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

Abstract

The invention discloses a high-strength high-magnesium aluminum alloy and a preparation method thereof. The high-strength high-magnesium aluminum alloy comprises the following components in percentage by weight: 0.10-0.30% of Si, 0.14-0.30% of Fe, less than 0.03% of Cu, 0.20-0.40% of Mn, 7.50-10.50% of Mg, less than 0.03% of Zn, 0.02-0.06% of Ti, less than 0.05% of La, less than 5ppm of Na, less than 0.05% of single content of other elements, less than 0.15% of total amount and the balance of aluminum. Wherein the grain refiner is Al < 5 > TiC < 0.2 > La. In the preparation method, the Na element content of the aluminum alloy is controlled, a Na-free covering agent, a refining agent and the like are used, chlorine is used for refining, and the Na element content is controlled to be 5 ppm or below. Meanwhile, in the preparation method, after casting is finished, the continuous cooling time of cooling water reaches 30 min or above, so that a cast ingot is fully cooled, and cracking is prevented.

Description

Technical Field

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

[0002] In Al-Mg alloys, increasing the magnesium content can improve the strength of the alloy. High-magnesium aluminum alloys have the characteristics of low density, high strength, good corrosion resistance, excellent thermal conductivity and electrical conductivity, and superior forming performance. They are 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 continuous eutectic Al-Al at the grain boundaries. 3 Mg 2 Phase network, which has an adverse effect on mechanical properties. Due to the high magnesium content, the fluidity of aluminum liquid becomes poor, and casting defects such as cold shut, tensile cracking, and even cracking are prone to occur during the casting process. At the same time, due to its high brittleness, it is easy to crack the edge 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 high-magnesium aluminum alloy and a preparation method thereof.

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

[0006] Add metallic silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot and rare earth alloy according to the composition and weight percentage, smelt and cast to obtain aluminum alloy ingot;

[0007] Adding grain refiners to the launder;

[0008] The aluminum alloy ingot is homogenized at a temperature of 450 to 470°C and a holding time of 8 to 12 hours;

[0009] The aluminum alloy ingot after homogenization treatment is sawn and milled;

[0010] The aluminum alloy ingot after milling 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;

[0011] The hot rolled coil is cold rolled to obtain a cold rolled coil of 0.2 to 1.5 mm in H1X state.

[0012] The cold rolled coil is subjected to intermediate annealing and final annealing;

[0013] Wherein, the plate temperature of the hot rolled plate during hot rolling is greater than 340°C;

[0014] The finished product annealing is low temperature stabilization annealing, and the stabilization annealing temperature is 80-100°C.

[0015] According to some embodiments of the present application, primary refining and secondary refining are sequentially performed after smelting.

[0016] According to some embodiments of the present application, the primary refining temperature is 755-770° C., and the refining time is 15-18 min.

[0017] According to some embodiments of the present application, the temperature of the secondary refining is 735-750° C., and the refining time is 15-18 min.

[0018] According to some embodiments of the present application, slagging and standing are further performed after the secondary refining;

[0019] The standing time is 30 to 60 minutes.

[0020] According to some embodiments of the present application, secondary filtration is performed before casting.

[0021] According to some embodiments of the present application, the filter plate mesh number is 40ppi.

[0022] According to some embodiments of the present application, the casting temperature is 690-705°C, and the cooling water temperature is 20-30°C.

[0023] According to some embodiments of the present application, the components and weight percentages of the aluminum alloy are: Si: 0.10-0.30%, Fe: 0.14-0.30%, Cu: <0.03%, Mn: 0.20-0.40%, Mg: 7.50-10.50%, Zn: <0.03%, Ti: 0.02-0.06%, La: <0.05%, Na: <5ppm, the individual content of other elements is <0.05%, the total amount is <0.15%, and the balance is aluminum.

[0024] According to some embodiments of the present application, the grain refiner is Al 5 TiC 0.2 La.

