High-yield-strength 5754 aluminum alloy material for automobiles and preparation method of high-yield-strength 5754 aluminum alloy material

Abstract

The invention relates to the technical field of aluminum alloy processing, in particular to a high-yield-strength 5754 aluminum alloy material for an automobile and a preparation method of the high-yield-strength 5754 aluminum alloy material. The content of Fe is 0.31 to 0.41 percent; the content of Cu is less than or equal to 0.15%; the content of Mn is less than or equal to 0.60%; the content of Mg is 3.25 to 3.35 percent; the content of Cr is less than or equal to 0.30%; zn content is less than or equal to 0.25%; the content of Ti is less than or equal to 0.20%; the yield strength of the material reaches 110-120 MPa, and the tensile strength and the percentage elongation after fracture are excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy processing, and in particular to a 5754 aluminum alloy material for automobiles with high yield strength and a preparation method thereof. Background Art

[0002] Reducing the weight of automobiles to reduce energy consumption, reduce exhaust emissions and improve efficiency has become an important direction for major automobile companies to improve their competitiveness. There are two main ways to achieve lightweighting of automobiles, namely structural optimization design and the use of lightweight materials. The main lightweight materials are: aluminum, magnesium alloys, low-strength alloyed steels, composite materials, resin-based materials, etc. Among them, aluminum alloys and their processed materials have a series of excellent properties, such as low density, high specific strength and specific stiffness, good elasticity, good impact resistance, corrosion resistance, wear resistance, good processing formability and high recycling and regeneration. In order to save non-renewable energy such as oil, reduce automobile exhaust pollution to the air and protect the deteriorating ozone layer, aluminum alloy materials have rapidly entered the automotive field.

[0003] 5000 series (Al-Mg) aluminum alloys are often used in the manufacture of key aircraft and automotive components, such as wheels, body panels, fuel tank inner covers, engine hood inner panels, and large aircraft skins. 5000 series aluminum alloys offer strong heat resistance, excellent stamping properties, and high strength, but their yield strength is difficult to achieve. Conventional 5754 automotive aluminum alloys achieve a yield strength of 80-110 MPa under the most fully annealed heat treatment regime, with cases exceeding 110 MPa being rare. The potential for increasing yield strength through annealing has reached its limit, while conventional 5182 aluminum alloys have a yield strength exceeding 110 MPa.

[0004] Therefore, there is an urgent need to provide a high-yield strength 5754 aluminum alloy material for automobiles and a preparation method, so that the material has excellent mechanical properties and a fine grain size, and the yield strength of the 5754 aluminum alloy reaches above 110 MPa without adding 4-5wt% Mg element, so as to meet the requirement of using 5754 aluminum alloy to replace 5182 aluminum alloy with a magnesium content of 4-5wt%. Summary of the Invention

[0005] The present invention aims to solve the technical problem of how to provide a high yield strength aluminum alloy material for automobiles and a preparation method thereof.

[0006] In order to achieve the above object, the first aspect of the present invention provides a high yield strength 5754 aluminum alloy material for automobiles, wherein the components and their weight percentages in the material are as follows: Si content is 0.25-0.35%; Fe content is 0.31-0.41%; Cu content ≤ 0.15%; Mn content ≤ 0.60%; Mg content is 3.25-3.35%; Cr content ≤ 0.30%; Zn content ≤ 0.25%; Ti content ≤ 0.20%; V content ≤ 0.10%; The content of other impurity elements is ≤0.05%; The total content of other impurity elements is ≤0.15%; The balance is Al.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned high yield strength automotive aluminum alloy material, wherein the method comprises: Melting, sawing and milling, heating, hot rolling, cold rolling, annealing, trimming, packaging; The conditions for the melting and casting include: a melting temperature of 725-765°C, a standing time of 30-45 minutes, and a refining temperature of 725-755°C; When the aluminum liquid temperature is 730-740°C, 0.05-1wt% Al-Ti-BC composite modifier is added, and electromagnetic stirring is adopted with a stirring speed of 200-300rpm and a stirring time of 15-20min.

