High-strength high-magnesium aluminum alloy material and preparation method thereof

Abstract

The invention discloses a high-strength high-magnesium aluminum alloy material and a preparation method thereof, and the preparation method comprises the following steps: smelting and casting according to the composition and weight percentage to obtain a cast ingot; the cast ingot is subjected to homogenization treatment, the temperature of the cast ingot is 520-540 DEG C, and the heat preservation time is 8-12 h; performing saw cutting and surface milling on the homogenized cast ingot; the cast ingot subjected to face milling is subjected to hot rolling, a hot-rolled coil is obtained, the heating temperature of hot rolling ranges from 460 DEG C to 480 DEG C, and the heat preservation time ranges from 2 h to 4 h; after the hot-rolled coil is subjected to first cold rolling to the middle thickness, intermediate annealing is conducted; and carrying out secondary cold rolling on the cold-rolled coil after intermediate annealing. The aluminum alloy comprises the following components in percentage by weight: 0.05 to 0.20 percent of Si, 0.15 to 0.25 percent of Fe, less than 0.05 percent of Cu, 0.9 to 1.2 percent of Mn, 4.0 to 6.0 percent of Mg, less than 0.10 percent of Zn, 0.02 to 0.05 percent of Ti, 0.05 to 0.15 percent of Cr, less than 8ppm of Na, less than 0.05 percent of single content of other elements, less than 0.15 percent of total amount and the balance of aluminum.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum alloy manufacturing, and in particular to a high-strength and high-magnesium aluminum alloy material and a preparation method thereof. Background Art

[0002] Aluminum-magnesium alloy is one of the common commercial aluminum alloys, with the advantages of high strength, low density and corrosion resistance. In Al-Mg alloy, increasing the magnesium content can improve the strength of the alloy. High-magnesium aluminum alloy has the characteristics of low density, high strength, good corrosion resistance, excellent thermal conductivity and electrical conductivity, and superior forming performance. It is widely used in aerospace, transportation, automobile manufacturing, medical equipment, 3C electronic products, shipbuilding and military industries.

[0003] However, when the magnesium content exceeds 5wt.%, the excess magnesium will lead to the formation of a continuous eutectic Al-Al3Mg2 phase network at the grain boundary, which will have an adverse effect on the mechanical properties. Due to the high magnesium content, the fluidity of the aluminum liquid deteriorates. In actual production, high-magnesium aluminum alloy flat ingots will have casting defects such as cracks, cold shuts, tensile cracks, and even cracks at the tail of the ingot during the casting process. The depth of the cracks exceeds the reasonable amount of sawing waste, reducing the yield rate. At the same time, due to its high brittleness, it is easy to crack or even crack during the rolling process, so the production and processing is more difficult. During the rolling process, as the work hardening increases, the plasticity decreases, resulting in poor forming performance during the actual application of the product. Summary of the invention

[0004] In order to solve the above-mentioned deficiencies in the art, the present application aims to provide a high-strength and high-magnesium aluminum alloy material and a preparation method thereof.

[0005] According to one aspect of the present application, a method for preparing a high-magnesium aluminum alloy material is provided, comprising:

[0006] Add metal additives such as metal silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot, chromium agent, etc. according to the composition and weight percentage, and perform smelting and casting to obtain ingots, and add grain refiner in the launder;

[0007] The ingot is homogenized at a temperature of 520-540°C and a holding time of 8-12 hours;

[0008] The homogenized ingot is sawn and milled;

[0009] The milled ingot is hot-rolled to obtain a hot-rolled coil, the heating temperature of the hot rolling is 460-480°C, and the holding time is 2-4h;

[0010] After the hot rolled coil is cold rolled to an intermediate thickness for the first time, intermediate annealing is performed;

[0011] The cold-rolled coil after intermediate annealing is subjected to a second cold rolling;

[0012] Wherein, the final rolling temperature of hot rolling is greater than 300°C;

[0013] The discharge temperature of the second cold rolling is 100-120°C.

