An aluminum-magnesium alloy sheet with both high formability and high weldability and its preparation method

Abstract

This invention discloses an aluminum-magnesium alloy sheet with both high formability and high weldability, and its preparation method. By controlling the precipitation and distribution of the Al3Mg2 phase, this invention obtains a 5xxx aluminum alloy material with medium strength, corrosion resistance, weldability, and good formability. This lays a scientific foundation for the research and development of aluminum alloys for automobiles and improves the supply and quality assurance capabilities of aluminum materials for automotive interior panels and structural components. The sheet material prepared by the ingots of this invention exhibits room temperature tensile properties of ≥260MPa, yield strength ≥125MPa, and elongation ≥23%; the minimum principal strain in the 0° direction of the forming curve is 0.197, and the minimum principal strain in the 90° direction is 0.189; the weldability coefficient is ≥0.99. This invention is applicable to the preparation of sheet materials for automotive interior panels and structural components in the field of automotive strength enhancement.

Description

Technical Field

[0001] This invention relates to an aluminum-magnesium alloy sheet with both high formability and high weldability, and a method for preparing the same. Background Technology

[0002] The demand for high-performance aluminum alloy sheets in passenger vehicles is increasing year by year, which places higher demands on the domestic production range of alloy composition, key preparation technologies, and industrialization processes for 5xxx series aluminum alloy sheets. Currently, 5xxx series aluminum alloy sheets used in passenger vehicle interior panels and structural components need to have high formability. However, after welding, such as with MIG / TIG welding, the strength of the sheet decreases, making it impossible to simultaneously achieve both formability and post-weld performance for 5xxx series aluminum alloy sheets. This affects their application as high-performance aluminum alloy sheets in passenger vehicle panels and structural components. Summary of the Invention

[0003] The present invention aims to solve the problem that existing 5xxx series aluminum alloy sheets cannot simultaneously achieve both formability and weldability, and provides an aluminum-magnesium alloy sheet with both high formability and high weldability, as well as a method for preparing the same.

[0004] The mass percentage of each element in the aluminum-magnesium alloy sheet of this invention, which has both high formability and high weldability, is as follows: Si: 0.06%~0.10%, Fe: 0.18~0.22%, Cu≤0.05%, Mn: 0.20%~0.24%, Mg: 4.7%~5.0%, Ti: 0.01~0.03%, Cr: ≤0.02%, alkali metals / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and the balance is Al.

[0005] A method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability, comprising the following steps:

[0006] I. Weigh out aluminum ingots, magnesium ingots, aluminum-manganese master alloys, aluminum-copper master alloys, aluminum-titanium master alloys, and aluminum-chromium master alloys for remelting according to the following elemental mass percentages: Si: 0.06%–0.10%, Fe: 0.18–0.22%, Cu≤0.05%, Mn: 0.20%–0.24%, Mg: 4.7%–5.0%, Ti: 0.01–0.03%, Cr: ≤0.02%, alkali metals / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and balance Al.

[0007] 2. Add the aluminum ingots, aluminum-manganese master alloy, aluminum-copper master alloy and aluminum-titanium master alloy weighed in step 1 to the melting furnace. The melting furnace temperature is 750-780℃ to obtain melt A.

[0008] 3. Cool melt A to 740°C, add the magnesium ingot and aluminum-chromium master alloy weighed in step 1, smelt, mix evenly, stir, and evenly spread the covering agent to obtain melt B.

[0009] 4. After holding melt B at a constant temperature for 25 minutes, it is introduced into a settling furnace and then refined using an Ar-Cl2 mixed gas to obtain an aluminum alloy melt.

[0010] 5. The aluminum alloy melt obtained in step 4 is filtered through a 30ppi ceramic filter and then cast using a semi-continuous casting method to obtain an ingot of 440mm*1700mm*5000mm.

[0011] 6. The ingot obtained in step 5 is milled to 410mm-420mm, and then placed in an ingot heating furnace for heating. The heating regime is as follows: furnace gas temperature is kept at 560℃ for 5 hours, then the temperature is lowered, the temperature is increased to 445℃ and held for 9.5 hours, then the temperature is increased to 560℃ for 3 hours, then the temperature is lowered to 525℃ and held for 7.5 hours, then the temperature is lowered to 470℃ and heated for 1 hour. After being taken out of the furnace, it is rolled. The temperature of the ingot metal is controlled at 440℃-470℃ during the initial rolling and the final rolling temperature is ≤330℃. Then it is rolled into a hot-rolled coil with a thickness of 6.0mm and a width of ≤1700mm.

