High-strength corrosion-resistant 5059 alloy plate for ships and preparation method thereof

Abstract

The application provides a novel high-strength corrosion-resistant 5059 alloy plate for ships and a preparation method thereof, and is characterized in that the 5059 alloy is used as a base alloy after optimization of Fe, Mn, Cr and Zr elements, double-stage heating treatment is performed before hot rolling of the alloy, 5-pass large-rolling reduction is adopted before hot rolling, 3-pass small-rolling reduction is adopted after cold rolling, and the heating rate and the cooling rate of the stabilization annealing are controlled, so that the high solid solution strengthening is ensured, the Mg2Al3 phase morphology, quantity and distribution are controlled, the technical problem that the Mg2Al3 phase is easily precipitated in a continuous network along the crystal, resulting in the decrease of the corrosion resistance of the high-magnesium 5059 aluminum alloy is solved, the synergistic control of the mechanical properties and the corrosion resistance of the alloy is realized, and the novel high-strength corrosion-resistant 5059 alloy plate for ships is prepared.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal materials technology, and particularly relates to a high-strength and corrosion-resistant 5059 alloy plate for ships and its preparation method. Background Technology

[0002] In recent years, alloys such as 5083 / 5086 / 5383 have been widely used in the manufacture of ship structural components. However, 5083 / 5086 / 5383 only possess moderate strength and corrosion resistance, which can only meet the requirements of general ships. AA5059 alloy plate, jointly developed by Corus of Germany and Alcoa of the United States, is beginning to emerge in shipbuilding as a new generation of high-strength, corrosion-resistant marine alloy. Its strength and corrosion resistance are significantly superior to 5083 / 5383 aluminum alloys, making it a promising new generation of marine alloy product.

[0003] AA5059 alloy is a Zr-containing alloy. Under conditions of large-scale industrial production, due to the complexity of the process, enterprises' understanding of the effects of Zr and other microalloying elements is still insufficient. The performance improvement effect of Zr and other microalloying elements in the alloy has not yet achieved the expected results, and there is a gap between theory and practice. The relevant reasons are not yet clear, and further research is needed on the mechanism of action of microalloying elements to improve related homogenization processes. Furthermore, due to a lack of systematic research and relevant production experience, the influence of key process parameters such as hot rolling, cold rolling, and stabilization annealing on intergranular corrosion resistance in the AA5059 plate preparation process is also unclear. Summary of the Invention

[0004] The purpose of this invention is to design processes such as 5059 aluminum alloy ingot casting, homogenization heat treatment, temperature-controlled rolling deformation, cold deformation, and stabilization heat treatment, based on 5059 alloy with optimized Fe, Mn, Cr, and Zr elements, to determine the optimal process window for the production of high-magnesium 5059 alloy plates under micro-alloying conditions, and to propose a method for preparing high-strength and corrosion-resistant 5059 aluminum alloy plates that can achieve integrated and synergistic regulation of strength and corrosion resistance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-strength, corrosion-resistant 5059 alloy plate for shipbuilding and its preparation method are disclosed. The mass percentages of each component are as follows: Mg 5.10%–5.95%, Zn 0.50%–0.65%, Cu 0–0.05%, Zr 0.10%–0.25%, Fe ≤0.10%, Si ≤0.05%, Mn 0.70%–1.00%, Cr ≤0.02%, Ni ≤0.01%, Ti 0.05%–0.07%, with the balance being Al and unavoidable impurities. Each unavoidable impurity element is less than 0.03%, and the total amount of unavoidable impurity elements is less than 0.1%.

[0007] As a preferred embodiment, the method for preparing high-strength and corrosion-resistant 5059 alloy sheet includes the following steps:

[0008] (1) Casting: According to the elemental composition ratio of high strength and corrosion resistant 5059 alloy plate, the raw materials and remelted aluminum ingots are placed in a 730℃ melting furnace for melting, composition adjustment, slag removal, refining, and degassing. After degassing, they are cast into flat ingots.

[0009] (2) Homogenization treatment: The flat ingot is pushed into the trolley furnace and subjected to single-stage homogenization treatment. After homogenization treatment, it is discharged from the furnace and cooled naturally to obtain the homogenized flat ingot.

[0010] (3) Milling: Mill the surface of the flat ingot after homogenization treatment to obtain a bright ingot without oxide layer;

[0011] (4) Hot rolling: The ingot is preheated in two stages and then hot rolled. The first 5 passes of hot rolling are hot roughing, and the total reduction rate of hot roughing is 35%-40%. The reduction of each intermediate pass is 5mm-6mm / pass, and the reduction of the last 3 passes is controlled at 6mm-9mm / pass. The target thickness of hot rolling is 6.0mm-19.0mm, and hot rolled plate is obtained. The large reduction rate of the first 5 passes of hot rolling will generate a large deformation heat to compensate for the heat loss of the alloy during the rolling process, which can make the matrix grain structure more uniform after homogenization treatment.