[0014] According to some embodiments of the present application, the composition and weight percentage of the aluminum alloy are: Si: 0.05-0.20%, Fe: 0.15-0.25%, Cu: <0.05%, Mn: 0.9-1.2%, Mg: 4.0-6.0%, Zn: <0.10%, Ti: 0.02-0.05%, Cr: 0.05-0.15%, Na: <8ppm, the individual content of other elements is <0.05%, the total amount is <0.15%, and the balance is aluminum;

[0015] According to some embodiments of the present application, a grain refiner is further added during smelting, and the grain refiner is Al5TiC.

[0016] According to some embodiments of the present application, primary refining and secondary refining are sequentially performed after smelting.

[0017] According to some embodiments of the present application, the primary refining temperature is 765-780° C., and the refining time is 15-18 min.

[0018] According to some embodiments of the present application, the temperature of the secondary refining is 740-755° C., and the refining time is 15-18 min.

[0019] According to some embodiments of the present application, slagging and standing are further performed after the secondary refining;

[0020] According to some embodiments of the present application, the standing time is 30 to 50 minutes.

[0021] According to some embodiments of the present application, secondary filtration is performed before casting.

[0022] Optionally, the mesh number of the filter plates for the secondary filtration is 40ppi.

[0023] According to some embodiments of the present application, the casting temperature is 695-705°C, and the cooling water temperature is 20-30°C.

[0024] According to some embodiments of the present application, the intermediate annealing thickness is calculated based on the finished product thickness and the second cold rolling processing rate of 75-80%.

[0025] According to another aspect of the present application, a high-magnesium aluminum alloy material prepared by the above preparation method is provided.

[0026] Compared with the prior art, this application has at least the following beneficial effects:

[0027] The high-strength aluminum alloy smelting process of the present invention strictly controls the Na content, uses chlorine gas refining, and controls the Na content below 8ppm. The grain refiner uses Al5TiC, which can provide more nucleation cores, smaller grain size, and more uniform grain size compared to traditional Al5TiB.

[0028] In the preparation method of the present application, the final rolling temperature during hot rolling is controlled to be not less than 310°C to prevent large cracks caused by too low a temperature during rolling. The discharge temperature of the finished cold rolling pass is controlled at 100-120°C, and the deformation heat generated by the alloy itself during the rolling process is used to make the alloy recover at low temperature, thereby reducing dislocation density, reducing lattice distortion, improving plasticity, and significantly reducing internal stress, thereby achieving the purpose of stabilizing and improving performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a phase diagram of the over-fired high-strength and high-magnesium aluminum alloy according to an exemplary embodiment of the present application.

[0030] Figure 2 This is a state diagram of the aluminum alloy material used as an example for the comparative example of this application. DETAILED DESCRIPTION

[0031] The technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0032] It is particularly important to point out that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all deemed to be included in the present application. Relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments.

[0033] If no specific conditions are specified in this application, the preparation shall be carried out under conventional conditions or the conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, for which the manufacturers are not specified, are all conventional products that can be obtained commercially.

[0034] The application is described in detail below.

[0035] At present, high magnesium aluminum alloys generally have the following problems:

[0036] (1) The fluidity of aluminum liquid deteriorates, and defects such as cold shut, cracking, and even cracking are prone to occur during the casting process.

[0037] (2) It is easy to crack or even break during hot rolling and cold rolling.

[0038] (3) It has good plasticity under high strength, which makes the alloy have good forming properties.

[0039] Based on the above problems, the present application provides a high-strength and high-magnesium aluminum alloy, the components and weight percentages of the aluminum alloy are: Si: 0.05-0.20%, Fe: 0.15-0.25%, Cu: <0.05%, Mn: 0.9-1.2%, Mg: 4.0-6.0%, Zn: <0.10%, Ti: 0.02-0.05%, Cr: 0.05-0.15%, Na: <8ppm, the individual content of other elements is <0.05%, the total content is <0.15%, and the balance is aluminum; wherein the grain refiner is Al5TiC.

