Preparation Process and Application of High-Elongation Anti-Fatigue Aluminum Alloy Sheets

Abstract

The present invention relates to a preparation process and application of a high-elongation anti-fatigue aluminum alloy sheet, belonging to the technical field of aluminum alloy sheets. The preparation process provided by the present invention comprises the following steps: (1) After preparing the raw materials, melting, stirring, refining, and heat-preserving in a melting furnace, and pouring into a mold for casting to obtain an ingot; (2) subjecting the ingot to homogenization treatment and cooling with the furnace to obtain a cooled ingot; (3) sandblasting and preheating the cooled ingot, impregnating it in a treatment solution, performing ultrasonic treatment, and rinsing with deionized water three times to obtain a treated ingot; (4) performing surface milling and hot rolling on the treated ingot to obtain a sheet, and performing cold rolling and stretching after cooling to room temperature to obtain a high-elongation anti-fatigue aluminum alloy sheet. The aluminum alloy sheet is prepared through a specific process and composition. Elements such as manganese and magnesium interact with rare earth elements, and a treatment solution is used to introduce alumina loaded with ethylene-propylene rubber particles to form a multi-layer protection on the surface of the ingot, further improving the alloy strength and anti-fatigue performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy sheets, and relates to the preparation process and application of high-elongation and fatigue-resistant aluminum alloy sheets. Background Art

[0002] With the increasingly strict requirements for environmental protection and energy conservation, the market's requirements for the performance of automotive manufacturing materials are constantly increasing. Due to its low density characteristics, aluminum alloy has become an ideal material choice for automotive lightweighting.

[0003] Traditional aluminum alloys mainly form strengthening phases in the matrix through heat treatment, thereby significantly improving the strength, hardness and other properties of aluminum alloys. However, the heat treatment process requires high energy consumption and long time, and in the manufacturing of some complex-shaped automotive parts, the internal structure and stress state of the material will change during the heat treatment process, and this change is difficult to be evenly distributed, thus easily causing local stress concentration and resulting in component deformation; in addition, the elongation and fatigue resistance of some aluminum alloys are insufficient to withstand the dynamic loads and frequent collisions during the vehicle's progress under various complex road conditions, and are prone to fracture under strong force or long-term repeated force, affecting the appearance, service life of the vehicle and the personal safety of passengers. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation process and application of high-elongation and fatigue-resistant aluminum alloy sheets. The present invention prepares aluminum alloy sheets through specific processes and compositions. Elements such as manganese and magnesium interact with rare earth elements to improve the strength, toughness, fatigue resistance, etc. of the alloy; and during the preparation process, a treatment liquid is used to introduce alumina loaded with ethylene-propylene rubber particles, and ultrasonic treatment is used to evenly disperse the components of the treatment liquid, forming a multi-layer protection on the surface of the ingot, further improving the strength and fatigue resistance of the alloy.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A preparation process of high-elongation and fatigue-resistant aluminum alloy sheets, the preparation process comprising the following steps:

[0007] (1) After preparing the raw materials, melt, stir, refine and keep warm in a melting furnace, and pour into a mold for casting to obtain an ingot;

[0008] (2) Perform homogenization treatment on the ingot, and cool it with the furnace to obtain a cooled ingot;

[0009] (3) Sandblast and preheat the cooled ingot, immerse it in the treatment liquid, perform ultrasonic treatment, and rinse with deionized water 3 times to obtain a treated ingot;

[0010] (4)The processed ingot is milled and hot-rolled to obtain a sheet, which is then cold-rolled and stretched at room temperature to obtain a high-elongation fatigue-resistant aluminum alloy sheet.

[0011] Further, by weight percentage, the raw materials in step (1) include 3-5 wt% magnesium, 0.63-0.68 wt% manganese, 0.18-0.24 wt% iron, 0.12-0.2 wt% silicon, 0.05-0.5 wt% scandium, 0.5-1.2 wt% ytterbium, and the balance aluminum.

