Method for removing impurity elements in molten metal and impurity element remover used in method

Abstract

The invention discloses a method for removing impurity elements in molten metal and an impurity element remover used in the method. The method for removing the impurity elements in the molten metal comprises the step that an impurity element remover makes contact with the molten metal, the impurity element remover comprises a base body and a membrane unit attached to the surface of the base body, and the membrane unit comprises a porous membrane structure composed of layered metal oxide. And the temperature of the impurity element remover is lower than that of the molten metal, so that impurity elements with the distribution coefficient K larger than 1 in the molten metal are segregated and solidified on the porous membrane structure of the impurity element remover. Through the porous membrane structure of the impurity element remover, impurity elements with the distribution coefficient K larger than 1 in the molten metal can be effectively removed.

Description

Technical Field

[0001] The present invention relates to a device and method for removing impurities, and in particular to a device and method for removing impurities from molten metal. Background Art

[0002] In directional solidification purification technology, the distribution relationship between the impurity elements in the liquid phase (metal melt) and the solidified phase (metal crystals segregated and solidified from the metal melt) can be understood by the distribution coefficient K (partition coefficient, or distribution coefficient). The distribution coefficient K of a certain impurity element is defined as: at temperature T, K = X S / X L , X S is the content of the impurity element in the solidified phase when the molten metal is cooled to T, X L It is the content of the impurity element in the liquid phase when the metal melt is cooled to T.

[0003] Taking the common trace impurity elements and their K values ​​existing in pure aluminum as an example, they are shown in the following table.

[0004] element K element K element K Ni 0.009 Ge 0.13 Sc 1.0 Co 0.02 Cu 0.15 Cr 2.0 Fe 0.03 Ag 0.2 Mo 2.0 Ca 0.08 Zn 0.4 Zr 2.5 Sb 0.09 Mg 0.5 V 3.7 Si 0.093 Mn 0.9 Ti 8.0

[0005] From the distribution coefficients of the above impurity elements, it is known that in aluminum melt, impurity elements with K less than 1 tend to segregate in the liquid phase, while on the contrary, impurity elements with K greater than 1 tend to segregate in the solidified phase. Therefore, when purifying with directional solidification purification technology, it is impossible to remove impurities with K less than 1 and K greater than 1 from the metal melt at the same time, especially impurity elements with K greater than 1, resulting in impurity elements with K>1 still contained in the solidified phase after purification. Summary of the invention

[0006] The first object of the present invention is to provide a method for removing impurity elements from molten metal that can solve the above-mentioned problems.

[0007] The method for removing impurity elements from a molten metal of the present invention comprises: providing an impurity element remover, which comprises a substrate and a membrane unit attached to the surface of the substrate, wherein the membrane unit comprises a porous membrane structure composed of a layered metal oxide; and contacting the impurity element remover with the molten metal, wherein the temperature of the impurity element remover is lower than the temperature of the molten metal, so that the impurity elements in the molten metal with a distribution coefficient K greater than 1 are segregated and solidified on the porous membrane structure of the impurity element remover.

[0008] The method for removing impurity elements from a molten metal of the present invention is to use the impurity element remover with a temperature range of 300°C to 500°C to contact the molten metal with a temperature range of 650°C to 750°C.

[0009] In the method for removing impurity elements from molten metal of the present invention, the time period during which the impurity element remover is in contact with the molten metal is in a range of 5 seconds to 2 minutes.

[0010] The method for removing impurity elements from molten metal of the present invention, the membrane unit of the impurity element remover also includes a dense membrane structure formed between the substrate and the porous membrane structure and composed of the layered metal oxide.

[0011] In the method for removing impurity elements from molten metal of the present invention, the layered metal oxide constituting the porous membrane structure and the dense membrane structure is selected from the group consisting of layered lithium aluminum oxide, layered aluminum oxide, layered zirconium oxide and any combination thereof.

[0012] The present invention provides a method for removing impurity elements from a metal melt. The layered lithium aluminum oxide includes α-LiAlO2 and LiAl5O8, and the porous membrane structure has a plurality of flakes formed by the layered lithium aluminum oxide, and a plurality of three-dimensional holes formed by staggered arrangement of the flakes.

