Preparation method of Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy cast ingot

Abstract

The invention provides an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy cast ingot preparation method which comprises the following steps: S1, mixing a Cu source, an Mg source, a Zn source, an Mn source, an Er source, a Zr source and an Al source, and smelting to obtain a smelted material; s2, the smelted material is subjected to purification treatment and casting treatment, and an ingot blank is obtained; the speed of casting treatment is 18-26 mm / min, and the flow of cooling water in the casting treatment is 6-16 m < 3 > / h; and S3, the ingot blank is subjected to homogenizing heat treatment, and the Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy cast ingot is obtained. Experimental results show that by adopting the preparation method provided by the invention, the forming rate and metallurgical quality of the Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy cast ingot can be improved, and the comprehensive mechanical property and corrosion resistance of the product can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of metal materials, and in particular to a method for preparing an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot. Background Art

[0002] Due to the needs of deep-sea engineering such as deep diving and drilling, the strength, corrosion resistance and welding performance of alloy materials need to meet higher requirements. Al-Zn-Mg-Cu-(Er, Zr) alloy is a new type of Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy formed by adding micro-alloying elements Er and Zr to Al-Zn-Mg-Cu alloy.

[0003] However, the new Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy has complex components and a high degree of alloying. It is easy to have compound segregation, poor casting performance of the alloy, and has a great tendency to thermal cracking and looseness. At present, its casting production process is prone to casting cracking, and there are also serious component segregation of large-sized ingots, poor mechanical properties and corrosion resistance, which seriously restricts the preparation process of large-sized ultra-high-strength, corrosion-resistant and weldable Al-Zn-Mg-Cu aluminum alloy pipes. Therefore, the chemical composition design, casting molding and heat treatment process of Al-Zn-Mg-Cu-(Er, Zr) alloy are very demanding. For Al-Zn-Mg-Cu aluminum alloy, the existing conventional production technology is difficult to ensure that the produced alloy meets the requirements of ultra-high-strength corrosion-resistant products.

[0004] Under industrial conditions, the uniform addition and smelting of composite microalloying elements such as Er and Zr are achieved, and the alloy composition is precisely controlled; and through double-stage homogenization heat treatment, the precipitation phase of microalloying strengthening particles is regulated to obtain industrial high metallurgical quality control technology for large-scale ingots of ultra-high strength, corrosion-resistant and weldable aluminum alloys. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot. The aluminum alloy ingot obtained by the preparation method has small segregation, less residual coarse second phase, dispersed distribution of compounds, uniform and fine structure, and the finished product has excellent mechanical properties and exfoliation corrosion resistance.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot, comprising:

[0008] S1: mixing a Cu source, a Mg source, a Zn source, a Mn source, an Er source, a Zr source and an Al source and smelting the mixture to obtain a smelt;

[0009] S2: purifying and casting the smelted product to obtain an ingot;

[0010] The casting process speed is 18-26 mm / min, and the flow rate of cooling water in the casting process is 6-16 m 3 / h / root;

[0011] S3: subjecting the ingot to homogenization heat treatment to obtain an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot.

[0012] Preferably, the casting process speed is 18-20 mm / min, and the flow rate of cooling water in the casting process is 8-10 m 3 / h / root.

[0013] Preferably, the smelt comprises, by mass percentage, Si≤0.10%, Fe≤0.12%, Cu 0.6~1.2%, Mn 0.2~0.5%, Mg 2.2~2.6%, Er 0.02~0.25%, Zn 7.7~8.5%, Zr 0.05~0.15%, and the balance is Al.

[0014] Preferably, the homogenization heat treatment includes a first stage homogenization heat treatment and a second stage homogenization heat treatment.

[0015] Preferably, the holding temperature of the first stage homogenization heat treatment is 340-375° C., and the holding time is 15-25 h.

[0016] Preferably, the second stage homogenization heat treatment has a holding temperature of 430-490° C. and a holding time of 30-40 h.

[0017] Preferably, the purification process comprises online degassing, online filtration and grain refinement in sequence.

[0018] Preferably, the refiner used for grain refinement is selected from any one or more of AlTi5B1, AlTi3B1 or AlTi3C0.15.

