Preparation method of low-alloying high-conductivity medium-strength aluminum alloy

Abstract

The invention provides a preparation method of a low-alloying high-conductivity medium-strength aluminum alloy. The preparation method comprises the steps of burdening, casting, extruding, stretching treatment and two-stage aging treatment. The aluminum alloy with the electric conductivity exceeding 60% IACS (International Annealed Copper Standard) is obtained by adjusting the contents of Fe and Si elements in the aluminum alloy components, adding a trace element B, controlling the single stretching amount to be 1-1.5% in the stretching treatment process, carrying out primary aging treatment within 5 hours after profile extrusion is completed, promoting the elements to be separated out from a matrix, and carrying out secondary aging treatment within 1 year after the primary aging treatment, so that the aluminum alloy with the electric conductivity exceeding 60% IACS (International Annealed Copper Standard) is obtained. And meanwhile, the yield strength, the tensile strength and the elongation of the alloy can reach 110 MPa, 140 MPa and 25% or above correspondingly, a cast rod does not need to be subjected to homogenization treatment, carbon emission can be effectively reduced, and energy consumption is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy processing and relates to a method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy. Background Art

[0002] There are two main types of conductive aluminum alloys commonly used internationally: one is 1xxx series aluminum alloy, and the other is 6xxx series aluminum alloy. The conductivity of 1xxx series aluminum alloy can reach 60% IACS, but its strength is extremely low. 6xxx series aluminum alloy is a very important deformable aluminum alloy. Although its strength is improved, its conductivity is less than 50% IACS. The main reason is that the conductivity and tensile strength of aluminum alloy are related. Within a certain range, the conductivity and tensile strength of aluminum alloy restrict each other.

[0003] At present, in order to improve the electrical conductivity while ensuring the mechanical properties of aluminum alloys, complex processes or the addition of rare earth elements are usually used. However, the complexity of the process or the addition of rare earths will increase the production cost. Therefore, it is necessary to provide a low-alloyed, high-conductivity, medium-strength aluminum alloy. Summary of the invention

[0004] The present invention proposes a method for preparing a low-alloyed, high-conductivity and medium-strength aluminum alloy to solve the problems of high cost, high alloying, mutual restriction of conductivity and tensile strength in the existing conductive aluminum alloy production process.

[0005] The present invention provides a method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy, comprising the following steps:

[0006] S1. Ingredients: Prepare aluminum alloy raw materials according to the following weight ratios: Mg: 0.35-0.50%, Si: 0.25-0.44%, Fe: 0.10-0.15, B: 0.02-0.04%, (Mn+Cr+Ti+V)≤0.005%; total impurities: ≤0.03%, the balance is Al;

[0007] S2. Casting: The aluminum alloy raw material prepared in step S1 is placed in a smelting furnace for conventional semi-continuous casting to obtain a cast rod;

[0008] S3 extrusion: the round ingot obtained in step S2 is placed in an extrusion device for extrusion molding, and after extrusion, strong wind cooling is used to obtain an aluminum alloy profile;

[0009] S4. Stretching treatment: The aluminum alloy profile obtained in step S3 is subjected to stretching treatment to obtain a profile with uniform overall deformation and stable mechanical properties;

[0010] S5. Aging treatment: The profile after the stretching treatment described in step S4 is subjected to a double-stage aging treatment.

[0011] A preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy according to some embodiments of the present application. In step S1, it is characterized in that in step S1, Si = Si Mg2Si + Si Fe is controlled, and Mg / Si Mg2Si = 1.73, and 1 ≤ Fe / Si Fe ≤ 2.

[0012] Si Mg2Si represents the Si content required for the Mg2Si phase; Si Fe represents the Si content required for the SiFe phase; Si represents the sum of the Si content required for the Mg2Si phase and the Si content required for the SiFe phase.

