A marine 5059 aluminum alloy thick plate and a preparation method thereof

Abstract

This invention relates to a marine 5059 aluminum alloy thick plate and its preparation method, belonging to the field of aluminum alloy processing technology. The preparation method of the marine 5059 aluminum alloy thick plate of the present invention is as follows: 5059 aluminum alloy sheet is smelted and refined, cast, stress relieved, milled, hot rolled (stabilized annealing), cold rolled, sawed, stretched, and sawed to produce 7-27mm thick 5059 aluminum alloy sheet. The 5059 aluminum alloy thick plate comprises: Si: ≤0.15%, Fe: ≤0.25%, Cu≤0.10%, Mn: 0.6-1.2%, Mg: 5.2-5.8%, Cr: ≤0.25%, Zn: 0.4-0.9%, Ti: 0.02-0.05%, Zr: 0.08-0.15%, single impurity ≤0.05%, total impurities ≤0.15%, and the balance is Al; its tensile properties meet the standards ≥370MPa, ≥270MPa, ≥10%, and intergranular corrosion mass loss ≤15mg / cm. 2 The product exhibits PA-level exfoliation corrosion resistance and, after stabilization annealing, demonstrates excellent long-term corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy processing technology, and relates to a marine 5059 aluminum alloy thick plate and its preparation method. Background Technology

[0002] 5059 aluminum alloy is a high-performance engineering material with excellent performance parameters and a wide range of applications. It is widely used in shipbuilding, aerospace, and other fields, and is recognized in the industry as one of the most technically challenging high-end marine aluminum alloys. Among the aluminum alloy materials listed in the CCS "Materials and Welding Specifications," the 5059 grade aluminum alloy has the highest strength and weldability indicators. Its performance parameters include high strength, good corrosion resistance, good machinability, and weldability. 5059 aluminum alloy is a 5xxx series alloy with a high magnesium content. It cannot be heat-treated for strengthening; its main strengthening methods are solid solution strengthening and work hardening, resulting in excellent corrosion resistance and high strength. It is widely used in shipbuilding, tank truck bodies, automobiles, construction, and rail transportation. Due to its excellent corrosion resistance and significantly higher strength than 5083 marine aluminum alloy, 5059 marine aluminum alloy is a new generation of high-end marine aluminum alloy products that can replace 5083 marine aluminum alloy.

[0003] 5059 aluminum alloy has a complex composition, with high levels of elements such as Mg, Mn, Zn, and Zr, making casting difficult. Furthermore, due to its high tensile and yield strength, it is prone to defects during work hardening, including surface scratches, vibration marks, edge cracks, delamination at the beginning and end, poor sheet shape, and slip lines during tensile testing, further complicating production. Currently, domestic manufacturers have limited research on the production process of 5059, and its manufacturing technology is not yet mature. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a 5059 aluminum alloy sheet with high strength and corrosion resistance and a method for preparing the same, which can produce 5059 aluminum alloy that meets the standard requirements.

[0005] A method for preparing a marine-grade 5059 aluminum alloy thick plate includes the following steps:

[0006] A. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: ≤0.15%, Fe: ≤0.25%, Cu: ≤0.10%, Mn: 0.6-1.2%, Mg: 5.2-5.8%, Cr: ≤0.25%, Zn: 0.4-0.9%, Ti: 0.02-0.05%, Zr: 0.08-0.15%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al;

[0007] B. Smelting: The prepared aluminum alloy raw materials are smelted into aluminum alloy melt, which is then poured into a refining furnace for refining.

[0008] C: Refining: Pass a mixture of chlorine and argon gas into the aluminum alloy melt and stir to remove impurity gases from the aluminum alloy melt. After refining and slag removal, let the aluminum alloy melt stand for 20-40 minutes.

[0009] D. Casting: Add grain refiner to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. Then filter the degassed aluminum alloy melt, and finally the aluminum alloy melt flows into the crystallizer for casting to obtain aluminum alloy ingots.

[0010] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace to obtain a stress-relieved ingot.

[0011] F. Sawing and milling: Sawing and milling the stress-relieved ingot. 300-400mm is cut off at the ingot end, 100-150mm is cut off at the gate end, 10-20mm is milled on the large surface, and 5-10mm is milled on the vertical surface.

