A method for preparing aluminum alloy castings

Abstract

The present invention belongs to the field of aluminum alloy manufacturing, and specifically relates to a method for preparing an aluminum alloy casting. The method for preparing an aluminum alloy casting of the present invention comprises the following steps: low-pressure casting of an aluminum alloy melt; the aluminum alloy casting is composed of the following percentages of components: Si: 1.7-1.9wt%, Mg: 0.4-0.6wt%, Zn: 0.05-0.1wt%, Cu: 0.4-0.6wt%, Fe: 0.05-0.1wt%, B: 0.05-0.07wt%, Mn: 0.02-0.04wt% and Sr: 0.02-0.04wt%, and the remainder is Al and other inevitable impurities. The present invention not only ensures good mechanical properties and high electrical conductivity, but also makes the obtained aluminum alloy casting have good elongation, and can greatly shorten the production cycle and reduce production costs.

Description

Technical Field

[0001] The invention belongs to the field of aluminum alloy manufacturing, and specifically relates to a method for preparing an aluminum alloy casting. Background Art

[0002] In high-voltage switch products, there are a large number of aluminum alloy conductive or electrical connection parts with complex structures. At present, such parts are basically cast with ZL101A aluminum alloy. This alloy has good casting performance, low cost, small elastic coefficient, isotropic structure, medium-strength mechanical properties, and is suitable for mass production.

[0003] However, the conductivity of ZL101A aluminum alloy has not been significantly improved, and it is difficult to meet the development needs of high-voltage switches with large capacity, miniaturization and high conductivity. The conductivity of ZL101A aluminum alloy often needs to be controlled by heat treatment. At present, the conductivity of the conventional domestic cast aluminum alloy ZL101A after T6 (solid solution treatment + artificial aging) heat treatment is only 33-36% IACS (International Annealed Copper Standard), and after T7 (solid solution treatment + stabilization treatment) treatment, it can reach 45% IACS. However, the mechanical properties of ZL101A aluminum alloy after T6 heat treatment are relatively high, but after T7 heat treatment, the mechanical properties are greatly reduced compared with T6.

[0004] In addition, since the internal parts of high-voltage switch products are generally complex thin-walled cavity castings, they are prone to deformation during heat treatment and bubbles are easily generated on the surface of the castings, which leads to the scrapping of the castings. In addition, heat treatment equipment occupies a large area, is expensive, and has a long heat treatment cycle, resulting in high production and preparation costs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing an aluminum alloy casting, so as to solve the problems of long preparation cycle, complex process and high cost in the prior art aluminum alloy casting casting method.

[0006] In order to achieve the above purpose, the preparation method of the aluminum alloy casting of the present invention comprises the following steps: low-pressure casting of aluminum alloy melt; the aluminum alloy casting is composed of the following components in percentage: Si: 1.7-1.9wt%, Mg: 0.4-0.6wt%, Zn: 0.05-0.1wt%, Cu: 0.4-0.6wt%, Fe: 0.05-0.1wt%, B: 0.05-0.07wt%, Mn: 0.02-0.04wt% and Sr: 0.02-0.04wt%, and the balance is Al and other inevitable impurities.

[0007] The preparation method of the aluminum alloy casting of the present invention eliminates the heat treatment process with a long processing cycle and complicated process in the prior art, avoids the problem that thin-walled cavity castings are easily deformed during heat treatment, and bubbles are easily generated on the surface of the castings, which leads to the scrapping of the castings. After the raw materials are smelted, they are transferred to a holding furnace for low-pressure casting. While ensuring the conductive performance and mechanical strength of the castings, the present invention not only makes the aluminum alloy castings have good elongation, but also can greatly shorten the production cycle and reduce the production cost.

[0008] Preferably, before low-pressure casting, the mold temperature is preheated to 260-290° C. Preheating the mold can prevent the aluminum alloy melt from solidifying due to cooling during the casting process, resulting in defects such as molding difficulties and cracks in the casting, and can also prevent mold damage caused by drastic temperature changes.

[0009] Preferably, during the low-pressure casting process, the liquid raising pressure is 1.5-1.7Psi, and the liquid raising time is 5-7s; the filling pressure is 7-8Psi, and the filling time is 10-15s; the holding pressure is 20-24Psi, and the holding time is 80-100s. By controlling the pressure and time during the low-pressure casting process, it is ensured that the aluminum alloy melt can smoothly enter the mold and fully fill the entire mold, thereby improving the finished product rate of the casting molding.

[0010] Preferably, during the low-pressure casting process, the mold temperature is preheated to 260-290° C. before filling. Preheating the mold can prevent the aluminum alloy melt from solidifying due to cooling during the casting process, resulting in defects such as molding difficulties and cracks in the casting, and can also prevent mold damage caused by drastic temperature changes.

[0011] Preferably, during the low-pressure casting process, when the aluminum alloy melt is poured into the mold, the temperature of the aluminum alloy melt is controlled to be 710-730° C. After the casting is completed, the pressure in the holding furnace is released, the casting in the mold is taken out, and cooled to room temperature in the air.

[0012] Preferably, the aluminum alloy melt is obtained by the following steps: melting the raw materials and stirring them evenly, adding a refining agent and a modifier to react. Specifically, the raw materials are first heated to 740-750°C to melt, and then cooled to 710-730°C after the raw materials are melted and stirred evenly.

[0013] Furthermore, the reaction time after adding the refining agent and the modifier is 15-25 minutes. Among them, the refining agent used is a conventional refining agent, which can be homemade or a commercially available product, for example, HZ-WYJ smokeless refining agent produced by Huazhong Aluminum. In the present invention, strontium is selected as a modifier, which can refine the grains, combine with other elements (such as silicon, iron, copper, etc.) in the aluminum alloy melt to form dispersion strengthening, reduce its solid solubility in the alloy, and then improve the electrical conductivity and mechanical strength.

[0014] Further, the aluminum alloy casting has the following percentage components: Si: 1.8wt%, Mg: 0.5wt%, Zn: 0.1wt%, Cu: 0.5wt%, Fe: 0.1wt%, B: 0.06wt%, Mn: 0.03wt% and Sr: 0.04wt%, the balance is Al and other inevitable impurities. The raw materials are selected from industrial pure aluminum, AlSi50 master alloy, pure magnesium, pure zinc, AlCu50 master alloy, AlFe20 master alloy, AlB master alloy, AlMn master alloy and aluminum strontium master alloy.

[0015] Preferably, after low-pressure casting, the aluminum alloy casting may be machined and surface polished to improve the surface quality of the aluminum alloy casting so that the aluminum alloy casting can meet the use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of an aluminum alloy casting prepared in Example 1 of the present invention;

[0017] Figure 2 This is a metallographic structure diagram of the aluminum alloy casting prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described in detail below in conjunction with specific implementation methods.

[0019] 1. An embodiment of the method for preparing the aluminum alloy casting of the present invention is as follows:

[0020] Example 1

[0021] The composition and proportion of the aluminum alloy casting prepared in this embodiment are as follows: Si: 1.8wt%, Mg: 0.5wt%, Zn: 0.1wt%, Cu: 0.5wt%, Fe: 0.1wt%, B: 0.06wt%, Mn: 0.03wt% and Sr: 0.03wt%, and the balance is Al and other inevitable impurities. The structure of the aluminum alloy casting is shown in the figure. Figure 1 The low pressure casting method of this embodiment comprises the following steps:

[0022] (1) Industrial pure aluminum, AlSi50 master alloy, pure magnesium, pure zinc, AlCu50 master alloy, AlFe20 master alloy, AlB master alloy and AlMn master alloy are added into a melting furnace, and after evacuation, high-purity argon gas is filled in as a protective gas, and the temperature is raised to 745° C. to melt the raw materials, and then the temperature is lowered to 720° C. and stirred evenly.

[0023] (2) After stirring evenly, the melted raw materials are transferred into a ladle, and a refining agent and a modifier are added and stirred to fully react to obtain an aluminum alloy melt. The reaction time is 20 minutes, and then the aluminum alloy solution is transferred to a heat preservation furnace for heat preservation. Among them, the refining agent is HZ-WYJ smokeless refining agent produced by Huazhong Aluminum, and the amount of the refining agent added is 0.4% of the total mass of the raw materials. The modifier is Sr, and the raw materials used are aluminum strontium master alloys.

[0024] (3) Spray a layer of release agent on the mold surface and then preheat the mold to 280°C.

[0025] (4) Air is introduced into the holding furnace to pressurize the furnace, and the liquid lifting pressure is controlled to be 1.6 Psi for a duration of 6 seconds, so that the molten aluminum alloy flows into the mold through the lifting pipe; then the pressure is increased to 7.5 Psi to fill the mold for 13 seconds, so that the molten aluminum alloy fills the mold; then the pressure of the holding furnace is increased to 22 Psi within 2-5 seconds to maintain the pressure of the molten aluminum alloy in the mold for 100 seconds; the pressure in the holding furnace is released, the casting in the mold is taken out, and it is cooled to room temperature in the air; wherein, the temperature of the molten aluminum alloy is maintained at 720°C during the process of increasing pressure and flowing into the mold.

[0026] (5) The casting is machined and surface polished to obtain a finished product. The metallographic structure of the obtained aluminum alloy casting is shown in the figure below: Figure 2 shown.

