Flux of magnesium-rare earth-zirconium magnesium alloy and composite refining process

Abstract

The invention discloses a flux of a magnesium-rare earth-zirconium magnesium alloy and a composite refining process, and particularly relates to the field of alloy smelting. Flux, magnesium ingots and foundry returns are added into a smelting container, and a first melt is obtained after furnace charge is smelted; a zinc ingot is added into the first melt, and a second melt is obtained after the zinc ingot is melted; adding hexachloroethane into the first melt, removing slag to obtain a third melt, and covering the liquid level of the third melt with a flux; adding rare earth elements into the third melt to obtain a fourth melt; a magnesium-zirconium intermediate alloy is added into the fourth melt, deslagging is conducted, a fifth melt is obtained, and the liquid level of the fifth melt is covered with a flux; the fifth melt is stirred, a flux is scattered on a liquid flow wave crest in the stirring process, deslagging and liquid surface covering with the flux are sequentially conducted, and a sixth melt is obtained; and the sixth melt is poured, and the magnesium-rare earth-zirconium magnesium alloy is obtained. Based on the process, the quality of the magnesium-rare earth-zirconium magnesium alloy can be improved.

Description

Technical Field

[0001] The present application relates to the field of alloy smelting, and in particular to a flux and a composite refining process for a magnesium-rare earth-zirconium series magnesium alloy. Background Art

[0002] Magnesium is a reactive metal. Without proper protection during the smelting process, molten magnesium reacts readily with atmospheric oxygen, moisture, and nitrogen, forming high-melting-point compounds such as magnesium oxide and magnesium nitride that are insoluble in the molten magnesium. These compounds eventually form inclusions in the casting, significantly reducing its mechanical properties. Fluxes are generally used to assist in the smelting of magnesium alloys. The primary functions of fluxes are coating and refining. During the smelting process, powdered solid flux is sprinkled onto the surface of the molten magnesium. Once melted, it forms a coating that insulates the molten magnesium from the atmosphere, preventing or minimizing the continued oxidation of the high-temperature molten magnesium. In the later stages of smelting, a bottom flux refining method is typically employed. By sprinkling powdered flux into the molten magnesium and stirring it thoroughly, the high-melting-point compounds in the molten magnesium dissolve in the flux or are adsorbed onto its surface. These compounds then settle to the bottom of the crucible along with the flux, purifying the molten magnesium.

[0003] MgCl2 is the primary component of conventional magnesium alloy fluxes. Molten MgCl2 has excellent adsorption capabilities for non-metallic inclusions such as MgO, Mg3N2, and SiO2 in the magnesium alloy melt, encapsulating them and transferring them into the flux, where they eventually sink to the bottom of the crucible. However, MgCl2 reacts with rare earth elements, resulting in the consumption of some rare earth elements.

[0004] The zirconium element in the magnesium-rare earth-zirconium magnesium alloy has a high melting point and needs to be added in the form of a magnesium-zirconium master alloy during smelting. When smelting the master alloy, high-melting-point by-products KF-MgF2 and KCl slag are produced. These slags are brought into the magnesium melt with the addition of the magnesium-zirconium master alloy, resulting in an increase in the content of impurities in the magnesium melt, making it more difficult to refine and purify the alloy; the high density of zirconium increases the viscosity of the magnesium melt, making inclusions easily suspended in the magnesium melt and difficult to sink, and the refining flux is also difficult to disperse in the magnesium melt, resulting in difficulty in slag-liquid separation, thereby reducing the quality of the magnesium-rare earth-zirconium magnesium alloy melt. Summary of the Invention

[0005] The main purpose of this application is to provide a flux and composite refining process for magnesium-rare earth-zirconium magnesium alloy, aiming to solve the problem of low quality of magnesium-rare earth-zirconium magnesium alloy melt obtained by existing alloy refining methods.