[0012] G. Heating: The sawn and milled ingot is homogenized and heated in a 1:3-1:5 pusher furnace. After the ingot is held at the temperature, it is taken out of the furnace to obtain the 5059 alloy ingot to be rolled.

[0013] H. Hot rolling: The 5059 alloy ingot to be rolled is rolled into 8-30mm 5059 aluminum alloy sheet using a hot rolling mill;

[0014] I. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy sheet after cold rolling is 7-27mm, and the total cold rolling processing rate is 5-15%.

[0015] J. Sawing and stretching: The cold-rolled 5059 aluminum alloy sheet is sawn at the head, tail and edges in the sawing process; the sawn 5059 aluminum alloy sheet is stretched in a stretching machine with a stretching rate of 0-3%; the stretched sheet is cut to length and sawn according to the specified dimensions using a precision saw.

[0016] Furthermore, the melting temperature described in step B is 740–770°C.

[0017] Furthermore, the refining temperature in step C is 730–760°C, and the refining time is 30–60 min.

[0018] Furthermore, in step C, the ratio of chlorine to argon in the chlorine-argon mixed gas is 1:3 to 1:5.

[0019] Furthermore, the grain refiner mentioned in step D is an Al-5Ti-1B alloy wire refiner; the filtration is carried out through a 40PPI+50PPI dual-stage plate filter; the casting process has a flow channel temperature of 680-700℃, a casting speed of 40-50mm / min, and a crystallizer water flow rate of 1500-3000L / min.

[0020] Furthermore, the heating and heat preservation process described in step E is as follows: the temperature is 400-460℃, and the time is 3-24h.

[0021] Furthermore, the homogenization and heating process described in step G is as follows: temperature 420-460℃, time 3-24h.

[0022] Further, the rolling parameters mentioned in step H are: initial rolling temperature of 410-460℃, total processing deformation of 95-98.7%, and hot rolling final rolling temperature controlled at 200-250℃.

[0023] Furthermore, a stabilization annealing process is added between step G and step H. The annealing regime is: temperature 230-260℃, time 2-6h, to improve the long-term corrosion resistance of the product.

[0024] A type of marine-grade 5059 aluminum alloy thick plate, comprising, by mass percentage: Si: ≤0.15%, Fe: ≤0.25%, Cu: ≤0.10%, Mn: 0.6-1.2%, Mg: 5.2-5.8%, Cr: ≤0.25%, Zn: 0.4-0.9%, Ti: 0.02-0.05%, Zr: 0.08-0.15%, individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al.

[0025] Compared with existing technologies, the 5059 aluminum alloy with high strength and corrosion resistance disclosed in this invention and its preparation method address the difficulties in casting and work hardening of 5059 aluminum alloy due to its high strength. By rationally designing the alloy composition, casting parameters, and rolling process, this invention produces a high-strength, corrosion-resistant 5059 aluminum alloy with satisfactory tensile properties and resistance to intergranular corrosion and exfoliation corrosion. This provides a new production process for producing high-strength, corrosion-resistant 5059 aluminum alloys.

[0026] The 5059 aluminum alloy sheet of this invention undergoes a process of smelting and refining, casting, stress relief, milling, hot rolling (stabilization annealing), cold rolling, sawing, stretching, and sawing, strictly adhering to process parameters to produce 7-27mm thick 5059 aluminum alloy sheets. The tensile properties meet the standards of ≥370MPa, ≥270MPa, and ≥10%, and the intergranular corrosion mass loss is ≤15mg / cm². 2 The product exhibits PA-level exfoliation corrosion resistance and, after stabilization annealing, demonstrates excellent long-term corrosion resistance. Attached Figure Description

[0027] Figure 1 This is a comparison of the weight loss due to intergranular corrosion after sensitization at 150℃ for 1-10h for products from Example 1 and Example 3. Detailed Implementation

[0028] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0029] Example 1

[0030] A marine-grade 5059 aluminum alloy thick plate and its preparation method, comprising the following steps:

[0031] A. Batching: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the proportions. The mass percentage proportions of each element in the 5059 aluminum alloy raw materials are as follows:

[0032] element Si Fe Cu Mn Mg Cr Zn Ti Zr Al content 0.05 0.17 0.03 0.76 5.59 0.02 0.65 0.04 0.08 margin

[0033] B. Melting: The prepared aluminum alloy raw materials are added to the melting furnace and mixed evenly to melt into liquid aluminum alloy at a melting temperature of 740-770℃. Then, the melted aluminum alloy is poured into the refining furnace for refining.

