Seawater corrosion resistant aluminum alloy pipe and manufacturing method thereof

Abstract

The invention discloses a seawater corrosion resistant aluminum alloy pipe and a manufacturing method thereof, and relates to the technical field of aluminum alloy pipes, and the aluminum alloy pipe comprises the following element components in percentage by mass: 0.15%-0.35% of Fe, 0.01%-0.2% of Si, 0.6%-1.2% of Mn, 0.15%-0.45% of Cu, 2.42%-2.96% of Mg, 0.05%-0.15% of Zn, 0.03%-0.1% of Ti, 0.03%-0.1% of Zr and 0.01%-0.05% of Sr. The manufacturing method of the pipe comprises the steps of smelting, refining, degassing, online filtering and the like, casting is carried out after molten aluminum melt is manufactured, and annealing, homogeneous heating, extrusion forming, quenching, aging treatment and other operation are sequentially carried out after casting. The aluminum alloy pipe has excellent mechanical property and corrosion resistance, the structure of the aluminum alloy pipe is not greatly changed even after heat treatment operation such as brazing, and the stability of the physical property of the aluminum alloy pipe is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy pipes, and in particular to a seawater corrosion-resistant aluminum alloy pipe and a manufacturing method thereof. Background Art

[0002] Seawater corrosion-resistant aluminum alloy pipes are one of the important parts of heat exchange systems and are mainly used in low-temperature multi-effect distillation desalination exchange systems. Compared with traditional copper pipes, titanium pipes, and steel pipes, they are widely used due to their light weight, high specific strength, high thermal efficiency, good seawater corrosion resistance, long service life, and easy processing.

[0003] By adding alloying elements such as Mg and Zn to Al, not only the specific strength but also the formability can be improved. However, alloying Al with various elements generally results in lower corrosion resistance than pure Al. For example, 2000 series and 7000 series Al alloys are materials in which Cu, Zn, etc. are added to pure Al, and it is well known that their pitting resistance is lower than that of pure Al.

[0004] At present, the aluminum alloy tubes used in equipment in contact with seawater contain high contents of silicon, iron, copper, zinc and other elements. In an environment in contact with seawater, pitting corrosion is very likely to occur, making the seawater corrosion resistance of such aluminum alloy tubes low. Among them, the aluminum alloy materials used for heat exchange tubes are mostly 3000 series aluminum alloys (such as aluminum 3003), which show good corrosion resistance. However, when 3000 series aluminum alloys are used to manufacture heat exchange tubes, heat treatment or brazing at high temperatures (above 460°C) can easily lead to a decrease in the strength and corrosion resistance of the tubes, and deterioration of quality. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a seawater corrosion-resistant aluminum alloy pipe and a manufacturing method thereof, aiming to provide a brazing-resistant aluminum alloy pipe, which has the advantages of high strength, high corrosion resistance and not easy to deform during heat treatment or brazing even after brazing.

[0006] In order to achieve the above-mentioned purpose, the aluminum alloy pipe proposed in the present invention contains the following element components in mass percentage: Fe 0.15-0.35%, Si 0.01-0.2%, Mn 0.6-1.2%, Cu 0.15-0.45%, Mg 2.42-2.96%, Zn 0.05-0.15%, Ti 0.03-0.1%, Zr 0.03-0.1%, Sr 0.01-0.05%.

[0007] To this end, the present invention also proposes a method for manufacturing a seawater corrosion-resistant aluminum alloy pipe, which specifically includes the following steps: adding aluminum ingots, aluminum-iron master alloys, aluminum-silicon master alloys, aluminum-manganese master alloys, and aluminum-copper master alloys to a smelting furnace for heating and melting, spraying a refining agent to refine the melt, adding magnesium ingots and zinc ingots to the smelting furnace for smelting, and spraying a refining agent to refine the melt again; adding aluminum-titanium master alloys, aluminum-zirconium master alloys, and aluminum-strontium master alloys to the smelting furnace for heating and melting, then performing refining, degassing, online filtration and other treatments in sequence, and then casting, and after casting, performing annealing, homogenization heat, extrusion molding, quenching, aging treatment and other operations in sequence.

