A method for producing a coarse-grained ring 6061 aluminum alloy bar

Abstract

A method for preparing a coarse-grained ring-free 6061 aluminum alloy rod belongs to the technical field of aluminum alloy processing and manufacturing. It solves the problem of coarse-grained ring in the production of existing 6061 aluminum alloy rods, which causes uneven mechanical properties, poor fatigue resistance and anodic oxidation appearance defects. The method comprises the following steps: precise alloy component adjustment, low-temperature casting of round ingots, homogenization annealing, temperature-controlled low-speed hot extrusion forming with a round arc working belt mold, high-temperature online quenching, tensile straightening and low-temperature artificial aging. The present application effectively inhibits the abnormal recrystallization and growth of surface grains during the extrusion process, completely eliminates the coarse-grained ring defects of the rod section, and the obtained product has uniform and fine grain structure, stable and excellent mechanical properties, the tensile strength is not less than 310 MPa, the yield strength is not less than 270 MPa, and the elongation after fracture is not less than 12%. The product is suitable for automobile structural parts, rail transit accessories, high-end mechanical equipment and other material scenes, the process is suitable for industrialized batch production, and the production stability is strong and the application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy processing and manufacturing technology, specifically relating to a method for preparing 6061 aluminum alloy bars without coarse grain rings. Background Technology

[0002] 6061 aluminum alloy belongs to the Al-Mg-Si-Cr series of commonly used wrought aluminum alloys. It has medium mechanical strength, excellent corrosion resistance, weldability and machinability, and is widely used in the production of structural load-bearing components such as automotive parts, rail transit vehicle body parts, general machinery, and high-end precision equipment.

[0003] In the current industrial production of 6061 aluminum alloy extruded bars, factors such as die friction and shearing, excessively rapid surface deformation rate, and excessively high local temperature rise cause the outer metal of the bar to easily undergo dynamic recrystallization, resulting in abnormally coarse grains. This ultimately forms a ring-shaped coarse-grained structure on the circumference of the bar, known as a coarse-grained ring defect. Coarse-grained rings significantly exacerbate the anisotropy of the material's mechanical properties, reducing the overall strength, hardness, and fatigue life of the product. They also easily lead to cracking and scrapping problems during subsequent forging and stamping secondary processing. Furthermore, the coarse-grained structure causes uneven anodizing coloring, resulting in color differences and streaks on the surface, failing to meet the appearance requirements of high-end products.

[0004] Existing conventional production processes, which only adjust composition parameters or extrusion temperature and speed, are insufficient to fundamentally suppress grain coarsening. Inappropriate alloy element ratios in the composition lead to insufficient pinning of dispersed phases or the precipitation of coarse, brittle phases. Furthermore, the lack of robust control over mold structure and ingot homogenization annealing processes results in unavoidable issues such as uneven metal flow and surface overheating, making it impossible to completely eliminate coarse grain ring defects and leading to poor product quality stability. Therefore, there is an urgent need to develop a complete process for preparing 6061 bars that can completely eliminate coarse grain rings and achieve uniform and stable microstructure and properties, making it practically applicable in production. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of coarse grain rings in the production of existing 6061 aluminum alloy bars, which cause uneven mechanical properties, poor fatigue resistance, and anodized appearance defects, and to provide a method for preparing 6061 aluminum alloy bars without coarse grain rings.

[0006] A method for preparing 6061 aluminum alloy bars without coarse grain rings, comprising the following steps:

[0007] I. Alloy composition blending:

[0008] According to the mass percentage, Si: 0.60%~0.65%, Fe≤0.20%, Cu: 0.19%~0.24%, Mn: 0.08%~0.12%, Cr: 0.25%~0.30%, Mg: 0.90%~0.95%, Zn≤0.15%, Ti: 0.08%~0.12%, with individual impurities ≤0.05% and total impurities ≤0.15%, and the balance being Al, the raw materials are prepared and weighed.

[0009] II. Melting and Casting:

[0010] The above raw materials are melted at 720℃~740℃, stirred evenly, and then the slag and floating slag are removed. Then Al-5Ti-1B wire is added at 730℃~740℃, and the materials are refined and filtered. Finally, the materials are cast into round ingots at a low temperature of 725℃~735℃.