[0034] C. Refining: Introduce chlorine-argon mixed gas and stir the melt to remove impurities from the aluminum alloy melt. The refining temperature is 730-760℃ and the refining time is 50 minutes. After refining and removing slag, let the aluminum alloy melt stand for 30 minutes.

[0035] D. Casting: Al-5Ti-1B wire refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered through a 40PPI+50PPI dual-stage plate filter. Finally, the aluminum alloy melt flows into the crystallizer for casting. The flow channel temperature is 680℃, the casting speed is 49mm / min, and the water flow rate of the double-ingot crystallizer is 2800L / min.

[0036] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace at 400℃ for 10 hours.

[0037] F. Sawing and milling: Sawing and milling the stress-relieved ingot, removing 350mm from the ingot end, 100mm from the gate end, 16mm from the large surface milling, and 7mm from the vertical surface milling.

[0038] G. Heating: The refined aluminum alloy ingot is homogenized and heated in a pusher furnace. The homogenization and heating regime is 450℃ / 10h. After the ingot is held at the temperature, it is taken out of the furnace for hot rolling.

[0039] H. Hot rolling: 5059 alloy ingots are rolled into 20mm aluminum alloy plates using a hot rolling mill. The initial rolling temperature is 420℃, the total processing deformation is 96.7%, and the final hot rolling temperature is controlled at 243℃.

[0040] I. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy strip after cold rolling is 18mm, and the total processing rate is 10.0%.

[0041] G. Sawing: The cold-rolled aluminum alloy sheet is sawn at the head, tail and edges during the sawing process.

[0042] K. Stretching: The cold-rolled aluminum alloy strip is stretched in the straightening process with a stretching rate of 0.3%.

[0043] L. Sawing: Using finished precision saws, the stretched sheet material is cut to length and then sawn according to the specified dimensions.

[0044] Example 2

[0045] A. Batching: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the proportions. The mass percentage proportions of each element in the 5052 aluminum alloy raw material are as follows:

[0046]

[0047] B. Melting: The prepared aluminum alloy raw materials are added to the melting furnace and mixed evenly to melt into liquid aluminum alloy at a melting temperature of 740-770℃. Then, the melted aluminum alloy is poured into the refining furnace for refining.

[0048] C: Refining: Introduce chlorine-argon mixed gas and stir the melt to remove impurity gases from the aluminum alloy melt. The refining temperature is 730-760℃ and the refining time is 50 minutes. After refining and removing slag, let the aluminum alloy melt stand for 30 minutes.

[0049] D. Casting: Al-5Ti-1B wire refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered through a 40PPI+50PPI dual-stage plate filter. Finally, the aluminum alloy melt flows into the crystallizer for casting. The flow channel temperature is 680℃, the casting speed is 49mm / min, and the water flow rate of the double-ingot crystallizer is 2800L / min.

[0050] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace at 400℃ for 10 hours.

[0051] F. Sawing and milling: Sawing and milling the stress-relieved ingot, removing 350mm from the ingot end, 100mm from the gate end, 16mm from the large surface milling, and 7mm from the vertical surface milling.

[0052] G. Heating: The refined aluminum alloy ingot is homogenized and heated in a pusher furnace. The homogenization and heating regime is 450℃ / 10h. After the ingot is held at the temperature, it is taken out of the furnace for hot rolling.

[0053] H. Hot rolling: 5059 alloy ingots are rolled into 30mm aluminum alloy plates using a hot rolling mill. The initial rolling temperature is 430℃, the total processing deformation is 95%, and the final hot rolling temperature is controlled at 241℃.

[0054] I. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy strip after cold rolling is 27mm, and the total processing rate is 10.0%.

[0055] G. Sawing: The cold-rolled aluminum alloy sheet is sawn at the head, tail and edges during the sawing process.

[0056] K. Stretching: The cold-rolled aluminum alloy strip is stretched in the straightening process with a stretching rate of 0.8%.

[0057] L. Sawing: Using finished precision saws, the stretched sheet material is cut to length and then sawn according to the specified dimensions.