[0012] Further, the melting temperature in step (1) is 745-765 °C; the refining agent selected for refining is hexachloroethane with a mass of 0.1-0.26 wt% of the total mass of the raw materials. Argon is introduced for degassing during refining, and the gas injection time is 10-30 min; the temperature and time for heat preservation are 720-730 °C and 20-30 min respectively; the casting temperature is 700-720 °C.

[0013] Further, the homogenization treatment in step (2) means putting the ingot into a heat treatment furnace and heating it to 500-550 °C at a rate of 5-10 °C / min, keeping the temperature unchanged for 10-14 h to obtain a homogenized ingot; the cooling rate of furnace cooling is controlled at 5-10 °C / min.

[0014] Further, the preparation steps of the treatment liquid in step (3) are as follows:

[0015] Sodium molybdate and benzotriazole are added to deionized water and stirred at a speed of 400-500 rmp for 40-50 min. Then, modified alumina with an average particle size of 40-60 nm is added, the rotation speed is increased to 600-800 rmp, and stirring is continued for 1-2 h. Then, polyvinyl alcohol and OP-10 are added, and stirring is continued for 30-40 min. The ultrasonic power is set to 100-200 W, the ultrasonic frequency is 10-30 kHz, and ultrasonic treatment is carried out for 20-30 min, and then filtered through a 0.22 μm filter membrane to obtain the treatment liquid.

[0016] Further, by weight parts, the ratio of sodium molybdate, benzotriazole, modified alumina with an average particle size of 40-60 nm, polyvinyl alcohol, OP-10, and deionized water in the treatment liquid is 0.4-0.6:0.25-0.35:0.8-1.3:0.042-0.054:0.1-0.2:18-24.

[0017] Further, the modified alumina is alumina loaded with ethylene-propylene rubber particles, and the preparation steps of the alumina loaded with ethylene-propylene rubber particles are as follows:

[0018] A1. Drop ammonia water with a mass concentration of 15 - 25 wt% into an aluminum nitrate solution with a mass concentration of 0.4 - 0.6 mol / L to adjust the pH to 8.5 - 9.5, and stir until precipitation occurs to obtain a precursor solution;

[0019] A2. Mix polystyrene microspheres and ethanol to obtain a polystyrene microsphere solution with a mass concentration of 8 - 12%. After mixing the polystyrene microsphere solution and the precursor solution in a volume ratio of 1:1, stir for 1 - 3 h. The obtained mixed solution is dried in an oven at 80 °C for 6 - 12 h, and then treated in a muffle furnace at 450 - 550 °C for 2 - 4 h to obtain mesoporous alumina;

[0020] A3. Mix 1.2 - 3 parts by weight of mesoporous alumina and 6 - 12 parts by weight of absolute ethanol, then add 0.3 - 0.7 parts by weight of ethylene - propylene rubber particles with an average particle size of 20 - 40 nm. Set the ultrasonic power to 300 - 500 W, the ultrasonic frequency to 50 - 60 kHz, ultrasonic for 20 - 40 min, then stir for 1 - 2 h, wash with absolute ethanol and extract for 72 h, and dry to obtain alumina loaded with ethylene - propylene rubber particles.

[0021] Further, the pressure of the sandblasting treatment in step (3) is 0.2 - 0.4 MPa; the temperature of the pre - heat treatment is 50 - 80 °C; the parameters of the ultrasonic treatment are: ultrasonic power is 200 - 400 W, ultrasonic frequency is 25 - 35 kHz, ultrasonic temperature is 38 - 42 °C, and ultrasonic time is 15 - 35 min.

[0022] Further, the milling depth in step (4) is controlled within 2 - 3 mm; in the hot - rolling step, the ingot after milling is heated to 370 - 420 °C, the hot - rolling reduction is controlled at 12 - 14% each time, and a total of 4 - 8 passes are carried out. The hot - rolling time for each pass is 0.5 - 1.5 min, and the hot - rolling speed is 8 - 9 m / min; the cold - rolling uses a four - high cold - rolling mill, the surface hardness of the roll is HRC60, the cold - rolling reduction is controlled at 8 - 9% each time, and a total of 3 - 5 passes are carried out. The cold - rolling time for each pass is 1.5 - 2.5 min, and the cold - rolling speed is controlled at 4 - 4.4 m / min; the parameters of the stretching step are: stretching temperature is 175 - 195 °C, and stretching speed is 1.5 - 1.7 mm / min.