[0008] The beneficial effects of the present invention are: The present invention regulates the alloy composition, adjusts the melting and casting process, strictly controls the hot rolling and cold rolling parameters, and adjusts the continuous annealing system. Without changing the annealing system or adding a straightening process, the 5754 automotive sheet aluminum alloy material with excellent yield strength and other mechanical properties is obtained. The material can replace the 5182 aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a scanning electron microscope image of the material of Example 1; Figure 2 This is a scanning electron microscope image of conventional 5754 aluminum alloy; Figure 3 Metallographic diagrams of the aluminum alloy materials of Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0010] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0011] In the existing technology, it is difficult to produce 5754 aluminum alloy materials with excellent yield strength due to the existing alloy composition and preparation process, making it difficult for the mechanical properties of the aluminum alloy materials to meet the requirements. Under the annealing system with the maximum annealing degree, the yield strength of 5754 aluminum alloy does not exceed 110MPa. Adjusting the annealing system cannot improve the material properties. Without adding a straightening production process, the existing production process cannot achieve straightening treatment, and it is impossible to improve the material properties through straightening.

[0012] In the present invention, the inventors found that if the alloy composition is controlled and the processing technology is adjusted, without changing the main production process (annealing system) or the production process (adding a straightening process), the performance of 5754 aluminum alloy material can reach the yield strength (R p0.2 ), and maintain tensile strength (R m )、Elongation at break(A 80 ), uniform elongation (Ag), work hardening index (n) and plastic strain ratio (r).

[0013] To achieve this goal, the inventors discovered that the above purpose can be achieved through specific component composition and homogenization process. Furthermore, specific extrusion and aging processes make the performance of aluminum alloy materials even better.

[0014] A first aspect of the present invention provides a high yield strength 5754 aluminum alloy material for automobiles, wherein the components and their weight percentages in the material are as follows: Si content is 0.25-0.35%; Fe content is 0.31-0.41%; Cu content ≤ 0.15%; Mn content ≤ 0.60%; Mg content is 3.25-3.35%; Cr content ≤ 0.30%; Zn content ≤ 0.25%; Ti content ≤ 0.20%; V content ≤ 0.10%; The content of other impurity elements is ≤0.05%; The total content of other impurity elements is ≤0.15%; The balance is Al.

[0015] In the present invention, the increase of Fe and Si content increases the alloy phase in the material structure, and the metallographic color is dark gray and light gray. Figure 1Under the scanning electron microscope, there are black and white phases, and there are round and irregular shapes in morphology. The larger irregular white phase contains Mn and Fe elements, which is the AlMnFe phase, and contains a small amount of Si elements. The smaller round white phase contains Mn, Fe, and Mg elements, which is the AlFeMnMg composite phase. The black phase has a higher content of Al and Mg, and also contains a small amount of Si elements. It should be the AlMgSi phase. The larger alloy phase reduces the elongation of the material. The power can be increased during hot rough rolling to break the large alloy phase.

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned high yield strength automotive aluminum alloy material, wherein the method comprises: Melting, sawing and milling, heating, hot rolling, cold rolling, annealing, trimming, packaging; The conditions for the melting and casting include: a melting temperature of 725-765°C, a standing time of 30-45 minutes, and a refining temperature of 725-755°C; When the aluminum liquid temperature is 730-740°C, 0.05-1.0wt% Al-Ti-BC composite modifier is added, and electromagnetic stirring is adopted with a stirring speed of 200-300rpm and a stirring time of 15-20min.

[0017] In the present invention, an ingot is obtained after melting and casting, the ingot is sawn and heated, the heated ingot is hot rolled to obtain a preliminary coil, the preliminary coil is cold rolled and continuously annealed, and then trimmed and packaged to obtain the aluminum alloy material of the present invention.

[0018] In the present invention, a specific content of Al-Ti-BC composite modifier Ti and B elements are introduced during the melting and casting process to form TiB2 particles, which serve as heterogeneous nucleation cores of α-Al grains and refine the grains; the C element can combine with Ti to form TiC particles, further increasing nucleation points and inhibiting grain growth. The specific content of Al-Ti-BC can also improve the alloy phase distribution, promote the uniform precipitation of strengthening phases such as AlFeMnMg composite phases, reduce the formation of large-sized irregular phases, and improve the uniformity of the mechanical properties of the material.

[0019] According to the present invention, the smelting and casting conditions further include: adding 40-80 wt / % of recycled aluminum.

[0020] In the present invention, the recycled aluminum is added in an amount of 40-80% based on the mass of the total raw materials.

[0021] According to the present invention, the sawing and milling conditions include: the saw belt speed is 2100-2300m / min, the saw belt feed speed does not exceed 500mm / min, when milling, the feed speed is 3.5-4.5m / min, the ingot guide end cutting waste is ≥380mm, the large face milling amount is ≥15mm, the small face milling amount is 5-10mm, and the thickness after milling is not less than 590mm.

[0022] According to the present invention, the heating conditions include: a heating temperature of 530-550° C. and a heating time of 240-300 min.

[0023] According to the present invention, the hot rolling conditions include: a total of 18-24 passes, in the first 1 / 2 passes, the rolling temperature is 450-470°C, in 1 / 2-3 / 4 passes, the rolling temperature is 430-450°C, and in the last 1 / 4 passes, the rolling temperature is 410-430°C.

[0024] In the present invention, when the number of passes cannot be divided by 2 or 4 to obtain an integer number of passes, the number of passes is rounded off to retain the decimal point.

[0025] According to the present invention, the vertical roller reduction is 2-4 mm, and gradually increases with each pass.

[0026] In the present invention, the gradient temperature can achieve different degrees of dynamic recrystallization during the rolling process. The high temperature in the early stage promotes recrystallization nucleation, and the low temperature in the latter stage suppresses grain growth, thereby obtaining fine and uniform recrystallized grains. The grain size can be controlled at 10-15μm. The gradually increasing vertical roll reduction is combined with the temperature gradient to enhance the crushing effect of coarse AlMnFe alloy phases, so that their size is refined from 5-10μm to 2-3μm, thereby improving the plasticity of the material.

[0027] According to the present invention, in the hot rolling process, after 3 / 4 of the passes, online water quenching is performed at a cooling rate of 5-10°C / s, and the temperature of the intermediate billet is reduced to 350-400°C.

[0028] According to the present invention, the cold rolling conditions include: a total of 4 passes, the tension of the first pass is 7-9 MPa, the thickness is from 4.5 mm to 2.6 mm, the tension of the second pass is 11-14 MPa, the thickness is from 2.6 mm to 1.6 mm, the tension of the third pass is 9-12 MPa, the thickness is from 1.6 mm to 1.237 mm, and the tension of the fourth pass is 5-8 MPa, and the thickness is from 1.237 mm to 1.2 mm.

[0029] According to the present invention, after the third pass, intermediate annealing is performed at a temperature of 210-230° C. for 0.5-3.5 hours.

[0030] In the present invention, variable tension rolling can change the rolling texture components, increase the favorable {111} texture content from 30% to 45%, improve the deep drawing performance of the material, and increase the n value by 0.1-0.2.

[0031] The change of tension in the same pass can adjust the residual stress distribution inside the plate and reduce the risk of cracking due to stress concentration. At the same time, intermediate annealing can eliminate part of the work hardening and create good organizational conditions for subsequent continuous annealing. The synergistic effect of variable tension and intermediate annealing can make the grain orientation more uniform, reduce anisotropy, and improve the consistency of plate performance.

[0032] According to the present invention, the continuous annealing conditions include: a continuous annealing heat treatment temperature of 350-380° C. and a heat preservation period of 25-35 seconds.

[0033] According to the present invention, the elongation of the continuous withdrawal line is 0.8-1.2%.

[0034] Test Method The test method for aluminum alloy material composition is in accordance with GB / T7999-2015 Aluminum and Aluminum Alloy Photoelectric Direct Reading Emission Spectroscopy Analysis Method, and the test equipment is ARL-3460 direct reading spectrometer.

[0035] The yield strength, tensile strength and elongation testing equipment is a 100KN universal material testing machine. The test standard is: ISO6892-1 "Metallic Materials - Tensile Tests - Part 1: Room Temperature Test Methods", and the test method is: GB / T16865-2023 "Specimens and Methods for Tensile Testing of Deformed Aluminum, Magnesium and Their Alloy Products".

[0036] The testing equipment is a 100KN universal material testing machine, the testing standard is ISO10113: "Determination of plastic elongation of thin sheets and strips of metallic materials", and the testing method is GB / T16865-2023 "Test specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products".

[0037] The testing equipment is a 100KN universal material testing machine, the testing standard is ISO10275: "Metallic materials. Sheet and strip. Test method for determination of tensile stress hardening index", and the testing method is GB / T16865-2023 "Test specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products".

[0038] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments implemented by those of ordinary skill in the art without making creative improvements are within the scope of protection of the present invention.

