Production method of 7-series aluminum alloy reverse extrusion automobile rod

Abstract

The application provides a production method of 7-series aluminum alloy reverse extrusion automobile rod, which comprises the following steps of batching, melting and casting, casting rod homogenization, extrusion, rod quenching, stretching and cutting, aging treatment and the like, wherein the first-stage homogenization system and the second-stage homogenization system are adopted in the casting rod homogenization, and the reverse extrusion die comprises a rear chamber and a working belt which are connected in sequence, the rear chamber comprises a first conical zone, a cylindrical zone and a second conical zone which are connected in sequence in the extrusion process. Through optimization of alloy components, improvement of the melting and casting process, adjustment of the die structure design and accurate control of the extrusion process parameters, the continuous online quenching production is realized, the surface quality defects are significantly reduced, the waste rate and the production cost are reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy processing technology, and specifically discloses a method for producing 7-series aluminum alloy reverse-extruded automotive bars. Background Technology

[0002] With the development of the automotive industry, the role and importance of aluminum alloy extruded bars in automobile manufacturing are becoming increasingly prominent. 7-series aluminum extruded bars, as a lightweight and high-strength material, are also suitable for the automotive industry, used to manufacture automotive parts such as body structures, frames, engine parts, and transmission components. 7-series aluminum extruded bars provide high strength and rigidity while reducing vehicle weight, improving fuel economy and handling performance; their role and importance in automobile manufacturing cannot be ignored. As a representative of ultra-high-strength aluminum alloys, 7-series aluminum alloys possess excellent comprehensive properties, which can optimize the microstructure of forged workpieces and reduce microstructural defects. However, due to the high deformation resistance of 7-series aluminum alloys, slow extrusion speeds, and susceptibility to coarse grains and surface defects, online quenching and extrusion cannot be achieved in conventional production, significantly reducing production efficiency.

[0003] Reverse extrusion is one of the methods for producing aluminum alloy bars. During reverse extrusion, the metal flows uniformly, there is no friction, the required extrusion pressure is low, alloys with higher deformation resistance can be extruded, the microstructure and mechanical properties of the extruded products are basically the same across length, waste such as excess material is significantly reduced, and the yield is high. While reverse extrusion has these advantages, it also has disadvantages. During reverse extrusion, dead zones are generated on the surface of the extruded bar. These dead zones easily participate in the flow, leading to defects such as delamination, bubbles, and peeling on the product surface, resulting in a decline in surface quality. Furthermore, due to the structural limitations of reverse extrusion equipment, continuous production is not possible, significantly impacting production efficiency. To address these problems, it is essential to research and design a novel reverse extrusion method for producing 7-series aluminum alloy automotive bars, overcoming the existing issues in automotive bar reverse extrusion production. Summary of the Invention

[0004] This invention addresses the problems encountered in the existing reverse extrusion production of automotive bars, such as the deterioration of product surface quality due to the participation of dead zones in the billet flow and the inability to produce continuously during the reverse extrusion process. It proposes a method for producing 7-series aluminum alloy reverse extruded automotive bars.

[0005] This invention provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars, comprising the following steps:

[0006] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.5%~2.55%, Mn: ≤0.07%, Mg: 2.4%~2.6%, Cr: 0.05%~0.1%, Zn: 6.8%~7.0%, Ti: 0.07%~0.1%, Zr: 0.15%~0.2%, Sc: 0.17%~0.2%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al;

[0007] S2. Melting and casting: The aluminum alloy raw material prepared in step S1 is placed into a melting furnace for melting and casting to obtain a casting rod;

[0008] S3. Homogenization of casting rod: The casting rod obtained in step S2 is subjected to a primary homogenization process and a secondary homogenization process to obtain a round casting ingot. The temperature of the primary homogenization annealing process is 305-315℃, and the holding time is 4-8 hours. The temperature of the secondary homogenization annealing process is 460-470℃, and the holding time is 20-23 hours.

[0009] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die includes a rear chamber and a working belt connected in sequence. The rear chamber includes a first conical zone, a cylindrical zone, and a second conical zone connected in sequence. The inlet diameter of the first conical zone is larger than the outlet diameter, and the outlet diameter of the first conical zone is equal to the diameter of the cylindrical zone. The inlet diameter of the second conical zone is equal to the diameter of the cylindrical zone, and the inlet diameter of the second conical zone is larger than the outlet diameter. The second conical zone is connected to the working belt, and the outlet diameter of the second conical zone is equal to the diameter of the working belt. The round ingot is heated by a stepped heating method. The heating temperature of the head end of the round ingot is 390-410℃, the heating temperature of the tail end is 370-390℃, the extrusion cylinder temperature is 390-420℃, the heating temperature of the reverse extrusion die is 400-450℃, and the product speed is 3.5m / min-4m / min.

