6-series aluminum alloy plate for new energy battery bottom plate protection plate and preparation method of 6-series aluminum alloy plate

Abstract

The invention relates to the technical field of aluminum alloy processing, in particular to a 6-series aluminum alloy plate for a new energy battery bottom plate protection plate and a preparation method of the 6-series aluminum alloy plate. The 6-series plate for the new energy battery bottom plate protection plate comprises the following components in percentage by weight: 0.75-0.90% of Si, 0.75-0.90% of Ni, 0.35-0.35% of Ni and the balance of The content of Fe is 0.20 to 0.35 percent; the content of Cu is 0.70 to 0.90 percent; the content of Mn is 0.20 to 0.80 percent; the content of Mg is 0.80 to 1.00 percent; the content of Cr is 0.10 to 0.40 percent; the content of Ti is 0.06 to 0.07 percent; the content of single other impurity elements is less than or equal to 0.05%; the total content of other impurity elements is less than or equal to 0.15%; the balance is Al; wherein the content ratio of (Mn + Cr) to Fe is (1.5-4.0): 1. The 6-series plate for the new energy battery bottom plate protection plate has the advantages of light weight, excellent mechanical property and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy processing, and in particular to a 6 series aluminum alloy sheet for a new energy battery bottom plate guard plate and a preparation method thereof. Background Art

[0002] The increasingly serious global carbon emission problem has pushed the use of new energy vehicles onto the fast track of the development of the times. As a green, environmentally friendly and low-pollution means of transportation, the protection of new energy vehicles' electronic components, especially battery packs, is very important. When driving on rough roads, splashing gravel or foreign objects often cause the bottom shell of the battery pack to deform or break, which poses certain driving and personal safety risks. Therefore, the selection of battery pack bottom plate materials also needs to be very cautious. "Lightweight" aluminum alloy bottom plate guards with multifunctional system integration and stronger deformation resistance will be the future development direction.

[0003] Chinese patent CN202010564620.3 discloses an ultra-high yield ratio steel and its production process, in which a dislocation source is provided by pre-strain treatment after rapid cooling of the strip steel, and a dislocation pinning strengthening treatment is adopted after the pre-strain treatment; wherein, the dislocation pinning strengthening steel belongs to low alloy steel with a carbon content of 0.02%-0.77%; its production process is: cold-rolled strip steel → continuous annealing → rapid cooling → pre-strain treatment → dislocation pinning strengthening treatment, and the ultra-high yield ratio steel of this scheme has sufficient plasticity and good welding performance. It can be used to make parts that require good shape stability, high deformation resistance, and high hole expansion requirements, such as battery guards, bumpers, seat rails, reinforcements, and measuring tools for automobiles. It can also be used to manufacture spring steel that requires a high elastic limit.

[0004] Chinese patent CN202010564620.3 discloses a process for preparing aluminum alloy for battery guard plate of new energy vehicle, including the following steps: step 1, weighing alloy raw materials according to the formula, putting them into a smelting furnace for smelting, and obtaining a melt after standing and degassing; step 2, placing the bubble wire steel mesh into a mold, and then pouring the melt into the mold for casting, and performing homogenization annealing; step 3, extrusion molding after annealing, adding quenching liquid for quenching and cooling, and obtaining an aluminum alloy for battery guard plate of new energy vehicle. The present invention uses bubble wire steel mesh as the raw material for preparing aluminum alloy for battery guard plate of new energy vehicle. The gap of the bubble wire steel mesh itself can increase the contact area with the melt, so that the melt and the bubble wire steel mesh are more evenly combined. The elastic properties of the steel wire spring can also reduce the deformation bending generated during the processing, so that the performance of the prepared product is more stable. Compared with aluminum alloy materials, traditional steel has a complex production process, a density three times that of aluminum alloy, is heavy and easily corroded, has poor processing performance, and is not as impact-resistant as aluminum alloy materials for automotive battery chassis. However, it is still difficult for aluminum alloy materials to simultaneously possess light weight, excellent mechanical properties, and corrosion resistance.

