Mg o-y 2 o 3 -based lightweight refractory raw material with core-shell structure and method for producing the same

Abstract

The application discloses a MgO-Y2O3-based light-weight refractory raw material with a core-shell structure and a preparation method thereof. The technical scheme is as follows: taking 45-64wt% of porous light-burned magnesium oxide, 34-52wt% of magnesium hydroxide and 2-5wt% of metallic yttrium as raw materials, additionally adding 1-1.5wt% of a nano calcium carbonate solution with a concentration of 500-4000ppm, ball milling for 1-3 hours, and machine pressing into a green body under the condition of 150-200MPa. The green body is heated to 700-900℃, and kept for 2-4 hours; then heated to 1520-1550℃, and kept for 1-3 hours; then heated to 1700-1800℃, and kept for 3-6 hours; and then naturally cooled in the furnace to obtain the MgO-Y2O3-based light-weight refractory raw material with the core-shell structure. The application has the advantages of simple process and low cost, and the prepared product has the advantages of low high-temperature vacuum volatilization rate, excellent thermal shock resistance and excellent hydration resistance, and is suitable for a high-temperature alloy vacuum smelting process or a vacuum secondary refining process of clean steel.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of MgO-Y2O3-based light-weight refractory raw materials. Specifically, it relates to a MgO-Y2O3-based light-weight refractory raw material with a core-shell structure and a preparation method thereof. BACKGROUND

[0002] Magnesia-based basic refractory materials have extremely high melting points, excellent slag penetration resistance, and certain ability to absorb S and P inclusions in the solution, so they are widely used in the smelting process of metal solutions. At the same time, magnesia raw materials generally have a large thermal expansion coefficient, resulting in poor thermal shock resistance, so they are generally used in combination.

[0003] For example, the patent technology "Yttria-magnesia infrared composite ceramic and preparation method thereof" (CN202111023487.1). This technology uses yttria nano powder and magnesia nano powder as raw materials, and through ball milling, drying, and grinding steps, and then through hot-pressing sintering to obtain yttria-magnesia infrared composite ceramic. The composite ceramic in this technology is made by high-temperature hot-pressing sintering. This sintering method not only has low production rate and high cost, but also causes MgO to decompose and produce Mg and O gas at high temperatures. These gases can affect the service performance of the magnesia lining and directly contaminate the melt with foreign inclusions.

[0004] For another example, the patent technology "Yttria-magnesia nano composite powder and preparation method thereof" (CN201811289297.2). This technology uses a metal ion solution of yttrium ions and magnesium ions, a dispersing agent, and a complexing agent as raw materials, and through sol-gel processing, freeze-drying, and high-temperature calcination processing to obtain yttria-magnesia nano composite powder. Although the yttria-magnesia nano composite powder prepared by this technology has uniform morphology and a particle size of less than 20 nm, the preparation process is complex. It is difficult to control the solution concentration change during the preparation process, and the prepared yttria-magnesia nano composite powder also cannot improve the problem of easy hydration during use, resulting in loose and peeling of the product.

[0005] For another example, the patent technology "Preparation method of coated spherical magnesia powder" (N202310764591.9). This technology uses magnesia as raw material, modifies it with coupling agent and water-soluble surface treatment agent, and through the processes of preparing slurry, spray granulation, and balling, finally calcining to obtain spherical magnesia powder. The MgO content of the magnesia powder is only greater than 95%, which not only has low purity of the prepared spherical magnesia powder, but also has a complex preparation process. Although the spherical magnesia powder prepared by this technology has good moisture resistance, the coupling agent used will introduce impurities into the raw material, affecting the high-temperature performance, and the preparation cost is high. SUMMARY

[0006] The present application aims at overcoming the defects of the prior art, and aims to provide a preparation method of MgO-Y2O3-based light-weight refractory raw material with core-shell structure, which has simple preparation process and low cost.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0008] Step 1, taking 45-64wt% of porous light-burned magnesium oxide, 34-52wt% of magnesium hydroxide and 2-5wt% of metal yttrium as raw materials, additionally adding 1-1.5wt% of nano calcium carbonate solution with a concentration of 500-4000ppm to the raw materials, ball milling for 1-3 hours, and machine pressing into a green body under the condition of 150-200MPa.

