A method for preparing Al-Mg-Si-Cu alloy rolled plate

Abstract

The invention discloses a method for preparing an Al-Mg-Si-Cu alloy plate, which relates to the technical field of aluminum alloys. The method comprises the following steps: melting and casting, head and tail cutting, milling, homogenizing heat treatment, gradient cooling rolling, solution quenching, and double-stage aging treatment. The ingot obtained by melting and casting an aluminum alloy raw material is subjected to head and tail cutting and surface milling, and then subjected to a homogenizing treatment and then directly subjected to temperature-controlled rolling using residual heat. After the temperature-controlled rolling is completed, the ingot is subjected to quenching and double-stage aging treatment to obtain the alloy rolled plate. The method controls the temperature of the homogenizing heat treatment, and then replaces the prior art "hot rolling→cold rolling→intermediate annealing→cold rolling" process with gradient cooling rolling, and is combined with double-stage aging treatment to optimize the production process and production technology, reduce the influence of aging dislocation recovery on product strength, shorten the production cycle, improve efficiency, reduce energy consumption, and simultaneously improve the mechanical strength and elongation of the product.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a method for preparing an Al-Mg-Si-Cu alloy rolled plate. Background Art

[0002] Lightweighting the battery pack can improve energy density and is also an effective way for new energy vehicles to increase their range. The battery pack bottom plate requires the material to have high strength and good stamping formability, adapt to processing technologies such as bending and SPR, have good corrosion resistance, and meet the design requirements of automobile safety and durability. The development and application of new high-strength aluminum alloy products play an important role in promoting the development of new energy vehicles.

[0003] The 6xxx series aluminum alloys for car bodies, including 6016 / 6014 / 6022, are in T4 state before baking, with excellent yield strength ratio, which is conducive to stamping forming, and the stamped parts are strengthened by aging during the electrophoretic paint baking process. The strength of high-alloyed 6xxx aluminum alloys such as 6111 alloy sheets after baking is higher than that of 6014 / 6016 / 6022, but the stamping ability is slightly weaker. The conventional production process of 6xxx-T4 aluminum alloy products is: melting and casting → homogenization heat treatment → cutting head and tail → milling → hot rolling → cold rolling → intermediate annealing → cold rolling → quenching → pre-aging. Adding artificial aging can obtain high-strength T6 state products, but the conventional process flow is complicated, the production cycle is long, the efficiency is low, and the energy consumption is high. Therefore, it is urgent to develop a method for preparing aluminum alloy sheets with a short production cycle, low energy consumption, and at the same time improving the mechanical strength and elongation of the product. Summary of the invention

[0004] In view of the above shortcomings, the present invention provides a method for preparing an Al-Mg-Si-Cu alloy rolled plate, which can shorten the production cycle, improve efficiency, reduce energy consumption, and improve the mechanical strength and elongation of the product. The specific technical scheme is as follows:

[0005] A method for preparing an Al-Mg-Si-Cu alloy rolled plate comprises the following steps: melting and casting, head and tail trimming, milling, homogenization heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The ingot obtained by melting and casting the aluminum alloy raw material is trimmed, milled, and then subjected to a homogenization treatment and then directly subjected to temperature-controlled rolling using residual heat. After the temperature-controlled rolling is completed, quenching and two-stage aging treatment are performed to obtain the alloy rolled plate.

[0006] In the melting and casting step, the mass percentages of the chemical components of the ingot are: Si: 0.2-1.5, Fe: ≤0.5, Cu: ≤1.2, Mn: 0.2-0.8, Mg: 0.2-1.5, Cr: ≤0.25, Zn: ≤0.3, Ti: ≤0.1, and the remainder is Al and other inevitable impurities.

[0007] Preferably, the temperature of the homogenization heat treatment process is 500-550° C. and the time is 5-15 hours.

[0008] Preferably, in the gradient cooling rolling process, the cooling rate of the first 5 to 10 passes is lower than that of the second half of the rolling process. The rolling lubricant can be used for forced cooling online. The metal temperature drops by more than 15°C after each rolling pass. A total of 15 to 30 rolling passes are performed, and the final metal temperature is less than 100°C.

[0009] Preferably, the temperature of the solution quenching process is 500-550°C and the time is 5-30 minutes.

[0010] Preferably, the two-stage aging treatment process includes primary aging treatment and secondary aging treatment; the temperature of the primary aging treatment is 120-160°C, and the insulation time is 1-3h; the temperature of the secondary aging treatment is 180-220°C, and the insulation time is 2-10h.

