A high-strength 5-series aluminum alloy sheet containing zirconium and a method for manufacturing the same

Abstract

The application provides a Zr-containing high-strength 5-series aluminum alloy plate strip and a preparation method thereof. The aluminum alloy plate strip comprises the following components in percentage by mass: Zr=0.05%-0.30%; Mg=5.0%-6.0%; Fe=0.10%-0.30%; Si=0.05%-0.20%; Cu=0.01%-0.05%; Mn=0.1%-0.50%; Cr=0.01%-0.30%; Cr+Mn=0.15%-0.50%; Ti=0.1%-0.25%, and the balance of Al and inevitable impurities. The preparation method comprises the following steps: (1) smelting and semi-continuous casting; (2) homogenizing annealing; (3) heating; (4) hot rolling; (5) cold rolling; and (6) finished product annealing. The application prepares an aluminum alloy plate strip with a thickness of 0.5-2.0 mm, the second phase and the grain size of the aluminum material are small, the elastic modulus is greater than or equal to 70 GPa, the tensile strength is greater than or equal to 350 MPa, the yield strength is greater than or equal to 250 MPa, the elongation is greater than or equal to 10%, the 0T bending does not crack (the bending pressure head radius R is less than 0.15 mm), and the technical requirements of the aluminum alloy plate strip on high strength and high forming performance of automobile body inner plate, cylinder head, clutch shell, oil pan and other components are met.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy materials, specifically relating to a Zr-containing high-strength 5-series aluminum alloy sheet and strip and its preparation method. Background Technology

[0002] The rapid development of new energy vehicles demands that the aluminum industry provide lighter and stronger aluminum alloys to reduce vehicle weight, save more energy, and reduce greenhouse gas emissions. Unlike traditional vehicles, new energy vehicles use batteries as their power source. Limited by battery weight and driving range, as well as stringent energy conservation and emission reduction policies, lightweighting has become a primary concern for automakers in vehicle design and material application. A 10% reduction in weight can increase the driving range of new energy vehicles by 5% to 6%. Therefore, lightweighting is one of the important development directions for new energy vehicles.

[0003] 5000 series aluminum alloys possess moderate strength, good processing and welding properties, and superior formability and corrosion resistance compared to ordinary steel sheets. They are commonly used for automotive interior panels and other complex-shaped components. Among them, 5182 aluminum alloy (4.0%~5.0% Mg) is the preferred material for automotive body panels. With the increasing demands for lightweighting in new energy vehicles, there is an urgent need to develop 5-series aluminum alloy sheets and strips with higher strength and better formability. Summary of the Invention

[0004] The purpose of this invention is to provide a Zr-containing high-strength 5-series aluminum alloy sheet and strip and its preparation method, which produces aluminum alloy sheet and strip with a thickness of 0.5~2.0mm. The aluminum material has a small second phase and grain size, an elastic modulus ≥70GPa, a tensile strength ≥350MPa, a yield strength ≥250MPa, an elongation ≥10%, and does not crack when bent at 0T (bending head radius R <0.15mm). This meets the technical requirements of high strength and high formability of aluminum alloy sheet and strip for components such as automotive body panels, cylinder heads, clutch housings, and oil pans.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the aluminum alloy sheet and strip comprises the following components by mass percentage: Zr=0.05%~0.30%; Mg=5.0%~6.0%; Fe=0.10%~0.30%; Si=0.05%~0.20%; Cu=0.01%~0.05%; Mn=0.1%~0.50%; Cr=0.01%~0.30%; Cr+Mn=0.15%~0.50%; Ti=0.1%~0.25%, and the balance being Al and unavoidable impurities; the preparation method includes the following steps: (1) smelting and semi-continuous casting; (2) homogenization annealing; (3) heating; (4) hot rolling; (5) cold rolling; (6) finished product annealing;

[0006] In step (1), the melting temperature is 740~765℃, the semi-continuous casting temperature is 695~715℃, the stable ingot production speed is 43~53mm / min, and the cooling water flow rate of the crystallizer is 135~153m³ / min. 3 / h, cooling water temperature ≤28℃;

[0007] In step (2), the furnace gas is set to 500°C. When the metal temperature reaches 475°C, the furnace gas is changed to 475-480°C and the holding time is 9-55 hours.