[0009] Step 2, first, the green body is heated to 700-900℃ and kept for 2-4 hours; then heated to 1520-1550℃ and kept for 1-3 hours; then heated to 1700-1800℃ and kept for 3-6 hours; and then naturally cooled in the furnace to obtain MgO-Y2O3-based light-weight refractory raw material with core-shell structure.

[0010] The microstructure of the MgO-Y2O3-based light-weight refractory raw material with core-shell structure has a full-grain boundary MgO-Y2O3 core-shell structure, and Y2O3 shell structure is continuously and densely generated in-situ on the grain boundary.

[0011] The MgO content in the porous light-burned magnesium oxide is >99.6wt%; and the micro-nano closed pores account for 45-55% of the total pores.

[0012] In the magnesium hydroxide, the Mg(OH)2 content is >99.7wt%, and the SiO2 content is <0.05wt%.

[0013] The Y content of the metal yttrium is >99.9wt%.

[0014] The preparation method of the nano calcium carbonate solution with a concentration of 500-4000ppm is as follows: according to the mass ratio of nano calcium carbonate: pure water being 1-8:1999, the nano calcium carbonate is added to the pure water, and stirred to obtain a nano calcium carbonate solution with a concentration of 500-4000ppm.

[0015] The CaCO3 content of the nano calcium carbonate is >99.9wt%.

[0016] The ball milling is as follows: taking corundum balls as the ball milling medium, and the mass ratio of the corundum balls: raw materials being 2-3:1.

[0017] Due to the adoption of the above technical solutions, the present application has the following positive effects compared with the prior art:

[0018] The present application uses high-purity magnesium hydroxide purified from salt lake and porous light-burned magnesia as composite raw materials, and in-situ decomposition of magnesium hydroxide generates pores at 700-900℃. The pores generated by the decomposition of magnesium hydroxide raw materials at this temperature still remain in the crystal structure of the mother body magnesium hydroxide, and a microcrystalline aggregate is formed. This phenomenon is "mother salt pseudomorph". The "mother salt pseudomorph" structure left by the magnesium hydroxide raw material ensures that the intracrystalline pores are not completely excluded during the medium-temperature sintering process, and ensures that the micro-nano closed pores account for a certain percentage of the total pores in the final prepared raw material. It is precisely due to the existence of such intracrystalline pores that the thermal stress of MgO-based raw materials can be dispersed under sharp temperature changes, thereby ensuring the thermal shock resistance of MgO-based raw materials. At the same time, due to the existence of pores, the bulk density of the magnesium-based raw material can be effectively reduced to achieve lightweight, and the intracrystalline pores also have the effect of avoiding contact with the external atmosphere, effectively improving the poor hydration resistance of lightweight magnesia.

[0019] After the first stage sintering, the present application is heated to 1520-1550℃ in the second stage for 1-3 hours, and in the second stage, the metal yttrium begins to melt and completely wets and wraps around the surface of MgO grains, forming a Y-MgO wrapping structure at high temperature. With the completion of the third stage high-temperature oxidation calcination process, the final complete oxidation forms a full-grain boundary MgO-Y2O3 core-shell structure, and the Y2O3 shell structure is continuously generated in-situ on the grain boundary; meanwhile, by taking advantage of the poor high-temperature solid solution ability of the CaO-Y2O3 binary structure, using CaO produced by the decomposition of nano-CaCO3 at high temperature as a sintering additive to reduce the sintering temperature and shorten the holding time in the final stage, the purpose of reducing energy consumption and improving material density is achieved. Y2O3 in the final prepared magnesium-based raw material can be uniformly distributed on the surface of MgO grains, and will not segregate and enrich on the surface; at the same time, there are a certain amount of nano-sized pores in the interior of MgO grains, which can effectively improve the thermal shock resistance of the product. This MgO-Y2O3 material with core-shell grain structure characteristics can use the uniformly distributed and stable Y2O3 shell on the grain boundary to hinder the contact of the external atmosphere with the MgO inside the core-shell, thereby improving the hydration resistance of the MgO-Y2O3-based lightweight refractory raw material with core-shell structure, and the Y2O3 wrapping structure on the grain boundary can also prevent the volatilization of MgO at high temperature, thereby reducing the volatilization rate of intracrystalline MgO at high temperature under vacuum.

