CaO-Al2O3-SrO casting powder for continuous casting of high-aluminum steel by adopting mixed alkali strategy

Abstract

The invention relates to the technical field of continuous casting, in particular to CaO-Al2O3-SrO casting powder for high-aluminum steel continuous casting by adopting a mixed alkali strategy. The casting powder comprises the following components: 18%-28% of CaO; 18% to 28% of Al2O3; 6%-16% of SrO; 5% to 10% of SiO2; 1% to 10% of Li2O; 1%-10% of Na2O; 1%-10% of K2O; 5% to 15% of B2O3; 5%-15% of F; c: 2%-8%; the balance is impurities; meanwhile, the formula that CaO + (SrO * 56.08) / 103.62: Al2O3 is equal to 0.7 to 1.3 is met; srO / (CaO + SrO) is equal to 0.2 to 0.5; li2O + Na2O + K2O > < = 20%, and Li2O = Na2O + K2O. A mixed alkali strategy is adopted, SrO is added, the physical and chemical properties of the CaO-Al2O3-based casting powder are cooperatively regulated and controlled, and the physical and chemical properties of the CaO-Al2O3-based casting powder in various aspects under the condition that the reactivity of slag steel is reduced are optimized to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting, and particularly relates to a CaO-Al2O3-SrO mold flux for continuous casting of high-aluminum steel adopting a mixed alkali strategy. Background Art

[0002] During the continuous casting process of high-aluminum steel (where [Al] ≥ 0.5% in the steel), since [Al] is an active metal, it is easy to react with components such as SiO2 in the mold flux, resulting in changes in the composition and properties of the mold flux, thereby causing quality problems of the cast slab such as depressions and cracks, as well as production accidents such as breakout.

[0003] Chinese patent application with publication number CN111570740A discloses a "continuous casting mold flux for high-aluminum steel and its preparation method". The composition of the mold flux by weight percentage is: CaO: 15% - 30%, SiO2: 11% - 20%, Al2O3: 10% - 20%, MgO: ≤ 1%, F: 7% - 13%, C: 5% - 10%, SrO + SrO: 10% - 30%, B2O3: 1% - 6%, Na2O + Fe2O3 + Li2O: ≤ 12%, and the rest are inevitable impurities. The content of basic oxides in this mold flux is relatively high, and there are problems such as poor lubricity during continuous casting. In addition, the content of SiO2 in this mold flux is relatively high, and it will still react with [Al] in the molten steel, resulting in the denaturation of the mold flux.

[0004] Chinese patent application with publication number CN106424622A discloses a "continuous casting mold flux for high-aluminum steel and its preparation method", ensuring that the weight percentage of the composition elements of the slag satisfies: CaO: 30% - 45%, Al2O3: 20% - 30%, SiO2: ≤ 3%, Li2O: 3% - 8%, SrO: 1% - 3%, Na2O: 5% - 10%, SrO: 3% - 6%, MgO: ≤ 3%, C: 2% - 4%, F: ≤ 2%, and the rest are inevitable impurities. The content of SiO2 in this mold flux is relatively small, and basically solves the problem of slag-steel reaction during the continuous casting of high-aluminum steel. However, under this condition, the proportion of the F component in the mold flux is low, and at the same time, the proportions of other flux components are also relatively low. Therefore, its CaO-Al2O3-based mold flux faces risks such as high viscosity and poor melting.

[0005] The Chinese patent application with the publication number CN102389955A discloses "a mold powder for continuous casting of high-aluminum steel". The weight percentage composition of the slag is guaranteed to be: CaO: 15% - 40%, SiO2: 3% - 15%, Al2O3: 10% - 20%, MgO: ≤3%, Fe2O3 ≤3%, F: 6% - 15%, Na2O: ≤1.5%, Li2O: 3% - 10%, SrO: 5% - 20%, SrO: ≤5%, B2O3: ≤5%, C: 2% - 15%, and the rest are inevitable impurities. Its goal is to reduce the reactivity between the slag and the steel to slow down the deterioration of the mold powder performance caused by the slag-steel reaction. However, the content of basic oxides in this mold powder is relatively high, and there are problems such as strong crystallization ability during continuous casting, which is not conducive to the mold powder flowing into the slag channel and deteriorates the lubrication function of the mold powder.

