A refining agent for rare earth element-containing magnesium alloy and a preparation method thereof

Abstract

The present application relates to the field of light metal material metallurgy, and particularly relates to a refining agent for rare earth element-containing magnesium alloy and a preparation method thereof. The raw material of the refining agent for rare earth element-containing magnesium alloy comprises 5-20% of magnesium chloride, 15-35% of potassium chloride, 1-10% of sodium chloride, 15-40% of barium chloride and 10-25% of calcium fluoride in terms of mass percentage. The present application greatly reduces the content of MgCl2 which reacts with rare earth elements, in order to improve the deslagging effect, increase the proportion of barium salt as a sedimentation agent, and at the same time, increase the proportion of KCl, so as to ensure the characteristics of low melting point, low viscosity and good fluidity of the flux, reduce the surface tension of the whole flux system, and be beneficial to the adsorption of non-metallic inclusions in the magnesium melt by the flux, and at the same time, reduce the loss of rare earth elements to the minimum.

Description

Technical Field

[0001] This invention relates to the field of light metal materials metallurgy technology, and in particular to a refining agent and preparation method for magnesium alloys containing rare earth elements. Background Technology

[0002] Magnesium is a close-packed hexagonal crystal and belongs to the new generation of green and environmentally friendly light metals. Due to its reactive chemical properties, magnesium readily reacts with water and oxygen in the air, making it difficult to exist in its elemental form. During the smelting process of magnesium alloys, the presence of numerous non-metallic inclusions often reduces the alloy's mechanical properties and corrosion resistance. Therefore, refining processes are necessary during magnesium alloy smelting to remove harmful inclusions and ensure the alloy's performance. Currently, calcium flux (i.e., RJ-2# flux) is widely used as a refining agent for magnesium alloys. However, because RJ-2# flux contains a high content of MgCl2, during the smelting of rare earth magnesium alloys, MgCl2 reacts with reactive rare earth elements in the following reaction: 3MgCl2 + 2[RE] → 2RECl3 + 3Mg. This reaction generates corresponding rare earth chlorides, leading to a significant loss of rare earth elements.

[0003] Some researchers have also tried using fluxes containing little or no MgCl2 for refining. The results show that reducing the amount of MgCl2 leads to a poorer refining and impurity removal effect. Although it can ensure a good rare earth recovery rate, the alloy contains more inclusions and has a poorer quality.

[0004] Therefore, there is an urgent need to develop a flux specifically for the smelting of rare earth magnesium alloys, which can ensure good refining and impurity removal during the smelting process while also suppressing the loss of rare earth elements. Summary of the Invention

[0005] The purpose of this invention is to provide a refining agent and preparation method for magnesium alloys containing rare earth elements, so as to solve the problem that conventional fluxes currently used in the market are difficult to simultaneously ensure the loss of rare earth elements and the effective removal of harmful inclusions during refining.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is a refining agent for magnesium alloys containing rare earth elements. The raw materials, by mass percentage, include: 5-20% magnesium chloride (MgCl2), 15-35% potassium chloride (KCl), 1-10% sodium chloride (NaCl), 15-40% barium chloride (BaCl2), and 10-25% calcium fluoride (CaF2).

[0008] This invention significantly reduces the content of MgCl2 that reacts with rare earth elements. In order to improve the slag removal effect, the proportion of barium salt in the sludge settling agent is increased, and the proportion of KCl is also increased. This ensures that the flux has the characteristics of low melting point, low viscosity and good fluidity, thereby reducing the surface tension of the entire flux system. This is beneficial for the flux to adsorb non-metallic inclusions in the magnesium melt, while minimizing the loss of rare earth elements.

[0009] The addition of calcium fluoride mainly increases the density and viscosity of the flux, so that the magnesium fluoride produced by the reaction has a certain slag-forming ability on magnesium oxide.

[0010] In order to generate a low-melting-point salt mixture, the proportions of potassium chloride and sodium chloride should be controlled within the above range as much as possible, so that the proportions of the three components reach a certain range.

[0011] The second technical solution of the present invention is a method for preparing the above-mentioned refining agent for magnesium alloys containing rare earth elements, comprising the following steps:

[0012] Sodium chloride, potassium chloride, and magnesium chloride are mixed and melted according to mass percentages, then cast into blocks, crushed, and the resulting refining agent powder is obtained.

[0013] The refining agent powder is mixed evenly with barium chloride and calcium fluoride, and then dried to obtain the refining agent for the magnesium alloy containing rare earth elements.

[0014] The drying temperature is 150-200℃.

[0015] The drying process is further integrated with the workshop. The drying process used in the workshop is generally maintained at 150-200℃, and the time should not be too long, about 2 hours is sufficient. The drying temperature does not need to be too high to avoid changing the physicochemical properties of the flux and to avoid unnecessary waste of resources. Medium and low temperature treatment can ensure that the flux is heated and dehumidified evenly.

[0016] Furthermore, the temperature at which the mixture melts is 710-750°C.

[0017] Furthermore, the particle size of the pulverized material is 80-120 mesh.

