Extrusion die repairing method for 6xxx aluminum alloy solid bar and bar

Abstract

The invention relates to the technical field of metal processing, and particularly discloses an extrusion die repairing method for a 6xxx aluminum alloy solid bar and the bar. The method comprises the steps that an original extrusion die is adopted for extrusion, a solid bar sample is formed, the solid bar sample is detected, and the structure defect type of the solid bar sample is judged. The structure defect type comprises a coarse grain ring and a secondary defect structure, and the secondary defect structure comprises a recrystallization influence ring and mixed crystals; an original extrusion die is repaired according to the tissue defect type, and when it is judged that a recrystallization influence ring exists in the solid bar sample, the flow guide stage number of the original extrusion die is reduced; and when it is judged that mixed crystals exist in the solid bar sample, the depth of a flow guide hole in the original extrusion die is reduced. According to the method, secondary defect structures such as recrystallization influence rings and mixed crystals which are easily caused by the newly added welding blocks of the original extrusion die can be effectively improved, the process is simple and easy to operate, and industrial production is facilitated.

Description

Technical Field

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

[0002] Extrusion is a process of forming a profile by passing a blank through a specific die hole under the action of three-dimensional compressive stress. The uniformity of the structure of the extruded material determines the uniformity of the product performance, including mechanical properties and oxidation properties, so it is particularly important to obtain a uniform and consistent structure.

[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 bars, which is called peripheral coarse-grained structure or coarse-grained ring.

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

[0005] However, it is found in actual production that although the formation of welding blocks 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 blocks, the extrusion pressure and friction force of 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 materials in these edge areas flow to the central area under the action of the welding blocks, resulting in a ring of coarse grain structure in the central area of ​​the final extruded rod (ie, the "recrystallization influence 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 defect characteristics of varying degrees 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 of a 6xxx aluminum alloy solid bar and a bar in view of 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 newly added welding blocks of 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 scheme:

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

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

[0010] Testing the solid bar sample to determine the type of tissue defects of the solid bar sample, wherein the type of tissue defects includes coarse grain rings and secondary defect tissues, and the secondary defect tissues include recrystallization-affected rings and mixed crystals;

[0011] The original extrusion die is repaired according to the tissue defect type, wherein:

[0012] When it is determined that the solid bar sample has a recrystallization influence 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 rod sample comprises:

[0015] Taking the concentric circle dividing line as the partition boundary, the cross section of the solid bar sample is divided into a middle area and a marginal area, the middle area is located inside 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, 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-power structural testing, wherein:

[0017] When the coarse-grained microstructure areas all fall within the marginal area, and the color difference of the middle 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 identification step includes:

[0021] The first grain distribution formula is used to determine whether the solid bar sample has a secondary defect structure in the middle region. The first grain distribution formula is as follows:

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

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

[0024] 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.

[0025] In some embodiments, the grain distribution identification step includes:

[0026] The central area is divided into a detection area and a non-detection area using a circular dividing line as a partition boundary, 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, r2 is the radius of the circular dividing line, and R is the radius of the cross section of the solid bar sample,

[0027] The grain distribution of the solid bar sample located in the middle region detection area is determined according to the second grain distribution formula, and the grain distribution formula is as follows:

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

[0029] Where D' max is the maximum grain size in the middle region, 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 mixed crystal defects, otherwise, it is determined that the solid rod sample has a recrystallization influence ring.

[0031] In some embodiments, the color difference testing step of the middle area includes:

[0032] Two groups of test points are taken in the middle area, the difference S between the center distances of the two groups of test points is greater than 0.3R, 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 in each group of test points have the same center distance;

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

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

[0035]

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

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

[0043] In the present invention, the original extrusion die is used to prepare solid rod samples, and then the samples are tested to distinguish the types of tissue defects of the samples, and then corresponding mold repair treatments are performed for different types of tissue defects, so that the tissue defect problem of the solid rod extruded by the repaired extrusion die is improved, and the internal structure of the prepared solid rod 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 of Example 1 of the present invention.

[0045] Figure 2 It is a 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 (welding 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 reduced depth.

[0049] Figure 6 This is a microstructure diagram of a solid rod sample having 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 with mixed crystals according to the present invention.

