Method for repairing an extrusion die for 6xxx aluminum alloy solid bar and bar

Abstract

The application relates to the technical field of metal processing, and particularly discloses an extrusion die repairing method for a 6xxx aluminum alloy solid rod and the rod, which comprises the following steps: adopting an original extrusion die to form a solid rod sample, detecting the solid rod sample, determining the organization defect type of the solid rod sample, the organization defect type comprising a coarse crystal ring and secondary defect organization, the secondary defect organization comprising a recrystallization influence ring and mixed crystals; and repairing the original extrusion die according to the organization defect type, wherein when it is determined that the solid rod sample has a recrystallization influence ring, the number of flow guide stages of the original extrusion die is reduced; and when it is determined that the solid rod sample has mixed crystals, the depth of a flow guide hole in the original extrusion die is reduced. The application can effectively improve the secondary defect organization such as the recrystallization influence ring and mixed crystals caused by the newly-added welding block of the original extrusion die, the process is simple and easy to operate, and the application is beneficial to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and in particular to a method for repairing an extrusion die of a 6xxx aluminum alloy solid bar and the bar. Background Art

[0002] Extrusion is the process of forcing a billet through a specific die orifice under triaxial compressive stress to form a profile. The uniformity of the extruded material's structure determines the uniformity of its performance, including mechanical and oxidation resistance. Therefore, achieving a uniform and consistent structure is crucial.

[0003] When aluminum alloy solid bars are heated, the outer grains may become coarse, forming a ring-shaped coarse-grained structure area around the edges of the bar, which is called peripheral coarse-grained structure or coarse-grained ring.

[0004] Patent CN114310141B discloses a method for repairing a solid bar extrusion die, comprising: (1) extruding the original extrusion die to obtain a sample; (2) detecting the distribution of coarse grain rings on the sample; (3) repairing the extrusion die based on the distribution of the coarse grain rings; when the coarse grain rings are distributed in a ring shape and the maximum thickness tmax of the coarse grain rings is ≥0.2D, adjusting the composition and heat treatment process of the aluminum alloy; when the coarse grain rings are distributed in a ring shape and the maximum thickness tmax of the coarse grain rings is <0.2D, forming a welding block on the face die of the extrusion die; when the coarse grain rings are distributed in a localized manner, shortening the length of the extrusion die working zone. The implementation of the present invention can effectively improve the uniformity of the internal structure of the product and reduce the distribution of coarse grain rings.

[0005] However, in actual production, it was found that although the formation of a welding block on the face die of the extrusion die can improve the coarse grain ring to a certain extent, due to the obstruction of the welding block, the extrusion pressure and friction force on the material in the edge area are greater than those in the central area, and it is easy to recrystallize to form coarse grains. The material in these edge areas flows to the central area under the action of the welding block, resulting in a ring of coarse grain structure in the central area of ​​the final extruded rod (ie, the "recrystallization-affected ring"). More seriously, the central area is prone to a mixed distribution of grains of different sizes (ie, "mixed crystals"), which makes the final extruded rod often show different degrees of defect characteristics in the subsequent machining and oxidation links, restricting the application range of the product. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for repairing an extrusion die for 6xxx aluminum alloy solid bars and a bar in response to the existing technical status. The present invention can effectively improve secondary defect structures such as recrystallization influence rings and mixed crystals that are easily caused by the addition of new welding blocks to the original extrusion die. The process is simple and easy to operate, which is conducive to industrial production.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides a method for repairing an extrusion die for a 6xxx aluminum alloy solid bar, comprising:

[0009] A solid bar sample is formed by extruding an original extrusion die, wherein a welding block is provided on a face die of the original extrusion die, and the original extrusion die comprises a flow guide portion and a single-hole extrusion portion;

[0010] Testing the solid bar sample to determine the type of structural defects of the solid bar sample, wherein the structural defect type includes a coarse grain ring and a secondary defect structure, and the secondary defect structure includes a recrystallization-affected ring and a mixed crystal;

[0011] Repair the original extrusion die according to the tissue defect type, wherein

[0012] When it is determined that the solid bar sample has a recrystallization-affected ring, reducing the number of diversion stages of the original extrusion die;

[0013] When it is determined that mixed crystals exist in the solid rod sample, the depth of the guide holes in the original extrusion die is reduced.