[0006] The Chinese patent application with the publication number CN102407306A discloses "a silicon-free vitreous mold powder". The weight percentage of the slag composition is guaranteed to be: Na2O: 4% - 10%, Li2O: 2% - 5%, MgO: 1% - 4%, SrO: 5% - 8%, SrO: 5% - 8%, C: 1% - 5%, impurity content: ≤5%, and the rest are CaO and Al2O3. Its goal is to reduce the degree of slag-steel reaction during the continuous casting of high-aluminum steel and generate vitreous slag to ensure the lubrication effect of the billet. However, there is no acidic oxide in the composition of this mold powder, that is, there is no stable glass-forming component, and only relies on the amphoteric oxide Al2O3 to form vitreous mold powder, and the stability of the glass performance of the molten slag is questionable.

[0007] The Chinese invention patent with the authorization announcement number CN101332497B discloses "a mold powder for high-aluminum steel and its manufacturing method". The weight percentage of the mold powder composition is: CaO + Al2O3: 50% - 60%, and CaO / Al2O3 = 0.7 - 1.3, SrO: 4% - 10%, SrO: 2% - 5%, MgO: 1% - 3%, Na2O: 10% - 16%, Li2O: 2% - 5%, F: 6% - 12%, C: 2% - 4%, and SiO2: ≤2% is maintained, and the rest are inevitable impurities. The content of the reactive component Na2O in this mold powder is relatively high, increasing the risk of reaction variability of the mold powder. At the same time, there is a lack of acidic oxides in this mold powder, and there is a risk of strong crystallization ability and deterioration of the lubrication effect of the mold powder during continuous casting.

[0008] The above-mentioned patent documents all relate to CaO-Al2O3-based mold fluxes with low reactivity, and all aim to solve the problem of intense slag-steel reaction during continuous casting of high-aluminum steel. However, for CaO-Al2O3-based mold fluxes with low reactivity, since the content of SiO2, which acts as an acidic oxide and a network former in traditional mold fluxes, is greatly reduced and replaced by the amphoteric oxide Al2O3, the ability of the mold flux to maintain glass properties is greatly reduced, and crystals are likely to precipitate during the temperature change process. Therefore, how to improve the glass properties of CaO-Al2O3-based mold fluxes and reasonably regulate the lubrication and heat transfer functions of the mold flux while taking into account the reactivity has become an urgent problem to be solved at present.

[0009] In the glass manufacturing industry, the mixed alkali effect is commonly used to prepare high-performance glass. Compared with single-alkali glass with the same number of molecules, the mixed-alkali glass has improved various properties such as glass transition temperature, chemical stability, ion diffusion coefficient, and viscosity. The molten mold flux is essentially in a glassy state. By introducing the mixed alkali effect (such as Li2O, Na2O, K2O) into the design of the mold flux, a series of physical and chemical reactions can be adjusted to improve the comprehensive physical and chemical properties of the mold flux. That is, by fully exerting the "mixed alkali" effect in the mold flux, it is helpful to develop mold flux products with better physical and chemical properties. Summary of the Invention

[0010] The present invention provides a CaO-Al2O3-SrO mold flux for continuous casting of high-aluminum steel using a mixed alkali strategy. By adopting the mixed alkali strategy (adding Li2O, Na2O, K2O in the optimal ratio) and adding SrO, the physical and chemical properties of the CaO-Al2O3-based mold flux are synergistically regulated, and the physical and chemical properties of the CaO-Al2O3-based mold flux in various aspects under the condition of reducing slag-steel reactivity are optimized to the greatest extent, providing a new design route for the development of low-reactivity CaO-Al2O3-based mold fluxes.

[0011] To achieve the above object, the present invention is implemented by the following technical solutions:

[0012] A CaO-Al2O3-SrO mold powder for continuous casting of high-aluminum steel using a mixed alkali strategy. The mold powder comprises the following components by weight percentage: CaO: 18% - 28%; Al2O3: 18% - 28%; SrO: 6% - 16%; SiO2: 5% - 10%; Li2O: 1% - 10%; Na2O: 1% - 10%; K2O: 1% - 10%; B2O3: 5% - 15%; F: 5% - 15%; C: 2% - 8%; the balance being unavoidable impurities; and simultaneously satisfying the alkali-aluminum ratio CaO+(SrO×56.08) / 103.62:Al2O3 = 0.7 - 1.3; the substitution rate of SrO SrO / (CaO+SrO) = 0.2 - 0.5; the total amount of alkali metal oxides, i.e., Li2O+Na2O+K2O) ≤ 20%, and additionally satisfying Li2O = Na2O+K2O.