[0058] Example 3

[0059] A. Batching: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the proportions. The mass percentage proportions of each element in the 5059 aluminum alloy raw materials are as follows:

[0060]

[0061] B. Melting: The prepared aluminum alloy raw materials are added to the melting furnace and mixed evenly to melt into liquid aluminum alloy at a melting temperature of 740-770℃. Then, the melted aluminum alloy is poured into the refining furnace for refining.

[0062] C: Refining: Introduce chlorine-argon mixed gas and stir the melt to remove impurity gases from the aluminum alloy melt. The refining temperature is 730-760℃ and the refining time is 50 minutes. After refining and removing slag, let the aluminum alloy melt stand for 30 minutes.

[0063] D. Casting: Al-5Ti-1B wire refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered through a 40PPI+50PPI dual-stage plate filter. Finally, the aluminum alloy melt flows into the crystallizer for casting. The flow channel temperature is 680℃, the casting speed is 49mm / min, and the water flow rate of the double-ingot crystallizer is 2800L / min.

[0064] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace at 400℃ for 10 hours.

[0065] F. Sawing and milling: Sawing and milling the stress-relieved ingot, removing 350mm from the ingot end, 100mm from the gate end, 16mm from the large surface milling, and 7mm from the vertical surface milling.

[0066] G. Heating: The refined aluminum alloy ingot is homogenized and heated in a pusher furnace. The homogenization and heating regime is 450℃ / 10h. After the ingot is held at the temperature, it is taken out of the furnace for hot rolling.

[0067] H. Hot rolling: 5059 alloy ingots are rolled into 20mm aluminum alloy plates using a hot rolling mill. The initial rolling temperature is 420℃, the total processing deformation is 96.7%, and the final hot rolling temperature is controlled at 223℃.

[0068] I. Stabilization Annealing: The hot-rolled sheet is annealed at 240℃ for 4 hours.

[0069] J. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy strip after cold rolling is 18mm, and the total processing rate is 10.0%.

[0070] K. Sawing: The cold-rolled aluminum alloy sheet is sawn at the head, tail and edges during the sawing process.

[0071] L. Stretching: The cold-rolled aluminum alloy strip is stretched in the straightening process with a stretching rate of 0.7%.

[0072] M. Sawing: Using finished precision saws, the stretched sheet material is cut to length and then sawn according to the specified dimensions.

[0073] Example 4

[0074] A. Batching: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the proportions. The mass percentage proportions of each element in the 5059 aluminum alloy raw materials are as follows:

[0075]

[0076] B. Melting: The prepared aluminum alloy raw materials are added to the melting furnace and mixed evenly to melt into liquid aluminum alloy at a melting temperature of 740-770℃. Then, the melted aluminum alloy is poured into the refining furnace for refining.

[0077] C: Refining: Introduce chlorine-argon mixed gas and stir the melt to remove impurity gases from the aluminum alloy melt. The refining temperature is 730-760℃ and the refining time is 50 minutes. After refining and removing slag, let the aluminum alloy melt stand for 30 minutes.

[0078] D. Casting: Al-5Ti-1B wire refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered through a 40PPI+50PPI dual-stage plate filter. Finally, the aluminum alloy melt flows into the crystallizer for casting. The flow channel temperature is 680℃, the casting speed is 49mm / min, and the water flow rate of the double-ingot crystallizer is 2800L / min.

[0079] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace at 400℃ for 10 hours. After the ingot is held, it is taken out of the furnace and hot rolled.

[0080] F. Sawing and milling: Sawing and milling the stress-relieved ingot, removing 350mm from the ingot end, 100mm from the gate end, 16mm from the large surface milling, and 7mm from the vertical surface milling.

[0081] G. Heating: The refined aluminum alloy ingot is homogenized and heated in a pusher furnace. The homogenization and heating regime is 450℃ / 10h. After the ingot is held at the temperature, it is taken out of the furnace for hot rolling.

[0082] H. Hot rolling: 5059 alloy ingots are rolled into 8mm aluminum alloy coils using a hot rolling mill. The initial rolling temperature is 420℃, the total processing deformation is 98.7%, and the final hot rolling temperature is controlled at 230℃.

[0083] I. Cross-cutting and Stabilizing Annealing: The hot-rolled coil is cross-cut into 8*2000*8000mm sheets and then annealed at 240℃ for 4 hours.