[0011] Preferably, the alloy rolled plate is a flat ingot with a width-to-thickness ratio of <50%.

[0012] Preferably, in the gradient cooling rolling process, the total rolling processing rate is greater than 98%.

[0013] Preferably, the aluminum in the aluminum alloy raw material also includes recycled aluminum from the consumer end.

[0014] Preferably, the cooling rate of the solution quenching process is greater than 50°C / s.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention provides a method for preparing an Al-Mg-Si-Cu alloy rolled plate, comprising the following steps: melting, cutting, milling, homogenizing heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The homogenizing temperature of the present invention is relatively low, which can avoid over-burning of the structure due to untimely cooling in the first pass of subsequent direct rolling. The solution temperature is relatively low, which can control the atomic solubility and avoid grain growth and dispersed phase growth. The gradient cooling rolling process of the scheme effectively breaks up the second phase and promotes dissolution, so that the precipitated phase distribution of the alloy is more uniform during the subsequent solution, quenching and aging processes. Through the implementation of this scheme, the Fe-rich phase and T phase (Al 20The average size of dispersed phases such as Cu2Mn3) is refined to less than 2μm, and the average size of precipitated phases such as β(Mg2Si), S(Al2CuMg), Q(Al5 Cu2 Mg8 Si6) and θ(Al2Cu) is less than 1000nm. The type and proportion of precipitated phases are affected by the actual composition, and the second phase is evenly distributed in the crystal and at the grain boundary. The grain boundary is distributed in a chain shape, and the distribution and size of the precipitated phase are regulated to improve the mechanical strength and corrosion resistance. In addition, the production process and production technology are optimized, the production cycle is shortened, the efficiency is improved, and the energy consumption is reduced.

[0017] 2. The present invention can use recycled aluminum from the consumer end as raw material, does not affect the mechanical properties of the product, increases the tolerance of recycled aluminum from the consumer end, and promotes the recycling of recycled aluminum in automobiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0020] Figure 2 This is the TEM image of the grain boundary and intragranular area of ​​the plate of Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention, etc. can be purchased from the market or can be prepared by existing methods.

[0022] As an example, the aluminum used in the embodiment of the present invention is recycled aluminum from the consumer end, but the present invention is not limited to this.

[0023] Example 1

[0024] A method for preparing an Al-Mg-Si-Cu alloy rolled plate comprises the following steps: melting and casting, head and tail cutting, surface milling, homogenization heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The specific steps are:

[0025] 1) Melting and casting: The raw materials are placed in a melting furnace for melting and casting to obtain an ingot; the mass percentage of chemical elements of the ingot after melting and casting is: Si: 0.82, Fe: 0.26, Cu: 0.74, Mn: 0.41, Mg: 0.63, Cr: 0.11, Zn: 0.16, Ti: 0.03, and the remainder is Al and other inevitable impurities.

[0026] 2) Head and tail trimming and surface milling: the ingot is subjected to head and tail trimming and surface milling to obtain a milled ingot.

[0027] 3) Homogenization heat treatment: The ingot after milling is subjected to homogenization heat treatment at a temperature of 520° C. for a holding time of 10 h to obtain a heat-treated ingot.

[0028] 4) Gradient cooling rolling: The heat-treated ingot is subjected to gradient cooling rolling. The metal temperature is reduced by 20°C after each rolling pass. A total of 20 rolling passes are performed. The final metal temperature is 80°C, and the total rolling processing rate is 99%.

[0029] 5) Solution quenching: The ingot rolled by gradient cooling is solution quenched at a temperature of 520°C for 20 minutes, and then cooled at a cooling rate of 60°C / s.

[0030] 6) Double-stage aging treatment: The ingot after solution quenching is subjected to double-stage aging treatment, including primary aging treatment and secondary aging treatment, the temperature of the primary aging treatment is 140° C., and the holding time is 2 h; the temperature of the secondary aging treatment is 200° C., and the holding time is 6 h, to obtain the aluminum alloy plate.

[0031] Example 2

[0032] A method for preparing an Al-Mg-Si-Cu alloy rolled plate comprises the following steps: melting and casting, head and tail cutting, surface milling, homogenization heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The specific steps are:

[0033] 1) Melting and casting: the raw materials are placed in a melting furnace for melting and casting to obtain an ingot; the mass percentage of chemical elements of the ingot after melting and casting is: Si: 0.43, Fe: 0.47, Cu: 0.26, Mn: 0.36, Mg: 0.35, Cr: 0.09, Zn: 0.23, Ti: 0.08, and the balance is Al and other inevitable impurities.