[0008] As a preferred embodiment of the present invention, the temperature of the molten aluminum alloy during casting may be 750 to 850°C; when the pouring temperature of the molten aluminum alloy exceeds 850°C, the fine structure of the casting becomes coarse. When the pouring temperature of the molten aluminum alloy is lower than 750°C, the molten aluminum alloy may have insufficient fluidity, thereby causing leakage that prevents the molding space from being densely filled with the alloy.

[0009] As a preferred embodiment of the present invention, the aluminum alloy can be subjected to some appropriate heat treatment after casting, such as annealing the obtained alloy pipe, that is, keeping it at 300-350℃ for more than 6h, air cooling after annealing, and the rate of heating or cooling is not higher than 100℃ / h. If the annealing temperature is too low or too high, it is easy to cause the β phase to precipitate continuously along the grain boundary, which is not conducive to the corrosion resistance of the alloy and it is difficult to achieve the required mechanical properties. Therefore, the preferred range is: keeping it at 305-325℃ for 8h. Furthermore, the homogenization heat treatment is applied to the aluminum ingot or aluminum billet to homogenize the alloying elements forming the aluminum alloy or remove the inhomogeneous structure such as segregation. Therefore, the appropriate heat treatment can make the physical properties of the aluminum alloy uniform and can inhibit the occurrence of local corrosion and intergranular corrosion.

[0010] Furthermore, the present invention manufactures a pipe by discontinuously injecting an ingot or billet made of an aluminum alloy into an extruder, and the extrusion speed during extrusion can be 3 to 10 m / min. When the extrusion speed is lower than 3 m / min, the surface of the manufactured pipe may be irregular or the physical properties thereof may be deteriorated.

[0011] Compared with the prior art, the present invention has the following beneficial effects: the present invention optimizes the element ratio and manufacturing method of the aluminum alloy pipe, determines the optimal process parameters, improves the alloy metallographic structure, reduces the harmful effects of gas and inclusions, and finally prepares an aluminum alloy pipe with excellent mechanical properties and corrosion resistance. Even after heat treatment operations such as brazing, the structure of the pipe does not change significantly, ensuring the stability of the physical properties of the aluminum alloy pipe, avoiding or minimizing the reduction of the performance of the aluminum alloy pipe during brazing and manufacturing, and having a corrosion resistance of more than 1600 hours in the seawater acetic acid test (SWAAT) (ASTMG85 standard). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0013] Figure 1 This is a process flow chart of the aluminum alloy pipe manufacturing process of the embodiment of the present application;

[0014] Figure 2 is a simplified three-dimensional structural diagram of an aluminum alloy pipe according to an embodiment of the present application (n=1);

[0015] Figure 3 is a simplified three-dimensional structural diagram of an aluminum alloy pipe according to an embodiment of the present application (n=2);

[0016] Figure 4 is a simplified three-dimensional structural diagram of an aluminum alloy pipe according to an embodiment of the present application (n=3); DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention are further described below in conjunction with examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and are not intended to limit the protection scope of the present invention.

[0018] The present application discloses a seawater corrosion-resistant aluminum alloy pipe and a manufacturing method thereof. The heat exchange tube has excellent mechanical strength and corrosion resistance, and solves the problem that when the existing 3000 series aluminum alloy is used to manufacture aluminum alloy pipes, it is easy to deteriorate and deform after heat treatment or brazing treatment at high temperature (above 460°C), thereby causing the strength and quality of the pipe to decrease.

[0019] As an embodiment of the present application, the present application optimizes the element ratio of the aluminum alloy to obtain a seawater corrosion-resistant aluminum alloy pipe containing the following element components in percentage by mass:

[0020] Fe 0.15~0.35%;

[0021] Si 0.01~0.2%;

[0022] Mn 0.6~1.2%;

[0023] Cu 0.15~0.45%;

[0024] Mg 2.42~2.96%;

[0025] Zn 0.05~0.15%;

[0026] Ti 0.03~0.1%;

[0027] Zr 0.03~0.1%;

[0028] Sr 0.01~0.05%;

[0029] The balance is Al, which also contains unavoidable impurities of not more than 0.05%.