[0020] The application utilizes the raw material characteristics of high chemical purity and few impurities of salt lake magnesium, and through the above-mentioned grain boundary core-shell material structure design and multi-section heat preservation sintering preparation process, the prepared MgO-Y2O3-based light refractory raw material with core-shell structure has excellent thermal shock resistance and hydration resistance, and has strong volatilization resistance in a high-temperature vacuum environment; meanwhile, high-purity magnesium hydroxide and porous light-burned magnesium oxide purified from a salt lake are used as main raw materials, which avoids a large amount of CO2 emission generated by decomposition of magnesite in the raw material preparation process, and is more conducive to reducing carbon emissions.

[0021] The MgO-Y2O3-based light refractory raw material with core-shell structure prepared by the application has the following properties: an apparent porosity of 5.6-11.2%; a bulk density of 3.25-3.45 g / cm 3 ; an MgO content of 95-97 wt%; a Y2O3 content of 2-5 wt%; a high-temperature vacuum volatilization rate of 0.75-1.22% under the conditions of a temperature of 1700 DEG C and a pressure of 10 Pa for 1 h; and a strength retention rate of 55-68% after three times of water cooling at 1100-20 DEG C.

[0022] Therefore, the application has the characteristics of simple process and low cost, and the prepared MgO-Y2O3-based light refractory raw material with core-shell structure has low high-temperature vacuum volatilization rate, excellent thermal shock resistance and excellent hydration resistance, and is suitable for a high-temperature alloy vacuum melting process or a clean steel vacuum secondary refining process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A photo of the MgO-Y2O3-based light refractory raw material with core-shell structure prepared by the application before high-temperature vacuum treatment.

[0024] Figure 2 A photo of the MgO-Y2O3-based light refractory raw material with core-shell structure prepared by the application after high-temperature vacuum treatment. Figure 1 A photo of the MgO-Y2O3-based light refractory raw material with core-shell structure prepared by the application after high-temperature vacuum treatment. DETAILED DESCRIPTION

[0025] In order to further understand the application, the application is further described below in combination with the drawings and specific embodiments, which are not limitations to the protection scope of the application.

[0026] A MgO-Y2O3-based light refractory raw material with core-shell structure and a preparation method thereof, the preparation method of the specific embodiment is:

[0027] Step 1, taking 45-64wt% porous light-burned magnesium oxide, 34-52wt% magnesium hydroxide and 2-5wt% metal yttrium as raw materials, adding 1-1.5wt% nano calcium carbonate solution with a concentration of 500-4000ppm to the raw materials, ball milling for 1-3 hours, and machine pressing into a green body under the condition of 150-200MPa.

[0028] Step 2, first heating the green body to 700-900℃ and keeping for 2-4 hours; then heating to 1520-1550℃ and keeping for 1-3 hours; then heating to 1700-1800℃ and keeping for 3-6 hours; and naturally cooling in the furnace to obtain MgO-Y2O3-based light-weight refractory raw material with core-shell structure.

[0029] The preparation method of the nano calcium carbonate solution with a concentration of 500-4000ppm is as follows: adding the nano calcium carbonate into purified water according to the mass ratio of nano calcium carbonate: purified water being 1-8:1999, stirring to obtain the nano calcium carbonate solution with a concentration of 500-4000ppm.

[0030] The ball milling is as follows: taking corundum balls as the ball milling medium, and the mass ratio of corundum balls: raw materials being 2-3:1.

[0031] In the specific embodiment:

[0032] The microstructure of the MgO-Y2O3-based light-weight refractory raw material with core-shell structure has a full-grain boundary MgO-Y2O3 core-shell structure, and Y2O3 shell structure is continuously and densely generated in-situ on the grain boundary.

