Aluminum alloy flat cast ingot for corrosion-resistant plate of ship and boat and manufacturing method of aluminum alloy flat cast ingot

Abstract

The invention discloses a ship corrosion-resistant plate aluminum alloy flat cast ingot and a manufacturing method thereof, and belongs to the field of alloy cast ingot manufacturing. The problem that the yield of cast ingots is low due to the fact that cracks are prone to being generated in the existing aluminum alloy flat cast ingot casting process or cracks are prone to being generated in the follow-up rolling process is solved. The material is composed of Si, Fe, Mg, Mn, Zr, Er, Zn, Cu, Ti, impurities and the balance Al. The method comprises the following steps: 1, weighing smelting raw materials; 2, smelting the smelting raw materials in sequence; and thirdly, the alloy melt is put into a natural gas heat preservation furnace to be cast, and the aluminum alloy flat cast ingot is obtained. The existing magnesium cage and the pure magnesium ingot are adopted, the burning loss of the magnesium ingot and the local temperature drop of the metal melt are reduced, the aluminum-zirconium intermediate alloy is added, the crusting thickness of the cast ingot is increased, the formation of vertical folds on the surface of the cast ingot is reduced, the cracking tendency of the cast ingot is reduced, and the production efficiency is improved by combining the adjustment of casting process parameters and the fine operation in the production process. And the yield of the aluminum alloy flat cast ingot reaches 80%.

Description

Technical Field

[0001] The invention belongs to the field of alloy ingot manufacturing, and in particular relates to an aluminum alloy flat ingot for corrosion-resistant plates of ships and boats and a manufacturing method thereof. Background Art

[0002] Marine aluminum alloys can be divided into deformed aluminum alloys and cast aluminum alloys according to different manufacturing processes. Corrosion resistance is an important performance of marine aluminum alloys. The corrosion resistance of alloys directly affects the reliability and service life of ships. Since marine aluminum alloys have special requirements for strength, corrosion resistance, weldability, etc., marine aluminum alloys are mostly aluminum-magnesium alloys, aluminum-magnesium-silicon alloys and aluminum-zinc-magnesium alloys. They have low density, high tensile strength, strong resistance to seawater and marine climate corrosion, and good welding performance. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that cracks are easily generated during the casting process of the existing aluminum alloy flat ingots or during the subsequent rolling process, thereby resulting in a low ingot yield, and to provide an aluminum alloy flat ingot for corrosion-resistant plates for boats and a manufacturing method thereof.

[0004] A corrosion-resistant plate aluminum alloy flat ingot for ships and boats, which comprises Si<0.25%, Fe<0.25%, Mg: 5.30%-6.30%, Mn: 0.40%-1.00%, Zr: 0.05%-0.15%, Er: 0.10%-0.30%, Zn: 0.30%-0.90%, Cu<0.1%, Ti<0.25%, single impurity<0.05%, total impurities≤0.15%, and the balance is Al.

[0005] The above-mentioned method for manufacturing the aluminum alloy flat ingot for corrosion-resistant plate material for ships and boats is carried out according to the following steps:

[0006] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 5.30% ~ 6.30%, Mn: 0.40% ~ 1.00%, Zr: 0.05% ~ 0.15%, Er: 0.10% ~ 0.30%, Zn: 0.30% ~ 0.90%, Cu < 0.1%, Ti < 0.25%, single impurity < 0.05%, total impurity ≤ 0.15%, the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloy, aluminum-zirconium master alloy and aluminum-erbium master alloy as smelting raw materials;

[0007] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0008] 3. The above aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 45mm / min-55mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 35-45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 80-90 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 5500 mm-6500 mm, thus completing the manufacturing.

[0009] Furthermore, the purity of the pure aluminum ingot in step 1 is 99.7%.

[0010] Furthermore, the amount of the No. 2 covering agent in step 2 is 0.4% to 0.6% of the total mass of the metal in the smelting furnace.

[0011] Furthermore, the covering agent No. 2 in step 2 is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in mass percentage.

[0012] Furthermore, the introduction rate of the argon-chlorine mixed gas in step 2 is 0.15-0.20 m 3 / min.

[0013] Furthermore, the volume ratio of argon to chlorine in the argon-chlorine mixed gas in step 2 is 1:1.

[0014] Advantages of the present invention:

[0015] The present invention adopts the existing magnesium cage and pure magnesium ingot to reduce the burning loss of magnesium ingot and the local temperature drop of metal melt, adds aluminum-zirconium master alloy to increase the crust thickness of the ingot, reduces the formation of vertical wrinkles on the surface of the ingot, and reduces the tendency of ingot cracks. Combined with the adjustment of casting process parameters and fine operation in the production process, the yield rate of aluminum alloy flat ingots reaches 80%.

