A high-strength and high-plasticity permanent mold casting aluminum alloy and its preparation method

Abstract

The present invention relates to the technical field of non-ferrous metal alloys, and specifically to a high-strength and high-plasticity permanent mold casting aluminum alloy and a preparation method thereof. A high-strength and high-plasticity permanent mold casting aluminum alloy contains the following components in weight percentages: 1-1.4% Mg, 2.33-2.5% Si, 1.1-1.3% Cu, 0.5-0.7% Mn, 0-0.3% impurities, and the balance is Al; the addition weight ratio of Mg and Si is 0.4-0.6. The preparation method includes S1 preheating; S2 melting; S3 refining; S4 casting. The present invention solves the technical problem that the existing aluminum-magnesium-silicon series casting aluminum alloy cannot achieve both good casting performance and mechanical properties, and precious metals need to be used to improve the alloy performance, resulting in high production costs.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal alloys, in particular to a high-strength and high-plasticity metal mold casting aluminum alloy and a preparation method thereof. Background Art

[0002] Cast aluminum alloy is one of the most widely used lightweight structural materials, with low density, easy processing and other characteristics, and is widely used in the fields of transportation, aerospace, etc. Among them, Al-Mg-Si (aluminum-magnesium-silicon) cast aluminum alloy has become a hot spot in aluminum alloy research and application due to its medium-high strength, good formability and corrosion resistance, good weldability, easy coloring, good surface quality after baking, and can be strengthened by heat treatment.

[0003] In the prior art, a Chinese patent with publication number CN112813318A provides an aluminum alloy material for casting, which uses rare earth elements to refine the alloy crystal structure by adding an aluminum-titanium-boron master alloy, and / or one or two of an aluminum-strontium master alloy and an aluminum-zirconium master alloy during the melting and casting process, thereby improving the strength and toughness of the alloy.

[0004] However, the above-mentioned prior art still has the following technical problems: the use of precious metals such as titanium, strontium and zirconium, although it improves the performance of aluminum alloy to a certain extent, it greatly increases the production cost of aluminum alloy casting and is not suitable for industrialized aluminum alloy production and large-scale application. Summary of the invention

[0005] The present invention provides a high-strength and high-plasticity metal mold casting aluminum alloy and a preparation method thereof, which are used to solve the technical problem that the existing aluminum-magnesium-silicon series casting aluminum alloy cannot achieve both casting performance and mechanical properties, and needs to use precious metals to improve the alloy performance, resulting in high production costs.

[0006] The present application provides the following technical solution: a high-strength and high-plasticity metal mold casting aluminum alloy, comprising the following components in weight percentage: 1-1.4% Mg, 2.33-2.5% Si, 1.1-1.3% Cu, 0.5-0.7% Mn, 0-0.3% impurities, and the balance is Al; wherein the added weight ratio of Mg to Si is 0.4-0.6.

[0007] Beneficial effects of this program:

[0008] The inventors of the present application found in the research process that silicon in Al-Mg-Si aluminum alloy can improve the casting properties of aluminum alloy. However, after adding silicon to the aluminum alloy, eutectic silicon, primary silicon and Mg2Si are easily formed, and as the silicon content increases, the content and size of eutectic silicon and primary silicon also increase accordingly. Although the casting properties of the alloy are improved to a certain extent, the mechanical properties of the alloy are damaged.

[0009] Those skilled in the relevant art usually adopt the following two methods to solve the above problems: 1. Reduce the addition amount of silicon element (below 1 wt.%), so that the Mg / Si mass ratio is usually above 1.73, thereby avoiding the formation of primary silicon and eutectic silicon and affecting the mechanical properties of the aluminum alloy. However, this will result in the loss of the casting performance of the aluminum alloy. 2. Add precious metals such as titanium, strontium, zirconium or rare earth metals to refine the crystals of the alloy during the casting process and reduce the influence of eutectic silicon and primary silicon on the mechanical properties of the alloy. However, this will increase the production cost of the aluminum alloy and is not conducive to the industrial production and large-scale use of aluminum alloy materials.

[0010] The inventor of the present application found a new way in the research. Without adding precious metals and significantly reducing the addition amount of silicon element, the prepared alloy has both mechanical properties and casting performance. This solution controls the morphology, size and distribution of eutectic silicon, primary silicon and Mg2Si in the alloy by regulating the Mg / Si mass ratio and adding Cu element, inhibits the formation of coarse eutectic silicon and primary silicon, and prepares a new type of aluminum-magnesium-silicon-based cast aluminum alloy with good casting performance and high strength and high plasticity.