[0010] S5. Bar quenching, stretching and cutting: The bar obtained in step S4 is quenched to obtain quenched bar. The quenched bar is then stretched and straightened before being cut into a specified length.

[0011] S6. Aging treatment: The cut bars from step S5 are subjected to aging treatment at an aging temperature of 157-163℃ for 14 hours to obtain automotive bars.

[0012] According to some embodiments of this application, a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S1, the ingredients are: Si: ≤0.05%, Fe: ≤0.39%, Cu: 2.52%~2.54%, Mn: ≤0.05%, Mg: 2.53%~2.58%, Cr: 0.07%~0.09%, Zn: 6.88%~6.95%, Ti: 0.08%~0.09%, Zr: 0.17%~0.19%, Sc: 0.17%~0.18%, individual impurities ≤0.05%, total impurities ≤0.15%, and the balance is Al.

[0013] According to some embodiments of this application, a method for producing 7-series aluminum alloy reverse-extruded automotive bars is described. In step S2, during melting and casting, a semi-continuous casting method is used. During the melting and casting process, foam ceramic filtration is employed, Al-Ti-B wire is used to refine the grains, the melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the amount of refining agent is 2.8kg / TAl, the amount of waste added is ≤10%, and the amount of hydrogen is 0.15ml / 100g.

[0014] According to some embodiments of this application, a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S3, the temperature of the first-stage homogenization annealing process is 310°C and the holding time is 6.5 hours; the temperature of the second-stage homogenization annealing process is 470°C and the holding time is 22 hours.

[0015] According to some embodiments of this application, a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S3, the round ingot is a Φ247mm round ingot.

[0016] According to some embodiments of this application, in a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S4, the included angle between the sidewall of the first conical region and the axis is 68° to 71°, and the included angle between the sidewall of the second conical region and the axis is 56.5° to 60°.

[0017] According to some embodiments of this application, in a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S4, the distance from the inlet to the outlet of the first conical region is 25 mm; the distance from the inlet to the outlet of the cylindrical region is 25 mm; and the distance from the inlet to the outlet of the second conical region is 15 mm.

[0018] According to some embodiments of this application, a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S5, the cooling method during quenching is water cooling, the quenching zone temperature is 420-450℃, and the exit temperature from the quenching zone is ≤50℃.

[0019] According to some embodiments of this application, in a method for producing 7-series aluminum alloy reverse-extruded automotive bars, the diameter of the cylindrical region in step S5 is 81 mm.

[0020] According to some embodiments of this application, in a method for producing 7-series aluminum alloy reverse-extruded automotive bars, in step S5, the stretching and straightening process has a stretching rate of 0.5%-1%.

[0021] This invention proposes a method for producing 7-series aluminum alloy reverse-extruded automotive bars. By optimizing alloy composition, improving casting process, adjusting die structure design, and precisely controlling extrusion process parameters, continuous online quenching production is achieved, significantly reducing surface quality defects. This invention effectively eliminates segregation in round ingots through primary and secondary homogenization processes, controlling the size and distribution of precipitated phases in the round ingots, thereby greatly improving the alloy's strength and recrystallization temperature, reducing the deformation resistance of the round ingots, and increasing extrudability. This ensures the performance of the produced automotive bars while improving alloy fluidity and surface quality. This invention employs a reverse-extruded die with first and second conical zones, reducing the volume of dead metal and preventing dead metal from flowing to the surface of the automotive bars, forming defects such as layering, bubbles, and peeling, thus improving the surface quality of the automotive bars. Furthermore, the first and second conical zones of the reverse-extruded die reduce extrusion pressure. In addition, the first and second conical zones of the reverse-extruded die increase the aluminum storage capacity of the die, enabling continuous extrusion production, reducing scrap rate and production costs, and improving production efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a method for producing 7-series aluminum alloy reverse-extruded automotive bars according to the present invention.

