MgO-Y2O3 refractory material with multi-scale core-shell structure and preparation method of MgO-Y2O3 refractory material

Abstract

The invention relates to a MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method of the MgO-Y2O3 refractory material. According to the technical scheme, the preparation method comprises the following steps: taking 14 to 18 weight percent of MgO-Y2O3 refractory aggregate I, 28 to 32 weight percent of MgO-Y2O3 refractory aggregate II and 12 to 18 weight percent of MgO-Y2O3 refractory aggregate III as aggregates, taking 9 to 16 weight percent of MgO-Y2O3 fine powder, 16 to 23 weight percent of magnesia fine powder and 2 to 8 weight percent of yttrium oxide micron powder as matrixes, and carrying out ball milling on the matrixes to obtain a matrix material; the preparation method comprises the following steps: placing aggregate in a stirrer, adding a composite binder accounting for 2-4wt% of the sum of the aggregate and the matrix, stirring, adding the matrix material, mixing, molding and drying under the condition of 100-200MPa, heating to 1500-1600 DEG C at the rate of 3-5 DEG C / min, keeping the temperature for 4-6 hours, and cooling along with a furnace to prepare the MgO-Y2O3 refractory material with the multi-scale core-shell structure. The product prepared by the invention has the characteristics of low cost, long service life, good high-temperature vacuum stability, excellent thermal shock resistance and excellent erosion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of MgO-Y2O3 refractory materials. In particular, it relates to a MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method thereof. BACKGROUND

[0002] MgO-Y2O3 refractory materials have great potential in the high-temperature alloy smelting field containing active metals due to their good chemical stability and high-temperature mechanical properties, and therefore have attracted the attention of those skilled in the art.

[0003] For example, the patent technology "Anti-erosion yttria permeable refractory material, preparation method and use" (CN202411892881.2) uses Y2O3 powder as raw material and one of TiO2, SrO and CaO as sintering aid to prepare a yttria refractory material. Although the sintering temperature of this refractory material is reduced and the anti-erosion performance is improved, the refractory material is prone to cracking when the temperature changes suddenly, resulting in poor thermal shock stability.

[0004] For example, the patent technology "MgO-Y2O3-based crucible for super-vacuum smelting of Ni-TiAl alloy and preparation method thereof" (CN202410177577.3) uses magnesium hydroxide, light-burned magnesium oxide, metallic yttrium, calcium carbonate, pure calcium aluminate cement and calcium fluoride as raw materials to prepare a MgO-Y2O3-based crucible. Although the thermal shock stability of this product is good, the sintering temperature of this process is high, the energy consumption is large, and impurities are introduced, which limits the anti-erosion performance of the crucible.

[0005] For example, the patent technology "Magnesia-based strong corrosion-resistant refractory material and preparation method thereof" (CN202210907410.9) uses forsterite, magnesium aluminate spinel, Sialon powder and calcium zirconate as raw materials to prepare a magnesia-based refractory material. Although the strength of this refractory material is high and the anti-erosion performance is good, the magnesium oxide in this refractory material is prone to volatilization in a high-temperature vacuum environment, resulting in poor high-temperature vacuum stability and low service life.

[0006] For example, the patent technology "Method for preparing yttria refractory material product by gel casting and crucible" (CN202210099193.5) uses pure yttria as raw material to prepare a yttria refractory material. Although the anti-erosion performance of this refractory material is good, the sintering temperature of this refractory material is high and the manufacturing cost is high, which is not conducive to popularization. In summary, the existing technologies have the following technical defects: high cost, low service life, poor high-temperature vacuum stability, poor thermal shock stability and poor anti-erosion performance. SUMMARY

[0007] The present application aims to overcome the existing technical defects, and aims to provide a preparation method of MgO-Y2O3 refractory material with multi-scale core-shell structure, and the MgO-Y2O3 refractory material with multi-scale core-shell structure prepared by the method has long service life, good high-temperature vacuum stability, excellent thermal shock stability and excellent corrosion resistance.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows: Step 1, mix 92-98wt% of light-burned magnesium oxide fine powder and 2-8wt% of yttrium oxide nano powder, ball mill for 2-4h, and then machine press forming under the condition of 100-200MPa; then heat to 1550-1650℃ at a rate of 2-5℃ / min in a high-temperature furnace, keep warm for 3-6h, cool down with the furnace, crush, and sieve, respectively obtain refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 fine powder.

[0009] Step 2, according to the mass ratio of binder:yttrium oxide micron powder is 100:2-6, batching, mixing, to obtain a composite binder.

[0010] Step 3, take 14-18wt% of refractory aggregate I, 28-32wt% of refractory aggregate II, 12-18wt% of refractory aggregate III as aggregate, take 9-16wt% of MgO-Y2O3 fine powder, 16-23wt% of magnesia fine powder and 2-8wt% of yttrium oxide micron powder as matrix.

[0011] Ball mill the matrix for 2-4h to obtain a matrix material; put the aggregate in a stirrer, add 2-4wt% of the composite binder outside the aggregate and the matrix material, stir, then add the matrix material and mix; machine press forming under the condition of 100-200MPa, dry at 100-200℃ for 20-26h; then heat to 1500-1600℃ at a rate of 3-5℃ / min, keep warm for 4-6h, cool down with the furnace, to obtain the MgO-Y2O3 refractory material with multi-scale core-shell structure.