[0012] (5) Cold rolling: The hot-rolled plate is cold-rolled at least three times, and the total deformation of the hot-rolled plate is controlled at 30%-80% to obtain the cold-rolled plate;

[0013] (6) Stabilization annealing: The cold-rolled sheet is stabilized and annealed in a heat treatment furnace to obtain alloy sheet;

[0014] (7) Fixed-length packaging: The 5059 alloy plates after stabilization and annealing are cut to length and packaged.

[0015] Preferably, in the homogenization process, the flat ingots are heated to 551-559°C in the furnace at a heating rate of 20-30°C / h, and then held at that temperature for 6-8 hours.

[0016] As a preferred option, in the hot rolling process, a two-stage preheating is performed before hot rolling: first, a first-stage preheating is performed at 420-450℃ and held for 4-6 hours; then, the temperature is raised to 490-510℃ and held for 2-5 hours, and after the holding period, the product is taken out of the furnace and rolled.

[0017] Preferably, in the hot rolling process, the initial rolling temperature is 450–490℃, and the final rolling temperature is controlled at 325–335℃.

[0018] Preferably, in the cold rolling process, an intermediate annealing treatment is performed after the first and second cold rolling processes, with the intermediate annealing conditions being 275–295°C for 1–2 hours.

[0019] As a preferred option, in the cold rolling process, the three cold rolling passes and subsequent cold rolling are all rolled with small reductions, controlling the reduction of each cold rolling pass to be between 0.5mm and 3.0mm; the target thickness of the cold rolling is 3.0mm to 4.5mm; and the three small reduction rolling passes after cold rolling are performed while meeting the total cold rolling reduction rate, which can accurately control the plate shape and thickness indicators.

[0020] Preferably, in the stabilization annealing step, the cold-rolled sheet is heated to 90-145°C at a heating rate of less than 30°C / h and held for 2-3 hours; after the stabilization annealing is completed, it is cooled at a cooling rate of 90-130°C / h; the purpose of 90-130°C / h is to ensure that the Mg2Al3 phase in the 5059 alloy matrix does not precipitate along or at a small proportion at the grain boundaries in a continuous network.

[0021] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0022] 1. The innovation of the invention lies in using the 5059 alloy with optimized Fe, Mn, Cr and Zr elements as the base alloy, subjecting the alloy to a two-stage heating treatment before hot rolling, and employing five passes of high reduction rate rolling before hot rolling and three passes of low reduction rate rolling after cold rolling. At the same time, the heating and cooling rates of the stabilization annealing are controlled to ensure high solid solution strengthening while regulating the morphology, quantity and distribution of the Mg2Al3 phase. This solves the technical problem of the easy intergranular continuous network precipitation of the Mg2Al3 phase in high magnesium 5059 aluminum alloy, which leads to a decrease in its corrosion resistance. It achieves synergistic control of alloy mechanics and corrosion resistance, and prepares high-strength and corrosion-resistant 5059 alloy plates for shipbuilding.

[0023] 2. The 5059 alloy plate for shipbuilding prepared by this invention undergoes processes such as melting and casting, homogenization heat treatment, milling, double-stage heating, hot rolling, cold rolling, intermediate annealing, cold rolling (with small reduction), stabilization annealing, and fixed-length packaging. The resulting 5059 ship plate has a longitudinal tensile strength of 382.3-397.3 MPa, a yield strength of 224.9-238.2 MPa, an elongation of 17.2-18.3%, a spalling corrosion (PA), and an intergranular corrosion mass loss of 9.6-14.0 mg / cm2.

[0024] Furthermore, the high-strength and corrosion-resistant 5059 alloy sheet for ships and its preparation method of the present invention can effectively solve the problem of delamination during rolling of high-magnesium 5059 alloy sheets due to high Mg content; and under the condition of ensuring excellent strength and corrosion resistance of alloy sheets, it can significantly improve the problems of warping and cracking of sheets during rolling, thereby increasing the yield of products. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a photograph of the aluminum alloy ingot after milling in Example 1;

[0027] Figure 2 Image of the microstructure of the aluminum alloy ingot in Example 1 (polarized light).

[0028] Figure 3 The image shows the polarized microstructure of the aluminum alloy ingot after homogenization heat treatment in Example 1.