[0023] Figure 2 This is a schematic cross-sectional view of the extrusion die of the present invention;

[0024] Figure 3 This is a top view of the extrusion die of the present invention;

[0025] Figure 4 This is a high-magnification microstructure image of the automotive bar produced in Example 3 of the present invention;

[0026] Figure 5 This is a high-magnification microstructure image of the automotive bar produced in Example 4 of the present invention;

[0027] Figure 6 This is a high-magnification microstructure image of the automotive bar produced in Example 5 of the present invention;

[0028] Figure 7 This is a high-magnification microstructure image of the automotive bar produced in Example 6 of the present invention;

[0029] Figure 8 This is a high-magnification microstructure image of the automotive bar produced in Example 7 of the present invention;

[0030] Figure 9 This is a high-magnification microstructure image of the automotive bar produced in Example 8 of the present invention;

[0031] Figure 10 This is a high-magnification microstructure image of the automotive bar produced in Example 9 of the present invention;

[0032] Figure 11 This is a high-magnification microstructure image of the automotive bar produced in Example 10 of the present invention;

[0033] Figure 12 This is a high-magnification microstructure image of the automotive bar produced in Example 11 of the present invention;

[0034] Figure 13 This is a high-magnification microstructure image of the automotive bar produced in Comparative Example 2 of this invention.

[0035] In the diagram: 1. Rear chamber; 1-1. First conical zone; 1-2. Cylindrical zone; 1-3. Second conical zone; 2. Working zone. Detailed Implementation

[0036] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0037] Example 1: This example provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars, such as... Figure 1 As shown, it includes the following steps:

[0038] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.5%~2.55%, Mn: ≤0.07%, Mg: 2.4%~2.6%, Cr: 0.05%~0.1%, Zn: 6.8%~7.0%, Ti: 0.07%~0.1%, Zr: 0.15%~0.2%, Sc: 0.17%~0.2%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al;

[0039] S2. Melting and casting: The aluminum alloy raw material prepared in step S1 is placed into a melting furnace for melting and casting to obtain a casting rod;

[0040] S3. Homogenization of casting rods: The casting rods obtained in step S2 are subjected to a primary homogenization process and a secondary homogenization process to obtain round castings. The temperature of the primary homogenization annealing process is 305-315℃, and the holding time is 4-8 hours. The temperature of the secondary homogenization annealing process is 460-470℃, and the holding time is 20-23 hours.

[0041] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die includes a rear chamber 1 and a working belt 2 connected in sequence. The rear chamber 1 includes a first conical zone 1-1, a cylindrical zone 1-2, and a second conical zone 1-3 connected in sequence. The inlet diameter of the first conical zone 1-1 is larger than the outlet diameter, and the outlet diameter of the first conical zone 1-1 is equal to the diameter of the cylindrical zone 1-2. The inlet diameter of the second conical zone 1-3 is equal to the diameter of the cylindrical zone 1-2. The inlet diameter of the conical zone 1-3 is larger than the outlet diameter. The second conical zone 1-3 is connected to the working zone 2. The outlet diameter of the second conical zone 1-3 is equal to the diameter of the working zone 2. The round ingot is heated by a stepped heating method. The heating temperature of the head end of the round ingot is 390-410℃, the heating temperature of the tail end is 370-390℃, the extrusion cylinder temperature is 390-420℃, the heating temperature of the reverse extrusion die is 400-450℃, and the product speed is 3.5m / min-4m / min.

[0042] S5. Bar quenching, stretching and cutting: Quench the bar obtained in step S4 to obtain quenched bar, stretch and straighten the quenched bar and then cut it into the specified length.

[0043] S6. Aging treatment: The cut bars from step S5 are subjected to aging treatment at an aging temperature of 157-163℃ for 14 hours to obtain automotive bars.

[0044] Example 2: This example provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars, including the following steps:

[0045] S1. Batching: The aluminum alloy raw materials are prepared according to the following weight ratios: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.5%~2.55%, Mn: ≤0.07%, Mg: 2.4%~2.6%, Cr: 0.05%~0.1%, Zn: 6.8%~7.0%, Ti: 0.07%~0.1%, Zr: 0.15%~0.2%, Sc: 0.17%~0.2%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al; In the Al-Zn-Mg-Cu alloy system, Zn and Mg are the main strengthening elements. Adding Cu can improve the corrosion resistance of the alloy, but the Zn content should be controlled to not exceed 7%, otherwise the fracture toughness, weldability, and corrosion resistance of the alloy will deteriorate. In addition, when the Mg content exceeds the amount required to form MgZn2, it can play a supplementary role in strengthening the alloy. Zr has low quenching sensitivity and good hardenability and weldability of the alloy. The addition of trace element Sc, which forms Al3(Sc,Zr) particles with Zr, significantly improves the grain refinement effect, increases the recrystallization temperature, and refines the grains.