[0013] The method for removing impurity elements from molten metal of the present invention, wherein the substrate of the impurity element remover is composed of a metal selected from aluminum, copper, magnesium, germanium and any combination thereof.

[0014] A second object of the present invention is to provide an impurity element remover that can solve the above-mentioned problems.

[0015] The impurity element remover of the present invention comprises a substrate and a membrane unit attached to the surface of the substrate, and the membrane unit comprises a porous membrane structure composed of a layered metal oxide.

[0016] The impurity element remover of the present invention, the membrane unit further comprises a dense membrane structure formed between the substrate and the porous membrane structure and composed of the layered metal oxide.

[0017] The impurity element remover of the present invention is composed of the layered metal oxide constituting the porous membrane structure and the dense membrane structure selected from the group consisting of layered lithium aluminum oxide, layered aluminum oxide, layered zirconium oxide and any combination thereof, and the matrix is ​​composed of a metal selected from aluminum, copper, magnesium, germanium and any combination thereof.

[0018] The beneficial effect of the present invention is that: through the porous membrane structure in the impurity element remover, and the temperature of the impurity element remover is lower than the temperature of the molten metal, the impurity elements with a distribution coefficient K greater than 1 in the molten metal are segregated and solidified in the porous membrane structure, so that the method for removing impurity elements in the molten metal can effectively remove the impurity elements with a distribution coefficient K greater than 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of an impurity element remover according to an embodiment of the present invention;

[0020] Figure 2 is a TEM photograph of a slice of the impurity element remover of the embodiment;

[0021] Figure 3 is a SEM photograph of the porous membrane structure in the impurity element remover of the embodiment;

[0022] Figure 4 is an XRD pattern of the slice of the impurity element remover of the embodiment;

[0023] Figure 5 is a SEM photograph of the layered metal hydroxide film in the precursor of the embodiment; and

[0024] Figure 6 is the XRD pattern of a slice of the precursor of the embodiment. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0026] The present invention will be further described with reference to the following examples, but it should be understood that the examples are merely illustrative and should not be construed as limitations of the present invention.

[0027] The present invention provides a method for removing impurity elements from a molten metal, in particular, removing impurity elements having a distribution coefficient K greater than 1; and provides an impurity element remover used in the method for removing impurity elements from a molten metal. The impurity element remover is first described in detail below, and then the method for removing impurity elements from a molten metal is described in detail.

[0028] See also Figure 1 The impurity element remover 1 of the present invention comprises a substrate 2 and a membrane unit 3 attached to the surface of the substrate 2. The membrane unit 3 comprises a porous membrane structure 31 composed of a layered metal oxide, and a dense membrane structure 32 formed between the substrate 2 and the porous membrane structure 31 and composed of the layered metal oxide.

[0029] The material constituting the substrate 2 is, for example, but not limited to, a metal such as aluminum, copper, magnesium or germanium, or graphite with a metal film formed of a metal such as aluminum, copper, magnesium or germanium coated on the outer surface. Preferably, the substrate 2 of the impurity element remover 1 is composed of a metal selected from aluminum, copper, magnesium, germanium and any combination thereof.

[0030] The layered metal oxide constituting the porous membrane structure 31 and the dense membrane structure 32 is, for example, but not limited to, layered lithium aluminum oxide, layered aluminum oxide, or layered zirconium oxide. Preferably, the layered metal oxide constituting the porous membrane structure 31 and the dense membrane structure 32 is selected from the group consisting of layered lithium aluminum oxide, layered aluminum oxide, layered zirconium oxide, and any combination thereof. The average pore size of the porous membrane structure 31 is in the range of 2 μm to 3 μm. The thickness of the porous membrane structure 31 is in the range of 450 nm to 500 nm.