[0008] In step (4), the initial hot rolling temperature is 450~500℃, and the final rolling temperature is ≥300℃;

[0009] In step (5), the material is cold-rolled to 3.0~4.5mm and then undergoes a first intermediate annealing at a temperature of 320~330℃; it is cold-rolled to 0.3~2.0mm and then undergoes a second intermediate annealing at a temperature of 290~300℃.

[0010] In step (6), the product is cold-rolled to a thickness of 0.2~2.0 mm and then annealed at a temperature of 130~150℃.

[0011] In the above preparation method, the main alloying element Zr in the aluminum alloy sheet and strip is 0.05~0.20%.

[0012] In the above preparation method, the Mg content in the aluminum alloy sheet and strip is 5.5%~6.0%.

[0013] In the above preparation method, the Cr+Mn content in the aluminum alloy sheet and strip is 0.15%~0.30%.

[0014] In step (1), Zr element is added to the material frame and pressed into the melt along with magnesium ingot in the form of aluminum zirconium master alloy and stirred. The melt is refined and degassed by high-purity Ar gas powder spraying.

[0015] The present invention also proposes a Zr-containing high-strength 5-series aluminum alloy sheet and strip, which is prepared by the aforementioned method. The tensile strength of the aluminum alloy sheet and strip is ≥350MPa, and the yield strength is ≥250MPa.

[0016] The aluminum alloy sheet / strip has an elongation of ≥10%, is 0T bend-free without cracking, and has a bending head radius R <0.15mm.

[0017] The main alloying element Zr in the aluminum alloy sheet and strip is 0.05~0.20%.

[0018] In the aluminum alloy sheet and strip, Mg content is 5.5%~6.0%.

[0019] The Cr+Mn content is 0.15%~0.30%.

[0020] The beneficial effects of this invention are: by regulating the smelting and melt purification process, this invention controls the loss of Mg during smelting and the gas content in the melt, while avoiding slag inclusions from entering the casting melt and affecting the quality of the ingot.

[0021] This invention promotes a smaller second phase and grain size in 5-series aluminum alloys by adding a certain amount of Zr. Compared with the second phase and grain size of conventional 5-series aluminum alloys, the aluminum material of this invention has a smaller second phase size and a significantly increased quantity, and a smaller average grain diameter.

[0022] This invention improves the strength of 5-series aluminum alloys by adding a certain amount of Zr. Compared with the tensile strength of conventional 5-series aluminum alloys, the aluminum material of this invention has a higher tensile strength, which is increased by 10%.

[0023] This invention improves the formability of 5-series aluminum alloys by adding a certain amount of Zr. Compared with the formability of conventional 5-series aluminum alloys, the aluminum material of this invention has superior formability, and does not crack during 0T bending (bending head radius R < 0.15 mm). Attached Figure Description

[0024] Figure 1 This is a diagram showing the distribution of the second phase in the finished aluminum material of Example 1;

[0025] Figure 2 This is a grain distribution diagram of the finished aluminum material in Example 1;

[0026] Figure 3 This is a diagram showing the distribution of the second phase in the finished aluminum product of Comparative Example 1.

[0027] Figure 4 This is a grain distribution diagram of the finished aluminum material in Comparative Example 1. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the invention in any way.

[0029] Example 1: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, the alloy composition is as follows: Zr=0.12%; Mg=5.5%; Fe=0.13%; Si=0.06%; Cu=0.02%; Mn=0.24%; Cr=0.03%; Ti=0.03% and the balance being Al and unavoidable impurities.

[0030] The preparation method includes the following steps:

[0031] (1) Melting and semi-continuous casting: Melting temperature 745℃, aluminum zirconium intermediate alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used to refine and degas the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 705℃, casting speed 45mm / min, crystallizer cooling water flow rate 141m3 / h, cooling water temperature 26℃;

[0032] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 480℃, and the holding time is 16h.