[0046] As a preferred embodiment, the ingredients can be: Si: ≤0.05%, Fe: ≤0.39%, Cu: 2.52%~2.54%, Mn: ≤0.05%, Mg: 2.53%~2.58%, Cr: 0.07%~0.09%, Zn: 6.88%~6.95%, Ti: 0.08%~0.09%, Zr: 0.17%~0.19%, Sc: 0.17%~0.18%, with individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al;

[0047] S2. Melting and casting: The aluminum alloy raw material prepared in step S1 is placed into a melting furnace for melting and casting to obtain a casting rod;

[0048] As a preferred embodiment, specifically, during the casting process, a semi-continuous casting method is used. During the casting process, foam ceramic filtration is used, Al-Ti-B wire is used to refine the grains, the melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the amount of refining agent is 2.8kg / TAl, the amount of waste added is ≤10%, and the amount of hydrogen is 0.15ml / 100g.

[0049] S3. Homogenization of the cast rod: The cast rod obtained in step S2 is subjected to a primary homogenization process and a secondary homogenization process to obtain a round ingot. The temperature of the primary homogenization annealing process is 305-315℃, and the holding time is 4-8 hours; the temperature of the secondary homogenization annealing process is 460-470℃, and the holding time is 20-23 hours. By setting the primary and secondary homogenization processes, segregation in the round ingot can be effectively eliminated, and the size and distribution of precipitated phases in the round ingot can be controlled, thereby greatly improving the strength and recrystallization temperature of the alloy, reducing the deformation resistance of the round ingot, and increasing extrudability. This can ensure the performance of the produced automotive rod while improving the alloy fluidity and surface quality.

[0050] As a preferred embodiment, specifically, the temperature of the first-stage homogenization annealing process is 310°C, and the holding time is 6.5 hours; the temperature of the second-stage homogenization annealing process is 470°C, and the holding time is 22 hours; the resulting round ingot can be a Φ247mm round ingot.

[0051] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die is as follows: Figure 2 and Figure 3 As shown, the reverse extrusion die includes a rear chamber 1 and a working belt 2 connected in sequence. The rear chamber 1 includes a first conical region 1-1, a cylindrical region 1-2, and a second conical region 1-3 connected in sequence. The inlet diameter of the first conical region 1-1 is larger than its outlet diameter, and the outlet diameter of the first conical region 1-1 is equal to the diameter of the cylindrical region 1-2. The inlet diameter of the second conical region 1-3 is equal to the diameter of the cylindrical region 1-2, and the inlet diameter of the second conical region 1-3 is larger than its outlet diameter. The second conical region 1-3 is connected to the working belt 2, and the outlet diameter of the second conical region 1-3 is equal to the diameter of the working belt 2. Heating is achieved through a stepped heating method. The round ingot is heated to 390–410°C at the head and 370–390°C at the tail. The extrusion cylinder is heated to 390–420°C, and the reverse extrusion die is heated to 400–450°C. The product speed is 3.5 m / min–4 m / min. The conventional flat die for bar extrusion is designed with an angled concave structure. Compared to conventional dies, the die angle is reduced, improving the uniformity of metal flow. The reduced die angle also reduces the dead zone volume, significantly mitigating defects such as layering, bubbles, and peeling caused by metal flowing to the product surface in the dead zone. This improves the surface quality of the extruded bar and reduces the extrusion pressure. Simultaneously, the addition of a first conical zone 1-1 and a second conical zone 1-3 increases the aluminum storage capacity of the die, preventing insufficient aluminum storage from disrupting continuous extrusion. In this embodiment, after the aluminum alloy round ingot is extruded, a blank is retained in the concave die and welded to the next ingot for continuous online production, improving production efficiency.

[0052] As a preferred embodiment, specifically, the angle between the sidewall of the first conical region 1-1 and the axis can be 68° to 71°, and the angle between the sidewall of the second conical region 1-3 and the axis can be 56.5° to 60°; the distance from the inlet to the outlet of the first conical region 1-1 can be 25mm; the distance from the inlet to the outlet of the cylindrical region 1-2 can be 25mm; the distance from the inlet to the outlet of the second conical region 1-3 can be 15mm; the diameter of the cylindrical region 1-2 can be 81mm, producing automotive bar stock with a diameter of 81mm;

[0053] S5. Bar quenching, stretching and cutting: Quench the bar obtained in step S4 to obtain quenched bar, stretch and straighten the quenched bar and then cut it into the specified length.