[0006] To achieve the above-mentioned purpose, the present application provides a composite refining process for magnesium-rare earth-zirconium series magnesium alloy, comprising: adding flux, magnesium ingot, and recycled material into a smelting container, and obtaining a first melt after the charge is melted; adding zinc ingot to the first melt at a temperature of 700°C-720°C, and obtaining a second melt after the zinc ingot is melted; adding hexachloroethane to the first melt at a temperature of 720°C-730°C, and performing slag removal to obtain a third melt, and covering the liquid surface of the third melt with flux; adding zinc ingot to the first melt at a temperature of 750°C-770°C, and performing slag removal to obtain a third melt; Rare earth elements are added to the third melt to obtain a fourth melt; at a temperature of 780°C-800°C, a magnesium-zirconium master alloy is added to the fourth melt, and slag is removed to obtain a fifth melt, and the liquid surface of the fifth melt is covered with flux; at a temperature of 760°C-780°C, the fifth melt is stirred, and flux is sprinkled on the liquid flow crest during the stirring process, and slag removal and liquid surface covering with flux are performed in sequence to obtain a sixth melt; at a temperature of 780°C-800°C, the sixth melt is cast to obtain a magnesium-rare earth-zirconium magnesium alloy.

[0007] Optionally, before pouring the sixth melt, the process further includes allowing the sixth melt to stand for 25 minutes to 30 minutes.

[0008] Optionally, during the stirring process, the mass of the flux sprinkled on the crest of the liquid flow is 1.0%-1.5% of the total weight of the charge.

[0009] Optionally, the mass of hexachloroethane is 2%-3% of the total weight of the charge.

[0010] Optionally, the mass of the recycled material is 55-60% of the total weight of the charge.

[0011] To achieve the above objectives, the present application also provides a flux for a magnesium-rare earth-zirconium magnesium alloy, the raw materials of which include the following components in terms of mass percentage: 18-26% magnesium chloride, 12-18% potassium chloride, 26-34% barium chloride, 12-18% sodium chloride, and 12-20% calcium fluoride, and the sum of the mass percentages of the above components is 100%.

[0012] To achieve the above-mentioned purpose, the present application also provides a method for preparing a flux of a magnesium-rare earth-zirconium magnesium alloy, which is characterized by comprising: placing magnesium chloride, potassium chloride, and sodium chloride in a reactor for melting according to the raw material composition; placing barium chloride in an iron box and baking it at a temperature of 120°C-150°C for 0.8-1.2 hours; adding the baked barium chloride to the reactor, and after the barium chloride is melted, keeping it boiling for 28-32 minutes, stirring it for 8 minutes-10 minutes, and pouring it into a mold to obtain a mixed solid; crushing the mixed solid and mixing it with calcium fluoride by ball milling to obtain a flux.

[0013] Compared with the prior art, the present invention has the following advantages: Through the primary refining, C2Cl6 is added to the melt to generate bubbles, so that hydrogen in the solution enters the bubbles. At the same time, inclusions are also adsorbed on the surface of the bubbles. After the bubbles float to the liquid surface, the hydrogen escapes into the atmosphere, and the inclusions float on the liquid surface to form slag and are removed, thereby reducing the hydrogen content in the melt, eliminating the inclusions brought in by the magnesium ingot and the master alloy itself, and the large amount of oxide inclusions generated by the solid-liquid phase transition, thereby reducing the consumption of rare earth elements; further secondary refining can remove the oxide inclusions generated in the process of adding rare earth and master alloy, as well as the high melting point slag brought in by the master alloy; the combination of primary refining and secondary refining can further improve the quality of magnesium-rare earth-zirconium magnesium alloy.

[0014] The flux of the present invention comprises potassium chloride, sodium chloride and magnesium chloride, and barium chloride is added to significantly increase the specific gravity difference between the flux and the melt, thereby facilitating the separation of the flux and the melt; calcium fluoride can react with the magnesium chloride in the flux to convert all of the calcium fluoride into magnesium fluoride, while the solubility of magnesium fluoride in chloride salts is very low and the solubility hardly changes with temperature; the appearance of insoluble solid magnesium fluoride particles increases the viscosity of the flux, thereby further ensuring the separation of the flux and the melt. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic flow chart of a composite refining process for a magnesium-rare earth-zirconium series magnesium alloy according to the present application.

[0016] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0018] The first embodiment of the present invention provides a composite refining process for magnesium-rare earth-zirconium series magnesium alloys, such as Figure 1 As shown, the specific steps include: Step S1, adding flux, magnesium ingot, and recycled materials into a smelting container, and obtaining a first melt after the materials are melted; wherein the mass of the recycled materials is 55-60% of the total weight of the materials.

[0019] Step S2, adding zinc ingots to the first melt at a temperature of 700° C. to 720° C., and melting the zinc ingots to obtain a second melt; Step S3, adding hexachloroethane to the first melt at a temperature of 720° C. to 730° C., and performing slag removal to obtain a third melt, and covering the liquid surface of the third melt with flux; wherein the mass of the hexachloroethane is 2% to 3% of the total weight of the charge.