[0016] The aluminum alloy flat ingot prepared by the present invention has a thickness of 420 mm, a width of 1620 mm, and a length of 5500 mm to 6500 mm, has no defects such as cracks, slag inclusions, coarse grains, etc. on its surface, has a high ingot yield, and is suitable for corrosion-resistant plates for ships and boats.

[0017] The invention is suitable for manufacturing aluminum alloy flat ingots for corrosion-resistant plates of ships and boats. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a physical picture of the aluminum alloy flat ingot in Example 4. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0020] Specific implementation method one: This implementation method is a flat ingot of aluminum alloy for corrosion-resistant plate materials for ships and boats, which is composed of Si<0.25%, Fe<0.25%, Mg: 5.30%~6.30%, Mn: 0.40%~1.00%, Zr: 0.05%~0.15%, Er: 0.10%~0.30%, Zn: 0.30%~0.90%, Cu<0.1%, Ti<0.25%, single impurity<0.05%, total impurities≤0.15%, and the balance is Al.

[0021] Specific embodiment 2: This embodiment is different from the specific embodiment 1 in that it is composed of Si<0.25%, Fe<0.25%, Mg: 6.0%, Mn: 0.70%, Zr: 0.11%, Er: 0.18%, Zn: 0.80%, Cu<0.1%, Ti<0.25%, single impurity<0.05%, total impurity≤0.15%, and the balance is Al. Others are the same as the specific embodiment 1.

[0022] Specific implementation method three: This implementation method is a method for manufacturing a flat ingot of aluminum alloy for corrosion-resistant plates for ships and boats, which is carried out according to the following steps:

[0023] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 5.30% ~ 6.30%, Mn: 0.40% ~ 1.00%, Zr: 0.05% ~ 0.15%, Er: 0.10% ~ 0.30%, Zn: 0.30% ~ 0.90%, Cu < 0.1%, Ti < 0.25%, single impurity < 0.05%, total impurity ≤ 0.15%, the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloy, aluminum-zirconium master alloy and aluminum-erbium master alloy as smelting raw materials;

[0024] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0025] 3. The above aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 45mm / min-55mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 35-45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 80-90 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 5500 mm-6500 mm, thus completing the manufacturing.

[0026] Specific implementation method 4: This implementation method is different from specific implementation method 3 in that the purity of the pure aluminum ingot in step 1 is 99.7%. Other steps and parameters are the same as those in specific implementation method 3.

[0027] Specific implementation method 5: This implementation method is different from specific implementation method 3 in that the amount of the No. 2 covering agent in step 2 is 0.4% to 0.6% of the total mass of the metal in the smelting furnace. Other steps and parameters are the same as those in specific implementation method 3.

[0028] Specific embodiment 6: This embodiment is different from specific embodiment 3 in that the No. 2 covering agent in step 2 is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 by mass percentage. Other steps and parameters are the same as those in specific embodiment 3.

[0029] Specific embodiment 7: This embodiment is different from specific embodiment 3 in that the introduction rate of the argon-chlorine mixed gas in step 2 is 0.15-0.20 m 3 / min. Other steps and parameters are the same as those in the third specific implementation mode.

[0030] Specific embodiment eight: This embodiment differs from specific embodiment three in that the volume ratio of argon gas to chlorine gas in the argon-chlorine mixed gas in step two is 1:1. Other steps and parameters are the same as those in specific embodiment three.

[0031] Specific embodiment 9: This embodiment is different from specific embodiment 3 in that in step 3, the casting speed is 48 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45m 3 / h, and semi-continuous casting is carried out under the conditions of the crystallizer metal liquid level being 85mm. Other steps and parameters are the same as those in the third specific implementation mode.

[0032] Specific embodiment 10: This embodiment is different from specific embodiment 3 in that the casting speed in step 3 is 50 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45 m 3 / h, and semi-continuous casting is carried out under the condition that the metal liquid level in the crystallizer is 90mm. Other steps and parameters are the same as those in the third specific implementation method.

[0033] The beneficial effects of the present invention are verified by the following examples:

[0034] Embodiment 1:

[0035] A method for manufacturing a flat ingot of aluminum alloy for corrosion-resistant plates for ships and boats, which is carried out according to the following steps:

[0036] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 5.5%, Mn: 0.6%, Zr: 0.10%, Er: 0.20%, Zn: 0.40%, Cu < 0.1%, Ti < 0.25%, individual impurities < 0.05%, total impurities ≤ 0.15%, and the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloys, aluminum-zirconium master alloys, and aluminum-erbium master alloys as smelting raw materials;

[0037] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0038] 3. The above aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 45mm / min-55mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 40m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 80 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 5500 mm, thus completing the manufacturing.