[0054] As a preferred embodiment, the cooling method during quenching is water cooling, the temperature in the quenching zone is 420-450℃, and the temperature exiting the quenching zone is ≤50℃; during the tensile straightening process, the tensile rate is 0.5%-1%.

[0055] S6. Aging treatment: The cut bars in step S5 are subjected to aging treatment at an aging temperature of 157-163℃ for 14 hours to obtain automotive bars.

[0056] As a preferred embodiment, the diameter of the automotive bar is 81 mm.

[0057] Example 3: This example provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars, specifically including the following steps:

[0058] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: 0.07%, Fe: 0.13%, Cu: 2.52%, Mn: 0.05%, Mg: 2.49%, Cr: 0.06%, Zn: 6.88%, Ti: 0.08%, Zr: 0.16%, Sc: 0.18%, single impurity: 0.05%, balance Al;

[0059] S2. Melting and Casting: The aluminum alloy raw materials prepared in step S1 are placed into a melting furnace for melting and casting to obtain a cast ingot. A semi-continuous casting method is used during melting and casting. Foam ceramic filtration and Al-Ti-B wire are used to refine the grains. The melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the refining agent dosage is 2.8kg / TAl, the waste addition is ≤10%, and the hydrogen content is 0.15ml / 100g. The slag content of the ingot meets the secondary requirements of GB / T32186-2015.

[0060] S3. Homogenization of casting rods: The casting rods obtained in step S2 are subjected to a primary homogenization process and a secondary homogenization process to obtain round castings. The temperature of the primary homogenization annealing process is 310℃ and the holding time is 6.5 hours; the temperature of the secondary homogenization annealing process is 470℃ and the holding time is 22 hours.

[0061] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die includes a first conical zone 1-1, a cylindrical zone 1-2, a second conical zone 1-3, and a working zone 2 connected in sequence. The angle between the side wall of the first conical zone 1-1 and the axis is 69.3°, and the angle between the side wall of the second conical zone 1-3 and the axis is 58.5°. The round ingot is heated by a stepped heating method, and Φ81mm bars are produced by a 20 MN reverse aluminum extrusion press. The round ingot is Φ247mm. The heating temperature of the head end of the round ingot is 405℃, the heating temperature of the tail end is 385℃, the heating temperature of the reverse extrusion die is 440℃, and the temperature of the extrusion cylinder is 403℃.

[0062] S5. Quenching, stretching and cutting of bar stock: Quenching of the bar stock obtained in step S4 is carried out by water cooling. The quenching temperature is 443℃ and the temperature outside the quenching zone is ≤50℃. The quenched bar stock is then stretched and straightened with a stretching rate of 0.5%-1%. The stretched and straightened bar stock is then cut into the specified length.

[0063] S6. Aging treatment: The cut bars from step S5 are subjected to aging treatment at a temperature of 160℃ for 14 hours to obtain automotive bars.

[0064] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 1.

[0065] Table 1 Mechanical property results

[0066]

[0067] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 2. Figure 4 As shown.

[0068] Table 2 Metallographic high-magnification structure

[0069]

[0070] Low-magnification test: The test equipment used an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 3.

[0071] Table 3 Low-magnification tissue test

[0072]

[0073] Example 4 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the angle between the sidewall of the first conical region 1-1 and the axis is 68°, and the angle between the sidewall of the second conical region 1-3 and the axis is 56.5°. The test results of the automotive bars produced in this example are shown below:

[0074] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 4.

[0075] Table 4 Mechanical property results

[0076]

[0077] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 5. Figure 5 As shown.

[0078] Table 5 Metallographic High Magnification Structure

[0079]

[0080] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 6.

[0081] Table 6 Low-magnification tissue test

[0082]

[0083] Example 5 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the angle between the sidewall of the first conical region 1-1 and the axis is 68°, and the angle between the sidewall of the second conical region 1-3 and the axis is 60°. The test results of the automotive bars produced in this example are shown below:

[0084] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 7.

[0085] Table 7 Mechanical property results

[0086]

[0087] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 8. Figure 6 As shown.

[0088] Table 8 Metallographic High Magnification Structure

[0089]

[0090] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 9.