[0030] In the embodiments of the present application, the content of iron (Fe) is limited to 0.15-0.35%. When the content of iron is less than 0.15%, the effect of grain refinement and the effect of improving the mechanical strength of the pipe will be low; on the contrary, when the content of iron exceeds 0.35%, the intermetallic compounds will become coarse and the corrosion resistance of the aluminum alloy pipe will be significantly reduced.

[0031] In the embodiment of the present application, the content of silicon (Si) is limited to 0.01-0.2%. When the content of silicon is less than 0.01%, the solid solution of silicon will decrease, which will reduce the high temperature molding property of the aluminum alloy, increase the shrinkage rate, increase the tendency of hot cracking, and reduce the strength and elongation. In contrast, when the content of silicon exceeds 0.2%, the corrosion resistance and compressive resistance of the aluminum alloy pipe will be significantly reduced.

[0032] In the embodiment of the present application, the addition of manganese (Mn) helps to improve the corrosion resistance of the aluminum alloy, and is distributed in the aluminum matrix in the form of fine Al-Mn intermetallic compounds. The manganese content is limited to 0.6-1.2%. When the manganese content is less than 0.6%, the corrosion resistance of the aluminum alloy may not achieve the expected effect; when the manganese content exceeds 1.2%, the corrosion resistance of the aluminum alloy is not significantly improved, and it is not economically feasible.

[0033] In the embodiment of the present application, copper (Cu) can increase the corrosion potential of aluminum alloy. Similar to manganese, copper improves the corrosion resistance of aluminum alloy. When copper exists in aluminum as an intermetallic compound, it can improve the mechanical strength of aluminum alloy by grain refinement. The copper content is limited to 0.15-0.45%. When the copper content is less than 0.15%, the tensile strength and corrosion resistance of aluminum alloy are insufficient; when the copper content exceeds 0.45%, coarse defects will appear in the intermetallic compound, thereby greatly reducing the corrosion resistance of aluminum alloy.

[0034] In the embodiment of the present application, magnesium is added to the aluminum silicon alloy. Magnesium (Mg) can form a stable Mg2Si compound with silicon. The compound can greatly improve the mechanical properties of the aluminum alloy material, and improve the strengthening phase morphology with the modification treatment of strontium. In addition to strengthening, magnesium can also improve the corrosion resistance of the pipe. The content of Mg is limited to 2.42-2.96%. When the content of magnesium is less than 2.42%, the strengthening effect of magnesium on the aluminum alloy material is insufficient, and the performance improvement is poor; when the content of copper exceeds 2.96%, the solubility of magnesium itself in the aluminum alloy is relatively limited, and the precipitation rate is not ideal. Adding too much magnesium will form an excess phase between the grains, which will reduce the strength at the grain boundary, and then cause the aluminum alloy to become brittle. In addition, when the content of magnesium is within the above range, it can combine with Zn to form a MgZn2 strengthening phase, which is evenly dispersed at the grain boundary of the aluminum alloy. The grain boundary of the aluminum alloy can be improved, which can ensure the strength and toughness of the aluminum alloy.

[0035] In the embodiment of the present application, the content of titanium (Ti) is limited to 0.03-0.1%. Due to the high melting point of titanium, titanium is generally added in the form of aluminum titanium diboride and exists in the aluminum alloy matrix in the form of Al-Ti intermetallic compounds, and can improve the mechanical strength of the aluminum alloy by grain refinement. The addition of titanium to the aluminum alloy can refine the grains and reduce the alloy grain size by precipitation of Al-Ti intermetallic compounds. The elongation of the aluminum alloy with the addition of titanium will be significantly improved, and the mechanical strength will not be affected. Therefore, the addition of titanium to the aluminum alloy has the advantage of improving the elongation of the material, which can facilitate the manufacture and post-processing of the heat exchange tube (including but not limited to the change of the tube body morphology). When the content of titanium is less than 0.03%, the effect of grain refinement and mechanical strength improvement of the aluminum alloy will be very small; in contrast, when the content of titanium exceeds 0.1%, its intermetallic compounds may coarsen, thereby greatly reducing the mechanical properties of the aluminum alloy pipe.

