CN114908305B - Combined heat treatment method for improving formability of 6000-series aluminum alloy plate strip and manufacturing method - Google Patents
Combined heat treatment method for improving formability of 6000-series aluminum alloy plate strip and manufacturing method Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
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Abstract
The invention discloses a combined heat treatment method for improving the formability of 6000 series aluminum alloy plates and strips, which comprises the following steps: carrying out two-stage homogenization treatment before the hot rolling step; after the hot rolling step and before the cold rolling step, carrying out high-temperature short-time annealing treatment, wherein the process of the high-temperature short-time annealing treatment comprises the following steps: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min. In addition, the invention also discloses a manufacturing method of the 6000 series aluminum alloy plate strip, which comprises the following steps: smelting and casting; (2) two-stage homogenization treatment; (3) hot rolling; (4) high-temperature short-time annealing treatment: heating a 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min; (5) cold rolling; (6) solution quenching treatment; and (7) carrying out pre-aging treatment within 24 h.
Description
Technical Field
The invention relates to a metal heat treatment method and a manufacturing method thereof, in particular to a combined heat treatment method for formability of an aluminum alloy plate strip and a manufacturing method thereof.
Background
In recent years, with the progress of weight reduction of automobiles, 6000 series aluminum alloy plates for automobiles have been studied more and more intensively. The main alloy element Si in the 6000 series aluminum alloy and the impurity element Fe easily form a thick lath-shaped beta-AlFeSi phase, and the plasticity of the alloy is obviously reduced by the thick lath-shaped beta-AlFeSi phase.
Studies have shown that high temperature homogenization treatment can promote the transformation of this β -AlFeSi phase into an α -AlFeSi phase that is more easily broken during subsequent deformation, but the non-equilibrium crystalline phase formed by semi-continuous (direct water cooling) casting can melt and over-fire during high temperature homogenization treatment. Meanwhile, after the cast ingot is rolled into a coil and slowly cooled, a large amount of MgSi is re-precipitated in the matrix, the content of solid-dissolved Mg and Si before recrystallization is reduced during low solid solution treatment, and the reduction of solid solution elements promotes the formation of a recrystallized cubic texture, so that the forming performance of the plate strip is deteriorated. In the conventional processing process in the prior art, the AlFeSi phase and the MgSi phase have obvious influence on the formation of the microstructure and the texture of the plate during subsequent cold rolling and heat treatment, and are not beneficial to improving the forming performance of the plate strip.
For example: chinese patent publication No. CN108642331A, published as 2018, 10, 12 and entitled "6181 aluminum alloy for automobile plate and method for preparing the same", discloses a two-stage soaking process, i.e., (440-480) ° c × (3-10) h → (520-550) × (14-20) h → air cooling. Meanwhile, mn element is added in the alloy to promote the transformation of a beta-AlFeSi phase into a fine granular alpha-AlFeSi phase. After rolling heat treatment is carried out on the homogenized cast ingot, the obtained plate has good mechanical property and forming property.
Another example is: the Chinese patent document with the publication number of CN109082566B and the publication date of 5.5.2020 and the name of 'a 6-series alloy aluminum plate strip for mobile phone frames and a soaking process of a preparation method thereof' adopts a two-stage homogenization process aiming at ingot casting, namely, the casting bar temperature is 320-380 ℃, the temperature is kept for 8-12 h, then the temperature is increased to 550-570 ℃, the temperature is kept for 30-40 h, and finally the obtained plate has the characteristics of high strength and excellent anodic oxidation appearance.
For another example: chinese patent document with publication number CN109402537A, publication date 3/1/2019 and name "an aluminum alloy ingot and aluminum alloy homogenizing process", wherein the temperature of homogenizing heating treatment in the first stage is 400-440 ℃, and the holding time is 8-10h; the temperature of the second stage of homogenization heating treatment is 520-560 ℃, and the heat preservation time is 20-26h; and rapidly cooling the aluminum alloy cast ingot subjected to the second-stage homogenization heating treatment. The two-stage homogenization treatment promotes the re-dissolution of the Fe phase, the rapid cooling of the second stage inhibits the precipitation of the MgSi phase, and finally the stamping performance of the plate is improved.