[0091] Table 9 Low-magnification tissue test

[0092]

[0093] Example 6 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the angle between the sidewall of the first conical region 1-1 and the axis is 71°, and the angle between the sidewall of the second conical region 1-3 and the axis is 56.5°. The test results of the automotive bars produced in this example are shown below:

[0094] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 10.

[0095] Table 10 Mechanical property results

[0096]

[0097] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 11. Figure 7 As shown.

[0098] Table 11 Metallographic Structure (High Magnification)

[0099]

[0100] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 12.

[0101] Table 12 Low-magnification tissue test

[0102]

[0103] Example 7 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the angle between the sidewall of the first conical region 1-1 and the axis is 71°, and the angle between the sidewall of the second conical region 1-3 and the axis is 60°. The test results of the automotive bars produced in this example are shown below:

[0104] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 13.

[0105] Table 13 Mechanical property results

[0106]

[0107] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 14. Figure 8 As shown.

[0108] Table 14 Metallographic High Magnification Structure

[0109]

[0110] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 15.

[0111] Table 15 Low-magnification tissue test

[0112]

[0113] Example 8 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the product speed is 3.5 m / min. The test results of the automotive bars produced in this example are shown below:

[0114] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 16.

[0115] Table 16 Mechanical property results

[0116]

[0117] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 17. Figure 9 As shown.

[0118] Table 17 Metallographic Structure (High Magnification)

[0119]

[0120] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 18.

[0121] Table 18 Low-magnification tissue test

[0122]

[0123] Example 9 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the product speed is 4 m / min. The test results of the automotive bars produced in this example are shown below:

[0124] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 19.

[0125] Table 19 Mechanical property results

[0126]

[0127] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 20. Figure 10 As shown.

[0128] Table 20 Metallographic High Magnification Structure

[0129]

[0130] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 21.

[0131] Table 21 Low-magnification tissue test

[0132]

[0133] Example 10 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the raw materials are: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.5%, Mn: ≤0.07%, Mg: 2.4%, Cr: 0.05%, Zn: 6.8%, Ti: 0.07%, Zr: 0.15%, Sc: 0.17%. The test results of the automotive bars produced in this example are shown below:

[0134] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 22.

[0135] Table 22 Mechanical property results

[0136]

[0137] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 23. Figure 11 As shown.

[0138] Table 23 Metallographic High Magnification Structure

[0139]

[0140] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 24.

[0141] Table 24 Low-magnification tissue test

[0142]

[0143] Example 11 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The reverse-extruded equipment and die used in Example 3 are employed, and the experimental steps and conditions are the same as in Example 3. The difference is that in this example, the raw materials are: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.55%, Mn: ≤0.07%, Mg: 2.6%, Cr: 0.05%~0.1%, Zn: 7.0%, Ti: 0.1%, Zr: 0.2%, Sc: 0.2%. The test results of the automotive bars produced in this example are shown below:

[0144] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 25.

[0145] Table 25 Mechanical property results

[0146]

[0147] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 26. Figure 12 As shown.

[0148] Table 26 Metallographic High Magnification Structure

[0149]

[0150] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 27.

[0151] Table 27 Low-magnification tissue test

[0152]

[0153] Comparative Example 1 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. The method uses the proportions from Example 3 to prepare the aluminum alloy raw materials. The difference from Example 3 is that a conventional reverse-extruded die is used for extrusion. The specific steps include:

[0154] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: 0.07%, Fe: 0.13%, Cu: 2.52%, Mn: 0.05%, Mg: 2.49%, Cr: 0.06%, Zn: 6.88%, Ti: 0.08%, Zr: 0.16%, Sc: 0.18%, single impurity: 0.05%, balance Al;

[0155] S2. Melting and Casting: The aluminum alloy raw materials prepared in step S1 are placed into a melting furnace for melting and casting to obtain a cast ingot. A semi-continuous casting method is used during melting and casting. Foam ceramic filtration and Al-Ti-B wire are used to refine the grains. The melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the refining agent dosage is 2.8kg / TAl, the waste addition is ≤10%, and the hydrogen content is 0.15ml / 100g. The slag content of the ingot meets the secondary requirements of GB / T32186-2015.

[0156] S3. Homogenization of casting rods: The casting rods obtained in step S2 are subjected to a primary homogenization process and a secondary homogenization process to obtain round castings. The temperature of the primary homogenization annealing process is 310℃ and the holding time is 6.5 hours; the temperature of the secondary homogenization annealing process is 470℃ and the holding time is 22 hours.