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

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

[0027] The present application provides a method for preparing a high-magnesium aluminum alloy, wherein the Mg content is as high as 7.50-10.50%. In the preparation method of the present application, the Na content of the aluminum alloy is controlled, and a Na-free covering agent, a refining agent, etc. are used. Chlorine gas refining is used, and the Na content is controlled below 5ppm. At the same time, in the preparation method of the present application, after the casting is completed, the cooling water continues to cool for more than 30 minutes to fully cool the ingot and prevent cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figure 2 This is a state diagram of a high-strength, high-magnesium aluminum alloy according to an exemplary embodiment of the present application.

[0030] Figure 3-Figure 5 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 high-magnesium aluminum alloy, the aluminum alloy composition and weight percentage are: Si: 0.10-0.30%, Fe: 0.14-0.30%, Cu: <0.03%, Mn: 0.20-0.40%, Mg: 7.50-10.50%, Zn: <0.03%, Ti: 0.02-0.06%, La: <0.05%, Na: <5ppm, other elements single content <0.05%, total <0.15%, the balance is aluminum, wherein the grain refiner uses Al 5 TiC 0.2 La.

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

[0041] Smelting: Calculate the weight of metal additives required based on the target content, add original aluminum ingots and metal silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot and rare earth alloy and other metal additives into the smelting furnace for smelting, and test the chemical composition after melting. The smelting temperature is 755-770℃. After the composition is qualified, chlorine gas refining is carried out, and the refining time is 15-18min.

[0042] Secondary refining: After smelting, pour it into a static furnace for secondary refining. The aluminum liquid temperature is 735-750℃, chlorine refining, and the refining time is 15-18min. After refining, the slag is removed and the static furnace is allowed to stand for 30-60min.

[0043] Casting and secondary filtration: The filter plate mesh numbers are 40ppi and 40ppi respectively, the casting temperature is 690-705℃, and the cooling water temperature is 20-30℃.

[0044] Homogenization treatment: Place the ingot into a homogenization annealing furnace at a casting temperature of 450-470°C and a holding temperature of 8-10 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. To prevent cracking, the plate temperature is measured after every 3-4 passes. If the temperature is lower than 340°C, the hot-rolled plate needs to be pushed into an online heating furnace for heating at 450°C for 30 minutes. After that, it is taken out of the furnace and continued to be rolled.

[0047] Cold rolling: The hot rolled coil is cold rolled to a H1X state cold rolled coil with a thickness of 0.2 to 1.5 mm.

[0048] Intermediate annealing: The intermediate annealing thickness is calculated based on the finished product thickness and the finished product processing rate of 27-50%.

[0049] Finished product annealing: Put the cold-rolled coil with a thickness of 0.2 to 1.5 mm into the annealing furnace for low-temperature stabilization annealing at a temperature of 80 to 100°C and keep it for 2 hours before taking it out of the furnace.

[0050] Inspection: In H1X state, when the processing rate is the lowest, i.e. 27%, the tensile strength is >470MPa and the yield strength is >460MPa. When the processing rate is 50%, the tensile strength can reach 587MPa and the yield strength can reach 530MPa. After low-temperature stabilization annealing, the tensile strength is >430MPa and can reach up to 550MPa, and the yield strength is >350MPa and can reach up to 474MPa.

[0051] The high magnesium aluminum alloy of the present application strictly controls the Na content during the smelting process, uses Na-free covering agents, refining agents, etc., uses chlorine gas refining, and controls the Na content below 5ppm. After casting, the cooling water continues to cool for more than 30 minutes to fully cool the ingot and prevent cracking.

[0052] Traditional Al 5 TiB refiner is easy to aggregate, which is easy to cause local stress concentration and has a greater risk of cracking. The aluminum alloy grain refiner used in this application uses Al 5 TiC 0.2 La can provide more nucleation cores, smaller grain size and more uniform grain size.

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

[0054] Lanthanide rare earths are added during the smelting process of the present application. A trace amount of metallic lanthanum can enhance the bonding ability of grain boundaries, prevent slip and loosening of grain boundaries, help improve tensile strength and yield strength, improve plasticity and ductility, and also increase fatigue resistance in aluminum alloys to prevent damage to the alloy during deformation. At the same time, metallic lanthanum forms a dense protective film in the aluminum alloy to prevent the aluminum alloy from being oxidized in a humid environment, thereby improving the corrosion resistance of the aluminum alloy.

