A method for judging the granular fracture defect of an aluminum profile extrusion weld

Abstract

The application provides a kind of aluminium profile extrusion weld granular fracture defect inspection determination method, the granular layer thickness t of aluminium alloy profile extrusion weld granular fracture is measured, and the wall thickness T of aluminium alloy profile, if t < 1 / 2T, then it is determined that the aluminium alloy profile extrusion fracture detection performance is qualified, if t >= 1 / 2T, then it is determined that the aluminium alloy profile extrusion fracture detection performance is unqualified.Currently, there is no judgment requirement for granular fracture in the related standards for aluminium profile extrusion weld detection. Through various tests, it is known that granular extrusion weld exists the phenomenon of reducing material performance. The application proposes that the granular layer thickness of extrusion weld granular fracture should be controlled to be less than 1 / 2 of the wall thickness in the product quality inspection process. Thus, the accuracy of the inspection is improved, and the overall quality of the product is improved, providing a new judgment method for aluminium profile extrusion weld performance detection.

Description

Technical Field

[0001] This invention relates to a method for testing the weldability of extruded welds in aluminum and aluminum alloys, specifically a method for determining granular fracture defects in extruded welds of aluminum profiles. Background Technology

[0002] Granular extrusion weld fracture is a type of extrusion weld fracture in coarse-grained layers. Currently, GB / T32790 only includes two fracture morphologies for extrusion welds: fibrous fracture and flush fracture. However, fibrous extrusion weld fracture is a type of extrusion weld fracture in fine-grained layers. In actual production inspection, another fracture morphology, namely granular fracture, has been found. Through sampling at the fracture site and conducting various mechanical and corrosion resistance tests, it was found that granular fracture reduces the mechanical properties of the material. Therefore, it is recommended to identify granular fracture to ensure the accuracy of the inspection.

[0003] Currently, different domestic vehicle and locomotive manufacturers have varying standards for coarse grain requirements, resulting in inconsistent material properties. Fine grain strengthening is a crucial method for improving the performance of aluminum profiles, as the properties of fine recrystallized grains are far superior to those of coarse recrystallized grains. Previously, the influence of grain size on microstructure properties was primarily determined from the perspective of metallographic structure. However, determining the impact from the thickness of the granular layer in the extruded weld fracture surface is currently a gap in the field. Extruded weld testing is an important inspection item for extruded aluminum profiles, providing a direct assessment of performance. In the extruded weld fracture surface, grains are directly manifested as fibrous and granular fractures. Currently, there are no relevant standards controlling granular extruded weld fracture surfaces. Various tests have shown that the mechanical properties of this characteristic fracture surface are lower than those of fibrous extruded weld fracture surfaces. The performance testing of extruded welds in aluminum profiles is a crucial inspection item for the performance of extruded aluminum profiles, and current relevant standards do not specify requirements for granular extruded weld fracture surfaces. Summary of the Invention

[0004] The technical objective of this invention is to address the shortcomings of the prior art by providing a method for determining granular fracture defects in extruded welds of aluminum profiles.

[0005] The technical solution adopted by the present invention to solve its technical problem is: a method for judging the granular fracture defect of aluminum profile extrusion weld, wherein the thickness t of the granular layer of the granular fracture of the aluminum alloy profile extrusion weld and the wall thickness T of the aluminum alloy profile are measured. If t < 1 / 2T, the aluminum alloy profile extrusion fracture test performance is deemed qualified; if t > 1 / 2T, the aluminum alloy profile extrusion fracture test performance is deemed unqualified.

[0006] Furthermore, when t = 1 / 2T, it is the critical point of bending limit of the extrusion fracture surface of the aluminum alloy profile, and the extrusion fracture surface test performance of the aluminum alloy profile is deemed unqualified.

[0007] Furthermore, the wall thickness of the aluminum alloy profile is the same as the thickness of the aluminum alloy profile.

[0008] Furthermore, the method for measuring the particle layer thickness of the granular fracture surface of the extruded weld of the aluminum alloy profile is as follows: the aluminum alloy profile is corroded to expose the weld, a hydraulic pressure testing machine is used to continuously press down on the weld position through the pressure head until the weld breaks, and the particle layer thickness is measured using a magnifying glass or microscope.

