A continuous casting powder with high self - adaptability and its preparation method

Abstract

The present invention provides a continuous casting powder with high self - adaptability and a preparation method thereof, belonging to the field of auxiliary materials for continuous casting processes. The powder comprises, by mass ratio: CaO 14.1% - 17.2%, SiO2 12.5% - 33.6%, Al2O3 14.3% - 25.1%, NaF 19.6% - 23.8%, MgO 1.8% - 2.3%, Li2O 0% - 4.8%, MnO 2.3% - 4.1%, CaF2 3.6 - 9.6%, C 2.8% - 5.5%, and inevitable impurities, and the atomic ratio of O and F is 2 - 3, and the atomic ratio of Si and Al is 0.3 - 2. By controlling the fluorine - oxygen ratio, the present invention destroys the network high - polymerization of the silicon - oxygen structure and the aluminum - oxygen structure, changes the melting point and viscosity of the slag, and at the same time controls the ratio of Si and Al to ensure that the melting point and viscosity are within a reasonable range, avoiding a significant increase in the melting point and a sudden increase in viscosity caused by too high SiO2 or Al2O3, and improving the protection effect.

Description

Technical Field

[0001] The invention belongs to the field of continuous casting process auxiliary materials, and in particular relates to a continuous casting protection slag with high adaptability and a preparation method thereof. Background Art

[0002] Continuous casting protection slag is a functional auxiliary material in the continuous casting process of iron and steel metallurgy. It plays the role of lubrication, heat preservation, prevention of secondary oxidation of molten steel, adsorption of floating inclusions and regulation of heat flow to the crystallizer during the continuous casting process. It is mainly used in the continuous casting crystallizer, melted on the surface of molten steel, and generally forms a three-layer structure of liquid slag layer, sintering layer and molten slag layer. Under normal continuous casting conditions, the slag fills the gap between the crystallizer and the ingot at the meniscus, which has an important influence on the surface quality of the ingot and the smooth progress of the continuous casting process. Continuous casting protection slag is generally composed of three major parts: base material, flux and carbonaceous material, containing CaO, SiO2, Na2O, CaF2, Al2O3, MgO, Li2O, C, etc. For molten steel with different compositions, the composition of the protection slag used will also be different. Protection slags with different compositions have different melting points and viscosities.

[0003] In the continuous casting process of high manganese and high aluminum steel, the Mn content in the high manganese and high aluminum steel water is as high as more than 20%, and the Al content is as high as more than 2.0%, which causes this type of steel to have the characteristics of low liquidus temperature and strong reactivity. In the continuous casting process, it is necessary to use a low melting point, appropriate viscosity, low basicity CaO-SiO2 based protective slag to meet the requirements of continuous casting, and to play the five major roles of the protective slag in heat insulation, oxidation prevention, inclusion absorption, shell lubrication and heat transfer control.

[0004] During continuous casting using CaO-SiO2-based protective slag, [Al] in high manganese and high aluminum steel is prone to undergo redox reactions with SiO2 and other components in the protective slag, resulting in a continuous decrease in SiO2 in the protective slag and a continuous increase in the Al2O3 content. The CaO-SiO2-based protective slag gradually changes to a CaO-SiO2-Al2O3-based protective slag. Finally, SiO2 is consumed and the protective slag changes to a CaO-Al2O3-based protective slag. During the change in the protective slag composition, the melting point of the protective slag even exceeds the liquidus temperature of the molten steel, resulting in poor melting of the protective slag, the formation of slag rings, a significant reduction in slag consumption, an increase in crystallization temperature, and the lubrication and heat transfer properties no longer meeting the requirements of continuous casting, resulting in difficulties in continuous casting and even steel leakage.

[0005] In the prior art, the problem of continuous casting mold slag for high manganese and high aluminum steel is generally solved by mixing different oxide ratios, adding a certain amount of CaF2 as a flux for the mold slag, or using pure oxides to prepare the mold slag. However, the above improvements to the mold slag still cannot meet the characteristics of high manganese and high aluminum steel, especially when multiple furnaces are continuously cast, it is impossible to ensure that the mold slag continues to protect the molten steel. Summary of the invention