[0013] By ensuring that Si = Si Mg2Si + Si Fe and Mg / Si Mg2Si = 1.73, the consumed Si Mg2Si can completely form a stable strengthening phase Mg2Si with Mg; the excessive Si can effectively eliminate the adverse effects of Fe on the aluminum alloy. It is necessary to strictly control 1 ≤ Fe / Si Fe ≤ 2. This is because when Fe / Si Fe < 1, Si cannot completely eliminate the adverse effects of the AlFe phase, and when Fe / Si Fe > 2, acicular β-Al 85 Fe 14 Si phases will be formed in the alloy, weakening the alloy properties. When 1 ≤ Fe / Si Fe ≤ 2, skeletal or flaky α-Al 12 Fe3Si phases can be optimally formed, and the alloy properties can reach the optimum.

[0014] A preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy according to some embodiments of the present application. In step S2, during melting and casting, after placing pure aluminum in a melting furnace and melting it into liquid aluminum alloy, Si and Mg are added. After complete melting, an Al-3%B master alloy is added. The melting temperature is 760 - 780 °C, and then semi-continuous casting is carried out. The casting temperature is 750 - 760 °C, and the casting speed is 40 - 65 mm / min to cast a casting rod.

[0015] A preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy according to some embodiments of the present application. In step S3, the extrusion die temperature is 440 - 450 °C, the heating temperature of the aluminum alloy casting rod is 480 - 500 °C, the extrusion speed is 4 - 6 m / min, and strong air cooling is used after extrusion.

[0016] According to a preparation method of a low-alloying high-conductivity medium-strength aluminum alloy according to some embodiments of the present application, in the step S4, the drawing amount of the drawing treatment is 3%-6%. Each drawing treatment is carried out in 3-5 times, the drawing amount each time is 1%-1.5%, and the interval between every two drawing treatments needs to be 10s-20s. Since a direct drawing treatment at one time will cause the aluminum alloy to have a springback phenomenon, resulting in insufficient deformation amount of the drawing treatment, and too short interval between every two times will cause inconsistent drawing amounts at different positions of the whole aluminum alloy, so the drawing treatment is carried out in 3-5 times and the interval between every two drawing treatments needs to be 10s-20s.

[0017] After the profile extrusion is completed, atomic clusters Cluster 1 will be formed in the alloy during natural parking, reducing the supersaturation of the alloy and resulting in a decrease in the number of precipitation phases and a decrease in strength during subsequent artificial aging. At the same time, the decrease in the number of precipitation phases means that fewer elements dissolved in the matrix will precipitate, which will lead to a decrease in conductivity. When the profile is subjected to drawing treatment, a large number of dislocations will be generated in the alloy, and these dislocations will prevent the formation of atomic clusters Cluster 1 in the alloy matrix during natural parking, thus preventing the phenomenon of reduction in the supersaturated solid solubility of the alloy. During subsequent artificial aging, more (Mg, Si) elements will precipitate from the alloy, improving the conductivity while increasing the strength.

[0018] According to a preparation method of a low-alloying high-conductivity medium-strength aluminum alloy according to some embodiments of the present application, in the step S5, the primary aging regime is (80-100)°C×(25-35) min, and the secondary aging regime is (190-220)°C×(3-7) h.

[0019] Primary aging treatment is carried out within 5 h after the profile extrusion is completed, which will form atomic clusters Cluster 2 in the alloy. The formation of atomic clusters Cluster 2 will inhibit the generation of atomic clusters Cluster 1, and at the same time, atomic clusters Cluster 2 can serve as the nucleation of the strengthening phase during subsequent artificial aging, improving the precipitation of elements from the matrix, thereby increasing the strength and conductivity. In addition, since the formation of atomic clusters Cluster 2 effectively inhibits atomic clusters Cluster 1, the time interval between primary aging and secondary aging can be as long as 1 year, providing sufficient time for the production plan.

[0020] According to a preparation method of a low-alloying high-conductivity medium-strength aluminum alloy according to some embodiments of the present application, in the step S5, the primary aging is carried out within 5 h after the profile extrusion is completed, and the time interval between the primary aging and the secondary aging does not exceed 1 year.

