A method for improving the melt purification of magnesium alloy super large components in die casting

Abstract

The application discloses a melt purification method for improving the die casting defects of a magnesium alloy super-large component, which comprises the steps of smelting and refining the magnesium alloy before die casting, and the improvement point is that the magnesium alloy melt after the refining is filtered and purified by step-by-step precipitation, and then is input into a die casting mold for die casting. The application has the advantages of better improving the melt purity, improving the melt quality, reducing the gas content of the melt, and improving the die casting effect.

Description

Technical Field

[0001] This invention relates to the field of automotive magnesium alloy component casting technology, and in particular to a melt purification method for improving defects in the die casting of ultra-large magnesium alloy components. Background Technology

[0002] Magnesium alloys are the lightest metallic structural materials, with a density only 2 / 3 that of aluminum alloys and 1 / 4 that of steel. They are among the most promising lightweight metallic materials, and their large-scale application is of great strategic significance for energy conservation, emission reduction, and alleviating the shortage of metal mineral resources in my country. To achieve the strategic goals of "carbon peaking and carbon neutrality," the demand for lightweighting in both traditional and new energy vehicles is urgent. Magnesium alloys have enormous potential for automotive lightweighting, and their widespread application will contribute to achieving my country's dual-carbon goals. With the deepening of dual-carbon and energy conservation and emission reduction efforts, and the upgrading of materials and process equipment, small and medium-sized magnesium alloy parts are gradually shifting towards large and ultra-large sizes. Many key automotive magnesium alloy components are developing towards "ultra-large size," "structural integration," and "functional integration." The lightweighting effect of integrated ultra-large magnesium alloy components will be even more significant. The integrated molding technology for ultra-large magnesium alloy castings can greatly simplify the complex processes of multi-component production and connection, significantly improving component dimensional stability. This not only saves time and manufacturing costs but also reduces production line and labor costs, resulting in more obvious energy conservation and emission reduction benefits, and has become an important future development trend. The HDC8800-ton die-casting machine, currently the world's largest in mass production capacity, has successfully mass-produced large automotive aluminum alloy rear floor components.

[0003] In the integrated die-casting process of ultra-large magnesium alloy structural components, strict quality control of the die-cast products is crucial. Defects in such large die-cast products not only significantly increase production costs compared to smaller die-cast parts but also hinder the lightweight application of magnesium alloys. Therefore, controlling die-casting defects is extremely important. The occurrence of die-casting defects is closely related to the quality of the alloy melt during die-casting, such as purity and gas content. Low melt purity or excessive gas content can contribute to defects such as hot cracking, gas entrapment, and cold shuts during the die-casting process, ultimately affecting the yield of the die-cast products. Therefore, strict control of the melt quality during die-casting is necessary to reduce the occurrence of die-casting defects and improve the product yield.

[0004] In conventional magnesium alloy die-casting processes, when improved melt purity is required, a refining step is typically added after the magnesium alloy melting process. This involves adding a refining agent to the molten metal to react with impurities and cause them to precipitate and form slag. After refining and slag removal, the molten metal is then poured into the die-casting mold for die casting. This can improve melt purity and reduce die-casting defects. However, this method still has a relatively low effect on improving melt purity and limited effectiveness in improving die-casting defects. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to provide a melt purification method for improving the die casting defects of magnesium alloy ultra-large components, which can better improve melt purity, improve melt quality, reduce melt gas content and improve die casting effect.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A melt purification method for improving defects in die casting of ultra-large magnesium alloy components includes the steps of melting and refining the magnesium alloy before die casting. The method is characterized in that the refined magnesium alloy melt is filtered and purified by step-by-step precipitation before being fed into the die casting mold for die casting.

[0007] In this way, filtering and purifying the refined magnesium alloy molten metal through step-by-step precipitation before die casting effectively precipitates impurities and removes gases from the molten metal. This improves the quality and purity of the melt, reduces its gas content, and consequently reduces defects and increases the yield rate of die-cast products. Ultra-large components typically refer to die-cast components with a projected area greater than 2 square meters.

