Purifying flux for magnesium-gadolinium-yttrium intermediate alloy

Abstract

The invention discloses a magnesium-gadolinium-yttrium intermediate alloy purification flux, and relates to the technical field of metal melt purification. The magnesium-gadolinium-yttrium intermediate alloy purification flux provided by the invention is suitable for purification of a magnesium-gadolinium-yttrium ternary rare earth-magnesium intermediate alloy, has a density system matched with the magnesium-gadolinium-yttrium intermediate alloy, and is easy to separate from the magnesium-gadolinium-yttrium intermediate alloy; and non-metal impurities and metal impurities in the magnesium-gadolinium-yttrium intermediate alloy can be effectively removed, the loss of rare earth elements is inhibited, the purity of the intermediate alloy is improved, and a foundation is laid for producing the high-quality magnesium-gadolinium-yttrium intermediate alloy.

Description

Technical Field

[0001] The invention relates to the technical field of metal melt purification, and in particular to a magnesium-gadolinium-yttrium master alloy purification flux. Background Art

[0002] Rare earth magnesium alloy is an important structural and functional integrated material. It is widely used in aerospace, weapon equipment, automotive 3C products, marine chemical industry and biomedical implant materials due to its high specific strength and specific stiffness, excellent damping performance, corrosion resistance and strong electromagnetic shielding ability. In recent years, Mg-Gd-Y high-strength heat-resistant magnesium alloy has attracted more and more attention from researchers due to its excellent mechanical properties and heat resistance.

[0003] The melting point and density differences of Gd and Y magnesium alloys are too high (the melting point of rare earth is greater than 1000℃, and the density of rare earth is 7.4g / cm 3 ~7.6g / cm 3 , magnesium alloy melting point 650℃, magnesium alloy density 1.73g / cm 3 ~4.4g / cm 3 ), resulting in a serious reduction in the uniformity of the alloy composition. During alloy smelting, the rare earth elements Gd and Y will be concentrated in the middle and lower parts of the alloy ingot, reducing the overall performance of the alloy. The high difference in melting points will make the smelting temperature extremely difficult to control. Low-temperature rare earths cannot be completely melted, and high-temperature magnesium is very flammable. Even under vacuum conditions, it will still cause burnout, resulting in cost loss.

[0004] At present, most Mg-Gd-Y alloys are melt-blended with two intermediate alloys, Mg-30Gd and Mg-30Y, with a purity of 99wt.% to 99.5wt.%. At the same time, many impurity particles will be generated during the melting process, causing various defects and reducing the purity of the alloy. The Y2O3 impurities produced will reduce the mechanical properties of the alloy. The presence of Y2O3 impurities will cause the distortion of the crystal structure, which will reduce the mechanical properties of the alloy and increase the possibility of cracks. The alloy will become brittle under low temperature conditions, which will reduce the toughness of the magnesium alloy, affecting its safety and reliability in actual use. An uneven phase will be formed on the alloy surface, resulting in stress concentration, thereby increasing the risk of corrosion or fatigue cracking. In addition, the Y2O3 impurity density is low and difficult to remove, which will cause great harm to the alloy. The element Fe reduces the corrosion resistance of the alloy and causes grain boundary segregation. Si is easy to form a brittle phase and produce a tendency to thermal cracking. Ca impurities will cause crystallization cracks, coarse grains, reduce plasticity and increase aging sensitivity. In addition, because the solubility of Ca impurities in magnesium alloys is relatively low, and the chemical properties of Ca are relatively stable, many fluxes cannot remove Ca impurities. After these impurity elements enter the terminal alloy, they will greatly affect the quality and performance of the terminal alloy material.