[0014] In some embodiments, the step of determining the tissue defect type of the solid bar sample comprises:

[0015] The cross section of the solid bar sample is divided into a central area and a marginal area using the concentric circle dividing line as the partition boundary. The central area is located within the concentric circle dividing line, and the marginal area is located outside the concentric circle dividing line. The center of the concentric circle dividing line coincides with the center of the cross section of the solid bar sample, and r1=0.8R, where r1 is the radius of the concentric circle dividing line and R is the radius of the cross section of the solid bar sample.

[0016] The solid bar sample is subjected to low-magnification tissue testing, wherein:

[0017] When all the coarse-grained microstructure areas fall within the marginal area and the color difference of the central area is ≤3, the microstructure defect type of the solid bar sample is determined to be a coarse-grained ring;

[0018] When the coarse-grained microstructure area falls within the middle area and the color difference of the middle area is greater than 3, the microstructure defect type of the solid bar sample is determined to be a recrystallization-affected ring;

[0019] When no coarse-grained structure area is detected in the solid bar sample under low-magnification structure detection, grain distribution identification is performed on the solid bar sample to determine whether the solid bar sample has a secondary defect structure.

[0020] In some embodiments, the grain distribution identifying step comprises:

[0021] According to a first grain distribution formula, it is determined whether the solid rod sample in the middle region has a secondary defect structure, and the first grain distribution formula is as follows:

[0022] C1 = (D max -D min ) / (D max +D min ),

[0023] In the formula, D max is the maximum grain size in the middle region, and D min is the minimum grain size in the middle region;

[0024] When C1 > 0.3, it is determined that the solid rod sample has a secondary defect structure, otherwise, it is determined that the solid rod sample does not have a secondary defect structure.

[0025] In some embodiments, the grain distribution identifying step comprises:

[0026] The middle region is divided into a detection region and a non-detection region with a circular boundary line as a division boundary line, the detection region is located within the circular boundary line, the non-detection region is located outside the circular boundary line, the center of the circular boundary line coincides with the center of the cross section of the solid rod sample, and 0 < r2 ≤ 0.15R, r2 is the radius of the circular boundary line, and R is the radius of the cross section of the solid rod sample,

[0027] According to a second grain distribution formula, it is determined the grain distribution of the solid rod sample in the detection region of the middle region, and the grain distribution formula is as follows:

[0028] C2 = (D' max -D' min ) / (D' max +D' min ),

[0029] In the formula, D' max is the maximum grain size in the middle region, and D' min is the minimum grain size in the middle region;

[0030] When C2 > 0.2, it is determined that the solid rod sample has a mixed grain defect, otherwise, it is determined that the solid rod sample has a recrystallization affected ring.

[0031] In some embodiments, the color difference test step of the middle region comprises:

[0032] Two groups of test points are selected in the middle region, and the difference S between the center distances of the two groups of test points is greater than 0.3R, where R is the radius of the cross section of the solid bar sample. Each group of test points includes at least one test site, and the test sites within each group of test points have the same center distance.

[0033] Testing the L value, a value, and b value of the test sites within each group of test points, and calculating the average L value, average a value, and average b value among the test sites within each group of test points;

[0034] The color difference ΔE is calculated according to the color difference formula, which is:

[0035]

[0036] Wherein, L1 is the average L value among each test site of the first group of test points, L2 is the average L value among each test site of the second group of test points, a1 is the average a value among each test site of the first group of test points, a2 is the average a value among each test site of the second group of test points, b1 is the average b value among each test site of the first group of test points, and b2 is the average b value among each test site of the second group of test points.

[0037] In some embodiments, the grain distribution identification step includes: performing metallographic analysis on the solid bar sample.

[0038] In some embodiments, the 6xxx aluminum alloy is a 6082 aluminum alloy.

[0039] In some embodiments, the reducing the number of diversion stages of the original extrusion die is to reduce the number of diversion stages by surfacing and / or milling along the peripheral wall of the diversion hole.

[0040] In some embodiments, reducing the depth of the guide hole in the original extrusion die is reducing the depth of the guide hole by surfacing in a direction perpendicular to the axis of the guide hole.