[0006] To solve the above problems, the present invention provides a continuous casting powder with high self - adaptability and a preparation method thereof. By controlling the atomic ratio of F and O, and the atomic ratio of Al and Si, fluorine atoms replace oxygen anions, forming Si - F bonds in the silicon - oxygen tetrahedron, reducing the bridging oxygen in the network structure formed by silicon and oxygen anion units, and forming more mono - bridging oxygen (Q 1 ), di - bridging oxygen (Q 2 ), etc., simple structures, while reducing the high - bridging oxygen forms of oxygen atoms in the silicon - oxygen tetrahedron, such as tri - bridging oxygen (Q 3 ), or tetra - bridging oxygen (Q 4 ), reducing the polymerization degree of the silicon - oxygen tetrahedron; at the same time, among the Al - F bond and Al - O bond, the bond energy of the Al - F bond is less than that of the Al - O bond. Fluoride ions are used to replace oxygen atoms in the Al - O anion group, forming aluminum - oxygen complex ions Al2OF6 2- and Al2O2F4 2- , destroying the stability of the bridging oxygen structure in Al2O3, further reducing the number of network structures, thereby reducing the melting point and viscosity of the powder; at the same time, for high - manganese and high - aluminum molten steel, after the powder reacts with the molten steel, for example, the reaction between SiO2 and [Al], the physical and chemical properties of the powder do not change violently, and the melting and replenishment of the new powder and the consumption of the powder entering the slag channel reach equilibrium, adapting to the strong reaction characteristics of high - manganese and high - aluminum steel, thus achieving high self - adaptability.

[0007] To achieve the above object, the technical solutions adopted in the embodiments of the present invention are as follows:

[0008] In a first aspect, an embodiment of the present invention provides a continuous casting powder with high self - adaptability. The powder includes, by mass percentage: CaO 14.1% - 17.2%, SiO2 12.5% - 33.6%, Al2O3 14.3% - 25.1%, NaF 19.6% - 23.8%, MgO 1.8% - 2.3%, Li2O 0% - 4.8%, MnO 2.3% - 4.1%, CaF2 3.6 - 9.6%, C 2.8% - 5.5%, and the rest are inevitable impurities. Among them, the atomic ratio of O and F in the continuous casting powder is 2.1 - 3.0, and the atomic ratio of Si and Al is 0.4 - 2.0.

[0009] In the mold powder, by adding NaF and CaF2 simultaneously and controlling the ratio of fluorine to oxygen, on the one hand, sufficient F ions are provided, so that the F ions replace the oxygen ions in Si-O and Al-O of the silicon-oxygen tetrahedron under the working state of high-temperature melting, thereby destroying the network high-polymerization of the silicon-oxygen structure and the aluminum-oxygen structure; on the other hand, the atomic ratio of O to F is controlled to be 2-3. On the premise of providing sufficient oxygen substitution, for the mold powder with an oxygen-fluorine ratio less than 2.0, the fluoride content is too high, which is easy to volatilize during use, resulting in the transformation of the properties of the mold powder and environmental pollution.

[0010] Fluoride ions have a destructive effect on the silicon-oxygen structure and the aluminum-oxygen structure. The core lies in the strong electronegativity and high activity of fluoride ions, which are specifically manifested in three aspects: the substitution of chemical bonds, the loosening of the network structure, and the disturbance of charge balance. In the network structure of the mold powder, both Si-O bonds and Al-O bonds will form a three-dimensional network structure of silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons connected by bridging oxygen. Specifically, fluoride ions have strong electronegativity and ionic radius, replacing the bridging oxygen in the silicon-oxygen tetrahedron or aluminum-oxygen tetrahedron to form Si-F bonds or Al-F bonds. This substitution reduces the stability of the tetrahedron structure. After fluoride ions replace the bridging oxygen, the formed Si-F bonds and Al-F bonds are terminal bonds and no longer connect other structural units, resulting in a decrease in the proportion of Q with high polymerization degree in the network, an increase in the proportion of Q with low polymerization degree, and a decrease in the long-chain or cyclic silicon-oxygen structure, leading to a decrease in the three-dimensional connectivity of the tetrahedron structure and the formation of a more loose network structure. The high nucleophilicity of fluoride ions enables them to preferentially form bonds with cations, weakening the binding ability between cations and silicon-oxygen or aluminum-oxygen tetrahedrons, resulting in a decrease in the cation density in the network. The network charge cannot be completely neutralized, and the aluminum-oxygen structure may change from a tetrahedron to an octahedron. The formation of this high-coordination aluminum further destroys the stability of the network structure. In the mold powder with a low oxygen-fluorine ratio (2.0-3.0), aluminum ions mainly exist in the four-coordination form. Fluoride ions will replace one or two oxygen ions in the inner aluminum-oxygen tetrahedron to form a network structure mainly composed of AlO3F and AlO2F2. In the traditional mold powder with an oxygen-fluorine ratio greater than 5.0, there must be a large number of AlO4 structures and a small number of Al-O-F structures. The introduction of fluoride ions will form terminal bonds Al-F, destroy the bridging oxygen bonds, reduce the network rigidity and connectivity of the aluminum-oxygen molecular group, and form a low-dimensional structure. In addition, fluoride ions can introduce additional weak interactions, such as the oxygen-fluorine coexistence effect, to further fine-tune the electronic environment around the aluminum-oxygen nucleus, release more free oxygen ions, further reduce the bridging oxygen in AlO3F and AlO2F2, form excessive AlO2F2 or AlOF3 structures, and reduce the proportion of the Q bridging oxygen structure in the aluminum-oxygen network, and Q 4 proportion decreases, and the proportion of low-polymerization Q 1 and Q 2 proportion increases. 3 The proportion of the Q bridging oxygen structure in the aluminum-oxygen network decreases, and Q 2 and Q 1The increase in the proportion of bridging oxygen structure further reduces the melting point and viscosity of the mold powder.

