A deformed aluminum alloy sheet and its indirect extrusion casting preparation method and application

Abstract

The present invention discloses an indirect extrusion casting preparation method for a deformed aluminum alloy sheet, comprising the following steps: pushing the aluminum alloy liquid to a distance of 10-20 mm from the mold gate at a first speed, then switching the speed, and then pressing the aluminum alloy liquid from the gate into the mold cavity for filling at a second speed, and then maintaining the pressure at a pressure of 100-200 MPa for 5-20 seconds, and demolding to obtain the sheet; the second speed is 180-200 mm / s, and the first speed is greater than the second speed. The present invention also claims protection for the deformed aluminum alloy sheet obtained by the preparation method, and the application of the deformed aluminum alloy sheet. The preparation method of the present invention can effectively solve the problems of thermal cracking and air entrainment in the preparation process of the deformed aluminum alloy sheet, and the produced aluminum alloy sheet has good quality and good mechanical properties, and can also be subjected to later anodizing processing, so that its appearance and mechanical properties meet the requirements, and has the advantages of wide application.

Description

Technical Field

[0001] The present invention relates to the field of aluminum alloy materials, and in particular to a method for preparing a deformed aluminum alloy thin plate by an indirect extrusion casting method, and also to the deformed aluminum alloy thin plate prepared by the method, and applications of the deformed aluminum alloy thin plate. Background Art

[0002] Existing aluminum alloy products, such as electronic product frames and electronic product back panels, are made of aluminum alloy sheets. In order to facilitate die casting, the existing aluminum alloy sheets (such as 0.8-1.3mm thickness) are usually made of cast aluminum alloys (such as ADC12) with high silicon content and good fluidity using traditional die casting methods (high speed and high pressure). Cast aluminum alloys have the advantages of good fluidity and easy casting due to their high silicon content, but their mechanical properties are not high and their anodizing properties are poor. For some products with high requirements for mechanical properties and appearance, they are difficult to meet the needs.

[0003] In view of this, when facing products with high requirements on mechanical properties and appearance, it is necessary to use deformed aluminum alloys with good mechanical properties and anodizing properties. However, due to the poor filling capacity of deformed aluminum alloys, during extrusion casting, heat problems will occur due to insufficient filling, resulting in cracks in the produced products. In order to solve the problem of insufficient filling capacity, in practice, people use rapid filling (i.e., increasing the filling speed of aluminum alloy liquid) to solve the problem of thermal cracking. However, although rapid filling can solve the problem of thermal cracking to a certain extent, rapid filling will produce defects such as air entrapment, and the produced products will have bubble defects. In practice, some people also compensate for shrinkage by extending the holding time, but too long a holding time will cause problems such as excessive production costs, difficulty in demolding, and reduced mold service life.

[0004] It can be seen that the existing extrusion casting production process of deformed aluminum alloy products is plagued by problems such as hot cracking and / or gas entrainment. Therefore, it is urgent to find a method for preparing a deformed aluminum alloy sheet that can solve both the gas entrainment problem and the hot cracking defect. Summary of the invention

[0005] The object of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a method for preparing a deformed aluminum alloy sheet that can solve both air entrainment defects and thermal cracking defects.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An indirect extrusion casting preparation method for a deformed aluminum alloy thin plate comprises the following steps: pushing the aluminum alloy liquid to a distance of 10-20 mm from a mold gate at a first speed, then switching the speed, and then pressing the aluminum alloy liquid from the gate into the mold cavity for filling at a second speed, and then maintaining the pressure at a pressure of 100-200 MPa for 5-20 seconds, and demolding to obtain the deformed aluminum alloy thin plate; the second speed is 180-200 mm / s, and the first speed is greater than the second speed.

[0008] In the present invention, a further preferred solution is that the gate ratio during the filling process is set to 40-43.

[0009] In the present invention, a further preferred solution is that the pouring temperature of the aluminum alloy liquid is 670-720°C, and the temperature of the mold is 200-300°C.

[0010] In the present invention, a further preferred solution is that the aluminum alloy liquid is pushed from a barrel connected to the mold to a position 10-20 mm from the mold gate at a first speed.

[0011] In the present invention, a further preferred solution is that the first speed is 300 mm / s and the second speed is 183 mm / s.