[0011] The functions of each element in the alloy of the present application are as follows: The Mg element balances the strength and plasticity of the alloy through solid solution strengthening and second-phase strengthening by forming compounds in the alloy; the Si element in the alloy can improve the mechanical properties of the alloy, and the casting performance of the alloy will be gradually improved with the increase of the Si content; the Mn element in the alloy can improve the performance of the alloy and form compounds with heavy metal elements such as Fe in the alloy to reduce the poisoning effect of the impurity element Fe; the Cu element in the alloy can change the precipitation sequence of the alloy, promote the precipitation kinetics and the growth of clusters, and promote the refinement and densification of the β″ phase.

[0012] The present application also includes a preparation method of a high-strength and high-plasticity metal mold casting aluminum alloy, comprising the following steps:

[0013] S1 Preheating: Preheat the combined mold and various raw materials used for melting respectively;

[0014] S2 Melting: Heat and melt the preheated various raw materials in sequence, and protect the melt during the melting process;

[0015] S3 Refining: After the raw materials are melted, first stir the melt to make the melting more uniform, then add a refining agent and heat up for refining. After refining, let it stand and cool, and skim off the scum;

[0016] S4 Casting: After the aluminum alloy melt is slightly cooled, pour the aluminum alloy melt into the preheated combined mold, and obtain an aluminum alloy ingot after cooling and solidifying to room temperature.

[0017] Further, the raw materials in S1 include aluminum materials, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-copper master alloy, and magnesium materials; the preheating temperature is 125 - 175°C, and the preheating time is 1.5 - 2.5 h.

[0018] Beneficial effects: Using master alloy synthesis can make refractory elements dissolve better in the melt, obtaining a metal material with uniform chemical composition and distribution. Preheating the raw materials and the mold can prevent the hot metal melt from causing thermal shock to the mold, resulting in premature thermal fatigue failure of the mold and shortening the service life of the mold. At the same time, it also avoids the loss of fluidity of the metal melt in the mold due to sudden cooling, causing the casting to not fill smoothly or even causing cracks on the surface of the casting.

[0019] Further, in the raw material melting steps of S2, the aluminum material is melted first, then the aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-copper master alloy are added and melted while raising the temperature, and finally the magnesium material is added and melted after cooling.

[0020] In this application, adding various raw materials in sequence can ensure sufficient melting of the raw materials and make the component raw materials mix evenly.

[0021] Further, the melting temperature of the aluminum material in S2 is 680 - 700°C; the melting temperatures of the aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-copper master alloy are 710 - 740°C; the melting temperature of the magnesium material is 680 - 700°C.

[0022] In this application, controlling the melting temperature of the raw materials can not only ensure the melting efficiency but also make the raw materials melt fully.

[0023] Further, the refining agent in S3 is hexachloroethane, and the addition amount is 0.3 - 0.7% of the total weight of the raw materials.

[0024] In this application, adding the refining agent can remove the impurity gases in the metal melt. At the same time, adding the refining agent can improve the mechanical properties and casting properties of the cast aluminum alloy. Excessive addition of the refining agent will generate toxic gases and pollute the environment during the preparation and production.

[0025] Further, the refining step of the refining agent in S3 is: using a hollow graphite rod to press the refining agent into about 2 / 3 of the liquid surface of the melt, and slowly rotating it clockwise evenly until the refining agent is completely dissolved.

[0026] In this application, using a hollow graphite rod to press the refining agent into the melt surface and slowly rotating it clockwise evenly can maintain stability and will not cause violent tumbling. At the same time, it can reduce the slag amount. During the refining process, the refining agent rotates and dissolves deep in the aluminum liquid, promoting the aggregation of fine impurities in the molten pool.

[0027] Further, in step S3, the refining temperature is 710 - 740 °C, the standing temperature is 700 - 720 °C, the standing time is 8 - 15 min; the dross skimming temperature is 680 - 700 °C.

[0028] In this application, the standing step can keep the composition of the metal melt unified, maintain a consistent environmental state for alloying elements before casting, and is conducive to improving the casting performance of the alloy.

[0029] Further, in step S4, the cooling and casting temperature of the aluminum alloy melt is 680 - 700 °C, and the cooling rate to room temperature is 8 - 30 °C / s.

[0030] In this application, controlling the cooling rate can improve the casting performance of the cast aluminum alloy. If the material cools too fast, the compounds in the alloy grow smaller, which will cause the surface of the alloy to grow rough and even cause problems such as casting failure.

[0031] Beneficial effects of this preparation method:

[0032] 1. Through the alloying casting method of the present invention, by controlling the reaction conditions, the refining agent and its addition amount, the morphology, size, and distribution of eutectic silicon, primary silicon, and Mg2Si in the alloy can be effectively controlled, the formation of coarse eutectic silicon and primary silicon can be inhibited, and a new type of aluminum - magnesium - silicon - based cast aluminum alloy with good casting performance and high strength and high plasticity can be prepared.

[0033] 2. In this application, by reducing the cooling rate, the solidification process time of the alloy becomes longer, the compounds in the alloy grow more fully, the size is larger, and the requirement for the fluidity of the alloy is relatively low, so the content of alloying elements in the alloy can be appropriately reduced. Description of the Drawings

[0034] Figure 1 It is the metallographic structure diagram of the cast aluminum alloy in Example 1 of the present invention;

[0035] Figure 2 It is the scanning electron microscope diagram of the cast aluminum alloy in Example 1 of the present invention;

[0036] Figure 3 It is the metallographic structure diagram of the cast aluminum alloy in Comparative Example 1 of the present invention;

[0037] Figure 4 It is the scanning electron microscope diagram of the cast aluminum alloy in Comparative Example 1 of the present invention. Detailed Embodiments

[0038] The following is a further detailed description through specific embodiments:

[0039] Example 1

[0040] In the aluminum alloy ingot of this embodiment, the weight percentage (wt.%) of each element is: 1.2% Mg, 2.4% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The microstructure diagram is shown in the attached figure. Figure 1 and 2 shown.

[0041] A method for preparing a high-strength and high-plasticity metal mold casting aluminum alloy in this embodiment comprises the following steps:

[0042] S1 Preheating: Preheat the combined mold and various raw materials used for smelting respectively;

[0043] Specifically, the modular mold was assembled, and then 2.0408 kg of aluminum material, 0.3 kg of aluminum silicon-20 master alloy, 0.075 kg of aluminum manganese-20 master alloy, 0.0542 kg of aluminum copper-60 master alloy and 0.03 kg of magnesium material were weighed and put into a box-type resistance furnace for preheating for 2 hours at a preheating temperature of 150° C. The above raw materials were purchased from Jiangsu Huaqi Aluminum Technology Co., Ltd.

[0044] S2 Melting: The preheated raw materials are heated and melted in sequence, and the melt is protected during the melting process;

[0045] Specifically, prepare a crucible resistance furnace for melting materials. First, evenly apply 4000 mesh graphite powder as a coating on the inner wall of the crucible to prevent the ingot from being difficult to demold. Open the crucible, dry the coating and keep the temperature, and add aluminum to melt. After the aluminum is melted, heat the crucible to 730°C, add aluminum-silicon intermediate alloy, aluminum-manganese intermediate alloy and aluminum-copper intermediate alloy in turn and stir until completely melted. After the intermediate alloy is completely melted, cool the crucible to 690°C and add magnesium to melt. During the melting process of magnesium, a hollow graphite rod is needed to press the magnesium into the melt to prevent the magnesium ingot from burning when it contacts the air on the surface of the melt.

[0046] S3 refining: after the raw materials are melted, refining agent is added and the temperature is raised for refining. After the refining is completed, the raw materials are allowed to stand and cool to remove the scum, and finally cooled to room temperature to obtain an aluminum alloy solution.

[0047] Specifically, after the magnesium material is melted, keep stirring and heat the crucible to 720°C, and add 0.02kg of hexachloroethane for refining. During the refining process, use a hollow graphite rod to press hexachloroethane into the aluminum alloy solution about 2 / 3 below the liquid surface and keep it rotating evenly and slowly clockwise, so that the hexachloroethane and the aluminum alloy solution can fully react to remove its impurities and gases. After refining for 2 minutes, lower the crucible temperature to 710°C and let it stand for 10 minutes to ensure the uniformity of the solution composition. After standing, lower the crucible temperature to 690°C and skim off the scum on the surface of the aluminum alloy solution.

[0048] S4 Casting: After the aluminum alloy melt is slightly cooled, the aluminum alloy melt is cast into a preheated combined mold, and an aluminum alloy ingot is obtained after cooling and solidifying to room temperature.

[0049] Specifically, when the aluminum alloy melt is cooled to 680 °C, the aluminum alloy melt is cast into the combined mold. Subsequently, the aluminum alloy melt is cooled to room temperature at a rate of 20 °C / s to obtain an aluminum alloy ingot.

[0050] Example 2

[0051] The difference between this example and Example 1 is that the weight fractions of Mg, Si, and Al in the aluminum alloy ingot are different. Specifically: 1% Mg, 2.6% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0052] Example 3

[0053] The difference between this example and Example 1 is that the weight fractions of Mg, Si, and Al in the aluminum alloy ingot are different. Specifically: 1.4% Mg, 2.2% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the weight fractions of Si and Al in the aluminum alloy ingot are different. Specifically: 1.2% Mg, 0.8% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. Its microstructure diagram is as shown in the appendix Figure 3 and 4 as shown. The weighed weights of the raw materials are adjusted accordingly.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the weight fractions of Si and Al in the aluminum alloy ingot are different. Specifically: 1.2% Mg, 0.48% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that the weight fractions of Si and Al in the aluminum alloy ingot are different. Specifically: 1.2% Mg, 1.2% Si, 1.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 lies in the different weight parts of Cu in the aluminum alloy ingot. Specifically: 1.2% Mg, 0.8% Si, 0.2% Cu, 0.6% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0062] Comparative Example 5

[0063] The difference between this comparative example and Example 1 lies in the different weight parts of Mn in the aluminum alloy ingot. Specifically: 1.2% Mg, 0.8% Si, 1.2% Cu, 0.2% Mn, the total amount of other impurities is less than or equal to 0.3%, and the balance is Al. The weighed weights of the raw materials are adjusted accordingly.

[0064] Comparative Example 6

[0065] The difference between this comparative example and Example 1 lies in the different cooling rates in Step S4. In this comparative example, the cooling rate is 50 °C / s.

[0066] Comparative Example 7

[0067] The difference between this comparative example and Example 1 lies in that the addition amount of the refining agent hexachloroethane is 0 kg.

[0068] The weight percentages of the components and other data of the above examples and comparative examples are all summarized and recorded in Table 1.

[0069] Table 1: Weight percentages of components and other data of examples and comparative examples

[0070]

[0071]

[0072] Experimental Example 1: Mechanical property test

[0073] This experimental example is used to test the mechanical properties of the permanent mold casting aluminum alloy prepared in the above examples and comparative examples. The specific steps are as follows:

[0074] S1: Tensile test: The sheet specimens for as-cast tensile test are cut from the bottom of the ingot and processed by wire electrical discharge machining. The specimens are tested on an MTS Exceed-E45 type electronic universal testing machine in accordance with the GB / T228-2002 standard, with a tensile speed of 0.5 mm / s, and the average value is determined by measuring 3 samples.

[0075] S2: Hardness Test: Conduct a hardness test on the specimen. First, grind the upper and lower surfaces of the specimen flat with 600# water sandpaper, then finely grind it successively with 800#, 1000#, 1200#, and 1500# water sandpaper, and then finely grind it successively with 2000# and 3000# metallographic sandpaper to make the upper and lower surfaces of the sample parallel and shiny. The hardness test uses a 450SVD Vickers hardness tester, with a load of 1 kg and a holding time of about 10 s. When conducting the hardness test, the test value is the average of 6 points to avoid errors caused by time.

[0076] Table 2: Mechanical Property Results of the Permanent Mold Casting Aluminum Alloys Prepared in the Above Examples and Comparative Examples

[0077]

[0078]

[0079] Experimental Example 2: Casting Property Test

[0080] This experimental example is used to test the casting properties of the permanent mold casting aluminum alloys prepared in the above examples and comparative examples. The specific steps are as follows: Preheat the test mold, the concentric spiral alloy fluidity measurement mold, to 150 °C, and pour the alloy melt cooled to 690 °C after refining in S4 into the mold to measure the casting properties of the alloy. The specific data is shown in Table 3 below.

[0081] Table 3: Casting Property Results of the Permanent Mold Casting Aluminum Alloys Prepared in the Above Examples and Comparative Examples

[0082]

[0083] From the experimental data in Table 2 and Table 3, it can be seen that the cast aluminum alloys prepared in Examples 1 to 3 show better performance in both mechanical properties and casting properties. Compared with the approximate cast aluminum alloys in "GB / T 1173-2013 Cast Aluminum Alloys", such as alloy codes ZL101 (R&F), ZL104 (R&F), and ZL111 (J&F), the cast aluminum alloys prepared in Examples 1 to 3 are higher than the standard in both tensile strength and hardness, and are even much higher than the standard value in elongation.