[0012] 7. The hot-rolled coil obtained in step 6 is cold-rolled to 1.7mm to obtain a cold-rolled coil;

[0013] 8. The cold-rolled coil obtained in step 7 is subjected to intermediate annealing at a metal temperature of 325℃~330℃ for 2 hours to obtain alloy coil.

[0014] 9. The alloy coil processed in step 8 is cold rolled to a final thickness of 1.2 mm;

[0015] 10. Anneal the coil material processed in step 9 using an air cushion heating furnace, holding it at 530℃ for 30 seconds to obtain an aluminum-magnesium alloy sheet with both high formability and high weldability.

[0016] This invention researches and develops aluminum-magnesium alloy sheets with high formability and weldability. It primarily focuses on alloy composition, controlling the types and amounts of the main element Mg and trace elements such as Mn, Cr, and Ti, while reducing the content of alkali metals and impurities. The invention reveals the correlation between the alloy's microstructure and properties during various processes including smelting and casting, homogenization annealing, high-deformation rolling, heat treatment, and welding. The developed sheet exhibits high room-temperature mechanical properties, as well as excellent weldability, formability, and corrosion resistance. This meets the demand for lightweight and efficient automotive interior body panels and structural components, reducing vehicle weight by improving sheet performance and reducing material usage, thereby achieving the goals of reducing carbon emissions and promoting environmental friendliness.

[0017] Beneficial effects of this invention:

[0018] This invention develops an aluminum-magnesium alloy sheet with both high formability and high weldability, and its preparation method, which can meet the application requirements of automotive interior panels and structural components.

[0019] (1) This invention discloses an aluminum-magnesium alloy sheet with high formability and high weldability, and its preparation method. It elucidates the influence mechanism of alloying elements on the microstructure and properties of the alloy by controlling the combination of the main alloying element Mg and trace elements Mn, Cr, Zr, Ti, and V, providing a new approach to improve the strength, corrosion resistance, formability, and weldability of aluminum alloys, and enriching the microalloying design theory of aluminum alloys. It elucidates the precipitation law of highly stable dispersed phases and their interaction with the main alloying elements, as well as their influence mechanism on the formation and evolution of alloy deformation microstructure. By regulating the precipitation and distribution state of the Al3Mg2 phase, it obtains 5xxx aluminum alloy materials with medium strength, corrosion resistance, formability, and weldability, laying a scientific foundation for the research and development of aluminum alloys for automotive lightweighting, providing technical support for solving problems such as stamping cracking and poor weldability of automotive aluminum alloy materials, greatly promoting the automotive lightweighting process, and supporting the achievement of energy conservation and emission reduction goals.

[0020] (2) The present invention provides an aluminum-magnesium alloy sheet with high formability and high weldability and its preparation method. By combining the results of previous market research and laboratory process exploration, the rolling temperature, cold rolling deformation rate, annealing temperature and annealing holding time are optimized to produce an aluminum-magnesium alloy sheet with flat surface, uniform thickness, good surface roughness, medium strength, good formability and excellent weldability. The aluminum-magnesium alloy sheet has a room temperature tensile strength ≥260MPa, yield strength ≥125MPa and elongation ≥23%; the minimum principal strain in the 0° direction of the forming curve is 0.197 and the minimum principal strain in the 90° direction is 0.189; the welding coefficient is ≥0.99. Attached Figure Description

[0021] Figure 1 The image shows the metallographic structure of the aluminum alloy ingot obtained in step two of Example 1.

[0022] Figure 2 The image shows the metallographic structure of an aluminum-magnesium alloy sheet with both high formability and high weldability obtained in Example 1.

[0023] Figure 3 The tensile fracture surface diagram of the welded joint of the aluminum-magnesium alloy sheet obtained in Example 1, which has both high formability and high weldability. Detailed Implementation

[0024] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0025] Specific Implementation Method 1: This implementation method provides an aluminum-magnesium alloy sheet with both high formability and high weldability, characterized in that the mass percentage of each element in the aluminum-magnesium alloy sheet is as follows: Si: 0.06%~0.10%, Fe: 0.18~0.22%, Cu≤0.05%, Mn: 0.20%~0.24%, Mg: 4.7%~5.0%, Ti: 0.01~0.03%, Cr: ≤0.02%, alkali metal impurities / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and the balance is Al.