[0013] Further, in the mold powder, by weight percentage, SiO2: 5% - 6%.

[0014] Further, in the mold powder, by weight percentage, Li2O / 2 = Na2O = K2O.

[0015] The physical properties of the mold powder are as follows: the melting point is 950 - 1050 °C, the viscosity at 1300 °C is 0.05 - 0.20 Pa·s, the turning point temperature is 950 - 1100 °C, and the crystalline phases are mainly calcium borate and calcium monoaluminate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1) In the CaO-Al2O3-SrO mold powder for high-aluminum steel of the present invention, the charge compensation effects of SrO (Sr 2+ ), Li2O (Li + ), Na2O (Na + ), and K2O (K + ) on [AlO4] 5- are all prior to those of CaO (Ca 2+ ). It can significantly improve the stability of [AlO4] 5- tetrahedrons in the melt, contribute to the stability of the melt structure, reduce phase separation or crystallization phenomena, and optimize the glass properties;

[0018] 2) In the CaO-Al2O3-SrO mold powder for high-aluminum steel of the present invention, SrO and CaO are elements of the same main group. By optimizing the content of SrO substituting CaO, the precipitation of high-melting-point phases in the mold powder can be inhibited; thereby significantly improving the melting performance, lubrication effect, and heat transfer performance of the mold powder, enhancing the stability of the continuous casting process and the surface quality of the billet, while reducing energy consumption and production costs;

[0019] 3) In the CaO-Al2O3-SrO mold powder for high-aluminum steel of the present invention, by reasonably regulating the content ratio of alkali metal oxides Li2O, Na2O, and K2O, the mixed alkali effect is fully exerted, improving the comprehensive physical and chemical properties of the mold powder; thereby optimizing the continuous casting process, improving the quality of the cast slab, and reducing energy consumption and production costs;

[0020] 4) The CaO-Al2O3-SrO mold powder for high-aluminum steel of the present invention has excellent glass properties, and reasonably optimizes the lubricating function of the CaO-Al2O3-based mold powder, having a lower melting temperature and viscosity, improving the fluidity of the mold powder, and solving the problems of strong crystallization performance and low slag consumption commonly existing in such mold powders. Brief Description of the Drawings

[0021] Figure 1 It is a graph showing the influence of alkali metal oxide Li2O on the Al-O coordination number in the CaO-Al2O3 mold powder.

[0022] Figure 2 It is a graph showing the influence of alkali metal oxide Na2O on the Al-O coordination number in the CaO-Al2O3 mold powder.

[0023] Figure 3 It is a graph showing the influence of alkali metal oxide K2O on the Al-O coordination number in the CaO-Al2O3 mold powder.

[0024] Figure 4 It is an XRD pattern of the CaO-Al2O3 mold powder under the synergistic regulation of SrO and mixed alkali. Detailed Embodiments

[0025] The [AlO4] 5- tetrahedron that plays the role of network former in the CaO-Al2O3-based mold powder has a much less stable structure than the [SiO4] 4- tetrahedron in the traditional CaO-SiO2-based mold powder, resulting in a significant reduction in the ability of the CaO-Al2O3-based mold powder to maintain glass properties and being prone to crystal precipitation during the temperature change process.

[0026] The present invention adopts a mixed alkali strategy (adding Li2O, Na2O, and K2O in the optimal ratio) and adds SrO to synergistically regulate the physical and chemical properties of the CaO-Al2O3-based mold powder, and develops a new type of low-reactivity mold powder for high-aluminum steel.