[0005] In summary, it is urgent to solve the problem in the existing technology that 6 series aluminum alloy plates used for new energy battery bottom plate guard plates are difficult to have both light weight, mechanical properties and corrosion resistance. Summary of the invention

[0006] The present invention aims to solve the technical problem that 6 series aluminum alloy plates used for new energy battery bottom plate guard plates are difficult to have both light weight, mechanical properties and corrosion resistance.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a 6 series aluminum alloy plate for a new energy battery bottom plate guard plate, wherein the components and their weight percentages in the plate are:

[0008] Si content is 0.75-0.90%;

[0009] Fe content is 0.20-0.35%;

[0010] Cu content is 0.70-0.90%;

[0011] Mn content is 0.20-0.80%;

[0012] Mg content is 0.80-1.00%;

[0013] Cr content is 0.10-0.40%;

[0014] Ti content is 0.06-0.07%;

[0015] The content of other single impurity elements is ≤0.05%;

[0016] The total content of other impurity elements is ≤0.15%;

[0017] The balance is Al;

[0018] Among them, the ratio of (Mn+Cr) to Fe content is 1.5-4.0:1.

[0019] The second aspect of the present invention provides a method for preparing the 6 series aluminum alloy sheet for the new energy battery bottom plate guard plate, wherein the preparation method comprises:

[0020] Mix and melt the aluminum alloy raw materials, the melting temperature does not exceed 760℃, refine, cast, online degassing, online refinement, online filtration, sawing and milling, heating, hot rolling, cold rolling, heat treatment, and cross-cutting plates;

[0021] The heating soaking system is 520-580°C×4-24h;

[0022] The hot rolling conditions include: after the ingot is homogenized and taken out of the furnace, the temperature is reduced by less than 50°C before entering the rough rolling process, the rough rolling passes are 19-23 passes, the single reduction amount of the 2nd to 5th hot rough rolling passes is ≥35mm, the thickness of the intermediate billet after rough rolling is 33-37mm, and then a 4-continuous finishing rolling process is performed, the finishing rolling reduction rate of each pass is 35-45%, the finishing rolling tension is 8-12MPa, the final finishing rolling line billet thickness is 4.5mm, and the coiling temperature is 300-340°C.

[0023] The third aspect of the present invention provides a 6 series aluminum alloy sheet for a new energy battery bottom plate guard plate produced by the above-mentioned preparation method.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention optimizes the alloy element ratio and controls the Mn+Cr / Fe ratio in the alloy to obtain an aluminum alloy plate having light weight, good mechanical properties, and resistance to intergranular corrosion and exfoliation corrosion.

[0026] (2) The present invention controls the hot rough rolling pass arrangement and conditions and adopts a single-stage uniform heating method to obtain an aluminum alloy plate with excellent corrosion resistance.

[0027] (3) The 6 series aluminum alloy plate material for the new energy battery bottom plate guard provided by the present invention has a thickness of 1.5 mm, which can effectively promote the realization of "lightweight" of automobiles compared with traditional steel plate materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The intergranular corrosion depth results of Examples 1 and 2 and Comparative Examples 1 and 2;

[0029] Figure 2 The exfoliation corrosion results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0031] The 6 series aluminum alloy plates used in the existing technology for the bottom plate guard of new energy batteries are difficult to combine light weight, mechanical properties and corrosion resistance.

[0032] In the present invention, the inventors found that if the alloy ratio of the 6-series aluminum alloy plate used for the new energy battery bottom plate guard plate is controlled and a specific preparation method is adopted, the 6-series aluminum alloy plate used for the new energy battery bottom plate guard plate has light weight, mechanical properties and corrosion resistance.

[0033] To achieve this goal, the inventors tried to optimize the composition and preparation method of each component of the 6 series aluminum alloy plate for the bottom plate guard of the new energy battery. The inventors found that the above purpose can be achieved through specific composition and preparation method of each component.