[0055] In the preparation method of the present application, the final rolling temperature during the hot rolling process is controlled to be not less than 340°C. If the temperature is lower than the target temperature, the steel is put into the furnace for heating to prevent rolling cracking caused by too low a temperature. At the same time, the discharge temperature of the finished cold rolling pass is controlled, 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.

[0056] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0057] Example 1

[0058] The composition and weight percentage of the aluminum alloy are: Si: 0.1%, Fe: 0.14%, Cu: 0.03%, Mn: 0.40%, Mg: 7.50%, Zn: 0.03%, Ti: 0.02%, La: 0.02%, Na: 0%, the content of other elements is less than 0.05%, the total content is less than 0.15%, and the balance is aluminum. Among them, the grain refiner uses Al 5 TiC 0.2 La.

[0059] The aluminum alloy of the present application is prepared by the following steps according to the above components:

[0060] 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 770℃, and chlorine gas refining is carried out after the composition is qualified, and the refining time is 15min.

[0061] Secondary refining: After smelting, pour it into a standing furnace for secondary refining. The aluminum liquid temperature is 750℃, chlorine refining, and the refining time is 15 minutes. After refining, the slag is removed and the standing time is 30 minutes.

[0062] Casting and secondary filtration: The filter mesh is 40ppi, the casting temperature is 705℃, and the cooling water temperature is 25℃.

[0063] Homogenization treatment: Place the ingot into a homogenization annealing furnace at a casting temperature of 470°C for 10 hours.

[0064] Sawing and milling: Saw 200mm at the head and tail of the ingot, mill both sides, and the single-side milling amount is 15mm.

[0065] Hot rolling: the ingot is placed in a heating furnace for heating at 480°C for 2 hours, and then taken out of the furnace for multiple hot rolling to a hot-rolled plate with a thickness of 8 mm. The plate temperature is measured after every 3 to 4 passes. If the temperature is lower than 340°C, the hot-rolled plate needs to be pushed into an online heating furnace for heating at 450°C for 30 minutes, and then taken out of the furnace for further rolling.

[0066] Cold rolling: The hot rolled coil is cold rolled to a 0.3 mm cold rolled coil in H1X state.

[0067] Intermediate annealing: The intermediate annealing thickness is calculated based on the finished product thickness and the finished product pass cold rolling processing rate of 27%.

[0068] Finished product annealing: Put the 0.22mm cold-rolled coil into the annealing furnace for low-temperature stabilization annealing at a temperature of 80-100°C and keep it warm for 2 hours before taking it out of the furnace.

[0069] Examples 1-6

[0070] The aluminum alloy materials of Examples 2-6 were prepared according to the steps in Example 1 and the parameters in Tables 1 and 2 below.

[0071] Table 1 Aluminum alloy composition

[0072] Example Si Fe Cu Mn Mg Zn Ti La Na 1 0.1 0.14 0.03 0.4 7.5 0.03 0.02 0.02 4.2 2 0.25 0.21 0.01 0.4 8.2 0.02 0.03 0.03 3.8 3 0.2 0.28 0.01 0.32 8.5 0.01 0.04 0.03 2.6 4 0.15 0.23 0.02 0.25 9.5 0.03 0.05 0.04 2.1 5 0.16 0.2 0.01 0.38 10 0.02 0.06 0.04 3.5 6 0.3 0.3 0.01 0.2 10.5 0.01 0.06 0.05 3.3

[0073] Table 2 Preparation process parameters

[0074]

[0075]

[0076] Comparative Example 1

[0077] An aluminum alloy was prepared according to the preparation steps of Example 5, except that the Na content was 10 ppm.

[0078] like Figure 3 As shown, the ingot quality is poor, severe cracking occurs during the hot rolling process, and the hot rolling process cannot be completed.