[0008] Furthermore, this method is carried out under a protective gas atmosphere, and the molten liquid is purified by stepwise precipitation in a closed environment. In this way, the protective gas can prevent the molten liquid from reacting with oxygen in the air for oxidation, and the gradual precipitation and purification in a closed environment can better facilitate the release of gas from the molten liquid.

[0009] Furthermore, the temperature during the filtration and step-by-step precipitation purification of the magnesium alloy melt is controlled within a range greater than the melt crystallization temperature but less than the smelting temperature. This is beneficial for controlling the melt's fluidity and subsequent die-casting.

[0010] Furthermore, this method relies on a magnesium alloy melt purification device, which includes an overall rectangular box-shaped outer shell. The inner cavity of the outer shell is sequentially divided into a melting chamber, a refining chamber, a dynamic settling chamber, and a discharge chamber by a horizontally arranged main partition from one end to the other. Each chamber is equipped with a heating module inside the outer shell. The upper end of the melting chamber is connected to a first protective gas inlet pipe and has a feeding port. A first connecting window is opened at the upper part of the main partition between the melting chamber and the refining chamber. A slag removal port is opened at the upper end of the refining chamber. A second connecting window is opened at the upper part of the main partition between the refining chamber and the dynamic settling chamber. The dynamic settling chamber is used to realize the step-by-step dynamic precipitation purification of the melt. A third connecting window is opened at the upper part of the main partition between the dynamic settling chamber and the discharge chamber. The upper end of the discharge chamber has a discharge port connected to a liquid discharge pipe.

[0011] In this device, before melting, a protective gas is first introduced. This protective gas permeates the inner cavity of the outer shell through all connecting windows, ensuring that each chamber is in a protective atmosphere. Then, the raw material is added into the melting chamber through the feeding port, and the heating module is activated for melting. After the first batch of raw material is melted, the molten metal in the melting chamber continuously enters the refining chamber. A refining solvent is added at the slag removal port at the top of the refining chamber to remove impurities. As raw material is continuously added to the melting chamber, the refined molten metal overflows from the refining chamber into the dynamic settling chamber, where it undergoes progressive dynamic sedimentation and purification. Finally, it enters the discharge chamber, and the purified molten metal is pumped out through the discharge pipe and sent to the die-casting device for die casting. Therefore, this device can separate the alloy smelting, slag removal, purification, and settling processes but concentrate them in the same device, making the entire process from smelting to die casting very smooth, the steps are simple, and it can significantly improve the quality of the melt, increase the purity of the melt, reduce the gas content of the melt, reduce defects in die-cast products, and increase the yield.

[0012] Furthermore, a second protective gas inlet pipe is also connected to the upper end of the refining chamber.

[0013] This allows for better gas protection during the refining and slag removal processes.

[0014] Furthermore, a filter screen is provided on the first connected window and / or the second connected window and / or the third connected window.

[0015] This allows for better filtration and purification of the melt. The filter screen used in this system is rectangular and replaceable.

[0016] Furthermore, a first short partition is provided downward on the upper surface of the smelting chamber near the first connecting window, with the lower end of the first short partition suspended and extending downward beyond the location of the first connecting window.

[0017] This avoids the material from entering the refining chamber directly through the first connecting window without being melted during the raw material feeding process.

[0018] Furthermore, a second short partition is provided downward on the upper surface of the refining chamber near the second connecting window, with the lower end of the second short partition suspended and extending downward beyond the location of the second connecting window.

[0019] This avoids the refining agent and slag material from directly entering the dynamic settling chamber through the second connecting window during the refining agent addition and slag removal processes.

[0020] Furthermore, the dynamic settling chamber is vertically arranged with multiple secondary baffles at intervals along the melt flow direction. Each secondary baffle divides the dynamic settling chamber into multiple small dynamic settling chambers, and each secondary baffle has a communication interface opened from low to high along the melt flow direction.