[0005] At present, the rare earth magnesium master alloy can be treated by flux purification to remove impurities and inclusions to obtain high-quality rare earth magnesium alloy. However, there is no purification flux related to the ternary master alloy, especially the magnesium-gadolinium-yttrium ternary master alloy. Due to the complexity of alloy properties caused by the interaction between magnesium, gadolinium and yttrium, it is usually easy to introduce many impurities and inclusions, which are very difficult to remove, and no special purification flux has been developed so far. Therefore, it is urgent to provide a solution to the above problems. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a purification flux suitable for magnesium-gadolinium-yttrium master alloy, which can significantly reduce the content of Fe, Ca and other non-metallic impurities (single impurity content ≤70ppm), inhibit the loss of gadolinium and yttrium (gadolinium recovery rate ≥95%, yttrium recovery rate ≥93.33%), improve the purity of the master alloy (≥99.9wt.%), and can specifically remove various impurities in the magnesium-yttrium-gadolinium master alloy, thereby obtaining a good, low-consumption purification effect.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a magnesium-gadolinium-yttrium master alloy purification flux, wherein the purification flux comprises a basic flux, a rare earth loss inhibitor and a density regulator.

[0009] The magnesium-gadolinium-yttrium master alloy purification flux provided by the invention can effectively remove Fe, Ca and other non-metallic impurities, inhibit the loss of rare earth elements gadolinium and yttrium, and improve the purity of the master alloy.

[0010] Optionally, the basic flux includes MgCl2, KCl, CaF2, B2O3 and NH4F.

[0011] Optionally, adding NH4F to the base flux can improve the flux's ability to remove Ca impurities.

[0012] Optionally, the rare earth damage inhibitor includes YCl3 and GdCl3.

[0013] Optionally, the density modifier includes any one of BaCl2, GdCl3, TICl, SrCl2 and CoCl2, preferably BaCl2.

[0014] Optionally, MgCl2, KCl, CaF2, B2O3 and NH4F in the basic flux account for 34% to 46%, 20% to 27%, 3% to 6.9%, 0.4% to 0.7% and 2% to 8% of the mass of the purified flux respectively.

[0015] Optionally, YCl3 and GdCl3 in the rare earth damage inhibitor account for 8% to 16% and 4% to 8% of the mass of the purified flux respectively.

[0016] Optionally, the density regulator accounts for 16% to 20% of the mass of the purified flux.

[0017] Optionally, the purity of each component in the magnesium-gadolinium-yttrium master alloy purification flux reaches above 99.99wt.%.

[0018] Optionally, to ensure the complexing effect, the mass ratio of MgCl2 to KCl is (1.20-1.35):1.

[0019] Optionally, to avoid loss of rare earth elements and inclusions in the flux, the mass ratio of YCl3 to GdCl3 is (1.8-2.2):1 and the sum of the masses of YCl3 and GdCl3 accounts for 15%-20% of the mass of the purified flux.

[0020] Optionally, adding a density regulator can control the density difference between the purified flux and the magnesium-gadolinium-yttrium master alloy to be 10% to 20%, so that the purified flux and the magnesium-yttrium-gadolinium master alloy can be easily separated.

[0021] Optionally, the surface tension coefficient of the purified flux can be adjusted to 27 mN·m by adding a base flux. -1 ~101mN·m -1 , providing the ability to purify flux and remove Fe impurities.

[0022] Optionally, the magnesium-gadolinium-yttrium master alloy purification flux needs to be fully dried before preparation, and after preparation, it is ground evenly with a mixing ball and passed through a 60-80 mesh sieve.

[0023] In a second aspect, the present invention provides a use of the above-mentioned magnesium-gadolinium-yttrium master alloy purification flux in purifying the magnesium-gadolinium-yttrium master alloy, comprising the following steps:

[0024] S1. Under a protective atmosphere, the molten magnesium-gadolinium-yttrium master alloy and the magnesium-yttrium-gadolinium master alloy purification flux are mixed and stirred and then allowed to stand;

[0025] S2, casting the magnesium-gadolinium-yttrium master alloy, demolding and peeling the master alloy to obtain a purified magnesium-gadolinium-yttrium master alloy.

[0026] The magnesium-gadolinium-yttrium master alloy purified by the magnesium-yttrium-gadolinium master alloy purification flux provided by the present invention can effectively remove non-metallic impurities and metallic impurities of the magnesium-yttrium-gadolinium master alloy, inhibit the loss of rare earth elements, and improve the purity of the master alloy. After purification, the purity of the magnesium-gadolinium-yttrium master alloy is ≥99.9wt.%, the single impurity content is ≤70ppm, the inclusion is ≤0.15Vol%, the gadolinium recovery rate is ≥95%, and the yttrium recovery rate is ≥93.33%.

