阅读说明：本技术 一种去除镁或镁合金熔体中氧化镁夹杂的方法 (Method for removing magnesium oxide inclusion in magnesium or magnesium alloy melt ) 是由 游国强 龙思远 周凯旋 姚繁锦 彭力真 于 2019-11-20 设计创作，主要内容包括：本发明公开了一种去除镁或镁合金熔体中氧化镁夹杂的方法,属于金属熔体净化技术领域。所述方法为在镁或镁合金熔炼过程中,向镁或镁合金熔体中加入能够与氧化镁发生还原反应的金属元素,使所加入的金属元素与氧化镁夹杂发生还原反应,生成密度比镁或镁合金密度大的金属氧化物和镁；再通过静置使新生成的金属氧化物沉降到炉底,达到净化镁或镁合金熔体的目的。本发明能够有效去除镁或镁合金熔体中的氧化镁夹杂的含量,特别是针对现有技术中无法除去的小尺寸氧化镁(尺寸小于0.5mm),去除镁合金夹杂的效果好,提升了镁或镁合金的品质。(The invention discloses a method for removing magnesium oxide inclusions in magnesium or magnesium alloy melt, and belongs to the technical field of metal melt purification. Adding a metal element capable of performing a reduction reaction with magnesium oxide into a magnesium or magnesium alloy melt in the smelting process of magnesium or magnesium alloy, so that the added metal element and magnesium oxide inclusion perform a reduction reaction to generate metal oxide and magnesium with the density higher than that of the magnesium or magnesium alloy; then the newly generated metal oxide is settled at the bottom of the furnace by standing, thereby achieving the purpose of purifying the magnesium or magnesium alloy melt. The method can effectively remove the content of the magnesium oxide inclusions in the magnesium or magnesium alloy melt, particularly has good effect of removing the magnesium alloy inclusions aiming at the small-size magnesium oxide (the size is less than 0.5mm) which cannot be removed in the prior art, and improves the quality of the magnesium or magnesium alloy.)

1. A method for removing magnesium oxide inclusion in magnesium or magnesium alloy melt is characterized in that in the smelting process of magnesium or magnesium alloy, a metal element capable of carrying out reduction reaction with magnesium oxide is added into the magnesium or magnesium alloy melt, so that the added metal element and the magnesium oxide inclusion carry out reduction reaction to generate metal oxide and magnesium with density higher than that of the magnesium or magnesium alloy; then the newly generated metal oxide is settled at the bottom of the furnace by standing, thereby achieving the purpose of purifying the magnesium or magnesium alloy melt.

2. The method for reducing magnesium oxide inclusions in a magnesium or magnesium alloy melt according to claim 1, wherein the method is specifically operated according to the following steps:

(1) keeping the temperature of the magnesium or magnesium alloy melt at 650 ~ 750 ℃ and adding weighed metal elements into the middle upper part of the magnesium melt by using a feeding tool;

(2) stirring for 5 ~ 30 minutes to ensure that the added metal elements and magnesium oxide inclusion are fully reacted;

(3) and (3) preserving the temperature and standing for 30 ~ 120 minutes to ensure that metal oxide which is generated by the reaction and has the density larger than that of magnesium or magnesium alloy is fully settled to the bottom of the furnace, thereby finishing the removal of magnesia inclusions.

3. The method of reducing magnesium oxide inclusions in a magnesium or magnesium alloy melt of claim 1 or 2 wherein said metallic element is one or more of Sn, Cd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu.

4. A method of reducing magnesium oxide inclusions in a magnesium or magnesium alloy melt according to claim 3 wherein the metallic element is added in the form of a pure metal or an intermediate alloy.

5. The method for reducing the magnesium oxide inclusions in the magnesium or magnesium alloy melt according to claim 1 or 2, wherein the metal elements are added in a total amount of 0 ~ 5% by mass of the magnesium or magnesium alloy melt.

6. The method for reducing the magnesium oxide inclusions in the magnesium or magnesium alloy melt according to claim 5, wherein the metal elements are added in a total amount of 0.2 ~ 1.2.2% by mass of the magnesium or magnesium alloy melt.

Technical Field

The invention relates to the technical field of metal melt purification, in particular to a method for removing magnesium oxide inclusions in magnesium or magnesium alloy melt.

