Method for manufacturing a low-cost high-formability magnesium alloy sheet for a capacitor housing

Abstract

The application discloses a preparation method of a low-cost high-formability magnesium alloy plate for a capacitor shell, and the method comprises the following steps: firstly, adopting a two-roll water-cooled casting mill to cast and roll the magnesium alloy, trimming the edge and coiling; secondly, after one-fire uncoiling and straightening, the magnesium alloy is automatically welded with a leading tape and coiled; thirdly, after two-fire uncoiling, the magnesium alloy is reversibly warm-rolled by adopting a six-roll warm rolling mill with a tape tension; fourthly, the magnesium alloy is warm-calibrated and sanded; and fifthly, after longitudinal edge trimming, the magnesium alloy is cleaned and cut to a fixed size. In the application, the casting rolling is carried out by adopting a large-rolling-force casting mill, and the rolling ranges of the two-fire warm rolling are all combined with large deformation in the first pass and small deformation in the subsequent passes, so that the internal organization of the plate blank is fully deformed, and the large casting organization is fully broken; in addition, the warm and tension rolling is adopted, the plate shape and residual stress of the rolled plate are improved, the uniformity of the fine magnesium alloy plate organization and the consistency of the mechanical properties and the microstructure are ensured, the high formability is obtained, and the application is suitable for capacitor shells.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy sheet and strip preparation technology, specifically relating to a method for preparing low-cost, highly formable magnesium alloy sheets for capacitor casings. Background Technology

[0002] Magnesium and magnesium alloys possess excellent comprehensive properties such as high specific strength and good electromagnetic shielding performance, making them widely used in many fields such as aerospace, rail transportation, electronics and information technology, and 3C (computers, communications, and consumer electronics). AZ-based magnesium alloys are magnesium alloys that combine strength and ductility; as the Zn content increases, the strength and electromagnetic shielding performance also improve. Compared with rare earth magnesium alloys, they have lower cost and higher ductility, thus exhibiting good formability.

[0003] AZ-based magnesium alloys are primarily used in aerospace and 3C (computer, communication, and consumer electronics) applications for weight reduction and electromagnetic shielding systems via extrusion. Currently, rolled magnesium alloy sheets are beginning to be used in secondary forming structural components to replace some steel parts, achieving weight reduction. If AZ-based magnesium alloys are widely used in capacitor casings, it will significantly reduce the overall weight of the capacitor, improve its heat dissipation capacity, and ensure operational stability. Capacitor casings require cold bending and welding, thus placing higher demands on the consistency of the material's plasticity and strength. Currently, the production of AZ-based sheets with a thickness of less than 3 mm mostly uses the ingot-rolling method. While this method can produce wide sheets, it heavily relies on the size and quality of the initial ingot, and the resulting sheets have significant edge cracks. The yield from ingot to finished sheet is less than 60%, and the surface quality requires subsequent sanding to achieve the required finish for shipment. Summary of the Invention

[0004] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a low-cost, high-formability magnesium alloy sheet preparation method for capacitor housings. This method employs a high-force casting and rolling mill, with both the initial large deformation rolling pass and subsequent small deformation rolling in the second-stage, second-stage, second-temperature rolling processes. This ensures sufficient deformation of the slab's internal structure, fully breaking down larger casting structures. Combined with differential temperature rolling and tension rolling, the shape and residual stress of the rolled sheet are improved, guaranteeing a fine and uniform magnesium alloy sheet structure and consistent mechanical properties and microstructure, resulting in high formability suitable for capacitor housings.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing low-cost, high-formability magnesium alloy sheet for capacitor casings, characterized in that the method includes the following steps:

[0006] Step 1: Using a casting and rolling mill with large roll diameter and high rolling force, the magnesium alloy melt that has been cleaned and purified is cast and rolled into magnesium alloy coils with a thickness of 4-6 mm and a width of 1300-1500 mm.

[0007] Step 2: Trim the magnesium alloy cast-rolled billet obtained in Step 1 online, with a trimming amount of 20-50mm, and then roll it up.

[0008] Step 3: Uncoil the magnesium alloy cast-rolled coil from Step 2 at a reheating temperature of 150-250℃. After uncoiling, straighten the coil, and then weld the upper guide strip using an automatic welding machine before coiling it up.

[0009] Step 4: The magnesium coil with the guide strip obtained in Step 3 is heated a second time at a temperature of 350-450℃. After heating, it is uncoiled, threaded, and then wound onto a drum after passing through a six-roll mill, so that the magnesium alloy sheet and strip are under tension.

[0010] Step 5: Heat and keep both ends of the magnesium alloy sheet coil from Step 4 in a coiling furnace at a temperature of 350-450°C. The temperature of the six-roll mill rolls is 100-200°C. The temperatures of the upper and lower work rolls can be adjusted independently. After multiple reversible rolling passes, a magnesium alloy rolled sheet coil with a thickness of 0.5-2.0 mm is obtained.

[0011] Step 6: The magnesium alloy rolled sheet obtained in Step 5 is subjected to warm leveling and sanding treatment, and after longitudinal shearing, the oil stains are cleaned. Finally, it is cut to length, packaged, and put into storage.