[0021] In this way, the secondary baffles divide the dynamic settling chamber into multiple secondary dynamic settling chambers along the melt flow direction. Since the connecting interfaces on the secondary baffles are arranged sequentially from low to high, impurities of different sizes and specific gravities can be gradually precipitated and purified during the horizontal flow of the melt. Larger and heavier impurities will precipitate first, while smaller and lighter impurities will precipitate later. This avoids interference between impurities of different sizes and specific gravities during precipitation, which is more conducive to the precipitation, separation, and purification of impurities, thus improving the melt purification effect. More importantly, the formation of impurities of different sizes and specific gravities is usually due to differences in their composition; therefore, this graded precipitation makes it easier to achieve subsequent classification and recycling of impurities.

[0022] Furthermore, the internal volume of each small dynamic settling chamber gradually increases along the direction of melt flow. This allows for a better fractional sedimentation separation effect, where larger and heavier impurities settle first, while smaller and lighter impurities settle later.

[0023] Furthermore, the secondary partitions are arranged diagonally in opposite directions, and the connecting interfaces on each secondary partition are located on the side adjacent to the next secondary partition.

[0024] This allows for a better extension of the melt's flow path within each small dynamic settling chamber in a smaller space, thus improving the sedimentation effect.

[0025] Furthermore, a removable top cover is provided on the top of the casing.

[0026] This allows for easy disassembly, facilitating the installation and cleaning of the device's internal cavity.

[0027] Furthermore, slag discharge ports are provided at the bottom of the smelting chamber, refining chamber, discharge chamber, and each small dynamic settling chamber.

[0028] This facilitates slag removal and also makes it easier to classify and recycle impurities separated by sedimentation.

[0029] In summary, the present invention has the advantages of improving melt purity, improving melt quality, and reducing melt gas content to improve die casting effect. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the magnesium alloy melt purification device used in the embodiments of the present invention.

[0031] Figure 2 for Figure 1 A cross-sectional schematic diagram. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to specific embodiments.

[0033] Example: A melt purification method for improving defects in die casting of ultra-large magnesium alloy components includes the steps of melting and refining the magnesium alloy before die casting. The method is characterized in that the refined magnesium alloy melt is filtered and purified by step-by-step precipitation before being fed into the die casting mold for die casting.

[0034] By filtering and purifying the refined magnesium alloy molten metal through step-by-step precipitation before die casting, impurities in the molten metal can be effectively precipitated and gases can be released. This improves the quality and purity of the melt, reduces its gas content, and consequently reduces defects in the die-cast products, increasing the yield rate.

[0035] In practice, this method is carried out under a protective gas atmosphere, and the molten liquid is purified through stepwise precipitation in a closed environment. In this way, the protective gas can prevent the molten liquid from reacting with oxygen in the air for oxidation, and the gradual precipitation and purification in a closed environment can better facilitate the release of gases from the molten liquid.

[0036] During implementation, the temperature for filtering and staged precipitation purification of the magnesium alloy melt is controlled within a range greater than the melt crystallization temperature but less than the smelting temperature. This facilitates the control of melt fluidity and subsequent die casting.

[0037] In practice, this method relies on a magnesium alloy melt purification device, which is described in [reference needed]. Figure 1 and Figure 2 Including the outer shell 12, which is in the shape of a rectangular box. Figure 1 The outer shell is made of transparent material to facilitate the display of the internal structure of the device. In specific implementation, the outer shell is made of high-temperature resistant alloy or ceramic material. The inner cavity of the outer shell is divided into a melting chamber 13, a refining chamber 15, a dynamic settling chamber 17, and a discharge chamber 19 by a horizontally arranged main partition 14 from one end to the other. Each chamber is equipped with a heating module inside the outer shell (not shown in the figure). The upper end of the melting chamber is connected to a first protective gas inlet pipe 1 and has a feeding port 3. The upper part of the main partition between the melting chamber 13 and the refining chamber 15 has a first connecting window 5. The upper end of the refining chamber 15 has a slag removal port 6. The upper part of the main partition between the refining chamber 15 and the dynamic settling chamber 17 has a second connecting window 8. The dynamic settling chamber is used to realize the step-by-step dynamic sedimentation and purification of the melt. The upper part of the main partition between the dynamic settling chamber 17 and the discharge chamber 19 has a third connecting window 10. The upper end of the discharge chamber has a discharge port 11 connected to the liquid discharge pipe.