[0157] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The extrusion die is a conventional bar extrusion die without a conical part. The round ingot is heated by a stepped heating method. The bar is produced by a 20MN reverse aluminum extrusion press with a diameter of 81mm. The round ingot is 247mm in diameter. The heating temperature of the head end of the round ingot is 405℃, the heating temperature of the tail end is 385℃, the heating temperature of the bar extrusion die is 440℃, and the temperature of the extrusion cylinder is 403℃.

[0158] In this embodiment, the surface of the extruded profile made by extruding bar stock through a flat die suffers from severe peeling, and continuous extrusion is not possible.

[0159] Comparative Example 2 provides a method for producing 7-series aluminum alloy reverse-extruded automotive bars. It uses the extrusion equipment and reverse-extruded die from Example 3 for extrusion. Unlike Example 3, this comparative example only employs a single homogenization process, specifically including the following steps:

[0160] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: 0.07%, Fe: 0.13%, Cu: 2.52%, Mn: 0.05%, Mg: 2.49%, Cr: 0.06%, Zn: 6.88%, Ti: 0.08%, Zr: 0.16%, Sc: 0.18%, single impurity: 0.05%, balance Al;

[0161] S2. Melting and Casting: The aluminum alloy raw materials prepared in step S1 are placed into a melting furnace for melting and casting to obtain a cast ingot. A semi-continuous casting method is used during melting and casting. Foam ceramic filtration and Al-Ti-B wire are used to refine the grains. The melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the refining agent dosage is 2.8kg / TAl, the waste addition is ≤10%, and the hydrogen content is 0.15ml / 100g. The slag content of the ingot meets the secondary requirements of GB / T32186-2015.

[0162] S3. Homogenization of casting rod: The casting rod obtained in step S2 is homogenized. Unlike Example 3, this comparative example only uses one homogenization. The homogenization temperature is 470°C and the holding time is 22h.

[0163] S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die includes a first conical zone 1-1, a cylindrical zone 1-2, a second conical zone 1-3, and a working zone 2 connected in sequence. The angle between the side wall of the first conical zone 1-1 and the axis is 69.3°, and the angle between the side wall of the second conical zone 1-3 and the axis is 58.5°. The round ingot is heated by a stepped heating method, and Φ81mm bars are produced by a 20 MN reverse aluminum extrusion press. The round ingot is Φ247mm. The heating temperature of the head end of the round ingot is 405℃, the heating temperature of the tail end is 385℃, the heating temperature of the reverse extrusion die is 440℃, and the temperature of the extrusion cylinder is 403℃.

[0164] S5. Quenching, stretching and cutting of bar stock: Quenching of the bar stock obtained in step S4 is carried out by water cooling. The quenching temperature is 443℃ and the temperature outside the quenching zone is ≤50℃. The quenched bar stock is then stretched and straightened with a stretching rate of 0.5%-1%. The stretched and straightened bar stock is then cut into the specified length.

[0165] S6. Aging treatment: The cut bars from step S5 are subjected to aging treatment at a temperature of 160℃ for 14 hours to obtain automotive bars.

[0166] Mechanical property testing: Testing equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T16865-2013 Tensile testing of wrought aluminum, magnesium and their alloy processed products. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 28.

[0167] Table 28 Mechanical property results

[0168]

[0169] High-magnification microstructure analysis: Testing equipment: AXIO universal research-grade inverted materials microscope. Testing standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Testing method: GB / T3246.1-2012 Deformed aluminum and aluminum alloy products - Microstructure inspection methods - Part 1: Microstructure inspection methods. One piece was randomly selected from the produced automotive bar stock for testing. The test results are shown in Table 29. Figure 13 As shown.

[0170] Table 29 Metallographic High Magnification Structure

[0171]

[0172] Low-magnification test: The test equipment uses an alkaline corrosive solution. Test standard: GB / T6892-2015 General industrial aluminum and aluminum alloy extruded profiles. Test method: GB / T3246.2-2012 Deformed aluminum and aluminum alloy products – Microstructure inspection methods – Part 2: Low-magnification microstructure inspection methods. Four pieces were randomly selected from the produced automotive bar stock and numbered. The results are shown in Table 30.