[0033] The MgO content in the porous light-burned magnesium oxide is >99.6wt%; and the micro-nano closed pores account for 45-55% of the total pores.

[0034] The Mg(OH)2 content in the magnesium hydroxide is >99.7wt%, and the SiO2 content is <0.05wt%.

[0035] The Y content in the metal yttrium is >99.9wt%.

[0036] The CaCO3 content in the nano calcium carbonate is >99.9wt%.

[0037] Example 1

[0038] A MgO-Y2O3-based light-weight refractory raw material with core-shell structure and a preparation method thereof, the preparation method of the specific embodiment is as follows:

[0039] Step 1, taking 45wt% porous light-burned magnesium oxide, 52wt% magnesium hydroxide and 3wt% metal yttrium as raw materials, adding 1.5wt% nano calcium carbonate solution with a concentration of 500ppm to the raw materials, and ball milling for 3 hours to form a green body under the condition of 180MPa.

[0040] Step 2, first heating the green body to 900℃ and keeping for 4 hours, then heating to 1530℃ and keeping for 2 hours, and then heating to 1750℃ and keeping for 5 hours, and naturally cooling in the furnace to obtain MgO-Y2O3-based light-weight refractory raw material with core-shell structure.

[0041] The preparation method of the nano calcium carbonate solution with a concentration of 500ppm is as follows: adding nano calcium carbonate into purified water according to the mass ratio of nano calcium carbonate: purified water = 1:1999, stirring to obtain a nano calcium carbonate solution with a concentration of 500ppm.

[0042] The ball milling is as follows: taking corundum balls as the ball milling medium, and the mass ratio of corundum balls: raw materials = 2:1.

[0043] The MgO-Y2O3-based light-weight refractory raw material with core-shell structure prepared in this embodiment is tested, and the results are as follows: the apparent porosity is 9.80%; the bulk density is 3.36g / cm 3 ; the MgO content is 97wt%; the Y2O3 content is 3wt%; the high-temperature vacuum volatilization rate is 1.04% under the condition of vacuum induction melting furnace temperature 1700℃ and pressure 10Pa for 1h (the high-temperature vacuum volatilization rate of the comparative sample 97 fused magnesia is 2.54%); the strength retention rate after three times of water cooling from 1100℃ to 20℃ is 56%, and the strength retention rate of the sample before and after water cooling is used to represent the thermal shock resistance and hydration resistance of the raw material.

[0044] Example 2

[0045] A MgO-Y2O3-based light-weight refractory raw material with core-shell structure and a preparation method thereof, the preparation method of the embodiment is as follows:

[0046] Step 1, taking 47wt% porous light-burned magnesium oxide, 48wt% magnesium hydroxide and 5wt% metal yttrium as raw materials, adding 1.5wt% nano calcium carbonate solution with a concentration of 4000ppm to the raw materials, and ball milling for 3 hours to form a green body under the condition of 200MPa.

[0047] Step 2, first heating the green body to 800℃ and keeping for 3 hours, then heating to 1550℃ and keeping for 3 hours, and then heating to 1800℃ and keeping for 3 hours, and naturally cooling in the furnace to obtain MgO-Y2O3-based light-weight refractory raw material with core-shell structure.

[0048] The preparation method of the nano calcium carbonate solution with the concentration of 4000 ppm is as follows: the nano calcium carbonate is added into purified water according to the mass ratio of 8:1999, and stirring is conducted to prepare the nano calcium carbonate solution with the concentration of 4000 ppm.

[0049] The ball milling is as follows: the corundum ball is used as the ball milling medium, and the mass ratio of the corundum ball to the raw material is 3:1.

[0050] The MgO-Y2O3-based light-weight refractory raw material with the core-shell structure prepared in the embodiment is tested, and the apparent porosity is 5.60%, the bulk density is 3.45 g / cm 3 , the MgO content is 95 wt%, the Y2O3 content is 5 wt%, the high-temperature vacuum volatilization rate is 0.75% (the high-temperature vacuum volatilization rate of a comparative sample 97 fused magnesia is 2.54%) under the condition that the temperature of the vacuum induction melting furnace is 1700 ℃ and the pressure is 10 Pa, and the strength retention rate after three times of water cooling from 1100 ℃ to 20 ℃ is 68%, and the strength retention rate of the sample before and after water quenching is used to represent the thermal shock resistance and hydration resistance of the raw material.