[0041] On the other hand, the present invention also provides a rod, which is extruded by an extrusion die, and the extrusion die is repaired by the above-mentioned extrusion die repair method for 6xxx aluminum alloy solid rods.

[0042] The beneficial effects of the present invention are:

[0043] In the present invention, the original extrusion die is used to prepare solid bar samples, and then the samples are tested to distinguish the types of tissue defects of the samples. Then, corresponding mold repair treatments are performed for different types of tissue defects, so that the tissue defect problems of the solid bars extruded by the repaired extrusion die are improved, and the internal structure of the prepared solid bars is more uniform, thereby improving the secondary defect structures such as recrystallization influence rings and mixed crystals that are easily caused by the newly added welding blocks of the original extrusion die. The process is simple and easy to operate, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of the extrusion die repair method for 6xxx aluminum alloy solid bar according to Example 1 of the present invention.

[0045] Figure 2 Schematic cross-sectional view of the guide portion of Example 1 of the present invention.

[0046] Figure 3 For the present invention Figure 2 Schematic diagram after reducing the number of diversion stages (surfacing treatment).

[0047] Figure 4 For the present invention Figure 2 Schematic diagram after reducing the number of diversion stages (milling treatment).

[0048] Figure 5 For the present invention Figure 2 Schematic diagram of depth reduction.

[0049] Figure 6 This is a microstructure diagram of a solid rod sample with a coarse grain ring according to the present invention.

[0050] Figure 7 Microstructure of a solid bar sample showing the presence of a recrystallization-affected ring according to the present invention.

[0051] Figure 8 This is a microstructure diagram of a solid rod sample containing mixed crystals according to the present invention.

[0052] Figure 9 This is a microstructure diagram of a solid rod sample without coarse grain rings and secondary defect structures according to the present invention.

[0053] Figure 10 This is the organizational diagram of the solid bar produced by the repaired extrusion die of the present invention. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0055] Example 1

[0056] See also Figure 1 As shown, this embodiment discloses a method for repairing an extrusion die of a 6xxx aluminum alloy solid bar, comprising:

[0057] S100. A solid bar sample is formed by extruding the original extrusion die, wherein the surface die of the original extrusion die is provided with a welding block, and the original extrusion die includes a guide portion and a single-hole extrusion portion;

[0058] S200. Detecting the solid bar sample to determine the type of microstructure defects of the solid bar sample, wherein the microstructure defect types include coarse grain rings and secondary defect structures, and the secondary defect structures include recrystallization-affected rings and mixed crystals;

[0059] S300. Repair the original extrusion die according to the tissue defect type, wherein,

[0060] See also Figures 2 to 4 and Figure 7 As shown, when it is determined that the solid bar sample has a recrystallization-affected ring, the level of the original extrusion die guide is reduced;

[0061] See also Figure 2 、 Figure 5 and Figure 8 As shown, when it is determined that mixed crystals exist in the solid rod sample, the depth of the guide hole in the original extrusion die is reduced.

[0062] In the present invention, the original extrusion die is used to prepare solid bar samples, and then the samples are tested to distinguish the types of tissue defects of the samples. Then, corresponding mold repair treatments are performed for different types of tissue defects, so that the tissue defect problems of the solid bars extruded by the repaired extrusion die are improved, and the internal structure of the prepared solid bars is more uniform, thereby improving the secondary defect structures such as recrystallization influence rings and mixed crystals that are easily caused by the newly added welding blocks of the original extrusion die. The process is simple and easy to operate, which is conducive to industrial production.

[0063] Specifically, in the present invention, when it is determined that a recrystallization influence ring exists in the solid bar sample, the number of diversion levels of the original extrusion die is reduced. Reducing the number of diversion levels can reduce the uneven deformation of the material during the extrusion process, thereby helping to control the recrystallization process and control the abnormal growth of grains in the edge material; when it is determined that mixed crystals exist in the solid bar sample, the depth of the diversion holes in the original extrusion die is reduced, thereby reducing the flow resistance of the material in the die, optimizing the flow pattern of the material in the die, and controlling the abnormal growth of grains in the edge material. At the same time, the cooling rates of the edge material and the middle material are more uniform, thereby making the grain size in different regions more uniform.