[0036] In the embodiment of the present application, the content of zirconium (Zr) is limited to 0.03-0.1%. When the content of zirconium is within this range, it can be effectively dissolved in the aluminum alloy matrix and form Al3Zr coarse phase, β′(Al3Zr) metastable phase and Al3Zr(DO 23) equilibrium phase, which can improve the strength, toughness and corrosion resistance of aluminum alloy pipes. In this embodiment, the ZrAl3 compound formed by adding zirconium can hinder the recrystallization process, refine the recrystallized grains, and improve the alloy's anti-scaling corrosion performance. Studies have found that when the zirconium content in the aluminum alloy ratio of the present application embodiment is greater than or equal to 0.03%, the Al and Zr particles in the alloy solid solution state are relatively small and evenly distributed. With the increase of zirconium content, the strength and corrosion resistance of the alloy are greatly improved. When the zirconium content is too much and greater than 0.1%, the strength and corrosion resistance of the alloy decrease with the increase of zirconium content. This is mainly because when the zirconium content in the alloy is too high, a coarse Al-Zr primary phase will precipitate, which reduces the Zr content dissolved in the matrix during alloy solidification, thereby reducing the beneficial effects of zirconium.

[0037] In the embodiments of the present application, strontium (Sr) is mainly used for the modification of aluminum alloy. The addition of Sr can simultaneously refine the α dendrites and eutectic silicon in the aluminum alloy and improve the overall organizational morphology. As a long-term modifier, Sr can be combined with Ti and Zr in the present invention to enhance the modification effect. The content of strontium in the present invention is limited to 0.01-0.05%. When its content is lower than 0.01%, the improvement effect cannot be achieved; when excessive addition is greater than 0.05%, it is easy to cause over-modification and aggravation of hydrogen absorption tendency. Strontium can change the effect of the intermetallic compound phase, so strontium can be used for modification to improve the plasticity of the alloy and the quality of the final aluminum alloy heat exchange tube. During the casting process, adding 0.01-0.05% strontium element to the aluminum alloy of the present invention can transform the β-AlFeSi phase in the ingot into the Chinese character α-AlFeSi phase, greatly reducing the ingot homogenization time, improving the mechanical properties and plastic processing properties of the aluminum alloy pipe, and improving the surface roughness of the pipe product.

[0038] The aluminum alloy pipe in the embodiment of the present application does not contain chromium in its elemental composition, thereby avoiding the occurrence of intermetallic compound precipitation between crystals, thereby improving the intergranular corrosion resistance of the pipe.

[0039] Example 1

[0040] This embodiment 1 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 1 below:

[0041] Table 1: Element composition and ratio of aluminum alloy in Example 1

[0042]

[0043] Example 2

[0044] This embodiment 2 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 2 below:

[0045] Table 2: Element composition and ratio of aluminum alloy pipe in Example 2

[0046]

[0047]

[0048] Example 3

[0049] This embodiment 3 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 3 below:

[0050] Table 3: Element composition and ratio of aluminum alloy pipe in Example 3

[0051]

[0052] Example 4

[0053] This embodiment 4 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 4 below:

[0054] Table 4: Element composition and ratio of aluminum alloy pipe in Example 4

[0055]

[0056] Example 5

[0057] This embodiment 5 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 5 below:

[0058] Table 5: Element composition and ratio of aluminum alloy pipe in Example 5

[0059]

[0060]

[0061] Example 6

[0062] This embodiment 6 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 6 below:

[0063] Table 6: Element composition and ratio of aluminum alloy pipe in Example 6

[0064]

[0065] Example 7

[0066] This embodiment 7 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 1 below:

[0067] Table 7: Element composition and ratio of aluminum alloy pipe in Example 7

[0068]

[0069] Example 8

[0070] This embodiment 8 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 8 below:

[0071] Table 8: Element composition and proportion of aluminum alloy pipe in Example 8

[0072]

[0073]

[0074] Example 9

[0075] This embodiment 9 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 9 below:

[0076] Table 9: Element composition and proportion of aluminum alloy pipe in Example 9

[0077]

[0078] Example 10

[0079] This embodiment 10 discloses a seawater corrosion resistant aluminum alloy pipe formula, which is composed of the element components in mass percentage as shown in Table 10 below:

[0080] Table 10: Element composition and ratio of aluminum alloy pipe in Example 10