[0027] The CaO-Al2O3-SrO mold powder for continuous casting of high-aluminum steel using a mixed-alkali strategy according to the present invention, the mold powder comprises the following components by weight percentage: CaO: 18% to 28%; Al2O3: 18% to 28%; SrO: 6% to 16%; SiO2: 5% to 10%; Li2O: 1% to 10%; Na2O: 1% to 10%; K2O: 1% to 10%; B2O3: 5% to 15%; F: 5% to 15%; C: 2% to 8%; the balance is inevitable impurities; at the same time, it satisfies the alkali-aluminum ratio CaO+(SrO×56.08) / 103.62:Al2O3 = 0.7 to 1.3; the substitution rate of SrO SrO / (CaO+SrO) = 0.2 to 0.5; the total amount of alkali metal oxides, namely Li2O+Na2O+K2O) ≤ 20%, and in addition, it satisfies Li2O = Na2O+K2O.

[0028] Further, in the mold powder, by weight percentage, SiO2: 5% to 6%.

[0029] Further, in the mold powder, by weight percentage, Li2O / 2 = Na2O = K2O.

[0030] The present invention fully considers the denaturing characteristics of the mold powder, and uses CaO-Al2O3 as the base component of the mold powder, replacing the design of the traditional CaO-SiO2 mold powder. The common problem of the CaO-Al2O3-based mold powder is that: the content of SiO2, which acts as an acidic oxide and a network former in the traditional mold powder, is greatly reduced, and is replaced by the amphoteric oxide Al2O3. The ability of the mold powder to maintain glass properties is greatly reduced, and crystals are likely to precipitate during the temperature change process. Therefore, starting from the theory of the microscopic network structure of the mold powder, on the basis of considering reactivity, SrO, Li2O, Na2O, and K2O that can promote the formation of [AlO4] 5- tetrahedral network structure are selected as the main additive components to improve the fluidity of the mold powder, and at the same time inhibit the crystallization ability of the mold powder, and B2O3 and CaF2 are selected to regulate the comprehensive physical and chemical properties of the mold powder.

[0031] The basis and considerations for adding each component in the present invention are as follows:

[0032] Using the CaO-Al2O3-SrO mold powder essentially weakens the reactivity between the mold powder and [Al] in the molten steel. Based on the low melting point region of CaO-Al2O3-SrO, the alkali-aluminum ratio (the alkali-aluminum ratio is expressed as CaO+(SrO×56.08) / 103.62:Al2O3 = 0.7 to 1.3. Among them, SrO can reduce the melting point and viscosity of the CaO-Al2O3-based mold powder, improve the fluidity of the mold powder, and at the same time, Sr 2+It can stabilize [AlO4] in the melt 5- tetrahedral structure, improve the stability of the glass properties of the mold powder, and is beneficial to improving the lubricity of the mold powder. Replacing CaO with SrO can form a solid solution containing both Sr 2+ and Ca 2+ , such as the solid solution of CaF2 and SrF2, and the solid solution of xCaO·yAl2O3 and xSrO·yAl2O3, effectively inhibiting the precipitation of high-melting-point crystalline phases 11CaO·7Al2O3·CaF2 (melting point 1577 °C) and 2CaO·Al2O3·SiO2 (melting point 1593 °C).

[0033] The present invention controls the replacement rate of SrO (CaO+SrO / CaO) to be 0.2 to 0.5.

[0034] SiO2 is an important acidic oxide in the mold powder, which is beneficial to stabilizing the glass properties of the mold powder. When its content is less than 10%, its reactivity with [Al] in the molten steel will be significantly reduced.

[0035] B2O3 is an acidic oxide with a melting point of 450 °C, which can effectively reduce the melting point and viscosity of the mold powder. Considering that B2O3 has a weak reactivity with [Al] in the molten steel, the present invention controls the content of B2O3 to be not more than 15%.

[0036] F can reduce the viscosity of CaO-Al2O3-based mold powder. However, considering that when CaO / Al2O3 is 1.0, a high-melting-point phase of 11CaO·7Al2O3·CaF2 may precipitate, the present invention controls the content of F within 15%.

[0037] C acts as a skeleton in the mold powder and can control the melting rate of the mold powder. The present invention controls the C content to be 2% to 8%.

