A method for manufacturing an al-zn-mg-cu series aluminum alloy slab

Abstract

The application discloses a manufacturing method of an Al-Zn-Mg-Cu system aluminum alloy flat ingot, and belongs to the field of deformed aluminum alloy casting. The method solves the problems of high crack tendency and low casting yield ratio of the existing production of the composite core material aluminum alloy with high Ti content. The method comprises the following steps: 1, weighing; 2, smelting; 3, preparing a casting melt; and 4, adopting a double-drainage crystallizer for semi-continuous casting. The crystallizer used in the semi-continuous casting adopts a double-drainage cooling mode, cooperates with a double-curved surface base, adopts a high casting speed, a low water flow rate and a short distance between the water-blocking rubber plate and the lower edge of the crystallizer at the beginning of the casting, and adopts the casting process parameters of a low casting speed, a high water flow rate and a long distance between the water-blocking rubber plate and the lower edge of the crystallizer after the casting is stable, so that the defects of aluminum leakage, suspension and cold cracks at the beginning of the casting are effectively solved, and the forming is guaranteed. The flat ingot manufactured by the application is free of cracks, the surface of the flat ingot is smooth, the metallographic structure is free of defects such as porosity and slag inclusion, and the yield ratio of the flat ingot is greater than 90%.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of wrought aluminum alloy casting, and particularly relates to a manufacturing method of Al-Zn-Mg-Cu system aluminum alloy flat ingot. BACKGROUND

[0002] The composite core material aluminum alloy has a series of outstanding advantages such as high strength, anti-exfoliation corrosion, strong stress corrosion cracking ability, excellent fracture toughness and anti-fatigue performance, and has important application value in automobiles. The existing production of the composite core material aluminum alloy with high Ti content has a large crack tendency, and cracks are easily generated in the casting process, even the aluminum liquid is splashed to cause safety accidents, and the casting yield is extremely low, and the ingot yield is only 80%. In order to improve the ingot yield and production efficiency and meet the needs of composite profile processing, a new composite core material aluminum alloy flat ingot operation process is the key to promote the application of the composite core material aluminum alloy. SUMMARY

[0003] The application aims to solve the problems of the existing production of the composite core material aluminum alloy with high Ti content, such as large crack tendency and low casting yield, and provide a manufacturing method of Al-Zn-Mg-Cu system aluminum alloy flat ingot.

[0004] A manufacturing method of Al-Zn-Mg-Cu system aluminum alloy flat ingot is carried out according to the following steps:

[0005] I. Weighing: according to the mass percentage of Cu: 1.70% to 2.30%, Mg: 1.50% to 2.30%, Zn: 7.20% to 8.50%, Zr: 0.05% to 0.15%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06% and the balance of Al, the refined aluminum ingot, copper metal, magnesium metal, zinc metal, Al-Zr intermediate alloy and Al-Ti intermediate alloy are weighed;

[0006] II. Melting: the refined aluminum ingot and the Al-Zr intermediate alloy are added to a natural gas melting furnace, the copper metal and the zinc metal are added after the refined aluminum ingot is melted, the magnesium metal and the Al-Ti intermediate alloy are added after the temperature is increased to 730-750℃, the electromagnetic stirring is performed for 20-30min, the chemical composition is analyzed and qualified, and the aluminum alloy melt is obtained;

[0007] III. Preparation of casting melt: the aluminum alloy melt is introduced into a holding furnace at 730-750℃, then argon-chlorine mixed gas is introduced for 30min, and then the casting melt is obtained after standing for 30min;

[0008] Four, forming: the above casting melt flows into an on-line double degassing device, then flows into a filtering device, and after filtering, is injected into a crystallizer through a flow disc, the casting speed used from the beginning of semi-continuous casting to when the casting reaches a length of 400 mm is 55-60 mm / min, the casting water flow is 20-30 m3 / h per ingot, the position of the water-blocking rubber plate is 190 mm away from the lower edge of the crystallizer, when the casting reaches a length of 400 mm, the casting speed used is 40-55 mm / min, the casting water flow is 30-40 m3 / h per ingot, the position of the water-blocking rubber plate is 300-400 mm away from the lower edge of the crystallizer, at the same time, Al-3Ti-0.15C wires are seeded into the casting melt at a speed of 123 mm / min per ingot, and an Al-Zn-Mg-Cu system aluminum alloy flat ingot is obtained, that is, the manufacturing method is completed.