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

[0053] Fig.10 This is the organizational diagram of the solid rod made by the repaired extrusion die of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, 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. The original extrusion die is used for extrusion to form a solid bar sample, wherein a welding block is provided on the face die of the original extrusion die, 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 tissue defects of the solid bar sample, wherein the tissue 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;

[0059] S300. Repairing 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 flow 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 holes in the original extrusion die is reduced.

[0062] In the present invention, the original extrusion die is used to prepare solid rod samples, and then the samples are tested to distinguish the types of tissue defects of the samples, and then corresponding mold repair treatments are performed for different types of tissue defects, so that the tissue defect problem of the solid rod extruded by the repaired extrusion die is improved, and the internal structure of the prepared solid rod 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 the solid bar sample has a recrystallization influence ring, 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 the solid bar sample has mixed crystals, 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 welding 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 three levels of flow guide. When the number of flow guide levels needs to be reduced, the following can be done: 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 rod.

[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. Taking the concentric circle dividing line as the partition boundary, the cross section of the solid bar sample is divided into a middle area and a marginal area, the middle area is located inside 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, 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. Perform low-magnification tissue testing on the solid bar sample, wherein:

[0075] See also Figure 6As shown, when the coarse-grained microstructure areas all fall within the marginal area, and the color difference of the middle area is ≤3, the microstructure defect type of the solid bar sample is determined to be a coarse-grained ring;

[0076] See also Figure 7 As shown, 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;

[0077] 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.

[0078] join Figures 6 to 8 As shown, after testing, compared with the coarse grain ring, the recrystallization influence ring and the mixed crystal also have coarse grains, but the grain size of their coarse grains is still much smaller than the coarse grain ring, and the grain size of the coarse grains of the recrystallization influence ring is greater than or less than 100μm. Therefore, the partially formed recrystallization influence ring can be detected in the low-magnification structure detection, while the grain size of the coarse grains of the mixed crystal is usually less than 100μm and cannot be directly detected under low-magnification structure detection.

[0079] When there is a large difference in grain size, the material reflectivity will be different, which will lead to differences in color difference, which can indirectly reflect the distribution of coarse grains. In the present invention, the color difference is combined with whether the coarse grain tissue area is detected in the low-magnification detection, which can more simply and accurately perform preliminary screening of the tissue defects of the solid bar sample.

[0080] Specifically, when the coarse-grained microstructure areas all fall within the marginal area and the color difference of the central area is ≤3, it indicates that there are coarse crystals of a size sufficient to be detected in low-magnification microstructure testing around the solid rod sample, and the grain size distribution in the central area is uniform, which meets the characteristics of a coarse-grained ring and can be accurately identified.

[0081] When the coarse-grained microstructure areas all fall within the middle area, and the color difference of the middle area is greater than 3, it indicates that there are coarse crystals in the middle area of ​​the solid bar sample that are large enough to be detected in low-magnification microstructure detection, and that there are large differences in grain size in the middle area, which meets the characteristics of the recrystallization influence ring and can be accurately identified.

[0082] For details, see Figure 7 The microstructure of the solid bar sample shown in the figure is that the original extrusion die is welded to reduce the number of flow levels, and the aluminum alloy solid bar is obtained as shown in the figure. Fig.10 As shown in the figure, metallographic analysis of the repaired aluminum alloy solid bar shows that the grains are small and uniform, and there is no coarse-grained structure defect formed by the aggregation of coarse grains.

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

[0084] Two groups of test points are taken in the middle region, and the difference between the center distances of the two groups of test points is S>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, 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 in each group of test points, and calculating the average L value, average a value and average b value among the test sites in each group of test points;

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

[0087]

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

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

[0090] Wherein, the grain distribution identification step includes: performing metallographic analysis on the solid bar sample, and further detecting the grain size distribution by means of metallographic analysis.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 2 is that, S230. the grain distribution identification step comprises:

[0093] S231. Determine whether there is a secondary defect structure in the middle area of ​​the solid bar sample according to the 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 means that the grain size distribution in the middle region is relatively dispersed, 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 the normal tissue will be classified as secondary defective tissue, resulting in misjudgment. The value of C1 should not be too large, otherwise the secondary defective tissue will be classified as normal tissue, resulting in misjudgment.

[0098] See also Fig. 9 As shown, 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 comprises:

[0100] S232. The central area is divided 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, and 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 middle region 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 rod sample has mixed crystal defects, otherwise, it is determined that the solid rod sample has a recrystallization influence ring.