[0012] The light-burned magnesium oxide fine powder is obtained by calcining magnesium hydroxide fine powder at 820-850℃ for 1-3h, the particle size of the light-burned magnesium oxide fine powder is <30μm, and the MgO content of the light-burned magnesium oxide fine powder is 97-99wt%.

[0013] The particle size of the magnesium hydroxide fine powder is <44μm, and the MgO content of the magnesium hydroxide fine powder is 65-66wt%.

[0014] The particle size of the yttrium oxide nano powder is <50nm, and the Y2O3 content of the yttrium oxide nano powder is >99.9wt%.

[0015] The ball mill uses high-aluminum corundum balls as the medium; the mass ratio of high-aluminum corundum balls to raw materials is 2-4:1.

[0016] The binder is a mixture obtained by mixing sodium carboxymethyl cellulose and deionized water at a mass ratio of 0.5-1.5:100 for 16-24 hours; or a mixture obtained by mixing polyvinyl butyral and ethanol at a mass ratio of 5.26-8.70:100 for 16-24 hours.

[0017] The particle size of the yttrium oxide micron powder is less than 10 μm; the Y2O3 content of the yttrium oxide micron powder is greater than 99 wt%.

[0018] The particle size of the MgO-Y2O3 fine powder is less than 70 μm; the MgO content of the MgO-Y2O3 fine powder is 92-98 wt%.

[0019] The particle size of the magnesia fine powder is less than 0.088 mm; and the MgO content of the magnesia fine powder is greater than 96 wt %.

[0020] The refractory aggregate I, refractory aggregate Ⅰ and refractory aggregate ⅢⅠ are respectively: MgO-Y2O3 refractory aggregate with a particle size less than 5mm and greater than or equal to 3mm, MgO-Y2O3 refractory aggregate with a particle size less than 3mm and greater than or equal to 1mm, and MgO-Y2O3 refractory aggregate with a particle size less than 1mm and greater than or equal to 0.088mm, and the MgO content of the refractory aggregate is 92~98wt%.

[0021] The MgO-Y2O3 refractory aggregate has a micron-scale core-shell structure with MgO microparticles as the core and continuous and dense Y2O3 as the shell; the average particle size of the MgO microparticles in the MgO-Y2O3 refractory aggregate is 30-50μm, and the thickness of the Y2O3 shell is 1-3μm.

[0022] The MgO-Y2O3 refractory material with a multi-scale core-shell structure is a multi-scale core-shell structure having a micron-scale MgO-Y2O3 refractory aggregate with MgO microparticles as the core and continuous and dense Y2O3 as the shell, and a continuous and dense Y2O3 layer distributed between the aggregate and the matrix as the shell; wherein: the thickness of the continuous Y2O3 layer distributed between the aggregate and the matrix is ​​0.2~0.4mm.

[0023] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art: The application designs the whole process from the aggregate to the product, and the MgO-Y2O3 refractory aggregate in the MgO-Y2O3 refractory material (hereinafter referred to as the product) with a multi-scale core-shell structure has a micron-scale core-shell structure with MgO microparticles as the core and continuous dense Y2O3 as the shell. Compared with the prior art, the core-shell structure is stable at high temperature, and the high-temperature vacuum volatility is lower. Secondly, a millimeter-scale Y2O3 shell is constructed on the surface of the aggregate with a micron-scale core-shell structure, a jagged occlusion-like interface structure is formed at the shell-aggregate interface, and Y2O3 micropowder is added to the matrix to form a micro-millimeter-scale core-shell structure and repair the possible damaged core-shell structure in the MgO-Y2O3 fine powder, and the shell on the surface of the aggregate and the MgO-Y2O3 refractory aggregate with a micron-scale core-shell structure together constitute a multi-scale core-shell structure.

[0024] The product prepared by the application has a multi-scale core-shell structure, which can effectively improve the high-temperature vacuum stability, thereby avoiding pollution of the product to the alloy melt. Firstly, the Y2O3 in the MgO-Y2O3 refractory aggregate with a micro-core-shell structure is uniformly pinned at the MgO grain boundary as a second phase to form a continuous dense Y2O3 layer wrapping the core-shell structure of MgO; secondly, by constructing a millimeter-scale continuous dense Y2O3 shell on the surface of the aggregate and a micro-core-shell structure in the matrix, the multi-scale Y2O3 shell isolates MgO from the high-temperature alloy liquid, avoiding the Mg, O vapor volatilized from MgO under high-temperature vacuum conditions from entering the alloy liquid. According to chemical reaction kinetics, when the vapor concentration in the shell increases, the decomposition reaction rate can be slowed down, greatly reducing the high-temperature vacuum volatility of the product, improving the high-temperature vacuum stability, making up for the problem of easy volatilization and peeling of traditional magnesia refractory materials, avoiding pollution of the product to the alloy melt, and prolonging the service life of the product.