[0039] The purity of the pure aluminum ingot in step 1 of this embodiment is 99.7%.

[0040] The amount of the No. 2 covering agent used in step 2 of this embodiment is 0.5% of the total mass of the metal in the smelting furnace.

[0041] The No. 2 covering agent described in step 2 of this embodiment is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in terms of mass percentage.

[0042] The introduction rate of the argon-chlorine mixed gas in step 2 of this embodiment is 0.20 m 3 / min.

[0043] In step 2 of this embodiment, the volume ratio of argon gas to chlorine gas in the argon-chlorine mixed gas is 1:1.

[0044] In this embodiment, the aluminum alloy flat ingot has no defects such as cracks, slag inclusions, coarse grains, etc. on the surface, and the yield rate reaches 67%, which is suitable for the manufacture of corrosion-resistant plates for ships and boats.

[0045] Embodiment 2:

[0046] A method for manufacturing a flat ingot of aluminum alloy for corrosion-resistant plates for ships and boats, which is carried out according to the following steps:

[0047] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 5.80%, Mn: 0.70%, Zr: 0.12%, Er: 0.20%, Zn: 0.60%, Cu < 0.1%, Ti < 0.25%, individual impurities < 0.05%, total impurities ≤ 0.15%, and the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloys, aluminum-zirconium master alloys, and aluminum-erbium master alloys as smelting raw materials;

[0048] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0049] 3. The aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 48 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 85 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 5700 mm, thus completing the manufacturing.

[0050] The purity of the pure aluminum ingot in step 1 of this embodiment is 99.7%.

[0051] The amount of the No. 2 covering agent used in step 2 of this embodiment is 0.5% of the total mass of the metal in the smelting furnace.

[0052] The No. 2 covering agent described in step 2 of this embodiment is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in terms of mass percentage.

[0053] The introduction rate of the argon-chlorine mixed gas in step 2 of this embodiment is 0.20 m 3 / min.

[0054] In step 2 of this embodiment, the volume ratio of argon gas to chlorine gas in the argon-chlorine mixed gas is 1:1.

[0055] In this embodiment, the aluminum alloy flat ingot has no defects such as cracks, slag inclusions, coarse grains, etc. on the surface, and the yield rate reaches 75%, which is suitable for the manufacture of corrosion-resistant plates for ships and boats.

[0056] Embodiment 3:

[0057] A method for manufacturing a flat ingot of aluminum alloy for corrosion-resistant plates for ships and boats, which is carried out according to the following steps:

[0058] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 6.30%, Mn: 0.8%, Zr: 0.13%, Er: 0.25%, Zn: 0.75%, Cu < 0.1%, Ti < 0.25%, individual impurities < 0.05%, total impurities ≤ 0.15%, and the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloys, aluminum-zirconium master alloys, and aluminum-erbium master alloys as smelting raw materials;

[0059] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0060] 3. The aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 52 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 90 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 6000 mm, thus completing the manufacturing.

[0061] The purity of the pure aluminum ingot in step 1 of this embodiment is 99.7%.

[0062] The amount of the No. 2 covering agent used in step 2 of this embodiment is 0.5% of the total mass of the metal in the smelting furnace.

[0063] The No. 2 covering agent described in step 2 of this embodiment is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in terms of mass percentage.

[0064] The introduction rate of the argon-chlorine mixed gas in step 2 of this embodiment is 0.20 m 3 / min.

[0065] In step 2 of this embodiment, the volume ratio of argon gas to chlorine gas in the argon-chlorine mixed gas is 1:1.

[0066] In this embodiment, the aluminum alloy flat ingot has no defects such as cracks, slag inclusions, coarse grains, etc. on the surface, and the yield rate reaches 70%, which is suitable for the manufacture of corrosion-resistant plates for ships and boats.

[0067] Embodiment 4:

[0068] A method for manufacturing a flat ingot of aluminum alloy for corrosion-resistant plates for ships and boats, which is carried out according to the following steps:

[0069] 1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 6.0%, Mn: 0.70%, Zr: 0.11%, Er: 0.18%, Zn: 0.80%, Cu < 0.1%, Ti < 0.25%, individual impurities < 0.05%, total impurities ≤ 0.15%, and the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloys, aluminum-zirconium master alloys, and aluminum-erbium master alloys as smelting raw materials;

[0070] 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt;

[0071] 3. The aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 48 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 85 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 6500 mm, thus completing the manufacturing.

[0072] The purity of the pure aluminum ingot in step 1 of this embodiment is 99.7%.

[0073] The amount of the No. 2 covering agent used in step 2 of this embodiment is 0.5% of the total mass of the metal in the smelting furnace.