[0011] Meanwhile, by limiting the atomic ratio of Si and Al to 0.3 - 2, controlling the silicon-aluminum ratio in the mold powder can ensure that the melting point and viscosity of the mold powder are within a reasonable range, avoiding the problems of a significant increase in the melting point of the mold powder and a sudden increase in viscosity caused by excessive SiO2 or Al2O3 in the slag.

[0012] The addition of MnO can effectively adjust the color of the mold powder film, which is conducive to controlling heat transfer and preventing defects such as billet depression and cracks.

[0013] In a preferred embodiment, the melting temperature of the continuous casting mold powder is 848 - 1077 °C.

[0014] In a preferred embodiment, the viscosity of the continuous casting mold powder at 1300 °C is 1.06 - 2.00 Pa·s.

[0015] In a preferred embodiment, the crystalline phase of the continuous casting mold powder includes melilite and / or sodium calcium aluminate.

[0016] In a preferred embodiment, the total volatile content of the continuous casting mold powder is ≤2%.

[0017] In a preferred embodiment, the fluctuation range of the consumption of the continuous casting mold powder after working in the mold for 20 min is within 20%.

[0018] In a second aspect, the embodiments of the present invention also provide a preparation method of a continuous casting mold powder with high adaptability, and the method includes:

[0019] Step S1, using limestone, bauxite, industrial soda ash and cryolite as raw materials, weighing and mixing the raw material powders according to the following ratio to obtain a mixed raw material; the ratio by mass percentage includes: CaO 14.1% - 17.2%, SiO2 12.5% - 33.6%, Al2O3 14.3% - 25.1%, NaF 19.6% - 23.8%, MgO 1.8% - 2.3%, Li2O 0% - 4.8%, MnO 2.3% - 4.1%, CaF2 3.6 - 9.6%, and the rest are inevitable impurities; wherein, the atomic ratio of O and F in the continuous casting mold powder is 2.1 - 3.0, and the atomic ratio of Si and Al is 0.4 - 2.0;

[0020] Step S2, heating the mixed raw material to a molten state, keeping it at the molten state for a predetermined time to remove volatile components, and obtaining a slag with uniform composition; the predetermined holding time here is generally 10 min - 2 hours;

[0021] Step S3: Quench and rapidly cool the slag to obtain a vitreous slag sample.

[0022] Step S4: Crush and screen the slag sample to obtain a powder sample with a predetermined particle size; the predetermined particle size here is 300 - 700 mesh.

[0023] Step S5: Add a carbonaceous material accounting for 2.8% - 5.5% by mass percentage to the powder sample, then add a binder, a dispersant, and water, and stir evenly to obtain a mixed slurry; the dosage of the binder is 0.1 - 0.8 wt%, and the dosage of the dispersant is 0.5 - 2.0 wt%; preferably, the binder is cellulose, and the dispersant is sodium methylnaphthalenesulfonate.

[0024] Step S6: Dry and screen the mixed slurry, and then granulate it to obtain a mold powder. In this step, the drying requirement is that the moisture content < 0.5 wt.%, and the granulation particle size is 0.01 - 1.8 mm.

[0025] The solution of the embodiment of the present invention has the following beneficial effects:

[0026] The high - self - adaptive continuous casting mold powder and its preparation method provided by the embodiment of the present invention, by limiting the fluorine - oxygen ratio, under the condition of ensuring the full substitution of fluorine for oxygen, destroys the network high - polymerization of the silicon - oxygen structure and the aluminum - oxygen structure, reduces the stability of the silicon - oxygen tetrahedron network structure, forms a low - dimensional structure based on Al - O, reduces the number of network structures, thereby reducing the melting point and viscosity of the mold powder; at the same time, controlling the atomic ratio of Si and Al to be 0.3 - 2, controlling the silicon - aluminum ratio in the mold powder can ensure that the melting point and viscosity of the mold powder are within a reasonable range, avoiding the problems of a sharp increase in the melting point of the mold powder and a sudden increase in viscosity caused by too high SiO2 or Al2O3 in the slag, and the physical and chemical properties of the mold powder do not change violently. The melting and replenishment of the new mold powder and the consumption of the mold powder entering the slag channel reach equilibrium, adapting to the strong reaction characteristics in high - manganese and high - aluminum steel, thereby achieving high self - adaptability; the continuous casting mold powder can form a stable liquid layer, has good lubrication effect, can well ensure the smooth continuous casting of multiple furnaces, effectively prevent the generation of defects such as billet depression and cracks, and enable the mold powder to better play the roles of heat insulation, preventing oxidation, absorbing inclusions, lubricating the billet shell, and controlling heat transfer, improving the protection effect on molten steel.