[0020] Step S4, adding rare earth elements to the third melt at a temperature of 750° C. to 770° C. to obtain a fourth melt; Step S5, adding magnesium-zirconium master alloy to the fourth melt at a temperature of 780° C. to 800° C., and performing slag removal to obtain a fifth melt, and covering the liquid surface of the fifth melt with flux; It is worth noting that the recycled materials involved in this embodiment generally refer to metal materials such as risers, pouring nozzles, and unqualified castings produced during the casting production process that can be re-smelted and reused. The recycled materials are divided into first, second, and third grades. Castings with unqualified dimensions and clean risers are first-grade and can be directly used for batching. Second and third-grade recycled materials need to be remelted and analyzed for chemical composition before they can be used for batching. The recycled materials used in batching require that their material grade is the same as the alloy grade to be smelted. Due to the high impurity content in the recycled materials, the usage ratio must be strictly controlled. Too high a content may cause fluctuations in the chemical composition of the alloy, and the usage should be controlled at less than 60%.

[0021] Understandably, since the production of raw materials such as magnesium ingots and recycled materials all undergoes a melting process, inclusions such as magnesium oxide are unavoidable. Once the ingots and recycled materials are added to the crucible, the flux does not fully cover the solid charge, and as a result, a large number of oxide inclusions inevitably form during the solid-liquid transition. Furthermore, magnesium alloys absorb significant amounts of gases during the smelting process, primarily hydrogen, due to its high solubility in magnesium alloy melts. At 730°C, the solubility of hydrogen is approximately 30 mL / 100 g, several dozen times that of aluminum alloys. For magnesium-rare earth-zirconium alloys, the hydrogen in the melt reacts with the rare earth elements, consuming them.

[0022] To address the above issues, the present application performs primary refining through steps S1-5. Gas is introduced into the melt (or chemicals are added to the melt to generate gas) to generate bubbles. Hydrogen in the melt enters the bubbles, and inclusions are adsorbed on the bubble surfaces. After the bubbles float to the surface, hydrogen escapes into the atmosphere, while inclusions float to the surface to form slag, which is removed. The specific reaction formula is: C2Cl6→2C+3Cl 2↑ Mg + Cl2 → MgCl2 2[H] + Cl2→2HCl ↑ The Cl₂ produced by this reaction is a reactive gas that does not dissolve in the magnesium melt, forming numerous bubbles within the melt. Because the hydrogen partial pressure within the Cl₂ bubbles is zero, hydrogen dissolved in the magnesium melt continuously enters the bubbles. Upon surfacing, the bubbles carry away hydrogen from the melt and inclusions on the bubble surface. The HCl produced by the reaction, a gaseous product, does not dissolve in the melt, escaping to the melt surface, further purifying the melt.

[0023] In this embodiment, the first-stage flotation refining process reduces the hydrogen content in the melt, eliminating inclusions introduced by the magnesium ingot and master alloy, as well as a large number of oxide inclusions generated by solid-liquid phase transition. This reduced hydrogen content reduces the extent of subsequent reaction between rare earth elements and hydrogen, thereby reducing rare earth element consumption. The pre-emptive removal of oxide inclusions also reduces flux consumption during the second-stage refining process, minimizing the amount of MgCl2 introduced into the melt by the flux and, consequently, reducing rare earth element consumption caused by reactions between rare earth elements and MgCl2.

[0024] Step S6, stirring the fifth melt at a temperature of 760°C-780°C, and during the stirring process, sprinkle a flux with a mass of 1.0%-1.5% of the total weight of the charge on the liquid flow crest, and then remove the slag and cover the liquid surface with the flux in sequence to obtain a sixth melt; specifically, during stirring, use a stirring spoon to penetrate 2 / 3 of the melt into a depth, and stir for 3 minutes to 10 minutes.

[0025] Step S7, when the temperature is 780° C.-800° C., stand for 25 min-30 min, and cast the sixth melt to obtain a magnesium-rare earth-zirconium magnesium alloy.

[0026] Secondary refining is performed in steps S6-7. Flux is added to the melt, causing inclusions to dissolve in the flux or be adsorbed by it. These inclusions then settle to the bottom of the crucible along with the flux residue, effectively removing them from the melt. This removes oxide inclusions generated during the addition of rare earth elements and the master alloy, as well as high-melting-point slag introduced by the master alloy. After refining in step S7, the temperature is raised and the slag is allowed to settle.