[0011] III. Homogenization Annealing:

[0012] The above-mentioned round ingots are heated to 560℃~570℃ and held for 8~10 hours. After the holding period, they are spray-cooled to room temperature at a rate of 15~25℃ / min to obtain homogenized annealed ingots.

[0013] IV. Hot extrusion molding:

[0014] The arc working zone mold is used and preheated to 470℃~490℃, the extrusion cylinder is preheated to 400℃~430℃, and then the above homogenized annealed ingot is heated to 485℃~515℃ and hot extruded to obtain the bar.

[0015] V. Online Quenching:

[0016] After extrusion, the above-mentioned bars are directly fed into a circulating water tank. The temperature of the bars is reduced to ≤80℃ under the conditions of water temperature ≤40℃ and cooling rate ≥80℃ / min, to obtain quenched bars.

[0017] VI. Stretching, straightening, and artificial aging:

[0018] After quenching, the bar is stretched and straightened, then placed in an aging furnace and held at 170℃~180℃ for 7~9 hours. After holding, it is air-cooled to room temperature to obtain a 6061 aluminum alloy bar without coarse grain rings, thus completing the preparation method described above.

[0019] Furthermore, the Al-5Ti-1B wire mentioned in step two is used as a grain refiner, with an addition rate of 2~3m / min and a dosage of 1~2kg per ton of aluminum alloy melt.

[0020] Furthermore, in step two, the refining and filtration process involves passing Ar gas with a purity of ≥99.9% through the filter for 15-20 minutes, followed by filtration through a double-layer ceramic filter plate of 30ppi+50ppi.

[0021] Furthermore, the diameter of the round ingot mentioned in step two is 120mm~200mm.

[0022] Furthermore, the radius of the arc working belt mold mentioned in step four is 3mm~5mm.

[0023] Furthermore, in step four, the hot extrusion molding process involves an extrusion speed of 2-4 m / min, an extrusion ratio of 10-20, and an extrusion outlet bar temperature of 490℃-510℃.

[0024] Furthermore, in step six, the stretching and straightening process involves a stretching deformation of 1% to 3%.

[0025] Advantages of this invention:

[0026] 1. Completely eliminate coarse grain ring defects: By precisely proportioning Cr and Mn, uniformly dispersed particles are formed, which pin grain boundaries and inhibit grain boundary migration; the arc mold reduces flow dead zones, and temperature-controlled extrusion reduces surface overheating; online quenching quickly locks in the microstructure, and multi-dimensional synergistic inhibition of abnormal grain growth results in 6061 aluminum alloy bars with no coarse grain rings in the cross section, and the grain size is ≥6 according to GB / T 3246.2.

[0027] 2. Excellent mechanical properties: Optimized composition + homogeneity + aging synergy, the reinforcing phase is fine and uniform, the tensile strength of the bar is ≥310MPa, the yield strength is ≥270MPa, the elongation is ≥12%, the performance is uniform and the anisotropy is small, and the fatigue resistance is significantly improved.

[0028] 3. Good surface quality: No coarse crystal rings, uniform surface color and no spots after anodizing, meeting the appearance requirements of high-end products.

[0029] 4. Stable process and controllable cost: The process parameters have a wide range and are easy to control. No special equipment is required. The process is stable for large-scale production and the cost is comparable to that of conventional processes, making it suitable for widespread application.

[0030] This invention is applicable to the preparation of 6061 aluminum alloy rods without coarse grain rings. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the cross-sectional metallographic structure of the 6061 aluminum alloy rod without coarse grain rings prepared in Example 1; where 1 represents the fine and uniform grain region of the matrix;

[0032] Figure 2This is a schematic diagram of the coarse-grained ring metallographic structure of the cross-section of the rod prepared in the comparative example; where 2 represents the surface coarse-grained ring structure region. Detailed Implementation

[0033] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0034] Specific Implementation Method 1: This implementation method provides a method for preparing 6061 aluminum alloy bars without coarse grain rings, which is carried out according to the following steps:

[0035] I. Alloy composition blending:

[0036] According to the mass percentage, Si: 0.60%~0.65%, Fe≤0.20%, Cu: 0.19%~0.24%, Mn: 0.08%~0.12%, Cr: 0.25%~0.30%, Mg: 0.90%~0.95%, Zn≤0.15%, Ti: 0.08%~0.12%, with individual impurities ≤0.05% and total impurities ≤0.15%, and the balance being Al, the raw materials are prepared and weighed.