[0064] It should be noted that since the original extrusion die of the present invention itself has been repaired with a weld block based on the repair method mentioned in the background technology, when it is determined that a coarse grain ring exists in the solid bar sample, the weld block can be adjusted based on the repair method mentioned in the background technology, which will not be repeated here.

[0065] The method of reducing the number of diversion stages of the original extrusion die is to reduce the number of diversion stages by surfacing and / or milling along the peripheral wall of the diversion hole.

[0066] For example, see Figure 2 As shown in the figure, the original extrusion die has 3 levels of diversion. When the number of diversion levels needs to be reduced, it can be done as follows: Figure 3 Overlay welding as shown or Figure 4 The milling method shown reduces the number of diversion stages to 2.

[0067] Wherein, the reducing the depth of the guide hole in the original extrusion die is to reduce the depth of the guide hole by surfacing in a direction perpendicular to the axis of the guide hole.

[0068] For example, see Figure 2 and Figure 5 As shown, the original depth of the guide hole is H, and the depth of the guide hole is reduced to h by surfacing.

[0069] On the other hand, the present invention also provides a rod, which is extruded by an extrusion die, and the extrusion die is repaired by the above-mentioned extrusion die repair method for 6xxx aluminum alloy solid rods.

[0070] The repair method of the present invention is applicable to 6xxx aluminum alloy solid bars, and is particularly applicable to 6082 aluminum alloy.

[0071] Example 2

[0072] The difference between this embodiment and embodiment 1 is that the step of determining the type of tissue defects of the solid bar sample in S200 includes:

[0073] S210. Divide the cross section of the solid bar sample into a central region and a marginal region using the concentric circle dividing line as the partition boundary, wherein the central region is located within the concentric circle dividing line, and the marginal region is located outside the concentric circle dividing line. The center of the concentric circle dividing line coincides with the center of the cross section of the solid bar sample, and r1=0.8R, where r1 is the radius of the concentric circle dividing line and R is the radius of the cross section of the solid bar sample.

[0074] S220. Performing low-magnification tissue testing on the solid bar sample, wherein:

[0075] See also Figure 6As shown, when the coarse grain structure area falls within the marginal area, and the color difference of the middle area is ≤3, it is determined that the structure defect type of the solid rod sample is a coarse grain ring;

[0076] Referring to Figure 7 As shown, when the coarse grain structure area falls within the middle area, and the color difference of the middle area is >3, it is determined that the structure defect type of the solid rod sample is a recrystallization affected ring.

[0077] When the solid rod sample is not detected to have a coarse grain structure area under macrostructure detection, the grain distribution of the solid rod sample is identified to determine whether the solid rod sample has a secondary defect structure.

[0078] Participate Figures 6 to 8 As shown, compared with the coarse grain ring and the recrystallization affected ring, the coarse grain ring has coarse grains, but the grain size of the coarse grains is much smaller than that of the recrystallization affected ring. The grain size of the coarse grains of the recrystallization affected ring is greater than or less than 100 μm, so that part of the recrystallization affected ring can be detected in the macrostructure detection, and the grain size of the coarse grains of the mixed crystal is usually less than 100 μm, which cannot be directly detected under macrostructure detection.

[0079] When there is a large difference in grain size, the reflectivity of the material is different, and the color difference is different, which can reflect the distribution of coarse grains. In the present application, the color difference is combined with whether the coarse grain structure area is detected in the macrostructure detection, so that the structure defects of the solid rod sample can be more simply and accurately screened.

[0080] Specifically, when the coarse grain structure area falls within the marginal area, and the color difference of the middle area is ≤3, it is determined that the solid rod sample has coarse grains with a size sufficient to be detected in the macrostructure detection, and the grain size distribution of the middle area is uniform, which meets the characteristics of the coarse grain ring and can be accurately identified.

[0081] When the coarse grain structure area falls within the middle area, and the color difference of the middle area is >3, it is determined that the solid rod sample has coarse grains with a size sufficient to be detected in the macrostructure detection, and the middle area has a large difference in grain size, which meets the characteristics of the recrystallization affected ring and can be accurately identified.

[0082] Specifically, referring to Figure 7 As shown in the structure diagram of the solid rod sample, the original extrusion die is reduced in flow guide series after welding, and the aluminum alloy solid rod is prepared as shown in Figure 10 As shown, the repaired aluminum alloy solid rod is analyzed by metallography, and the grain is small and uniform, and there is no coarse grain structure defect caused by aggregation of coarse grains.