[0051] Embodiment 3

[0052] A MgO-Y2O3-based light-weight refractory raw material with a core-shell structure and a preparation method thereof, the preparation method of the embodiment is as follows:

[0053] Step 1: 64 wt% of porous light-burned magnesium oxide, 34 wt% of magnesium hydroxide and 2 wt% of metallic yttrium are used as raw materials, and 1 wt% of nano calcium carbonate solution with the concentration of 2000 ppm is additionally added, and ball milling is conducted for 2 hours, and the green body is formed by machine pressing under the condition that the pressure is 180 MPa.

[0054] Step 2: the green body is first heated to 700 ℃ and kept for 4 hours, then heated to 1520 ℃ and kept for 3 hours, and then heated to 1700 ℃ and kept for 6 hours, and the MgO-Y2O3-based light-weight refractory raw material with the core-shell structure is prepared by natural cooling in the furnace.

[0055] The preparation method of the nano calcium carbonate solution with the concentration of 2000 ppm is as follows: the nano calcium carbonate is added into purified water according to the mass ratio of 4:1999, and stirring is conducted to prepare the nano calcium carbonate solution with the concentration of 2000 ppm.

[0056] The ball milling is as follows: the corundum ball is used as the ball milling medium, and the mass ratio of the corundum ball to the raw material is 2.5:1.

[0057] The MgO-Y2O3-based light-weight refractory raw material with the core-shell structure prepared in the embodiment is tested, and the apparent porosity is 11.2%, the bulk density is 3.25 g / cm3 ; MgO content is 98wt%; Y2O3 content is 2wt%; under the condition of vacuum induction melting furnace temperature 1700℃ and pressure 10Pa, heat preservation and pressure 1h, high temperature vacuum volatile rate is 1.22%(comparative sample 97 fused magnesite 2.54%), strength retention rate after three times of water cooling from 1100℃ to 20℃ is 55%, the pressure strength retention rate of the sample before and after water quenching is used to represent the thermal shock resistance and hydration resistance of the raw material.

[0058] Example 4

[0059] A MgO-Y2O3-based lightweight refractory raw material with core-shell structure and a preparation method thereof, the preparation method of the embodiment is:

[0060] Step 1, taking 50wt% porous light burned magnesia, 46wt% magnesium hydroxide and 4wt% metal yttrium as raw materials, adding 1wt% of the raw material 1000ppm concentration nano calcium carbonate solution, ball milling for 1 hour, and machine pressing into a green body under the condition of 150MPa.

[0061] Step 2, first heat the green body to 700℃ and keep for 2 hours; then heat to 1550℃ and keep for 1 hour; then heat to 1780℃ and keep for 4 hours; natural cooling in the furnace, to obtain a MgO-Y2O3-based lightweight refractory raw material with core-shell structure.

[0062] The preparation method of the 1000ppm concentration nano calcium carbonate solution is: according to the mass ratio of nano calcium carbonate: pure water is 2:1999, the nano calcium carbonate is added to the pure water, stirred, to obtain a 1000ppm concentration nano calcium carbonate solution.

[0063] The ball milling is: taking corundum balls as the ball milling medium, the mass ratio of corundum balls: raw materials is 2.5:1.

[0064] The MgO-Y2O3-based lightweight refractory raw material with core-shell structure prepared in this embodiment is tested: apparent porosity is 7.6%; bulk density is 3.41g / cm 3 ; MgO content is 96wt%; Y2O3 content is 4wt%; under the condition of vacuum induction melting furnace temperature 1700℃ and pressure 10Pa, heat preservation and pressure 1h, high temperature vacuum volatile rate is 0.81%(comparative sample 97 fused magnesite 2.54%), strength retention rate after three times of water cooling from 1100℃ to 20℃ is 58%, the pressure strength retention rate of the sample before and after water quenching is used to represent the thermal shock resistance and hydration resistance of the raw material.