[0019] Preferably, the mass ratio of the refiner to the smelt is (1.8~2.2) kg:1 t.

[0020] Preferably, the casting process further includes a bottom laying process.

[0021] Preferably, the bottoming treatment uses pure aluminum liquid to lay the bottom.

[0022] Preferably, the temperature of the pure aluminum liquid is 730-760° C., and the thickness of the pure aluminum liquid bottom is 40-100 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for preparing an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot. The method first optimizes the chemical composition and its ratio in the smelt, which can effectively improve the mechanical properties and corrosion resistance of the final ingot; after the smelt is purified and cast to obtain an ingot, the ingot is forged, and the speed of the casting process and the flow rate of cooling water in the casting process are reasonably controlled to ensure that the ingot is not easy to crack. Experimental results show that the preparation method provided by the present invention can improve the forming rate and metallurgical quality of the Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot, and improve the comprehensive mechanical properties of the product (pipe yield strength 520~600 MPa, tensile strength 560~675 MPa, elongation 10%~15%), corrosion resistance (exfoliation corrosion EA grade), etc. At the same time, the Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot has small segregation, less residual coarse second phase, dispersed distribution of compounds, and uniform and fine structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a physical picture of the ingot in Example 1;

[0026] Figure 2 This is a physical picture of the transverse annular crack of the ingot in Comparative Example 1;

[0027] Figure 3 This is a physical picture of the ingot in Comparative Example 2. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In view of the Al- - -Cu aluminum alloy ingot, it is difficult to ensure that the alloy produced by the existing conventional production technology meets the requirements of ultra-high strength and corrosion-resistant products. The present invention provides a method for preparing Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot, comprising:

[0030] S1: mixing a Cu source, a Mg source, a Zn source, a Mn source, an Er source, a Zr source and an Al source and smelting the mixture to obtain a smelt;

[0031] S2: purifying and casting the smelted product to obtain an ingot;

[0032] The casting process speed is 18-26 mm / min, and the flow rate of cooling water in the casting process is 6-16 m 3 / h / root;

[0033] S3: subjecting the ingot to homogenization heat treatment to obtain an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot.

[0034] The present invention firstly mixes a Cu source, a Mg source, a Zn source, a Mn source, an Er source, a Zr source and an Al source and then smelts them to obtain a smelt. The present invention preferably performs the smelting in a smelting furnace. In some embodiments of the present invention, a Cu plate, a Mg ingot, a Zn ingot, an AlMn15 master alloy, an AlEr5 master alloy, an AlZr4 master alloy and an Al99.90 original aluminum ingot are heated by natural gas to obtain a smelt.

[0035] In the present invention, the content of each element in the Cu source, Mg source, Zn source, Mn source, Er source, Zr source and Al source needs to be strictly controlled to ensure the comprehensive mechanical properties and corrosion resistance of the final ingot product. The specific description is as follows:

[0036] (1) Reasonable control of the content of Cu, Zn and Mg elements

[0037] The corrosion resistance of Al-Zn-Mg alloy is poor. When 0.6~1.2 wt% Cu is added, its stress corrosion resistance will be greatly improved, and the tensile strength can be increased. At the same time, adding Cu within a certain range of Mg and Zn content can maintain the alloy with high strength while improving the plasticity of the alloy. The elements Zn and Mg are the main strengthening elements, producing the main strengthening phases MgZn2 and Mg3Zn3Al2. The increase in Zn and Mg content can greatly improve the strength and hardness of the alloy, but at the same time it will reduce the plasticity, stress corrosion resistance and fracture toughness of the alloy. Therefore, although the addition of Zn and Mg will optimize the performance of the alloy, this effect will only be achieved if the Zn / Mg ratio is controlled within a specific range.

[0038] Therefore, the present invention controls the Cu in the smelt to be 0.6-1.2 wt%, the Mg to be 2.2-2.6 wt%, the Zn to be 7.7-8.5 wt%, and the Zn / Mg to be ≥2.9, preferably ≥3.2.