[0018] The third technical solution of the present invention is a method for applying the above-mentioned refining agent for magnesium alloys containing rare earth elements, wherein the refining agent for magnesium alloys containing rare earth elements is added to magnesium liquid for refining, and then cast after refining is completed.

[0019] The refining agent for the rare earth element magnesium alloy is added each time an intermediate alloy is added. The amount of refining agent added each time is 1 / 3 to 1 / 2 of the total amount of refining agent added. The refining time for each addition of the refining agent is 10-20 minutes.

[0020] Furthermore, the magnesium liquid is a magnesium alloy melt containing rare earth elements; the temperature of the magnesium liquid is 720-750℃.

[0021] Furthermore, the amount of the refining agent added for magnesium alloys containing rare earth elements is 3-5% of the mass of the magnesium liquid.

[0022] Furthermore, after refining, a settling step is also included; specifically, the settling is performed until the surface of the molten magnesium exhibits a bright mirror-like finish.

[0023] The refining agent for magnesium alloys containing rare earth elements of this invention is applicable to the refining of various magnesium alloys containing rare earth elements, such as ZM6 rare earth magnesium alloy, ZM2 rare earth magnesium alloy, and WE43 rare earth magnesium alloy.

[0024] The present invention discloses the following technical effects:

[0025] The refining agent prepared in this invention has significant advantages over the commonly used RJ-2 flux on the market. This invention significantly reduces the proportion of MgCl2 additive in the flux, thus reducing the loss of rare earth elements during refining. It creates a low-melting-point salt mixture in the ternary system composed of MgCl2, KCl, and NaCl, and by appropriately increasing the proportion of KCl, the flux exhibits lower viscosity and better fluidity. To compensate for the poor slag removal effect caused by the low MgCl2 content, the proportion of BaCl2 is appropriately increased as a weighting agent in the flux. During refining, this allows non-metallic inclusions in the magnesium melt to adhere to the refining agent particles and settle to the bottom of the crucible under gravity. Using this refining agent can both suppress the loss of rare earth elements and ensure good refining and slag removal effects. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] Example 1

[0032] A refining agent for magnesium alloys containing rare earth elements, comprising (by mass percentage) 5% magnesium chloride (MgCl2), 25% potassium chloride (KCl), 5% sodium chloride (NaCl), 40% barium chloride (BaCl2) and 25% calcium fluoride (CaF2).

[0033] A method for preparing the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0034] The crucible is heated to 200°C, and sodium chloride, potassium chloride, and magnesium chloride are added sequentially. The mixture is then heated to 720°C until fully melted, stirred evenly, and cast into blocks. These blocks are then crushed and ball-milled until they are powdered to approximately 80 mesh, yielding refining agent powder. This refining agent powder is thoroughly mixed with barium chloride granules and calcium fluoride powder, stirred evenly, and dried to obtain a refining agent for magnesium alloys containing rare earth elements (hereinafter referred to as: refining agent). This mixture is then sealed in a closed container for later use.

[0035] One method for applying the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0036] The smelting process of rare earth magnesium alloys, taking ZM6 alloy as an example, is as follows: First, prepare the materials (including pure magnesium ingots, pure zinc ingots, various intermediate alloys, and flux), and check the crucible to ensure it is clean and free of impurities. Then, load the furnace for melting, adding 1.5% refining agent. At 720℃, introduce argon gas and stir for 10 minutes (8-12 minutes is technically equivalent to 10 minutes). When the temperature reaches 780℃, add magnesium-zirconium alloy, along with 1% refining agent, and continue refining for 10 minutes. Add zinc ingots and magnesium-neodymium alloy, along with 1.5% refining agent, controlling the refining temperature at 720℃, and continue refining for 20 minutes (the flux must be continuous and uniform during refining). After refining, let it stand for 10 minutes until the surface of the molten magnesium exhibits a bright mirror finish, then begin casting.

[0037] The above method was used for smelting ZM6 rare earth magnesium alloy, and the rare earth element Nd recovery rate reached 83%, while the impurity Fe element content was reduced to 0.0045%.

[0038] Example 2

[0039] A refining agent for magnesium alloys containing rare earth elements, comprising (by mass percentage) 10% magnesium chloride (MgCl2), 30% potassium chloride (KCl), 10% sodium chloride (NaCl), 25% barium chloride (BaCl2) and 25% calcium fluoride (CaF2).

[0040] A method for preparing the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0041] The crucible is heated to 200°C, and sodium chloride, potassium chloride, and magnesium chloride are added sequentially. The mixture is then heated to 730°C until fully melted, stirred evenly, and cast into blocks. These blocks are then crushed and ball-milled until they are powdered to approximately 100 mesh, yielding refining agent powder. This refining agent powder is thoroughly mixed with barium chloride granules and calcium fluoride powder, stirred evenly, and dried to obtain a refining agent for magnesium alloys containing rare earth elements (referred to as: refining agent). This mixture is then sealed in a closed container for later use.