In conclusion, the homogenization treatment can promote the transformation of the beta-AlFeSi phase into the alpha-AlFeSi phase which is easier to break in the subsequent deformation process, and promote the dissolution of the MgSi phase in advance, which has an important effect on improving the forming performance of the 6-series aluminum alloy plate strip product for the automobile body. However, the prior art cannot achieve as complete a solid solution of the MgSi phase as possible in the matrix for the strengthening phase of the 6000 series aluminum alloy.
Based on the method, on the premise of ensuring the feasibility of the process, the invention provides a combined heat treatment method and a manufacturing method for improving the formability of 6000 series aluminum alloy plates and strips, and the combined heat treatment method and the manufacturing method can effectively promote the formation and refinement of alpha-AlFeSi phase and Mg in an aluminum matrix 2 The Si phase is fully dissolved, so that the content of the recrystallized cubic texture in the solution treatment plate strip before delivery is effectively weakened, and the formability of the plate is improved.
Disclosure of Invention
The invention aims to provide a combined heat treatment method for improving the formability of 6000 series aluminum alloy plate strips, which can promote the transformation of beta-AlFeSi into alpha-AlFeSi phase and the crushing and refining of the alpha-AlFeSi phase in the rolling deformation process, promote the induction and nucleation of second phase particles, refine tissue grains, and promote the coarse and large Mg by combining with the high-temperature intermediate annealing treatment after hot rolling 2 Si phase re-dissolves, the volume fraction of cubic recrystallization texture in the plate after hot rolling and annealing is reduced, and the formability of the final plate is further obviously improved.
In order to achieve the purpose, the invention provides a combined heat treatment method for improving the formability of 6000-series aluminum alloy plates and strips, which comprises the following steps:
carrying out two-stage homogenization treatment before the hot rolling step;
after the hot rolling step and before the cold rolling step, carrying out high-temperature short-time annealing treatment, wherein the process of the high-temperature short-time annealing treatment comprises the following steps: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min.
The combined heat treatment process provided by the invention is carried out before the cogging hot rolling step and before the cold rolling step after the hot rolling step of the 6000 series aluminum alloy ingot.
In the technical scheme of the invention, the beta-AlFeSi is converted into the alpha-AlFeSi phase through two-stage homogenization treatment before the hot rolling step on the basis of eliminating nonequilibrium phase and dendrite segregation so as to facilitate the subsequent hot rolling deformation, crushing and refining. The high-temperature short-time annealing treatment is carried out after the hot rolling step and before the cold rolling step, and the intermediate annealing and the rapid quenching can be carried outFire fully dissolves Mg 2 Si-phase particles. By the combination of the ingot casting homogenization system and the recrystallization annealing system, alpha-AlFeSi phase refinement and second phase particle full dissolution in the matrix after recrystallization annealing can be effectively realized. A large amount of alpha-AlFeSi phase particles form a local deformation zone in the subsequent cold rolling process, and promote the recrystallization nucleation of non-cubic orientation crystal grains in the subsequent solution heat treatment process before delivery; meanwhile, a large amount of solid-dissolved Mg and Si atoms can inhibit the nucleation and growth of cubic oriented crystal grains, so that the cubic texture in the plate after the solid solution treatment before delivery is weakened, and the forming performance of the final plate is effectively improved.
In addition, in the invention, the first homogenization treatment in the two-stage homogenization treatment aims to eliminate solute segregation and dendrite segregation in the ingot caused by Mg and Si elements in the original ingot, and the second homogenization treatment aims to promote the coarse flaky beta-AlFeSi phase in the matrix to be fully converted into granular alpha-AlFeSi, and the granular alpha-AlFeSi is crushed and refined in the subsequent hot rolling deformation process to create conditions for the nucleation of grain-induced recrystallization to form a non-cubic orientation texture in the solution treatment process before delivery.