[0012] The present invention also claims protection for a deformed aluminum alloy sheet produced by any of the above methods.

[0013] In the present invention, a further preferred scheme is that the aluminum alloy liquid includes the following components in weight percentage: Fe≤0.5%, 0.6-1% Si, 0.2-0.8% Mn, Cr≤0.1%, 0.6-1.1% Cu, Ti≤0.1%, Zn≤0.25%, 0.8-1.2% Mg, other inevitable impurities 0.2%, and the balance is Al.

[0014] In the present invention, a further preferred solution is that the thickness of the deformed aluminum alloy thin plate is 0.8-1.3 mm; further, its length is 100-200 mm and its width is 60-120 mm.

[0015] In the present invention, a further preferred scheme is that the deformed aluminum alloy thin plate has a tensile yield strength of 340-360Mpa, an ultimate tensile strength of 400-425MPa, an elongation at break of 8.4-8.8%MIN, a hardness of HV5=140-150, a conductivity of 40-44MIN%IACS, and an average grain size of ≤50-200μm.

[0016] The deformed aluminum alloy sheet of the present invention can be widely used in products in many fields such as aerospace, automobiles, daily necessities, and construction, such as in the preparation of any product of electronic product frames, electronic product back panels, curtain walls, windows, wings, car bodies, and car doors.

[0017] Compared with the prior art, the beneficial effect of the present invention is that the thin plate produced by the preparation process of the present invention has neither cracks caused by thermal defects nor bubbles caused by air entrapment defects, so that the produced aluminum alloy thin plate is of good quality and has good mechanical properties, and can also be subjected to subsequent anodizing processing so that its appearance and mechanical properties meet the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a photograph of the crack of the deformed aluminum alloy sheet obtained in Comparative Example 1-1 in Example 1;

[0019] Figure 2 This is a photo of the bubble area of ​​the deformed aluminum alloy sheet obtained in Comparative Examples 1-6 in Example 1;

[0020] Figure 3 The X-ray image of the bubble of the deformed aluminum alloy sheet obtained in Comparative Examples 1-6 in Example 1;

[0021] Figure 4 is an X-ray photograph of the deformed aluminum alloy sheet obtained in Example 1-1 in Example 1;

[0022] Figure 5 is an X-ray image of the deformed aluminum alloy sheet obtained in Example 1-1 in Example 1;

[0023] in, Figure 1-Figure 5 , which are photos / pictures obtained by taking pictures of parts of the same area on the deformed aluminum alloy thin plates of the corresponding embodiments and comparative examples, and the area size is 50mm×80mm. DETAILED DESCRIPTION

[0024] Below, the present invention is further described in conjunction with the specific implementation methods and the drawings of the specification. It should be noted that, under the premise of no conflict, the various embodiments described below or the various technical features can be arbitrarily combined to form a new embodiment. Unless otherwise specified, the materials and equipment used in this embodiment can be purchased from the market. The specific embodiments are exemplary and are only used to explain this application, and cannot be understood as limiting the scope of protection of this application.

[0025] An indirect extrusion casting preparation method for a deformed aluminum alloy thin plate comprises the following steps: pushing the aluminum alloy liquid to a distance of 10-20 mm from a mold gate at a first speed, then switching the speed, and then pressing the aluminum alloy liquid from the gate into the mold cavity for filling at a second speed, and then maintaining the pressure at a pressure of 100-200 MPa for 5-20 seconds, and demolding to obtain the obtained plate; the second speed is 180-200 mm / s, and the first speed is greater than the second speed.

[0026] For deformed aluminum alloys, due to their poor fluidity, their filling capacity is insufficient, and hot cracking defects will occur during the indirect extrusion casting process to produce thin plates. The reasons for the hot cracking are, on the one hand, the crystallization interval of the deformed aluminum alloy is relatively wide (wide solidification interval), and a coarse αAl dendrite skeleton will be formed during the crystallization process, while the eutectic components with the filling and shrinkage function are relatively small, and the coarse dendrites are blocked and difficult to flow and fill the mold, resulting in cracks; on the other hand, the thickness of the aluminum alloy thin plate mold cavity is narrow and the width is extremely large. During the filling process, the alloy liquid will exchange heat with the mold surface in a very short time, and quickly cool and solidify, further hindering its filling and causing cracks. In order to solve this problem, the inventors have made many attempts and found that the thermal cracking defects of aluminum alloy thin plates can be greatly improved by increasing the injection speed during the filling process of aluminum alloy liquid. However, if the injection speed is too high, the gas flow of the alloy liquid will be unstable after entering the mold cavity, resulting in air entanglement, which will cause bubbles in the formed thin plates. Since the thickness of the aluminum alloy thin plates is very thin, once bubbles are generated, the corresponding products will not meet the requirements in appearance and performance, and cannot be processed and used in subsequent products and can only be scrapped, resulting in a lot of waste.