[0025] The application improves the thermal shock stability of the product by Y2O3 second phase strengthening and toughening mechanism. Firstly, Y2O3 in the aggregate is uniformly pinned at the MgO grain boundary as a second phase, which can prevent abnormal grain growth, refine the grains, and increase the number of grain boundaries in the aggregate, thereby improving the strength and making the micro-cracks generated by thermal shock be reflected and absorbed at the grain boundaries multiple times, reducing the formation of macro-cracks. For the product, due to the difference between the thermal expansion coefficients of magnesium oxide and yttrium oxide, when the temperature rises, MgO expands faster, and the Y2O3 shell layer has a low expansion coefficient which can constrain its expansion, generating compressive stress; when the temperature decreases, MgO shrinks faster, and the Y2O3 shell layer provides tensile stress buffering. This stress interaction can reduce the thermal stress concentration caused by uneven thermal expansion and contraction in the material, thereby reducing crack generation. Secondly, the Y2O3 layer as a second phase can induce crack deflection, branching or passivation when the generated crack encounters the Y2O3 layer during the propagation process, thereby inhibiting the rapid propagation of the crack. Finally, the multi-scale core-shell structure prepared by the application forms a serrated occlusion-like interface structure at the aggregate-shell-matrix interface, which makes the aggregate-shell and shell-matrix tightly combined, thereby improving the strength and thermal shock stability of the product.

[0026] The application utilizes the multi-scale core-shell structure and the raw material with certain activity, and combines the characteristics of Y2O3 which is not easy to react with alloy liquid, thereby reducing the preparation cost and improving the erosion resistance of the product. Firstly, the aggregate uses light-burned MgO as the raw material, which retains certain lattice distortion, thereby providing diffusion channels for the subsequent sintering process, reducing the sintering temperature while ensuring the density of the aggregate, thereby reducing the preparation cost and being more conducive to popularization; meanwhile, Y2O3 in the aggregate is uniformly pinned at the MgO grain boundary as a second phase, which reduces the pores that are difficult to remove due to abnormal grain growth during the sintering process, and promotes the sintering process, thereby improving the erosion resistance of the aggregate and reducing the preparation cost. Secondly, in the vacuum melting and casting of alloys with active metals, the high-activity metal is easy to chemically react with the crucible and cause pollution, and Y element has extremely strong reducibility, so the generated oxide is difficult to be replaced by other metals. The reaction between the common active metals Ti and Al and Y2O3 is calculated thermodynamically, and the Gibbs free energy at 2500 DEG C is as high as 145.76 KJ, so it is difficult to react. Therefore, after the multi-scale Y2O3 shell is introduced, the multi-scale shell can isolate MgO from the high-temperature alloy liquid, and the alloy is difficult to directly contact MgO and react with it, thereby having extremely high chemical stability, improving the erosion resistance of the product, and overcoming the problem of reducing the service life due to the chemical reaction between the crucible and the alloy.

[0027] The MgO-Y2O3 refractory aggregate is detected to have a apparent porosity of 0.6-1.14%, a bulk density of 3.73-3.88 g / cm 3The high-temperature vacuum evaporation rate of the MgO-Y2O3 refractory material with the multi-scale core-shell structure prepared by the method is 0.5-1.02% under the condition of a temperature of 1700 DEG C and a pressure of 10 Pa.

[0028] The MgO-Y2O3 refractory material with the multi-scale core-shell structure prepared by the method has the following performance indexes: the apparent porosity is 1.23-2.56%; the bulk density is 3.23-3.69 g / cm 3 ; and the high-temperature bending strength is 14-20 MPa at 1500 DEG C.

[0029] The detection standards of the performance indexes are as follows: the apparent porosity and the bulk density are detected according to GB / T2997-2000; and the high-temperature bending strength is detected according to GB / T3002-2004.

[0030] Therefore, the MgO-Y2O3 refractory material with the multi-scale core-shell structure prepared by the method has the characteristics of low cost, long service life, good high-temperature vacuum stability, excellent thermal shock stability and excellent corrosion resistance. DETAILED DESCRIPTION

[0031] The application will be further described in combination with the specific embodiments, but is not limited to the protection scope.

[0032] The application relates to a MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method thereof. The preparation method comprises the following steps: Step 1, 92-98 wt% of light-burned magnesia fine powder and 2-8 wt% of yttrium oxide nano-powder are mixed, ball-milled for 2-4 h, and then formed into a shape under the condition of 100-200 MPa; then the temperature is raised to 1550-1650 DEG C at a rate of 2-5 DEG C / min in a high-temperature furnace, the temperature is kept for 3-6 h, the furnace is cooled, the product is broken and sieved, and refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 fine powder are obtained.

[0033] Step 2, the composite binder is obtained by mixing according to the mass ratio of the binder to yttrium oxide micron powder of 100:2-6.

[0034] Step 3, 14-18 wt% of the refractory aggregate I, 28-32 wt% of the refractory aggregate II, 12-18 wt% of the refractory aggregate III are used as the aggregate, 9-16 wt% of the MgO-Y2O3 fine powder, 16-23 wt% of the magnesia fine powder and 2-8 wt% of the yttrium oxide micron powder are used as the matrix.