[0012] The above-mentioned method for preparing a low-cost, highly formable magnesium alloy sheet for capacitor casing is characterized in that the mass content of aluminum in the AZ-based magnesium alloy slab in step one is 0.9% to 8.3%, and the content of zinc is 0.5% to 2.5%.

[0013] The above-mentioned method for preparing a low-cost, high-formability magnesium alloy sheet for capacitor housing is characterized in that the magnesium alloy cast-rolled billet mentioned in step one is produced by a high-rolling-force casting and rolling mill with a rolling force of not less than 2000 T, the Fe content of the magnesium alloy melt is less than 20 ppm, and the volume content of harmful impurities is ≤0.8%.

[0014] The above-mentioned method for preparing a low-cost, high-formability magnesium alloy sheet for capacitor housing is characterized in that the magnesium alloy sheet described in step six has a transverse and longitudinal plasticity of more than 20%, and the difference in various mechanical properties in the transverse and longitudinal directions is within 10%, thus achieving isotropy.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. This invention uses a casting and rolling mill with a large roll diameter and high rolling force to cast and roll the purified magnesium alloy melt, so that the as-cast grains in the mushy region of the magnesium alloy are fully broken, ensuring that the internal structure of the roll is fine and uniform, thereby obtaining a large roll with high plasticity and a width of 1300-1500 mm and a thickness of 4-6 mm.

[0017] 2. This invention uses a six-roll warm rolling mill for tensioned reversible warm rolling after the second uncoiling, which reduces the rolling deformation resistance. Combined with subsequent small deformation rolling, the internal structure of the slab is fully deformed, and the larger casting structure is fully broken, ensuring the consistency of the shape and microstructure of the magnesium alloy thin plate.

[0018] 3. This invention improves the shape and residual stress of the rolled sheet by using a combination of large deformation in the first pass and differential temperature rolling in the second heat rolling process, thus ensuring the fine and uniform structure of the magnesium alloy sheet and the consistency of mechanical properties and microstructure, and achieving high formability.

[0019] To more clearly illustrate the content of this invention, the invention will be further described in a non-limiting manner below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the preparation method of magnesium alloy thin sheet of the present invention;

[0021] Figure 2 This is a metallographic image of the ZA21 magnesium alloy thin sheet prepared in Example 1 of this invention;

[0022] Figure 3 This is a metallographic image of the AZ31 magnesium alloy thin sheet prepared in Example 2 of this invention;

[0023] Figure 4 This is a metallographic image of the AZ61 magnesium alloy thin sheet prepared in Example 3 of the present invention. Detailed Implementation Example 1

[0024] like Figure 1 As shown, this embodiment includes the following steps:

[0025] Step 1: Using a casting and rolling mill with a roll diameter of 800 mm and a rolling force of 2500 T, the ZA21 magnesium alloy melt, after impurity removal and purification, is cast and rolled into a magnesium alloy coil with a thickness of 6 mm and a width of 1300 mm.

[0026] Step 2: Trim the magnesium alloy cast-rolled coil obtained in Step 1 online, with a trimming amount of 50 mm, and then roll it up.

[0027] Step 3: Uncoil the magnesium alloy cast-rolled coil from Step 2 at a reheating temperature of 150℃. After uncoiling, straighten the coil, and then weld the upper guide strip using an automatic welding machine before coiling it up.

[0028] Step 4: The magnesium coil with the guide strip obtained in Step 3 is heated a second time to a temperature of 350℃. After heating, it is uncoiled, threaded, and then wound onto a drum after passing through a six-roll mill, so that the magnesium alloy plate strip is under tension of 40KN.

[0029] Step 5: Heat and keep both ends of the magnesium alloy sheet coil from Step 4 in a coiling furnace at a temperature of 350°C. The temperature of the six-roll mill rolls is 100°C. The temperatures of the upper and lower work rolls can be adjusted independently. After multiple passes of reversible rolling, a magnesium alloy rolled sheet coil with a thickness of 2.0 mm is obtained.

[0030] Step 6: The magnesium alloy rolled sheet obtained in Step 5 is subjected to warm straightening and sanding. After longitudinal shearing of 30mm, the oil stains are cleaned, and finally cut to length, packaged, and stored.

[0031] Figure 2 This is a metallographic image of the ZA21 magnesium alloy thin sheet prepared in this embodiment. Figure 2 As can be seen, the microstructure of the ZA21 magnesium alloy sheet is uniform and fine. Example 2

[0032] Step 1: Using a casting and rolling mill with a roll diameter of 800 mm and a rolling force of 2500 T, the AZ31 magnesium alloy melt, after impurity removal and purification, is cast and rolled into a magnesium alloy coil with a thickness of 5 mm and a width of 1500 mm.

[0033] Step 2: Trim the magnesium alloy cast-rolled coil obtained in Step 1 online, with a trimming amount of 40 mm, and then roll it up.

[0034] Step 3: Uncoil the magnesium alloy cast-rolled coil from Step 2 at a reheating temperature of 200℃. After uncoiling, straighten the coil, and then weld the upper guide strip using an automatic welding machine before coiling it up.