[0026] In this embodiment, Fe, Si and other elements are derived from aluminum ingots. Other individual impurities besides Fe and Si are ≤0.05%. Alkali metal elements are derived from aluminum ingots. Impurities within this range have no effect on the performance of aluminum alloy foil.

[0027] Specific Implementation Method Two: This implementation method provides a method for preparing an aluminum-magnesium alloy sheet that combines high formability and high weldability, comprising the following steps:

[0028] I. Weigh out aluminum ingots, magnesium ingots, aluminum-manganese master alloys, aluminum-copper master alloys, aluminum-titanium master alloys, and aluminum-chromium master alloys for remelting according to the following elemental mass percentages: Si: 0.06%–0.10%, Fe: 0.18–0.22%, Cu≤0.05%, Mn: 0.20%–0.24%, Mg: 4.7%–5.0%, Ti: 0.01–0.03%, Cr: ≤0.02%, alkali metals / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and balance Al.

[0029] 2. Add the aluminum ingots, aluminum-manganese master alloy, aluminum-copper master alloy and aluminum-titanium master alloy weighed in step 1 to the melting furnace. The melting furnace temperature is 750-780℃ to obtain melt A.

[0030] 3. Cool melt A to 740°C, add the magnesium ingot and aluminum-chromium master alloy weighed in step 1, smelt, mix evenly, stir, and evenly spread the covering agent to obtain melt B.

[0031] 4. After holding melt B at a constant temperature for 25 minutes, it is introduced into a settling furnace and then refined using an Ar-Cl2 mixed gas to obtain an aluminum alloy melt.

[0032] 5. The aluminum alloy melt obtained in step 4 is filtered through a 30ppi ceramic filter and then cast using a semi-continuous casting method to obtain an ingot of 440mm*1700mm*5000mm.

[0033] 6. The ingot obtained in step 5 is milled to 410mm-420mm, and then placed in an ingot heating furnace for heating. The heating regime is as follows: furnace gas temperature is kept at 560℃ for 5 hours, then the temperature is lowered, the temperature is increased to 445℃ and held for 9.5 hours, then the temperature is increased to 560℃ for 3 hours, then the temperature is lowered to 525℃ and held for 7.5 hours, then the temperature is lowered to 470℃ and heated for 1 hour. After being taken out of the furnace, it is rolled. The temperature of the ingot metal is controlled at 440℃-470℃ during the initial rolling and the final rolling temperature is ≤330℃. Then it is rolled into a hot-rolled coil with a thickness of 6.0mm and a width of ≤1700mm.

[0034] 7. The hot-rolled coil obtained in step 6 is cold-rolled to 1.7mm to obtain a cold-rolled coil;

[0035] 8. The cold-rolled coil obtained in step 7 is subjected to intermediate annealing at a metal temperature of 325℃~330℃ for 2 hours to obtain alloy coil.

[0036] 9. The alloy coil processed in step 8 is cold rolled to a final thickness of 1.2 mm;

[0037] 10. Anneal the coil material processed in step 9 using an air cushion heating furnace, holding it at 530℃ for 30 seconds to obtain an aluminum-magnesium alloy sheet with both high formability and high weldability.

[0038] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the aluminum-titanium master alloy mentioned in step one is an Al-4%Ti master alloy. Everything else is the same as in Specific Implementation Method 2.

[0039] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two or Three in that the temperature of melt A in step two is ≥750℃. Everything else is the same as in Specific Implementation Method Two or Three.

[0040] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods Two to Four in that the covering agent mentioned in step three is flux No. 2. Everything else is the same as in Specific Implementation Methods Two to Four.

[0041] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods Two to Five in that the amount of covering agent added in step three is 0.55% of the total weight of the metal added to the smelting furnace. Everything else is the same as in Specific Implementation Methods Two to Five.

[0042] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Two to Six in that the volume ratio of argon to chlorine in the Ar-Cl2 mixed gas described in step four is (31.5–33):1. Everything else is the same as in Specific Implementation Methods Two to Six.

[0043] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods Two to Seven in that: during casting in step five, the aluminum-titanium-boron grain refiner is applied at a speed of 450 mm / min. Everything else is the same as in Specific Implementation Methods Two to Seven.

[0044] The grain refiner for aluminum-titanium-boron alloy is Al-5%Ti-1%B.

[0045] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Two to Eight in that the cold rolling deformation in step seven is 70% to 75%. Everything else is the same as in Specific Implementation Methods Two to Eight.

