Aluminum alloy, aluminum alloy continuous pipe and manufacturing method of aluminum alloy continuous pipe

Abstract

The invention provides an aluminum alloy, an aluminum alloy continuous pipe and a manufacturing method of the aluminum alloy continuous pipe. The aluminum alloy comprises the following alloy components in percentage by weight: less than or equal to 0.40% of Si, less than or equal to 0.40% of Fe, less than or equal to 0.10% of Cu, 0.40-1.3% of Mn, 4.0-5.1% of Mg, 0.15-0.45% of Cr, less than or equal to 0.25% of Zn, less than or equal to 0.15% of Ti, less than or equal to 0.3% of Ce, less than or equal to 0.01% of Sc and the balance of Al and impurities. The invention further provides an aluminum alloy continuous pipe made of the aluminum alloy and a manufacturing method of the aluminum alloy continuous pipe. According to the aluminum alloy and the aluminum alloy continuous pipe, the technical effects that the seawater corrosion resistance and strength of the continuous pipe are improved, and the quality of the continuous pipe is reduced are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum and natural gas pipes, and in particular to an aluminum alloy, an aluminum alloy continuous pipe and a manufacturing method thereof. Background Art

[0002] As onshore oil and gas resources become increasingly scarce, the development of offshore oil and gas resources has received more and more attention. In offshore oil and gas projects, if traditional drill pipes are used, the drill pipes need to be connected one by one, which is not only inefficient but also takes a long time to operate. However, due to the large difference between the offshore operating environment and the land, higher requirements are placed on the corrosion resistance and ocean current turbulence of the continuous oil pipe. The common continuous pipe is not resistant to seawater corrosion and is heavy and not conducive to offshore lifting. These problems seriously restrict the development of continuous pipes in the marine field. At present, there are no reports on continuous pipes specifically for offshore oil and gas production at home and abroad.

[0003] In view of the above problems, it is necessary to develop a continuous pipe and a manufacturing method thereof that is resistant to seawater corrosion, has high strength, is light in weight, and is suitable for oil and gas production in a low-temperature marine environment. Summary of the invention

[0004] The main purpose of the present invention is to provide an aluminum alloy, an aluminum alloy coiled tube and a manufacturing method thereof, so as to solve the problem that the coiled tube in the prior art is not suitable for offshore oil and gas production due to its lack of seawater corrosion resistance and heavy weight.

[0005] In order to achieve the above-mentioned purpose, the present invention provides an aluminum alloy on the one hand, which comprises the following alloy components by weight percentage: Si≤0.40%, Fe≤0.40%, Cu≤0.10%, Mn is 0.40-1.3%, Mg is 4.0-5.1%, Cr is 0.15-0.45%, Zn≤0.25%, Ti≤0.15%, Ce≤0.3%, Sc≤0.01% and the remainder of Al and impurities.

[0006] Furthermore, the aluminum alloy contains the following alloy components in percentage by weight: 0.01-0.2% Si, 0.2-0.4% Fe, 0.05-0.1% Cu, 0.5-1.0% Mn, 4.0-4.5% Mg, 0.18-0.34% Cr, 0.001-0.20% Zn, 0.08-0.13% Ti, 0.15-0.3% Ce, 0.005-0.01% Sc and the remainder of Al and impurities.

[0007] Furthermore, the weight ratio of Cr, Mn, Ce, Ti and Sc is (0.18-0.34%):(0.5-1.0):(0.15-0.3):(0.08-0.13):(0.005-0.01).

[0008] In order to achieve the above object, another aspect of the present invention further provides an aluminum alloy coiled tube made of the above aluminum alloy.

[0009] Another aspect of the present invention provides a method for manufacturing the above-mentioned aluminum alloy coiled tube, comprising the following steps:

[0010] 1) preparing raw materials according to the composition of the above-mentioned aluminum alloy and preparing aluminum alloy coils;

[0011] 2) Coiling the aluminum alloy sheets into aluminum alloy strips, and butting the two aluminum alloy strips together through a first friction stir welding process;

[0012] 3) The butted aluminum alloy strips are subjected to forming processing, and then the formed aluminum alloy strips are welded through a second friction stir welding process to form an aluminum alloy continuous tube.

[0013] Furthermore, the process of preparing the aluminum alloy coil includes smelting, refining, casting, hot rolling, cold rolling and finishing the raw materials in sequence, wherein the smelting temperature is 715°C to 740°C; the refining temperature is 735°C to 750°C, and the time is 35min to 40min; the casting conditions are a temperature of 490 to 525°C and a hydrogen content of ≤0.15mL / 100gAl.