[0034] To this end, the first aspect of the present invention provides a 6 series aluminum alloy plate for a new energy battery bottom plate guard plate, wherein the components and their weight percentages in the plate are:

[0035] Si content is 0.75-0.90%;

[0036] Fe content is 0.20-0.35%;

[0037] Cu content is 0.70-0.90%;

[0038] Mn content is 0.20-0.80%;

[0039] Mg content is 0.80-1.00%;

[0040] Cr content is 0.10-0.40%;

[0041] Ti content is 0.06-0.07%;

[0042] The content of other single impurity elements is ≤0.05%;

[0043] The total content of other impurity elements is ≤0.15%;

[0044] The balance is Al;

[0045] Among them, the ratio of (Mn+Cr) to Fe content is 1.5-4.0:1.

[0046] In the present invention, the inventors found that Fe, as a conventional impurity element, is easy to form Al3Fe phase. When it is dispersed in the aluminum matrix, there is a certain degree of potential difference with the aluminum matrix, so it is easy to form pitting. When pitting develops along the intergranular space, it will aggravate the corrosion degree of the alloy and have an adverse effect on the corrosion resistance of the alloy. The addition of Mn element will form Al6Mn dispersed particles, which will hinder the recrystallization of the alloy, thereby achieving the purpose of refining the recrystallized grains. At the same time, the addition of Cr element, together with Mn, can reduce the generation of Al-Fe binary phase and generate Al-Fe-Mn-Si-Cr multi-phase. However, when the addition amount is large, the multi-phase will become coarse, so strictly controlling the ratio of Mn+Cr / Fe can effectively reduce the generation of Al3Fe binary phase, thereby effectively improving the corrosion resistance of aluminum alloy.

[0047] The addition of Ti element can play a metamorphic role in the melting and casting process, and to a certain extent refine the grain size of the original aluminum ingot during the casting process, which is beneficial to improve the comprehensive performance of the subsequent aluminum alloy plate. The Ti content is strictly controlled within the above range, and the generated Al3Ti has good oxidation resistance. In addition, Ti can also form a dense titanium oxide film with alumina, further improving the corrosion resistance of the alloy and improving the mechanical properties of the product; Mg and Si are the main elements in 6 series aluminum alloys. In traditional theory, the mass ratio of Mg and Si is generally less than 1.73 to ensure that the alloy has good strength and plasticity. At the same time, the excess Si element can improve the fluidity of the aluminum melt and improve the casting success rate.

[0048] The second aspect of the present invention provides a method for preparing the 6 series aluminum alloy sheet for the new energy battery bottom plate guard plate, wherein the preparation method comprises:

[0049] Mix and melt the aluminum alloy raw materials, the melting temperature does not exceed 760℃, refine, cast, online degassing, online refinement, online filtration, sawing and milling, heating, hot rolling, cold rolling, heat treatment, and cross-cutting plates;

[0050] The heating soaking system is 520-580°C×4-24h;

[0051] The hot rolling conditions include: after the ingot is homogenized and taken out of the furnace, the temperature is reduced by less than 50°C before entering the rough rolling process, the rough rolling passes are 19-23 passes, the single reduction amount of the 2nd to 5th hot rough rolling passes is ≥35mm, the thickness of the intermediate billet after rough rolling is 33-37mm, and then a 4-continuous finishing rolling process is performed, the finishing rolling reduction rate of each pass is 35-45%, the finishing rolling tension is 8-12MPa, the final finishing rolling line billet thickness is 4.5mm, and the coiling temperature is 300-340°C.

[0052] In the present invention, a specific single-stage homogenization is adopted, the temperature drop rate is fast, the second phase is precipitated and does not have sufficient time to grow, and through hot rough rolling, the second phase is fine and dispersed in the matrix. In the subsequent heat treatment process, the matrix has a high degree of supersaturation, and a large number of strengthening phases are precipitated during the aging process. The overall performance meets customer standards.

[0053] In the present invention, the first few passes in the hot rough rolling process adopt large reduction rolling, which can effectively break up the coarse second phase in the ingot, especially the iron-rich phase, and can subsequently improve the corrosion resistance of the alloy and the uniformity of the mechanical properties of the plate.