[0039] (2) Reasonable control of Si and Fe element content

[0040] Si and Mg form Mg2Si phase, which can reduce the amount of the main strengthening phases MgZn2 and Mg3Zn3Al2 in the alloy, thereby reducing the strength of the alloy. Fe will affect the corrosion resistance to a certain extent; at the same time, the increase in Si and Fe content will also increase the tendency of casting cracks.

[0041] Therefore, the present invention controls Si≤0.10 wt% and Fe≤0.12 wt% in the smelt.

[0042] (3) Reasonable control of the content of Mn, Er and Zr elements

[0043] Er and Zr are common microalloying elements. They can generate highly stable Al3Er particles or Al3(Zr) at higher temperatures. X Er 1-X ) produces dispersion strengthening effect. Adding a small amount of Mn, Er, and Zr can increase the recrystallization temperature, inhibit recrystallization, refine the recrystallized grains, refine the grains, and improve the stress corrosion resistance of the ingot.

[0044] Therefore, in order to improve casting performance, refine grains, and improve the corrosion resistance of the ingot, the present invention controls Mn 0.2-0.5 wt%, Er 0.02-0.25 wt%, and Zr 0.05-0.15 wt% in the smelt.

[0045] The present invention has no particular limitation on the Cu source, Mg source, Zn source, Si source, Fe source, Mn source, Er source, Zr source and Al source and their sources, and any common commercially available source known to those skilled in the art may be used.

[0046] After the smelting is completed, the present invention preferably samples the obtained melt to analyze the melt composition, and then adjusts the element composition accordingly according to the content requirements of the above-mentioned elements. The adjustment method is a method well known to those skilled in the art. If the alloying element exceeds the control range, it can be diluted by adding Al ingots. If the alloying element is lower than the control range, an intermediate alloy is added to perform a feed operation to adjust the chemical composition.

[0047] After the composition adjustment is completed, the present invention preferably adopts powder spray refining or an equivalent refining effect process for the first step of refining, and then adopts argon or argon-chlorine mixed gas refining for the second step of refining. The time of the first step of refining is 15-25 min, preferably 20-25 min; the time of the second step of refining is 15-25 min, preferably 20-25 min. The powder spray refining is preferably carried out using a granular refining agent, which is composed of 55-58 wt% KCl and 41-44 wt% MgCl2, as well as a small amount of impurities.

[0048] After the refining is completed, the present invention preferably allows the melt to stand to obtain a smelt. The standing time is 30 to 120 min, preferably 50 to 120 min, and more preferably 80 to 100 min.

[0049] After obtaining the smelt, the present invention preferably performs purification treatment and casting treatment on the smelt to obtain an ingot, wherein the purification treatment preferably includes online degassing, online filtration and grain refinement in sequence.

[0050] In the present invention, the specific operation of the online degassing can be carried out according to the means known to those skilled in the art. In the present invention, argon or argon chlorine + chlorine mixed gas is preferably used as the refining gas, and the amount of the refining gas is 3.5~4.5 m 3 / h, preferably reducing the hydrogen content in the smelt to less than 0.12 mL / 100 g Al to ensure the metallurgical quality of the ingot.

[0051] After the online degassing is completed, the present invention preferably adopts plate filtration, and specifically can adopt two-stage ceramic filter plate for filtration, the first stage adopts 40 ppi and above precision filter plate, and the second stage adopts 50 ppi and above precision filter plate.

[0052] The present invention preferably uses a refiner for grain refinement. The refiner can be selected from any one or more of AlTi5B1, AlTi3B1 or AlTi3C0.15, preferably AlTi5B1. Too high a dosage of the refiner will lead to the generation and aggregation of Ti-containing compounds, thereby affecting the performance and flaw detection results, while too low a dosage will result in a larger ingot grain size. Therefore, the present invention preferably controls the mass ratio of the refiner to the smelt to be (1.8~2.2) kg:1 t, more preferably (1.9~2.0) kg:1 t.

