Aluminum alloy for high-strength vehicle body material and preparation method of aluminum alloy

Abstract

The invention relates to an aluminum alloy for a high-strength vehicle body material and a preparation method of the aluminum alloy, and belongs to the technical field of aluminum alloys. The aluminum alloy for the high-strength vehicle body material comprises the following components in percentage by mass: less than or equal to 0.3% of silicon, less than or equal to 0.35% of iron, less than or equal to 0.2% of copper, 0.2-0.7% of manganese, 1.0-2.0% of magnesium, less than or equal to 0.3% of chromium, 4.0-5.0% of zinc, less than or equal to 0.2% of titanium, less than or equal to 0.25% of zirconium and the balance of aluminum. The invention further provides a preparation method of the aluminum alloy for the high-strength vehicle body material. The aluminum alloy for the high-strength vehicle body material provided by the invention is easy to process when being used for preparing a vehicle body profile, and can be used for extruding a large wide profile which is complex in shape and relatively thin in wall thickness. The aluminum alloy material is excellent in mechanical property, can meet the requirement of a vehicle body structure for the bearing capacity, is high in fatigue strength, can bear the complex stress environment due to the high fatigue strength, and reduces the generation and expansion of fatigue cracks.

Description

Technical Field

[0001] This invention relates to the technical field of aluminum alloys, and more specifically to a high-strength aluminum alloy for vehicle body materials and its preparation method. Background Technology

[0002] With the continuous development of the automotive manufacturing industry, automakers are constantly improving the fuel efficiency of vehicles to optimize their kinetic energy. Early vehicle bodies were primarily made of steel, but to reduce energy consumption and emissions, aluminum alloys have become an alternative. This is because aluminum alloys have advantages such as low density (approximately 2.7 g / cm³) and good corrosion resistance. Furthermore, aluminum alloy automotive parts have a high recycling rate, allowing for significant weight reduction, energy conservation, and environmental benefits. However, traditional aluminum alloys (such as 5xxx series Al-Mg and 6xxx series Al-Mg-Si) have the following problems: insufficient strength: the tensile strength in the annealed state is mostly below 300 MPa, making it difficult to meet the requirements of vehicle body profiles; limited formability: high-strength aluminum alloys (such as 7xxx series Al-Zn-Mg) are prone to cracking during extrusion processing; poor weldability: high alloying composition leads to high sensitivity to welding hot cracking.

[0003] Patent CN112375949A discloses a heat treatment process for high-strength 7-series aluminum alloy sheets used in vehicle bodies. This process involves hot rolling, cold rolling, solution quenching, and multi-stage aging (three-stage aging: 50℃, 100℃, and 145℃) to obtain a high-strength 7-series aluminum alloy for vehicle bodies. The goal of patent CN112375949A is to improve the toughness, bending performance, corrosion resistance, and weldability of the aluminum alloy. However, the vehicle body aluminum alloy obtained by the aforementioned patent still does not have ideal mechanical properties, especially when applied to large, wide vehicle body profiles formed by extrusion, where the aluminum alloy strength is not high. Summary of the Invention

[0004] To address the problem of low strength in existing aluminum alloy vehicle body materials, this invention provides a high-strength aluminum alloy for vehicle body materials and its preparation method, thereby solving the aforementioned problem.

[0005] The technical solution of this invention is as follows: In a first aspect, the present invention provides an aluminum alloy for high-strength vehicle body materials, comprising the following components by mass percentage: silicon ≤0.3%, iron ≤0.35%, copper ≤0.2%, manganese 0.2%~0.7%, magnesium 1.0%~2.0%, chromium ≤0.3%, zinc 4.0%~5.0%, titanium ≤0.2%, zirconium ≤0.25%, with the balance being aluminum.

[0006] Secondly, the present invention provides a method for preparing the above-mentioned high-strength aluminum alloy for vehicle body materials, comprising the following steps: (1) Batching and melting; (2) Slag removal; (3) Settling; (4) Refining; (5) Casting; (6) Extrusion.

[0007] Further, the specific steps of step (1) are as follows: The components after batching are added to a melting furnace for melting. During the melting process, an electromagnetic stirrer is turned on to enhance stirring. The melting temperature is 740℃~750℃. After melting, refining is performed using a sodium-free granular refining agent. The refining temperature is 740℃~750℃, the refining agent dosage is 1±0.2 kg / t.Al, and the time is 15±2 minutes. A W and Z type dual-tube refining method is used, with the bubble height below 80 mm. The refining tube is replaced every 7~8 minutes, and after replacement, it is cleaned promptly and coated with boron nitride.

[0008] The sodium-free granular refining agent mainly consists of KCl and MgCl2; wherein the MgCl2 content is 43%~60%, the KCl content is 40%~57%, and the MgO content is ≤1.0%.

[0009] Furthermore, the specific steps of step (2) are as follows: the stainless steel slag removal tool is cleaned and coated with boron nitride in the first 3 meters, the slag on the surface of the melt is removed, and after the sample analysis is qualified, the converter is converted, and the converter temperature is controlled at 740 ℃~750 ℃.

[0010] Furthermore, the specific steps of step (3) are as follows: the settling time is 50 min ~ 60 min (from the end of slag removal to the opening of the plate), and electromagnetic stirring is prohibited.

[0011] Further, the specific steps of step (4) are as follows: Spanish aluminum-titanium-boron wire is added according to a calculation of 1.2 kg / t.Al; after refining, degassing is performed at a speed of 400~450 r / min, and a 40+70 ppi filter plate is used for dual-stage filtration.

[0012] Furthermore, the specific steps of step (5) are as follows: the casting pan temperature is controlled at 700 ℃±5 ℃, the hydrogen content is controlled below 0.15 ml / 100 g.Al, and tempering is performed at the end. The casting speed is 78 mm / min, and the water volume is about 3000.

[0013] Further, the specific steps of step (6) are as follows: the cast bar is extruded, the extrusion pressure of the extrusion press is 36 MN, the extrusion cylinder temperature is 435 ℃~ 445 ℃, the die temperature is 440 ℃~ 460 ℃, the temperature is held for 6~14 hours, the temperature is held in the low temperature furnace at 350 ℃≤24 hours, the outlet temperature is 470 ℃~ 500 ℃, the air-cooled online quenching is carried out, and the artificial aging is carried out at 115±5 ℃×12 hours+155±5 ℃×8 hours, and finally the profile is obtained.

[0014] The beneficial effects of this invention are as follows: The high-strength aluminum alloy for vehicle bodies and its preparation method provided by this invention are easy to process during the fabrication of vehicle body profiles, enabling the extrusion of large, wide profiles with complex shapes and thin walls. It exhibits excellent mechanical properties, meeting the load-bearing requirements of vehicle body structures. Furthermore, it possesses high fatigue strength. During long-term vehicle operation, the vehicle body is subjected to repeated alternating stresses; the high fatigue strength of this aluminum alloy allows it to withstand this complex stress environment, reducing the generation and propagation of fatigue cracks. Its overall performance is relatively stable. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0016] Example 1 A method for preparing a high-strength aluminum alloy for vehicle body materials includes the following steps: (1) Batching and melting: Batching is carried out in the following proportions: silicon 0.06%, iron 0.13%, copper 0.05%, manganese 0.50%, magnesium 1.53%, chromium 0.13%, zinc 4.61%, titanium 0.04%, zirconium 0.12%, with the balance being aluminum.

[0017] The batched components are added to the casting furnace for melting. During melting, an electromagnetic stirrer is activated to enhance agitation. The melting temperature is 745 °C. After melting, refining is performed using a sodium-free granular refining agent (composed of MgCl2: 44.59%, KCl: 54.82%, MgO: 0.238%). The refining temperature is 745 °C, the refining agent dosage is 1 kg / t.Al, and the refining time is 15 minutes. A W and Z type dual-tube refining process is used, with a bubble height below 80 mm. The refining tube is replaced every 7-8 minutes, and after replacement, it is thoroughly cleaned and coated with boron nitride.

[0018] (2) Slag removal: The stainless steel slag removal tool is cleaned and coated with boron nitride in the first 3 meters. The slag on the surface of the melt is removed. After the sample is taken again and the analysis is qualified, the converter is converted. The converter temperature is controlled at 745 ℃.

[0019] (3) Settling: The settling time is 60 min (from the end of slag removal to the opening of the plate), and electromagnetic stirring is prohibited.

[0020] (4) Refining: Spanish aluminum-titanium-boron wire was added at a rate of 1.2 kg / t.Al. After refining, degassing was performed at a speed of 430 r / min, using a two-stage filtration system with 40+70 ppi filter plates.

[0021] (5) Casting: The casting temperature is controlled at 700 ℃, and the hydrogen content is controlled below 0.15 ml / 100 g.Al. Tempering is performed at the end. The casting speed is 78 mm / min, and the water volume is about 3000 L.

[0022] (6) Extrusion: The cast bar is extruded with an extrusion pressure of 36 MN, an extrusion cylinder temperature of 440℃, a die temperature of 450℃, and a holding time of 10 hours. The bar is then held in a low-temperature furnace at 350℃ for ≤24 hours, and the outlet temperature is 500℃. The bar is then quenched online by air mist and aged artificially at 115℃ for 12 hours + 155℃ for 8 hours to obtain the final profile.

[0023] Example 2 A method for preparing a high-strength aluminum alloy for vehicle body materials includes the following steps: (1) Batching and melting: Batching is carried out in the following proportions: silicon 0.06%, iron 0.13%, copper 0.04%, manganese 0.51%, magnesium 1.48%, chromium 0.14%, zinc 4.58%, titanium 0.04%, zirconium 0.12%, with the balance being aluminum.

[0024] The batched components are added to a casting furnace for melting. During melting, an electromagnetic stirrer is activated to enhance agitation. The melting temperature is 750 °C. After melting, refining is performed using a sodium-free granular refining agent (composed of MgCl2: 44.59%, KCl: 54.82%, MgO: 0.238%). The refining temperature is 750 °C, the refining agent dosage is 1.2 kg / t.Al, and the refining time is 13 minutes. A W and Z-type dual-tube refining process is used, with a bubble height below 80 mm. The refining tube is replaced every 7-8 minutes, and after replacement, it is thoroughly cleaned and coated with boron nitride.

[0025] (2) Slag removal: The stainless steel slag removal tool is cleaned and coated with boron nitride in the first 3 meters. The slag on the surface of the melt is removed, and after the sample is taken and analyzed and found to be qualified, it is converted to a converter. The converter temperature is controlled at 750 ℃.

[0026] (3) Settling: The settling time is 50 min (from the end of slag removal to the opening of the plate), and electromagnetic stirring is prohibited.

[0027] (4) Refining: Spanish aluminum-titanium-boron wire was added at a rate of 1.2 kg / t.Al. After refining, degassing was performed at a speed of 450 r / min, and a two-stage filtration process was adopted using 40+70 ppi filter plates.

[0028] (5) Casting: The casting temperature is controlled at 705 ℃, and the hydrogen content is controlled below 0.15 ml / 100 g.Al. Tempering is performed at the end. The casting speed is 78 mm / min, and the water volume is about 3000 L.

[0029] (6) Extrusion: The cast bar is extruded with an extrusion pressure of 36 MN, an extrusion cylinder temperature of 445℃, a die temperature of 460℃, and a holding time of 10 hours. The bar is then held in a low-temperature furnace at 350℃ for ≤24 hours, and the outlet temperature is 500℃. The bar is then quenched online by air mist and artificially aged at 120℃ for 12 hours + 160℃ for 8 hours to finally obtain the profile.

[0030] Comparative Example 1 A method for preparing a high-strength aluminum alloy for vehicle body materials includes the following steps: (1) Batching and melting: Batching is carried out in the following proportions: silicon 0.08%, iron 0.38%, copper 0.05%, manganese 0.18%, magnesium 2.2%, chromium 0.10%, zinc 4.53%, titanium 0.05%, zirconium 0.26%, with the balance being aluminum.

[0031] The batched components are added to the casting furnace for melting. During melting, an electromagnetic stirrer is activated to enhance agitation. The melting temperature is 755 ℃. After melting, refining is performed using a sodium-free granular refining agent (composed of MgCl2: 44.59%, KCl: 54.82%, MgO: 0.238%). The refining temperature is 755 ℃, the refining agent dosage is 1.2 kg / t.Al, and the refining time is 15 minutes. A W and Z type dual-tube refining process is used, with a bubble height below 80 mm. The refining tube is replaced every 7-8 minutes, and after replacement, it is thoroughly cleaned and coated with boron nitride.

[0032] (2) Slag removal: The stainless steel slag removal tool is cleaned and coated with boron nitride in the first 3 meters. The slag on the surface of the melt is removed. After the sample is taken again and the analysis is qualified, the converter is converted. The converter temperature is controlled at 755 ℃.

[0033] (3) Settling: Settling time is 55 min (from the end of slag removal to the opening of the plate), and electromagnetic stirring is prohibited.

[0034] (4) Refining: Spanish aluminum-titanium-boron wire was added at a rate of 1.2 kg / t.Al. After refining, degassing was performed at a speed of 350 r / min, using a two-stage filtration system with 40+70 ppi filter plates.