[0009] Further, the purity of the refined aluminum ingot in step one is greater than or equal to 99.99%, the Al-Zr intermediate alloy is Al-3% Zr, and the Al-Ti intermediate alloy is Al-6% Ti.

[0010] Further, when the magnesium metal is added in step two, 0.025% of Al-Be intermediate alloy is also added, and the use amount of the Al-Be intermediate alloy is 0.25 kg per ton of aluminum alloy melt.

[0011] Further, the molar content of argon and chlorine in the argon-chlorine mixed gas in step three is 94% and 6%, respectively.

[0012] Further, the filtering device in step four: 30 ppi+50 ppi ceramic filter sheets are used for filtering.

[0013] Further, the crystallizer in step four: the crystallizer adopts a double water cooling mode, and the shape and size of the crystallizer are a rectangle of 420 mm*1320 mm.

[0014] Further, the temperature of the casting in step four is 685-705 ℃, and the temperature of the cooling water used for the casting is 18-26 ℃.

[0015] Further, the Al-3Ti-0.15C wires used as grain refiners in step four are used in an amount of 3-4 kg per ton of casting melt.

[0016] Further, the on-line double degassing device in step four: argon is used, the argon gas flow is 20-35 nm / hr, the rotation speed is 350 rpm / min, and the purity of the argon is greater than or equal to 99.996%. 3

[0017] Advantages of the present application:

[0018] ​1. This invention uses an advanced water-cooling control system to provide a stable water flow for casting. The crystallizer used in semi-continuous casting adopts a double-drainage cooling method, and is combined with a hyperboloid base and casting process parameters such as high casting speed, low water flow, and shortened distance between the water-blocking rubber plate and the lower edge of the crystallizer at the beginning of casting, and reduced casting speed, high water flow, and extended distance between the water-blocking rubber plate and the lower edge of the crystallizer after casting stabilizes. This effectively solves defects such as aluminum leakage, hanging, and cold cracking at the beginning of casting, and ensures molding.

[0019] 2. This invention employs low-speed casting in the semi-continuous casting process, effectively ensuring the steady-state forming of the ingot; an automatic lubrication system is used in the semi-continuous casting process to provide stable oil supply to the casting ingot, ensuring lubrication and avoiding scratches and cracks; electromagnetic stirring is used in the melting process to stir the melt, ensuring the uniformity of melt composition and temperature; and 30ppi+50ppi dual-stage ceramic filter sheets are used in the casting process to effectively remove inclusions in the melt and ensure purification effect.

[0020] 3. The Al-Zn-Mg-Cu aluminum alloy flat ingots prepared by the method of the present invention have a thickness of 420 mm, a width of 1320 mm, and a length of 4000-7000 mm. They are free of cracks, and the ingot surface is flat with no defects such as porosity or slag inclusions in the metallographic structure. The ingot yield is greater than 90%.

[0021] This invention is applicable to the manufacture of Al-Zn-Mg-Cu series aluminum alloy flat castings. Attached Figure Description

[0022] Figure 1 The image shows the metallographic structure of the Al-Zn-Mg-Cu aluminum alloy flat ingot produced in the example.

[0023] Figure 2 The image shows a physical picture of the Al-Zn-Mg-Cu aluminum alloy flat ingot manufactured in the example. Detailed Implementation

[0024] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0025] Specific Implementation Method 1: This implementation method describes a method for manufacturing Al-Zn-Mg-Cu series aluminum alloy flat castings, which is carried out according to the following steps:

[0026] I. Weighing: Cu: 1.70% to 2.30%, Mg: 1.50% to 2.30%, Zn: 7.20% to 8.50%, Zr: 0.05% to 0.15%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06%, and the balance of Al are weighed according to the mass percentage content, and refined aluminum ingot, copper metal, magnesium metal, zinc metal, Al-Zr intermediate alloy, and Al-Ti intermediate alloy are weighed;