[0027] Optionally, the protective atmosphere in step S1 is an insulating gas atmosphere, specifically a mixed atmosphere of N2+SF6, which is a protective gas specially used for magnesium alloy smelting.

[0028] Optionally, in step S1, the mass ratio of the magnesium-yttrium-gadolinium master alloy to the magnesium-yttrium-gadolinium master alloy purification flux is 1:(0.02-0.05).

[0029] Optionally, when executing step S1, it includes: preheating the magnesium-gadolinium-yttrium master alloy to 700°C-800°C in a protective atmosphere to melt, adding the magnesium-yttrium-gadolinium master alloy purification flux and stirring for 5min-10min, and then standing at 750°C-900°C for 30min-60min.

[0030] Optionally, the magnesium-yttrium-gadolinium master alloy purification flux can be applied to the purification of other rare earth magnesium master alloys, including magnesium-gadolinium-neodymium master alloy and magnesium-lanthanum-cerium master alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the metallographic image of Mg-21.46Gd-5.06Y master alloy before purification;

[0032] Figure 2 The SEM analysis results of Mg-21.46Gd-5.06Y master alloy before purification, where 1 is C / O / Al inclusion, 2 is pure Mg phase, 3 is C / O inclusion, 4 is Mg3Gd phase, and 5 is Y-containing precipitate phase;

[0033] Figure 3 is a metallographic image of the Mg-21.46Gd-5.06Y master alloy after purification according to Example 1;

[0034] Figure 4 The results of SEM analysis of the Mg-21.46Gd-5.06Y master alloy after purification according to Example 1, wherein 1 is the Mg3Gd phase, 2 is the pure Mg phase, and 3 is the blocky Y / O particles;

[0035] Figure 5 This is the metallographic image of Mg-19.09Gd-8.68Y master alloy before purification;

[0036] Figure 6 The SEM analysis results of Mg-19.09Gd-8.68Y master alloy before purification, where 1 is the cluster Y / O particles, 2 is the pure Mg phase, and 3 is the Mg3Gd phase;

[0037] Figure 7 is a metallographic image of the Mg-19.09Gd-8.68Y master alloy after purification according to Example 2;

[0038] Figure 8The results of SEM analysis of the Mg-19.09Gd-8.68Y master alloy after purification according to Example 2, wherein 1 is a cluster of Y / O particles, 2 is a pure Mg phase, and 3 is a Mg3Gd phase;

[0039] Fig. 9 This is the metallographic image of Mg-22.23Gd-9.16Y master alloy before purification;

[0040] Fig.10 The SEM analysis results of Mg-22.23Gd-9.16Y master alloy before purification, where 1 is C / O inclusion, 2 is Y precipitation phase, 3 is Mg3Gd phase, and 4 is pure Mg phase;

[0041] Fig.11 is a metallographic image of the Mg-22.23Gd-9.16Y master alloy after purification according to Example 3;

[0042] Fig.12 The results of SEM analysis of the Mg-22.23Gd-9.16Y master alloy after purification according to Example 3, wherein 1 is pure Mg phase and 2 is Mg3Gd phase. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described through the following embodiments in conjunction with the accompanying drawings. However, the following embodiments are illustrative and are only used to specifically describe the present invention rather than to limit the present invention.

[0044] The invention provides a magnesium-gadolinium-yttrium master alloy purification flux, which comprises a basic flux, a rare earth loss inhibitor and a density regulator.

[0045] In some embodiments, the base flux includes MgCl2, KCl, CaF2, B2O3 and NH4F.

[0046] In some embodiments, the rare earth damage inhibitor includes YCl3 and GdCl3.

[0047] In some embodiments, the density modifier includes any one of BaCl2, GdCl3, TICl, SrCl2 and CoCl2, preferably BaCl2.

[0048] In some embodiments, MgCl2, KCl, CaF2, B2O3 and NH4F in the base flux account for 34% to 46%, 20% to 27%, 3% to 6.9%, 0.4% to 0.7% and 2% to 8% of the mass of the purified flux, respectively.