[0021] Beneficial effects: A preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy proposed by the present invention, by adjusting the Fe and Si contents, adding trace element B, simultaneously performing tensile treatment on the profile, and performing double-stage aging treatment on it, an aluminum alloy with a conductivity exceeding 60% IACS is obtained. At the same time, the yield strength, tensile strength, and elongation rate of the alloy can reach up to 120 MPa, 149 MPa, and more than 25% respectively. Pure aluminum scrap and 6-series aluminum alloy scrap are added during the melting and casting process, and the casting rod does not need to be homogenized, which can effectively reduce carbon emissions and energy consumption. The first-stage aging treatment is carried out within 5 hours after the profile extrusion is completed to promote the precipitation of elements from the matrix, thereby improving the alloy strength and conductivity. Specific embodiments

[0022] The following further describes the embodiments of the present invention in detail in conjunction with examples, comparative examples, and attached tables. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0023] Example 1. This example provides a preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy, including the following steps:

[0024] S1. Batching: Prepare aluminum alloy raw materials according to the following weight ratio: Mg: 0.35%, Si: 0.25%, Fe: 0.10%, B: 0.02%, (Mn + Cr + Ti + V): 0.004%; the total content of other impurity elements ≤ 0.03%; the balance is Al.

[0025] S2. Melting and casting: Use the conventional semi-continuous casting method. After melting pure aluminum into liquid aluminum alloy in a melting furnace, add Si and Mg, and after complete melting, add Al-3%B master alloy. Raise the temperature of the melting furnace to 760 °C, fully melt and stir evenly, degas and refine, then remove slag, and then perform semi-continuous casting. The casting temperature is 750 °C, and the casting speed is 40 mm / min.

[0026] S3. Extrusion: The extrusion die temperature is 440 °C, the heating temperature of the aluminum alloy casting rod is 480 °C, the extrusion speed is 4 m / min, and strong air cooling is used after extrusion.

[0027] S4. Tensile treatment is performed on the extruded aluminum alloy profile, and the tensile amount is 3%, which is divided into 3 times, with each tensile amount being 1%, and an interval of 10 s is required between every two tensile treatments.

[0028] S5. Double-stage aging treatment is performed on the profile after tensile treatment. First, perform first-stage aging at 80 °C for 35 min, and then perform second-stage aging at 190 °C for 7 h. The interval between double-stage aging is 30 days.

[0029] Example 2. This example provides a preparation method of a low-alloyed high-conductivity medium-strength aluminum alloy, including the following steps:

[0030] S1. Ingredients: Prepare aluminum alloy raw materials according to the following weight ratio: Mg: 0.50%, Si: 0.44%, Fe: 0.15%, B: 0.04%, (Mn + Cr + Ti + V): 0.002%; the total content of other impurity elements ≤ 0.03%; the balance is Al.

[0031] S2. Melting and casting: Use the conventional semi - continuous casting method. After melting pure aluminum into liquid aluminum alloy in a melting furnace, add Si and Mg. After complete melting, add Al - 3%B master alloy. Raise the temperature of the melting furnace to 780°C, fully melt and stir evenly. After degassing and refining, remove slag, and then perform semi - continuous casting. The casting temperature is 760°C and the casting speed is 65 mm / min.

[0032] S3. Extrusion: The temperature of the extrusion die is 450°C, the heating temperature of the aluminum alloy ingot is 500°C, the extrusion speed is 6 m / min, and strong air cooling is used after extrusion.

[0033] S4. Stretch the extruded aluminum alloy profile. The stretching amount is 6%, which is carried out in 5 times, with each stretching amount being 1.2%. The interval between every two stretching treatments is 20 s.

[0034] S5. Perform double - stage aging treatment on the stretched profile. First, perform primary aging at 100°C for 25 min, and then perform secondary aging at 220°C for 3 h. The interval between double - stage aging is 365 days.

[0035] Example 3. This example provides a method for preparing a low - alloyed high - conductivity medium - strength aluminum alloy, including the following steps:

[0036] S1. Ingredients: Prepare aluminum alloy raw materials according to the following weight ratio: Mg: 0.40%, Si: 0.35%, Fe: 0.12%, B: 0.03%, (Mn + Cr + Ti + V): 0.003%; the total content of other impurity elements ≤ 0.03%; the balance is Al.

[0037] S2. Melting and casting: Use the conventional semi - continuous casting method. After melting pure aluminum into liquid aluminum alloy in a melting furnace, add Si and Mg. After complete melting, add Al - 3%B master alloy. Raise the temperature of the melting furnace to 770°C, fully melt and stir evenly. After degassing and refining, remove slag, and then perform semi - continuous casting. The casting temperature is 755°C and the casting speed is 55 mm / min.

[0038] S3. Extrusion: The temperature of the extrusion die is 445°C, the heating temperature of the aluminum alloy ingot is 490°C, the extrusion speed is 5 m / min, and strong air cooling is used after extrusion.

[0039] S4. The aluminum alloy profile obtained by extrusion is stretched by 4% in 4 times, each time by 1%, and there is a 15s interval between each two stretching treatments.

[0040] S5. The stretched profile is subjected to a double-stage aging treatment, firstly a primary aging treatment at 90°C for 30 min, and then a secondary aging treatment at 200°C for 5 h, with an interval of 180 days between the two-stage aging treatments.

[0041] The following comparative examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0042] Comparative Example 1: This comparative example provides a method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy, comprising the following steps:

[0043] S1. Ingredients: Prepare aluminum alloy raw materials according to the following weight ratio: Mg: 0.40%, Si: 0.50%, Fe: 0.18%, B: 0.03%, (Mn+Cr+Ti+V): 0.003%; the total content of other impurity elements is ≤0.03%; the balance is Al.

[0044] S2. Melting and casting: conventional semi-continuous casting method is adopted. After pure aluminum is placed in a melting furnace and melted into liquid aluminum alloy, Si and Mg are added. After they are completely melted, Al-3% B master alloy is added. The temperature of the melting furnace is raised to 770°C. After fully melting, the mixture is stirred evenly. After degassing and refining, slag is removed and semi-continuous casting is performed. The casting temperature is 755°C and the casting speed is 55mm / min.

[0045] S3. Extrusion: The extrusion die temperature is 445°C, the heating temperature of the aluminum alloy cast rod is 490°C, the extrusion speed is 5m / min, and strong wind cooling is used after extrusion.

[0046] S4. The aluminum alloy profile obtained by extrusion is stretched by 4% in 4 times, each time by 1%, and there is a 15s interval between each two stretching treatments.

[0047] S5. The stretched profile is subjected to a double-stage aging treatment, firstly a primary aging treatment at 90°C for 30 min, and then a secondary aging treatment at 200°C for 5 h, with an interval of 180 days between the two-stage aging treatments.

[0048] Comparative Example 2: This comparative example provides a method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy, comprising the following steps:

[0049] S1. Ingredients: Prepare the aluminum alloy raw materials according to the following weight ratio: Mg: 0.40%, Si: 0.35%, Fe: 0.12%, B: 0.03%, (Mn + Cr + Ti + V): 0.003%; the total content of other impurity elements ≤ 0.03%; the balance is Al.

[0050] S2. Melting and casting: Use the conventional semi - continuous casting method. After melting pure aluminum into liquid aluminum alloy in a melting furnace, add Si and Mg. After complete melting, add Al - 3%B master alloy. Raise the temperature of the melting furnace to 770°C, stir evenly after full melting, degas and refine, then remove slag, and then carry out semi - continuous casting. The casting temperature is 755°C and the casting speed is 55 mm / min.

[0051] S3. Extrusion: The temperature of the extrusion die is 445°C, the heating temperature of the aluminum alloy ingot is 490°C, the extrusion speed is 5 m / min, and strong air cooling is used after extrusion.

[0052] S4. Stretch the extruded aluminum alloy profiles. The stretching amount is 2%, which is carried out in 2 times, with each stretching amount being 1%, and an interval of 5 s is required between every two stretching treatments.

[0053] S5. Carry out two - stage aging treatment on the stretched profiles. First, carry out primary aging at 90°C for 30 min, and then carry out secondary aging at 200°C for 5 h. The interval between the two - stage aging is 180 days.

[0054] Comparative Example 3. This comparative example provides a preparation method of a low - alloyed high - conductivity medium - strength aluminum alloy, including the following steps:

[0055] S1. Ingredients: Prepare the aluminum alloy raw materials according to the following weight ratio: Mg: 0.40%, Si: 0.35%, Fe: 0.12%, B: 0.03%, (Mn + Cr + Ti + V): 0.003%; the total content of other impurity elements ≤ 0.03%; the balance is Al.