Accordingly, although the two-stage homogenization treatment has eliminated the solute segregation of the Mg, si elements, during the slow cooling in hot rolling, mg partially redissolved 2 The Si phase precipitates again from the aluminum matrix. In the present invention, mg can be made by subjecting the steel sheet to a high-temperature short-time annealing treatment and then immediately water-cooling the steel sheet after the hot rolling step and before the cold rolling step 2 Si phase is totally dissolved back in the matrix, and conditions are created for inhibiting nucleation and growth of cubic oriented recrystallized grains during subsequent solution treatment
Further, in the combined heat treatment method of the invention, in the high-temperature short-time annealing treatment step, when the thickness of the 6000 series aluminum alloy hot rolled plate is less than 3.0mm, an air cushion furnace is used for heating.
Further, in the combined heat treatment method, in the high-temperature short-time annealing treatment step, when the thickness of the 6000 series aluminum alloy hot rolled plate is more than or equal to 3.0mm, salt bath heating is adopted.
Further, in the combined heat treatment method of the present invention, in the two-stage homogenization treatment step, the first-stage homogenization treatment process is: heating the 6000 series aluminum alloy casting blank to 460-500 ℃, and preserving the heat for 22-26 h.
Further, in the combined heat treatment method, in the first-stage homogenization treatment process, the heating rate is 150-200 ℃/h.
Further, in the combined heat treatment method of the present invention, in the two-stage homogenization treatment step, the second-stage homogenization treatment process includes: continuously heating to 550-570 ℃, preserving the heat for 10-14 h, and then cooling to room temperature.
Further, in the combined heat treatment method, in the second-stage homogenization treatment process, the heating rate is 150-200 ℃/h.
Further, in the combined heat treatment method, the temperature reduction rate is 50-100 ℃/h in the second-stage homogenization treatment process.
Correspondingly, the invention also aims to provide a manufacturing method of the 6000 series aluminum alloy plate strip, the manufacturing method is simple in production and easy to realize, the formability of the manufactured 6000 series aluminum alloy plate strip can be obviously improved by adopting the manufacturing method, and the manufacturing method has good popularization prospect and application value.
In order to achieve the above object, the present invention provides a method for manufacturing a 6000 series aluminum alloy sheet strip, comprising the steps of:
(1) Smelting and casting;
(2) Two-stage homogenization treatment;
(3) Hot rolling;
(4) High-temperature short-time annealing treatment: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min;
(5) Cold rolling;
(6) Solution quenching treatment;
(7) And carrying out pre-aging treatment within 24 h.
In the technical scheme of the invention, the manufacturing method adopts the combined heat treatment method. The manufacturing method can effectively solve the problem of poor formability caused by large AlFeSi phase particle size and high recrystallization texture content before cold rolling of the 6000 series aluminum alloy plate under the existing heat treatment process system, and can also obviously improve the formability of the plate.
In addition, the manufacturing method can realize process optimization only by setting parameters on the basis of the existing aluminum alloy heat treatment production line, has quite wide applicability and has very good popularization prospect and application value.
Further, in the manufacturing method, in the step (2), the temperature of the 6000 series aluminum alloy casting blank is raised to 460-500 ℃ at the heating rate of 150-200 ℃/h, and the temperature is kept for 22-26 h; then continuously heating to 550-570 ℃ at the heating rate of 150-200 ℃/h, preserving the heat for 10-14 h, and then cooling to room temperature at the cooling rate of 50-100 ℃/h.