[0027] In order to reduce / avoid bubble / pore defects and thermal cracking defects in the production process of aluminum alloy thin plates, the following improvements can be made: select a suitable injection speed (second speed 180-200mm / s) during the filling process; and in order to reduce the gas content and impurities in the molten alloy, select a first speed higher than the second speed to push the molten aluminum alloy to the vicinity of the gate; in addition, select a suitable distance (10-20mm from the mold gate) for switching from the first speed to the second speed.

[0028] The above settings have the following effects:

[0029] 1) Selecting a first speed higher than the second speed to push the aluminum alloy liquid to the vicinity of the gate can shorten the time the alloy liquid travels in the barrel, reduce the alloy liquid cooling time and the time it contacts the air, and can reduce product quality defects caused by low alloy liquid temperature and long contact time with the air; at the same time, the relatively small second speed is conducive to the exhaust of the alloy liquid, avoiding product quality defects caused by air entrainment problems;

[0030] 2) The speed switching is performed at a distance of 10-20mm from the gate in order to better improve the forming quality of the deformed aluminum alloy sheet and reduce defects; when the speed switching is performed at a distance of more than 20mm (i.e. >20mm) from the gate, the second speed, which is slower than the first speed, will intervene in advance, resulting in a longer filling time, and the corresponding alloy liquid will travel in the barrel for a longer time, which will reduce the temperature of the alloy liquid, reduce the filling capacity of the alloy liquid and cause thermal cracking, and also prolong the contact time between the alloy liquid and the air, which is easy to produce oxides. Impurities; when the speed is switched at a distance of less than 10mm (i.e. <10mm) from the gate, the speed switching distance is too short, which is not conducive to the control of the second speed, and it is even possible that the speed is not switched to the second speed, and part of the mold is filled at the first speed, resulting in too fast filling speed, which is easy to form air entrapment and cause product quality defects; while choosing to switch the speed at a distance of 10-20mm from the gate can make the switching between the first speed and the second speed smooth, and help the gas discharge, avoiding the product quality defects caused by the lowering of the alloy liquid temperature and the long contact time with the air;

[0031] 3) The second speed is selected to be 180-200mm / s, which can fill the mold at a higher speed. During the filling process, the injection speed of the aluminum alloy liquid can break the blocked coarse dendrites, and the flow filling capacity is enhanced, so as to better fill the mold and compensate for shrinkage, and effectively solve the thermal cracking defect; at the same time, the aluminum alloy liquid at this speed fills the mold relatively smoothly, and is conducive to the exhaust of the aluminum alloy liquid, which can effectively solve the product quality defects caused by the air entrapment problem; if the second speed is less than this range value, the alloy liquid will have insufficient filling capacity and will cause thermal cracking defects; if the second speed is greater than this range value, the alloy liquid will involve more gas and will cause bubble defects;

[0032] 4) The produced thin plates have neither cracks caused by thermal defects nor bubbles caused by air entrapment defects, so that the produced aluminum alloy thin plates are of good quality and have good mechanical properties, and can also be subjected to subsequent anodizing processing, so that their appearance and mechanical properties meet the requirements.

[0033] The speed switching in the present invention refers to adjusting the first speed to the second speed. Since the first speed is greater than the second speed, when the first speed and the second speed are different, the initial first speed needs to be converted to the second speed. A buffer distance for speed switching can be set. In order to better control the production quality, such a setting can be made to switch when the alloy liquid is at a certain distance from the gate, and the distance can be selected as 10-20mm; in some embodiments, the position for speed switching can be selected at 10-13mm, 13.5-16mm, 16.5-18mm, 18.5-20mm from the gate.