[0027] Of course, when implementing any product or method of the present invention, it is not necessarily required to simultaneously achieve all the above - mentioned advantages. Detailed implementation mode

[0028] After discovering the above problems, the inventors of the present application conducted a detailed study on existing continuous casting fluxes, especially fluxes for high manganese and high aluminum molten steel. The study found that according to the coexistence theory, in the high-temperature melt of the flux, components such as CaO, Na2O, and MgO will decompose to form simple cations and free oxygen ions; in the CaO-SiO2-based flux, anionic groups mainly composed of silicon-oxygen tetrahedrons will be formed, where O atoms will exist in the form of bridging oxygen, connecting multiple silicon-oxygen tetrahedrons to form large molecular groups with a complex network structure; the free oxygen ions formed by the decomposition of components such as CaO and Na2O have a significant destructive effect on the bridging oxygen structure, decomposing the network structure into chain-like or monomeric structures, resulting in a decrease in both the melting point and viscosity of the flux. In comparison, the effect of free oxygen ions on destroying the Al-O structure in the CaO-Al2O3-based flux is limited, and large molecular groups with a complex network structure will be formed in the melt, causing the melting point and viscosity of the flux to increase. If a high-alkalinity CaO-Al2O3-based weak (non)-reactive flux is used during continuous casting, reducing or avoiding the use of SiO2 in the flux is beneficial for reducing the slag-steel reaction and controlling the change of flux composition and performance deterioration. However, it is difficult for free oxygen ions to destroy the large-sized molecular groups existing in the CaO-Al2O3-based flux, resulting in problems such as poor melting, easy slag ring formation, and low consumption, and it is rarely used in actual production.

[0029] Therefore, in both CaO-SiO2-based and CaO-Al2O3-based high manganese and high aluminum steel fluxes, the key to solving the melting point and viscosity lies in controlling the large-sized network anionic groups. Silicon and oxygen are connected by covalent bonds to form anionic elementary units. As network formers, they form a network structure of silicon-oxygen tetrahedrons, where most oxygen atoms exist in the form of high bridging oxygen, such as three-bridging oxygen (Q 3 ) or four-bridging oxygen (Q 4 ), and fluorine atoms can replace the bridging oxygen in this highly polymerized network structure to form more simple structures such as mono-bridging oxygen (Q 1 ) and di-bridging oxygen (Q 2 ), reducing the polymerization degree of the silicon-oxygen tetrahedrons; the bond lengths of the Al-F bond and the Al-O bond are 0.1895 nm and 0.1745 nm respectively, and the bond energy of the Al-F bond is less than that of the Al-O bond. Therefore, using fluoride ions to replace the oxygen atoms in the anionic group to form aluminum-oxygen complex ions Al2OF6 2- and Al2O2F4 2- will destroy the stability of the bridging oxygen structure in Al2O3 and reduce the number of network structures, thereby reducing the melting point and viscosity of the flux.

[0030] It should be noted that the defects and solutions in the above prior art solutions are all the results obtained by the inventors after practice and careful research. Therefore, the process of discovering the above problems and the solutions proposed by the embodiments of the present invention below for the above problems should all be the contributions made by the inventors to the present invention during the process of the present invention.

[0031] Based on the above in-depth analysis, an embodiment of the present invention proposes a continuous casting mold powder with high self-adaptability and a preparation method. The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] Embodiment 1

[0033] This embodiment provides a continuous casting mold powder with high self-adaptability and a preparation method, and the continuous casting mold powder is particularly suitable for casting high manganese and high aluminum steel.

[0034] The continuous casting mold powder, by mass percentage, includes: CaO 15.4%, SiO2 30.2%, Al2O3 15.8%, NaF 23.1%, MgO 2.3%, Li2O 3.5%, MnO 2.3%, CaF2 3.6%, C 3.5%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting mold powder is 3, and the atomic ratio of Si and Al is 1.6.

[0035] The preparation method of the continuous casting mold powder is as follows:

[0036] Step S1, the raw materials are limestone, bauxite, industrial soda ash, and cryolite; proportioning is carried out according to the above component ratios, followed by grinding and screening, with the particle size requirement of passing through a 45μm (325 mesh) sieve; all raw materials are added to a stirrer and stirred and mixed for 30 minutes to obtain a uniform mixed raw material;

[0037] Step S2, the mixed raw material is heated to 1500°C for melting, and kept warm for 10 minutes to obtain a slag with uniform composition, which is qualified after chemical analysis and testing;

[0038] Step S3, the slag is quenched and rapidly cooled with water to obtain a glassy slag sample;

[0039] Step S4, the slag sample is crushed, ground, and screened to obtain a powder sample, and the particle size requirement of the powder sample is to pass through a 45μm (325 mesh) sieve, and the sieve residue is not more than 5%;