[0054] According to the present invention, the refining conditions include: temperature of 720-750°C, time of 45-65 min, standing temperature of 710-740°C, standing time of 30 min-40 min, rotor speed of 180-220 r / min, argon flow rate of 14-18 m 3 / h, chlorine gas flow rate is 4-6m 3 / h.

[0055] According to the present invention, the conditions for online refining include: adding Al-5Ti-1B refining wire, and the amount of titanium at the online point is 0.004-0.008%.

[0056] According to the present invention, the online degassing conditions include: the rotor speed is controlled at 450-550r / min, the argon flow rate is 6-10m 3 / h.

[0057] According to the present invention, after the online degassing, the hydrogen content of the melt is less than 0.15 ml / 100 g Al.

[0058] According to the present invention, the filtering conditions include: using a deep bed filter device and single-stage plate filtration, wherein the pore size of the single-stage plate filtration is ≥50ppi, the filter box is preheated to above 350°C in advance, and the filtration temperature is 690-740°C.

[0059] According to the present invention, the sawing and milling conditions include: the successfully cast aluminum alloy ingot guide end is cut ≥350mm, the large surface is milled ≥12mm, the small surface and side bevel are milled ≥5mm, and the side bevel milling angle is 7-11°.

[0060] According to the present invention, it is characterized in that the cold rolling passes are 4.5mm-2.2mm-1.5mm.

[0061] According to the present invention, the heat treatment conditions include: heat treatment temperature of 530-560°C, heating rate of 7-12°C / s, holding time of 10-20s, online water cooling, water cooling pressure of 1-2bar, stretching amount of 0.2-0.5%, placed in a pre-aging furnace, and curling temperature of 75-95°C.

[0062] According to the present invention, the conditions for the transverse shear plate include: the straightening machine outlet is 1.2-1.8 mm, and the straightening machine inclination is 1-1.6 mm.

[0063] In this field, the straightening machine inclination angle currently uses the spacing between input rollers to convert the internal angle of the system into a process that meets the production requirements.

[0064] The third aspect of the present invention provides a 6 series aluminum alloy sheet for a new energy battery bottom plate guard plate produced by the above-mentioned preparation method.

[0065] Test Method

[0066] Tensile strength R m Measured according to GB / T 228.1.

[0067] Yield Strength R p0.2 Measured according to GB / T 228.1.

[0068] Elongation after fracture A 80 Measured according to GB / T 228.1.

[0069] The intergranular corrosion performance is measured according to GB / T 7998.

[0070] Exfoliation corrosion performance is measured according to GB / T 22639.

[0071] The technical scheme of the present invention is further described in detail below in conjunction with 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 ordinary technicians in this field without making creative improvements belong to the protection scope of the present invention.

[0072] Embodiment 1:

[0073] A. The alloy element formula (wt / %) is: Si: 0.77, Fe: 0.22, Cu: 0.78, Mn: 0.43, Mg: 0.88, Cr: 0.24, Ti: 0.064, the balance is Al, and the ratio of Mn + Cr / Fe is controlled to be 3.0;

[0074] B. Melting and casting: Add the prepared aluminum alloy raw materials into the melting furnace, mix them evenly, and then melt them into liquid aluminum alloy. The melting temperature is 752℃. After slag removal and alloying, pour the liquid aluminum alloy in the melting furnace into the refining furnace for refining; the refining temperature is controlled at 740℃, the refining time is 60min, and the melt is allowed to stand for 40min after refining. The standing temperature is 727℃, the rotor speed is 200r / min, and the argon flow rate is 15m 3 / h, chlorine gas flow rate 4.9m 3 / h;

[0075] C. Online refinement: Add Al-5Ti-1B refinement wire to the degassed and impurity-removed aluminum alloy melt for online refinement, and control the online titanium content at about 0.006%;

[0076] D. Online degassing: The refined aluminum alloy melt is introduced into high-purity argon gas and stirred to remove impurity gases in the aluminum alloy melt. The rotor speed is controlled at 490r / min and the argon flow rate is 8m 3 / h, online hydrogen content is 0.12ml / 100gAl;