[0029] Figure 4 Photograph of aluminum alloy hot-rolled sheet material in Example 1;

[0030] Figure 5 The image shows the polarized microstructure of the finished aluminum alloy sheet from Example 1. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0032] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0033] Example 1, such as Figures 1-5 As shown, a high-strength, corrosion-resistant 5059 alloy plate for shipbuilding and its preparation method are described below:

[0034] The composition of the 5059 aluminum alloy used includes: Mg 5.6957%, Zn 0.5687%, Cu 0.0004%, Zr 0.1521%, Fe 0.0972%, Si 0.0208%, Mn 0.7830%, Cr 0.0033%, Ni 0.0010%, Ti 0.0596%, with the balance being Al and unavoidable impurities. Each unavoidable impurity element is less than 0.03%, and the total amount of unavoidable impurity elements is less than 0.1%.

[0035] The preparation method is as follows:

[0036] (1) Casting: According to the above raw material ratio, the remelted aluminum ingots are placed in a 730℃ melting furnace for melting, composition adjustment, slag removal, refining, and degassing. After degassing, they are cast into flat ingots.

[0037] (2) Homogenization treatment: The flat ingot is pushed into the trolley furnace and a single-stage homogenization treatment is performed on the flat ingot: the flat ingot is heated to 551.0℃ with the furnace at a heating rate of 20℃ / h, and then held for 8h. After the homogenization heat treatment is completed, it is taken out of the furnace and cooled naturally to obtain the homogenized flat ingot.

[0038] (3) Milling: Mill the surface of the flat ingot after homogenization treatment to obtain a bright ingot without oxide layer;

[0039] (4) Hot rolling: The ingot is subjected to a two-stage preheating treatment before hot rolling in a bogie furnace: first, the temperature is heated to 425℃ and held for 6 hours. After the first stage of preheating, the temperature is raised to 495℃ at a rate of 40℃ / h and held for 5 hours. The total preheating treatment time shall not exceed 12 hours.

[0040] After the preheating treatment, hot rolling begins at a starting temperature of 468℃. The hot rolling process consists of 16 passes. The first 5 passes reduce the thickness from 127.5mm to 78.5mm. The reduction in the intermediate passes is controlled at 5mm / pass, and the reduction in the last 3 passes is controlled at 7mm / pass, ultimately yielding a 17.5mm hot-rolled plate. Surface lubrication is achieved using emulsion throughout the hot rolling process.

[0041] (5) Cold rolling: The hot-rolled plate is cold-rolled. The reduction of the first and second cold rolling is 3mm / pass. After the second cold rolling, the intermediate annealing treatment is carried out at 275℃ for 2h. After the intermediate annealing treatment, the third cold rolling and subsequent cold rolling treatment are carried out. The reduction of the cold rolling in this stage is 2mm / pass. The final cold-rolled plate is 3.5mm.

[0042] (6) Stabilization annealing: The cold-rolled plate is subjected to stabilization annealing treatment, wherein the cold-rolled plate is heated to 140℃ in the furnace at a heating rate of 30℃ / h and held for 2h; after the end, the fan is used to cool the plate. The actual cooling rate of the plate measured by the thermocouple is 90.3℃ / h, ensuring that the Mg2Al3 phase in the 5059 alloy matrix does not precipitate along or in a small proportion at the grain boundaries in a continuous network.

[0043] Example 2: A high-strength, corrosion-resistant 5059 alloy plate for ships and its preparation method:

[0044] The composition of the 5059 aluminum alloy used includes: Mg 5.8705%, Zn 0.5644%, Cu 0.0004%, Zr 0.1416%, Fe 0.0976%, Si 0.0188%, Mn 0.7675%, Cr 0.0126%, Ni 0.0026%, Ti 0.0606%, with the balance being Al and unavoidable impurities. Each unavoidable impurity element is less than 0.03%, and the total amount of unavoidable impurity elements is less than 0.1%.

[0045] The preparation method is as follows:

[0046] (1) Casting: According to the above raw material ratio, the remelted aluminum ingots are placed in a 730℃ melting furnace for melting, composition adjustment, slag removal, refining, and degassing. After degassing, they are cast into flat ingots.

[0047] (2) Homogenization treatment: The flat ingot is pushed into the trolley furnace and a single-stage homogenization treatment is performed on the flat ingot: the flat ingot is heated to 555.0℃ with the furnace at a heating rate of 25℃ / h, and then held for 6h. After the homogenization heat treatment is completed, it is taken out of the furnace and cooled naturally to obtain the homogenized flat ingot.