[0053] After the above purification treatment is completed, the present invention performs a casting process on the obtained product. Since Al-Zn-Mg-Cu-(Er, Zr) φ482mm or larger round ingots have a high tendency to crack, a bottom laying operation can be performed before casting, because pure aluminum has good plasticity and a large linear shrinkage coefficient, and can resist the tensile stress at the bottom by effective deformation, which can effectively prevent cracks at the bottom of the ingot. Therefore, the present invention preferably uses pure aluminum liquid to lay the bottom before casting. In some embodiments of the present invention, the pure aluminum liquid is obtained by melting an aluminum ingot with a grade of Al99.70, and the temperature of the pure aluminum liquid is 730~760°C, preferably 740~750°C, and the aluminum thickness of the pure aluminum liquid bottom is 40~100 mm, preferably 50~80 mm.

[0054] After the bottoming treatment is completed, the casting process begins. In the casting process, the speed of the casting process and the amount of cooling water used are extremely critical. If the speed is too high, a central crack will be generated during the casting process, and even leakage may occur. If the speed is too low, the surface quality of the ingot will be poor and affect its use, and even the ingot and the tooling will stick together. If the amount of cooling water is too high, it will cause water flow rebound and ingot cracking. If the amount of cooling water is too low, aluminum will leak and the casting will be stopped. Therefore, in the present invention, the speed of the casting process is controlled to 18~20 mm / min, preferably 18.5~19.5 mm / min, and more preferably 19 mm / min; the flow rate of cooling water in the casting process is controlled to 8~10 m 3 / h / root, preferably 8.5~10 m 3 / h / root, preferably 9 m 3 The casting temperature is 720-750°C, preferably 730-745°C, and more preferably 735-740°C.

[0055] After the casting process is completed, the ingot can be obtained. In order to eliminate the stress of the ingot, reduce the segregation of the ingot and obtain a dispersed compound to meet the requirements of the ultra-high strength corrosion-resistant pipe structure, the ingot needs to be subjected to high-temperature homogenization treatment to obtain an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot. In the present invention, the homogenization heat treatment preferably includes a first-stage homogenization heat treatment and a second-stage homogenization heat treatment. The present invention preferably heats up at a heating rate of 50~100℃ / h, heats up for 3~8h to a temperature of 340~375℃, preferably 350~360℃ to enter the first-stage insulation, and the first-stage insulation time is 15~25h, preferably 20h. Then, at the same heating rate, the temperature is raised to 430~490℃, preferably 450~470℃ to enter the second-stage insulation, and the second-stage insulation time is 30~40h, preferably 33~36h.

[0056] After completing the homogenization heat treatment, the present invention preferably performs post-processing on the aluminum alloy ingot obtained by the homogenization heat treatment, and the post-processing includes ingot sawing, processing and testing. The post-processing can be performed according to actual production needs, and the present invention does not make any special limitations.

[0057] The present invention also provides an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot, which is prepared according to the above-mentioned preparation method and has excellent comprehensive mechanical properties (pipe yield strength 520-600 MPA, tensile strength 560-675 MPA, elongation 10%-15%), corrosion resistance (exfoliation corrosion EA grade), etc. At the same time, the Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot has small segregation, less residual coarse second phase, dispersed distribution of compounds, and uniform and fine structure.

[0058] The Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot comprises chemical components, by mass percentage, including: Si≤0.10 wt%, Fe≤0.12 wt%, Cu 0.6~1.2 wt%, Mn 0.2~0.5 wt%, Mg 2.2~2.6 wt%, Er0.02~0.25 wt%, Zn 7.7~8.5 wt%, Zr 0.05~0.15 wt%, and the balance is Al; preferably, Si≤0.08 wt%, Fe≤0.10 wt%, Cu 0.6~1.0 wt%, Mn 0.2~0.4 wt%, Mg 2.3~2.5 wt%, Er 0.02~0.20 wt%, Zn7.7~8.3 wt%, Zr 0.05~0.12 wt%, and the balance is Al. The mass ratio of Zn to Mg is ≥2.9, preferably ≥3.2, and generally does not exceed 3.7.

[0059] In order to further illustrate the present invention, the following examples are provided for detailed description.

[0060] The aluminum source involved in the following is an aluminum ingot with a grade of Al99.70 or above; the copper source is a pure metal Cu plate; the zinc source is a pure metal Zn ingot; the Mn source is an AlMn15 master alloy, the Er source is an AlEr5 master alloy; and the Mg source is a pure metal Mg ingot.