[0037] II. Melting and Casting:

[0038] The above raw materials are melted at 720℃~740℃, stirred evenly, and then the slag and floating slag are removed. Then Al-5Ti-1B wire is added at 730℃~740℃, and the materials are refined and filtered. Finally, the materials are cast into round ingots at a low temperature of 725℃~735℃.

[0039] III. Homogenization Annealing:

[0040] The above-mentioned round ingots are heated to 560℃~570℃ and held for 8~10 hours. After the holding period, they are spray-cooled to room temperature at a rate of 15~25℃ / min to obtain homogenized annealed ingots.

[0041] IV. Hot extrusion molding:

[0042] The arc working zone mold is used and preheated to 470℃~490℃, the extrusion cylinder is preheated to 400℃~430℃, and then the above homogenized annealed ingot is heated to 485℃~515℃ and hot extruded to obtain the bar.

[0043] V. Online Quenching:

[0044] After extrusion, the above-mentioned bars are directly fed into a circulating water tank. The temperature of the bars is reduced to ≤80℃ under the conditions of water temperature ≤40℃ and cooling rate ≥80℃ / min, to obtain quenched bars.

[0045] VI. Stretching, straightening, and artificial aging:

[0046] After quenching, the bar is stretched and straightened, then placed in an aging furnace and held at 170℃~180℃ for 7~9 hours. After holding, it is air-cooled to room temperature to obtain a 6061 aluminum alloy bar without coarse grain rings, thus completing the preparation method described above.

[0047] In step one of this embodiment, the alloy composition must be strictly controlled in terms of element content. The purpose is to balance the quantity and size of dispersed phases, avoid coarse compounds, and maximize the suppression of coarse grain rings. Specifically, the control of Si content is to ensure the Mg2Si strengthening phase, the control of Fe content is to reduce impurity phases, the control of Cu content is to improve strength, the control of Mn and Cr content is to form CrAl7 and MnAl6 dispersed particles, pinning grain boundaries and inhibiting grain growth, the control of Mg content is to form a strengthening phase with Si, and the control of Ti content is to refine the as-cast grains.

[0048] In step two of this implementation method, low-temperature melting, online refining, and multi-stage filtration are used to ensure the purity of the melt and the refinement of the grains; low-temperature casting aims to reduce casting stress and component segregation.

[0049] In step three of this embodiment, heating the round ingot to 560℃~570℃ and holding it at that temperature for 8~10 hours aims to achieve homogeneous diffusion, eliminate casting segregation, dissolve coarse compounds, and precipitate a uniformly dispersed phase. Spray cooling and controlling the cooling rate aim to avoid excessively rapid cooling leading to internal stress, or excessively slow cooling leading to coarse dispersed phases. The homogenization annealing process can increase the recrystallization temperature during subsequent extrusion and enhance the grain boundary pinning effect.

[0050] In step four of this embodiment, the use of an arc-shaped working belt mold, precise temperature control, and medium-speed extrusion reduces surface shear deformation and temperature concentration. The use of an arc-shaped working belt mold with a radius of 3mm to 5mm eliminates dead zones in metal flow and reduces the difference in deformation rates between the surface and the core. Preheating ensures uniform metal flow. Medium-speed extrusion after heating aims to avoid excessively low temperatures leading to high deformation resistance and easy cracking, and excessively high temperatures exacerbating surface grain coarsening. This balances deformation heat and heat dissipation, preventing surface overheating.

[0051] In step five of this embodiment, the high residual heat after the bar extrusion allows for immediate online quenching, which can suppress recrystallization and grain growth, ensure a supersaturated solid solution, and prevent grain coarsening caused by high-temperature dwell.

[0052] In step six of this embodiment, the bar stock has internal stress after quenching. Stretching and straightening can eliminate the internal stress, improve the straightness, and further refine the grains, thereby improving the uniformity of the microstructure.