[0040] Step S5, add carbonaceous material to the powder sample according to the ratio, add 0.3% cellulose as a binder and 1% sodium methylnaphthalenesulfonate as a dispersant, add an appropriate amount of water, and add the raw materials to a stainless-steel high-speed stirring tank and stir and mix for 100 min to obtain a mixed slurry;

[0041] Step S6, use a spray granulation drying tower to dry and granulate the mixed slurry. The uniformly mixed slurry is introduced into a ball mill and ground finely. The pressure of the plunger pump is set at 1.5 MPa, and it is sprayed upward into the central part of the drying tower through a spray gun and atomized into small droplets. The small droplets form circular spheres under the action of the surface tension of water; it is generated by the hot air system and sprayed into the drying tower from the top inlet by a blower. The inlet air temperature of the drying tower is 600 °C, and the outlet air temperature is 160 °C. The drying requires the moisture to be less than 0.5%; the dried hollow granular mold powder is screened in a closed vibrating screen, and the granulation particle size is 0.01 - 1.8 mm. The mold powder particles are transported to the finished product bin by a belt conveyor.

[0042] It is measured that the melting temperature of the continuous casting mold powder obtained in this example is 848 °C, the viscosity at 1300 °C is 2 Pa·s, the crystalline phase is melilite, the volatilization amount at 1500 °C is 1.89%, the initial slag consumption is 0.34 kg / m 2 and the slag consumption after 20 min is 0.3 kg / m 2 .

[0043] Example 2

[0044] This example also provides a continuous casting mold powder with high self - adaptability and a preparation method. The continuous casting mold powder is particularly suitable for the casting of high - manganese and high - aluminum steel.

[0045] The continuous casting mold powder, by mass percentage, includes: CaO 17.2%, SiO2 33.6%, Al2O3 14.3%, NaF 19.6%, MgO 1.9%, MnO 2.3%, CaF2 7.4%, C 3.8%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting mold powder is 2.7, and the atomic ratio of Si and Al is 2.

[0046] The preparation method of the continuous casting mold powder is as follows:

[0047] Step S1, the raw materials are limestone, bauxite, industrial soda ash and cryolite; proportion the ingredients according to the above component ratio, grind and screen, and the particle size requirement is to pass through a 50 - μm (300 - mesh) sieve; all raw materials are added to a stirrer and stirred and mixed for 30 min to obtain a uniform mixed raw material;

[0048] Step S2, heat the mixed raw material to 1500 °C for melting, keep it warm for 30 min to obtain a slag with uniform composition, and it is qualified after chemical analysis and testing;

[0049] Step S3: Quench and rapidly cool the slag to obtain a vitreous slag sample;

[0050] Step S4: Crush, grind, and screen the slag sample to obtain a powder sample. The particle size requirement of the powder sample is to pass through a 50-μm (300-mesh) sieve, and the sieve residue is not more than 5%;

[0051] Step S5: Add carbonaceous materials to the powder sample according to the ratio, add 0.3% cellulose as a binder, 1% sodium methylnaphthalenesulfonate as a dispersant, add an appropriate amount of water, and add the raw materials to a stainless-steel high-speed stirring tank and stir and mix for 100 min to obtain a mixed slurry;

[0052] Step S6: Use a spray granulation drying tower to dry and granulate the mixed slurry. The uniformly mixed slurry is introduced into a ball mill and ground finely. The pressure of the piston pump is set to 1.5 MPa, and it is sprayed upward into the central part of the drying tower through a spray gun and atomized into small droplets. The small droplets form spherical bodies under the action of the surface tension of water; it is generated by a hot air system and sprayed into the drying tower from the top inlet by a blower. The inlet air temperature of the drying tower is 600 °C, and the outlet air temperature is 160 °C. The drying requirement is that the moisture content is less than 0.5%; the dried hollow particle mold powder is screened in a closed vibrating screen. The granulation particle size is 0.01 - 1.8 mm, and the mold powder particles are transported to the finished product bin by a belt conveyor.

[0053] It is measured that the melting temperature of the continuous casting mold powder obtained in this example is 1001 °C, the viscosity at 1300 °C is 1.34 Pa·s, the crystalline phases are melilite and sodium calcium aluminate, the volatilization amount at 1500 °C is 1.69%, and the initial slag consumption is 0.41 kg / m 2 and the slag consumption after 20 min is 0.34 kg / m 2 .

[0054] Example 3

[0055] This example provides a continuous casting mold powder with high self-adaptability and a preparation method. The continuous casting mold powder is particularly suitable for the casting of high-manganese and high-aluminum steel.

[0056] The continuous casting mold powder, by mass percentage, includes: CaO 14.1%, SiO2 18.2%, Al2O3 24.5%, NaF 20.2%, MgO 2.0%, Li2O 4.5%, MnO 4.1%, CaF2 9.6%, C 2.8%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting mold powder is 2.5, and the atomic ratio of Si and Al is 0.6.