[0027] It is worth noting that the addition amounts of magnesium ingot, zinc ingot, rare earth elements and magnesium-zirconium master alloy in the above method are determined in advance according to the composition of the magnesium-rare earth-zirconium series magnesium alloy to be prepared, and the addition amounts of each raw material are different for different alloys.

[0028] A second embodiment of the present invention provides a flux for a magnesium-rare earth-zirconium alloy, wherein the raw materials thereof include the following components in percentage by mass: 18-26% magnesium chloride, 12-18% potassium chloride, 26-34% barium chloride, 12-18% sodium chloride, 12-20% calcium fluoride, the sum of the mass percentages of the above components is 100%.

[0029] The third embodiment of the present application provides a preparation method of a flux of a magnesium-rare earth-zirconium magnesium alloy, characterized in that the method comprises the following steps: In step S10, according to the raw material composition, magnesium chloride, potassium chloride and sodium chloride are placed in a reactor for melting; In step S20, barium chloride is placed in an iron box and baked at a temperature of 120-150℃ for 0.8-1.2h to remove moisture; In step S30, the baked barium chloride is added to the reactor, and after the barium chloride is melted, boiling is maintained for 28-32min, and stirring is performed for 8-10min, and then the mixture is poured into a mold to obtain a mixed solid; In step S40, the mixed solid is crushed and ball-milled with calcium fluoride to obtain the flux.

[0030] In this embodiment, the magnesium chloride can react with oxygen and moisture in the atmosphere at high temperature to generate chlorine, hydrogen chloride and hydrogen, and form a protective atmosphere on the surface of the melt; the generated chlorine and hydrogen chloride can rapidly react with magnesium to form a layer of magnesium chloride, covering the surface of the melt without the flux, thereby playing a role of slowing down the oxidation of the melt and inhibiting combustion. The liquid magnesium chloride has good wettability to the inclusions such as magnesium oxide and magnesium nitride in the melt, and can effectively adsorb the inclusions such as magnesium oxide and magnesium nitride suspended in the solution. The three chlorides of potassium chloride, sodium chloride and magnesium chloride form a MgCl2-NaCl-KCl ternary system, which not only effectively reduces the melting point of the flux, but also adjusts the density and viscosity of the flux. The melting point of the ternary system is lower than that of the magnesium alloy, and the ternary system is in a liquid state at the melting temperature of the magnesium alloy, thereby effectively playing a protective role. The barium chloride can significantly increase the specific gravity difference between the flux and the melt, which is beneficial to the separation of the flux and the melt. The calcium fluoride is a "thickening agent" for increasing the viscosity of the flux. The calcium fluoride can react with the magnesium chloride in the flux: CaF2+MgCl2=MgF2+CaCl2; almost all of the calcium fluoride is converted into magnesium fluoride, and the solubility of the magnesium fluoride in the chloride is very small and almost does not change with temperature. The presence of the insoluble solid magnesium fluoride particles increases the viscosity of the flux. In order to avoid the chemical reaction between the magnesium chloride and the rare earth elements, the content of the magnesium chloride in the flux component of the magnesium alloy is controlled at a suitable proportion, and the addition of the calcium fluoride also consumes part of the magnesium chloride, so that the content of the magnesium chloride in the flux is maintained at a low level. For fluxes used for both covering and refining magnesium alloys, the melting point of the flux must be lower than that of the melt, and the flux should have a large density difference with the melt. The viscosity of the flux must be appropriate, so that it can spread quickly on the surface of the melt during covering, and not be mixed into the melt during pouring, and can just adsorb inclusions during refining operations. At the melting temperature, the flux cannot chemically react with the elements in the melt, the furnace lining, and the furnace gas. The flux of this application can fully meet the above requirements. The raw material standards and specifications of this application are shown in Table 1; Table 1 Standards and specifications of raw materials for magnesium-rare earth-zirconium alloy flux

[0031] Example 1 Step 100, 66 kg of magnesium chloride, 48 kg of potassium chloride, and 48 kg of sodium chloride are placed in a reactor for melting; Step S200: Place the barium chloride in an iron box and bake it at 150° C. for 1.2 hours to remove moisture. Step S300: Add 90 kg of baked barium chloride into the reactor and wait for the barium chloride to melt. After that, keep boiling for 30 minutes and stirring for 10 minutes, pour into a mold to obtain a mixed solid; In step S400, the mixed solid is crushed, ball-milled with 48 kg of calcium fluoride for 30 minutes, and then sieved (mesh size 30 / 50) to obtain a flux.