[0035] The matrix is ball milled for 2-4 h to obtain a matrix material; the aggregate is placed in a blender, 2-4 wt% of a composite binder based on the total weight of the aggregate and the matrix material is added, and stirred, and then the matrix material is added and mixed; the mixture is formed by machine pressing under a pressure of 100-200 MPa, and dried at 100-200 ℃ for 20-26 h; then the temperature is raised to 1500-1600 ℃ at a rate of 3-5 ℃ / min, and held for 4-6 h, and then cooled in the furnace to obtain the MgO-Y2O3 refractory material with a multi-scale core-shell structure.

[0036] The light-burned magnesium oxide fine powder is obtained by calcining the magnesium hydroxide fine powder at 820-850 ℃ for 1-3 h, and the MgO content of the light-burned magnesium oxide fine powder is 97-99 wt%.

[0037] The MgO content of the magnesium hydroxide fine powder is 65-66 wt%.

[0038] The Y2O3 content of the yttrium oxide nano-powder is >99.9 wt%.

[0039] The mass ratio of the high-alumina corundum balls to the raw material is 2-4:1.

[0040] The binder is a mixture obtained by mixing carboxymethylcellulose sodium and deionized water at a mass ratio of 0.5-1.5:100 for 16-24 h, or a mixture obtained by mixing polyvinyl butyral and ethanol at a mass ratio of 5.26-8.70:100 for 16-24 h.

[0041] The Y2O3 content of the yttrium oxide micro-powder is >99 wt%.

[0042] The MgO content of the MgO-Y2O3 fine powder is 92-98 wt%.

[0043] The MgO content of the magnesia fine powder is >96 wt%.

[0044] The MgO content of the refractory aggregate is 92-98 wt%.

[0045] In the specific embodiment: The particle size of the light-burned magnesium oxide fine powder is <30 μm.

[0046] The particle size of the magnesium hydroxide fine powder is <44 μm.

[0047] The particle size of the yttrium oxide nano-powder is <50 nm.

[0048] The ball milling is performed using high-alumina corundum balls as the medium.

[0049] The particle size of the yttrium oxide micro-powder is <10 μm.

[0050] The MgO-Y2O3 fine powder has a particle size < 70 μm.

[0051] The magnesia fine powder has a particle size < 0.088 mm.

[0052] The refractory aggregate I, the refractory aggregate II and the refractory aggregate III are MgO-Y2O3 refractory aggregates with a particle size < 5 mm, < 3 mm and < 1 mm respectively.

[0053] The MgO-Y2O3 refractory aggregate has a micron-scale core-shell structure with MgO microparticles as the core and continuous dense Y2O3 as the shell; the MgO microparticles in the MgO-Y2O3 refractory aggregate have an average particle size of 30-50 μm, and the Y2O3 shell layer has a thickness of 1-3 μm.

[0054] The MgO-Y2O3 refractory material with a multi-scale core-shell structure has a multi-scale core-shell structure with the MgO-Y2O3 refractory aggregate with a micron-scale core-shell structure as the core and a continuous dense Y2O3 layer distributed between the aggregate and the matrix as the shell; the continuous Y2O3 layer distributed between the aggregate and the matrix has a thickness of 0.2-0.4 mm.

[0055] The embodiments are not described again.

[0056] Embodiment 1 A MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method thereof. The preparation method of the embodiment comprises the following steps: Step 1, mix 98 wt% of light-burned magnesia fine powder and 2 wt% of yttria nano-powder, ball mill for 2 h, and then machine-press into a shape under the condition of 100 MPa; then heat to 1650 ℃ at a rate of 4 ℃ / min in a high-temperature furnace, keep the temperature for 5 h, cool down with the furnace, crush, and sieve to obtain refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 fine powder respectively.

[0057] Step 2, mix according to the mass ratio of the binder to yttria micropowder of 100:2 to obtain a composite binder.

[0058] Step 3, take 18 wt% of the refractory aggregate I, 30 wt% of the refractory aggregate II and 12 wt% of the refractory aggregate III as the aggregate, and take 15 wt% of the MgO-Y2O3 fine powder, 23 wt% of the magnesia fine powder and 2 wt% of the yttria micropowder as the matrix.

[0059] The matrix is ball milled for 3h to obtain a matrix material; the aggregate is placed in a blender, 4wt% of a composite binder based on the total weight of the aggregate and the matrix material is added, and stirred, and then the matrix material is added and mixed; the mixture is formed by machine pressing under a pressure of 100MPa, dried at 150℃ for 23h, and then heated at a rate of 5℃ / min to 1600℃, held for 6h, and then cooled in the furnace to obtain a MgO-Y2O3 refractory material having a multi-scale core-shell structure.

[0060] The light-burned magnesium oxide fine powder is obtained by calcining magnesium hydroxide fine powder at 832℃ for 2.5h, and the MgO content of the light-burned magnesium oxide fine powder is 99wt%.

[0061] The MgO content of the magnesium hydroxide fine powder is 66wt%.

[0062] The Y2O3 content of the yttrium oxide nano-powder is 99.92wt%.

[0063] The mass ratio of the high-alumina corundum balls to the raw material is 3:1.

[0064] The binder is a mixture obtained by mixing carboxymethylcellulose sodium and deionized water at a mass ratio of 0.7:100 for 19h.