[0038] Li2O, Na2O, and K2O can all improve the stability of the [AlO4] 5- tetrahedral network structure. Among them, Li + has the smallest ionic radius and the strongest self-diffusion ability, and is the best in improving the high-temperature fluidity of the mold powder; K + has the smallest field strength (Z / r 2 ), and is the best in providing charge compensation for [AlO4] 5- tetrahedron and stabilizing the glass properties of the mold powder; Na + plays a role between Li + and K +Among them. In the present invention, different-sized alkali ions are added to the new type of mold powder. There is an interaction between different alkali ion pairs formed with the oxygen ion as the medium. The repulsive force between single alkali ions is greater than that between different alkali ions, and the binding force between the alkali ions and the network in the mixed alkali is greater than that in the single alkali system, thereby increasing the diffusion activation energy of the alkali ions in the mold powder using the mixed alkali. At the same time, when large ions (such as K + and Na + ) replace small ions (such as Li + ), the holes left by the small ions hinder the migration of the large ions. The chemical stability of the mold powder depends on the migration of the alkali ions. Therefore, the mixed alkali effect can greatly improve the chemical stability of the mold powder. At the same time, Li + , Na + , and K + compete with different cations to form a coordination structure with the [AlO4] 5- anion group, inhibiting the precipitation of the high-melting-phase LiAlO2 (melting point 1700 °C) and improving the glass properties of the mold powder. In the present invention, the addition ratio of alkali metals with the optimal mixed alkali effect is set as Li2O / 2 = Na2O = K2O (weight percentage), and within this range, the comprehensive physical and chemical properties of the mold powder are optimal.

[0039] The CaO-Al2O3-SrO mold powder for continuous casting of high-aluminum steel according to the present invention adopts the "mixed alkali effect" strategy of adding multiple alkali metal oxides, achieving the effect of better improving the chemical stability and glass properties of the mold powder. At the same time, Na2O and K2O are selected to replace part of the expensive Li2O and added to the mold powder, reducing the production cost of the mold powder.

[0040] The physical properties of the mold powder are as follows: the melting point is 950 - 1050 °C, the viscosity at 1300 °C is 0.05 - 0.20 Pa·s, the turning point temperature is 950 - 1100 °C, and the crystalline phases are mainly calcium borate and calcium monoaluminate.

[0041] The influence of the alkali metal oxide Li2O on the Al-O coordination number in the CaO-Al2O3 mold powder is as Figure 1 shown, the influence of the alkali metal oxide Na2O on the Al-O coordination number in the CaO-Al2O3 mold powder is as Figure 2 shown, and the influence of the alkali metal oxide K2O on the Al-O coordination number in the CaO-Al2O3 mold powder is as Figure 3 shown. The XRD pattern of the CaO-Al2O3 mold powder co-regulated by SrO and the mixed alkali is as Figure 4 shown.

[0042] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be obviously obtained by those skilled in the art within the technical scope disclosed by the present invention, including simple changes or equivalent substitutions, is within the protection scope of the present invention.

[0043]

Example

[0044] In each example, a CaO-Al2O3-SrO mold powder for high-aluminum steel using a mixed alkali strategy was used, and the chemical composition is shown in Table 1. The preparation process of the CaO-Al2O3-SrO mold powder for high-aluminum steel is as follows: Weigh the mold powder raw materials according to the target composition, uniformly mix them by mechanical stirring, then heat and pre-melt the mixed slag materials to remove volatile components and gaseous substances. Then, the pre-melted slag materials are quenched with water, crushed, finely ground, and an appropriate amount of carbonaceous material is added to make a slurry. The prepared slurry is sprayed into a spray granulation tower for granulation. The mold powder obtained after granulation is cooled through a cooling bed, and it is required that the moisture content of the finished product is less than 0.3%, the particle size is in the range of 0.15 - 1 mm, and it is sealed and bagged for standby.

[0045] The main physical property indexes of the CaO-Al2O3-SrO mold powder for high-aluminum steel prepared in each example are shown in Table 1.

[0046] Table 1 Chemical composition (wt%) and main physical properties of the mold powder in Examples 1 - 3

[0047]

[0048]

Comparative Example

[0049] In each comparative example, the chemical composition of the mold powder is shown in Table 2, and the preparation process is the same as that in the example. The main material properties of the mold powder are shown in Table 2.