[0032] Chemical analysis of the flux composition revealed the following percentages: 22.18% magnesium chloride, 15.5% potassium chloride, 30.1% barium chloride, 15.4% sodium chloride, 15.8% calcium fluoride, 0.75% MgO, and 0.6% water.

[0033] Example 2 The difference from Example 1 is that in this example, 78 kg of magnesium chloride, 42 kg of potassium chloride, 42 kg of sodium chloride, 78 kg of barium chloride, and 60 kg of calcium fluoride are added; Chemical analysis of the flux composition revealed the following percentages: 25.8% magnesium chloride, 13.6% potassium chloride, 26.01% barium chloride, 13.5% sodium chloride, 19.95% calcium fluoride, 0.85% MgO, and 0.67% water.

[0034] Example 3 The difference from Example 1 is that in this example, 54 kg of magnesium chloride, 54 kg of potassium chloride, 54 kg of sodium chloride, 102 kg of barium chloride, and 36 kg of calcium fluoride are added; Chemical analysis of the flux composition revealed the following percentages: 17.9% magnesium chloride, 17.8% potassium chloride, 33.8% barium chloride, 17.95% sodium chloride, 12.1% calcium fluoride, 0.8% MgO, and 0.89% water.

[0035] Example 4: Melting of ZM3 alloy Table 2 Main elements and impurity element contents of ZM3 alloy

[0036] The total weight of the charge is 300 kg. The weight of the ingredients of cerium-rich mixed rare earth, zinc, magnesium-zirconium master alloy (containing 40% zirconium), and magnesium are calculated according to the percentage of the main components in Table 2. 50% of the ZM3 alloy is used as the recycled charge.

[0037] Step S110, preheating the crucible to a dark red color, adding the flux, magnesium ingot, and recycled material obtained in Example 1 into the smelting container, and obtaining a first melt after the material is melted; Step S310, adding a zinc ingot preheated to 250°C to the first melt at a temperature of 700°C-720°C, and stirring for 3 minutes to obtain a second melt; Step S410: At a temperature of 720°C-730°C, hexachloroethane compressed into blocks is added in batches to the melt using a bell jar. The bell jar is inserted into the crucible to a depth of 2 / 3 and rotated along the crucible until the reaction is complete. The amount of hexachloroethane used is 3% of the weight of the charge. Slag on the liquid surface is then removed using a slag scoop to obtain a third melt, and the surface of the third melt is covered with flux. Step S510, adding rare earth elements preheated to 250°C to the third melt at a temperature of 750°C-770°C, stirring for 2 minutes after the rare earth elements are completely melted, to obtain a fourth melt; Step S610: adding a magnesium-zirconium master alloy preheated to 350°C to the fourth melt at a temperature of 780°C-800°C. After the magnesium-zirconium master alloy is completely melted, stirring the melt for 5 minutes, removing the slag, and obtaining a fifth melt. The surface of the fifth melt is then covered with flux. Step S710: When the temperature is 760°C-780°C, use a stirring spoon to penetrate 2 / 3 of the melt and stir for 3 minutes. During stirring, continuously sprinkle flux with a mass of 1.5% of the total weight of the charge on the peak of the liquid flow. Then, remove the slag and cover the liquid surface with flux in sequence to obtain a sixth melt. Step S810 , when the temperature is 780° C.-800° C., the sixth melt is allowed to stand for 25 min-30 min, and the temperature is rapidly cooled to the casting temperature, and then cast to obtain a magnesium-rare earth-zirconium magnesium alloy.

[0038] The effects of the magnesium-rare earth-zirconium series magnesium alloy flux and melt composite refining method of the present invention are evaluated by considering the following items.

[0039] 1. In steps S410-710 of this embodiment, the flux obtained in Example 1 is used for liquid surface covering and alloy refining. Visual observation shows that the flux can form a complete and tight covering layer.

[0040] 2. When pouring with a ladle in step S810, after the ladle pushes away the flux covering layer on the surface of the melt and scoops up the melt, the speed at which the flux on the liquid surface closes and forms a complete covering layer again is moderate; when pouring with a crucible, the flux layer on the surface of the melt can still remain intact and can be blocked by the baffle and not fall into the liquid flow.