[0014] Furthermore, the conditions of the first friction stir welding process are groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

[0015] Furthermore, the conditions of the second friction stir welding process are as follows: groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

[0016] Furthermore, in steps 2) and 3), the surface of the aluminum alloy strip to be welded is processed into an I-type groove; and the forming process is performed by a UOE row roller forming method.

[0017] By applying the technical solution of the present invention, a seawater corrosion-resistant continuous pipe aluminum alloy material is provided, which is characterized by high Cr and high Mn, and the addition of rare earth alloy elements such as Ce, Ti, and Sc can refine the grains and improve the mechanical properties and corrosion resistance of the aluminum alloy. The use of aluminum alloy materials to manufacture continuous pipes can significantly reduce the weight of the finished pipes, and the weight reduction has a positive effect on the hoisting operation and downhole operation of offshore operating platforms. The aluminum alloy continuous pipe of the present invention has excellent seawater corrosion resistance, high strength, light weight, low temperature resistance and other excellent properties, and is suitable for oil and gas production in low-temperature marine environments. The continuous pipe manufacturing method of the present invention uses stir friction welding for aluminum alloy strip butt welding and whole pipe welding. Compared with laser welding and plasma welding, the weld has no spatter, no smoke, no pores during welding, and no need to add welding wire and shielding gas. There is no large-scale thermoplastic change process at the joint. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0019] As described in the background art, the conventional coiled pipe is not suitable for offshore oil and gas production due to its poor seawater corrosion resistance and heavy weight. In order to solve the above technical problems, the present application provides an aluminum alloy, which comprises the following alloy components by weight percentage: Si≤0.40%, Fe≤0.40%, Cu≤0.10%, Mn is 0.40-1.3%, Mg is 4.0-5.1%, Cr is 0.15-0.45%, Zn≤0.25%, Ti≤0.15%, Ce≤0.3%, Sc≤0.01% and the balance of Al and impurities.

[0020] The present invention provides a seawater corrosion-resistant continuous tube aluminum alloy material, which is characterized by high Cr and Mn, and the addition of rare earth alloy elements Ce, Ti, and Sc, which can refine the grains and improve the mechanical properties and corrosion resistance of the aluminum alloy. The use of aluminum alloy materials to manufacture continuous tubes can significantly reduce the weight of the finished tubes, and the weight reduction has a positive effect on the hoisting operation of offshore operating platforms, downhole operations, etc.

[0021] In the aluminum alloy material of the present invention, appropriate Cr helps to improve the wear resistance of the alloy and delay the natural aging process, thereby improving the strength after natural aging. The addition of Cr element can also refine the grains, mainly because Cr forms AlCrSi or AlFeCrSi dispersed phases in the alloy, which hinders recrystallization and grain growth, thereby achieving the effect of refining the grains.

[0022] The role of the Mn element is to make the primary silicon containing Mn form fine and dispersed second phase particles in the aluminum alloy during the homogenization of the ingot, which hinders the recrystallization process, refines the grains, and improves the strength, plasticity and intergranular corrosion resistance of the alloy. In addition, the dispersed phase containing Mn produces pinned dislocations during the stretching process, hindering the movement of dislocations, making the slip distribution of dislocations uniform, and at the same time hindering the migration and movement of subgrain boundaries, which has a stabilizing effect on the substructure, thereby producing substructure strengthening.

[0023] The role of Ce element is to modify, purify the iron-rich phase and micro-alloy in the casting process of aluminum alloy, improve the solidification structure, refine the grains, change the properties of inclusions, and form a passivation film on the surface. It also has strengthening effects such as solid solution strengthening, grain refinement strengthening, and second phase strengthening on aluminum alloys. It can significantly improve the mechanical properties and corrosion resistance of steel.

[0024] Ti element plays a major role in the modification of aluminum alloys. It not only improves the casting performance and mechanical properties of aluminum alloys, but also forms fine grains in the thick wall of the casting to reduce the wall thickness effect. Ti element also helps to eliminate the tendency of thermal cracks generated during the casting process.

[0025] Sc is an effective microalloying element for aluminum alloys. A small amount of Sc can cause significant modification in aluminum alloys, resulting in aluminum alloys with excellent performance. The Al3Sc phase formed by Sc in aluminum alloys has good plasticity, high melting point, and good lattice mismatch with the Al matrix, which increases the strength of the binary alloy.