[0065] The Y2O3 content of the yttrium oxide micro-powder is 99.3wt%.

[0066] The MgO content of the MgO-Y2O3 fine powder is 98wt%.

[0067] The MgO content of the magnesia fine powder is 98wt%.

[0068] The MgO content of the refractory aggregate is 98wt%.

[0069] The MgO-Y2O3 refractory aggregate is detected to have an apparent porosity of 1.14%, a bulk density of 3.73g / cm 3 , and a high-temperature vacuum volatilization rate of 1.02% The MgO-Y2O3 refractory material having a multi-scale core-shell structure prepared by the method has an apparent porosity of 2.56%, a bulk density of 3.32g / cm 3 , and a 1500℃ high-temperature bending strength of 14MPa.

[0070] Example 2 A MgO-Y2O3 refractory material having a multi-scale core-shell structure and a preparation method thereof. The preparation method of the present embodiment comprises the following steps: Step 1, 93wt% of light-burned magnesia fine powder and 7wt% of yttria nano-powder are mixed, ball-milled for 3.5h, and then molded under the condition of 200MPa; then the temperature is raised to 1550℃ at a rate of 2℃ / min in a high-temperature furnace, and the temperature is kept for 3h, and the furnace is cooled down, and then the product is broken and sieved to obtain refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 fine powder.

[0071] Step 2, the composite binder is obtained by mixing the binder and yttria micro-powder according to the mass ratio of 100:5.

[0072] Step 3, 14wt% of refractory aggregate I, 28wt% of refractory aggregate II, 17wt% of refractory aggregate III are used as aggregate, and 16wt% of MgO-Y2O3 fine powder, 18wt% of magnesia fine powder and 7wt% of yttria micro-powder are used as matrix.

[0073] The matrix is ball-milled for 2h to obtain matrix material; the aggregate is placed in a blender, and 2.5wt% of the composite binder is added, and then the aggregate and the matrix material are stirred, and then the matrix material is added and mixed; the product is molded under the condition of 165MPa, and dried at 100℃ for 26h; then the temperature is raised to 1500℃ at a rate of 3.5℃ / min, and the temperature is kept for 4.5h, and the furnace is cooled down to obtain MgO-Y2O3 refractory material with multi-scale core-shell structure.

[0074] The light-burned magnesia fine powder is obtained by calcining magnesium hydroxide fine powder at 820℃ for 3h, and the MgO content of the light-burned magnesia fine powder is 98wt%.

[0075] The MgO content of the magnesium hydroxide fine powder is 65.8wt%.

[0076] The Y2O3 content of the yttria nano-powder is 99.93wt%.

[0077] The mass ratio of the high-alumina corundum ball to the raw material is 2:1.

[0078] The binder is a mixture obtained by mixing polyvinyl butyral and ethanol according to the mass ratio of 7.2:100 for 22h.

[0079] The Y2O3 content of the yttria micro-powder is 99.5wt%.

[0080] The MgO content of the MgO-Y2O3 fine powder is 93wt%.

[0081] The MgO content of the magnesia fine powder is 99wt%.

[0082] The MgO content of the refractory aggregate is 93wt%.

[0083] The MgO-Y2O3 refractory aggregate is detected to have an apparent porosity of 0.92%, a bulk density of 3.79 g / cm 3 and a high-temperature vacuum volatilization rate of 0.63% under the conditions of a temperature of 1700 DEG C and a pressure of 10 Pa.

[0084] The MgO-Y2O3 refractory material prepared in the application has an apparent porosity of 1.89%, a bulk density of 3.52 g / cm 3 , and a high-temperature bending strength of 18.2 MPa at 1500 DEG C.

[0085] Embodiment 3 A MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method thereof. Step 1, 95wt% of light-burned magnesium oxide fine powder and 5wt% of yttrium oxide nano powder are mixed, ball-milled for 3h, and then formed into a shape under the condition of 150 MPa; then, the temperature is raised to 1580 DEG C at a rate of 3.5 DEG C / min in a high-temperature furnace, and the temperature is kept for 4h, and then the furnace is cooled, broken, and sieved to obtain refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 fine powder.

[0086] Step 2, the composite binder is obtained by mixing according to the mass ratio of the binder to the yttrium oxide micron powder of 100:3.5.

[0087] Step 3, 15wt% of the refractory aggregate I, 32wt% of the refractory aggregate II, and 18wt% of the refractory aggregate III are used as the aggregate, 9wt% of the MgO-Y2O3 fine powder, 21wt% of the magnesia fine powder, and 5wt% of the yttrium oxide micron powder are used as the matrix.

[0088] The matrix is ball-milled for 2.5h to obtain a matrix material; the aggregate is placed in a blender, 3wt% of the composite binder is added, stirred, and then the matrix material is added and mixed; the aggregate is formed into a shape under the condition of 130 MPa, dried at 200 DEG C for 24h; then, the temperature is raised to 1550 DEG C at a rate of 3 DEG C / min, and the temperature is kept for 4h, and then the furnace is cooled to obtain the MgO-Y2O3 refractory material with a multi-scale core-shell structure.