[0053] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that, in step one, the raw materials are weighed and proportioned according to the following mass percentages: Si: 0.62%, Fe: 0.18%, Cu: 0.21%, Mn: 0.1%, Cr: 0.28%, Mg: 0.92%, Zn: 0.12%, Ti: 0.10%, with individual impurities ≤0.05%, total impurities: 0.10%, and the balance being Al. Other steps and parameters are the same as in Specific Implementation Method One.

[0054] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 in that, in step two, the raw materials are melted at 730℃, stirred evenly, and then the slag and floating slag are removed. Al-5Ti-1B wire is then added at 735℃, followed by refining and filtration. Finally, the material is cast into a round ingot at a low temperature of 730℃. Other steps and parameters are the same as in Specific Implementation Method 1.

[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method One in that the Al-5Ti-1B wire mentioned in step two is used as a grain refiner, with an addition rate of 2~3 m / min and a dosage of 1~2 kg per ton of molten aluminum alloy. Other steps and parameters are the same as in Specific Implementation Method One.

[0056] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method One in that, in step two, the refining and filtration are performed by introducing Ar gas with a purity ≥99.9% for 15-20 minutes, followed by filtration through a double-layer ceramic filter plate of 30ppi + 50ppi. Other steps and parameters are the same as in Specific Implementation Method One.

[0057] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method One in that the diameter of the round ingot mentioned in step two is 120mm~200mm. Other steps and parameters are the same as in Specific Implementation Method One.

[0058] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method One in that, in step three, the round ingot is heated to 565℃ and held at that temperature for 9 hours. After the holding period, it is spray-cooled to room temperature at a rate of 20℃ / min, resulting in a homogenized annealed ingot. Other steps and parameters are the same as in Specific Implementation Method One.

[0059] Specific Implementation Method Eight: Similar to Specific Implementation Method, in step four, an arc-shaped working belt mold is used and preheated to 480°C, the extrusion cylinder is preheated to 410°C, and then the above-mentioned homogenized annealed ingot is heated to 495°C for hot extrusion molding to obtain a bar. Other steps and parameters are the same as in Specific Implementation Method One.

[0060] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method One in that the radius of the arc-shaped working belt mold mentioned in step four is 3mm~5mm. Other steps and parameters are the same as in Specific Implementation Method One.

[0061] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method One in that, in step four, the hot extrusion molding process involves an extrusion speed of 2-4 m / min, an extrusion ratio of 10-20, and an extrusion outlet bar temperature of 490℃-510℃. Other steps and parameters are the same as in Specific Implementation Method One.

[0062] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Method One in that, in step five, the temperature of the bar is reduced to 70°C under conditions of a water temperature of 30°C and a cooling rate of 90°C / min. Other steps and parameters are the same as in Specific Implementation Method One.

[0063] Specific Implementation Method Twelve: This implementation method differs from Specific Implementation Method One in that, in step six, the stretching and straightening deformation is 1% to 3%. Other steps and parameters are the same as in Specific Implementation Method One.

[0064] Specific Implementation Method Thirteen: This implementation method differs from Specific Implementation Method One in that step six involves maintaining the temperature at 175°C for 8 hours. All other steps and parameters are the same as in Specific Implementation Method One.

[0065] The beneficial effects of the present invention are verified through the following embodiments:

[0066] The following description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0067] Example 1:

[0068] A method for preparing 6061 aluminum alloy bars without coarse grain rings, comprising the following steps:

[0069] I. Alloy composition blending:

[0070] According to the mass percentage, Si: 0.62%, Fe: 0.18%, Cu: 0.21%, Mn: 0.1%, Cr: 0.28%, Mg: 0.92%, Zn: 0.12%, Ti: 0.10%, individual impurities ≤ 0.05%, total impurities: 0.10%, balance Al, the raw materials are weighed and prepared;

[0071] II. Melting and Casting:

[0072] The above raw materials are melted at 730℃, stirred evenly, and then the slag and floating slag are removed. Then Al-5Ti-1B wire is added at 735℃, and the materials are refined and filtered. Finally, they are cast into round ingots at 730℃.