[0040] The present application also provides a method for preparing the above-mentioned high-strength high-magnesium aluminum alloy, comprising:

[0041] Smelting: Add the original aluminum ingot and metal silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot, chromium agent and other metal additives into the smelting furnace, detect the chemical composition after melting, calculate the weight of the required metal additives according to the target content and add them, close the furnace door and continue smelting; the smelting temperature is 765-780℃, and chlorine gas refining is carried out after the composition is qualified, and the refining time is 15min.

[0042] Secondary refining: After smelting, pour it into a static furnace for secondary refining. The aluminum liquid temperature is 740-755℃, chlorine refining, and the refining time is 15 minutes. After refining, the slag is removed and the static furnace is allowed to stand for 30-50 minutes.

[0043] Casting and secondary filtration: The filter plate mesh numbers are 40ppi and 40ppi respectively, the casting temperature is 695-705℃, and the cooling water temperature is 20-30℃.

[0044] Homogenization treatment: Place the ingot into a homogenization annealing furnace at a temperature of 520-540°C for 10 hours.

[0045] Sawing and milling: Saw 200mm at the head and tail of the ingot, mill both sides, and the single-side milling amount is 15mm.

[0046] Hot rolling: the ingot is placed in a heating furnace and heated at 460-480°C for 2-4 hours. After being taken out of the furnace, it is hot-rolled for multiple passes to a hot-rolled plate with a thickness of 8 mm. The final rolling temperature is controlled at above 300°C.

[0047] First cold rolling: The hot rolled coil is rolled to the intermediate thickness through multiple cold rolling passes.

[0048] Intermediate annealing: Place the cold rolled coil of intermediate thickness into the annealing furnace for intermediate annealing at a temperature of 300-320°C for 3 hours. The intermediate annealing thickness is calculated based on the finished product thickness and the finished product pass processing rate of 75-80%.

[0049] Second cold rolling: The cold rolled coil after intermediate annealing is rolled to the finished product thickness, and the discharge temperature of the final pass is controlled at 100-120°C.

[0050] Inspection: H18 state, tensile strength>380MPa, yield strength>340MPa

[0051] The high-magnesium aluminum alloy of the present application has a strictly controlled Na content during the smelting process, is refined using chlorine, and has a Na content below 8 ppm. The crystallizer is lubricated with oil before and during casting.

[0052] Traditional Al5TiB grain refiners are prone to aggregation, which can easily cause local stress concentration and a greater risk of cracking. The aluminum alloy grain refiner of the present application uses Al5TiC, which can provide more nucleation cores, smaller grain size, and more uniformity.

[0053] The metallographic structure after homogenization of this application provides different pictures, high temperature overburning (such as Figure 1 ), which is the over-burning metallographic phase diagram of the present application, it can be seen that the homogenization treatment process of the present application is reasonable.

[0054] In the preparation method of the present application, the final rolling temperature during hot rolling is controlled to be not less than 310°C to prevent large cracks caused by too low a temperature during rolling. The discharge temperature of the finished cold rolling pass is controlled at 100-120°C, and the deformation heat generated by the alloy itself during the rolling process is used to make the alloy recover at low temperature, thereby reducing dislocation density, reducing lattice distortion, improving plasticity, and significantly reducing internal stress, thereby achieving the purpose of stabilizing and improving performance.

[0055] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0056] Example 1

[0057] The components and weight percentages of the aluminum alloy are: Si: 0.05%, Fe: 0.15%, Cu: 0.02%, Mn: 1.2%, Mg: 4.0%, Zn: 0.05%, Ti: 0.02%, Cr: 0.05%, Na: 7ppm, the individual content of other elements is <0.05%, the total content is <0.15%, and the balance is aluminum, wherein Al5TiC is used as a grain refiner.