[0027] II. Melting: the refined aluminum ingot and Al-Zr intermediate alloy are added to a natural gas melting furnace, and after the refined aluminum ingot is melted, the copper metal and zinc metal are added, the temperature is raised to 730-750°C, and then the magnesium metal and Al-Ti intermediate alloy are added, and the electromagnetic stirring is performed for 20-30 min, and after the sampling analysis of the chemical composition is qualified, the aluminum alloy melt is obtained;

[0028] III. Preparing a casting melt: the aluminum alloy melt is introduced into a holding furnace at 730-750°C, and then argon-chlorine mixed gas is introduced for 30 min for refining, and then it is left for 30 min to obtain a casting melt;

[0029] IV. Forming: the casting melt flows into an online double degassing device, and then flows into a filtering device, and after filtering, it is injected into a crystallizer through a flow disc, and the casting speed is 55-60 mm / min from the start of semi-continuous casting to the length of 400 mm, the water flow is 20-30 m3 / h per rod, and the position of the water-blocking rubber plate is 190 mm away from the lower edge of the crystallizer, and when the casting reaches a length of 400 mm, the casting speed is 40-55 mm / min, the water flow is 30-40 m3 / h per rod, and the position of the water-blocking rubber plate is 300-400 mm away from the lower edge of the crystallizer, and at the same time, Al-3Ti-0.15C wire is seeded into the casting melt at a speed of 123 mm / min per rod, and an Al-Zn-Mg-Cu system aluminum alloy flat ingot is obtained, i.e., the manufacturing method is completed.

[0030] In step I of the embodiment, Si, Fe, Mn, and Cr are all impurity elements, and the impurities within the range have no effect on the forming and metallurgical quality of the ingot, and the lower the content is in actual production, the better.

[0031] In step II of the embodiment, the sampling analysis of the chemical composition is qualified, and the purpose is to obtain a qualified aluminum alloy melt, and the chemical composition meets Cu: 1.70% to 2.30%, Mg: 1.50% to 2.30%, Zn: 7.20% to 8.50%, Zr: 0.05% to 0.15%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06%, and the balance of Al according to the mass percentage content.

[0032] The electromagnetic stirring in step two of the embodiment is carried out in the middle of the furnace bottom to stir by convection.

[0033] Specific embodiment two: the embodiment is different from the specific embodiment one in that the mass percentage content of Cu, Mg, Zn, Zr, Si, Fe, Mn, Cr, Ti and Al in step one is 1.80%, 2.0%, 8.05%, 0.11%, ≤0.06%, ≤0.08%, ≤0.04%, ≤0.04%, ≤0.06% and the balance of Al respectively. The other steps and parameters are the same as those in the specific embodiment one.

[0034] Specific embodiment three: the embodiment is different from the specific embodiment one in that the mass purity of the refined aluminum ingot in step one is ≥99.99%, the Al-Zr intermediate alloy is Al-3%Zr and the Al-Ti intermediate alloy is Al-6%Ti. The other steps and parameters are the same as those in the specific embodiment one.

[0035] Specific embodiment four: the embodiment is different from the specific embodiment one in that the Al-Be intermediate alloy with a mass content of 0.025% is added when the magnesium metal is added in step two, and the use amount of the Al-Be intermediate alloy is 0.25 kg per ton of aluminum alloy melt. The other steps and parameters are the same as those in the specific embodiment one.

[0036] The Al-Be intermediate alloy is added in the embodiment to improve the structure of the oxide film of the aluminum alloy, prevent the oxidation and burning loss of the magnesium element and the aluminum element, and produce oxide pollution in the melt.

[0037] Specific embodiment five: the embodiment is different from the specific embodiment one in that the molar content of argon and chlorine in the argon-chlorine mixed gas in step three is 94% and 6% respectively. The other steps and parameters are the same as those in the specific embodiment one.

[0038] Specific embodiment six: the embodiment is different from the specific embodiment one in that the filter device in step four adopts 30 ppi+50 ppi ceramic filter sheets for filtering. The other steps and parameters are the same as those in the specific embodiment one.

[0039] Specific embodiment seven: the embodiment is the same as the specific embodiment one in that the crystallizer in step four adopts double-row water cooling, and the shape and size of the crystallizer is a rectangle of 420 mm x 1320 mm. The other steps and parameters are the same as those in the specific embodiment one.