[0074] The No. 2 covering agent described in step 2 of this embodiment is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in terms of mass percentage.

[0075] The introduction rate of the argon-chlorine mixed gas in step 2 of this embodiment is 0.20 m 3 / min.

[0076] In step 2 of this embodiment, the volume ratio of argon gas to chlorine gas in the argon-chlorine mixed gas is 1:1.

[0077] In this embodiment, the aluminum alloy flat ingot has no defects such as cracks, slag inclusions, coarse grains, etc. on the surface, and the yield rate reaches 80%. Figure 1The aluminum alloy flat ingot shown is well formed and suitable for the manufacture of corrosion-resistant plates for ships and boats.

Claims

1. A flat ingot of aluminum alloy for corrosion-resistant plate material for ships and boats, characterized in that The composition by weight percentage is Si<0.25%, Fe<0.25%, Mg: 5.30%~6.30%, Mn: 0.40~1.00%, Zr: 0.05%~0.15%, Er: 0.10%~0.30%, Zn: 0.30%~0.90%, Cu<0.1%, Ti<0.25%, individual impurities<0.05%, total impurities≤0.15%, and the balance is Al.

2. The aluminum alloy flat ingot for corrosion-resistant plate material for ships and boats according to claim 1, characterized in that Its composition by weight percentage is Si<0.25%, Fe<0.25%, Mg: 6.0%, Mn: 0.70%, Zr: 0.11%, Er: 0.18%, Zn: 0.80%, Cu<0.1%, Ti<0.25%, individual impurities<0.05%, total impurities ≤0.15%, and the balance is Al.

3. A method for producing a corrosion-resistant aluminum alloy flat ingot for shipbuilding as claimed in claim 1, characterized in that It proceeds as follows:

1. Weighing materials: According to the weight percentage composition, Si < 0.25%, Fe < 0.25%, Mg: 5.30% ~ 6.30%, Mn: 0.40% ~ 1.00%, Zr: 0.05% ~ 0.15%, Er: 0.10% ~ 0.30%, Zn: 0.30% ~ 0.90%, Cu < 0.1%, Ti < 0.25%, single impurity < 0.05%, total impurity ≤ 0.15%, the balance is Al; weigh pure aluminum ingots, metal Zn, pure magnesium ingots, aluminum-manganese master alloy, aluminum-zirconium master alloy and aluminum-erbium master alloy as smelting raw materials; 2. Melting: adding the weighed pure aluminum ingot, aluminum-manganese master alloy and aluminum-zirconium master alloy into a melting furnace, the melting temperature is 750-800°C, adding metal Zn when the melt temperature reaches above 750°C, stirring once, adding aluminum-erbium master alloy when the melt temperature reaches above 780°C, stirring once after keeping warm for 20 minutes, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, stirring once again after keeping warm for 20 minutes when the melt temperature rises to 780°C, and then cooling the melt, when the melt temperature drops to 750°C, adding pure magnesium ingot using a magnesium cage, stirring, and adding No. 2 covering agent to obtain an aluminum alloy melt; 3. The above aluminum alloy melt is introduced into a natural gas holding furnace at 770-780°C, and argon-chlorine mixed gas is introduced for refining for 30 minutes, and then allowed to stand for 30 minutes. Then, the casting speed is 45mm / min-55mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 35-45m 3 / h, and semi-continuous casting is carried out under the conditions of a crystallizer metal liquid level of 80-90 mm to obtain an aluminum alloy flat ingot with a thickness of 420 mm, a width of 1620 mm, and a length of 5500 mm-6500 mm, thus completing the manufacturing.

4. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that The purity of the pure aluminum ingot in step 1 is 99.7%.

5. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that The amount of the No. 2 covering agent used in step 2 is 0.4% to 0.6% of the total mass of the metal in the smelting furnace.

6. The method for manufacturing a flat cast ingot of aluminum alloy for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that The No. 2 covering agent described in step 2 is composed of 45% KCl, 30% NaCl and 25% Na3AlF6 in terms of mass percentage.

7. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that The introduction rate of the argon-chlorine mixed gas in step 2 is 0.15-0.20 m 3 / min.

8. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that The volume ratio of argon to chlorine in the argon-chlorine mixed gas in step 2 is 1:

1.

9. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that In step 3, the casting speed is 48 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45 m 3 / h, and semi-continuous casting is carried out under the conditions of molten metal level of 85mm.

10. The method for manufacturing a flat cast aluminum alloy ingot for corrosion-resistant plate material for ships and boats according to claim 3, characterized in that In step 3, the casting speed is 50 mm / min, the casting temperature is 750-770°C, and the casting cooling water flow rate is 45 m 3 / h, and semi-continuous casting is carried out under the conditions of 90mm crystallizer metal level.

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