[0034] 2) Head and tail trimming and surface milling: the ingot is subjected to head and tail trimming and surface milling to obtain a milled ingot.

[0035] 3) Homogenization heat treatment: The ingot after milling is subjected to homogenization heat treatment at a temperature of 500° C. for a holding time of 15 h to obtain a heat-treated ingot.

[0036] 4) Gradient cooling rolling: The heat-treated ingot is subjected to gradient cooling rolling. The metal temperature is reduced by 20°C after each rolling pass. A total of 15 rolling passes are performed. The final metal temperature is 70°C, and the total rolling processing rate is 99%.

[0037] 5) Solution quenching: The ingot rolled by gradient cooling is solution quenched at a temperature of 500°C for 30 minutes, and then cooled at a cooling rate of 70°C / s.

[0038] 6) Double-stage aging treatment: The ingot after solution quenching is subjected to double-stage aging treatment, including primary aging treatment and secondary aging treatment, the temperature of the primary aging treatment is 120° C., and the holding time is 3 h; the temperature of the secondary aging treatment is 180° C., and the holding time is 10 h, to obtain the aluminum alloy plate.

[0039] Example 3

[0040] A method for preparing an Al-Mg-Si-Cu alloy rolled plate comprises the following steps: melting and casting, head and tail cutting, surface milling, homogenization heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The specific steps are:

[0041] 1) Melting and casting: The raw materials are placed in a melting furnace for melting and casting to obtain an ingot; the mass percentage of chemical elements of the ingot after melting and casting is: Si: 1.28, Fe: 0.16, Cu: 0.91, Mn: 0.63, Mg: 0.40, Cr: 0.21, Zn: 0.13, Ti: 0.05, and the remainder is Al and other inevitable impurities.

[0042] 2) Head and tail trimming and surface milling: the ingot is subjected to head and tail trimming and surface milling to obtain a milled ingot.

[0043] 3) Homogenization heat treatment: The ingot after milling is subjected to homogenization heat treatment at a temperature of 550° C. for a holding time of 5 h to obtain a heat-treated ingot.

[0044] 4) Gradient cooling rolling: The heat-treated ingot is subjected to gradient cooling rolling. The metal temperature is reduced by 25°C after each rolling pass. A total of 30 rolling passes are performed. The final metal temperature is 90°C, and the total rolling processing rate is 99%.

[0045] 5) Solution quenching: The ingot rolled by gradient cooling is solution quenched at a temperature of 550°C for 5 minutes, and then cooled at a cooling rate of 60°C / s.

[0046] 6) Double-stage aging treatment: The ingot after solution quenching is subjected to double-stage aging treatment, including primary aging treatment and secondary aging treatment, the temperature of the primary aging treatment is 160° C., and the holding time is 1 h; the temperature of the secondary aging treatment is 220° C., and the holding time is 2 h, to obtain the aluminum alloy sheet.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that the temperature of the homogenization heat treatment is different, that is, 570°C / 10h, and the ingot is cooled to 540°C after being taken out of the furnace and then hot rolling is started. The other processes are the same as in Example 1.

[0049] Comparative Example 2

[0050] The difference from Example 1 is that the hot rolling process is different. The ingot is heated to 540°C, hot rolled after being taken out of the furnace, the temperature of hot rough rolling to finishing rolling is 380°C, and the finishing rolling final rolling temperature is 280°C. The other steps are the same as Example 1.

[0051] Comparative Example 3

[0052] The difference from Example 1 is that the hot rolling process is different. The hot rolling start temperature is 540°C, the hot rough rolling to finishing rolling temperature is 400°C, and the finishing rolling final rolling temperature is 330°C. The other steps are the same as Example 1.

[0053] Comparative Example 4

[0054] The difference from Example 1 is that the aging treatment is different, the temperature is 190° C., and the time is 8 h. The other processes are the same as Example 1.

[0055] Comparative Example 5

[0056] This comparative example is a conventional production process, including: melting and casting, homogenization heat treatment, head and tail cutting, milling, hot rolling, cold rolling, intermediate annealing, cold rolling, quenching, and two-stage aging treatment. The specific process is: homogenization heat treatment at 560°C / 10h, heating the ingot to 540°C after milling, hot rolling after being taken out of the furnace, the temperature of hot rough rolling to finishing rolling is 410°C, the finishing rolling temperature is 280°C, cold rolling after natural cooling, the cold rolling finishing temperature is 70°C, solution quenching is 560°C / 3min, and aging treatment is 180°C / 10h.