[0077] E. Online filtration: The melt passes through a deep bed filter + single-stage plate filter (pore size ≥ 50ppi), preheat the filter box to 379°C in advance, and the filtration temperature is controlled at 715°C;

[0078] F. Sawing and milling: Cut the successfully cast aluminum alloy ingot lead-in end by 660mm, mill the large surface by 20mm, mill the small surface and side bevel by 7mm, and the side bevel milling angle is 8°;

[0079] G. Heating: The aluminum alloy ingot after sawing and milling is placed in a pusher heating furnace for heating at a temperature of 550°C / 10h, that is, the aluminum alloy ingot is kept at 550°C for 10h, and then directly taken out of the furnace for hot rolling;

[0080] H. Hot rolling: After being discharged from the furnace, the ingot enters the hot rough rolling process. The hot rough rolling start temperature is 505°C, and the number of passes is 21. The reductions of the 2nd to 5th hot rough rolling passes are 37mm, 37mm, 38mm and 39mm respectively. The thickness of the intermediate billet after rough rolling is controlled to be 35mm. Then a 4-continuous finishing rolling process is carried out. The finishing rolling reduction rates of each pass are 37%, 41%, 42% and 44% respectively. The finishing rolling tension is 11MPa. The final thickness of the finished rolling line billet is 4.5mm, and the coiling temperature is controlled at 321°C.

[0081] I. Cold rolling: cold rolling is carried out strictly according to the process arrangement. Rolling pass: 4.5mm-2.2mm-1.5mm;

[0082] J. Heat treatment: The cold-rolled aluminum alloy strip is placed in an air cushion quenching furnace for heat treatment, and the temperature is raised to 540°C at a rate of 10°C / s, and kept at this temperature for 20s, and then water-cooled online, with a water cooling pressure of 1.5 bar and a stretching amount of 0.3%. Finally, it is placed in a pre-aging furnace for heat treatment, and the curling temperature is 81°C;

[0083] K. Sheared plate: The finished strip is placed in the shearing machine for plate processing. The parameters of the shearing and straightening machine are: outlet 1.7mm, straightening machine inclination 1.4mm. The 6 series aluminum alloy plate A1 for the bottom plate of the new energy battery is obtained.

[0084] Example 2

[0085] A. The alloy element formula (wt / %) is: Si: 0.79, Fe: 0.28, Cu: 0.75, Mn: 0.31, Mg: 0.86, Cr: 0.23, Ti: 0.067, the balance is Al, and the ratio of Mn + Cr / Fe is strictly controlled to be 2.0;

[0086] B. Melting and casting: Add the prepared aluminum alloy raw materials into the melting furnace, mix them evenly, and then melt them into liquid aluminum alloy. The melting temperature is 754℃. After slag removal and alloying, pour the liquid aluminum alloy in the melting furnace into the refining furnace for refining; the refining temperature is controlled at 735℃, the refining time is 60min, and the melt is allowed to stand for 35min after refining. The standing temperature is 730℃, the rotor speed is 200r / min, and the argon flow rate is 15m 3 / h, chlorine gas flow rate 4.7m 3 / h;

[0087] C. Online refinement: Add Al-5Ti-1B refinement wire to the degassed and impurity-removed aluminum alloy melt for online refinement, and control the online titanium content at about 0.006%;

[0088] D. Online degassing: The refined aluminum alloy melt is introduced into high-purity argon gas and stirred to remove impurity gases in the aluminum alloy melt. The rotor speed is controlled at 484r / min and the argon flow rate is 8m 3 / h, online hydrogen content is 0.13ml / 100gAl;

[0089] E. Online filtration: The melt passes through a deep bed filter + single-stage plate filter (pore size ≥ 50ppi), preheat the filter box to 370°C in advance, and the actual filtration temperature is controlled at 717°C;

[0090] F. Sawing and milling: Cut 650mm of the successfully cast aluminum alloy ingot lead-in end, mill 15mm of the large surface, 5mm of the small surface and side bevel, and the side bevel milling angle is 8°;