[0027] Example 2

[0028] The composition and proportion of the aluminum alloy casting prepared in this embodiment are as follows: Si: 1.7wt%, Mg: 0.4wt%, Zn: 0.05wt%, Cu: 0.4wt%, Fe: 0.05wt%, B: 0.05wt%, Mn: 0.02wt% and Sr: 0.02wt%, and the balance is Al and other inevitable impurities. The low-pressure casting method of this embodiment includes the following steps:

[0029] (1) Industrial pure aluminum, AlSi50 master alloy, pure magnesium, pure zinc, AlCu50 master alloy, AlFe20 master alloy, AlB master alloy and AlMn master alloy are added into a melting furnace, and after evacuation, high-purity argon gas is filled in as a protective gas, and the temperature is raised to 740° C. to melt the raw materials, and then the temperature is lowered to 710° C. and stirred evenly.

[0030] (2) After stirring evenly, the melted raw materials are transferred into a ladle, and a refining agent and a modifier are added and stirred to fully react to obtain an aluminum alloy melt. The reaction time is 15 minutes, and then the aluminum alloy solution is transferred to a heat preservation furnace for heat preservation. Among them, the refining agent is HZ-WYJ smokeless refining agent produced by Huazhong Aluminum, and the amount of the refining agent added is 0.4% of the total mass of the raw materials. The modifier is Sr, and the raw materials used are aluminum strontium master alloys.

[0031] (3) Spray a layer of release agent on the mold surface and then preheat the mold to 260°C.

[0032] (4) Air is introduced into the holding furnace to pressurize the furnace, and the liquid lifting pressure is controlled to be 1.5 Psi for a duration of 7 seconds, so that the molten aluminum alloy flows into the mold through the lifting pipe; then the pressure is increased to 7 Psi to fill the mold, and the filling time is 15 seconds, so that the molten aluminum alloy fills the mold; then the pressure of the holding furnace is increased to 20 Psi within 2-5 seconds to maintain the pressure of the molten aluminum alloy in the mold for 100 seconds; the pressure in the holding furnace is released, the casting in the mold is taken out, and it is cooled to room temperature in the air; wherein, the temperature of the molten aluminum alloy is maintained at 710°C during the process of increasing pressure and flowing into the mold.

[0033] (5) The casting is machined and surface polished to obtain the finished product.

[0034] Example 3

[0035] The composition and proportion of the aluminum alloy casting prepared in this embodiment are as follows: Si: 1.9wt%, Mg: 0.6wt%, Zn: 0.1wt%, Cu: 0.6wt%, Fe: 0.1wt%, B: 0.07wt%, Mn: 0.04wt% and Sr: 0.04wt%, and the balance is Al and other inevitable impurities. The low-pressure casting method of this embodiment includes the following steps:

[0036] (1) Industrial pure aluminum, AlSi50 master alloy, pure magnesium, pure zinc, AlCu50 master alloy, AlFe20 master alloy, AlB master alloy and AlMn master alloy are added into a melting furnace, which is evacuated and filled with high-purity argon as a protective gas. The temperature is raised to 750° C. to melt the raw materials, and the raw materials are stirred evenly at a temperature of 730° C.

[0037] (2) After stirring evenly, the melted raw materials are transferred into a ladle, and a refining agent and a modifier are added and stirred to fully react to obtain an aluminum alloy melt. The reaction time is 25 minutes, and then the aluminum alloy solution is transferred to a heat preservation furnace for heat preservation. Among them, the refining agent is HZ-WYJ smokeless refining agent produced by Huazhong Aluminum, and the amount of the refining agent added is 0.4% of the total mass of the raw materials. The modifier is Sr, and the raw materials used are aluminum strontium master alloys.

[0038] (3) Spray a layer of release agent on the mold surface and then preheat the mold to 290°C.

[0039] (4) Air is introduced into the holding furnace to increase the pressure, and the liquid lifting pressure is controlled to be 1.7 Psi for a duration of 5 seconds, so that the aluminum alloy melt flows into the mold through the lifting pipe; then the pressure is increased to 8 Psi to fill the mold, and the filling time is 10 seconds, so that the aluminum alloy melt fills the mold; then the pressure of the holding furnace is increased to 24 Psi within 2-5 seconds to maintain the pressure of the aluminum alloy melt in the mold for 80 seconds; then the pressure in the holding furnace is released, the casting in the mold is taken out, and cooled to room temperature in air; wherein, the temperature of the aluminum alloy melt is maintained at 730°C during the process of increasing pressure and flowing into the mold.

[0040] (5) The casting is machined and surface polished to obtain the finished product.

[0041] 2. Comparison

[0042] Comparative Example 1

[0043] The composition and proportion of the aluminum alloy casting prepared in this comparative example are the same as those in Example 1. The casting method of this comparative example comprises the following steps:

[0044] (1) Industrial pure aluminum, AlSi50 master alloy, pure magnesium, pure zinc, AlCu50 master alloy, AlFe20 master alloy, AlB master alloy and AlMn master alloy are added into a melting furnace, and after evacuation, high-purity argon gas is filled in as a protective gas, and the temperature is raised to 745° C. to melt the raw materials, and then the temperature is lowered to 720° C. and stirred evenly.