Compared with the prior art, the combined heat treatment method for improving the formability of the 6000-series aluminum alloy plate strip and the manufacturing method have the following advantages and beneficial effects:
(1) The combined heat treatment method for improving the formability of the 6000 series aluminum alloy plate strip and the manufacturing method can effectively solve the problem of poor formability caused by large AlFeSi phase particle size and high recrystallization texture content before cold rolling of the 6000 series aluminum alloy plate under the existing heat treatment process system.
(2) In the combined heat treatment method for improving the formability of the 6000 series aluminum alloy plate strip and the manufacturing method thereof, two-stage homogenization treatment is required before the hot rolling step. The two-stage homogenization treatment of the technical scheme can effectively promote the conversion of beta-AlFeSi into alpha-AlFeSi phase, and the alpha-AlFeSi phase is crushed and refined in the rolling deformation process, so that the second phase particles are promoted to induce nucleation, the structure grains are refined, and the coarse Mg can be promoted by combining the high-temperature intermediate annealing treatment after hot rolling 2 Si phase re-dissolves, the volume fraction of cubic recrystallization texture in the plate after hot rolling and annealing is reduced, and the formability of the plate is further obviously improved.
Drawings
FIG. 1 is an EBSD map of the matrix of the 6000 series aluminum alloy plate strip of example 5 after annealing treatment.
FIG. 2 is an EBSD map of the matrix of the comparative aluminum alloy strip of comparative example 1 after annealing treatment.
FIG. 3 is an EBSD map of the base of the 6000 series aluminum alloy strip of example 5 after solution quenching treatment.
FIG. 4 is an EBSD map of the matrix of the comparative aluminum alloy strip of comparative example 1 after solution quenching treatment.
Figure 5 schematically shows the dimensions of the tensile specimen required during the tensile test.
Detailed Description
The combined heat treatment method for improving the formability of 6000 series aluminum alloy strip and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to specific examples, which, however, should not be construed to unduly limit the technical scope of the present invention.
Examples 1 to 6 and comparative example 1
In the present invention, the chemical compositions of the 6000 series aluminum alloy strip of examples 1-6 and the comparative aluminum alloy of comparative example 1 are completely the same, and the same chemical composition is used, as shown in table 1.
Table 1 shows the chemical compositions of the 6000 series aluminium alloy strip of examples 1-6 and the comparative aluminium alloy of comparative example 1.
Table 1 (wt.%, balance Al and other unavoidable impurities)
In the 6000 series aluminum alloy strips of examples 1-6 of the invention and the comparative aluminum alloy of comparative example 1, the aluminum alloy ingots of the examples and the comparative example were prepared according to the chemical compositions shown in table 1 by smelting and casting operations. And then homogenizing the aluminum alloy cast ingot, carrying out hot rolling after homogenizing, finishing annealing, then cold-rolling the aluminum alloy cast ingot into a cold-rolled sheet with the thickness of 1mm, and then carrying out solution quenching and pre-aging treatment.
The 6000 series aluminum alloy plates and strips of examples 1-6 were all prepared by the following steps:
(1) Smelting and casting were carried out according to the chemical compositions shown in Table 1.
(2) Two-stage homogenization treatment: heating up a 300mm 6000 series aluminum alloy thick cast ingot in a homogenization heat treatment furnace along with the furnace, heating up to 460-500 ℃ at a heating rate of 150-200 ℃/h, and preserving heat for 22-26 hours; then entering a high-temperature section, continuously heating to 550-570 ℃ at a heating rate of 150-200 ℃/h, preserving heat for 10-14 hours, and then cooling to room temperature at a cooling rate of 50-100 ℃/h.
(3) Hot rolling: and controlling the finish rolling temperature to be 260-300 ℃, wherein the thickness of the plate after rolling is 4mm.
(4) High-temperature short-time annealing treatment: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min.
(5) Cold rolling: and when the annealed hot rolled plate blank is subjected to cold rolling, the pass reduction rate is not lower than 40%, and a cold rolled plate with the thickness of 1mm is obtained through cold rolling.