[0042] One method for applying the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0043] The smelting process of rare earth magnesium alloys, taking ZM6 alloy as an example, is as follows: First, prepare the materials (including pure magnesium ingots, pure zinc ingots, various intermediate alloys, and flux), and check the crucible to ensure it is clean and free of impurities. Then, load the furnace for melting, adding 1.5% refining agent. At 720℃, introduce argon gas and stir for 10 minutes (8-12 minutes is technically equivalent to 10 minutes). When the temperature reaches 780℃, add magnesium-zirconium alloy, along with 1% refining agent, and continue refining for 10 minutes. Add zinc ingots and magnesium-neodymium alloy, along with 1.5% refining agent, controlling the refining temperature at 720℃, and continue refining for 20 minutes (the flux must be continuous and uniform during refining). After refining, let it stand for 10 minutes until the surface of the molten magnesium exhibits a bright mirror finish, then begin casting.

[0044] The above method was used for smelting ZM6 rare earth magnesium alloy, and the rare earth element Nd recovery rate reached 87%, while the impurity Fe element content was reduced to 0.0040%.

[0045] Example 3

[0046] A refining agent for magnesium alloys containing rare earth elements, comprising (by mass percentage) 8% magnesium chloride (MgCl2), 35% potassium chloride (KCl), 8% sodium chloride (NaCl), 30% barium chloride (BaCl2) and 19% calcium fluoride (CaF2).

[0047] A method for preparing the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0048] The crucible is heated to 300°C, and sodium chloride, potassium chloride, and magnesium chloride are added sequentially. The mixture is then heated to 740°C until fully melted, stirred evenly, and cast into blocks. These blocks are then crushed and ball-milled until they are powdered to approximately 120 mesh, yielding the refining agent powder. This refining agent powder is thoroughly mixed with barium chloride granules and calcium fluoride powder, stirred evenly, and dried to obtain the refining agent for magnesium alloys containing rare earth elements (hereinafter referred to as the refining agent). It is then stored in a sealed container for later use.

[0049] One method for applying the above-mentioned refining agent for magnesium alloys containing rare earth elements is as follows:

[0050] The smelting process of rare earth magnesium alloys, taking ZM6 alloy as an example, is as follows: First, prepare the materials (including pure magnesium ingots, pure zinc ingots, various intermediate alloys, and flux), and check the crucible to ensure it is clean and free of impurities. Then, load the furnace for melting, adding 1.5% refining agent. At 720℃, introduce argon gas and stir for 10 minutes (8-12 minutes is technically equivalent to 10 minutes). When the temperature reaches 780℃, add magnesium-zirconium alloy, along with 1% refining agent, and continue refining for 10 minutes. Add zinc ingots and magnesium-neodymium alloy, along with 1.5% refining agent, controlling the refining temperature at 720℃, and continue refining for 20 minutes (the flux must be continuous and uniform during refining). After refining, let it stand for 10 minutes until the surface of the molten magnesium exhibits a bright mirror finish, then begin casting.

[0051] The above method was used for smelting ZM6 rare earth magnesium alloy, and the rare earth element Nd recovery rate reached 92%, while the impurity Fe element content was reduced to 0.0036%.

[0052] When the refining agents of Examples 1-3 of this application are used to produce ZM2 rare earth magnesium alloy, the recovery rate of cerium (Ce) can reach 92%-96%, the content of impurity Si can be as low as 0.001-0.003%, and the content of Fe can be reduced to 0.0005-0.003%. When used to produce WE43 rare earth magnesium alloy, the recovery rates of yttrium (Y) and gadolinium (Gd) are both above 90%. The content of impurity Cu can be reduced to 0.0001-0.0005%, and the content of Fe can be reduced to 0.001-0.003%.

[0053] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a refining agent for magnesium alloys containing rare earth elements, characterized in that, The raw materials of the refining agent, by mass percentage, are: 5-10% magnesium chloride, 25-35% potassium chloride, 5-10% sodium chloride, 25-40% barium chloride and 19-25% calcium fluoride; The preparation method includes the following steps: Sodium chloride, potassium chloride, and magnesium chloride are mixed and melted according to mass percentages, then cast into blocks, crushed, and the resulting refining agent powder is obtained. The refining agent powder is mixed evenly with barium chloride and calcium fluoride, and then dried to obtain the refining agent for the magnesium alloy containing rare earth elements. The temperature at which the mixture is melted is 710-750°C; The particle size of the pulverized material is 80-120 mesh.

2. A method for applying the refining agent for magnesium alloys containing rare earth elements, prepared by the method of claim 1, characterized in that, The refining agent for magnesium alloys containing rare earth elements is added to the magnesium liquid for refining, and then the mixture is cast after refining.

3. The application method according to claim 2, characterized in that, The temperature of the magnesium liquid is 720-750°C.

4. The application method according to claim 2, characterized in that, The amount of the refining agent added to the magnesium alloy containing rare earth elements is 3-5% of the mass of the magnesium liquid.

5. The application method according to claim 2, characterized in that, The refining process includes a settling step; specifically, the settling is performed until the surface of the molten magnesium exhibits a bright, mirror-like finish.