[0033] (3) Hot rolling: initial rolling temperature 480℃, final rolling temperature 350℃;

[0034] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 330℃;

[0035] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 300℃;

[0036] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 150℃.

[0037] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 20μm, a tensile strength of 359MPa, a yield strength of 256MPa, and an elongation of 13.0%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0038] Example 2: A Zr-containing high-strength 5-series aluminum alloy sheet and strip and its preparation method. The alloy composition is as follows: Zr=0.22%; Mg=5.8%; Fe=0.15%; Si=0.08%; Cu=0.02%; Mn=0.34%; Cr=0.05%; Ti=0.05%, with the balance being Al and unavoidable impurities. The preparation method includes the following steps:

[0039] (1) Melting and semi-continuous casting: Melting temperature 750℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 710℃, casting speed 45mm / min, and crystallizer cooling water flow rate 150m 3 / h, cooling water temperature 26℃;

[0040] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 18h.

[0041] (3) Hot rolling: initial rolling temperature 480℃, final rolling temperature 330℃;

[0042] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 330℃;

[0043] (5) Secondary cold rolling: 4.5mm is thinned to 2.5mm and intermediate annealing is carried out at a temperature of 300℃;

[0044] (6) Three-stage cold rolling: the thickness is reduced from 2.5mm to 2.0mm, and the finished product is annealed at a temperature of 150℃.

[0045] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 18.5 μm, a tensile strength of 366 MPa, a yield strength of 268 MPa, and an elongation of 12.5%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0046] Example 3: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.08%; Mg=5.0%; Fe=0.1%; Si=0.1%; Cu=0.03%; Mn=0.2%; Cr=0.28%; Ti=0.15%, and the balance being Al and unavoidable impurities.

[0047] The preparation method includes the following steps:

[0048] (1) Melting and semi-continuous casting: Melting temperature 760℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 708℃, casting speed 44mm / min, and crystallizer cooling water flow rate 141m 3 / h, cooling water temperature 26℃;

[0049] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas is set to 500℃ and the metal temperature is raised to 475℃. The furnace gas temperature is set to 475℃ and the holding time is 52h.

[0050] (3) Hot rolling: initial rolling temperature 470℃, final rolling temperature 350℃;

[0051] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 330℃;

[0052] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 300℃;

[0053] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 150℃.

[0054] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 20.4 μm, a tensile strength of 364 MPa, a yield strength of 258 MPa, and an elongation of 11.9%. They exhibit excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0055] Example 4: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, with the following alloy composition: Zr=0.06%; Mg=5.2%; Fe=0.12%; Si=0.05%; Cu=0.04%; Mn=0.25%; Cr=0.03%; Ti=0.12%, and the balance being Al and unavoidable impurities.

[0056] The preparation method includes the following steps:

[0057] (1) Melting and semi-continuous casting: Melting temperature 745℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 713℃, casting speed 43mm / min, and crystallizer cooling water flow rate 136m 3 / h, cooling water temperature 28℃;

[0058] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 18h.

[0059] (3) Hot rolling: initial rolling temperature 450℃, final rolling temperature 340℃;

[0060] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 320℃;

[0061] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 290℃;

[0062] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 130℃.

[0063] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 19.3 μm, a tensile strength of 367 MPa, a yield strength of 260 MPa, and an elongation of 10.7%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0064] Example 5: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.12%; Mg=5.6%; Fe=0.18%; Si=0.06%; Cu=0.02%; Mn=0.3%; Cr=0.15%; Ti=0.15% and the balance being Al and unavoidable impurities.

[0065] The preparation method includes the following steps:

[0066] (1) Melting and semi-continuous casting: Melting temperature 740℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 695℃, casting speed 50mm / min, and crystallizer cooling water flow rate 152m 3 / h, cooling water temperature 27℃;

[0067] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 48h.

[0068] (3) Hot rolling: initial rolling temperature 450℃, final rolling temperature 345℃;

[0069] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 320℃;

[0070] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 290℃;

[0071] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 130℃.