[0009] Furthermore, microcracks appeared in the bending test of the aluminum alloy profile when the thickness of the granular fracture surface reached 1 / 2 of the total wall thickness; cracks appeared in the bending test of the aluminum alloy profile when the thickness of the granular fracture surface reached 2 / 3 of the total wall thickness; and the aluminum alloy profile fractured in the bending test when the thickness of the granular fracture surface was equal to the wall thickness, and the bending test performance was severely reduced.

[0010] Furthermore, as the thickness of the granular layer at the fracture surface increases, the mechanical tensile properties and corrosion resistance of aluminum alloy profiles gradually decrease; as the thickness of the granular layer at the fracture surface increases, the bending performance gradually decreases, surface cracks gradually worsen, until fracture occurs; bending performance also gradually decreases as the thickness of the granular layer at the fracture surface increases.

[0011] This invention improves the product quality of fracture surfaces with granular extrusion welds by adding a defect criterion that the granular layer thickness is less than half the wall thickness. This improves the quality of fracture surfaces with a granular layer thickness from the previously unacceptable 2 / 3 wall thickness to a 1 / 2 wall thickness, resulting in the following improvements: 2-6% increase in mechanical yield strength, 2-4% increase in tensile strength, 6-10% increase in maximum bending force, and 6-15% improvement in corrosion resistance. For fracture surfaces with a granular layer thickness equal to the total wall thickness, the improvement to a 1 / 2 wall thickness granular layer is: 5-10% increase in mechanical yield strength, 5-8% increase in tensile strength, 40-60% increase in maximum bending force, and 20-30% improvement in corrosion resistance. The granular layer is an unavoidable defect in aluminum alloys during extrusion. Its presence should be controlled in production; the granular layer thickness of granular extrusion weld fracture surfaces should be controlled to be less than half the wall thickness.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] Currently, relevant standards for inspecting extruded welds in aluminum profiles lack specific requirements for judging granular fracture surfaces. Various tests have shown that granular extruded welds can reduce material performance. This invention proposes that the thickness of the granular layer in the granular fracture surface of extruded welds should be controlled to be less than half the wall thickness during product quality inspection. This improves inspection accuracy, thereby enhancing overall product quality and providing a new method for judging the performance of extruded welds in aluminum profiles. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0015] The method for measuring the granular layer thickness of the extruded weld fracture surface of the aluminum alloy profile specimens in each embodiment is as follows: First, the aluminum profile is corroded with sodium hydroxide to expose the weld. Then, a pressure testing machine is used to press the weld until it fractures. The fracture surface is observed to see if it is granular. If so, the granular layer is measured using a ruler with a precision of 0.1 mm. If there is any discrepancy, a stereomicroscope can be used to accurately measure the granular layer thickness. The aluminum profile wall thickness is then measured, and the ratio of the granular layer thickness to the wall thickness is calculated.

[0016] Example 1

[0017] Taking 6005A-T6 3mm thick extruded profiles as the research object, samples with different thicknesses of granular fracture surface at the extrusion weld were selected. Three samples were selected for each group for testing. Among them, the granular layer thickness of samples a1, a2, and a3 accounted for 1 / 5 of the wall thickness (3mm), the granular layer thickness of samples b1, b2, and b3 accounted for 1 / 3 of the wall thickness, the granular layer thickness of samples c1, c2, and c3 accounted for 1 / 2 of the wall thickness, the granular layer thickness of samples d1, d2, and d3 accounted for 2 / 3 of the wall thickness, and the granular layer thickness of samples e1, e2, and e3 was equal to the wall thickness.

[0018] According to the judgment method for the inspection of granular fracture defects in extruded welds of aluminum profiles, the extrusion fracture test performance of aluminum alloy profiles a1, a2, a3; b1, b2, b3 is deemed qualified, while the extrusion fracture test performance of aluminum alloy profiles c1, c2, c3; d1, d2, d3; e1, e2, e3 is deemed unqualified.

[0019] Mechanical tensile tests, bending tests, folding tests, and corrosion resistance tests were conducted on each sample. The results of mechanical tensile properties, maximum bending force, and intergranular corrosion depth are shown in Table 1, where a, b, c, d, and e are the average values ​​for samples a1, a2, a3; b1, b2, b3; c1, c2, c3; d1, d2, d3; and e1, e2, e3, respectively.