[0040] Specific embodiment eight: the embodiment is different from the specific embodiment one in that the temperature for casting in step four is 685-705 ℃, and the temperature of the cooling water used for casting is 18-26 ℃. The other steps and parameters are the same as those in the specific embodiment one.

[0041] Specific embodiment nine: this embodiment is different from the specific embodiment one in that the Al-3Ti-0.15C wire in step four is used as grain refiner, and the amount is 3-4 kg per ton of casting melt. The other steps and parameters are the same as those in the specific embodiment one.

[0042] Specific embodiment ten: this embodiment is different from the specific embodiment one in that the on-line double degassing device in step four is: argon gas, argon gas flow is 20-35 nm 3 / hr, rotation speed is 350 rpm / min, and argon purity is ≥99.996%. The other steps and parameters are the same as those in the specific embodiment one.

[0043] The beneficial effects of the present application are verified by the following examples:

[0044] Example:

[0045] A manufacturing method of an Al-Zn-Mg-Cu series aluminum alloy flat ingot, which is performed according to the following steps:

[0046] I. Weighing: according to the mass percentage of Cu: 1.80%, Mg: 2.0%, Zn: 8.05%, Zr: 0.11%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06%, and the balance of Al, the refined aluminum ingot, pure copper plate, pure magnesium ingot, pure zinc ingot, Al-Zr intermediate alloy, and Al-Ti intermediate alloy are weighed;

[0047] II. Melting: the refined aluminum ingot and Al-Zr intermediate alloy are added into a natural gas melting furnace, the pure copper plate and pure zinc ingot are added after the refined aluminum ingot is melted, the pure magnesium ingot and Al-Ti intermediate alloy are added after the temperature is raised to 730℃, the electromagnetic stirring is performed for 20-30 min, the chemical composition is analyzed and qualified, and then the aluminum alloy melt is obtained;

[0048] III. Preparation of casting melt: the aluminum alloy melt is introduced into a holding furnace at 730-750℃, then argon-chlorine mixed gas is introduced for 30 min, and then it is statically placed for 30 min, and then the casting melt is obtained;

[0049] Four, forming: the above casting melt flows into an on-line double degassing device, then flows into a filtering device, and after filtering, is injected into a crystallizer through a flow disc. The casting speed used from the beginning of semi-continuous casting to when the casting reaches a length of 400 mm is 55 mm / min, the casting water flow rate is 20 m3 / h per ingot, the water-blocking rubber plate position is 190 mm away from the lower edge of the crystallizer, when the casting reaches a length of 400 mm, the casting speed used is 40 mm / min, the casting water flow rate is 35 m3 / h per ingot, the water-blocking rubber plate position is 350 mm away from the lower edge of the crystallizer, and at the same time, Al-3Ti-0.15C wires are seeded into the casting melt at a speed of 123 mm / min per ingot, to obtain an Al-Zn-Mg-Cu system aluminum alloy flat ingot, i.e. to complete the manufacturing method.

[0050] The purity of the refined aluminum ingot in step one of the embodiment is ≥99.99%, the Al-Zr intermediate alloy is Al-3% Zr, and the Al-Ti intermediate alloy is Al-6% Ti.

[0051] In step two of the embodiment, 0.025% of Al-Be intermediate alloy is added at the same time as the magnesium metal, and the use amount of the Al-Be intermediate alloy is 0.25 kg per ton of aluminum alloy melt.

[0052] In step three of the embodiment, the argon-chlorine mixed gas: the molar content of argon and chlorine is 94% and 6%, respectively.

[0053] In step four of the embodiment, the filtering device: 30 ppi+50 ppi ceramic filter sheets are used for filtering.

[0054] In step four of the embodiment, the crystallizer: the crystallizer adopts a double water-cooling cooling mode, and the shape and size of the crystallizer is a rectangle of 420 mm x 1320 mm.

[0055] In step four of the embodiment, the casting temperature is 685-705°C, and the cooling water temperature used for casting is 18-26°C.

[0056] In step four of the embodiment, the Al-3Ti-0.15C wires are used as grain refiners, and the use amount is 3.6 kg per ton of casting melt.

[0057] In step four of the embodiment, the on-line double degassing device: argon is used, the argon gas flow rate is 20-35 nm 3 / hr, the rotation speed is 350 rpm / min, and the purity of the argon is ≥99.996%.