[0061] Example 1

[0062] This embodiment provides a round ingot for Al-Zn-Mg-Cu-(Er, Zr) alloy thick-walled pipe, and the preparation method is as follows:

[0063] (1) Chemical composition control: Si 0.03 wt%, Fe 0.05 wt%, Cu 0.99 wt%, Mn 0.28 wt%, Mg2.38 wt%, Er 0.08 wt%, Zn 7.88 wt%, Ti 0.03 wt%, Zr 0.10 wt%, the balance is Al, Zn / Mg=3.31;

[0064] (2) Smelting: First add Al source to the smelting furnace for melting. After more than 1 / 3 of the aluminum source is melted, add copper source and zinc source. When the aluminum source is completely melted into liquid aluminum, when the temperature rises to 745°C, add Mn source, Mg source, Zr source, etc., and the reaction time is 25 minutes. When the melt is heated to 775°C, add Er source, and the reaction time is ≥40 minutes. The reaction time is 50 minutes to obtain the smelt; take samples, and adjust the composition according to the rapid analysis results and the control requirements in the above technical solution;

[0065] (3) Melt purification: The smelting furnace uses powder spray refining for melt purification. The powder sprayer introduces Ar gas to evenly spray 20 kg of granular refining agent (including 58 wt% KCl and 41 wt% MgCl2, the remainder is impurities) into the melt. The static furnace adopts artificial T-type refining, and Ar+Cl2 gas is introduced into the entire melt for refining, degassing and deslagging. The online degassing adopts double rotor rotary degassing. The introduced Ar gas is dispersed into fine bubbles through high-speed rotation and sprayed out to the bottom of the melt, floating up and taking out the gas in the melt to achieve the degassing effect. The rotor speed is set at 350 r / min. The online filtration adopts a ceramic filter plate with a filtration accuracy of 40+50ppi to filter out fine slag inclusions in the melt.

[0066] (4) Refining: AlTi5B1 is added online through a wire feeding device at a rate of 1.8 kg / t into the flowing melt;

[0067] (5) Bottom: The present invention uses pure aluminum as the bottom during casting. The bottom is made of aluminum ingot with grade Al99.70. The bottom aluminum liquid temperature is 752°C and the bottom aluminum thickness is 6 mm. Figure 1 . All 5 castings were completed;

[0068] (6) Casting process: Casting speed is 20 mm / min, water flow rate is 8 m 3 / h / root, 5 roots are cast and all formed, see Figure 1 ;

[0069] (7) After the melt is cast, an ingot is obtained, and the ingot is subjected to a high-temperature homogenization annealing treatment, specifically: a heating rate of 50-100°C / h, a first-stage heating time of 4.5 h, a holding time of 16 h, a holding temperature of 350°C, a second-stage heating time of 2.5 h, a second-stage holding temperature of 470°C, and a second-stage holding time of 36 h.

[0070] Example 2

[0071] This embodiment provides a round ingot for Al-Zn-Mg-Cu-(Er, Zr) alloy thick-walled pipe, and the preparation method is as follows:

[0072] (1) Chemical composition control: Si 0.04 wt%, Fe 0.06 wt%, Cu 0.77 wt%, Mn 0.25 wt%, Mg2.35 wt%, Er 0.09 wt%, Zn 7.82 wt%, Ti 0.02 wt%, Zr 0.09 wt%, the balance is Al, Zn / Mg=3.33;

[0073] (2) Smelting: First add Al source to the smelting furnace for melting. After more than 1 / 3 of the aluminum source is melted, add copper source and zinc source. When it is completely melted into aluminum liquid, when the temperature rises to 743°C, add Mn source, Mg source, Zr source, etc., and the reaction time is 20 minutes. When the melt is heated to 775°C, add Er source, and the reaction time is ≥40 minutes. The reaction time is 55 minutes to obtain the smelt; take samples and adjust the composition according to the rapid analysis results and the control requirements in the above technical solution;