[0073] III. Homogenization Annealing:

[0074] The above-mentioned round ingots were heated to 565℃ and held for 9 hours. After the holding period, they were spray-cooled to room temperature at a rate of 20℃ / min to obtain homogenized annealed ingots.

[0075] IV. Hot extrusion molding:

[0076] The arc working zone mold is used and preheated to 480°C, the extrusion cylinder is preheated to 410°C, and then the above homogenized annealed ingot is heated to 495°C for hot extrusion molding to obtain the bar.

[0077] V. Online Quenching:

[0078] After extrusion, the above-mentioned bars are directly fed into a circulating water tank, where the temperature of the bars is reduced to 70°C under the conditions of water temperature of 30°C and cooling rate of 90°C / min, to obtain quenched bars.

[0079] VI. Stretching, straightening, and artificial aging:

[0080] After quenching, the bar is stretched and straightened, then placed in an aging furnace and held at 175°C for 8 hours. After holding, it is air-cooled to room temperature to obtain a 6061 aluminum alloy bar without coarse grain rings, thus completing the preparation method described above.

[0081] In step two of this embodiment, the Al-5Ti-1B wire is used as a grain refiner, with an addition rate of 2~3m / min and a dosage of 1~2kg per ton of aluminum alloy melt.

[0082] The refining and filtration process described in step two of this embodiment involves passing Ar gas with a purity of ≥99.9% through the filter for 18 minutes, followed by filtration through a double-layer ceramic filter plate of 30ppi+50ppi.

[0083] The diameter of the round ingot mentioned in step two of this embodiment is 150mm.

[0084] The radius of the arc working belt mold mentioned in step four of this embodiment is 4mm.

[0085] The hot extrusion molding described in step four of this embodiment has the following characteristics: extrusion speed of 3 m / min, extrusion ratio of 15, and extrusion outlet bar temperature of 500℃.

[0086] In step six of this embodiment, the stretching straightening process involves a stretching deformation of 2%.

[0087] The 6061 aluminum alloy rod without coarse grain rings prepared in this embodiment is as follows: Figure 1 As shown, the overall cross-section has uniform grain size, no layered coarse grain structure, and is composed of dense, uniform, and fine grains throughout.

[0088] Example 2:

[0089] The difference between this embodiment and Embodiment 1 is that:

[0090] I. Alloy composition: Mn: 0.08%, Cr: 0.25%;

[0091] 2. Homogenization annealing: Heat to 560℃ and hold for 10 hours;

[0092] III. Hot extrusion molding: The ingot is heated to 485°C; the extrusion speed is 2m / min; other steps are the same as in Example 1.

[0093] Example 3:

[0094] The difference between this embodiment and Embodiment 1 is that:

[0095] I. Alloy composition: Mn: 0.12%, Cr: 0.30%;

[0096] 2. Homogenization annealing: Heat to 570℃ and hold for 8 hours;

[0097] III. Hot extrusion molding: The ingot is heated to 515℃; the extrusion speed is 4m / min; other steps are the same as in Example 1.

[0098] Comparative example (conventional process)

[0099] Composition: Si: 0.55%, Fe: 0.25%, Cu: 0.15%, Mn: 0.05%, Mg: 0.85%, Cr: 0.20%, Zn: 0.20%, Ti: 0.05%, balance Al;

[0100] Melting and casting: conventional melting, argon-free refining, single-layer filtration;

[0101] Homogenization annealing: 550℃ for 6 hours;

[0102] Extrusion: Flat working belt die, ingot 525℃, extrusion speed 5m / min;

[0103] Quenching: Air cool to room temperature;

[0104] Duration: Keep warm at 190℃ for 6 hours.

[0105] The cross-section of the rods prepared in the comparative example has a coarse-grained ring metallographic structure, such as... Figure 2As shown, there is a distinct annular region of coarse grains on the outer edge of the bar, which is significantly different in size from the internal matrix grains, and the coarse grain defects are clearly visible.