[0081]

[0082] Embodiment 11

[0083] With respect to the aluminum alloy formulas of Examples 1-10, this Example 11 discloses a method for manufacturing a seawater corrosion-resistant aluminum alloy pipe, comprising the following steps:

[0084] Step 1: Add aluminum ingots with a purity greater than 99.7%, aluminum-iron master alloys, aluminum-silicon master alloys, aluminum-manganese master alloys, and aluminum-copper master alloys into a melting furnace, and heat the furnace to a melting temperature of 715°C to 725°C at a rate of 20°C / min. After the raw materials in the melting furnace are completely melted, perform electromagnetic stirring for 2 hours, take samples for spectral analysis, and control the melt composition within the required range;

[0085] Step 2: Spraying a powder refining agent equivalent to 0.32% of the mass of the melt into the melt in the smelting furnace with argon as a carrier for refining, and then skimming; wherein the powder refining agent is a mixture of NaCl, KCl and Na3AlF6 in a mass ratio of 4:2.5:2;

[0086] Step 3: Raise the temperature of the melt to 750°C to 760°C, add magnesium ingots and zinc ingots with a purity of 99.90% into the smelting furnace for melting, and after the raw materials are completely melted, perform electromagnetic stirring for 1.5 hours, take samples for spectral analysis, and control the melt composition within the required range;

[0087] Step 4: using argon as a carrier, spraying a powder refining agent equivalent to 0.28% of the melt mass into the melt in the smelting furnace for refining, and then performing slag removal; wherein the powder refining agent is a mixture of NaCl, KCl and Na3AlF6 in a mass ratio of 7:5:4;

[0088] Step 5: Raise the melt temperature to 815°C to 825°C, add aluminum-titanium master alloy, aluminum-zirconium master alloy, and aluminum-strontium master alloy into the melting furnace for melting, and after the raw materials are completely melted, perform electromagnetic stirring for 1.5 hours and keep warm for 45 minutes;

[0089] Step 6: After the insulation is completed, sampling and analysis are carried out. After the analysis is qualified, the melt is poured into a static furnace and refined in the furnace using a breathable brick at the bottom of the furnace. The melt temperature of the pouring furnace is 780°C, the refining temperature in the furnace is 780°C, the refining time in the furnace is set to 35min, the gas used for refining in the furnace is argon, and the argon flow rate is 18L / min. The refining bubble height on the surface of the melt refined in the furnace is less than 80mm; the melt after furnace refining is degassed by an Alpur device, double rotor degassing, the rotor speed is set to 250rmp / root, the rotor uses argon and chlorine gases, and the argon flow rate is 4.5Nm 3 / h / root, chlorine flow rate is 40L / h / root; hydrogen content in the melt after online refining and degassing is <0.15mL / 100gAl;

[0090] Step 7: Use a double-stage foam ceramic filter plate to filter the aluminum melt online, and the porosity of the double-stage foam ceramic filter plate is 30 / 50PPI;

[0091] Step 8: Cast the aluminum melt at a temperature of 750℃~850℃, a casting speed of 35~45mm / min, and a casting water flow rate of 28-32m 3 / h / root, aluminum alloy ingot is obtained;

[0092] Step 9: Anneal the ingot at a temperature of 305-325°C for 8 hours. After air cooling, homogenize the ingot at 540-560°C for 16 hours. After air cooling, preheat the ingot to 490-510°C for extrusion molding at an extrusion speed of 3-10 m / min. Quench the extruded aluminum alloy pipe at a quenching temperature of 460-480°C for 3.5 hours. The cooling medium is water at a water temperature of 70-90°C. Then, perform aging treatment at a temperature of 165-175°C for 12 hours. After being air-cooled out of the furnace until room temperature, the aluminum alloy pipe is obtained.