[0089] The light-burned magnesium oxide fine powder is obtained by calcining magnesium hydroxide fine powder at 850 DEG C for 1h, and the MgO content of the light-burned magnesium oxide fine powder is 98.5wt%.

[0090] The MgO content of the magnesium hydroxide fine powder is 65wt%.

[0091] The Y2O3 content of the yttrium oxide nano powder is 99.91wt%.

[0092] The mass ratio of the high-alumina corundum ball to the raw material is 2.5:1.

[0093] The binder is a mixture obtained by mixing polyvinyl butyral and ethanol at a mass ratio of 5.26:100 for 16 hours.

[0094] The Y2O3 content of the yttrium oxide micropowder is 99.4wt%.

[0095] The MgO content of the MgO-Y2O3 micropowder is 95wt%.

[0096] The MgO content of the magnesia micropowder is 96wt%.

[0097] The MgO content of the refractory aggregate is 95wt%.

[0098] The MgO-Y2O3 refractory aggregate is detected to have an apparent porosity of 0.75%, a bulk density of 3.82g / cm 3 , and a high-temperature vacuum volatilization rate of 0.79% under the conditions of a temperature of 1700℃ and a pressure of 10Pa for 1h.

[0099] The MgO-Y2O3 refractory material with a multi-scale core-shell structure prepared by the method is detected to have an apparent porosity of 2.16%, a bulk density of 3.46g / cm 3 , and a high-temperature bending strength of 20MPa at 1500℃.

[0100] Example 4 A MgO-Y2O3 refractory material with a multi-scale core-shell structure and a preparation method thereof. The preparation method of the embodiment comprises the following steps: Step 1, 92wt% of light-burned magnesia micropowder and 8wt% of yttrium oxide nanometer powder are mixed and ball milled for 4h, and then are formed into a shape under the condition of 180MPa; then the shape is heated to 1600℃ at a rate of 5℃ / min in a high-temperature furnace, and is cooled in the furnace for 6h, and is broken and sieved to obtain refractory aggregate I, refractory aggregate II, refractory aggregate III and MgO-Y2O3 micropowder.

[0101] Step 2, a composite binder is obtained by mixing the binder and the yttrium oxide micropowder at a mass ratio of 100:6.

[0102] Step 3, 18wt% of the refractory aggregate I, 29wt% of the refractory aggregate II, 16wt% of the refractory aggregate III are used as aggregates, and 13wt% of the MgO-Y2O3 micropowder, 16wt% of the magnesia micropowder and 8wt% of the yttrium oxide micropowder are used as a matrix.

[0103] The matrix is ground for 4h to obtain a matrix material; the aggregate is placed in a blender, 2wt% of the sum of the additional aggregate and the matrix material of a composite binder is added, stirred, and then the matrix material is added and mixed; the mixture is formed by machine pressing under the condition of 200MPa, dried at 140℃ for 20h, then heated at a rate of 4℃ / min to 1580℃, kept for 5h, and cooled in the furnace to obtain the MgO-Y2O3 refractory material with a multi-scale core-shell structure.

[0104] The light-burned magnesium oxide fine powder is obtained by calcining the magnesium hydroxide fine powder at 845℃ for 2h, and the MgO content of the light-burned magnesium oxide fine powder is 97wt%.

[0105] The MgO content of the magnesium hydroxide fine powder is 65.3wt%.

[0106] The Y2O3 content of the yttrium oxide nano-powder is 99.95wt%.

[0107] The mass ratio of the high-alumina corundum ball to the raw material is 4:1.

[0108] The binder is a mixture obtained by mixing carboxymethylcellulose sodium and deionized water at a mass ratio of 1.5:100 for 24h.

[0109] The Y2O3 content of the yttrium oxide micro-powder is 99.1wt%.

[0110] The MgO content of the MgO-Y2O3 fine powder is 92wt%.

[0111] The MgO content of the magnesia fine powder is 97wt%.

[0112] The MgO content of the refractory aggregate is 92wt%.

[0113] The MgO-Y2O3 refractory aggregate is detected: the apparent porosity is 0.6%; the bulk density is 3.88g / cm 3 ; under the conditions of a temperature of 1700℃ and a pressure of 10Pa, the high-temperature vacuum volatilization rate is 0.5% after keeping for 1h.

[0114] The MgO-Y2O3 refractory material with a multi-scale core-shell structure prepared in the application is detected: the apparent porosity is 1.23%; the bulk density is 3.69g / cm 3 ; the high-temperature bending strength at 1500℃ is 16.7MPa.

[0115] Compared with the prior art, the embodiment has the following positive effects: The embodiment designs the whole process from the aggregate to the product. The MgO-Y2O3 refractory aggregate in the MgO-Y2O3 refractory material with a multi-scale core-shell structure (hereinafter referred to as the product) has a micron-scale core-shell structure with MgO microparticles as the core and continuous dense Y2O3 as the shell. Compared with the prior art, the core-shell structure is stable at high temperature, and the high-temperature vacuum volatility is low. Secondly, the micron-scale Y2O3 shell is constructed on the surface of the aggregate, the sawtooth occlusion interface structure is formed at the shell-aggregate interface, and the Y2O3 micropowder is added to the matrix to form the micro-millimeter-scale core-shell structure and repair the possible damaged core-shell structure in the MgO-Y2O3 fine powder. The shell on the surface of the aggregate and the MgO-Y2O3 refractory aggregate with a micron-scale core-shell structure together constitute a multi-scale core-shell structure.