[0072] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 20.6 μm, a tensile strength of 368 MPa, a yield strength of 261 MPa, and an elongation of 10.8%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0073] Example 6: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.15%; Mg=5.5%; Fe=0.16%; Si=0.08%; Cu=0.01%; Mn=0.34%; Cr=0.15%; Ti=0.2%, and the balance being Al and unavoidable impurities.

[0074] The preparation method includes the following steps:

[0075] (1) Melting and semi-continuous casting: Melting temperature 750℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 700℃, casting speed 46mm / min, and crystallizer cooling water flow rate 145m 3 / h, cooling water temperature 28℃;

[0076] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 30h.

[0077] (3) Hot rolling: initial rolling temperature 460℃, final rolling temperature 350℃;

[0078] (4) Cold rolling: 7.0mm is thinned to 3.0mm, and intermediate annealing is carried out at a temperature of 325℃;

[0079] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 295℃;

[0080] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 140℃.

[0081] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 20.7 μm, a tensile strength of 365 MPa, a yield strength of 259 MPa, and an elongation of 11.0%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0082] Example 7: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.18%; Mg=5.8%; Fe=0.2%; Si=0.15%; Cu=0.03%; Mn=0.4%; Cr=0.02%; Ti=0.2% and the balance being Al and unavoidable impurities.

[0083] The preparation method includes the following steps:

[0084] (1) Melting and semi-continuous casting: Melting temperature 748℃, aluminum zirconium master alloy and magnesium ingots are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 698℃, casting speed 53mm / min, and crystallizer cooling water flow rate 150m 3 / h, cooling water temperature 20℃;

[0085] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 12h.

[0086] (3) Hot rolling: initial rolling temperature 460℃, final rolling temperature 355℃;

[0087] (4) Cold rolling: 7.0mm is thinned to 3.0mm, and intermediate annealing is carried out at a temperature of 325℃;

[0088] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 295℃;

[0089] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 140℃.

[0090] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 18.2 μm, a tensile strength of 362 MPa, a yield strength of 258 MPa, and an elongation of 11.3%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0091] Example 8: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.23%; Mg=5.4%; Fe=0.25%; Si=0.18%; Cu=0.02%; Mn=0.45%; Cr=0.03%; Ti=0.24%, and the balance being Al and unavoidable impurities.

[0092] The preparation method includes the following steps:

[0093] (1) Melting and semi-continuous casting: Melting temperature 758℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 710℃, casting speed 53mm / min, and crystallizer cooling water flow rate 154m 3 / h, cooling water temperature 24℃;

[0094] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 20h.

[0095] (3) Hot rolling: initial rolling temperature 490℃, final rolling temperature 360℃;

[0096] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at a temperature of 322℃;

[0097] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 298℃;

[0098] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 145℃.

[0099] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 19.6 μm, a tensile strength of 357 MPa, a yield strength of 256 MPa, and an elongation of 11.4%. They exhibit excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0100] Example 9: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.25%; Mg=6.0%; Fe=0.28%; Si=0.12%; Cu=0.04%; Mn=0.15%; Cr=0.02%; Ti=0.25%, and the balance being Al and unavoidable impurities.

[0101] The preparation method includes the following steps:

[0102] (1) Melting and semi-continuous casting: Melting temperature 762℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 700℃, casting speed 43mm / min, and crystallizer cooling water flow rate 150m 3 / h, cooling water temperature 18℃;

[0103] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 26h.

[0104] (3) Hot rolling: initial rolling temperature 500℃, final rolling temperature 360℃;

[0105] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at 328℃;

[0106] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 290℃;

[0107] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 135℃.

[0108] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 21.4 μm, a tensile strength of 372 MPa, a yield strength of 268 MPa, and an elongation of 10.3%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0109] Example 10: A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, wherein the alloy composition is as follows: Zr=0.3%; Mg=5.3%; Fe=0.22%; Si=0.1%; Cu=0.02%; Mn=0.28%; Cr=0.02%; Ti=0.15%, and the balance being Al and unavoidable impurities.