[0084] Compared with Example 1, in Comparative Examples 1 to 3, the addition amount of silicon is reduced, making the Mg / Si weight ratio 1.5, 2.5, and 1, which is similar to the Mg / Si weight ratio in the existing cast aluminum alloys. In the mechanical properties, the measured elongation rates are all lower, and correspondingly, in the casting properties, the secondary dendrite arm spacing and fluidity are lower than those in Example 1, which affects the casting properties of the aluminum alloy.

[0085] Compared with Example 1, the copper addition amount was reduced in Comparative Example 4. In terms of mechanical properties, the yield strength, tensile strength, and hardness all decreased in Comparative Example 4. In terms of casting properties, a relatively obvious decrease occurred in the fluidity of Comparative Example 4.

[0086] Compared with Example 1, the manganese addition amount was reduced in Comparative Example 5. In terms of mechanical properties, the yield strength, tensile strength, and hardness all decreased in Comparative Example 5. In terms of casting properties, a decrease occurred in the fluidity of Comparative Example 4.

[0087] Compared with Example 1, the cooling rate of the aluminum alloy in S4 was increased in Comparative Example 6. It can be seen from the data that increasing the cooling rate of the aluminum alloy led to a significant decrease in the casting properties of the aluminum alloy, which was not conducive to the casting of the aluminum alloy.

[0088] Compared with Example 1, the refining agent hexachloromethane was not added in Comparative Example 7. It can be seen from the data comparison in Table 2 that a significant decrease occurred in the mechanical properties of Comparative Example 7.

[0089] The above are only the embodiments of the present invention. The present invention is not limited to the fields involved in these embodiments. Common knowledge such as the specific structures and characteristics known in the solutions is not described in detail here. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A high-strength and high-plasticity permanent mold casting aluminum alloy, characterized in that: It contains the following components in weight percentages: 1-1.4% Mg, 2.33-2.5% Si, 1.1-1.3% Cu, 0.5-0.7% Mn, 0-0.3% impurities, and the balance is Al; the added weight ratio of Mg and Si is 0.4-0.

6.

2. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 1, characterized in that, It includes the following steps: S1 Preheating: Preheat the combined mold and various raw materials used for melting respectively. S2 Melting: Heat and melt the preheated various raw materials in sequence, and protect the melt during the melting process. S3 Refining: After the raw materials are melted, first stir the melt to make the melting more uniform, then add the refining agent and heat up for refining. After refining is completed, let it stand and cool, and skim off the dross. S4 Casting: After the aluminum alloy melt is slightly cooled, cast the aluminum alloy melt into the preheated combined mold. After cooling and solidifying to room temperature, an aluminum alloy ingot is obtained.

3. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 2, characterized in that: In S1, the raw materials include aluminum material, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-copper master alloy, and magnesium material; the preheating temperature is 125-175 °C, and the preheating time is 1.5-2.5 h.

4. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 3, wherein: In S2, the sequence of melting the raw materials is: first melt the aluminum material, then heat up and add the aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-copper master alloy to melt, and finally add the magnesium material to melt after cooling down.

5. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 4, characterized in that: In S2, the melting temperature of the aluminum material is 680-700 °C; the melting temperatures of the aluminum-silicon master alloy, aluminum-manganese master alloy, and aluminum-copper master alloy are 710-740 °C; the melting temperature of the magnesium material is 680-700 °C.

6. The preparation method of a high-strength and high-ductility permanent mold casting aluminum alloy according to claim 5, characterized in that: In S3, the refining agent is hexachloroethane, and the addition amount is 0.3-0.7% of the total weight of the raw materials.

7. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 5, characterized in that: In S3, the refining step of the refining agent is: Use a hollow graphite rod to press the refining agent about 2 / 3 below the melt surface, and rotate it clockwise evenly and slowly until the refining agent is completely dissolved.

8. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 7, characterized in that: In S3, the refining temperature is 710-740 °C, the standing temperature is 700-720 °C, the standing time is 8-15 min; the temperature for skimming off the dross is 680-700 °C.

9. The preparation method of a high-strength and high-plasticity permanent mold casting aluminum alloy according to claim 8, wherein: In S4, the cooling and casting temperature of the aluminum alloy melt is 680-700 °C, and the cooling rate to room temperature is 8-30 °C / s.

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