[0056] S2. Melting and casting: Use the conventional semi - continuous casting method. After melting pure aluminum into liquid aluminum alloy in a melting furnace, add Si and Mg. After complete melting, add Al - 3%B master alloy. Raise the temperature of the melting furnace to 770°C, stir evenly after full melting, degas and refine, then remove slag, and then carry out semi - continuous casting. The casting temperature is 755°C and the casting speed is 55 mm / min.

[0057] S3. Extrusion: The temperature of the extrusion die is 445°C, the heating temperature of the aluminum alloy ingot is 490°C, the extrusion speed is 5 m / min, and strong air cooling is used after extrusion.

[0058] S4. Stretch the extruded aluminum alloy profiles. The stretching amount is 4%, which is carried out in 4 times, with each stretching amount being 1%. There is a 15 - second interval between every two stretching processes.

[0059] S5. Carry out aging treatment on the stretched profiles at 175 °C for 8 hours.

[0060] Test results of mechanical properties and electrical conductivity of examples and comparative examples

[0061]

[0062]

[0063] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed forms. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical applications, and to enable those of ordinary skill in the art to understand the invention so as to design various embodiments with various modifications suitable for specific purposes.

Claims

1. A method for preparing a low-alloyed, high-conductivity, medium-strength aluminum alloy, characterized in that: The steps include: S1. Ingredients: Prepare aluminum alloy raw materials according to the following weight ratios: Mg: 0.35-0.50%, Si: 0.25-0.44%, Fe: 0.10-0.15%, B: 0.02-0.04%, (Mn+Cr+Ti+V)≤0.005%; total impurities: ≤0.03%, the balance is Al; S2. Casting: The aluminum alloy raw material prepared in step S1 is placed in a melting furnace for semi-continuous casting to obtain an aluminum alloy round ingot; S3 extrusion: the round ingot obtained in step S2 is placed in an extrusion device for extrusion molding, and after extrusion, strong wind cooling is used to obtain an aluminum alloy profile; S4 stretching treatment: the aluminum alloy profile described in step S3 is stretched; S5. Aging treatment: The profile after the stretching treatment described in step S4 is subjected to a double-stage aging treatment.

2. The method for preparing a low-alloyed, high-conductivity, medium-strength aluminum alloy according to claim 1, characterized in that: In step S1, Si=Si Mg2Si +Si Fe ,Mg / Si Mg2Si =1.73, 1≤Fe / Si Fe ≤2.

3. The method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy according to claim 1, characterized in that: In the step S2, during the casting, pure aluminum is placed in a smelting furnace and melted into a liquid aluminum alloy, and then Si and Mg are added. After they are completely melted, Al-3% B intermediate alloy is added, and the melting temperature is 760-780°C. After that, semi-continuous casting is performed, the casting temperature is 750-760°C, and the casting speed is 40-65mm / min.

4. The method for preparing a low-alloyed high-conductivity medium-strength aluminum alloy according to claim 1, characterized in that: In the step S3, the extrusion die temperature is 440-450° C., the heating temperature of the aluminum alloy cast rod is 480-500° C., the extrusion speed is 4-6 m / min, and strong wind cooling is adopted after extrusion.

5. The method for preparing a low-alloyed, high-conductivity, medium-strength aluminum alloy according to claim 1, characterized in that: In step S4, the stretching treatment is performed in 3-5 times, and the total stretching amount is 3%-6%; the stretching amount each time is 1%-1.5%, and there is a 10s-20s interval between each two stretching treatments.

6. The method for preparing a low-alloyed, high-conductivity, medium-strength aluminum alloy according to claim 1, characterized in that: In step S5, the primary aging system is (80-100)°C×(25-35)min, and the secondary aging system is (190-220)°C×(3-7)h.

7. The method for preparing a low-alloyed, high-conductivity, medium-strength aluminum alloy according to claim 6, characterized in that: The primary aging is carried out within 5 hours after the profile extrusion is completed, and the interval between the primary aging and the secondary aging shall not exceed 1 year.

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