[0093] Example 12

[0094] like Figure 2-Figure 4 As shown, this embodiment discloses a flat aluminum alloy tube structure, the vertical section of the tube is a waist-shaped hole structure, and the tube cavity has n (n≥1) partition structures arranged along the length of the tube, and the partition separates the tube cavity into n+1 chambers, wherein the tube wall thickness of the aluminum alloy tube is preferably 1.5mm~3.5mm, and the partition thickness is preferably 1mm~2mm. When the thickness of the aluminum alloy tube is less than 1.5mm, it may be damaged by external pressure when it is applied to heat exchange tubes or other occasions. When the thickness of the aluminum alloy tube is greater than 3.5mm, the heat exchange efficiency will decrease, the weight of the heat exchanger will naturally increase, and post-processing such as expansion, contraction, bending, etc. may be difficult to implement. The aluminum alloy tube using the structure of this embodiment has good extrusion resistance and service life.

[0095] Comparative group

[0096] The present application also discloses the aluminum alloy pipe formula and the manufacturing method of the pipe of the comparative example group (1-11), as shown in the following Table 11:

[0097] Table 11: Element composition and ratio of aluminum alloy pipes in the comparative group

[0098]

[0099]

[0100] Test example

[0101] The aluminum alloy pipes manufactured by the formulas of Examples 1-10 and Comparative Examples 1-19 were made into test specimens for performance testing. The test contents are as follows:

[0102] (1) Brazing simulation: The sample was heated from room temperature to 610°C at a rate of 50°C / min and kept at this temperature for 3 minutes. It was then cooled under nitrogen for 10 minutes and then air-cooled.

[0103] (2) Tensile strength test of samples after brazing: The samples after brazing simulation were prepared into tensile test samples according to EN10002-1 standard, with a gauge length of 50 mm, and then subjected to tensile test at room temperature at a tensile speed of 20 mm / min.

[0104] (3) Corrosion resistance test:

[0105] Corrosion resistance was evaluated according to ASTM-G85-94-A3 (SWAAT - Seawater Acidification Test), where the specimens after brazing simulation were placed in a closed chamber and exposed to a climate change consisting of a two-part repetitive cycle of continuous indirect spraying of an acidified (pH 2.8 to 3.0) synthetic seawater solution for 30 minutes at a rate of 1.0 to 2.0 ml / 80 cm 2 / h rate falls on the sample; followed by 90 minutes of exposure to a high humidity climate above 98% RH. The entire test cycle is carried out at a constant chamber temperature of +49°C, and the cycle is repeated 800 times (1600 hours) to observe whether the sample has any abnormalities.

[0106] The test results of the above test contents are shown in Table 12 below:

[0107] Table 12:

[0108]

[0109]

[0110] It can be seen from the statistical test results in Table 12 that the aluminum tubes of Examples 1 to 10 of the present application can exhibit a high tensile strength of 236-267 MPa after brazing thermal simulation treatment and a high corrosion resistance of 1600 hours or longer in the SWAAT-seawater acidification test, which is much higher than the tensile strength and corrosion resistance of the tubes made of aluminum alloy used in the current prior art.

[0111] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the iron element is removed in Comparative Example 1, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 1 is significantly reduced, the mechanical properties are deteriorated, and there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0112] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 2 only increases the content of iron, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 2 is reduced, the mechanical properties are deteriorated, rust spots are found in the SWAAT-seawater acidification test, and the corrosion resistance is significantly reduced.

[0113] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the silicon element is removed in Comparative Example 3, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 3 is reduced and the mechanical properties are deteriorated, but no abnormality is found on the surface after SWAAT-seawater acidification test, and the corrosion resistance does not change significantly.

[0114] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 4 only increases the content of silicon, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 4 is reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0115] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 5 only reduces the content of manganese, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 5 is significantly reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0116] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 6 only increases the content of manganese, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 6 is reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0117] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the copper element is removed in Comparative Example 7, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 7 is significantly reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0118] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 8 only increases the content of copper element, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 8 is reduced, the mechanical properties are deteriorated, rust spots are found in the SWAAT-seawater acidification test, and the corrosion resistance is significantly reduced.

[0119] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 9 only reduces the content of magnesium, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 9 is reduced and the mechanical properties are deteriorated, but the surface does not show any abnormality after SWAAT-seawater acidification test, and the corrosion resistance does not change significantly.

[0120] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 10 only increases the content of magnesium, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 10 is reduced and the mechanical properties are deteriorated, but the surface does not show any abnormality after SWAAT-seawater acidification test, and the corrosion resistance does not change significantly.