[0048] (3) Milling: Mill the surface of the flat ingot after homogenization treatment to obtain a bright ingot without oxide layer;

[0049] (4) Hot rolling: The ingot is subjected to a two-stage preheating treatment before hot rolling in a bogie furnace: first, the temperature is heated to 440℃ and held for 5 hours. After the first stage of preheating, the temperature is raised to 500℃ at a rate of 40℃ / h and held for 4 hours. The total preheating treatment time shall not exceed 12 hours.

[0050] After the preheating treatment, hot rolling begins at a starting temperature of 476℃. The hot rolling process consists of 15 passes. The first 5 passes reduce the thickness from 127.5mm to 75.6mm. The reduction in the intermediate passes is controlled at 6mm / pass, and the reduction in the last 3 passes is controlled at 8mm / pass, ultimately yielding a 9.6mm hot-rolled plate. Surface lubrication is achieved using emulsion throughout the hot rolling process.

[0051] (5) Cold rolling: The hot-rolled plate is cold-rolled. The reduction of the first and second cold rolling is 2.5 mm / pass. After the second cold rolling, the plate is subjected to intermediate annealing at 285℃ for 1.5 h. After the intermediate annealing, the plate is subjected to third cold rolling and subsequent cold rolling. The reduction of the cold rolling in this stage is 1.6 mm / pass. The final cold-rolled plate is 3.0 mm.

[0052] (6) Stabilization annealing: The cold-rolled plate is subjected to stabilization annealing treatment, wherein the cold-rolled plate is heated to 135℃ in the furnace at a heating rate of 25℃ / h and held for 2h; after the end, the fan is used to cool the plate. The actual cooling rate of the plate measured by the thermocouple is 101.5℃ / h, to ensure that the Mg2Al3 phase in the 5059 alloy matrix does not precipitate along or in a small proportion at the grain boundaries in a continuous network.

[0053] Example 3: A high-strength, corrosion-resistant 5059 alloy plate for ships and its preparation method:

[0054] The composition of the 5059 aluminum alloy used includes: Mg 5.9455%, Zn 0.6339%, Cu 0.0129%, Zr 0.1268%, Fe 0.0898%, Si 0.0404%, Mn 0.8488%, Cr 0.0033%, Ni 0.0026%, Ti 0.0632%, with the balance being Al and unavoidable impurities. Each unavoidable impurity element is less than 0.03%, and the total amount of unavoidable impurity elements is less than 0.1%.

[0055] The preparation method is as follows:

[0056] (1) Casting: According to the above raw material ratio, the remelted aluminum ingots are placed in a 730℃ melting furnace for melting, composition adjustment, slag removal, refining, and degassing. After degassing, they are cast into flat ingots.

[0057] (2) Homogenization treatment: The flat ingot is pushed into the trolley furnace and a single-stage homogenization treatment is performed on the flat ingot: the flat ingot is heated to 558.0℃ with the furnace at a heating rate of 30℃ / h, and then held for 6h. After the homogenization heat treatment is completed, it is taken out of the furnace and cooled naturally to obtain the homogenized flat ingot.

[0058] (3) Milling: Mill the surface of the flat ingot after homogenization treatment to obtain a bright ingot without oxide layer;

[0059] (4) Hot rolling: The ingot is subjected to a two-stage preheating treatment before hot rolling in a bogie furnace: first, the temperature is heated to 450℃ and held for 4 hours. After the first stage of preheating, the temperature is raised to 510℃ at a rate of 40℃ / h and held for 3 hours. The total preheating treatment time shall not exceed 12 hours.

[0060] After the preheating treatment, hot rolling begins at an initial rolling temperature of 489℃. The hot rolling process consists of 17 passes. The first 5 passes reduce the thickness from 127.5mm to 79.3mm. The reduction in the intermediate passes is controlled at 5mm / pass, and the reduction in the last 3 passes is controlled at 9mm / pass, ultimately yielding a 7.3mm hot-rolled plate. Surface lubrication is achieved using emulsion throughout the hot rolling process.

[0061] (5) Cold rolling: The hot-rolled plate is cold-rolled. The reduction of the first and second cold rolling is 1.5 mm / pass. After the second cold rolling, the intermediate annealing treatment is carried out at 295℃ for 1 hour. After the intermediate annealing treatment, the third cold rolling and subsequent cold rolling treatment are carried out. The reduction of the cold rolling in this stage is 1.3 mm / pass. The final cold-rolled plate is 3.0 mm.