[0084] G. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy strip after cold rolling is 7mm, and the total processing rate is 12.5%.

[0085] K. Sawing: The cold-rolled aluminum alloy sheet is sawn at the head, tail and edges during the sawing process.

[0086] L. Stretching: The cold-rolled aluminum alloy strip is stretched in the straightening process with a stretching rate of 0.3%.

[0087] M. Sawing: Using finished precision saws, the stretched sheet material is cut to length and then sawn according to the specified dimensions.

[0088] Example 5

[0089] A. Batching: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the proportions. The mass percentage proportions of each element in the 5059 aluminum alloy raw materials are as follows:

[0090]

[0091] B. Melting: The prepared aluminum alloy raw materials are added to the melting furnace and mixed evenly to melt into liquid aluminum alloy at a melting temperature of 740-770℃. Then, the melted aluminum alloy is poured into the refining furnace for refining.

[0092] C: Refining: Introduce chlorine-argon mixed gas and stir the melt to remove impurity gases from the aluminum alloy melt. The refining temperature is 730-760℃ and the refining time is 50 minutes. After refining and removing slag, let the aluminum alloy melt stand for 30 minutes.

[0093] D. Casting: Al-5Ti-1B wire refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered through a 40PPI+50PPI dual-stage plate filter. Finally, the aluminum alloy melt flows into the crystallizer for casting. The flow channel temperature is 680℃, the casting speed is 49mm / min, and the water flow rate of the double-ingot crystallizer is 2800L / min.

[0094] E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace at 400℃ for 10 hours. After the ingot is held, it is taken out of the furnace and hot rolled.

[0095] F. Sawing and milling: Sawing and milling the stress-relieved ingot, removing 350mm from the ingot end, 100mm from the gate end, 16mm from the large surface milling, and 7mm from the vertical surface milling.

[0096] G. Heating: The refined aluminum alloy ingot is homogenized and heated in a pusher furnace. The homogenization and heating regime is 450℃ / 10h. After the ingot is held at the temperature, it is taken out of the furnace for hot rolling.

[0097] H. Hot rolling: 5059 alloy ingots are rolled into 56mm aluminum alloy coils using a hot rolling mill. The initial rolling temperature is 420℃, the total processing deformation is 90.7%, and the final hot rolling temperature is controlled at 250℃.

[0098] I. Stabilization Annealing: The hot-rolled sheet is annealed at 240℃ for 4 hours.

[0099] G. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy strip after cold rolling is 50mm, and the total processing rate is 10.7%.

[0100] K. Sawing: The cold-rolled aluminum alloy sheet is sawn at the head, tail and edges during the sawing process.

[0101] L. Stretching: The cold-rolled aluminum alloy strip is stretched in the straightening process with a stretching rate of 0.8%.

[0102] M. Sawing: Using finished precision saws, the stretched sheet material is cut to length and then sawn according to the specified dimensions.

[0103] Tables 1-5 show the mechanical and corrosion properties of Examples 1-5, respectively. Mechanical properties were tested according to GB / T 16865, and corrosion properties were tested according to ASTM G66 and ASTM G67. The mechanical and corrosion properties of Examples 1-5 all meet the standards.

[0104] Comparison through sensitization tests (Table 6) Figure 1 It was found that after adding a stabilizing annealing process between the hot rolling and cold rolling processes, the product of Example 3 had better long-term corrosion resistance.

[0105] Table 1 Mechanical and corrosion properties of the plate material in Example 1

[0106]

[0107] Table 2 Mechanical and corrosion properties of the plates used in Example 2

[0108]

[0109] Table 3 Mechanical and corrosion properties of the plates used in Example 3

[0110]

[0111] Table 4 Mechanical and corrosion properties of the plate material in Example 4

[0112]

[0113] Table 5 Mechanical and corrosion properties of the plate material in Example 5

[0114]

[0115] Table 6. Weight loss due to intergranular corrosion after sensitization at 150℃ for 1-10 hours for the products of Examples 1 and 3.