[0049] In some embodiments, YCl3 and GdCl3 in the rare earth damage inhibitor account for 8% to 16% and 4% to 8% of the mass of the purified flux, respectively.

[0050] In some embodiments, the density modifier accounts for 16% to 20% of the mass of the purified flux.

[0051] In some embodiments, the purity of each component in the magnesium-gadolinium-yttrium master alloy purification flux reaches above 99.99 wt.%.

[0052] In some embodiments, the mass ratio of MgCl2 to KCl is (1.20-1.35):1.

[0053] In some embodiments, the mass ratio of YCl3 to GdCl3 is (1.8-2.2):1 and the mass sum of YCl3 and GdCl3 accounts for 15%-20% of the mass of the purification flux.

[0054] In some embodiments, the magnesium-gadolinium-yttrium master alloy purification flux needs to be fully dried before preparation, and after preparation, it is ground evenly with a mixing ball and passed through a 60-80 mesh sieve.

[0055] The present invention also provides the use of the above-mentioned magnesium-gadolinium-yttrium master alloy purification flux in purifying the magnesium-gadolinium-yttrium master alloy, comprising the following steps:

[0056] S1. Under a protective atmosphere, the molten magnesium-gadolinium-yttrium master alloy and the magnesium-yttrium-gadolinium master alloy purification flux are mixed and stirred and then allowed to stand;

[0057] S2, casting the magnesium-gadolinium-yttrium master alloy, demolding and peeling the master alloy to obtain a purified magnesium-gadolinium-yttrium master alloy.

[0058] In some embodiments, when executing step S1, the protective atmosphere is an insulating gas atmosphere, specifically a mixed atmosphere of N2+SF6.

[0059] In some embodiments, when performing step S1, the mass ratio of the magnesium-yttrium-gadolinium master alloy to the magnesium-yttrium-gadolinium master alloy purification flux is 1:(0.02-0.05).

[0060] In fact, when executing step S1, the following sub-steps are included:

[0061] S1.1. In a protective atmosphere, heat the magnesium-gadolinium-yttrium master alloy to 700°C to 800°C to melt;

[0062] S1.2. Add magnesium-gadolinium-yttrium master alloy purification flux to the molten magnesium-gadolinium-yttrium master alloy and stir for 5 to 10 minutes, then stand at 750°C to 900°C for 30 to 60 minutes.

[0063] In some embodiments, the magnesium-yttrium-gadolinium master alloy purification flux can be applied to the purification of other rare earth magnesium master alloys, including magnesium-gadolinium-neodymium master alloys and magnesium-lanthanum-cerium master alloys.

[0064] Preparation Example 1

[0065] Preparation Example 1 of the present invention provides a magnesium-yttrium-gadolinium master alloy purification flux (Mg-21.46Gd-5.06Y, density ~2.170g / cm 3 ), comprising the following steps:

[0066] 7g MgCl2, 5.378g KCl, 0.9g CaF2, 0.122g B2O3, 0.4g NH4F, 2g YCl3, 1g GdCl3 and 3.2g BaCl2 were mixed and ground evenly, and then passed through a 60-mesh sieve to prepare a Mg-21.46Gd-5.06Y master alloy purification flux.

[0067] Preparation Example 2

[0068] Preparation Example 2 of the present invention provides a magnesium-yttrium-gadolinium master alloy purification flux (Mg-19.09Gd-8.68Y, density ~2.180g / cm 3 ), comprising the following steps:

[0069] 6.97 g MgCl2, 5.4 g KCl, 0.9 g CaF2, 0.13 g B2O3, 0.4 g NH4F, 2 g YCl3, 1 g GdCl3 and 3.2 g BaCl2 were mixed and ground evenly, and then passed through a 60-mesh sieve to prepare a Mg-19.09Gd-8.68Y master alloy purification flux.

[0070] Preparation Example 3

[0071] Preparation Example 3 of the present invention provides a magnesium-yttrium-gadolinium master alloy purification flux (Mg-22.23Gd-9.16Y, density ~2.258g / cm 3 ), comprising the following steps:

[0072] 6.98 g MgCl2, 5.38 g KCl, 0.9 g CaF2, 0.14 g B2O3, 0.4 g NH4F, 2 g YCl3, 1 g GdCl3 and 3.2 g BaCl2 were mixed and ground evenly, and then passed through a 60-mesh sieve to prepare a Mg-22.23Gd-9.16Y master alloy purification flux.