[0057] The preparation method of the continuous casting mold powder is as follows:

[0058] Step S1, the raw materials are limestone, bauxite, industrial soda ash and cryolite; the ingredients are prepared according to the above-mentioned component proportions, and the particles are ground and sieved to pass a 45 μm (325 mesh) sieve; all the raw materials are added into a stirrer and stirred for 30 minutes to obtain a uniform mixed raw material;

[0059] Step S2, heating the mixed raw materials to 1500°C to melt, and keeping the temperature for 10 minutes to obtain slag with uniform composition, which is qualified after chemical testing;

[0060] Step S3, quenching the molten slag with water to obtain a glassy slag sample;

[0061] Step S4, crushing, grinding and sieving the slag sample to obtain a powder sample, wherein the powder sample particle size is required to pass through a 45 μm (325 mesh) sieve, and the sieve residue is not greater than 5%;

[0062] Step S5, adding carbonaceous materials to the powder sample according to a proportion, adding 0.3% cellulose as a binder, 1% sodium methylnaphthalene sulfonate as a dispersant, adding an appropriate amount of water, adding the raw materials into a stainless steel high-speed stirring tank and stirring and mixing for 100 minutes to obtain a mixed slurry;

[0063] Step S6, using a spray granulation drying tower to dry and granulate the mixed slurry, the mixed slurry is introduced into a ball mill for grinding, the plunger pump pressure is set to 1.5MPa, and it is sprayed upward into the center of the drying tower through a spray gun and atomized into small droplets, which form round spheres under the surface tension of water. The hot air system is generated and sprayed into the drying tower from the top entrance by a blower. The inlet wind temperature of the drying tower is 600℃, the outlet wind temperature is 160℃, and the moisture content of the drying tower is less than 0.5%. The dried hollow particle protective slag is sieved in a closed vibrating screen, and the granulation size is 0.01-1.8mm. The protective slag particles are transported to the finished product silo by a belt conveyor.

[0064] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1070°C, the viscosity is 1.22 Pa·s at 1300°C, the crystal phase is calcium sodium aluminate, the volatilization amount at 1500°C is 1.75%, and the initial slag consumption is 0.43 kg / m 2 , slag consumption after 20 minutes is 0.35kg / m 2 .

[0065] Example 4

[0066] The present embodiment provides a continuous casting mold slag with high adaptability and a preparation method thereof. The continuous casting mold slag is particularly suitable for casting high manganese and high aluminum steel.

[0067] The continuous casting powder, by mass percentage, comprises: CaO 14.2%, SiO2 12.5%, Al2O3 25.1%, NaF 23.8%, MgO 1.8%, Li2O 4.8%, MnO 3.6%, CaF2 8.7%, C 5.5%, and the balance being inevitable impurities. At this time, the atomic ratio of O to F in the continuous casting powder is 2.1, and the atomic ratio of Si to Al is 0.4.

[0068] The preparation method of the continuous casting powder is as follows:

[0069] Step S1: The raw materials are limestone, bauxite, industrial soda ash, and cryolite. Batching is carried out according to the above component ratio, followed by grinding and screening, with the particle size requirement being to pass through a 45μm (325 mesh) sieve. All raw materials are added to a stirrer and stirred and mixed for 30 minutes to obtain a uniform mixed raw material.

[0070] Step S2: The mixed raw material is heated to 1500°C for melting and kept warm for 10 minutes to obtain a slag with uniform composition, which is qualified through chemical analysis and testing.

[0071] Step S3: The slag is quenched and rapidly cooled to obtain a vitreous slag sample.

[0072] Step S4: The slag sample is crushed, ground, and screened to obtain a powder sample. The particle size requirement for the powder sample is to pass through a 45μm (325 mesh) sieve, and the sieve residue is not more than 5%.

[0073] Step S5: Carbonaceous materials are added to the powder sample according to the ratio, 0.3% cellulose is added as a binder, 1% sodium methylnaphthalenesulfonate is added as a dispersant, and an appropriate amount of water is added. The raw materials are added to a high-speed stainless steel stirring tank and stirred and mixed for 100 minutes to obtain a mixed slurry.

[0074] Step S6: The mixed slurry is dried and granulated using a spray granulation drying tower. The uniformly mixed slurry is introduced into a ball mill for fine grinding. The pressure of the plunger pump is set at 1.5 MPa, and it is sprayed upward into the central part of the drying tower through a spray gun and atomized into small droplets. The small droplets form round spheres under the action of the surface tension of water. It is generated by a hot air system and sprayed into the drying tower from the top inlet by a blower. The inlet air temperature of the drying tower is 600°C, and the outlet air temperature is 160°C. The drying requirement is that the moisture content is less than 0.5%. The dried hollow particle powder is screened in a closed vibrating screen, and the granulation particle size is 0.01 - 1.8 mm. The powder particles are transported to the finished product bin by a belt conveyor.