[0091] G. Heating: The aluminum alloy ingot after sawing and milling is placed in a pusher heating furnace for heating at a temperature of 550°C / 10h, that is, the aluminum alloy ingot is kept at 550°C for 10h, and then directly taken out of the furnace for hot rolling;

[0092] H. Hot rolling: After being heated and taken out of the furnace, the ingot enters the hot rough rolling process. The hot rough rolling start temperature is 512°C, and the number of passes is 21. The single reduction of the 2nd to 5th hot rough rolling passes is 35mm, 36mm, 37mm and 37mm respectively. The thickness of the intermediate billet after rough rolling is controlled to be 35mm. Then a 4-continuous finishing rolling process is carried out. The finishing rolling reduction rate of each pass is 38%, 40%, 41% and 44% respectively. The finishing rolling tension is 10MPa. The final thickness of the finished rolling line billet is 4.5mm, and the coiling temperature is controlled at 330°C.

[0093] I. Cold rolling: cold rolling is carried out strictly according to the process arrangement. Rolling pass: 4.5mm-2.2mm-1.5mm;

[0094] J. Heat treatment: The cold-rolled aluminum alloy strip is placed in an air cushion quenching furnace for heat treatment, and the temperature is raised to 540°C at a rate of 10°C / s, and kept at this temperature for 20s, and then water-cooled online, with a water cooling pressure of 1.6 bar and a stretching amount of 0.3%. Finally, it is placed in a pre-aging furnace for heat treatment, and the coiling temperature is 80°C;

[0095] K. Sheared plate: The finished strip is placed in the shearing machine for plate processing. The parameters of the shearing and straightening machine are: outlet 1.7mm, straightening machine inclination 1.4mm. The 6 series aluminum alloy plate A2 for the bottom plate of the new energy battery is obtained.

[0096] Example 3

[0097] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared according to the method of Example 1, except that the alloy element formula (wt / %) was: Si: 0.75, Fe: 0.31, Cu: 0.7, Mn: 0.22, Mg: 0.8, Cr: 0.25, Ti: 0.06, the balance was Al, and the ratio of Mn+Cr / Fe was strictly controlled to be 1.5; a 6-series aluminum alloy sheet A3 for a new energy battery bottom plate guard plate was obtained.

[0098] Example 4

[0099] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared according to the method of Example 1, except that the alloy element formula (wt / %) was: Si: 0.9, Fe: 0.25, Cu: 0.9, Mn: 0.7, Mg: 1, Cr: 0.31, Ti: 0.07, the balance was Al, and the ratio of Mn+Cr / Fe was strictly controlled to be 4.0. A 6-series aluminum alloy sheet A4 for a new energy battery bottom plate guard plate was obtained.

[0100] Example 5

[0101] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared according to the method of Example 1, except that the intermediate billet thickness was 33 mm, the finishing rolling tension was 9 MPa, and the curling temperature was 305° C. A 6-series aluminum alloy sheet A5 for a new energy battery bottom plate guard plate was prepared.

[0102] Example 6

[0103] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared according to the method of Example 1, except that the intermediate billet thickness was 37 mm, the finishing rolling tension was 12 MPa, and the curling temperature was 338° C. A 6-series aluminum alloy sheet A6 for a new energy battery bottom plate guard plate was obtained.

[0104] Comparative Example 1

[0105] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared in the manner of Example 1, except that in the heating step, a two-stage soaking system of 550°C / 10h+500°C / 7h was adopted, that is, the aluminum alloy ingot was first kept at 550°C for 10h, then cooled to 500°C in the furnace and kept for another 7h. A 6-series aluminum alloy sheet DA1 for a new energy battery bottom plate guard plate was obtained.

[0106] Comparative Example 2

[0107] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared in the same manner as in Example 2, except that in the heating step, a two-stage soaking system of 550°C / 10h+500°C / 7h was adopted, that is, the aluminum alloy ingot was first kept at 550°C for 10h, then cooled to 500°C in the furnace and kept for another 7h. A 6-series aluminum alloy sheet DA2 for a new energy battery bottom plate guard plate was obtained.