(6) Solution quenching treatment: keeping the temperature for 1 minute at 540 ℃ and then cooling with water.
(7) And (3) performing pre-aging treatment within 24 h: controlling the temperature at 160 ℃, and keeping the temperature for 5min.
In the step (4), when the thickness of the 6000 series aluminum alloy hot rolled plate is less than 3.0mm, an air cushion furnace can be used for heating; when the thickness of the 6000 series aluminum alloy hot rolled plate is more than or equal to 3.0mm, salt bath heating can be adopted.
The relevant process designs of the 6000 series aluminum alloy hot rolled plates of the embodiments 1 to 6 of the invention all meet the requirements of the design specifications of the invention.
While the process design of the comparative aluminum alloy of comparative example 1 does not meet the design specification requirements of the present invention, the comparative aluminum alloy of comparative example 1 employs a single-stage homogenization treatment: heating to 560 ℃ at the speed of 100 ℃/h, preserving the heat for 12 hours, and then cooling to room temperature at the speed of 20 ℃/h; the hot rolled plate blank is kept at 420 ℃ for 2 hours and then cooled to room temperature at the speed of 5 ℃/min; then the same process of the invention is adopted for cold rolling, solid solution and pre-aging treatment.
Table 2 shows the specific process parameters of the 6000 series aluminum alloy sheet strip of examples 1 to 6 and comparative example 1 in the above process steps.
Table 2.
The obtained 6000-series aluminum alloy strips of examples 1 to 6 and the comparative aluminum alloy strip of comparative example 1, which are 1mm thick, were sampled after natural aging for 2 weeks, respectively, and the relevant formability tests were performed, and the test results of the obtained examples and comparative examples are shown in table 3, respectively.
The test means adopted by the related forming performance test is as follows:
room temperature tensile test: the wire cut processing of the tensile specimens was performed according to ASTM E8, and the dimensions of the tensile specimens were as shown in FIG. 5, with a gauge length of 50mm. Room temperature tensile sample rolling direction RD from plate strip to plate strip
(Rolling orientation) at an angle of 0 deg. The tensile test is carried out on an MTS810 tensile testing machine, the tensile rate is controlled to be 2mm/min, and the tensile property is the average result of three parallel samples. The stress corresponding to the plastic elongation of 0.2% is defined as the yield strength σ 0.2 The tensile strength σ is obtained by the corresponding maximum force on the stress-strain curve m And then calculating the yield ratio through the ratio of the yield strength to the tensile strength, and calculating the elongation through measuring the change of the gauge length of the sample before and after the fracture.
The strain index n and the plastic strain ratio r measured by the tensile test can indirectly reflect the formability of the automobile body plate. The value of n represents the hardening capacity of the plate in plastic deformation, and reflects the deformation uniformity, the forming limit, whether cracks are generated or not and the like. The larger the value of n, the higher the hardening capacity of the material and the more uniform the plastic deformation of the part thickness. The n value is obtained by automatically collecting data by an automatic tensile tester and a data processing program and calculating a method of linear regression by the formula (1).
lns＝n×lne+lnC (1)
In the above formula (1), s is the true stress, e is the true strain, and C is the strength coefficient.
The samples tested by the plastic strain ratio r value are cut from the strip in two directions which respectively form 0 degree and 90 degrees with the strip rolling direction, three samples are cut in each direction to be parallel samples, and the size of the samples is the same as that of the normal-temperature tensile samples. The r value is determined according to the GB/T5027-2007 standard, the size schematic diagram is the same as that of the figure 5, and the gauge length is 50mm. The experiment was carried out on a MTS810 tensile tester at a tensile rate of 0.5mm/min. The definition of the r value is shown in the following formula (2):
in the above formula (2), ε b True plastic strain in the width direction; epsilon a Is the true plastic strain in the thickness direction.