Background

The magnesium and the magnesium alloy have low density, high specific strength and specific stiffness, high damping and shock absorption performance, excellent heat conduction and electromagnetic shielding performance, good casting and machining process performance and rich resource support, become one of the most potential metal materials, and have wide application prospects in the fields of ground vehicles, aerospace, 3C products and the like.

From the perspective of the whole life cycle, the production of magnesium and magnesium alloy ingots (including semi-continuous ingots required for plastic processing), casting production and scrap magnesium remelting regeneration all necessarily involve smelting operations, i.e. magnesium or magnesium alloy melts are required. Therefore, the quality of the melt is an important factor in determining the quality of magnesium and its alloy products. The solid-state inclusion content is one of the main indicators for measuring the quality of magnesium or magnesium alloy melts.

It is known that magnesium metal is chemically active, has a strong affinity with oxygen, and is very likely to react with oxygen to form magnesium oxide in a high-temperature molten state. In industrial production, magnesium oxide accounts for more than 85% of solid inclusions in magnesium or magnesium alloy melts. The theoretical density of the magnesium oxide is 3.58g/cm³The actual magnesium oxide density in the melt is generally also below this theoretical value (in particular lumpy magnesium oxide inclusions), in combination with the density of the magnesium or magnesium alloy melt (1.5-1.6 g/cm)³) The phase difference is not large enough, and when the density difference principle is utilized to realize sedimentation separation, the separation efficiency is low and the separation effect is poor. This is especially true for small size (less than 0.5mm in size) magnesium oxide, which tends to be retained as solid inclusions. In addition, because the magnesium oxide and the surface of the magnesium or magnesium alloy melt are wetted, the interface of the magnesium oxide and the magnesium or magnesium alloy melt has stronger physical adsorption, and is not beneficial to separation, and especially for small-size magnesium oxide (less than 0.5mm), the negative effect caused by surface wetting is more remarkable. Therefore, magnesium oxide is difficult to separate and remove due to a large amount of impurities contained in the magnesium or magnesium alloy melt, and is easy to remain as solid impurities; small size (less than 0.5)mm) is more difficult to separate and remove and is easier to be retained as solid inclusions.

The most common method for removing impurities from magnesium or magnesium alloy melt in the industry at present is flux refining, namely solid impurities are absorbed and captured by a flux taking chlorine salt as a main component, and the impurity removing effect depends on the mixing and contact degree of the flux and the magnesium or magnesium alloy melt, but the two are very different in physical characteristics, so that the full mixing is difficult to realize really, and the satisfactory impurity removing effect cannot be achieved usually. Further, flux refining has the following problems: chlorine salts in the flux release Cl at high temperatures₂And poisonous and harmful gases such as HCl and the like, the pollution is serious; residues are easy to generate, and secondary pollution to the melt is caused; for magnesium melt containing zirconium and rare earth, chlorine salt in the flux can react with the zirconium and the rare earth, and the yield of the zirconium and the rare earth is difficult to guarantee. Flux refining will face the possibility of being rejected.

For this reason, a great deal of theoretical research and technical development has been conducted in academia and industry. According to the research and the discovery of the literature, CN10380648A discloses a magnesium alloy melt purification method, which comprises the steps of firstly carrying out gas rotary blowing purification on a magnesium alloy melt and then carrying out foamed ceramic filtration purification treatment. CN106011512A discloses a magnesium alloy melt four-stage purification method, which comprises the following steps: under the protection of hydrogen, adding a purification flux into a magnesium ingot or magnesium intermediate alloy melt for refining to remove gas and nonmetallic inclusions in the melt; secondary purification is carried out in the tundish, and a rotary nozzle is adopted to blow mixed gas to remove gas contained in the magnesium alloy melt in the tundish; the third-stage purification is carried out on the magnesium liquid flowing out through a foamed ceramic filter before the liquid outlet of the smelting furnace enters a launder, and the magnesium liquid flowing out is filtered, degassed and deslagged; and (4) blowing hydrogen into the casting heat-preserving furnace in the fourth-stage purification, and adding a purification flux into the furnace for secondary refining and deslagging. CN101037729A discloses a flux-free remelting refining method for magnesium alloy furnace charge and a device thereof, which are characterized in that after the magnesium alloy furnace charge is preheated and dried, a composite multi-stage refining method is adopted to refine magnesium melt, and the steps of furnace charge melting, stirring refining or blowing refining, forced settling, filtering refining, standing refining, tapping and casting are included, so that impurities and gases in various magnesium alloy furnace charges can be effectively removed, and the high-quality purification of the melt is realized. In the above invention, gas refining, filtration refining and standing refining are involved in addition to partial need of using flux refining which faces elimination, and the following are analyzed respectively:

1) gas refining: the principle makes and relies on the bubble to adsorb and catch solid-state inclusion in the fuse-element, and the floating through the bubble will be mingled with and take to the fuse-element surface, reaches the purpose of getting rid of the inclusion, and its edulcoration effect depends on the adsorption efficiency of bubble to the inclusion and the diffusion degree of bubble. For magnesium oxide in magnesium or magnesium alloy melt, because the interface of the magnesium oxide and the magnesium alloy melt is wet and the mutual adsorption effect is strong, the adsorption and capture effect of the argon bubbles commonly used at present on the magnesium oxide is poor; the bubbles are difficult to ensure to contact with one hundred percent of melt, so that inclusion residues always exist; in the case of magnesium or magnesium melt, the surface is flame-retarded by flux or fluorine-containing protective gas, and a large amount of bubbles emerge to destroy the integrity of the flame-retardant layer on the surface of the melt, so that the risk of combustion exists.

2) And (3) filtering and refining: in both the foam-type and the orifice-type filter media, the filter channel size of the filter media for industrial use has a limit minimum value of about 1mm due to the need for magnesium or magnesium alloy liquid to flow through and the limitation of the preparation process thereof, so that the filtering method cannot be applied to solid inclusions smaller than the size.

3) Settling and refining: the settling refining relies mainly on the density difference, surface behavior and size between inclusions and the magnesium or magnesium alloy melt. For magnesium oxide in magnesium or magnesium alloy melt, the density of the magnesium oxide is 1.5-1.6g/cm³The density of the latter is less than or equal to 3.58g/cm³And the surfaces of the two are wet, and the interface has stronger physical adsorption, which is not beneficial to sedimentation separation, especially for small-size magnesium oxide.

Because the methods for removing magnesium or magnesium alloy melt and impurities in the prior art have respective defects, particularly for small-size magnesium oxide inclusions in magnesium or magnesium alloy melt, the small-size magnesium oxide inclusions are difficult to remove. Therefore, there is a need to design a method for removing magnesium oxide inclusions from a magnesium or magnesium alloy melt to solve the above problems.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to solve the problems that magnesium oxide, particularly small-size magnesium oxide, in magnesium and magnesium alloy melt is difficult to remove, so that the magnesium oxide is retained to become solid inclusion and the quality of the magnesium or magnesium alloy melt is reduced, and provides a method for removing the magnesium oxide inclusion in the magnesium or magnesium alloy melt.

In order to solve the technical problem, the technical scheme adopted by the invention is as follows:

a method for removing magnesium oxide inclusion in magnesium or magnesium alloy melt, in the process of smelting magnesium or magnesium alloy, adding a metal element capable of carrying out reduction reaction with magnesium oxide into the magnesium or magnesium alloy melt, and carrying out reduction reaction on the added metal element and the magnesium oxide to generate metal oxide and magnesium with density higher than that of the magnesium or magnesium alloy; then the newly generated metal oxide is settled at the bottom of the furnace by standing, thereby achieving the purpose of purifying the magnesium or magnesium alloy melt.

Further, the operation is specifically carried out according to the following steps:

(1) keeping the temperature of the magnesium or magnesium alloy melt at 650-750 ℃, and adding the weighed metal elements into the middle upper part of the magnesium melt by using a feeding tool;

(2) stirring for 5-30 minutes to ensure that the added metal elements and the magnesium oxide are mixed and fully reacted;

(3) and (3) preserving heat and standing for 30-120 minutes to ensure that metal oxide with the density larger than that of magnesium or magnesium alloy generated by the reaction is fully settled to the bottom of the furnace, thereby completing the removal of magnesium oxide inclusions.