[0020] Table 1 Test results of the samples

[0021]

[0022] The bending test results were as follows: no cracks on the surfaces of a1, a2, and a3; no cracks on the surfaces of b1, b2, and b3; microcracks on the surfaces of c1 and c2; no cracks on the surface of c3; cracks on the surfaces of d1, d2, and d3; and fractures on the surfaces of e1, e2, and e3.

[0023] Various tests show that as the thickness of the fracture granular layer increases, the mechanical tensile yield strength, tensile strength, and maximum bending force decrease. When the thickness of the fracture granular layer is greater than 1 / 2, the bending test fails. When the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, not all bending test results are qualified. Among them, c1 and c2 have microcracks on the surface, while c3 has no cracks on the surface. At this time, the results are both qualified and unqualified. Therefore, the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, which is the critical point of bending limit. It is determined that the bending test fails when the thickness of the fracture granular layer is greater than or equal to 1 / 2 of the wall thickness.

[0024] In summary, the determination method described in this invention accurately assesses the performance of profile extrusion fracture tests. If the thickness of the granular layer in the granular extrusion weld fracture is controlled, from 2 / 3 to 1 / 2 of the total wall thickness, the mechanical yield strength increases by 3.2%, tensile strength by 2.1%, maximum bending force by 9.1%, and corrosion resistance by 13.57%. When the granular layer thickness is equal to or less than 1 / 2 of the total wall thickness, the mechanical yield strength increases by 5.2%, tensile strength by 5.1%, maximum bending force by 49.6%, and corrosion resistance by 24.8%.

[0025] Example 2

[0026] Taking 6005A-T6 4mm thick extruded profiles as the research object, samples with different thicknesses of granular fracture surface at the extrusion weld were selected. Three samples were selected for each group for testing. Among them, the granular layer thickness of samples a10, a20, and a30 accounted for 1 / 5 of the wall thickness (4mm), the granular layer thickness of samples b10, b20, and b30 accounted for 1 / 3 of the wall thickness, the granular layer thickness of samples c10, c20, and c30 accounted for 1 / 2 of the wall thickness, the granular layer thickness of samples d10, d20, and d30 accounted for 2 / 3 of the wall thickness, and the granular layer thickness of samples e10, e20, and e30 was equal to the wall thickness.

[0027] According to the judgment method for the inspection of granular fracture defects in extruded welds of aluminum profiles, the extrusion fracture test performance of aluminum alloy profiles a10, a20, a30; b10, b20, b30 is deemed qualified, while the extrusion fracture test performance of aluminum alloy profiles c10, c20, c30; d10, d20, d30; e10, e20, e30 is deemed unqualified.

[0028] Mechanical tensile tests, bending tests, folding tests, and corrosion resistance tests were conducted on each sample. The results of mechanical tensile properties, maximum bending force, and intergranular corrosion depth are shown in Table 2. Here, a0, b0, c0, d0, and e0 represent the average values ​​for samples a10, a20, a30; b10, b20, b30; c10, c20, c30; d10, d20, d30; and e10, e20, e30, respectively.

[0029] Table 2 Test Results of Samples

[0030]

[0031] The bending test results were as follows: a10, a20, and a30 had no cracks on their surfaces; b10, b20, and b30 had no cracks on their surfaces; c20 had microcracks on its surface; c10 and c30 had no cracks on their surfaces; d10, d20, and d30 had cracks on their surfaces; and e10, e20, and e30 fractured.

[0032] Various tests show that as the thickness of the fracture granular layer increases, the mechanical tensile yield strength, tensile strength, and maximum bending force decrease. When the thickness of the fracture granular layer is greater than 1 / 2, the bending test fails. When the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, not all bending test results are qualified. Among them, C20 has microcracks on the surface, while C10 and C30 have no cracks on the surface. At this time, the results are both qualified and unqualified. Therefore, the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, which is the critical point of bending limit. It is determined that the bending test fails when the thickness of the fracture granular layer is greater than or equal to 1 / 2 of the wall thickness.

[0033] In summary, the determination method described in this invention accurately assesses the performance of profile extrusion fracture tests. When the thickness of the granular layer in the granular extrusion weld fracture is controlled from 2 / 3 to 1 / 2 of the total wall thickness, the mechanical yield strength of the fracture increases by 2.7%, tensile strength by 2.5%, maximum bending force by 8.7%, and corrosion resistance by 6.6%. When the thickness of the granular layer in the granular fracture is equal to or less than 1 / 2 of the total wall thickness, the mechanical yield strength increases by 8.7%, tensile strength by 7.4%, maximum bending force by 49.1%, and corrosion resistance by 24.1%.