[0026] Mg plays a strengthening role in aluminum alloys. For every 1wt.% increase in Mg content, the tensile strength δb of the aluminum alloy can increase by 20 to 30MPa. However, excessive Mg content will reduce the dissolution of Mg2Si phase in aluminum, thereby causing the precipitation of strengthening phase in the matrix, reducing the strength and corrosion resistance of the aluminum alloy.

[0027] In a preferred embodiment, by weight percentage, Si is 0.01-0.2%, Fe is 0.2-0.4%, Cu is 0.05-0.1%, Mn is 0.5-1.0%, Mg is 4.0-4.5%, Cr is 0.18-0.34%, Zn is 0.001-0.20%, Ti is 0.08-0.13%, Ce is 0.15-0.3%, Sc is 0.005-0.01%, and the remainder is Al and impurities.

[0028] In a preferred embodiment, in the above-mentioned aluminum alloy, the weight ratio of Cr, Mn, Ce, Ti and Sc is (0.18~0.34%):(0.5~1.0):(0.15~0.3):(0.08~0.13):(0.005~0.01).

[0029] Another aspect of the present application provides an aluminum alloy continuous tube, which is made of the above-mentioned aluminum alloy.

[0030] The use of aluminum alloy materials to manufacture continuous pipes can significantly reduce the weight of finished pipes. The weight reduction has a positive effect on the hoisting operations of offshore platforms and downhole operations. For example, the mass per unit length of the carbon steel coiled tube is 3.53kg, and the mass per unit length of the aluminum alloy coiled tube is 0.88kg. The aluminum alloy coiled tube of the present invention has excellent seawater corrosion resistance, high strength, light weight, low temperature resistance and other excellent properties, is suitable for oil and gas production in low-temperature marine environments, reduces the cost of offshore oil and gas production, and can use smaller equipment for operations, can achieve scale operations, and improve the economy and applicability of offshore oil and gas production.

[0031] In a preferred embodiment, the aluminum alloy continuous tube of the present invention has a yield strength ≥359MPa, a tensile strength ≥455MPa, an elongation ≥20.5%, an outer diameter range of Φ25.4 to Φ88.9mm, a wall thickness range of 1.9 to 6.4mm, a length greater than 61 meters, and a hardness ≤22HRC.

[0032] Another aspect of the present application provides a method for manufacturing the above-mentioned aluminum alloy coiled tube, comprising the following steps:

[0033] 1) preparing raw materials according to the composition of the above-mentioned aluminum alloy and preparing aluminum alloy coils;

[0034] 2) Coiling the aluminum alloy sheets into aluminum alloy strips, and butting the two aluminum alloy strips together through a first friction stir welding process;

[0035] 3) The butted aluminum alloy strips are subjected to forming processing, and then the formed aluminum alloy strips are welded through a second friction stir welding process to form an aluminum alloy continuous tube.

[0036] The continuous tube manufacturing method of the present invention adopts stir friction welding to butt-joint and whole tube welding of aluminum alloy strips. During welding, the weld is free of spatter, smoke, and pores, and no welding wire and shielding gas need to be added. There is no large-scale thermoplastic change process at the joint. The conventional continuous tube manufacturing method of the prior art conventionally adopts high-frequency welding and laser welding, and when aluminum alloy is welded by the above two welding methods, large welding spatter and many welding defects such as pores and cracks will be generated. The temperature of the stir friction welding process is relatively low, and the material does not melt, which can not only avoid large spatter, but also significantly improve the strength loss phenomenon caused by softening of the heat affected zone of the joint.

[0037] In a preferred embodiment, after the above step 3), the process further comprises winding the formed aluminum alloy continuous tube onto a reel to continuously produce the aluminum alloy continuous tube.

[0038] In a preferred embodiment, the process of preparing aluminum alloy coil includes smelting, refining, casting, hot rolling, cold rolling and finishing the raw materials in sequence, wherein the smelting temperature is 715°C to 740°C; the refining temperature is 735°C to 750°C, and the time is 35min to 40min; the casting conditions are a temperature of 490°C to 525°C and a hydrogen content of ≤0.15mL / 100gAl.