[0050] Table 2 Chemical composition (wt%) and main physical properties of the mold powder in Comparative Examples 1 - 3

[0051]

[0052] Six kinds of mold fluxes prepared in Examples 1-3 and Comparative Examples 1-3 were used for the continuous casting of high-aluminum steel with an Al weight percentage content of 2.0 wt%. The cross-sectional size of the mold was 1050 mm×210 mm, the casting speed was 1.0 m / min, and the continuous casting process required the thickness of the molten slag layer to be maintained in the range of 8-12 mm. After pouring a single ladle (200 t) of molten steel in double-strand casting, the chemical compositions of the mold fluxes in Examples 1-3 and Comparative Examples 1-3 are shown in Table 3. By comparing the two, it can be seen that the compositional changes of the mold fluxes prepared in Examples 1-3 are relatively small. The actual consumption of the mold fluxes in each example and comparative example is shown in Table 4.

[0053] Table 3 Actual chemical compositions (wt%) of the mold fluxes after slag-steel reaction in Examples 1-3

[0054]

[0055] Table 4 Actual slag consumption (kg / t steel) in Examples 1-3 and Comparative Examples 1-3

[0056] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Slag consumption 0.46 0.41 0.40 0.3 0.27 0.25

[0057] Compared with Comparative Example 1, the consumption of the mold flux in Example 1 increased by 53%; compared with Comparative Example 2, the consumption of the mold flux increased by 70%; compared with Comparative Example 3, the consumption of the mold flux increased by 84%.

[0058] Compared with Comparative Example 1, the consumption of the mold flux in Example 2 increased by 37%; compared with Comparative Example 2, the consumption of the mold flux increased by 52%; compared with Comparative Example 3, the consumption of the mold flux increased by 64%.

[0059] Compared with Comparative Example 1, the consumption of the mold flux in Example 3 increased by 33%; compared with Comparative Example 2, the consumption of the mold flux increased by 48%; compared with Comparative Example 3, the consumption of the mold flux increased by 60%.

[0060] It can be seen from the comparison that the CaO-Al2O3-SrO mold flux for high-aluminum steel using the mixed alkali strategy described in the present invention has the characteristic of low reactivity, and at the same time, various service performances and parameters (such as melting point, viscosity, inflection point temperature, and crystallization characteristics, etc.) can meet the requirements of the continuous casting process of high-aluminum steel. The present invention solves the problems of too strong crystallization ability and low slag consumption of the low-reactivity CaO-Al2O3-based mold flux, and the effect is remarkable.

[0061] The above is only the preferred specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A CaO-Al2O3-SrO mold flux for continuous casting of high-aluminum steel using a mixed alkali strategy, characterized in that, The mold powder comprises the following components by weight percentage: CaO: 18% - 28%; Al2O3: 18% - 28%; SrO: 6% - 16%; SiO2: 5% - 10%; Li2O: 1% - 10%; Na2O: 1% - 10%; K2O: 1% - 10%; B2O3: 5% - 15%; F: 5% - 15%; C: 2% - 8%; the balance being inevitable impurities; simultaneously satisfying the basicity-aluminum ratio CaO+(SrO×56.08) / 103.62:Al2O3 = 0.7 - 1.3; the replacement rate of SrO SrO / (CaO+SrO) = 0.2 - 0.5; the total amount of alkali metal oxides, i.e., Li2O+Na2O+K2O) ≤ 20%, and further satisfying Li2O = Na2O+K2O.

2. The CaO-Al2O3-SrO mold powder for continuous casting of high-aluminum steel adopting a mixed alkali strategy according to claim 1, wherein, In the mold powder, by weight percentage, SiO2: 5% - 6%.

3. The CaO-Al2O3-SrO mold flux for continuous casting of high-aluminum steel adopting a mixed alkali strategy according to claim 1, characterized in that, In the mold powder, by weight percentage, Li2O / 2 = Na2O = K2O.

4. The CaO-Al2O3-SrO mold flux for continuous casting of high-aluminum steel adopting a mixed alkali strategy according to claim 1, characterized in that, The physical properties of the mold powder are as follows: the melting point is 950 - 1050 °C, the viscosity at 1300 °C is 0.05 - 0.20 Pa·s, the inflection point temperature is 950 - 1100 °C, and the crystalline phases are mainly calcium borate and calcium monoaluminate.

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