[0062] (6) Stabilization annealing: The cold-rolled plate is subjected to stabilization annealing treatment, wherein the cold-rolled plate is heated to 120°C in the furnace at a heating rate of 20°C / h and held for 3h; after the end, the fan is used to cool the plate. The actual cooling rate of the plate measured by the thermocouple is 125.8°C / h, ensuring that the Mg2Al3 phase in the 5059 alloy matrix does not precipitate along or in a small proportion at the grain boundaries in a continuous network.

[0063] After sampling and cutting the plates from Examples 1, 2, and 3 to length, mechanical properties and peeling corrosion properties were tested. The test results are shown in Table 1.

[0064] Table 1. Test results of mechanical properties and exfoliation corrosion properties of the plates from Examples 1 to 3.

[0065]

[0066] The high-strength and corrosion-resistant 5059 alloy plate for ships prepared in Examples 1 to 3 of this invention and the preparation method thereof yield 5059 ship plates with tensile strength of 382.3-397.3 MPa, yield strength of 224.9-238.2 MPa, elongation of 17.2-18.3%, spalling corrosion (PA), and intergranular corrosion mass loss of 9.6-14.0 mg / cm2.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength corrosion-resistant 5059 alloy plate for ships, characterized in that the high-strength corrosion-resistant 5059 alloy plate comprises the following components in percentage by mass: Mg 5.10%-5.95%, Zn 0.50%-0.65%, Cu 0-0.05%, Zr 0.10%-0.25%, Fe≤0.10%, Si≤0.05%, Mn 0.70%-1.00%, Cr≤0.02%, Ni≤0.01%, Ti 0.05%-0.07%, and the balance being Al and unavoidable impurities, each of the unavoidable impurities being less than 0.03%, and the total amount of the unavoidable impurities being less than 0.1%. The method for preparing the high-strength corrosion-resistant 5059 alloy plate comprises the following steps: (1) Ingot casting: raw materials and remelted aluminum ingots are placed in a 730℃ smelting furnace to perform smelting, composition adjustment, slagging, refining, and degassing, and then the ingots are cast into flat ingots after degassing; (2) Homogenization treatment: the flat ingots are pushed into a trolley furnace, and single-stage homogenization treatment is performed on the flat ingots, and the flat ingots are naturally cooled after being taken out of the furnace to obtain flat ingots after homogenization treatment; (3) Milling: the flat ingots after homogenization treatment are milled to obtain bright ingots without an oxidation layer; (4) Hot rolling: the ingots are preheated in two stages, and then hot rolling is performed, the first five passes of hot rolling are hot rough rolling, the total reduction rate of the hot rough rolling is 35%-40%, the reduction amount of each intermediate pass is 5mm-6mm / pass, and the reduction amount of the last three passes is controlled to be 6mm-9mm / pass, the target thickness of the hot rolling is 6.0mm-19.0mm, and hot rolled plates are obtained; (5) Cold rolling: the hot rolled plates are cold rolled for at least three times, and the total deformation amount of the hot rolled plates is controlled to be 30%-80%, and cold rolled plates are obtained; (6) Stabilization annealing: the cold rolled plates are subjected to stabilization annealing in a heat treatment furnace to obtain alloy plates; (7) Fixed-size packaging: the 5059 alloy plates after stabilization annealing are sawn and packaged; In the hot rolling step, two-stage preheating is performed before hot rolling: first-stage preheating is performed at 420-450℃ for 4-6h, and then the temperature is raised to 490-510℃ for 2-5h, and the hot rolling is performed after the end of the preheating; In the stabilization annealing step, the cold rolled plates are heated at a heating rate lower than 30℃ / h to 90-145℃, and the temperature is maintained for 2-3h, and the cold rolled plates are cooled at a cooling rate of 90-130℃ / h after the end of the stabilization annealing; In the cold rolling step, small reduction amount rolling is performed for the three times of cold rolling and subsequent cold rolling, and the reduction amount of each pass is controlled to be 0.5mm-3.0mm, and the target thickness of the cold rolling is 3.0mm-4.5mm. In the homogenization treatment step, the flat ingots are heated to 551-559℃ at a heating rate of 20-30℃ / h, and then the temperature is maintained for 6-8h.

2. The method for preparing a high-strength and corrosion-resistant 5059 alloy plate for a naval vessel according to claim 1, characterized in that, In the hot rolling step, the opening rolling temperature is 450-490℃, and the final rolling temperature is controlled to be 325-335℃.

3. The method of claim 1, wherein the method is characterized by the steps of: In the cold rolling step, intermediate annealing is performed after the end of the second cold rolling, and the intermediate annealing conditions are 275-295℃ for 1-2h.

4. The method of claim 1, wherein the method is characterized by the steps of: ​

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