[0041] 3. At the end of smelting (after step S710), a fracture inspection is performed to ensure that there is no visible slag inclusion on the fracture.

[0042] 4. Physical and chemical testing of the magnesium-rare earth-zirconium magnesium alloy showed that the chemical composition was in compliance with the requirements of Table 2. The mechanical properties of the single-cast test bar in the T2 heat treatment state met the requirements of HB7780-2005, namely: σb ≥ 120 MPa, σ0.2 ≥ 85 MPa, and δ5 (%) ≥ 1.5%.

[0043] An X-ray inspection of magnesium-rare earth-zirconium alloy castings shows that the internal pores and slag inclusions of the castings meet the standards allowed by HB7780-2005.

[0044] 5. When preparing the ingredients, the cerium-rich mixed rare earth content is calculated to be 4.0%. The chemical sample analysis results after smelting show that the rare earth content is 3.8%. The calculated rare earth element burnout rate is: 5.0%.

[0045] Example 5 Melting of ZM6 alloy Table 3 Main elements and impurity element contents of ZM6 alloy

[0046] The total weight of the charge is 300 kg. The weight of the rare earth metal neodymium, zinc, magnesium-zirconium master alloy (containing 40% zirconium), and magnesium is calculated according to the percentage of the main components in Table 3. 50% of the ZM6 alloy is used as the recycled charge.

[0047] Step S110, preheating the crucible to a dark red color, adding the flux, magnesium ingot, and recycled material obtained in Example 1 into the smelting container, and obtaining a first melt after the material is melted; Step S310, adding a zinc ingot preheated to 250°C to the first melt at a temperature of 700°C-720°C, and stirring for 3 minutes to obtain a second melt; Step S410: At a temperature of 720°C-730°C, hexachloroethane compressed into blocks is added in batches to the melt using a bell jar. The bell jar is inserted into the crucible to a depth of 2 / 3 and rotated along the crucible until the reaction is complete. The amount of hexachloroethane used is 3% of the weight of the charge. Slag on the liquid surface is then removed using a slag scoop to obtain a third melt, and the surface of the third melt is covered with flux. Step S510, adding rare earth metal neodymium preheated to 250°C to the third melt at a temperature of 750°C-770°C, stirring for 2 minutes after the third melt is completely melted, to obtain a fourth melt; Step S610: adding a magnesium-zirconium master alloy preheated to 350°C to the fourth melt at a temperature of 780°C-800°C. After the magnesium-zirconium master alloy is completely melted, stirring the melt for 5 minutes, removing the slag, and obtaining a fifth melt. The surface of the fifth melt is then covered with flux. Step S710: When the temperature is 760°C-780°C, use a stirring spoon to penetrate 2 / 3 of the melt and stir for 3 minutes. During stirring, continuously sprinkle flux with a mass of 1.5% of the total weight of the charge on the peak of the liquid flow. Then, remove the slag and cover the liquid surface with flux in sequence to obtain a sixth melt. Step S810 , when the temperature is 780° C.-800° C., the sixth melt is allowed to stand for 25 min-30 min, and the temperature is rapidly cooled to the casting temperature, and then cast to obtain a magnesium-rare earth-zirconium magnesium alloy.

[0048] The effects of the magnesium-rare earth-zirconium series magnesium alloy flux and melt composite refining method of the present invention are evaluated by considering the following items.

[0049] 1. In steps S410-710 of this embodiment, the flux obtained in Example 1 is used for liquid surface covering and alloy refining. Visual observation shows that the flux can form a complete and tight covering layer.

[0050] 2. When pouring with a ladle in step S810, after the ladle pushes away the flux covering layer on the surface of the melt and scoops up the melt, the speed at which the flux on the liquid surface closes and forms a complete covering layer again is moderate; when pouring with a crucible, the flux layer on the surface of the melt can still remain intact and can be blocked by the baffle and not fall into the liquid flow.

[0051] 3. During the later stage of smelting, the fracture surface was inspected and no slag inclusions were visible to the naked eye.

[0052] 4. Physical and chemical testing of the magnesium-rare earth-zirconium alloy revealed that the product's chemical composition complies with the requirements of Table 3. The mechanical properties of single-cast test bars in the T6 heat-treated state meet the requirements of HB7780-2005, namely: σb ≥ 225 MPa; σ0.2 ≥ 135 MPa; and δ5 (%) ≥ 3%. Measured data show that the average tensile strength σb exceeds the standard by more than 10%, and the average elongation exceeds the standard by more than 15%.