[0065] Compared with the prior art, the embodiment has the following positive effects:

[0066] The embodiment uses high-purity magnesium hydroxide purified from salt lake and porous light-burned magnesium oxide as composite raw materials, and in-situ decomposition of magnesium hydroxide generates pores at 700-900°C. The pores generated by decomposition of the magnesium hydroxide raw material at the temperature still remain in the crystal structure of the mother body magnesium hydroxide, and microcrystalline aggregates are formed. This phenomenon is "mother salt pseudomorph". The "mother salt pseudomorph" structure left by the magnesium hydroxide raw material guarantees that the intracrystalline pores are not completely excluded in the medium-temperature sintering process, and guarantees that the micro-nano closed pores in the final prepared raw material account for a certain ratio of the total pores. It is just because of the existence of the intracrystalline pores that the thermal stress borne by the MgO-based raw material can be dispersed under sharp temperature change, thereby guaranteeing the thermal shock resistance of the MgO-based raw material. At the same time, the existence of the pores can effectively reduce the bulk density of the magnesium-based raw material to achieve lightweight, and the intracrystalline pores also have the effect of avoiding contact with the external atmosphere, thereby effectively improving the poor hydration resistance of the lightweight magnesia.

[0067] The embodiment heats to 1520-1550°C in the second stage after the first stage sintering, and keeps for 1-3 hours. In the second stage, the metal yttrium begins to melt and completely wets and wraps the surface of the MgO crystal grains, and a Y-MgO wrapping structure is formed at high temperature. With the completion of the third stage high-temperature oxidation calcination process, the final complete oxidation forms a full-grain boundary MgO-Y2O3 core-shell structure, and the Y2O3 shell structure is continuously generated in-situ on the grain boundary. At the same time, by using the poor high-temperature solid solution ability of the CaO-Y2O3 binary structure, the CaO produced by decomposition of the nano CaCO3 at high temperature is used as a sintering additive to reduce the sintering temperature and shorten the holding time in the final stage, so as to reduce the energy consumption and improve the material density. The Y2O3 in the finally prepared magnesium-based raw material can be uniformly distributed on the surface of the MgO crystal grains, and will not be segregated and enriched on the surface. At the same time, there is a certain amount of nano-sized pores in the interior of the MgO crystal grains, and this nano-sized pore structure can effectively improve the thermal shock resistance of the product. The MgO-Y2O3 material with the core-shell grain structure characteristics can use the uniformly distributed and stable Y2O3 shell on the grain boundary to hinder the contact of the external atmosphere with the MgO inside the core-shell, thereby improving the hydration resistance of the material. At the same time, the Y2O3 wrapping structure on the grain boundary can also prevent the volatilization of MgO at high temperature, thereby reducing the volatilization rate of the intracrystalline MgO under high-temperature vacuum. As shown in Figure 1 and Figure 2 It can be seen that: the MgO-Y2O3-based lightweight refractory raw material with the core-shell structure prepared in Example 1 generates MgO whiskers on the surface under high-temperature vacuum, and has excellent anti-volatilization ability; wherein: Figure 1 is a photo of the MgO-Y2O3-based lightweight refractory raw material with the core-shell structure prepared in Example 1 before high-temperature vacuum treatment; Figure 2 Figure 1 is a photo of the MgO-Y2O3-based lightweight refractory raw material with the core-shell structure shown in the drawing after high-temperature vacuum treatment at 1700°C×1h, 10Pa.

[0068] The embodiment utilizes the characteristics of high chemical purity and few impurities of the raw material of salt lake magnesium, and through the above-mentioned grain boundary core-shell material structure design and multi-section heat preservation sintering preparation process, the prepared MgO-Y2O3-based lightweight refractory raw material with core-shell structure has excellent thermal shock resistance and hydration resistance, and has strong volatility resistance in a high-temperature vacuum environment. Meanwhile, high-purity magnesium hydroxide purified by a salt lake and porous light-burned magnesium oxide are used as main raw materials, which avoids the emission of a large amount of CO2 generated by the decomposition of magnesite in the raw material preparation process, and is more conducive to reducing carbon emissions.