[0023] Further, the aluminum alloy sheet is applied to automobile doors, automobile hoods, and automobile front and rear fenders.

[0024] The beneficial effects of the present invention:

[0025] (1)The present invention prepares an aluminum alloy sheet through a specific process and composition. Elements such as manganese and magnesium and rare earth elements interact with each other to form intermetallic compounds, further improving the strength and toughness of the alloy. At the same time, the grain size is refined to reduce the stress concentration at grain boundaries, thereby improving the fatigue resistance of the alloy.

[0026] (2)In the preparation process of the present invention, a treatment liquid is used, and alumina loaded with ethylene-propylene rubber particles is introduced and filled on the surface of the ingot. The ethylene-propylene rubber particles have good elasticity and toughness, and deform when the alloy is subjected to external force, absorbing part of the energy, thereby reducing stress concentration, reducing the generation and propagation of fatigue cracks, and improving the toughness and fatigue resistance of the alloy; alumina itself has a high hardness and can be deposited on the surface of the ingot to form a physical barrier. Moreover, molybdenum ions in sodium molybdate react with oxygen in the air on the surface of the ingot to form a dense molybdenum oxide film. Benzotriazole molecules can form stable complexes with metal ions on the surface of the aluminum alloy and adsorb on the surface of the ingot; at the same time, with the aid of ultrasonic treatment, the uniformly dispersed components of the treatment liquid can better contact the surface of the ingot, thereby forming a multi-layer protection, further improving the strength of the alloy, and thus improving the fatigue resistance of the alloy. Detailed implementation mode

[0027] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in combination with embodiments, details the specific implementation mode, structure, features and their effects of the present invention as follows.

[0028] Embodiment 1

[0029] The preparation process of a high-elongation fatigue-resistant aluminum alloy sheet. The preparation process of this embodiment includes the following steps:

[0030] (1)After preparing the raw materials, melt, stir, refine and keep warm in a melting furnace, and pour them into a mold for casting to obtain an ingot.

[0031] (2)Perform homogenization treatment on the ingot and cool it with the furnace to obtain the cooled ingot.

[0032] (3)Sandblast and preheat the cooled ingot, immerse it in the treatment liquid, perform ultrasonic treatment, and rinse it 3 times with deionized water to obtain the treated ingot.

[0033] (4)Mill and hot-roll the treated ingot to obtain a sheet, and then perform cold rolling and stretching at room temperature to obtain a high-elongation fatigue-resistant aluminum alloy sheet.

[0034] In step (1), the raw materials of this embodiment are calculated by weight percentage, including 3wt% magnesium, 0.63wt% manganese, 0.18wt% iron, 0.12wt% silicon, 0.05wt% scandium, 0.5wt% ytterbium and the balance aluminum.

[0035] In step (1), the melting temperature in this embodiment is 745 °C; the refining agent selected for refining is hexachloroethane with a mass of 0.1 wt% of the total mass of the raw materials. Argon is introduced for degassing while refining, and the gas passing time is 10 min; the holding temperature and time are 720 °C and 20 min respectively; the casting temperature is 700 °C.

[0036] In step (2), the homogenization treatment in this embodiment means putting the ingot into a heat treatment furnace, heating it to 500 °C at a rate of 5 °C / min, keeping the temperature unchanged for 10 h to obtain the homogenized ingot; the cooling rate of furnace cooling is controlled at 5 °C / min.

[0037] In step (3), the preparation steps of the treatment liquid in this embodiment are as follows:

[0038] Sodium molybdate and benzotriazole are added to deionized water, stirred at a speed of 400 rmp for 40 min, then modified alumina with an average particle size of 40 nm is added, the rotation speed is increased to 600 rmp, and stirred for 1 h. Then polyvinyl alcohol and OP-10 are added, and stirring is continued for 30 min. The ultrasonic power is set to 100 W and the ultrasonic frequency is 10 kHz, and ultrasonic treatment is carried out for 20 min, and then filtered through a 0.22 μm filter membrane to obtain the treatment liquid.

[0039] By weight, the ratio of sodium molybdate, benzotriazole, modified alumina with an average particle size of 40 nm, polyvinyl alcohol, OP-10 and deionized water in the treatment liquid of this embodiment is 0.4:0.25:0.8:0.042:0.1:18.

[0040] The modified alumina in this embodiment is alumina loaded with ethylene-propylene rubber particles. The preparation steps of alumina loaded with ethylene-propylene rubber particles are as follows:

[0041] A1. Dropwise add ammonia water with a mass concentration of 15 wt% into an aluminum nitrate solution with a mass concentration of 0.4 mol / L to adjust the pH to 8.5, and stir until precipitation occurs to obtain a precursor solution;

[0042] A2. Mix polystyrene microspheres and ethanol to obtain a polystyrene microsphere solution with a mass concentration of 8%. After mixing the polystyrene microsphere solution and the precursor solution according to a volume ratio of 1:1, stir for 1 h. The obtained mixed solution is dried in an oven at 80 °C for 6 h, and then treated in a muffle furnace at 450 °C for 2 h to obtain mesoporous alumina;

[0043] A3. After mixing 1.2 parts by weight of mesoporous alumina and 6 parts by weight of absolute ethanol, add 0.3 parts by weight of ethylene-propylene rubber particles with an average particle size of 20 nm. Set the ultrasonic power to 300 W, the ultrasonic frequency to 50 kHz, ultrasonic for 20 min, then stir for 1 h, wash with absolute ethanol and extract for 72 h, and dry to obtain alumina loaded with ethylene-propylene rubber particles.

[0044] In step (3), the pressure of the sandblasting treatment in this embodiment is 0.2 MPa; the preheating temperature is 50 °C; the parameters of the ultrasonic treatment are: ultrasonic power is 200 W, ultrasonic frequency is 25 kHz, ultrasonic temperature is 38 °C, and ultrasonic time is 15 min.

[0045] In step (4), the milling depth in this embodiment is controlled at 2 mm; in the hot rolling step, the ingot after milling is heated to 370 °C, the hot rolling reduction is controlled at 12% each time, and a total of 4 passes are carried out. The hot rolling time for each pass is 0.5 min, and the hot rolling speed is 8 m / min; the cold rolling uses a four-high cold rolling mill, the surface hardness of the rolls is HRC60, the cold rolling reduction is controlled at 8% each time, and a total of 3 passes are carried out. The cold rolling time for each pass is 1.5 min, and the cold rolling speed is controlled at 4 m / min; the parameters of the stretching step are: stretching temperature is 175 °C, and stretching speed is 1.5 mm / min.

[0046] The aluminum alloy sheet of this embodiment is applied to automobile doors, automobile hoods, and automobile front and rear fenders.

[0047] Example 2

[0048] The preparation process of a high-elongation and fatigue-resistant aluminum alloy sheet. The preparation process of this embodiment includes the following steps:

[0049] (1) After preparing the raw materials, melt, stir, refine, and keep warm in a melting furnace, and pour into a mold for casting to obtain an ingot.

[0050] (2) Carry out homogenization treatment on the ingot and cool it with the furnace to obtain the cooled ingot.

[0051] (3) Sandblast and preheat the cooled ingot, immerse it in the treatment liquid, carry out ultrasonic treatment, and rinse with deionized water 3 times to obtain the treated ingot.

[0052] (4) Carry out milling and hot rolling on the treated ingot to obtain a sheet, and then carry out cold rolling and stretching after cooling to room temperature to obtain a high-elongation and fatigue-resistant aluminum alloy sheet.

[0053] In step (1), the raw materials of this embodiment are calculated by weight percentage, including 5 wt% magnesium, 0.68 wt% manganese, 0.24 wt% iron, 0.2 wt% silicon, 0.5 wt% scandium, 1.2 wt% ytterbium, and the balance aluminum.

[0054] In step (1), the melting temperature in this embodiment is 765°C; the refining agent selected for refining is hexachloroethane with a mass of 0.26 wt% of the total mass of the raw materials. Argon is introduced for degassing during refining, and the gas passing time is 30 min; the holding temperature and time are 730°C and 30 min respectively; the casting temperature is 720°C.

[0055] In step (2), the homogenization treatment in this embodiment means putting the ingot into a heat treatment furnace, heating it to 550°C at a rate of 10°C / min, keeping the temperature unchanged for 14 h to obtain the homogenized ingot; the cooling rate of furnace cooling is controlled at 10°C / min.

[0056] In step (3), the preparation steps of the treatment liquid in this embodiment are as follows:

[0057] Sodium molybdate and benzotriazole are added to deionized water, stirred at a speed of 500 rmp for 50 min, then modified alumina with an average particle size of 60 mm is added, the rotation speed is increased to 800 rmp, and stirred for 2 h. Then polyvinyl alcohol and OP-10 are added, and stirring is continued for 40 min. The ultrasonic power is set to 100 - 200 W and the ultrasonic frequency is 30 kHz, and ultrasonic treatment is carried out for 30 min, and then filtered through a 0.22 μm filter membrane to obtain the treatment liquid.

[0058] By weight, the ratio of sodium molybdate, benzotriazole, modified alumina with an average particle size of 60 nm, polyvinyl alcohol, OP-10 and deionized water in the treatment liquid of this embodiment is 0.6:0.35:1.3:0.054:0.2:24.

[0059] The modified alumina in this embodiment is alumina loaded with ethylene-propylene rubber particles. The preparation steps of alumina loaded with ethylene-propylene rubber particles are as follows:

[0060] A1. Dropwise add ammonia water with a mass concentration of 5 wt% into a nitric acid aluminum solution with a mass concentration of 0.6 mol / L to adjust the pH to 9.5, and stir until precipitation occurs to obtain a precursor solution;

[0061] A2. Mix polystyrene microspheres and ethanol to obtain a polystyrene microsphere solution with a mass concentration of 12%. After mixing the polystyrene microsphere solution and the precursor solution according to a volume ratio of 1:1, stir for 3 h. The obtained mixed solution is dried in an oven at 80°C for 12 h, and then treated in a muffle furnace at 550°C for 4 h to obtain mesoporous alumina;

[0062] A3. After mixing 3 parts by weight of mesoporous alumina and 12 parts by weight of absolute ethanol, 0.7 part by weight of ethylene-propylene rubber particles with an average particle size of 40 nm is added. The ultrasonic power is set to 500 W, the ultrasonic frequency is 60 kHz, ultrasonic treatment is carried out for 40 min, then stirring is carried out for 2 h, and after washing with absolute ethanol, extraction is carried out for 72 h, followed by drying to obtain alumina loaded with ethylene-propylene rubber particles.

[0063] In step (3), the pressure of the sandblasting treatment in this embodiment is 0.4 MPa; the temperature of the preheating treatment is 80 °C; the parameters of the ultrasonic treatment are: the ultrasonic power is 400 W, the ultrasonic frequency is 35 kHz, the ultrasonic temperature is 42 °C, and the ultrasonic time is 35 min.

[0064] In step (4), the milling depth in this embodiment is controlled at 3 mm; in the hot rolling step, the ingot after milling is heated to 420 °C, the hot rolling reduction is controlled at 14% each time, and a total of 8 passes are carried out. The hot rolling time for each pass is 1.5 min, and the hot rolling speed is 9 m / min; the cold rolling uses a four-high cold rolling mill, the surface hardness of the roll is HRC60, the cold rolling reduction is controlled at 9% each time, and a total of 5 passes are carried out. The cold rolling time for each pass is 2.5 min, and the cold rolling speed is controlled at 4.4 m / min; the parameters of the stretching step are: the stretching temperature is 195 °C, and the stretching speed is 1.7 mm / min.

[0065] The aluminum alloy sheet of this embodiment is applied to automobile doors, automobile hoods, and front and rear fenders of automobiles.

[0066] Example 3

[0067] The preparation process of a high-elongation and anti-fatigue aluminum alloy sheet. The preparation process of this embodiment includes the following steps:

[0068] (1) After preparing the raw materials, they are melted, stirred, refined, and kept warm in a melting furnace, and then poured into a mold for casting to obtain an ingot.