[0116] The product prepared by the embodiment has a multi-scale core-shell structure, which can effectively improve the high-temperature vacuum stability, thereby avoiding the pollution of the product to the alloy melt. Firstly, the Y2O3 in the MgO-Y2O3 refractory aggregate with a micro-core-shell structure is uniformly pinned at the MgO grain boundary as a second phase to form a continuous dense Y2O3 layer wrapping the core-shell structure of MgO. Secondly, by constructing a micron-scale continuous dense Y2O3 shell on the surface of the aggregate and a micro-core-shell structure in the matrix, the multi-scale Y2O3 shell isolates MgO from the high-temperature alloy liquid, avoiding the Mg and O vapors volatilized from MgO under high-temperature vacuum conditions from entering the alloy liquid. According to chemical reaction kinetics, when the vapor concentration in the shell increases, the decomposition reaction rate can be slowed down, greatly reducing the high-temperature vacuum volatility of the product and improving its high-temperature vacuum stability. The problem of easy volatilization and peeling of traditional magnesia refractory materials is solved, the product pollution to the alloy melt is avoided, and the service life of the product is improved.

[0117] The specific embodiment improves the thermal shock stability of the product by Y2O3 second phase strengthening mechanism. Firstly, Y2O3 in the aggregate is uniformly pinned at the MgO grain boundary as a second phase, which can prevent abnormal grain growth, refine the grains, and increase the number of grain boundaries in the aggregate, which can not only improve the strength, but also make the micro-cracks generated by thermal shock be reflected and absorbed at the grain boundaries multiple times, reducing the formation of macro-cracks. For the product, due to the difference between the thermal expansion coefficients of magnesium oxide and yttrium oxide, when the temperature rises, MgO expands faster, and the Y2O3 shell layer has a low expansion coefficient that can constrain its expansion, generating compressive stress; when the temperature decreases, MgO shrinks faster, and the Y2O3 shell layer provides tensile stress buffering. This stress interaction can reduce the thermal stress concentration caused by uneven thermal expansion and contraction in the material, thereby reducing crack generation. Secondly, the Y2O3 layer as a second phase can induce crack deflection, branching or passivation when the generated crack encounters the Y2O3 layer during propagation, thereby inhibiting the rapid propagation of the crack. Finally, the multi-scale core-shell structure prepared in the specific embodiment forms a serrated occlusion-like interface structure at the aggregate-shell-matrix interface, making the aggregate-shell and shell-matrix tightly combined, which improves the strength and thermal shock stability of the product.

[0118] The specific embodiment utilizes the multi-scale core-shell structure and the raw material with certain activity, and combines the characteristics of Y2O3 that is not easy to react with the alloy liquid, to reduce the preparation cost while improving the erosion resistance of the product. Firstly, the aggregate uses light-burned MgO as the raw material, which retains certain lattice distortion, providing diffusion channels for the subsequent sintering process, reducing the sintering temperature while ensuring the density of the aggregate, which reduces the preparation cost and is more conducive to popularization; at the same time, Y2O3 in the aggregate is uniformly pinned at the MgO grain boundary as a second phase, which reduces the pores that are difficult to remove due to abnormal grain growth during the sintering process, and promotes the sintering process, both of which improve the erosion resistance of the aggregate and reduce the preparation cost. Secondly, in the vacuum melting and casting of alloys with active metals, high-activity metals are easy to chemically react with the crucible and cause pollution. Since Y has extremely strong reducing property, the generated oxide is difficult to be replaced by other metals. The reaction between the common active metals Ti and Al and Y2O3 is thermodynamically calculated, and the Gibbs free energy at 2500°C is as high as 145.76 KJ, which is difficult to react. Therefore, after introducing the multi-scale Y2O3 shell, the multi-scale shell can isolate MgO from the high-temperature alloy liquid, and the alloy is difficult to directly contact MgO and react with it, thereby having extremely high chemical stability, improving the erosion resistance of the product, and overcoming the problem of reducing the service life due to the chemical reaction between the crucible and the alloy.

[0119] The MgO-Y2O3 refractory aggregate is detected to have an apparent porosity of 0.6-1.14%, a bulk density of 3.73-3.88 g / cm 3; under the condition of temperature 1700 DEG C and pressure 10 Pa, holding for 1 h, the high-temperature vacuum evaporation rate is 0.5-1.02%.

[0120] The MgO-Y2O3 refractory material with multi-scale core-shell structure prepared in the embodiment is detected: the apparent porosity is 1.23-2.56%; the bulk density is 3.23-3.69 g / cm 3 ; the high-temperature bending strength at 1500 DEG C is 14-20 MPa.

[0121] The detection standard of the performance index involved in the embodiment is: the apparent porosity and the bulk density are detected according to GB / T2997-2000; the high-temperature bending strength is detected according to GB / T3002-2004.

[0122] Therefore, the MgO-Y2O3 refractory material with multi-scale core-shell structure prepared in the embodiment has the characteristics of low cost, long service life, good high-temperature vacuum stability, excellent thermal shock stability and excellent corrosion resistance.