[0035] (5) Casting: The casting temperature is controlled at 700 ℃, and the hydrogen content is controlled below 0.15 ml / 100 g.Al. Tempering is performed at the end. The casting speed is 88 mm / min, and the water volume is about 3000 L.

[0036] (6) Extrusion: The cast bar is extruded with an extrusion pressure of 36 MN, extrusion cylinder temperature of 450 ℃, die temperature of 430 ℃, heat preservation for 10 hours, low temperature furnace heat preservation of 350 ℃≤24 hours, outlet temperature of 500 ℃, air-cooled online quenching, artificial aging at 160 ℃×12 hours, and finally the profile is obtained.

[0037] Comparative Example 2 A method for preparing a high-strength aluminum alloy for vehicle body materials includes the following steps: (1) Batching and melting: Batching is carried out in the following proportions: silicon 1.2%, iron 0.18%, copper 0.04%, manganese 0.15%, magnesium 2.8%, chromium 0.15%, zinc 5.5%, titanium 0.05%, zirconium 0.12%, with the balance being aluminum.

[0038] The batched components are added to a casting furnace for melting. During melting, an electromagnetic stirrer is activated to enhance agitation. The melting temperature is 720 °C. After melting, refining is performed using a sodium-free granular refining agent (composed of MgCl2: 44.59%, KCl: 54.82%, MgO: 0.238%). The refining temperature is 720 °C, the refining agent dosage is 0.8 kg / t.Al, and the refining time is 15 minutes. A W and Z type dual-tube refining process is used, with a bubble height below 80 mm. The refining tube is replaced every 7-8 minutes, and after replacement, it is thoroughly cleaned and coated with boron nitride.

[0039] (2) Slag removal: The stainless steel slag removal tool is cleaned and coated with boron nitride in the first 3 meters. The slag on the surface of the melt is removed, and the sample is taken again for analysis. After passing the analysis, the melt is converted to a converter. The converter temperature is controlled at 720 ℃.

[0040] (3) Settling: Settling time is 50 min (from the end of slag removal to the opening of the plate), and electromagnetic stirring is prohibited.

[0041] (4) Refining: Spanish aluminum-titanium-boron wire was added at a rate of 1.2 kg / t.Al. After refining, degassing was performed at a speed of 460 r / min, and a two-stage filtration process was adopted using 40+70 ppi filter plates.

[0042] (5) Casting: The casting temperature is controlled at 700 ℃, and the hydrogen content is controlled below 0.15 ml / 100 g.Al. Tempering is performed at the end. The casting speed is 78 mm / min, and the water volume is about 3000 L.

[0043] (6) Extrusion: The cast bar is extruded with an extrusion pressure of 36 MN, extrusion cylinder temperature of 425 ℃, die temperature of 425 ℃, heat preservation for 14 hours, low temperature furnace heat preservation of 350 ℃≤24 hours, outlet temperature of 450 ℃, air-cooled online quenching, artificial aging at 100 ℃×8 hours + 140 ℃×12 hours, and finally the profile is obtained.

[0044] Comparative Example 3 The method described in patent CN112375949A is used to prepare a high-strength aluminum alloy for vehicle body materials, comprising the following steps: (1) Batching and melting: Batching is carried out in the following proportions: silicon: 0.30%, iron: 0.35%, copper: 0.08%, manganese: 0.32%, magnesium: 1.10%, chromium: 0.20%, zinc: 4.50%, titanium: 0.03%, zirconium: 0.15%, individual impurities ≤0.05%, total ≤0.15%, and the balance is Al.

[0045] The ingredients are added to the melting furnace and melted. During the melting process, the electromagnetic stirrer is turned on to enhance the stirring.

[0046] (2) Degassing and slag removal: A mixture of chlorine and argon is used to degas the aluminum alloy melt. The inertness of argon and the easy reaction of chlorine with liquid hydrogen are used to remove the liquid hydrogen in the melt. The buoyancy of the gas is used to float the impurities to the surface of the melt, and the slag remover is used to remove the impurities.