[0039] In a preferred embodiment, the conditions of the first friction stir welding process are groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

[0040] In a preferred embodiment, the conditions of the second friction stir welding process are groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

[0041] For the above-mentioned parameters of the friction stir welding process, if the welding speed is too fast, the plasticity of the welded material will be poor, the weld cannot be filled, and a tunnel-type defect will be formed; if the welding pressure is too high, serious flash and grooves will appear, and if the pressure is too low, holes and tunnel-type defects will easily appear inside the weld. If the parameters exceed the above range, black lines may appear on the film during X-ray flaw detection of the weld, and there will be holes and tunnel-type defects in the weld; for welds with parameters within the above range, there will be no cracks, inclusions, pores, etc. after X-ray flaw detection, the appearance will be smooth, there will be no excess height after welding, and the deformation will be much smaller than that of fusion welding.

[0042] In a preferred embodiment, in the above steps 2) and 3), the surface of the aluminum alloy strip to be welded is processed into an I-type groove; the forming process is performed by a UOE roller forming method.

[0043] By using stir friction welding for welding, it is only necessary to process the surfaces to be welded into I-type grooves, that is, the surfaces to be welded are polished flat and then directly connected, without the need to grind the angled grooves, thus simplifying the manufacturing process.

[0044] In a preferred embodiment, the method for manufacturing an aluminum alloy coiled tube comprises the following steps:

[0045] Step 1: Preparation of the coil:

[0046] According to the composition of the aluminum alloy, alloy components are prepared, and the prepared alloy components are added into a smelting furnace for smelting at a smelting temperature of 750° C., and then refined in a static furnace at a refining temperature of 730° C. for 60 minutes; casting is performed at a temperature of 490 to 525° C., and the hydrogen content is detected during casting to be ≤0.15 ml / 100 gAl; hot rolling, cold rolling, and finishing are performed to form an aluminum alloy coil with a thickness of 2.0 to 6.35 mm and a length of more than 300 meters;

[0047] Step 2: Coil slitting and strip extension:

[0048] The aluminum alloy coil is cut into 50-300mm steel strips by a longitudinal shearing unit according to the specifications of the continuous tube. The ends of the front and rear steel strips are processed into 45° and then processed into I-type grooves. The stir friction welding method is adopted, the groove gap is ≤0.1mm, the rotation speed is 250-1400r / min, the welding speed is 100-550mm / min, the downward pressure is 0.1-0.5mm, the inclination angle is 1-3°, and the steel strips are butt welded. After welding, water cooling or air cooling is performed. When the weld is cooled, the weld surface is polished and cleaned;

[0049] Step 3: Forming and welding:

[0050] According to the requirements of the final continuous tube outer diameter and wall thickness, the side of the aluminum alloy strip is planed into an I-shaped groove by the milling method, the width of the aluminum alloy strip and the verticality of the plate edge are controlled, and the UOE row roller forming method is used to control the forming of the aluminum alloy strip; the stir friction welding method is used, the groove gap is ≤0.1mm, the rotation speed is 250-1400r / min, the welding speed is 100-550mm / min, the downward pressure is 0.1-0.5mm, the inclination angle is 1-3°, and the formed aluminum alloy strip is longitudinally welded, and no heat treatment is performed after welding; the aluminum alloy continuous tube with a tube diameter of Φ25.4-Φ88.9mm and a wall thickness of 1.9-6.4mm is manufactured;

[0051] Step 4: Continuous Curl:

[0052] The continuous tube after forming and welding is precisely sized to form an aluminum alloy continuous tube with a diameter of Φ25.4 to Φ88.9 mm and a wall thickness of 1.9 to 6.4 mm, and then wound onto a reel with an appropriate core diameter through a coiler to continuously produce a continuous tube with a length of 61 to 10,000 m.

[0053] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0054] Example 1

[0055] Aluminum alloy coiled tube is manufactured by the following steps:

[0056] 1. Coil rolling

[0057] The chemical composition mass fraction of the plate is as follows: Si: 0.12; Fe: 0.35; Cu: 0.08; Mn: 0.84; Mg: 4.1; Cr: 0.25; Zn: 0.18; Ti: 0.11; Ce: 0.19; Sc: 0.006; the balance is Al and unavoidable impurities. The raw materials are added to the melting furnace in proportion for melting at a melting temperature of 750°C, and then refined in a static furnace at a refining temperature of 730°C for 60 minutes; cast between 490 and 525°C; after hot rolling, cold rolling and finishing, a 3mm thick aluminum alloy coil is formed;

[0058] 2. Coil slitting and strip extension:

[0059] The pipe is 800 meters in length and 50.8mm in outer diameter. The prepared coil is cut into 159.59mm steel strips by the longitudinal shearing unit according to the specifications of the continuous pipe. The ends of the front and rear steel strips are processed into 45°. The steel strips are butt welded by the friction stir welding method. The groove processing is I-type. During welding, the stirring needle rotates at a speed of 1100r / min, the welding speed is 400mm / min, the downward pressure is 0.12mm, the inclination angle is 1.8°, and air cooling is performed after welding. After the weld is cooled, the weld surface is polished and cleaned;

[0060] 3. Welding forming and curling:

[0061] The side of the steel strip is planed into an I-shaped groove by the milling method, the width of the steel strip and the verticality of the plate edge are accurately controlled, and the UOE roller forming method is used to control the forming of the steel strip; the stir friction welding technology is used to longitudinally weld the formed steel strip. During welding, the rotation speed is 1100r / min, the welding speed is 400mm / min, the downward pressure is 0.12mm, the inclination angle is 1.8°, and no heat treatment is performed after welding; the continuous tube after forming and welding is precisely sized to make an aluminum alloy stainless steel continuous tube with a diameter of Φ50.8mm, and then it is wound onto a reel with an appropriate core diameter through a coiler.

[0062] Example 2

[0063] The difference from Example 1 is that the chemical composition mass fractions of the plate are as follows: Si: 0.24; Fe: 0.35; Cu: 0.08; Mn: 0.4; Mg: 4.1; Cr: 0.17; Zn: 0.18; Ti: 0.08; Ce: 0.15; the remainder is Al and unavoidable impurities.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the chemical composition mass fractions of the plate are as follows: Si: 0.18; Fe: 0.35; Cu: 0.08; Mn: 0.2; Mg: 3.3; Cr: 0.1; Zn: 0.18; Ti: 0.08; the remainder is Al and unavoidable impurities.

[0066] Comparative Example 2

[0067] The steel coiled tube is manufactured through the following steps.

[0068] 1. Coil rolling

[0069] The chemical composition of the plate is as follows: C: 0.10; Si: 0.22; Mn: 1.40; P: 0.010; S: 0.004; Ni: 0.13; Cr: 0.55; Mo: 0.12; Cu: 0.23; V: 0.04, and the balance is Fe and inevitable impurities. The above materials are smelted in an oxygen-blown converter, refined outside the furnace, vacuum degassed, and continuously cast into a thick slab with a thickness of about 100 mm, and then heated at 1000-1100°C for rough rolling, and finished at 750-950°C. The cooling rate after rolling is 15-20°C / s to form a hot-rolled coil with a thickness of 3 mm.

[0070] 2. Coil slitting and strip extension:

[0071] The prepared hot-rolled coils are cut into 159.59 steel strips by a longitudinal shear. To meet the length requirements of the steel strips and continuous pipes, the steel strips are butt-welded, the head and tail of the strips are processed to 45°, and the steel strips are connected by plasma welding.

[0072] 3. Welding forming and curling:

[0073] Use steel strip to produce straight seam high-frequency resistance welded steel pipe: the plate edge adopts the milling method to control the strip width and the verticality of the plate edge; the UOE row roller forming method is used to control the plate edge waveform; adjust the welding current and voltage parameters; control the extrusion amount of the weld to 1.6-2.0mm, the opening angle θ is controlled at 5°, and the welding is carried out at a welding speed of 10-15m / min. After welding, the welded pipe body is normalized at 930-960℃. The continuous pipe after forming and welding is precisely sized to make a carbon steel continuous pipe with a diameter of Φ50.8mm, and then wound onto a reel with an appropriate core diameter through a coiler.

[0074] The performance parameters of the coiled tubes prepared in Examples 1-2 and Comparative Examples 1-2 were measured, and the results are shown in the following table.

[0075] The measurement methods are as follows: Strength test: Test the yield strength, tensile strength and elongation according to the GB / T 34204-2017 Coiled Tubing standard;

[0076] Fatigue testing: Fatigue life testing is carried out according to the API RP 5C8-2017 standard;

[0077] Corrosion rate: The corrosion rate of seawater was tested according to GB 10124-88. The corrosive medium was the liquid taken from the offshore drilling platform. The main ion concentration was Cl - :19150mg / L,HCO3 - :536.7mg / L, SO4 2- :1075.6mg / L,Na + :11523mg / L,K + :574.2mg / L,Ca + : 1243.8 mg / L, temperature 85°C, time 720 hours;

[0078] Weight per meter: Weigh the coiled tubing of a specific length and calculate the weight of the coiled tubing per meter.