[0039] Example 1 Ingredients: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the ratio: Si: 0.335%, Fe: 0.387%, Cu: 0.002%, Mn: 0.384%, Mg: 3.333%, Cr: 0.01%, Zn: 0.009%, Ti: 0.02%, V: 0.0131%, other single ≤0.05%, other total ≤0.15%, the balance is Al.

[0040] Melting and casting: The prepared aluminum alloy raw materials are added into the melting furnace and evenly mixed, and then melted into liquid aluminum alloy. After melting at 752℃, 40% recycled aluminum is added. When the aluminum liquid temperature is 733℃, 0.08% Al-Ti-BC composite modifier is added. Electromagnetic stirring is adopted with a stirring speed of 238rpm and a stirring time of 17min. After standing for 35min, refining at 738℃, slagging, online degassing and filtering processes, the liquid aluminum alloy is melted and cast into aluminum alloy ingots.

[0041] Sawing and milling: Saw belt speed 2285m / min, saw belt feed speed 432mm / min, milling surface feed speed 3.9m / min, ingot guide end waste cutting 397mm, large face milling amount 15mm, small face milling amount 5mm, milling thickness 595mm.

[0042] Heating: The heating temperature is 532℃ and the heating time is 240min.

[0043] Hot rolling: a total of 24 passes, the rolling temperature of the first 12 passes is 455℃, the rolling temperature of the middle 4 passes is reduced to 437℃, and the rolling temperature of the last 8 passes is 426℃. The vertical roll reduction is 2-4mm, and the vertical roll reduction increases gradually according to the pass. At the same time, online water quenching cooling is added after the 12th pass, with a cooling rate of 7℃ / s, so that the temperature of the intermediate billet is quickly reduced to 382℃. The grain size of the aluminum alloy material after hot rolling is 2.5μm.

[0044] Cold rolling: 4 passes in total, the tension of the first pass is 7MPa, the thickness is from 4.5mm to 2.6mm, the tension of the second pass is 12MPa, the thickness is from 2.6mm to 1.6mm, the tension of the third pass is 12MPa, the thickness is from 1.6mm to 1.237mm, the tension of the fourth pass is 7MPa, the thickness is from 1.237mm to 1.2mm, after the third pass, intermediate annealing is carried out, the intermediate annealing temperature is 210℃, and the heat preservation is 1h.

[0045] Continuous annealing: The continuous annealing heat treatment temperature is 370℃, holding time is 30s, and the continuous annealing line elongation is 1.1%.

[0046] Aluminum alloy material A1 was obtained.

[0047] Example 2 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.320%, Fe: 0.380%, Cu: 0.004%, Mn: 0.376%, Mg: 3.326%, Cr: 0.005%, Zn: 0.003%, Ti: 0.018%, and V: 0.0128%.

[0048] Aluminum alloy material A2 is obtained.

[0049] Example 3 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.321%, Fe: 0.377%, Cu: 0.002%, Mn: 0.380%, Mg: 3.330%, Cr: 0.065%, Zn: 0.006%, Ti: 0.019%, and V: 0.0133%.

[0050] Aluminum alloy material A3 is obtained.

[0051] Example 4 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.25%, Fe: 0.31%, Cu: 0.001%, Mn: 0.001%, Mg: 3.25%, Cr: 0.0011%, Zn: 0.0021%, Ti: 0%, and V: 0.001%.

[0052] Aluminum alloy material A4 is obtained.

[0053] Example 5 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.35%, Fe: 0.41%, Cu: 0.15%, Mn: 0.60%, Mg: 3.35%, Cr: 0.30%, Zn: 0.25%, Ti: 0.20%, and V: 0.10%.

[0054] Aluminum alloy material A5 was obtained.

[0055] Example 6 An aluminum alloy material was prepared according to the processing method of Example 1, except that 0.05% Al-Ti-BC composite modifier was added when the aluminum liquid temperature was 730° C., and electromagnetic stirring was used with a stirring speed of 200 rpm and a stirring time of 15 min.

[0056] Aluminum alloy material A6 was obtained.

[0057] Example 7 An aluminum alloy material was prepared according to the processing method of Example 1, except that 1% Al-Ti-BC composite modifier was added when the aluminum liquid temperature was 740° C., and electromagnetic stirring was used with a stirring speed of 300 rpm and a stirring time of 20 min.

[0058] Aluminum alloy material A7 was obtained.