[0057] TEM test

[0058] The sample of Example 1 was electropolished with HNO3+CH3OH solution, and the microstructure was observed using a Tecnai G2 F20 transmission electron microscope. It was observed that in addition to particles larger than micrometers, there were also nanoscale fine particles distributed at the grain boundaries and within the grains. The fine nanoscale particles at the grain boundaries were mostly precipitated by aging. Figure 2 shown.

[0059] The aluminum alloy plates in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests according to ASTM standards, and each example was repeated 3 times. The test results are shown in the following table:

[0060]

[0061]

[0062] In summary, the method for preparing the Al-Mg-Si-Cu alloy rolled plate in the embodiment of the present invention controls the temperature of the homogenization heat treatment, and then replaces the prior art "hot rolling → cold rolling → intermediate annealing → cold rolling" process with gradient cooling rolling, and is matched with a two-stage aging treatment. The homogenization temperature in the embodiment of the present invention is relatively low, which can avoid overburning of the structure due to untimely cooling in the first pass of subsequent direct rolling. The relatively low control of the solid solution temperature can control the atomic solubility and avoid grain growth and dispersed phase growth. The gradient cooling rolling process of the scheme effectively breaks up the second phase and promotes dissolution, so that the precipitated phase distribution of the alloy is more uniform during the subsequent solid solution, quenching and aging processes. Through the implementation of the present invention, the Fe-rich phase and the T phase (Al 20 The average size of dispersed phases such as β(Mg2Si), S(Al2CuMg) and θ(Al2Cu) is refined to less than 2μm, and the average size of precipitated phases such as β(Mg2Si), S(Al2CuMg) and θ(Al2Cu) is less than 1000nm. The second phase is evenly distributed in the crystal and at the grain boundary, and the grain boundary is distributed in a chain shape. The distribution and size of the precipitated phase are regulated to improve the mechanical strength and corrosion resistance. The production process and production technology are optimized, the production cycle is further shortened, the production efficiency is improved, and the energy consumption is reduced. The embodiment of the present invention uses recycled aluminum at the consumer end as raw material, which does not affect the mechanical properties of the product, increases the tolerance of recycled aluminum at the consumer end, and promotes the recycling of recycled aluminum in automobiles.

[0063] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for preparing an Al-Mg-Si-Cu alloy sheet, characterized in that: The process comprises the following steps: melting and casting, cutting heads and tails, milling, homogenizing heat treatment, gradient cooling rolling, solution quenching, and two-stage aging treatment. The ingot obtained by melting and casting the aluminum alloy raw material is cut heads and tails, milled, and then subjected to a homogenizing treatment and then directly subjected to temperature-controlled rolling using residual heat. After the temperature-controlled rolling is completed, quenching and two-stage aging treatment are performed to obtain the alloy rolled plate. In the melting and casting step, the mass percentages of the chemical components of the ingot are: Si: 0.2-1.5, Fe: ≤0.5, Cu: ≤1.2, Mn: 0.2-0.8, Mg: 0.2-1.5, Cr: ≤0.25, Zn: ≤0.3, Ti: ≤0.1, and the remainder is Al and other inevitable impurities.

2. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The temperature of the homogenization heat treatment process is 500-550° C. and the time is 5-15 hours.

3. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: In the gradient cooling rolling process, the metal temperature drops by more than 15°C after each rolling pass, and a total of 15 to 30 rolling passes are performed, and the final metal temperature is less than 100°C.

4. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The temperature of the solution quenching process is 500-550°C and the time is 5-30 minutes.

5. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The two-stage aging treatment process includes a primary aging treatment and a secondary aging treatment; the temperature of the primary aging treatment is 120-160° C., and the insulation time is 1-3 hours; the temperature of the secondary aging treatment is 180-220° C., and the insulation time is 2-10 hours.

6. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The ingot is a flat ingot with a width-to-thickness ratio of less than 50%.

7. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: In the gradient cooling rolling process, the total rolling processing rate is greater than 98%.

8. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The aluminum in the aluminum alloy raw material also includes recycled aluminum from the consumer end.

9. The method for preparing an Al-Mg-Si-Cu alloy sheet according to claim 1, characterized in that: The cooling rate of the solution quenching process is greater than 50°C / s.

10. An alloy rolled plate obtained by the method for preparing an Al-Mg-Si-Cu alloy plate as claimed in any one of claims 1 to 9.

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