[0069] (2) The ingot is subjected to homogenization treatment and cooled in the furnace to obtain a cooled ingot.

[0070] (3) The cooled ingot is sandblasted and then preheated, immersed in a treatment solution, subjected to ultrasonic treatment, and rinsed 3 times with deionized water to obtain a treated ingot.

[0071] (4) The treated ingot is milled and hot rolled to obtain a sheet, and after cooling to room temperature, it is cold rolled and stretched to obtain a high-elongation and anti-fatigue aluminum alloy sheet.

[0072] In step (1), the raw materials of this embodiment are by weight percentage, including 4 wt% magnesium, 0.655 wt% manganese, 0.21 wt% iron, 0.16 wt% silicon, 0.275 wt% scandium, 0.85 wt% ytterbium, and the balance aluminum.

[0073] In step (1), the melting temperature in this embodiment is 755 °C; the refining agent selected for refining is hexachloroethane with a mass of 0.18 wt% of the total mass of the raw materials. Argon is introduced for degassing while refining, and the gas passing time is 20 min; the holding temperature and time are 725 °C and 25 min respectively; the casting temperature is 710 °C.

[0074] In step (2), the homogenization treatment in this embodiment means putting the ingot into a heat treatment furnace, heating it to 525 °C at a rate of 7.5 °C / min, keeping the temperature unchanged for 12 h to obtain the homogenized ingot; the cooling rate of furnace cooling is controlled at 7.5 °C / min.

[0075] In step (3), the preparation steps of the treatment liquid in this embodiment are as follows:

[0076] Sodium molybdate and benzotriazole are added to deionized water, stirred at a speed of 450 rmp for 45 min, then modified alumina with an average particle size of 50 nm is added, the rotation speed is increased to 700 rmp, and stirred for 1.5 h. Then polyvinyl alcohol and OP-10 are added, and stirring is continued for 35 min. The ultrasonic power is set to 150 W and the ultrasonic frequency is 20 kHz, and ultrasonic treatment is carried out for 25 min, and then filtered through a 0.22 μm filter membrane to obtain the treatment liquid.

[0077] By weight, the ratio of sodium molybdate, benzotriazole, modified alumina with an average particle size of 50 nm, polyvinyl alcohol, OP-10 and deionized water in the treatment liquid of this embodiment is 0.5:0.3:1.05:0.048:0.15:21.

[0078] The modified alumina in this embodiment is alumina loaded with ethylene-propylene rubber particles. The preparation steps of alumina loaded with ethylene-propylene rubber particles are as follows:

[0079] A1. Dropwise add ammonia water with a mass concentration of 20 wt% into a nitric acid aluminum solution with a mass concentration of 0.5 mol / L to adjust the pH to 9, and stir until precipitation occurs to obtain a precursor solution;

[0080] A2. Mix polystyrene microspheres and ethanol to obtain a polystyrene microsphere solution with a mass concentration of 10%. After mixing the polystyrene microsphere solution and the precursor solution according to a volume ratio of 1:1, stir for 2 h. The obtained mixed solution is dried in an oven at 80 °C for 9 h, and then treated in a muffle furnace at 500 °C for 3 h to obtain mesoporous alumina;

[0081] A3. Mix 2.1 parts by weight of mesoporous alumina and 9 parts by weight of absolute ethanol, then add 0.5 parts by weight of ethylene-propylene rubber particles with an average particle size of 30 nm. Set the ultrasonic power to 400 W, the ultrasonic frequency to 55 kHz, sonicate for 30 min, then stir for 1.5 h. Wash with absolute ethanol and extract for 72 h, then dry to obtain alumina loaded with ethylene-propylene rubber particles.

[0082] In step (3), the pressure of the sandblasting treatment in this example is 0.3 MPa; the preheating temperature is 75 °C; the parameters of the ultrasonic treatment are: ultrasonic power is 300 W, ultrasonic frequency is 30 kHz, ultrasonic temperature is 40 °C, and ultrasonic time is 25 min.