[0031] In one embodiment of the present invention, the substrate 2 of the impurity element remover 1 is made of metal aluminum. The layered metal oxide constituting the porous membrane structure 31 and the dense membrane structure 32 is a layered lithium aluminum oxide, and the layered lithium aluminum oxide includes α-LiAlO2 and LiAl5O8. Figure 2 The TEM photo is a structure of a slice of the impurity element remover 1 analyzed using a transmission electron microscope (brand: JEOL, model: JEM-2100F). In the TEM photo, the bottom is the substrate 2 composed of metal aluminum, the top is the porous membrane structure 31 composed of the layered lithium aluminum oxide (thickness is 500nm), and between the two is the dense membrane structure 32 composed of the layered lithium aluminum oxide (thickness is 237nm). Figure 3 The SEM photo of the porous membrane structure 31 is obtained by analyzing the appearance of the porous membrane structure 31 using a scanning electron microscope (brand: JEOL, model: JSM-6700F). It can be seen that the porous membrane structure 31 has a plurality of flakes (the average width of the flakes is 0.3 μm and the average thickness is 40 nm), and a plurality of three-dimensional holes (the average pore size of the holes is 0.3 μm×0.3 μm) formed by the staggered arrangement of the flakes. Figure 4 The XRD spectrum is the result of analyzing the slice of the impurity element remover 1 using an X-ray diffractometer (brand: Bruker, model: D8 Advance ECO), and it can be seen that the membrane unit 3 is composed of α-LiAlO2 and LiAl5O8.

[0032] The impurity element remover 1 of the present invention is manufactured by a method comprising the following steps: (1) growing a layered metal hydroxide film on the surface of a substrate 2 to obtain a precursor; and (2) calcining the precursor to cause the layered metal hydroxide film to undergo a phase change to form a membrane unit 3 attached to the surface of the substrate 2. The substrate 2 and the membrane unit 3 are as described above and are not described in detail herein. The layered metal hydroxide film is composed of a layered metal hydroxide, such as but not limited to layered lithium aluminum hydroxide, layered aluminum hydroxide or layered zirconium hydroxide.

[0033] In the embodiment of the present invention, in the step (1), 1.2 g of lithium hydroxide (LiOH) is dissolved in 500 g of pure water to form a lithium ion aqueous solution, and then 0.39 g of aluminum is added to the lithium ion aqueous solution and stirred continuously until precipitation is produced and bubbles begin to be generated, and then stirring is stopped to obtain a lithium ion-aluminum ion aqueous solution, and then a pure aluminum rod (size 10 cm×1 cm×0.5 cm) is immersed in the lithium ion-aluminum ion aqueous solution as a cathode, and a platinum titanium mesh or a 316 stainless steel sheet is used as an anode to perform an electrodeposition method in an atmospheric environment to grow a layered metal hydroxide film composed of layered lithium aluminum hydroxide on the surface of the pure aluminum rod, so as to obtain a precursor. In step (2), after step (1), the precursor is calcined at 600°C in the atmosphere for 3 hours to cause the layered metal hydroxide film to undergo a phase change. See. Figure 5 The SEM photograph is obtained by analyzing the appearance of the layered metal hydroxide film using the scanning electron microscope; Figure 6 The XRD spectrum is the result of analyzing all the slices of the precursor using the X-ray diffractometer, Figure 6 "Li-Al-CO3 LDH" means the chemical formula is [LiAl2(OH)6](CO3) 1 / 2 1.5H2O layered lithium aluminum hydroxide, where CO3 is derived from CO2 in the atmosphere.

[0034] The method for removing impurity elements from a metal melt of the present invention comprises the following steps: contacting an impurity element remover 1 as described above with a metal melt, wherein the temperature of the impurity element remover 1 is lower than the temperature of the metal melt, so that the impurity elements in the metal melt with a distribution coefficient K greater than 1 diffuse to the surroundings of the impurity element remover 1, and then segregate and solidify on the porous membrane structure 31 of the impurity element remover 1.

[0035] The molten metal is, for example but not limited to, molten metal aluminum, molten metal copper, molten metal magnesium or molten metal germanium, etc. Also, for example but not limited to, the impurity element remover 1 with a temperature range of 300° C. to 500° C. contacts the molten metal with a temperature range of 650° C. to 750° C., and the impurity element remover 1 contacts the molten metal for a time range of 5 seconds to 2 minutes.