[0110] The preparation method includes the following steps:

[0111] (1) Melting and semi-continuous casting: Melting temperature 760℃, aluminum zirconium master alloy and magnesium ingot are added to the material frame and pressed into the melt and stirred. High-purity Ar gas is used for powder refining and degassing of the melt. Plate-type double-stage filtration is used. Semi-continuous casting temperature 695℃, casting speed 48mm / min, and crystallizer cooling water flow rate 135m 3 / h, cooling water temperature 15℃;

[0112] (2) Homogenization treatment: After the ingot is cut off, the upper and lower surfaces are milled by 15mm. The furnace gas temperature of the heat treatment furnace is set to 500℃, the metal temperature is raised to 475℃, the furnace gas temperature is set to 475℃, and the holding time is 16h.

[0113] (3) Hot rolling: initial rolling temperature 470℃, final rolling temperature 350℃;

[0114] (4) Cold rolling: 7.0mm is thinned to 3.0mm and intermediate annealing is carried out at 328℃;

[0115] (5) Secondary cold rolling: 3.0mm is thinned to 0.45mm and intermediate annealing is carried out at a temperature of 295℃;

[0116] (6) Three-stage cold rolling: the thickness is reduced from 0.45mm to 0.3mm, and the finished product is annealed at a temperature of 135℃.

[0117] The aluminum alloy sheet and strip prepared by this composition and process have a small second phase size, with an average grain diameter of 20.3 μm, a tensile strength of 357 MPa, a yield strength of 253 MPa, and an elongation of 12.1%. They have excellent strength and formability, meeting the technical requirements of lightweight aluminum materials for new energy vehicles.

[0118] Comparative Example 1: Based on the alloy composition of Example 1, the semi-continuous casting temperature was 690℃, the casting speed was 55mm / min, and the cooling water volume of the crystallizer was 130m³. 3The process remains unchanged, with other preparation steps remaining the same. The aluminum strip produced by this process exhibits increased second-phase size, with an average grain diameter of 30 μm, tensile strength of 336 MPa, yield strength of 228 MPa, and elongation of 13.5%, failing to meet the technical requirements for tensile strength of aluminum in display panels. This is because the low temperature, high casting speed, and insufficient cooling water in the semi-continuous casting process result in inadequate cooling of the ingot. Insufficient cooling of the molten aluminum during ingot solidification allows sufficient time for the second phase, primarily composed of Al-Fe phases containing Mn, Si, and Zr, to precipitate and grow. Simultaneously, the ingot grains also grow due to insufficient cooling, ultimately leading to coarse second-phase and grain size in the rolled aluminum strip, directly affecting the final performance of the aluminum strip.

[0119] Comparative Example 2: The alloy composition of Comparative Example 2 does not contain Zr. The contents of other elements are as follows: Mg=5.5%; Fe=0.13%; Si=0.06%; Cu=0.02%; Mn=0.24%; Cr=0.03%; Ti=0.03%, with the balance being Al and unavoidable impurities. The preparation process is the same as in Example 1. The aluminum sheet and strip prepared by this alloy composition and process has a tensile strength of 318 MPa, a yield strength of 223 MPa, and an elongation of 10.0%, which does not meet the technical requirements for lightweight aluminum materials in new energy vehicles. The reason for this is that the Zr element added in Example 1 affects the recrystallization process of the aluminum alloy. The ZrAl3 phase precipitated during the homogenization process of the Zr-containing aluminum alloy ingot has a strong effect on inhibiting recrystallization and grain growth, ensuring that the final aluminum sheet and strip product has finer and more uniform grains.

[0120] Comparative Example 3: Based on the alloy composition and semi-continuous casting process of Example 1, the homogenization heat treatment furnace gas was set to 490°C. When the metal temperature reached 465°C, the furnace gas temperature was reduced to 470°C, and the holding time was 24 hours. Other preparation processes remained unchanged. The aluminum strip prepared by this process had a large second phase size and exhibited cracking. The average grain diameter was 35 μm, which did not meet the technical requirements for the tensile strength of aluminum in the display panel. The reason for this was that the furnace gas temperature was low at the beginning of the homogenization treatment and was lowered before the ingot reached the required temperature, resulting in insufficient homogenization. The alloying elements were not dissolved back into the aluminum matrix in time, and a large number of undissolved coarse second phases existed at the grain boundaries, causing cracking of the aluminum strip during the rolling process.