[0116] serial number Not sensitized 150℃ / 1h 150℃ / 3h 150℃ / 6h 150℃ / 10h Example 1 4 5.3 11.2 16.7 27.4 Example 3 9.4 10.8 12.7 12.9 15.6

[0117] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing marine-grade 5059 aluminum alloy thick plates, characterized in that, Includes the following steps: A. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: ≤0.15%, Fe: ≤0.25%, Cu≤0.10%, Mn: 0.6-1.2%, Mg: 5.2~5.8%, Cr: ≤0.25%, Zn: 0.4-0.9%, Ti: 0.02~0.05%, Zr: 0.08-0.15%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al; B. Smelting: The prepared aluminum alloy raw materials are smelted into aluminum alloy melt, which is then poured into a refining furnace for refining. C: Refining: Pass a mixture of chlorine and argon gas into the aluminum alloy melt and stir to remove impurity gases from the aluminum alloy melt. After refining and slag removal, let the aluminum alloy melt stand for 20-40 minutes. D. Casting: Grain refiner is added to the aluminum alloy melt entering the flow channel for online refinement, and argon gas is introduced for online degassing. The degassed aluminum alloy melt is then filtered, and finally the aluminum alloy melt flows into the crystallizer for casting to obtain aluminum alloy ingots. E. Stress relief: The refined aluminum alloy ingot is heated and held in a heating furnace to obtain a stress-relieved ingot. F. Sawing and milling: Sawing and milling the stress-relieved ingot. 300-400mm is cut off at the ingot end, 100-150mm is cut off at the gate end, 10-20mm is milled on the large surface, and 5-10mm is milled on the vertical surface. G. Heating: The sawn and milled ingot is homogenized and heated in a 1:3-1:5 pusher furnace. After the ingot is held at the temperature, it is taken out of the furnace to obtain the 5059 alloy ingot to be rolled. The homogenization and heating regime in step G is: temperature 420-460℃, time 3-24h. H. Hot rolling: The 5059 alloy ingot to be rolled is rolled into 5059 aluminum alloy sheet with a thickness of 8-30mm using a hot rolling mill; the rolling parameters mentioned in step H are: the initial rolling temperature is 410-460℃, the total processing deformation is 95~98.7%, and the final hot rolling temperature is controlled at 200-250℃. A stabilizing annealing process is added between step H and step I. The annealing regime is: temperature 230-260℃, time 2-6h, to improve the long-term corrosion resistance of the product. I. Cold rolling: 5059 aluminum alloy sheet is cold rolled using a rolling mill. The thickness of the aluminum alloy sheet after cold rolling is 7-27mm, and the total cold rolling processing rate is 5-15%. J. Sawing and Stretching: The cold-rolled 5059 aluminum alloy sheet is sawn at the ends and edges during the sawing process; the sawn 5059 aluminum alloy sheet is then stretched in a stretching machine with a stretching rate of 0-3%. The stretched sheet material is cut to length and sawn according to the specified dimensions using a finished precision saw.

2. The method for preparing marine 5059 aluminum alloy thick plates according to claim 1, characterized in that, The melting temperature described in step B is 740~770℃.

3. The method for preparing marine 5059 aluminum alloy thick plate according to claim 1, characterized in that, The refining temperature in step C is 730~760℃, and the refining time is 30-60min.

4. The method for preparing marine 5059 aluminum alloy thick plate according to claim 1, characterized in that, The ratio of chlorine to argon in the chlorine-argon mixed gas in step C is 1:3 to 1:

5.

5. The method for preparing marine 5059 aluminum alloy thick plate according to claim 1, characterized in that, The grain refiner mentioned in step D is an Al-5Ti-1B alloy wire refiner; the filtration is achieved through a 40PPI+50PPI dual-stage plate filter; the casting process involves a flow channel temperature of 680-700℃, a casting speed of 40-50mm / min, and a crystallizer water flow rate of 1500-3000L / min.

6. The method for preparing marine 5059 aluminum alloy thick plate according to claim 1, characterized in that, The heating and heat preservation process described in step E is as follows: temperature 400-460℃, time 3-24h.

7. A marine-grade 5059 aluminum alloy thick plate, prepared by the method described in any one of claims 1-6, characterized in that, The aluminum alloy thick plate comprises, by weight percentage: Si: ≤0.15%, Fe: ≤0.25%, Cu: ≤0.10%, Mn: 0.6-1.2%, Mg: 5.2-5.8%, Cr: ≤0.25%, Zn: 0.4-0.9%, Ti: 0.02-0.05%, Zr: 0.08-0.15%, individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al.

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