[0059] Example 8 An aluminum alloy material was prepared according to the processing method of Example 1, except that there were 24 passes in total, the rolling temperature of the first 12 passes was 450°C, the rolling temperature of the middle 4 passes was reduced to 430°C, and the rolling temperature of the last 8 passes was 410°C. The vertical roll reduction gradually increased according to the pass number, and online water quenching cooling was added after the 12th pass at a cooling rate of 5°C / s to quickly reduce the intermediate billet temperature to 350°C. The grain size of the aluminum alloy material after hot rolling was 2 μm.

[0060] Aluminum alloy material A8 was obtained.

[0061] Example 9 An aluminum alloy material was prepared according to the processing method of Example 1, except that there were 17 passes in total, the rolling temperature of the first 8 passes was 470°C, the rolling temperature of the middle 4 passes was reduced to 450°C, and the rolling temperature of the last 5 passes was 430°C. The vertical roll reduction gradually increased according to the pass number, and online water quenching cooling was added after the 12th pass at a cooling rate of 10°C / s to quickly reduce the intermediate billet temperature to 400°C. The grain size of the aluminum alloy material after hot rolling was 3 μm.

[0062] Aluminum alloy material A9 was obtained.

[0063] Example 10 An aluminum alloy material was prepared according to the processing method of Example 1, except that the tension of the first pass was 7 MPa, the tension of the second pass was 11 MPa, the tension of the third pass was 9 MPa, and the tension of the fourth pass was 5 MPa. After the third pass, intermediate annealing was performed at a temperature of 210°C for 0.5 h.

[0064] Aluminum alloy material A10 was obtained.

[0065] Example 11 An aluminum alloy material was prepared according to the processing method of Example 1, except that the tension of the first pass was 9 MPa, the tension of the second pass was 14 MPa, the tension of the third pass was 12 MPa, and the tension of the fourth pass was 8 MPa. After the third pass, intermediate annealing was performed at a temperature of 230°C for 3.5 hours.

[0066] Aluminum alloy material A11 was produced.

[0067] Example 12 An aluminum alloy material was prepared according to the processing method of Example 1, except that the continuous annealing treatment temperature was 350° C., the heat preservation time was 25 seconds, and the continuous annealing line elongation was 0.8%.

[0068] Aluminum alloy material A12 is produced.

[0069] Example 13 An aluminum alloy material was prepared according to the processing method of Example 1, except that the continuous annealing treatment temperature was 380° C., the heat preservation time was 35 seconds, and the continuous annealing line elongation was 1.2%.

[0070] Aluminum alloy material A13 is produced.

[0071] Comparative Example 1 Ingredients: Calculate the amount of each aluminum alloy raw material and prepare the aluminum alloy raw materials according to the ratio: Si: 0.322%, Fe: 0.349%, Cu: 0.011%, Mn: 0.432%, Mg: 3.343%, Cr: 0.105%, Zn: 0.001%, Ti: 0.020%, V: 0.003%, other individual ≤0.05%, other total ≤0.15%, the balance is Al.

[0072] Melting and casting: The prepared aluminum alloy raw materials are added into the melting furnace and evenly mixed, and then melted into liquid aluminum alloy. After melting at 744℃ without adding recycled aluminum, 0.06% Al-Ti-BC composite modifier is added when the aluminum liquid temperature is 738℃. Electromagnetic stirring is adopted with a stirring speed of 219rpm and a stirring time of 20min. After standing for 44min, refining at 749℃, slagging, online degassing and filtering processes, the liquid aluminum alloy is cast into aluminum alloy ingots.

[0073] Sawing and milling: Saw belt speed 2169m / min, saw belt feed speed 424mm / min. Milling feed speed 3.6m / min. 389mm of scrap was removed from the ingot starter end, 16mm of large face milling, 5mm of small face milling, and a final milling thickness of 592mm.

[0074] Heating: The heating temperature is 549°C and the heating time is 257 minutes.

[0075] Hot rolling: 17 rough rolling passes, 35mm reduction in the 2nd to 6th rough rolling passes, intermediate billet temperature 411°C, 4 finishing passes with power additions of 33%, 36%, 40%, 42% respectively, and coil offline temperature 331°C.

[0076] Cold rolling: 4 passes in total, the tension of the first pass is 7MPa, the thickness is from 4.5mm to 2.6mm, the tension of the second pass is 12MPa, the thickness is from 2.6mm to 1.6mm, the tension of the third pass is 11MPa, the thickness is from 1.6mm to 1.237mm, the tension of the fourth pass is 6MPa, the thickness is from 1.237mm to 1.2mm.