[0034] In some embodiments, the second speed (i.e., the speed at which the aluminum alloy liquid is pressed into the mold cavity from the pouring gate) can also be selected to be 180-190mm / s or 190-200mm / s, or a range of 182-186mm / s, 186-190mm / s, 192-196 and 196-200mm / s can be selected, and 183mm / s can be preferably selected.

[0035] Regarding the pouring temperature of the alloy liquid, when the pouring temperature is greater than 720℃, the fluidity of the aluminum alloy liquid increases. Although it is beneficial to filling the mold, it is easy to increase the amount of gas inhaled, resulting in defects such as pores caused by air entrapment, and too high a temperature can easily lead to a reduction in the life of the mold; when the pouring temperature is less than 670℃, the fluidity of the aluminum alloy liquid will decrease, which is not conducive to filling the mold and is prone to thermal cracking defects. In addition, the alloy liquid is also prone to form a hard shell layer in the barrel, which hinders the punch from applying pressure to the alloy liquid, causing uneven heat transfer and defects; selecting a pouring temperature of the alloy liquid of 670-720℃ can reduce product quality defects such as air entrapment and thermal cracking, and can also increase the service life of the mold.

[0036] The temperature of the mold during indirect extrusion casting also has a certain impact on the product quality. When the mold temperature is less than 200℃, the alloy liquid will quickly exchange heat when it encounters the mold wall during filling, resulting in insufficient filling near the mold wall, which is prone to defects such as cold shut and cracks; further, when the mold temperature is lower than 120℃, the moisture in the release agent cannot be completely evaporated, and air curling will form, resulting in an increase in bubbles on the molded product; when the mold temperature is greater than 300℃, the cooling time of the alloy liquid will become longer, which will increase the crystal particle size and affect some mechanical properties of the product. In addition, excessively high mold temperature will reduce the effect of the release agent, easily causing adhesion between the mold and the casting, resulting in mold sintering, which reduces the service life of the mold; and selecting the mold temperature in the indirect extrusion casting process to be 200-300℃ can reduce product quality defects such as cold shut and cracks, and can also increase the service life of the mold.

[0037] In the filling process, the gate ratio is set to 40-43. With this setting, the flow uniformity of the alloy liquid in the mold is good and the product molding quality is high; if the gate ratio is less than 40 (excluding 40), the time for the aluminum alloy liquid to enter the mold will be relatively longer, resulting in insufficient filling capacity and prone to defects such as cracks; if the gate ratio is greater than 40 (excluding 43), the time for the aluminum alloy to enter the mold is relatively fast, which is prone to air entrapment defects.

[0038] In the present invention, the aluminum alloy liquid can be pushed to 10-20 mm from the mold gate at a first speed in a barrel connected to the mold. The present invention also claims protection for a deformed aluminum alloy sheet obtained by any of the above methods.

[0039] The deformed aluminum alloy sheet of the present invention can be a 6 series deformed aluminum alloy sheet, such as a 6013 deformed aluminum alloy sheet, and can be formed by indirect extrusion casting of aluminum alloy liquid using the above-mentioned manufacturing method. The aluminum alloy liquid includes the following components in weight percentage: Fe≤0.5%, 0.6-1% Si, 0.2-0.8% Mn, Cr≤0.1%, 0.6-1.1% Cu, Ti≤0.1%, Zn≤0.25%, 0.8-1.2% Mg, other inevitable impurities 0.2%, and the balance is Al.

[0040] The deformed aluminum alloy thin plate of the present invention can have a thickness of 0.8-1.3 mm, a length of 120-140 mm, and a width of 60-80 mm.

[0041] The deformed aluminum alloy thin plate of the present invention has good physical properties because it solves the defects of bubble and crack. Its tensile yield strength is 340-360Mpa, its ultimate tensile strength is 400-425MPa, its elongation at break is 8.4-8.8%MIN, its hardness HV5=140-150, its conductivity is 40-44MIN%IACS, and its average grain size is ≤50-200μm.

[0042] The deformed aluminum alloy sheet of the present invention can be widely used in products in many fields such as aerospace, automobiles, daily necessities, and construction, such as in the preparation of any product of electronic product frames, electronic product back panels, curtain walls, windows, wings, car bodies, and car doors.