[0046] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Two to Nine in that: in step eight, the cold-rolled coil is subjected to intermediate annealing in a box furnace, with the metal temperature monitored by a thermocouple at 330℃~325℃, and held for 2 hours. Everything else is the same as in Specific Implementation Methods Two to Nine.

[0047] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Methods Two to Ten in that: in step nine, the coil is cold-rolled, and the cold-rolling deformation is controlled within 25% to 30%. Everything else is the same as in Specific Implementation Methods Two to Ten.

[0048] The beneficial effects of the present invention are verified using the following embodiments:

[0049] Example 1:

[0050] In this embodiment, the mass percentage of each element in an aluminum-magnesium alloy sheet with both high formability and high weldability is as follows: Si: 0.06%~0.10%, Fe: 0.18~0.22%, Cu≤0.05%, Mn: 0.20%~0.24%, Mg: 4.7%~5.0%, Ti: 0.01~0.03%, Cr: ≤0.02%, alkali metal impurities / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and the balance is Al.

[0051] The aluminum-magnesium alloy sheet with both high formability and high weldability, and its preparation method, are specifically carried out according to the following steps:

[0052] I. Weigh out aluminum ingots, magnesium ingots, aluminum-manganese master alloys, aluminum-copper master alloys, aluminum-titanium master alloys, and aluminum-chromium master alloys for remelting according to the following elemental mass percentages: Si: 0.06%–0.10%, Fe: 0.18–0.22%, Cu≤0.05%, Mn: 0.20%–0.24%, Mg: 4.7%–5.0%, Ti: 0.01–0.03%, Cr: ≤0.02%, alkali metal impurities / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and balance Al.

[0053] 2. Add the aluminum ingots, aluminum-manganese master alloy, aluminum-copper master alloy, and aluminum-titanium master alloy weighed in step 1 to a dry melting furnace and melt at 750℃~780℃ for 8 hours. After cooling the melt to 740℃, add the magnesium ingots and aluminum-chromium master alloy weighed in step 1 and melt for 14 hours, mixing thoroughly and stirring. Evenly spread a covering agent on the resulting melt and hold it at that temperature for 25 minutes. Then, transfer the melt to a settling furnace and refine it using an Ar-Cl2 mixed gas to obtain an aluminum alloy melt. Filter the aluminum alloy melt through a 30ppi ceramic filter. The aluminum alloy melt is then subjected to the following conditions: 725℃ temperature, casting speed 2.6m / h, cooling water strength 0.03MPa, cooling water temperature 20℃, and refining agent Al-5%Ti-1%B wire, with a feeding rate of [missing information]. Under a flow rate of 450 mm / min, a semi-continuous casting method was used to produce aluminum alloy ingots with dimensions of 440 mm * 1700 mm * 5000 mm. The ingots were then sawn at both ends and milled, and placed into a bogie furnace. Heating was performed using the following regime: a constant furnace temperature of 560℃ for 5 hours, followed by cooling to 445℃ and holding for 9.5 hours, then heating to 560℃ for 3 hours, followed by cooling to 525℃ and holding for 7.5 hours, and finally cooling to 470℃ and heating for 1 hour. The ingots were then rolled, with the initial rolling temperature controlled between 440℃ and 470℃, and the final rolling temperature ≤ 330℃. The resulting hot-rolled coils had a thickness of 6.0 mm and a width ≤ 1700 mm. These hot-rolled coils were then cold-rolled using a 2100 mm cold rolling mill to obtain cold-rolled coils with a thickness of 1.7 mm.

[0054] 3. Place the cold-rolled coil into a box furnace for intermediate annealing, and use a thermocouple to detect the metal temperature. The metal temperature is 325℃~330℃ and held for 2 hours. Then, use a 2100mm cold rolling mill to cold roll the coil to obtain a cold-rolled coil with a thickness of 1.2mm.

[0055] Fourth, straighten and trim the cold-rolled coil to the finished width, and anneal it in an air-cushion heating furnace, holding it at 530℃ for 30 seconds to obtain an aluminum-magnesium alloy sheet with both high formability and high weldability.

[0056] Figure 1 The image shows the microstructure of the 440mm*1700mm*5000mm aluminum alloy ingot obtained in step two of this embodiment. There is no obvious network eutectic structure in the as-cast microstructure, and the bright white and light gray primary phases mainly exist in the form of fish bones.

[0057] Figure 2 The image shows the metallographic structure of the aluminum-magnesium alloy sheet obtained in step four of this embodiment, which has both high formability and high weldability. The grain size is uniform and consistent, with a grain size of 35 μm.