[0074] (3) Melt purification: The smelting furnace uses powder spray refining for melt purification. The powder sprayer introduces Ar gas to evenly spray 20 kg of granular refining agent (including 55 wt% KCl and 44 wt% MgCl2, the remainder is impurities) into the melt; the static furnace adopts artificial T-type refining, and Ar+Cl2 gas is introduced into the entire melt for refining, degassing and slag removal; online degassing adopts double rotor rotary degassing, and the introduced Ar gas is dispersed into fine bubbles through high-speed rotation and sprayed out and dispersed at the bottom of the melt, floating up and carrying out the gas in the melt to achieve the degassing effect. The rotor speed is set at 350 r / min; online filtration uses a ceramic filter plate with a filtration accuracy of 40+50 ppi to filter out fine slag inclusions in the melt;

[0075] (4) Refining: AlTi5B1 is added online through the wire feeding device at a rate of 2.0 kg / t into the flowing melt;

[0076] (5) Bottom: Pure aluminum is used for the bottom, grade Al99.70 aluminum ingot is used for the bottom, the bottom aluminum liquid temperature is 760℃, and the bottom aluminum thickness is 80 mm;

[0077] (6) Casting process: Casting speed is 26 mm / min, water flow rate is 10 m 3 / h / root, 6 roots were cast and all formed;

[0078] (7) After the melt is cast, an ingot is obtained, and the ingot is subjected to a high-temperature homogenization annealing treatment, specifically: a heating rate of 50-100°C / h, a first-level heating time of 3.5 h, a holding time of 16 h, a holding temperature of 350°C, a second-level heating time of 2.5 h, a second-level holding temperature of 470°C, and a second-level holding time of 36 h.

[0079] Example 3

[0080] This embodiment provides a round ingot for Al-Zn-Mg-Cu-(Er, Zr) alloy thick-walled pipe, and the preparation method is as follows:

[0081] (1) Chemical composition control: Si 0.03 wt%, Fe 0.083 wt%, Cu 0.75 wt%, Mn 0.50 wt%, Mg2.58 wt%, Er 0.094 wt%, Zn 8.30 wt%, Ti 0.02 wt%, Zr 0.09 wt%, the balance is Al, Zn / Mg=3.21;

[0082] (2) Smelting: First add Al source to the smelting furnace for melting. After more than 1 / 3 of the aluminum source is melted, add copper source and zinc source. When it is completely melted into aluminum liquid, when the temperature rises to 747°C, add Mn source, Mg source, Zr source, etc., and the reaction time is 30 minutes. When the melt is heated to 775°C, add Er source, and the reaction time is ≥40 minutes. The reaction time is 60 minutes to obtain the smelt; take samples and adjust the composition according to the rapid analysis results and the control requirements in the above technical solution;

[0083] (3) Melt purification: The smelting furnace uses powder spray refining for melt purification. The powder sprayer introduces Ar gas to evenly spray 20 kg of granular refining agent (including 56 wt% KCl and 43 wt% MgCl2, the remainder is impurities) into the melt; the static furnace adopts artificial T-type refining, and Ar+Cl2 gas is introduced into the entire melt for refining, degassing and deslagging; online degassing adopts double rotor rotary degassing, and the introduced Ar gas is dispersed into fine bubbles through high-speed rotation and sprayed out and dispersed at the bottom of the melt, floating up and carrying out the gas in the melt to achieve the degassing effect. The rotor speed is set at 350 r / min; online filtration uses a ceramic filter plate with a filtration accuracy of 40+50 ppi to filter out fine slag inclusions in the melt;

[0084] (4) Refining: AlTi5B1 is added online through a wire feeding device at a rate of 2.2 kg / t into the flowing melt;

[0085] (5 Bottom: Pure aluminum bottom, Al99.70 aluminum ingot, bottom aluminum liquid temperature 760℃, bottom aluminum thickness 85mm. Three castings are fully formed;

[0086] (6) Casting process: Casting speed is 18 mm / min, water flow rate is 16 m 3 / h / root, 3 roots were cast and all formed;

[0087] (7) After the melt is cast, an ingot is obtained, and the ingot is subjected to a high-temperature homogenization annealing treatment, specifically: a heating rate of 50-100°C / h, a first-stage heating time of 3.5 h, a holding time of 16 h, a holding temperature of 350°C, a second-stage heating time of 3 h, a second-stage holding temperature of 470°C, and a second-stage holding time of 35 h.