[0058] The aluminum alloy of the present application is prepared by the following steps according to the above components:

[0059] Smelting: Add the original aluminum ingot and metal additives into the smelting furnace, detect the chemical composition after melting, calculate the weight of the metal additives required according to the target content and add them, close the furnace door and continue smelting; the smelting temperature is 765℃, and chlorine gas refining is carried out after the composition is qualified, and the refining time is 15min.

[0060] Secondary refining: After smelting, pour it into a static furnace for secondary refining. The aluminum liquid temperature is 740℃, chlorine refining, and the refining time is 15 minutes. After refining, the slag is removed and the static furnace is allowed to stand for 30 minutes.

[0061] Casting and secondary filtration: The filter mesh is 40ppi, the casting temperature is 695℃, and the cooling water temperature is 25℃.

[0062] Homogenization treatment: Place the ingot into a homogenization annealing furnace with an ingot temperature of 540°C and a holding time of 10 hours.

[0063] Sawing and milling: Saw 200mm at the head and tail of the ingot, mill both sides, and the single-side milling amount is 15mm.

[0064] Hot rolling: the ingot is placed in a heating furnace and heated to 480°C for 2 hours. After being taken out of the furnace, it is hot-rolled for multiple passes to a hot-rolled plate with a thickness of 8 mm. The final rolling temperature is controlled at above 300°C.

[0065] First cold rolling: The hot rolled coil is cold rolled in multiple passes to an intermediate thickness of 1.2 mm.

[0066] Intermediate annealing: Place the cold rolled coil of intermediate thickness into the annealing furnace for intermediate annealing at 320°C for 3 hours. The intermediate annealing thickness is calculated based on the finished product thickness and the finished product pass processing rate of 75%.

[0067] Second cold rolling: The cold rolled coil after intermediate annealing is rolled to the finished product thickness, and the discharge temperature of the final pass is controlled at 115°C.

[0068] Examples 1-5

[0069] The aluminum alloy materials of Examples 2-5 were prepared according to the steps in Example 1 and the parameters in Tables 1 and 2 below.

[0070] Table 1 Aluminum alloy composition

[0071] Example Si Fe Cu Mn Mg Zn Ti Cr Na 1 0.05 0.15 0.02 1.2 4 0.05 0.02 0.05 7 2 0.09 0.25 0.02 0.95 4.6 0.01 0.047 0.11 7 3 0.2 0.18 0.04 1.05 5 0.03 0.04 0.1 6 4 0.15 0.21 0.03 1.13 5.5 0.02 0.05 0.15 5 5 0.08 0.23 0.01 0.9 6 0.04 0.03 0.08 6

[0072] Table 2 Preparation process parameters

[0073]

[0074] Comparative Example 1

[0075] An aluminum alloy was prepared according to the preparation steps of Example 2, except that the Na content was 11 ppm.

[0076] like Figure 2 As shown, the ingot quality is poor, the edge cracks are large during the hot rolling process, and transverse cracks have appeared at the head and tail. Continuing rolling will have the risk of strip breakage, so the hot rolling process is stopped.

[0077] Comparative Example 2

[0078] An aluminum alloy is prepared according to the preparation steps of Example 2, except that no intermediate annealing is performed and the aluminum alloy is directly cold-rolled to the finished product thickness in one step.

[0079] Since no intermediate annealing was carried out, due to the large work hardening and the large number of edge cracks, it was difficult to press down when cold rolling to 0.8mm. Due to the large cracks, the strip broke and the cold rolling failed.

[0080] Comparative Example 3

[0081] The aluminum alloy was prepared according to the preparation steps of Example 2, except that the discharge temperature of the final pass of the second cold rolling was 150°C.

[0082] The strength will further decrease, below the target value. (Strength decreases as the annealing temperature increases.)

[0083] Comparative Example 4

[0084] The aluminum alloy was prepared according to the preparation steps of Example 2, except that the discharge temperature of the final pass of the second cold rolling was 80°C.