[0105] Through experiments, it was found that although there is an annular coarse crystal area formed by coarse crystals in the recrystallization influence ring, its central position still maintains a normal organizational structure with fine and uniform grains, while mixed crystals show an organizational structure with a mixture of coarse crystals and fine crystals in the central position. In the present invention, the grain distribution at the central position is identified through 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, which meets the characteristics of mixed crystals. It is determined that the solid rod sample has mixed crystal defects. Otherwise, it is determined that the solid rod 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 by manually observing the grain distribution image requires a high level of professionalism from the operator and has large errors, which can easily lead to misjudgment 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, in S100, the original extrusion die is used for extrusion, and the steps of forming a solid bar sample include:

[0110] Using the ingot of 6xxx aluminum alloy 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 a solid rod sample.

[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 present invention adjusts the ratio of Mg and Si in the raw materials, forms a Mg2Si strengthening phase in the aluminum matrix, achieves the effect of precipitation strengthening through heat treatment, and also has a certain regulating effect on the grain size. Mn effectively avoids grain deformation and stretching easily caused by too fast flow of materials during extrusion, reduces the formation of large grains during extrusion, and indirectly plays a role in refining grains by introducing Cr and Mn to form a dispersed phase and pin the grain boundaries. The addition of Ti increases the cooling rate of the material, so that the front edge of the solid-liquid interface produces component supercooling, which is beneficial to grain refinement. At the same time, intermediate phases such as Al3Ti can be formed, and these phases can serve as heterogeneous nucleation cores to promote grain refinement.

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

[0117] Among them, the Ti content should not be too high. Too high Ti content is easy to form a new coarse crystal phase, and the refinement effect will decrease.

[0118] The Mn content should not be too high. Too high a Mn content can easily lead to an uneven internal structure of the grains and even form larger grains.

[0119] The content of Fe should not be too high. During the extrusion process, high content of Fe can easily cause the material to produce larger grains, especially under high temperature conditions, where iron can promote abnormal growth of grains. At the same time, iron has poor wettability to aluminum, causing local metal flow to be too fast.

[0120] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the field can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for repairing an extrusion die of a 6xxx aluminum alloy solid bar, characterized in that: include: The solid bar sample is formed by extruding with an original extrusion die, wherein a welding block is provided on the face die of the original extrusion die, and the original extrusion die comprises a guide part and a single-hole extrusion part; Testing the solid bar sample to determine the type of tissue defects of the solid bar sample, wherein the type of tissue defects includes coarse grain rings and secondary defect tissues, and the secondary defect tissues include recrystallization-affected rings and mixed crystals; The original extrusion die is repaired according to the tissue defect type, wherein: When it is determined that the solid bar sample has a recrystallization influence 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, characterized in that: The step of determining the type of tissue defects of the solid bar sample comprises: Taking the concentric circle dividing line as the partition boundary, the cross section of the solid bar sample is divided into a middle area and a marginal area, the middle area is located inside 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, 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-power structural testing, wherein: When the coarse-grained microstructure areas all fall within the marginal area, and the color difference of the middle 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, characterized in that: The grain distribution identification step comprises: The first grain distribution formula is used to determine whether the solid bar sample has a secondary defect structure in the middle region. 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, characterized in that: 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 partition boundary, 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, 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 region detection area is determined according to the 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 rod sample has mixed crystal defects, otherwise, it is determined that the solid rod 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, characterized in that: The color difference test steps of the central area include: Two groups of test points are taken in the middle area, the difference S between the center distances of the two groups of test points is greater than 0.3R, 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 in each group of test points have the same center distance; Testing the L value, a value and b value of the test sites in each group of test points, and calculating the average L value, average a value and average b value among the test sites in each group of test points; The color difference ΔE is calculated according to the color difference formula, and the color difference formula is: Wherein, L1 is the average L value between each test site of the first group of test points, L2 is the average L value between each test site of the second group of test points, a1 is the average a value between each test site of the first group of test points, a2 is the average a value between each test site of the second group of test points, b1 is the average b value between each test site of the first group of test points, and b2 is the average b value between 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, characterized in that: 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, characterized in that: 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, characterized in that: The method of reducing the number of diversion stages of the original extrusion die is to reduce the number of diversion stages by surfacing welding 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, characterized in that: The method of 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 material, 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 rods according to any one of claims 1 to 9.

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