[0079] Comparative Example 2

[0080] An aluminum alloy is prepared according to the preparation steps of Example 5, except that no low-temperature stabilization annealing is performed.

[0081] The finished product has low elongation and poor plasticity. It is prone to cracking during the bending and stamping process and cannot meet the forming requirements of bending, stamping, etc.

[0082] Comparative Example 3

[0083] An aluminum alloy was prepared according to the preparation steps of Example 5, except that the plate temperature was not controlled during the hot rolling process, that is, hot rolling was continued even when the temperature was lower than 340°C.

[0084] like Figure 4 As shown, the edges cracked significantly during the hot rolling process and the rolling could not be completed.

[0085] Comparative Example 4

[0086] The aluminum alloy was prepared according to the preparation steps of Example 1, except that the annealing temperature of the finished product was 120°C.

[0087] The strength will further decrease, with a tensile strength of 420MPa, lower than the target value of 430MPa, a yield strength of 331MPa, lower than the target value of 350MPa, and an elongation of 10.6%. (As the annealing temperature increases, the strength decreases.)

[0088] Comparative Example 5

[0089] The aluminum alloy was prepared according to the preparation steps of Example 1, except that no homogenization was performed. Figure 5 As shown, the unhomogenized aluminum alloy material cracks during the hot rolling process and cannot be rolled further.

[0090] Experimental example

[0091] The aluminum alloy materials of Examples 1-6 were tested, and the results are shown in Table 3.

[0092] Table 3 Mechanical properties test results of the embodiments and comparative examples

[0093]

[0094] Inspection: In H1X state, when the processing rate is the lowest, i.e. 27%, the tensile strength is >470MPa and the yield strength is >460MPa. When the processing rate is 50%, the tensile strength can reach 587MPa and the yield strength can reach 530MPa. After low-temperature stabilization annealing, the tensile strength is >430MPa, and the maximum can reach 550MPa. The yield strength is >350MPa, and the maximum can reach 474MPa.

[0095] 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, characterized in that: include: Add metallic silicon, iron agent, aluminum-copper master alloy, manganese agent, magnesium ingot, zinc ingot and rare earth alloy according to the composition and weight percentage, smelt and cast to obtain aluminum alloy ingot; Adding grain refiners to the launder; The aluminum alloy ingot is homogenized at a temperature of 450 to 470° C. for a holding time of 8 to 12 hours; Sawing and milling the aluminum alloy ingot after the homogenization treatment; Hot rolling the milled aluminum alloy 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; The hot rolled coil is cold rolled to obtain a cold rolled coil of 0.2 to 1.5 mm in H1X state, The cold rolled coil is subjected to intermediate annealing and final annealing; Wherein, the plate temperature of the hot-rolled plate during hot rolling is greater than 340°C; The finished product annealing is low temperature stabilization annealing, and the stabilization annealing temperature is 80-100°C.

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

3. The preparation method according to claim 2, characterized in that: The temperature of the primary refining is 755-770° C., and the refining time is 15-18 minutes.

4. The preparation method according to claim 2, characterized in that: The secondary refining temperature is 735-750° C., and the refining time is 15-18 minutes.

5. The preparation method according to claim 2, characterized in that: After the secondary refining, slag removal and standing are performed; The standing time is 30 to 60 minutes.

6. The preparation method according to claim 1, characterized in that: Performing secondary filtration before casting; Optionally, the filter mesh size is 40ppi.

7. The preparation method according to claim 1, characterized in that: The casting temperature is 690-705°C, and the cooling water temperature is 20-30°C.

8. The preparation method according to claim 1, characterized in that: The aluminum alloy components and weight percentages are: Si: 0.10-0.30%, Fe: 0.14-0.30%, Cu: <0.03%, Mn: 0.20-0.40%, Mg: 7.50-10.50%, Zn: <0.03%, Ti: 0.02-0.06%, La: <0.05%, Na: <5ppm, the individual content of other elements is <0.05%, the total content is <0.15%, and the balance is aluminum.

9. The preparation method according to claim 1, characterized in that: The grain refiner is Al5TiC 0.2 La.

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

Images