[0058] Figure 3 The location of the tensile fracture of the aluminum-magnesium alloy plate welded joint with high formability and high weldability obtained in step four of this embodiment is where all fractures occur at the base material.

[0059] The aluminum-magnesium alloy sheet produced has a flat surface, uniform thickness, good surface roughness, medium strength, good formability, and excellent weldability. Tested according to GB / T228.1 standard, the sheet exhibits the following tensile properties at room temperature: tensile strength of 260-270 MPa, yield strength of 125-135 MPa, and elongation of 23%-24%. The minimum principal strain in the 0° direction of the forming curve is 0.197, and the minimum principal strain in the 90° direction is 0.189. The weldability coefficient is 0.99-1.

Claims

1. A method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability, characterized in that... This method is performed in the following steps: I. Weigh out aluminum ingots, magnesium ingots, aluminum-manganese master alloys, aluminum-copper master alloys, aluminum-titanium master alloys, and aluminum-chromium master alloys for remelting according to the following elemental mass percentages: Si: 0.06%~0.10%, Fe: 0.18%~0.22%, Cu≤0.05%, Mn: 0.20%~0.24%, Mg: 4.7%~5.0%, Ti: 0.01%~0.03%, Cr: ≤0.02%, alkali metals / each ≤2ppm, single impurity ≤0.05%, total impurities ≤0.15%, and balance Al.

2. Add the aluminum ingots, aluminum-manganese master alloy, aluminum-copper master alloy and aluminum-titanium master alloy weighed in step 1 to the melting furnace. The melting furnace temperature is 750-780℃ to obtain melt A.

3. Cool melt A to 740°C, add the magnesium ingot and aluminum-chromium master alloy weighed in step 1, smelt, mix evenly, stir, and evenly spread the covering agent to obtain melt B.

4. After holding melt B at a constant temperature for 25 minutes, it is introduced into a settling furnace and then refined using an Ar-Cl2 mixed gas to obtain an aluminum alloy melt.

5. The aluminum alloy melt obtained in step 4 is filtered through a 30ppi ceramic filter and then cast using a semi-continuous casting method to obtain an ingot of 440 mm*1700 mm*5000 mm.

6. The ingot obtained in step 5 is milled to 410mm-420mm, and then placed in an ingot heating furnace for heating. The heating regime is as follows: furnace gas temperature is kept at 560℃ for 5 hours, then the temperature is lowered to 445℃ for 9.5 hours, then the temperature is raised to 560℃ for 3 hours, then the temperature is lowered to 525℃ for 7.5 hours, then the temperature is lowered to 470℃ for 1 hour, and then the ingot is removed from the furnace and rolled. The temperature of the ingot metal is controlled at 440℃-470℃ during the initial rolling and the final rolling temperature is ≤330℃. Then it is rolled into a hot-rolled coil with a thickness of 6.0mm and a width of ≤1700mm.

7. The hot-rolled coil obtained in step 6 is cold-rolled to 1.7mm to obtain a cold-rolled coil; 8. The cold-rolled coil obtained in step 7 is subjected to intermediate annealing at a metal temperature of 325℃~330℃ for 2 hours to obtain alloy coil.

9. The alloy coil processed in step 8 is cold rolled to a final thickness of 1.2 mm; 10. Anneal the coil material processed in step 9 using an air cushion heating furnace, holding it at 530℃ for 30 seconds to obtain an aluminum-magnesium alloy sheet with both high formability and high weldability.

2. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... The aluminum-titanium master alloy mentioned in step one is an Al-4%Ti master alloy.

3. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... In step two, the temperature of melt A is ≥750℃.

4. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... The covering agent mentioned in step three is flux No.

2.

5. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... In step four, the volume ratio of argon to chlorine in the Ar-Cl2 mixed gas is (31.5~33):

1.

6. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... In step five, during casting, an aluminum-titanium-boron grain refiner is fed in at a speed of 450 mm / min.

7. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... The deformation amount in step seven, cold rolling, is 70% to 75%.

8. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... Step 8: The cold-rolled coil is subjected to intermediate annealing in a box furnace. The metal temperature is monitored by thermocouples and maintained at 325℃~330℃ for 2 hours.

9. The method for preparing an aluminum-magnesium alloy sheet with both high formability and high weldability according to claim 1, characterized in that... Step nine involves cold rolling the coil, with the cold rolling deformation controlled at 25% to 30%.

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