[0053] X-ray inspection of magnesium-rare earth-zirconium magnesium alloy shows that the internal pores and slag inclusions of the castings meet the standards allowed by HB7780-2005.

[0054] 5. When mixing the ingredients, neodymium was calculated as 2.75%. The chemical sample analysis results after smelting showed that the neodymium content was 2.6%. The calculated rare earth element burnout rate was: 5.4%.

[0055] Example 6 (Comparative Example) Melting of ZM6 Alloy Compared with Example 4, Example 6 omitted step S410, i.e., no hexachloroethane was used for refining. Results indicate a rare earth element burnout rate exceeding 15%. This means that the neodymium content must be calculated at 3.1% during batching, so that chemical analysis of the smelting sample will reveal a neodymium content of 2.5-2.6%. Furthermore, the mechanical properties of the single-cast test bar in the T6 heat-treated state meet the requirements of HB7780-2005, but with insufficient margin.

[0056] Example 5 (Comparative Example) Melting of ZM6 Alloy The steps of Example 5 are the same as those of Example 4, except that commercial flux RJ4 is used instead, and its formula is: Magnesium chloride 32-38%, potassium chloride 32-36%, barium chloride 12-16%, calcium fluoride 12-16%; The results showed that the melt purification was not thorough and X-ray examination of the castings showed the presence of large-area slag inclusion defects.

[0057] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A composite refining process for magnesium-rare earth-zirconium series magnesium alloy, characterized in that: include: Adding flux, magnesium ingot, and recycled materials into the smelting container, and obtaining a first melt after the materials are melted; When the temperature is 700° C.-720° C., adding zinc ingots to the first melt and melting the zinc ingots to obtain a second melt; When the temperature is 720° C.-730° C., hexachloroethane is added to the first melt, and slag is removed to obtain a third melt, and the liquid surface of the third melt is covered with a flux; adding rare earth elements to the third melt at a temperature of 750° C. to 770° C. to obtain a fourth melt; At a temperature of 780° C. to 800° C., adding magnesium-zirconium master alloy to the fourth melt and performing slag removal to obtain a fifth melt, and covering the liquid surface of the fifth melt with flux; Stirring the fifth melt at a temperature of 760° C. to 780° C., sprinkling flux onto the crest of the liquid flow during the stirring process, and sequentially performing slag removal and liquid surface covering with flux to obtain a sixth melt; The sixth melt is poured at a temperature of 780° C. to 800° C. to obtain a magnesium-rare earth-zirconium series magnesium alloy.

2. The composite refining process of magnesium-rare earth-zirconium series magnesium alloy according to claim 1, characterized in that: Before pouring the sixth melt, the process further includes allowing the sixth melt to stand for 25 minutes to 30 minutes.

3. The composite refining process of magnesium-rare earth-zirconium series magnesium alloy according to claim 1, characterized in that: During the stirring process, the mass of flux sprinkled on the crest of the liquid flow should be 1.0%-1.5% of the total weight of the charge.

4. The composite refining process of magnesium-rare earth-zirconium series magnesium alloy according to claim 1, characterized in that: The mass of hexachloroethane is 2%-3% of the total weight of the charge.

5. The composite refining process of magnesium-rare earth-zirconium series magnesium alloy according to claim 1, characterized in that: The mass of recycled materials is 55-60% of the total weight of the furnace materials.

6. A flux for magnesium-rare earth-zirconium alloy, characterized in that: The raw materials include the following components in terms of mass percentage: 18-26% magnesium chloride, 12-18% potassium chloride, 26-34% barium chloride, 12-18% sodium chloride, 12-20% calcium fluoride, the sum of the mass percentages of the above components is 100%.

7. A method for preparing a flux for magnesium-rare earth-zirconium alloy according to claim 6, characterized in that: include: According to the raw material composition, magnesium chloride, potassium chloride and sodium chloride are placed in a reactor for melting; Place barium chloride in an iron box and bake at 120-150°C for 0.8-1.2 hours; Add the baked barium chloride into the reactor, keep boiling for 28-32 minutes after the barium chloride is melted, stir for 8-10 minutes, and pour into a mold to obtain a mixed solid; The mixed solid is crushed and mixed with calcium fluoride by ball milling to obtain a flux.

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