[0088] Comparative Example 1

[0089] This comparative example provides a round ingot for thick-walled pipes of Al-Zn-Mg-Cu-(Er, Zr) alloy, and the preparation method is as follows:

[0090] (1)~(4) refer to Example 1;

[0091] (6) Casting process: Casting speed is 15 mm / min, water flow rate is 18 m 3 / h / root, transverse cracks appeared during casting, casting was stopped, see Figure 2 ,scrapped.

[0092] In Comparative Example 1, since the cooling water flow rate is large but the speed is slow during the casting process, a cold shut is easily formed during the ingot formation. If the cold shut is deep enough, transverse annular cracks will be generated.

[0093] Comparative Example 2

[0094] This comparative example provides a round ingot for thick-walled pipes of Al-Zn-Mg-Cu-(Er, Zr) alloy, and the preparation method is as follows:

[0095] (1)~(4) refer to Example 1;

[0096] (6) Casting process: Casting speed 17 mm / min, water flow 18 m 3 / h / root, casting molding, but the depth of surface defects detected by low magnification is 14~24 mm, many raw materials are scrapped, see Figure 3 .

[0097] In this comparative example 2, compared with comparative example 1, the speed is appropriately increased, the cold shut is not serious and normal production can be carried out, but the surface defects detected by low-magnification inspection are too deep and the processing allowance is insufficient.

[0098] It can be seen that if the cooling water flow rate is too high and the casting speed is too low, the surface quality of the ingot will be affected.

[0099] It should be noted that if the casting speed is too fast and the water flow rate is too low, the casting will fail at the beginning. Therefore, it is necessary to keep the casting speed and water flow rate within the appropriate range.

[0100] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot, It is characterized in that include: S1: mixing a Cu source, a Mg source, a Zn source, a Mn source, an Er source, a Zr source and an Al source and smelting the mixture to obtain a smelt; S2: purifying and casting the smelted product to obtain an ingot; The casting process speed is 18-26 mm / min, and the flow rate of cooling water in the casting process is 6-16 m 3 / h / root; S3: subjecting the ingot to homogenization heat treatment to obtain an Al-Zn-Mg-Cu-(Er, Zr) aluminum alloy ingot.

2. The preparation method according to claim 2, It is characterized in that The casting process speed is 18-20 mm / min, and the flow rate of cooling water in the casting process is 8-10 m 3 / h / root.

3. The preparation method according to claim 1 or 2, It is characterized in that The smelt includes, by mass percentage, Si≤0.10%, Fe≤0.12%, Cu 0.6~1.2%, Mn 0.2~0.5%, Mg 2.2~2.6%, Er 0.02~0.25%, Zn7.7~8.5%, Zr 0.05~0.15%, and the balance is Al.

4. The preparation method according to claim 1 or 2, It is characterized in that The homogenization heat treatment includes a first-stage homogenization heat treatment and a second-stage homogenization heat treatment; The first stage homogenization heat treatment has a holding temperature of 340-375°C and a holding time of 15-25 h; The second stage homogenization heat treatment has a holding temperature of 430-490°C and a holding time of 30-40 h.

5. The preparation method according to claim 1, It is characterized in that The purification process includes online degassing, online filtration and grain refinement in sequence.

6. The preparation method according to claim 5, It is characterized in that The refiner used for grain refinement is selected from any one or more of AlTi5B1, AlTi3B1 or AlTi3C0.

15.

7. The preparation method according to claim 6, It is characterized in that The mass ratio of the refiner to the smelt is (1.8~2.2) kg:1 t.

8. The preparation method according to claim 1, It is characterized in that The casting process also includes a bottom laying process before the casting process.

9. The preparation method according to claim 8, It is characterized in that The bottoming treatment uses pure aluminum liquid to lay the bottom.

10. The preparation method according to claim 9, It is characterized in that The temperature of the pure aluminum liquid is 730-760° C., and the thickness of the pure aluminum liquid bottom is 40-100 mm.

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