[0045] (2) After stirring evenly, the melted raw materials are transferred into a ladle, and a refining agent and a modifier are added and stirred to fully react to obtain an aluminum alloy melt. The reaction time is 25 minutes, and then the aluminum alloy solution is transferred to a heat preservation furnace for heat preservation. Among them, the refining agent is HZ-WYJ smokeless refining agent produced by Huazhong Aluminum, and the amount of the refining agent added is 0.4% of the total mass of the raw materials. The modifier is Sr, and the raw materials used are aluminum strontium master alloys.

[0046] (3) Spray a layer of release agent on the mold surface and then preheat the mold to 290°C.

[0047] (4) Air is introduced into the holding furnace to pressurize the furnace, and the liquid lifting pressure is controlled to be 1.7 Psi for a duration of 5 s, so that the molten aluminum alloy flows into the mold through the lifting pipe; then the pressure is increased to 8 Psi to fill the mold for 10 s, so that the molten aluminum alloy fills the mold; then the pressure of the holding furnace is increased to 24 Psi within 2-5 s to maintain the pressure of the molten aluminum alloy in the mold for 80 s; the pressure in the holding furnace is released, the casting in the mold is taken out, and cooled to room temperature in air; wherein, the temperature of the molten aluminum alloy is maintained at 730°C during the process of increasing pressure and flowing into the mold.

[0048] (5) The aluminum alloy casting obtained in step (4) is subjected to solution treatment and aging treatment by adopting T6 heat treatment process: the solution treatment comprises: keeping the temperature at 525°C for 6 hours, and then quenching the aluminum alloy casting with cooling water and cooling it to 190°C; the aging treatment comprises: keeping the temperature at 190°C for 6 hours, and then cooling it to room temperature in air.

[0049] (6) The aluminum alloy casting after heat treatment is machined and surface polished to obtain a finished product.

[0050] 3. Experimental Examples

[0051] This experimental example is used to verify the electrical conductivity and mechanical properties of the aluminum alloy castings obtained in Examples 1-3 and Comparative Example 1, as follows:

[0052] Conductivity test: The conductivity of the aluminum alloy castings prepared in Examples 1-3 and Comparative Example 1 was tested using a Shanghai Leici portable conductivity meter DDS-11A.

[0053] Mechanical property test: According to GB / T 1173-1995-Casting Aluminum Alloys, the aluminum alloy castings prepared in Examples 1-3 and Comparative Example 1 were subjected to mechanical property tests.

[0054] The results are shown in Table 1:

[0055] Table 1

[0056]

[0057] The tensile strength and electrical conductivity requirements of aluminum alloy conductor castings are 180 MPa and 45%. It can be seen from the table that the aluminum alloy castings prepared by the method for preparing aluminum alloy castings according to the present invention not only have better elongation than comparative example 1 while ensuring good mechanical properties and high electrical conductivity, but also omit the heat treatment step, and the preparation method is simple and easy to control, greatly shortening the preparation cycle and reducing the preparation cost.

Claims

1. A method for preparing an aluminum alloy casting, characterized in that: The aluminum alloy melt is subjected to low-pressure casting; Aluminum alloy castings are composed of the following percentages Composition: Si: 1.7-1.9wt%, Mg: 0.4-0.6wt%, Zn: 0.05-0.1wt%, Cu: 0.4-0.6wt%, Fe: 0.05-0.1wt%, B: 0.05-0.07wt%, Mn: 0.02-0.04wt% and Sr: 0.02-0.04wt%, the balance is Al and other inevitable impurities; the aluminum alloy melt is obtained by the following steps: melting the raw materials and stirring them evenly, adding a refining agent and a modifier to react, first heating to 740-750℃ to melt the raw materials, and then heating the raw materials to molten aluminum. After melting, the temperature is lowered to 710-730℃ and stirred evenly; in the low-pressure casting process, the liquid rising pressure is 1.5-1.7psi, the liquid rising time is 5-7s, the filling pressure is 7-8psi, the filling time is 10-15s, the holding pressure is 20-24psi, and the holding time is 80-100s; in the low-pressure casting process, when the aluminum alloy melt is poured into the mold, the temperature of the aluminum alloy melt is controlled to be 710-730℃. After casting, the pressure in the holding furnace is released, the casting in the mold is taken out, cooled to room temperature in the air, and the casting is machined and surface polished to obtain the finished product.

2. The method for preparing an aluminum alloy casting according to claim 1, characterized in that: In the low pressure casting process, the mold temperature is preheated to 260-290°C before filling.

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