[0035] Step 4: The magnesium coil with the guide strip obtained in Step 3 is heated a second time to a temperature of 400℃. After heating, it is uncoiled, threaded, and then wound onto a drum after passing through a six-roll mill, so that the magnesium alloy plate strip is under tension of 40 KN.

[0036] Step 5: Heat and keep both ends of the magnesium alloy plate coil from Step 4 in a coiling furnace at a temperature of 350°C. The temperature of the six-roll mill rolls is 150°C. The temperatures of the upper and lower work rolls can be adjusted independently. After multiple reversible rolling passes, a magnesium alloy rolled plate coil with a thickness of 1.0 mm is obtained.

[0037] Step 6: The magnesium alloy rolled sheet obtained in Step 5 is subjected to warm straightening and sanding. After longitudinal shearing of 40mm, the oil stains are cleaned, and finally cut to length, packaged, and stored.

[0038] Figure 3 This is a metallographic image of the AZ31 magnesium alloy thin sheet prepared in this embodiment. Figure 3 As can be seen, the microstructure of the AZ31 magnesium alloy sheet is uniform and fine. Example 3

[0039] Step 1: Using a casting and rolling mill with a roll diameter of 800 mm and a rolling force of 2500 T, the AZ61 magnesium alloy melt, after impurity removal and purification, is cast and rolled into a magnesium alloy coil with a thickness of 4 mm and a width of 1400 mm.

[0040] Step 2: Trim the magnesium alloy cast-rolled billet obtained in Step 1 online, with a trimming amount of 45 mm, and then roll it up.

[0041] Step 3: Uncoil the magnesium alloy cast-rolled coil from Step 2 at a reheating temperature of 250℃. After uncoiling, straighten the coil, then weld the upper guide strip using an automatic welding machine and coil it up.

[0042] Step 4: The magnesium coil with the guide strip obtained in Step 3 is heated a second time to a temperature of 450℃. After heating, it is uncoiled, threaded, and then wound onto a drum after passing through a six-roll mill, so that the magnesium alloy plate strip is under tension of 40 KN.

[0043] Step 5: Heat and keep both ends of the magnesium alloy sheet coil from Step 4 in a coiling furnace at a temperature of 350°C. The temperature of the six-roll mill rolls is 200°C. The temperatures of the upper and lower work rolls can be adjusted independently. After multiple reversible rolling passes, a magnesium alloy rolled sheet coil with a thickness of 2.0 mm is obtained.

[0044] Step 6: The magnesium alloy rolled sheet obtained in Step 5 is subjected to warm straightening and sanding. After longitudinal shearing of 45mm, the oil stains are cleaned, and finally cut to length, packaged, and stored.

[0045] Figure 4 This is a metallographic image of the AZ61 magnesium alloy thin sheet prepared in this embodiment. Figure 4 As can be seen, the microstructure of the AZ61 magnesium alloy sheet is uniform and fine.

[0046] It should be noted that, based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the spirit and scope of protection of the present invention.

Claims

1. A method for preparing a low-cost, highly formable magnesium alloy sheet for capacitor housings, characterized in that, The method includes the following steps: Step 1: Using a casting and rolling mill with a roll diameter of 800mm and a rolling force of ≥2000T, cast and roll magnesium alloy melt with Fe content <20ppm and harmful impurity volume content ≤0.8% to produce magnesium alloy coils with a thickness of 4~6 mm and a width of 1300~1500 mm. Step 2: Trim the magnesium alloy cast-rolled billet obtained in Step 1 online, with a trimming amount of 20~50 mm, and then roll it up. Step 3: Uncoil the magnesium alloy cast-rolled coil from Step 2 at a reheating temperature of 150~250℃. After uncoiling, straighten the coil, and then weld the upper guide strip using an automatic welding machine and roll it up. Step 4: The magnesium coil with the guide strip obtained in Step 3 is heated a second time at a temperature of 350~450℃. After heating, it is uncoiled, threaded, and then wound onto a drum after passing through a six-roll mill, so that the magnesium alloy plate strip is under tension of 40KN. Step 5: Heat and keep both ends of the magnesium alloy sheet coil from Step 4 in a coiling furnace at a temperature of 350~450℃. The temperature of the six-roll mill rolls is 100~200℃. The temperatures of the upper and lower work rolls can be adjusted independently. After multiple reversible rolling passes, a magnesium alloy rolled sheet coil with a thickness of 0.5~2.0 mm is obtained. Step 6: The magnesium alloy rolled sheet obtained in Step 5 is subjected to warm leveling and sanding treatment, and after longitudinal shearing, the oil stains are cleaned. Finally, it is cut to length, packaged, and put into storage.

2. The method for preparing low-cost, high-formability magnesium alloy sheet for capacitor housings according to claim 1, characterized in that, The magnesium alloy sheet described in step six has a transverse and longitudinal plasticity of over 20%, and the difference in various mechanical properties in the transverse and longitudinal directions is within 10%, achieving isotropy.

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