The strain level at which the value of the plastic strain ratio r is tested should exceed the yield elongation stage and be lower than the plastic elongation at maximum force, i.e. the value of the strain ratio r must be tested before necking, so that the volume-invariant principle is met, namely:
ε l +ε b +ε a ＝0 (3)
in the above formula (3), ε l Is the true plastic strain in the length direction.
From equations (2) and (3), we can derive:
then
Is epsilon l And ε b Regression of the true strain data in the length and width directions within the selected region yields the slope of the line through the origin, in m r And then:
therefore, only need to obtain epsilon l And ε b Slope m of the regression line r The minimum value of the r values tested in two directions of 0 degrees and 90 degrees with the rolling direction in the plane of the test plate can be used as the r value of the product.
The plate strip edge covering performance test can be carried out according to GMW15421-2018, samples are cut from two directions of 0 degree and 90 degrees of an included angle between the aluminum plate and the plate Rolling direction RD (Rolling direction), and three parallel samples are taken from each direction. The aluminum alloy edge covering performance test sample is a strip sample with the thickness of 50mm multiplied by 30mm, and the test method comprises the following steps: firstly, pre-stretching an aluminum alloy plate by 10 percent; and (2) carrying out a 180-degree three-point bending test on the aluminum alloy plate.
The key point of the test is to judge whether the aluminum strip reaches the bending limit. Through visual observation, 3 different states exist on the outer surface of the bending part of the automobile aluminum plate: (1) no cracks and microcracks; (2) the presence of crack initiation lines; (3) there are significant cracks or microcracks. Wherein only the bending test sample without cracks and microcracks can be accepted, and the bending test sample with cracks, microcracks or crack initiation lines can not be accepted.
In the present invention, the edge-covering factor R is adopted min The ratio of the minimum bending radius to the thickness (also called bending limit) is used as a measure of the quality of the bending properties of the aluminum alloy sheet. Edge-covering factor R min The smaller the/t, the better the hemming performance of the aluminum alloy sheet. Taking the R measured in two directions of 0 degree and 90 degree with the rolling direction in the plane of the plate min Average value as R of the product min Calculating the edge-covering factor R min And/t is used as the edge-covering factor of the product.
Table 3 shows the test results of the 6000-series aluminium alloy sheets of examples 1-6 and the comparative aluminium alloy sheet of comparative example 1.
Table 3.
As shown in table 3, the formability of the 6000-series aluminum alloy sheet strips of examples 1 to 6 and the comparative aluminum alloy sheet strip of comparative example 1 subjected to the present invention was evaluated by the r value, n value, elongation, edge-covering factor, and yield ratio of the sheet strips of examples 1 to 6 and comparative example 1.
As can be seen from table 3, compared with the comparative aluminum alloy strip of comparative example 1, the r value of the 6000-series aluminum alloy strips of examples 1 to 6 of the present invention is significantly larger, the edge-covering factor and the yield ratio are lower, the formability of the sheet material is effectively improved, and the basic performance index requirements of the automobile body sheet can be satisfied.
FIG. 1 is an EBSD map of the substrate of the 6000 series aluminum alloy strip of example 5 after annealing treatment.
FIG. 2 is an EBSD map of the matrix of the comparative aluminum alloy strip of comparative example 1 after annealing treatment.
FIG. 3 is an EBSD map of the base of the 6000 series aluminum alloy strip of example 5 after solution quenching treatment.
FIG. 4 is an EBSD map of the matrix of a comparative aluminum alloy sheet strip of comparative example 1 after solution quenching treatment.
As can be seen from the combination of FIGS. 1, 2, 3 and 4, the grain size of the hot-rolled sheet of example 5 according to the present invention was about 123 μm, and the grain size of the hot-rolled sheet of comparative example 1 was about 200 μm. After the plate had been subjected to solution quenching treatment, the grain size of example 5 was about 65 μm and that of comparative example 1 was about 90 μm. It can be seen that the two-stage homogenization treatment is performed before the hot rolling step in example 5, and the high-temperature short-time annealing treatment is performed after the hot rolling step and before the cold rolling step, which effectively reduces the grain size of the sheet.