[0079]

[0080] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0081] By comparing Examples 1 and 2 with Comparative Example 2, it can be seen that the aluminum alloy of the present invention and the coiled tube made therefrom have similar strength and significantly improved elongation, fatigue life, corrosion resistance and significantly lighter weight than the steel coiled tube in the prior art, solving the problem that the coiled tube in the prior art is not resistant to seawater corrosion and is heavy, making it unsuitable for offshore oil and gas production.

[0082] Comparing Examples 1 and 2 with Comparative Example 1, it can be seen that the aluminum alloy having the specific composition of the present invention (Si≤0.40%, Fe≤0.40%, Cu≤0.10%, Mn is 0.40-1.3%, Mg is 4.0-5.1%, Cr is 0.15-0.45%, Zn≤0.25%, Ti≤0.15%, Ce≤0.3%, Sc is ≤0.01% and the balance is Al and impurities) and the continuous tube made therefrom have improved strength, elongation, fatigue life, corrosion resistance and lighter weight.

[0083] Comparing Example 1 with Example 2, it can be seen that the aluminum alloy having the preferred composition of the present invention (Si is 0.01-0.2%, Fe is 0.2-0.4%, Cu is 0.05-0.1%, Mn is 0.5-1.0%, Mg is 4.0-4.5%, Cr is 0.18-0.34%, Zn is 0.001-0.20%, Ti is 0.08-0.13%, Ce is 0.15-0.3%, Sc is 0.005-0.01%, and the balance is Al and impurities) and the continuous tube made thereof have further improved strength, elongation, fatigue life, corrosion resistance and lighter weight.

[0084] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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. An aluminum alloy, characterized in that: Measured in percentage by weight, the aluminum alloy contains the following alloy components: Si≤0.40%, Fe≤0.40%, Cu≤0.10%, Mn is 0.40-1.3%, Mg is 4.0-5.1%, Cr is 0.15-0.45%, Zn≤0.25%, Ti≤0.15%, Ce≤0.3%, Sc≤0.01% and the remainder of Al and impurities.

2. The aluminum alloy according to claim 1, characterized in that The aluminum alloy comprises the following alloy components by weight percentage: 0.01-0.2% Si, 0.2-0.4% Fe, 0.05-0.1% Cu, 0.5-1.0% Mn, 4.0-4.5% Mg, 0.18-0.34% Cr, 0.001-0.20% Zn, 0.08-0.13% Ti, 0.15-0.3% Ce, 0.005-0.01% Sc and the remainder of Al and impurities.

3. The aluminum alloy according to claim 1 or 2, characterized in that: The weight ratio of the Cr, the Mn, the Ce, the Ti and the Sc is (0.18-0.34%):(0.5-1.0):(0.15-0.3):(0.08-0.13):(0.005-0.01).

4. An aluminum alloy coiled tube, characterized in that: The aluminum alloy coiled tube is made of the aluminum alloy described in any one of claims 1 to 3.

5. A method for manufacturing an aluminum alloy coiled tube according to claim 4, characterized in that: The manufacturing method comprises the following steps: 1) preparing raw materials according to the composition of the aluminum alloy according to any one of claims 1 to 3, and preparing aluminum alloy coils; 2) rolling the aluminum alloy plate into an aluminum alloy strip, and butting two of the aluminum alloy strips together through a first friction stir welding process; 3) forming the butted aluminum alloy strips, and then welding the formed aluminum alloy strips through a second friction stir welding process to form the aluminum alloy continuous tube.

6. The method according to claim 5, characterized in that The process for preparing aluminum alloy coils comprises sequentially smelting, refining, casting, hot rolling, cold rolling and finishing the raw materials, wherein the smelting temperature is 715°C to 740°C; the refining temperature is 735°C to 750°C, and the time is 35min to 40min; the casting conditions are a temperature of 490°C to 525°C and a hydrogen content of ≤0.15mL / 100gAl.

7. The method according to claim 5, characterized in that The conditions of the first friction stir welding process are: groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

8. The method according to claim 5, characterized in that The conditions of the second friction stir welding process are as follows: groove gap ≤ 0.1 mm, rotation speed 250-1400 r / min, welding speed 100-550 mm / min, downward pressure 0.1-0.5 mm, and inclination angle 1-3°.

9. The method according to claim 5, characterized in that In steps 2) and 3), the surface of the aluminum alloy strip to be welded is processed into an I-type groove; and the forming process is performed by a UOE row roller forming method.

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