Wherein the metal element is one or more of Sn, Cd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu. The metal element is added in the form of pure metal or intermediate alloy. The total amount of the metal elements added is 0-5% of the mass of the magnesium or magnesium alloy melt. The total amount of the metal elements added is 0.2-1.2% of the mass of the magnesium or magnesium alloy melt. The density of the oxide generated by the reaction of the added metal element and the magnesium oxide and the density of the produced oxide are shown in table 1, and the added metal can perform a reduction reaction with the magnesium oxide inclusion to generate the oxide with the density far greater than that of magnesium and magnesium alloy, so that the oxide can be easily separated from the magnesium and magnesium alloy to achieve the purpose of removing the magnesium oxide inclusion.

TABLE 1 addition of oxides of metal elements reacted with magnesium oxide

Compared with the prior art, the invention has the following advantages:

1. the method for removing the magnesium oxide inclusions in the magnesium or magnesium alloy melt can effectively remove the content of the magnesium oxide inclusions in the magnesium or magnesium alloy melt, particularly has good effect of removing the magnesium alloy inclusions aiming at small-size magnesium oxide (the size is less than 0.5mm) which cannot be removed in the prior art, and improves the quality of the magnesium or magnesium alloy. The removal distances in the invention are: because the metal elements added in the invention are all reducing elements, the magnesium and the metal oxides can be generated by reduction reaction with magnesium oxide inclusions in magnesium or magnesium melt. The generated magnesium is taken as a harmless component to enter the magnesium or magnesium alloy melt, and the generated metal oxide has high self density (6.95-9.42 g/cm)³) The magnesium oxide complex has the characteristics of poor wettability with magnesium melt, and also has the capability of complex agglomeration with magnesium oxide to form a composite oxide with a more compact surface and a larger size, so that magnesium oxide inclusions, particularly small-size magnesium oxide inclusions, can be complex agglomerated to form a metal oxide with a larger size. Under the drive of increased density difference and size, the newly generated high-density large-size metal oxide can be settled to the furnace bottom by standing by utilizing the density difference principle, so that the metal oxide is removed.

2. The method has high efficiency of reducing or removing the magnesia impurities. Because the added metal elements are uniformly distributed in the molten body after being melted, the magnesium oxide inclusion is ensured to be contacted and reacted with all the magnesium oxide inclusions, the efficiency of removing the magnesium oxide inclusions is high, and the problems that the magnesium oxide inclusions cannot be ensured to be completely contacted, and the efficiency of reducing or removing the magnesium oxide inclusions is low in the existing flux refining and gas refining are solved.

3. The invention does not need additional equipment, and the process is simple and feasible. The method provided by the invention can be directly implemented on the existing magnesium or magnesium alloy smelting operation equipment, no additional equipment and devices are needed, the method can be implemented only by adopting a conventional operation mode similar to alloy addition, and the method has the advantages of simple and feasible process and strong flexibility.

Detailed Description

The present invention will be further described with reference to the following examples.

A method for removing magnesium oxide inclusion in magnesium or magnesium alloy melt, in the process of smelting magnesium or magnesium alloy, adding a metal element capable of carrying out reduction reaction with magnesium oxide into the magnesium or magnesium alloy melt, and carrying out reduction reaction on the added metal element and the magnesium oxide to generate metal oxide and magnesium with density larger than that of the magnesium or magnesium alloy; then the newly generated metal oxide is settled at the bottom of the furnace by standing, thereby achieving the purpose of purifying the magnesium or magnesium alloy melt.

The method for removing the magnesium oxide inclusion in the magnesium or magnesium alloy melt is specifically operated according to the following steps:

(1) keeping the temperature of the magnesium or magnesium alloy melt at 650-750 ℃, and adding the weighed metal elements into the middle upper part of the magnesium melt by using a feeding tool;

(2) stirring for 5-30 minutes to ensure that the added metal elements and the magnesium oxide are mixed and fully reacted;

(3) and (3) preserving heat and standing for 30-120 minutes to ensure that metal oxide with the density larger than that of magnesium or magnesium alloy generated by the reaction is fully settled to the bottom of the furnace, thereby completing the removal of magnesium oxide inclusions.

Wherein the added metal elements are one or more of Sn, Cd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu.