Process for reducing the yield strength ratio of an al-mg-si-cu-mn aluminum alloy

Abstract

The application discloses a process method for reducing the yield strength ratio of Al-Mg-Si-Cu-Mn aluminum alloy, and belongs to the technical field of metal alloys.The application can select a proper hot rolling temperature and a reduction amount according to alloy components, the hot rolling temperature is controlled in a range of 450-550 DEG C, the reduction amount is 1-3 mm each time, and the total reduction rate in the hot rolling stage is greater than or equal to 50%.The reduction amount is 1-3 mm each time in the cold rolling stage, and the total reduction rate in the cold rolling stage is less than or equal to 50%.After the cold rolling is completed, annealing is carried out at 150-200 DEG C, and finally the yield strength ratio of the Al-Mg-Si-Cu-Mn aluminum alloy is reduced.

Description

Technical Field

[0001] This invention belongs to the field of metal alloy technology and relates to a process method for reducing the yield strength ratio of Al-Mg-Si-Cu-Mn aluminum alloy. Technical Background

[0002] In recent years, with the continuous development of the automotive industry, especially the rapid rise of new energy vehicles, people's travel experiences have become more comfortable. However, new energy vehicles still face problems such as insufficient mileage, which restricts their development. To achieve longer mileage, vehicle lightweighting is essential. Aluminum alloys, with their high specific strength, good formability, excellent corrosion resistance, and recycling potential, are ideal candidates to replace heavier materials in automobiles. Among them, heat-treatable 6000 series aluminum alloys are widely used in automotive bodies due to their good formability, surface quality, and paint hardening properties. Al-Mg-Si-Cu-Mn alloys are often the first choice for 6000 series aluminum alloys used in vehicle bodies.

[0003] Automotive crash beams are a critical component of the front-end structure of a vehicle, requiring alloys with a low yield strength ratio to absorb energy generated during a collision. Therefore, this invention, based on an Al-Mg-Si-Cu-Mn alloy, utilizes a combination of hot and cold rolling processes, followed by annealing at a suitable temperature for a specific time, to design a method for reducing the alloy's yield strength ratio. This method is applicable to automotive crash beams and other front-end structures in automobiles. Summary of the Invention

[0004] The purpose of this invention is to provide a process for reducing the yield strength ratio of Al-Mg-Si-Cu-Mn aluminum alloys.

[0005] The mass percentage range of each constituent element in the Al-Mg-Si-Cu-Mn alloy of this invention is as follows: Mg (0.70wt%-1.60wt%), Si (0.80wt%-1.40wt%), Cu (0.70wt%-1.60wt%), and Mn (0.40wt%-0.60wt%). Small amounts of Er and Zr are added to prevent recrystallization and grain growth, with the following mass percentage ranges: Er (0.05wt%-0.15wt%) and Zr (0.05wt%-0.15wt%).

[0006] To achieve the above objectives, the process steps are as follows: casting → homogenization → hot rolling → solution treatment → cold rolling → annealing.

[0007] Specifically, the steps include the following:

[0008] (1) Casting: Alloy ingots were prepared by melting in graphite crucibles and casting in iron molds. The raw materials used were pure aluminum, pure magnesium and Al-Mn, Al-Cu, Al-Zr, Al-Si and Al-Er master alloys. Pure magnesium is prone to burn-off during the melting process, so 10% more was added. Pure magnesium was added 10 minutes before casting. The melting temperature was 780±10℃. After reaching the melting temperature, the temperature was held for 2 hours and then cast in iron molds to prepare the alloy.

[0009] (2) Homogenization: Select a suitable homogenization temperature according to the overheating temperature of the alloy. The homogenization temperature of the material used in this invention is 530-550℃, the heating time is 1-5h, and after reaching the specified temperature, it is held for 8-14h and cooled with the furnace. After cooling, the alloy is sawn and milled to obtain an alloy plate with a thickness of 15±5mm.