[0043] Example 1

[0044] A deformed aluminum alloy thin plate is prepared by an indirect extrusion casting preparation method, and the preparation method comprises the following steps: pushing aluminum alloy liquid to a distance of 20 mm from a mold gate at a first speed, then switching the speed, and then pressing the aluminum alloy liquid from the gate into the mold cavity at a second speed for filling, and then maintaining the pressure at a pressure of 200 MPa for 5 seconds, and demolding to obtain the deformed aluminum alloy thin plate; the first speed is 300 mm / s, and the second speed is 180-200 mm / s;

[0045] The pouring temperature of the aluminum alloy liquid is 680° C., and the temperature of the mold is 200° C.;

[0046] The deformed aluminum alloy (6013 deformed aluminum alloy) thin plate has a thickness of 0.8 mm, a width of 70 mm, and a length of 140 mm;

[0047] The deformed aluminum alloy liquid has the following components in weight percentage: Fe≤0.5%, 0.8% Si, 0.4% Mn, Cr≤0.1%, 0.8% Cu, Ti≤0.1%, Zn≤0.25%, 1.2% Mg, other inevitable impurities 0.2%, and the balance is Al.

[0048] The indirect extrusion casting equipment adopts a liquid die segment machine sold by a certain company on the market, wherein the punch diameter is 75 mm and the pressure chamber cross-sectional area As=44.2 cm 2 , Gate cross-sectional area Ag = 1.06 cm 2 , gate ratio is 41.53;

[0049] According to the above conditions, "Example 1-1" to "Example 1-12" and "Comparative Example 1-1" to "Comparative Example 1-6" were constructed with the second speed set at a gradient, as shown in the following table:

[0050] Example 1-1 Example 1-2 Examples 1-3 Examples 1-4 Examples 1-5 Examples 1-6 Second speed 180 182 183 184 186 188 Examples 1-7 Examples 1-8 Examples 1-9 Examples 1-10 Examples 1-11 Examples 1-12 Second speed 190 192 194 196 198 200 Comparative Example 1-1 Comparative Example 1-2 Comparative Examples 1-3 Comparative Examples 1-4 Comparative Examples 1-5 Comparative Examples 1-6 Second speed 173 176 178 202 204 207

[0051] Take the deformed aluminum alloy thin plates obtained by the indirect squeeze casting method of the above-mentioned embodiment and comparative example, and perform T6 heat treatment on them. After the heat treatment, the cracks and bubbles on the deformed aluminum alloy thin plates are observed, and the tensile yield strength (TYS, unit MPa), ultimate tensile strength (UTS, unit MPa), elongation at break (EB, unit %), hardness (HR, unit HV5), electrical conductivity (unit, %IACS) and average grain size (unit μm) of the deformed aluminum alloy thin plates are tested;

[0052] Among them, cracks and bubbles are observed with the naked eye and detected by X-rays respectively (the crack width is averaged according to the three largest cracks on the plate. If the number of cracks is less than 3, the average value is calculated according to the actual number of cracks. If the number of cracks is 1, it is the measured value of the crack; the bubble diameter is averaged by the five largest bubbles on the plate. If the number of bubbles is less than 5, the average value is calculated according to the actual number of bubbles. If the number of bubbles is 1, it is the measured value of the bubble); the tensile yield strength and ultimate tensile strength are tested by a "Tensile Three-Item WDS-100KE Tensile Testing Machine" of a certain company on the market; the electrical conductivity is detected by the method of "GB / T 12966-2022" standard; the average strength of the grains is detected by a "metallographic microscope of a certain company's brand on the market"; the hardness is tested according to the "Webster Hardness Test Method for Aluminum Alloy (YS / T 420-2000)".

[0053] "Example 1-1" to "Example 1-12" and "Comparative Example 1-1" to "Comparative Example 1-6" were tested, and the test data are shown in the following table:

[0054]

[0055]

[0056] It can be seen from the data in the above table that under the conditions of this embodiment, the second speed is selected to be 180-200mm / s, and the deformed aluminum alloy thin plates obtained have neither cracks nor bubbles, and the corresponding aluminum alloy thin plates have good mechanical properties; when the second speed is less than 180mm / s, a certain number of cracks will be generated, but no bubbles; when the second speed is greater than 200mm / s, a certain number of bubbles will be generated, but no cracks.