[0069] The MgO-Y2O3-based lightweight refractory raw material with core-shell structure prepared in the embodiment is detected to have an apparent porosity of 5.6-11.2%, a bulk density of 3.25-3.45 g / cm 3 , an MgO content of 95-97 wt%, a Y2O3 content of 2-5 wt%, a high-temperature vacuum volatility of 0.75-1.22% under the conditions of a temperature of 1700°C and a pressure of 10 Pa for 1 h of heat preservation and pressure preservation, and a strength retention rate of 55-68% after three times of water cooling at 1100-20°C. The strength retention rate of the sample before and after water cooling is used to represent the thermal shock resistance and hydration resistance of the raw material.

[0070] Therefore, the embodiment has the characteristics of simple process and low cost, and the prepared MgO-Y2O3-based lightweight refractory raw material with core-shell structure has low high-temperature vacuum volatility, excellent thermal shock resistance and excellent hydration resistance, and is suitable for a high-temperature alloy vacuum melting process or a clean steel vacuum secondary refining process.

Claims

1. A method for producing MgO-Y203-based lightweight refractory raw material having a core-shell structure, characterized by The preparation method is as follows: Step 1, taking 45-64 wt% of porous light-burned magnesium oxide, 34-52 wt% of magnesium hydroxide and 2-5 wt% of metal yttrium as raw materials, plus 1-1.5 wt% of nano calcium carbonate solution with a concentration of 500-4000 ppm of the raw materials, ball milling for 1-3 hours, and machine pressing into a green body under the condition of 150-200 MPa; Step 2, first heat the green body to 700-900℃, and keep for 2-4 hours; then heat to 1520-1550℃, and keep for 1-3 hours; then heat to 1700-1800℃, and keep for 3-6 hours; and cool naturally in the furnace, to obtain MgO-Y2O3-based light-weight refractory raw material with core-shell structure.

2. The method of producing MgO-Y203-based lightweight refractory raw material having a core-shell structure according to claim 1, characterized in that The MgO content in the porous light-burned magnesium oxide is >99.6 wt%; the micro-nano closed pores account for 45-55% of the total pores.

3. The method of producing MgO-Y203-based lightweight refractory raw material having a core-shell structure according to claim 1, characterized in that The Mg(OH)2 content in the magnesium hydroxide is >99.7 wt%, and the SiO2 content is <0.05 wt%.

4. The method of producing MgO-Y203-based light weight refractory raw material having a core-shell structure according to claim 1, characterized in that The Y content of the metal yttrium is >99.9 wt%.

5. The method of producing MgO-Y2O3 based lightweight refractory raw material having a core-shell structure according to claim 1, characterized in that The preparation method of the nano calcium carbonate solution with a concentration of 500-4000 ppm is: according to the mass ratio of nano calcium carbonate: pure water of 1-8:1999, the nano calcium carbonate is added to the pure water, stirred, to obtain a nano calcium carbonate solution with a concentration of 500-4000 ppm; The CaCO3 content of the nano calcium carbonate is >99.9 wt%.

6. The method of producing MgO-Y203-based light weight refractory raw material having a core-shell structure according to claim 1, characterized in that The ball milling is: taking corundum balls as the ball milling medium, and the mass ratio of corundum balls: raw materials is 2-3:

1.

7. A MgO-Y203 based lightweight refractory raw material having a core-shell structure, characterized in that The MgO-Y2O3-based light-weight refractory raw material with core-shell structure is prepared according to the preparation method of the MgO-Y2O3-based light-weight refractory raw material with core-shell structure according to any one of claims 1-6.

8. The MgO-Y203-based lightweight refractory raw material having a core-shell structure according to claim 7, characterized in that The microstructure of the MgO-Y2O3-based light-weight refractory raw material with core-shell structure has a full-grain boundary MgO-Y2O3 core-shell structure, and Y2O3 shell structure is continuously dense in situ on the grain boundary.

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