[0034] Example 3

[0035] Taking 6005A-T6 2.3mm thick extruded profiles as the research object, samples with different thicknesses of granular fracture surface at the extrusion weld were selected. Three samples were selected for each group for testing. Among them, the granular layer thickness of samples A1, A2, and A3 accounted for 1 / 5 of the wall thickness (2.3mm), the granular layer thickness of samples B1, B2, and B3 accounted for 1 / 3 of the wall thickness, the granular layer thickness of samples C1, C2, and C3 accounted for 1 / 2 of the wall thickness, the granular layer thickness of samples D1, D2, and D3 accounted for 2 / 3 of the wall thickness, and the granular layer thickness of samples E1, E2, and E3 was equal to the wall thickness.

[0036] According to the judgment method for the inspection of granular fracture defects in extruded welds of aluminum profiles, the extrusion fracture test performance of aluminum alloy profiles A1, A2, A3; B1, B2, B3 is deemed qualified, while the extrusion fracture test performance of aluminum alloy profiles C1, C2, C3; D1, D2, D3; E1, E2, E3 is deemed unqualified.

[0037] Mechanical tensile tests, bending tests, folding tests, and corrosion resistance tests were performed on each sample. The results of their mechanical tensile properties, maximum bending force, and intergranular corrosion depth are shown in Table 3. A, B, C, D, and E represent the average values ​​of samples A1, A2, A3; B1, B2, B3; C1, C2, C3; D1, D2, D3; and E1, E2, E3, respectively.

[0038] Table 3 Test Results of Samples

[0039]

[0040] The bending test results were as follows: A1, A2, and A3 had no cracks on their surfaces; B1, B2, and B3 had no cracks on their surfaces; C1 and C2 had microcracks on their surfaces; C3 had no cracks on its surface; D1, D2, and D3 had cracks on their surfaces; and E1, E2, and E3 were fractured.

[0041] Various tests show that as the thickness of the fracture granular layer increases, the mechanical tensile yield strength, tensile strength, and maximum bending force decrease. When the thickness of the fracture granular layer is greater than 1 / 2, the bending test fails. When the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, not all bending test results are qualified. Among them, C1 and C2 have microcracks on the surface, while C3 has no cracks. At this time, the results are both qualified and unqualified. Therefore, the thickness of the fracture granular layer is equal to 1 / 2 of the wall thickness, which is the critical point of bending limit. It is determined that the bending test fails when the thickness of the fracture granular layer is greater than or equal to 1 / 2 of the wall thickness.

[0042] In summary, the determination method described in this invention accurately assesses the performance of profile extrusion fracture tests. When the thickness of the granular layer in the granular extrusion weld fracture is controlled from 2 / 3 to 1 / 2 of the total wall thickness, the mechanical yield strength of the fracture increases by 6%, tensile strength by 3.7%, maximum bending force by 6.4%, and corrosion resistance by 11.3%. When the thickness of the granular layer in the granular fracture is equal to or less than 1 / 2 of the total wall thickness, the mechanical yield strength increases by 9.5%, tensile strength by 6.8%, maximum bending force by 52.1%, and corrosion resistance by 24.5%.

[0043] The above technical solutions illustrate the technical concept of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any modifications or alterations made to the above technical solutions based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for determining granular fracture defects in extruded welds of aluminum profiles, characterized in that: The thickness t of the granular layer and the wall thickness T of the extruded weld of 6005A-T6 aluminum alloy profile are measured. If t < 1 / 2T, the extruded fracture test performance of the aluminum alloy profile is deemed qualified. If t > 1 / 2T, the extruded fracture test performance of the aluminum alloy profile is deemed unqualified. When t = 1 / 2T, it is the bending limit critical point of the extruded fracture of the aluminum alloy profile, and the extruded fracture test performance of the aluminum alloy profile is deemed unqualified. The method for measuring the particle layer thickness is as follows: the aluminum alloy profile is corroded to expose the weld, and a hydraulic pressure testing machine is used to continuously press down on the weld position with the pressure head until the weld breaks, and the particle layer thickness is measured.

2. The method for determining granular fracture defects in extruded welds of aluminum profiles according to claim 1, characterized in that: The wall thickness of the aluminum alloy profile is the same as the thickness of the aluminum alloy profile.

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