[0075] It is measured that the melting temperature of the continuous casting powder obtained in this example is 1077°C, the viscosity at 1300°C is 1.06 Pa·s, the crystalline phase is calcium sodium aluminate, the volatilization amount at 1500°C is 1.95%, and the initial slag consumption is 0.51 kg / m 2, the slag consumption after 20 min is 0.42 kg / m 2 .

[0076] Comparative Example 1

[0077] A continuous casting powder, by mass percentage, includes: CaO 30.8%, SiO2 7.1%, Al2O3 29.2%, NaF 15.2%, MgO 1.1%, Li2O 3.5%, MnO 2.4%, CaF2 5.2%, C 5.5%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting powder is 6.4, and the atomic ratio of Si and Al is 0.21.

[0078] The preparation method of the continuous casting powder is the same as that of Example 1, except for the raw material ratio. This comparative example uses the raw material ratio in this comparative example.

[0079] It is measured that the melting temperature of the continuous casting powder obtained in this comparative example is 1168 °C, the viscosity at 1300 °C is 0.961 Pa·s, the crystalline phase is calcium sodium aluminate, the volatilization amount at 1500 °C is 1.91%, and the initial slag consumption is 0.42 kg / m 2 , the slag consumption after 20 min is 0.11 kg / m 2 .

[0080] Comparative Example 2

[0081] A continuous casting powder, by mass percentage, includes: CaO 14%, SiO2 10%, Al2O3 35%, NaF 24%, MgO 3.5%, Li2O 6%, MnO 3.5%, CaF2 9%, C 5.5%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting powder is 6.4, and the atomic ratio of Si and Al is 0.21.

[0082] The preparation method of the continuous casting powder is the same as that of Example 1, except for the raw material ratio. This comparative example uses the raw material ratio in this comparative example.

[0083] It is measured that the melting temperature of the continuous casting powder obtained in this example is 1220 °C, the viscosity at 1300 °C is 1.247 Pa·s, the crystalline phase is melilite and cuspidine, the volatilization amount at 1500 °C is 1.51%, and the initial slag consumption is 0.38 kg / m 2 , the slag consumption after 20 min is 0.13 kg / m 2 .

[0084] Comparative Example 3

[0085] A continuous casting powder, by mass percentage, includes: CaO 13.5%, SiO2 35%, Al2O3 11.6%, NaF 19.5%, MgO 1.9%, MnO 2.5%, CaF2 9.5%, C 6%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting powder is 2.5, and the atomic ratio of Si and Al is 3.

[0086] The preparation method of the continuous casting powder is the same as that of Example 1, except for the raw material ratio. This comparative example uses the raw material ratio in this comparative example.

[0087] It is measured that the melting temperature of the continuous casting powder obtained in this example is 1044 °C, the viscosity at 1300 °C is 0.18 Pa·s, the crystalline phases are cuspidine and calcium fluoride, the volatilization amount at 1500 °C is 5.68%, and the initial slag consumption is 0.86 kg / m 2 and the slag consumption after 20 minutes is 0.55 kg / m 2 .

[0088] Comparative Example 4

[0089] A continuous casting powder, by mass percentage, includes: CaO 15.8%, SiO2 10%, Al2O3 30%, NaF 22.5%, MgO 3%, Li2O 4.5%, MnO 3%, CaF2 9%, C 3.9%, and the rest are inevitable impurities. At this time, the atomic ratio of O and F in the continuous casting powder is 3, and the atomic ratio of Si and Al is 0.2.

[0090] The preparation method of the continuous casting powder is the same as that of Example 1, except for the raw material ratio. This comparative example uses the raw material ratio in this comparative example.

[0091] It is measured that the melting temperature of the continuous casting powder obtained in this example is 1254 °C, the viscosity at 1300 °C is 5.15 Pa·s, the crystalline phases are melilite and calcium sodium aluminate, the volatilization amount at 1500 °C is 2.68%, and the initial slag consumption is 0.18 kg / m 2 and the slag consumption after 20 minutes is 0.09 kg / m 2 .

[0092] It can be seen from the comparison between Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention that in Examples 1 to 4, the oxygen-fluorine ratio of the mold powder is maintained between 2.0 and 3.0, the melting temperature is 848°C to 1077°C, the viscosity is 1.06 to 2.00 Pa·s, and the crystalline phase is mainly melilite and calcium aluminosilicate. In Comparative Examples 1 and 2, traditional CaO-SiO2-based and CaO-Al2O3-based mold powders have a relatively high oxygen-fluorine ratio. In the CaO-SiO2-based mold powder, SiO2 is extremely easy to react with [Al] in the steel, resulting in a drastic change in the composition of the mold powder and an increase in the Al2O3 content; in the CaO-Al2O3-based low (non)-reactive mold powder, the Al2O3 content will also increase after the slag-steel reaction. The Al2O3 content in both types of mold powders generally reaches more than 40%. Excessive Al2O3 will cause the performance of the mold powder to deteriorate after a period of time, reduce the slag consumption, delay the renewal of the mold powder, increase the residence time, and continuously deteriorate the composition and performance of the mold powder, resulting in difficulties in continuous casting.