[0038] In this device, before melting, a protective gas is first introduced. This protective gas permeates the inner cavity of the outer shell through all connecting windows, ensuring that each chamber is in a protective atmosphere. Then, the raw material is added into the melting chamber through the feeding port, and the heating module is activated for melting. After the first batch of raw material is melted, the molten metal in the melting chamber continuously enters the refining chamber. A refining solvent is added at the slag removal port at the top of the refining chamber to remove impurities. As raw material is continuously added to the melting chamber, the refined molten metal overflows from the refining chamber into the dynamic settling chamber, where it undergoes progressive dynamic sedimentation and purification. Finally, it enters the discharge chamber, and the purified molten metal is pumped out through the discharge pipe and sent to the die-casting device for die casting. Therefore, this device can separate the alloy smelting, slag removal, purification, and settling processes but concentrate them in the same device, making the entire process from smelting to die casting very smooth, the steps are simple, and it can significantly improve the quality of the melt, increase the purity of the melt, reduce the gas content of the melt, reduce defects in die-cast products, and increase the yield.

[0039] The upper end of the refining chamber 15 is also connected to a second protective gas inlet pipe 2.

[0040] This allows for better gas protection during the refining and slag removal processes.

[0041] A filter screen is provided on the first connecting window 5 and / or the second connecting window 8 and / or the third connecting window 10.

[0042] This allows for better filtration and purification of the melt. The filter screen used in this system is rectangular and replaceable.

[0043] Among them, a first short partition 4 is provided on the upper surface of the inner cavity of the melting chamber 13, near the first connecting window 5, with the lower end of the first short partition 4 suspended and extending downward beyond the position of the first connecting window.

[0044] This avoids the material from entering the refining chamber directly through the first connecting window without being melted during the raw material feeding process.

[0045] Among them, a second short partition 7 is provided on the upper surface of the refining chamber near the second connecting window, with the lower end of the second short partition 7 suspended and extending downward beyond the location of the second connecting window.

[0046] This avoids the refining agent and slag material from directly entering the dynamic settling chamber through the second connecting window during the refining agent addition and slag removal processes.

[0047] The dynamic settling chamber is provided with multiple secondary baffles 9 at intervals along the melt flow direction. Each secondary baffle 9 divides the dynamic settling chamber 17 into multiple small dynamic settling chambers. Each secondary baffle 9 has a connecting interface 16 opened from low to high along the melt flow direction.

[0048] In this way, the secondary baffles divide the dynamic settling chamber into multiple secondary dynamic settling chambers along the melt flow direction. Since the connecting interfaces on the secondary baffles are arranged sequentially from low to high, impurities of different sizes and specific gravities can be gradually precipitated and purified during the horizontal flow of the melt. Larger and heavier impurities will precipitate first, while smaller and lighter impurities will precipitate later. This avoids interference between impurities of different sizes and specific gravities during precipitation, which is more conducive to the precipitation, separation, and purification of impurities, thus improving the melt purification effect. More importantly, the formation of impurities of different sizes and specific gravities is usually due to differences in their composition; therefore, this graded precipitation makes it easier to achieve subsequent classification and recycling of impurities.

[0049] In this design, the internal volume of each small dynamic settling chamber gradually increases along the direction of melt flow. This allows for a better fractional sedimentation separation effect, where larger and heavier impurities settle first, while smaller and lighter impurities settle later.

[0050] The secondary partitions are arranged diagonally in opposite directions, and the connecting interface 16 on each secondary partition 9 is located on the side adjacent to the next secondary partition.