In addition, in comparative example 1, the ratio of coarse grains (≧ 100 μm) in the sheet is 30%, which is mainly oriented by the cubic texture, the oriented grain structure is accumulated on the sheet surface to easily form a roping line, and the sheet surface quality and formability are reduced.
It should be noted that the combination of the features in the present application is not limited to the combination described in the claims or the combination described in the embodiments, and all the features described in the present application can be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications thereto which can be directly or easily inferred from the disclosure of the present invention by those skilled in the art are intended to be within the scope of the present invention.
Claims (4)
1. A combined heat treatment method for improving the formability of 6000 series aluminum alloy plates and strips is characterized by comprising the following steps:
carrying out two-stage homogenization treatment before the hot rolling step, wherein the first-stage homogenization treatment comprises the following processes: heating a 6000 series aluminum alloy casting blank to 460-500 ℃, and preserving heat for 22-26 h, wherein the heating rate is 150-200 ℃/h; the second-stage homogenization treatment process comprises the following steps: continuously heating to 550-570 ℃, preserving the heat for 10-14 h, and then cooling to room temperature; in the second-stage homogenization treatment process, the heating rate is 150-200 ℃/h; the cooling rate is 50-100 ℃/h;
after the hot rolling step and before the cold rolling step, carrying out high-temperature short-time annealing treatment, wherein the process of the high-temperature short-time annealing treatment comprises the following steps: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min.
2. The combined heat treatment method according to claim 1, wherein in the high-temperature short-time annealing treatment step, when the thickness of the 6000 series aluminum alloy hot rolled plate is less than 3.0mm, heating is performed by using an air cushion furnace.
3. The combined heat treatment method according to claim 1, wherein in the high-temperature short-time annealing treatment step, when the thickness of the 6000 series aluminum alloy hot rolled plate is equal to or more than 3.0mm, salt bath heating is used.
4. A manufacturing method of 6000 series aluminum alloy plates and strips is characterized by comprising the following steps:
(1) Smelting and casting;
(2) Two-stage homogenization treatment: heating a 6000 series aluminum alloy casting blank to 460-500 ℃ at the heating rate of 150-200 ℃/h, and preserving the heat for 22-26 h; then continuously heating to 550-570 ℃ at the heating rate of 150-200 ℃/h, preserving the heat for 10-14 h, and then cooling to room temperature at the cooling rate of 50-100 ℃/h
(3) Hot rolling;
(4) High-temperature short-time annealing treatment: heating the 6000 series aluminum alloy hot rolled plate to 500-550 ℃, preserving heat for 5-15 min, and then cooling to room temperature at the speed of 150-200 ℃/min;
(5) Cold rolling;
(6) Solution quenching treatment;
(7) And carrying out pre-aging treatment within 24 h.
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| JP4495623B2 (en) * | 2005-03-17 | 2010-07-07 | 株式会社神戸製鋼所 | Aluminum alloy plate excellent in stretch flangeability and bending workability and method for producing the same |
| JP4939093B2 (en) * | 2006-03-28 | 2012-05-23 | 株式会社神戸製鋼所 | Method for producing 6000 series aluminum alloy plate for automobile panel having excellent hem bendability and bake hardness |
| CN103757507B (en) * | 2014-02-25 | 2016-04-27 | 北京科技大学 | A kind of automobile body outer board high bake hardening aluminum alloy materials and preparation method thereof |
| CN104018040B (en) * | 2014-06-23 | 2017-08-08 | 北京科技大学 | A kind of automobile high formability aluminum alloy materials |
| CN109722573A (en) * | 2019-01-23 | 2019-05-07 | 北京工业大学 | A kind of high formability Al-Mg-Si-Cu-Zn-Er-Zr alloy and preparation method thereof |
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