[0058] The Al-Zn-Mg-Cu system aluminum alloy flat ingot manufactured in the embodiment has a thickness of 420 mm, a width of 1320 mm, and a length of 4000-7000 mm; for example, Figure 1As shown, the metallographic structure is free of defects such as porosity and slag inclusion. The Al-Zn-Mg-Cu series aluminum alloy flat ingot is free of cracks, the ingot surface is well shaped, the internal performance is up to standard, the metallographic structure is free of porosity, and the yield of the ingot is more than 90%. Figure 2

[0059] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as the modifications, equivalent replacements, improvements, etc. are within the spirit and principles of the present application.​

Claims

1. A method of manufacturing an Al-Zn-Mg-Cu aluminum alloy slab, characterized by It is carried out in the following steps: I. Weighing: according to the mass percentage of Cu: 1.70%~2.30%, Mg: 1.50%~2.30%, Zn: 7.20%~8.50%, Zr: 0.05%~0.15%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06% and the balance of Al, the refined aluminum ingot, copper metal, magnesium metal, zinc metal, Al-Zr intermediate alloy and Al-Ti intermediate alloy are weighed; II. Melting: the above-mentioned refined aluminum ingot and Al-Zr intermediate alloy are added to a natural gas melting furnace, and after the refined aluminum ingot is melted, copper metal and zinc metal are added, and after the temperature is raised to 730~750℃, magnesium metal and Al-Ti intermediate alloy are added, and electromagnetic stirring is carried out for 20~30min, and after the chemical composition of the sample is analyzed and qualified, an aluminum alloy melt is obtained; III. Preparing a casting melt: the above-mentioned aluminum alloy melt is introduced into a holding furnace at 730~750℃, and then argon-chlorine mixed gas is introduced for 30min, and then it is left for 30min to obtain a casting melt; IV. Forming: the above casting melt flows into an on-line double degassing device, then into a filtering device, and after filtering, is injected into a crystallizer through a flow disc. The casting speed used from the beginning of semi-continuous casting to when the casting reaches a length of 400 mm is 55-60 mm / min, the casting water flow is 20-30 m 3 / h per ingot, and the position of the water-blocking rubber plate is 190 mm from the lower edge of the crystallizer. When the casting reaches a length of 400 mm, the casting speed used is 40-55 mm / min, the casting water flow is 30-40 m 3 / h per ingot, and the position of the water-blocking rubber plate is 300-400 mm from the lower edge of the crystallizer. At the same time, Al-3Ti-0.15C wire is seeded into the casting melt at a speed of 123 mm / min per ingot, and an Al-Zn-Mg-Cu system aluminum alloy flat ingot is obtained, i.e. the manufacturing method is completed. The refined aluminum ingot in step I has a mass purity of ≥99.99%, the Al-Zr intermediate alloy is Al-3%Zr, and the Al-Ti intermediate alloy is Al-6%Ti; In step II, 0.025% of Al-Be intermediate alloy is added when magnesium metal is added, and the use amount of Al-Be intermediate alloy is 0.25kg per ton of aluminum alloy melt; In step III, the argon-chlorine mixed gas: the molar content of argon and chlorine is 94% and 6%, respectively; In step IV, the filter device: 30ppi+50ppi ceramic filter sheet is used for filtration; In step IV, the crystallizer: the crystallizer adopts double-row water cooling, and the shape and size of the crystallizer are 420mm×1320mm rectangular; In step IV, the casting temperature is 685~705℃, and the cooling water temperature used for casting is 18~26℃; In step IV, the Al-3Ti-0.15C wire is used as a grain refiner, and the use amount is 3~4kg per ton of casting melt; The on-line double degassing device in step four: adopt argon, argon gas flow is 20-35 nm 3 / hr, rotation speed is 350 rpm / min, and argon purity is greater than or equal to 99.996%.

2. The method of producing an Al-Zn-Mg-Cu alloy flat ingot according to claim 1, characterized by In step I, according to the mass percentage of Cu: 1.80%, Mg: 2.0%, Zn: 8.05%, Zr: 0.11%, Si≤0.06%, Fe≤0.08%, Mn≤0.04%, Cr≤0.04%, Ti≤0.06% and the balance of Al.

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