[0073] Example 1

[0074] Embodiment 1 of the present invention provides an application of the master alloy purification flux prepared in Preparation Example 1 in the purification of Mg-21.46Gd-5.06Y master alloy, comprising the following steps:

[0075] S1.1. Add Mg-21.46Gd-5.06Y master alloy into a crucible coated with a release agent, heat to 800°C in an insulating gas atmosphere of N2+SF6 to melt the Mg-21.46Gd-5.06Y master alloy;

[0076] S1.2, 500g of molten Mg-21.46Gd-5.06Y master alloy was mixed with 20g of Mg-21.46Gd-5.06Y master alloy purification flux, and stirred vertically for 5min, and then allowed to stand at 800℃ for 35min;

[0077] S2. Casting, demoulding and peeling of the Mg-21.46Gd-5.06Y master alloy are performed to obtain the purified Mg-21.46Gd-5.06Y master alloy.

[0078] Figure 1 and Figure 2 They are the metallographic image and SEM analysis results of Mg-21.46Gd-5.06Y master alloy before purification. Figure 3 and Figure 4 They are the metallographic diagram and scanning electron microscope analysis results of the Mg-21.46Gd-5.06Y master alloy after purification.

[0079] Example 2

[0080] Example 2 of the present invention provides an application of the intermediate alloy purification flux prepared in Preparation Example 2 in the purification of Mg-19.09Gd-8.68Y intermediate alloy. The difference from Example 1 is that the melting temperature in step S1.1 is 750°C, and the standing condition is standing at 750°C for 40 minutes.

[0081] Figure 5 and Figure 6 They are the metallographic diagram and SEM analysis results of Mg-19.09Gd-8.68Y master alloy before purification. Figure 7 and Figure 8 They are the metallographic diagram and scanning electron microscope analysis results of the Mg-19.09Gd-8.68Y master alloy after purification.

[0082] Example 3

[0083] Example 3 of the present invention provides an application of the intermediate alloy purification flux prepared in Preparation Example 3 in the purification of Mg-22.23Gd-9.16Y intermediate alloy. The difference from Example 1 is that the melting temperature in step S1.1 is 850°C, and the standing condition is standing at 850°C for 30 minutes.

[0084] Fig. 9 and Fig.10 These are the metallographic images and SEM analysis results of Mg-22.23Gd-9.16Y master alloy before purification. Fig.11 and Fig.12 They are the metallographic diagram and scanning electron microscope analysis results of the Mg-22.23Gd-9.16Y master alloy after purification.

[0085] Performance Testing

[0086] The purity and structure analysis of the purified master alloys of Examples 1 to 3 were respectively performed, wherein the sample purity was based on the element determination specification in gadolinium magnesium alloy in GB / T 26414, and the detection method indicated in the national standard "Chemical Analysis Method for Non-rare Earth Impurities in Rare Earth Metals and Their Oxides" was used to respectively determine the components of Mg-21.46Gd-5.06Y master alloy, Mg-19.09Gd-8.68Y master alloy and Mg-22.23Gd-9.16Y master alloy, including C, O, Si, Cl, Fe, Ni, Ca, Al, Cu, Gd, and Mg as the remainder. Among them, C was detected by a high-frequency infrared carbon sulfur instrument, O was detected by a pulse-infrared absorption method, and the remaining elements were detected by ICP-AES. The components of the purified samples are shown in Table 1.