[0010] (3) Hot rolling: Hot rolling at 450-550℃, with a reduction of 1-3mm each time, and a total reduction rate of ≥50% during the hot rolling stage, preferably 70%;

[0011] (4) Solution treatment: After hot rolling, the hot-rolled plate is kept at 530-570℃ for 1-5 hours and then water-quenched.

[0012] (5) Cold rolling: The sheet metal is immediately cold rolled after water quenching. The reduction amount is 1-3 mm each time. The total reduction rate during the cold rolling stage is ≤50%, and a total reduction rate of 40% is better.

[0013] (6) Annealing: After cold rolling, anneal at 150-200℃. The annealing time depends on the material composition.

[0014] The advantages of this invention are that the process is simple and has few steps, which helps to reduce production time and thus reduce production costs. Attached Figure Description

[0015] Figure 1 #1 Alloy Room Temperature Tensile Stress-Strain Curve.

[0016] Figure 2 #2 Alloy Room Temperature Tensile Stress-Strain Curve.

[0017] Figure 3 #3 Alloy Room Temperature Tensile Stress-Strain Curve. Detailed Implementation

[0018] The feasibility of this process is illustrated below with actual test results, but the present invention is not limited to the following embodiments.

[0019] Example 1

[0020] 1. The raw materials used are pure aluminum, pure magnesium, and master alloys of Al-10Mn, Al-50Cu, Al-10Zr, Al-20Si, and Al-5Er. Pure magnesium is added 10 minutes before casting. Alloy #1 is smelted at 780℃ and held at that temperature for 2 hours. The measured composition values ​​of alloy #1 are shown in Table 1.

[0021] Table 1. Measured composition values ​​of alloy #1 (mass fraction %)

[0022] #1 0.88 1.12 1.01 0.48 0.092 0.10 Bal.

[0023] 2. The smelted ingot is homogenized at 540℃. The time to raise the temperature from room temperature to 540℃ is 3 hours, and the holding time is 12 hours. The ingot is then sawn and milled to obtain an alloy plate with a thickness of 15mm.

[0024] 3. Hot rolling at 500℃, with a reduction of 1mm each time, from 15mm to 5mm.

[0025] 4. Perform solution treatment by holding the hot-rolled sheet at 540℃ for 1 hour and then water quenching.

[0026] 5. After water quenching, cold rolling begins, from 5mm to 3mm, with a reduction of 1mm each time.

[0027] 6. Anneal the cold-rolled sheet at 175℃ for 30 minutes.

[0028] 7. Specific results are as follows Figure 1 As shown in Table 2.

[0029] Table 2. Tensile properties test of alloy #1 at room temperature (in accordance with GB / T 228.2-2015 standard)

[0030] #1 22 432 117 13.5

[0031] Example 2

[0032] 1. Alloy #2 was melted at 780℃ and held at that temperature for 2 hours. The measured composition values ​​of alloy #2 are shown in Table 3.

[0033] Table 3. Measured composition values ​​of alloy #2 (mass fraction %)

[0034] #2 1.54 0.95 0.98 0.50 0.086 0.11 Bal.

[0035] 2. The smelted ingot is homogenized at 540℃. The time to raise the temperature from room temperature to 540℃ is 3 hours, and the holding time is 12 hours. The ingot is then sawn and milled to obtain an alloy plate with a thickness of 15mm.

[0036] 3. Hot rolling at 500℃, with a reduction of 1mm each time, from 15mm to 5mm.

[0037] 4. Perform solution treatment by holding the hot-rolled sheet at 540℃ for 1 hour and then water quenching.

[0038] 5. After water quenching, cold rolling begins, from 5mm to 3mm, with a reduction of 1mm each time.

[0039] 6. Anneal the cold-rolled sheet at 175℃ for 30 minutes.

[0040] 7. Specific results are as follows Figure 2 As shown in Table 4.

[0041] Table 4. Tensile properties test of alloy #2 at room temperature (in accordance with GB / T 228.2-2015 standard)

[0042] #2 22 416 152 13.5

[0043] Example 3

[0044] 1. Alloy #3 was melted at 780℃ and held at that temperature for 2 hours. The measured composition values ​​of alloy #3 are shown in Table 5.