[0057] Example 2 (Pouring temperature, mold temperature)

[0058] On the basis of "Example 1-1" (at this time, the corresponding fixed mold temperature is 200°C, the first speed is 300mm / s, the second speed is 180mm / s, the holding pressure is 200MPa, and the holding time is 5s), "Example 2-1" to "Example 2-6" are constructed with the pouring temperature as the gradient;

[0059] On the basis of "Example 1-1" (at this time, the corresponding fixed pouring temperature is 680°C, the mold temperature is 200°C, the first speed is 300mm / s, the second speed is 180mm / s, the holding pressure is 200MPa, and the holding time is 5s), "Example 2-1" to "Example 2-6" are constructed with the mold temperature as the gradient, as shown in the following table;

[0060]

[0061]

[0062] Then the cracks and bubbles were tested using the test method in Example 1. The specific test results are shown in the following table:

[0063]

[0064] From the data in the above table combined with the content of Example 1, it can be seen that when the pouring temperature is selected to be 670-720°C, the deformed aluminum alloy sheet obtained has neither cracks nor bubbles, while when the pouring temperature is selected outside this range, there are a certain number of cracks / bubbles, but the corresponding pouring temperature has less effect on the hot cracking and air entrainment defects generated in the indirect extrusion casting process of the aluminum alloy than the second speed; when the mold temperature is selected to be 200-300°C, the deformed aluminum alloy sheet obtained has neither cracks nor bubbles, and when the mold temperature is selected to be lower than 200°C (excluding 200°C), there will be a certain number of cracks and no bubbles, but the corresponding mold temperature has less effect on the indirect extrusion casting process. The impact of hot cracking defects generated in the aluminum alloy process is smaller than that of the second speed; relatively speaking, the mold temperature / pouring temperature mainly affects the filling flow performance of the alloy liquid, so it has a more direct impact on hot cracking, and relatively speaking, the impact on air entrainment is smaller; in addition, when the mold temperature is selected to be higher than 300℃ (excluding 300℃), the corresponding product does not produce bubbles and cracks, but sintering and aluminum sticking will occur. It can be seen that when the mold temperature is too high (higher than 300℃), the sintering, aluminum sticking and other problems will hinder normal production, and additional mold repair will be required during the next production, which increases manpower and material costs, and also leads to a decrease in mold life.

[0065] Example 3 (holding pressure, time)

[0066] On the basis of "Example 1-1" (at this time, the corresponding fixed mold temperature is 200°C, the pouring temperature is 680°C, the first speed is 300mm / s, the second speed is 180mm / s, and the holding time is 5s), "Example 3-1" to "Example 3-6" are constructed with the holding pressure as the gradient;

[0067] On the basis of "Example 1-1" (at this time, the corresponding fixed pouring temperature is 680°C, the mold temperature is 200°C, the first speed is 300mm / s, the second speed is 180mm / s, and the holding pressure is 200MPa), "Example 3-7" to "Example 3-12" are constructed with the holding time as the gradient;

[0068] Example 3-1 Example 3-2 Example 3-3 Embodiment 3-4 Embodiment 3-5 Embodiment 3-6 Holding pressure 90 95 100 150 220 250 Embodiment 3-7 Embodiment 3-8 Embodiment 3-9 Embodiment 3-10 Example 3-11 Example 3-12 Holding time 3s 4s 10s 15s 20s 25s

[0069] Then the cracks and bubbles were tested using the test method in Example 1. The specific test results are shown in the following table:

[0070]

[0071]

[0072] From the data in the above table combined with the content of Example 1, it can be seen that the holding pressure and holding time have little effect on the hot cracking defects generated in the process of indirect extrusion casting of aluminum alloy, and both have little effect on air entrainment. Relatively speaking, too low holding pressure will affect the filling of alloy liquid to a certain extent. The appropriate holding pressure is greater than or equal to 100MPa, which can solve the filling problem; the appropriate holding pressure range is 100-200MPa, which can not only solve the filling problem, but also avoid the wing failure when the holding pressure is greater than 200MPa, and can also avoid the adverse effects of sintering and aluminum sticking on the mold, and can also reduce the load on the mold and increase the life of the mold; in addition, the size of the holding pressure has little effect on air entrainment. The holding time can reach 5s, but the holding time should not be too long. Too long holding time will cause waste of casting cost. The appropriate holding time can be selected between 5-20s.