[0121] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the zinc element is removed in Comparative Example 11, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 11 is reduced and the mechanical properties are deteriorated, but no abnormality is found on the surface after SWAAT-seawater acidification test, and the corrosion resistance does not change significantly.

[0122] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 12 only increases the content of zinc, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 12 is reduced and the mechanical properties are deteriorated, but the surface does not show any abnormality after the SWAAT-seawater acidification test, and the corrosion resistance does not change significantly.

[0123] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 13 only removes the titanium element, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 13 is significantly reduced, the mechanical properties are deteriorated, and there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0124] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 14 only increases the content of titanium, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 14 is significantly reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0125] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the zirconium element is removed in Comparative Example 15, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 15 is reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0126] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 16 only increases the content of zirconium, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 16 is significantly reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0127] Compared with the element ratio of the aluminum alloy pipe in this embodiment, only the strontium element is removed in Comparative Example 17, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 17 is reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0128] Compared with the element ratio of the aluminum alloy pipe in this embodiment, Comparative Example 18 only increases the content of zirconium, and the remaining components are within the range recorded in the embodiment. Combined with Table 12, it can be concluded that the tensile strength of the aluminum alloy pipe prepared in Comparative Example 18 is significantly reduced, the mechanical properties are deteriorated, there is discoloration after SWAAT-seawater acidification test, and the corrosion resistance is also reduced.

[0129] Relative to the element ratio of the aluminum alloy pipe in the present embodiment, Comparative Example 19 is 3003 aluminum alloy, the iron content in 3003 aluminum alloy is higher than that in the present embodiment, the silicon content is higher than that in the present embodiment, the manganese content is the same as that in the present embodiment, the copper content is lower than that in the present embodiment, the magnesium content is lower than that in the present embodiment, the zinc content is higher than that in the present embodiment, and does not contain titanium, zirconium and strontium elements. After brazing simulation, it is found that the tensile strength of the 3003 aluminum alloy is reduced by 90.4%-108.8% compared with that in the present embodiment, and there is a leakage point phenomenon in the SWAAT-seawater acidification test, and the corrosion resistance is insufficient.

[0130] It can be seen from the comparative example group that the tensile strength and corrosion resistance of the aluminum alloy pipe prepared in the present application are affected by the raw material ratio. The aluminum alloy pipe prepared by selecting the raw material ratio within the range has excellent tensile strength and corrosion resistance. If the content of each element component is not within the protection scope of the present application, or some components are out of the formula, or some chemical composition ratios do not meet the requirements, the mechanical properties and corrosion resistance of the aluminum alloy pipe cannot achieve the expected effect.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A seawater corrosion resistant aluminum alloy pipe, characterized in that: Contains the following elements in percentage by mass: Fe 0.15~0.35%, Si 0.01~0.2%, Mn 0.6~1.2%, Cu 0.15~0.45%, Mg 2.42~2.96%, Zn 0.05~0.15%, Ti 0.03~0.1%, Zr 0.03~0.1%, Sr 0.01~0.05%.

2. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: It contains the following element compositions in mass percentage: Fe 0.15%, Si 0.01%, Mn 0.6%, Cu 0.15%, Mg 2.42%, Zn 0.05%, Ti 0.03%, Zr 0.03%, Sr 0.01%.

3. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: It contains the following element compositions in mass percentage: Fe 0.35%, Si 0.2%, Mn 1.2%, Cu 0.45%, Mg 2.96%, Zn 0.15%, Ti 0.1%, Zr 0.1%, Sr 0.05%.

4. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: It contains the following element compositions in mass percentage: Fe 0.25%, Si 0.1%, Mn 0.9%, Cu 0.3%, Mg 2.69%, Zn 0.1%, Ti 0.06%, Zr 0.06%, Sr 0.03%.

5. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: The alloy contains the following elemental compositions in percentage by mass: Fe 0.15%, Si 0.01%, Mn 0.7%, Cu 0.2%, Mg 2.5%, Zn 0.08%, Ti 0.03%, Zr 0.03%, Sr 0.01%.

6. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: It contains the following element compositions in mass percentage: Fe 0.15%, Si 0.01%, Mn 1.2%, Cu 0.45%, Mg 2.96%, Zn 0.15%, Ti 0.1%, Zr 0.1%, Sr 0.05%.