[0108] Comparative Example 3

[0109] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared in the manner of Example 1, except that in the hot rolling step, a two-stage soaking system of 500°C / 12h+450°C / 6h was adopted, that is, the aluminum alloy ingot was first kept at 500°C for 12h, then cooled to 450°C in a furnace and kept for another 6h. A 6-series aluminum alloy sheet DA3 for a new energy battery bottom plate guard plate was obtained.

[0110] Comparative Example 4

[0111] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared in the same manner as in Example 1, except that the alloy element formula was Si: 0.71, Fe: 0.21, Cu: 0.78, Mn: 0.79, Mg: 0.88, Cr: 0.32, Ti: 0.064, the remainder was Al, and the ratio of Mn+Cr / Fe was strictly controlled to be 5.0. A 6-series aluminum alloy sheet DA4 for a new energy battery bottom plate guard plate was obtained.

[0112] Comparative Example 5

[0113] A 6-series aluminum alloy sheet for a new energy battery bottom plate guard plate was prepared in the manner of Example 1, except that in the hot rolling step, the hot rough rolling start temperature was 510°C, the number of passes was 21, and the thickness of the intermediate billet after rough rolling was controlled to be 35 mm. Then, a 4-continuous finishing rolling process was performed, with the finishing rolling reduction rates of 38%, 40%, 41% and 44% for each pass, the finishing rolling tension was 10 MPa, the final finishing rolling line billet thickness was 4.5 mm, and the coiling temperature was controlled at 362°C.

[0114] Performance tests were performed on A1-A6 and DA1-DA4, as shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] It can be seen from the mechanical property results in Table 1 that the mechanical properties under the conditions of Comparative Example 1 and Comparative Example 2 fail to meet the customer standards, while Examples 1 and 2 can meet the customer standards. Through comparative analysis, it can be seen that with the use of two-stage homogenization, part of the second phase re-precipitates and grows from the solid solution during the second stage of cooling, and is distributed on the aluminum alloy grain boundaries. In the subsequent high-temperature short-time heat treatment in the air cushion quenching furnace, it fails to be completely dissolved in the aluminum matrix, and the matrix supersaturation is low, which will lead to a small number of precipitated phases in the subsequent aging process, and the overall mechanical properties are low. However, with the use of a specific single-stage homogenization, the temperature drop rate is faster, the second phase precipitates and does not have sufficient time to grow, and through hot rough rolling, the second phase is small and dispersed in the matrix. In the subsequent heat treatment process, the matrix supersaturation is high, and the number of strengthening phases precipitated during the aging process is large, and the overall performance meets customer standards.

[0119] At the same time, it can be seen from the corrosion performance results in Table 1 that the overall corrosion situation of Example 1 is better than that of Example 2. This is because in aluminum alloys, Fe, as an impurity element, easily forms Al3Fe phase with Al. When it is dispersed in the matrix, there is a potential difference of 0.4V with the aluminum matrix, so it is easy to form pitting corrosion. When the pitting corrosion develops along the intergranular space, it will become exfoliation corrosion, which has an adverse effect on the corrosion resistance of the alloy. In aluminum alloys, when the Mn+Cr / Fe ratio is 2.0-4.0, the generation of Al-Fe binary phase can be reduced, and Al-Mn-Fe-Si-Cr multi-phase can be generated, which can effectively improve the corrosion resistance of the alloy. At the same time, the Ti content is between 0.06-0.07, which effectively improves the mechanical properties of the alloy.

[0120] It can be seen from Table 1 that under the system of Comparative Example 3, the homogenization temperature is lower than the low melting point eutectic phase and cannot be fully dissolved back into the matrix, and dendrite segregation still exists, making the performance of the finished product far below the customer standard.

[0121] Instruction Manual Figure 1 In the figure, a is the intergranular corrosion depth result of Example 1, b is the intergranular corrosion depth result of Example 2, c is the intergranular corrosion depth result of Comparative Example 1, and d is the intergranular corrosion depth result of Comparative Example 2. The results show that the intergranular corrosion resistance of Examples 1 and 2 is better than that of Comparative Examples 1 and 2.