[0077] Continuous annealing: Continuous annealing adopts rising temperature heating, heat treatment temperature is 525℃, heat preservation is 0s, maximum material temperature is 525℃, elongation is 0.6%, and aluminum alloy material DA1 is produced.

[0078] Comparative Example 2 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.249%, Fe: 0.301%, Cu: 0.001%, Mn: 0.0016%, Mg: 3.248%, Cr: 0.003%, Zn: 0.0019%, Ti: 0.0012%, and V: 0.0014%.

[0079] Aluminum alloy material DA2 was produced.

[0080] Comparative Example 3 An aluminum alloy material was prepared according to the processing method of Example 1, except that the components of the aluminum alloy were Si: 0.351%, Fe: 0.411%, Cu: 0.151%, Mn: 0.610%, Mg: 3.351%, Cr: 0.301%, Zn: 0.251%, Ti: 0.201%, and V: 0.101%.

[0081] Aluminum alloy material DA3 was produced.

[0082] Comparative Example 4 An aluminum alloy material was prepared according to the processing method of Example 1, except that 0.04% Al-Ti-BC composite modifier was added when the aluminum liquid temperature was 729° C., and electromagnetic stirring was used with a stirring speed of 199 rpm and a stirring time of 14 min.

[0083] Aluminum alloy material DA4 was produced.

[0084] Comparative Example 5 An aluminum alloy material was prepared according to the processing method of Example 1, except that 1.1% Al-Ti-BC composite modifier was added when the aluminum liquid temperature was 741° C., and electromagnetic stirring was used with a stirring speed of 301 rpm and a stirring time of 21 min.

[0085] Aluminum alloy material DA5 was produced.

[0086] Comparative Example 6 An aluminum alloy material was prepared according to the processing method of Example 1, except that there were 24 passes in total, the rolling temperature of the first 12 passes was 449°C, the rolling temperature of the middle 4 passes was reduced to 429°C, and the rolling temperature of the last 8 passes was 409°C. The vertical roll reduction gradually increased according to the pass number, and online water quenching cooling was added after the 12th pass at a cooling rate of 4°C / s to quickly reduce the intermediate billet temperature to 349°C. The grain size of the aluminum alloy material after hot rolling was 9 μm.

[0087] Aluminum alloy material DA6 was produced.

[0088] Comparative Example 7 An aluminum alloy material was prepared according to the processing method of Example 1, except that there were 24 passes in total, the rolling temperature of the first 12 passes was 471°C, the rolling temperature of the middle 4 passes was reduced to 451°C, and the rolling temperature of the last 8 passes was 431°C. The vertical roll reduction gradually increased according to the pass number, and online water quenching cooling was added after the 12th pass at a cooling rate of 11°C / s to quickly reduce the intermediate billet temperature to 401°C. The grain size of the aluminum alloy material after hot rolling was 16 μm.

[0089] Aluminum alloy material DA7 was produced.

[0090] Comparative Example 8 An aluminum alloy material was prepared according to the processing method of Example 1, except that the tension of the first pass was 6 MPa, the tension of the second pass was 10 MPa, the tension of the third pass was 8 MPa, and the tension of the fourth pass was 4 MPa. After the third pass, intermediate annealing was performed at a temperature of 209°C for 0.9 h.

[0091] Aluminum alloy material DA8 was produced.

[0092] Comparative Example 9 An aluminum alloy material was prepared according to the processing method of Example 1, except that the tension of the first pass was 10 MPa, the tension of the second pass was 15 MPa, the tension of the third pass was 13 MPa, and the tension of the fourth pass was 9 MPa. After the third pass, intermediate annealing was performed at a temperature of 231°C for 1.1 h.

[0093] Aluminum alloy material DA9 was produced.

[0094] Comparative Example 10 An aluminum alloy material was prepared according to the processing method of Example 1, except that the continuous annealing treatment temperature was 349° C., the heat preservation time was 24 seconds, and the continuous annealing line elongation was 0.7%.

[0095] Aluminum alloy material DA10 was produced.

[0096] Comparative Example 11 An aluminum alloy material was prepared according to the processing method of Example 1, except that the continuous annealing treatment temperature was 381° C., the heat preservation time was 36 seconds, and the continuous annealing line elongation was 1.3%.

[0097] Aluminum alloy material DA11 was produced.

[0098] Performance tests were conducted on A1-A13 and DA1-DA11, as shown in Table 1. Table 1 By comparing the examples with the comparative examples, it can be seen that the material designed in the present invention, by optimizing the alloy composition, adjusting the melting and casting process, optimizing the rolling process, and adjusting the continuous annealing system, can replace the 5182 aluminum alloy with a magnesium content of 4-5wt% without adding 4-5wt% Mg element, which not only reduces the production cost but also obtains the 5754 alloy with a yield strength of 110-120 MPa and other excellent mechanical properties.

[0099] Attached to the instruction manual Figure 3 It can be seen that due to the low annealing temperature, the grain sizes of Examples 1 and 2 are relatively small, while the grain size of the aluminum alloy in Comparative Example 1 is 25 μm, which is larger.

[0100] The above description is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high yield strength 5754 aluminum alloy material for automobiles, characterized in that: The components and their weight percentages in the material are: Si content is 0.25-0.35%; Fe content is 0.31-0.41%; Cu content ≤ 0.15%; Mn content ≤ 0.60%; Mg content is 3.25-3.35%; Cr content ≤ 0.30%; Zn content ≤ 0.25%; Ti content ≤ 0.20%; V content ≤ 0.10%; The content of other impurity elements is ≤0.05%; The total content of other impurity elements is ≤0.15%; The balance is Al.

2. A method for preparing the high yield strength automotive aluminum alloy material according to claim 1, characterized in that: The method comprises: Melting, sawing and milling, heating, hot rolling, cold rolling, annealing, trimming, packaging; The conditions for the melting and casting include: a melting temperature of 725-765°C, a standing time of 30-45 minutes, and a refining temperature of 725-755°C; When the aluminum liquid temperature is 730-740°C, 0.05-1.0wt% Al-Ti-BC composite modifier is added, and electromagnetic stirring is adopted with a stirring speed of 200-300rpm and a stirring time of 15-20min.

3. The method according to claim 2, characterized in that The smelting and casting conditions also include: adding 40-80wt% of recycled aluminum.

4. The method according to claim 2, characterized in that The sawing and milling conditions include: a saw belt speed of 2100-2300m / min, a saw belt feed speed not exceeding 500mm / min, a feed speed of 3.5-4.5m / min when milling the surface, waste cutting at the ingot guide end ≥380mm, a large face milling amount ≥15mm, a small face milling amount of 5-10mm, and a thickness after milling of not less than 590mm.

5. The method according to claim 2, characterized in that The heating conditions include: a heating temperature of 530-550° C. and a heating time of 240-300 min.

6. The method according to claim 2, characterized in that The hot rolling conditions include: a total of 17-24 passes, a rolling temperature of 450-470° C. in the first 1 / 2 pass, a rolling temperature of 430-450° C. in the first 1 / 2-3 / 4 pass, and a rolling temperature of 410-430° C. in the last 1 / 4 pass; Among them, the vertical roller pressure is 2-4mm, and gradually increases with the number of passes; Among them, the grain size of the aluminum alloy material after hot rolling is 2-3 μm.

7. The method according to claim 6, characterized in that In the hot rolling process, after 3 / 4 of the passes, online water quenching is carried out with a cooling rate of 5-10℃ / s, and the temperature of the intermediate billet drops to 350-400℃.

8. The method according to claim 2, characterized in that The cold rolling conditions include: a total of 4 passes, the first pass has a tension of 7-9 MPa, the thickness is reduced from 4.5 mm to 2.6 mm, the second pass has a tension of 11-14 MPa, the thickness is reduced from 2.6 mm to 1.6 mm, the third pass has a tension of 9-12 MPa, the thickness is reduced from 1.6 mm to 1.237 mm, and the fourth pass has a tension of 5-8 MPa, the thickness is reduced from 1.237 mm to 1.2 mm; Among them, after the third pass, intermediate annealing is carried out, the intermediate annealing temperature is 210-230℃, and the heat preservation time is 0.5-3.5h.

9. The method according to claim 2, characterized in that The continuous annealing conditions include: a continuous annealing heat treatment temperature of 350-380° C. and a heat preservation time of 25-35 seconds.

10. The method according to claim 2, characterized in that The elongation of the continuous withdrawal line is 0.8-1.2%.

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