[0093] In Examples 1 to 4, the initial slag consumption is comparable to that in Comparative Examples 1 and 2. After casting for 20 minutes, the slag consumption slightly decreases, but the slag consumption generally remains at a normal level. When the slag consumption is large, the molten mold powder is timely replenished into the liquid slag layer after melting, and the mold powder maintains rapid renewal, offsetting part of the compositional changes caused by the reduction of SiO2. The lubrication is good, avoiding slag skimming and slag changing operations, ensuring the smooth progress of continuous casting work, improving the surface depressions, cracks and other defects of the cast billets produced, and increasing the number of continuous casting heats of high manganese and high aluminum steel. In Comparative Example 3, the melting point of the mold powder is relatively low, the thick liquid slag layer leads to a large consumption of the mold powder, and the thickness of the slag film formed increases, which is not conducive to controlling the heat transfer between the billet shell and the copper plate. At the same time, the high NaF content leads to a large evaporation amount at 1500°C, which is easy to damage the environment and corrode the equipment. In Comparative Example 4, the melting point of the slag is too high and the slag consumption is too low, and it basically cannot play a lubricating role.

[0094] In Examples 1 to 4, the initial slag consumption and the slag consumption after 20 minutes are moderate, the crystalline phase is stable, and the evaporation amount during continuous casting is less than 2%. This is due to the fact that the Al2O3 inclusions in the steel float to the steel-slag interface and are absorbed by the mold powder, and the mold powder has excellent inclusion absorption performance.

[0095] The above description is only the preferred embodiments of the present invention and the description of the applied technical principles, and is not intended to limit the scope of the present invention claimed. Instead, it only represents the preferred embodiments of the present invention. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

Claims

1. A continuous casting mold slag with high adaptability, characterized in that: The protective slag comprises, by mass percentage, CaO 14.1%-17.2%, SiO2 12.5%-33.6%, Al2O3 14.3%-25.1%, NaF 19.6%-23.8%, MgO 1.8%-2.3%, Li2O 0%-4.8%, MnO2.3%-4.1%, CaF2 3.6%-9.6%, C 2.8%-5.5%, and the rest are unavoidable impurities. The atomic ratio of O to F in the continuous casting mold slag is 2.5-3.0, and the atomic ratio of Si to Al is 0.4-2.0; and the viscosity of the continuous casting mold slag at 1300° C. is 1.06-2.00 Pa×s.

2. The continuous casting mold slag according to claim 1, characterized in that: The melting temperature of the continuous casting protection slag is 848-1077°C.

3. The continuous casting mold slag according to claim 1, characterized in that: The crystalline phase of the continuous casting mold slag includes pyroxene and / or calcium sodium aluminate.

4. The continuous casting mold slag according to claim 1, characterized in that: The total volatile content of the continuous casting protection slag is ≤2%.

5. The continuous casting mold slag according to claim 1, characterized in that: The fluctuation range of the consumption of the continuous casting protection slag after working in the crystallizer for 20 minutes is within 20%.

6. A method for preparing continuous casting mold slag according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Step S1, using limestone, bauxite, industrial soda ash and cryolite as raw materials, weighing ingredient powders according to the following ratio, stirring and mixing evenly to obtain a mixed raw material; the ratio includes, by mass percentage: CaO 14.1%~17.2%, SiO2 12.5%~33.6%, Al2O3 14.3%~25.1%, NaF 19.6%~23.8%, MgO 1.8%~2.3%, Li2O 0%~4.8%, MnO 2.3%~4.1%, CaF2 3.6~9.6%, and the rest are inevitable impurities; wherein, in the continuous casting mold slag, the atomic ratio of O to F is 2.5~3.0, and the atomic ratio of Si to Al is 0.4~2.0; Step S2, heating the mixed raw materials to a molten state, keeping the mixture in the molten state for a predetermined time, removing volatile components, and obtaining slag with uniform components; Step S3, quenching the molten slag with water to obtain a glassy slag sample; Step S4, crushing and screening the slag sample to obtain a powder sample of a predetermined particle size; Step S5, adding 2.8% to 5.5% by mass of carbonaceous material to the powder sample, and then adding a binder, a dispersant and water, and stirring to obtain a mixed slurry; Step S6, drying, sieving, and granulating the mixed slurry to obtain protective slag.

7. The preparation method according to claim 6, characterized in that: The predetermined particle size in step S4 is 300-700 mesh.

8. The preparation method according to claim 6, characterized in that: In step S5, the amount of the binder is 0.1-0.8wt%, and the amount of the dispersant is 0.5-2.0wt%; the binder is cellulose, and the dispersant is sodium methylnaphthalene sulfonate.

9. The preparation method according to claim 6, characterized in that: In step S6, the drying requires a moisture content of <0.5 wt.%, and a granulation size of 0.01-1.8 mm.