[0051] This allows for a better extension of the melt's flow path within each small dynamic settling chamber in a smaller space, thus improving the sedimentation effect.

[0052] The outer casing 12 has a removable top cover.

[0053] This allows for easy disassembly, facilitating the installation and cleaning of the device's internal cavity.

[0054] Each of the smelting chamber 13, refining chamber 15, discharge chamber 19, and each small dynamic settling chamber is equipped with a slag discharge port 18 at its bottom. During implementation, an external discharge pipe and switch valve are connected to the slag discharge port, which are not shown in the diagram.

[0055] This facilitates slag removal and also makes it easier to classify and recycle impurities separated by sedimentation.

Claims

1. A melt purification method for improving defects in die casting of ultra-large magnesium alloy components, comprising steps of melting and refining the magnesium alloy before die casting, characterized in that, After the refined magnesium alloy melt is filtered and purified by step-by-step sedimentation, it is then fed into the die-casting mold for die casting. This method relies on a magnesium alloy melt purification device, which includes a rectangular box-shaped outer shell. The inner cavity of the shell is divided into a melting chamber, a refining chamber, a dynamic settling chamber, and a discharge chamber by a horizontally arranged main partition. Each chamber has a corresponding heating module inside the outer shell. The melting chamber has a protective gas inlet pipe at its upper end and a feeding port. A first connecting window is located at the upper part of the main partition between the melting and refining chambers. A slag removal port is located at the upper end of the refining chamber. A second connecting window is located at the upper part of the main partition between the refining and dynamic settling chambers. The dynamic settling chamber is used to achieve step-by-step dynamic sedimentation purification of the melt. A third connecting window is located at the upper part of the main partition between the dynamic settling chamber and the discharge chamber. The discharge chamber has a discharge port connected to a liquid discharge pipe at its upper end. A second short partition is provided on the upper surface of the refining chamber near the second connecting window. The lower end of the second short partition is suspended and extends downward beyond the location of the second connecting window. The dynamic settling chamber is vertically arranged with multiple secondary baffles at intervals along the melt flow direction. Each secondary baffle divides the dynamic settling chamber into multiple small dynamic settling chambers. Each secondary baffle has a connecting interface from low to high along the melt flow direction, so that impurities of different specific gravities can be gradually precipitated and purified during the horizontal flow of the melt. Impurities with a higher specific gravity will precipitate first, and impurities with a lower specific gravity will precipitate later. The internal volume of each small dynamic settling chamber gradually increases along the direction of melt flow; each small dynamic settling chamber is equipped with a slag discharge port at the bottom. The secondary partitions are arranged diagonally in opposite directions, and the connecting interfaces on each secondary partition are located on the side adjacent to the next secondary partition.

2. The melt purification method for improving die-casting defects in ultra-large magnesium alloy components as described in claim 1, characterized in that, This method is carried out under a protective gas atmosphere and the melt is purified by stepwise precipitation in a closed environment.

3. The melt purification method for improving die-casting defects in ultra-large magnesium alloy components as described in claim 1, characterized in that, During the filtration and step-by-step precipitation purification of magnesium alloy melt, the temperature is controlled within a range greater than the melt crystallization temperature and less than the smelting temperature.

4. The melt purification method for improving die-casting defects in ultra-large magnesium alloy components as described in claim 1, characterized in that, A filter screen is provided on the first connected window and / or the second connected window and / or the third connected window.

5. The melt purification method for improving die-casting defects in ultra-large magnesium alloy components as described in claim 1, characterized in that, A first short partition is provided on the upper surface of the smelting chamber near the first connecting window, with the lower end of the first short partition suspended and extending downward beyond the location of the first connecting window.

6. The melt purification method for improving die-casting defects in ultra-large magnesium alloy components as described in claim 1, characterized in that, The top of the casing is equipped with a removable top cover; Slag discharge ports are provided at the bottom of the smelting chamber, refining chamber, and discharge chamber.

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