[0036] In the embodiment of the present invention, the impurity element remover 1 at 300°C is placed in a 670°C aluminum melt for 30 seconds. In order to verify the effect of the impurity element remover 1 in removing impurity elements with a distribution coefficient K greater than 1 in the embodiment, before the impurity element remover 1 is placed in the aluminum melt, an inductively coupled plasma mass spectrometer (ICP-MS, brand: Thermo, model: Element 2) is used to analyze the titanium element (Ti) content in the aluminum melt, and it is found that the titanium element content in the aluminum melt is 0.0106±0.0022%. In addition, after the impurity element remover 1 is placed in the aluminum melt for 30 seconds, a sample is taken from the aluminum melt and analyzed by the inductively coupled plasma mass spectrometer, and it is found that the titanium element content in the aluminum melt drops to <0.0002±0%, and the reduction rate of the titanium element content is as high as 98.11%.

[0037] It should be noted that the distribution coefficient K of titanium is as high as 8.0, which is much higher than other elements with a distribution coefficient K greater than 1. Therefore, being able to segregate and solidify titanium on the porous membrane structure 31 means that other elements with a distribution coefficient K greater than 1 can be segregated and solidified on the porous membrane structure 31. This proves that the present invention can indeed effectively remove impurity elements with a distribution coefficient K greater than 1 in the molten metal.

[0038] In summary, the present invention enables the method for removing impurity elements from molten metal to effectively remove impurity elements with a distribution coefficient K greater than 1 in the molten metal through the porous membrane structure 31 in the impurity element remover 1. In addition, the molten metal from which the impurity elements with a distribution coefficient K greater than 1 are removed by the method of the present invention can subsequently be subjected to a purification process known in the segregation solidification technology to remove impurity elements with a distribution coefficient K less than 1. Therefore, the purpose of the present invention can be truly achieved.

[0039] However, the above is only an embodiment of the present invention and should not be used to limit the scope of the present invention. All simple equivalent changes and modifications made according to the claims and description of the present invention are still within the scope of the present invention.

Claims

1. A method for removing impurity elements from molten metal, characterized in that Include: An impurity element remover is provided, comprising a substrate, and a membrane unit attached to a surface of the substrate, wherein the membrane unit comprises a porous membrane structure composed of a layered metal oxide; and The impurity element remover is contacted with the molten metal, and the temperature of the impurity element remover is lower than the temperature of the molten metal, so that the impurity elements with a distribution coefficient K greater than 1 in the molten metal are segregated and solidified on the porous membrane structure.

2. The method for removing impurity elements from molten metal according to claim 1, characterized in that: The impurity element remover at a temperature in the range of 300°C to 500°C contacts the molten metal at a temperature in the range of 650°C to 750°C.

3. The method for removing impurity elements from molten metal according to claim 1, characterized in that: The time period during which the impurity element remover is in contact with the molten metal ranges from 5 seconds to 2 minutes.

4. The method for removing impurity elements from molten metal according to claim 1, characterized in that: The membrane unit of the impurity element remover further includes a dense membrane structure formed between the substrate and the porous membrane structure and composed of the layered metal oxide.

5. The method for removing impurity elements from molten metal according to claim 4, characterized in that: The layered metal oxide constituting the porous membrane structure and the dense membrane structure is selected from the group consisting of layered lithium aluminum oxide, layered aluminum oxide, layered zirconium oxide and any combination thereof.

6. The method for removing impurity elements from molten metal according to claim 5, characterized in that: The layered lithium aluminum oxide includes α-LiAlO2 and LiAl5O8, and the porous membrane structure has a plurality of flakes formed by the layered lithium aluminum oxide and a plurality of three-dimensional holes formed by staggered arrangement of the flakes.

7. The method for removing impurity elements from molten metal according to claim 1, characterized in that: The substrate of the impurity element remover is made of a metal selected from aluminum, copper, magnesium, germanium and any combination thereof.

8. An impurity element remover, characterized in that Include: substrate; and The membrane unit is attached to the surface of the substrate and comprises a porous membrane structure composed of layered metal oxide.

9. The impurity element remover according to claim 8, characterized in that: The membrane unit further includes a dense membrane structure formed between the substrate and the porous membrane structure and composed of the layered metal oxide.

10. The impurity element remover according to claim 9, characterized in that: The layered metal oxide constituting the porous membrane structure and the dense membrane structure is selected from the group consisting of layered lithium aluminum oxide, layered aluminum oxide, layered zirconium oxide and any combination thereof, and the matrix is ​​composed of a metal selected from aluminum, copper, magnesium, germanium and any combination thereof.

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