[0083] In step (4), the milling depth in this example is controlled at 2.5 mm; in the hot rolling step, the ingot after milling is heated to 395 °C, the hot rolling reduction is controlled at 13% each time, and a total of 68 passes are carried out. The hot rolling time for each pass is 1 min, and the hot rolling speed is 8.5 m / min; the cold rolling uses a four-high cold rolling mill, the surface hardness of the roll is HRC60, the cold rolling reduction is controlled at 8.5% each time, and a total of 4 passes are carried out. The cold rolling time for each pass is 2 min, and the cold rolling speed is controlled at 4.2 m / min; the parameters of the stretching step are: stretching temperature is 185 °C, and stretching speed is 1.6 mm / min.

[0084] The aluminum alloy sheet of this example is applied to automobile doors, automobile hoods, and automobile front and rear fenders.

[0085] Comparative Example 1

[0086] On the basis of Example 3, keeping other conditions the same, change step (3) to: Immerse the cooled ingot in the treatment liquid, perform ultrasonic treatment, and rinse with deionized water 3 times to obtain the treated ingot.

[0087] Comparative Example 2

[0088] On the basis of Example 3, keeping other conditions the same, change step (3) to: Sandblast and preheat the cooled ingot, immerse it in the treatment liquid for 25 min, and rinse with deionized water 3 times to obtain the treated ingot.

[0089] Comparative Example 3

[0090] On the basis of Example 3, remove step (3), and other conditions are the same as those in Example 3.

[0091] Comparative Example 4

[0092] On the basis of Example 3, do not perform the loading treatment on the alumina in the treatment liquid, and other conditions are the same as those in Example 3.

[0093] Taking the aluminum alloy sheets prepared in Examples 1-3 and Comparative Examples 1-4 as samples, the elongation rate of the samples was tested according to GB / T228.1-2010, and tested according to ASTM G 47 specification to determine whether the aluminum alloy sheets had stress corrosion cracking within 30 days under a stress of 250 MPa. The test results are shown in Table 1 below.

[0094] Table 1

[0095]

[0096] As can be seen from Table 1, the aluminum alloy sheets prepared by the present invention have a high elongation rate and good fatigue resistance. In Comparative Example 1, the sandblasting step before using the treatment liquid was removed, and in Comparative Examples 2-4, the use or preparation of the treatment liquid was changed. The treatment liquid used in the present invention introduces alumina loaded with ethylene-propylene rubber particles on the surface of the ingot. The ethylene-propylene rubber particles have good elasticity and toughness. When the alloy is subjected to external force, they deform and absorb part of the energy, thereby reducing stress concentration, reducing the generation and propagation of fatigue cracks, improving the toughness and fatigue resistance of the alloy, and other components in the treatment liquid can adhere to the surface of the ingot to play a protective role, thereby increasing the strength of the alloy, and further improving the toughness and fatigue resistance of the alloy.

[0097] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the technical content disclosed above without departing from the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments based on 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 technical solution of the present invention.