7. A method for manufacturing a seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: The following steps are involved: Aluminum ingots, aluminum-iron master alloys, aluminum-silicon master alloys, aluminum-manganese master alloys, and aluminum-copper master alloys are added to the smelting furnace for heating and melting, and a refining agent is sprayed into the smelting furnace for refining the melt. Magnesium ingots and zinc ingots are added to the smelting furnace for smelting, and a refining agent is sprayed into the smelting furnace for refining the melt again. Aluminum-titanium master alloys, aluminum-zirconium master alloys, and aluminum-strontium master alloys are added to the smelting furnace for heating and melting, followed by refining, degassing, online filtering, and other treatments, and then casting. After casting, annealing, homogenization heat, extrusion molding, quenching, aging treatment, and other operations are performed in sequence.

8. The manufacturing method according to claim 7, characterized in that: The following steps are involved: Step 1: Add aluminum ingots, aluminum-iron master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-copper master alloy into a melting furnace, raise the temperature to 715°C to 725°C, and perform electromagnetic stirring after the raw materials in the melting furnace are completely melted; Step 2: Spraying a powder refining agent equivalent to 0.32% of the melt mass into the melt in the smelting furnace using argon as a carrier for refining, and then skimming off the slag; Step 3: Raise the temperature of the melt to 750°C to 760°C, add magnesium ingots and zinc ingots with a purity of 99.90% into the smelting furnace for melting, and perform electromagnetic stirring for 1.5 hours after the raw materials are completely melted; Step 4: using argon as a carrier, spraying a powder refining agent equivalent to 0.28% of the melt mass into the melt in the smelting furnace for refining, and then skimming off the slag; Step 5: Raise the temperature of the melt to 815°C to 825°C, add aluminum-titanium master alloy, aluminum-zirconium master alloy, and aluminum-strontium master alloy into the melting furnace for melting, and perform electromagnetic stirring after the raw materials are completely melted, and keep warm for 45 minutes; Step 6: After the insulation is completed, the melt is poured into a static furnace and refined in the furnace using a breathable brick at the bottom of the furnace. The melt temperature of the pouring furnace is 780°C, the refining temperature in the furnace is 780°C, the refining time in the furnace is set to 35min, the gas used for furnace refining is argon, and the argon flow rate is 18L / min, and the refining bubble height on the surface of the melt refined in the furnace is less than 80mm; the melt after furnace refining is degassed using an Alpur device, double rotor degassing, the rotor speed is set to 250rmp / root, the rotor uses argon and chlorine gases, and the argon flow rate is 4.5Nm 3 / h / root, chlorine flow rate is 40L / h / root; hydrogen content in the melt after online refining and degassing is <0.15mL / 100gAl; Step 7: Use a double-stage foam ceramic filter plate to filter the aluminum melt online, and the porosity of the double-stage foam ceramic filter plate is 30 / 50PPI; Step 8: Cast the aluminum melt at a temperature of 750℃~850℃, a casting speed of 35~45mm / min, and a casting water flow rate of 28-32m 3 / h / root, aluminum alloy ingot is obtained; Step 9: Anneal the ingot at a temperature of 305-325°C for 8 hours. After air cooling, homogenize the ingot at 540-560°C for 16 hours. After air cooling, preheat the ingot to 490-510°C for extrusion molding at an extrusion speed of 3-10 m / min. Quench the extruded aluminum alloy pipe at a quenching temperature of 460-480°C for 3.5 hours at a water temperature of 70-90°C. Then perform aging treatment at a temperature of 165-175°C for 12 hours. Remove from the furnace and air cool to room temperature.

9. The manufacturing method according to claim 7, characterized in that: The powder refining agent is a mixture of NaCl, KCl and Na3AlF6 in a mass ratio of 4:2.5:2, or a mixture in a mass ratio of 7:5:

4.

10. The seawater corrosion resistant aluminum alloy pipe according to claim 1, characterized in that: The tube is a flat structure, and its vertical section is a waist-shaped hole structure. The tube cavity is provided with n (n≥1) partition structures arranged along the length of the tube, and the partition divides the tube cavity into n+1 chambers.

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