[0045] Table 5. Measured composition values ​​of alloy #3 (mass fraction %)

[0046] #3 0.91 1.08 1.46 0.48 0.082 0.070 Bal.

[0047] 2. The smelted ingot is homogenized at 540℃. The time to raise the temperature from room temperature to 540℃ is 3 hours, and the holding time is 12 hours. The ingot is then sawn and milled to obtain an alloy plate with a thickness of 15mm.

[0048] 3. Hot rolling at 500℃, with a reduction of 1mm each time, from 15mm to 5mm.

[0049] 4. Perform solution treatment by holding the hot-rolled sheet at 540℃ for 1 hour and then water quenching.

[0050] 5. After water quenching, cold rolling begins, from 5mm to 3mm, with a reduction of 1mm each time.

[0051] 6. Anneal the cold-rolled sheet at 175℃ for 30 minutes.

[0052] 7. Specific results are as follows Figure 3 As shown in Table 6.

[0053] Table 6. Room temperature tensile properties test of alloy #3 (in accordance with GB / T 228.2-2015 standard)

[0054] #3 22 444 124 14.5

[0055] The results above show that Al-Mg-Si-Cu-Mn alloys with different compositions exhibit low yield strength ratios after processing using this process. All equivalent changes and modifications made within the scope of the claims of this invention should be covered by this invention.

Claims

1. A method for reducing the yield strength ratio of Al-Mg-Si-Cu-Mn aluminum alloys, comprising the following steps: (1) Casting: Alloy ingots were prepared by melting in graphite crucibles and casting in iron molds. The raw materials used were pure aluminum, pure magnesium and Al-Mn, Al-Cu, Al-Zr, Al-Si and Al-Er master alloys. Pure magnesium is prone to burn-off during the melting process, so 10% more was added. Pure magnesium was added 10 minutes before casting. The melting temperature was 780±10℃. After reaching the melting temperature, the temperature was held for 2 hours. Then, the alloy was cast in iron molds. (2) Homogenization: Select a suitable homogenization temperature according to the overheating temperature of the alloy. The material homogenization temperature is 530-550℃, the heating time is 1-5h, and after reaching the specified temperature, hold for 8-14h and cool with the furnace. After cooling, saw the alloy and mill the surface to obtain an alloy plate with a thickness of 15±5mm. (3) Hot rolling: Hot rolling at 450-550℃, with a reduction of 1-3mm each time, and a total reduction rate of ≥50% in the hot rolling stage; (4) Solution treatment: After hot rolling, the hot-rolled plate is kept at 530-570℃ for 1-5 hours and then water-quenched; (5) Cold rolling: The sheet metal is immediately cold rolled after water quenching, with a reduction of 1-3 mm each time, and the total reduction rate during the cold rolling stage is ≤50%; (6) Annealing: After cold rolling, anneal at 150-200℃. The annealing time depends on the material composition. The mass percentage range of each constituent element in the Al-Mg-Si-Cu-Mn alloy is as follows: Mg 0.70wt%-1.60wt%, Si 0.80wt%-1.40wt%, Cu 0.70wt%-1.60wt%, and Mn 0.40wt%-0.60wt%. Small amounts of Er and Zr are added to prevent recrystallization and grain growth, with the following mass percentage ranges: Er 0.05wt%-0.15wt% and Zr 0.05wt%-0.15wt%.

2. The method according to claim 1, characterized in that, (3) Hot rolling: Total reduction rate is 70%.

3. The method according to claim 1, characterized in that, (5) Cold rolling: The total reduction rate is 40%.

4. An Al-Mg-Si-Cu-Mn aluminum alloy is prepared according to any one of claims 1-3.

5. The Al-Mg-Si-Cu-Mn aluminum alloy prepared according to any one of claims 1-3 is applied to the front-end structure of an automobile anti-collision beam.

Images