[0083] The color difference test step of the central area includes:

[0084] Two groups of test points are taken in the middle region, and the difference in the center distance S between the two groups of test points is greater than 0.3R, where R is the radius of the cross section of the solid bar sample, so as to avoid the two groups of test points being too close to each other, resulting in the two groups of test points simultaneously taking the coarse grain region or the fine grain region. Each group of test points includes at least one test site, and the test sites in each group of test points have the same center distance;

[0085] Testing the L value, a value, and b value of the test sites within each group of test points, and calculating the average L value, average a value, and average b value among the test sites within each group of test points;

[0086] The color difference ΔE is calculated according to the color difference formula, which is:

[0087]

[0088] Wherein, L1 is the average L value among each test site of the first group of test points, L2 is the average L value among each test site of the second group of test points, a1 is the average a value among each test site of the first group of test points, a2 is the average a value among each test site of the second group of test points, b1 is the average b value among each test site of the first group of test points, and b2 is the average b value among each test site of the second group of test points.

[0089] Exemplarily, a group of test points is taken at 0.1R and 0.6R away from the center of the middle area, and each group of test points has three test sites, four test sites or five test sites, but is not limited thereto.

[0090] The grain distribution identification step includes: performing metallographic analysis on the solid bar sample, and further detecting the grain size distribution through metallographic analysis.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 2 is that, in S230, the step of identifying the grain distribution includes:

[0093] S231. Determine whether there is a secondary defect structure in the middle region of the solid bar sample according to a first grain distribution formula, wherein the first grain distribution formula is as follows:

[0094] C1=(D max -D min ) / (D max +D min ),

[0095] Where D max is the maximum grain size in the middle region, D min is the minimum grain size in the middle region;

[0096] When C1>0.3, it indicates that the grain size distribution in the central region is relatively dispersed, and there are coarse grains and fine grains with large size differences, and the uniformity is poor. It is determined that the solid bar sample has secondary defect structure. Otherwise, it is determined that the solid bar sample does not have secondary defect structure.

[0097] The value of C1 should not be too small, otherwise normal tissue will be classified as secondary defect tissue, resulting in misjudgment. The value of C1 should not be too large, otherwise secondary defect tissue will be classified as normal tissue, resulting in misjudgment.

[0098] See also Figure 9 As shown in the figure, although there is color difference, it is calculated that C1 is 0.12, the grain size distribution is uniform, the concentration is high, there is no secondary defect structure, and the color difference is caused by other factors, so this repair method is not necessary.

[0099] Wherein, the grain distribution identification step includes:

[0100] S232. Divide the central area into a detection area and a non-detection area using a circular dividing line as a partitioning line, wherein the detection area is located within the circular dividing line, and the non-detection area is located outside the circular dividing line. The center of the circular dividing line coincides with the center of the cross section of the solid bar sample, and 0 < r2 ≤ 0.15R, where r2 is the radius of the circular dividing line and R is the radius of the cross section of the solid bar sample.

[0101] S233. Determine the grain distribution of the solid bar sample located in the central detection area according to a second grain distribution formula, wherein the grain distribution formula is as follows:

[0102] C2=(D' max -D' min ) / (D' max +D' min ),

[0103] Where D' max is the maximum grain size in the middle region, D' min is the minimum grain size in the middle region;

[0104] When C2>0.2, it is determined that the solid bar sample has mixed crystal defects; otherwise, it is determined that the solid bar sample has a recrystallization influence ring.

[0105] After testing, it was found that although the recrystallization influence ring has an annular coarse grain area formed by coarse crystals, its central position still maintains a normal organizational structure with fine and uniform grains, while the mixed crystal shows an organizational structure with a mixture of coarse crystals and fine crystals at the central position. In the present invention, the grain distribution at the central position is identified by the second grain distribution formula. When C2>0.2, it proves that the grain size distribution in this area is relatively dispersed, and there are coarse crystals and fine crystals with large size differences, poor uniformity, and consistent with the characteristics of mixed crystals. It is determined that the solid bar sample has mixed crystal defects. Otherwise, it is determined that the solid bar sample has a recrystallization influence ring.