[0087] The analysis results show that in Example 1, the non-metallic inclusions of the Mg-21.46Gd-5.06Y master alloy after purification decreased by 61.29%, and the comprehensive impurity removal rate was 88.35%, wherein the Ca impurity removal rate was as high as 98.96%, the Ni impurity removal rate was as high as 85.25%, the Al impurity removal rate was as high as 92.42%, the Fe impurity removal rate was as high as 89.77%, the Si impurity removal rate was as high as 43.33%, the Cu impurity removal rate was as high as 81.05%, the Gd element yield was 98.84%, the Y element yield was 96.64%, and the purity of the master alloy was increased to 99.91wt.%; in Example 2, the non-metallic inclusions of the Mg-19.09Gd-8.68Y master alloy after purification decreased by 46.43%, the comprehensive impurity removal rate was 97.33%, the Ca impurity removal rate was as high as 99.77%, the Ni impurity removal rate was 32.97%, and the A impurity removal rate was 1.3%. l impurity removal rate is as high as 83.87%, Fe impurity removal rate is as high as 67.14%, Si impurity removal rate is as high as 97.80%, Cu impurity removal rate is as high as 96.81%, and Gd element yield is 99.27%, Y element yield is 98.04%, and the purity of the intermediate alloy is increased to 99.91wt.%; in Example 3, the non-metallic inclusions of the Mg-22.23Gd-9.16Y intermediate alloy decreased by 40% after purification, the comprehensive impurity removal rate was 96.14%, the Ca impurity removal rate was as high as 99.68%, the Ni impurity removal rate was 57.50%, the Al impurity removal rate was as high as 78%, the Fe impurity removal rate was as high as 88%, the Si impurity removal rate was as high as 97.33%, the Cu impurity removal rate was as high as 94.07%, the Gd element yield was 98.88%, the Y element yield was 97.27%, and the purity of the intermediate alloy was increased to 99.91wt.%.

[0088] Table 1 Comparison of purification effects of magnesium-gadolinium-yttrium master alloy

[0089]

[0090] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A magnesium-gadolinium-yttrium master alloy purification flux, characterized in that: The purified flux comprises a basic flux, a rare earth damage inhibitor and a density regulator.

2. The purifying flux according to claim 1, characterized in that: The basic flux includes MgCl2, KCl, CaF2, B2O3 and NH4F; the rare earth damage inhibitor includes YCl3 and GdCl3; the density regulator includes any one of BaCl2, GdCl3, TICl, SrCl2 and CoCl2.

3. The purifying flux according to any one of claims 1 to 2, characterized in that: MgCl2, KCl, CaF2, B2O3 and NH4F in the basic flux account for 34% to 46%, 20% to 27%, 3% to 6.9%, 0.4% to 0.7% and 2% to 8% of the mass of the purified flux respectively; YCl3 and GdCl3 in the rare earth loss inhibitor account for 8% to 16% and 4% to 8% of the mass of the purified flux respectively; the density regulator accounts for 16% to 20% of the mass of the purified flux.

4. The purifying flux according to any one of claims 1 to 3, characterized in that: The purity of each component in the purified flux reaches above 99.99wt.%.

5. Use of the purification flux according to any one of claims 1 to 4 in purifying magnesium-gadolinium-yttrium master alloy, characterized in that: The following steps are involved: S1. Under a protective atmosphere, the molten magnesium-gadolinium-yttrium master alloy and the magnesium-yttrium-gadolinium master alloy purification flux are mixed and stirred and then allowed to stand; S2, demoulding and peeling the magnesium-gadolinium-yttrium master alloy after casting, so as to obtain the purified magnesium-gadolinium-yttrium master alloy.

6. The use according to claim 5, characterized in that: The protective atmosphere is an insulating gas atmosphere; and / or, the mass ratio of the magnesium-yttrium-gadolinium master alloy to the magnesium-yttrium-gadolinium master alloy purification flux is 1:(0.02-0.05).

7. The use according to claim 5, characterized in that: When executing step S1, the magnesium-gadolinium-yttrium master alloy is preliminarily heated to 700° C. to 800° C. in a protective atmosphere to be melted, and the magnesium-yttrium-gadolinium master alloy purification flux is added and stirred for 5 min to 10 min, and then allowed to stand at 750° C. to 900° C. for 30 min to 60 min.

8. The use of the purification flux according to any one of claims 1 to 4, or the use according to any one of claims 5 to 7 in purifying other rare earth magnesium intermediate alloys, characterized in that: The other master alloys include magnesium-gadolinium-neodymium master alloy and magnesium-lanthanum-cerium master alloy.

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