Claims

1. A method for preparing a MgO-Y2O3 refractory material with a multi-scale core-shell structure, characterized in that The preparation method is: Step 1, 92-98 wt% of light-burned magnesium oxide fine powder and 2-8 wt% of yttrium oxide nanopowder are mixed, ball-milled for 2-4 hours, and then pressed into shape under 100-200 MPa; then heated to 1550-1650°C at a rate of 2-5°C / min in a high-temperature furnace, kept warm for 3-6 hours, cooled with the furnace, crushed, and sieved to obtain refractory aggregate I, refractory aggregate II, refractory aggregate III, and MgO-Y2O3 fine powder, respectively; Step 2: preparing ingredients according to a mass ratio of binder to yttrium oxide micron powder of 100:2-6, mixing to obtain a composite binder; Step 3, using 14-18wt% of refractory aggregate I, 28-32wt% of refractory aggregate II, and 12-18wt% of refractory aggregate III as aggregates, and using 9-16wt% of MgO-Y2O3 fine powder, 16-23wt% of magnesia fine powder, and 2-8wt% of yttrium oxide micron powder as a matrix; The matrix is ​​ball-milled for 2-4 hours to obtain a matrix material; the aggregate is placed in a mixer, and a composite binder of 2-4 wt% of the sum of the aggregate and the matrix material is added and stirred, and then the matrix material is added and mixed; the MgO-Y2O3 refractory material is formed by machine pressing at 100-200 MPa and dried at 100-200°C for 20-26 hours; then the temperature is raised to 1500-1600°C at a rate of 3-5°C / min, kept at this temperature for 4-6 hours, and cooled with the furnace to obtain a MgO-Y2O3 refractory material with a multi-scale core-shell structure.

2. The method for preparing a MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The light-burned magnesium oxide fine powder is obtained by calcining magnesium hydroxide fine powder at 820-850° C. for 1-3 hours. The particle size of the light-burned magnesium oxide fine powder is less than 30 μm, and the MgO content of the light-burned magnesium oxide fine powder is 97-99 wt %. The particle size of the magnesium hydroxide fine powder is less than 44 μm, and the MgO content of the magnesium hydroxide fine powder is 65-66 wt %.

3. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The particle size of the yttrium oxide nanopowder is less than 50 nm; the Y2O3 content of the yttrium oxide nanopowder is greater than 99.9 wt%.

4. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The ball mill uses high-aluminum corundum balls as the medium; the mass ratio of high-aluminum corundum balls to raw materials is 2-4:

1.

5. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The binder is a mixture obtained by mixing sodium carboxymethyl cellulose and deionized water at a mass ratio of 0.5-1.5:100 for 16-24 hours; or a mixture obtained by mixing polyvinyl butyral and ethanol at a mass ratio of 5.26-8.70:100 for 16-24 hours.

6. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The particle size of the yttrium oxide micron powder is less than 10 μm; the Y2O3 content of the yttrium oxide micron powder is greater than 99 wt%.

7. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The particle size of the MgO-Y2O3 fine powder is less than 70 μm; the MgO content of the MgO-Y2O3 fine powder is 92-98 wt%.

8. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The particle size of the magnesia fine powder is less than 0.088 mm; and the MgO content of the magnesia fine powder is greater than 96 wt %.

9. The method for preparing the MgO-Y2O3 refractory material having a multi-scale core-shell structure according to claim 1, characterized in that: The refractory aggregate I, refractory aggregate Ⅰ and refractory aggregate ⅢⅠ are respectively: MgO-Y2O3 refractory aggregate with a particle size of less than 5mm and greater than or equal to 3mm, MgO-Y2O3 refractory aggregate with a particle size of less than 3mm and greater than or equal to 1mm, and MgO-Y2O3 refractory aggregate with a particle size of less than 1mm and greater than or equal to 0.088mm, and the MgO content of the refractory aggregate is 92-98wt%; The MgO-Y2O3 refractory aggregate has a micron-scale core-shell structure with MgO microparticles as the core and continuous and dense Y2O3 as the shell; the average particle size of the MgO microparticles in the MgO-Y2O3 refractory aggregate is 30-50μm, and the thickness of the Y2O3 shell is 1-3μm.

10. A MgO-Y2O3 refractory material with a multi-scale core-shell structure, characterized in that The MgO-Y2O3 refractory material with a multi-scale core-shell structure is a MgO-Y2O3 refractory material with a multi-scale core-shell structure according to any one of claims 1 to 9. The method for preparing the MgO-Y2O3 refractory material with a multi-scale core-shell structure is based on the prepared MgO-Y2O3 refractory material with a multi-scale core-shell structure; The MgO-Y2O3 refractory material with a multi-scale core-shell structure is a multi-scale core-shell structure having a micron-scale MgO-Y2O3 refractory aggregate with MgO microparticles as the core and continuous and dense Y2O3 as the shell, and a continuous and dense Y2O3 layer distributed between the aggregate and the matrix as the shell; wherein: the thickness of the continuous Y2O3 layer distributed between the aggregate and the matrix is ​​0.2~0.4mm.