[0122] Instruction Manual Figure 2 In the figure, a is the exfoliation corrosion depth result of Example 1, b is the exfoliation corrosion depth result of Example 2, c is the exfoliation corrosion depth result of Comparative Example 1, and d is the exfoliation corrosion depth result of Comparative Example 2. The results show that the exfoliation corrosion resistance of Examples 1 and 2 is better than that of Comparative Examples 1 and 2.

[0123] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A 6 series aluminum alloy sheet for a new energy battery bottom plate guard plate, characterized in that: The components and their weight percentages in the plate are: Si content is 0.75-0.90%; Fe content is 0.20-0.35%; Cu content is 0.70-0.90%; Mn content is 0.20-0.80%; Mg content is 0.80-1.00%; Cr content is 0.10-0.40%; Ti content is 0.06-0.07%; The content of other single impurity elements is ≤0.05%; The total content of other impurity elements is ≤0.15%; The balance is Al; Among them, the ratio of (Mn+Cr) to Fe content is 1.5-4.0:

1.

2. A method for preparing the 6-series aluminum alloy sheet for the new energy battery bottom plate guard plate according to claim 1, characterized in that: The preparation method comprises: Mix and melt the aluminum alloy raw materials, the melting temperature does not exceed 760℃, refine, cast, online degassing, online refinement, online filtration, sawing and milling, heating, hot rolling, cold rolling, heat treatment, and cross-cutting plates; The heating soaking system is 520-580°C×4-24h; The hot rolling conditions include: after the ingot is homogenized and taken out of the furnace, the temperature is reduced by less than 50°C before entering the rough rolling process, the rough rolling passes are 19-23 passes, the single reduction amount of the 2nd to 5th hot rough rolling passes is ≥35mm, the thickness of the intermediate billet after rough rolling is 33-37mm, and then a 4-continuous finishing rolling process is performed, the finishing rolling reduction rate of each pass is 35-45%, the finishing rolling tension is 8-12MPa, the final finishing rolling line billet thickness is 4.5mm, and the coiling temperature is 300-340°C.

3. The preparation method according to claim 2, characterized in that: The refining conditions include: temperature of 720-750°C, time of 45-65 min, standing temperature of 710-740°C, standing time of 30 min-40 min, rotor speed of 180-220 r / min, argon flow rate of 14-18 m 3 / h, chlorine gas flow rate is 4-6m 3 / h; The conditions for the online refinement include: adding Al-5Ti-1B refinement wire, the amount of online point titanium is 0.004-0.008%; The online degassing conditions include: the rotor speed is controlled at 450-550r / min, the argon flow rate is 6-10m 3 / h; After the online degassing, the hydrogen content of the melt is less than 0.15 ml / 100 g Al.

4. The preparation method according to claim 2, characterized in that: The filtering conditions include: using a deep bed filter device and single-stage plate filtration, wherein the pore size of the single-stage plate filtration is ≥50ppi, the filter box is preheated to above 350°C in advance, and the filtering temperature is 690-740°C.

5. The preparation method according to claim 2, characterized in that: The conditions for sawing and milling the surface include: the successfully cast aluminum alloy ingot guide end is cut to a waste of ≥350mm, the large surface is milled to ≥12mm, the small surface and side bevel are milled to ≥5mm, and the side bevel milling angle is 7-11°.

6. The preparation method according to claim 2, characterized in that: The cold rolling passes are 4.5 mm-2.2 mm-1.5 mm.

7. The preparation method according to claim 2, characterized in that: The heat treatment conditions include: heat treatment temperature of 530-560°C, heating rate of 7-12°C / s, holding time of 10-20s, online water cooling, water cooling pressure of 1-2bar, stretching amount of 0.2-0.5%, placed in a pre-aging furnace, and curling temperature of 75-95°C.

8. The preparation method according to claim 2, characterized in that: The conditions of the transverse shear plate include: the straightening machine outlet is 1.2-1.8 mm, and the straightening machine inclination is 1-1.6 mm.

9. A 6 series aluminum alloy sheet for a new energy battery bottom plate guard plate prepared by the preparation method described in any one of claims 2 to 8.

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