[0085] Due to the low discharge temperature, only a single pass of rolling can be carried out, and continuous rolling with the previous pass is not possible, so the production efficiency is low, and the alloy has low elongation and poor plasticity. To obtain better plasticity, the coil needs to be annealed again, which increases the production process and reduces the production efficiency.

[0086] Comparative Example 5

[0087] An aluminum alloy was prepared according to the preparation steps of Example 2, except that the final rolling temperature of hot rolling was lower than 300°C.

[0088] There are many cracks on the hot rolled coil edge, cold rolling is difficult, and multiple trimmings are required to complete the rolling. The production efficiency is low, the elongation of the finished product is relatively low, and the plasticity is relatively poor.

[0089] Experimental example

[0090] The aluminum alloy materials of the embodiments and comparative examples were tested, and the results are shown in Table 3.

[0091] Table 3 Mechanical properties test results of the embodiments and comparative examples

[0092] Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 346.8 389.6 7.5 Example 2 355.4 397.1 6.9 Example 3 395.8 427.6 3.4 Example 4 405.1 433.4 2.2 Example 5 407.8 442.6 3.7 Comparative Example 1 / / / Comparative Example 2 / / / Comparative Example 3 362.7 311.6 11.5 Comparative Example 4 423.5 428.3 1.2 Comparative Example 5 377.3 415.7 3.9

[0093] It can be seen from the above table that the preparation method of the exemplary embodiment of the present application has high production efficiency, and the prepared aluminum alloy materials have good tensile strength, yield strength and elongation.

[0094] The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a high-strength high-magnesium aluminum alloy material, characterized in that: include: Add metallic silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot, and chromium agent according to the composition and weight percentage, smelt and cast to obtain an ingot; Adding grain refiners to the launder; The ingot is homogenized at a temperature of 520 to 540° C. and a holding time of 8 to 12 hours; Saw and mill the homogenized ingot; Hot rolling the milled ingot to obtain a hot-rolled coil, wherein the heating temperature of the hot rolling is 460-480° C. and the holding time is 2-4 hours; After the hot rolled coil is cold rolled to an intermediate thickness for the first time, intermediate annealing is performed; The cold-rolled coil after intermediate annealing is subjected to a second cold rolling; Wherein, the final rolling temperature of the hot rolling is greater than 300°C; The discharge temperature of the second cold rolling is 100-120°C.

2. The preparation method according to claim 1, characterized in that: The composition and weight percentage are: Si: 0.05-0.20%, Fe: 0.15-0.25%, Cu: <0.05%, Mn: 0.9-1.2%, Mg: 4.0-6.0%, Zn: <0.10%, Ti: 0.02-0.05%, Cr: 0.05-0.15%, Na: <8ppm, the individual content of other elements is <0.05%, the total content is <0.15%, and the balance is aluminum; Optionally, a grain refiner is further added during the smelting, and the grain refiner is Al5TiC.

3. The preparation method according to claim 1, characterized in that: After the smelting, primary refining and secondary refining are carried out in sequence.

4. The preparation method according to claim 3, characterized in that: The temperature of the primary refining is 765-780° C., and the refining time is 15-18 minutes.

5. The preparation method according to claim 3, characterized in that: The secondary refining temperature is 740-755° C., and the refining time is 15-18 minutes.

6. The preparation method according to claim 3, characterized in that: After the secondary refining, slag removal and standing are performed; The standing time is 30 to 50 minutes.

7. The preparation method according to claim 2, characterized in that: Performing secondary filtration before casting; Optionally, the mesh number of the filter plates of the secondary filtration is 40ppi.

8. The preparation method according to claim 2, characterized in that: The casting temperature is 695-705°C, and the cooling water temperature is 20-30°C.

9. The preparation method according to claim 2, characterized in that: The intermediate annealing thickness is calculated based on the finished product thickness and the second cold rolling processing rate of 75-80%.

10. A high-strength, high-magnesium aluminum alloy material prepared by the preparation method according to any one of claims 1 to 9.

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