The specification of the diluted boron nitride is 1:3 - 1:4, so as to increase the durability of the diverter plate, extend the service life of the diverter plate, and enable the plate surface to be separated from the aluminum slag quickly after casting to protect the plate surface.