[0106] result:

[0107] The performance test results are shown in Table 1:

[0108] coarse crystal ring none none none Yes (thickness 3mm) Grain size (grade) 7.0 6.5 6.5 3.0 Tensile strength (MPa) 325 315 320 280 Yield strength (MPa) 285 275 280 240 Elongation (%) 14.0 13.0 13.5 9.0

[0109] As shown in Table 1, the test data of the three sets of examples show that the products prepared by the examples are free of coarse crystal rings, with fine and uniform grains. The mechanical properties are significantly better than those of products prepared by traditional processes, indicating that the technical solutions are highly reliable and have significant improvement effects.

Claims

1. A method for preparing 6061 aluminum alloy rods without coarse grain rings, characterized in that, It proceeds in the following steps: I. Alloy composition blending: According to the mass percentage, Si: 0.60%~0.65%, Fe≤0.20%, Cu: 0.19%~0.24%, Mn: 0.08%~0.12%, Cr: 0.25%~0.30%, Mg: 0.90%~0.95%, Zn≤0.15%, Ti: 0.08%~0.12%, with individual impurities ≤0.05% and total impurities ≤0.15%, and the balance being Al, the raw materials are prepared and weighed. II. Melting and Casting: The above raw materials are melted at 720℃~740℃, stirred evenly, and then the slag and floating slag are removed. Then Al-5Ti-1B wire is added at 730℃~740℃, and the materials are refined and filtered. Finally, the materials are cast into round ingots at a low temperature of 725℃~735℃. III. Homogenization Annealing: The above-mentioned round ingots are heated to 560℃~570℃ and held for 8~10 hours. After the holding period, they are spray-cooled to room temperature at a rate of 15~25℃ / min to obtain homogenized annealed ingots. IV. Hot extrusion molding: The arc working zone mold is used and preheated to 470℃~490℃, the extrusion cylinder is preheated to 400℃~430℃, and then the above homogenized annealed ingot is heated to 485℃~515℃ and hot extruded to obtain the bar. V. Online Quenching: After extrusion, the above-mentioned bars are directly fed into a circulating water tank. The temperature of the bars is reduced to ≤80℃ under the conditions of water temperature ≤40℃ and cooling rate ≥80℃ / min, to obtain quenched bars. VI. Stretching, straightening, and artificial aging: After quenching, the bar is stretched and straightened, then placed in an aging furnace and held at 170℃~180℃ for 7~9 hours. After holding, it is air-cooled to room temperature to obtain a 6061 aluminum alloy bar without coarse grain rings, thus completing the preparation method described above.

2. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, In step one, the ingredients are prepared and weighed according to the following mass percentages: Si: 0.62%, Fe: 0.18%, Cu: 0.21%, Mn: 0.1%, Cr: 0.28%, Mg: 0.92%, Zn: 0.12%, Ti: 0.10%, with individual impurities ≤0.05%, total impurities: 0.10%, and the balance being Al.

3. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, In step two, the raw materials are melted at 730℃, stirred evenly, and then the slag and floating slag are removed. Then, Al-5Ti-1B wire is added at 735℃, and the materials are refined and filtered. Finally, the materials are cast into round ingots at a low temperature of 730℃.

4. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, The Al-5Ti-1B wire mentioned in step two is used as a grain refiner, with an addition rate of 2~3m / min and a dosage of 1~2kg per ton of aluminum alloy melt.

5. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, The refining and filtration described in step two: Ar gas with a purity of ≥99.9% is introduced for refining for 15~20 minutes, and then filtered through a double-layer ceramic filter plate of 30ppi+50ppi.

6. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, The diameter of the round ingot mentioned in step two is 120mm~200mm.

7. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, In step three, the round ingot is heated to 565℃ and held for 9 hours. After the holding period, it is spray-cooled to room temperature at a rate of 20℃ / min to obtain a homogenized annealed ingot.

8. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, The radius of the arc working zone mold mentioned in step four is 3mm~5mm.

9. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, The hot extrusion molding described in step four: the extrusion speed is 2~4m / min, the extrusion ratio is 10~20, and the temperature of the extruded bar is 490℃~510℃.

10. The method for preparing 6061 aluminum alloy rods without coarse grain rings according to claim 1, characterized in that, In step six, the stretching and straightening process involves a stretching deformation of 1% to 3%.

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