[0121] Comparative Example 4: Based on the alloy composition, semi-continuous casting, and homogenization heat treatment of Example 2, the hot rolling start temperature was 490℃, the final rolling temperature was 285℃, the first intermediate annealing temperature was 310℃, the second intermediate annealing temperature was 275℃, and the final annealing temperature was 160℃. Other preparation processes remained unchanged. The aluminum sheet and strip prepared by this process had a tensile strength of 335MPa, a yield strength of 227MPa, and an elongation of 8.9%, which does not meet the technical requirements for lightweight aluminum materials in new energy vehicles. The reason for this is that the final rolling temperature and intermediate annealing temperature are relatively low, resulting in insufficient recrystallization and a high rolling texture, thus leading to a low final elongation of the aluminum sheet. Due to the high final annealing temperature, the aluminum material recovers more fully, resulting in a decrease in both the tensile strength and yield strength of the sheet.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the specific implementation of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the pending claims.

Claims

1. A method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip, characterized in that: The aluminum alloy sheet and strip have the following components by mass percentage: Zr = 0.22%~0.30%; Mg = 5.0%~6.0%; Fe = 0.10%~0.30%; Si = 0.05%~0.20%; Cu = 0.01%~0.05%; Mn = 0.1%~0.50%; Cr = 0.01%~0.30%; Cr+Mn = 0.15%~0.50%; Ti = 0.1%~0.25%, and the balance being Al and unavoidable impurities; its preparation method includes the following steps: (1) smelting and semi-continuous casting; (2) homogenization annealing; (3) heating; (4) hot rolling; (5) cold rolling; (6) finished product annealing; In step (1), Zr element is added to the feed frame and pressed into the melt along with magnesium ingots in the form of aluminum-zirconium master alloy and stirred. The melt is refined and degassed by high-purity Ar gas powder injection. The melting temperature is 740~765℃, the semi-continuous casting temperature is 695~715℃, the stable ingot production speed is 43~53mm / min, and the cooling water flow rate of the crystallizer is 135~153m³ / min. 3 / h, cooling water temperature ≤28℃; In step (2), the furnace gas is set to 500°C. When the metal temperature reaches 475°C, the furnace gas is changed to 475-480°C and the holding time is 9-55 hours. In step (4), the initial hot rolling temperature is 450~500℃, and the final rolling temperature is ≥300℃; In step (5), the material is cold-rolled to 3.0~4.5mm and then subjected to a first intermediate annealing at a temperature of 320~330℃; and cold-rolled to 0.3~2.0mm and then subjected to a second intermediate annealing at a temperature of 290~300℃. In step (6), the product is cold-rolled to a thickness of 0.2~2.0 mm and then annealed at a temperature of 130~150℃.

2. The method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip according to claim 1, characterized in that: In aluminum alloy sheets and strips, Mg content is 5.5%~6.0%.

3. The method for preparing Zr-containing high-strength 5-series aluminum alloy sheet and strip according to claim 1, characterized in that: In aluminum alloy sheets and strips, Cr+Mn content is 0.15%~0.30%.

4. A Zr-containing high-strength 5-series aluminum alloy sheet and strip, characterized in that: The aluminum alloy sheet and strip prepared by the preparation method described in claim 1 has a tensile strength ≥350MPa and a yield strength ≥250MPa.

5. The Zr-containing high-strength 5-series aluminum alloy sheet and strip according to claim 4, characterized in that: The aluminum alloy sheet / strip has an elongation of ≥10%, is 0T bend-free without cracking, and has a bending head radius R <0.15mm.

6. The Zr-containing high-strength 5-series aluminum alloy sheet and strip according to claim 4, characterized in that: In aluminum alloy sheets and strips, Mg content is 5.5%~6.0%.

7. The Zr-containing high-strength 5-series aluminum alloy sheet and strip according to claim 4, characterized in that: In aluminum alloy sheets and strips, Cr+Mn content is 0.15%~0.30%.

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