[0173] Table 30 Low-magnification tissue test

[0174]

[0175] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for producing 7-series aluminum alloy reverse-extruded automotive bars, characterized in that, Includes the following steps: S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratios: Si: ≤0.08%, Fe: ≤0.50%, Cu: 2.5%~2.55%, Mn: ≤0.07%, Mg: 2.4%~2.6%, Cr: 0.05%~0.1%, Zn: 6.8%~7.0%, Ti: 0.07%~0.1%, Zr: 0.15%~0.2%, Sc: 0.17%~0.2%, individual impurities ≤0.05%, total impurities ≤0.15%, balance Al; S2. Melting and casting: The aluminum alloy raw material prepared in step S1 is placed into a melting furnace for melting and casting to obtain a casting rod; S3. Homogenization of casting rod: The casting rod obtained in step S2 is subjected to a primary homogenization process and a secondary homogenization process to obtain a round casting ingot. The temperature of the primary homogenization annealing process is 305-315℃, and the holding time is 4-8 hours. The temperature of the secondary homogenization annealing process is 460-470℃, and the holding time is 20-23 hours. S4. Extrusion: The round ingot from step S3 is placed into a reverse extrusion device for extrusion to obtain a bar. The reverse extrusion die includes a rear chamber (1) and a working belt (2) connected in sequence. The rear chamber (1) includes a first conical region (1-1), a cylindrical region (1-2), and a second conical region (1-3) connected in sequence. The inlet diameter of the first conical region (1-1) is larger than the outlet diameter, and the outlet diameter of the first conical region (1-1) is equal to the diameter of the cylindrical region (1-2). The inlet diameter of the second conical region (1-3) is equal to the diameter of the cylindrical region (1-2), and the inlet diameter of the second conical region (1-3) is larger than the outlet diameter. The conical zone (1-3) is connected to the working belt (2). The outlet diameter of the second conical zone (1-3) is equal to the diameter of the working belt (2). The angle between the side wall of the first conical zone (1-1) and the axis is 68° to 71°. The angle between the side wall of the second conical zone (1-3) and the axis is 56.5° to 60°. The round ingot is heated by a stepped heating method. The heating temperature of the head end of the round ingot is 390 to 410°C, the heating temperature of the tail end is 370 to 390°C, the extrusion cylinder temperature is 390 to 420°C, the heating temperature of the reverse extrusion die is 400 to 450°C, and the product speed is 3.5m / min to 4m / min. S5. Bar quenching, stretching and cutting: The bar obtained in step S4 is quenched to obtain quenched bar. The quenched bar is then stretched and straightened before being cut into a specified length. S6. Aging treatment: The cut bars from step S5 are subjected to aging treatment at an aging temperature of 157-163℃ for 14 hours to obtain automotive bars.

2. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S1, the ingredients are: Si: ≤0.05%, Fe: ≤0.39%, Cu: 2.52%~2.54%, Mn: ≤0.05%, Mg: 2.53%~2.58%, Cr: 0.07%~0.09%, Zn: 6.88%~6.95%, Ti: 0.08%~0.09%, Zr: 0.17%~0.19%, Sc: 0.17%~0.18%, with individual impurities ≤0.05%, total impurities ≤0.15%, and the balance being Al.

3. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S2, during the casting process, a semi-continuous casting method is used. Foam ceramic filtration is employed, and Al-Ti-B wires are used to refine the grains. The melting temperature is 690℃-750℃, the refining temperature is 720℃-740℃, the refining agent dosage is 2.8kg / TAl, the waste addition is ≤10%, and the hydrogen element is 0.15ml / 100g.

4. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S3, the temperature of the first-stage homogenization annealing process is 310°C and the holding time is 6.5 hours; the temperature of the second-stage homogenization annealing process is 470°C and the holding time is 22 hours.

5. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S3, the round ingot is a Φ247mm round ingot.

6. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S4, the distance from the inlet to the outlet of the first conical region (1-1) is 25mm; the distance from the inlet to the outlet of the cylindrical region (1-2) is 25mm; and the distance from the inlet to the outlet of the second conical region (1-3) is 15mm.

7. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S5, the cooling method during quenching is water cooling, the temperature of the quenching zone is 420-450℃, and the temperature exiting the quenching zone is ≤50℃.

8. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S4, the diameter of the cylindrical region (1-2) is 81 mm.

9. The method for producing 7-series aluminum alloy reverse-extruded automotive bars according to claim 1, characterized in that, In step S5, the stretching and straightening process involves a stretching rate of 0.5%-1%.

Images