[0073] Example 4 (first speed, distance from gate)

[0074] On the basis of "Example 1-1" (at this time, the corresponding fixed mold temperature is 200°C, the pouring temperature is 680°C, the second speed is 180 mm / s, the holding time is 5s, and the holding pressure is 200 MPa), "Example 4-1" to "Example 4-12" are constructed with the first speed as the gradient;

[0075] On the basis of "Example 1-1" (at this time, the corresponding fixed pouring temperature is 680°C, the mold temperature is 200°C, the first speed is 300mm / s, the second speed is 180mm / s, the holding pressure is 200MPa, and the holding time is 5s), "Example 4-7" to "Example 4-12" are constructed with the distance from the gate when the speed starts to switch as the gradient;

[0076] Example 4-1 Example 4-2 Example 4-3 Example 4-4 Embodiment 4-5 Embodiment 4-6 First Speed 50 100 130 250 310 350 Embodiment 4-7 Embodiment 4-8 Embodiment 4-9 Embodiment 4-10 Embodiment 4-11 Embodiment 4-12 Distance from gate 7 9 15 18 21 25

[0077] Then the cracks and bubbles were tested using the test method in Example 1. The specific test results are shown in the following table:

[0078]

[0079] From the data in the above table combined with the content in Example 1, it can be seen that the first speed and the distance from the gate when the speed is switched initially affect the hot cracking and air entrainment defects generated during the indirect extrusion casting of aluminum alloy: when the first speed is less than 100 mm / hour, the alloy liquid takes a relatively long time to reach the gate, which will result in a lower temperature of the alloy liquid, poor filling, insufficient shrinkage compensation, certain cracks, and possibly a small number of bubbles; when the first speed is greater than 310 mm / hour, a small number of bubbles will be generated, but no cracks; when the distance from the gate is less than 10 mm when the speed is switched initially, the alloy liquid enters the mold faster, a small number of bubbles will be generated, but no cracks; when the distance from the gate is greater than 20 mm when the speed is switched initially, the alloy liquid takes a relatively long time to reach the gate, which will result in a lower temperature of the alloy liquid, poor filling, insufficient shrinkage compensation, a small number of cracks, but no bubbles.

[0080] Finally, it should be noted that the above-mentioned implementation modes are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention are within the scope of protection required by the present invention.

Claims

1. A method for preparing a deformed aluminum alloy sheet by indirect extrusion casting, characterized in that The method comprises the following steps: pushing the aluminum alloy liquid to a position 10-20 mm away from the mold gate at a first speed, then switching the speed, and then pressing the aluminum alloy liquid from the gate into the mold cavity at a second speed for filling, and then maintaining the pressure at a pressure of 100-200 MPa for 5-20 seconds, and demolding to obtain the product; the second speed is 180-200 mm / s, and the first speed is greater than the second speed; the aluminum alloy liquid is pushed from a barrel connected to the mold to a position 10-20 mm away from the mold gate at a first speed; the first speed is 300 mm / s; the thickness of the deformed aluminum alloy sheet is 0.8-1.3 mm; The aluminum alloy liquid includes the following components in weight percentage: Fe≤0.5%, 0.6-1% Si, 0.2-0.8% Mn, Cr≤0.1%, 0.6-1.1% Cu, Ti≤0.1%, Zn≤0.25%, 0.8-1.2% Mg, other inevitable impurities 0.2%, and the balance Al; The deformed aluminum alloy thin plate has a tensile yield strength of 340-360 MPa, an ultimate tensile strength of 400-425 MPa, an elongation at break of 8.4-8.8% MIN, a hardness of HV5=140-150, a conductivity of 40-44 MIN% IACS, and an average grain size of ≤50-200 μm.

2. The method according to claim 1, characterized in that The gate ratio during the filling process is set to 40-43.

3. The method according to claim 1, characterized in that The pouring temperature of the aluminum alloy liquid is 670-720°C, and the temperature of the mold is 200-300°C.

4. The method according to claim 1, characterized in that: The second speed is 183 mm / s.

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