[0106] Among them, r2 should not be too large, otherwise the annular coarse-grained area of ​​the recrystallization-affected ring will be easily included in the middle area.

[0107] Determining the type of tissue defects solely by manually observing grain distribution images requires a high level of professionalism from the operator and is subject to large errors, which can easily lead to misjudgments and affect subsequent repair operations. The above-mentioned grain distribution identification steps can effectively improve the accuracy of tissue defect identification.

[0108] Example 3

[0109] The difference between this embodiment and embodiment 1 is that the steps of using the original extrusion die for extrusion in S100 to form a solid bar sample include:

[0110] Using 6xxx aluminum alloy ingot as raw material, the ingot is homogenized:

[0111] The ingot is heated to 490°C to 530°C within 2h to 6h, and the first stage of heat preservation is carried out for 1h to 10h; then the temperature is raised to 540°C to 575°C with the furnace, and the second stage of heat preservation is carried out for 3h to 10h; the ingot after heat preservation is cooled to ≤200°C within 1h to 8h to obtain the alloy matrix.

[0112] The alloy matrix was extruded using the original extrusion die to form solid rod samples.

[0113] The raw materials of the aluminum alloy solid bar include the following components in percentage by mass:

[0114] Mg 0.2wt%~1.2wt%, Si 0.1wt%~1.0wt%, Cu 0wt%~1.0wt%, 0wt%<Mn≤0.5wt%, Cr 0wt%~0.5wt%, 0wt%<Ti≤0.02wt%, Fe≤0.3wt% and Zn≤0.05wt%, the content of a single impurity element is ≤0.05%, the total amount of impurities is ≤0.15%, and the balance is Al.

[0115] The application forms Mg2Si strengthening phase in the aluminum matrix by adjusting the ratio of Mg and Si in the raw material, achieves the effect of precipitation strengthening through heat treatment, and has certain regulation effect on the grain size. Mn effectively avoids the grain deformation and stretching caused by the too fast flow of material in the extrusion process, reduces the formation of large grains in the extrusion process, forms a dispersed phase by introducing Cr and Mn, pins the grain boundary, and indirectly plays a role in refining the grain. The addition of Ti increases the cooling rate of the material, makes the composition supercooling generated in front of the solid-liquid interface, is beneficial to grain refinement, and can form Al3Ti and other intermediate phases at the same time. These phases can act as heterogeneous nucleation core and promote grain refinement.

[0116] 0.005wt%≤Ti≤0.01wt%, 0.1wt%≤Mn≤0.3wt%, Fe≤0.2wt%.

[0117] The content of Ti should not be too high, and too high Ti content is easy to form new coarse crystal phase, and the refining effect is decreased.

[0118] The content of Mn should not be too high, and too high Mn content is easy to cause the internal structure of the grain to be uneven, and even form larger grains.

[0119] The content of Fe should not be too high, and high content of Fe is easy to produce larger grains in the material during the extrusion process, especially under high temperature conditions, iron can promote abnormal growth of the grain. At the same time, iron has poor wettability to aluminum, which causes the local metal to flow too fast.

[0120] The above only describes the preferred embodiments of the application, and does not limit the application in any form. Although the application has been disclosed as above, it is not intended to limit the application. Any skilled person in the art can make some changes or modifications to the above-mentioned technical content without departing from the scope of the technical solution of the application, and any simple modification, equivalent change and modification of the above-mentioned embodiments according to the technical essence of the application are still within the scope of the application.

Claims

1. A method for repairing an extrusion die for a 6xxx aluminum alloy solid bar, characterized in that: include: A solid bar sample is formed by extruding an original extrusion die, wherein a welding block is provided on a face die of the original extrusion die, and the original extrusion die comprises a flow guide portion and a single-hole extrusion portion; Testing the solid bar sample to determine the type of structural defects of the solid bar sample, wherein the structural defect type includes a coarse grain ring and a secondary defect structure, and the secondary defect structure includes a recrystallization-affected ring and a mixed crystal; Repair the original extrusion die according to the tissue defect type, wherein When it is determined that the solid bar sample has a recrystallization-affected ring, reducing the number of diversion stages of the original extrusion die; When it is determined that mixed crystals exist in the solid rod sample, the depth of the guide holes in the original extrusion die is reduced.

2. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 1, wherein: The step of determining the type of tissue defects of the solid bar sample comprises: The cross section of the solid bar sample is divided into a central area and a marginal area using the concentric circle dividing line as the partition boundary. The central area is located within the concentric circle dividing line, and the marginal area is located outside the concentric circle dividing line. The center of the concentric circle dividing line coincides with the center of the cross section of the solid bar sample, and r1=0.8R, where r1 is the radius of the concentric circle dividing line and R is the radius of the cross section of the solid bar sample. The solid bar sample is subjected to low-magnification tissue testing, wherein: When all the coarse-grained microstructure areas fall within the marginal area and the color difference of the central area is ≤3, the microstructure defect type of the solid bar sample is determined to be a coarse-grained ring; When the coarse-grained microstructure area falls within the middle area and the color difference of the middle area is greater than 3, the microstructure defect type of the solid bar sample is determined to be a recrystallization-affected ring; When no coarse-grained structure area is detected in the solid bar sample under low-magnification structure detection, grain distribution identification is performed on the solid bar sample to determine whether the solid bar sample has a secondary defect structure.

3. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 2, wherein: The grain distribution identification step comprises: The presence of a secondary defect structure in the middle region of the solid bar sample is determined according to a first grain distribution formula, wherein the first grain distribution formula is as follows: C1=(D max -D min ) / (D max +D min ), Where D max is the maximum grain size in the middle region, D min is the minimum grain size in the middle region; When C1>0.3, it is determined that the solid bar sample has a secondary defect structure; otherwise, it is determined that the solid bar sample does not have a secondary defect structure.

4. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 3, wherein: The grain distribution identification step comprises: The central area is divided into a detection area and a non-detection area using a circular dividing line as a partitioning line. The detection area is located within the circular dividing line, and the non-detection area is located outside the circular dividing line. The center of the circular dividing line coincides with the center of the cross section of the solid bar sample, and 0 < r2 ≤ 0.15R, where r2 is the radius of the circular dividing line and R is the radius of the cross section of the solid bar sample. The grain distribution of the solid bar sample located in the middle detection area is determined according to a second grain distribution formula, and the grain distribution formula is as follows: C2=(D’ max -D’ min ) / (D’ max +D’ min ), Where D' max is the maximum grain size in the middle region, D' min is the minimum grain size in the middle region; When C2>0.2, it is determined that the solid bar sample has mixed crystal defects; otherwise, it is determined that the solid bar sample has a recrystallization influence ring.

5. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 2, wherein: The color difference testing steps of the central area include: Two groups of test points are selected in the middle region, and the difference S between the center distances of the two groups of test points is greater than 0.3R, where R is the radius of the cross section of the solid bar sample. Each group of test points includes at least one test site, and the test sites within each group of test points have the same center distance. Testing the L value, a value, and b value of the test sites within each group of test points, and calculating the average L value, average a value, and average b value among the test sites within each group of test points; The color difference ΔE is calculated according to the color difference formula, which is: Wherein, L1 is the average L value among each test site of the first group of test points, L2 is the average L value among each test site of the second group of test points, a1 is the average a value among each test site of the first group of test points, a2 is the average a value among each test site of the second group of test points, b1 is the average b value among each test site of the first group of test points, and b2 is the average b value among each test site of the second group of test points.

6. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 2, wherein: The grain distribution identification step includes: performing metallographic analysis on the solid bar sample.

7. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 1, wherein: The 6xxx aluminum alloy is 6082 aluminum alloy.

8. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 1, wherein: The method of reducing the number of diversion stages of the original extrusion die is to reduce the number of diversion stages by surfacing and / or milling along the peripheral wall of the diversion hole.

9. The method for repairing an extrusion die of a 6xxx aluminum alloy solid bar according to claim 1, wherein: The reducing the depth of the guide hole in the original extrusion die is to reduce the depth of the guide hole by surfacing in a direction perpendicular to the axis of the guide hole.

10. A rod, characterized in that: The rod is extruded by an extrusion die, and the extrusion die is repaired by the extrusion die repair method for 6xxx aluminum alloy solid rod according to any one of claims 1 to 9.

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