[0047] (3) Casting: The aluminum liquid filtered by the ceramic filter plate is used to obtain flat ingots with good surface quality by electromagnetic casting. (4) Hot rolling: A zoned heating ingot pusher furnace is used, which is divided into two furnace zones. The heating temperature of the first furnace zone is set at 480 ℃ and the heating temperature of the second furnace zone is set at 430 ℃. The ingot is held in the first furnace zone for 10 h and in the second furnace zone for 2 h. After the ingot is heated and held, it is subjected to multi-pass reciprocating rolling. The initial rolling temperature is 400 ℃, the intermediate billet thickness is 40 mm, the final rolling temperature is 320 ℃, and the final rolling thickness is 10 mm. The aluminum alloy coil is rolled after hot rolling, and the hot rolling deformation is 91%. (5) Cold rolling: The hot-rolled aluminum alloy is cold-rolled by a cold rolling mill to a thickness of 4.0 mm and a cold rolling deformation rate of >66.7%; (6) Solution quenching: The cold-rolled aluminum alloy coils are solution-treated on a continuous annealing line. Before solution treatment, the coils are degreased by alkaline washing to ensure surface quality. The solution temperature is 480℃, and the holding time is 240 s. Quenching is carried out by spraying. The tension leveling amount on the continuous annealing line is 1.0%. (8) Three-stage aging: The cross-cut aluminum alloy coils are subjected to three-stage aging treatment. The first stage is to raise the temperature from room temperature to 50°C at a rate of 60°C / h and hold for 2 hours. The second stage is to raise the temperature from 50°C to 100°C at a rate of 60°C / h and hold for 8 hours. The third stage is to raise the temperature from 100°C to 145°C at a rate of 40°C / h and hold for 10 hours.

[0048] Test case The profiles prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to performance testing, and the test results are shown in Table 1 below: Table 1 - Profile Performance Test Results

[0049] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. An aluminum alloy for high-strength vehicle body materials, characterized in that, The composition includes the following components by mass percentage: silicon ≤0.3%, iron ≤0.35%, copper ≤0.2%, manganese 0.2%~0.7%, magnesium 1.0%~2.0%, chromium ≤0.3%, zinc 4.0%~5.0%, titanium ≤0.2%, zirconium ≤0.25%, with the balance being aluminum.

2. A method for preparing a high-strength aluminum alloy for vehicle body materials as described in claim 1, characterized in that, Includes the following steps: (1) Batching and melting; (2) Slag removal; (3) Settling; (4) Refining; (5) Casting; (6) Extrusion.

3. The preparation method according to claim 2, characterized in that, The specific steps of step (1) are as follows: each component is added to the melting furnace for melting, and an electromagnetic stirrer is turned on to strengthen the stirring during the melting process. The melting temperature is 740 ℃~750℃.

4. The preparation method according to claim 3, characterized in that, After melting, the material is refined using a sodium-free granular refining agent from Pyrotech. The refining temperature is between 740 ℃ and 750 ℃, the amount of refining agent is 1±0.2 kg / t.Al, and the time is 15±2 minutes. A W and Z type dual-tube refining method is used, and the bubble height is below 80 mm.

5. The preparation method according to claim 4, characterized in that, Replace the refining tube every 7-8 minutes. After replacement, clean it thoroughly and apply boron nitride.

6. The preparation method according to claim 2, characterized in that, The specific steps of step (2) are as follows: the stainless steel slag removal tool is cleaned and boron nitride is applied to the first 3 meters. The slag on the surface of the melt is removed. After the sample analysis is qualified, the furnace is converted. The furnace temperature is controlled at 740 ℃~750 ℃.

7. The preparation method according to claim 2, characterized in that, The specific steps of step (3) are as follows: the standing time is 50 min ~ 60 min, and electromagnetic stirring is prohibited.

8. The preparation method according to claim 2, characterized in that, The specific steps of step (4) are as follows: Spanish aluminum-titanium-boron wire is added at a rate of 1.2 kg / t.Al; after refining, degassing is performed at a speed of 400~450 r / min, and a two-stage filtration is carried out using a 40+70 ppi filter plate.

9. The preparation method according to claim 2, characterized in that, The specific steps of step (5) are as follows: the casting head temperature is controlled at 700 ℃±5 ℃, the hydrogen content is controlled below 0.15 ml / 100 g.Al, and tempering is performed at the end; the casting speed is 78 mm / min and the water volume is 3000 L.

10. The preparation method according to claim 2, characterized in that, The specific steps of step (6) are as follows: the cast bar is extruded, the extrusion pressure of the extrusion press is 36 MN, the extrusion cylinder temperature is 435 ℃~ 445 ℃, the die temperature is 440 ℃~ 460 ℃, the temperature is held for 6~14 hours, the temperature is held in a low temperature furnace at 350 ℃≤24 hours, the outlet temperature is 470 ℃~ 500 ℃, the bar is quenched online by air mist, and artificially aged at 115±5 ℃×12 hours + 155±5 ℃×8 hours to finally obtain the profile.

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