Claims

1. A process for preparing a high elongation fatigue-resistant aluminum alloy sheet, characterized in that: The preparation process comprises the following steps: (1) After the raw materials are prepared, they are melted, stirred, refined, and kept warm in a smelting furnace, poured into a mold for casting, and an ingot is obtained; (2) homogenizing the ingot and cooling it in the furnace to obtain a cooled ingot; (3) sandblasting the cooled ingot and preheating it, immersing it in a treatment solution, ultrasonically treating it, and rinsing it with deionized water for 3 times to obtain a treated ingot; (4) milling and hot rolling the treated ingot to obtain a plate, cooling it to room temperature and then cold rolling and stretching it to obtain a high elongation fatigue-resistant aluminum alloy plate; The steps for preparing the treatment solution in step (3) are as follows: Sodium molybdate and benzotriazole are added to deionized water, stirred at 400-500 rpm for 40-50 min, then modified alumina with an average particle size of 40-60 nm is added, the speed is increased to 600-800 rpm, stirred for 1-2 h, then polyvinyl alcohol and OP-10 are added, stirring is continued for 30-40 min, the ultrasonic power is set to 100-200 W, the ultrasonic frequency is set to 10-30 kHz, the ultrasonic is performed for 20-30 min, and the treated liquid is filtered through a 0.22 μm filter membrane to obtain the treated liquid; The modified alumina is alumina loaded with EPDM rubber particles, and the preparation steps of the alumina loaded with EPDM rubber particles are as follows: A1. Add 15-25 wt% ammonia water to a 0.4-0.6 mol / L aluminum nitrate solution, adjust the pH to 8.5-9.5, and stir until a precipitate is formed to obtain a precursor solution. A2, polystyrene microspheres and ethanol are mixed to obtain a polystyrene microsphere solution with a mass concentration of 8-12%, the polystyrene microsphere solution and the precursor solution are mixed in a volume ratio of 1:1, stirred for 1-3 hours, and the obtained mixed solution is dried in an oven at 80°C for 6-12 hours, and then treated in a muffle furnace at 450-550°C for 2-4 hours to obtain mesoporous alumina; A3. After mixing 1.2-3 parts by weight of mesoporous alumina and 6-12 parts by weight of anhydrous ethanol, add 0.3-0.7 parts by weight of ethylene-propylene rubber particles with an average particle size of 20-40 nm, set the ultrasonic power to 300-500 W, the ultrasonic frequency to 50-60 kHz, ultrasonicate for 20-40 min, stir for 1-2 h, wash with anhydrous ethanol, extract for 72 h, and dry to obtain alumina loaded with ethylene-propylene rubber particles.

2. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: The raw materials in step (1) include, by weight percentage, 3-5wt% magnesium, 0.63-0.68wt% manganese, 0.18-0.24wt% iron, 0.12-0.2wt% silicon, 0.05-0.5wt% scandium, 0.5-1.2wt% ytterbium and the balance aluminum.

3. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: The melting temperature of step (1) is 745-765°C; the refining agent selected for refining is hexachloroethane in an amount of 0.1-0.26wt% of the total mass of the raw material; argon is introduced for degassing during refining, and the ventilation time is 10-30min; the insulation temperature and time are 720-730°C and 20-30min respectively; and the casting temperature is 700-720°C.

4. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: The homogenization treatment in step (2) refers to placing the ingot into a heat treatment furnace, heating it to 500-550°C at a rate of 5-10°C / min, maintaining the temperature for 10-14 hours, and obtaining the ingot after homogenization treatment; the cooling rate of the furnace cooling is controlled at 5-10°C / min.

5. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: In parts by weight, the ratio of sodium molybdate, benzotriazole, modified alumina with an average particle size of 40-60 nm, polyvinyl alcohol, OP-10 and deionized water in the treatment solution is 0.4-0.6:0.25-0.35:0.8-1.3:0.042-0.054:0.1-0.2:18-24.

6. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: The pressure of the sandblasting treatment in step (3) is 0.2-0.4 MPa; the temperature of the preheating treatment is 50-80°C; the parameters of the ultrasonic treatment are: ultrasonic power is 200-400 W, ultrasonic frequency is 25-35 kHz, ultrasonic temperature is 38-42°C, and ultrasonic time is 15-35 min.

7. The process for preparing the high elongation fatigue-resistant aluminum alloy sheet according to claim 1, characterized in that: In step (4), the milling depth is controlled at 2-3 mm; in the hot rolling step, the ingot after milling is heated to 370-420° C., the hot rolling pressure is controlled to be 12-14% each time, 4-8 passes are performed in total, the hot rolling time for each pass is 0.5-1.5 min, and the hot rolling speed is 8-9 m / min; the cold rolling adopts a four-roll cold rolling mill, the surface hardness of the rolling roll is HRC60, the cold rolling pressure is controlled to be 8-9% each time, 3-5 passes are performed in total, the cold rolling time for each pass is 1.5-2.5 min, and the cold rolling speed is controlled to be 4-4.4 m / min; the parameters of the stretching step are: the stretching temperature is 175-195° C., and the stretching speed is 1.5-1.7 mm / min.

8. The high elongation and fatigue-resistant aluminum alloy sheet according to any one of claims 1 to 7, characterized in that: The aluminum alloy sheet is applied to automobile doors, automobile engine hoods, and automobile front and rear fenders.

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